Numerical Simulation Of DME Fuel Injection Process By Means Of GT-FUEL

DME (Dimethyl ether) is an ideal alternative oxygenous fuel for diesel engines due to its physical and chemical properties and excellent combustion characteristics. Fueled with DME, a diesel engine can give off remarkably lower harmful emissions especially nitrogen oxides and particulate. The theoretical researches and experimental investigations have come into fashion worldwide. The author has read a great deal of papers in relative area in order to be kept informed of the updated progress which may throw light on the solutions of certain critical problems such as the variability of DME liquid density, the changeability of local speed of sound and the cavitations within the fuel channel. In this paper the dynamics of fuel supply cam were calculated so as to figure out the lift, velocity, and acceleration of it, which could be extremely important for the startup of simulations. The thermodynamic properties of both DME liquid and its vapor were computed with the use of some agreeable computing techniques the author picked out from tons of thermodynamical equations after extensive comparisons and tradeoffs. As for the equation of state for DME liquid, the author has adopted the GTI equation of state which has been proven awfully effective within a wide range of pressure by forthgoers. On the basis of the equation of state for DME liquid, the changeable density of DME liquid and the variable local speed of sound were calculated and compared with the measured data, which showed an approved consistence. By means of GT-FUEL,this paper established the physical and mathematical model of the Pump-Line-Nozzle (PLN) fuel injection system of an S295 diesel engine on the basis of one-dimensional unstable compressible flow theory, and carried out a numerical simulation of it using the finite volume method, based on which the variability of fuel density, the changeability of local sound speed and the leakage phenomenon due to the low viscosity of DME were all deeply investigated. Ultimately the author made comparisons between the simulated results and measured data of fuel pressure at both pump side and nozzle side, which showed an excellent consistence and proved GT-FUEL practical for the simulation of fuel injection process of diesel engines. And by use of the optimization module "Optimizer"integrated in GT-FUEL, the author carried out parametric optimization for some influential structural parameters and its mechanism. It showed that optimizing the fuel injection system by GT-FUEL is doubtlessly practical and theoretically estimable for it could not only cut down the experimental workload but uncover some physical phenomena out of reach for experimental investigations.