增压直喷汽油机热平衡和平衡试验对比

Experimental Comparison of Heat and Exergy Balance in a Turbocharged Direct-Injected Gasoline Engine

为提高内燃机能量利用效率,针对增压直喷汽油机联合开展了万有特性下热平衡和平衡试验.基于热力学第一定律和第二定律,建立内燃机热力学分析模型,结合试验数据得出该机的热平衡图和平衡图,在此基础上分析了内燃机工作参数对各种形式能量流和流的分布影响,并对热平衡和平衡进行了对比分析.结果表明:从热平衡分析来看,燃料能量主要损失在废热中,各种形式能量流分数大小呈明显的波动变化;从平衡分析来看,不可逆损所占比例最大,是限制内燃机效率的主要因素;热效率和排气能量分数分别与效率和排气流分数的等值线形态相似;排气分数峰值出现在高速高负荷区,传热分数峰值出现在低速低负荷区.针对分析结果,提出了几点改善汽油机能量利用效率的建议.

To improve energy utilization efficiency of engine, the heat and exergy balances were studied in a turbocharged direct-injected gasoline engine under mapping characteristics. Based on the first law and the second law of thermodynamics, a thermodynamic model of engine was built. From engine test data, the heat balance maps and exergy balance maps were obtained. The effects of engine operating parameters on various forms of energy flow and exergy flow distributions were analyzed. Meanwhile, comparative analysis on heat balance and exergy balance were made. Results show that, from heat balance, fuel en- ergy is mainly lost as the waste heat energy, and the proportions of various forms of energy flow fluctu- ates. From exergy balance, the irreversible exergy loss is the largest proportion, and it is＂ the key factor limits the engine exergy efficiency. The isoline shapes of thermal efficiency and exhaust energy percentage are similar to those of exergy efficiency and exhaust exergy percentage. Maximum percentage of exhaust exergy appears at high-speed and high-load area, while maximum percentage of heat transfer exergy ap- pears at low-speed and low-load area. The study provides the suggestions for improving engine energy utilization efficiency.