Influence of Temperature Distribution on Radial Growth of Compressor Disks

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Dario Luberti ◽  
Hui Tang ◽  
James A. Scobie ◽  
Oliver J. Pountney ◽  
J. Michael Owen ◽  
...  
Keyword(s):  
Temperature Distribution ◽  
Radial Distribution ◽  
Radial Growth ◽  
Transfer Problem ◽  
Pressure Ratio ◽  
Operating Conditions ◽  
Accurate Prediction ◽  
Tip Clearance ◽  
Linear Quadratic ◽  
Element Analysis

Abstract For the next generation of aero-engines, manufacturers are planning to increase the overall compressor pressure ratio from the existing values around 50:1 to values of 70:1. The requirement to control the tight clearances between the blade tips and the casing overall engine-operating conditions is a challenge for the engine designer attempting to minimize tip-clearances losses. Accurate prediction of the tip clearance requires an accurate prediction of the radial growth of the compressor rotor, which depends on the temperature distribution of the disk. The flow in the rotating cavities between adjacent disks is buoyancy-driven, which creates a conjugate heat transfer problem: the disk temperature depends on the radial distribution of the Nusselt number, which in turn depends on the radial distribution of disk temperature. This paper focuses on calculating the radial growth of a simplified compressor disk in isolation from the other components. Calculations were performed using steady one-dimensional (1D) theoretical and two-dimensional numerical computations (2D finite element analysis (FEA)) for overall pressure ratios (OPRs) of 50:1, 60:1, and 70:1. At each pressure ratio, calculations were conducted for five different temperature distributions; the distribution based on an experimentally validated buoyancy model was used as the datum case, and the results from this were compared with those from linear, quadratic, cubic, and quartic power laws. The results show that the assumed distribution of disk temperature has a significant effect on the calculated disk growth, whereas the pressure ratio has only a relatively small effect. Good agreement between the growth calculated by the 1D theoretical model and the FEA suggests that the 1D model should be useful for design purposes. Although the results were obtained for steady-state conditions, a method is outlined for calculating the growth under transient conditions.

Influence of Temperature Distribution on Radial Growth of Compressor Discs

2019 ◽  
Author(s):  
Dario Luberti ◽  
Hui Tang ◽  
James A. Scobie ◽  
Oliver J. Pountney ◽  
J. Michael Owen ◽  
...  
Keyword(s):  
Temperature Distribution ◽  
Radial Distribution ◽  
Radial Growth ◽  
Transfer Problem ◽  
Pressure Ratio ◽  
Power Laws ◽  
Operating Conditions ◽  
Accurate Prediction ◽  
Tip Clearance ◽  
Linear Quadratic

Abstract For the next generation of aero-engines, manufacturers are planning to increase the overall compressor pressure ratio from existing values around 50:1 to values of 70:1. The requirement to control the tight clearances between the blade tips and the casing over all engine-operating conditions is a challenge for the engine designer attempting to minimise tip-clearances losses. Accurate prediction of the tip clearance requires an accurate prediction of the radial growth of the compressor rotor, which depends on the temperature distribution of the disc. The flow in the rotating cavities between adjacent discs is buoyancy-driven, which creates a conjugate heat transfer problem: the disc temperature depends on the radial distribution of Nusselt number, which in turn depends on the radial distribution of disc temperature. This paper focuses on calculating the radial growth of a simplified compressor disc in isolation from the other components. Calculations were performed using one-dimensional (1D) theoretical and two-dimensional finite-element computations (2D FEA) for overall pressure ratios (OPR) of 50:1, 60:1 and 70:1. At each pressure ratio, calculations were conducted for five different temperature distributions; the distribution based on an experimentally-validated buoyancy model was used as the datum case, and results from this were compared with those from linear, quadratic, cubic and quartic power laws. The results show that the assumed distribution of disc temperature has a significant effect on the calculated disc growth, whereas the pressure ratio has only a relatively small effect. The good agreement between the growth calculated by the 1D theoretical model and the FEA suggests that the 1D model should be useful for design purposes.

