On the effects of inlet swirl on adiabatic film cooling effectiveness and net heat flux reduction of a heavily film-cooled vane (original) (raw)
Related papers
On the Effect of an Aggressive Inlet Swirl Profile on the Aero-thermal Performance of a Cooled Vane
Energy Procedia, 2015
A high-pressure vane equipped with a realistic film-cooling configuration has been studied. The vane is characterized by the presence of multiple rows of fan-shaped holes along pressure and suction side while the leading edge is protected by a showerhead system. Steady three-dimensional Reynolds-Averaged Navier-Stokes (RANS) simulations have been performed. A preliminary grid sensitivity analysis has been performed (with uniform inlet flow) to quantify the effect of the spatial resolution. Turbulence model has been assessed in comparison with available experiment data. The effects of a realistic inlet swirl on the aero-thermal performance of the cooling system are then investigated by means of comparison between two different kinds of simulations. The first one using a uniform inlet flow while the second one with aggressive swirl derived from the EU-funded project TATEF2. Clocking effects are also accounted for. The effect of the swirling flow in determining the coolant transport are investigated, evidencing the key role that these phenomena have in determining the effectiveness of the cooling.
Effects of Realistic Inflow Conditions on the Aero-Thermal Performance of a Film-Cooled Vane
A high-pressure vane equipped with a realistic film-cooling configuration has been studied. The vane is characterized by the presence of multiple rows of fan-shaped holes along pressure and suction side while the leading edge is protected by a showerhead system of cylindrical holes. Steady three-dimensional Reynolds-Averaged Navier-Stokes simulations have been performed. A preliminary grid sensitivity analysis has been performed with uniform inlet flow to quantify the effect of the spatial resolution. Turbulence model has been assessed in comparison with available experimental data. The effects of a realistic inflow condition on the thermal behaviour of the cooled vane are then investigated by means of comparison between two conjugate heat transfer simulations. The first one is characterized by a uniform inlet flow while the second one presents a temperature distortion and a superimposed aggressive swirl derived from the EU-funded TATEF2 project. The effect of the swirling flow in d...
HP Vane Aerodynamics and Heat Transfer in the Presence of Aggressive Inlet Swirl
Journal of Turbomachinery, 2012
Modern lean burn combustors now employ aggressive swirlers to enhance fuel-air mixing and improve flame stability. The flow at combustor exit can therefore have high residual swirl. A good deal of research concerning the flow within the combustor is available in open literature. The impact of swirl on the aerodynamic and heat transfer characteristics of an HP turbine stage is not well understood, however. A combustor swirl simulator has been designed and commissioned in the Oxford Turbine Research Facility (OTRF), previously located at QinetiQ, Farnborough UK. The swirl simulator is capable of generating an engine-representative combustor exit swirl pattern. At the turbine inlet plane, yaw and pitch angles of over 640 deg have been simulated. The turbine research facility used for the study is an engine scale, short duration, rotating transonic turbine, in which the nondimensional parameters for aerodynamics and heat transfer are matched to engine conditions. The research turbine was the unshrouded MT1 design. By design, the center of the vortex from the swirl simulator can be clocked to any circumferential position with respect to HP vane, and the vortex-to-vane count ratio is 1:2. For the current investigation, the clocking position was such that the vortex center was aligned with the vane leading edge (every second vane). Both the aligned vane and the adjacent vane were characterized. This paper presents measurements of HP vane surface and end wall heat transfer for the two vane positions. The results are compared with measurements conducted without swirl. The vane surface pressure distributions are also presented. The experimental measurements are compared with full-stage three-dimensional unsteady numerical predictions obtained using the Rolls Royce in-house code Hydra. The aerodynamic and heat transfer characterization presented in this paper is the first of its kind, and it is hoped to give some insight into the significant changes in the vane flow and heat transfer that occur in the current generation of low NO x combustors. The findings not only have implications for the vane aerodynamic design, but also for the cooling system design.
