Three Dimensional Aerodynamic Optimization for an Ultra-Low Aspect Ratio Transonic Turbine Stator Blade

2005 ◽  
Author(s):  
Martina Hasenja¨ger ◽  
Bernhard Sendhoff ◽  
Toyotaka Sonoda ◽  
Toshiyuki Arima
Keyword(s):  
Aspect Ratio ◽  
Static Pressure ◽  
Multi Objective Optimization ◽  
Aerodynamic Loss ◽  
Low Aspect Ratio ◽  
Turbine Stator ◽  
Static Pressure Distribution ◽  
Stator Blade ◽  
Transonic Turbine ◽  
Single Objective

A modern numerical stochastic optimization method, namely the evolution strategy (ES), was applied to an ultra-low aspect ratio transonic turbine stator blade in order to seek a new aerodynamic design concept for lower secondary flow losses. The low stator blade count is selected to avoid the direct viscous interaction of the stator wake with the downstream rotor blade. This led to the ultra-low aspect ratio stator blade. In the optimization, two kinds of objective functions were used, that is, (1) minimization of the “aerodynamic loss” (a single objective), (2) minimization of the “aerodynamic loss” and of the “variation of circumferential static pressure distribution” downstream of the stator blade (multi-objective optimization). In the case of the single objective, the aerodynamic loss is improved by an extreme aft-loaded airfoil with a noticeable bent part near the trailing edge, although the circumferential static distribution is slightly worse than that of the baseline. In the case of the multi-objective optimization, we observe a trade-off relation between aerodynamic loss and variation of static pressure distribution which is not easily resolved. A new design concept to achieve lower aerodynamic loss for ultra-low aspect ratio transonic turbine stator blades is discussed.

The Effect of a Downstream Rotor on the Measured Performance of a Transonic Turbine Nozzle

1986 ◽  
Vol 108 (2) ◽  
pp. 269-274
Author(s):  
R. G. Williamson ◽  
S. H. Moustapha ◽  
J. P. Huot
Keyword(s):  
Performance Evaluation ◽  
Aspect Ratio ◽  
Flow Field ◽  
Large Scale ◽  
Outer Wall ◽  
Nozzle Flow ◽  
Turning Angle ◽  
Low Aspect Ratio ◽  
Transonic Turbine ◽  
Mach Numbers

Two nozzle designs, involving the same low aspect ratio, high turning angle vanes, and differing in outer wall contour, were tested over a range of exit Mach numbers up to supersonic values. The experiments were conducted on a large-scale, full annular configuration with and without a representative rotor downstream. Nozzle performance was found to be significantly affected by rotor operation, the influence depending on the detailed characteristics of the nozzle flow field, as well as on the design and operation of the rotor itself. It is suggested that performance evaluation of low aspect ratio nozzles of high turning angle may require appropriate testing with a rotor.

Analysis of the Mixing Plane Interface Between Stator and Rotor of a Transonic Axial Turbine Stage

2000 ◽  
Author(s):  
P. Giangiacomo ◽  
V. Michelassi ◽  
F. Martelli
Keyword(s):  
Mass Flow ◽  
Static Pressure ◽  
Three Dimensional ◽  
Turbine Stage ◽  
Flow Rates ◽  
Tip Leakage ◽  
Mass Flow Rates ◽  
Stator Blade ◽  
Transonic Turbine ◽  
Rotor Mass

A three-dimensional transonic turbine stage is computed by means of a numerical simulation tool. The simulation accounts for the coolant ejection from the stator blade and for the tip leakage of the rotor blade. The stator and rotor rows interact via a mixing plane, which allows the stage to be computed in a steady manner. The analysis is focused on the matching of the stator and rotor mass flow rates. The computations proved that the mixing plane approach allows the stator and rotor mass flow rates to be balanced with a careful choice of the stator-rotor static pressure interface. At the same time, the pitch averaged distribution of the transported quantities at the interface for the stator and rotor may differ slightly, together with the value of the static pressure at the hub.

scholarly journals Stall Inception in a High-Speed Low Aspect Ratio Fan Including the Effects of Casing Treatments

1994 ◽  
Author(s):  
S. E. Gorrell ◽  
P. M. Russler
Keyword(s):  
Aspect Ratio ◽  
High Speed ◽  
Static Pressure ◽  
Pressure Ratio ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Stall Inception ◽  
Casing Treatment ◽  
Low Aspect Ratio ◽  
Casing Treatments

