Browse Topic: Nozzles

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Research on the Damage Behavior of the Aluminum Alloy Nozzle Closure in Solid Rocket Motor during the Bursting Process2026-99-16127/24/2026
When the aluminum alloy closure of the solid rocket motor nozzle is opened, tearing occurs at the root of the adhesive surface, which belongs to damage failure under a complex stress state. To help in the prediction and control of blasting pressure and nozzle closure failure morphology, this work designed and manufactured various shapes of 1060 aluminum alloy test specimens, performed damage tests, and calibrated the damage constitutive model parameters. The results gathered were utilized to create a finite element model of the nozzle aluminum alloy closure, and the blasting procedure was calculated. We conducted air pressure explosive tests on closures to confirm the finite element results. The numerical predictions and experimental results are very consistent, and the closure breaks along the adhesive surface. The constitutive characteristics obtained during material testing accurately characterize the closure’s damage process, providing a theoretical framework for the design and verification of aluminum alloy closures.
Jia, Kai, Li, Weinan
Aircraft Engine–Specific Thrust and Visibility from 2D and Circular Nozzle Exits2026-01-60037/7/2026
In modern warfare, military control of the airspace determines aircraft survivability against the most widespread missile threats. The aero-engine exhaust system is an important source of infrared (IR) signatures from the rear aspect, particularly in the 2–3 μm and 3–5 μm IR bands. Two-dimensional (2D; non-axisymmetric) nozzle exits with high aspect ratio (AR > 5) are widely used in stealth aircraft engines due to their low IR signature, ease in thrust vectoring, and high maneuverability and agility. This analytical study compares the specific thrust (for choked and unchoked flow regimes) and the visible planar areas of a 2D nozzle exit with different ARs with those of a circular nozzle, as seen from the direct rear view. The nozzle’s isentropic efficiency (ηis,noz) is obtained in terms of the total pressure ratio, and the effect of AR on ηis,noz is examined for 1 ≤ AR ≤ 15. It is found that ηis,noz decreases with increasing AR, but this decrease is more rapid in unchoked flow than in choked flow. For the same value of nozzle exit cross-sectional area, the corresponding visible planar areas of aero-engine hot parts are compared for a 2D nozzle exit with different AR with that of the baseline case (circular nozzle), from bore-sight. This study shows that the optical blocking of aero-engine hot parts by a round-to-rectangular nozzle of AR ≤ 4 is almost the same as that of a circular nozzle, from bore-sight.
Baranwal, Nidhi
Investigation into Cooling Loss Reduction Associated with Changes in In-Cylinder Flame Distribution by Offset Orifice Nozzle2026-37-00036/9/2026
An increase in compression ratio has been widely recognized as one of the essential technologies for improving the thermal efficiency of heavy-duty diesel engines. However, a higher compression ratio tends to result in increased cooling loss, which could diminish the thermal efficiency gains. It was found that an offset orifice nozzle, in which the orifices are drilled with a small offset from the radial center of the nozzle, improves thermal efficiency and reduces cooling loss simultaneously. This study investigates the mechanism of cooling-loss reduction associated with changes in flame distribution when using an offset orifice nozzle, through in-cylinder combustion observations, two-color method image analysis, and local heat-flux measurements. High-speed combustion visualization was conducted to capture the growth of luminous flames. Radial profiles of the mean and standard deviation were computed at each crank angle to quantify spatial temperature non-uniformity. Furthermore, multiple thin-film thermocouples embedded in the piston were employed to measure transient surface temperature and to derive heat flux over the entire cycle. The results indicated that the luminous flame distribution with the offset orifice nozzle was significantly different from that with a conventional nozzle, leading to reduction in the spatial non-uniformity of high-temperature regions in the observed area. The piston surface temperature measured at multiple points suggested reduced spatial non-uniformity in surface temperature, with suppressed instantaneous heat flux. These findings confirm the hypothesis that cooling-loss reduction is achieved by suppressing localized hot spots on the piston surface through the altered flame distribution.
Mukayama, Tomoyuki, Enomoto, Yoshiteru, Mikami, Naotaka, Nomoto, Shigeru, Uchida, Noboru
Optimization of Adaptive Mesh Refinement Strategy for VOF-DPM Method2026-99-07265/15/2026
When simulating spray atomization process involving VOF method, a core problem is the conflict between high grid detail and limited computer power. Although VOF and DPM methods have recently been coupled to reduce computational cost, their application in practical engineering calculations still imposes a considerable computational burden. To solve this, a better adaptive mesh refinement (AMR) plan is put forward. This plan uses a 0.2 mm initial grid (twice the usual 0.1mm) and allows refinement up to four levels. This improved technique makes high computational efficiency for large-scale simulations. Two types of nozzles are employed to evaluate the proposed method. However, for circular nozzles, the new method does not increase calculation speed, while lowers the accuracy of the simulation.In contrast, for square nozzles, it greatly boosts computation speed and keeping high accuracy. This makes the technique a useful tool for modeling transverse jet atomization in industry. Overall, the work gives clear advice for better mesh refinement in multiphase flow research. It is particularly advantageous for large-scale simulation domains where conventional methods become computationally prohibitive.
Zhou, Taotao, Ma, Ming, Zhang, Haitao, Zhang, Fengan, Chen, Xianhui, Chen, Qi, Xia, Hongwei
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 Renewable Fuel Blends on Particulate Emissions in Warm-Up Conditions in a GDI Engine2026-01-03044/7/2026
Renewable gasoline offers significant benefits in reducing greenhouse gas (GHG) emissions. In this study, five gasolines with different renewable hydrocarbon classes and varying distillation curves were taken to investigate their effect on particle number (PN) emissions in a spark-ignition GDI engine at 10 bar indicated mean effective pressure (IMEP) and 2000 rpm. The engine coolant temperature was varied from 90°C to 35°C to investigate the effect of fuel evaporation on soot formation. Injectors with various spray plume targets and start of injection (SOI) timing (300° and 260° bTDC) were used to assess how different gasolines affect engine performance and to determine engine calibration requirements. A simplified transient cycle examines how engine motoring influences PN emissions for test gasolines. A high-speed camera and endoscope were used to identify the sources of soot during fuel combustion. Simulations were done to assess the quality of fuel-air mixing in support of the experimental data. The results revealed that the type of hydrocarbons in gasoline was crucially affecting PN emissions. Particles with >10 nm increased with increasing fuel’s aromatics. Paraffin-rich gasoline showed 71% and 98% lower PN than aromatics-rich gasoline under hot and cold engine conditions. Paraffin-rich gasoline showed lower PN in cold tests than in hot tests with retarded SOI. Replacing ~10% paraffins with olefins and naphthene reduced >10 nm PN by 15-77%. However, replacing 19% of paraffins with olefins and naphthene increases PN emissions. Optimal SOI timing reduces PN by 80% for aromatics-rich gasoline. Fuel consumption and hydrocarbon (HC) emissions increased with increasing aromatics and paraffins in gasoline under cold conditions. Yellow flames on the piston top and near the injector tip were the primary sources of soot. Simulation results showed that the liquid fuel mass increased by 14% when the coolant temperature was reduced by 55 K.
Muniappan, Krishnamoorthi, Dahlander, Petter, Helmantel, Ayolt, Alemahdi, Nika, Lehto, Kalle
Preliminary Design and Analysis of a Dual Throat Fluidic Thrust Vectoring Nozzle for Supersonic Aerospace Application2026-28-01062/12/2026
The Dual Throat Nozzle (DTN) is a unique nozzle configuration that enables fluidic thrust vectoring (FTV), improving aircraft maneuverability while reducing the mechanical complexity of traditional vectoring systems. In this study, a two-dimensional DTN was developed based on a validated NASA Langley model, incorporating a newly designed plenum geometry guided by area expansion ratio principles. Numerical simulations were carried out in ANSYS Fluent using a density-based, steady-state solver with the SST k–ω turbulence model to capture key compressible flow features such as shock waves, flow separation, and jet deflection. Secondary injection rates were determined using choked-flow relations, and a 12-case parametric study was conducted to analyze the effects of Nozzle Pressure Ratio (NPR), injection rate, and injection angle on thrust deflection and efficiency. The simulation results at NPR = 4 with 3% injection showed strong agreement with NASA experimental data, validating the computational setup. It was observed that higher NPR values reduced jet deflection but improved overall thrust efficiency, with the best performance achieved at NPR = 2 and a 150° injection angle. The findings provide valuable insight into optimizing DTN design parameters for lightweight, efficient fluidic thrust vectoring systems suited to future supersonic applications.
