Numerical computations are performed on three configurations of a model gas turbine combustor geometry for cold flow conditions. The purpose of this study is to understand the effect of changes to combustor passage section on the location of peak convective heat transfer along the combustor liner. A Reynolds Averaged Navier-Stokes equations based turbulence model is used for all the numerical computations. Simulations are performed on a 3D sector geometry. The first geometry is a straight cylindrical combustor section. The second model has an upstream diverging section before the cylindrical section. Third one has a converging section following the upstream cylindrical section. The inlet air flow has a Reynolds number of 50000 and a swirl number of 0.7. The combustor liner is subjected to a constant heat flux. Finally, liner heat transfer characteristics for the three geometries are compared. It is found that the peak liner heat transfer occurs far downstream of the combustor for full cylinder and downstream convergent cases compared to that in the upstream divergent case. This behavior may be attributed to the resultant pressure distribution due to the combustor passage area changes. Also the magnitude of peak liner heat transfer is reduced for the former two cases since the high turbulent kinetic energy regions within the combustor are oriented axially instead of expanding radially outward. As a consequence, the thermal load on the liner is found to reduce.

The present paper describes the first phase of the design and development of a realistic, high-pressure, full-scale research gas turbine combustor at Virginia Tech. The final test rig will be capable of operating at inlet temperatures of 650 K, pressures up to 9.28 Bar (120 psig), maximum air inlet flow rates of 1.27 kg/s (2.8 lbm/s), and allow for variations in the geometry of the combustor model. The first phase consists of a low-pressure (atmospheric) optical combustor for heat transfer and flow-field measurements at isothermal and reacting conditions. The combustor model is equipped with an industrial low emission fuel injector from Solar Turbines Incorporated, used in their land based gas turbine Taurus-60. The primary objective of the developed rig is to provide additional insight into the heat transfer processes that occur within gas turbine combustors, primarily the convective component, which has not been characterized. A future phase of the test rig development will incorporate a pressure vessel that will allow for the operation of the combustor simulator at higher pressures. In the present publication, the design methodology and considerations, as well as the challenges encountered during the design of the first phase of the simulator are briefly discussed. An overview is given on the design of the instrumentation and process piping surrounding the test rig, including ASME codes followed as well as the instrumentation and equipment selected. A detailed description of the test section design is given, highlighting the design for high temperature operation. As an example of the capabilities of the rig, representative measurements are presented. Characterization of the isothermal flow field using planar Particle Image Velocimetry (PIV) at a Reynolds number of 50 000 was performed and compared with flame imaging data at the same inlet conditions operating at an equivalence ratio of 0.7. The data suggests that the flame location follows the maximum turbulent kinetic energy as measured in the isothermal field. Representative data from the computational efforts are also presented and compared with the experimental measurements. Future work will expand on both reacting and isothermal PIV and heat transfer measurements, as well as computational validations.

Modern combustor design optimization is contingent on the accurate characterization of the combustor flame side heat loads. The present work focuses on the experimental measurement of the isothermal (non-reacting) convective heat transfer along a fused silica optical can combustor liner for Reynolds numbers ranging between 11 500 and 138 000. The model combustor was equipped with the SoLoNOx swirl fuel nozzle from Solar Turbines Incorporated, subjecting the liner walls to realistic isothermal flow and turbulence fields. Infrared (IR) imaging through fused silica was demonstrated, and a novel estimation of the three-dimensional conduction heat losses for steady state constant heat flux experiments was developed. A maximum heat transfer augmentation of ~18 was observed with respect to fully developed turbulent pipe flow correlations. Contrary to other investigations, the augmentation magnitude and distribution are shown to be approximately constant with Reynolds number (particularly away from the impingement location). Particle Image Velocimetry (PIV) was included to support the heat transfer measurements, suggesting that peak heat transfer occurred 0.12 nozzle diameters upstream of the jet reattachment point along the liner. Reynolds-Averaged Navier Stokes (RANS) computations are shown to yield peak heat transfer predictions within 17.4% of the experimental results when using the realizable k-ε turbulence model and enhanced wall treatment. The measurements were further analyzed in the context of results from other heat transfer studies on gas turbine combustors.

In this study, we provide detailed wall heat flux measurements and flow details for reacting flow conditions in a model combustor. Heat transfer measurements inside a gas turbine combustor provide one of the most serious challenges for gas turbine researchers. Gas turbine combustor improvements require accurate measurement and prediction of reacting flows. Flow and heat transfer measurements inside combustors under reacting flow conditions remain a challenge. The mechanisms of thermal energy transfer must be investigated by studying the flow characteristics and associated heat load. This paper experimentally investigates the effects of combustor operating conditions on the reacting flow in an optical single can combustor. The swirling flow was generated by an industrial lean premixed, axial swirl fuel nozzle. Planar particle image velocimetry (PIV) data were analyzed to understand the characteristics of the flow field. Liner surface temperatures were measured in reacting condition with an infrared camera for a single case. Experiments were conducted at Reynolds numbers ranging between 50,000 and 110,000 (with respect to the nozzle diameter, DN); equivalence ratios between 0.55 and 0.78; and pilot fuel split ratios of 0 to 6%. Characterizing the impingement location on the liner, and the turbulent kinetic energy (TKE) distribution were a fundamental part of the investigation. Self-similar characteristics were observed at different reacting conditions. Swirling exit flow from the nozzle was found to be unaffected by the operating conditions with little effect on the liner. Comparison between reacting and nonreacting flows (NR) yielded very interesting and striking differences.

The current computational study deals with the isothermal fluid flow and heat transfer analysis of a gas turbine combustor subject to different boundary conditions. A 90 degree sector model was studied computationally in order to identify the impingement and peak heat transfer locations along the combustor liner in addition to heat transfer augmentation. Validation experiments were carried out for the full scale industrial swirler-fuel nozzle using PIV and IR thermography to obtain flow and heat transfer data. Inlet conditions into the swirler were set to a Reynolds number of 50000 and the outlet was set to atmospheric conditions. The swirler vanes provided a radially varying swirl to the flow entering into the combustor. The k-w SST turbulence model was employed to investigate the effects of different inlet turbulence parameters on the accuracy of the simulation, i.e., calculations with experimental inlet turbulent kinetic energy and deduced dissipation rate profiles, and prescribed constant turbulent intensity and length scale. It was observed that the former provided conforming results with the experiments at specific locations and improved convergence, while both cases showed discrepancy in velocity profiles within the central recirculation region of the combustor. The peak heat transfer and impingement location along the liner were in excellent agreement with the experimental data. However the peak magnitude prediction was over-predicted up to 27%. This discrepancy was attributed to the limitations of two-equation turbulence model predictions near the stagnation region. An additional study was performed to investigate the effect of different inlet swirl angles on the impingement location. It was observed that a higher swirl angle shifts the impingement location upstream. Overall, the present study provides a probe into the capability of steady RANS models to predict combustor swirling flows and wall heat transfer; and also aids in using the steady state results as initialization data for the future scale resolved turbulence model based simulations. In spite of the quantitative discrepancies, the liner heat transfer trends are expected to provide valuable insight to the industrial community in the design of combustor liners based on less expensive computational tools.