Browse Topic: Two stroke engines

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Assessment of E-Fuels Applicability as Gasoline Replacement in a Small Two-Stroke Engine2025-32-005811/03/2025
The push for reducing greenhouse gas emissions has extended to various sectors, including outdoor power equipment. While electrification is a promising solution for low-power gardening tools, the substitution of small two-stroke engines becomes critical for applications requiring higher power and range. Biofuels and e-fuels produced from renewable sources present a viable short-term alternative, leveraging existing engine technologies to minimize dependence on fossil fuels. However, the ability of current engines to operate with these fuels while maintaining performance and emission levels without modifications requires thorough evaluation. This study investigates the feasibility of using e-fuels as sustainable alternatives to gasoline in small two-stroke engines. Preliminary computational fluid dynamics (CFD) simulations were conducted to evaluate the performance of the e-fuel after defining a proper fuel surrogate. Experimental tests were then carried out to assess combustion
Breda, Sebastiano, Fontanesi, Stefano, Merolla, Santo, Gagliardi, Vincenzo, Cicalese, Giuseppe, Pati, Matteo, Dalseno, Luca, Kuschel, Mario
Clean Cuts, Clear Conscience: Advanced Engines, Optimized Tools, Eco-Friendly Fuels2025-32-008711/03/2025
Handheld outdoor power equipment is utilized globally to shape and maintain the environment, serving as daily assistants in forestry under demanding conditions. In the power tool sector, the transition from petrol to battery-powered products is already well underway, particularly for consumer applications. However, internal combustion engines will continue to be indispensable for professional users of power tools, who place the highest demands on their equipment in terms of performance and energy density. These power tools are often used in remote locations and thus far away from a possible charging infrastructure. To contribute to climate protection, biofuels and RFNBOs are crucial. The continuous optimization of engine technology and its overall system, including cutting tools (such as saw chains and cutting wheels), is a key development goal for STIHL. The optimized interaction between the saw chain, guide bar, and power train is necessary for efficient work progress and ergonomic
Beck, Kai W., Maier, Georg, Müller, Matthias, Lux, Thomas, Kölmel, Armin, Lochmann, Holger, Melder, Jens
Performance Prediction of a Two-Stroke Aviation S.I. Engine by Means 0D/1D Thermo-Fluid Dynamic Simulation Code2025-32-002611/03/2025
Two-stroke engines represent an attractive solution for aviation industry applications (UAVs, VTOL aircraft, and ultralight aircraft) due to their compact size, high power-to-weight ratio, reduced number of moving parts, and the ability to operate with different fuels. This work presents a 0D/1D methodology for simulating the gas exchange, combustion, and unsteady flow of a two-stroke aviation engine. The scavenging and combustion processes, as well as the unsteady flow within the induction and exhaust systems, are investigated using a 0D/1D modeling approach. This study is motivated by the need to assess the accuracy of such models in predicting engine performance. For this purpose, the thermo-fluid dynamic code GASDYN has been applied and enhanced. The proposed 0D model is embedded into a 1D fluid-dynamic code for simulating the entire engine system. To characterize the baseline configuration, which includes tangential ports that facilitate a loop-scavenging process, computed results
Cerri, Tarcisio, Giussani, Alessandro, Lucchini, Tommaso, Marinoni, Andrea, Montenegro, Gianluca, Onorati, Angelo
Study of Combustion Characteristics of a Two-Stroke Opposed Piston Engine using Low-Octane Fuels2025-32-002811/03/2025
Various fuels are being considered as the next generation of carbon neutral fuels, including methanol, ethanol, and SAF. These have widely different ignition properties. Methanol and ethanol are high-octane fuels, so there are no major problems with their use in gasoline engines. However, SAF is a hydrocarbon with a large molecular weight, so it has a fundamentally low octane rating and is not easy to use in SI engines. In order to put carbon-neutral fuels of various properties into practical use, it is effective to develop a technology that allows fuels with low octane to be operated in SI engines. Therefore, in this study, basic research was conducted on the combustion of fuels with low octane using PRF fuel in opposed-piston engines. Opposed piston engines are characterized by their light weight due to the absence of a cylinder head, low S/V ratio due to the ultra-long stroke, reduced cooling loss due to the long stroke, and reduced vibration due to the offsetting of the
Yamazaki, Yoshiaki, Okawara, Ikumi, Liu, Jinru, Iijima, Akira
Effect of Plasma-Assisted Ignition on Combustion and Emission Characteristics of Two Stroke Engines with Different Fuels2025-32-003011/03/2025
This study explores the effect of plasma-assisted ignition (PAI) on combustion stability and emissions in two-stroke spark-ignition engines. Two engine platforms were evaluated: a conventional single-cylinder two-stroke engine and a thermodynamically advanced opposed-piston two-stroke (OP2S) engine. The OP2S engine configuration offers reduced heat loss and higher power density due to its uniflow scavenging and favorable geometry, but suffers from high residual gas fraction, which increases ignition difficulty and combustion instability. To address this, nanosecond-pulsed PAI was applied in various spatial arrangements and discharge voltages, using both gasoline and a low-reactivity gasoline/DMC blend fuel. Spark ignition timing was held constant at the minimum advance for best torque across all tests. Combustion stability was assessed via indicated mean effective pressure (IMEP) and its coefficient of variation, while CO and HC emissions were measured as environmental indicators
Liu, Jinru, Yamazaki, Yoshiaki, Otaki, Yusuke, Kato, Hayato, Kobayashi, Daichi, Umegaki, Tetsuo, Asai, Tomohiko, Iijima, Akira
Development of Supercharged Direct-Injection Two Stroke Engine with Intake and Exhaust Valve for Series Hybrid (2nd Report)- To Realize Lean Burn -2025-32-002311/03/2025
The two-stroke engine, known for its small displacement and high performance, is space-efficient when installed in a vehicle. As such, incorporating two-stroke engines into HEVs is an effective way to reduce vehicle weight and optimize engine space. However, one downside is that the amount of unfired elements in the exhaust gas increases due to the air/fuel mixture being expelled into the exhaust system during the scavenging process. Moreover, combustion can become unstable due to the large volume of residual burned gases in the cylinder. To address these issues, we propose a two-stroke engine equipped with intake and exhaust valves that directly inject fuel into the cylinder. In our first report, we presented an engine design and method that enable high scavenging efficiency and stable combustion in a two-stroke engine [1]. In this second report, we share the results of our research aimed at improving fuel efficiency and achieving low emissions, all while maintaining the high
Sakurai, Yota, Hisano, Atsushi, Saitou, Masahito, Ichi, Satoaki
Computational Investigation on a Boosted Uniflow Scavenged Direct-Injection Combustion Engine (BUSDICE) with Alcohol Fuels2025-32-002711/03/2025
