Measurement Method Research On High Speed Flow External Flow Field Of Laval Nozzle Under Variable Working Conditions

High-speed jet widely exists in practical engineering, but the general engineeringapplication in speed measuring equipment is hard to obtain high speed jet velocity. Andthe existing high-speed jet speed measuring equipment is expensive and the latemaintenance of suffering. It is mainly used in fluid laboratory. So it is difficult to widelyapplied to practical engineering. In this paper, using numerical simulation method tosimulate flow field of speed. Use Laval nozzle as a high-speed jet generator, pitot tube asa measure of high-speed jet equipment. Since the pitot tube measurement point in theprocess of measuring the downstream flow field disturbance, affected the static pressurevalue measurement. Calculate the Mach number to conform the practical engineeringapplication in the range of allowable errors.High-speed jet generator of Laval nozzle uses in this article. The physical model forthe contraction part uses the five power curve to draw and the expansion period uses thecircular arc which the radius is124millimeter and the circular is0.24. Contraction andexpansion period need to smooth connection. Nozzle using air as working medium fornumerical simulation test, and establish the control equations and k-epsilon turbulencemodel. Then respectively by using CFD software to carry out the numerical simulationexperiments in different survey points, different inlet pressure and different inlettemperature. Then using the polynomial equation to fit the measured results and the actualresults. Through the numerical simulation results, the Mach number of relative error lessthan1.5%in different measurement point and the Mach number of relative error less than0.08%in different temperature conditions. Due to the size of the inlet pressure had agreater influence on the flow field, the Mach number relative error is less than3%indifferent inlet pressure within the range of0.70Mpa to1.00Mpa.