Total Pressure Losses in Rotor Systems With Radial Inflow

2000 ◽  
Author(s):  
D. Brillert ◽  
D. Lieser ◽  
A. W. Reichert ◽  
H. Simon
Keyword(s):  
Gas Turbines ◽  
Total Pressure ◽  
Simple Calculation ◽  
Calculation Model ◽  
Navier Stokes ◽  
Test Bed ◽  
Rotor Systems ◽  
Pressure Losses ◽  
Flow Phenomena ◽  
Cooling Air

Gas turbines with a splined-disc rotor design allow the compressor bleed pressure to be adapted precisely to the requirements of rotor cooling air systems in which the cooling air is routed through the spaced between the rotating discs. Calculation of such flows is extremely difficult; particularly so if the flow is directed radially inward. In such cases the circumferential component of the absolute velocity can be very high and can thus lead to pronounced total pressure losses. The paper gives a brief description of the flow phenomena, and details in the calculation methods cited in the literature. Navier–Stokes calculations were carried out for the flow through a model test bed engine. The results are compared with experimental data. A simple calculation model is discussed and its result compared with test data. The model predicts the flow pattern more accurately than the Navier-Stokes calculations, and this paper shows that the simple model can be improved further.

Strut Influences Within a Diffusing Annular S-Shaped Duct

1998 ◽  
Author(s):  
G. Norris ◽  
R. G. Dominy ◽  
A. D. Smith
Keyword(s):  
Gas Turbines ◽  
Total Pressure ◽  
Pressure Measurements ◽  
Computational Results ◽  
Flow Conditions ◽  
Test Rig ◽  
General Flow ◽  
Flow Phenomena ◽  
Physical Features ◽  
Cooling Air

Inter-turbine diffusers which provide flow continuity between the H.P. and L.P. turbines, are increasingly important within modern aero gas turbines, as the fan and hence L.P. turbine diameters increase with thrust. These gas turbines rely on struts within the inter-turbine diffuser to serve both as load bearing supports for inner spools and as passages to supply the engine with vital services such as cooling air and lubrication oil. Experimental measurements have been made on a representative test rig in order to investigate the affect of a ring of struts on both the local and general flow phenomena as well as investigating their effect on overall duct performance. More realistic flow conditions are made available by the use of inlet wakes representative of those created by an upstream turbine row. Measurements include static pressures on the strut and duct surfaces along with velocity and total pressure measurements at various axial locations. From these results calculations of total pressure loss have been made. The experimental results presented in this paper have been used to validate C.F.D. flow predictions on the duct with and without struts. The computational results included, capture the main physical features of the flow but clear limitations are observed and are discussed in this paper.

scholarly journals Impact of a Cooled Cooling Air System on the External Aerodynamics of a Gas Turbine Combustion System

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
A. Duncan Walker ◽  
Bharat Koli ◽  
Liang Guo ◽  
Peter Beecroft ◽  
Marco Zedda
Keyword(s):  
Gas Turbines ◽  
Pressure Loss ◽  
Total Pressure ◽  
Outer Wall ◽  
Total Pressure Loss ◽  
Test Facility ◽  
Combustion System ◽  
Air System ◽  
External Aerodynamics ◽  
Cooling Air

To manage the increasing turbine temperatures of future gas turbines a cooled cooling air system has been proposed. In such a system some of the compressor efflux is diverted for additional cooling in a heat exchanger (HX) located in the bypass duct. The cooled air must then be returned, across the main gas path, to the engine core for use in component cooling. One option is do this within the combustor module and two methods are examined in the current paper; via simple transfer pipes within the dump region or via radial struts in the prediffuser. This paper presents an experimental investigation to examine the aerodynamic impact these have on the combustion system external aerodynamics. This included the use of a fully annular, isothermal test facility incorporating a bespoke 1.5 stage axial compressor, engine representative outlet guide vanes (OGVs), prediffuser, and combustor geometry. Area traverses of a miniature five-hole probe were conducted at various locations within the combustion system providing information on both flow uniformity and total pressure loss. The results show that, compared to a datum configuration, the addition of transfer pipes had minimal aerodynamic impact in terms of flow structure, distribution, and total pressure loss. However, the inclusion of prediffuser struts had a notable impact increasing the prediffuser loss by a third and consequently the overall system loss by an unacceptable 40%. Inclusion of a hybrid prediffuser with the cooled cooling air (CCA) bleed located on the prediffuser outer wall enabled an increase of the prediffuser area ratio with the result that the system loss could be returned to that of the datum level.

