Experimental Investigation of Total Pressure Loss Development in a Highly Loaded Low-Pressure Turbine Cascade

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Philip Bear ◽  
Mitch Wolff ◽  
Andreas Gross ◽  
Christopher R. Marks ◽  
Rolf Sondergaard
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Pressure Loss ◽  
Total Pressure ◽  
Low Pressure ◽  
Total Pressure Loss ◽  
Low Pressure Turbine ◽  
Pressure Transport ◽  
Secondary Flow Field ◽  
Highly Loaded

Improvements in turbine design methods have resulted in the development of blade profiles with both high lift and good Reynolds lapse characteristics. An increase in aerodynamic loading of blades in the low-pressure turbine (LPT) section of aircraft gas turbine engines has the potential to reduce engine weight or increase power extraction. Increased blade loading means larger pressure gradients and increased secondary losses near the endwall. Prior work has emphasized the importance of reducing these losses if highly loaded blades are to be utilized. The present study analyzes the secondary flow field of the front-loaded low-pressure turbine blade designated L2F with and without blade profile contouring at the junction of the blade and endwall. The current work explores the loss production mechanisms inside the LPT cascade. Stereoscopic particle image velocimetry (SPIV) data and total pressure loss data are used to describe the secondary flow field. The flow is analyzed in terms of total pressure loss, vorticity, Q-Criterion, turbulent kinetic energy, and turbulence production. The flow description is then expanded upon using an implicit large eddy simulation (ILES) of the flow field. The Reynolds-averaged Navier–Stokes (RANS) momentum equations contain terms with pressure derivatives. With some manipulation, these equations can be rearranged to form an equation for the change in total pressure along a streamline as a function of velocity only. After simplifying for the flow field in question, the equation can be interpreted as the total pressure transport along a streamline. A comparison of the total pressure transport calculated from the velocity components and the total pressure loss is presented and discussed. Peak values of total pressure transport overlap peak values of total pressure loss through and downstream of the passage suggesting that the total pressure transport is a useful tool for localizing and predicting loss origins and loss development using velocity data which can be obtained nonintrusively.

Experimental Investigation of Total Pressure Loss Development in a Highly Loaded Low Pressure Turbine Cascade

2017 ◽  
Author(s):  
Philip Bear ◽  
Mitch Wolff ◽  
Andreas Gross ◽  
Christopher R. Marks ◽  
Rolf Sondergaard
Keyword(s):  
Flow Field ◽  
Pressure Loss ◽  
Total Pressure ◽  
Low Pressure ◽  
Total Pressure Loss ◽  
Turbine Cascade ◽  
Low Pressure Turbine ◽  
Pressure Transport ◽  
Secondary Flow Field ◽  
Highly Loaded

Improvements in turbine design methods have resulted in the development of blade profiles with both high lift and good Reynolds lapse characteristics. An increase in aerodynamic loading of blades in the low pressure turbine section of aircraft gas turbine engines has the potential to reduce engine weight or increase power extraction. Increased blade loading means larger pressure gradients and increased secondary losses near the endwall. Prior work has emphasized the importance of reducing these losses if highly loaded blades are to be utilized. The present study analyzes the secondary flow field of the front-loaded low-pressure turbine blade designated L2F with and without blade profile contouring at the junction of the blade and endwall. The current work explores the loss production mechanisms inside the low pressure turbine cascade. Stereoscopic particle image velocimetry data and total pressure loss data are used to describe the secondary flow field. The flow is analyzed in terms of total pressure loss, vorticity, Q-Criterion, turbulent kinetic energy and turbulence production. The flow description is then expanded upon using an Implicit Large Eddy Simulation of the flow field. The RANS momentum equations contain terms with pressure derivatives. With some manipulation these equations can be rearranged to form an equation for the change in total pressure along a streamline as a function of velocity only. After simplifying for the flow field in question the equation can be interpreted as the total pressure transport along a streamline. A comparison of the total pressure transport calculated from the velocity components and the total pressure loss is presented and discussed. Peak values of total pressure transport overlap peak values of total pressure loss through and downstream of the passage suggesting that total pressure transport is a useful tool for localizing and predicting loss origins and loss development using velocity data which can be obtained non-intrusively.

