速度梯度、近壁效应和Re数对压力探针测量误差的影响

EFFECTS OF VELOCITY GRADIENT,WALL-PROXIMITY AND REYNOLDS NUMBER ON MEASURING ERRORS OF PRESSURE PROBES

通过模拟实验研究，分析了速度梯度、近壁效应和Ｒｅ数对几种叶轮机流场测量用压力探针测量误差的影响。实验结果表明，横向梯度能引起偏转角测量误差；纵向梯度能引起俯仰角测量误差；梯度使气流方向测量值向负梯度方向偏转。圆柱探针和锥形多孔探针相比，气流方向测量误差对速度梯度更敏感，纵向梯度对俯仰角测量值的影响尤其大。速度梯度一般使静压测量值偏小，使总压测量值偏高。纵向速度梯度对圆柱探针的静压测量值的影响规律例外，正速度梯度引起大的静压正误差，负速度梯度引起大的静压负误差。圆柱探针比锥形多孔探针近壁效应严重。近壁引起测出的气流方向偏离壁面。近壁一般使静压测量值偏小，但圆柱探针头部近叶轮机机匣时静压值反而偏高。近壁对总压测量影响不大。速度梯度和近壁对测量误差的影响还与来流方向有关。低Ｒｅ数使静压测量值偏大，几何形状不同的探针Ｒｅ数的影响范围不同。

Model experiments were made to investigate the effects of velocity gradient, wall-proximity and Reynolds number on measuring errors of pressure probes.The results indicate that,transverse velocity gradient causes measuring error of yaw angle while perpendicular velocity gradient causes measuring error of pitch angle,the velocity gradient makes the flow direction measured turn to the side of lower velocity.The velocity gradient,especially the perpendicular velocity gradient,leads the measuring error of flow angle with cylindrical probe to be larger than with conical multi-hole probe.The velocity gradient generally makes the static pressure measured lower and the total pressure measured higher. The wall-proximity of the cylindrical probes is more serious than that of the conical multi-hole probes. The wall-proximity causes the flow direction measured to deflect away from the wall,and generally makes the measured static pressure lower while having few effects on total pressure measurements.The effects of the velocity gradient and wall-proximity on the measuring errors are related to the flow direction.The lower the Reynolds number,the higher the measured static pressure.The effects of the Reynolds number on the measuring errors are different when multi-hole probes having different geometry.