Browse Topic: Marine engines

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Analysis of the Cause of Knocking Noise in a Marine Dual-Power Dual-Branch Transmission Gear System2026-99-16507/24/2026
This study investigates the knocking noise phenomenon in a marine dual-power dual-branch transmission gear system. Vibration mechanisms are analyzed, and potential failure modes are assessed. System vibration data were evaluated using time-domain and frequency-domain methods. Results show that overall vibration levels remained within acceptable limits, with no indication of imminent failure. Physical inspection confirmed that the shaft, gears, bearings, housing, and installation met specifications, with no observed performance degradation or structural damage. By correlating noise occurrence with vessel loading conditions, a strong relationship was identified among gear transmission torque, the power distribution ratio between high-and low-pressure turbines, and the onset of knocking. Specifically, under low-load conditions, uneven power and torque distribution among the four gear branches led to insufficient loading on the low-pressure side. This light-load state induced instability in the low-pressure gears, resulting in periodic tooth disengagement or back-side tooth contact, which is established as the root cause of the knocking noise.
Gu, Chengzhong, Xu, Hanwei, Luo, Rirong, Ren, Fushan
Optimization of Turbine Discrete Noise by Non-Uniformly Distributed Blade Design2026-99-16177/24/2026
The Mellin non-uniformly distributed moving blade method was adopted to conduct CFD numerical analysis and sample experimental tests on the axial-flow turbines before and after optimization using the uniformly distributed and non-uniformly distributed design methods, respectively. In the original design, five blades were evenly distributed in the 360° circumferential direction, and the non-uniformly distributed angles were 46°, 102°, 46°, 83°, and 83°. CFD numerical analysis shows that due to the low rotational speed of the turbine and the absence of a sealing structure at the blade tip, factors such as tip noise leakage and backflow have little impact, and the flow field pulsation is mainly caused by the blades themselves. The non-uniformly distributed design can significantly enhance the work-doing capacity of the blades. At 90% of the blade height, the torque can be increased by up to 60%, but at the same time, the axial force on the blades also increases accordingly. Near 80% - 90% of the blade height, the axial force increases by 33%. The flow rate performance of the non-uniformly distributed design is slightly inferior to that of the uniformly distributed design, but the overall noise is better than that of the uniformly distributed design, with maximum optimization of 0.48 dB (A); the maximum values of the first three orders of discrete noise are significantly improved, with a maximum improvement of 0.75 dB (A), and the discrete noise orders of the non-uniformly distributed turbine can avoid blade - related factors and disperse the energy to nearby orders.
Wu, Aiping, Ma, Tianli, Wang, Shiming, Ding, Chengling
Experimental Investigation on Unburned Methanol and Formaldehyde Emissions from a Direct-Injection Diesel / Methanol Dual-Fuel Engine2026-99-16467/24/2026
For large-bore marine methanol / diesel dual-fuel engines, this study investigates the formation characteristics of unregulated emissions through experimental methods and explores the mechanisms by which engine load and injection timing influence the emissions of unburned methanol and formaldehyde. The study was carried out on a supercharged intercooled inline six-cylinder engine, and Fourier Transform Infrared Spectroscopy (FTIR) was used to monitor the exhaust composition in real time. The study shows that methanol released in the exhaust is due to the incomplete combustion of the methanol fuel. In the combustion process of methanol fuel, formaldehyde mainly arises from two pathways, the first of which is the partial oxidation of methanol inside the cylinder; secondly, the unburned methanol in the exhaust gas oxidizes in the exhaust pipe to generate formaldehyde. As the load increased from 25% to 100%, the unburned methanol emissions decreased by 29%, and formaldehyde emissions decreased by 71%. This is mainly attributed to the enhanced oxidation reaction and reduced wall crevice effect due to the increased combustion temperature. Methanol injection timing optimization was effective in controlling unregulated emissions, with methanol emissions lower at -7° CA ATDC and formaldehyde emissions reaching larger values under this condition. Delaying the diesel injection to -16°CA ATDC led to a 38% increase in unburned methanol emissions, caused by fuel spray interactions and longer stagnation, whereas formaldehyde emissions showed minimal change.
Jiang, Yuqi, Li, Hongmei, Zhang, Wenzheng, Li, Xiao, Zheng, Liang, Meng, Yangqian, Gu, Xianan, Hua, Hanqing
Development of a Hybrid-Driven Computational Model for Cylinder Pressure in Marine Low-Speed Engines2026-99-05257/10/2026
To address the high operating cost of online cylinder pressure monitoring systems for low-speed engines in ships and the limitations of existing alternatives - i.e., the lack of flexibility of the mechanical model under different operating conditions and the lack of physical interpretability of the data-driven model - this study proposes a hybrid-driven based in-cylinder pressure calculation model. Taking the 6EX340EF marine low-speed engine as the object of study, the method first constructs a mechanical model and optimizes the Wiebe function parameters using the Dung Beetle Optimizer (DBO). Subsequently, the mapping relationships between operating parameters, Wiebe parameters, initial compression stage temperature and charge mass are learned by constructing a combined neural network of Convolutional Neural Network (CNN) and Bi-directional Long and Short-Term Memory Network (Bi-LSTM). Finally, the overall calculation of in-cylinder pressure was realized by integrating a multidimensional parametric framework of engine configuration parameters, real-time running inputs and dynamic MAP maps. The results show IMEP R2 = 0.9864 and peak pressure error ≤ 2%, confirming that the model can provide technical support for long-term real-time pressure measurement and closed-loop optimization control based on in-cylinder pressure for marine low-speed engines.
Huang, Jialong
Study on Diesel-Methanol Non-Premixed Combustion Characteristics of a Marine Dual-Fuel Engine at Different Methanol Substitution Rate2026-99-05177/10/2026
Methanol use in marine engines has the potential to reduce nitrogen oxide emissions, particulates, and greenhouse gas emissions. A turbocharged four-stroke marine diesel powerplant was converted to run as a double-DI (direct injection) diesel-methanol hybrid engine. Experimental studies using a non-premixed combustion scheme showed that higher methanol substitution ratios (MSR) led to increased peak heat release rates. The combustion process displayed distinctive two-phase behaviors. Increasing MSR caused retarded ignition timing, shortened combustion duration, and improved thermal efficiency. Combustion stability was significantly improved at higher MSR. Emissions results showed NOX and HC were increased in proportion to MSR, whilst particulate emissions and CO concentrations were inversely reduced. Methanol enrichment was found to enhance NOX and HC formation processes but also accelerate soot particulate decomposition and CO oxidation mechanisms.
Li, Xiao, Jiang, Yuqi, Yan, Ping, Zheng, Liang, Li, Hongmei, Zhang, Wenzheng, Chen, Chao, Man, Zhongguo
A Methodology for the Conversion from Physics-Based to Ultrafast-Running Data-Driven Powertrain Models for Real-Time Applications03-19-04-00177/3/2026
The virtualization of powertrain systems is a key enabler for modern powertrain development. While physics-based 0D/1D simulation models provide accuracy and interpretability, these models are typically computationally demanding, prolonging the development process and usage throughout the V-cycle. Moreover, achieving real-time-capable simulation models through model simplifications remains challenging, as it often leads to significant losses in accuracy. In contrast, data-driven approaches can achieve high computational efficiency without significantly compromising model accuracy. This opens the possibility for not only online control applications, such as model predictive control or reinforcement learning, but also for computational expensive offline control prototyping using ultrafast-running data-driven digital twins. This work focuses on the elaboration of a scalable methodology for the development of ultrafast-running powertrain models for stationary and transient engine operation. This includes the efficient generation of training data with great variance, data analysis, and preparation, an optimized partitioning method using the Jensen–Shannon distance, feature engineering, model training of a multilayer perceptron (MLP), a long short-term memory (LSTM), and gated recurrent unit (GRU) network, followed by the model evaluation using test data and the concluding model deployment. In order to demonstrate the concept, a calibrated 0D/1D model of a dual-fuel marine main engine provided by WinGD Ltd. for a pure car and truck carrier is utilized as the reference physics-based model. The case study provides a comprehensive examination of the development of ultrafast-running data-driven fuel consumption models in both stationary and transient engine operation. The results show that the proposed methodology yields robust results and minimizes the loss of accuracy to 1.80%–2.14% for the MLP predicting the steady-state fuel consumption and to 0.67%–0.96% (GRU) and 1.52%–1.68% (LSTM) for predicting the transient fuel consumption, while achieving a multiple 104-fold reduction of the real-time factor (RTF) on an identical CPU.
Weller, Louis, Zanelli, Alessandro, Yang, Qirui, Brutsche, Martin, Grill, Michael, Kulzer, André Casal
Rapid Fuel Distribution Prediction in RCCI Marine Engines Using CFD-Informed, Active Learning Framework2026-37-00176/9/2026
Accurate prediction of in-cylinder fuel distribution (FD) is fundamental to reduced-order combustion modeling and emissions prediction yet remains computationally prohibitive with high-fidelity CFD alone. This work develops a CFD-informed machine-learning surrogate for spatial FD in a large-bore diesel engine, based on a Wärtsilä W20 injector and representative engine conditions. A fully coupled injector–spray–engine CFD framework under engine-like RCCI inert conditions determines the needle-lift profile and resolves the combined effects of injector geometry, needle dynamics, and operating conditions on in-cylinder flow, capturing physical phenomena not reproducible by isolated free-spray simulations. A high-fidelity database is generated using Latin Hypercube Sampling, from which FD is extracted at 15 CAD before top dead center within an annular multi-zone (MZ) representation consistent with reduced-order combustion models. A multi-output Random Forest (RF) surrogate, augmented with uncertainty-driven active learning, is trained to predict the complete spatial FD vector. Prediction errors are higher near the combustion chamber core than in liner-adjacent zones, reflecting stronger nonlinear coupling and localized data sparsity. To address this, four additional CFD samples are selected from regions of maximum predictive uncertainty and incorporated into the training dataset. This targeted enrichment markedly improves surrogate performance, reducing mean absolute error (MAE) under worst-case input conditions. Although localized error amplification persists in a few zones, these regions are systematically identified and can be mitigated through further adaptive sampling using candidates proposed by the updated surrogate. Convergence of the active-learning framework is assessed using mean MAE, worst-zone MAE, global L1 error, and ensemble-based predictive uncertainty, ensuring robust and consistent accuracy across the design space. The framework integrates CFD-resolved physics, machine-learning surrogates, uncertainty quantification, and adaptive sampling, providing a scalable and physically consistent approach for efficient FD prediction in advanced engines.