Navier-Stokes Analysis of the Pump Flow Field of an Automotive Torque Converter

1995 ◽  
Vol 117 (1) ◽  
pp. 116-122 ◽  
Author(s):  
R. R. By ◽  
R. Kunz ◽  
B. Lakshminarayana
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Pressure Loss ◽  
Total Pressure ◽  
Three Dimensional ◽  
Torque Converter ◽  
Major Effect ◽  
Total Pressure Loss ◽  
Navier Stokes ◽  
Secondary Flow Field

A three-dimensional, incompressible, viscous flow code, developed by NASA AMES (INS3D) using the pseudo-compressibility method, is modified for torque converter flow field computations. The code is used to predict the velocity and pressure fields in the pump of an automotive torque converter. Numerical results are compared to measured static pressure and velocity distributions. Results show that: 1) the code can fairly well predict the Cp distribution, the distribution of the through-flow velocity, and the secondary flow field, 2) pump rotation has a major effect on the secondary flow field and on the mass-averaged total pressure loss, and 3) inlet velocity profiles have a profound effect on the mass-averaged total pressure loss.

The Influence of Different Rim Seal Geometries on Hot-Gas Ingestion and Total Pressure Loss in a Low-Pressure Turbine

2010 ◽  
Author(s):  
P. Schuler ◽  
W. Kurz ◽  
K. Dullenkopf ◽  
H.-J. Bauer
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Gas Flow ◽  
Low Pressure ◽  
Total Pressure Loss ◽  
Pressure Loss Coefficient ◽  
Low Pressure Turbine ◽  
Hot Gas ◽  
Flow Through ◽  
Total Pressure Loss Coefficient

In order to prevent hot-gas ingestion into the rotating turbo machine’s inside, rim seals are used in the cavities located between stator- and rotor-disc. The sealing flow ejected through the rim seal interacts with the boundary layer of the main gas flow, thus playing a significant role in the formation of secondary flows which are a major contributor to aerodynamic losses in turbine passages. Investigations performed in the EU project MAGPI concentrate on the interaction between the sealing flow and the main gas flow and in particular on the influence of different rim seal geometries regarding the loss-mechanism in a low-pressure turbine passage. Within the CFD work reported in this paper static simulations of one typical low-pressure turbine passage were conducted containing two different rim seal geometries, respectively. The sealing flow through the rim seal had an azimuthal velocity component and its rate has been varied between 0–1% of the main gas flow. The modular design of the computational domain provided the easy exchange of the rim seal geometry without remeshing the main gas flow. This allowed assessing the appearing effects only to the change of rim seal geometry. The results of this work agree with well-known secondary flow phenomena inside a turbine passage and reveal the impact of the different rim seal geometries on hot-gas ingestion and aerodynamic losses quantified by a total pressure loss coefficient along the turbine blade. While the simple axial gap geometry suffers considerable hot-gas ingestion upstream the blade leading edge, the compound geometry implying an axial overlapping presents a more promising prevention against hot-gas ingestion. Furthermore, the effect of rim seals on the turbine passage flow field has been identified applying adequate flow visualisation techniques. As a result of the favourable conduction of sealing flow through the compound geometry, the boundary layer is less lifted by the ejected sealing flow, thus resulting in a comparatively reduced total pressure loss coefficient over the turbine blade.

