Browse Topic: Two stroke engines
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.
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
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.
An afterburner-assisted turbocharged single-cylinder 425 cc two-stroke SI-engine is described in this simulation study. This engine is intended as a Backup Range Extender (REX) application for heavy-duty battery electric vehicles (BEV) when external electric charging is unavailable. The 425 cc engine is an upscaled version of a 125 cc port-injected engine [26] which demonstrated that the selected technology could provide a specific power level of 400 kW/L and the desired 150 kW in a heavy duty BEV application. The 425 cc single cylinder two-stroke engine is an existing engine as one half of a 850 cc snowmobile engine. This simulation study includes upscaling of the swept volume, impact on engine speed and gas exchange properties. In the same way as for the 125cc engine [26], the exhaust gases reaches the turbine through a tuned exhaust pipe and an afterburner or oxidation catalyst. The intent with the afterburner is to convert some of the air and hydrocarbons (HC) to heat to provide
In this work, a novel opposed piston architecture is proposed where one crankshaft rotates at twice the speed of the other. This results in one piston creating a 2-stroke profile and another with a 4-stroke profile. In this configuration, the slower piston operates in the 2-stroke CAD domain, while the faster piston completes 2 reciprocating cycles in the same amount of time (4-stroke). The key benefit of this cycle is that the 4-stroke piston increases the rate of compression and expansion (dV/dθ), which lowers the combustion-induced pressure rise rate after top dead center (crank angle location of minimum volume). Additionally, it lowers in-cylinder temperatures and pressures more rapidly, resulting in a lower residence time at high temperatures, which reduces residence time for thermal NOx formation and reduces the temperature differential between the gas and the wall, thereby reducing heat transfer. In this work, a custom 0D thermodynamic model was used to study the sensitivity of
This paper presents analytical research conducted into the level of fuel consumption improvement that can be expected from turbocompounding a medium-duty opposed-piston 2-stroke engine, which is part of a hybridized vehicle propulsion system. It draws on a successful earlier study which showed a non-compounded opposed-piston engine to be clearly superior to other forms of 2-stroke engine, such as the widely adopted uniflow-scavenged poppet valve configuration. Electrical power transmission is proposed as the method of providing the necessary variable-speed drive to transmit excess turbine power to the system energy storage medium. The work employs one-dimensional engine simulation on a single-cylinder basis, using brake specific fuel consumption (BSFC) as the reportable metric, coupled with positive or negative power flow to the engine from the compounder; this is a variation on an approach successfully used in earlier work. Here it shows the sensitivities of the overall system to
Power dense internal combustion engines (ICEs) are interesting candidates for onboard charging devices in different electric powertrain applications where the weight, volume and price of the energy storage components are critical. Single-cylinder naturally aspirated two-stroke spark-ignited (SI) engines are very small and power dense compared to four-stroke SI engines and the installation volume from a single cylinder two-stroke engine can become very interesting in some concepts. During charged conditions, four-stroke engines become more powerful than naturally aspirated two-stroke engines. The performance level of a two-stroke SI engines with a charging system is less well understood since only a limited number of articles have so far been published. However, if charging can be successfully applied to a two-stroke engine, it can become very power dense. This article outlines some of the challenges related to charging systems for a single-cylinder crank case scavenged two-stroke SI
Two-stroke opposed piston engines (2sOPEs) have great potential for industrial applications due to their simple design, technology and high efficiency, particularly with a turbocharging system. The paper presents possibilities for altering 2sOPE working parameters by changing geometrical parameters and boosting parameters. Obtaining higher engine efficiency is realised by altering the crank phase shift of the exhaust piston in relation to the transfer piston. It has been assumed that only the piston of the exhaust cylinder changes its position relative to the piston in the cylinder with transfer ports. Modifying the scavenging process by changing pistons’ position through connecting with two crankshafts enables asymmetrical scavenging timing. Closing the exhaust ports before the compression process and extending the time allotted to empty exhaust gases from the cylinder provides greater engine work, and a high boost ratio increases engine power. This type of engine was recently
