• XI CHEN

      Articles written in Sadhana

    • Thermodynamic and numerical analysis of intake air humidification of a turbocharged GDI engine

      BIN CHEN LI ZHANG XI CHEN QING ZHANG

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      Reducing the temperature and increasing the specific heat capacity of working medium of gasoline engines are the most efficient methods of mitigating knock tendency. The charge cooling effect of intake air humidification is helpful for decreasing the initial temperature of intake air, and the increase of the specific heat capacity of working medium can reduce the temperature rise in the in-cylinder process. This study established a mathematical model of intake air humidification of gasoline engines, and analyzed the effects of the technique on the thermodynamic process of a turbocharged gasoline engine with Ricardo WAVE Code. The results indicated that the intake air humidification is an isenthalpic process; the vapor influences the working process of the engine by altering the thermodynamic parameters of the working medium. A decrease in the initial temperature and adiabatic index and an increase in the specific heat capacity of working medium lowered the in cylinder temperature and pressure, hence suppressing the knock occurrence. After the humidification of intakeair, the engine performance slightly increased, and the thermal efficiency showed different levels of improvements at all the working conditions.

    • Experimental investigation about effect of double-spark plug ignition on cyclic variation and knocking for SI engine

      HUICHAO SHANG LI ZHANG XI CHEN PENGYAN GUO HUAWEI ZHANG

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      In order to analyze the effect of the double-spark plug ignition (DSI) on the heat release rate, cyclic variation in combustion and engine knocking, four different single- and double-spark plug ignition strategies are used for testing. Combustion diagnosis results show that when the DSI strategy is used, it can effectively promote the combustion process, increase the maximum combustion pressure, shorten the combustion duration and reduce the coefficient of cyclic variation (COV). Under low load condition, the effects are more pronounced.Test data reveals the following phenomenon. With the DSI strategy, both the cyclic variation in the early period of rapid-burning and in the later period of rapid-burning are reduced, especially in the early period of rapid burning. Then, the cyclic variation rate of the combustion duration is significantly reduced. Since the burning rate in the early period of rapid-burning is greatly accelerated, knocking tendency of the DSI engine is more obvious than that of the single-spark SI engine. The potential to improve engine performance and fuel economyby the DSI strategy largely depends on the optimization of the spark advance. Based on the optimization of the ignition timing of the DSI strategy S28&28, the break mean effective pressure (BMEP) is improved by about 5%- 6% compared to the original 158FMI engine.

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