The Effect of Wake Induced Structures on Compressor Boundary-Layers

2006 ◽  
Vol 129 (4) ◽  
pp. 705-712 ◽  
Author(s):  
Andrew P. S. Wheeler ◽  
Robert J. Miller ◽  
Howard P. Hodson
Keyword(s):  
Boundary Layer ◽  
Pressure Transducer ◽  
Leading Edge ◽  
Compressor Blade ◽  
Blade Surface ◽  
Cfd Simulations ◽  
Compressor Blades ◽  
System A ◽  
Dynamic Head ◽  
Pressure Perturbations

The interaction of a convected wake with a compressor blade boundary layer was investigated. Measurements within a single-stage compressor were made using an endoscopic PIV system, a surface mounted pressure transducer, hotfilms and hotwire traverses, along with CFD simulations. The wake/leading-edge interaction was shown to lead to the formation of a thickened laminar boundary-layer, within which turbulent spots formed close to the leading edge. The thickened boundary-layer became turbulent and propagated down the blade surface, giving rise to pressure perturbations of 7% of the inlet dynamic head in magnitude. The results indicate that wake/leading-edge interactions have a crucial role to play in the performance of compressor blades in the presence of wakes.

The Effect of Wake Induced Structures on Compressor Boundary-Layers

2006 ◽  
Author(s):  
Andrew P. S. Wheeler ◽  
Robert J. Miller ◽  
Howard P. Hodson
Keyword(s):  
Boundary Layer ◽  
Pressure Transducer ◽  
Leading Edge ◽  
Compressor Blade ◽  
Blade Surface ◽  
Cfd Simulations ◽  
Compressor Blades ◽  
System A ◽  
Dynamic Head ◽  
Pressure Perturbations

The interaction of a convected wake with a compressor blade boundary-layer was investigated. Measurements within a single-stage compressor were made using an endoscopic PIV system, a surface mounted pressure transducer, hotfilms and hotwire traverses, along with CFD simulations. The wake/leading-edge interaction was shown to lead to the formation of a thickened laminar boundary-layer, within which turbulent spots formed close to the leading-edge. The thickened boundary-layer became turbulent and propagated down the blade surface, giving rise to pressure perturbations of 7% of the inlet dynamic head in magnitude. The results indicate that wake/leading-edge interactions have a crucial role to play in the performance of compressor blades in the presence of wakes.

Experimental Evaluation of Compressor Blade Fouling

2016 ◽  
Author(s):  
Rainer Kurz ◽  
Grant Musgrove ◽  
Klaus Brun
Keyword(s):  
Boundary Layer ◽  
Gas Turbines ◽  
Blade Surface ◽  
Air Filtration ◽  
Ambient Conditions ◽  
Compressor Blades ◽  
Performance Deterioration ◽  
Quantitative Results ◽  
The Impact ◽  
Dust Retention

Fouling of compressor blades is an important mechanism leading to performance deterioration in gas turbines over time. Experimental and simulation data are available for the impact of specified amounts of fouling on performance, as well as the amount of foulants entering the engine for defined air filtration systems and ambient conditions. This study provides experimental data on the amount of foulants in the air that actually stick to a blade surface for different conditions of the blade surface. Quantitative results both indicate the amount of dust as well as the distribution of dust on the airfoil, for a dry airfoil, as well as airfoils that were wet from ingested water, as well as different types of oil. The retention patterns are correlated with the boundary layer shear stress. The tests show the higher dust retention from wet surfaces compared to dry surfaces. They also provide information about the behavior of the particles after they impact on the blade surface, showing that for a certain amount of wet film thickness, the shear forces actually wash the dust downstream, and off the airfoil. Further, the effect of particle agglomeration of particles to form larger clusters was observed, which would explain the disproportional impact of very small particles on boundary layer losses.

scholarly journals Leading Edge Separation Bubbles on Turbomachine Blades

1993 ◽  
Author(s):  
R. E. Walraevens ◽  
N. A. Cumpsty
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Turbine Blades ◽  
Leading Edge ◽  
Freestream Turbulence ◽  
Compressor Blades ◽  
Pressure Distributions ◽  
Quantitative Measurements ◽  
Small Influence ◽  
Separation Bubbles

