CFD Analyses of HPT Blade Air Delivery System With and Without Impellers

2011 ◽  
Author(s):  
Charles Wu ◽  
Boris Vaisman ◽  
Kevin McCusker
Keyword(s):  
Delivery System ◽  
Pressure Loss ◽  
Aerodynamic Performance ◽  
Operating Conditions ◽  
Manufacturing Cost ◽  
Cfd Analysis ◽  
Swirl Ratio ◽  
Blade Cooling ◽  
Supply Pressure ◽  
Cooling Air

In the design of a HPT blade cooling air delivery system, sufficient supply pressure is required to guarantee HPT blades are working properly in the high temperature environment. A design goal is to set a pressure level at the blade inlet that will prevent the ingestion of gaspath air into the blades which is caused by pressure fluctuations under various operating conditions and other uncertainties. Traditional 1-D design tools are not sophisticated enough for detailed system analysis. Therefore, CFD (Computational Fluid Dynamics) analysis was utilized for designing HPT blade cooling air delivery system to guarantee meeting the supply pressure requirement. Two HPT blade air delivery systems were explored. The baseline is a cooling air delivery system without radial impellers. It provides a simplistic design at low manufacturing cost, however CFD analysis shows that the system has a larger pressure loss at the broach slot entrance and delivers low supply pressure. The alternative is a cooling air delivery system with radial impellers. CFD analysis shows that the system with impellers results in much better aerodynamic performance at the broach slots and provides high supply pressure, but comes with the price of high manufacturing cost and lower TSFC due to the parasitic drag induced by impellers. For the alternative approach, three high solidity impeller designs were analyzed. The alternative approaches analyzed had inlet angles of 0°, 30°, 90° and exit angles of 0°, respectively. Comparisons of detailed aerodynamic performance are presented in the paper. CFD simulation reveals that the source of pressure loss without impellers is caused by mismatch of the swirl ratio at broach slot entrance. CFD results show that a system with radial impellers produces a better matched swirl ratio at broach slot entrance. Radial impellers enhance aerodynamic performance and improve pressure distribution within broach slots.

CFD Investigation of Vane Nozzle and Impeller Design for HPT Blade Cooling Air Delivery System

2013 ◽  
Author(s):  
Shuqing Tian ◽  
Qin Zhang ◽  
Hui Liu
Keyword(s):  
Delivery System ◽  
Pressure Loss ◽  
Aerodynamic Performance ◽  
Blade Cooling ◽  
System Pressure ◽  
Total Temperature ◽  
Swirl Vane ◽  
Radial Outflow ◽  
Cooling Air ◽  
Main Factor

In the design of a HPT blade cooling air delivery system, sufficient supply pressure and lower relative total temperature are required to guarantee HPT blades working properly in the high temperature environment. The pre-swirl vane nozzles and the radial impellers are used in the delivery system with lower radial location of pre-swirl nozzle to achieve the requirements. In this paper, CFD analysis is utilized for designing the vane nozzles and the radial impellers. Two HPT blade cooling air delivery systems were explored. The baseline is a system without impellers, and the alternative is a system with impellers. The results show that the impeller contributes to the delivery system by pumping effectiveness thus decreasing the extracted air pressure. The parity of swirl ratio between the flow and the broach slots is a main factor that decreases the system pressure loss, which can be improved by the radial impellers. The well-designed contoured radial-impeller vane with 30° front angle and 20° trailing angle is recommended in the blade cooling air delivery system design because of its good aerodynamic performance and closely radial outflow. The cascade vane nozzle with more than 70° angle turn is recommended in the pre-swirl nozzle design. It has a good aerodynamic performance with discharge coefficient greater than 0.99 and deviation angle less than 1.3°. The well-designed radial impeller pays big contributions to the blade cooling air delivery system with 11.4% increase of the thermal effectiveness and 10.2% decrease of the pressure loss versus the system without impellers.