Suresh, Vignesh, M, Akash, Senthilkumar, Nikil, Sundararaj, Senthilkumar, A, Garry Kiristen, Singh, Swaraj
Rear Wiper Motor with Nozzle Integration2026-26-06001/16/2026
In today's dynamic driving environments, reliable rear wiping functionality is essential for maintaining safe rearward visibility. This study sharing the next-generation rear wiper motor assembly that seamlessly integrates the washer nozzle, delivering improved performance alongside key benefits such as better Buzz, Squeak, and Rattle (BSR) characteristics, reduced system complexity, cost savings, and enhanced perceived quality. This integrated design simplifies the hose routing which improves the compactness and the efficiency of the design. This also enhances the spray coverage and minimizes the dry wiping unlike the traditional systems that position the washer nozzle separately. A non-return valve (NRV) is incorporated to eliminate spray delays ass it maintains consistent water flow giving cleaning effectiveness. Since this makes the nonfunctional parts completely leak proof due to the advanced sealing, it increases the durability and reliability in long run. As this proposal offers a sustainable solution, it can be considered as the new benchmark in rear wiper technology.
Dhage, Prashant, K, Nagarajan, G, Sabari Rajan
Case Study: Nanocomposite-Based 3D Printing and the Implementation of Quality Management to Enhance the Production of Automotive Parts2025-36-020612/18/2025
Additive manufacturing is one of the pillars of technologies of the industry 4.0 and enables rapid prototyping, testing of new materials, and customized manufacturing of parts with personalized design. Poly(lactic acid) (PLA) is a bio-based and biodegradable polymer that is used in packaging, medical applications, and consumer goods. However, it presents low mechanical strength and thermal stability, which limits its use in automotive parts. The use of reinforcement materials such as cellulose nanofibers (CNF) aim to increase the mechanical strength and thermal stability of PLA without reducing its ecological appeal. However, the addition of nanofibers in the 3D printing process can lead to reproducibility problems and constant clogging of the extruder nozzle due to the material’s lower printability. These difficulties may restrict its application to industrial processes due to reduced productivity. To address the challenges in the production of automotive parts with PLA/CNF composites, this paper explored the implementation of a quality management tool to improve the additive manufacturing process using nanocomposite-based filaments. The Ishikawa diagram was used to understand the difficulties observed during production and based on the potential root causes an action plan was developed using 5W2H (five whys and two hows) technique. Through the implementation of the Ishikawa diagram, it was possible to identify critical areas of improvement. Through the 5W2H, specific actions were defined in the whole process, from the nanocomposite and filament manufacturing process to 3D printing parameters. Additionally, standard operating procedures (SOPs) with special routines for the maintenance of the equipment and also for continuously monitoring all the actions that were implemented along the processing stages. For future work, new quality management tools such as checklists and operation flowcharts will be implemented to guarantee better performance of nanocomposites in 3D printing manufacturing processes.
Oliveira, Vinícius, Horiuchi, Lucas Nao, Gonçalves, Ana Paula, Souza, Mariana, Polkowski, Rodrigo
Validation of Pressure Vessels According to ASME VIII, Division 1 and AD 2000 Standards2025-36-004212/18/2025
In this study, using the American Society of Mechanical Engineers - ASME VIII Div.1 and the German AD - MERKBLÄTTER 2000 (that is a code of practice for pressure vessels and other pressure equipment, it was drawn up by the German Pressure Vessel Association which includes many German associations and institutions specialized in boilers and pressure vessels). This pressure vessel had its geometry generated from the Inventor software, which has equipment specification for industrial applications. The validation of two types of horizontal cylindrical vessels was performed: one without and one with four nozzles (A, B, C, D). For this, two common parameters between both standards were considered: the minimum required thickness in millimeters (of the cylindrical shell, elliptical head, and nozzles A, B, C, and D), as well as the maximum membrane stress (in the presence and absence of nozzles). The percentage differences between both standards, considering the membrane stress of the vessel without nozzles, was not significant. However, regarding the vessel with nozzles, the percentage differences between nozzles B and D (18.26% and 13.64%, respectively) are considerable. Finally, for the case of the minimum required thickness, the percentage differences for each of the components (shell, head, nozzle A, nozzle B, nozzle C, and nozzle D) show high disparity (99.2%, 79.7%, 180.5%, 159.2%, 180.5%, 189.5%, respectively). Based on these percentage differences, comments and conclusions are drawn regarding the applicability of both standards in real-world pressure vessel validation contexts. For numerical simulations, Ansys Workbench software [15] was used, as well as DIMy, from the company TÜV NORD.
Pereira, Mateus Penido, Castro, Thais Santos, Grandinetti, Francisco Jose, Bimestre, Thiago Averaldo, Reis de Faria Neto, dos Antonio, Dias, Erica Ximenes, Martins, Marcelo Sampaio
Analysis of Combustion Process in HVO-Hydrogen Dual-Fuel Operation Using Simultaneous Imaging of OH* and CH* Chemiluminescence2025-32-005311/3/2025
This study investigated the combustion process in a hydrotreated vegetable oil (HVO)–hydrogen dual-fuel operation using simultaneous imaging of the OH* and CH* chemiluminescence in a rapid compression and expansion machine (RCEM). In this operation, hydrogen served as the primary fuel, ignited by a small quantity of pilot fuel. CH* chemiluminescence was primarily detected in the pilot fuel combustion regions, whereas OH* chemiluminescence was detected in both the pilot fuel and hydrogen combustion regions, enabling the separation of pilot ignition and hydrogen flame propagation. The combustion mechanism was found to proceed through four distinct stages: autoignition of the pilot fuel, combustion of the mixture in the lean pilot fuel region, propagation of the hydrogen–air premixture flame, and flame propagation toward the wall and squish area. Furthermore, the effects of the pilot injection parameters on the combustion characteristics were systematically evaluated by varying the injection quantity, injection pressure, and nozzle specifications (hole diameter and number of holes). Increasing the pilot injection quantity improved the degree of constant volume of combustion but intensified the combustion near the wall, potentially increasing the cooling loss. Reducing the injection pressure shifted the autoignition location toward the center of the piston bowl, potentially reducing cooling loss but prolonging the combustion duration. With smaller injection quantities, fewer nozzle holes resulted in a higher second heat release rate peak, owing to the increased space for hydrogen flame propagation. Conversely, with larger injection quantities, a greater number of nozzle holes led to a shorter combustion duration while maintaining the combustion away from the wall.
Yukitani, Takumi, Une, Naoto, Mukhtar, Ghazian, Horibe, Naoto, Kawanabe, Hiroshi, Koda, Kazuyuki, Hiraoka, Kenji
A Novel Nozzle Orifice Design of a Heavy-Duty Diesel Engine to Achieve Higher Thermal Efficiency with Significantly Reduced Heat Loss2025-24-00379/7/2025
This study investigated a novel nozzle orifice design to improve thermal efficiency. The offset orifice nozzle has holes drilled offset of less than 0.5 mm from the radial center of the nozzle. Engine performance test and in-cylinder combustion observation were carried out by means of a heavy-duty diesel engine. The experimental results demonstrated that the offset orifice nozzle achieved significant improvements in both heat loss and thermal efficiency, regardless of the compression ratio and operating load conditions. However, the underlying mechanisms have not been revealed yet. Therefore, investigation into the mechanisms behind heat loss reduction and thermal efficiency improvements with the offset orifice geometry is the purpose for establishing design guidelines for optimization. It was revealed by the combustion visualization that the flame tip length of the offset orifice nozzle was shortened with significantly wider flame cone angle from very close to the orifice exit even though the fuel injection rate was slightly higher than that of the referenced radial orifice nozzle. The asymmetrical spray structure along with the nozzle internal flow were confirmed by a numerical simulation. From these findings, the main cause of heat loss reduction was assumed to be more homogeneous wall surface temperature distribution by the modified spatial flame distribution.
