Investigation of Tip Clearance Modeling Techniques for a Transonic Compressor Rotor

2009 ◽  
Author(s):  
Sean T. Barrows ◽  
Ravishankar Balasubramian ◽  
Jen-Ping Chen
Keyword(s):  
Pressure Ratio ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Vena Contracta ◽  
Transonic Compressor ◽  
Compressor Rotor ◽  
Radial Depth ◽  
Modeling Techniques ◽  
Final Approach ◽  
Viable Approach

Computational fluid dynamics (CFD) codes are becoming an integral part of the design and analysis process involved with creating and improving upon new engine designs. This necessitates the investigation and development of accurate modeling techniques for flow simulations with a quick turn around time of typically 48 hours. The present paper is focused on increasing the fidelity of compressor rotor simulations by examining three rotor tip clearance modeling techniques. The first approach models the tip clearance region as a loss-less, periodic, un-gridded region as first proposed by Kirtley et al. The second approach is a modification of this technique to study the vena-contracta effects. The tip clearance region remains un-gridded, but, the physical radial depth of tip clearance is gradually reduced to the smallest constriction typically seen in the tip clearance because of flow phenomena such as the shroud and blade-tip boundary layers. The final approach is a completely gridded tip clearance region of full depth to verify the vena-contracta approach as well as to determine if any increase in fidelity is achieved through this computationally costly procedure. These three tip clearance modeling approaches are applied to the NASA transonic compressor rotor, Rotor-35, in a rotor only configuration and the predicted operational ranges are compared to available LDV data. Span-wise performance characteristics such as total pressure ratio and total temperature ratio are compared at a near peak efficiency and at a near-stall operating point. Tip-vortex resolution and predictions are also examined. The merits and demerits of the three approaches are discussed and recommendations are made for a viable approach in terms of accuracy and computational resources.

scholarly journals Calculation of Tip Clearance Effects in a Transonic Compressor Rotor

1998 ◽  
Vol 120 (1) ◽  
pp. 131-140 ◽  
Author(s):  
R. V. Chima
Keyword(s):  
Tip Clearance ◽  
Tip Vortex ◽  
Vena Contracta ◽  
Transonic Compressor ◽  
Compressor Rotor ◽  
Laser Anemometer ◽  
Flow Through ◽  
Gap Height ◽  
Operating Points ◽  
Clearance Model

The flow through the tip clearance region of a transonic compressor rotor (NASA rotor 37) was computed and compared to aerodynamic probe and laser anemometer data. Tip clearance effects were modeled both by gridding the clearance gap and by using a simple periodicity model across the ungridded gap. The simple model was run with both the full gap height, and with half the gap height to simulate a vena-contracta effect. Comparisons between computed and measured performance maps and downstream profiles were used to validate the models and to assess the effects of gap height on the simple clearance model. Recommendations were made concerning the use of the simple clearance model. Detailed comparisons were made between the gridded clearance gap solution and the laser anemometer data near the tip at two operating points. The computed results agreed fairly well with the data but overpredicted the extent of the casing separation and underpredicted the wake decay rate. The computations were then used to describe the interaction of the tip vortex, the passage shock, and the casing boundary layer.

scholarly journals Calculation of Tip Clearance Effects in a Transonic Compressor Rotor

1996 ◽  
Author(s):  
Rodrick V. Chima
Keyword(s):  
Tip Clearance ◽  
Tip Vortex ◽  
Vena Contracta ◽  
Transonic Compressor ◽  
Compressor Rotor ◽  
Laser Anemometer ◽  
Flow Through ◽  
Gap Height ◽  
Operating Points ◽  
Clearance Model

The flow through the tip clearance region of a transonic compressor rotor (NASA rotor 37) was computed and compared to aerodynamic probe and laser anemometer data. Tip clearance effects were modeled both by gridding the clearance gap and by using a simple periodicity model across the ungridded gap. The simple model was run with both the full gap height, and with half the gap height to simulate a vena-contracta effect. Comparisons between computed and measured performance maps and downstream profiles were used to validate the models and to assess the effects of gap height on the simple clearance model. Recommendations were made concerning the use of the simple clearance model. Detailed comparisons were made between the gridded clearance gap solution and the laser anemometer data near the tip at two operating points. The computed results agreed fairly well with the data but overpredicted the extent of the casing separation and underpredicted the wake decay rate. The computations were then used to describe the interaction of the tip vortex, the passage shock, and the casing boundary layer.