2008
One way to increase cycle efficiency of a gas turbine engine is to operate at higher turbine inlet temperature (TIT). In most engines, the turbine inlet temperatures have increased to be well above the metallurgical limit of engine components. Film cooling of gas turbine components (blades and vanes) is a widely used technique that allows higher turbine inlet temperatures by maintaining material temperatures within acceptable limits. In this cooling method, air is extracted from the compressor and forced through internal cooling passages within turbine blades and vanes before being ejected through discrete cooling holes on the surfaces of these airfoils. The air leaving these cooling holes forms a film of cool air on the component surface which protects the part from hot gas exiting the combustor. Design optimization of the airfoil film cooling system on an engine scale is a key as increasing the amount of coolant supplied yields a cooler airfoil that will last longer, but decreases engine core flow-diminishing overall cycle efficiency. Interestingly, when contemplating the physics of film cooling, optimization is also a key to developing an effective design. The film cooling process is shown to be a complex function of at least two important mechanisms: Increasing the amount of coolant injected reduces the driving temperature (adiabatic wall temperature) of convective heat transfer-reducing heat load to the airfoil, but coolant injection also disturbs boundary layer and augments convective heat transfer coefficient due to local increase in freestream turbulence. Accurate numerical modeling of airfoil film cooling performance is a challenge as it is complicated by several factors such as film cooling hole shape, coolant-to-freestream blowing ratio, coolant-to-freestream momentum ratio, surface curvature, approaching boundary layer state, Reynolds number, Mach number, combustor-generated high freestream turbulence, turbulence length scale, and secondary flows just to name a few. Until computational methods are able to accurately simulate these factors affecting film cooling performance, experimental studies are required to assist engineers in designing effective film cooling schemes. I deeply feel a gratitude to Almighty Allah, THE MOST GRACIOUS AND MERCIFUL, who capacitated me to complete my Ph.D. degree. Almighty Allah provided me strength and enthusiasm, without of which nothing could have been done. Although the feelings are deep, but the words too little, to illustrate completely the depth of feelings.
Three-Dimensional Film-Cooled Vane CFD Simulations and Preliminary Comparison to Experiments
49th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition, 2011
Reynolds-Averaged Navier Stokes (RANS) computational fluid dynamics (CFD) simulations are conducted using the Wilcox k-ω turbulence model within a code called LEO on a threedimensional fully film-cooled modern turbine inlet vane called the High Impact Technologies (HIT) Research Turbine Vane (RTV). External flows at operating conditions around the vane and their interaction with film cooling flows from the vane leading edge, pressure side (PS), suction side (SS), trailing edge, and hub and tip endwalls are modeled. The film cooling is modeled using a local source term in the governing equations for the added mass flux at the appropriate locations in the fluid domain along the vane surface. Cooled and uncooled isothermal vane simulations are conducted. Predictions of stream-wise distributions of heat flux and net heat flux reduction (NHFR) at two span locations are provided and compared to vane-only-configuration heat flux data recently obtained in the Air Force Research Laboratory (AFRL) Turbine Research Facility (TRF) short-duration blowdown facility. Details on proper matching of experimental boundary conditions for the CFD simulations are also given in order to provide a validation case for the maturing CFD code. Uncooled and cooled experimental data show appropriate relative trends, as do the uncooled and cooled predictions. However, comparing heat flux data to predictions shows disparities that require further investigation of the cooling modeling technique and appropriate assumptions going into the model. Nomenclature
Experimental and Computational Comparisons of Fan-Shaped Film Cooling on a Turbine Vane Surface
Journal of turbomachinery, 2006
The flow exiting the combustor in a gas turbine engine is considerably hotter than the melting temperature of the turbine section components, of which the turbine nozzle guide vanes see the hottest gas temperatures. One method used to cool the vanes is to use rows of film-cooling holes to inject bleed air that is lower in temperature through an array of discrete holes onto the vane surface. The purpose of this study was to evaluate the row-by-row interaction of fan-shaped holes as compared to the performance of a single row of fan-shaped holes in the same locations. This study presents adiabatic film-cooling effectiveness measurements from a scaled-up, two-passage vane cascade. High-resolution film-cooling measurements were made with an infrared camera at a number of engine representative flow conditions. Computational fluid dynamics predictions were also made to evaluate the performance of some of the current turbulence models in predicting a complex flow such as turbine film-cooling. The renormalization group (RNG) k-turbulence model gave a closer prediction of the overall level of film effectiveness, while the v 2-f turbulence model gave a more accurate representation of the flow physics seen in the experiments.
