The effects of tip gap variation on transonic turbine blade tip leakage flow based on VLES approach

Effects of Inlet Temperature Uniformity and Nonuniformity on the Tip Leakage Flow and Rotor Blade Tip and Casing Heat Transfer Characteristics

Steady simulations were performed to investigate tip leakage flow and heat transfer characteristics on the rotor blade tip and casing in a single-stage gas turbine engine. A typical high-pressure gas turbine stage was modeled with a pressure ratio of 3.2. The predicted isentropic Mach number and adiabatic wall temperature on the casing showed good agreement with available experimental data under similar operating condition. The present numerical study focuses extensively on the effects of tip clearance heights and rotor rotational speeds on the blade tip and casing heat transfer characteristics. It was observed that the tip leakage flow structure is highly dependent on the height of the tip gap and the speed of the rotor. In all cases, the tip leakage flow was seen to separate and recirculate just around the corner of the pressure side of the blade tip. This region of re-circulating flow enlarges with increasing clearance heights. The separated leakage flow reattaches afterwards on the tip surface. Leakag...

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Tip Leakage Flow and Heat Transfer on Turbine Blade Tip and Casing, Part 1: Effect of Tip Clearance Height and Rotation Speed

Purpose – One of the most critical gas turbine engine components, the rotor blade tip and casing, is exposed to high thermal load. It becomes a significant design challenge to protect the turbine materials from this severe situation. The purpose of this paper is to study numerically the effect of turbine inlet temperature on the tip leakage flow structure and heat transfer.Design/methodology/approach – In this paper, the effect of turbine inlet temperature on the tip leakage flow structure and heat transfer has been studied numerically. Uniform low (LTIT: 444 K) and high (HTIT: 800 K) turbine inlet temperature, as well as non‐uniform inlet temperature have been considered.Findings – The results showed the higher turbine inlet temperature yields the higher velocity and temperature variations in the leakage flow aerodynamics and heat transfer. For a given turbine geometry and on‐design operating conditions, the turbine power output can be increased by 1.33 times, when the turbine inlet temperature increases...

Effect of turbine inlet temperature on rotor blade tip leakage flow and heat transfer

Unsteady simulations were performed to investigate time dependent behaviors of the leakage flow structures and heat transfer on the rotor blade tip and casing in a single stage gas turbine engine. This paper mainly illustrates the unsteady nature of the leakage flow and heat transfer, particularly, that caused by the stator–rotor interactions. In order to obtain time-accurate results, the effects of varying the number of time steps, sub iterations, and the number of vane passing periods was firstly examined. The effect of tip clearance height and rotor speeds was also examined. The results showed periodic patterns of the tip leakage flow and heat transfer rate distribution for each vane passing. The relative position of the vane and vane trailing edge shock with respect to time alters the flow conditions in the rotor domain, and results in significant variations in the tip leakage flow structures and heat transfer rate distributions. It is observed that the trailing edge shock phenomenon results in a crit...

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Tip leakage flow and heat transfer on turbine stage tip and casing: effect of unsteady stator–rotor interactions

The purpose of the present work is to conduct an unsteady study of the tip leakage flow adjacent to the shroud in real gas turbine engines using an in-house industrial computational fluid dynamics code. Both time-averaged and time-dependent data for the velocity, temperature, and mass flow rate in the tip clearance region are presented in parts 1 and 2, respectively. In part 2 of the present work, the effect of tip clearance height, inlet turbulence intensity, inlet total temperature, and rotor angular velocity on the tip leakage flow pattern is investigated. It is found that the separationbubbleisalwayspresentnearthepressuresideofthebladetipatalltimesandthatitssizevarieswith flow conditions. For smaller tip clearance heights, the mass flow rate entering the tip clearance region is lower, due to the smallerarea,whichresultsinasmallerseparationbubble.Athigherstagnationtemperatures,theseparationbubble size is also reduced, due to the flow’s higher velocity, which allows the leakage flow to dominate over the bubble growth.Also,atlowerangularvelocities,theeffectoftheshroudrelativemotionisreduced,andsomoreleakage flow is allowed to enter, thereby suppressing the growth of the separation bubble.

Unsteady Numerical Investigation of Blade Tip Leakage, Part 2: Time-Dependent Parametric Study

DOI: 10.2514/1.29312 In today’s modern gas turbine engines, the region between the rotor and the stationary shroud has the most extreme fluid-thermal conditions in the entire turbine and is characterized by a periodically unsteady threedimensional flowfield. The purpose of the present work is to conduct an unsteady study of the tip leakage flow adjacent to the shroud in real gas turbine engines using an in-house industrial computational fluid dynamics code. Both time-averaged and time-dependent data for the velocity, temperature, and mass flow rate in the tip clearance region are presented in parts 1 and 2, respectively. In part 1, it was found that near the pressure side of the tip clearance region and near the blade tip on the suction side, the leakage flow is dominant, whereas opposing flows entering through the suction side dominate near the shroud and at the suction side. This opposing flow is the combined effect of the shroud relative motion and the crossflow originating from the adjacent blade passage on the suction side. A small recirculation region was observed above the rotor passage and was attributed to the bladepassagecrossflowinteractingwiththehigh-pressureregionfoundatthesuctionsideoftheblade.Thishigh-pressure region is caused by the combined effect of the crossflow with the shroudboundary-layer flow interacting with the tip leakage flow inside the tip clearance region.

Patricia Phutthavong

Papers

Unsteady Numerical Investigation of Blade Tip Leakage, Part 2: Time-Dependent Parametric Study

Unsteady Numerical Investigation of Blade Tip Leakage, Part 1: Time-Averaged Results