The Impact of Real Geometries on Three-Dimensional Separations in Compressors

2011 ◽  
Vol 134 (2) ◽  
Author(s):  
Martin N. Goodhand ◽  
Robert J. Miller
Keyword(s):  
Three Dimensional ◽  
Leading Edge ◽  
Suction Surface ◽  
Blade Loading ◽  
Flow Parameters ◽  
Surface Transition ◽  
Edge Roughness ◽  
Large Growth ◽  
Edge Quality ◽  
The Impact

This paper considers the effect of small variations in leading edge geometry, leading edge roughness, leading edge fillet, and blade fillet geometry on the three-dimensional separations found in compressor blade rows. The detrimental effects of these separations have historically been predicted by correlations based on global flow parameters, such as blade loading, inlet boundary layer skew, etc., and thus ignoring small deviations such as those highlighted above. In this paper it is shown that this may not be the case and that certain, engine representative geometry deviations can have an effect equivalent to an increase in blade loading of 10%. Experiments were performed at the stator hub of a low-speed, single-stage compressor. The results show that any deviation which causes suction surface transition to move to the leading edge over the first 30% of span will cause a large growth in the size of the hub separation, doubling its impact on loss. The geometry deviations that caused this, and are thus of greatest concern to a designer, are changes in leading edge quality and roughness around the leading edge, which are characteristic of an eroded blade.

The Impact of Real Geometries on Three-Dimensional Separations in Compressors

2010 ◽  
Author(s):  
Martin N. Goodhand ◽  
Robert J. Miller
Keyword(s):  
Three Dimensional ◽  
Leading Edge ◽  
Suction Surface ◽  
Blade Loading ◽  
Flow Parameters ◽  
Surface Transition ◽  
Edge Roughness ◽  
Large Growth ◽  
Edge Quality ◽  
The Impact

This paper considers the effect of small variations in leading edge geometry, leading edge roughness, leading edge fillet and blade fillet geometry on the three dimensional separations found in compressor blade rows. The detrimental effects of these separations have historically been predicted by correlations based on global flow parameters, such as blade loading, inlet boundary layer skew etc, and thus ignoring small deviations such as those highlighted above. In this paper it is shown that this may not to be the case and that certain, engine representative geometry deviations can have an effect equivalent to an increase in blade loading of 10%. Experiments were performed at the stator hub of a low-speed, single-stage compressor. The results show that any deviation which causes suction surface transition to move to the leading edge over the first 30% of span will cause a large growth in the size of the hub separation, doubling its impact on loss. The geometry deviations that caused this, and are thus of greatest concern to a designer, are changes in leading edge quality and roughness around the leading edge, characteristic of an eroded blade.

scholarly journals Reduction of Unsteady Blade Loading by Beneficial Use of Vortical and Potential Disturbances in an Axial Compressor With Rotor Clocking

1998 ◽  
Vol 120 (4) ◽  
pp. 705-713 ◽  
Author(s):  
S. T. Hsu ◽  
A. M. Wo
Keyword(s):  
Large Scale ◽  
Axial Compressor ◽  
Leading Edge ◽  
Forced Response ◽  
Suction Surface ◽  
Blade Loading ◽  
Beneficial Use ◽  
Unsteady Loading ◽  
Vortical Disturbance ◽  
First Time

This paper demonstrates reduction of stator unsteady loading due to forced response in a large-scale, low-speed, rotor/stator/rotor axial compressor rig by clocking the downstream rotor. Data from the rotor/stator configuration showed that the stator response due to the upstream vortical disturbance reaches a maximum when the wake impinges against the suction surface immediately downstream of the leading edge. Results from the stator/rotor configuration revealed that the stator response due to the downstream potential disturbance reaches a minimum with a slight time delay after the rotor sweeps pass the stator trailing edge. For the rotor/stator/rotor configuration, with Gap1 = 10 percent chord and Gap2 = 30 percent chord, results showed a 60 percent reduction in the stator force amplitude by clocking the downstream rotor so that the time occurrence of the maximum force due to the upstream vortical disturbance coincides with that of the minimum force due to the downstream potential disturbance. This is the first time, the authors believe, that beneficial use of flow unsteadiness is definitively demonstrated to reduce the blade unsteady loading.