Alcohol fuels, produced from renewable energy sources, are considered a crucial solution for achieving life-cycle carbon neutrality in internal combustion engines. The Boosted Uniflow Scavenged Direct-Injection Combustion Engine (BUSDICE) exhibits significant potential for high thermal efficiency with an aggressive downsizing design. In this study, a computational investigation was carried out to assess the spray mixing and combustion characteristics of BUSDICE fuelled with methanol and ethanol, compared with gasoline, under a high-load condition. The injection duration of methanol and ethanol is significantly longer than that of iso-octane, leading to incomplete evaporation. The mixture exhibits an “outer-rich, central-lean” stratification pattern due to the short mixing time and swirl flow transportation for all three fuels. However, the prolonged injection of methanol induces stronger turbulence, which can enhance the local mixing. The spatial mixture stratification, particularly
Feng, Yizhuo, Lu, Enshen, Dong, Shuo, Keshtkar, Hossein, Wang, Xinyan, Zhao, Hua
Optimum Bore-to-Stroke Ratio for a Flathead Uniflow Two-Stroke SI Engine and its Impact on Different Fuels2025-32-002411/03/2025
This numerical study investigates a spark-ignited, two-stroke engine employing uniflow scavenging, flathead cylinder head design, and an exhaust valve system to identify the optimal bore-to-stroke (B/S) ratio for maximizing brake efficiency at fixed displacement. A single-cylinder prototype engine was constructed, and its experimental data validated a 1D GT-SUITE simulation model. This validated model was then utilized to simulate a full-scale, 1.5-liter displacement, horizontally opposed four-cylinder engine with supercharger-assisted boosting, intended for small aircraft propulsion. The simulations explored a range of B/S ratios from undersquare (0.7) to oversquare (1.5), maintaining a consistent brake power output of 60 kW at 3000 rpm and lambda 0.9. Results showed that increasing the B/S ratio enhanced brake efficiency from 26.0% at B/S=0.7 to 27.0% at B/S=1.5, largely due to reduced frictional losses attributed to shorter stroke and lower piston speeds, decreased heat transfer
Zanchin, Guilherme, Hausen, Roberto, Fagundez, Jean Lucca, Lanzanova, Thompson, Martins, Mario
Numerical Analysis of In-Nozzle Flow of Methanol Injectors for Large Marine Two-Stroke Engines2025-24-006909/07/2025
A statistical method for analyzing momentum deflection angles of fuel injectors based on Computational Fluid Dynamics (CFD) simulation of the internal nozzle flow is proposed. This method is especially relevant for large marine two stroke engines where the spray is often deflected due to an eccentric and asymmetric design of the internal injector geometry. Unsteady Reynolds-Averaged Navier-Stokes (URANS) CFD simulations are employed to analyze the internal flow of different cavitating injectors which have four and five nozzle holes, respectively, for a 50 cm bore and a 95 cm bore dual-fuel engine operating on methanol. The in-nozzle flow dynamics vary from one to another significantly. The use of the statistical analysis on the distribution of deflection angles at the fuel nozzle hole exit further assists at explaining differences in measured surface temperatures of the exhaust valve bottom and piston bowl. The corrected spray angles obtained from these in-nozzle simulations also serve
Quist, Nicolai Arent, Matlok, Simon, Pang, Kar Mun, Norman, Thomas Schaldemose, Mayer, Stefan, Walther, Jens Honoré
Integrated CFD-Experimental Methodology for Hydrogen-Fuelled Small Loop Scavenged Two-Stroke Engines2025-24-001409/07/2025
This paper presents an integrated methodology for the analysis of hydrogen-fueled 2-Stroke engines, combining experimental data, 1D-CFD simulations, and 3D-CFD combustion calculations. The proposed approach aims to enhance the understanding of scavenging, injection, and combustion processes in a 50 cm3 loop-scavenged engine with low-pressure direct hydrogen injection, experimentally studied on a test bench. The hydrogen-fueled engine was capable of achieving a maximum power output of 3.1 kW, using a slightly lean air-to-fuel ratio (lambda = 1.3). The maximum engine speed for stable combustion without knocking was achieved at wide open throttle at 7119 RPM. The developed 1D-CFD model, based on the engine layout at the test bench, was calibrated using average experimental data and specific full load operating points. 3D-CFD simulations were performed for one full load operating point, focusing on combustion dynamics and fuel distribution within the chamber, with combustion model
Caprioli, Stefano, Ferretti, Luca, Scrignoli, Francesco, Fiaschi, Matteo, D'Elia, Matteo, Oswald, Roland, Schoegl, Oliver, Nambully, Suresh Kumar, Rothbauer, Rainer, Mattarelli, Enrico, Kirchberger, Roland, Rinaldini, Carlo
Design of a New Overhead Two-Stroke Engine Braking Device and Braking Performance Evaluation2025-01-504807/01/2025
The braking safety of heavy-duty vehicles is widely concerned. This paper proposed a new purely mechanical transmitted OHC two-stroke braking device. The rigid–flexible coupled dynamics model of the device and the engine working process simulation model were used for joint simulation. The effects of CR lift, environmental conditions, compression ratio, and braking type on the engine braking performance were comprehensively evaluated. The result shows: good consistency of valve operation is obtained by using pure mechanical transmission. During the braking process, the in-cylinder pressure acts directly on the valves and significantly affects the maximum valve lift of the CR phase, therefore excessive in-cylinder pressure will reduce the reliability of the braking device. When the CR lift increases from 1.9 to 2.8 mm, the braking power per liter increases at low altitude, but first increases and then decreases at high altitude. The decrease in engine speed and compression ratio as well
Cui, Jingchen, Wang, Bing, Tian, Hua, Tian, Jiangping, Long, Wuqiang
Effect of Ignition Condition and Fuel Octane Number on Knock Intensity in a Small 2-Stroke Engine2025-01-021106/16/2025
Internal combustion engines (ICEs) remain widely used in automotive transportation for their high energy storage system efficiency and economic benefits. The 4-stroke engine has dominated all other forms to date, because the Otto cycle is relatively simple to understand. However, the significant benefits such as less pumping work and friction, lighter construction of 2-stroke engine, are attractive for applications that prioritize the simplicity and power density as well as meet the emission regulations. The disadvantages of the 2-stroke engine are mainly caused by the lack of sufficient scavenging process. Also, the overlap of the intake and exhaust phases results in charge short-circuiting, more fuel consumption and high unburned hydrocarbon emissions. For these reasons, it is difficult for 2-stroke engines to achieve stoichiometric combustion, making them incompatible with three-way catalyst to control emissions. The residual exhaust gas in the cylinder makes the spark ignition
Liu, Jinru, Yamazaki, Yoshiaki, Otaki, Yusuke, Kato, Hayato, Yokota, Takumi, Iijima, Akira
Two-Stroke-Cycle Engine Oil Fluidity/Miscibility ClassificationJ1536_202505 (Current)05/16/2025
This SAE Recommended Practice is intended for use by engine manufacturers in determining the Fluidity/Miscibility Grades to be recommended for use in their engines and by oil marketers in formulating and labeling their products.