Moradi, Jamshid, Salahi, Mahdi, Heidarabadi, Shadab, Andwari, Amin, Konno, Juho, Wik, Christer, Mikulski, Maciej
Methane Emission Mitigation in Large-Bore Dual-Fuel Engines via Negative Valve Overlap Diesel Injection: Thermochemical Pathways and Reactivity Control2026-37-00456/9/2026
Low-load natural gas–diesel reactivity controlled compression ignition (RCCI) in medium-speed marine engines is constrained by an insufficient charge thermal state. This limitation leads to partial fuel oxidation, producing high methane emissions. This work evaluates the use of negative valve overlap (NVO) combined with NVO diesel injection as an in-cylinder reactivity enhancement strategy. The simulation study was performed using the University of Vaasa’s advanced thermo-kinetic multi-zone model (UVATZ), extended for reactive simulations during NVO. The extended framework was validated against test-bench data from a prototype Wärtsilä 6L20 dual-fuel engine operating in RCCI mode. The baseline low-load operating point for reforming simulations was defined by reducing the intake manifold temperature to replicate conditions close to partial misfire with 52% combustion efficiency. The parametric sweeps of NVO injection timing and ratio showed that the strategy can be used for in-cycle fast thermal management, effectively restoring complete combustion on an individual cycle basis. In simulated conditions, the best performance was obtained with an NVO injection ratio of 0.3, with the injection scheduled before top dead center. In contrast, increasing the NVO fraction beyond ~0.3 provided no benefit and led to complete misfire due to excessive reduction of main-event high-reactivity fuel. The simulations revealed a coupled thermal–chemical control mechanism. Early NVO injections stabilize combustion through recompression heat release and an increased next-cycle intake valve closing temperature. Sufficiently late injections stabilize combustion by carrying unreacted diesel into the subsequent cycle. Injections near NVO TDC primarily undergo fuel conversion to CO, H2O, and unsaturated light/mid-range hydrocarbons with negligible thermal boost, yielding an overall reactivity deficit.
Soleimani, Amir, Nurmi, Mikael, Hunicz, Jacek, Kim, Jeyoung, Hyvonen, Jari, Mikulski, Maciej
Effect of Burning Biomass Fuel Cyclohexanol on Diesel Engine Performance2026-99-17085/22/2026
Against the backdrop of growing global demands for energy sustainability and stricter emission regulations for diesel engines, this study investigates the performance implications of incorporating cyclohexanol—a renewable oxygenated fuel—into diesel fuel blends. Using a marine medium-speed diesel engine as the experimental platform, the research systematically evaluates engine performance and emission characteristics across a range of cyclohexanol-diesel blend ratios under low, medium, and high load conditions. Experimental findings reveal multifaceted effects of cyclohexanol blending on engine operation. Combustion of the blended fuels enhances the engine’s dynamic performance, particularly under medium and high loads, where the maximum in-cylinder burst pressure exhibits a noticeable increase. This improvement is attributed to cyclohexanol’s oxygen-carrying capacity, which promotes more vigorous and sustained combustion reactions. In terms of emissions, increasing the proportion of cyclohexanol in the fuel blend leads to significant reductions in soot and carbon monoxide (CO) emissions, reflecting the cleaner-burning properties of the oxygenated component. However, this is accompanied by an uptick in nitrogen oxide (NOx) emissions, likely due to the elevated combustion temperatures generated by the more efficient fuel oxidation process. From an economic perspective, cyclohexanol blending at consistent load levels induces a postponement in the crank angle at which peak heat release occurs during combustion. This temporal shift prolongs the effective combustion duration, enabling more complete fuel utilization within the cylinder. Consequently, fuel consumption rates decrease, and overall engine efficiency improves, highlighting the potential of cyclohexanol blends to enhance operational economy in marine propulsion systems. In summary, this study underscores the complex trade-offs associated with cyclohexanol-diesel blends: while they offer tangible benefits in power output, fuel efficiency, and reduced particulate emissions, managing the increase in NOx emissions remains a critical challenge. The results provide a foundational framework for advancing biofuel applications in marine engines, emphasizing the need for integrated emission control strategies to optimize the balance between performance and environmental sustainability.
Chen, Ke, Yang, Chenxi, Wang, Yibin, Fan, Jinyu, Liu, Yuchen, Ye, Zixiao, Huang, Jialiang
Small Craft - Marine Propulsion Engine and Systems - Power Measurements and DeclarationsJ1228_202605 (Current)5/7/2026
This SAE Standard specifies the test requirements in addition to those given in ISO 3046-1 for determining the power, at a single point or as a power curve, of marine propulsion engines or systems for recreational craft and other small craft using similar propulsion equipment of less than 24 m length of the hull. It also provides the means for documenting and checking the declared (rated) power published by the manufacturer.
Marine Technical Steering Committee
Development of a Variable Interface Finite Volume Method for Simulating One- and Three-Dimensional Unsteady Gas Flow and Performances of Underwater Marine Diesel Engines03-19-03-00125/6/2026
Diesel engines used for the main power supplier of submarine normally run in high back pressure and low intake pressure, causing unstable performances. Furthermore, when a submarine runs under the sea the exhaust pipe of the diesel engine is under the seawater. Once the lowest pressure in the exhaust pipe is not sufficient to push all the water out, the water will flow into the exhaust pipe and damage the diesel engine. Modeling can provide a useful guide for designing diesel engines, intake and exhaust pipes, and turbocharging systems to avoid water flowing into diesel engine. However, existing simulation methods cannot well simulate the exhaust system of an underwater diesel engine, in which the interface between the liquid water and the exhaust gas is variable. To overcome the drawbacks of existing simulation methods in handling the variable interface between the two phases, a variable interface finite volume method (FVM) is proposed, and a corresponding model is developed in this work. This is the major contribution of this work. A detailed model description and numerical treatment of governing equations are given. The new model is validated using the experiment conducted in this work on the procedure of gas pushing water in a pipe. The validation results show that the variable interface FVM is effective and reliable. Due to the complexity of the exhaust gas flow at the tailpipe, three-dimensional (3D) flow at the exit of exhaust pipe under different exhaust gas speeds is studied. Results show that, when the exhaust gas speed is below 20 m/s, after the bubble leaves the exit, a part of seawater will flow into the exhaust pipe and flow down along the pipe wall under gravity. With the increase in speed, this phenomenon disappears. Using the newly developed one-dimensional (1D) and 3D model, the 16V-MTU396SE84 underwater diesel engine’s performance was simulated under different back pressures. Also, the effect of silencer’s volume on the stability of diesel engine’s exhaust system was studied. Simulation results show that, with the increase in exhaust back pressure, the excess air factor becomes smaller, combustion turns worse, combustion pressure and maximum in-cylinder pressure become lower, the combustion temperature, maximum temperature, and brake specific fuel consumption go up. In addition, silencer’s volume is very important to the stability of engine performance. The bigger the silencer, the more stable the exhaust system. The flow in the 16V-MTU396SE84 diesel engine’s exhaust pipe under the seawater was also calculated. Simulation results are consistent with engine tests showing that when the engine runs under full load the exhaust gas pressure and the pushing water speed in the exhaust pipe are high, whereas in the part load, the exhaust gas pressure and the water speed become a little lower. The correct results of these simulated performances of underwater marine diesel engines indicate that the models newly developed in this work are reliable.
Guo, Dongshao, Zhang, Licheng, Yang, Shiyou, Sun, Yong, Abidin, Zainal, Lin, Shujun
Experimental Study on Macroscopic Characteristics of Ammonia Spray under Flash Boiling and Non-Flash Boiling Conditions with Large-Diameter Single-Hole Nozzles2026-01-03394/7/2026
Ammonia is regarded as a potential alternative fuel, and its spray characteristics are crucial for efficient combustion in engines. For large-bore engines suitable for heavy-duty vehicles or ships, the adoption of large-diameter nozzles is expected to ensure an appropriate fuel flow rate while improving fuel-air mixing efficiency, thereby enhancing in-cylinder combustion performance. This paper conducted an experimental study on the characteristics of liquid ammonia sprays under wide thermodynamic conditions, a wide range of injection pressures, and a wide range of nozzle diameters. The study found that at room temperature, as the ambient pressure increases from 0.1 MPa to 4 MPa, the development of spray penetration slows down. However, at 0.05 MPa, the radial expansion of the near-field spray is greater, and the penetration is slightly behind that at 0.1 MPa. The liquid penetration increases with the increase in ambient temperature. This was because the increase in temperature reduced the ambient gas density, thereby decreasing the aerodynamic resistance. Under the high-temperature and high-pressure ambient conditions of 4 MPa and 800 K, the liquid penetration is greatly limited when a 0.2 mm nozzle is used due to insufficient spray momentum and high spray vaporization rate, with the maximum penetration only about 40 mm. In contrast, the penetration of the 0.7 mm nozzle could develop to more than 85 mm. Under the ambient conditions of 4 MPa and 800 K, a "stagnation" of penetration was observed for the 0.7 mm nozzle with injection pressure of 60 MPa, where the penetration does not increase continuously. This was the result of the synergy between spray velocity gradient, aerodynamic shear force, and high-temperature evaporation. This paper conducts the first experimental study on liquid ammonia sprays using large-diameter nozzles up to 0.7 mm, providing an experimental basis for the injection optimization of large-bore liquid ammonia direct-injection engines.