Assessment of Unsteady Flows in Turbines

1992 ◽  
Vol 114 (1) ◽  
pp. 79-90 ◽  
Author(s):  
O. P. Sharma ◽  
G. F. Pickett ◽  
R. H. Ni
Keyword(s):  
Unsteady Flow ◽  
Three Dimensional ◽  
Flow Simulation ◽  
Experimental Investigations ◽  
Flow Parameters ◽  
Research Activities ◽  
Flow Features ◽  
Computational Fluid Dynamics Cfd ◽  
Turbine Design ◽  
The Impact

The impacts of unsteady flow research activities on flow simulation methods used in the turbine design process are assessed. Results from experimental investigations that identify the impact of periodic unsteadiness on the time-averaged flows in turbines and results from numerical simulations obtained by using three-dimensional unsteady Computational Fluid Dynamics (CFD) codes indicate that some of the unsteady flow features can be fairly accurately predicted. Flow parameters that can be modeled with existing steady CFD codes are distinguished from those that require unsteady codes.

Optimization of Trenched Film Cooling Using RSM Coupled CFD

2018 ◽  
Vol 0 (0) ◽  
Author(s):  
V.G. Krishna Anand ◽  
K.M. Parammasivam
Keyword(s):  
Film Cooling ◽  
Three Dimensional ◽  
Response Surfaces ◽  
Test Surface ◽  
Response Factor ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Flow Parameters ◽  
Considerable Impact ◽  
The Impact

AbstractThe trench film cooling employs film holes embedded in a slot created on the surface that requires protection from the impact of hot mainstream flow. The present investigation employs Response Surface Methodology (RSM) approach coupled with CFD analysis to develop a regression predictive model and to optimize the trench geometric and flow parameters viz., trench width (w), trench depth (d), film hole compound angle (β) and blowing ratio (M). The Area-averaged film cooling effectiveness (ȠAA) were chosen as a response factor for RSM and with trench design and flow parameters used as input factors for regression analysis. Analysis of variance (ANOVA) analysis was carried out on the regression model to identify the influence of individual parameters. Three dimensional response surfaces that relate the effect of input parameters on the response factor were analyzed. Experimental results of a case identified from the RSM matrix was found to correlate well with computational investigations. Results from the study indicate that the parameters d, β and M have considerable impact on film cooling performance of test surface with trenches.

The Impact of Geometric Variation on Compressor Two-Dimensional Incidence Range

2014 ◽  
Vol 137 (2) ◽  
Author(s):  
Martin N. Goodhand ◽  
Robert J. Miller ◽  
Hang W. Lung
Keyword(s):  
Design Process ◽  
Design Space ◽  
Leading Edge ◽  
Critical Value ◽  
Two Dimensional ◽  
Suction Surface ◽  
Design Intent ◽  
Manufacture Process ◽  
The Impact ◽  
Geometric Variation

An important question for a designer is how, in the design process, to deal with the small geometric variations which result from either the manufacture process or in-service deterioration. For some blade designs geometric variations will have little or no effect on the performance of a row of blades, while in others their effects can be significant. This paper shows that blade designs which are most sensitive are those which are susceptible to a distinct switch in the fluid mechanisms responsible for limiting blade performance. To demonstrate this principle, the sensitivity of compressor 2D incidence range to manufacture variations is considered. Only one switch in mechanisms was observed, the onset of flow separation at the leading edge. This switch is only sensitive to geometric variations around the leading edge, 0–3% of the suction surface. The consequence for these manufacture variations was a 10% reduction in the blade's positive incidence range. For this switch, the boundary in the design space is best defined in terms of the blade pressure distribution. Blade designs where the acceleration exceeds a critical value just downstream of the leading edge are shown to be robust to geometric variation. Two historic designs, supercritical blades and blades with sharp leading edges, though superior in design intent, are shown to sit outside this robust region and thus, in practice, perform worse. The improved understanding of the robust, region of the design space is then used to design a blade capable of a robust, 5% increase in operating incidence range.