Advanced Rayleigh Pressure Loss Model for High-Swirl Combustion in a Rotating Combustion Chamber

2015 ◽  
Author(s):  
Andreas Penkner ◽  
Peter Jeschke
Keyword(s):  
Heat Transfer ◽  
Combustion Chamber ◽  
Dynamic Model ◽  
Gas Turbines ◽  
Total Pressure ◽  
Fluid Flows ◽  
Pressure Losses ◽  
Gas Dynamic ◽  
Swirl Combustion ◽  
Transfer Problems

This paper considers the effect of excessive total pressure losses for heat transfer problems in fluid flows with a high circumferential swirl component. At RWTH Aachen University, a novel gas generator concept is under research. This design avoids some disadvantages of small gas turbines and uses a rotating combustion chamber. During the pre-design of the rotating combustion chamber using CFD tools, unexpected high total pressure losses were detected. To analyze this unknown phenomenon, a gas-dynamic model of the rotating combustion chamber has been developed to explain the unexpected high Rayleigh pressure losses. The derivation of the gas-dynamic model, the physical phenomenon related to the high total pressure losses in high-swirl combustion, the influencing factors, as well as thermodynamic interpretation of the Rayleigh pressure losses, are presented in this paper. In addition, the CFD results are validated by the gas-dynamic model derived. The results presented here are of possible interest for a wide range of applications, since these fundamental findings can be transferred to all heat transfer problems in fluid flows with a high circumferential swirl component.

Aerodynamic Loss Characteristics of a Turbine Blade With Trailing Edge Coolant Ejection: Part 2 — External Aerodynamics, Total Pressure Losses and Predictions

2000 ◽  
Author(s):  
Oğuz Uzol ◽  
Cengiz Camcı
Keyword(s):  
Turbine Blade ◽  
Total Pressure ◽  
Stokes Equations ◽  
Threshold Level ◽  
Reynolds Stress Model ◽  
Navier Stokes ◽  
Main Stream ◽  
Trailing Edge ◽  
Aerodynamic Loss ◽  
Pressure Losses

Investigation of the internal fluid mechanic losses for a turbine blade with trailing edge coolant ejection was presented in Uzol, Camci and Glezer (2000). The current study is a detailed experimental investigation of the external subsonic flowfield near the trailing edge and the investigation of the external aerodynamic loss characteristics of the turbine blade with trailing edge coolant ejection system. Particle Image Velocimetry experiments and total pressure surveys in the near wake of the blade are conducted for two different Reynolds Numbers and four different ejection rates. Two different trailing edge configurations with different cut-back lengths are also investigated. Numerical simulations of the flowfield are also performed for qualitative flow visualization purposes. Two dimensional, incompressible and steady solutions of Reynolds Averaged Navier Stokes equations are obtained. A two equation standard k-ε turbulence model coupled with an Algebraic Reynolds Stress Model is used for the simulation of the turbulent flowfield. The results show that the aerodynamic penalty levels in the wake region near the trailing edge are increased due to the mixing of the coolant and main stream flows for 0 to 3% ejection rates. However after a threshold level (5% ejection rate), the ejected coolant flow has enough momentum to fill the wake of the blade which in turn results in a decrease in the aerodynamic penalty levels.

Experimental Study on Pressure Losses in Circular Orifices for the Application in Internal Cooling Systems

2014 ◽  
Vol 137 (3) ◽  
Author(s):  
Christian Binder ◽  
Mats Kinell ◽  
Esa Utriainen ◽  
Daniel Eriksson ◽  
Mehdi Bahador ◽  
...  
Keyword(s):  
Gas Turbines ◽  
Discharge Coefficient ◽  
Air Flow ◽  
Internal Cooling ◽  
Cooling Systems ◽  
Pressure Losses ◽  
Flow Through ◽  
Cooling Air Flow ◽  
New Phenomena ◽  
Cooling Air