Experimental Investigations on Mixed Flow Impeller and Vane Diffuser Under Various Operating Conditions

2012 ◽  
Author(s):  
D. Ramesh Rajakumar ◽  
S. Ramamurthy ◽  
M. Govardhan
Keyword(s):  
Pressure Ratio ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Experimental Investigations ◽  
Compressor Stage ◽  
Mixed Flow ◽  
Tip Clearance Flow ◽  
Clearance Flow ◽  
Flow Compressor ◽  
Vane Diffuser

Experimental Investigations are carried out to study the effect of tip clearance flow in a mixed flow compressor stage. Two configurations, namely; constant and variable clearance gaps between impeller and stationary shroud are considered. For the purpose of the present investigations, a mixed flow compressor stage is designed and fabricated. The flow investigations were carried out in a closed circuit compressor rig. Detailed steady and unsteady measurements were carried out for three clearance gaps, namely; 0.5 mm, 0.75 mm, 0.9 mm. From the experimental investigations it is shown that constant tip clearance configurations show better performance in terms of pressure ratio and efficiency compared to variable clearance configurations. For a given configuration the pressure ratio and efficiency of the stage decrease with increase in the tip gap without indicating any optimum value. Tip clearance flow has considerable effect on the flow through the diffuser and the unsteady flow gets amplified and carried away into the vane diffuser.

scholarly journals Efficiency Scaling - Influence of Reynolds and Mach Number on Fan Performance

2021 ◽  
pp. 1-17
Author(s):  
Peter F. Pelz ◽  
Sebastian Saul ◽  
Johannes Brötz
Keyword(s):  
Mach Number ◽  
Standardized Test ◽  
Pressure Ratio ◽  
Reference Method ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Scaling Method ◽  
Scaled Model ◽  
Type Size ◽  
Shaft Power

Abstract The efficiency, pressure ratio and shaft power of a fan depends on type, size, working medium and operating condition. For acceptance tests, a dissimilarity in Reynolds number, Mach number, relative roughness and relative blade tip clearance of the scaled model and prototype is unavoidable. Hence, the efficiency differs between model and prototype. This difference is quantified by scaling methods. This paper presents a validated and physics based, i. e. reliable scaling method for the efficiency, pressure ratio and shaft power of axial and centrifugal fans operating at subsonic conditions. The method is validated using test results gained on standardized test rigs for different fan types, sizes and operating conditions. For all scenarios the presented scaling method provides a much reduced scaling uncertainty compared to the reference method described in ISO 13348.

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.

Gas Labyrinth Seals: Improved Prediction of Leakage in Gas Labyrinth Seals Using an Updated Kinetic Energy Carry-Over Coefficient

2020 ◽  
Author(s):  
Tingcheng Wu ◽  
Luis San Andrés
Keyword(s):  
Kinetic Energy ◽  
Mass Flow ◽  
Pressure Ratio ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Bulk Flow ◽  
Radial Clearance ◽  
Labyrinth Seals ◽  
Leakage Model ◽  
Carry Over