Design and Test of a Transonic Axial Splittered Rotor

2015 ◽  
Author(s):  
Garth V. Hobson ◽  
Anthony J. Gannon ◽  
Scott Drayton
Keyword(s):  
Mass Flow ◽  
Pressure Ratio ◽  
Axial Compressor ◽  
Design Procedure ◽  
Tip Clearance ◽  
Turbine Engine ◽  
Transonic Compressor ◽  
Compressor Rotor ◽  
Transonic Axial Compressor ◽  
Commercial Off The Shelf

A new design procedure was developed that uses commercial-off-the-shelf software (MATLAB, SolidWorks, and ANSYS-CFX) for the geometric rendering and analysis of a transonic axial compressor rotor with splitter blades. Predictive numerical simulations were conducted and experimental data were collected in a Transonic Compressor Rig. This study advanced the understanding of splitter blade geometry, placement, and performance benefits. In particular, it was determined that moving the splitter blade forward in the passage between the main blades, which was a departure from the trends demonstrated in the few available previous transonic axial compressor splitter blade studies, increased the mass flow range with no loss in overall performance. With a large 0.91 mm (0.036 in) tip clearance, to preserve the integrity of the rotor, the experimentally measured peak total-to-total pressure ratio was 1.69 and the peak total-to-total isentropic efficiency was 72 percent at 100 percent design speed. Additionally, a higher than predicted 7.5 percent mass flow rate range was experimentally measured, which would make for easier engine control if this concept were to be included in an actual gas turbine engine.

Tip-Clearance and Secondary Flows in a Transonic Compressor Rotor

1999 ◽  
Vol 121 (4) ◽  
pp. 751-762 ◽  
Author(s):  
G. A. Gerolymos ◽  
I. Vallet
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Main Flow ◽  
Secondary Flows ◽  
Tip Clearance ◽  
Computational Method ◽  
Tip Vortex ◽  
Computational Results ◽  
Transonic Compressor ◽  
Compressor Rotor

The purpose of this paper is to investigate tip-clearance and secondary flows numerically in a transonic compressor rotor. The computational method used is based on the numerical integration of the Favre-Reynolds-averaged three-dimensional compressible Navier–Stokes equations, using the Launder–Sharma near-wall k–ε turbulence closure. In order to describe the flowfield through the tip and its interaction with the main flow accurately, a fine O-grid is used to discretize the tip-clearance gap. A patched O-grid is used to discretize locally the mixing-layer region created between the jetlike flow through the gap and the main flow. An H–O–H grid is used for the computation of the main flow. In order to substantiate the validity of the results, comparisons with experimental measurements are presented for the NASA_37 rotor near peak efficiency using three grids (of 106, 2 X 106, and 3 X 106 points, with 21, 31, and 41 radial stations within the gap, respectively). The Launder–Sharma k–ε model underestimates the hub corner stall present in this configuration. The computational results are then used to analyze the interblade-passage secondary flows, the flow within the tip-clearance gap, and the mixing downstream of the rotor. The computational results indicate the presence of an important leakage-interaction region where the leakage-vortex after crossing the passage shock-wave mixes with the pressure-side secondary flows. A second trailing-edge tip vortex is also clearly visible.

