柴油机可调涡流比燃烧过程三维仿真

在柴油机进气歧管前安装蝶形涡流调节阀，通过调整直气道侧的有效流通面积改变缸内涡流强度。在稳流吹风试验平台，研究涡流调节阀角度对进气道流量因数和涡流比的影响，并结合粒子图像测速（particle image velocimetry，PIV）分析缸内涡流的形成过程。采用计算流体力学（computational fluid dynamics，CFD）评估涡流调节阀角度对缸内混合气体形成过程的影响，计算结果可复现三维 PIV测量的缸内流场结构和相似的涡心位置。随着进气门关闭，涡流比从0.57提高到2.05，油气在周向的相互作用增强，从而加速预混燃烧阶段的放热速度，促使燃烧重心提前、燃烧持续期缩短。在相同进气流量条件下，强涡流运动也促使累积放热量增加。

3D simulation of combustion process in diesel engine with variable swirl ratio

A butterfly swirl control valve is installed at the front of intake manifold of diesel engine. The swirl intensity in cylinder is changed by adjusting the effective flow area of straight airway side. The influence of swirl control valve angle on flow factor of intake port and swirl ratio is studied on a steady flow blowing test platform. The formation of in cylinder swirl is analyzed combining with particle image velocimetry(PIV). The effect of swirl control valve angle on the in cylinder mixing process of air fuel gas is estimated using computational fluid dynamics(CFD). The results can reappear the flow field structure and similar vortices position at in cylinder measured by 3D PIV. When the intake valve is closed, the swirl ratio increases from 0.57 to 2.05, and the air fuel interaction is enhanced in the circumferential direction, and then the heat release rate in premixed combustion stage is accelerated. Hence, the combustion focal point is brought forward, and the combustion duration is shorted. Under the condition of same intake flow rate, the strong swirl motion can increase accumulated heat release also.