矿用防爆柴油机瞬态工况特性及参数优化

Transient condition characteristics and parameter optimization of mine explosion-proof diesel engine

现有防爆柴油机是在地面柴油机的进气系统和排气系统加装防爆阻火器改造而成。煤矿井下工况复杂,防爆柴油机经常处于启停、加减速等瞬态工况,而防爆阻火器的加装导致柴油机进排气严重受阻,瞬态工况下进排气系统迟滞加重,瞬态工况特性恶化严重。针对该问题,利用GT-POWER建立了防爆柴油机稳态仿真模型,利用Simulink建立了防爆柴油机瞬态工况控制模型,并将瞬态工况控制模型与稳态仿真模型耦合形成防爆柴油机瞬态仿真模型。基于防爆柴油机瞬态仿真模型,对恒转速变转矩和恒转矩变转速2种典型瞬态工况下防爆柴油机动力性能进行了仿真分析,结果表明:恒转速变转矩瞬态工况下,与防爆改造前柴油机相比,防爆柴油机空燃比下降更快,缸内最大爆发压力降低,转矩迟滞现象更明显,且转矩升高越快,迟滞效应越严重;恒转矩变转速瞬态工况下,防爆柴油机空燃比随着转速增大而减小,但小负荷增转速过程对空燃比的影响较小。为合理优化防爆柴油机参数,仿真分析了喷油提前角和进排气防爆阻火器栅栏数量对防爆柴油机动力和排放性能的影响,结果表明:缸内最大爆发压力、最高燃烧温度、摩擦转矩和功率均随喷油提前角增大而增大,CO和HC体积分数随喷油提前角增大而减小,NO;体积分数随喷油提前角增大而增大;随着进排气防爆阻火器栅栏数量增多,防爆柴油机缸内最大爆发压力增大、最高燃烧温度减小,进排气防爆阻火器栅栏数量增多对防爆柴油机摩擦转矩和功率的影响几乎可以忽略不计,但对尾气排放浓度有一定的抑制作用;适当增大喷油提前角和进排气防爆阻火器栅栏数量,可在一定程度上改善防爆柴油机瞬态工况特性。

The existing explosion-proof diesel engine is transformed by adding explosion-proof flame arrester to the intake system and exhaust system of ground diesel engine. Coal mine underground conditions are complex, explosion-proof diesel engine is often in start-stop, acceleration and deceleration and other transient conditions. And the installation of explosion-proof flame arrester leads to serious obstruction of diesel intake and exhaust, aggravating the hysteresis of intake and exhaust system under transient conditions, and seriously deteriorating the transient conditions characteristics. In order to solve this problem, the steady-state simulation model of explosion-proof diesel engine is established by GT-POWER, and the transient condition control model of explosion-proof diesel engine is established by Simulink, and the transient simulation model of explosion-proof diesel engine is formed by coupling the transient condition control model with the steady-state simulation model. Based on the transient simulation model of explosion-proof diesel engine, the dynamic performance of explosion-proof diesel engine under two typical transient conditions of constant speed and variable torque and constant torque and variable speed is simulated and analyzed. The results show that under the transient condition of constant speed and variable torque, compared with the diesel engine before the explosion-proof transformation, the air-fuel ratio of the explosion-proof diesel engine decreases faster, the maximum burst pressure in the cylinder decreases, and the torque hysteresis is more obvious. Moreover, the faster torque rises, the more serious the hysteresis effect. Under the transient condition of constant torque and variable speed, the air-fuel ratio of explosion-proof diesel engine decreases with the increase of speed, but the process of increasing speed with small load has little effect on the air-fuel ratio. In order to optimize the parameters of explosion-proof diesel engine, the effects of injection advance angle and the number of flame arrester barriers on the power and emission performance of explosion-proof diesel engine are analyzed by simulation. The results show that the maximum burst pressure, maximum combustion temperature, friction torque and power in the cylinder all increase with the increase of the injection advance angle, the volume fraction of CO and HC decreases with the increase of the injection advance angle, and the volume fraction of NO;increases with the increase of the injection advance angle. With the increase in the number of intake and exhaust explosion-proof flame arrester fences, the maximum burst pressure in the cylinder of the explosion-proof diesel engine increases and the maximum combustion temperature decreases. The increase of the number of intake and exhaust explosion-proof flame arrester fences has a negligible effect on the friction torque and power of the explosion-proof diesel engine, but it can inhibit the exhaust emission concentration to a certain extent. Properly increasing the fuel injection advance angle and the number of intake and exhaust explosion-proof flame arrester fences can improve the transient condition characteristics of explosion-proof diesel engines to a certain extent.