高原环境柴油机喷嘴内部流场与缸内温度场的三维数值模拟

3D Numerical Simulation of Diesel Engine Nozzle Internal Flow and In-cylinder Temperature Field in Plateau

采用广安博之等准维模型,建立柴油机高原运行工作过程模型;通过环境模拟台架试验验证了模型的可信性。将准维计算结果作为喷嘴内部气液两相流动和缸内燃烧三维模拟的初始条件,就高原低压、低温、低氧条件对喷孔内燃油流动状态与分布、缸内燃烧过程的影响进行三维数值模拟。海拔3 700m计算结果表明:与平原环境相比,柴油机喷嘴内空穴现象加剧,燃油流动速度增加,喷孔出口燃油分布不均匀度增加;缸内燃烧平均温度比平原最多高出300℃且分布不均匀,燃烧室局部热负荷偏高。研究初步揭示了高原环境柴油机性能劣化机理,为通过优化缸内喷雾和燃烧过程改善高原运行发动机性能提供参考。

The model of working process for diesel engine run in plateau was proposed with Hiroyasu quasi-dimensional model and its feasibility was verified by the engine bench test. Taking the quasi-dimensional results as the boundary conditions of noz zle internal gas-fluid flow and in-cylinder combustion simulation, the influences of low pressure, low temperature and little oxy-gen environment on fuel flow state and distribution inside nozzle and in cylinder combustion process were simulated. The calcu lated results of 3 700 m altitude show that,compared with the plain environment, the cavity phenomenon inside diesel engine nozzle intensifies, the fuel flow velocity increases and the unevenness of fuel distribution in nozzle outlet increases. The average in-cylinder combustion temperature in plateau is 300 ℃ higher than that in plain and distributes uneven, and the local thermal loads of chamber are on the high side. The research elementarily reveals the degradation mechanism of diesel engine plateau performance, which brings the reference for improving engine high-altitude performance by optimizing the in-cylinder spray and combustion process.