Roland Liebe

Heat Transfer Enhancement by Impingement Cooling in a Combustor Liner Heat Shield

As part of an industrial gas turbine research program, the present study provides the results of a basic investigation of the heat transfer in an impingement cooled combustor heat shield. Because of the complexity and the irregularity of the impingement pattern of the heat shield, standard correlations for regular impingement fields are insufficient and the investigation of local heat transfer enhancement is required therefore. The model to represent a simplified heat shield is made out of perspex, and heat transfer experiments are performed using a transient liquid crystal method. The local air temperature is measured at several positions within the model. The distributions of the Nusselt number on the impingement target plate as well as on the side rims and along the central bolt recess of the heat shield are shown for different impingement Reynolds numbers. The results are compared with respect to the local and overall heat transfer.Copyright

A Study on Local Heat Transfer Enhancement in a Rectangular Dimpled Channel With a Large Aspect Ratio

In this paper the convective heat transfer in a rectangular dimpled channel with an aspect ratio of six is studied. Applications could be for gas turbine vanes, vane shrouds, ring segments and hot components in the combustor. Basic heat transfer experiments have been performed using heater foils and a steady-state method with liquid crystals. The cooling effect is achieved by a dimple configuration combined with rib turbulators. The specific subject of this study is to focus on the heat transfer enhancement in the corner regions of the dimpled large aspect ratio channel. Different configurations of rib turbulators are investigated at different Reynolds numbers. Detailed heat transfer distributions are presented for the different configurations, showing the local effect of turbulator placement and angle with respect to the main flow direction. They are complemented by pressure drop measurements and compared with numerical simulations. It is shown that locally implemented rib configurations can enhance the heat transfer in these critical regions without large pressure loss penalties.Copyright