Modern gas turbines are working in a high temperature environment. The needs for cooling the first stage discs and airfoils are inevitable. In order to avoid overcooling it is necessary to have as much information of the temperature redistribution along the flow path as possible. This paper presents results from both a numerical and an experimental investigation of the temperature redistribution.
The numerical part of this investigation is based on 3D Navier-Stokes calculations, where a single stage test turbine is modeled. Combined with an experimental testing of the calculated geometry the influences of the slot flow, which enters the main gas from a slot at the hub section between the stator and the rotor, are evaluated.
The test turbine is working with air at low temperature, typically in the order of atmospheric conditions. In order to simulate the temperature distribution caused by the slot flow trace gas technique is used.
The influence of three parameters, the slot mass flow, the velocity ratio and the pressure ratio, was studied.
The main result of changing the slot mass flow is a change in the absolute value of the temperature minimum. In addition a slight dependence of the penetration depth was observed.
The spanwise transport of the slot flow within the rotor is highly dependent on the velocity ratio. However, some distance downstream of the trailing edge, the core of the slot flow merges together for different velocity ratios.
Varying the turbine stage pressure ratio, from 1.14 to 1.34, did not affect the spanwise transport. Since the pressure ratio is a representative of the main gas mass flow, a decreased pressure ratio results in a higher degree of cooling, as less main gas is present.