Numerical Investigation on the Effect of Slot Leakage on a NGV With 2D Contoured Endwall: Adiabatic Effectiveness and Aerodynamic Loss

2017 ◽  
Author(s):  
Pingting Chen ◽  
Xueying Li ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Numerical Method ◽  
Main Flow ◽  
Secondary Flows ◽  
Leakage Flow ◽  
Experiment Data ◽  
Aerodynamic Loss ◽  
Pressure Loss Coefficient ◽  
Adiabatic Effectiveness ◽  
Total Pressure Loss Coefficient ◽  
Typical Design

Endwall 2D contouring is a typical design to reduce the strength of secondary flows within the passage. Such contouring can lead to significant changes in the passage flow. A leakage slot at the combustor-turbine interface is a typical turbine endwall design. The leakage flow can be used to cool the endwall and vane surface. Moreover, the leakage flow interacts with the main flow and results in the change of aerodynamic loss. A 3D numerical method was used to investigate endwall adiabatic effectiveness and passage total pressure loss coefficient (TPLC) on a NGV with 2D contoured endwall under a series of mass flow ratios (MFRs). The numerical method was validated by comparision with the experiment data. The results indicate that under the condition of this study, When MFR<0.625%, there is ingestion, and when 0.625%<MFR<1.0%, the TPLC is high. When 0.875%<MFR<1.0%, the area averaged adiabatic effectiveness (AAAE) decreases and the TPLC stays high as the MFR increases. When 1.0%<MFR<1.5%, the adiabatic effectiveness is high and the TPLC is low. To accomplish high adiabatic effectiveness, low aerodynamic loss and slight ingestion, the recommended range of MFR is 1.0%<MFR<1.5%.

Interaction of Shroud Leakage Flow and Main Flow in a Three-Stage LP Turbine

2003 ◽  
Vol 127 (4) ◽  
pp. 649-658 ◽  
Author(s):  
Jochen Gier ◽  
Bertram Stubert ◽  
Bernard Brouillet ◽  
Laurent de Vito
Keyword(s):  
Main Flow ◽  
Secondary Flows ◽  
Test Facility ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Jet Engines ◽  
Flow Interactions ◽  
Lp Turbine ◽  
The Impact ◽  
The Ideal

Endwall losses significantly contribute to the overall losses in modern turbomachinery, especially when aerodynamic airfoil load and pressure ratios are increased. In turbines with shrouded airfoils a large portion of these losses are generated by the leakage flow across the shroud clearance. Generally the related losses can be grouped into losses of the leakage flow itself and losses caused by the interaction with the main flow in subsequent airfoil rows. In order to reduce the impact of the leakage flow and shroud design related losses a thorough understanding of the leakage losses and especially of the losses connected to enhancing secondary flows and other main flow interactions has to be understood. Therefore, a three stage LP turbine typical for jet engines is being investigated. For the three-stage test turbine 3D Navier-Stokes computations are performed simulating the turbine including the entire shroud cavity geometry in comparison with computations in the ideal flow path. Numerical results compare favorably against measurements carried out at the high altitude test facility at Stuttgart University. The differences of the simulations with and without shroud cavities are analyzed for several points of operation and a very detailed quantitative loss breakdown is presented.

Different Effects of Cantilevered and Shrouded Stators on Axial Compressor Performance

2017 ◽  
Author(s):  
Xiayi Si ◽  
Jinfang Teng ◽  
Xiaoqing Qiang ◽  
Jinzhang Feng
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Loss Coefficient ◽  
Total Pressure Loss ◽  
Axial Position ◽  
Leakage Flow ◽  
Flow Angle ◽  
Design Point ◽  
Pressure Loss Coefficient ◽  
Total Pressure Loss Coefficient

Numerical simulations with the steady 3D RANS were performed on the rear stage of a modern high pressure compressor. The labyrinth seal cavity model of the shrouded stator was simplified according to the actual stator structure, which the seal cavity gap is 1% of blade height. Several typical configurations (shrouded stator, idealized stator and cantilevered stators) were designed and carried out, and cantilevered stators contained no gap, small gap (CS1%), design gap (CS2.5%) and large gap (CS4%/CS5%). The results indicate due to the effect of leakage flow from 1% span seal cavity gap, the total pressure loss of SS is larger than IS, while IS instead of SS in the process of the compressor design, the stall margin will be enlarged nearly 6% numerically. At the design point, when the hub gap is 3.5% span clearance CS has the same loss with IS, and when the hub gap is 4.5% span clearance CS has almost the same loss with SS. Among all operation range, the total pressure loss of S1 increases with the increase of the hub clearance. When the hub gap is 0 (CS0), there is no leakage flow and the loss is the least. At the design point, comparing with SS, the total pressure loss coefficient of CS0 decreases 18.34%, CS2.5% decreases 8.46% and IS decreases 6.45%. It means if the cantilevered stator with 2.5% span hub clearance were adopted in the HPC, the performance would be better than the shrouded stator. However, because of the matching condition, the rotor that follows after cantilevered stator should be redesigned according to blade loading and inlet flow angle changed. The performance of cantilevered stator is impacted of various hub clearance, the loss below 25% span increases significantly with hub clearance, the maximum value of outlet flow angle deviation is 2.3 degree. The stator hub peak loading is shifted upstream toward the leading edge when hub clearance size is increased. The total pressure loss coefficient and pressure coefficient at different axial position had the function relation. When the hub clearance increases, the position of double leakage flow start backwards, in the rear part of stator the secondary flow becomes stronger leading to more mixing loss and lower total pressure.

