Film Cooling Effectiveness Distributions Research Articles

Study on effects of inlet nonuniformities on aerothermal performance of NGV pressure side with different film cooling designs

High pressure (HP) turbine works under nonuniform inlet conditions produced mainly by modern lean burn combustors. This article employed the conjugate heat transfer method to investigate the influences of nonuniform inflow conditions and film hole arrangements on the film coolant coverage and heat transfer characteristics. The researched region is on the pressure side (PS) of the nozzle guiding vane (NGV). A scaled-up model of the GE-E3 engine HP turbine stator vane was used and the film cooling performances of four different film hole arrangement schemes on the PS were discussed. In addition, the results of four nonuniform inflow conditions, including positive/negative swirl aligned with the stator vane leading edge (case PSW-LE and NSW-LE), and positive/negative swirl aligned with the stator vane mid passage (case PSW-PA and NSW-PA), were compared with the uniform inlet condition. The results indicate that the temperature distributions of stator vane PS are dominated by the film hole arrangements and the nonuniform inlet conditions. In the positive swirl (PSW) influenced region, film cooling effectiveness can be improved if the coolant orientation is consistent with the swirl direction. The film cooling effectiveness can be improved by 12%–20% under the Leading Edge (LE) clocking position and 45% under the Passage (PA) clocking position. In contrast, the negative swirl dominates the film cooling effectiveness distribution. Under the PA clocking position, the highest film cooling effectiveness can be enhanced by 45% compared with the LE. In contrast, the design of film holes has a weak contribution to the coolant outflow direction under the negative swirl (NSW) condition. However, the film holes with negative angles can enhance the cooling effectiveness behind the 13th row holes.

TPIV Experimental Investigation of Film Coolant-to-Mainstream Interaction From Shaped Cooling Holes With Various Inlet Geometries

Abstract In this investigation, multiple sets of time-averaged tomographic particle imaging velocimetry measurements are completed for laid-back, fan-shaped film cooling holes with “racetrack” shaped inlets. Traditional 10-10-10, laid-back, fan-shaped holes are inclined 30 deg to the mainstream flow on a flat plate. The inlet cross section varies from round to two elongated racetrack shapes. The cross-sectional area and the outlet-to-inlet area ratio for all the geometries are held constant. The flat plate is installed in a low-speed wind tunnel with a mainstream turbulence intensity of 8% and an average velocity of 21.6 m/s. The blowing ratios of the film jets range from 0.6 to 1.5 and the density ratio is 1. The Reynolds number of the cooling jet varies from 2600 to 8400. The characteristics of the resulting flowfield are coupled with the detailed film cooling effectiveness distributions. It can be noted from the results that the counter-rotating vortex pair generated by the 2:1 inlet is the closest to the surface and weakest in strength, likely caused by the minimum peak jet momentum of the three. The Reynolds stresses downstream of the 2:1 and 4:1 inlets are significantly lower than those downstream of the shaped hole with a round inlet. An inverse relation between volumetric turbulence accumulation (TA), and surface effectiveness (η), can be correlated for the blowing ratios considered. The turbulence accumulation term can thus be used to evaluate the performance of a film cooling hole design with flowfield data.

Effects of blowing ratio on surface heat transfer characteristics of a transonic turbine squealer blade tip with a double plenum film cooling supply arrangement

Investigated are the effects of blowing ratio on the surface heat transfer characteristics of a film cooled transonic turbine squealer blade tip with a unique double plenum supply arrangement for the coolant. The present configuration is unique because the forward film cooling holes are supplied by an upstream plenum, while the aft film cooling holes are supplied separately by a second downstream plenum. Considered are varying forward blowing ratios as the aft blowing ratio is maintained constant. Nine total blowing ratio combinations are investigated, such that the forward blowing ratio is varied from 1.89 to 3.07, whereas the aft blowing ratio is varied from 0.96 to 1.45. Surface data are provided along the upper pressure side surface and the squealer tip surface of the turbine blade. Included are spatially-resolved and line-averaged distributions of heat transfer coefficient ratio and adiabatic film cooling effectiveness, which vary in a complex manner as upstream and downstream blowing ratios are altered. Local adiabatic film cooling effectiveness distributions evidence good film coverage along the squealer tip surface for all considered blowing ratios, especially for portions of the trailing edge, recess, and pressure side rim regions. Results indicate that the optimal blowing ratio associated with holes supplied by the upstream plenum depends upon the blowing ratio value associated with holes supplied by the downstream plenum.