Mukayama, Tomoyuki, Uchida, Noboru
High-Pressure Hydrogen Flows through Single- and Multi-Hole Nozzles: A Computational Study13-06-03-00249/1/2025
Efficient propulsion technologies that utilize alternative fuels are becoming increasingly critical to achieve high efficiency at the vehicle scale while fulfilling global regulations in terms of emissions and criteria pollutants. In this scenario, hydrogen (H2) represents an important and appealing part of the solution due to its molecular composition and unique physical and chemical properties. With reference to internal combustion engines, much research is needed to overcome technical challenges that make H2 use not yet viable at the industrial scale. This work focuses on the computational modeling of some of the fundamental aspects of H2’s physical behavior, which can be useful to the development of high-pressure H2 injection systems. Computational fluid dynamics simulations are discussed with the goal of understanding the near- and far-nozzle behavior of H2 using single- and multi-hole nozzles. This study presents the validation of the computational framework against literature data, followed by its extension to a multi-hole geometry relevant to the automotive industry. The role of parameters such as ambient gas composition, minimum allowable temperature in the domain, different turbulence models, and grid strategies are all discussed in detail while keeping into consideration computational costs. The authors’ goal is to provide a series of best practices and guidelines that can be useful to researchers in the automotive industry who are interested in understanding the behavior of H2 injectors by means of numerical simulations.
Torelli, Roberto, Park, Ji-Woong, Pei, Yuanjiang
Influence of Pre-Chamber Nozzle Orientation on Dilution Tolerance in a Constant-Volume Optical Engine03-18-05-00318/14/2025
This study presents an analysis of the effects of pre-chamber nozzle orientation on dilution tolerance in a light-duty, optical, single-cylinder, constant-volume optical engine. Seven different nozzles with varying nozzle orientation to area-to-volume (A/V) ratio were studied using a combination of experimental and numerical methodologies. The findings reveal that the swirling nozzles were found to have lowest dilution tolerance of 6% tolerance due to the complexity of their internal flow dynamics and increased heat loss through nozzle surfaces. whereas straight nozzles with varying A/V ratio were stable up to 15% dilution. Pre-chambers combining swirling and straight nozzle orientations fail to synergize the benefits of each type, and instead, exacerbate challenges such as heat loss, flame quenching, and unfavorable flow dynamics. Furthermore, an increase in the number of nozzles, for a fixed area-to-volume ratio, tends to enhance ignition performance and stability across a range of dilution scenarios, primarily due to an increase in ignition points and a larger ignition surface area. These findings emphasize the complexity and nuanced trade-offs involved in optimizing pre-chamber design for improved dilution tolerance and suggest potential directions for future research in this area. These findings emphasize the complexity and nuanced trade-offs involved in optimizing pre-chamber design for improved dilution tolerance and suggest potential directions for future research in this area.
Lee, Dong Eun, Yu, Tianxiao, Alam, Afaque, Iyer, Claudia, Wooldridge, Steven, Yi, Jianwen James, Qiao, Li
Investigation of Expansion Characteristics of Convergent–Divergent Nozzles with a Variable Geometry Sudden Expanded Duct01-18-02-00107/9/2025
In recent years, there has been a significant rise in research focused on estimating the base pressure (Pb) characteristics of convergent–divergent nozzles with sudden expansion regions. This study explores the use of geometrical parameters as a control strategy for nozzles experiencing abrupt expansion at supersonic Mach numbers within an axisymmetric duct. It focuses on four distinct novel expansion duct configurations: square nozzle (SN), step square nozzle (SSN), curved nozzle (CN), and double curved nozzle (DCN). In this work, the high-speed compressible flow investigation is carried out numerically using control volume method on the nozzle with a fixed area ratio (AR) and L/D nozzle. Standard k-ε turbulence model is used in the analysis to access the recirculation region formed near the nozzle walls. The recirculation zone directly influences the Pb and shock cell. For NPR range from 2 to 10, SSN and CN shows an increase in Pb, which further increases the thrust and decreases the base drag provided by the nozzle. The thrust performance analysis shows that at NPR 2, the SN configuration delivers up to 61.8% higher thrust than other nozzles, while at high NPRs (6 to 10), SSN and CN configurations exhibit superior performance with thrust improvements of up to 59.2%. It is also evident that the L/D of the nozzle is also an important parameter that impacts the Pb as well as expansion in the nozzle.
Raj, R. Jini, Kumar, P. Deepak, Panchksharayya, D. V., Kousik Kumaar, R., Praveen, N.
Morphology Experiment of Icing Effect on Spray Propagation2025-01-02226/16/2025
The working conditions of combustion systems have been going extreme under the desire of human beings exploring the unknown. Cold environments can be a significant impact on the spraying of fuel not only by changing the fuel properties including viscosity and surface tension, but also by freezing the parts. In the present study, methanol spray from a commercial injector is studied via high-speed imaging, with the liquid fuel being frozen to sub-zero degrees at the injector tip. It is observed that water components from the environment will freeze at the injector tip, creating crystal structures on the surface. During the injection, the ice components will be flushed by the liquid, and the spray morphology of the starting cycle will be strongly altered, resulting in wider spray angles, much shorter penetrations, and particle structures can be observed in the downstream of the flow field. The results of the experiment provide a clear view and quantified evaluation of the freezing impact on spray development from practical injectors, and gives a sketch of the most extreme condition of the fuel spray before the valve is chilled to the bone and unable to open.
Zeng, Tingxi, Wang, Shangning, Zhang, Yijia, Hung, David, Xu, Min
Higher Content n-Butanol Blending Ratios in Diesel Fuel Spray and Combustion Characteristics: Addressing Oxygenated Fuel Challenges with Spark-Assisted Combustion Strategies2025-01-02106/16/2025
This study investigates the effects of oxygenated fuels, specifically long-chain alcohols, impact fuel atomization and combustion behavior in CI engines. The objective is to examine how higher n-butanol blending ratios in diesel fuel influence spray dynamics and combustion performance under varying engine conditions using an advanced combustion strategy. Experiments were conducted using a constant volume chamber (CVC) and a rapid compression-expansion machine (RCEM), both designed to replicate CI engine conditions. N-butanol was blended with diesel at ratios ranging from 70% to 90% with 10% increments, and key parameters such as spray formation, cone angle, penetration length, in-cylinder pressure, combustion performance, and efficiency were analyzed. The study also evaluated the effects of varying injection pressures on spray behavior. The results demonstrate that increasing n-butanol content significantly alters spray and combustion characteristics. Higher n-butanol proportions lead to longer spray tip penetration and larger spray areas at higher injection pressures, while the cone angle remains relatively unchanged. The 90% n-butanol blend exhibited the most distinct differences from pure diesel. However, due to n-butanol’s high latent heat of vaporization, in-cylinder temperatures decreased, resulting in longer ignition delays. To mitigate this, a spark-assisted compression ignition (SACI) strategy was employed, with adjustable spark duration to assess its impact. Compared to pure diesel, SACI-applied n-butanol/diesel blends exhibited higher peak in-cylinder pressure and heat release rates, improving indicated thermal efficiency. Additionally, ringing intensity (RI) assessments confirmed that all tested conditions remained below the 5 MW/m2 threshold, ensuring acceptable combustion stability. This study provides a comprehensive analysis of n-butanol/diesel blends under SACI conditions, demonstrating their potential to enhance spray and combustion characteristics. The findings underscore n-butanol’s promise as a sustainable alternative fuel, addressing key challenges in dual-fuel combustion strategies.
Warsita, I Wayan, Lim, Ocktaeck
Study on the Optimal Pre-Chamber Geometry for Active Pre-Chamber Gas Engines2024-32-00234/18/2025
In a pre-chamber engine, fuel in the main-chamber is ignited and combusted by the combustion gas injected from the pre-chamber. Therefore, further fuel dilution is possible and thermal efficiency can be also improved. However, adding a pre-chamber to an engine increases the number of design parameters which have a significant impact on the main combustion and the exhaust gas. Then, in this study, the optimum geometry of the pre-chamber in an active pre-chamber gas engine was investigated. The considered parameters were the volume of pre-chamber, the diameter of a nozzle hole, and the number of nozzle holes. 18 types of pre-chambers with different geometries were prepared. Using these pre-chambers, engine experiments under steady conditions were conducted while changing the conditions such as engine speeds, mean indicated pressure and air excess ratio. Based on the experimental data, neural network models were constructed that predict thermal efficiency, NOx and CO emissions from the pre-chamber geometries and the engine operation conditions. Employing these models as objective function, the optimal geometry of the pre-chamber is obtained as Pareto solutions. The availability of this method to determine the optimal geometry of pre-chamber was proved since the general trade-off relationship between thermal efficiency and NOx was shown.
