应用CFD防爆车辆发动机排气系统处理结构设计

Structural Design of Exhaust System of Explosion-Proof Vehicle Engine Based on CFD

排气系统废气温度高是防爆车辆设计时必须重点考虑的因素。针对防爆发动机排气系统废气处理结构进行分析,基于内部的热力学机理,分析废气处理结构的热力学模型,提出水汽之间发生显热交换和潜热交换;利用CFD建立了水汽两相流模型,初始条件依据试验数据,得到不同时间内高温烟气穿越水箱液池的形态变化图,分析进气管长度和直径对于气体穿越液池深度的影响。利用防爆柴油机试验台架,对废气处理结构的功率和扭矩消耗进行分析。结果可知:初始时刻高温烟气从进口流入废气处理箱时,气体在进气管进口处堆积形成泡状堆积气泡结构;气泡会随着时间慢慢增大直到破碎,气体壁面液膜破裂气体扰动液体,同时液体扰动气体从而气液发生强烈的湍流运动;气体穿越液池深度随着进气速度的增加而增加,随着管径的增加而减小,随着长度的增加而增加;安装排气系统防爆装置后,柴油机功率和扭矩随转速变化曲线基本低于拆除装置后的曲线,功率下降了15.04%,扭矩下降了3.4%;分析结果为此类设计提供参考。

The high exhaust gas temperature of the exhaust system is a design factor that must be considered when designing an explosion-proof vehicle. The exhaust gas treatment structure of the explosion-proof engine exhaust system was analyzed. Based on the internal thermodynamic mechanism,the thermodynamic model of the exhaust gas treatment structure was analyzed,and the sensible heat exchange and latent heat exchange between water vapor were proposed. The water vapor two-phase flow model was established based on CFD. The initial conditions were based on the experimental data. The morphological change diagram of the high temperature flue gas passing through the tank liquid pool was obtained. The influence of the length and diameter of the intake pipe on the gas penetration depth was analyzed. The power and torque consumption of the exhaust gas treatment structure was analyzed using an explosion-proof diesel test bench. The results show that:at the initial moment,when the high-temperature flue gas flows into the exhaust gas treatment tank from the inlet,the gas accumulates at the inlet of the intake pipe to form a bubble-like stacked bubble structure. The bubble will gradually increase with time until it breaks,and the gas film on the gas wall ruptures the gas to disturb the liquid,while the liquid disturbs the gas and the gas and liquid undergo a strong turbulent motion. The depth of the gas traversing liquid pool increases with the increase of the intake air velocity,and decreases with the increase of the pipe diameter,and increases with the increase of the length. After installing the exhaust system explosion-proof device,the diesel engine power and torque with the speed change curve is basically lower than the curve after the removal device,the power decreased by 15.04%,the torque decreased by 3.4%;the analysis results provide a reference for such design.