Abstract
The leading edge is the critical portion for a gas turbine blade and is often insufficiently cooled due to the adverse effect of Crossflow in the cooling chamber. A novel internal cooling structure, wall jet cooling, can suppress Crossflow effect by changing the coolant flow direction. In this paper, the conjugate heat transfer and aerodynamic characteristics of blades with three different internal cooling structures, including impingement with a single row of jets, swirl cooling, and wall jet cooling, are investigated through RANS simulations. The results show that wall jet cooling combines the advantages of impingement cooling and swirl cooling, and has a 19–54% higher laterally-averaged overall cooling effectiveness than the conventional methods at different positions on the suction side. In the blade with wall jet cooling, the spent coolant at the leading edge is extracted away through the downstream channels so that the jet could accurately impinge the target surface without unnecessary mixing, and the high turbulence generated by the separation vortex enhances the heat transfer intensity. The Coriolis force induces the coolant air to adhere to the pressure side’s inner wall surface, preventing the jet from leaving the target surface. The parallel cooling channels eliminate the common Crossflow effect and make the flow distribution of the orifices more uniform. The trailing edge outlet reduces the entire cooling structure’s pressure to a low level, which means less penalty on power output and engine efficiency.
Highlights
Received: 9 December 2021Turbine blades work in extreme conditions, including high temperature, high pressure, and huge centrifugal force
Some potential internal cooling designs have been presented with the rise of casting technology, such as matrix cooling [3,4] and double-wall cooling [5], the conventional method, jet impingent cooling, is still the most widely used for the protection of blade leading edge because of its intense unsteady disturbance and high local heat transfer coefficient [6]
With the development of additive manufacturing, more and more researchers are focusing on combining the target surface of impingement cooling with heat transfer enhancing features, including pin-fin [13,14], micro pin-fin [15], dimple [16,17], conical and ring protuberances [18]
Summary
Turbine blades work in extreme conditions, including high temperature, high pressure, and huge centrifugal force. Further improves the heat-dissipating rate of impingement cooling with a little increment of pressure penalty, but the manufacturing cost is still a problem Swirl cooling is another kind of cooling structure used at the leading edge of turbine blades. In actual turbine blade cooling with radial cooling cavities, including jet impingement cooling and swirl cooling, the Crossflow of spent air exists and has a critical impact on the cooling performance. Unlike the radial internal cooling schemes, a design allowing coolant air to flow along the blade profile to avoid Crossflow was put forward by Zhang et al [30] in 2017, named multi-channel wall cooling. Wall jet cooling maximizes the heat transfer performance of impingement cooling and is simple enough to be accommodated in blade leading edge.
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