2002
Objective. The objective of the current investigation is to help reduce the risk associated with developing new gas turbine systems with advanced low NOx combustors. The current experimental investigation, which is being conducted at the University of North Dakota, involves developing a heat transfer and film-cooling database for two cascade geometries. One geometry involves a linear cascade, which uses a fully loaded vane design and the second cascade has a strongly contracting inlet and features an aft loaded vane design. The large-scale low speed cascades used in this study have eleven to one scaling to allow well-resolved heat transfer and film cooling measurements. The current analytical investigation, which is being conducted at Rolls Royce, involves developing predictions for the heat transfer and film cooling database and using the computational models to transfer the results to engine-like conditions. The heat transfer and film cooling data are being acquired over chord exit Reynolds numbers ranging from 500,000 to 2,000,000 using up to five different turbulence inlet conditions tested over two separate cascade geometries. The computational predictions are being conducted using a 3-D RANS method, which uses a multiblock method to speed computation convergence time. Vane and endwall heat transfer predictions are being made for both cascade geometries by the Aerothermal Methods Group at Rolls Royce. Selected results will be transferred to engine relevant conditions using the code. Experimental Effort. The experimental effort has resulted in acquisition of full surface heat transfer data on the endwall of the conventionally loaded cascade for four turbulence generator geometries at Reynolds numbers ranging from 500,000 to 2,000,000. Inlet boundary layer profiles and turbulence spectra have been acquired for all test conditions. Midline vane heat transfer measurements have been acquired for six turbulence conditions taken over the full range of Reynolds numbers. These data have are viewed as an excellent test case for grounding predictive methods for vane and endwall heat transfer. Work continues on the current cascade to obtain endwall film cooling distributions for both two rows of film cooling holes and for a slot. The film cooling supply system has been completed and the film cooling plenums have been installed. One of the problems we have encountered in developing our system includes uncovering and fixing a temperature stratification in the film cooling supply system. This anomaly was reduced by adding a mixer for our film cooling air upstream of our plenum distribution holes. Another problem we are currently encountering is related to having an uncooled laboratory. During the summer temperatures can rise to well over 30 C inside our laboratory and cooling water temperatures can rise to over 20 C. Since we use 29 C and 37 C start narrow band liquid crystals, we have difficulty maintaining the inlet air at a low enough temperature to acquire the lower effectiveness levels. However, we are planning to acquire endwall heat transfer measurements with film cooling through the remainder of the summer and will defer the film cooling measurements until cooler weather arrives. Contoured Endwall Cascade Fabrication. The contoured endwall cascade is nearing completion and we expect to begin qualification measurements by the beginning of September. This summer we have cast and assembled the instrumented vanes for heat transfer and pressure distributions, laid up the instrumented endwall surface, assembled and installed the bleed flow adjustments, and are currently in the process of adding the tailboards and installing the slave vanes. We have already completed both the nozzle and the turbulence generator casing to accommodate the contoured inlet. Analytical Effort. We have had a significant setback in the analytical portion of this contract due to changes in personnel at Rolls Royce. In the last half year the engineer at Rolls Royce responsible for the project, Eric Bermingham, and the technical lead on the project, Dr. Edward Hall have both left Rolls Royce. Unfortunately, the majority of the analytical work has not been completed. On the brighter side, the new CFD specialist on the project, Dr. Todd Simmons comes highly recommended. Additionally, due to the problems encountered by the change of employment of two key people on the subcontract, we are currently focusing on developing analytical solutions for vane and endwall heat transfer for the two cascade geometries. Graduate Student Education. Three graduate students are currently associated with the project. Pierre Barbot who was responsible for acquiring and analyzing the endwall heat transfer measurements is currently working as a CNA to gain medical experience for entry into medical school and is working part time on this master's thesis. Chao Wang, an Engineering Ph.D student from China, is currently responsible for acquiring endwall film cooling measurements and endwall heat transfer measurements with film cooling. Chao Wang was also responsible for acquiring all the hot wire anemometry data to date on the cascade. Chao is being supported ¼ time through the UND's School of Engineering and Mine's Energy Engineering Ph.D program and ¼ time by the current AGTSR contract. In addition, this spring we were able to attract Matthew Argenziano to work on the program. Matt is responsible for the new contoured endwall cascade and is expected to acquire vane and endwall heat transfer data with the cascade. Matt is receiving half-time support through the University of North Dakota. Presentations, Papers, and Information Requests. Through the efforts of AGTSR and the PI information about this research is spreading throughout the gas turbine community. On February 9 th , I was invited to make a presentation to Catalytica Energy Systems in Phoenix, Arizona. On the 25 th and 26 th of February a poster entitled "The Influence of Catalytic and Dry Low NOx Combustor Turbulence on Vane and Endwall Heat Transfer" was presented at the NETL sponsored Turbine Power Systems Conference in Galveston, Texas. Addtionally, two papers covering the vane and endwall heat transfer measurements are attached to this report.