Liu, Yi, Zhong, Jie, Hu, Yuchen, Zhu, Wuzhe, Yunliang, Qi, Qingchu, Chen, Wang, Zhi
Effect of Passive Pre-Chamber Geometry on Performance and Emissions of a Single-Cylinder Natural Gas Large Bore Engine2026-01-03334/7/2026
The maritime industry is one of the most energy-intensive sectors, characterized by high fuel consumption and significant environmental impact. As global trade relies on shipping, the challenge of reducing pollutants and greenhouse gas emissions becomes ever more pressing. Natural gas (NG) is considered as a transitional fuel, capable of lowering CO₂ emissions by 20–30% compared to conventional marine fuels. However, to fully harness this potential, significant advances in combustion technology are necessary, particularly with ultra-lean combustion strategies. One of the most promising pathways is pre-chamber combustion, a solution that can simultaneously improve the efficiency and sustainability of NG marine engines. In this scenario, the passive pre-chamber geometry plays a key role, as it directly influences ignition behavior, combustion stability, and exhaust emissions. This work presents an experimental study conducted on a single-cylinder marine engine prototype, retrofitted from a diesel baseline, and equipped alternatively with four passive pre-chambers featuring different geometrical configurations. The tests were conducted at an engine speed of 1500 rpm and different loads to evaluate the influence of pre-chamber geometry on engine performance and exhaust emissions. Key parameters such as combustion phasing, efficiency, and pollutant formation were analyzed and compared between the four setups. Results showed that pre-chamber design affects the interaction between the turbulent jets and the main chamber mixture, leading to significant variations in both combustion efficiency and emission trends. These findings provide new insights into the role of passive pre-chamber geometry in optimizing large-bore NG marine engines, offering a valuable contribution to the development of cleaner and more efficient propulsion systems for the maritime sector.
Marchitto, Luca, Tornatore, Cinzia, Pennino, Vincenzo, Mariani PhD, Antonio, Beatrice, Carlo, Accurso, Francesco, Gorietti, Valentina, Pesce, Francesco, Giardino, Angelo, Vitti, Luciano
Influence of Lubrication Oil on Hydrogen Fuel-Share Combustion in a Conventional Medium-Speed Marine Diesel Engine2026-01-50142/23/2026
Carbon-free fuels present a potential solution for achieving climate-neutral operation of marine engines. However, their availability is minimal at the moment, though a steady increase can be expected in the coming years. During this transition phase, engine concepts that offer conventional diesel operation and a partial blending of alternative fuels to substitute diesel become interesting. This can be achieved, for example, by blending hydrogen in the intake air of a diesel engine, known as hydrogen fuel-share. Due to the high reactivity of hydrogen, its use in engines is limited by abnormal combustion phenomena (e.g., pre-ignition, knocking combustion), which current research on pure gas engines has shown to be strongly promoted by lube oil reactivity. Building on these fundamental investigations, this paper examines the influence of lubricating oil on the combustion characteristics of a H2 fuel-share medium-speed diesel engine and quantifies the potential to increase the hydrogen share using a less reactive engine oil. For this purpose, single-cylinder engine tests were conducted and supported by 0D/1D simulations with GT-Power and Cantera. The engine was configured as a conventional medium-speed marine diesel, equipped with a hydrogen port fuel injection (PFI) system on the cylinder head. A thermally stable ester-based gas engine oil was used for reducing reactivity compared to a state-of-the-art mineral diesel engine oil. The results show reduced auto-ignition tendency during compression and a mitigation of backfire. An increase in average effective CO2 reduction of up to 17 percentage points is demonstrated, resulting in a total CO2 reduction of 39% on a standard load profile for main propulsion engines. These findings highlight that the choice of lubricating oil can play a key role in increasing the hydrogen share in H2 fuel-share diesel engines, thereby supporting the transition toward climate-neutral propulsion concepts.
Achenbach, Tobias, Meinert, Robert, Mahler, Kay, Kunkel, Christian, Rösler, Sebastian, Prager, Maximilian, Jaensch, Malte
Potential of a Hydrogen Fuel-Share Combustion Concept for a Conventional Medium-Speed Marine Diesel Engine2026-01-50072/2/2026
To meet the International Maritime Organization’s (IMO) short-term greenhouse gas (GHG) reduction targets, partial decarbonization of the existing fleet, often powered by medium-speed diesel engines, is required. One approach for reducing CO2 emissions is to enrich the charge air with hydrogen to substitute diesel. However, hydrogen’s high reactivity can lead to combustion abnormalities such as backfire, pre-ignition, and knocking, thus limiting the feasible admixture rates. These challenges are particularly relevant in medium-speed diesel engines designed for high power output and efficiency at low rpm. While hydrogen fuel-share has previously been tested in small-bore engines at moderate loads, this study investigates the influence on combustion and achievable hydrogen admixture rates in a medium-speed, 4-stroke diesel engine operating with up to 30 bar net indicated mean effective pressure (net IMEP). To minimize retrofitting efforts and to preserve diesel performance, the investigations were conducted on a single-cylinder engine with representative design features of a conventional diesel engine: a high compression ratio, Miller valve timing, valve overlap, and a piston with deep valve pockets. The piston ring system is suited for heavy fuel oil (HFO) operation. Hydrogen was supplied via a port fuel injection (PFI) system. 0D/1D process simulations supplement the experimental data. Findings indicate that energetic hydrogen admixture rates of up to 43% are achievable at low loads, limited by an advancing start of combustion, and up to 15% hydrogen share at high loads, constrained by backfire. This results in an average CO2 reduction of ~22% on the E2 cycle for constant-speed main propulsion engines. Due to rising NOx emissions, the results are only applicable when meeting IMO Tier II limits with selective catalytic reduction (SCR). The results demonstrate that conventional medium-speed diesel engines are suited for hydrogen fuel-share operation and that CO2 reductions comparable to liquid natural gas (LNG) conversions are feasible.
Achenbach, Tobias, Meinert, Robert, Mahler, Kay, Kunkel, Christian, Rösler, Sebastian, Prager, Maximilian, Jaensch, Malte
Rolls-Royce pursues pure methanol for marine engines26TOFHP02_052/1/2026
Rolls-Royce has successfully tested the world's first high-speed marine engine powered exclusively by methanol on its test bench in Friedrichshafen, Germany. The company began this engine-development journey six years ago when it gathered experts to determine what the future fuel of the maritime industry should be, according to Denise Kurtulus, senior vice president of global marine at Rolls-Royce. “For us, it's clear. It's methanol,” she said. Rolls-Royce worked with industry partners as part of the joint project meOHmare, which is funded by the German Federal Ministry for Economic Affairs and Energy. Injection system specialist Woodward L'Orange and the WTZ Roßlau technology and research center contributed their expertise. Their goal was to not only develop a comprehensive concept for a CO2-neutral marine engine based on green methanol, but also to run it on the test bench by the end of 2025.
Gehm, Ryan
1D Simulation Approach for Common Rail Injection Systems for a Marine 2 Stroke Diesel Engine2026-26-03951/16/2026
This study presents a comprehensive 1D simulation approach of an automotive solenoid-based diesel fuel injector and a common rail injection system for a marine engine using Simcenter AMESim. The injector model was developed to analyse the injection rate and total injected fuel at various solenoid actuation durations (1.2 ms and 2.0 ms) and common rail pressures. The experimental results from a well-established research study are used for validating the simulation results of the solenoid-based injector. Overall error in total fuel injected ranges from -6.14 percent to 1.93 percent, while timing errors for the start of injection vary from 1.7° crank angle (CA) to 0.08° CA and the end of injection from 2.8° CA to 0.20° CA at 1200 rpm demonstrating strong agreement at higher rail pressures (above 1000 bar) and solenoid actuation times. Building on this validated injector model, a detailed marine common rail system was developed incorporating key hydraulic components: a check valve to maintain pressure inside the rail, flow limiting valves to prevent overpressure in the fuel injector, and a combination pressure relief valve. The simulation was used to study rail pressure dynamics at 50 percent of the engine load for varying rail lengths, diameters, and injector flow rates. The experimental results for the common rail pressure test match closely with the simulated common rail pressure dynamics. Parametric studies reveal sensitivity of rail pressure to geometric variations, which in turn influence injection characteristics. The developed model serves as a useful tool for assessing design changes in high-pressure injection systems and optimizing performance in marine engine applications.
Bhoware, Yash, Pise, Uday, Saha, Dipta, Gaikwad, Nilesh
Numerical Analysis of the Combustion Process in a Pre-Chamber Marine Engine Fueled with Ammonia-Hydrogen Mixtures2025-24-00219/7/2025
Ammonia and hydrogen, as carbon-neutral fuels, possess the potential to play a crucial role in the decarbonization of the mobility sector. This research examines the optimization of the combustion process in a marine spark-ignition engine through the use of a passive pre-chamber. The study has been carried out using computational fluid dynamics (CFD) models. Considering a hydrogen content in the fuel blend of 15% by volume, at a fixed equivalence ratio equal to 0.8, two different nozzle diameters have been tested, and the optimal spark timings have been identified. Then, the effect of different hydrogen amounts in the fuel mixture on the engine’s performance and emissions has been assessed. An optimal spark timing of 712 CAD has been found for both 3 mm and 5 mm nozzles at the specified operating point. The 5 mm nozzle provides slightly higher IMEPH and gross efficiency, with minimal impact on emissions. Reducing hydrogen in the fuel blend from 15% to 10% lowers IMEPH from 31 to 12 bar and gross efficiency from 46.9% to 18.8%. At 5% hydrogen, combustion cannot start. This decrease in the hydrogen amount raises unburned ammonia, NO2, and N2O emissions, while NO emissions are significantly reduced. Decreasing hydrogen content reduces turbulent kinetic energy in the combustion chamber.
