Research of the impacts of in-cylinder steam injection and ignition timing on the performance and NO emission of a LPG engine

In the study, the effects of in-cylinder steam injection (ICSI) on the liquefied petroleum gas (LPG) engine were investigated in consideration of the impacts of steam on the in-cylinder combustion, to improve its fuel economy and reduce NO. First, a quasi-dimensional model of a baseline engine is established. Then, based on the model, the effects of ICSI on the engine in-cylinder combustion, performance and NO are discussed. After that, according to the impacts of ICSI on the engine, the influences of ignition timing on the engine with ICSI are further analyzed. Finial, with optimum ignition timing, the potentials of ICSI for the engine fuel savings and NO reduction are evaluated. The results show that the laminar flame speed of LPG is decreased by steam. ICSI leads to remarkable increases of flame development angle and rapid burning angle. By adjusting ignition timing, the combustion phase of the engine with ICSI is changed. With optimum ignition timing, engine performance and NO characteristic are remarkably improved by ICSI. At all engine speeds, compared with the baseline engine, with ICSI and optimum ignition timing, the torque is increased by 0.8-6.6%, the BSFC is decreased by 0.6-6.4% and the NO is reduced by 54.0-61.7%.(c) 2022 Elsevier Ltd. All rights reserved.