Transpiration Cooled Turbines

1970 ◽  
Vol 185 (1) ◽  
pp. 943-951 ◽  
Author(s):  
F. J. Bayley ◽  
A. B. Turner
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Air Cooling ◽  
Transpiration Cooling

This paper lists the steps in the development chain of air cooling for gas turbine components, and represents transpiration cooling as the ultimate method. The three modes of heat transfer involved in transpiration cooling, gas side heat transfer, coolant side heat transfer and interstitial heat transfer, are discussed separately. Finally, consideration is given to the practical problems of transpiration cooling in advanced gas turbines.

Numerical Investigation on Mist/Air Cooling in Rectangular Ribbed Channels With Various Aspect Ratios

2017 ◽  
Author(s):  
Junxiong Zeng ◽  
Tieyu Gao ◽  
Jun Li ◽  
Jianying Gong
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Aspect Ratio ◽  
Secondary Flow ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Secondary Flows ◽  
Air Cooling ◽  
Mass Ratio ◽  
Aspect Ratios

Continuously increasing gas turbine inlet temperature to further improve thermal efficiency and power output of gas turbines leads to acquiring a higher cooling effectiveness of gas turbine blades and vanes to protect them from high temperature corrosion and creeping damage. One of the new and promising technologies to greatly increase heat transfer is mist cooling by injecting a small amount of tiny droplets into coolant flow. This paper aims to numerically study the flow and heat transfer behaviors of mist/air coolant in rectangular ribbed channels with various aspect ratios of 1/4, 1/2, 1/1, 2/1 and rib angle of 60°. In addition, the distribution of secondary flows in the four ribbed channels and its effect on heat transfer are analyzed in detail. The effects of Reynolds number ranging from 10,000 to 60,000, mist mass ratios ranging from 1% to 4%, and droplet sizes ranging from 5 μm to 20 μm on heat transfer characteristics of mist/air cooling are investigated. As a comparison, the air-only coolant is also considered in the present study. The Eulerian-Lagrangian particle tracking method is adopted in this study to simulate the two-phase flow mist/air cooling. Turbulence model validation has been conducted for air-only, indicating that the numerical results with SST k-ω model are fairly consistent with experimental data. The results show that the aspect ratio has insignificant influence on longitudinal secondary flow distribution in the four ribbed channels, but greatly affects the size of main secondary flows. The channel with a smaller aspect ratio obtains a larger size of main secondary flow, which may result in decreasing the heat transfer coefficient. The average Nu on ribbed surfaces presents an increasing trend with Reynolds number and mist mass ratio for mist/air cooling. The heat transfer enhancement of mist/air as compared to air-only increases from 12.3% to 91.86% when Reynolds number ranges from 10,000 to 60,000 with injecting 2% mist into air coolant, while that increases from 7.96% to 113.15% when mist mass ratio increases from 1% to 4%. The average Nu initially increases with droplet size and then decreases. A peak value of average Nu is obtained in the case of 15μm mist among all the sizes of droplets. The case of AR = 2/1 obtains the highest average Nu, followed by the cases of AR = 1/2, 1/1 and 1/4 for both air-only and mist/air. The channel with aspect ratio of 1/2 obtains the best thermal performance in mist/air cooling channel.

scholarly journals Two-Stage Evaporative Inlet Air Gas Turbine Cooling

Energies ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1382
Author(s):  
Obida Zeitoun
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Evaporative Cooling ◽  
Air Cooling ◽  
Vapor Compression ◽  
Two Stage ◽  
Turbine Cooling ◽  
Riyadh City ◽  
Vapor Compression Refrigeration ◽  
Gas Turbine Cooling

Gas turbine inlet air-cooling (TIAC) is an established technology for augmenting gas turbine output and efficiency, especially in hot regions. TIAC using evaporative cooling is suitable for hot, dry regions; however, the cooling is limited by the ambient wet-bulb temperature. This study investigates two-stage evaporative TIAC under the harsh weather of Riyadh city. The two-stage evaporative TIAC system consists of indirect and direct evaporative stages. In the indirect stage, air is precooled using water cooled in a cooling tower. In the direct stage, adiabatic saturation cools the air. This investigation was conducted for the GE 7001EA gas turbine model. