scholarly journals Aerothermal Analysis of a Turbine Casing Impingement Cooling System

2012 ◽  
Vol 2012 ◽  
pp. 1-10 ◽  
Author(s):  
Riccardo Da Soghe ◽  
Bruno Facchini ◽  
Mirko Micio ◽  
Antonio Andreini
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Cooling System ◽  
Control Valve ◽  
Impinging Jets ◽  
Present System ◽  
Air Supply ◽  
Supply Pipe ◽  
Turbine Casing ◽  
Cooling Air

Heat transfer and pressure drop for a representative part of a turbine active cooling system were numerically investigated by means of an in-house code. This code has been developed in the framework of an internal research program and has been validated by experiments and CFD. The analysed system represents the classical open bird cage arrangement that consists of an air supply pipe with a control valve and the present system with a collector box and pipes, which distribute cooling air in circumferential direction of the casing. The cooling air leaves the ACC system through small holes at the bottom of the tubes. These tubes extend at about 180° around the casing and may involve a huge number of impinging holes; as a consequence, the impinging jets mass flow rate may vary considerably along the feeding manifold with a direct impact on the achievable heat transfer levels. This study focuses on the performance, in terms of heat transfer coefficient and pressure drop, of several impinging tube geometries. As a result of this analysis, several design solutions have been compared and discussed.

Heat Transfer and Pressure Drop Analysis of a Turbine Casing Impingement Cooling System

2012 ◽  
Author(s):  
Riccardo Da Soghe ◽  
Bruno Facchini ◽  
Mirko Micio ◽  
Daniele Coutandin
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Cooling System ◽  
Control Valve ◽  
Impinging Jets ◽  
Present System ◽  
Air Supply ◽  
Supply Pipe ◽  
Turbine Casing ◽  
Cooling Air

Heat transfer and discharge coefficient behaviour for a representative part of a turbine active cooling system were numerically investigated by means of an in-house code. This code has been developed in the framework of an internal research program and has been validated by experiments and CFD. The analysed system represents the classical open bird cage arrangement that consists of an air supply pipe with a control valve and the present system with a collector box and pipes, which distribute cooling air in circumferential direction of the casing. The cooling air leaves the ACC system through small holes at the bottom of the tubes. These tubes extend at about 180° around the casing and may involve a huge number of impinging holes; as a consequence, the impinging jets mass flow rate may vary considerably along the feeding manifold with a direct impact on the achievable heat transfer levels. This study focuses on the performance, in terms of heat transfer coefficient and pressure drop, of several impinging tube geometries. As a result of this analysis, several design solutions have been compared and discussed.

Heat Transfer and Pressure Drop Characteristics for a Turbine Casing Impingement Cooling System

2010 ◽  
Author(s):  
F. Ben Ahmed ◽  
B. Weigand ◽  
K. Meier
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Mach Number ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Cooling System ◽  
Impinging Jets ◽  
Turbine Casing ◽  
The Heat Transfer Coefficient

Flow mechanisms, heat transfer and discharge coefficient characteristics for a representative part of a turbine casing cooling system, consisting of an array of 20 impinging jets, were numerically investigated. The study focused on the influence of the jet Mach number while maintaining the Reynolds number constant at Re = 7,500. Therefore, the orifice bore diameter or the fluid density had to be varied. The objectives of the current CFD simulations have not been adressed before in literature, not only because heat transfer characteristics and pressure drop are given for impingement jet Mach numbers up to 0.72 at a constant relatively low Reynolds number, but also because fundamental understanding of physical phenomena of the flow in the cylindrical plenum and in the small sharp-edged orifices at the bottom side of the tube is provided. Increasing the Mach number by simultaneously reducing the orifice diameters led to slightly decreasing Nusselt numbers, with average deviations of the order of 14%. However, the heat transfer coefficient increased considerably with increasing Mach number. On the contrary, the variation of the Mach number by varying the density showed only a slight influence on the heat transfer coefficient. The predicted discharge coefficients increased significantly by augmenting the Mach number.

