TL;DR: In this paper , the shape of the combustion chamber of a two-cylinder diesel engine with high-pressure common rail direct injection (CRDI) system was determined by comparing the fuel economy and soot emission of diesel engines.
Abstract: In this paper, a bench test of a two-cylinder diesel engine with high-pressure common rail direct injection (CRDI) system for the external characteristics was carried out. The shape of combustion chamber was determined by comparing the fuel economy and soot emission of diesel engines. Based on this result, the effects of different nozzle parameters attempted at reducing brake specific fuel consumption (BSFC) and smoke were investigated. The experimental results show that the improved combustion chamber with a high central convex platform can significantly reduce BSFC and it has little impact on smoke. The appropriate decrease of the nozzle tip penetration (NTP) as well as increase of nozzle-hole diameter contribute to reducing fuel consumption and soot emission. The BSFC at the spray angle of 156° is reduced by 16% at the engine speed of 4000 r/min compared with that at the spray angle of 150°. Comparative results on fuel consumption and smoke emission at all engine speeds reveal that the injector with 153° spray angle, 1.8 mm NTP, 6 injection holes and 0.12 mm nozzle-hole diameter is a better choice of the two-cylinder diesel engine.
TL;DR: In this paper , a 3-dimentional transient model of in-cylinder flow and combustion process is established by the Forte platform, and the engine test system is set up.
Abstract: Heavy-fuel aviation piston engines (HF-APEs) are widely used in general aviation and unmanned aerial vehicle (UAV) due to their safety and fuel economy. This paper describes a numerical and experimental study of scavenging and combustion processes on a 2-Stroke Direct Injected HF-APEs for light aircraft, with its cylinder specifically designed as cross scavenging. A 3-Dimentional transient model of in-cylinder flow and combustion process is established by the Forte platform, and the engine test system is set up. By comparing the simulation results to the experimental results, it showed that multi-ports cross scavenging can generate unbalanced aerodynamic torque in the cylinder. In the compression process, the swirl ratio (SR) gradually increases, and the peak SR reaches 15. Moreover, approximately 25% of exhaust residual gas in the cylinder is conducive to the fuel atomization and evaporation process in a high-altitude environment. When the injection timing is between −8 °CA and −16 °CA, the engine has the optimal power and economy performance at different altitudes. Finally, when the injection advance angle moves forward by 4 °CA, the maximum pressure increases by 2 MPa, with the rising rate decreasing gradually. The results have important significance for the development of the combustion system of small 2-Stroke Direct Injected HF-APEs.