Heat release rate and performance simulation of DME fuelled diesel engine using oxygenate correction factor and load correction factor in double Wiebe function

Abstract

A computer simulation scheme with a rapid thermodynamic model is developed to predict the diesel engine HRR (heat release rate) and performance characteristics with DME as a fuel. The bmeps (MPa) are simulated as 0.5 (optimum power output) and 0.3, 0.4, 0.6 (other power outputs) with diesel and with DME in four steps sequentially. Initially, HRR is predicted by modifying four double Wiebe function parameters; the equations of heat release and combustion duration of diffusion phase and the efficiency factors of premixed and diffusion phase as 2.25 and 3.25 respectively (obtained by qualitative and approximate fitting by trial and error method). Obviously 99% combustion efficiency assumption with efficiency factor as 6.9 is excluded. Secondly, all Wiebe parameters are computed by using LCF (load correction factor which is the ratio between mass flow rates of diesel of optimum and other power output) alone and by using LCF and OCF (oxygenate correction factor which is the ratio between mass flow rates of DME and diesel of identical power output) in other steps. Premixed and diffusion phase peaks (J/degree) with DME are 13.73 and 31.47 (0.3 MPa); 23.18 and 47.25 (0.6 MPa). Performance predicted with 1.2% accuracy is validated by SAE and USA Army literature.