Experimental investigation and numerical assessment the effects of EGR and hydrogen addition strategies on performance, energy and exergy characteristics of a heavy-duty lean-burn NGSI engine

Abstract

In order to investigate the influences of hydrogen addition and exhaust gas recirculation (EGR) strategies on performance, combustion, emissions, energy and exergy balance of a lean-burn and high compression ratio (CR) (13.6) natural gas spark ignition (NGSI) engine fueled with 99% methane content is tested on the engine bench under different hydrogen contents. A corresponding 1D GT-Power simulation model is built and validated according to experimental data. In the first stage, both peak cylinder pressure (PCP) and peak heat release rate (HRR) increase with the hydrogen addition but decrease with increased EGR ratio. Besides, EGR addition will retard the effect of various hydrogen contents on performance and combustion of the engine. In the second stage, the NOx emissions increase with hydrogen enrichment but decrease with the increase of EGR rate due to the variation of in-cylinder temperature, which emphasizes effective method of EGR addition strategies to reduce the NOx emissions on the lean-burn NGSI engine fueled with natural gas-hydrogen (HNG). Finally, the change trends of exergy terms are similar to their corresponding energy, but the percentages of heat transfer exergy and exhaust exergy are about 7.05 and 2.61 times lower than their corresponding energy. Furthermore, the simulation model and data in the paper can be applied to evaluate and optimize the energy distribution and performance by changing different technologies, strategies and fuels in the future. What is more, the analysis of the energy and exergy balance can provide a new thought for the future research to improve engine’s performance.