The stall inception process in high-speed compressor components is important to understand in order to increase stage loading while maintaining stall margin. This paper presents the results of an in depth experimental investigation on the stall inception of a two stage, high-speed, low aspect ratio fan that is representative of current operational commercial and military fan technology. High-response static pressure measurements are presented which detail the stall inception process of the fan under various operating conditions. These conditions include: varied corrected speeds, a smooth case, a circumferential groove casing treatment, and a recirculating cavity casing treatment. Stage pressure characteristics and radial pressure ratio profiles are presented for the different operating conditions. The stage performance data, together with the static pressure data, are analyzed to provide a clear and thorough understanding of the stall inception process and how the process may vary under different conditions. Experimental results show that a stage may stall on the positive, neutral, or negative sloped part of the pressure characteristic. The three casing treatments had a significant effect on the rotor tip flow and these variations changed the stall inception path of the fan. Stall inception was characterized by the formation of a stall inception cell which grew to fully developed rotating stall. Properties affected by the changing tip flow include the stall inception duration, stall inception cell frequency, existence of modal waves, duration of modal waves, and modal wave frequency. In some instances modal waves appear to play a role in stall inception, in others they do not.

scholarly journals Transonic Probe Blockage Effects in a Calibration Wind–Tunnel and Stator Blade Passage

1996 ◽  
Author(s):  
Frank Truckenmüller ◽  
Martin Renner ◽  
Heinz Stetter ◽  
Hans–Georg Hosenfeld
Keyword(s):  
Wind Tunnel ◽  
Static Pressure ◽  
Guide Vane ◽  
Calibration Procedure ◽  
Wind Tunnels ◽  
Pressure Probe ◽  
Blade Passage ◽  
Stator Blade ◽  
Flow Through ◽  
Transonic Turbine

Probe blockage effects are presented for transonic flow through a calibration wind–tunnel as well as through a guide vane row in a three–stage model turbine. Accurate experimental data from measurements in a transonic turbine are needed for the verification of CFD results. The accuracy of etatic pressure measurements in transonic turbine stages is severely affected by the pressure probe stem disturbing the surrounding flow–field. These disturbance effects are present during calibration procedures in wind–tunnels, as well as during measurements in–between turbomachinery blade rows. Therefore, the phenomenon associated with this blockage effect must be investigated for both procedures. The influence of the blockage ratios on the static pressure readings of the four–hole wedge probe during the calibration procedure is investigated for two different wind–tunnels. The aim is to measure the blockage effects on the blade passage flow which are produced by a pneumatic pressure probe immersed in the flow between two adjacent blade rows. In order to measure these effects, two stator blades are instrumented with static pressure taps along the blade chord, as well as along the blade span. During the investigations, the radial and circumferential positions of the probes relative to the blade channel are varied. Pressure probe readings of two four–hole wedge probes with different stem diameters are compared as well as correlated to the static pressure readings of the stator blade pressure taps. The apparent deviations of the different readings are discussed.

Unsteady Analysis of Inter-Rows Stator-Rotor Spacing Effects on a Transonic, Low-Aspect Ratio Turbine

2015 ◽  
Author(s):  
Etienne Tang ◽  
Gilles Leroy ◽  
Mickaël Philit ◽  
Jacques Demolis
Keyword(s):  
Experimental Data ◽  
Aspect Ratio ◽  
High Pressure Turbine ◽  
Low Aspect Ratio ◽  
Spacing Effects ◽  
Air Turbine ◽  
Flow Features ◽  
Aerodynamic Performances ◽  
Flow Through ◽  
Transonic Turbine

The aerodynamic performances of an axial turbine are affected by the distance between the stator and the rotor. Previous studies have shown different trends, depending mainly on whether the turbine is subsonic or not. The present paper aims at improving the understanding of the effect of rows spacing on the flow through a transonic turbine. A one-stage, low aspect ratio, high pressure turbine case is investigated using CFD. Steady and unsteady phase-lagged RANS computations are performed on this configuration with different inter-blade rows distances. The results are successfully compared with experimental data from a cold air turbine rig. Entropy production balances are used to emphasize the main loss areas and the loss variations caused by changes in inter-blade rows distance. Two techniques are compared for computing these balances, and one of them appears to perform much better. The flow features causing these losses are then identified. Finally, an optimal inter-rows spacing is found. It is a compromise between the losses created by strong stator-rotor interactions at small inter-rows gaps and the losses generated at the endwalls in the inter-rows space at large distances.