Fuels and Lubricants TC 1 Engine Lubrication
Basic Investigation of Thermodynamic Effects on a Hydrogen Two-Stroke Engine2024-32-003904/18/2025
The spark ignited two-stroke engine, as a cost-efficient power unit with low maintenance demand, is used millionfold for the propulsion of hand-held application, motorcycles, scooters, boats and others. The outstanding power to weight ratio is the key advantage for two-stroke engines. However, poor exhaust emissions, caused by high scavenge losses, especially on port controlled two-stroke engines, and a low efficiency are disadvantages of this combustion process. Under the aspect of increasing environment- and health awareness, the two-stroke technology driven with fossil resources, shows no future advantage. The anthropogenic climate change force for sustainable development of combustion engines whereby reduction of fuel consumption or usage of alternative fuels is an important factor. Best way of a decarbonization to fulfil future climate goals is the utilization of non-carbon fuels. In this field of fuels, hydrogen, with its high energy content and close inexhaustible availability
Yasuda, Terutaka, Oswald, Roland, Kirchberger, Roland
Enhancements in Hydrogen Low Pressure Injection on Small Two-Stroke Engines2024-32-004704/18/2025
The use of small 2-stroke crankcase scavenged engines running on hydrogen is very attractive for low power rates, when low cost and compact dimensions are the fundamental design constraints. However, achieving optimal performance with hydrogen fuel presents challenges, including uneven air-fuel mixtures, fuel losses, and crankcase backfiring. This research focuses on a small 50cc 2-stroke loop-scavenged engine equipped with a patented Low-Pressure Direct Injection (LPDI) system, modified for hydrogen use. Experimental results demonstrate performance comparable to the gasoline counterpart, but further optimizations are needed. Consequently, CFD-3D simulations are employed to analyses the injection process and guide engine development. The numerical analysis focuses on a fixed operating condition: 6000 rpm, Wide Open Throttle (WOT), with a slightly lean mixture and injection pressure fixed at 5 bar. A numerical model of the entire engine is set up with the primary objective of improving
Caprioli, Stefano, Schoegl, Oliver, Oswald, Roland, Kirchberger, Roland, Mattarelli, Enrico, Rinaldini, Carlo Alberto
Research on Basic Characteristics of a Two-Stroke Opposed Piston Engine2024-32-011204/18/2025
This study investigated the performance characteristics of a two-stroke opposed piston engine that is capable of constantly operating with high power output and high efficiency. An investigation was also made of the performance obtained by applying a pseudo uniflow condition as a measure against large hydrocarbon (HC) emissions owing to blow-by of unburned mixture, which is an issue of two-stroke engines. The test engine had a displacement of 127 cm3 and a bore and stroke of 48 x 70 mm. One-point and dual-point ignition systems were used, and regular gasoline was supplied as the test fuel using a carburetor-based fueling system. Experiments were conducted at engine speeds of 1500 and 3000 rpm at ignition timings of 45 deg. and 35 deg. before top dead center. The results showed that large quantities of HC emissions were emitted because stable combustion was not achieved. This revealed that a stronger uniflow condition must be applied as a countermeasure rather than a simple pseudo
Fukushima, Shumpei, Uehara, Ryota, Hayashi, Yoshiaki, Igarashi, Ryo, Tokita, Kazuho, Iijima, Akira
Achieving Ultra-Low NO x and Meeting Full Useful Life Requirement for CARB 2027 NO x and GHG 2027 Phase 2 CO 2 Regulation w/Opposed Piston 2-Stroke Engine and a Conventional ATS2025-01-839104/01/2025
Internal combustion engines are expected to continue to play an important on-going role in the future of transportation, particularly in long haul transit and off-road applications. Substantially reducing criteria emissions of heavy-duty (HD) commercial vehicle engines while also reducing fuel consumption is the quickest way to achieve more sustainable transportation. The opposed-piston (OP) engine developed by Achates Power has demonstrated the ability to meet the most stringent ultralow NOx emissions requirements using only a conventional, underfloor aftertreatment system, offering reduced cost, complexity and compliance risk compared to other diesel engines. This paper is focused on the measurement results of Achates Power heavy-duty engine achieving CARB proposed ultralow NOx emission for 2027 and 2031+ full useful life requirements while also meeting the EPA Greenhouse Gas (GHG) Phase 2 limits with a conventional aftertreatment system (ATS), which was aged to 435k, 600k and 800k
Kale, Vaibhav, Bako, Zoltan
Experimental Study on Combustion and Emission Characteristics of a Two-Stroke Engine applying PODE/Methanol Blends Direct Injection2025-01-711201/31/2025
In order to realize the Paris Agreement, which aims to strengthen the global response to climate change, conventional internal combustion engines (ICE) need to contribute to reducing carbon emissions and improving thermal efficiency. More importantly, in the face of energy shortages, it is urgent to search for sustainable fuels. Poly-oxymethylene dimethyl ethers (PODE) and methanol are both regard as important low-carbon, alternative fuels due to their high oxygen content. Using PODE can overcome the characteristics of methanol as a low-reactivity fuel with a low cetane number and poor ignition properties. In this study, the combustion and emission characteristics of PODE/methanol blends were investigated in a two-stroke direct injection engine. Firstly, the performance of the engine under pure PODE (P100) and PODE/methanol blends (P50) was compared. The results show that at BMEP of 0.31 MPa and injection timing of -8°CA ATDE, P50 blends have lower CO2, CO, NOX and THC emissions than
Dong, Pengbo, Sun, Zhuohan, Wang, Qingyang, Wang, Yang, Cui, Jingchen, Zhang, Zhenxian, Long, Wuqiang
Lubricants for Two-Stroke-Cycle Gasoline EnginesJ1510_202501 (Current)01/21/2025
The information in this SAE Recommended Practice has been compiled by Technical Committee 1 (Engine Lubrication) of the SAE Fuels and Lubricants Division. The intent is to provide those concerned with the design and maintenance of two-stroke-cycle engines with a better understanding of the properties of two-stroke-cycle lubricants. Reference is also made to test procedures which may be used to measure the chemical and physical characteristics of these lubricants.
