Вплив чисел Маха і Рейнольдса на аеродинамічні характеристики соплової решітки газової турбіни

The data of experimental studies of a circular nozzle cascade for a small-sized gas turbine with a medium ratio of the diameter to the blade height as part of a turbine stage, as well as in conditions of joint operation with a radial diffuser have been presented. In the presence of an impeller, the Mach number varied in the range of 0.3 to 0.85, and in static conditions it varied in the range of 0.3 to 1.4. The flow rate coefficient was determined by the integral method using drains, and the loss coefficients and averaged flow angles were determined based on the data of detailed measurements of the flow parameters behind the cascade using pneumometric probes. The aerodynamic efficiency of the nozzle cascade is at a very high level and in the calculated transonic mode the kinetic energy loss coefficient is 0.052, and the total loss coefficient is 0.09. For modes, where the Mach number is equal to 0.6, a very strong effect of the boundary conditions behind the nozzle cascade on its aerodynamic characteristics is recorded and it is indicative of the drawbacks of experiments without an impeller. It is established that the impeller can be abandoned if the Mach number exceeds 0.85. It is also established that for a Mach number above 1.15, the Reynolds number of 10,5×105 is self-similar for the flow rate coefficient. When the Mach number is increased to 1.25, the nozzle cascade is completely closed, and the flow coefficient in the self-similarity zone reaches a maximum in terms of the Reynolds number. For the thermal calculations of the stage, the averaged angle of the flow exit from the nozzle cascade and its total loss coefficient that takes into account not only kinetic energy losses, but also kinematic losses should be used.