Effect of arbitrary blade tip design on tip leakage flow

2019 ◽  
Vol 234 (1) ◽  
pp. 19-30
Author(s):  
Jiahui Jin ◽  
Yanping Song ◽  
Jianyang Yu ◽  
Fu Chen
Keyword(s):  
Flow Rate ◽  
Total Pressure ◽  
Leakage Flow ◽  
Exit Section ◽  
Turbine Cascade ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Pressure Loss Coefficient ◽  
Blade Tip ◽  
Total Pressure Loss Coefficient

Tip geometry modification is frequently used to suppress the tip leakage flow in the turbine cascade however a universally beneficial tip geometry modification design has not been fully discovered. In this paper, the two-surface coupling arbitrary blade tip design method in three-dimensional physical space which satisfies the simple trigonometric function law is proposed and the mathematical parametric description is presented. The effects of different arbitrary blade tips on tip leakage flow have been studied numerically in a highly loaded axial turbine cascade. The aerodynamic performance of different tips is assessed by the tip leakage mass flow rate and the total pressure loss coefficient at the exit section. The Kriging model and genetic optimization algorithm are used to optimize the arbitrary blade tips to obtain the optimal arbitrary blade tip. Compared with the flat tip, the tip leakage mass flow rate is decreased by 10.57% and the area-average total pressure loss coefficient at the exit section is reduced by 8.91% in the optimal arbitrary blade tip.

Numerical Investigations on the Effect of Pivot Shapes in Part Clearance Flow Field of Variable Area LP Turbine Nozzle Vane

2020 ◽  
Author(s):  
Hardikkumar Bhavsar ◽  
Chetan S. Mistry
Keyword(s):  
Turbine Engines ◽  
Leakage Flow ◽  
Gas Turbine Engines ◽  
Power Demand ◽  
Pressure Loss Coefficient ◽  
Clearance Flow ◽  
Different Shapes ◽  
Lp Turbine ◽  
Total Pressure Loss Coefficient ◽  
Better Than

Abstract The performance of the gas turbine engines deteriorates under off-design conditions with the change of required power demand. The performance of the engine can be improved by actively controlling the mass flow rate through the engine turbine section using the variable area nozzle turbine (VANT). However, to implement VANT, vanes of the turbine nozzle need to be rotated, which demands part clearance to be provided near both the hub and tip region. In order to keep constant part clearance during vane turning, endwalls are modified to spherical shapes in such a way that distance between vane and upstream as well downstream rotor remains unaffected. Also, vanes are rotated about its pivot, which creates a blockage to the leakage flow in the part clearance. As pivot creates a blockage to the leakage flow, the shape of the pivot need to be selected in such a way that leakage losses can be reduced effectively. Hence, to analyze the effect of different pivot shapes on leakage losses, two different shapes of the pivot i.e., circular and elliptic, are explored in the present study. Also, three vane turning angles are analyzed to observe the effectiveness of these pivot shapes. The effect of the pivot is analyzed by entropy contours and total pressure loss coefficient in the exit plane, and it is found that the elliptic pivot performs better than a circular pivot as an elliptic pivot provides more blockage to the leakage flow and hence minimizing the overall losses.

Aerodynamic Loss for a Turbine Blade With Endwall Leakage Features and Contouring

2013 ◽  
Author(s):  
Stephen P. Lynch ◽  
Karen A. Thole ◽  
Atul Kohli ◽  
Christopher Lehane ◽  
Tom Praisner
Keyword(s):  
Turbine Blade ◽  
Aerodynamic Performance ◽  
Secondary Flows ◽  
Leakage Flow ◽  
Aerodynamic Loss ◽  
Endwall Contouring