D'Antuono, Gabriele, Lanni, Davide, Galloni, Enzo, Fontana, Gustavo
Exhaust Thermal Management in a Dual-Fuel Marine Engine via Fully Variable Valve Actuation and Wastegate Lambda Control2025-24-00859/7/2025
Dual-fuel combustion is emerging as a promising solution to address the growing focus on maritime decarbonization, because it is adaptable and needs minimal system modifications. However, natural gas as an alternative fuel must deal with the issue of methane slip, because methane has greater global warming potential than CO2. Conventional aftertreatment systems may incorporate a methane oxidation catalyst to mitigate methane emissions, but effective methane oxidation requires high temperatures of approximately 400 °C. Therefore, exhaust thermal management (ETM) is crucial for maintaining high exhaust gas temperature (EGT) and ensuring conversion efficiency. This study investigates the effectiveness of fully variable valve actuation (VVA), including early exhaust valve opening (EEVO) and early intake valve closing (EIVC), along with lambda control via wastegate control. Each strategy’s effect on exhaust gas temperature is evaluated, while considering potential trade-offs with efficiency. The research uses a model-based approach, simulating a state-of-the-art, six-cylinder natural gas/diesel dual-fuel marine engine (Wärtsilä 6L20 DF), equipped with a two-stage turbocharger with wastegates. Numerical simulations are conducted using a one-dimensional (1D) engine model within GT-Suite across two different load conditions. The model is validated using baseline valve timings and a comprehensive dataset of experimental data. Results indicate that all three strategies can contribute to EGT elevation. EEVO raises EGT by 73 K, but incurs a 3.85% reduction in brake thermal efficiency (BTE). EIVC achieves a substantial EGT increase of 122.7 K at medium load, with a slight BTE improvement of 0.4%. Wastegate lambda control elevates EGT by 91.5 K at low load, exhibiting a negligible BTE impact. Thus, VVA-based ETM and lambda control enable rapid warm-up of exhaust aftertreatment systems (EATS) in large-bore engines with a minor efficiency penalty. This helps compliance with stricter emission regulations which contribute to maritime decarbonization, eventually enhancing air quality and the maritime ecosystem.
Soleimani, Amir, Kim, Jeyoung, Axelsson, Martin, Hyvonen, Jari, Mikulski, Maciej
Zero-Carbon Port Fueling for Heavy Propulsion through a Recuperated Split Cycle Engine2025-24-00449/7/2025
Upcoming global emissions regulations demand innovation in heavy-duty road and marine transport. This research explores emissions-compliant concepts using both experiments and simulations focused on the Recuperated Split Cycle Engine (RSCE), which separates compression and expansion to enable internal heat recovery and quasi-isothermal compression. A single-cylinder research engine representing the expansion cylinder of an RSCE demonstrated direct injection diesel and port injection hydrogen co-firing. A validated Chemkin-Pro Multi-Zone model first reproduced, then extended this work, evaluating partial diesel substitution with hydrogen or ammonia alongside secondary working fluids (SWF’s liquid N₂, H₂O, NH₃). For the extension, two variants of the split cycle architecture were employed; the RSCE in combination with hydrogen fueling for the heavy-duty road sector, and the novel recuperated reformed split cycle engine (R2SCE), a new architectural and simulation contribution enabling on-board ammonia reforming and dual-role use of SWFs for the maritime sector. In the RSCE configuration, 10%Vol H₂ with H₂O as SWF delivered 13% NOx and 45% CO₂ reductions, along with a 33% improvement in brake specific fuel consumption (BSFC). System-level evaluation of this configuration demonstrated the potential of Euro 7 compliant NOx with typical after-treatments. In the R2SCE configuration, while SWFs N₂ and H₂O reduced thermal NOx via dilution, the use of NH₃ as a dual role SWF - combined with a Recuperator-Reformer (59% NH₃-to-H₂ conversion) - delivered a 4% increase in total fuel energy and reduced NOx emissions across all tested NH₃ injection levels. The R2SCE system level comparison between 6%Vol NH₃ and diesel-only operation showed 10% and 43% reduction in BSFC and CO₂ per unit work, with NOx within maritime regulatory targets with typical after-treatments. These quantified outcomes serve as reference points for performance benchmarking, demonstrating how, compared to a contemporary conventional engine, the increased flexibility offered by the novel R2SCE concept can maximise fuel-to-power conversion for zero-carbon fuels.
Wylie, Elisa, Panesar, Angad
Lignin as Cetane Booster for Methanol and Ethanol2025-24-00759/7/2025
Low carbon, though poorly igniting (i.e., low cetane) fuels, such as methanol, ethanol, and ammonia, are gaining momentum in the maritime fuel market. The most adopted strategy to address the fact that these fuels will not, under typical two-stroke marine engine conditions, auto-ignite, is to co-inject a pilot fuel, such as (very) low sulfur marine fuel oil, which does auto-ignite and furthermore doubles as a spark of sorts for the poorly igniting base fuel. This so-called dual-fuel approach is costly and cumbersome. Cetane boosters are known to improve ignitability of alcohol fuels to the point that a pilot fuel is no longer required. In our earlier research, we found some indication that lignin model compounds could likewise improve the ignitability of alcohols. This paper builds further on this hypothesis, now using commercially available lignin rather than model compounds. Auto-ignition behavior of methanol and ethanol was investigated with up to 10 wt% of therein solubilized lignin in both an Advanced Fuel Ignition Delay Analyzer (AFIDA) and (two-stroke) spray combustion chamber. The results suggest that lignin indeed improves the ignitability of both alcohols and that pilotless auto-ignition is possible under realistic two-stroke marine engine conditions when 10% of (alcohol-soluble) lignin is blended into ethanol, with the associated cetane number being close to 10.
Sementa, Paolo, Tornatore, Cinzia, Catapano, Francesco, Lazzaro, Maurizio, Iannuzzi, Stefano, Kouris, Panos, Boot, Michael
Effects of Varying the Air-Fuel Equivalence Ratio at Different EGR-Rates on a Medium-Speed LNG-Diesel Dual-Fuel Engine2025-24-00419/7/2025
The dual-fuel combustion process, which is offered as a retrofit solution for conventional diesel engines by various manufacturers, represents an option for reducing emissions from internal combustion engines and is already available today. Current dual-fuel engines run on liquefied natural gas (LNG), which is usually of fossil origin. Due to the existing infrastructure and the possibility of producing LNG by means of electrolysis and methanation, LNG can already be produced in a 100% climate-neutral way and thus make a contribution to climate neutrality in the shipping industry. The adoption of exhaust gas recirculation (EGR) systems in the maritime sector became more significant in 2020 following the enforcement of the sulphur emission cap. By lowering the sulphur content in the fuel, technologies in the exhaust tract are also conceivable without the use of expensive scrubber systems. Dual-fuel LNG/diesel engines are typically operated in lean-burn mode to reduce the risk of knocking and to comply with the nitrogen oxide limits in accordance with IMO TIER III. However, one disadvantage of the lean-burn combustion process is climate-damaging methane (CH4) slip due to incomplete combustion. To address this issue, an EGR system can be employed to mitigate nitrous oxides (NOx) emissions and prevent engine knocking at richer air-fuel mixtures, as an alternative to increasing the air-fuel equivalence ratio lambda. In the context of this paper, experimental investigations are conducted on a single cylinder medium speed dual-fuel engine, where EGR rates of up to 35% are examined across various lambda values. The adjustment of lambda is achieved by varying the charge air pressure using an externally driven compressor station for charge air supply. The results of the presented investigations provide insights into the emission reduction potential of a targeted variation in EGR rates and lambda, thus making an important contribution to more environmentally friendly ship propulsion systems.
Seipel, Pascal, Glauner, Manuel, Dinwoodie, Jules, Buchholz, Bert
Experimental and Numerical Study on the Performance and Exhaust Emissions of a Single-Cylinder Natural Gas Large Bore Engine Equipped with Passive Pre-Chamber2025-24-00229/7/2025
The maritime industry is among the most energy-intensive sectors, and achieving fleet decarbonization is crucial to significantly reduce greenhouse gas emissions. As a transitional fuel, natural gas (NG) presents a viable short-to-midterm solution. Compared to conventional marine fuels, NG has the potential to lower carbon dioxide emissions by approximately 20–30%. However, to fully leverage this potential on carbon footprint reduction, substantial advancements in combustion technologies are required. One promising approach to enhance the efficiency of SI NG engines is the implementation of Passive Pre-Chamber (PPC) technology. This strategy enables leaner combustion, improving thermal efficiency, mitigating the occurrence of knocking, and reducing NOx emissions. This study presents both experimental and numerical investigations to analyze the impact of charge dilution and ignition timing on the performance and emissions of a single-cylinder prototype NG PPC SI engine for marine application, retrofitted from baseline diesel architecture. Numerical simulations combining 1D and 3D CFD approaches were used to guide the combustion system and engine component design, optimizing valve timing, compression ratio, and fuel injection parameters to mitigate knock and improve thermal efficiency. Based on numerical simulations, excess air effects on thermodynamic efficiency and flame speed were evaluated. The experimental tests were conducted at 1500 rpm constant engine speed under different load conditions. Variation of the air-to-fuel ratio and spark advance were performed to characterize their effects on engine operation. The results were utilized to validate a 1D model, which demonstrated a high level of accuracy in reproducing the combustion evolution. PPC technology enabled high charge dilution (λ≈1.7). The coefficient of variation of IMEP remained below 1.5% throughout a wide range of λ values and combustion phasing conditions, indicating stable combustion. The engine exhibited indicated efficiencies of over 45%, marginally exceeding the predictions obtained from numerical simulations. This research underscores the potential of PPC technology in enhancing the efficiency and sustainability of NG-fueled marine engines, offering valuable insights to optimize combustion strategies for future low-emission propulsion systems.
