In expansion tube and shock tunnel facilities, freestream properties are generally inferred from the measurement of shock speeds using wall-mounted instrumentation. By measuring the shock arrival time at known locations along the facility wall, their spacing can be used to calculate the shock speed. These shock arrival measurements are generally taken using high-frequency pressure transducers. For operation at low pressures and shock speeds in excess of 10 km/s, the transducer rise time and its small voltage response to the passing shock wave can become the largest source of uncertainty in the found shock arrival time. In these situations, shock arrival can also be found optically by measuring the radiative emission of the passing shock wave using photomultiplier tubes or photodiodes, which can have rise times of much lower than a microsecond and potentially a larger voltage response to the passing shock wave. This paper presents a photodiode system that has been used to optically measure shock arrival in the X2 hypervelocity expansion tube at the University of Queensland. Experimental results show that for challenging low-density, high shock speed conditions, the photodiode system is able to measure shock arrival with a much larger signal-to-noise ratio than a comparable pressure transducer while operating with a similar or higher-frequency response. This behaviour makes the photodiode system an ideal sensor for detecting shock arrival in these situations.

在膨胀管和冲击隧道设施中，自由流特性通常是通过使用壁挂式仪器测量冲击速度来推断的。通过测量沿设施墙已知位置的冲击到达时间，它们的间距可用于计算冲击速度。这些冲击到达测量通常使用高频压力传感器进行。对于在低压和超过 10 公里/秒的冲击速度下运行，换能器上升时间及其对通过的冲击波的小电压响应可能成为发现的冲击到达时间的最大不确定性来源。在这些情况下，也可以通过使用光电倍增管或光电二极管测量通过的激波的辐射发射，以光学方式找到激波到达，它的上升时间可能远低于一微秒，并且可能对通过的冲击波有更大的电压响应。本文介绍了一种光电二极管系统，该系统已用于光学测量昆士兰大学 X2 超高速膨胀管中的激波到达。实验结果表明，对于具有挑战性的低密度、高冲击速度条件，光电二极管系统能够以比类似压力传感器大得多的信噪比来测量冲击到达，同时以相似或更高的频率响应运行。这种行为使光电二极管系统成为在这些情况下检测冲击到达的理想传感器。本文介绍了一种光电二极管系统，该系统已用于光学测量昆士兰大学 X2 超高速膨胀管中的激波到达。实验结果表明，对于具有挑战性的低密度、高冲击速度条件，光电二极管系统能够以比类似压力传感器大得多的信噪比来测量冲击到达，同时以相似或更高的频率响应运行。这种行为使光电二极管系统成为在这些情况下检测冲击到达的理想传感器。本文介绍了一种光电二极管系统，该系统已用于光学测量昆士兰大学 X2 超高速膨胀管中的激波到达。实验结果表明，对于具有挑战性的低密度、高冲击速度条件，光电二极管系统能够以比类似压力传感器大得多的信噪比来测量冲击到达，同时以相似或更高的频率响应运行。这种行为使光电二极管系统成为在这些情况下检测冲击到达的理想传感器。光电二极管系统能够以比类似压力传感器大得多的信噪比来测量冲击到达，同时以相似或更高的频率响应运行。这种行为使光电二极管系统成为在这些情况下检测冲击到达的理想传感器。光电二极管系统能够以比类似压力传感器大得多的信噪比来测量冲击到达，同时以相似或更高的频率响应运行。这种行为使光电二极管系统成为在这些情况下检测冲击到达的理想传感器。