抽吸腔反压对抽吸槽内流场结构影响试验研究

Experimental Investigation for Effects of Bleed Chamber Pressure on Flow Field

关键词:  流场结构  反压  抽吸  流量系数  深宽比

Key words:  Flow field structure  Chamber pressure  Bleed  Mass flow coefficient  Length-to-width ratio

摘要:

为了研究抽吸腔反压对抽吸槽内流场结构的影响规律，在国防科学技术大学吸气式超声速风洞中开展了马赫数2的试验研究，采用纳米粒子平面激光散射技术(NPLS)、纹影两种非接触测量与显示技术对不同抽吸腔反压时抽吸槽内局部流场结构进行了显示和诊断。同时试验还测量了抽吸质量流量，对抽吸性能进行了分析。NPLS结果和纹影结果清晰地展示了抽吸槽附近的局部流场结构，包括分离区、剪切层、膨胀波、障碍激波、激波串等典型结构。研究表明，当压比达到0.25左右时，抽吸槽内开始出现激波串。随着抽吸腔反压的增加，气流膨胀角度逐渐变小，障碍激波下半段长度逐渐变短，且向下游移动，同时音速流量系数随抽吸腔反压的增加逐渐减小。当压比达到0.6左右时，激波串消失。当压比在0.18附近时，随着抽吸槽深宽比的增加，抽吸槽内分离区由开口状态变为闭口状态，同时气流膨胀角度逐渐增加，障碍激波逐渐向上游移动，音速流量系数逐渐增加。当抽吸槽深宽比大于1时，低反压情况下抽吸槽内分离区为闭口状态，高反压情况下抽吸槽内分离区为开口状态。

Abstract:

In order to study the effects of the bleed chamber pressure on the flow field structure in the bleed slots， experiments were carried out in a continuous supersonic wind tunnel of National University of Defense Technology. The flow field structure in the bleed slots at different chamber pressure was obtained and diagnosed by non-touched measurement， including NPLS and schlieren. The bleed mass flow rate was measured and the bleed performance was analyzed. The NPLS results and schlieren results clearly show the local flow field structure near the bleed slot， including a series of typical flow field structure， such as the separation bubble， shear layer， expansion wave， barrier shock and shock train. The results show that shock train appears in the bleed slot when pressure ratio increased to 0.25. With the increase of bleed chamber pressure， the expansion angle of the gas flow decreases and the length of the lower half of barrier shock gradually becomes shorter and moves to the downstream， and sonic mass flow coefficient decreases with the increase of bleed chamber pressure. Shock train disappears when pressure ratio increased to 0.6. When chamber pressure is around 0.18， the separation in the bleed slot varied from open state to closed state with the increase of length-to-width ratio. At the same time， the expansion angle of the gas flow increases， the barrier shock gradually moves to the upstream， and sonic mass flow coefficient increases.When the length-to-width ratio of the bleed slot is larger than 1， the separation bubble in the bleed chamber is closed at low chamber pressure， and it is open at high chamber pressure.