Improved clearance designs to minimize aerodynamic losses in a variable geometry turbine vane cascade

2017 ◽  
Vol 232 (17) ◽  
pp. 3085-3101 ◽  
Author(s):  
Jie Gao ◽  
Ming Wei ◽  
Pengfei Liu ◽  
Guoqiang Yue ◽  
Qun Zheng
Keyword(s):  
Gas Turbines ◽  
Strong Interactions ◽  
Variable Geometry ◽  
Specific Flow ◽  
Pressure Losses ◽  
Variable Geometry Turbine ◽  
Gap Height ◽  
Yaw Angle ◽  
Vane Tip ◽  
Aerodynamic Losses

Variable geometry turbine exists in small mobile gas turbines or some marine gas turbines to enhance the part-load performance. However, there are efficiency penalties associated with the vane partial gap, which is needed for the movement of variable vanes. This paper investigates the vane-end clearance leakage flow for a flat tip, a cavity tip, a winglet tip, a tip with passive injection, and a cavity-winglet tip to assess the possibility of minimizing vane-end clearance losses in a variable geometry turbine cascade. First, calculations were done at the test rig conditions for comparison with measured data, and they were used for validation of computational fluid dynamics model. Then, numerical calculations were done for turbine typical conditions. Specific flow structures of the various clearance designs of variable vanes are described, and then the effects of vane turning, including exit Mach numbers of 0.34, 0.44, and 0.54 as well as turning angles of –6°, 0°, and 6° on total pressure losses and outflow yaw angle for different vane tips are shown. In addition, the sensitivity of aerodynamic losses to vane tip gap height is evaluated. Results show that the strong interactions near the tip endwall region change the near-tip loading distribution significantly. With winglet and cavity-winglet tip designs, the loading distribution becomes very similar to the typical fixed vane, and the total loading is reduced, thus reducing the vane-end losses. Among the different vane tips presented, the cavity-winglet tip achieves the best aerodynamic performance, and the cavity tip has the lowest sensitivity to vane tip gap height. Overall, the cavity-winglet tip is found to be the best choice for variable vanes. The research results can provide useful reference for the vane design in a real high endwall-angle variable geometry turbine.

Part-Load Versus Downrated Industrial Gas Turbine Performance

2004 ◽  
Author(s):  
Cleverson Bringhenti ◽  
Joa˜o R. Barbosa
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Cycle Performance ◽  
Variable Geometry ◽  
Part Load ◽  
Distributed Power Generation ◽  
Development Costs ◽  
Base Engine ◽  
Variable Geometry Turbine ◽  
Industrial Gas Turbine

For distributed power generation, sometimes the available gas turbines cannot match the power demands. It has been usual to uprate an existing gas turbine in the lower power range by increasing the firing temperature and speeding it up. The development costs are high and the time to make it operational is large. In the other hand, de-rating an existing gas turbine in the upper power range may be more convenient since it is expected to cut significantly the time for development and costs. In addition, the experience achieved with this engine may be easily extrapolated to the new engine. This paper deals with the performance analysis of an existing gas turbine, in the range of 25 MW, de-rated to the range of 18 MW, concerning the compressor modifications that could be more easily implemented. Analysis is performed for the base engine, running at part-load of MW. A variable geometry compressor is derived from the existing one. Search for optimized performance is carried out for new firing temperatures. A variable geometry turbine analysis is performed for new NGV settings, aiming at better cycle performance.

scholarly journals Advances in variable geometry turbine aerodynamic technology for gas turbines

2018 ◽  
Vol 48 (11) ◽  
pp. 1141-1150
Author(s):  
Jie GAO ◽  
Qun ZHENG ◽  
GuoQiang YUE ◽  
Ping DONG ◽  
YuTing JIANG
Keyword(s):  
Gas Turbines ◽  
Variable Geometry ◽  
Variable Geometry Turbine

scholarly journals Influence of Cascade Parameters on the Deposition of Small Particles

1990 ◽  
Author(s):  
D. D. Kladas ◽  
D. P. Georgiou
Keyword(s):  
Gas Turbines ◽  
Deposition Velocity ◽  
Optimization Method ◽  
Eddy Diffusion ◽  
Hostile Environment ◽  
Small Particles ◽  
Pressure Losses ◽  
Turbine Cascades ◽  
Calculation Code ◽  
Aerodynamic Losses