The cooling air flow in a gas turbine is governed by the flow through its internal passages and controlled by restrictors such as circular orifices. If the cooling air flow is incorrectly controlled, the durability and mechanical integrity of the whole turbine may be affected. Consequently, a good understanding of the orifices in the internal passages is important. This study presents experimental results for a range of pressure ratios and length-to-diameter ratios common in gas turbines including even very small pressure ratios. Additionally, the chamfer depth at the inlet was also varied. The results of the chamfer depth variation confirmed its beneficial influence on decreasing pressure losses. Moreover, important effects were noted when varying more than one parameter at a time. Besides earlier mentioned hysteresis at the threshold of choking, new phenomena were observed, e.g., a rise of the discharge coefficient for certain pressure and length-to-diameter ratios. A correlation for the discharge coefficient was attained based on the new experimental data with a generally lower error than previous studies.

Large eddy simulation applications in gas turbines

2009 ◽  
Vol 367 (1899) ◽  
pp. 2827-2838 ◽  
Author(s):  
Kevin Menzies
Keyword(s):  
Large Eddy Simulation ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Complex Geometry ◽  
Navier Stokes ◽  
Eddy Simulation ◽  
Wide Range ◽  
Large Eddy ◽  
Design Cycle ◽  
Flow Phenomena

The gas turbine presents significant challenges to any computational fluid dynamics techniques. The combination of a wide range of flow phenomena with complex geometry is difficult to model in the context of Reynolds-averaged Navier–Stokes (RANS) solvers. We review the potential for large eddy simulation (LES) in modelling the flow in the different components of the gas turbine during a practical engineering design cycle. We show that while LES has demonstrated considerable promise for reliable prediction of many flows in the engine that are difficult for RANS it is not a panacea and considerable application challenges remain. However, for many flows, especially those dominated by shear layer mixing such as in combustion chambers and exhausts, LES has demonstrated a clear superiority over RANS for moderately complex geometries although at significantly higher cost which will remain an issue in making the calculations relevant within the design cycle.

Investigations of Dust Separation in a Gasturbine Pre-Swirl Cooling Air System Using New, Enhanced Simulation Methods

2005 ◽  
Author(s):  
O. Schneider ◽  
H. J. Dohmen ◽  
F. K. Benra ◽  
K. Jarzombek
Keyword(s):  
Film Cooling ◽  
Gas Turbines ◽  
Navier Stokes ◽  
Flow Conditions ◽  
System A ◽  
Air System ◽  
Physical Effects ◽  
Film Cooling Holes ◽  
Cooling Air ◽  
First Time

In the last years the leading manufacturers enhanced the performance of heavy-duty gas turbines rapidly. With the increasing amount of cooling air passing the internal air system, a rising amount of air borne particles are transported to the film cooling holes at the turbine blade surface. Due to the size, these holes are critical for blockage. Experience with gas turbines during operation showed a complex interaction of cooling air under different flow conditions and its particle load. In this paper the results of a new Lagrange-Tracking simulation algorithm based on 3D-Navier-Stokes flow solution are shown for the first time. Compared to previously shown simulations the algorithm is enhanced by models, taking additional, relevant physical effects into account. The new simulation results are compared to experimental results and former simulations.

Numerical Investigation of the Effect of an Axial Pre-Swirl Nozzle With a Radial Angle in a Pre-Swirl Rotor-Stator System

2021 ◽  
Author(s):  
Gang Zhao ◽  
Shuiting Ding ◽  
Tian Qiu ◽  
Shenghui Zhang
Keyword(s):  
Gas Turbines ◽  
Pressure Loss ◽  
Total Pressure ◽  
Discharge Coefficient ◽  
Pressure Ratio ◽  
Temperature Drop ◽  
Tangential Velocity ◽  
Total Pressure Loss ◽  
Adiabatic Effectiveness ◽  
Cooling Air