Experimental investigation of full-coverage film cooling characteristic of single/double-wall cooling vane

This paper employed the pressure sensitive paint (PSP) technique to measure the adiabatic film cooling effectiveness distributions of both the single-wall cooling vane (SCV) and the double-wall cooling vane (DCV). The experiments were implemented in an annual cascade under a Reynolds number of 3.0 × 105 condition. Furthermore, the effects of mass flow ratio (MFRs include 4.99 %, 6.65 %, 8.32 %, 9.98 %, and 11.65 %) and density ratio (DRs include 1.0, 1.5, and 2.0) on the adiabatic effectiveness distribution were also investigated. The results reveal that the DCV improves dramatically the film cooling effectiveness of the pressure side and the suction side compared with the SCV, and the effectiveness is elevated by 12 % and 25 %, respectively. As the MFR increases, the lateral average film cooling effectiveness of the SCV initially increases and then decreases, while that of the DCV enhances monotonously. Additionally, when the DR is raised from 1.0 to 1.5, the lateral average film cooling effectiveness of the pressure side of the SCV is increased by 50 % at the MFR = 6.65 %. Also, the DCV presents both high and even film cooling effectiveness contour distribution at high density ratio conditions, and the surface average film cooling effectiveness of the DCV is greater than 0.4 when the MFR ≥ 8.32 %.

Assessment of Binary Pressure-Sensitive Paint for Temperature and Heat Transfer Coefficient Measurement of Leading-Edge Film Cooling

Abstract Film cooling is a common technique for protecting gas turbine components from the hot combustor exhaust. Highly resolved film cooling effectiveness distributions are often obtained by measuring the mass transfer of a foreign gas coolant in mainstream air using pressure-sensitive paint (PSP). However, PSP is not able to measure the heat transfer coefficient, which is necessary to fully quantify the impact of film cooling. Instead, binary pressure-sensitive paint (BPSP) has an additional luminophore that is sensitive to temperature and can be used to measure the heat transfer coefficient. In this experiment, the film cooling effectiveness and heat transfer coefficient were measured using BPSP on the leading edge of a cylinder. The cylinder had a 7.62-cm diameter with two rows of cooling holes at ±15 deg from the leading edge. Each row contained ten holes with a 0.475-cm diameter, spaced 4 diameters apart in the spanwise direction, and angled 30 deg from the cylinder axis. The mainstream Reynolds number was 100,000 based on cylinder diameter with a turbulence intensity of 7.1%. The coolant-to-mainstream density ratio was 1.0, and the blowing ratio was 0.8. The heat transfer coefficient was measured in a transient heat transfer experiment using the reference signal from the BPSP. Despite the high uncertainty of the measurement, ranging from 24.0% to 71.1%, the results demonstrate the feasibility of the method and identify the best test methodology to minimize conduction errors.

Effect of Upstream Leakage Flow on Film Cooling Characteristic of a Turbine Convex Endwall

Abstract This paper investigates the effect of upstream leakage coolant flow on the film cooling performance of the convex endwall. The experiment is conducted in an annular passage with four vanes, and the endwall film cooling effectiveness distribution is measured by the pressure-sensitive paint technique. The near-wall flow field distribution predicted by computational fluid dynamics is employed to gain a deeper understanding of the influence of the passage secondary flow on the film cooling characteristic of the endwall. Furthermore, the effect of mass flow ratios (MFR = 0.75%, 1.0%, 1.25%, and 1.5%), leakage slot inclination angles (α = 30 deg, 45 deg, and 60 deg), density ratios (DR = 1.0, 1.5, and 2.0), as well as Reynolds number (Re = 2.0 × 105, 3.0 × 105, and 4.0 × 105) on the endwall film cooling is also investigated. Results indicate that the mass flow ratio has a great influence on the endwall film cooling effectiveness distribution, and a larger uncooled region can be observed when MFR is less than 1.25% due to the cooling air more easily being entrained by the secondary flow near the endwall. Reducing the inclination angle of the leakage slot enhances the axial velocity component of the coolant flow, thereby weakening the secondary flow near the endwall and improving the film cooling effectiveness distribution of the endwall. As the density ratio increases, the jet momentum of the leakage flow is reduced, particularly for higher MFR cases, which results in a significant reduction in the film cooling performance of the endwall. Besides, thinning the incoming boundary layer of the passage reduces the strength and size of the secondary flow in the passage and improves the endwall adiabatic effectiveness distribution when the Reynolds number is increased.

