Study on Combustion Characteristics of a
Direct-Injection Engine Fueled with Liquefied Petroleum Gas£¯Diesel Blends
Qi Donghui,Liu Shenghua,Gong Yanfeng,Zhou Longbao
(School of Energy and Power Engineering, Xi'an Jiaotong University, Xi'an 710049, China)
Abstract: The cylinder pressure was sampled and analyzed to study the combustion heat
release rule when direct-injection diesel engine run using diesel blended with liquefied
petroleum gas (LPG). The results show that the combustion heat release rule of the blends
is similar to that of diesel when the LPG mass fraction in blends is lower than 10%,and
with the increase of LPG mass fraction, the peak cylinder pressure and pressure rise rate
decrease, and the corresponding crank angles at which the peak pressure and pressure rise
rate occur retard. Moreover,at lower engine speeds, the ignition time of blends delays by
7. -11. compared with diesel when the LPG mass fraction is greater than 20%, and the peak
heat release rate is slightly higher than that of diesel but the corresponding angles
retard. Also the premixing combustion increases and the diffusion combustion decreases,
and the combustion duration is shortened by about 6. -9. .Furthermore,at higher engine
speeds, the ignition time delays by 11. -13. when the LPG mass fraction is higher than 20%
and the peak heat release rate is far lower than that of diesel, and the combustion
duration is extended by about 22. -25. . It can be indicated that the LPG mass fraction in
blends should be less than 20% when engine parameter, such as the injection advance angle,
is not optimized.
Keywords: engine;liquefied petroleum gas£¯diesel blends; direct injection; combustion
characteristics