Numerical Simulation of Clocking Effect on Wake Transportation and Interaction in a 1.5-Stage Axial Turbine

2010 ◽  
Author(s):  
Wei Li ◽  
Hua Ouyang ◽  
Zhao-hui Du
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Leading Edge ◽  
Navier Stokes ◽  
Maximum Efficiency ◽  
Suction Surface ◽  
Navier Stokes Equations ◽  
Pressure Surface ◽  
Turbine Efficiency ◽  
Small Influence

To give insight into the clocking effect and its influence on the wake transportation and its interaction, the unsteady three-dimensional flow through a 1.5-stage axial low pressure turbine is simulated numerically using a density-correction based, Reynolds-Averaged Navier-Stokes equations commercial CFD code. The 2nd stator clocking is applied over ten equal tangential positions. The results show that the harmonic blade number ratio is an important factor affecting the clocking effect. The clocking effect has a very small influence on the turbine efficiency in this investigation. The efficiency difference between the maximum and minimum configuration is nearly 0.1%. The maximum efficiency can be achieved when the 1st stator wake enters the 2nd stator passage near blade suction surface and its adjacent wake passes through the 2nd stator passage close to blade pressure surface. The minimum efficiency appears if the 1st stator wake impinges upon the leading edge of the 2nd stator and its adjacent wake of the 1st stator passed through the mid-channel in the 2nd stator.

HP Vane Aerodynamics and Heat Transfer in the Presence of Aggressive Inlet Swirl

2012 ◽  
Vol 135 (2) ◽  
Author(s):  
Imran Qureshi ◽  
Andy D. Smith ◽  
Thomas Povey
Keyword(s):  
Heat Transfer ◽  
Cooling System ◽  
Three Dimensional ◽  
Leading Edge ◽  
Good Deal ◽  
Vortex Center ◽  
Research Facility ◽  
Lean Burn ◽  
Numerical Predictions ◽  
The Impact

Modern lean burn combustors now employ aggressive swirlers to enhance fuel-air mixing and improve flame stability. The flow at combustor exit can therefore have high residual swirl. A good deal of research concerning the flow within the combustor is available in open literature. The impact of swirl on the aerodynamic and heat transfer characteristics of an HP turbine stage is not well understood, however. A combustor swirl simulator has been designed and commissioned in the Oxford Turbine Research Facility (OTRF), previously located at QinetiQ, Farnborough UK. The swirl simulator is capable of generating an engine-representative combustor exit swirl pattern. At the turbine inlet plane, yaw and pitch angles of over ±40 deg have been simulated. The turbine research facility used for the study is an engine scale, short duration, rotating transonic turbine, in which the nondimensional parameters for aerodynamics and heat transfer are matched to engine conditions. The research turbine was the unshrouded MT1 design. By design, the center of the vortex from the swirl simulator can be clocked to any circumferential position with respect to HP vane, and the vortex-to-vane count ratio is 1:2. For the current investigation, the clocking position was such that the vortex center was aligned with the vane leading edge (every second vane). Both the aligned vane and the adjacent vane were characterized. This paper presents measurements of HP vane surface and end wall heat transfer for the two vane positions. The results are compared with measurements conducted without swirl. The vane surface pressure distributions are also presented. The experimental measurements are compared with full-stage three-dimensional unsteady numerical predictions obtained using the Rolls Royce in-house code Hydra. The aerodynamic and heat transfer characterization presented in this paper is the first of its kind, and it is hoped to give some insight into the significant changes in the vane flow and heat transfer that occur in the current generation of low NOx combustors. The findings not only have implications for the vane aerodynamic design, but also for the cooling system design.