Abstract Though simple and fast, bulk-flow models (BFMs) for gas labyrinth seals (LSs) often predict the mass flow inaccurately. The BFM models rely on classical Neumann’s equation model to characterize the flow through a labyrinth tooth. Presently, a CFD analysis quantifies the effects of tip clearance (Cr) and operating conditions on the prediction of LS mass flow, and then derives an updated kinetic energy carry-over coefficient (μ1i) to improve the accuracy of Neumann’s leakage equation. μ1i is a function of the seal tip clearance (Cr), the tooth pitch, and the total teeth number; but it does not depend on the seal supply or discharge pressures. The analysis selects a fourteen teeth on stator LS (Length/Diameter = L/D = 0.29) with clearance Cr = (1/733)D and operating at nominal supply (Pin) and discharge (Pout) pressures equal to 73 bar and 51 bar, respectively, and at a rotor speed of 12 krpm (surface speed = 138 m/s.). The CFD produces flow fields for LSs with a clearance varying from 80% to 200% of the nominal Cr, a gas supply pressure from 60 bar to 100 bar, and with various discharge pressures giving a pressure ratio (PR = Pout/Pin) ranging from 0.40 to 0.85. The numerous predictions deliver the mass flow as well as the bulk-flow velocities and cavity pressures within the seals. The kinetic energy carry-over coefficient (μ1i) increases with respect to the seal radial clearance (Cr). μ1i shows a parabolic correlation with PR; at first μ1i increases with a rise in PR from a low value; and then a further increase in PR leads to a decrease in μ1i. The coefficient μ1i is only sensitive to the pressure ratio and not to the magnitude of either the supply or discharge pressures. Lastly, for use with Neumann’s leakage model, the CFD predictions produce an updated μ1i, a function of the seal geometry and the PR condition. Integration of the new μ1i correlation into a BFM code improves its accuracy to predict LS mass flow rate, a 19% difference against test data reduces to within 6%. A TOS LS tested by Ertas et al. (2012) serves to further validate the accuracy of the modified leakage model.

scholarly journals Secondary Flows and Vortex Motion in a High-Efficiency Backswept Impeller at Design and Off-Design Conditions

1989 ◽  
Author(s):  
C. Hah ◽  
H. Krain
Keyword(s):  
Flow Pattern ◽  
High Efficiency ◽  
Pressure Ratio ◽  
Vortex Motion ◽  
Secondary Flows ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Optimum Shape ◽  
Discharge Velocity ◽  
Type Flow

The 3-D viscous flowfield of a 4.7:1 pressure ratio backswept impeller was studied experimentally and numerically by using laser velocimetry and an advanced 3-D viscous code. The impeller was designed by a CAD method, and a maximum rotor efficiency of 94% was achieved. Both the experimental and the theoretical approach revealed comparatively smooth impeller discharge velocity profiles at all three operating conditions (design, choke, and near surge) differing widely from the well-known jet/wake type flow pattern. The 3-D viscous code was used for detailed flowfield studies, i.e., secondary flows; vortex motion and tip-clearance effects were analyzed at design and off-design conditions. The comparison of experimental and numerical results indicates that the tip-clearance effect should be properly modeled to predict the impeller flow pattern properly and that optimum shape of rotor exit flow pattern can be obtained by controlling the swirling vortex motion.

3D CFD Compressor Map Computation of a Multi-Stage Axial Compressor With Off-Design Adjusted Rotor Geometries

2016 ◽  
Author(s):  
Christian Janke ◽  
Markus Goller ◽  
Ivo Martin ◽  
Lilia Gaun ◽  
Dieter Bestle
Keyword(s):  
High Speed ◽  
Pressure Ratio ◽  
Axial Compressor ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Design Point ◽  
Multi Stage ◽  
Compressor Design ◽  
Compressor Map ◽  
Aero Engines

Compressor maps of aero engines show the relation between corrected mass flow, corrected shaft speed, pressure ratio, and efficiency, where different operating conditions of the compressor are represented by different speed lines. These speed lines are an important information for the compressor design process, since they show important operation bounds like surge and choke. Typically, 3D CFD compressor maps are computed with the so called hot geometry given by the aerodynamic design point. But in reality aerofoil shapes change depending on engine speeds and gas loads resulting in twist of the blades and changes of tip clearance. In order to obtain a higher quality compressor map, all these effects must be taken into account. Therefore, a process is utilized which uses coupled CFD and FE analyses to account for load adjusted geometries aside the design point. For transformation of FE results into the CFD model a cold-to-hot blade morphing technique is used. The studies are performed for a 4.5 stage high speed axial compressor, where effects of varying tip clearance and geometry deformation are considered separately from each other. Finally, their combined effects are studied.