Pre-Swirl Cooling Air Delivery System Performance Study

2012 ◽  
Author(s):  
Roman A. Didenko ◽  
Dmitry V. Karelin ◽  
Dmitry G. Ievlev ◽  
Yuri N. Shmotin ◽  
Georgy P. Nagoga
Keyword(s):  
Delivery System ◽  
System Performance ◽  
Turbine Rotor ◽  
Operating Conditions ◽  
Cover Plate ◽  
Performance Study ◽  
Blade Cooling ◽  
Rotating Cavity ◽  
Cooling Air ◽  
Cavity Width

This paper reports the results from numerical simulations of the turbine blade cooling air delivery system performance using commercial CFD code Ansys CFX v11. Computations have been performed with variation of pre-swirl nozzle location radius, rotor-rotor rotating cavity width and the way of air transmission through the cover-plate. There are two ways of air transmission depending on the cover-plate design: through the CAO (circular array of orifices) or CAS (continuous annular slot). Computations are performed within the parameter range similar to gas-turbine engine operating conditions: 0.375<λT<0.98; 0.548<β0<2.5; 1.69·107<Reφ<2.33·107; 2.79·105<Cw<5.73·105. It has been shown that the selection of optimum radius of pre-swirl nozzle location is determined by different factors and depends on design and boundary conditions. The rotor-rotor rotating cavity width does not affect delivery system performances and is selected by a designer based on the constructional necessity, strength, weight and dynamic behavior of the turbine rotor. Rotating orifices reduce the swirl ratio βb before the blade cooling rim slot reduce adiabatic effectiveness Θ and increase loss coefficient ζ.

Flow and Heat Transfer in a Preswirl Rotor–Stator System

1997 ◽  
Vol 119 (2) ◽  
pp. 364-373 ◽  
Author(s):  
M. Wilson ◽  
R. Pilbrow ◽  
J. M. Owen
Keyword(s):  
Heat Transfer ◽  
Gas Turbines ◽  
Heat Fluxes ◽  
Valuable Insight ◽  
Swirl Ratio ◽  
Blade Cooling ◽  
Nusselt Numbers ◽  
Air Temperatures ◽  
Via Holes ◽  
Cooling Air

Conditions in the internal-air system of a high-pressure turbine stage are modeled using a rig comprising an outer preswirl chamber separated by a seal from an inner rotor-stator system. Preswirl nozzles in the stator supply the “blade-cooling” air, which leaves the system via holes in the rotor, and disk-cooling air enters at the center of the system and leaves through clearances in the peripheral seals. The experimental rig is instrumented with thermocouples, fluxmeters, pitot tubes, and pressure taps, enabling temperatures, heat fluxes, velocities, and pressures to be measured at a number of radial locations. For rotational Reynolds numbers of Reφ ≃ 1.2 × 106, the swirl ratio and the ratios of disk-cooling and blade-cooling flow rates are chosen to be representative of those found inside gas turbines. Measured radial distributions of velocity, temperature, and Nusselt number are compared with computations obtained from an axisymmetric elliptic solver, featuring a low-Reynolds-number k–ε turbulence model. For the inner rotor-stator system, the computed core temperatures and velocities are in good agreement with measured values, but the Nusselt numbers are underpredicted. For the outer preswirl chamber, it was possible to make comparisons between the measured and computed values for cooling-air temperatures but not for the Nusselt numbers. As expected, the temperature of the blade-cooling air decreases as the inlet swirl ratio increases, but the computed air temperatures are significantly lower than the measured ones. Overall, the results give valuable insight into some of the heat transfer characteristics of this complex system.

Heat Transfer in a “Cover-Plate” Pre-Swirl Rotating-Disc System

1998 ◽  
Author(s):  
Robert Pilbrow ◽  
Hasan Karabay ◽  
Michael Wilson ◽  
J. Michael Owen
Keyword(s):  
Heat Transfer ◽  
Reynolds Numbers ◽  
Cover Plate ◽  
Swirl Ratio ◽  
Rotating Disc ◽  
Blade Cooling ◽  
Nusselt Numbers ◽  
Flow And Heat Transfer ◽  
Turbine Disc ◽  
Cooling Air

