Effects of Circumferential Nonuniform Tip Clearance on Flow Field and Performance of a Transonic Turbine

2021 ◽  
Author(s):  
Yun Zheng ◽  
Xiubo Jin ◽  
Hui Yang ◽  
Qingzhe Gao ◽  
Kang Xu
Keyword(s):  
Flow Field ◽  
Tip Clearance ◽  
Transonic Turbine ◽  
And Performance

Effects of Circumferential Nonuniform Tip Clearance on Flow Field and Performance of a Transonic Turbine

2020 ◽  
Author(s):  
Yun Zheng ◽  
Xiubo Jin ◽  
Hui Yang ◽  
Qingzhe Gao ◽  
Kang Xu
Keyword(s):  
Flow Field ◽  
Numerical Study ◽  
Circumferential Direction ◽  
Tip Clearance ◽  
Computational Domain ◽  
Aerodynamic Efficiency ◽  
Aerodynamic Loss ◽  
The Difference ◽  
And Performance ◽  
Downstream Flow

Abstract The numerical study is performed by means of an in-house CFD code to investigate the effect of circumferential nonuniform tip clearance due to the casing ovalization on flow field and performance of a turbine stage. A method called fast-moving mesh is used to synchronize the non-circular computational domain with the rotation of the rotor row. Four different layouts of the circumferential nonuniform clearance are calculated and evaluated in this paper. The results show that, the circumferential nonuniform clearance could reduce the aerodynamic performance of the turbine. When the circumferential nonuniformity δ reaches 0.4, the aerodynamic efficiency decreases by 0.58 percentage points. Through the analysis of the flow field, it is found that the casing ovalization leads to the difference of the size of the tip clearance in the circumferential direction, and the aerodynamic loss of the position of large tip clearance is greater than that of small tip clearance, which is related to the scale of leakage vortex. In addition, the flow field will become nonuniform in the circumferential direction, especially at the rotor exit, which will adversely affect the downstream flow field.

Fluid Dynamics and Performance of Partially and Fully Shrouded Axial Turbines

2004 ◽  
Author(s):  
L. Porreca ◽  
T. Behr ◽  
J. Schlienger ◽  
A. I. Kalfas ◽  
R. S. Abhari ◽  
...  
Keyword(s):  
Flow Field ◽  
Detailed Comparison ◽  
Labyrinth Seal ◽  
Tip Clearance ◽  
Field Analysis ◽  
Test Cases ◽  
Flow Measurements ◽  
And Performance ◽  
Partial Shroud ◽  
Stage Efficiency

A unique comparative experimental and numerical investigation carried out on two test cases with shroud configurations differing only in the labyrinth seal path, is presented in this paper. The blade geometry and tip clearance is identical in the two test cases. The geometries under investigation are representative of an axial turbine with a full and partial shroud, respectively. Global performance and flow field data were acquired and analyzed. Computational simulations were carried out to complement the investigation and to facilitate the analysis of the steady and unsteady flow measurements. A detailed comparison between the two test cases is presented in terms of flow field analysis and performance evaluation. The analysis focuses on the flow effects reflected on the overall performance in a multi-stage environment. Strong interaction between the cavity flow and the blade tip region of the rotor blades is observed up to the blade mid span. A marked effect of this interaction can be seen in the downstream second stator where different vortex structures are observed. Moreover, in the partial shroud test case, a strong tip leakage vortex is developed from the first rotor and transported through the downstream blade row. A measurable change in the second stage efficiency was observed between the two test cases. In low aspect ratio blades within a multistage environment, small changes in the cavity geometry can have a significant effect on the mainstream flow. The present analysis has shown that an integrated and matched blade-shroud aerodynamic design has to be adopted to reach optimal performances. The additional losses resulting from small variations of the sealing geometry could result in a gain of up to one point in the overall stage efficiency.

