Study On Spray Mixing And Combustion Characteristics Of LPG/Diesel Fuel Blend

The problem of energy crisis and environmental pollution become more and more serious, renovations in the traditional energy technology are being focused. As a main energy consumer and the main emission source of pollution, the automotive engine faces double stresses as energy saving and environment protection.The Liquefied-Petroleum Gas (LPG) Which can improve the economics and limited emission is very prospective to use on direct inject engines(DI) as alternative fuels. The characteristics of fuel spray are important to understand fundamental mechanism and influence parameters of the LPG/diesel fuel blend combustion process in these kinds of engines. In this study, the mixing characteristics and mechanism of the LPG/diesel fuel blend spray and the influence factors are investigated by experimental and numerical studies.based on the references and previous experience, the author designed and established the experiment sets of High Speed Photography on LPG/diesel fuel blend spray in constant volume chamber to investigate how the character of fuel, injection starting pressure, environment pressure and spray orifice diameter influence the development of LPG/diesel fuel blend spray.The author also designed and established the experiment sets of LPG/diesel double-fuels DI engine. With most of the parameters of the diesel combustion system unchanged, the load experiment is done to explore how to make the DI engine which using LPG/diesel fuel blend to be more effecter and more cleaner. The result of the experiment show that the DI engine which using LPG/diesel fuel blend can meet the original impetus, also the NOX and CO₂ emissions is superior to the original level, and its fuel economy also improved. According the comparative analysis of different ratio of LPG/diesel blend, a further improver of can be gotten by adjust the parameter of oil system.Because the thermophysical properties of LPG is different from that of diesel, the thermophysical of LPG/diesel blend must be konwed to simulation its spray character. Based on the character of diesel and LPG, using previous experience equation to calculation the LPG/diesel blend's thermophysical properties including enthalpy,critical parameters , Thermal conductivity,Latent heat evaporation,vapor pressure , surface tension , and saturated liquid viscosity,Diffusivity and construct the database used for simulation.This paper also performs the numeric simulation of the spray process for LPG/diesel fuel blend in the constant volume chamber using KIVA-3V program and quasi-dimensional gas jet model to analyses the spray field in detail. Through comparison with the experiment, it show that the quasi-dimensional gas jet model and KIVA program can accurately forecast the spray expand and mixing process of LPG/diesel fuel blend. The character of spray from simulation and test is basically consistent with the each other.