氩-氧氛围中氢气射流喷射与混合特性的研究

Characteristics of Injection and Mixing for Hydrogen Jet Under Argon-Oxygen Atmosphere

氩气循环氢燃料发动机以氩-氧(Ar-O2)混合气代替空气作为工质气体,可提高发动机效率,并避免NOx的产生.基于纹影法研究了氩-氧氛围中不同压力边界下氢气射流喷射与混合特性,结果表明:氢气射流锥角总体上随着喷射过程的发展逐渐减小,然后趋于稳定,且受压力边界的影响较小,稳定在28.5°~33.5°;射流截面积随着喷射过程的发展近似呈线性增长;提高喷射压力以获得大贯穿距离是提高射流截面积及体积的有效方法;射流内部过量氧气系数φo随着喷射过程的发展呈上升趋势,选取高喷射压力有助于增大射流内部过量氧气系数,且对于一定的喷射压力,存在实现最大过量氧气系数的最佳环境压力.通过对不同压力边界下射流贯穿距离与喷射时间的关系拟合分析,获得一种基于压力边界预测气体射流贯穿距离的方法.

Replacing air with argon-oxygen(Ar-O2)as working gas for an argon-circulated hydrogen engine can improve the thermal efficiency and avoid NOx formation.The injection and mixing characteristics of the hydrogen jet under different pressures in Ar-O2 atmosphere were studied by schlieren method.The experimental results show that hydrogen jet dispersion angle gradually decreases and then tends to be steady,and hydrogen jet cross-section area increases linearly with the development of the injection process.Hydrogen jet dispersion angle is less affected by the pressures and stabilized at 28.5°-33.5°.In order to increase jet cross-section area and volume,a large penetration length can be obtained by raising the injection pressure.The excess oxygen coefficient increases with the development of the gaseous jet.Adopting high injection pressure contributes to increase the excess oxygen coefficient.There is an appropriate ambient pressure to reach the maximum excess oxygen coefficient for a certain injection pressure.By fitting the relationship between the penetration length and the injection time under different pressures,a new method for predicting gas jet penetration length based on pressure is obtained.