Effects of Upstream Endwall Film Cooling on a Vane Cascade Flowfield
Journal of Propulsion and Power, 2017
The effects of film-cooling on the endwall region flow and aerodynamic losses are investigated experimentally as the film-flow is delivered from the slots in the endwall upstream of a linear vane cascade. Four slots inclined at 30° deliver the film-jet parallel to the main flow at four blowing ratios between 1.1 and 2.3 and at a temperature ratio of 1.0. The slots are employed in two configurations pitchwise-all four slots open (case-1) and two middle slots open (case-2). The inlet Reynolds number to the cascade is 2.0E+05. Measurements of the blade surface pressure, axial vorticities, yaw angles, and total pressure loss distributions along the cascade are reported with and without (Baseline) the film-cooling flow. The results show the film-flow changes the orientations, distributions, and strength of the endwall secondary flows and boundary layer. The case-1 of film-cooling provides more massflux and momentum than the case-2 affecting the passage vortex legs. The overall total pressure losses at the cascade exit are always lower for the film-cooling cases than for the Baseline. The overall losses are also lower at the low blowing ratios, but higher at the high blowing ratios for the film-cooling case-1 than for the case-2.
Energy Procedia, 2014
The continuous demand for increased performance and reliability of gas turbines leads to the improvement of prediction tools. Having regard to the effects of heat transfer on the residual life of gas turbine components, it is necessary to achieve a high level of accuracy in the evaluation of thermal loads. Computational fluid dynamics is able to provide reliable data in a limited lapse of time. In this paper, the numerical analysis of the cooled vane of the MT1 high-pressure turbine stage is presented. A grid dependence analysis based on the evaluation of the aero-thermal characteristics of the vane has been performed. Turbulence is modeled using the k T-k L-method whose performance in this kind of configuration is rarely debated in the scientific literature. Model parameters have been tuned to match the experimental data. The final objective of the present activity is to assess the capability of numerical methods to deal with an annular, transonic high-pressure vane with a realistic film cooling configuration. Adiabatic effectiveness, heat transfer coefficient and net heat flux reduction distributions have been evaluated, the latter providing relevant information on the performance of the cooling system. The coupled fluid-solid simulation of the cooled configuration has also been performed to evaluate the impact of conjugate heat transfer on the prediction of thermal loads. Results show a non-negligible difference in the wall temperature evaluation between the decoupled and the coupled approach, mainly caused by the heat conduction in the solid.
Meccanica, 2010
In this presentation, influences of axial vane swirler on heat transfer augmentation and fluid flow are investigated both experimentally and numerically. The swirl generator is installed at the inlet of the annular duct to generate decaying swirling pipe flow. Three different blade angels of 30°, 45°and 60°were examined. Meanwhile, flow rate was adjusted at Reynolds numbers ranging from 10000 to 30000. Study has been done under uniform heat flux condition and air was used as working fluid. Experimental results confirm that the use of vane swirler leads to a higher heat transfer compared with those obtained from plain tubes. Depending on blade angle, overall Nusselt augmentation is found from 50% to 110% while friction factor increases by the range of 90-500%. Thermal Performance evaluation has been done for test section and test section together with swirler. In both cases, thermal performance increases as vane angle is raised and decreases by growth of Re number. When increasing the blade angle, higher decay rate has been observed for local Nusselt number. In CFD analysis, time-averaged governing equations were solved numerically and RSM model was applied as the turbulence model. Here, the simulation results of axial and tangential velocities, turbulent kinetic energy, wall stresses and swirl intensity are provided. They illustrate the effect of swirling pattern on mean flow and turbulence structure, as well as on improving heat transfer enhancement in the annular duct.