In most gas turbines, blade-cooling air is supplied from stationary pre-swirl nozzles that swirl the air in the direction of rotation of the turbine disc. In the “cover-plate” system, the pre-swirl nozzles are located radially inward of the blade-cooling holes in the disc, and the swirling air flows radially outwards in the cavity between the disc and a cover-plate attached to it. In this combined computational and experimental paper, an axisymmetric elliptic solver, incorporating the Launder-Sharma and the Morse low-Reynolds-number k-ε turbulence models, is used to compute the flow and heat transfer. The computed Nusselt numbers for the heated “turbine disc” are compared with measured values obtained from a rotating-disc rig. Comparisons are presented, for a wide range of coolant flow rates, for rotational Reynolds numbers in the range 0.5 × 106 to 1.5 × 106, and for 0.9 < βp < 3.1, where βp is the pre-swirl ratio (or ratio of the tangential component of velocity of the cooling air at inlet to the system to that of the disc). Agreement between the computed and measured Nusselt numbers is reasonably good, particularly at the larger Reynolds numbers. A simplified numerical simulation is also conducted to show the effect of the swirl ratio and the other flow parameters on the flow and heat transfer in the cover-plate system.

scholarly journals Performance of Pre-Swirl Rotating-Disc Systems

1999 ◽  
Author(s):  
Hasan Karabay ◽  
Robert Pilbrow ◽  
Michael Wilson ◽  
J. Michael Owen
Keyword(s):  
Heat Transfer ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Tangential Velocity ◽  
Turbulence Models ◽  
Cover Plate ◽  
Swirl Ratio ◽  
Rotating Disc ◽  
Blade Cooling ◽  
Cooling Air

This paper summarises and extends recent theoretical, computational and experimental research into the fluid mechanics, thermodynamics and heat transfer characteristics of the so-called cover-plate pre-swirl system. Experiments were carried out in a purpose-built rotating-disc rig, and the Reynolds-averaged Navier-Stokes equations were solved using 2D (axisymmetric) and 3D computational codes, both of which incorporated low-Reynolds-number k-ε turbulence models. The free-vortex flow, which occurs inside the rotating cavity between the disc and cover-plate, is controlled principally by the pre-swirl ratio, βp: this is the ratio of the tangential velocity of the air leaving the nozzles to that of the rotating disc. Computed values of the tangential velocity are in good agreement with measurements, and computed distributions of pressure are in close agreement with those predicted by a one-dimensional theoretical model. It is shown theoretically and computationally that there is a critical pre-swirl ratio, βp,crit, for which the frictional moment on the rotating discs is zero, and there is an optimal pre-swirl ratio, βp,opt, where the average Nusselt number is a minimum. Computations show that, for βp < βp,opt, the temperature of the blade-cooling air decreases as βp increases; for βp > βp,opt, whether the temperature of the cooling air increases or decreases as βp increases depends on the flow conditions and on the temperature difference between the disc and the air. Owing to the three-dimensional flow and heat transfer near the blade-cooling holes, and to unquantifiable uncertainties in the experimental measurements, there were significant differences between the computed and measured temperatures of the blade-cooling air. In the main, the 3D computations produced smaller differences than the 2D computations.

Influence of Tailored Boundary Layer Suction on Aerodynamic Performance in Bowed Compressor Cascades

2017 ◽  
Author(s):  
Ding Jun ◽  
Du Xin ◽  
Chen Shaowen ◽  
Zhou Xun ◽  
Wang Songtao ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Pressure Loss ◽  
Three Dimensional ◽  
Aerodynamic Performance ◽  
Stagnation Pressure ◽  
Operating Conditions ◽  
Design Parameters ◽  
Computational Domain ◽  
Separation Region ◽  
Boundary Layer Suction

