A small inward flow radial gas turbine comprising a ring of

A small inward flow radial gas turbine, comprising a ring of nozzle blades, a radial vaned impeller and an axial diffuser, operates at its design point with a total to total efficiency of 0.90. At turbine entry the stagnation pressure and temperature of the gas is 400 kPa and 1, 140 K. The flow leaving the turbine is diffused to a pressure of 100kPa and has negligible final velocity. Given that the flow is just choked (M_2 =1) at nozzle exit, determine the impeller peripheral speed and the flow outlet angle from the nozzles. The mass flow rate of gas through the turbine given in Problem 1 is 3.1 kg/s, the ratio of the impeller axial width/impeller tip radius (b^2/r_2) is 0.1 and the nozzle isentropic velocity ratio (psi2=V_2/V_2s) is 0.96. Assuming that the space between nozzle exit and impeller entry is negligible and ignoring the effects of blade blockage, determine: the static pressure and static temperature at nozzle exit: the impeller tip diameter and rotational speed: the power transmitted assuming a mechanical efficiency of 93.5%

Solution

The static pressure and the status temp is 6 bar and 345 Kelvin.

The impeller tip diameter is .022 cm while the speed is about 890rpm.