Turbine Guide Vane Research Articles

Film Cooling Effectiveness on Pressure Surface and Suction Surface of Turbine Guide Vane With Diffusion Slot Holes

Abstract This paper investigated the film-cooling effectiveness of diffusion slot holes in a turbine nozzle guide vane. The pressure-sensitive paint measurement technique was employed to obtain the film-cooling effectiveness at a density ratio of DR = 1.5. The mainstream Reynolds number based on the axial chord length and the exit velocity was 6 × 105. The mainstream turbulence intensity was approximately 3.7%. Three diffusion slot hole geometries with cross-sectional aspect ratios (ASs) of 2.3, 3.4, and 4.9 were tested and compared with a typical fan-shaped hole. The experiments were performed at three typical hole row locations on the pressure surface (PS) and suction surface (SS). The average blowing ratios varied from M = 0.5 to 2.5. The results showed that throughout the blowing ratio range, on the PS, a substantially higher film-cooling effectiveness than the fan-shaped hole is always obtained from the diffusion slot hole with a large aspect ratio (AS = 4.9); on the SS, the diffusion slot hole with a small AS (AS = 2.3). The influence of hole row positioning is inconsistent for diffusion slot holes with different ASs. The diffusion slot hole is less affected by the PS when the AS is moderate and less affected by the SS when the AS is large. The film-cooling effectiveness of the diffusion slot holes is basically the lowest where the PS has a maximum concave curvature and the highest where the SS has a large favorable pressure gradient.

XCT damage evaluation and analysis of SiC/SiC turbine guide vanes after thermal shocks

AbstractIn this paper, the two‐dimensional (2D) (0°/90°) plain‐woven Amosic‐3 SiC/SiC turbine guide vane (TGV) was fabricated using the chemical vapor infiltration method. Thermal and stress analysis of the TGV was conducted using the finite element method analysis. Multiple thermal shock tests at T = 1250, 1350, 1400, 1420, 1450, 1470, and 1480°C were conducted for N = 100, 100, 400, 300, 200, 200, and 700 cycles. After thermal shock tests, the surface damage of the TGV was observed visually, and the micro damage mechanism was analyzed using the scanning electronic microscopy. Micro X‐ray computed tomography was adopted to characterize the internal damages in the SiC/SiC guide vanes. The delamination occurred at the positions approaching internal hollow, due to the weak binding force along the thickness direction and the high thermal shock stress caused by the temperature change. The diameter, area, volume, and sphericity distributions of the pores inside of the guide vanes were also obtained.

Effect of Hot Streak on Aerothermal Performance of High Pressure Turbine Guide Vane under Different Swirl Intensities

In advanced civil aero-engine, the gas exiting combustor typically features hot streak (HS) and swirl that affect the aerothermal performances of the high pressure (HP) nozzle guide vane (NGV). The purpose of this paper is to study the influences of HS on HP NGV aerothermal behaviors under swirl with various intensities. The numerical investigations were conducted on the first NGV of GE-E3 HP turbine. Four swirl intensities (|SN| = 0, 0.25, 0.50, 0.75) and two swirl orientations (positive and negative) were considered. The result indicates that the relative strengths between the swirl and its induced radial pressure gradient dominate the flow patterns on vane surfaces. Thus, the diverse streamlines distributions appear on the surfaces and the dominated factor on each surface does not vary with swirl intensity. The swirl redistributes the cold and hot fluid and thus generates the relatively hot oblique strip and cold region at the upstream of vane. The heat load on the vane that is not directly impinged by HS is dictated by the radial migration of the fluids originating from the regions aforementioned at |SN| = 0.25 and 0.50. However, at |SN| = 0.75, the transverse movement of HS due to the intense swirl causes additional thermal load. The heat load on the vane that faces HS is mainly determined by the radial migration of HS. The swirl alters the heat transfer distribution on vane surfaces remarkably. With positive swirl, the heat transfer coefficients at the lower span of suction side and pressure side are enhanced and weakened respectively. As expected, the opposite trends are observed in the negative swirl case. Swirl also affects boundary layer transition, and then affecting heat transfer. Positive and negative swirls both advance the transition on the suction side of vane directly impinged by the swirl, and with the increase of swirl intensity, transition onset shifts toward upstream.