Marchitto, Luca, Pesce, Francesco, Accurso, Francesco, Tornatore, Cinzia, Gorietti, Valentina, Buzzi, Luca, Grosso, Alessandro, Luci, Matteo, Napolitano, Pierpaolo, Pennino, Vincenzo, Beatrice, CARLO, Di Domenico, Davide, Giardino, Angelo
Numerical Investigation on an Injection strategy Optimization for Dual Fuel Marine Engine Fuelled by Ammonia2025-24-00139/7/2025
In the context of greenhouse gas emissions (GHG) reduction the most viable short-term solution in the maritime sector is the use of renewable carbon-free fuels. Among these, ammonia represents a possible alternative in compression ignition (CI) engines operating in dual fuel (DF) mode. Although, such fuel features low chemical reactivity, especially in lean mixtures, resulting in poor combustion efficiency, exhaust ammonia slip and low engine performance, DF combustion can be an interesting strategy to overcome such limitations. In this work a wide numerical examination of diesel injection strategies is presented, while ammonia acts as the primary fuel with energy supply around 80%. Since the original marine engine, fuelled with natural gas (NG), presents a single diesel injection, firstly, a pilot injection is added and different diesel mass shares between pilot and main are investigated, by varying the injection rate shape and the pilot start of injection (SOI). Calculations are performed with a CFD approach using ANSYS Forte® code on a closed-valve cylinder domain. The results demonstrate that with an appropriate strategy it is possible to maintain the nominal value of the indicated mean effective pressure (IMEP) with limited ammonia exhaust losses by adopting a split injection and an adequate shape of the injection profile, a parameter with a great influence on the spray evolution. Namely, a pilot SOI of 20° BTDC, with a total diesel mass of 80 mg split into two equal injections with a sine-shaped injection rate, leads to better results in terms of IMEP and ammonia emissions. Being ammonia a compound of nitrogen, particular attention is paid to NOx and N2O emissions, providing a quantification of its emission index for all simulated cases.
Cameretti, Maria Cristina, De Robbio, Roberta, Palomba, Marco
High Tension Ignition Cable Assemblies - MarineJ1191_202508 (Current)8/18/2025
This Standard covers the requirements for all marine inboard and outboard gasoline engine ignition assemblies and components.
Marine Technical Steering Committee
Devices Providing Backfire Flame Control for Gasoline Engines in Marine ApplicationsJ1928_202508 (Current)8/13/2025
This SAE Standard covers the minimum requirements for design, construction, and testing of devices to prevent the propagation of backfire flame from within the gasoline engine to the surrounding atmosphere.
Marine Technical Steering Committee
Experimental Investigation of Performance and Emission Characteristics of a Diesel Light-Duty Engine Fuelled with Pure Hydrogen2025-01-03147/2/2025
Transitioning to zero-carbon fuels is pivotal for expediting the reduction of carbon emissions. Hydrogen demonstrates significant adaptability and emerges as a principal zero-carbon alternative fuel for fossil fuel internal combustion engine (ICE) platforms. Implementing hydrogen in both spark ignition (SI) and compression ignition (CI) engines has proven to be both economically viable and timely. In this study, a conventional diesel engine was operated with pure hydrogen with minimal modification to engine hardware. It features a proactive, automated shutdown system to mitigate intake backfire risks associated with hydrogen port fuel injection (PFI) systems. A comprehensive engine characterisation was conducted using a lambda sweep test, measuring values from 1.5 to 4.5 with an integrated in-cylinder pressure transducer for high-resolution data. The study used an advanced Bandpass, Rectify, Integrate, Compare (BRIC) knock detection method for engine health monitoring and assessed stability through various metrics over 300 cycles. The performance and emission characteristics of a 100% hydrogen engine were analysed. Additionally, other low-carbon fuels, including methane and hythane (a blend of gaseous fuel with 80 % methane and 20% hydrogen by volume), were used for engine experiments to compare their performance with hydrogen. The results indicate that hydrogen can function effectively in a diesel light-duty engine utilising a port-fuel injection and spark ignition system, achieving an indicated thermal efficiency of approximately 40%. The engine operates with exceptional stability, reflected in a Coefficient of Variation of Indicated Mean Effective Pressure (COVIMEP) of less than 1.6% at a maximum lambda of 4.2. Additionally, it maintains a high combustion efficiency of 97.4%, with minimal hydrogen slip observed in the exhaust. The hydrogen fuel demonstrates nearly zero carbon emissions, with NOx levels recorded below 50 ppm at lambda 2.5 and approaching zero NOx at lambda 3. Compared to methane and hythane, hydrogen can achieve better emission characteristics with near zero NOx and unburnt hydrocarbon. However, the power output of pure hydrogen operation is lower than that of methane and hythane, as a result of leaner operating conditions.
Mohamed, Mohamed, Zaman, Zayne, Lu, Enshen, Feng, Yizhuo, Wang, Xinyan, Zhao, Hua
Low-Temperature Coolant Circuit Nomenclature and ApplicationsJ3136_202506 (Current)6/17/2025
The document provides clarity related to multiple temperature coolant circuits used with on-highway and off-highway, gasoline, and light-duty to heavy-duty diesel engine cooling systems, or hybrid vehicle systems. These multiple temperature systems include engine jacket coolant plus at least one lower temperature system. Out of scope are the low temperature systems used in electric vehicles. This subject is covered in SAE J3073. Note that some content in SAE J3073 is likely to be of interest for hybrid vehicles. Out of scope are the terms and definitions of thermal flow control valves used in either low-temperature or high-temperature coolant circuits. This subject is covered in SAE J3142.
Cooling Systems Standards Committee
Ammonia-Diesel Engines Segmented Modeling Approach and Simplified Combustion model Research2025-01-02326/16/2025
Ammonia-diesel dual-fuel engines can effectively reduce greenhouse gas (GHG) emissions. Aiming at the real-time control requirements of ammonia/diesel dual-fuel engines, this study proposes a segmented real-time modeling method and a heat release rate model simplification strategy by linearized heat release rate curves. First, the engine working cycle is divided into three parts: intake and exhaust stage, compression and expansion stage, and combustion process. Different simulation steps and modeling strategies are designed to optimize computational efficiency while maintaining the necessary level of accuracy at each stage. Secondly, based on the calibrated heat release rate (HRR) curves, feature points are extracted to construct a simplified linear heat release model. In the absence of calibration data, the characteristic points of the HRR curves are obtained through interpolation. Compared with the commonly used combustion model, the Wiebe model, the proposed simplified model can more easily obtain the parameters required for calibration while maintaining accuracy. Finally, the effectiveness of the model was verified experimentally under various cases. The results showed that the real-time modeling method can keep single-cycle simulation time in 2ms, the prediction deviations of the indicated mean effective pressure (IMEP) under 4% and the peak pressure in the cylinder (pmax) deviations are less than 2%, and the deviations of specific combustion angle (CA10, CA50, CA90) are controlled within 1°crankshaft angle (CA). It provides a model basis for the real-time control of ammonia diesel engines and is of great value in promoting the engineering application of ammonia fuel in transportation fields such as ship power systems.
Li, Guangyuan, Chen, Run, Wang, Xinran, Li, Tie, Zheng, Kexiong, Liu, Shaoling, Liu, Yanzhao, Lyu, Xiaodong
The Similarity Study of the Transient Heat Transfer of Impinging Flames under CI Engine-Like Conditions2024-32-01194/18/2025
The optimization of engine combustion systems based on scaled model experiments can reduce the cost of the development of large-bore marine diesel engines. Illustrating the transient heat transfer similarity of impinging flames would be beneficial to scaled engine model experiments in the development and optimization of large-bore compression ignition engines. In this work, the investigation of the similarity of the transient heat transfer of wall-impinging flames was performed in a high-pressure high-temperature constant-volume vessel. Two different injectors featuring different hole sizes and different flame impingement distances were applied to simulate the diesel spray impinging flames under the large-bore and the small-bore compression ignition engine-like conditions with a geometry similarity ratio equal to 0.7. By varying the injection parameters such as injection pressure and injection duration, the scaling laws based on constant injection pressure, constant engine speed, and constant lift-off length were achieved and examined. Two-color pyrometry was used to record and compare the flame luminosity and the temperature and soot distributions between the large-type and small-type impinging flames. The fast-response thermocouple was installed on the impinging wall to calculate the local transient heat flux through the wall. The similarity ratio of the heat transfer coefficient and transient Nusselt number and Reynolds number using different scaling laws was theoretically verified. The results indicate that different scaling laws show good performance in predicting the spray-impinging flame tip penetration, flame height, and radius of the impinging flame between the large-type and small-type impinging flames. Theoretical analysis was conducted to derive the similarity ratio of heat transfer coefficient. Results show that the scaling rule based on engine speed exhibits great potential for predicting the transient heat transfer through the impinging wall, and heat transfer correlations of the impinging flame under engine-like conditions.