Yasuda, Kotaro, Yamasaki, Yudai, Sako, Takahiro, Takashima, Yoshitane, Suzuki, Kenta
Impact of Injector Geometry and Parcel Injection Location on Flash Boiling Spray Simulations of the ECN Spray G Injector2025-01-84624/1/2025
For fuels sprays under flash boiling conditions, the near nozzle region experiences rapid changes in ambient conditions due to the flashing liquid. So, it is crucial to understand the influence of spray boundary conditions on parcel-based simulations for improved predictions of fuel spray behavior in engine applications. This study builds upon previous research investigating the impact of detailed injector tip geometry on parcel simulations of non-flash boiling conditions by investigating how flash boiling behaviors affect the near nozzle region and parcel initialization conditions. Four key parameters were varied individually from a baseline spray simulation model, which resulted in a total of five cases. The parameter variations were the presence of detailed injector tip geometry versus a simplified flat surface, parcel initialization at the nozzle exit versus at the counterbore exit, the use of experimental rate-of-injection versus one-way coupling with an internal nozzle Volume of Fluid (VOF) simulation, and Large-eddy Simulation (LES) versus Reynolds Averaged Navier-Stokes (RANS) turbulence model. The penetration length exhibited limited sensitivity to these variations. However, local data such as the liquid volume fraction near the injector displayed significant differences, which could affect mixing and combustion predictions in engine simulations. These findings emphasize the need to reassess simulation assumptions and refine guidelines for accurately predicting spray characteristics in advanced engine modeling.
Kumar, Aman, Van Dam, Noah
CFD Modeling of Elastomeric Silicone Material Dispensing to Enable Equipment Design & Optimization for Efficient Automotive Manufacturing2025-01-83184/1/2025
In the automotive industry, it is essential to consider not only how well specialty materials perform and are formulated, but also how efficiently and economically they can be applied during manufacturing. This becomes especially important during the early stages of development to prevent issues when these materials are used in new designs by automotive suppliers or manufacturers. With the rapid growth of electric vehicles (EVs), new materials are being used more frequently, and these materials may not have been as thoroughly tested as those used in traditional internal combustion engine (ICE) vehicles. Therefore, it is crucial to ensure that these materials can be applied correctly and efficiently from the start. One way to speed up the development process is through Computational Fluid Dynamics (CFD) modeling. CFD helps predict how materials will behave when dispensed, which is essential for developing the right equipment and conditions for applying these materials. Working with Graco, a leading manufacturer of fluid management and dispense solutions, Dow and Graco have used these models to design better equipment solutions and improve the software used. This ensures high-quality and efficient application at start up. This paper will present two case studies how material models were developed, tested, and validated with real-world data to ensure they work as intended. The goal is to demonstrate how optimizing dispensing equipment based on material characteristics is critical for maintaining process windows and product quality. By doing so, manufacturers can achieve better results, reduce waste, and ensure the reliability of new materials in automotive applications.
Kenney, J. Andy, Delgado, Roberto, Hossain, Arif, Ng, Sze-Sze, Thomas, Ryan, Chyasnavichyus, Marius, Tsang, Chi-Wei, Hwang, Margaret, Wu, Lance, Dietsche, Laura, Mcmichael, Jonathan, Raines, Kevin, Nelson, Grant
Numerical Investigation on Behaviors of Under-Expanded Hydrogen Jets: Influence of Straight Nozzle Geometry2025-01-84594/1/2025
In internal combustion engines, hydrogen is considered as one of the most promising alternatives to replace fossil fuels and reduce CO2 emissions. In such a context, traditional injectors for hydrocarbon fuels are currently being tailored to be used with hydrogen, or a single-hole/multi-hole cap mounted at the injector tip was used to obtain better mixing and air utilization. Nevertheless, the hydrogen injection can be accompanied by the formation of highly under-expanded jets and will significantly influence the downstream mixing process. Therefore, in order to achieve a better understanding on hydrogen-air mixture, this work aims to numerically investigate the influence of the nozzle geometry on the jet behaviors in the near nozzle region. The nozzle diameter ranges from 0.1 mm to 2.0 mm and the nozzle length is from 1mm to 2mm. The injection pressure ranges from 10 bar to 70 bar. As the boundary condition varied, differences in both the internal flow of different nozzle structures and the development of external jets through these nozzles were found, as well as the close connection between the internal flow and the external under-expanded jet development. This work will provide a theoretical basis for the design of hydrogen injectors.
Jiahui, Lang, Li, Yanfei, Xu, Lubing, Xiao, Ma, Shuai, Shijin
Investigation of Dimethyl Ether Injection Profiles in High-Pressure Direct Injection System2025-01-84644/1/2025
The majority of transportation systems continue to rely on internal combustion engines powered by fossil fuels. Heavy-duty applications, in particular, depend on diesel engines due to their high brake efficiency, power density, and robustness. Despite significant advancements in diesel engine technology that have reduced emissions and improved efficiency, complex and costly after-treatment systems remain necessary to meet the stringent emission regulations. Dimethyl ether (DME), which can be produced from various renewable feedstocks and possesses high chemical reactivity, is a promising alternative for heavy-duty applications, particularly in compression ignition direct injection engines. Its high reactivity, volatility, and oxygenated composition offer significant potential to address emission challenges while reducing reliance on after-treatment systems. However, DME’s lower energy density requires adjustments in injection parameters (such as injection pressure and duration) or modifications to the injector geometry to match the energy levels of diesel fuels. Although previous studies have explored adjustments like increasing injection pressure and duration to compensate for DME’s lower energy density, the impact of nozzle diameter on the rate of injection profile and spray morphology remains unclear. This study investigated the injection characteristics of DME in a high-pressure direct injection system. The rate of injection profile was measured using a custom-designed long tube platform based on the Bosch method. The results from the Bosch method showed strong consistency with those obtained from a commercial injection test bench based on Zeuch method. Additionally, the rate of injection profiles for two different nozzle diameters were measured to assess the impact of nozzle size on the rate of injection profiles. The effects of increased nozzle diameter on spray morphology were examined using high-speed photography.
Cong, Binghao, Leblanc, Simon, Tjong, Jimi, Ting, David, Yu, Xiao, Zheng, Ming
A Hybrid Algorithm for Optimizing Machining and Spraying Parameters in MQL-Turning of Inconel 800H2025-28-00422/7/2025
Inconel 800H superalloy is a difficult-to-turn material. This study aims to achieve optimal machining results, including reduced cutting force, improved surface roughness, and minimized residual stress, by optimizing input machining parameters like cutting speed, feed rate, spraying angle, and nozzle distance on Inconel 800H. The Taguchi L27 method is utilized for experimentation, while the Harris hawks optimizer (HHO) is applied in a multi-objective optimization model. Additionally, the Technique for Order of Preference by Similarity to the Ideal Solution (TOPSIS) is used to identify the optimal input parameters. Five distinct weight schemes were employed, including the Analytic Hierarchy Process (AHP), the Entropy weight method, Criteria Importance through Inter-Criteria Correlation (CRITIC), Grey relational analysis (GRA), and Principal Component Analysis (PCA) to determine response weights. The analysis revealed that the primary factor affecting all measured weights is the feed rate, with the nozzle angle closely followed, as determined by ANOVA, based on a comprehensive evaluation of all output responses. Notable enhancement in MQL turning when contrasted with dry turning, reflected in the output responses of roughness, force, and residual stress at 72.62%, 8.08%, and 19.32%, respectively, using AHP-TOPSIS compared to AHP-HHO.
Kannan, Venkatesan, Mokshajna, Kotha
Aerospace & Defense Technology: February 202525AERP022/6/2025
The Art of Reverse Engineering Yesteryear for Aerospace and Defense Data Storage Drives Manufacturing Spotlight: Machining Complex Parts and Materials for Space Flight and Exploration Notre Dame's New Boundary Breaking Mach 10 Quiet Wind Tunnel Shape-Shifting Antenna Poised to Transform Communications British Army Completes First Test of Drone Killing Radio Frequency Weapon A Swarm of Sensors, Rovers and Astronauts Explore the 'Moon' Researchers at the German Aerospace Center have developed a new approach to networked communications that could theoretically occur on the Moon or in environments on Earth where conventional communications are unavailable. Army Researchers Examine Nanotechnology for Climate Solutions Army scientists are joining forces with experts from across the nation to tackle the climate crisis using the power of nanotechnology Airman Brings Fuel Sampling Innovation to Eglin, Possibly Air Force The U.S. Air Force is testing a new prototype single point nozzle adapter that drastically reduces the time required for jet fuel quality sampling. Atomic Fountain for Research in Quantum Sensing Nears Completion of First Phase Naval Postgraduate School (NPS) physicists are on track to bring the institution's new atomic fountain online - the largest of its kind in the world - for applications to quantum sensing experiments in precise navigation and timekeeping. Revolutionizing the Waves: A Breakthrough in Surf Observation Technology for Sailors and Marines A team of Army and Navy scientists and engineers have developed a real-time sensing technology for deciding whether conditions are suitable for landing troops on enemy shores.
