Effect of Compression Ratio on Combustion and Emission Characteristics of Hybrid Engine

Taking a special hybrid engine as the prototype, the conventional cycle (compression ratio 11.5) and Miller cycle are studied the results show that when the compression ratio is 11.5, 12.5 and 15 under low load conditions, compared with the conventional cycle, the throttle opening increases, the pump loss decreases and the thermal efficiency increases; when the compression ratio of Miller cycle is 15, the thermal efficiency increases by 1.62% compared with the conventional cycle. When the compression ratio of Miller cycle is 11.5 under high load conditions, compared with the conventional cycle, the knock tendency is weakened, the combustion phase is optimized and the economy is slightly improved; When the compression ratio is increased to 12.5, the fuel consumption is still improved due to the dominant knock suppression ability of Miller cycle. However, when the compression ratio is increased to 15, the influence of compression ratio is dominant. At this time, the knock tendency is serious and the thermal efficiency is reduced. In terms of emission, after Miller cycle, the combustion temperature decreases, NOx emission decreases, HC and CO emissions increase, and particle emission improves; After increasing the compression ratio, the combustion temperature increases, NOx and CO emissions increase, HC emissions increase slightly, and particle emissions increase. © 2022, Science Press. All right reserved.