Fluid Dynamics and Performance of Partially and Fully Shrouded Axial Turbines

2004 ◽  
Vol 127 (4) ◽  
pp. 668-678 ◽  
Author(s):  
L. Porreca ◽  
T. Behr ◽  
J. Schlienger ◽  
A. I. Kalfas ◽  
R. S. Abhari ◽  
...  
Keyword(s):  
Flow Field ◽  
Detailed Comparison ◽  
Tip Clearance ◽  
Field Analysis ◽  
Test Cases ◽  
Flow Measurements ◽  
Multi Stage ◽  
And Performance ◽  
Partial Shroud ◽  
Stage Efficiency

A unique comparative experimental and numerical investigation carried out on two test cases with shroud configurations, differing only in the labyrinth seal path, is presented in this paper. The blade geometry and tip clearance are identical in the two test cases. The geometries under investigation are representative of an axial turbine with a full and partial shroud, respectively. Global performance and flow field data were acquired and analyzed. Computational simulations were carried out to complement the investigation and to facilitate the analysis of the steady and unsteady flow measurements. A detailed comparison between the two test cases is presented in terms of flow field analysis and performance evaluation. The analysis focuses on the flow effects reflected on the overall performance in a multi-stage environment. Strong interaction between the cavity flow and the blade tip region of the rotor blades is observed up to the blade midspan. A marked effect of this interaction can be seen in the downstream second stator where different vortex structures are observed. Moreover, in the partial shroud test case, a strong tip leakage vortex is developed from the first rotor and transported through the downstream blade row. A measurable change in the second stage efficiency was observed between the two test cases. In low aspect ratio blades within a multi-stage environment, small changes in the cavity geometry can have a significant effect on the mainstream flow. The present analysis has shown that an integrated and matched blade-shroud aerodynamic design has to be adopted to reach optimal performances. The additional losses resulting from small variations of the sealing geometry could result in a gain of up to one point in the overall stage efficiency.

The Use of 3D Viscous Flow Calculations in the Design and Analysis of Industrial Centrifugal Compressors

1992 ◽  
Vol 114 (1) ◽  
pp. 27-37 ◽  
Author(s):  
M. V. Casey ◽  
P. Dalbert ◽  
P. Roth
Keyword(s):  
Flow Field ◽  
Surface Flow ◽  
Secondary Flows ◽  
Tip Clearance ◽  
Centrifugal Impeller ◽  
Suction Surface ◽  
Meridional Velocity ◽  
Thin Region ◽  
And Performance ◽  
Operating Points

The 3D viscous codes of Denton and Dawes have been used to predict the flow field and performance of a back-swept industrial centrifugal impeller without an inducer (the Eckardt impeller “B”). The calculated flow field and performance agree very well with measurements at several operating points from surge to choke. Both codes predict that the suction surface flow near the impeller inlet is on the verge of separation at the design point. Calculations with tip clearance using the Dawes code predict a thin region of backflow in the clearance jet near the casing wall. The secondary flows arising from the meridional curvature in the impeller redistribute the losses generated on the blades and give rise to a spanwise stratification of the circumferentially mass-averaged losses. The resulting spanwise entropy gradient can be included in a throughflow calculation to improve the prediction of the meridional velocity distribution at impeller exit.

Experimental Investigation Into the Effects of the Steady Wake-Tip Clearance Vortex Interaction in a Compressor Cascade

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Andreas Krug ◽  
Peter Busse ◽  
Konrad Vogeler
Keyword(s):  
Flow Field ◽  
Experimental Studies ◽  
Axial Compressor ◽  
Field Measurements ◽  
Tip Clearance ◽  
Compressor Cascade ◽  
Unsteady Interaction ◽  
Linear Compressor Cascade ◽  
Tip Clearance Vortex ◽  
The Impact

