负阀重叠早喷模式HCCI燃烧数学模型与计算分析

Mathematical Model and Computational Analysis of HCCI Combustion Based on NVO Early Injection Mode

针对早喷模式中的排气上止点燃油喷射(ETCI)模式,综合广安博之模型、Bai模型的优点加以改进,并将空间均质燃烧与油膜蒸发燃烧相耦合,建立了一种新型的基于喷雾、燃油附壁、油膜蒸发、燃烧等一系列过程适用于缸内早喷模式的数学模型。利用该模型对135单缸柴油机ETCI燃烧模式进行校核计算,并通过试验验证进一步对燃烧过程中的工况参数及调节参数进行了研究。研究结果表明:在ETCI模式下,存在部分油膜附壁,油膜的蒸发主要与缸内的气体温度与壁温有关,且存在明显的两阶段加热过程。累积放热率与排气门关闭时刻和壁温基本呈线性关系,排气门关闭时刻提前10°CA,累积放热率上升约6%;壁温升高50K,累积放热率上升4%。增压压力升高,累积放热率降低,增压压力越大,累积放热率降低的幅度越小。

Based on exhaust top dead center injection compression ignition（ETCI） combustion mode, improved Hiroyasu Model and Bai Model to calculate fuel wall wetting and coupled with single Wiebe combustion model and film evaporation model, a new numerical model for early injection mode including injection, fuel wall wetting, film evaporation and combustion was set up. Used for calculating ETCI combustion in a Model 135 single cylinder diesel engine, the new model was validated by experiment data. Parameters of combustion process including condition parameters and adjusting parameters were studied. Results show that film evaporation mainly relates to cylinder gas and wall temperatures, and there exists an evident two-stage heating process. The accumulative heat release rate has linear relationship with exhaust valve closing （EVC） timing and wall temperature. The accumulative heat release rate increases 6% when EVC angle advancing 10°CA, and it increases 40/60 when wall temperature increasing 50 K. The accumulative heat release rate decreases with intake pressure increasing, the higher the intake pressure, the smaller the decrease margin.