Numerical Investigation of Heat Transfer and Pressure Drop Characteristics for Different Hole Geometries of a Turbine Casing Impingement Cooling System

2011 ◽  
Author(s):  
F. Ben Ahmed ◽  
R. Tucholke ◽  
B. Weigand ◽  
K. Meier
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Cooling System ◽  
Ambient Air ◽  
Impinging Jets ◽  
Nozzle Geometry ◽  
Impingement Cooling ◽  
Pressure Losses ◽  
Aspect Ratios ◽  
Mach Numbers

A representative part of an active clearance control system for a low pressure turbine has been numerically investigated. The setup consisted of a cylindrical plenum with 20 inline arranged impinging jets at the bottom side discharging on a flat plate. The study focused on the influence of the nozzle geometry on the flow as well as heat transfer characteristics at the impingement plate and the discharge pressure drop. CFD (Computational Fluid Dynamics) simulations were performed for a constant Reynolds number ReD = 7,500 and different mean jet Mach numbers up to 0.7. Different length-to-diameter ratios of the jet holes (L/D) and various hole shapes (cylindrical, elliptic, convergent and divergent conical) were investigated to evaluate the performance of the impingement cooling configurations. The predictions showed a significant influence of the length-to-diameter ratio of the orifice bores on the heat transfer and the pressure losses. For L/D = 2 no suction of the ambient air in the nozzles was observed. In comparison to the configuration with L/D = 0.25 an improvement of the discharge coefficient of 9% for Ma = 0.7 and 20% for Ma = 0.17 was achieved. However, the highest heat transfer was observed for the smallest L/D-ratio of 0.25. The shape variation showed that only the elliptic jet holes with a ratio of AR = 0.5 enhanced the overall heat transfer and simultaneously reduced the pressure losses because of discharging onto the target plate. This result was found to be valid for all investigated jet Mach numbers. Additionally, for both elliptic jet aspect ratios of 0.5 and 2 the axis-switchover phenomenon of the flow was observed.

Effect of pre-swirl nozzle closure modes on unsteady flow and heat transfer characteristics in a pre-swirl system of aero-engine

2021 ◽  
pp. 095441002110191
Author(s):  
Gaowen Liu ◽  
Zhao Lei ◽  
Aqiang Lin ◽  
Qing Feng ◽  
Yan Chen
Keyword(s):  
Heat Transfer ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Temperature Drop ◽  
Thermodynamic Characteristics ◽  
Circumferential Direction ◽  
Temperature Changes ◽  
Air Supply ◽  
Cooling Air

The pre-swirl system is of great importance for temperature drop and cooling air supply. This study aims to investigate the influencing mechanism of heat transfer, nonuniform thermodynamic characteristics, and cooling air supply sensitivity in a pre-swirl system by the application of the flow control method of the pre-swirl nozzle. A novel test rig was proposed to actively control the supplied cooling air mass flow rate by three adjustable pre-swirl nozzles. Then, the transient problem of the pre-swirl system was numerically conducted by comparison with 60°, 120°, and 180° rotating disk cavity cases, which were verified with the experiment results. Results show that the partial nozzle closure will aggravate the fluctuation of air supply mass flow rate and temperature. When three parts of nozzles are closed evenly at 120° in the circumferential direction, the maximum value of the nonuniformity coefficient of air supply mass flow rate changes to 3.1% and that of temperature changes to 0.25%. When six parts of nozzles are closed evenly at 60° in the circumferential direction, the maximum nonuniformity coefficient of air supply mass flow rate changes to 1.4% and that of temperature changes to 0.20%. However, different partial nozzle closure modes have little effect on the average air supply parameters. Closing 14.3% of the nozzle area will reduce the air supply mass flow rate by 9.9% and the average air supply temperature by about 1 K.

Cooling of a Finned Cylinder by a Jet Flow of Air

2002 ◽  
Author(s):  
F. Gori ◽  
F. De Nigris ◽  
E. Pippione ◽  
G. Scavarda
Keyword(s):  
Heat Transfer ◽  
Cooling System ◽  
Jet Flow ◽  
Impinging Jets ◽  
Transfer Coefficients ◽  
Electric System ◽  
Heavy Trucks ◽  
Turbo Compressor ◽  
University Of Rome ◽  
The University