Cao, Jiale, Li, Tie, Zhou, Xinyi, Xu, Xingyu, Chen, Run, Li, Shiyan, Ogawa, Hideyuki
Detecting Piston Ring–Cylinder Liner Metal–Metal Contact in a Fired Large Marine Diesel Engine Using Piezoelectric Transducers03-18-03-00174/9/2025
Shear-polarized ultrasonic sensors have been instrumented onto the outer liner surface of an RTX-6 large marine diesel engine. The sensors were aligned with the first piston ring at top dead center and shear ultrasonic reflectometry (comparing the variation in the reflected ultrasonic waves) was used to infer metal–metal contact between the piston ring and cylinder liner. This is possible as shear waves are not supported by fluids and will only transmit across solid-to-solid interfaces. Therefore, a sharp change in the reflected wave is an indicator of oil film breakdown. Two lubricant injection systems have been evaluated—pulse jet and needle lift-type injectors. The needle lift type is a prototype injector design with a reduced rate of lubricant atomization relative to pulse jet injectors. This is manifested as a smaller reduction in the reflected ultrasonic wave, showing less metal–metal contact had occurred. During steady-state testing, the oil feed rate was varied; the high flow rate case was shown to reduce the amount of piston ring–liner contact, while no changes in the lubricant film thickness had previously been detected using traditional longitudinal ultrasonic sensors. This displays the increased sensitivity of shear sensors relative to longitudinal sensors in respect to the quantity of lubricant present. Piston ring oil film breakdown was also studied at a range of steady-state loading levels and engine slow down, showing the amount of contact decreased as engine load decreased, providing a real-time indication of the lubrication regime of the piston rings. When the load was further decreased, into total shutdown of the engine, the amount of contact increased until the engine had stopped rotating. The study has demonstrated the capability of shear ultrasonic sensors to detect changes in solid contact caused by injector design, oil feed rate, engine load, and engine shut down.
Rooke, Jack, Li, Xiangwei, Dwyer-Joyce, Robert S.
Enhancing Dual Fuel Combustion Simulation: A Novel Geometric Approach for Accurate Flame Entrainment Estimation2025-01-83664/1/2025
Maritime transportation plays a vital role in the economy and is one of the most energy-efficient modes of transportation. However, it is a growing source of greenhouse gas emissions. A potential solution to lower carbon emissions from maritime transport is to use renewable fuels in marine engines. Hydrogen or methanol can serve as the primary energy source in internal combustion (IC) engines. However, their high autoignition temperatures require an external ignition source to start combustion in compression ignition (CI) engines. The Dual Fuel (DF) approach offers an effective method for incorporating these fuels. To accurately simulate dual fuel combustion, certain parameters need to be carefully addressed. One crucial parameter to investigate is estimating the flame entrainment area, as it directly affects the mass burning rate. In this work, a novel geometric approach is developed to estimate the evolution of the flame entrainment area. This model is integrated into a multi-zone dual fuel combustion model in GT-Power and evaluated against experimental data from a single-cylinder engine (SCE) running on methanol in dual fuel mode, specifically 25 different cases with a bore size of 240 mm (SCE1) and 25 cases with a bore size of 256 mm (SCE2). The results show that using the new flame area model reduces the root mean square error (RMSE) in predicting combustion phasing (CA90) from about 10 crank angle degrees (CAD) to approximately 3.5 CAD for SCE1 and from 18 CAD to 8 CAD for SCE2. Additionally, there is a reduction in RMSE for predicting the indicated mean effective pressure (IMEP), from 2.3 bar to 1.3 bar for SCE1 and from 1.5 bar to 1.0 bar for SCE2. Significant improvements are also observed in the heat release rate curve, specifically in the tail of combustion.
Parsa, Somayeh, Daenens, Arthur, Verschaeren, Roel, Dierickx, Jeroen, Verhelst, Sebastian
Assessment of a Heavy-Duty Diesel Engine Retrofitted to Dual-Fuel and Neat Methanol SI Operation2025-01-84404/1/2025
This paper explores the potential of leveraging methanol's knock-resistant properties to facilitate both dual fuel (DF) and spark ignition (SI) operation in retrofitted heavy-duty (HD), high-speed marine engines. The study involves retrofitting an original 6-cylinder 7.15L CI diesel engine with port fuel injection (PFI) of methanol to enable DF operation. Later, the diesel injectors were replaced with six spark plugs allowing SI operation. Notably, efforts were made to minimize adaptations to the existing diesel engine, maintaining the compression ratio (CR) at 17.6:1 and retaining the same turbocharging pressure. This research aims to assess the feasibility of retrofitting conventional HD diesel engines (high CR, large bore) for dual-fuel and SI operation on methanol, with a focus on optimizing engine performance, while preserving key characteristics for HD applications, e.g. high torque and high power density. The high CR required spark retarding to prevent knock at higher loads in SI operation. Despite this, efficiencies comparable with diesel were obtained for both diesel-methanol dual-fuel as SI operation on 100% methanol, although differences were noticeable depending on the load. Tests were performed at 1500 rpm with a BMEP of 3.5, 7.1 and 10.6 bar, respectively 22, 44 and 66% of the maximum engine load. The maximum load achievable in stoichiometric SI operation was 12.3 bar BMEP, corresponding to 77% of the original maximum load with diesel CI. At this load, a brake thermal efficiency of 38.5% at stoichiometric conditions was attained. At lean conditions (λ=1.25) an efficiency of 40.1% was reached, with no significant difference compared to a 40.3% efficiency attained in diesel-only operation.
Dejaegere, Quinten, Ballerini, Alberto, Demiddeleer, Sheldon, Vanderbeken, Thomas, Bracke, Kwinten, Gyselinck, Ben, D'Errico, Gianluca, Verhelst, Sebastian
Analysis of Injection Characteristics and Structural Reliability of Marine Methanol Fuel Injectors2025-01-71161/31/2025
Nowadays, the energy transition is at the most critical moment. In order to achieve the emission reduction target of ships, a form of boosting piston inside methanol fuel injector has been carried out. The physical property fluctuations and phase change of methanol under high pressure have been considered in the design phase. 1D-3D coupling method is used to comprehensively evaluate the performace of the injector. To this end, an Amesim simulation model is established to systematically study and analyze the injection characteristics. The injection performance of the injector under four typical loads are calculated, which is evaluated from the perspectives of injection quantity, injection duration, valve response, and leakage of boost components. In the nozzle block, the cavitation intensity of methanol is stronger than that of diesel. To reduce the possibility of cavitation erosion, as a consequence, a CFD model is established to optimize the structure of nozzle components. By adding rounded corners at the inlet of the nozzle to weaken cavitation intensity and improve injection stability. Furthermore, the mass flow rate of optimized nozzle can be improved by at least 30%. The equivalent stress and deformation of the nozzle and needle valve body under alternating thermal stress are calculated to ensure that they meet the design requirements(<1600MPa). The safety factor of fatigue also meets the requirements(>1.1). Through the complete design and simulation work, we can break through the problem of insufficient technical reserves of marine methanol injectors in China and assist in the development of low-carbon engines for self-owned brand.
Yang, Li, Wen, Liming, Zhang, Hanwen, Lu, Gangao, Dong, Weijie
Study on Injection Parameters of Ammonia/Diesel Dual Direct Injection Low-Speed Engine2025-01-71141/31/2025
With the adoption of the IMO Greenhouse Gas Emission Reduction Strategy Revision, the international shipping industry is facing huge pressure to reduce greenhouse gas emissions, and the conversion of ship power from traditional fossil fuels to low-carbon and zero-carbon fuels is the fundamental solution, and ammonia fuel, as a zero-carbon fuel, is an important direction for the development of ship power in the future. Based on a marine low-speed diesel engine with a bore of 520 mm, computational fluid dynamics (CFD) numerical simulation was carried out to study the effects of different diesel energy fractions, ammonia injection pressure, ammonia injection timing and ammonia diesel injection interval on the combustion and emission characteristics of the engine under the dual-fuel combustion mode of high-pressure dual direct injection. The calculation results show that under the condition of the current engine, 5% of diesel energy can reduce carbon emissions by 92.8% under the premise of successful ignition. Increasing the injection pressure of ammonia fuel results in more effective work, greater turbulent kinetic energy, better mixing effect of ammonia fuel and diesel flame, and reduces unburned ammonia and greenhouse gas emissions, but there is a trade-off between high NOx or high N2O emissions. Diesel ammonia 2CA injection in advance can take into account various emission data well, and is the most suitable injection interval.
Yang, Jincheng, Liu, Long, Gui, Yong
Fault Detection of Diesel Engines Using Artificial Neural Network03-18-02-00101/20/2025
This study presents a method for identifying the reliability state of diesel engines by utilizing artificial neural networks (ANNs). The Sulzer 6AL20/24 marine diesel engine was selected as the test subject for this research. Vibration signals were collected during tests conducted on a laboratory test stand under normal operating conditions and during simulations of six different engine faults. Next, the recorded signals were analyzed and transformed into labeled samples for supervised learning. In this phase, the time histories of the vibration signals were divided into segments and augmented, with several key features calculated for each segment. Highly correlated signals were excluded from further analysis based on the Pearson correlation coefficient. The processed samples were then used to train and fine-tune the ANN. The trained ANN was subsequently used to identify the engine’s reliability state and classify the present fault type. To evaluate the effectiveness of the proposed method, the results obtained from the ANN were compared with those from technical state space identification and other machine learning classifiers. Finally, the ANN was tested on the reliability state of the engine in scenarios where the simulated fault was not present in the training dataset. A detailed discussion and analysis of the proposed identification method’s performance are presented in this article’s concluding sections.
Pająk, Michał, Kluczyk, Marcin, Muślewski, Łukasz, Lisjak, Dragutin
Marine Control Cable Connection - Engine Clutch LeverJ960_202409 (Current)9/9/2024
The purpose of this SAE Recommended Practice is to provide guides toward standard conditions for operating marine hydraulic transmissions where push-pull cable control is applicable. For control cable information see SAE J917.
Marine Technical Steering Committee
Marine Control Cable Connection - Engine Throttle LeverJ961_202409 (Current)9/9/2024
The purpose of this SAE Recommended Practice is to provide guides toward standard conditions for operating marine engine throttles (gasoline or diesel) where push-pull cable control is applicable. For control cable information see SAE J917.