Abstract Pre-swirl nozzles are often used in gas turbines to deliver the cooling air to the turbine blades. The static axial nozzles swirl the cooling air in the direction of rotation of the turbine disk, thereby reducing the relative total temperature of the air. Most studies about nozzles focus on its shape, radial location, tangential angle to reduce the pressure loss and increase the temperature drop of the pre-swirl system, but few of them consider the benefit of a radial angle of nozzles. This paper investigated numerically the performance of a pre-swirl system whose pre-swirl nozzles have a radial angle. Six radial angles are selected to study the flow dynamics of a direct-transfer pre-swirl system in terms of the total pressure loss coefficient of the pre-swirl cavity, the discharge coefficient of the receiver holes, and the adiabatic effectiveness. It is shown that the nozzles with radial angles can adjust the tangential velocity and radial velocity and thus can influence the performance of a pre-swirl system. There is a lowerest value of total pressure loss in pre-swirl cavity, that is α = 90°, which can hardly be influenced by the radial angle of nozzle and pressure ratio π. For a specific swirl ratio β∞, there exists an optimal αopt where the discharge coefficient of receiver hole is maximum. Moreover, αopt decreases as pressure ratio π increases. And so is the adiabatic effectiveness Θad.

scholarly journals Correlation between total pressure losses of highly loaded annular diffusers and integral stage design parameters

2018 ◽  
Vol 2 ◽  
pp. I9AB30 ◽  
Author(s):  
Dajan Mimic ◽  
Christoph Jätz ◽  
Florian Herbst
Keyword(s):  
Boundary Layer ◽  
Gas Turbines ◽  
Pressure Loss ◽  
Total Pressure ◽  
Total Pressure Loss ◽  
Pressure Recovery ◽  
Design Parameters ◽  
Pressure Losses ◽  
Tip Leakage ◽  
Highly Loaded

Diffusers convert kinetic flow energy into a rise in static pressure. This pressure recovery is the primary aerodynamic design objective for exhaust gas diffusers in power-generating steam and gas turbines. The total pressure loss is an equally important diffuser design parameter. It is strongly linked to the pressure recovery and the residual kinetic energy of the diffuser outlet flow. A reduction benefits the overall thermodynamic cycle, which requires the adjacent components of a diffuser to be included in the design process. This paper focuses on the total pressure losses in the boundary layer of a highly loaded annular diffuser. Due to its large opening angle the diffuser is susceptible to flow separation under uniform inlet conditions, which is a major source for total pressure losses. However, the unsteady tip leakage vortices of the upstream rotor, which are a source of losses, stabilise the boundary layer and prevent separation. Experiments and unsteady numerical simulation conducted show that the total pressure loss reduction caused by the delayed boundary layer separation exceed the vortex-induced losses by far. This flow interaction between the rotor and diffuser consequently decreases the overall total pressure losses. The intensity of the tip leakage vortex is linked to three rotor design parameters, namely work coefficient, flow coefficient and reduced blade-passing frequency. Based on these parameters, we propose a semi-empiric correlation to predict and evaluate the change in total pressure losses with regards to design operating conditions.

Limitations on Gas Turbine Performance Imposed by Large Turbine Cooling Flows

2000 ◽  
Author(s):  
J. H. Horlock ◽  
D. T. Watson ◽  
T. V. Jones
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Pressure Loss ◽  
Combustion Temperature ◽  
Pressure Ratio ◽  
Stagnation Temperature ◽  
Optimum Pressure ◽  
Pressure Losses ◽  
Semi Empirical ◽  
Cooling Air

Calculations of the performance of modern gas turbines usually include allowance for cooling air flow rate; assumptions are made for the amount of the cooling air bled from the compressor, as a fraction of the mainstream flow, but this fractional figure is often set in relatively arbitrary fashion. There are two essential effects of turbine blade cooling: [i] the reduction of the gas stagnation temperature at exit from the combustion chamber [entry to the first nozzle row] to a lower stagnation temperature at entry to the first rotor and [ii] a pressure loss resulting from mixing the cooling air with the mainstream. Similar effects occur in the following cooled blade rows. The paper reviews established methods for determining the amount of cooling air required and semi-empirical relations, for film cooled blading with thermal barrier coatings, are derived. Similarly, the pressure losses related to elements of cooling air leaving at various points round the blade surface are integrated over the whole blade. This gives another semi-empirical expression, this time for the complete mixing pressure loss in the blade row, as a function of the total cooling air used. These two relationships are then used in comprehensive calculations of the performance of a simple open-cycle gas turbine, for varying combustion temperature and pressure ratio. These calculations suggest that for maximum plant efficiency there may be a limiting combustion temperature [below that which would be set by stoichiometric combustion]. For a given combustion temperature, the optimum pressure ratio is reduced by the effect of cooling air.

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