Results are presented for separation bubbles of the type which can form near the leading edges of thin compressor or turbine blades. These often occur when the incidence is such that the stagnation point is not on the nose of the aerofoil. Tests were carried out at low speed on a single aerofoil to simulate the range of conditions found on compressor blades. Both circular and elliptic shapes of leading edge were tested. Results are presented for a range of incidence, Reynolds number and turbulence intensity and scale. The principal quantitative measurements presented are the pressure distributions in the leading edge and bubble region, as well as the boundary layer properties at a fixed distance downstream where most of the flows had reattached. Reynolds number was found to have a comparatively small influence, but a raised level of freestream turbulence has a striking effect, shortening or eliminating the bubble and increasing the magnitude of the suction spike. Increased freestream turbulence also reduces the boundary layer thickness and shape parameter after the bubble. Some explanations of the processes are outlined.

Compressor Blade Boundary Layers: Part 1 — Test Facility and Measurements With No Incident Wakes

1989 ◽  
Author(s):  
Y. Dong ◽  
N. A. Cumpsty
Keyword(s):  
Boundary Layer ◽  
Boundary Layers ◽  
Compressor Blade ◽  
Test Facility ◽  
Compressor Blades ◽  
Present Part

The boundary layers on compressor blades are sensitive to the conditions at which transition occurs and transition can be affected by the convection of wakes from upstream blade rows. This paper and its companion, Part 2 by the same authors, describes an experiment to study the effect of the moving wakes on the boundary layer of a compressor blade. This paper describes the background and facility devised to introduce wakes together with results obtained on the blades in tests without the wakes present. Part II describes the measurements made with the wakes present and presents conclusions for the whole project. Further details of all aspects of the work can be found in Dong (1988).

On Line Compressor Washing on Large Frame 9-FA Gas Turbines: Erosion on R0 Compressor Blade Leading Edge — Field Performance With a Novel On Line Wash System

2007 ◽  
Author(s):  
Jos Oosting ◽  
Klaas Boonstra ◽  
Annemarie de Haan ◽  
Dick van der Vecht ◽  
Jean-Pierre Stalder ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Leading Edge ◽  
Compressor Blade ◽  
Cleaning Efficiency ◽  
Compressor Blades ◽  
Erosion Risk ◽  
Plant Operator ◽  
On Line ◽  
Blade Leading Edge

On line compressor washing is an established practice amid gas turbine operators. Among these operators is the Netherlands Division of Electrabel who is operating at Eemshaven 5 x GE Frame 9-FA units since 1995. The plant operator used to perform routinely a daily on line wash and a single off line wash every year at shut down of the units for the annual inspection or maintenance outage. The on line water wash (OLWW) systems installed on these 5 engines are of the Turbotect Mk1 nozzle design and were originally procured and supplied by the OEM. To our knowledge, all other manufactured gas turbines in the 7/9-FA fleet are equipped with the OEMs’ own engineered OLWW nozzle systems. The OLWW regime of washing was reduced in June 2001 upon receipt of a recommendation by the OEM to inspect the first stages of the compressor for erosion marks. This recommendation was issued because some events have lead to investigation on erosion issues which materialized in the R0 (first stage rotor) compressor blades in some engines of the 7/9-FA fleet operating with the OEM OLWW system and resulting from frequent compressor wash routine, and/or from water ingestion used in power augmentation. Likewise, during the same time, some gas turbines at Eemscentrale had undergone their first major overhaul which allowed the compressor first row blading to be examined for signs of erosion. It was found that only minor erosion at the R0 blade leading edge had occurred over more than seven years of operation, during which period a daily on line wash had been performed. However, because of the erosion concerns among the 7/9-FA fleet and the OEM-recommended frequent inspections and measures to mitigate the rate of erosion due to droplet impingement, Electrabel investigated independently for a way of further reducing the erosion rate while maintaining on line washing over the lifetime of the gas turbine and improving the cleaning efficiency. To this effect, the OLWW system on unit EC-6 was upgraded in June 2004 with a new on line nozzle system specifically developed for use in large gas turbines. This paper presents the investigation results after some 24 months of operation and routine on line compressor washing. The Turbotect Mk3 OLWW nozzle system demonstrated and confirmed that it is contributing to mitigate the erosion risk on the R0 compressor blade leading edge, and in turn to decrease the number of blending operations over the life time of the R0 compressor blades. This nozzle designed for on line compressor cleaning of large gas turbines achieved a substantially improved cleaning effectiveness, respectively a lower rate in power degradation, by approx. 30 to 40% as compared to the current in use Mk1 OLWW nozzle system.