Experimental Investigation of Stepped Tip Gap Effects on the Performance of a Transonic Axial-Flow Compressor Rotor

1998 ◽  
Vol 120 (3) ◽  
pp. 477-486 ◽  
Author(s):  
D. W. Thompson ◽  
P. I. King ◽  
D. C. Rabe
Keyword(s):  
Mass Flow ◽  
Pressure Ratio ◽  
Axial Flow ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Axial Flow Compressor ◽  
Transonic Compressor ◽  
Compressor Rotor ◽  
Percent Improvement ◽  
Flow Compressor

The effects of stepped-tip gaps and clearance levels on the performance of a transonic axial-flow compressor rotor were experimentally determined. A two-stage compressor with no inlet guide vanes was tested in a modern transonic compressor research facility. The first-stage rotor was unswept and was tested for an optimum tip clearance with variations in stepped gaps machined into the casing near the aft tip region of the rotor. Nine causing geometries were investigated consisting of three step profiles at each of three clearance levels. For small and intermediate clearances, stepped tip gaps were found to improve pressure ratio, efficiency, and flow range for most operating conditions. At 100 percent design rotor speed, stepped tip gaps produced a doubling of mass flow range with as much as a 2.0 percent increase in mass flow and a 1.5 percent improvement in efficiency. This study provides guidelines for engineers to improve compressor performance for an existing design by applying an optimum casing profile.

Experimental Investigation of Stepped Tip Gap Effects on the Performance of a Transonic Axial-Flow Compressor Rotor

1997 ◽  
Author(s):  
Donald W. Thompson ◽  
Paul I. King ◽  
Douglas C. Rabe
Keyword(s):  
Mass Flow ◽  
Pressure Ratio ◽  
Axial Flow ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Axial Flow Compressor ◽  
Transonic Compressor ◽  
Compressor Rotor ◽  
Compressor Performance ◽  
Flow Compressor

The effects of stepped tip gaps and clearance levels on the performance of a transonic axial-flow compressor rotor were experimentally determined. A two-stage compressor with no inlet guide vanes was tested in a modern transonic compressor research facility. The first-stage rotor was unswept and was tested for an optimum tip clearance with variations in stepped gaps machined into the casing near the aft tip region of the rotor. Nine casing geometries were investigated consisting of three step profiles at each of three clearance levels. For small and intermediate clearances, stepped tip gaps were found to improve pressure ratio, efficiency, and flow range for most operating conditions. At 100% design rotor speed, stepped tip gaps produced a doubling of mass flow range with as much as a 2.0% increase in mass flow and a 1.5% improvement in efficiency. This study provides guidelines for engineers to improve compressor performance for an existing design by applying an optimum casing profile.

Tip-Clearance and Secondary Flows in a Transonic Compressor Rotor

1998 ◽  
Author(s):  
G. A. Gerolymos ◽  
I. Vallet
Keyword(s):  
Stokes Equations ◽  
Mixing Layer ◽  
Main Flow ◽  
Secondary Flows ◽  
Tip Clearance ◽  
Computational Method ◽  
Tip Vortex ◽  
Computational Results ◽  
Transonic Compressor ◽  
Compressor Rotor

The purpose of this paper is to numerically investigate tip-clearance and secondary flows in a transonic compressor rotor. The computational method used is based on the numerical integration of the Favre-Reynolds-averaged 3-D compressible Navier-Stokes equations, using the Launder-Sharma near-wall k-ε turbulence closure. In order to accurately describe the flowfield through the tip and its interaction with the main flow, a fine O-grid is used to discretize the tip-clearance-gap. A patched O-grid is used to discretize locally the mixing-layer region created between the jet-like flow through the gap and the main flow. An H-O-H grid is used for the computation of the main flow. In order to substantiate the validity of the results comparisons with experimental measurements are presented for the NASA_37 rotor near peak efficiency using 3 grids (of 106, 2 × 106, and 3 × 106 points, with 21, 31, and 41 radial stations within the gap respectively). The Launder-Sharma k-ε model underestimates the hub corner stall present in this configuration. The computational results are then used to analyze the interblade-passage secondary flows, the flow within the tip-clearance gap and the mixing downstream of the rotor. The computational results indicate the presence of an important leakage-interaction-region where the leakage-vortex after crossing the passage shock-wave mixes with the pressure-side secondary flows. A second trailing-edge-tip-vortex is also clearly visible.