Marine Technical Steering Committee
Numerical Investigation of Premixed and Non-premixed Ammonia Main Charge Configurations Ignited by a Hydrogen-Fired Prechamber03-17-08-00608/14/2024
Ammonia-fired reciprocating engines have emerged as a promising technology in the maritime and power generation sector at medium-to-large scale (1–80 MW). The use of “on-the-fly” partial ammonia decomposition to produce a relatively small amount of hydrogen that can be used as combustion promoter, replacing fossil fuels in this function, enables this technology to provide carbon-free propulsion and power generation. In this context, it is envisioned that a hydrogen-fired prechamber ignition strategy offers significant advantages by accelerating the ammonia ignition and complete combustion process, increasing its reliability and robustness while still aiming to achieve low NO x , N2O, and NH3 emissions. This study exploits an OpenFOAM-based Large Eddy Simulation (LES) numerical modeling framework to investigate the ignition and combustion behavior of an ammonia main charge ignited by a hydrogen-fired prechamber. First, a conventional port-injection premixed configuration for the ammonia main charge is considered whereas the hydrogen-fired prechamber is found to provide a sufficiently strong ignition source for all ammonia–air mixtures investigated. The effect of the main charge equivalence ratio and the wall temperature on combustion efficiency and emissions formation is evaluated. Second, considering a non-premixed configuration for comparison, an identically configured hydrogen-fired prechamber is used to study the ignition and combustion process for ammonia main charges directly injected as liquid sprays and modeled as Lagrangian particle tracking (LPT) in conjunction with the LES model. The LES results suggest that the relative timing and angle of injection between the liquid sprays and the hydrogen jet flames emerging from the prechamber play a major role in controlling the ignition and combustion process. Finally, the non-premixed ammonia main charge configuration is found to significantly reduce the formation of pollutants and extend the operating range to leaner global equivalence ratios, compared to the premixed ammonia main charge configuration.
Indlekofer, Thomas, Haugen, Nils Erland, Førde, Olav Øyvind, Gruber, Andrea
Experimental Study of Lignin Fuels for CI Engines2024-37-00226/12/2024
This study explores the feasibility of using a sustainable lignin-based fuel, consisting of 44 % lignin, 50 % ethanol, and 6 % water, in conventional compression ignition (CI) marine engines. Through experimental evaluations on a modified small-bore CI engine, we identified the primary challenges associated with lignin-based fuel, including engine startup and shutdown issues due to solvent evaporation and lignin solidification inside the fuel system, and deposit formation on cylinder walls leading to piston ring seizure. To address these issues, we developed a fuel switching system transitioning from lignin-based fuel to cleaning fuel with 85 vol% of acetone, 10 vol% of water and 5 vol% of ignition improving additive, effectively preventing system clogs. Additionally, optimizing injection parameters, adopting a constant pressure delivery valve, and fine-tuning injection timing mitigated lignin deposit formation related to incomplete combustion or spray tip penetration to the cylinder wall. The successful combustion of the lignin-based fuel in the small-bored CI engine was confirmed in a wide range of chamber temperatures. The ignition delay was measured and analyzed using Arrhenius equation. The ignition quality of the lignin fuel was comparable with 1-pentanol with a cetane number of 18.2, which is acceptable for 2-stroke marine engines. Although further investigation is needed to assess long-term reliability, our findings underscore the potential of lignin-based fuel as a viable alternative fuel for marine engines.
Terauchi, Motoki, Simonsen, Tor, Mortensen, Simon, Schramm, Jesper, Ivarsson, Anders
Small Craft - Graphic SymbolsJ1449_202405 (Current)5/24/2024
This SAE Recommended Practice specifies graphic symbols for operator controls, gauges, tell-tales, indicators, instructions, and warning against risks in small craft and for engines and other equipment intended to be used in small craft.
Marine Technical Steering Committee
Comparison of Tabulated and Complex Chemistry Approaches for Ammonia–Diesel Dual-Fuel Combustion Simulation03-17-07-00554/18/2024
Using ammonia as a carbon-free fuel is a promising way to reduce greenhouse gas emissions in the maritime sector. Due to the challenging fuel properties, like high autoignition temperature, high latent heat of vaporization, and low laminar flame speeds, a dual-fuel combustion process is the most promising way to use ammonia as a fuel in medium-speed engines. Currently, many experimental investigations regarding premixed and diffusive combustion are carried out. A numerical approach has been employed to simulate the complex dual-fuel combustion process to better understand the influences on the diffusive combustion of ammonia ignited by a diesel pilot. The simulation results are validated based on optical investigations conducted in a rapid compression–expansion machine (RCEM). The present work compares a tabulated chemistry simulation approach to complex chemistry-based simulations. The investigations evaluate the accuracy of both modeling approaches and point out the limitations and weaknesses of the tabulated chemistry approach. When using two fuels, the tabulated chemistry approach cannot reproduce misfiring events due to inherent model limitations. By adjusting the model parameters of the tabulated chemistry model, it is possible to reproduce experimental results accurately for a specific case. However, using the adjusted parameters for simulations with changed injection timing or interaction angle between the sprays shows that no predictive calculations are possible. The parameter set is only valid for a single operation point. Further simulations show that the complex chemistry approach can capture the complex interaction between both directly injected fuels for different operation points. It correctly predicts the ignition as well as heat release. Therefore, the approach allows predictive combustion simulations. Furthermore, it reproduces the occurrence of misfiring in cases of unsuitable interaction of both sprays and injection timing.
Krnac, Dominik, Manickam, Bhuvaneswaran, Holand, Peter, Pathak, Utkarsh, Scharl, Valentin, Sattelmayer, Thomas
A Study on the Relationship between ECN Spray D and Marine-Sized Nozzles Using FGM Combustion Model2024-01-26954/9/2024
Present work investigates the relationship between the combustion parameters of a well-known ECN heavy-duty nozzle called Spray D and marine-size nozzles. The study is carried out in OpenFOAM software within the framework of RANS turbulence modelling, using a flamelet based tabulation technique known as FGM to model the combustion. The large nozzles are tested in a constant volume chamber representative of marine engines, for which a CFD setup is validated against inert data in literature. The reacting results have been validated first with experimental data, initializing the domain with a highly reactive environment (23% oxygen) and engine-like swirl. Then, a less reactive initial condition was set up in the domain (15% oxygen) without swirl, to achieve a Spray D-like environment. The main goal is to study the variation of the combustion parameters Ignition Delay Time (IDT) and Lift-Off Length (LOL) as function of nozzle diameter, leading to a mathematical correlation to estimate the IDT and the LOL for different nozzle sizes from the well-known Spray D. The resulting dependency was well captured by a polynomial relationship y(x) = axb + c. Only the smaller nozzle of 300μm, does not follow this trend, possibly confining its validity to a range of diameters larger than two times the Spray D nozzle.
Di Matteo, Andrea, Somers, Bart
On the Application of Joule-Cycle-Based Waste Heat Recovery to Heavy-Duty Vehicles2024-01-25894/9/2024
Internal combustion engines are becoming ever more efficient as mankind seeks to mitigate the effects of climate change while still maintaining the benefits that a mechanized society has brought to the global economy. As peak values, mass production spark-ignition engines can now achieve approximately 40% brake thermal efficiency and heavy-duty truck compression-ignition engines can approach 50%. While commendable, the unfortunate truth is that the remainder gets emitted as waste heat and is sent to the atmosphere to no useful purpose. Clearly, if one could recover some of this waste heat for beneficial use then this is likely to become important as new means of mitigating fossil CO2 emissions are demanded. A previous study by the authors has identified that the closed Joule cycle (or complications of it beginning to approximate the closed Ericsson cycle) could reasonably be developed to provide a practical means of recovering exhaust heat when applied to a large ship engine. In that previous work there was a sensitivity shown between overall pressure ratio and the ratio of specific heats of the gas being used as the working fluid and, providing those variables were appropriately chosen, relatively high efficiencies and specific work outputs appeared to be achievable. While marine engines might seem to be ideal applications for this technology, in no small part due to the effectively infinite and relatively low-temperature sink available at the bottom of the cycle, their low exhaust temperatures (arising from their inherently high efficiencies) and the existing placement of scrubbers and economizers in the exhaust gas run makes the practical application of waste heat recovery (WHR) more difficult on them; nevertheless, using real exhaust gas compositions, the previous work clearly showed some significant potential in that arena, even if the exact level of upper temperature available in the cycle is still unknown. Given the early indications that Joule-cycle based WHR could work in already-efficient marine applications, this paper investigates the practicality of such methods of recovering exhaust heat in another sector – heavy-duty road transport. In this application, the challenge of a more difficult rejection of heat to the atmosphere on the cold side of the cycle is offset by a hotter exhaust gas temperature. Versus light-duty applications, long-distance transport can offer the chance for more continuous operation with fewer transients to reduce average efficiency, plus a direct economic payback in the form of lower operating costs. To investigate this opportunity modelling was performed using data in the literature already published for a diesel-engined truck which was then input to one of the Joule-cycle-based WHR models already developed for the initial marine-based project. These results show that this WHR concept could usefully be applied to truck use. An open Joule cycle system is then proposed and this too is investigated; here an increased benefit was predicted because, unlike for the closed Joule cycle approach, the working fluid flow rate in the system can be varied over a wider range, and the final heat exchange is avoided, giving a reduced lower cycle temperature.