Research on Cavitation Flow Characteristics in Thermal Sensitive Future Fuel Nozzles2025-01-71081/31/2025
In order to clarify the cavitation flow characteristics in future fuel nozzles and guide the design of new nozzle structural blocks, this research work was carried out in both experimental and simulation aspects. In the experiment, it was found that under high injection pressure, methanol showed more severe cavitation than diesel. By adding frosted glass, a better light effect was achieved in the nozzle hole. It was found that the front section of the nozzle had geometric induced cavitation, the middle section had vortex cavitation, and the rear section had expanded vortex cavitation. Traditional numerical models cannot accurately calculate this phenomenon. To this end, the two-phase physical properties that change with temperature and pressure were constructed, combined with multiphase, turbulence, and energy models, CFD calculations were performed and verified based on visualization results. On this basis, a comparative analysis of the flow mechanism in future fuel and traditional diesel fuel nozzles was carried out, and the influence of injection pressure, fuel temperature, and nozzle structure on the flow characteristics in future fuel nozzles was studied. The relevant research conclusions provide theoretical guidance for the design of future fuel systems.
Zhang, Hanwen, Fan, Liyun, Li, Bo, Wei, Yunpeng, Zhang, Dianhao
Parametric Study of Enhanced Combustion Based on Nozzle Protrusion and Spray Angle of High-Power-Density Diesel Engine2024-01-428011/5/2024
The goal of high-power-density diesel engines is to enhance combustion efficiency and reduce fuel consumption, which has always been the focus of diesel engines in addressing energy and environmental challenges. A high injection pressure allows a significant amount of fuel to be injected in a short period. However, this also increases the risk of spray impingement in small-bore diesel engines. Therefore, optimizing the nozzle protrusion and spray angle to achieve appropriate spray and flame extension is crucial for complete combustion. First, the flame development characteristics of nozzle protrusions ranging from 2 to 5.5 mm were analyzed with fixed spray angles and spray impingement points, respectively. The spray impingement point was optimized by comparing the combustion quality at different spray angles. Finally, the matching of the nozzle protrusion was performed based on the corrected points. The results indicate that the flames in small-bore diesel engines possess significant kinetic energy after impingement. During its development from the piston to the cylinder head, premixed combustion remained dominant. Longer spray penetration promotes the formation of a larger flame surface, and the combination of different nozzle protrusions and spray angles can alter the adhesion of combustibles along the wall. A smaller spray angle and shorter nozzle protrusion can enhance the thermal efficiency by 3.7% and reduce the heat loss by 0.2%, respectively. This research provides valuable insights for optimizing the design of fuel injection parameters and combustion chamber shapes for small-bore diesel engines.
Liu, Long, Wang, Xinhao, Niu, Xiaoxiao, Wang, Yang
3D-Printed Engines Propel Next Industrial RevolutionTBMG-5197611/5/2024
In the fall of 2023, NASA hot fire tested an aluminum-based, 3D-printed rocket engine nozzle. What made the event remarkable is that aluminum isn’t typically used for additive manufacturing because the process causes it to crack, and it isn’t used in rocket engines due to its low melting point. Yet the test was a success.
Comparison of Different Injector Nozzles for the Utilization of Polyoxymethylene Dimethyl Ethers2024-01-429711/5/2024
Oxygenated substances are a promising approach in the field of alternative fuels. A current example of such a fuel are Polyoxymethylene Dimethyl Ethers (OME). With their physical and chemical properties, alternative fuels like OME pose new challenges for diesel engine injection systems. As the heating value is low compared to conventional Diesel fuel, measures must be taken to increase the amount of fuel injected. Possible solutions include increasing the nozzle hole diameter, the injection pressure, and the number of nozzle holes. All mentioned adaptions have an influence on the mixture formation and make it necessary to examine the injection process in detail also with regard to phenomena such as cavitation. In this study, three passenger car Diesel injector nozzles are compared, two of which are adapted in terms of nozzle hole diameter (increase by 20%) and number of nozzle holes (increase from 8 to 12) in order to increase the mass flow rate of fuel to the required elevated level. The injectors are examined under various operating conditions using the optical measurement methods of Mie scattering and Schlieren photography in a constantly purged high-temperature and -pressure injection chamber. Mixture formation is analyzed on basis of the measurement results for different fuels and blends. Results show that adaptions such as increasing the nozzle hole diameter or the number of nozzle holes are unavoidable, as increasing the injection pressure alone cannot realistically compensate for the lower calorific value of OME. In addition, strong cavitation can be observed without adjustments to the nozzle holes. With the adapted nozzles, increasing the nozzle hole diameter leads to an increase in the local fuel/air ratio, while increasing the number of nozzle holes leads to a decrease.
Riess, Sebastian, Fuchs, Thorsten, Strauß, Lukas, Günthner, Michael, Wensing, Michael
Numerical Analysis of the Expansion–Deflection Dual-Bell Nozzle Performance2024-01-60038/23/2024
The objective of this paper is to identify the optimum supersonic Mach number for expansion–deflection dual-bell nozzle. The numerical analysis is carried for expansion–deflection dual-bell nozzle (EDDBN) with different free stream conditions. Numerical study observes that the transition pressure ratio and Mach contours are studied through inside and outside of the nozzle. The results proved that increasing the Mach number leads to decrease in the static pressure as well as reduce the performance of EDDBN nozzle. The analysis was carried out for four different Mach number, out of which Mach number 1.2 provides the optimum results. In the present study, the influence of Mach number behavior affects the pressure and Mach configuration inside and outside of the EDDBN nozzle. This novel concept is used in supersonic vehicles for higher performances. Also, it provides a way to improve the existing nozzle design configuration.
Balaji, K., Kalekar, Yashdeep, Naik, Atharva, Walave, Gurudas, Charapalle, Samruddhi
Cavitation Phenomenon and Spray Atomization in Different Types of Diesel Engine Nozzles: A Systematic Review03-17-06-00427/13/2024
The high-pressure common rail fuel injection system for diesel engines is one of the core technologies that need to be addressed in the automobile industry. The control of the internal flow in multi-hole injector nozzles is the key to achieve accurate control of the fuel injection and spray process. There are various types of research on cavitation phenomena currently conducted on various types of test benches, but there is no conclusive discussion. Therefore, it is to summarize these studies in order to identify the highlights of existing studies and point out their shortcomings. This article compares and analyzes the developing patterns of cavitation phenomena on four test benches through literature review and has obtained rich research data on these four types of nozzles, but they still have their own shortcomings at the same time, even with numerical simulation. Based on this, the article has conducted a detailed and critical discussion on the current research situation and completed a summary. Specifically, it mainly involves four geometry parameters, two dynamic factors, and three fuel physical property parameters. The discussion conducted can contribute to the future development of cavitation models, further improving the energy-saving and -reducing emission reduction of diesel engines.
Cao, Tianyi, Jin, Jianjiao, Qu, Yu Pu
An Approach to Design an Air–Liquid Supersonic Ejector for Producing Aerosol Spray2024-01-50686/25/2024
This study aims to design a supersonic ejector, referred to as a liquid spray gun, with a simple operating procedure for producing an aerosol spray with adjustable droplet size distributions. A CFD model was developed to determine the influence of nozzle exit position and the primary air pressure on the supersonic patterns formed within the ejectors, providing a valuable insight into their internal physics. Based on the single-phase numerical results, at an air primary pressure of 2 bar, the flow may not reach a choking condition, possibly resulting in unstable ejector operation. However, at pressures exceeding 5 bar, the jet patterns emerging from the primary nozzle cause flow separation or the formation of vortex rings. This phenomenon leads to a flow configuration comparable to the diameter of the mixing tube, thereby reducing the available area for entrainment of suction flow. The suitable ejector was identified with a nozzle exit position of 13 mm and a primary pressure ranging from 3 to 4 bar. Consequently, a high-speed imaging shadowgraph system was successfully developed to experimentally analyze the water spray pattern within the designed ejector. The experimental results indicate that the ejector performs effectively under different operating conditions, producing a fine water spray with predominantly small droplet sizes below 30 μm when the air pressure is within the range of 3 to 4 bar. These results highlight the capability of the supersonic ejector as a spray gun for generating aerosols suitable for contaminated surface cleaning and other relevant applications.