Effects of dusting film cooling placement and configuration on surface heat transfer characteristics of a transonic turbine squealer blade tip

Investigated are the effects of dusting hole film cooling placement and configuration on the surface heat transfer characteristics of a transonic turbine squealer blade tip. Three different blade tip arrangements are investigated, which are denoted C1, C2, and C3. Data are provided which include spatially-resolved and line-averaged distributions of heat transfer coefficient ratio and adiabatic film cooling effectiveness. The University of Alabama in Huntsville SS/TS/WT (supersonic/transonic/wind tunnel) blow down facility is employed with a transonic test section containing a five blade linear cascade for the investigation. Spatially-resolved surface heat transfer characteristics are measured using time- and spatially-resolved infrared thermography, in conjunction with an impulse response transient measurement procedure. Film coolant is supplied with a carbon dioxide injection system. Results indicate that heat transfer coefficient and adiabatic film cooling effectiveness distributions vary significantly as dusting hole placement and configuration are altered. For example, heat transfer coefficients for the C1 and C2 blade configurations are substantially lower, compared to baseline values with no film cooling, within the squealer recess region downstream of the dusting holes. Smaller heat transfer coefficient deviations, relative to baseline values, are present when the C3 configuration is employed. In general, distributions and magnitudes of local adiabatic film cooling effectiveness indicate that all three dusting hole configurations provide reasonably good film coverage within portions of squealer recess regions. For downstream portions of the blades, the C1 and C3 configurations both provide good surface protection which are indicated by film cooling effectiveness values, whereas coverage provided by the C2 arrangement ends abruptly at the location of a structural rib which is located within the squealer recess region.

Coupling of Volumetric Flowfield and Surface Effectiveness Measurements for Flat-Plate Film Cooling With Cylindrical Holes Using Tomographic Particle Image Velocimetry and Pressure-Sensitive Paint

AbstractIn this study, a series of time-averaged tomographic particle image velocimetry (TPIV) measurements are completed for simple angle, cylindrical film cooling holes on a flat plate with an inclination angle of 30 deg and a diameter of 4 mm. The flat plate is installed in a low-speed wind tunnel with a mainstream turbulence intensity of Tu=8% and an average velocity of 21.6 m/s. The blowing ratios of the jet range from M = 0.3 to M = 1.5, and the density ratio of the jet is fixed at DR = 1. The Reynolds number of the cooling jet varies from 1700 to 8400. The repeatability and accuracy of the tomographic particle imaging velocimetry (TPIV) measurements are compared against the results obtained by other flowfield measurement techniques. The results of the TPIV measurements are presented in velocity and vorticity iso-surface distributions in 3D, as well as 2D planar slices of velocity, vorticity, turbulence intensity, and Reynolds Stress distributions within the measurement volume. The characteristics of the flowfield are coupled with the detailed film cooling effectiveness distribution obtained using the pressure-sensitive paint (PSP) technique. An inverse relation among volumetric turbulence accumulation (TA) and surface film effectiveness, η, can be correlated.

Effect of blowing ratio, rotation, and film hole row location on film cooling on the suction surface of a rotating turbine blade

Experiments and simulations were performed to study the single-row film cooling performance on a turbine blade suction surface. Effects of blowing ratio, rotation, film hole row location, and the combine effects of the above three factors on single-row film cooling performance were studied. Totally three injection row locations of 12.4% S, 23.2% S, and 34% S were taken into consideration, where S refers to the suction side streamwise length. Experiments were carried out under turbine speeds of 400rpm, 600rpm, and 800rpm respectively with average blowing ratios change in the region of 0.5 to 1.5. Rotational Reynolds number corresponding to the turbine speeds was 3.57 × 105, 5.36 × 105, and 7.15 × 105. Pressure sensitive paint (PSP) technique was employed in obtaining film cooling effectiveness distribution. To assist explain the experimental results, numerical simulations were performed to acquire the mainstream and coolant jet flow field and local blowing ratio of each film hole. Results showed that film traces on the suction surface are bent toward the blade mid-span, and the downstream jet deflects more. Increasing blowing ratio and rotational Reynolds number will slightly reduce the inward film deflection. The local blowing ratios at hole exits are not evenly distributed along streamwise and spanwise direction under the combine effects of the three factors, which result in different film cooling performance at different streamwise locations and different blade heights.

