Development of Time-Efficient Multi-hole Pressure Probe Calibration Facility

Multi-hole pressure probes have a wide range of applications in terms of measurements in special applications like turbomachines flow field, wind tunnel experimentation applications, etc. The primary measurement variables of interest are static pressure, dynamic pressure, three velocity components, flow direction, etc., which we can measure using a multi-hole pressure probes with higher accuracy. The applications of such probes in measurement fields demands for higher accuracy of calibration, especially in terms of flow angularity and precision. The manual calibration of the multi-hole probe is a difficult and time-consuming task in an acceptable range of pitch, and yaw angles. The present paper discusses the low-speed multi-hole pressure probe calibration facility developed at IIT Kharagpur using a two-axis angular traverse mechanism. Special algorithms using LabVIEW were developed for automatic traverse both for yaw and pitch direction and also for pressure data acquisition using pressure scanner, to achieve precious measurement with short time spend with angular precision in terms of 0.5°. This facility is capable of calibrating multi-hole pressure probes for different Reynolds numbers and angular ranges. The paper also discusses the initial calibration of the tunnel using total pressure probe rakes. A four-hole probe was calibrated using non-nulling calibration technique using the aforementioned test facility. It was calibrated for yaw and pitch angle range of ±30° and ±70°, respectively. In this study, we are discussing three calibration methods, namely, the conventional method, the two-zone method and three-zone method to understand their behavior in terms of calibration coefficients, operable angular range, and uncertainty. The range for the pitch angle of the conventional method was observed to be \(\pm 35^\circ\). However, an extended range for pitch angle up to \(\pm 60^\circ\) for two-zone method and three-zone method was observed. The uncertainty analyses of the results have been performed to study the sensitivity of the probes at prescribed angular ranges.