中文摘要：

基于纹影法，对不同孔径的单孔喷嘴在多种气源压力和背压条件下的高压燃气射流宏观结构特性进行研究．结果表明：即使在很小的压力差条件下，喷孔出口处仍然会形成不充分膨胀气体射流，而气体在出口处的膨胀、加速过程和诱导激波是区别于液体喷雾的主要特征．背压变化对气源与背压比的影响明显，其对射流贯穿距及锥角的影响要大于气源压力和孔径带来的影响．虽然甲烷和氮气的密度差别较大，但在相同条件下贯穿距结果无明显区别，壅塞现象对高压燃气喷射具有重要影响．由此，初步提出了针对高压燃气喷射的射流贯穿距经验公式．喷孔出口处的膨胀过程使燃气射流的近场锥角要明显大于远场锥角，同时使气体速度达到超声速，但对射流前锋面速度无明显影响，在喷射时间TASOI=1ms之后，前锋面速度便降低到了50m／s以下．在低背压条件下，燃气射流表现出较强的空间拓展和分布能力，但随着背压增加，气体射流的面积和体积明显减小．

英文摘要：

The macroscopic structure characteristic of gas jet through a single-hole nozzle was analyzed under different origin pressure and ambient pressure conditions by using schlieren imaging system. Experimental results show that an under-expanded supersonic gas jet is observed on the downstream of nozzle exit. The expansion and acceleration of the gas, as well as induced shock wave, are the important characteristics which are distinguished from the liquid fuel spray. The variation of ambient pressure changes the ratio of origin pressure and ambient pressure signifi- cantly. Therefore, it leads to more significant effect on jet tip penetration and jet angle, comparing with origin pressure and orifice diameter. The density of methane is smaller than that of nitrogen, but which does not cause a significant difference in the results of jet tip penetration. Choking phenomenon at the nozzle exit has important influence on the high-pressure gas fuel injection. The empirical formula of high-pressure gas jet tip penetration is proposed preliminarily. In addition, the expansion process occurring at orifice exit leads that the near-field angle is bigger than the farfield angle. Meanwhile, it also makes the gas to accelerate and reach the supersonic speed. But the acceleration does not promote the front-edge velocity of methane. In fact, the front-edge velocity will reduce to below 50 m/s after TASOI = 1 ms. Gas jet shows strong spatial expansion and distribution capacity in low ambient pressure condition. But the area and volume of gas jet decreases obviously, when the ambient pressure increases.