Alexandria Engineering Journal (Oct 2020)
Numerical investigation on the effect of rotation on impingement cooling of the gas turbine leading edge
Abstract
Currently, gas turbine engines play a vital role in our daily lives. Some of the uses of gas turbine engines include aircraft propulsions, helicopters, submarines, and industrial applications. The thermal efficiency and power output of such engines can be enhanced by increasing the turbine inlet temperature. As a result, different cooling methods are often employed to increase the turbine blade lifetime and efficiency. One of the primary cooling techniques used is the jet impingement cooling method. This technique is mostly used inside the leading edge, which is the most critical area of the blade. In the present work, a 3D numerical simulation using the turbulent SST k-ω model and a very intense mesh of eight million elements is employed, to study the flow field and heat transfer performance of a rotational gas turbine blade leading edge, that is exposed to constant heat flux under internal cooling using seven jets. The study covers a range of jet Reynolds numbers from 7500 to 30,000 for rotations of 0, 250, 500, and 750 rpm. The results demonstrate that the Nussels number increases as the Reynold number increases. The rotation has a clear effect at lower Reynold numbers and is diminished for higher Reynold numbers, as observed in the flow and produced pressure fields. The jet impingement is an efficient method of cooling the gas turbine blade leading edge, the cooling performance is strongly influence of the individual jet location, the developed flow jet impingement flow field, developed pressure, the cross flow and rotation effect, especially at low Reynolds numbers. The effect of rotation is diminished on the heat transfer performance as the Reynolds number increases. A mathematical relation between Nusselt number to jet Rotation and jet Reynolds number is developed to support designing the cooling passages for gas turbine blade.