Nguyen, Quan Q., Phung, Duoc V., Nguyen, Kien T., Pham, Hoang Q., Pham, Thin V., Vu, Tuan N., Pham, Phuong X., Duong, Cuong Q.
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
Influences of High-Pressure Pump and Injector Nozzle Geometry on Hydraulics Characteristics of a Mechanical Diesel Direct-Injection System2024-01-50616/4/2024
The geometry of high-pressure pump and injector nozzles crucially influences hydraulic behaviors (e.g., 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 fuel atomization, fuel–air mixing, combustion quality, and the formation of emissions. The main geometry parameters such as plunger diameter and the number and diameter of nozzles lead to the system complexity, requiring careful analysis, design, and calibration. 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. Additionally, a model was developed using GT-Fuel package built within the GT-Suite of simulation tools 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 analyze the influence of each parameter or assess their overall impact. The results indicate that an increase in plunger diameter advances the start of injection (SOI). Furthermore, an increase in the number and/or diameter of nozzles results in a higher amount of fuel delivered per cycle. Overall, replacing an injection system with 10 mm plungers and injectors with 7 × 250 μm nozzles with one featuring 12 mm plungers and injectors having 8 × 300 μm nozzles can increase the fuel delivery by 1.85 fold. This approach could be useful for practical applications, including turbocharging 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.
Nguyen, Quan Q., Vu, Manh D., Phung, Duoc V., Nguyen, Kien T., Vu*, Tuan N., Pham, Phuong X.
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
The New China Automotive Technology and Research Center Aerodynamic-Acoustic and Climatic Wind Tunnels2024-01-25414/9/2024
The China Automotive Technology and Research Center (CATARC) has completed two new wind tunnels at its test centre in Tianjin, China: an aerodynamic/aeroacoustic wind tunnel (AAWT), and a climatic wind tunnel (CWT). The AAWT incorporates design features to provide both a very low fan power requirement and a very low background noise putting it amongst the quietest in the automotive world. These features are also combined with high flow quality, a full boundary layer control system with a 5-belt rolling road, an automated traversing system, and a complete acoustic measurement system including a 3-sided microphone array. The CWT, located in the same building as the AAWT, has a flexible nozzle to deliver 250 km/h with an 8.25 m2 nozzle, and 130 km/h with a 13.2 m2 nozzle. The temperature range of the CWT is -40 °C to +60 °C with a controlled humidity range of 5% to 95%. Additional integrated systems include a variable angle solar simulator array, and a rain and snow spray system. This paper provides descriptions of the AAWT and CWT facilities including their sub-systems. The aerodynamic and acoustic performance of the AAWT and the CWT are summarized. Comparisons to published data from comparable wind tunnels are included. In addition, flow uniformity measurements in the AAWT from multiple axial planes are shown together to indicate the development of the flow over the first half of the turntable region.
Waudby-Smith, Peter, Bender, Trevor, Sooriyakumaran, Christopher, Zhang, Yilun, Wang, Haiyang, Zhao, Feng, Fan, Guangjun, Sun, Jinhong, Liu, Xuelong
Optical Investigation of Lean Combustion Characteristics of Non-Uniform Distributed Orifice Passive Pre-Chamber on a High Compression Ratio GDI Engine2024-01-21014/9/2024
The passive pre-chamber (PC) is valued for its jet ignition (JI) and is suitable for wide use in the field of gasoline direct injection (GDI) for small passenger cars, which can improve the performance of lean combustion. However, the intake, exhaust, and ignition combustion stability of the engine at low speed is a shortcoming that has not been overcome. Changing the structural design to increase the fluidity of the main chamber (MC) and pre-chamber (PC) may reduce jet ignition performance, affecting engine dynamics. This investigation is based on non-uniformly nozzles distributed passive pre-chamber, which is adjusted according to the working medium exchange between PC and MC. The advantages and disadvantages of the ignition mode of PC and SI in the target engine speed range are compared through optical experiments on a small single-cylinder GDI engine. The results show that with the increase of λ from 1.0 to 1.6, the promotion effect of PCJI on dynamic performance gradually decreases, and it is beneficial for the λ=1.0 condition close to the stoichiometric combustion at low speed. However, not all pre-chambers can improve lean burn performance. In addition to many existing conclusions on structural design, the combustion performance is also closely related to the relative arrangement of PC and MC.
Tang, Yuanzhi, Lou, Diming, Fang, Liang, Fan, Benzheng, Wu, Xijiang, Wang, Zhiyu, Zhang, Yunhua, Tan, Piqiang, Hu, Zhiyuan
Development and optimization of jet impingement on dimpled plate for maximizing cooling performance of an inverter2024-01-22164/9/2024
A need to develop a cooling method with high cooling performance like jet impingement is increased as high power of an inverter is required. Jet Impingement on the dimpled plate would increase thermal performance than that of flat plate. Many previous researchers have dealt with the multi jet impingement on flat plate and some results of the study on dimpled plate evaluate the effect on heat transfer coefficients on several limited cases, making it difficult to apply them to inverter designs. Therefore, in this paper, heat transfer performance, pressure drop, and robustness at micro-scale of jet impingement on the dimpled plate were investigated in detail and the correlations of each performance were proposed. Finally, the optimal design was presented. The cooling performance was influenced by the jet array and the effect of depth and width of the dimples. The former can be expressed in terms of the Reynolds number, the ratio of height to nozzle diameter(H/D), the ratio of pitch to diameter(S/D). The latter can be expressed in terms of the ratio of dimple depth to dimple diameter(t/Dd) and the ratio of dimple width to pitch(SD/S). Although the heat transfer coefficient of the shallow dimple is larger than that of the deep dimple, the heat transfer coefficient decreases when the width of the dimple becomes too wide. The correlations were proposed and presented to the characteristics of heat transfer depending on jet array and the dimple. Uncertainty was introduced to evaluate the robustness. The optimal design was derived by swinging variables based on the correlations and considering the robustness of performance maximizing heat transfer under pressure drop below 300mbar. Compared to the base design, the thermal resistance of optimum design was improved by 6.0% from 0.2350K/W to 0.2210K/W. The correction-based optimization results were consistent with the 3D CFD results.
LEE, Hyeseung, Yang, Ilsuk, Jeong, Hojin, Park, Minkyu
Detailed Specification for Aircraft Pressure Refueling NozzleAS5877C (Current)4/1/2024
This SAE Aerospace Standard (AS) prescribes requirements for the various types of nozzles that are used for the refueling and defueling of aircraft fitted with pressure fuel servicing systems. It is to be used as a replacement for MIL-N-5877 and MS29520 and for all commercial applications.
AE-5C Aviation Ground Fueling Systems Committee
Computational Modelling of Hypersonic Nozzles: The Influence of Enthalpy on the Flow Thermochemistry2024-01-19353/5/2024
In this work, an investigation of the enthalpy effects on the thermochemical non-equilibrium in hypersonic nozzles is performed. Three different nozzles, with different geometries and stagnation enthalpy conditions are used in this study. The three cases, two of them with stagnation enthalpy conditions of 3.3 MJ/kg and 7.56 MJ/kg, use molecular nitrogen as the testing fluid and in the third case, corresponding to the higher enthalpy condition of 23.8 MJ/kg, the fluid is partially dissociated air composed by five neutral species (N2, O2, NO, N and O). A reliable numerical model, previously validated by the authors, using non-equilibrium Navier-Stokes-Fourier equations within a density-based algorithm is here employed in the OpenFOAM framework. After an estimation of the discretization uncertainties by using the Richardson extrapolation method and Roache’s Grid Convergence Index, the results are obtained by using a sufficient independent grid for each case. It was found that the nozzle with the higher non-equilibrium impact on the flow properties, was the one with the higher expansion ratio, with the difference between equilibrium and non-equilibrium of 17% for the Mach number, 35% for the static pressure and 38% for the static temperature. Using three different stagnation conditions, of 4.92 MJ/kg, 5.98 MJ/kg, and 7.56 MJ/kg, for that nozzle, it was revealed that the increasing of the stagnation enthalpy at the reservoir leads to an increment of the degree of non-equilibrium inside the nozzle, reaching its maximum at the nozzle exit. Increasing the stagnation enthalpy in 1.58 MJ/kg leads to an increment of the non-equilibrium degree in 3.4% for the Mach number, 5.5% for the static pressure and 6.6% for the static temperature.
