Comparison of performance of a Greener direct-injection stratified-charge (DISC) engine with a spark-ignition engine using a simplified model

摘要

The direct-injection stratified charge (DISC) engine is a hybrid between spark ignition (SI) and compression-ignition engines, it combines many of the best features of both with some unique advantages of its own. This includes multi-fuel capability, high thermal efficiency, low NOx production, and low particulate emissions.This work shows how simple semi-global models can predict the performance of the SI and DISC engines with reasonable accuracy, without going to details of modeling for internal processes such as: swirl, mixing and detailed combustion kinetics.The operating variables studied were inlet manifold pressure p_i, exhaust manifold pressure p_e, engine speed N, equivalence ratio Φ, and volumetric efficiency % at different loads. The corresponding performance parameters were the brake mean effective pressure bmep, brake power P_b, and brake thermal efficiency η_(b,th). The main contribution of this work is the production of friendly set of curve-fitting correlations for engine performance. The bmep and the P_b increase with the load for both engines. For spark ignition engines the bmep increases by about 70% when load increases from 50% to 100%. With the DISC engine, this ratio increases to 75%. The percent improvement in η_(b,th) for the DISC to the SI engine is around 50% which increases with part load, lower compression ratio r_c and p_i.