Numerical investigations of unsteady passing wake effects on turbine blade tip aerothermal performance with different tip clearances

Abstract

Purpose The purpose of this paper is to numerically investigate the effect of guide vane unsteady passing wake on the rotor blade tip aerothermal performance with different tip clearances. Design/methodology/approach The geometry and flow conditions of the first stage of GE-E3 high-pressure turbine have been used to obtain the blade tip three-dimensional heat transfer characteristics. The first stage of GE-E3 high-pressure turbine has 46 guide vanes and 76 rotor blades, and the ratio of the vane to the blade is simplified to 38:76 to compromise the computational resources and accuracy. Namely, each computational domain comprises of one guide vane passage and two rotor blade passages. The investigations are conducted at three different tip gaps of 1.0, 1.5 and 2.0 per cent of the average blade span. Findings The results show that the overall discrepancy of the heat transfer coefficient between steady results and unsteady time-averaged results is quite small, but the dramatic growth of the instantaneous heat transfer coefficient along the pressure side is in excess of 20 per cent. The change of the aerothermal performance is mainly driven by turbulence-level fluctuations of the unsteady flow field within gap regions. In addition, the gap size expansion has a marginal impact on the variation ratio of tip unsteady aerothermal performances, even though it has a huge influence on the leakage flow state within the tip region. Originality/value This paper emphasizes the change ratio of unsteady instantaneous heat transfer characteristics and detailed the mechanism of blade tip unsteady heat transfer coefficient fluctuations, which provide some guidance for the future blade tip design and optimization.

Aerothermal and aerodynamic performance of turbine blade squealer tip under the influence of guide vane passing wake

“…Figure 6 presents the distribution of HTC and wall heat flux on different squealer tips. The squealer tip has completely different characteristics from that of the flat tip, 26 and different regions also show obvious distinctions. At the Rim, the HTC is high at the leading edge caused by the entrance effect, similar to the of the flat tip.…”

“…The mesh of computational domain was multi-block hexahedral structured mesh generated by ICEM CFD, and the ANSYS CFX 18.0 was employed to solve steady and unsteady Reynolds Averaged Navier-Stokes (RANS) equations. The numerical method validation and mesh independence test have been performed detailed in the previous work 26 regarding the same blade profile and flow conditions, and some major results are represented here. Figures 3 and 4 presents the distribution of HTC on the blade tip and pressure ratio on the shroud of experimental and numerical predictions respectively.…”

Effect of casing purge flow on heat transfer and cooling performance of blade squealer tip for a gas turbine stage

“…Because accurate value of T ad is difficult to obtain directly, this paper uses Zhang et al 34 formulation to calculate h. In range of small wall temperature difference, wall heat flux from two different wall temperatures is subtracted to calculate heat transfer coefficient h as follows:…”