Computational design studies for a high-efficiency and low-emissions free piston engine prototype
Computational design studies for a high-efficiency and low-emissions free piston engine prototype
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DOI：
10.4271/2004-01-2928
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发表时间：
2004-10
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影响因子：
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通讯作者：
A. Kleemann;J. Dabadie;S. Henriot
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文献类型：
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作者：
A. Kleemann;J. Dabadie;S. Henriot
目前的工作基于二冲程、单流扫气自由活塞发动机原型的计算设计优化，用于串联混合动力汽车，以达到高效率水平和低排放。这里通过均质充量压缩点火 (HCCI) 柴油燃烧以及增加废气再循环 (EGR) 和直接喷射水平来尝试实现性能目标。为了获得最佳的混合物制备和成分，需要高度调节的气体交换系统，并且还需要调整喷射参数以诱导上止点 (TDC) 周围的热量释放。基于零维、一维和简化计算流体动力学 (CFD) 模拟之间的迭代开发了一种计算方法，用于定义提供最佳发动机性能的操作条件和整体几何参数。基于这些发现，更详细的三维 CFD 计算已被用来指定最佳的进气口和排气口配置以及喷射特性。它们还可以作为验证迭代性能结果的基础。事实证明，通过采用直喷和提前喷射正时的高压缩比、提高的 EGR 率和 HCCI 燃烧，可以确保超过 50% 的指示效率以及较低的碳烟和氮氧化物排放水平。
The current work is based on the computational design optimisation for a two-stroke, uniflow scavenging free piston engine prototype for use in series hybrid vehicles to reach high efficiency levels combined with low emissions. Here the performance goals have been attempted via Homogeneous Charge Compression Ignition (HCCI) Diesel combustion with increased levels of exhaust gas recirculation (EGR) and direct injection. For optimal mixture preparation and composition, a highly tuned gas exchange system is required and also adapted injection parameters are needed to induce heat release at around top dead center (TDC). A computational methodology has been developed based on iterations between zero-, one-dimensional and simplified Computational Fluid Dynamics (CFD) simulations to define the operating conditions and overall geometrical parameters which give the best engine performance. Based on these findings, more detailed three-dimensional CFD calculations have been used to specify the optimal intake and exhaust port configurations and injection characteristics. They also serve as a basis for validation of the performance results from the iterations. It is demonstrated that an indicated efficiency of above 50% and low emission levels for soot and NOx can be ensured via a high compression ratio, elevated EGR rates and HCCI combustion using direct injection and early injection timing.