Influence of a Novel 3D Leading Edge Geometry on the Aerodynamic Performance of Low Pressure Turbine Blade Cascade Vanes

2014 ◽  
Author(s):  
A. Asghar ◽  
W. D. E. Allan ◽  
M. LaViolette ◽  
R. Woodason
Keyword(s):  
Turbine Blade ◽  
Pressure Loss ◽  
Total Pressure ◽  
Separated Flow ◽  
Leading Edge ◽  
Low Pressure ◽  
Aerodynamic Performance ◽  
Total Pressure Loss ◽  
Low Pressure Turbine ◽  
Edge Geometry

This paper addresses the issue of aerodynamic performance of a novel 3D leading edge modification to a reference low pressure turbine blade. An analysis of tubercles found in nature and used in some engineering applications was employed to synthesize new leading edge geometry. A sinusoidal wave-like geometry characterized by wavelength and amplitude was used to modify the leading edge along the span of a 2D profile, rendering a 3D blade shape. The rationale behind using the sinusoidal leading edge was that they induce streamwise vortices at the leading edge which influence the separation behaviour downstream. Surface pressure and total pressure measurements were made in experiments on a cascade rig. These were complemented with computational fluid dynamics studies where flow visualization was also made from numerical results. The tests were carried out at low Reynolds number of 5.5 × 104 on a well-researched profile representative of conventional low pressure turbine profiles. The performance of the new 3D leading edge geometries was compared against the reference blade revealing a downstream shift in separated flow for the LE tubercle blades; however, total pressure loss reduction was not conclusively substantiated for the blade with leading edge tubercles when compared with the performance of the baseline blade. Factors contributing to the total pressure loss are discussed.

Secondary Flow Loss Reduction Through Blowing for a High-Lift Front-Loaded Low Pressure Turbine Cascade

2012 ◽  
Vol 135 (2) ◽  
Author(s):  
Stuart I. Benton ◽  
Jeffrey P. Bons ◽  
Rolf Sondergaard
Keyword(s):  
Reynolds Number ◽  
Pressure Loss ◽  
Total Pressure ◽  
Control Method ◽  
Low Pressure ◽  
Total Pressure Loss ◽  
Suction Surface ◽  
High Lift ◽  
Blade Loading ◽  
Low Pressure Turbine

Efforts to increase individual blade loading in the low pressure turbine have resulted in blade geometries optimized for midspan performance. Many researchers have shown that increased blade loading and a front-loaded pressure distribution each separately contribute to increased losses in the endwall region. A detailed investigation of the baseline endwall flow of the L2F profile, which is a high-lift front loaded profile, is performed. In-plane velocity vectors and total pressure loss maps are obtained in five planes oriented normal to the blade surface for three Reynolds numbers. A row of pitched and skewed jets are introduced near the endwall on the suction surface of the blade. The flow control method is evaluated for four momentum coefficients at the high Reynolds number, with a maximum reduction of 42% in the area averaged total pressure loss coefficient. The same blade is also fitted with midspan vortex-generator jets and is tested at a Reynolds number of 20,000, resulting in a 21% reduction in the area averaged total pressure loss.

On the Unsteady Formation of Secondary Flow Inside a Rotating Turbine Blade Passage

2013 ◽  
Vol 136 (6) ◽  
Author(s):  
C. M. Schneider ◽  
D. Schrack ◽  
M. Kuerner ◽  
M. G. Rose ◽  
S. Staudacher ◽  
...  
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Guide Vane ◽  
Low Pressure ◽  
Flow Structures ◽  
Low Pressure Turbine ◽  
Interaction Processes ◽  
Nozzle Guide Vane ◽  
Nozzle Guide ◽  
Secondary Flow Field

