Prediction of ignition delay time of Liquefied Gas for Vehicle (LGV)

Abstract

Abstract. Ignition delay time of liquefied petroleum for vehicle (LGV) fuel was predicted in this research. The method was using a detailed kinetic model of oxidation and combustion of propane/n-butane mixture. The validation of the model used experimental data in shock tubes in the temperature range from 1300 K to 1500 K and the pressure range from 2.5 bar to 10 bar for pure propane and pure n-butane. Calculated results of ignition delay time using the model have good agreement with experimental results indicating that the model may be used for LGV fuel. Simulation results of the model of LGV fuel show that the ignition delay time is faster when the n-butane fraction in the fuel is higher. The switchover of the ignition delay time order among different compositions of the fuels takes place at the initial temperature of 1200 K for the equivalence ratios of 1 and the initial pressure of 10 bar. IntroductionLiquefied gas for vehicle (LGV) is liquefied petroleum gas (LPG) used as a fuel in internal combustion engines in vehicles as well as in stationary applications such as generators. It is a mixture of propane and butane. It is a green fuel since it reduces CO 2 exhaust emissions. It has an octane rating (RON) that is between 93.5 and 109.4 [1] and an energy content (higher heating value-HHV) that is between 25.5 MJ/L (for pure propane) and 28.7 MJ/L (for pure butane) depending upon the actual fuel composition.One of combustion characteristics in internal combustion engines is autoignition. In diesel engine autoignition of a fuel is desired when the fuel injected into combustion chamber. The autoignition is caused by the high temperature which the air achieves when it greatly compressed. There is a period between the start of injection and the start of combustion, which is called delay time. In diesel engines, the delay time consists of physical delay wherein atomization, vaporization and mixing of air-fuel occur, and of chemical delay attributed to pre-combustion reactions [2]. The latter is caller ignition delay time. In spark-ignition engines which use spark plugs to ignite an air-fuel mixture autoignition is unwanted. The autoignition occurs because the increases in temperature and pressure of the unburned end gas cause it to ignite before it has been consumed by the propagating flame. This raises audible knocking. This malfunction is a serious limitation to the power developed and could lead to engine damage [3].Research on the oxidation and combustion of LPG has been carried out by Kim et al. in a rapid compression machine [4]. It used pure butane and propane/butane mixture as the fuel. It investigated the ignition delay times of the fuel in the temperature ranging from 720 K to 900 K, the pressure range of 16 bar  18 bar and equivalence ration of 1. The autoignition of LPG in spark-ignition engines was