Experimental Study of the Effect of Probe Calibration on the Mass Flow and Velocity Measurement of Hot Air at High-Subsonic Mach Numbers

In this research, the possibility of measuring total pressure, mass flow, and velocity of a high energy flow of air at 0.6-0.7 Mach is investigated experimentally, using 6 different types of commercial sensors. For this end, a fixed area annular nozzle, mounted at the exit of micro-turbojet engine, was used. Also, a test bench with the capability of measuring total pressure, static pressure, total temperature, mass flow, RPM, and the thrust force was used. The results of the L-type sensors calibrated for such velocities indicate that the total pressure and velocity are similar, near to each other, and among the engineering precision. The largest difference between the measured and calculated mass flow was 9.1% and related to L-type probes with the length of 68mm and the outside diameter of 3mm. This difference for all other probes was less than 8%. Also, the calculated mass flow based on Rod-type probe data shows a difference of only 4.4% with the measured mass flow; so, there is a distinct difference between these two kinds of probes. Also, the measurements include useful information of the variations of main flow characteristics along the length of annular nozzle, among which the most important are an intense drop of about 29% in total pressure and about 48°C drop in total temperature.