Numerical Investigation of Single-Row Double-Jet Film Cooling of a Turbine Guide Vane under High-Temperature and High-Pressure Conditions

Single-row double-jet film cooling (DJFC) of a turbine guide vane is numerically investigated in the present study, under a realistic aero-thermal condition. The double-jet units are positioned at specific locations, with 57% axial chord length (Cx) on the suction side or 28% Cx on the pressure side with respect to the leading edge of the guide vane. Three spanwise spacings (Z) in double-jet unit (Z = 0, 0.5d, and 1.0d, here d is the film hole diameter) and four spanwise injection angles (β = 11°, 17°, 23°, and 29°) are considered in the layout design of double jets. The results show that the layout of double jets affects the coupling of adjacent jets and thus subsequently changes the jet-in-crossflow dynamics. Relative to the spanwise injection angle, the spanwise spacing in a double-jet unit is a more important geometric parameter that affects the jet-in-crossflow dynamics in the downstream flowfield. With the increase in the spanwise injection angle and spanwise spacing in the double-jet unit, the film cooling effectiveness is generally improved. On the suction surface, DJFC does not show any benefit on film cooling improvement under smaller blowing ratios. Only under larger blowing ratios does its positive potential for film cooling enhancement start to show. Compared to the suction surface, the positive potential of the DJFC on enhancing film cooling effectiveness behaves more obviously on the pressure surface. In particular, under large blowing ratios, the DJFC plays dual roles in suppressing jet detachment and broadening the coolant jet spread in a spanwise direction. With regard to the DJFC on the suction surface, its main role in film cooling enhancement relies on the improvement of the spanwise film layer coverage on the film-cooled surface.

Numerical Investigation of a Radially Cooled Turbine Guide Vane Using Air and Steam as a Cooling Medium

Gas turbine performance is closely linked to the turbine inlet temperature, which is limited by the turbine guide vanes ability to withstand the massive thermal loads. Thus, steam cooling has been introduced as an advanced cooling technology to improve the efficiency of modern high-temperature gas turbines. This study compares the cooling performance of compressed air and steam in the renowned radially cooled NASA C3X turbine guide vane, using a numerical model. The conjugate heat transfer (CHT) model is based on the RANS-method, where the shear stress transport (SST) k−ω model is selected to predict the effects of turbulence. The numerical model is validated against experimental pressure and temperature distributions at the external surface of the vane. The results are in good agreement with the experimental data, with an average error of 1.39% and 3.78%, respectively. By comparing the two coolants, steam is confirmed as the superior cooling medium. The disparity between the coolants increases along the axial direction of the vane, and the total volume average temperature difference is 30 K. Further investigations are recommended to deal with the local hot-spots located near the leading- and trailing edge of the vane.

Experimental research on the performance of a rotating detonation combustor with a turbine guide vane

Rotating detonation engines (RDEs) have received significant attention from industry and academia alike, owing to their numerous advantages, such as pressure gain combustion, high operation frequency, and near-constant thrust output. Furthermore, there is considerable interest in combining RDEs with gas-turbine engines to further improve their overall system performance. This study examines the propagation characteristics of continuous rotating detonation waves (CRDWs) with a turbine guide vane (TGV). We develop an experimental model of a hydrogen–air rotating detonation combustor integrated with a TGV section and record the high-frequency pressure oscillations and static pressure upstream and downstream of the TGV section. The experimental results indicate that: the interactions between CRDW and the turbine blade cause the reflected shock propagating backwards to the combustor. Both pressure oscillation amplitude and static pressure decline at downstream of TGV. Notably, the pressure oscillation attenuation by the TGV is influenced by the direction of CRDW propagation. When the CRDW propagation direction and the flow path direction of the guide vane are opposite to each other, the pressure oscillation attenuation increases. The findings obtained herein provide benchmark data that help improve the fundamental understanding of CRDW and TGV interaction, and can be used to develop detonation-based propulsion technology.