Teixeira, Odelma, Pascoa, Jose
In-Cylinder Flow Characterization of a Hydrogen-Ammonia Fueled Rotary Engine2023-01-707312/31/2023
At present, the problem of global warming is becoming more and more serious, and the transformation of energy structure is very important. The rotary engine has the advantages of small size, high power-to-weight ratio, and high fuel adaptability, which makes it promising for application in the fields of new energy vehicle range extender and unmanned aerial vehicle. To this end, this paper proposes the idea of hydrogen/ammonia dual-fuel combination applied to rotary engine, using the experimentally verified three-dimensional simulation model of rotary engine, to study the process of hydrogen/ammonia rotary engine in-cylinder mixture formation under the direct-injection dilute combustion mode, and to analyze the impact of different dual-fuel injection strategies on the performance of rotary engine, and finds that delaying the moment of injection leads to the ammonia concentration in the middle and front of the combustion chamber; when the ammonia nozzle is located in the intake port, the effect of different ammonia injection moments on the hydrogen distribution is not significant, and the hydrogen distribution is basically the same, mainly in the middle and front part of the combustion chamber, and the ammonia is uniformly distributed in the combustion chamber; when the ammonia nozzle is located in the upper part of the cylinder block, with the delay of the ammonia injection moments, the distribution of hydrogen in the rear part of the combustion chamber is increased; when the ammonia nozzle is located in the lower part of the cylinder block, the effect of the ammonia injection on the distribution of hydrogen is not significant. In this paper, the in-cylinder flow process of hydrogen/ammonia fuel rotary engine is investigated, and the results can provide theoretical guidance and reference significance for the in-cylinder flow of hydrogen/ammonia fuel rotary engine.
Chen, Wei, Yang, Xu, Yu, Shiwu, Liu, Xu, He, Weibiao, Zuo, Qingsong
Non-Evaporating Kerosene Fuel Spray Tip Penetration: A Comparison between Phenomenological Models and Experiments2023-01-163510/31/2023
Interest in the use of kerosene fuel in diesel engines has garnered researchers’ attention in the past few years due to its improve premixed combustion and its ability to decrease soot emission. The potential of using kerosene in the design stage of a diesel engine is thus a great motivator to study fuel spray development and to evaluate known fuel spray tip correlations and models with respect to their predictive capability with such a fuel. Therefore, the present paper proposes to investigate the spray development of a multi-hole solenoid injector fueled with kerosene under non-evaporative conditions. Moreover, the experimental results are used to evaluate how different phenomenological models proposed in the literature for diesel fuel are able to predict kerosene spray tip penetration. The experimental test rig is composed of a constant-volume pressurized vessel and a camera allowing to visualize the liquid phase using a backlight illumination technique. The influence of the injection pressure is studied at 400, 800 and 1600 bar, while three different injection durations (0.5, 1, and 2 ms) and five ambient pressures (2.5, 5, 10, 15 and 20 bar) are investigated. The experimental results are presented using a nondimensional time and fuel spray tip penetration to facilitate the analysis. The results show, as expected, that increasing the injection pressure or decreasing the ambient pressure results in a faster fuel spray tip penetration. The models that are evaluated include a constant ambient density hypothesis formulation, a variable ambient density model and three empirical correlations. A comparison between the models and experimental results shows that low injection pressure and short injection duration are two conditions in which the models have difficulty to predict the fuel spray tip penetration. Overall, the best performance was offered by the variable density model, which predicted the experimental data well.
Billerot, Pierre-Lou, Tétrault, Pascal, Fleischmann, Antoine, Lemaire, Romain, Seers, Patrice
Experimental Investigation on Near-Nozzle and Macroscopic Structure of a Supercritical Fuel Injected into Subcritical Environment2023-01-163610/31/2023
The supercritical fluid combustion technology was regarded as an effective method to increase fuel gas mixing rate and performance. During the injection process, critical characteristics dominate the jet development to behave as different spray structure. Due to the limited researches about supercritical gasoline-like fuel injection characteristics, macroscopic and near-nozzle microscopic spray structures of supercritical n-heptane injected into atmosphere condition were observed and compared with the injection of cryogenic nitrogen in this work. A supercritical fuel injection device was designed able to heat the fuel temperature up to 773 K and maintain the fuel injection pressure stable at 4 MPa. Backlight illumination and schlieren imaging technologies were applied to capture the liquid and overall jet structure. The effect of initial fuel temperature on the spray structure was analyzed and some novel near-nozzle structures were also discussed. Results show that with the increase of initial fuel temperature, the jet behaves as narrow linear structure at first, and then transforms to gray mist along radial direction, and almost vanishes except for near-nozzle region at last. As for the microscopic spray structure, there is a closed shock structure near the nozzle. The axial distance of the Mach disk of the shock can be predicted by empirical correlations which are suitable for the ideal gas, but the radial distance of the Mach disk is larger than that of the ideal gas.
Liu, Rui, Huang, Li, Ni, Xinmin, Ju, Dehao, Yi, Ran, Ma, Yue
Simulation Study of the Effect of Nozzle Position and Hydrogen Injection Strategy on Hydrogen Engine Combustion Characteristic2023-01-701810/30/2023
Hydrogen energy is a kind of secondary energy with an abundant source, wide application, green, and is low-carbon, which is important for building a clean, low-carbon, safe, and efficient energy system and achieving the goal of carbon peaking and being carbon neutral. In this paper, the effect of nozzle position, hydrogen injection timing, and ignition timing on the in-cylinder combustion characteristics is investigated separately with the 13E hydrogen engine as the simulation object. The test results show that when the nozzle position is set in the middle of the intake and exhaust tracts (L2 and L3), the peak in-cylinder pressure is slightly higher than that of L1, but when the nozzle position is L2, the cylinder pressure curve is the smoothest, the peak exothermic rate is the lowest, and the peak cylinder temperature is the lowest. When the ignition timing is consistent, with the delay of hydrogen injection timing, the peak in-cylinder pressure decreases and the peak phase remains the same, the peak in-cylinder temperature and peak exothermic rate increase, and the peak phase is advanced; the stall period is the shortest when the hydrogen injection timing is 120°CA BTDC; and the combustion DOC is the most stalled when the hydrogen injection timing is 160°CA BTDC. When the hydrogen injection timing is consistent with the advance of the ignition timing, the peak of in-cylinder pressure and in-cylinder temperature increases, the stall period of in-cylinder combustion increases, the pre-burn period shortens, and the post-burn period shortens. When the ignition advance angle is 15°CA BTDC, the lowest heat release rate is 130 J/°CA, and when the ignition advance angle is 25°CA BTDC, the highest heat release rate is 208 J/°CA.
Tan, Piqiang, Tian, Yuan, Lou, Diming, Zhang, Yunhua, Liu, Dengcheng, Zhao, Keqin
Study on Novel Combustion Technologies to Achieve “High-heels” Heat Release Rate Profile in a Higher-compression-ratio Diesel Engine2023-32-00779/29/2023
For further increase in thermal efficiency of heavy-duty diesel engines, flexible regulation of the heat release rate (HRR) profile combined with higher compression ratio could have more rooms to improve indicated thermal efficiency by overcoming various drawbacks relevant to higher compression ratio. A new ideal HRR profile, which starts as a kind of delta shape to fulfil the isobaric cycle from top-dead-center (TDC) and is followed by the significant increase in HRR to reach the maximum cylinder pressure in the retarded timing, was proposed. We call it as ‘High-heels’ HRR profile from its two-step-increase delta shape. To confirm the potential of the ideal HRR profile by utilizing a single- cylinder heavy-duty diesel engine, a variable fuel injection rate equipment, novel combustion chamber designs, and an offset orifices nozzle were investigated as the technologies for modifying HRR profile. The experimental results confirmed slight improvement in the thermal efficiency from the baseline, even though the maximum HRR in the late part of combustion and indicated thermal efficiency have not achieved the target with the integrated technologies yet.