Experimental Evaluation of Compressor Blade Fouling

2016 ◽  
Vol 139 (3) ◽  
Author(s):  
Rainer Kurz ◽  
Grant Musgrove ◽  
Klaus Brun
Keyword(s):  
Boundary Layer ◽  
Gas Turbines ◽  
Blade Surface ◽  
Air Filtration ◽  
Ambient Conditions ◽  
Compressor Blades ◽  
Performance Deterioration ◽  
Quantitative Results ◽  
The Impact ◽  
Dust Retention

Fouling of compressor blades is an important mechanism leading to performance deterioration in gas turbines over time. Experimental and simulation data are available for the impact of specified amounts of fouling on the performance as well as the amount of foulants entering the engine for defined air filtration systems and ambient conditions. This study provides experimental data on the amount of foulants in the air that actually stick to a blade surface for different conditions. Quantitative results both indicate the amount of dust as well as the distribution of dust on the airfoil, for a dry airfoil, and also the airfoils that were wet from ingested water, in addition to, different types of oil. The retention patterns are correlated with the boundary layer shear stress. The tests show the higher dust retention from wet surfaces compared to dry surfaces. They also provide information about the behavior of the particles after they impact on the blade surface, showing for a certain amount of wet film thickness, the shear forces actually wash the dust downstream and off the airfoil. Further, the effect of particle agglomeration of particles to form larger clusters was observed, which would explain the disproportional impact of very small particles on boundary layer losses.

Leading Edge Separation Bubbles on Turbomachine Blades

1995 ◽  
Vol 117 (1) ◽  
pp. 115-125 ◽  
Author(s):  
R. E. Walraevens ◽  
N. A. Cumpsty
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Free Stream ◽  
Turbine Blades ◽  
Leading Edge ◽  
Compressor Blades ◽  
Free Stream Turbulence ◽  
Pressure Distributions ◽  
Small Influence ◽  
Separation Bubbles

Results are presented for separation bubbles of the type that can form near the leading edges of thin compressor or turbine blades. These often occur when the incidence is such that the stagnation point is not on the nose of the aerofoil. Tests were carried out at low speed on a single aerofoil to simulate the range of conditions found on compressor blades. Both circular and elliptic shapes of leading edge were tested. Results are presented for a range of incidence, Reynolds number, and turbulence intensity and scale. The principal quantitative measurements presented are the pressure distributions in the leading edge and bubble region, as well as the boundary layer properties at a fixed distance downstream, where most of the flows had reattached. Reynolds number was found to have a comparatively small influence, but a raised level of free-stream turbulence has a striking effect, shortening or eliminating the bubble and increasing the magnitude of the suction spike. Increased free-stream turbulence also reduces the boundary layer thickness and shape parameter after the bubble. Some explanations of the processes are outlined.

scholarly journals Boundary Layer and Navier-Stokes Analysis of a NASA Controlled-Diffusion Compressor Blade

1990 ◽  
Author(s):  
Y. K. Ho ◽  
G. J. Walker ◽  
P. Stow
Keyword(s):  
Boundary Layer ◽  
Turbulence Modeling ◽  
Separation Bubble ◽  
Leading Edge ◽  
Adverse Pressure Gradient ◽  
Compressor Blade ◽  
Navier Stokes ◽  
Laminar Separation ◽  
Controlled Diffusion ◽  
Pressure Distributions

Performance calculations for a NASA controlled-diffusion compressor blade have been carried out with a coupled inviscid-boundary layer code and a time-marching Navier-Stokes solver. Comparisons with experimental test data highlight and explain the strengths and limitations of both these computational methods. The boundary layer code gives good results at and near design conditions. Loss predictions however deteriorated at off-design incidences. This is mainly due to a problem with leading edge laminar separation bubble modelling; coupled with an inability of the calculations to grow the turbulent boundary layer at a correct rate in a strong adverse pressure gradient. Navier-Stokes loss predictions on the other hand are creditable throughout the whole incidence range, except at extreme positive incidence where turbulence modeling problems similar to those of the coupled boundary layer code are observed. The main drawback for the Navier-Stokes code is the slow rate of convergence for these low Mach number cases. Plans are currently under review to address this problem. Both codes give excellent predictions of the blade surface pressure distributions for all the cases considered.