An important aspect of the aerodynamic flow field in the tip region of axial compressor rotors is the unsteady interaction between the tip clearance vortex (TCV) and the incoming stator wakes. In order to gain an improved understanding of the mechanics involved, systematic studies need to be performed. As a first step toward the characterization of the dynamic effects caused by the relative movement of the blade rows, the impact of a stationary wake-induced inlet disturbance on a linear compressor cascade with tip clearance will be analyzed. The wakes were generated by a fixed grid of cylindrical bars with variable pitch being placed at discrete pitchwise positions. This paper focuses on experimental studies conducted at the newly designed low-speed cascade wind tunnel in Dresden. The general tunnel configuration and details on the specific cascade setup will be presented. Steady state flow field measurements were carried out using five-hole probe traverses up- and downstream of the cascade and accompanied by static wall pressure readings. 2D-particle image velocimetry (PIV) measurements complemented these results by visualizing the blade-to-blade flow field. Hence, the structure of the evolving secondary flow system is evaluated and compared for all tested configurations.

Evaluating the Influence of Rotor-Casing Eccentricity on Turbine Efficiency Including Time-Resolved Flow Field Measurements

2021 ◽  
pp. 1-33
Author(s):  
Eric DeShong ◽  
Shawn Siroka ◽  
Reid A. Berdanier ◽  
Karen A. Thole
Keyword(s):  
Flow Field ◽  
Magnetic Levitation ◽  
Field Measurements ◽  
Tip Clearance ◽  
Time Resolved ◽  
Flow Angle ◽  
Turbine Efficiency ◽  
Eccentric Rotor ◽  
Blade Tip ◽  
Manufacturing Techniques

Abstract The clearance that exists between the casing and turbine blade tips is one of the key drivers of efficiency in gas turbine engines. For this reason, engine manufacturers utilize precise manufacturing techniques and may employ clearance control systems to minimize tip clearances to reduce associated losses. Despite these efforts, turbines typically exhibit some nominal casing ovality or rotor-casing eccentricity, and changes to blade tip clearance during operation commonly occur due to thermal and mechanical stresses. The present study investigates non-axisymmetric tip clearance effects by creating a rotor-casing eccentricity in a one-stage axial test turbine operating in a continuous-duration mode at engine relevant conditions with engine representative hardware. A magnetic levitation bearing system was leveraged to move the turbine shaft to vary the rotor-casing eccentricity without test section disassembly. The results of this study indicate that rotor-casing eccentricity does not affect overall turbine efficiency over the range that was tested, but does locally influence efficiency and the rotor exit flow field. Comparisons of flow angle and secondary flow kinetic energy agreed with previous studies and existing analytical methods, respectively. Collectively, these results indicate that tip clearance can be studied locally on an eccentric rotor.

Compliant Plate Seals: Design and Performance Simulations

2012 ◽  
Author(s):  
Hrishikesh V. Deo ◽  
Ajay Rao ◽  
Hemant Gedam
Keyword(s):  
Gas Turbines ◽  
Tip Clearance ◽  
Outer Diameter ◽  
Aircraft Engines ◽  
Steam Turbines ◽  
Flow Rates ◽  
Cfd Models ◽  
Low Leakage ◽  
And Performance ◽  
Large Rotor

Compliant Plate Seals are being developed for various turbomachinery sealing applications including gas turbines, steam turbines, aircraft engines and oil & gas compressors. These seals consist of compliant plates attached to a stator in a circumferential fashion around a rotor. The compliant plates have a slot that extends radially inwards from the seal outer diameter, and an intermediate plate extends inwards into this slot from stator. This design is capable of providing passive hydrostatic feedback forces acting on the compliant plates that balance at a small tip–clearance. Due to this self–correcting behavior, this seal is capable of providing high differential pressure capability and low leakage within a limited axial span, and non–contact operation even in the presence of large rotor transients. CFD models have been developed to predict the leakage flow rates and hydrostatic lift and blowdown forces, and a design philosophy is proposed to predict the feedback phenomenon from the CFD results.

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