This paper addresses the unsteady formation of secondary flow structures inside a turbine rotor passage. The first stage of a two-stage, low-pressure turbine is investigated at a Reynolds Number of 75,000. The design represents the third and the fourth stages of an engine-representative, low-pressure turbine. The flow field inside the rotor passage is discussed in the relative frame of reference using the streamwise vorticity. A multistage unsteady Reynolds-averaged Navier–Stokes (URANS) prediction provides the time-resolved data set required. It is supported by steady and unsteady area traverse data acquired with five-hole probes and dual-film probes at rotor inlet and exit. The unsteady analysis reveals a nonclassical secondary flow field inside the rotor passage of this turbine. The secondary flow field is dominated by flow structures related to the upstream nozzle guide vane. The interaction processes at hub and casing appear to be mirror images and have characteristic forms in time and space. Distinct loss zones are identified, which are associated with vane-rotor interaction processes. The distribution of the measured isentropic stage efficiency at rotor exit is shown, which is reduced significantly by the secondary flow structures discussed. Their impacts on the steady as well as on the unsteady angle characteristics at rotor exit are presented to address the influences on the inlet conditions of the downstream nozzle guide vane. It is concluded that URANS should improve the optimization of rotor geometry and rotor loss can be controlled, to a degree, by nozzle guide vane (NGV) design.

Experimental Investigation of the Effects of Waveform Tip Injection in a Low Pressure Turbine Cascade

2012 ◽  
Author(s):  
Bayram Mercan ◽  
Eda Doğan ◽  
Yashar Ostovan ◽  
Oğuz Uzol
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Flow Direction ◽  
Low Pressure ◽  
Total Pressure Loss ◽  
Wake Flow ◽  
Injection Technique ◽  
Low Pressure Turbine ◽  
Passage Vortex ◽  
Tip Injection

This paper presents the results of an experimental study that investigates the effects of uniform/waveform tip injection along the camberline on the total pressure loss and wake flow characteristics downstream of a row of Low Pressure Turbine (LPT) blades. The experiments are performed in a low speed cascade facility. This injection technique involves spanwise jets at the tip that are issued from a series of holes along the camber line normal to the freestream flow direction. The injection mass flow rate from each hole is individually controlled using computer driven solenoid valves and therefore the flow injection geometrical pattern at the tip can be adjusted to any desired waveform shape, and can be uniform as well as waveform along the camber. Measurements involve Kiel probe traverses for different injection scenarios 0.5 axial chords downstream of the blades as well as Time-Resolved Particle Image Velocimetry (Tr-PIV) measurements at different spanwise locations. Results show that tip injection significantly reduces the total pressure loss levels created by the leakage vortex. Highest overall loss reduction occurs in the case of reversed-triangular injection. The least effective waveform is triangular injection. Loss levels do not seem to get reduced significantly in the passage vortex zone. Velocity, vorticity and turbulence fields created by the passage and leakage vortices get influenced by tip injection. There is significant reduction in the extent of the low momentum zone of the leakage vortex with injection. This effect is much less pronounced for the passage vortex. On the other hand, complex flow patterns are observed within the passage vortex, especially in the case of reversed-triangular injection, such as a possible embedded vortical structure along the passage vortex core, which creates double peaks in the velocity and turbulent kinetic energy fields and complex patterns in Reynolds shear stress.

On the Unsteady Formation of Secondary Flow Inside a Rotating Turbine Blade Passage

2013 ◽  
Author(s):  
C. M. Schneider ◽  
D. Schrack ◽  
M. Kuerner ◽  
M. G. Rose ◽  
S. Staudacher ◽  
...  
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Guide Vane ◽  
Low Pressure ◽  
Flow Structures ◽  
Low Pressure Turbine ◽  
Interaction Processes ◽  
Nozzle Guide Vane ◽  
Nozzle Guide ◽  
Secondary Flow Field

This paper addresses the unsteady formation of secondary flow structures inside a turbine rotor passage. The first stage of a two-stage low pressure turbine is investigated at a Reynolds Number of 75 000. The design represents the third and the fourth stages of an engine representative low pressure turbine. The flow field inside the rotor passage is discussed in the relative frame of reference using the streamwise vorticity. A multi-stage URANS prediction provides the time-resolved data set required. It is supported by steady and unsteady area traverse data acquired with five-hole probes and dual-film probes at rotor inlet and exit. The unsteady analysis reveals a non-classical secondary flow field inside the rotor passage of this turbine. The secondary flow field is dominated by flow structures related to the upstream nozzle guide vane. The interaction processes at hub and casing appear to be mirror images and have characteristic forms in time and space. Distinct loss zones are identified which are associated with vane-rotor interaction processes. The distribution of the measured isentropic stage efficiency at rotor exit is shown which is reduced significantly by the secondary flow structures discussed. Their impacts on the steady as well as on the unsteady angle characteristics at rotor exit are presented to address the influences on the inlet conditions of the downstream nozzle guide vane.

