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.

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.

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.

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.

A Variable-Geometry Power Turbine for Marine Gas Turbines

1989 ◽  
Author(s):  
Karl W. Karstensen ◽  
Jesse O. Wiggins
Keyword(s):  
Fuel Consumption ◽  
Gas Turbines ◽  
Part Load ◽  
Surface Ship ◽  
Marine Propulsion ◽  
Medium Speed ◽  
Power Turbine ◽  
Wide Range ◽  
Electrical Generator ◽  
Variable Power

Gas turbines have been accepted in naval surface ship applications, and considerable effort has been made to improve their fuel consumption, particularly at part-load operation. This is an important parameter for shipboard engines because both propulsion and electrical-generator engines spend most of their lives operating at off-design power. An effective way to improve part-load efficiency of recuperated gas turbines is by using a variable power turbine nozzle. This paper discusses the successful use of variable power turbine nozzles in several applications in a family of engines developed for vehicular, industrial, and marine use. These engines incorporate a variable power turbine nozzle and primary surface recuperator to yield specific fuel consumption that rivals that of medium speed diesels. The paper concentrates on the experience with the variable nozzle, tracing its derivation from an existing fixed vane nozzle and its use across a wide range of engine sizes and applications. Emphasis is placed on its potential in marine propulsion and auxiliary gas turbines.

Production and Development of Secondary Flows and Losses in Two Types of Straight Turbine Cascades: Part 1—A Stator Case

1987 ◽  
Vol 109 (2) ◽  
pp. 186-193 ◽  
Author(s):  
A. Yamamoto
Keyword(s):  
Secondary Flow ◽  
Total Pressure ◽  
Experimental Information ◽  
Secondary Flows ◽  
Accumulation Process ◽  
Flow Angle ◽  
Turning Angle ◽  
Pressure Losses ◽  
Flow Vectors ◽  
Turbine Cascades

The present study intends to give some experimental information on secondary flows and on the associated total pressure losses occurring within turbine cascades. Part 1 of the paper describes the mechanism of production and development of the loss caused by secondary flows in a straight stator cascade with a turning angle of about 65 deg. A full representation of superimposed secondary flow vectors and loss contours is given at fourteen serial traverse planes located throughout the cascade. The presentation shows the mechanism clearly. Distributions of static pressures and of the loss on various planes close to blade surfaces and close to an endwall surface are given to show the loss accumulation process over the surfaces of the cascade passage. Variation of mass-averaged flow angle, velocity and loss through the cascade, and evolution of overall loss from upstream to downstream of the cascade are also given. Part 2 of the paper describes the mechanism in a straight rotor cascade with a turning angle of about 102 deg.

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.

Oxy-Fuel Turbine Through-Flow Design

2014 ◽  
Author(s):  
Majed Sammak ◽  
Srikanth Deshpande ◽  
Magnus Genrup
Keyword(s):  
Mach Number ◽  
Total Pressure ◽  
Tangential Velocity ◽  
Flow Angle ◽  
Power Turbine ◽  
Through Flow ◽  
The Mean ◽  
Line Design ◽  
Reaction Degree ◽  
Relative Flow

The objective of the paper is to present the through-flow design of a twin-shaft oxy-fuel turbine. The through-flow design is the subsequent step after the turbine mean-line design. The through-flow phase analyses the flow in both axial and radial directions, where the flow is computed from hub to tip and along streamlines. The parameterization of the through-flow is based on the mean-line results, so principal features such as blade angles at the mean-line into the through-flow phase should be retained. Parameters such as total inlet pressure and temperature, mass flow, rotation speed and turbine geometries are required for the through-flow modelling. The through-flow study was performed using commercial software — AxCent(™) from Concepts NREC. The rotation speed of the twin-shaft power turbine was set to 7200 rpm, while the power turbine was set to 4800 rpm. The mean-line design determined that the twin-shaft turbine should be designed with two compressor turbine stages and three power turbine stages. The through-flow objective was to study the variations in the thermodynamic parameters along the blade. The power turbine last-stage design was studied because of the importance of determining exit Mach number distribution of the rotor tip. The last stage was designed with damped forced condition. The term ‘damped’ is used because the opening from the tip to the hub is limited to a certain value rather than maintaining the full concept of forced vortex. The study showed the parameter distribution of relative Mach number, total pressure and temperature, relative flow angle and tangential velocity. Through-flow results at 50% span and mean-line results showed reasonable agreement between static pressure, total pressure, reaction degree and total efficiency. Other parameters such as total temperature and relative Mach number showed some difference which can be attributed to working fluid in AxCent being pure CO2. The relative tip Mach number at rotor exit was 1.03, which is lower than the maximum typically allowed value of 1.2. The total pressure distribution was smooth from hub to tip which minimizes the spanwise gradient of total pressure and thus reduces the strength of secondary vortices. The reaction degree distribution was presented in the paper and no problems were revealed in the reaction degree at the hub. Rotor blades were designed to produce a smooth exit relative flow angle distribution. The relative flow angle varied by approximately 5° from hub to tip. The tangential velocity distribution was proportional to blade radius, which coincided with forced vortex design. Through-flow design showed that the mean-line design of a twin-shaft oxy-fuel turbine was suitable.

A Variable-Geometry Power Turbine for Marine Gas Turbines

1990 ◽  
Vol 112 (2) ◽  
pp. 165-174 ◽  
Author(s):  
K. W. Karstensen ◽  
J. O. Wiggins
Keyword(s):  
Fuel Consumption ◽  
Gas Turbines ◽  
Part Load ◽  
Surface Ship ◽  
Marine Propulsion ◽  
Medium Speed ◽  
Power Turbine ◽  
Wide Range ◽  
Electrical Generator ◽  
Variable Power

Gas turbines have been accepted in naval surface ship applications, and considerable effort has been made to improve their fuel consumption, particularly at part-load operation. This is an important parameter for shipboard engines because both propulsion and electrical-generator engines spend most of their lives operating at off-design power. An effective way to improve part-load efficiency of recuperated gas turbines is by using a variable power turbine nozzle. This paper discusses the successful use of variable power turbine nozzles in several applications in a family of engines developed for vehicular, industrial, and marine use. These engines incorporate a variable power turbine nozzle and primary surface recuperator to yield specific fuel consumption that rivals that of medium speed diesels. The paper concentrates on the experience with the variable nozzle, tracing its derivation from an existing fixed vane nozzle and its use across a wide range of engine sizes and applications. Emphasis is placed on its potential in marine propulsion and auxiliary gas turbines.

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