Present day turbine cascades are being optimized, usually, for minimum total pressure losses. Gas Turbines, however, operating in a dirty environment or using dirty fuels need cascades that minimize the erosion and the corrosion implications of the hostile environment of the flue gasses. The present study employs the parametric cascade optimization method by Mcdonald to study the influence of a number of parameters on the deposition velocity of various particles, typical of those in a PFBC Gas Turbine. The calculation code employs the TSONIC and the STAN5 codes plus the method of Stewart for the aerodynamic losses and two property chosen models for the eddy diffusion one. The results indicate that control is possible only for particles with a diameter of less than 10.0 μm and this usually at the expense of an increase in the aerodynamic losses.

Numerical Investigation on Aerodynamic Characteristics of Variable Geometry Turbine Vane Cascade for Marine Gas Turbines

2020 ◽  
Author(s):  
Jie Gao ◽  
Dongchen Huo
Keyword(s):  
Energy Loss ◽  
Gas Turbines ◽  
Aerodynamic Characteristics ◽  
Loss Coefficient ◽  
Operating Conditions ◽  
Numerical Calculations ◽  
Variable Geometry ◽  
Turning Angle ◽  
Tip Leakage ◽  
Variable Geometry Turbine

Abstract Variable geometry turbines for marine gas turbines typically use variable vane technology to regulate turbine performance under variable operating conditions, but the variable geometry turbine produces additional losses as compared to the fixed geometry turbine. The method of combining experiment and numerical calculations was adopted to investigating the variable vane tip leakage loss at different vane turning angles, and its influence on the vane aerodynamic characteristics. The numerical calculations were performed using the ANSYS CFX 18.0 numerical prediction code, adopting the SST k-ω turbulence model to investigate the aerodynamic parameter distribution downstream of the variable vane under five different vane turning angles (−6°, −3°, 0°, +5° and +10°) and three different Mach Numbers (0.3, 0.5 and 0.6). The results showed that the tip leakage is the main source of aerodynamic loss of variable vanes. The tip leakage vortex and passage vortex show strong mixing characteristics in the downstream of variable vanes, especially at the 0.3Mach condition. The change of the vane turning angle alters not only the incidence angle to the vane itself, but also the outflow angle downstream of the vane. There is a linear relationship between the downstream outflow angle and the turning angle of the vane. The total pressure loss coefficient and energy loss coefficient decrease as the Mach number increases, and the changes of energy loss coefficient value from 0.3Mach to 0.5Mach are most obvious. Results from this investigation are well presented and discussed in this paper.

Experimental Investigation of Variable Geometry Turbine Annular Cascade for Marine Gas Turbines

2016 ◽  
Author(s):  
Xiying Niu ◽  
Chen Liang ◽  
Xuemei Jing ◽  
Jia Wei ◽  
Kaidi Zhu
Keyword(s):  
Gas Turbines ◽  
Total Pressure ◽  
Radial Clearance ◽  
Variable Geometry ◽  
Flow Angle ◽  
Turning Angle ◽  
Part Load ◽  
Power Turbine ◽  
Variable Geometry Turbine ◽  
Outlet Flow

Gas turbines are widely used as the marine main power system with its higher power density, react quickly, such as LM2500 and MT30. However, it works under design conditions only during running times of 3% to 10%, and it works under part load during most of the time, leading to low efficiency, and it could not achieve full speed or braking at an instant if sudden emergencies happen. Variable geometry turbines can improve this condition by variable angle nozzle (VAN) technology. And, it could enhance engine braking ability, reduce the fuel consumption under part load, improve the aerodynamic performance of engines, enhance accelerating ability of engines, and implement stalling protection to the power turbine. However, the VAN adjustment needs complicated regulating systems, which makes it difficult to turbine structural design, and leads to increased weight. Besides, there is a performance penalty associated with the vane-end part radial clearance required for the movement of variable vanes. In order to increase the part load efficiency of an intercooled recuperated gas turbine, the power turbine is converted from fixed to variable geometry. And, in order to reduce the losses caused by the radial clearance both of vane ends while vane turning, spherical ends are introduced to keep the clearance constant at all turning angles, and the baseline clearance is 0.77% of blade span. In order to determine the effects of VAN on aerodynamic performance of a variable vane, experimental investigations with a variable geometry turbine annular sector cascade have been conducted under five different turning angles (−6°, −3°, 0°, +5° and +10°) and three Mach numbers (0.3Ma, 0.5Ma and 0.6Ma). The parameter distributions were measured at cascade downstream by a five-hole probe and three-axis auto-traversing system, including outlet flow angle, total pressure loss coefficient, energy loss coefficient. The sector measurement results show that, as the vane turning angle is changed from closed to open, the outlet flow angle are increased under all three test Mach number conditions, which affects the flow mismatching between variable vane and downstream row. And, the total pressure losses is increased with the turning angle changed from design to closed or open, and the total pressure loss increases much more when the vane is closed than when it is open. In addition, vane-end clearances have significantly effects on the flow field. Especially on the hub, the leakage loss is higher, that may be due to the adverse effect of intermediate turbine ducts. Detailed results about these are presented and discussed in the paper.