The paper describes a patented proposal to use jets of air in the cooling system of heavy trucks. Preliminary tests have been carried out, in the Heat Transfer Laboratory of the University of Rome “Tor Vergata”, to evaluate the heat transfer characteristics of a jet flow of air, impinging onto an externally finned cylinder. The cylinder is internally heated with an electric system. Thermocouples, located inside the cylinder, allow to measure the wall temperatures, in order to calculate the local and average convective heat transfer coefficients. A preliminary design of the practical apparatus, applied to heavy trucks, has been done in cooperation with Iveco. Nozzles are designed to be put after the fan of heavy trucks to converge air, in the form of jets, onto the tube where the charged air is flowing from the outlet of the turbo-compressor. The efficiency of the jet flow increases the cooling performances but, due to the high temperature at the outlet of the turbo-compressor, it may not be enough. The heat transfer cooling performances are enhanced if the tube to be cooled is externally finned. Some preliminary experiments have been carried out in a real scale bank test of an heavy truck engine at the Engineering Testing Laboratories Department of Iveco. Comparisons are done between the experiments and a simple theoretical model. Some conclusions are drawn about the cooling at different fluid dynamics conditions of the impinging jets.

Heat Transfer and Pressure Drop in a Converging Pedestal Array With Exit Area Variation

2018 ◽  
Author(s):  
L. W. Soma ◽  
F. E. Ames ◽  
S. Acharya
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Flow Rate ◽  
Film Cooling ◽  
Reynolds Numbers ◽  
Flow Path ◽  
Internal Cooling ◽  
Channel Measurements ◽  
Trailing Edge ◽  
Cooling Air

The trailing edge of a vane is one of the most difficult areas to cool due to a narrowing flow path, high external heat transfer rates, and deteriorating external film cooling protection. Converging pedestal arrays are often used as a means to provide internal cooling in this region. The thermally induced stresses in the trailing edge region of these converging arrays have been known to cause failure in the pedestals of conventional solidity arrays. The present paper documents the heat transfer and pressure drop through two high solidity converging rounded diamond pedestal arrays. These arrays have a 45 percent pedestal solidity. One array which was tested has nine rows of pedestals with an exit area in the last row consistent with the convergence. The other array has eight rows with an expanded exit in the last row to enable a higher cooling air flow rate. The expanded exit of the eight row array allows a 30% increase in the coolant flow rate compared with the nine row array for the same pressure drop. Heat transfer levels correlate well based on local Reynolds numbers but fall slightly below non converging arrays. The pressure drop across the array naturally increases toward the trailing edge with the convergence of the flow passage. A portion of the cooling air pressure drop can be attributed to acceleration while a portion can be attributed to flow path losses. Detailed array static pressure measurements provide a means to develop a correlation for the prediction of pressure drop across the cooling channel. Measurements have been acquired over Reynolds numbers based on exit flow conditions and the characteristic pedestal length scale ranging from 5000 to over 70,000.

Flow and Heat Transfer in a Rotating Cavity With a Stationary Stepped Casing

2000 ◽  
Author(s):  
Abdul A. Jaafar ◽  
Fariborz Motallebi ◽  
Michael Wilson ◽  
J. Michael Owen
Keyword(s):  
Heat Transfer ◽  
Cooling System ◽  
Laser Doppler Anemometry ◽  
Tangential Component ◽  
Rotating Disc ◽  
Turbine Engine ◽  
Flow And Heat Transfer ◽  
Rotating Cavity ◽  
Rotating Discs ◽  
Cooling Air

In this paper, new experimental results are presented for the flow in a co-rotating disc system with a rotating inner cylinder and a stationary stepped outer casing. The configuration is based on a turbine disc-cooling system used in a gas turbine engine. One of the rotating discs can be heated, and cooling air is introduced through discrete holes angled inward at the periphery of this disc. The cooling air leaves the system through axial clearances between the discs and the outer casing. Some features of computed flows, and both measured and computed heat transfer, were reported previously for this system. New velocity measurements, obtained using Laser Doppler Anemometry, are compared with results from axisymmetric, steady, turbulent flow computations obtained using a low-Reynolds-number k-ε turbulence model. The measurements and computations show that the tangential component of velocity is invariant with axial location in much of the cavity, and the data suggest that Rankine (combined free and forced) vortex flow occurs. The computations fail to reproduce this behaviour, and there are differences between measured and computed details of secondary flow recirculations. Possible reasons for these discrepancies, and their importance for the prediction of associated heat transfer, are discussed.