Secondary flows near the endwall of a turbine blade contribute to a loss in aerodynamic performance in the engine. Further reductions in performance occur when the secondary flows interact with leakage flow from necessary clearance features, such as the clearance gap between the blade rotor and an upstream stator or gaps between adjacent blade platforms. Non-axisymmetric endwall contouring has been shown to reduce the strength of secondary flows near the endwall, but relatively little research has been done to test the sensitivity of the contouring to the endwall leakage features. This paper describes aerodynamic measurements taken downstream of a cascade with representative leakage features. In general, upstream leakage flow with swirl relative to the blade increased aerodynamic loss, relative to leakage that was matched to the blade wheelspeed. Non-axisymmetric contouring for an endwall without a platform gap reduced underturning of the flow but had no effect on overall loss, relative to a flat endwall without a gap. A contoured endwall with a platform gap had 12% higher mixed-out loss than a contoured endwall without a gap.

scholarly journals Effect of Incidence on Secondary Flows in a Linear Turbine Cascade

1994 ◽  
Author(s):  
G. V. Ramana Murty ◽  
N. Venkatrayulu
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Leading Edge ◽  
Loss Coefficient ◽  
Secondary Flows ◽  
Total Pressure Loss ◽  
Turbine Cascade ◽  
Local Loss ◽  
Pressure Loss Coefficient ◽  
Total Pressure Loss Coefficient

The effect of incidence on the generation and growth of secondary flows in a linear turbine cascade was studied in the present investigations using a Variable Density Cascade Tunnel at an exit Mach number of 0.43 and a Reynolds number of 8 × 105. The angles of incidence chosen were +15°, +50, 0°, −5° and −8.5°. The flow field was surveyed at five axial stations from cascade inlet to exit with a view to understanding the development of the secondary flow with the help of the variation of mass averaged total pressure loss coefficient and the contours of local loss coefficients in the pitch and spanwise directions. The total pressure loss coefficient and the net secondary loss coefficient have shown a steady growth along the cascade upto about 74 of the axial chord from the leading edge and thereafter rose very rapidly. The incidence is found to have an effect on the passage vortex and the loss cores due to the inlet boundary layer.

Interaction of Shroud Leakage Flow and Main Flow in a Three-Stage LP Turbine

2003 ◽  
Author(s):  
Jochen Gier ◽  
Bertram Stubert ◽  
Bernard Brouillet ◽  
Laurent de Vito
Keyword(s):  
Main Flow ◽  
Secondary Flows ◽  
Test Facility ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Jet Engines ◽  
Flow Interactions ◽  
Lp Turbine ◽  
The Impact ◽  
The Ideal

Endwall losses significantly contribute to the overall losses in modern turbomachinery, especially when aerodynamic airfoil load and pressure ratios are increased. In turbines with shrouded airfoils a large portion of these losses are generated by the leakage flow across the shroud clearance. Generally the related losses can be grouped into losses of the leakage flow itself and losses caused by the interaction with the main flow in subsequent airfoil rows. In order to reduce the impact of the leakage flow and shroud design related losses a thorough understanding of the leakage losses and especially of the losses connected to enhancing secondary flows and other main flow interactions has to be understood. Therefore, a three stage LP turbine typical for jet engines is being investigated. For the three-stage test turbine 3D Navier-Stokes computations are performed simulating the turbine including the entire shroud cavity geometry in comparison with computations in the ideal flow path. Numerical results compare favourably against measurements carried out at the high altitude test facility at Stuttgart University. The differences of the simulations with and without shroud cavities are analysed for several points of operation and a very detailed quantitative loss breakdown is presented.

Investigation on the Aerodynamic Performance of the Compressor Cascade Using Blended Blade and End Wall

2018 ◽  
Vol 0 (0) ◽  
Author(s):  
Weilin Yi ◽  
Jiabin Li ◽  
Lucheng Ji
Keyword(s):  
Flow Field ◽  
Incidence Angle ◽  
Compressor Cascade ◽  
Experiment Data ◽  
Corner Separation ◽  
Pressure Loss Coefficient ◽  
Numerical Studies ◽  
Sst Turbulence Model ◽  
End Wall ◽  
Total Pressure Loss Coefficient

Abstract Corner separation limits the increase of the aerodynamic loading in the compressor. Previous numerical studies indicate that the Blended Blade and End Wall (BBEW) technology is useful in delaying, or reducing, or even eliminating the corner separation. This paper presents combined experimental and numerical investigations on a BBEW cascade and its prototype. The experimental results show that the design of Blended Blade and End Wall (BBEW) can improve the performance of the cascade when the incidence angle was positive or at the design point, and the total pressure loss coefficient was reduced by 7 %-8 %. The performance improvement mainly located from 10 %-25 % span heights. Compared with the experiment data, the SST turbulence model shows the best results of the flow field. Based on the numerical results, the details of the flow field and the effect of the Blended Blade and End Wall (BBEW) design on the corner separation are discussed and analyzed.

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