Fuels and Lubricants TC 1 Engine Lubrication
A Computational Study of Hydrogen Direct Injection Using a Pre-Chamber in an Opposed-Piston Engine2024-01-301007/02/2024
Combustion characteristics of a hydrogen (H2) direct-injected (DI) pre-chamber (PC)-assisted opposed piston two-stroke (OP2S) engine are investigated by 3D computational fluid dynamics (CFD) simulations. The architecture of the OP2S engine has potential features for reducing wall heat losses, as the DI H2 jets are not directed towards the piston face. To overcome the high resistance to autoignition of H2, a PC technology was implemented in order to enhance the ignition of the mixture by the multiple hot reactive jets. To further investigate the interaction between the H2 plume and the chamber walls, three different piston bowl designs were evaluated and ranked based on a merit function. For the cases under study, the flat piston design was found to be most favorable (compared to the narrow and wide pistons) due to its reduced surface area for lower wall heat losses. The results also showcase that a co-optimization approach considering various parameters is an effective strategy to
Menaca, Rafael, Moreno Cabezas, Kevin, Shakeel, Mohammad Raghib, Vorraro, Giovanni, Turner, James W. G., Im, Hong G.
Application of MAN Loop Scavenging in a 125 cc Two-Stroke Racing EngineSAE-PP-0039505/08/2024
The use of MAN-type loop scavenging port arrangements in a 125 cc two-stroke racing engi-ne is being investigated. These make it possible to provide larger cross-sections for the trans-fer ports, but at the expense of the exhaust port cross-section. The investigation is carried out using 1D calculations with GT-Suite. It is shown that significantly higher maximum outputs are possible in this way. However, this requires large exhaust widths, as otherwise the exhaust port is too small and the advantage of the larger transfer cross-section is overcompensated. Mixed forms between the original MAN loop scavenging and Schnürle loop scavenging can represent a good compromise. One open point is the quality of the scavenging. A study found in the literature on the use of MAN loop scavenging on a small engine shows significantly worse results than is known from large engines. There is still a need for further investigation here.
Eilts, Peter
Evaluating the Effects of an Electrically Assisted Turbocharger on Scavenging Control for an Opposed Piston Two Stroke (OP2S) Compression Ignition Engine2024-01-238804/09/2024
Opposed piston two-stroke (OP2S) diesel engines have demonstrated a reduction in engine-out emissions and increased efficiency compared to conventional four-stroke diesel engines. Due to the higher stroke-to-bore ratio and the absence of a cylinder head, the heat transfer loss to the coolant is lower near ‘Top Dead Center.’ The selection and design of the air path is critical to realizing the benefits of the OP2S engine architecture. Like any two-stroke diesel engine, the scavenging process and the composition of the internal residuals are predominantly governed by the pressure differential between the intake and the exhaust ports. Without dedicated pumping strokes, the two-stroke engine architecture requires external devices to breathe. In the unique OP2S engine architecture studied in this work, the external pumping devices present in the air path include an electrically assisted turbocharger (EAT), an electrified EGR pump, and a back-pressure valve (BPv) located downstream of the
Bhatt, Ankur, Gandolfo, John, Huo, Ming, Gainey, Brian, Lawler, Benjamin
1D-3D CFD Investigations to Improve the Performance of Two-Stroke Camless Engine2024-01-268604/09/2024
The transportation sector still depends on conventional engines in many countries as the alternative technologies are not mature enough to reduce carbon footprints in society. The four-stroke diesel engines, primarily used for heavy-duty applications, need either high intake boosting or a large bore to produce higher torque and power output. There is an alternative where a four-stroke engine operated in two-stroke mode with the help of a fully flexible variable valve actuation (VVA) system can achieve similar power density without raising the intake boosting or engine size. A fully flexible VVA is required to control the valve events (lift, timing, and durations) independently so that the four-stroke events can be completed in one cycle. In this study, 1D-3D CFD coupled simulations were performed to develop a gas exchange process for better air entrapment in the cylinder and evacuate the exhaust products simultaneously. The intake and exhaust valve closing timings were optimized based
Tripathy, Srinibas, Dahlander, Petter, Somhorst, Joop, Kuylenstierna, Claes
A Renewable-Fuel 60% Efficient Engine - Insights from the General Cycle EquationSAE-PP-0037011/25/2023
The General Cycle is a thermodynamic cycle that includes all six steps common to engine cycles. Thus it includes other engine cycles as subsets, each of these lacking one or more of the steps. The General Cycle engine, outside the realm of more commonly known thermodynamic cycles, is best suited to attain highest efficiency. Essential strategies for attaining 60% efficiency in an internal combustion engine are: (1) optimize parameters in the General Cycle, (2) reduce friction and heat transfer losses, and (3) preserve combustion efficiency. Obtaining a practical 60% efficient engine is a struggle against engine cost and power density. Add to that the problem of using only a renewable fuel with the intent of satisfying three additional goals: (1) net-zero-carbon emissions, (2) compatible with existing infrastructure and fuel systems, and (3) able to replace all current fossil fuel use. These conditions will require the highest efficiency in order to satisfy market demand given a limited
Rogers, Ernie, Collett, Glen
ZERO-EMISSION INTERNAL COMBUSTION ENGINESAE-PP-0036811/17/2023
