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首页> 外文会议>Proceedings of the 2009 spring technical conference of the ASME Internal Combustion Engine Division >MULTIDIMENSIONAL MODELING OF NATURAL GAS JET AND MIXTURE FORMATION IN Dl SI ENGINES - DEVELOPMENT AND VALIDATION OF A VIRTUAL INJECTOR MODEL
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MULTIDIMENSIONAL MODELING OF NATURAL GAS JET AND MIXTURE FORMATION IN Dl SI ENGINES - DEVELOPMENT AND VALIDATION OF A VIRTUAL INJECTOR MODEL

机译：Dl SI发动机中天然气射流和混合气形成的多维建模-虚拟喷射器模型的开发和验证

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During the last years, the integration of computational CFD tools in the internal combustion (IC) engine design process has continuously been increased, allowing to save time and cost as the need of experimental prototypes has diminished. Numerical analyses of IC engine flows are rather complex from both the conceptual and operational sides. In fact, such flows involve a variety of unsteady phenomena, and the right balance between numerical solution accuracy and computational cost should be always reached.rnThe present paper is focused on computational modeling of natural gas (NG) direct injection (DI) processes from a poppet-valve injector into a bowl-shaped combustion chamber. At high injection pressures, the efflux of gas from the injector and the mixture formation processes include compressible and turbulent flow features, such as rarefaction waves and shock formation, which are difficult to be accurately captured by the numerical simulation, particularly when combustion chamber geometry is complex and piston and intake/exhaust valve grids are moving.rnA three-dimensional moving grid model of the combustion engine chamber, originally developed by the authors, was enhanced by increasing the accuracy in the sonic section proximity of the critical valve seat nozzle, in order to precisely capture the expansion dynamics the methane undergoes inside the injector and immediately downstream from it.rnThe enhanced numerical model was validated by comparing numerical results to Schlieren experimental images for nitrogen injection into a constant-volume bomb. Then, numerical studies were carried out in order to characterize the fuel jet properties and the evolution of mixture-formation for a centrally-mounted injector configuration in both cases of a pancake test chamber and the real-shaped engine chamber.rnFinally, the fluid properties computed by the model in the throat-section of the critical nozzle were taken as reference data for developing a new effective 'virtual injector' model, which allows the designer to remove the whole computational domain upstream from the sonic section of the nozzle, keeping the flowrnproperties practically unchanged. The outcomes of such a virtual injector model were shown to be in very good agreement with the results of the enhanced complete injector model, confirming the reliability of the proposed novel approach.
机译：在过去的几年中，计算CFD工具在内燃机（IC）发动机设计过程中的集成不断增加，由于减少了实验原型的需求，从而节省了时间和成本。从概念和操作两方面对内燃机的流量进行数值分析是相当复杂的。实际上，这样的流动涉及各种不稳定的现象，应该始终在数值解的精度和计算成本之间达到正确的平衡。rn本文重点研究了天然气（NG）直接注入（DI）过程的计算模型。提升阀阀喷射器进入碗形燃烧室。在高喷射压力下，来自喷射器的气体外流和混合物形成过程包括可压缩和湍流特征，例如稀疏波和冲击形成，这些特征很难通过数值模拟准确地捕获，特别是当燃烧室的几何形状为复杂的结构以及活塞和进气/排气门的网格正在移动。rn最初由作者开发的三维内燃机运动网格模型通过提高关键阀座喷嘴的声波截面附近的精度而得到增强。为了精确捕获甲烷在喷油器内部以及紧接喷油器下游所经历的膨胀动力学。通过将数值结果与Schlieren实验图像进行比较，以验证将氮气注入到定量炸弹中的效果，从而验证了增强的数值模型。然后，进行了数值研究，以表征在薄饼测试室和实形发动机室两种情况下集中安装的喷油嘴配置的燃料射流特性和混合物形成的演变过程。该模型在关键喷嘴的喉部截面中计算出的数值被用作开发新的有效“虚拟喷油器”模型的参考数据，该模型可以使设计人员从喷嘴的声波截面上游移除整个计算域，从而保持flowrnproperties几乎不变。事实证明，这种虚拟喷油器模型的结果与增强型完整喷油器模型的结果非常吻合，证实了所提出的新方法的可靠性。

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