Study On The Influence Of Pilot Diesel Injection Timing On The Performance Of A Common Rail Diesel / LNG Dual-Fuel Engine

The rapid development of auto industry has promoted the rapid development of global economy. But with the rapid increase of vehicle population, automobile exhaust pollution, the deletion of oil resources, city road congestion caused by increase of vehicle population have become serious problems that can not be ignored. Natural gas is a clean alternative vehicle fuel internationally recognized. As a kind of clean energy, compared with gasoline and diesel, natural gas has the advantages of environmental protection and economy. As a vehicle fuel, it embraces the characteristics such as low pollution, economical and reliable security. The dual fuel engine operated with pilot diesel fuel and liquefied natural gas with its good economic performance and emission performance, flexibility, convenient modified and other advantages has attracted wide attention of scholars.This paper conducted in-depth discussion about exploitation and performance test of dual-fuel engine. It discussed in detail about the LNG supply system, dual-fuel electric control system used in the test. Diesel/LNG dual-fuel engine was refitted from the YC6G270-30 electronic controlled common rail diesel engine. The influence of pilot diesel injection timing on the performance and exhaust emission of the dual-fuel engine was investigated at the rated torque speed of 1400r/min and 1800r/min, under the load ratio of 30%,60% and 100%. The engine performance include torque, power, specific fuel consumption, HC, CO, NOX and smoke emission. The combustion characteristics of the dual-fuel engine with different injection timing of pilot diesel was analyzed under 1400r/min at the load ratio of 60%.The result shows that: with the increase of 1°~2°CA pilot diesel injection timing based on the optimal pilot diesel fuel injection timing, HC、CO and smoke emission can effectively reduce. HC emission decreases 14.3% on average, CO emission decreases 10%, and smoke emission decreases 31.8% on average. At low load, NOX emission also decreases; but at high load, NOX emission increases, while power and economic performance are not significantly reduced, the range is less than 5%. Although the in-cylinder peak pressure and peak rate of pressure rise increase, the cycle-by-cycle variations of peak pressure and cycle-by-cycle variations of rate of peak pressure rise decrease, which improve the emission characteristics, stability and reliability of dual fuel engine to a certain extent. The ignition timing is advanced, but the whole combustion process is still near the TDC, and the combustion duration shorten.