Turner, James, Kenkoh, Kesty Yong, Gubba, Sreenivasa, Vorraro, Giovanni
Hydraulics Characteristics of a Mechanical Diesel Direct Injection System: The Influence of Diameter of High Pressure Pump’s Plunger, Number and Diameter of Injector Nozzles.SAE-PP-0037412/26/2023
The diameter of the high pressure pump plunger, the number and diameter of injector nozzles play a crucial role in influencing hydraulic behaviors such as the start of injection, the pressure profiles developed in the high pressure line, needle lift, and injection rates in Diesel engines. These factors, in turn, significantly impact the distribution of fuel within the engine combustion chamber, fuel-air mixing, combustion quality, and the formation of emissions. However, as the plunger diameter and the number and diameter of nozzles vary, the system's complexity also rises, necessitating careful analysis, design, and calibration. Therefore, further examinations are critically essential to gain deeper insights into this topic. In this study, a high-speed shadowgraph system and a high-resolution pressure recording system were developed to capture the start of injection, spray structure, and pressure profiles in the high-pressure line. The fuel injection system under experimental investigation featured a 10mm plunger and a 7-nozzle injector with a nozzle diameter of 250µm. Additionally, GT-fuel simulation models were created to explore different plunger diameters and numbers and diameters of injector nozzles. These models were validated using the pressure profiles, fuel quantity, and start of injection timing obtained from the experiments. This approach can either individually analyse the influence of each parameter or assess their overall impact. The results indicate that an increase in plunger diameter from 10mm to 12mm advances the start of injection (SOI) to 30.7 degree from 31.4 degree of crankshaft angle. Furthermore, an increase in the number and/or diameter of nozzles results in a higher amount of fuel delivered per cycle. Overall, replacing a an injection system with 10mm plungers and injectors with 7x250µm nozzles by one featuring 12mm plungers and injectors having 8x300µm nozzles can increase the fuel delivery by 1.85 folds. This studying approach could be useful for practical applications, including boosting engines and/or designing more efficient fuel systems. Future investigations into the high-speed shadowgraph images captured in this study could offer additional insights into the Rayleigh-Taylor and Kelvin-Helmholtz models concerning the primary and secondary atomization processes.
Pham, Phuong, Vu, Tuan, Nguyen, Kien, Phung, Duoc, Manh, Vu
Effects of the Combustion Enhancer Containing Alkyl Nitrate (CEN) to Dodecane and HVO as Pilot Fuels on a Compression Ignition Engine Operating in Dual-Fuel with Ammonia2023-01-162510/31/2023
Ammonia is a widely used and known chemical. Today it is seen as a carbon free solution to fuel thermal engines especially in applications where other solutions would not be realistic. For marine applications, electrical or fuel cells solutions for example would not allow spans long enough to sustain big cargo ships ranges. Engine manufacturer such as MAN, Wartsila or Win-GD have already announced the development of marine engine running on ammonia. But while ammonia is a non-CO2 emitting fuel, it has some caveats such as being gaseous in standard conditions and hard to ignite. As it is now, ammonia is usually used in compression ignition engines with the help of highly reactive carbonated pilot fuels. Many forms of dual-fuel combustion are conceivable, although all the simple ones use a carbon-based fuel and quite often originated from fossil oil. The addition of High Reactivity Fuel to Ammonia is an interesting combustion mode that can be used to calibrate different fuel parameters and explore the mechanisms surrounding ammonia ignition and combustion. In this study Dodecane or HVO are used as the pilot fuel with a combustion enhancer containing alkyl nitrates (CEN). The pilot fuels injections were maintained to stay at 2% of the total energy provided by the fuel & the pilot fuel. The effects of the combustion additive were observed and measured. Adding 1% of volume fraction of the additive the Dodecane/HVO pilot fuel allows for better cycle to cycle stability (Coefficient of Variation – CoVIMEP) and higher Indicated Mean Effective Pressure (IMEP). 10% of volume fraction additive in the pilot fuel further increases engine power output and smoothens the combustive event by lengthening it. It was difficult to truly investigate the emissions due to ammonia FTIR spectrum, but in this study IMEP, with the IMEP, CoVIMEP, noticeable crank angle degrees (CA10, CA50, CA90) and Indicated Thermal Efficiency (ITE) were measured with ammonia preheated (80°C) while kept at ambient pressure at intake. Three IMEP values (12 – 8 – 4 bar) were targeted for a one-cylinder engine with a displacement of 0.499L and a compression ratio of 16.4. The strategy of this study allowed to conclude that the combustive additive and the pilot fuel used in relatively low ratios vs. ammonia (2% energetic ratio) have a synergetic activity allowing for better ignition (than the pilot fuel alone), better cycle to cycle stabilization, better power output, and displacing the combustive event toward ammonia combustion in conditions (richness and engine loads) where it’s been otherwise repeatedly observed impossible.
Samson, Richard, Morin, Anne-Gaëlle, Foucher, Fabrice
Numerical Study of the Effect of Direct-Injection Timing of Methanol and Excess Air Ratio on the Combustion Characteristics of a Marine Diesel-Methanol Dual-Fuel Engine2023-01-162610/31/2023
Methanol is a suitable alternative fuel to relieve the problem of energy shortage and decrease the emission of greenhouse gases. The effect of direct-injection timing of methanol and diesel on the combustion characteristics of a marine diesel engine with bore of 210 mm was simulated with a 3-dimentional computational fluid dynamic (CFD) software AVL-FIRE. The combustion model was set-up and validated by the experimental data from the marine diesel engine. Results show that there are two peaks on the heat release rate (HRR) curves with the normal diesel-methanol combustion process. The first HRR peak is caused by the combustion of diesel. The second HRR peak is resulted from the hybrid combustion process of diesel and methanol. The injection timing of diesel influences the peak pressure rise rate (PPRR) and ignition timing. The indicated mean effective pressure (IMEP), the maximum in-cylinder pressure and combustion duration are influenced by the direct-injection timing of methanol. With direct-injection of diesel and methanol, the nitrogen oxide (NOx) and soot can be reduced simultaneously. The emission of nitrogen oxide is 70% lower than the original diesel engine when the lambda is higher than 2.0. A suitable range of dwell between direct-injection timing of diesel and methanol and excess air ratio can ensure the output of engine power and make emissions under a low level simultaneously.
Li, Xiao, Yan, Ping, Li, Hong-Mei, Zheng, Liang, Shen, Gang, Hu, Yu-Chen, Han, Dan
A Study on Combustion and Emission Characteristics of Ammonia, Hydrogen and Diesel Tri-Fuel Engines2023-32-01039/29/2023
Ammonia is a promising alternative to conventional fossil fuels for internal combustion engines, especially in the maritime industry, because it does not emit carbon dioxide. Since redundancy is important in marine engines, a dual fuel system with diesel oil is currently widely applied to use alternative fuels such as liquefied natural gas, and a similar system is expected for ammonia-fueled ships. However, ammonia has low ignitability and low burning speed, hence improvement of combustion efficiency is major challenge. In addition, the emission of N2O which has a high global warming effect is also problematic as well as emission of NOX as air pollutant. To overcome these challenges, a mixing with hydrogen, which has high ignitability and high burning speed, can be effective. Therefore, in this study, combustion and emission characteristics of tri-fuel combustion engines, in which ammonia and hydrogen-air mixture is ignited by μ-pilot injection of diesel oil, were investigated. Numerical analysis showed that the increase in combustion temperature due to mixing with hydrogen and reduction in excess air ratio were effective in reducing unburned NH3 and N2O emissions. Experimental results showed that the higher the hydrogen mixing ratio, the shorter the combustion duration. At the same time, unburned NH3 and N2O emissions decreased simultaneously. These results indicate that hydrogen blending is effective in improving combustion efficiency and reducing GHG emissions derived from N2O, while NOX, which increases with increasing combustion temperature, has a trade-off relationship with N2O.
Matsunaga, Daichi, Tentora, Takafumi, Hiraoka, Kenji, Toshinaga, Kazuteru
Prediction of combustion process and NOx emission for dual fuel marine engines using a phenomenological model2023-32-01589/29/2023
A phenomenological model for high-pressure direct injection natural gas-diesel dual-fuel marine engine was developed, which includes natural gas mixing process using Musculus discrete control volume transient diesel jet model, combustion process using quasi-steady model and Woschini heat transfer model, NO generation using Zeldovich mechanism. Effects of natural gas injection pressure and the start of injection timing on the mixing and combustion process were investigated. The results indicated that increasing the injection pressure with fixed injection mass, the NO emission decreased. While the start of injection timing was before TDC, retarding the injection start timing will increase NO generation.
Xiong, Qian, Liang, Dezhi, Wang, Lujiang, Shi, Xinru, Liu, Long, Ma, Xiuzhen
Comparison of the effect of diesel and hydrogen addition on ammonia combustion characteristics in a marine engine2023-32-00659/29/2023
Ammonia, as a carbon-free fuel, is a promising alternative fuel source for decarbonization of the shipping industry. Nevertheless, the poor flammability and low flame speed restrict its potential application as marine engine fuel. In order to explore the ammonia application feasibility and methods in marine engines, the effects of two combustion promoters, including n-heptane and hydrogen, on improving the ammonia combustion characteristics were compared and discussed theoretically in this study, in terms of flammable intake boundary conditions and laminar flame speed under engine operating conditions. A new detailed reaction mechanism of ammonia/n-heptane dual fuel was developed and validated to characterize the combustion of ammonia and diesel. The results demonstrate that the flammability of ammonia is more sensitive to intake temperature as compared to equivalence ratio and intake pressure. The introduction of n-heptane or hydrogen has been observed to have a noteworthy impact on the combustion characteristics of ammonia, resulting in a decrease in the necessary intake temperature. The promotion effect is more pronounced with an increase in the volume fraction of the combustion promoter. However, n-heptane exhibits a superior ability to support combustion in comparison to hydrogen, which allows significantly lower intake temperature requirement for ammonia combustion, even reaching room temperature levels. The reaction pathway of the ammonia/n-heptane mixture indicated that the OH radicals produced by the low-temperature oxidation of n-heptane play a crucial role in facilitating ammonia combustion. Furthermore, the addition of n-heptane has the potential to significantly enhance the laminar flame speed of ammonia up to 34 cm/s, when a 10% volume fraction of n-heptane is employed. Ultimately, the map of NOx and unburned hydrocarbon emissions was illustrated, followed by the proposal of a stratified charge combustion approach aimed at the simultaneous reduction of unburned hydrocarbon and NOx emissions.
Liu, Long, Wu, Yue, Wang, Yang, Wu, Jie, Wang, Xiqing
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