Degradation analysis on high-cycle bending fatigue for woven SiC/SiC composites based on Wiener process model

A comprehensive investigation of degradation analysis under high-cycle bending fatigue (HCBF) loading for composite materials was conducted based on the Wiener process model. Degradation data are generated by conducting the probabilistic progressive damage analysis of composite materials considering the variability of material properties including mechanical properties and strength. Based on the degradation data, the Wiener process model is established with the power time transformation function and linear time-scale functions. The HCBF tests of composite cantilever beam specimen (CBS) and turbine guide vane (TGV) are conducted to evaluate the degradation process of composite materials. Compared with the experimental data and Monte Carlo simulation (MCS) method, the proposed methodology has the promising potentials to improve computational efficiency with acceptable computational accuracy for the CBSs. As for the TGV, the maximum relative errors for mean fatigue life are within 17.89%, while the degradation tendency from experiments is similar to the simulated degradation curves, verifying the rationality of the proposed method based on Wiener process model. Moreover, reliability analysis is conducted based on the stochastic degradation process, which can be used to determine whether the performance of the structure meets the design requirement.

Influence of propagation direction on operation performance of rotating detonation combustor with turbine guide vane

Due to the pressure gain combustion characteristics, the rotating detonation combustor (RDC) can enhance thermodynamic cycle efficiency. Therefore, the performance of gas-turbine engine can be further improved with this combustion technology. In the present study, the RDC operation performance with a turbine guide vane (TGV) is experimentally investigated. Hydrogen and air are used as propellants while hydrogen and air mass flow rate are about 16.1 g/s and 500 g/s and the equivalence ratio is about 1.0. A pre-detonator is used to ignite the mixture. High-frequency dynamic pressure transducers and silicon pressure sensors are employed to measure pressure oscillations and static pressure in the combustion chamber. The experimental results show that the steady propagation of rotating detonation wave (RDW) is observed in the combustion chamber and the mean propagation velocity is above 1650 m/s, reaching over 84% of theoretical Chapman-Jouguet detonation velocity. Clockwise and counterclockwise propagation directions of RDW are obtained. For clockwise propagation direction, the static pressure is about 15% higher in the combustor compared with counterclockwise propagation direction, but the RDW dominant frequency is lower. When the oblique shock wave propagates across the TGV, the pressure oscillations reduces significantly. In addition, as the detonation products flow through the TGV, the static pressure drops up to 32% and 43% for clockwise and counterclockwise propagation process respectively.

Numerical Investigation of Influence of Entropy Wave on the Acoustic and Wall Heat Transfer Characteristics of a High-Pressure Turbine Guide Vane

As an indirect noise source generated in the combustion chamber, entropy waves are widely prevalent in modern gas turbines and aero-engines. In the present work, the influence of entropy waves on the downstream flow field of a turbine guide vane is investigated. The work is mainly based on a well-known experimental configuration called LS89. Two different turbulence models are used in the simulations which are the standard k-ω model and the scale-adaptive simulation (SAS) model. In order to handle the potential transition issue, Menter’s ð-Reθ transition model is coupled with both models. The baseline cases are first simulated with the two different turbulence models without any incoming perturbation. Then one forced case with an entropy wave train set at the turbine inlet at a given frequency and amplitude is simulated. Results show that the downstream maximum Mach number is rising from 0.98 to 1.16, because the entropy waves increase the local temperature of the flow field; also, the torque of the vane varies as the entropy waves go through, the magnitude of the oscillation is 7% of the unforced case. For the wall (both suction and pressure side of the vane) heat transfer, the entropy waves make the maximum heat transfer coefficient nearly twice as the large at the leading edge, while the minimum heat transfer coefficient stays at a low level. As for the averaged normalized heat transfer coefficient, a maximum difference of 30% appears between the baseline case and the forced case. Besides, during the transmission process of entropy waves, the local pressure fluctuates with the wake vortex shedding. The oscillation magnitude of the pressure wave at the throat is found to be enhanced due to the inlet entropy wave by applying the dynamic mode decomposition (DMD) method. Moreover, the transmission coefficient of the entropy waves, and the reflection and transmission coefficients of acoustic waves are calculated.