Experimental and Computational Investigation of Stepped Tip Gap Effects on the Flowfield of a Transonic Axial-Flow Compressor Rotor

1998 ◽  
Author(s):  
Donald W. Thompson ◽  
Paul I. King ◽  
Chunill Hah ◽  
Douglas C. Rabe
Keyword(s):  
Fluid Dynamic ◽  
Pressure Ratio ◽  
Effective Means ◽  
Axial Flow ◽  
Tip Clearance ◽  
Axial Flow Compressor ◽  
Transonic Compressor ◽  
Compressor Rotor ◽  
Compressor Performance ◽  
Flow Compressor

The effects of stepped tip gaps and clearance levels on the flowfield of a transonic axial-flow compressor rotor were experimentally and computationally determined. This paper complements a previous experimental study by the authors regarding the effects of stepped tip gaps and clearance levels on the performance of an axial-flow compressor rotor. In the current study, the generation of blockage associated with the variation of geometry in the rotor tip region was examined. The shock-vortex interaction generating the blockage was characterized, and a theory and mechanism for relocation of blockage in the rotor tip region was developed. A two-stage compressor with no inlet guide vanes was tested in a modern transonic compressor research facility. The first-stage rotor was unswept and was tested with stepped gaps machined into the casing near the aft tip region of the rotor. Nine casing geometries were investigated consisting of three step profiles at each of three clearance levels. Computational Fluid Dynamic modeling of tip geometry effects also was performed. Increased tip clearance was found to increase the amount of flow blockage near the rotor tip. Stepped tip gaps were found to be an effective means of reducing the effects of tip region blockage, resulting in improved pressure ratio, efficiency, and mass flow. This study provides guidelines for engineers to improve compressor performance for an existing design by applying an improved casing profile.

scholarly journals A Three-Dimensional Shock Loss Model Applied to an Aft-Swept, Transonic Compressor Rotor

1996 ◽  
Author(s):  
Steven L. Puterbaugh ◽  
William W. Copenhaver ◽  
Chunill Hah ◽  
Arthur J. Wennerstrom
Keyword(s):  
Flow Rate ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Numerical Results ◽  
Design Flow ◽  
Design System ◽  
Loss Model ◽  
Transonic Compressor ◽  
Compressor Rotor ◽  
Shock Loss

An analysis of the effectiveness of a three-dimensional shock loss model used in transonic compressor rotor design is presented. The model was used during the design of an aft-swept, transonic compressor rotor. The demonstrated performance of the swept rotor, in combination with numerical results, is used to determine the strengths and weaknesses of the model. The numerical results were obtained from a fully three-dimensional Navier-Stokes solver. The shock loss model was developed to account for the benefit gained with three-dimensional shock sweep. Comparisons with the experimental and numerical results demonstrated that shock loss reductions predicted by the model due to the swept shock induced by the swept leading edge of the rotor were exceeded. However, near the tip the loss model under-predicts the loss because the shock geometry assumed by the model remains swept in this region while the numerical results show a more normal shock orientation. The design methods and the demonstrated performance of the swept rotor is also presented. Comparisons are made between the design intent and measured performance parameters. The aft-swept rotor was designed using an inviscid axisymmetric streamline curvature design system utilizing arbitrary airfoil blading geometry. The design goal specific flow rate was 214.7 kg/sec/m2 (43.98 lbm/sec/ft2), the design pressure ratio goal was 2.042, and the predicted design point efficiency was 94.0. The rotor tip sped was 457.2 m/sec (1500 ft/sec). The design flow rate was achieved while the pressure ratio fell short by 0.07. Efficiency was 3 points below prediction, though at a very high 91 percent. At this operating condition the stall margin was 11 percent.

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