Secondary Flow Loss Reduction Through Blowing for a High-Lift Front-Loaded Low Pressure Turbine Cascade

2012 ◽  
Author(s):  
Stuart Benton ◽  
Jeffrey P. Bons ◽  
Rolf Sondergaard
Keyword(s):  
Reynolds Number ◽  
Pressure Loss ◽  
Total Pressure ◽  
Control Method ◽  
Low Pressure ◽  
Total Pressure Loss ◽  
Suction Surface ◽  
High Lift ◽  
Blade Loading ◽  
Low Pressure Turbine

Efforts to increase individual blade loading in the low pressure turbine have resulted in blade geometries optimized for midspan performance. Many researchers have shown that increased blade loading and a front-loaded pressure distribution each contribute separately to increased losses in the endwall region. A detailed investigation is performed of the baseline endwall flow of the L2F profile, a high-lift, front loaded profile. In-plane velocity vectors and total pressure loss maps are obtained in five planes oriented normal to the blade surface, for three Reynolds numbers. A row of pitched and skewed jets are introduced near the endwall on the suction surface of the blade. The flow control method is evaluated for four momentum coefficients at the high Reynolds number, with a maximum reduction of 42% in the area averaged total pressure loss coefficient. The same blade is also fitted with midspan vortex-generator jets and is tested at a Reynolds number of 20,000, resulting in a 21% reduction in area averaged total pressure loss.

Second Vane Total Pressure Loss Due to Endwall Iceform Contouring

2008 ◽  
Author(s):  
Ronald S. LaFleur
Keyword(s):  
Heat Transfer ◽  
Secondary Flow ◽  
Pressure Loss ◽  
Total Pressure ◽  
Aerodynamic Drag ◽  
Pressure Coefficient ◽  
Secondary Flows ◽  
Total Pressure Loss ◽  
Surface Shape ◽  
Exit Plane

The iceformation design method generates an endwall contour, altering the secondary flows that produce elevated endwall heat transfer load and total pressure losses. Iceformation is an analog to regions of metal melting where a hot fluid alters the isothermal surface shape of a part as it is maintained by a cooling fluid. The passage flow, heat transfer and geometry evolve together under the constraints of flow and thermal boundary conditions. The iceformation concept is not media dependent and can be used in analogous flows and materials to evolve novel boundary shapes. In the past, this method has been shown to reduce aerodynamic drag and total pressure loss in flows such as diffusers and cylinder/endwall junctures. A prior paper [1] showed that the Reynolds number matched iceform geometry had a 24% lower average endwall heat transfer than the rotationally symmetric endwall geometry of the Energy Efficiency Engine (E3). Comparisons were made between three endwall geometries: the ‘iceform’, the ‘E3’ and the ‘flat’ as a limiting case of the endwall design space. This paper adds to the iceformation design record by reporting the endwall aerodynamic performances. Second vane exit flow velocities and pressures were measured using an automated 2-D traverse of a 1.2 mm diameter five-hole probe. Exit plane maps for the three endwall geometries are presented showing the details of the total pressure coefficient contours and the velocity vectors. The formation of secondary flow vortices is shown in the exit plane and this results in an impact on exit plane total pressure loss distribution, off-design over- and under-turning of the exit flow. The exit plane contours are integrated to form overall measures of the total pressure loss. Relative to the E3 endwall, the iceform endwall has a slightly higher total pressure loss attributed to higher dissipation of the secondary flow within the passage. The iceform endwall has a closer-to-design exit flow pattern than the E3 endwall.

Sign in / Sign up

Export Citation Format

Share Document