Experimental and numerical investigations on the unsteady flow and film cooling characteristics of the trailing edge cutback

The film cooling characteristics of the trailing edge cutback slot of a high pressure turbine were experimentally and numerically investigated. The unsteady flows have an important effect on the mixing process of the mainstream and coolant flow, resulting in deteriorated film performance. To illustrate the interaction between the unsteady flows and coolant injection, eight blowing ratios ranging from 0.3 to 1.2 were considered for the baseline cases. Pressure sensitive paint measurements were conducted to acquire the adiabatic film cooling effectiveness distribution. The counter-intuitive decrease of the film cooling effectiveness was confirmed and further revealed. Particle image velocimetry showed that the unsteady flow patterns downstream of the trailing edge slot varied with increasing blowing ratio. Furthermore, the high-fidelity RANS/LES hybrid method was employed to resolve the detailed flow fields. The numerical method was carefully validated, and it successfully predicted the unsteady flows and mixing process. The spanwise vorticity showed that the two branches of the shedding vortices alternatively become strong. At the blowing ratio of 0.75, the strength of the two branches was comparative, yielding the worst cooling performance. Additionally, the density ratio and lip thickness to slot height ratio were investigated. Thus, the density ratio affects the coolant velocity ratio, causing the forward movement of the inflection point of the film cooling effectiveness map. The decrease of the lip thickness to slot height ratio leads to the reduction of the strength of the shedding vortices and therefore increases the film cooling effectiveness.

Effects of pressure side film cooling hole placement and condition on adiabatic film cooling effectiveness characteristics of a transonic turbine blade tip

The effects of film cooling hole placement location along the upper pressure side of a transonic squealer are considered. The thermal performance of four different film cooling configurations; B1, B2, B3 and B4, are considered using the University of Alabama in Huntsville's SS/TS/WT (supersonic/transonic/wind tunnel) experimental facility and a simulated turbine blade row using a linear cascade. Surface-varying results are provided for both the squealer blade tip surface, and for the upper pressure side of the squealer blade. These results are given for blowing ratios ranging from 0.42 to 3.20 in the form of spatially-resolved and spatially-averaged adiabatic film cooling effectiveness distributions. Because local static pressure variations and gradients vary in a significant manner at different blade locations, coolant accumulations near surfaces (and the associated surface thermal protection and film effectiveness distributions) produced by the different film cooling configurations are vastly different along the squealer blade tip surface. The B1 and B3 film cooling configurations show that substantial magnitudes of adiabatic film cooling effectiveness are present along the pressure side rim and the suction side rim. Also present is a considerable region of locally increased film cooling effectiveness and a wider region of surface protection within the squealer recess region for the B2 film cooling configuration. The contributions are unique because of a deficit of experimental data for film cooled squealer blades which operate with transonic flow, and because the present investigation is the first to consider the effects of hole placement location for upper pressure side film cooling arrangements with transonic flow conditions.

Effects of plasma actuation and hole configuration on film cooling performance

In this paper, plasma actuators are arranged asymmetrically downstream the wall to improve film cooling performance. Effects of blowing ratio, hole configuration and applied voltage on flow characteristics and film cooling effectiveness were investigated numerically on a flat plate. Results show that highest film cooling effectiveness distribution is obtained both in the spanwise and streamwise directions under blowing ratio of 0.5. Average wall film cooling effectiveness of cylindrical hole increases by 251.9% under blowing ratio of 0.5 compared to that under blowing ratio of 1.5. The scale of the counter rotating vortex pairs (CRVP) from fan shaped hole and sister hole are significantly reduced compared to that from cylindrical hole. The console hole has an anti-counter rotating vortex pair (Anti-CRVP), which weakens the entrainment of the CRVP to the coolant air near the wall. Compared with the cylindrical hole, average wall film cooling effectivenesses for fan shaped hole, sister hole and console hole increase by 73.1%, 97.5% and 119.9%. The adherent performance of the coolant air is enhanced after applying plasma actuator. The aerodynamic actuation of the plasma results in the rebound of the fluid close to the wall at 24 kV applied voltage. Average wall film cooling effectiveness of the console hole at 12 kV applied voltage is 10.6% higher than that without plasma.

Deep learning method for fast prediction of film cooling performance

This study examines the predictive capability of deep learning method for adiabatic film cooling effectiveness distribution with variable operating conditions and geometric layouts. A conditional generative adversarial network is trained to establish nonlinear mapping from input to output. We embed the boundary condition information directly into the input tensor, thereby imparting the capability to address variable operating conditions. The processed input tensors include different blowing ratios M, incoming turbulence intensity Tu, geometry profile controlled by the inclination angle ϕ, compound angle θ, number of hole rows n, pitch between hole rows Px, and span-wise hole pitch Py. The output data are adiabatic film cooling effectiveness fields generated by Reynolds-averaged Navier–Stokes simulations. The prediction results are in good agreement with the computational fluid dynamics results in terms of various statistical assessments. Furthermore, compared with conventional methods of solving Navier–Stokes equations, predictions based on deep learning result in better response times. Therefore, the method proposed in this study is of high significance in the early design of cooling structures for turbine blades.