The impact of boundary layer suction on the aerodynamic performance of bowed compressor cascades is discussed in this paper. Preliminary studies are conducted in the context of a highly loaded compressor cascade with peak diffusion factor of 0.60 and camber angle of 60 degrees. Comparison between numerical simulation results and experiment data shows that blade bowing may well help to modify the radial migration of flow features and prevent the blade suction surface boundary layer from separating. It is noteworthy that there exists an optimum blade bowing design with different operating conditions to increase the incidence range and reduce the loss over the incidence range. With the introduction of the boundary layer suction, the blade design becomes more complicated. This paper, therefore, conducts a thorough numerical study on design parameters including bowed blade geometry, aspirated flow fraction, and aspiration slot location based on mechanical simplicity and fabrication constraints. For a better understanding of the flow physics, the aspiration slot and plenum are included as part of the computational domain. The aspirated fluid passes into the plenum and is removed through both the hub and the shroud of the blade. From there it can be dumped overboard or carried to another point in the engine to be used as cooling air. Without considering the stagnation pressure loss of the aspirated flow, the blade lose can be sustainably decreased with the growing aspirated flow fractions from 0.5% to 2.5% of the inlet mass flow. However, when the aspirated flow’s effect on stagnation pressure loss is properly quantified, the blade’s loss decreasing trend will be relatively stable or even reversed with the aspirated flow fraction increasing. The calculations show that the application of aspiration on the flow path needs to be investigated and combined with blade bowing to partly counter the negative impacts with the application of aspiration. The application of blade bowing on aspirated blade makes it possible to achieve the same loss reduction by using lower amounts of aspirated flow. In other words, the increase in spanwise pressure gradient near the endwalls can be further utilized to reduce the effects of secondary flow by bowed blade with the same aspirated flow fraction. Aspiration should not be isolated from blade bowing, the optimum blade bowing angle is different on the basis of different aspirated flow fraction and aspiration slot location. The aspiration slot location is determined by the flow phenomena such as the three-dimensional separation in the cascade corner. In consideration of the stagnation pressure loss from the aspirated flow, aspiration inside of the three-dimensional separation region has a beneficial impact on the blade loss. Conversely, it will quickly lose its effectiveness, or even lead to slight deterioration of the aerodynamic performance if aspiration location is in the midspan, outside the three-dimensional separation region.

Aerodynamic Performance Investigation of Modern Marine Gas Turbine Intake System

2012 ◽  
Author(s):  
Peng Sun ◽  
Haiyang Gao ◽  
Jingjun Zhong ◽  
Muxiao Yang
Keyword(s):  
Pressure Distribution ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Pressure Loss ◽  
Total Pressure ◽  
Aerodynamic Performance ◽  
Operating Conditions ◽  
Measuring Point ◽  
Intake System ◽  
Flow Parameters

Gas turbines (GTs) have been used on board for many years. To safe guard these engines working efficiently and stably, several types of air intake system have been employed. The aerodynamic performance of marine gas turbine intake system is one of the important aspects which is associated with the marine operating conditions and should be studied carefully. In this paper, numerical simulation is carried out on the flow parameters of a vessel and her intake system. How vessel operating conditions and the environment conditions influence the intake system inlet boundary is studied firstly. Under some certain assumptions, the intake inlet total pressure value and the angle between wind and heading direction approximately follow the sine law. Then, unsteady simulation is carried out on the intake system. The total pressure loss variation and which measuring point can represent the pressure loss properly are discussed. It is found that the total pressure distribution varies with the measuring location. Following this, flow parameters at the volute outlet is analyzed in detail, especially the flow field structure and the distortion intensity. The total pressure distribution is non-uniform, which will influence the GT performance and stability significantly.

scholarly journals Flow and Heat Transfer in a Pre-Swirl Rotor-Stator System

1995 ◽  
Author(s):  
Michael Wilson ◽  
Robert Pilbrow ◽  
J. Michael Owen
Keyword(s):  
Heat Transfer ◽  
Gas Turbines ◽  
Heat Fluxes ◽  
Valuable Insight ◽  
Swirl Ratio ◽  
Blade Cooling ◽  
Nusselt Numbers ◽  
Swirl Chamber ◽  
Air Temperatures ◽  
Cooling Air

