The development of multi-element temperature sensors for a compressible fluid flow velocity measurement

Abstract

When measuring the temperature of a stream of compressible fluid using a temperature sensor, experimenters must address the problem of the effect of the compressibility of the locally decelerated fluid in the near neighborhood of the sensor on the rendered temperature. Generally said, the temperature rendered by a temperature probe positioned within an airflow depends on the external flow velocity, the specific heat of the fluid, the thermodynamic temperature, and the recovery factor of the probe. A method of measuring the velocity of a flowing compressible fluid that takes advantage of these properties is called Recovery Temperature Anemometry (RTA). This, unfortunately, means there are two unknown properties in real-time measurements – the velocity and the thermodynamic temperature of the fluid. This article is focused on a possible solution to the mentioned problem and the development of appropriate probes. By using two probes with different recovery factors, the need for knowing the thermodynamic temperature is eliminated so that a combination of two temperature probes with different recovery factors can be used for the velocity measurement. As described in this paper, by using multiple temperature sensors with different recovery factors, the temperature of the flowing fluid can be eliminated, leaving only one unknown quantity in the entire problem, which is the velocity of the flowing fluid. The article describes the theoretical basis of the problem, the purpose of multi-element probe, the verification multi-element temperature probe behavior, the measurement technique, and the results.