A new concept of internal combustion engine has been developed. The purpose is to have an engine that can burn hydrocarbon fuels without discharging any greenhouse gas or other harmful substances into the atmosphere. The new engine, the zero-emission engine, inducts no air from the environment. Instead, the engine exhaust gas, with added oxygen, is used in performance of the combustion cycle. Carbon dioxide, the main byproduct of combustion is captured, stored, and unloaded during refueling for further storage, sequestration, or recycling. The zero-emission engine displacement can be significantly smaller than in a conventional air-inducting engine of equal power, with a significantly higher power density. The engine is unthrottled and it can operate with a much higher compression ratio without an increase in the cylinder temperature. The above concept also envisions recycling the captured carbon dioxide by using it with water to produce hydrocarbon fuel and oxygen that can be supplied
Schechter, Michael, schechter, victor
The Flathead Valved Boosted Uniflow Two Stroke Engine2023-01-182610/24/2023
Experimental aviation engines face numerous challenges, including the need for energy efficiency, alternative fuel sources, reduced weight and size, greater durability with reliability, emissions reduction, and integration with advanced control and monitoring systems. This study presents the performance of a two-stroke engine with a Uniflow scavenging system with a flathead valve concept, with lower specific fuel consumption than conventional two-stroke aircraft engines. The engine’s maximum speed is limited to 3000 rpm for better cylinder scavenging efficiency, which also eliminates the need for a reduction gearbox, simplifies the design, and reduces the engine’s total mass. 1D simulations were conducted to evaluate combustion and performance parameters using aviation. At the maximum speed of 3000 rpm, the engine achieved a power of approximately 23 kW with boost around 3bar, while at cruise speeds between 2400 and 2700 rpm, the maximum torque is approximately 80 Nm, with specific
Hausen, Roberto Begnis, Martins, Mario, silveira, Juliano, Fagundez PhD, Jean Lucca
Development of Supercharged Two-Stroke Engine with Intake and Exhaust Valve for Hybrid System2023-01-182310/24/2023
The two-stroke engine has a small displacement and high output, and therefore saves space when the engine is installed in a vehicle. Thus, the application of two-stroke engines to HEVs is a very effective means of reducing vehicle weight and securing engine space. On the other hand, the unfired element increases in the exhaust gas with a two-stroke engine because the air-fuel mixture is blown through to the exhaust system during the scavenging process inside the cylinder. Moreover, combustion becomes unstable due to the large amount of residual burnt gas in the cylinder. To solve these problems, we propose a two-stroke engine that has intake and exhaust valves that injects fuel directly into the cylinder. We describe the engine shape and the method that can provide high scavenging efficiency and stable combustion in such a two-stroke engine.
Hisano, Atsushi, Saitou, Masahito, Sakurai, Yota, Matsuda, Yoshimoto, ichi, Satoaki
A Study of the Mechanism of High-Speed Knocking in a Two-Stroke SI Engine with High Compression Ratio2023-01-182410/24/2023
Experimental methods and numerical analysis were used to investigate the mechanism of high-speed knocking that occurs in small two-stroke engines. The multi-ion probe method was used in the experiments to visualize flame propagation in the cylinder. The flame was detected by 14 ion probes grounded in the end gas region. A histogram was made of the order in which flames were detected. The characteristics of combustion in the cylinder were clarified by comparing warming up and after warming up and by extracting the features of the cycle in which knocking occurred. As a result, regions of fast flame propagation and regions prone to auto-ignition were identified. In the numerical analysis, flow and residual gas distribution in the cylinder, flame propagation and self-ignition were visualized by 3D CFD using 1D CFD calculation results as boundary conditions and initial conditions. Flame propagation calculated by 3D CFD was found to be directional due to in-cylinder flow caused by scavenging
Eto, Kuniyoshi, Kuboyama, Tatsuya, Moriyoshi, Yasuo, Yamada, Toshio, Yatsufusa, Tomoaki, Suzuki, Yusuke
On the Effects of Piston Pocket, Intake Port, and Transfer Duct Geometries in a Small Stratified-Scavenging Two-Stroke Engine2023-01-182510/24/2023
The regulatory framework of pollutant emissions concerning non-road small internal combustion engines is becoming increasingly challenging. The upcoming scenario threatens to cut out small two-stroke engines because of the fuel short circuit occurring during transfer and exhaust ports overlap, causing the emission of unburned hydrocarbons and reducing engine efficiency. Despite this challenge, small two-stroke engines are unmatched in high power density applications in which weight and autonomy hinder the diffusion of electric technologies. The continuation of small two-stroke engines in the market will thus depend on the capability of mitigating fuel short circuit. From this perspective, some of the Authors found the low-pressure injection technology fulfilling the purpose at engine full load; however, in addition to system complexity and costs, a lack of mixture homogenization was noted at low load. Another solution concerns the adoption of a pocket milled in the piston skirt
Ciampolini, Marco, Raspanti, Sandro, Romani, Luca, Ferrara, Giovanni, Merolla, Santo, Gagliardi, Vincenzo
Numerical Investigation of Knocking in a Small Two-Stroke Engine with a High Compression Ration to Improve Thermal Efficiency2023-32-007909/29/2023
This study aimed to achieve both a high compression ratio and low knock intensity in a two-stroke engine. Previous research has suggested that knock intensity can be reduced by combining combustion chamber geometry and scavenging passaging design for the same engine specifications with a compression ratio of 13.7. In this report, we investigate whether low knock intensity can be achieved at compression ratios of 14.4 and 16.8 by adjusting the combustion chamber geometry and scavenging passage design. As a result, the mechanism by which combustion chamber geometry and scavenging passage design change knock intensity was clarified.