Scale-Resolving Simulations of Bypass Transition in a High-Pressure Turbine Cascade Using a Spectral Element Discontinuous Galerkin Method

The application of a new computational capability for accurate and efficient high-fidelity scale-resolving simulations of turbomachinery is presented. The focus is on the prediction of heat transfer and boundary layer characteristics with comparisons to the experiments of Arts et al. (1990, “Aero–Thermal Investigation of a Highly Loaded Transonic Linear Turbine Guide Vane Cascade,” von Karman Institute for Fluid Dynamics, Rhode St. Genese, Belgium, Technical Note No. 174.) for an uncooled, transonic, linear high-pressure turbine (HPT) inlet guide vane cascade that includes the effects of elevated inflow turbulence. The computational capability is based on an entropy-stable, discontinuous Galerkin (DG) spectral element approach that extends to arbitrarily high orders of spatial and temporal accuracy. The suction side of the vane undergoes natural transition for the clean inflow case, while bypass transition mechanisms are observed in the presence of elevated inflow turbulence. The airfoil suction-side boundary layer turbulence characteristics during the transition process thus differ significantly between the two cases. Traditional simulations based on the Reynolds-averaged Navier–Stokes (RANS) fail to predict these transition characteristics. The heat transfer characteristics for the simulations with clean inflow agree well with the experimental data, while the heat transfer characteristics for the bypass transition cases agree well with the experiment when higher inflow turbulence levels are prescribed. The differences between the clean and inflow turbulence cases are also highlighted through a detailed examination of the characteristics of the transitional and turbulent flow fields.

Multiconfiguration Shape Optimization of Internal Cooling Systems of a Turbine Guide Vane Based on Thermomechanical and Conjugate Heat Transfer Analysis

This study concerns optimization of shapes, locations, and dimensions of internal cooling passages within a turbine vane under severe environments. The basic aim is to achieve a design that minimizes the average temperature and ensures the structural strength. Considering the prohibitive computational cost of 3D models, numerical optimization process is performed based on 2D cross-sectional models with available experimental temperature data as boundary conditions of thermomechanical analysis. To model the cooling channels, three kinds of shape configurations, i.e., circle, superellipse, and near-surface holes, are taken into account and compared. Optimization results of 2D models are obtained by using a globally convergent method of moving asymptotes (GCMMA). Furthermore, full conjugate heat transfer (CHT) analyses are made to obtain temperature distributions of 3D models extruded from 2D ones by means of shear stress transport (SST) k-ω turbulence model. It is shown that optimization of cooling passages effectively improves the thermomechanical performances of turbine vanes in comparison with those of initial C3X vane. The maximum temperature of optimized vane could be reduced up to 50 K without degrading mechanical strength.

Application of the Turbulent Potential Model to Heat Transfer Predictions on a Turbine Guide Vane

The accurate numerical simulation of the flow through turbomachinery depends on the reliable prediction of laminar to turbulent boundary layer transition phenomena. The aim of this paper is to study the ability of the turbulent potential model to predict those nonequilibrium turbulent flows for several test cases. Within this model turbulent quantities are described by the turbulent scalar and turbulent vector potentials of the turbulent body force—the divergence of the Reynolds stress tensor. For model validation first flat plate test cases with different inlet turbulence intensities, zero pressure gradient, and nonuniform pressure gradient distributions along the plate were calculated and compared by means of skin friction values measured in the experiments. Finally the model was validated by heat transfer measurement data obtained from a highly loaded transonic turbine guide vane cascade for different operating conditions.

External Heat Transfer Predictions in a Highly Loaded Transonic Linear Turbine Guide Vane Cascade Using an Upwind Biased Navier–Stokes Solver

External heat transfer predictions are performed for two-dimensional turbine blade cascades. The Reynolds-averaged Navier–Stokes equations with algebraic (Arnone and Pacciani, 1998), one-equation (Spalart and Allmaras, 1994), and two-equation (low-Re k–ε, Biswas and Fukuyama, 1994) turbulence closures are solved with a fully implicit time-marching finite volume method. Comparisons with measurements (Arts et al., 1990; Arts, 1994) for a highly loaded transonic turbine nozzle guide vane cascade show good agreement in some cases, but also reveal problems with transition prediction and turbulence modeling. Special attention has been focused on the low-Re k–ε model concerning the influence of the inlet boundary condition for the ε-equation and problems in the stagnation point region.