p pressure R radius This paper presents investigations of the development for a shower-head cooling configuration for a modem industrial turbine Re Reynolds number guide vane. One aim is to find suitable locations for cooling gas AR radially directed distance ejection with the lowest cooling gas mass flow possible. The blade spacing investigations begin with a numerical experiment. After the

A modem nozzle guide vane with showerhead cooling is investigated. The showerhead design consists of four rows of ejection holes at the leading edge in the stagnation region and has been worked out on the basis of a former design with only two rows. The experimental analysis is performed in a cold-air test turbine by means of LDV. In order to overcome the thermal limitations of the test rig, the heat transfer analysis is performed with CHT-Flow, a numerical method that has been developed at the Institute of Steam and Gas Turbines and that works in a conjugate manner. This means that no thermal boundary conditions such as heat transfer coefficients have to be described on the vane surface for thermal analysis. The first part of the investigation deals with the aerodynamics. At first, air is used as a cooling fluid leading to a density ratio of Πρ = 1.2. Then, in order to take density effects into account in the experiments. CO2 is used as a cooling gas providing a density ratio Πρ = 1.8 representative for modern engine operating conditions. The results are compared to the simulations. It is shown that the cooling gas does not penetrate the main flow as far under realistic density ratios. Thus, the aerodynamic losses are reduced and there is better attachment of the cooling film to the airfoil. The second part analyses the heat transfer. It is shown that lowering the blowing ratio has different influences on the material temperature locally. On the suction side, the cooling gas film attachment is enhanced and the surface temperature is lowered. In contrast, the surface temperature rises slightly on the pressure side.

This paper presents the experimental investigation of the flow and the numerical analysis of the flow and heat transfer in a turbine guide vane with showerhead cooling for two different blowing ratios. The aerodynamic results are compared with those of the experiments. Starting with a showerhead design of two rows of ejection holes, two additional rows have to be used in an enhanced design due to hot gas contact in the leading edge area. Thus, the cooling gas mass flow is doubled when keeping the blowing ratio constant at m = 1.5. Lowering the amount of cooling gas needed whilst still guaranteeing sufficient cooling is the motivation for the analysis of the influence of a lower blowing ratio on the cooling efficiency. The investigated blowing ratios are m = 1.5 and m = 1.0. The experiments are conducted using a non-intrusive LDA technique. The numerical results are gained with a conjugate heat transfer and flow computer code that has been developed at the Institute of Steam and Gas Turbines. The results show that the blowing ratio has to be chosen carefully as the leading edge flow pattern and the heat transfer are strongly influenced by the blowing ratio. Lower blowing ratios lead to a better attachment of the cooling film and thus they hardly disturb the main flow. With the lower blowing ratio, the material temperature increases up to 1.5% of the total inlet temperature in the leading edge area on the pressure side, whereas it decreases locally for about 0.8% for the lower blowing ratio on the suction side. This is due to the enhanced attachment of the cooling gas film.