This paper shows experimental results on engine's characteristics in a single cylinder diesel Common Rail engine AVL5402 converted to LPG/diesel dual fuel.
Findings from the study show that at full load, higher LPG mass fraction can be reached at lower engine speed due to knocking limit however the economic efficiency with dual fuel is better at higher engine speeds as at these operating regimes the better injection quality and better fuel evaporation can help combustion improve. Comparing to the original engine, when LPG/diesel dual fuel is used, the smoke number and carbon monoxide (CO) decreases at almost all running modes while total hydrocarbon (THC) and nitrogen oxide (NOx) are higher. The improvement of combustion process is a reason for lower smoke number and CO, and higher NOx emissions. Higher THC is explained by unburned hydrocarbon, mainly unburned LPG-air mixture.
Advancing diesel injection timing and increasing pilot injection timing at full load, 1400 rpm and 2000 rpm speeds present similar effects in engine's performance and exhaust emissions. Of which, there is no significant changes of engine's power, the ignition time is advanced, and CO and smoke number are reduced but THC and NOx. In addition, the noise of the engine is reduced remarkably with pilot injection as it help reduce pressure rise rate.