Eto, Kuniyoshi, Kuboyama, Tatsuya, Moriyoshi, Yasuo, Yamada, Toshio, Yamazaki, Takahiro, Yamaguchi, Shiro
Investigation of Liquid Lignin-Methanol Blends under Realistic Two-Stroke Marine Engines Conditions2023-24-008508/28/2023
With a view to reducing the environmental impact of fossil fuels, advanced lignin-based biofuels could provide a valuable contribute, since lignin is the most abundant biopolymer on earth after cellulose. However, its thermophysical properties would hamper its use as a pure fuel. In this work we investigated the combustion behavior of sprays of a liquid lignin-methanol blend and evaluated its potential as a low-carbon marine fuel for large two-stroke engines. To this end, an experimental campaign was conducted in an optically accessible combustion chamber whose main dimensions correspond to those of a single cylinder for large two-stroke engines. The chamber is provided with optical accesses for optical diagnostics of the combustion process. The combustion of the mixture was ignited using a diesel pilot jet as the ignition source. Two marine injectors are mounted in the chamber, namely “main” and “pilot” injectors. The tests were performed in environmental conditions around 40 bar and
Lazzaro, Maurizio, Sementa, Paolo, Catapano, Francesco, Tornatore, Cinzia, Iannuzzi, Stefano, Boot, Michael, Kouris, Panos
High Performance and Near Zero Emissions 2-Stroke H 2 Engine2023-24-006808/28/2023
The paper presents a preliminary study on a virtual 2-stroke 3-cylinder 0.9 L DI SI supercharged engine running on Hydrogen (H2), able to meet both high performance targets and ultra-low emissions limits (NOx<20 ppm). Combustion is similar to a conventional 4-stroke H2 DI engine, while the design of the cylinder and the actuation law of both intake and exhaust valves are specifically optimized for the 2-stroke cycle. In comparison to a more conventional 2-stroke loop scavenged engine, with piston-controlled ports, the use of poppet valves enables a more flexible control of the gas exchange process and to maintain the same design of a 4-stroke engine for pistons, cylinders block, crankcase and lubrication system. On the other hand, it is more difficult to avoid the short-circuit of the fresh charge, while permeability of the valves becomes quite critical at high engine speed. Therefore, particular care was devoted to the optimization of the intake and exhaust ports geometry, as well as
Caprioli, Stefano, Volza, Antonello, Mattarelli, Enrico, Rinaldini, Carlo Alberto
A Case Study of an Integrated Starter Generator Failure and Benefits of Time Domain Torsional Vibration Analysis2024-01-412508/10/2023
An Integrated Starter Generator (ISG) was integrated between an opposed piston two stroke engine and a 32 speed binary shift transmission for use in the Advanced Powertrain Demonstrator (APD). The initial design of the ISG integration and accompanying frequency domain torsional vibration analysis was performed considering driveline characteristics within the normal operating speed range of the engine. After a short period of time, the ISG suffered a catastrophic failure. The root cause of this failure is analyzed with special attention to the torsional behavior of the system. Multiple methods are employed to assess the torsional behavior including time domain torsional analysis. The time domain torsional analysis revealed that a significant number of torsional vibration cycles were occurring outside of the normal operating range of the engine as the engine accelerated from engine cranking speed to engine idle speed. The cycle accumulation during these short excursions through resonance
Srodawa, John
Investigation of In-Cylinder Pressure Measurement Methods within a Two-Stroke Spark Ignition Engine01-17-01-000405/12/2023
This work describes an investigation of measurement techniques for the indicated mean effective pressure (IMEP) on a 55 cc single-cylinder, 4.4 kW, two-stroke, spark ignition (SI) engine intended for use on Group 1 and Group 2 remotely piloted aircraft (RPAs). Three different sensors were used: two piezoelectric pressure transducers (one flush mount and one measuring spark plug) for measuring in-cylinder pressure and one capacitive sensor for determining the top dead center (TDC) position of the piston. The effort consisted of three objectives: to investigate the merits of a flush mount pressure transducer compared to a pressure transducer integrated into the spark plug, to perform a parametric analysis to characterize the effect of the variability in the engine test bench controls on the IMEP, and to determine the thermodynamic loss angle for the engine. The results indicate that as a spark plug, the measuring spark plug is not statistically different from the stock spark plug at the
Ausserer, Joseph K., Polanka, Marc D., Litke, Paul J., Grinstead, Keith D.
Numerical Study on High-Load Performance of a Two-Stage Boosted Poppet-Valved Two-stroke Diesel Engine2023-01-044304/11/2023
Two-stroke cycle is one of the most effective methods to increase the torque and power output of a four-stroke engine due to the doubled firing frequency compared to four-stroke cycle at the same engine speed. As the two-stroke cycle lacks separate intake and exhaust strokes, the positive pressure difference between intake and exhaust ports is required to drive fresh charge into the cylinder, and is affected by intake port structures due to the different amounts of short-circuited fresh charge during scavenging process. To evaluate the effects of intake port structures on the high-load performance of a boosted poppet-valved two-stroke diesel engine, one-dimensional gas dynamic model and three-dimensional computational fluid dynamics model were established and used to predict the high-load performance of the boosted two-stroke diesel engine with top-entry intake ports, inclined side-entry intake ports, and side-entry intake ports, respectively. The results show that the engine with
Fu, Xue-Qing, Zhang, Yan, Ding, Zhanming, Zhuang, Anbang, Zhu, Wei, Hou, Linlin, cheng, Jianghua, Zhang, Shuyong
Research of Spark Ignition Engine and Internal Mixture Formation Using Single-Zone, Two-Zone and Three-Zone Calculation Model of It Working Process1325110/27/2022
Thermodynamic models based on the volume balance method for calculating the working process of an engine with spark ignition and internal mixture formation are presented. The single-zone model makes it possible to determine the pressure and average temperature of gases in the engine cylinder during the working process. The two-zone combustion model takes into account the change in the volume of the exhaust gases zone and the air-fuel mixture zone. The model makes it possible to determine the pressure of gases in the cylinder and the temperature in the zones under consideration when the air-fuel mixture is distributed over the entire above-piston volume at the moment of ignition. The three-zone combustion model takes into account the change in the volume of the exhaust gases zone, air-fuel mixture zones and air zones when organizing the stratification of the air-fuel charge, allows you to determine the gas pressure in the cylinder and the temperature in the zones under consideration
Korohodskyi, Volodymyr
Improving the Performance of Internal Combustion Engines and Reducing Emissions by Injecting Water with the Air Entering the Engines04-16-01-000510/17/2022
The current work experimentally and theoretically studied the effect of water injection on improving the performance of three different types of single-cylinder internal combustion engines. The first engine is a four-stroke diesel, the second is a four-stroke gasoline, and the third is a two-stroke gasoline engine. Different amounts of water were injected relative to fuel consumption for the three engines to find how it affected the performance, exhaust gas temperatures, and emissions. Comparing the experimental and theoretical results was done to determine the effect of spraying water on lowering the temperatures of the exhaust gases, increasing the thermal efficiency, and lowering specific fuel consumption. The experimental results for the various tested engines show that, in general, the exhaust gas temperature and gas emission decreases by increasing the mass of water injection; these differences vary based on the engine and the operating conditions. Water injected at the inlet of
Hadidi, Haitham M., Hassan, Ahmed S. A.
