Comparative investigation of diesel and mixed liquefied petroleum gas/diesel injection engines

Experiments are conducted on engine performance and sprays and a characteristics analysis is made between diesel and mixed liquefied petroleum gas (LPG)/diesel injection engines. The performance test results show that with LPG the mixed ratio increases, engine power reduces slightly, fuel consumption and engine noise have almost no change, pollutant emissions of smoke, CO and NO, at full load are improved significantly, but the amount of unburned HC increases. The experimental results of the sprays indicate that because of flash boiling injection of mixed fuel, mean diameters in a spray decrease, the number distribution curve of fuel droplet size moves towards smaller diameters, small-size droplet numbers increase, spray quality is good and engine smoke reduces accordingly. Because large-size droplet diameters show almost no change and small-size droplet diameters decrease, the relative span factor and dispersion boundary factor of the droplet diameter increase. High-resolution digital camera photography is invaluable when carrying out a comparative investigation of spray.