Conditions in the internal-air system of a high-pressure turbine stage are modelled using a rig comprising an outer pre-swirl chamber separated by a seal from an inner rotor-stator system. Pre-swirl nozzles in the stator supply the “blade-cooling” air, which leaves the system via holes in the rotor, and disc-cooling air enters at the centre of the system and leaves through clearances in the peripheral seals. The experimental rig is instrumented with thermocouples, fluxmeters, pitot tubes and pressure taps enabling temperatures, heat fluxes, velocities and pressures to be measured at a number of radial locations. For rotational Reynolds numbers of Reϕ ≃ 1.2 × 106, the swirl ratio and the ratios of disc-cooling and blade-cooling flow rates are chosen to be representative of those found inside gas turbines. Measured radial distributions of velocity, temperature and Nusselt number are compared with computations obtained from an axisymmetric elliptic solver, featuring a low-Reynolds-number k-ε turbulence model. For the inner rotor-stator system, the computed core temperatures and velocities are in good agreement with measured values, but the Nusselt numbers are underpredicted. For the outer pre-swirl chamber, it was possible to make comparisons between the measured and computed values for cooling-air temperatures but not for the Nusselt numbers. As expected, the temperature of the blade-cooling air decreases as the swirl ratio increases, but the computed air temperatures are significantly lower than the measured ones. Overall, the results give valuable insight into some of the heat transfer characteristics of this complex system.

Application of a Flow Optimizer in a Limited Space to Increase Series Fan Performance

2010 ◽  
Vol 7 (4) ◽  
pp. 181-188
Author(s):  
Jonathan Jilesen ◽  
Howard Harrison ◽  
Fue-Sang Lien ◽  
Darryl McCumber
Keyword(s):  
Power Consumption ◽  
Flow Rate ◽  
Operating Conditions ◽  
Cfd Analysis ◽  
Original Series ◽  
Fan Performance ◽  
Limited Space ◽  
Cooling Fans ◽  
Rate Of Cooling ◽  
Cooling Air

The performance increase of cooling for a 1U SunFire 4100 server through the introduction of multiple flow optimizers is investigated in this article. We found that the power consumption of cooling fans could be decreased by 17–33% depending on operating conditions. The use of flow optimizers was found to reduce noise produced by cooling fans by at least 5.3 dB(A). We also discuss the use of the increased performance to increase thermal head room by increasing the flow rate of cooling air by 6.5–20.4%. In addition, we found that a primary fan used with an exit stator allowed the overall fan module length to be reduced without a loss in performance. Reducing the length allowed the flow optimizers to fit into the standard 56-mm space previously occupied by the original series fans. CFD analysis was performed to better understand the effect of this stator on airflow.

Performance of Pre-Swirl Rotating-Disc Systems

2000 ◽  
Vol 122 (3) ◽  
pp. 442-450 ◽  
Author(s):  
Hasan Karabay ◽  
Robert Pilbrow ◽  
Michael Wilson ◽  
J. Michael Owen
Keyword(s):  
Heat Transfer ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Tangential Velocity ◽  
Cover Plate ◽  
Two Dimensional ◽  
Swirl Ratio ◽  
Rotating Disc ◽  
Blade Cooling ◽  
Cooling Air

This paper summarizes and extends recent theoretical, computational, and experimental research into the fluid mechanics, thermodynamics, and heat transfer characteristics of the so-called cover-plate pre-swirl system. Experiments were carried out in a purpose-built rotating-disc rig, and the Reynolds-averaged Navier-Stokes equations were solved using two-dimensional (axisymmetric) and three-dimensional computational codes, both of which incorporated low-Reynolds-number k-ε turbulence models. The free-vortex flow, which occurs inside the rotating cavity between the disc and cover-plate, is controlled principally by the pre-swirl ratio, βp: this is the ratio of the tangential velocity of the air leaving the nozzles to that of the rotating disc. Computed values of the tangential velocity are in good agreement with measurements, and computed distributions of pressure are in close agreement with those predicted by a one-dimensional theoretical model. It is shown theoretically and computationally that there is a critical pre-swirl ratio, βp,crit, for which the frictional moment on the rotating discs is zero, and there is an optimal pre-swirl ratio, βp,opt, where the average Nusselt number is a minimum. Computations show that, for βp<βp,opt, the temperature of the blade-cooling air decreases as βp increases; for βp>βp,opt, whether the temperature of the cooling air increases or decreases as βp increases depends on the flow conditions and on the temperature difference between the disc and the air. Owing to the three-dimensional flow and heat transfer near the blade-cooling holes, and to unquantifiable uncertainties in the experimental measurements, there were significant differences between the computed and measured temperatures of the blade-cooling air. In the main, the three-dimensional computations produced smaller differences than the two-dimensional computations. [S0742-4795(00)01902-5]

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