Large eddy simulation of internal coolant crossflow orientation effects on film-cooling effectiveness of fan-shaped holes

In modern gas turbine engines, the coolant is typically injected through the small cooling holes on the surface of the blade using an internal crossflow. Most experimental and numerical studies have used a stagnant plenum to feed the cooling holes without considering the influence of the internal coolant crossflow orientation. Therefore, in this study, we used large eddy simulations (LES) to investigate the effect of internal coolant crossflow orientations on film-cooling effectiveness and turbulent flow structures of fan-shaped cooling holes. A 7-7-7 laidback fan-shaped hole with an injection angle of 30-degree located on a flat plate surface was selected as a reference case. Three different internal coolant crossflow orientations (parallel/perpendicular with respect to the mainstream flow) were numerically conducted at a density ratio (DR) of 1.5 and two different blowing ratios (M = 1.5 and 3.0). The computational data were validated by the measurements of the reference case with a stagnant plenum in terms of flow and thermal fields. At both blowing ratios, the coolant channel parallel to the mainstream flow direction showed the best cooling performance among the cases. The coolant channel perpendicular to the mainstream flow displayed the minimum area-averaged film-cooling effectiveness, with a reduction of about 17% compared to the stagnant plenum. The velocity-field analysis showed an asymmetric pattern inside the cooling hole for the perpendicular coolant channel case due to the cooling hole entrance effect, which affects the distributions of film-cooling effectiveness on the flat plate. Furthermore, the time-space assessment of the velocity-field revealed greater flow unsteadiness and a wavy pattern for the crossflow perpendicular to the direction of coolant injection.

Investigations into heat transfer and film cooling effect on winglet-squealer tips in a turbine stage

Heat transfer and film cooling effect on three kinds of winglet-squealer tips (i.e., conventional squealer tip, no P.S. rim tip and P.S. winglet tip) in a turbine stage are numerically investigated at two operation conditions (i.e., laboratory testing condition and sea-level take-off condition) and three cooling hole arrangements (i.e., un-cooled, with tip holes, and with both tip and pressure side holes), and the numerical results are also compared with those in stationary cascades. To reduce the heat transfer while enhancing film cooling effect on the P.S. winglet tip, ejection angles for the tip and pressure side cooling holes are varied to reveal the superior performance of P.S. winglet tip in turbine stage. The results show that the heat transfer coefficient and film cooling effectiveness distributions on three kinds of tips exhibit different trends in the stationary and rotating cases. Tip rotating significantly affects the trajectories of cooling flow in the conventional squealer tip and no P.S. rim tip due to different vortex system induced in the cavity. However, the relative rotating has little influence on the flow structures in the P.S. winglet tip. In un-cooled condition, the area-averaged heat transfer coefficient on P.S. winglet tip is lower than the conventional squealer tip by 11.6%. For the vertical ejection case in turbine stage, the P.S. winglet tip has a slightly worse heat transfer and film cooling effect than the conventional squealer tip. However, with inclined ejections, the area-averaged heat transfer coefficient on winglet tip in turbine stage is lower than the conventional squealer tip by 15.3%, and the area-averaged film cooling effectiveness on winglet tip is higher than the conventional squealer tip by 12.1%.

Theoretical model for two-dimensional film cooling effectiveness distribution prediction

Film cooling is commonly categorized as a jet in crossflow phenomenon. Due to its fully three-dimensional flow field, characteristically two-dimensional (2-D) cooling effectiveness distributions are observed on the target wall. A theoretical method for 2-D film cooling effectiveness distribution predictions is developed by modeling the diffusion and convective transportation in the lateral direction. The effective diffusion coefficient is introduced to quantify the combined effects of the turbulent and laminar expansion. The convection effect, mainly the vortex entrainment, is quantified based on the analytical Oseen vortex. The intensity, scale, and location of the kidney vortex are modeled, respectively. The 2-D model in the current study can well satisfy the demand both academically and industrially. The time consumption of a 2-D effectiveness distribution calculation is on the magnitude of 1 ×10−2 s. The prediction error is within 8% if given especially correlated model coefficients, or within 14% otherwise.