Secondary Flows and Vortex Motion in a High-Efficiency Backswept Impeller at Design and Off-Design Conditions

1990 ◽  
Vol 112 (1) ◽  
pp. 7-13 ◽  
Author(s):  
C. Hah ◽  
H. Krain
Keyword(s):  
Flow Pattern ◽  
High Efficiency ◽  
Pressure Ratio ◽  
Vortex Motion ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Optimum Shape ◽  
Discharge Velocity

The three-dimensional viscous flow field of a 4.7:1 pressure ratio backswept impeller was studied experimentally and numerically by using laser velocimetry and an advanced three-dimensional viscous code. The impeller was designed by a CAD method, and a maximum rotor efficiency of 94 percent was achieved. Both the experimental and the theoretical approach revealed comparatively smooth impeller discharge velocity profiles at all three operating conditions (design, choke, and near surge) differing widely from the well-known jet/wake-type flow pattern. The three-dimensional viscous code was used for detailed flowfield studies, i.e., secondary flows; vortex motion and tip-clearance effects were analyzed at design and off-design conditions. The comparison of experimental and numerical results indicates that the tip-clearance effect should be properly modeled to predict the impeller flow pattern properly and that optimum shape of rotor exit flow pattern can be obtained by controlling the swirling vortex motion.

Gas Labyrinth Seals: Improved Prediction of Leakage in Gas Labyrinth Seals Using an Updated Kinetic Energy Carry-Over Coefficient

2020 ◽  
Vol 142 (12) ◽  
Author(s):  
Tingcheng Wu ◽  
Luis San Andrés
Keyword(s):  
Kinetic Energy ◽  
Mass Flow ◽  
Pressure Ratio ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Bulk Flow ◽  
Radial Clearance ◽  
Labyrinth Seals ◽  
Leakage Model ◽  
Carry Over

Abstract Though simple and fast, bulk-flow models (BFMs) for gas labyrinth seals (LSs) often predict the mass flow inaccurately. The BFM models rely on classical Neumann's equation model to characterize the flow through a labyrinth tooth. Presently, a computational fluid dynamics (CFD) analysis quantifies the effects of tip clearance (Cr) and operating conditions on the prediction of LS mass flow, and then derives an updated kinetic energy carry-over coefficient (μ1i) to improve the accuracy of Neumann's leakage equation. μ1i is a function of the seal tip clearance (Cr), the tooth pitch, and the total teeth number; but it does not depend on the seal supply or discharge pressures. The analysis selects a 14-teeth on stator LS (length/diameter = L/D = 0.29) with clearance Cr = (1/733)D and operating at nominal supply (Pin) and discharge (Pout) pressures equal to 73 bar and 51 bar, respectively, and at a rotor speed of 12 krpm (surface speed = 138 m/s). The CFD produces flow fields for LSs with a clearance varying from 80% to 200% of the nominal Cr, a gas supply pressure from 60 bar to 100 bar, and with various discharge pressures giving a pressure ratio (PR = Pout/Pin) ranging from 0.40 to 0.85. The numerous predictions deliver the mass flow as well as the bulk-flow velocities and cavity pressures within the seals. The kinetic energy carry-over coefficient (μ1i) increases with respect to the seal radial clearance (Cr). μ1i shows a parabolic correlation with PR; at first, μ1i increases with a rise in PR from a low value; and then, a further increase in PR leads to a decrease in μ1i. The coefficient μ1i is only sensitive to the PR and not to the magnitude of either the supply or discharge pressures. Lastly, for use with Neumann's leakage model, the CFD predictions produce an updated μ1i, a function of the seal geometry and the PR condition. Integration of the new μ1i correlation into a BFM code improves its accuracy to predict LS mass flow rate, a 19% difference against test data reduces to within 6%. A TOS LS tested by Ertas et al. (2012, Rotordynamic Force Coefficients for Three Types of Annular Gas Seals With Inlet Preswirl and High Differential Pressure Ratio,” ASME J. Eng. Gas Turbine Power, 134(4), p. 4250301) serves to further validate the accuracy of the modified leakage model.

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