Effect of Clocking on the Second Stator Pressure Field of a One and a Half Stage Transonic Turbine

2004 ◽  
Author(s):  
J. Gadea ◽  
R. De´nos ◽  
G. Paniagua ◽  
N. Billiard ◽  
C. H. Sieverding
Keyword(s):  
Pressure Distribution ◽  
Static Pressure ◽  
Pressure Field ◽  
Pressure Fluctuations ◽  
Leading Edge ◽  
Fast Response ◽  
Time Resolved ◽  
Pressure Transducers ◽  
Static Pressure Distribution ◽  
Transonic Turbine

This paper focuses on the experimental investigation of the time-averaged and time-resolved pressure field of a second stator tested in a one and a half stage high-pressure transonic turbine. The effect of clocking and its influence on the aerodynamic and mechanical behaviour are investigated. The test program includes four different clocking positions, i.e. relative pitch-wise positions between the first and the second stator. Pneumatic probes located upstream and downstream of the second stator provide the time-averaged component of the pressure field. For the second stator airfoil, both time-averaged and time-resolved surface static pressure fields are measured at 15, 50 and 85% span with fast response pressure transducers. Regarding the time-averaged results, the effect of clocking is mostly observed in the leading edge region of the second stator, the largest effects being observed at 15% span. The surface static pressure distribution is changed locally, which is likely to affect the overall performance of the airfoil. The phase-locked averaging technique allows to process the time-resolved component of the data. The pressure fluctuations are attributed to the passage of pressure gradients linked to the traversing of the upstream rotor. The pattern of these fluctuations changes noticeably as a function of clocking. Finally, the time-resolved pressure distribution is integrated along the second stator surface to determine the unsteady forces applied on the vane. The magnitude of the unsteady force is very dependent on the clocking position.

Effect of End Wall Contouring on Performance of Ultra-Low Aspect Ratio Transonic Turbine Inlet Guide Vanes

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Toyotaka Sonoda ◽  
Martina Hasenjäger ◽  
Toshiyuki Arima ◽  
Bernhard Sendhoff
Keyword(s):  
Aspect Ratio ◽  
Secondary Flow ◽  
Three Dimensional ◽  
Design Concept ◽  
Guide Vanes ◽  
Low Aspect Ratio ◽  
Inlet Guide Vanes ◽  
Turbine Inlet ◽  
Transonic Turbine ◽  
End Wall

In our previous work on ultralow-aspect ratio transonic turbine inlet guide vanes (IGVs) for a small turbofan engine (Hasenjäger et al., 2005, “Three Dimensional Aerodynamic Optimization for an Ultra-Low Aspect Ratio Transonic Turbine Stator Blade,” ASME Paper No. GT2005-68680), we used numerical stochastic design optimization to propose the new design concept of an extremely aft-loaded airfoil to improve the difficult-to-control aerodynamic loss. At the same time, it is well known that end wall contouring is an effective method for reducing the secondary flow loss. In the literature, both “axisymmetric” and “nonaxisymmetric” end wall geometries have been suggested. Almost all of these geometric variations have been based on the expertise of the turbine designer. In our current work, we employed a stochastic optimization method—the evolution strategy—to optimize and analyze the effect of the axisymmetric end wall contouring on the IGV’s performance. In the optimization, the design of the end wall contour was divided into three different approaches: (1) only hub contour, (2) only tip contour, and (3) hub and tip contour, together with the possibility to observe the correlation between hub/tip changes with regard to their joint influence on the pressure loss. Furthermore, three-dimensional flow mechanisms, related to a secondary flow near the end wall region in the low-aspect ratio transonic turbine IGV, was investigated, based on the above optimization results. A design concept and secondary flow characteristics for the low-aspect ratio full annular transonic turbine IGV is discussed in this paper.

Blade Lean and Shroud Leakage Flows in Low Aspect Ratio Turbines

2008 ◽  
Author(s):  
Budimir Rosic ◽  
Liping Xu
Keyword(s):  
Aspect Ratio ◽  
Numerical Study ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Leakage Flow ◽  
Industrial Practice ◽  
Leakage Flows ◽  
Low Aspect Ratio ◽  
Stator Blade ◽  
Different Levels

Blade lean, i.e. non-radial blade stacking, has been intensively used over the past in the design process of low aspect ratio gas and steam turbines. Although its influence on turbine efficiency is not completely understood, it has been proved as an effective way of controlling blade loading and secondary flows on blade passage endwalls. Three-dimensional blade designs in modern industrial practice are usually carried out using clean endwalls. The influence of the leakage flows on three-dimensional blade design is traditionally neglected. This paper presents an experimental study where two different stator blades, with different levels of compound lean, were tested in a low speed three-stage model turbine with the shroud leakage flow geometry representative of industrial practice. The experimental measurements were compared with numerical tests, conducted on the same blade geometries. The influence of the compound lean on the stator flow field was analysed in detail. In order to analyse the combined effects of both the stator hub and rotor shroud leakage flow on the blade lean, in the second part of the paper a numerical study on a two stage turbine with both leakage flow paths representative of a real turbine was carried out. Performance of three different stator blade designs (two different levels of compound lean and a straight blade) was investigated. The aim of this study is to understand the mechanism and the consequence of the stator blade lean on stage performance in an environment with leakage flows and associated cavities.

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