传统缸内壁面传热模型在氢内燃机中的适用性

Applicability of Conventional Wall Heat Flux Models in Hydrogen Engines

针对传统内燃机缸内传热模型在氢内燃机传热预测计算中的适用性问题,研究了LaunderSpalding模型、Huh模型、Poinsot模型、Han-Reitz模型和Rakopoulos模型在氢内燃机的压缩和膨胀冲程中的应用,为此编制程序将上述模型嵌入到开源计算流体动力学(CFD)工具包OpenFOAM的求解器中,并对一个氢内燃机缸内反应流动的算例进行了传热的预测计算和实验验证。研究表明:相对其他模型,Rakopoulos模型对氢内燃机传热热流的预测最为准确,优于AVL-Fire软件中推荐的Han-Reitz模型,可作为AVL-Fire软件二次开发进行氢内燃机的相关模拟计算;除Rakopoulos模型之外的模型适用性较差的原因是,不能准确描述氢内燃机缸内边界层中的工质物性及湍流黏性的分布规律,通过改进氢内燃机缸内边界层中的密度、黏度、湍流普朗特数分布有望提高氢内燃机传热模型的适用性;准确预测壁面热流峰值时刻需要对燃烧模型的火焰传播过程计算进行详细校核。

Five conventional internal combustion engines wall heat flux models, Launder-Spalding model, Huh model, Poinsot model, Han-Reitz model and Rakopoulos model, and their applicability in hydrogen engine compression and expansion stokes are discussed. These five models are codified into OpenFOAM CFD solver, an open source CFD toolkit, and implemented in a hydrogen engine reacting flow case. The experimental data are used to validate the numerical calculation and evaluate the performance of these five models. The results show that Rakopoulos model works best in hydrogen engines application cases, instead of Han-Reitz model recommended by the widely used code AVL-Fire. The poor performance of the other four models is due to the failure in predicting distributions of thermo-physical properties and turbulent viscosity inside the hydrogen engine in-cylinder boundary layer, although these models work well in the conventional fuel engines. Thus improved predictions of ρ＋, v＋ and PrT inside the boundary layer facilitate heightening the applicability of these models in hydrogen engines. It is suggested that the validation of flame propagation modeling becomes necessary to calculate the peak heat flux time.