Estimation of Aircraft Engine Flight Mission Severity Caused by Erosion

2021 ◽  
pp. 1-23
Author(s):  
Tim Brandes ◽  
Christian Koch ◽  
Stephan Staudacher
Keyword(s):  
Particle Separation ◽  
Leading Edge ◽  
Aircraft Engine ◽  
Compressor Blade ◽  
Operating Point ◽  
Compressor Blades ◽  
Engine Operation ◽  
Local Flow ◽  
Engine Model ◽  
Physical Phenomena

Abstract More and more attention is being devoted to assessing severity of the engine operation for a high number of flights in a minimum of time. Compressor erosion is one of the physical phenomena contributing to this severity. Hence, an effective method is developed which allows a general judgment of the severity of engine operation with regards to compressor erosion. The shortening of the camber line at blade leading edge is selected as the parameter describing the degree of severity. The particle impingement conditions experienced by compressor blades throughout a flight mission are computed using a flight mission simulation and a non-dimensional engine model. Local flow conditions of all compressor blade rows are derived from mean line computations. A dimensional analysis of a straight through swirling annulus flow led to a simplified model of particle separation within the compressor blade rows. It turns out, that bypass ratio, bleed setting and degree of particle separation changing from operating point to operating point are significant drivers of erosion. Fan root and booster suffer less from compressor erosion than the high pressure compressor. The flight segments taxi, take-off, take-off climb, climb and cruise are significantly impacting the severity of a flight mission with regards to compressor erosion.

Compressor blade leading edges in subsonic compressible flow

2000 ◽  
Vol 214 (1) ◽  
pp. 221-242 ◽  
Author(s):  
L Tain ◽  
N. A. Cumpsty
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Mach Number ◽  
Free Stream ◽  
Separation Bubble ◽  
Leading Edge ◽  
Inviscid Flow ◽  
Compressor Blade ◽  
Free Stream Turbulence ◽  
Mach Numbers

The flow around the leading edge of a compressor blade is interesting and important because there is such a strong interaction between the viscous boundary layer flow and the inviscid flow around it. As the velocity of the inviscid flow just outside the boundary layer is increased from subsonic to supersonic, the type of viscous-inviscid interaction changes; this has important effects on the boundary layer downstream and thus on the performance of the aerofoil or blade. An investigation has been undertaken of the flow in the immediate vicinity of a simulated compressor blade leading edge for a range of inlet Mach numbers from 0.6 to 0.95. The two-dimensional aerofoil used has a circular leading edge on the front of a flat aerofoil. The incidence, Reynolds number and level of free-stream turbulence have been varied. Measurements include the static pressure around the leading edge and downstream and the boundary layer profile far enough downstream for the leading edge bubble to have reattached. Schlieren pictures were also obtained. The flow around the leading edge becomes supersonic when the inlet Mach number is 0.7 for the zero-incidence case; for an inlet Mach number of 0.95 the peak Mach number was approximately 1.7. The pattern of flow around the leading edge alters as the Mach number is increased, and at the highest Mach number tested here the laminar separation bubble is removed. Positive incidence, raised free-stream turbulence or increased Reynolds number at intermediate inlet Mach numbers tended to promote flow patterns similar to those seen at the highest inlet Mach number. Both increased free-stream turbulence and increased Reynolds number, for the same Mach number and incidence, produced thinner shear layers including a thinner boundary layer well downstream. The measurements were supported by calculations using the MSES code (the single aerofoil version of the MISES code); the calculations were helpful in interpreting the measured results and were demonstrated to be accurate enough to be used for design purposes.

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