An optimization method for three-dimensional turbine blade design including end wall contouring control with non-axis-symmetric geometry has been developed. This design optimization method consists of three-dimensional parametric modeling module for blades and end walls, optimization algorithm module and the design evaluation method using Computational Fluid Dynamics code. This paper presents the advanced and more applicative study to enhance this optimization methodology from a single turbine stage to two turbine stages with stator blade hub leakage and rotor blade tip leakage influences. Results of present fluid dynamic design optimization study with consideration of tip and hub leakage show that the efficiency of the current well designed high pressure steam turbine stage has been enhanced by 0.21%. Using parallel optimization algorithm and a cluster PC system, the design cycle can be shortened to seven days for an optimization with one thousand iterations of two turbine stage CFD on 20 CPUs of 2.0G cluster PC.

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Ingress occurs when hot mainstream gas from the turbine annulus is ingested through a rim seal into the wheel-space between a rotating turbine disc (the rotor) and an adjacent stationary casing (the stator). The stationary vanes and rotating blades in the annulus create circumferential variations of pressure that drive hot gas inwards into the wheel-space in regions of high external pressure. This is called externally-induced ingress. (The rotating flow in the wheel-space creates a radial pressure gradient that separately promotes radially inward flow into the wheel-space. This is known as rotationally-induced ingress). The high temperature of the ingested mainstream gas in an engine can lead to fatigue and damage to important components. This paper describes simplified computational studies of externally-induced ingress into a rotor-stator system with an axial clearance rim seal. Axisymmetric steady-state computations are carried out using the commercial computational fluid dynamics code CFX. The SST model of turbulence is used. The model geometry and boundary conditions are based on an experimental rig designed and built at the University of Bath to study fundamental features of ingestion and rim seal effectiveness, in a related project having substantial industrial involvement. It is known that simplified steady flow models can significantly underestimate ingestion from the mainstream annulus into the wheel-space. In the present work, ingestion is prescribed in the steady model through the use of boundary conditions at the axial clearance seal. The computation of the flow and heat transfer in the wheel-space is validated by comparison with previously-published experimental measurements for a simple rotor-stator system without ingestion. The computations are carried out for values of rotational Reynolds number up to around 1.25 x 106 as typically used in experimental studies, and using sealing air flow-rates corresponding to non-dimensional values relevant to engine applications. The computed results show that the flow structure and heat transfer in the wheel-space at high sealing flow rates agree well with measured values for rotor-stator systems, the effects of differences between geometries being mostly small. Due to the recirculating secondary flow in the wheel-space, ingested fluid is drawn toward the surface of the stator. At lower sealing flow rates, the higher swirl of the ingested mainstream flow causes changes in the flow structure in the wheel-space. The ingested mainstream flow can come into contact with the rotor, and this could have serious consequences in practice.

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This paper presents a heat transfer and details flowfield measurements of multiple cooling holes. Normal cylindrical hole with steeper inclined angle of 20° arranged to perform a 5 times 4 cooling holes matrix have been considered. Experiments have been done at a single Reynolds number base on the hole diameter equal to 6200 at three blowing ratios of 0.5, 1.0 and 2.0 for the heat transfer and only for the later two for aerodynamics measurements. The heat transfer experiments involved the IR camera to capture the surface temperature data while the aerodynamics experiments involved the three dimensional Laser Doppler Velocimeter for velocity measurements. Results of heat transfer consists of overall film cooling effectiveness distribution and laterally average film cooling effectiveness in x-direction represented by a contour plot and a graph respectively. Four measurement planes have been considered in the aerodynamics experiments which are located at x/D = 7, 17, 27 and 37. The aerodynamics results presented in this paper include of various contour plots which represent the distribution of normalize velocity for u, v, and w components, normalize root mean square velocity for u, v, and w components and the Reynolds stress tensor. Both set of results have been discussed in such, a clear relation between the flow behavior and heat transfer phenomena have been established.

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The purpose of the present study is to clarify the heat transfer characteristics with multiple jet impingement aiming at the highly efficient cooling performance. In the study, we investigated the effect of injection parameters on circular jet array impingement heat transfer. As we focus on interference among the adjacent impinging jets, tests are mainly conducted at the minimum crossflow condition. The experiments are also conducted at injection distance from 2 to 8 jet hole diameters and jet-to-jet spacing from 4 to 8 jet hole diameters. Jet hole diameter Reynolds number is 4,680. Thermochromic liquid crystal is used to obtain heat transfer coefficient. Wall pressure measurement and oil flow visualization on the target surface are performed to understand the flow pattern of impinging jet and wall jet. The effect of injection parameters, such as injection distance, jet-to-jet spacing and number of jets, on jet array impingement heat transfer is clarified.

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It is well known that asymmetric vane spacing can result in decreased levels of the excitation at specific frequencies. In this paper, the resonant response reduction of mistuned bladed disks due to asymmetric vane spacing is studied theoretically for the most probable asymmetric vane, in which the vane count of the upper and lower half is slightly different. First, a method for predicting the maximum amplitude of the mistuned bladed disk for the asymmetric vane spacing is proposed. Second, a parametric study is carried out using Monte Carlo simulation to clarify the vibration response characteristics of the mistuned bladed disk for the asymmetric vane spacing. From these results, it is concluded that asymmetric vane spacing is effective for reduction of resonant amplitudes of a mistuned bladed disk if a multi-resonance phenomenon does not appear.

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This study deals with the experimental and numerical studies of the effect of free-stream turbulence on turbine blade leading edge film cooling. The study examines several test cases with two blowing ratios (BR=1.0 and 2.0) and three mainstream turbulence intensities (1.0, 3.3 and 12.0 %) using two types of leading edge models with cylindrical holes and diffuser holes [1]. The leading edge model consists of a semi-circular part of 80mm diameter and a flat after-body. Film effectiveness and heat transfer coefficient on the model surface are measured by the transient method using thermochromatic liquid crystal with video camera. In addition, detailed investigation of the film cooling is carried out using CFD simulations. RANS approach using Shear Stress Transport turbulence model was employed to solve the flow field. In the case of diffuser hole, the effect of mainstream turbulence intensity appears significantly, and spanwise averaged film effectiveness is decreased.

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