In connection with the tightening of environmental standards, the leading manufacturers of marine low-speed engines are carrying out intensive work on their conversion to gas fuels. Due to the design features in this class of engines, only internal mixture formation is possible. For the organization of which two different approaches are possible. To date, only two are currently implemented. MAN started production of engines with gas fuel supply to the working cylinder under high pressure at the end of the compression stroke, and WinGD under low pressure at the beginning of the compression stroke. The analysis, performed by the authors, showed, that increasing the pressure before the gas supplying mechanisms to 3.5...6.0 MPa can reduce the residence time of the gas-air mixture in the working cylinder and reduce the likelihood of detonation combustion. The supply of gas fuel to the working cylinder with a changing back pressure significantly affects on the flow characteristics of the gas
An opposed piston two-stroke engine is more suitable for use in an unmanned aerial vehicle because of its small size, excellent self-balancing, stable operation, and low noise. Consequently, in this study, based on experimental data for a prototype opposed piston two-stroke engine, numerical simulation models were established using GT-POWER for 1D simulation and AVL-FIRE for 3D CFD simulation. The mesh grid and solver parameters for the numerical model of the CFD simulation were determined to guarantee the accuracy of the numerical simulation, before studying and optimizing the ventilation efficiency of the engine with different dip angles. Furthermore, the fuel spray and combustion were analyzed and optimized in details.
Dual-fuel engines for marine propulsion are gaining in importance due to operational and environmental benefits. Here the combustion in a dual-fuel marine engine operating on diesel and natural gas, is studied using a multiple high-speed camera arrangement. By recording the natural flame emission from three different directions the flame position inside the engine cylinder can be spatially mapped and tracked in time. Through space carving a rough estimate of the three-dimensional (3D) flame contour can be obtained. From this contour, properties like flame length and height, as well as ignition locations can be extracted. The multi-camera imaging is applied to a dual-fuel marine two-stroke engine, with a bore diameter of 0.5 m and a stroke of 2.2 m. Both liquid and gaseous fuels are directly injected at high pressure, using separate injection systems. Optical access is obtained using borescope inserts, resulting in a minimum disturbance to the cylinder geometry. In this type of engine
Two-stroke engines have to face the problems of insufficient charge for short intake time and the loss of intake air caused by long valve overlap. In order to promote the power of a two-stroke poppet valve diesel engine, measures are taken to help optimize intake port structure. In this work, the scavenging and combustion processes of three common types of intake ports including horizontal intake port (HIP), combined swirl intake port (CSIP) and reversed tumble intake port (RTIP) were studied and their characteristics are summarized based on three-dimensional simulation. Results show that the RTIP has better performance in scavenging process for larger intake air trapped in the cylinder. Its scavenging efficiency reaches 84.7%, which is 1.7% higher than the HIP and the trapping ratio of the RTIP reaches 72.3% due to less short-circuiting loss, 11.2% higher than the HIP. The RTIP also behaves better in mixture formation and combustion performance with higher air utilization and superior
A 500-hour test cycle has been used to evaluate the durability of a prototype high pressure common rail injection system operating up to 1800 bar with E10 gasoline. Some aspects of the original diesel based hardware design were optimized in order to accommodate an opposed-piston, two-stroke engine application and also to mitigate the impacts of exposure to gasoline. Overall system performance was maintained throughout testing as fueling rate and rail pressure targets were continuously achieved and no physical damage was observed in the low-pressure components. Injectors showed no deviation in their flow characteristics after exposure to gasoline and high resolution imaging of the nozzle spray holes and pilot valve assemblies did not indicate the presence of cavitation damage. The high pressure pump did not exhibit any performance degradation during gasoline testing and teardown analysis after 500 hours showed no evidence of cavitation erosion. Despite the lack of lubricity-improving
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