Assessment of the Combustion Process in Ultra-Lean (λ>1.8) Natural Gas Engines2022-01-106108/30/2022
The majority of today’s natural gas fired engines are applying a premixed combustion concept, which is commonly assumed to be based on the turbulence-enhanced propagation of a thin flame separating the burnt and unburnt fractions of the mixture volume. This concept has been confirmed by means of comprehensive experimental investigations on passenger car engines operating at air/fuel ratios close to stoichiometry; however, for larger industrial engines (4-stroke and 2-stroke) designed for ultra-lean (λ >1.8) operation in order to achieve highest efficiencies, this assumption is no longer valid, as will be shown in the following. On these engines, the combustion process is largely controlled by the reaction kinetics of the chemistry and hence exhibits more similarity to homogeneous charge or spark assisted compression ignition (HCCI or SACI) combustion concepts. This is substantiated by a detailed review on theoretical and experimental investigations of ultra-lean combustion processes, a
Unfug, Fridolin, Weisser, German Andreas
Research of Spark Ignition Engine and Internal Mixture Formation Using Single-Zone, Two-Zone and Three-Zone Calculation Model of It Working Process2022-01-100008/30/2022
Thermodynamic models based on the volume balance method for calculating the working process of an engine with spark ignition and internal mixture formation are presented. The single-zone model makes it possible to determine the pressure and average temperature of gases in the engine cylinder during the working process. The two-zone combustion model takes into account the change in the volume of the exhaust gases zone and the air-fuel mixture zone. The model makes it possible to determine the pressure of gases in the cylinder and the temperature in the zones under consideration when the air-fuel mixture is distributed over the entire above-piston volume at the moment of ignition. The three-zone combustion model takes into account the change in the volume of the exhaust gases zone, air-fuel mixture zones and air zones when organizing the stratification of the air-fuel charge, allows you to determine the gas pressure in the cylinder and the temperature in the zones under consideration
Korohodskyi, Volodymyr, Leontiev, Dmitry, Rogovyi, Andrii, Kryshtopa, Sviatoslav, Gritsuk, Igor, Voronkov, Oleksandr, Prokopiuk, Demian
An Investigation into the Effects of Swirl on the Performance and Emissions of an Opposed-Piston Two-Stroke Engine using Large Eddy Simulations2022-01-103908/30/2022
Opposed-piston two-stroke (OP-2S) engines have the potential to achieve higher thermal efficiency than a conventional four-stroke diesel engine. However, the uniflow scavenging process is difficult to control over a wider range of speed and loads due to its sensitivity to pressure dynamics, port timings, and port design. Specifically, the angle of the intake ports can be used to generate swirl which has implications for open and closed cycle effects. This study proposes an analysis of the effects of port angle on the in-cylinder flow distribution and combustion performance of an OP-2S using computational fluid dynamics engine. Large Eddy Simulation (LES) was used to model turbulence given its ability to predict in-cylinder mixing and cyclic variability. A three-cylinder model was validated to experimental data collected by Achates Power and the grid was verified using an LES quality approach from the literature. The model was used to simulate port angles from 12 to 29 degrees at
O'Donnell, Patrick Christopher, Gainey, Brian, Vorwerk, Erik, Prucka, Robert, Lawler, Benjamin, Huo, Ming, Salvi, Ashwin
Effects of Port Angle on Scavenging of an Opposed Piston Two-Stroke Engine2022-01-059003/29/2022
Opposed-piston 2-stroke (OP-2S) engines have the potential to achieve higher thermal efficiency than a typical diesel engine. However, the uniflow scavenging process is difficult to control over a wide range of speeds and loads. Scavenging performance is highly sensitive to pressure dynamics, port timings, and port design. This study proposes an analysis of the effects of port vane angle on the scavenging performance of an opposed-piston 2-stroke engine via simulation. A CFD model of a three-cylinder opposed-piston 2-stroke was developed and validated against experimental data collected by Achates Power Inc. One of the three cylinders was then isolated in a new model and simulated using cycle-averaged and cylinder-averaged initial/boundary conditions. This isolated cylinder model was used to efficiently sweep port angles from 12 degrees to 29 degrees at different pressure ratios. Results indicate that scavenging performance is correlated with the bulk swirl ratio generated by these
O'Donnell, Patrick Christopher, Gandolfo, John, Gainey, Brian, Vorwerk, Erik, Prucka, Robert, Filipi, Zoran, Lawler, Benjamin, Hessel, Randy, Kokjohn, Sage, Huo, Ming, Salvi, Ashwin
Usage of 2-Stroke Engines for Hybrid Vehicles13-03-02-001103/24/2022
As the automotive industry moves toward electrification, battery costs and vehicle range are two large issues that will delay this movement. These issues can be partially resolved through the use of series-hybrid vehicles, which can replace a portion of the batteries with a small engine that serves to recharge the battery. Given the size, weight, and operational constraints of this engine, a 2-stroke engine makes sense. Indeed, 2-stroke engines are currently being used for a number of applications including consumer products, small ground vehicles, boats, and drones. The technology has significantly improved to allow for reduced emissions and increased efficiency, especially through the use of direct injection. This article discusses the state of technology for 2-stroke engines and its application in series-hybrid vehicles. In particular, the use of a 2-stroke engine as a range extender provides significant benefit in range and cost over fully electric vehicles. The study found that
Shah, Rajesh, Khan, Muqsit, Mittal, Vikram
Numerical Investigation of the Effect of Engine Speed and Delivery Ratio on the High-Speed Knock in a Small Two-Stroke SI Engine2022-32-008001/09/2022
Knocking occurs within the high-speed range of small two-stroke engines used in handheld work equipment. High-speed knock may be affected by the engine speed and delivery ratio. However, evaluation of these factors independently using experimental methods is difficult. Therefore, in this study, these factors were independently evaluated using numerical calculations. The purpose of this study was to clarify the mechanism by which the intensity of high-speed knocking that occurs in small two-stroke engines becomes stronger. The results suggest that temperature inhomogeneity due to insufficient mixing of fresh air and previously burned gas may induce high-speed knocking in the operating range at high engine speeds.
Eto, Kuniyoshi, Kuboyama, Tatsuya, Moriyoshi, Yasuo, Yamada, Toshio
Impact of Zero CO 2 Fuels on Engine Behaviour of Two-Stroke Engines in Hand-Held Powertools2022-32-006101/09/2022
One possible path to reduce the CO2 emissions of hand-held power tools are fuels with different amount of renewable content. Within this paper test bench measurements on a small two-stroke engine were carried out. We are trying to reduce CO2 emissions by using fuels which absorbed CO2 from the air during its lifetime or production, so called Zero CO2 fuels The focus was set on the investigation of combustion behaviour, performance and emissions of Zero CO2 fuels in comparison to commonly available fuels. For our measurements we chose a 46 cc serial engine, which was slightly modified for scientific research. This paper shows findings on effects of renewable fuels on engine characteristics. Additionally, the chemical properties of each fuel were investigated in order to form a comprehensive picture, together with the performed dyno measurements.