Numerical study of the impact of water injection holes arrangement on cavitation flow control

2019 ◽  
Vol 103 (1) ◽  
pp. 003685041987774 ◽  
Author(s):  
Wei Wang ◽  
Qingdian Zhang ◽  
Tao Tang ◽  
Shengpeng Lu ◽  
Qi Yi ◽  
...  
Keyword(s):  
Flow Field ◽  
Numerical Study ◽  
Water Injection ◽  
Three Dimensional ◽  
Hydrodynamic Performance ◽  
Cavitation Flow ◽  
Suction Surface ◽  
Double Row ◽  
Suppression Effect ◽  
The Impact

A method of water injection to flow field using distributed holes on the suction surface of hydrofoil is presented in this article to control cavitation flow. Modified renormalization group k–ε turbulence model is coupled with full-cavitation model to calculate periodical cavitation patterns and the dynamic characteristics of the NACA66(MOD) hydrofoil. Water injection is found to be highly effective for cavitation suppression. The cavitation suppression effect of distributed regulation of jet holes and porosities along three-dimensional spanwise hydrofoil is also investigated. The appropriate porosities of single row spanwise jet holes and optimal jet position of double row jet holes are revealed for both cavitation suppression and good hydrodynamic performance. Double row jet holes setting in forward trapezoidal arrangement shows great potential for cavitation suppression and hydrodynamic performance. This research provides a method of water injection to flow field to actively control cavitation, which will facilitate development of engineering designs.

Effects of Flow Injection From Outer Casing Upon Turbine Nozzle Vane Flow Field

2002 ◽  
Author(s):  
K. Funazaki ◽  
C. F. F. Favaretto ◽  
T. Tanuma
Keyword(s):  
Flow Field ◽  
Flow Injection ◽  
Three Dimensional ◽  
Leading Edge ◽  
Main Stream ◽  
Flow Angle ◽  
Aerodynamic Loss ◽  
Nozzle Vane ◽  
Design Variables ◽  
The Impact

In the present paper steady three-dimensional numerical calculations were performed in order to investigate the effects of flow injection from the outer casing upon turbine nozzle vane flow field. Several test cases were analyzed by applying different nozzle vane configurations such as the blade lean, injection slot width and distance from the leading edge. Numerical simulations were conducted considering the no injection case, 5% and 10% main stream flow injection from the outer casing. The impact of the flow injection design variables and the blade lean angle on the aerodynamic loss in terms of the energy loss coefficient and the outlet flow angle were analyzed through a parametric study.

scholarly journals Impact of Leading Edge Roughness in Cavitation Simulations around a Twisted Foil

Fluids ◽  
2020 ◽  
Vol 5 (4) ◽  
pp. 243
Author(s):  
Abolfazl Asnaghi ◽  
Rickard E. Bensow
Keyword(s):  
Three Dimensional ◽  
Leading Edge ◽  
Flow Structures ◽  
Vortical Structures ◽  
Vorticity Distribution ◽  
Eddy Simulation ◽  
Roughness Elements ◽  
Edge Roughness ◽  
Large Eddy ◽  
Implicit Large Eddy Simulation

The simulation of fully turbulent, three-dimensional, cavitating flow over Delft twisted foil is conducted by an implicit large eddy simulation (LES) approach in both smooth and tripped conditions, the latter by including leading-edge roughness. The analysis investigates the importance of representing the roughness elements on the flow structures in the cavitation prediction. The results include detailed comparisons of cavitation pattern, vorticity distribution, and force predictions with the experimental measurements. It is noted that the presence of roughness generates very small cavitating vortical structures which interact with the main sheet cavity developing over the foil to later form a cloud cavity. Very similar to the experimental observation, these interactions create a streaky sheet cavity interface which cannot be captured in the smooth condition, influencing both the richness of structures in the detached cloudy cavitation as well as the extent and transport of vapour. It is further found to have a direct impact on the pressure distribution, especially in the mid-chord region where the shed cloud cavity collapses.

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