轻型车用柴油机燃烧过程数值模拟

Combustion Simulation for Turbocharged Small Diesel Engine

本文以正庚烷和菲作为代表物质,组成理论空燃比和自燃特性与普通柴油较为接近的表征燃料,开发了较为精简的、包含26种组分、30个反应的柴油燃烧简化机理。在此基础上,针对某型轻型车用柴油机开展研究,通过CFD耦合反应机理技术对其燃烧过程进行了数值模拟,并与台架试验测量结果对比验证。计算得到的燃烧始点、燃烧相位、最高压力等均与实测数据符合得较好。对于1800r/min的工况,其对改变喷油提前角控制燃烧过程的预测体现出很高的精度。研究还发现,对于因扩散燃烧造成的两阶段放热现象,需要使用更精细的网格进行燃烧的数值模拟。

N-heptane and phenanthrene were chosen to setup a primary reference of diesel fuel considering self-ignition and stoichiometrie ratio. A reduced oxidation mechanism which contains 26 species and 30 reactions was obtained. Numerical investigation of light-duty diesel combustion by CFD coupling of oxidation mechanism was carried out and validated by experimental test. It is shown that the calculated combustion phase and maximum pressure in cylinder fitted the experimental data very well, especially for injection shift scanning when engine speed is 1800r/min. Meanwhile, a greater refinement of meshing was necessary for two-stage heat release of diffusion combustion.