Gschanes, Dominik, Schmidt, Stephan, Kirchberger, Roland
Increased Reliability and Usability through the Introduction of a User Interface Module for Hand-Held Small Engines2022-32-004801/09/2022
Mobile hand-held or back-carried small engines must be weight-optimized due to their operability. At the same time there is enormous cost pressure within this market segment. Therefore, not all comfort and additional functions to increase user-friendliness can be adopted from the stationary applications. These include, for example, electric starting devices or additional sensors and actuators that take over advanced control processes to prevent or detect and report user or system errors. In the mobile small engine segment, this situation leads to the problem that the systems have many requirements for the user. These include, for example: physical ability to operate a pull starter know-how about the functioning of a combustion engine (2-stroke and 4-stroke) know-how for detecting failures and remedial actions If the knowledge about the behavior of engines is not given, or failures are overlooked, this automatically leads to a form of physical strain on the user due to the many
Öztürk, Bahattin, Stoffregen, Thorsten
E-Fuel applications in Non Road Mobile Machinery2022-32-007401/09/2022
Professional users in particular will continue to rely on internal combustion engine drives in the future due to high power requirements and high daily energy consumption. Especially if they have to work in rural areas without the possibility of recharging batteries, such as in forestry or maintenance of road verges or railway lines. For these applications, it must be possible to run sustainable fuels for defossilization and drastically reduced CO2 emissions. This paper provides insights into a possible future fuel market and describes its evolution towards a more sustainable future from the perspective of a handheld equipment manufacturer. As developments in the fuel market are currently difficult to predict, manufacturers of hand-held power tools with combustion engines need to be prepared for changes in the composition of fuels that might become available on the market. This paper presents the engine performance results of both a 2-stroke engine and a 4-stroke engine, each with
von Gaertringen, Christoph Hiller, Schwerin, René, Schweiger, Stefan, Kölmel, Armin, Lochmann, Holger, Schmidt, Stephan, Zinner, Christian, Kirchberger, Roland, Gschanes, Dominik
On the Potential of Transfer Port Injection Strategies for a Two-Stroke Engine2022-32-005701/09/2022
The main drawback of an in-cylinder Low Pressure Direct Injection (LPDI) in a two-stroke engine is the difficulty of achieving a satisfactory vaporization level in low load conditions. The liquid droplets are characterized by large diameters and, when the temperature level and the velocity of the scavenging flow field are low, the time needed for the droplet vaporization and the homogenization with fresh air becomes too long to guarantee a suitable mixture formation. A transfer port injection allows a higher flexibility, due to the possibility of performing a mixed injection either directly in the cylinder or indirectly in the crank case, depending on the load request or engine speed. Also, an even lower injection pressure can be adopted with respect to an in-cylinder LPDI injection, which is relevant in case of lightweight and low power applications. On the other hand, the time available for the direct in-cylinder injection is limited to the scavenge phase. In the present work, a
Balduzzi, Francesco, Romani, Luca, Ferrara, Giovanni, Trassi, Paolo, Fiaschi, Jacopo
Study of Pre-chamber Jet Combustion Behavior using a Small Two-stroke Optically Accessible Engine2022-32-007601/09/2022
A small 2-stroke engine can be an effective power source for an electric generator mounted on a series hybrid electric vehicle. In recent years, a technology referred to as pre-chamber jet combustion has attracted attention as a means of enhancing thermal efficiency by improving mixture ignitability. In this study, experiments were conducted to investigate differences in combustion behavior between the application of spark-ignited (SI) combustion and pre-chamber jet combustion to a small, two-stroke engine. The experimental equipment used was a two-stroke, single-cylinder, optically accessible engine with a displacement of 63.3 cm3. Differences between conventional SI combustion and pre-chamber jet combustion were examined by means of in-cylinder pressure analysis, in-cylinder combustion visualization and image processing software. The diameter of the connecting orifice of the pre-chamber was varied between two types. The results revealed that the combustion time and indicated mean
DEUSHI, Takato, NAKA, Takuma, TSUJIGUCHI, Tatsuya, IIJIMA, Akira, YAMAGUCHI, Shiro, KUROIWA, Minoru, ETO, Kuniyoshi
Describing the Auto-Ignition Quality in Small, Air Cooled, Two Stroke Engines2022-32-006301/09/2022
Auto-ignition quality is one of the most important properties in gasoline. Auto-ignition quality is today described by the Motor Octane Number (MON) and the Research Octane Number (RON). For modern, light duty, gasoline engines it has been quite well established that RON is the most accurate number. However, no study has been performed on hand held forest and garden products, such as chainsaws. Is the auto-ignition quality best described in the same way for these engines as for light duty engines? In this paper, a matrix of six different fuels with different combinations of MON and RON values were tested on a Husqvarna 550 XP Mark II, a modern air cooled, sequential stratified scavenging 2-stroke chainsaw engine. Ignition timing sweeps were performed and knock limited spark advance (KLSA) were calculated. Then the data has been analyzed with a multi-variate analysis of KLSA against both MON and RON to try to determine how MON and RON should be combined to best describe the anti-knock
Risberg, Per, Elm, Thomas, Bergman, Mikael, Hellquist, Fredrik, Karvo, Anna, Tripathi, Rupali
Design and Implementation of An Oxidation Catalyst for A Spark Ignited Two Stroke Snowmobile Engine2022-32-000501/09/2022
The primary goal of this project was to design and implement an oxidation catalyst specific to a high-performance spark ignited two stroke engines to reduce vehicle-out emissions. The primary challenges of two stroke catalysis at high loads include controlling the catalytic reaction temperature as well as minimizing the increase in exhaust back pressure due to the addition of a catalyst. Reaction temperature is difficult to control due to high HC and CO concentrations paired with an excess of oxygen in the exhaust stream. By limiting catalyst conversion efficiency, the reaction temperatures were controlled. Two stroke engines are also inherently sensitive to changes in exhaust back pressure and therefore location and sizing of the catalyst are key design considerations. Because of these challenges significant effort was directed toward developing the two-stroke specific catalyst design process. Through these efforts several key outcomes were reached including a better understanding of
Squires, Noah, A. Miers, Scott
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