单区放热率计算中考虑传热影响的比热比自适应估计方法

单区放热率算法广泛应用于汽油机燃烧放热诊断,但比热比和传热难以被合理估计,影响了分析结果的可靠性.在单区放热率模型的基础上研究了一种考虑传热影响的比热比估计方法:计算压缩和膨胀期间的多变指数,在燃烧区间内基于工质温度对其插值以获取变化的比热比,用于总放热率的计算.从循环释放能量和燃烧控制参数的角度出发,使用汽油机试验数据将其与现存方法进行了对比验证.结果表明此方法计算的循环累计放热总量更加精准,燃烧终点提前,且燃烧控制参数间的相关性得到明显改善.此算法能更加准确地描述缸内燃烧历程.

Adaptive estimation method of specific heat ratio in a single-zoneheat-release rate model considering heat transfer effect

The single-zone heat-release rate algorithm is widely used in combustion heat-release diagnosis in gasoline engine. However, it is difficult to reasonably estimate the specific heat ratio and heat transfer, which affects the reliability of the analysis results. Based on the single-zone heat-release rate model, a specific-heat-ratio estimation method considering the influence of heat transfer is proposed, which calculates the polytropic exponent during compression and expansion, and interpolates it based on the gas temperature in the combustion interval to obtain the variable specific heat ratio for the calculation of the total heat release. From the perspectives of the energy released during the cycle and the combustion control parameters, the proposed method is compared with the existing method by using the experimental data of the gasoline engine. The results show that the total cumulative heat release calculated by this method is more accurate, the combustion end point is advanced, and the correlation between the combustion control parameters is significantly improved, indicating that this algorithm can describe the combustion history in the cylinder more accurately.