Effects of Holes Arrangement on the Superposition Characteristics of Film Cooling Effectiveness

The purpose of the current research is to test and analyze the applicability of the Sellers model in different arrangements and configurations of film cooling holes and then to modify the Sellers model to improve the accuracy of the superposition prediction. The film cooling effectiveness distributions at different blowing ratios are obtained using the infrared thermometry technology. The flat plate experiments are completed in a low-speed closed-loop wind tunnel facility. The mainstream Reynolds number based on the film hole diameter is 6300, and the blowing ratios range from 0.8 to 1.8. The superposition characteristics are described in three different cases: double rows of cylindrical holes in an inline arrangement, double rows of cylindrical holes in a staggered arrangement, and double rows of compound angle holes in an inline arrangement. The results indicate that the Sellers model cannot accurately predict the film cooling effectiveness in certain conditions, which is mainly attributed to the interaction between counter-rotating vortex pairs of the adjacent rows and the increasing momentum of mainstream near the wall surface. For all cases, the corresponding modified superposition prediction methods are given in this paper.

Direct and Inverse Model for Single-Hole Film Cooling With Machine Learning

Abstract The direct prediction model for adiabatic film cooling effectiveness distribution and inverse prediction model for design parameters are studied in this article. Convolutional neural networks (CNNs) are trained on a set of simulated adiabatic film cooling effectiveness contours parameterized by blowing ratio, density ratio, mainstream turbulence intensity, injection angle, and compound angle. The direct model and the inverse model are able to approximate the data in the test set with plausible accuracy. The absolute error of spatial averaged effectiveness no larger than 0.03 could be obtained in the test set by a direct model with time consumption less than 1 ms for a single case. The inverse model is the first model of its kind, which accomplished the inverse mapping from contours to parameters. It has been demonstrated that the concatenation of inverse model with the pretrained direct model, which can be treated as a complex loss function, has preferable approximation performance compared with simple mean squared error (MSE) loss function in the training of the inverse model, thus confirming the necessity of adopting specialized modeling strategies for inverse problems.

Large Eddy Simulations on Film Cooling Flow Behaviors with Upstream Turbulent Boundary Layer Generated by Circular Cylinder

Large eddy simulations on film cooling hole array on a flat plate was carried out to investigate upstream turbulence effect. Circular cylinders were configured to create a turbulent boundary layer and its diameter has been adjusted to generate 13% upstream turbulence intensity in the main flow. Due to the small pitch to diameter configuration of the cylinder, two-dimensional LES analysis was carried out in advance and the results showed that LES was an essential method to resolve flow field around and downstream circular cylinder, which was not available in RANS simulations. The three-dimensional LES results showed reasonable agreement in turbulence intensity and normalized velocity distributions along the vertical with measured data. According to the blowing ratio, the cooling flow coverage on the surface along the stream-wise direction was varied and well agreed with measured data. Additionally, upstream boundary flows were partially ingested inside the cooling hole and discharged again near along the centerline of the cooling hole. This accounted for film cooling effectiveness distribution inside the cooling hole surface and along the centerline. The current study revealed that the LES for predicting turbulent boundary layer behaviors due to upstream turbulence generation source was an effective and feasible method. Moreover, the LES effectively resolved flow fields such as film cooling flow behaviors and corresponding film cooling effectiveness distributions.

Large eddy simulation of film cooling with vortex generators between two consecutive cooling rows

Film cooling approaches are widely applied in modern high-performance turbine engines to improve thermal efficiency. In the current film cooling investigation, vortex generators of delta winglets and the micro ramp installed between two consecutive cooling rows are studied by large eddy simulation (LES). Time-averaged and instantaneous results present the film cooling effectiveness distributions and vortical structure systems in the flow field. It is indicated that film cooling effectiveness is enhanced significantly when applying delta winglets and the micro ramp. An anticounter-rotating vortex pair (anti-CRVP) is generated by the vortex generators, which suppresses the coolant lift-off, weakens the strength of the detrimental counter-rotating vortex pair (CRVP), and enlarges the spanwise coolant coverage. Comparisons of the two vortex generators show that the micro ramp introduces stronger anti-CRVP than that evolved from the delta winglets. For the case without vortex generators, it is observed that the upstream CRVP merges with the downstream one weakening the cooling performance. The effects of vortex generators on the upstream shear layer vortices are examined. Temperature distributions of delta winglets and the micro ramp are discussed to improve the durability when applying them in gas turbine engines.