Advances in aerodynamic, structural design and test technology of variable geometry turbines

2021 ◽  
pp. 095765092110356
Author(s):  
Jie Gao ◽  
Yu Liu ◽  
Qun Zheng ◽  
Chen Liang
Keyword(s):  
Structural Design ◽  
Gas Turbines ◽  
Design Method ◽  
Turbine Blades ◽  
Load Condition ◽  
Aerodynamic Characteristics ◽  
Variable Geometry ◽  
Part Load ◽  
Test Technology ◽  
Variable Geometry Turbine

The variable geometry turbine is one of the technical means to effectively improve the part-load performance, part-load condition stability and manoeuvrability of gas turbines, aeroengines or even turbochargers. However, the design of the variable geometry turbine is very difficult, and the decrease in efficiency offsets some of the engine cycle benefits caused by turbine variable geometry. Therefore, it is very necessary to carry out research on variable geometry turbine technology so that the technology can be successfully applied to various types of gas turbine engines as soon as possible. This paper summarizes and analyzes the recent advances in the field of aerodynamic, structural design and test of variable geometry turbines. This review covers the following topics that are important for variable geometry turbine designs: (1) flow mechanisms and aerodynamic characteristics, (2) wide-condition aerodynamic design method for turbine blades, (3) variable vane turning design method, (4) structural design technology of variable vane system and (5) aerodynamic characteristics and reliability test technology for variable geometry turbines. The emphasis is placed on the variable vane turning design method. We also present our own insights regarding the current research trends and the prospects for future developments.

scholarly journals Experimental and numerical investigations of tip clearance flow and loss in a variable geometry turbine cascade

2017 ◽  
Vol 232 (2) ◽  
pp. 157-169 ◽  
Author(s):  
Jie Gao ◽  
Weiliang Fu ◽  
Fukai Wang ◽  
Qun Zheng ◽  
Guoqiang Yue ◽  
...  
Keyword(s):  
Vortex Core ◽  
Three Dimensional ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Variable Geometry ◽  
Numerical Predictions ◽  
Rear Part ◽  
Clearance Flow ◽  
Variable Geometry Turbine ◽  
Vane Tip

Variable geometry turbines are widely employed to improve the off-design performance of gas turbine engines; however, there is a performance penalty associated with the vane-end partial gap required for the movement of variable vanes. This paper is a continuation of the previous work and aims to understand the leakage flow and loss mechanisms under the influence of the pivoting axis. Experimental investigations with a variable geometry turbine linear cascade have been conducted for tip gap heights of 1.1% and 2.2% blade spans as well as setting angles of −6°, 0°, and 6°, so as to reveal the three-dimensional clearance flow characteristics associated with partial gaps. Besides, numerical predictions are also carried out to better understand the experimental results. Pressure measurements were performed on the tip endwall as well as on the vane surface, and three-dimensional clearance flow fields downstream of the variable cascade were measured with a five-hole probe. The results show that as the vane setting angle is changed from design to closed, the vane loading increases and tends to be more aft-loaded, thus increasing the tip leakage loss, and vice versa. There are strong interactions between the flow around the pivoting axis and the leakage flow in the vane tip rear part, which leads to a low-pressure region on the tip endwall. The leakage vortex core is made up of the leakage flow in the vane tip rear part at both two tip gap heights, and the leakage vortex core formation process is different from the one in the rotor blade. The present results can provide useful references for the vane-end clearance design of variable geometry turbines.

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