A computational study of direct injection gasoline HCCI engine with secondary injection
A computational study of direct injection gasoline HCCI engine with secondary injection
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DOI：
10.1016/j.fuel.2006.02.013
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发表时间：
2006-09
期刊：
影响因子：
7.4
通讯作者：
Zhi Wang;S. Shuai;Jian-xin Wang;G. Tian
中科院分区：
文献类型：
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作者：
Zhi Wang;S. Shuai;Jian-xin Wang;G. Tian
通过将多维计算流体力学（CFD）代码与详细的化学动力学相结合，研究了高辛烷值压燃式发动机的详细进气、喷雾、燃烧和污染形成过程。构建了用于高辛烷值燃料的扩展碳氢化合物氧化反应机理，并引入了用于发动机仿真的3D-CFD/化学耦合建模策略，以满足模拟整个发动机物理化学过程（包括进气、压缩、喷射和燃烧过程）可接受的执行时间要求。使用直喷 HCCI 发动机的实验数据验证了改进的 3D CFD/化学模型。然后，采用CFD/化学模型对采用两级喷射策略的汽油直喷HCCI发动机的进气、喷雾、燃烧和污染物形成过程进行了模拟。该模型考虑了复杂的多维几何形状中的进气流结构、喷雾雾化、液滴蒸发和气相化学。计算结果表明，第二次喷射形成的富油区外围首先着火，随后富油区点火，并作为起爆点点燃第一次喷射形成的周围贫混合气区。两区 HCCI 导致顺序燃烧，这使得点火正时和燃烧速率可控。此外，HCCI负载范围还可扩展。但燃料富集区外围燃烧剧烈，导致NOx排放略高。
The detailed intake, spray, combustion and pollution formation processes of compression ignition engine with high-octane fuel are studied by coupling multi-dimensional computational fluid dynamic (CFD) code with detailed chemical kinetics. An extended hydrocarbon oxidation reaction mechanism used for high-octane fuel was constructed and a modeling strategy of 3D-CFD/chemistry coupling for engine simulation is introduced to meet the requirements of execution time acceptable to simulate the whole engine physicochemical process including intake, compression, spray and combustion process. The improved 3D CFD/chemistry model was validated using the experimental data from HCCI engine with direct injection. Then, the CFD/chemistry model has been employed to simulate the intake, spray, combustion and pollution formation process of gasoline direct injection HCCI engine with two-stage injection strategy. The models account for intake flow structure, spray atomization, droplet evaporation and gas phase chemistry in complex multi-dimensional geometries. The calculated results show that the periphery of fuel-rich zone formed by the second injection ignited first, then the fuel-rich zone ignited and worked as an initiation to ignite the surrounding lean mixture zone formed by the first injection. The two-zone HCCI leads to sequential combustion, this makes ignition timing and combustion rate controllable. In addition, HCCI load range can be extended. However, the periphery of fuel-rich zone leads to fierce burning, which results in slightly high NOxemissions.