A Study of Convective Heat Transfer and Pressure Drop Phenomena in Curved Microchannels

2010 ◽  
Author(s):  
Heng-Chih Tang ◽  
Tien-Chien Jen ◽  
Yi-Hsin Yen ◽  
Jyh-Tong Teng
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Cooling System ◽  
Outer Wall ◽  
Flow Patterns ◽  
Hydraulic Diameter ◽  
Main Stream ◽  
Dean Number

The research conducted in this paper was based on numerical simulation analysis that investigated the relationships between convective heat transfer and pressure drops and the flow patterns between conventional straight channels and curved microchannels. The main goal is to thoroughly investigate thermo-fluidic phenomena in curved microchannels and to determine the optimal design for the curved microchannel cooling system. Commercial numerical software (ESI-CFD) was used to simulate all cases studied in this paper. The computer simulated results were compared with actual experimental results to evaluate its accuracy. Six cases of different dimensions were studied. Results obtained from this study showed that when the dimensions of curved microchannels are smaller than 40 μm in height, conventional macro fluidic theory can still be used, since the numerically simulated results are in good agreement (<6% difference) with those obtained experimentally. Hydraulic diameter is the factor affects the pressure drop. Larger hydraulic diameter causes smaller pressure drop while smaller hydraulic diameter results in higher pressure drop. Secondary flow patterns and Nusselt numbers are also illustrated in this paper. When the Dean number is lower than 400, the pressure drop of fluid in 40 μm height models is similar to that found in straight microchannels. For the velocity profiles in the curved microchannels, the main stream is at the center of the curved microchannel first. But it is gradually offsets to the outer wall when the mass flow rates increases. The centrifugal force due to the curve geometry is the main reason that results in the shifting of the main flow toward the outer wall of the microchannel.

Recent Trends of Impingement Cooling System Enhancement for Gas Turbine

2013 ◽  
Vol 465-466 ◽  
pp. 496-499
Author(s):  
Mohd Firdaus Bin Abas ◽  
Abdullah Aslam ◽  
Hamidon bin Salleh ◽  
Nor Adrian Bin Nor Salim
Keyword(s):  
Heat Transfer ◽  
Cooling System ◽  
Turbine Blades ◽  
Impinging Jets ◽  
Target Plate ◽  
Impingement Cooling ◽  
Impingement Jet ◽  
Rib Turbulators ◽  
Recent Trends ◽  
Plate Distance

Efforts have been given to improve the turbine blades ability to withstand high temperature for a long period of time by implementing effective cooling system. There are many aspects that should be considered when implementing impingement cooling. This paper will only cover two trending aspects in impingement cooling implementation; the jet-to-target plate distance and the application of ribs in promoting better impingement cooling performance. For target plate distance to impingement jet diameter value, H/d > 1, the area-averaged Nusselt number also decreases as the H/d value increases. This may have been due to a reduction of the amount of momentum exerted by the impinging jets onto the target plate. For H/d < 1, the results have been proven otherwise. Heat transfer in impingement/effusion cooling system in crossflow with rib turbulators showed higher heat transfer rate than that of a surface without ribs because the ribs prevent the wall jets from being swept away by the crossflow and increase local turbulence of the flow near the surface. It could be concluded that both H/d ratio and ribs installation play an important role in enhancing impingement cooling systems heat transfer effectiveness.

Gas Turbine Combustor Cooling by Augmented Backside Convection

1979 ◽  
Vol 101 (1) ◽  
pp. 109-115 ◽  
Author(s):  
D. M. Evans ◽  
M. L. Noble
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Film Cooling ◽  
Cooling System ◽  
Exhaust Gas ◽  
Confined Space ◽  
Gas Turbine Combustor ◽  
Exhaust Gas Emission ◽  
Cooling Air ◽  
Cooling Methods

Traditionally, gas turbine combustor walls have been cooled by one or more of the various film cooling methods. The current motivation to control exhaust gas emission composition has led to the serious consideration of backside convection wall cooling, where the cooling air is introduced to the main gas stream not prior to the dilution zone. Due to the confined space and the severe nature of the wall cooling problem, it is essential to maximize the heat transfer/pumping power characteristic, which suggests an augmented convection technique. A particular heat transfer design of a combustor cooled by means of transverse rib turbulence promoters applied to the exterior wall of the annular spaces surrounding the primary and secondary zones is described. Analytical methods for designing such a cooling system are reviewed and a comparison between analytical and experimental results is presented.

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