Uchida, Noboru, Watanabe, Kazumasa
Prediction of Natural Gas Wall-Impingement Spray Characteristics by ANN Model2023-32-00119/29/2023
In this study, the effect of injection pressure, impingement distance and angle, wall temperature on the macroscopic of wall impingement were investigated experimentally, predicted by using deep neural network in the MATLAB environment. With respect to obtaining data from experiments, input factors affecting impingement phenomena are trained, validated to develop model, which was applied to estimate output such as spray tip penetration and height. According to the results, the estimate parameters by coefficient of determination, root mean square error between 0.998 and 0.029. The ANN_GA model is found to be an effective tool to predict spray behaviors output with minimal experimentation.
Pham, Quangkhai, Choi, Byungchul, Park, Suhan
The influence of fluid properties on near nozzle sprays in clean and fouled GDI injectors2023-32-00549/29/2023
Physical fluid properties and GDI injector deposits are known to impact the internal nozzle flow and external spray morphology. Furthermore, deposits can affect injector calibration and damage the delicate mixing and combustion processes. Despite this, there is a lack of experimental data demonstrating the discrete influence of fluid properties and how this influence evolves with the formation of injector deposits. This article aims to further the existing knowledge on the effect of fluid properties such as density, kinematic viscosity and surface tension, along with distillation on fuel spray characteristics and provide insight into how sprays change over the lifetime of GDI injectors due to fouling. In this investigation, four gasoline fuels with varying concentrations of ethanol and typical GDI additive, including one being representative of a renewable gasoline formulation, were used with clean and fouled multi-hole GDI fuel injectors. A low-pressure constant-volume chamber was used to produce a controlled inert atmosphere at various ambient and injection conditions. Shadowgraph images were recorded using two high- speed cameras at the micro and macro scales to simultaneously visualise the fluid dynamic processes in the near nozzle and downstream regions. Image analysis demonstrated that fouling had a significant impact on the spray angle. Standard error of the mean was used to determine the repeatability of the measurements taken, and it was found that the spray width at the nozzle tip had a very low standard error. In contrast, a comparatively high standard error was calculated for spray dispersion angle exhibited for the fouled and clean injectors. Due to high repeatability on spray width measurements, positive correlations were found between the spray width at the nozzle tip and initial boiling point, surface tension and kinematic viscosity, and negative correlations with density and final boiling point.
Gander, Alex, de Sercey, Guillaume, Crua, Cyril
Impact of Passive Pre-Chamber Nozzle Diameter on Jet Formation Patterns and Dilution Tolerance in a Constant-Volume Optical Engine03-17-02-00139/11/2023
Pre-chamber jet ignition technologies have been garnering significant interest in the internal combustion engine field, given their potential to deliver shorter burn durations, increased combustion stability, and improved dilution tolerance. However, a clear understanding of the relationship between pre-chamber geometry, operating condition, jet formation, and engine performance in light-duty gasoline injection engines remains under-explored. Moreover, research specifically focusing on high dilution levels and passive pre-chambers with optical accessibility is notably scarce. This study serves to bridge these knowledge gaps by examining the influence of passive pre-chamber nozzle diameter and dilution level on jet formation and engine performance. Utilizing a modified constant-volume gasoline direct injection engine with an optically accessible piston, we tested three passive pre-chambers with nozzle diameters of 1.2, 1.4, and 1.6 mm, while nitrogen dilution varied from 0 to 20%. With the help of high-speed imaging, we captured pre-chamber jet formations and subsequent flame propagation within the main chamber. Our novel findings reveal that asymmetric temporal and spatial jet formation patterns arising from pre-chambers significantly impact engine performance. The larger-nozzle-diameter pre-chambers exhibited the least variation in jet formation due to their improved scavenging and main mixture filling processes, but had the slowest jet velocity and lowest jet penetration depth. At no dilution condition, the 1.2 mm-PC demonstrated superior performance attributed to higher pressure build-up in the pre-chamber, resulting in accelerated jet velocity and increased jet penetration depth. However, at high dilution condition, the 1.6 mm-PC performed better, highlighting the importance of scavenging and symmetry jet formation. This study emphasizes the importance of carefully selecting the pre-chamber nozzle diameter, based on the engine’s operating conditions, to achieve an optimal and balanced configuration that can improve both jet formation and jet characteristics, as well as scavenging.
Lee, Dong Eun, Iyer, Claudia, Wooldridge, Steven, Qiao, Li, Yi, Jianwen J.
Gas-Dynamic Interactions between Pre-Chamber and Main Chamber in Passive Pre-Chamber Ignition Gasoline Engines03-17-01-00088/30/2023
Pre-chamber turbulent jet ignition (TJI) is a method of generating distributed ignition sites through multiple high-speed turbulent jets in order to achieve an enhanced burn rate in the engine cylinder when compared to conventional spark plug ignition. To study the gas-dynamic interactions between the two chambers in a gasoline engine, a three-dimensional numerical model was developed using the commercial CFD code CONVERGE. The geometry and parameters of the engine used were based on a modified turbocharged GM four-cylinder 2.0 L GDI gasoline engine. Pre-chambers with nozzle diameters of 0.75 mm and 1.5 mm were used to investigate the effect of pre-chamber geometry on pre-chamber charging, combustion, and jet formation. The local developments of gas temperature and velocity were captured by adaptive mesh refinement, while the turbulence was resolved with the k-epsilon model of the Reynolds averaged Navier–Stokes (RANS) equations. The combustion process was modeled with the extended coherent flamelet model (ECFM). Data from engine experiments were compared with the computed main chamber pressures and heat release rates, and the results show good consistency with the model calculations. The scavenging and air–fuel equivalence ratio (λ) distribution of the pre-chambers improved with the larger nozzle, while the smaller nozzle generated jets with higher velocity, greater turbulence kinetic energy, and longer penetration length. Moreover, after the primary jet formation, secondary pre-chamber charging, combustion, and secondary jet formation were observed.
Yu, Tianxiao, Lee, Dong Eun, Gore, Jay P., Qiao, Li
Additional Comparison of Ice Shapes on Full-Chord and Truncated Swept Wing Models from January 20222023-01-13876/15/2023
A research program was conducted to evaluate the effectiveness of icing tunnel hybrid model design. A hybrid design is where the full-scale leading edge of a wing section is maintained only to a certain percentage of the local chord, while the aft section of the model is redesigned into a shortened or truncated planform. An initial study was conducted in 2020 where the ice shape geometries on a full-chord length version of the swept CRM65 wing model were compared to those from the hybrid version of CRM65 that were obtained in the NASA Icing Research Tunnel in 2015. The results were reported in a 2021 paper. For most test conditions, the overall size and shape of the ice shapes compared well. However, the ice shapes from the full-chord model were generally slightly smaller than those from the hybrid model. A follow-on test was conducted in 2022 and obtained ice shapes on both full-chord and hybrid wing models during the same test campaign to eliminate the differences in the tunnel spray nozzle configuration and calibration as a cause for the differences observed during the previous investigation. The ice shapes obtained on the full-chord model compared much better to those obtained on the hybrid model during the 2022 test, with nearly identical cross sections and ice mass values generally within 5%.
Lee, Sam, Broeren, Andy
Monitoring Melting Ice Formations in Aircraft Fuel Tank by Acoustic Emission2023-01-14376/15/2023
Considerable amounts of water accumulate in aircraft fuel tanks due to condensation of vapor during flight or directly during fueling with contaminated kerosene. This can result in a misreading of the fuel meters. In certain aircraft types, ice blocks resulting from the low temperatures at high altitude flights or in winter time can even interfere with the nozzles of the fuel supply pipes from the tanks to the engines. Therefore, as part of the maintenance operations, water has to be drained in certain intervals ensuring that no remaining ice is present. In the absence of an established method for determining residual ice blocks inside, the aircraft operator has to wait long enough, in some cases too long, to start the draining procedure, leading potentially to an unnecessary long ground time. A promising technology to determine melting ice uses acoustic signals generated and emitted during ice melting. With acoustic emissions, mainly situated in the ultrasonic frequency range, a very high number of events can be recorded to characterize stress relaxation processes that occur during conversions from ice to water. In the present paper, in addition to the case of the fuel tank, the icing of a fuselage panel is also considered. The results obtained provide evidence that it is possible to determine the moment when all ice has melted. However, it is not possible to give exact figures on the amount of ice remaining or melted, which is not a limitation in practice.
Pfeiffer, Helge, Reynaert, Johan, Seveno, David, Jordaens, Pieter-Jan, Ceyhan, Ozlem, Wevers, Martine
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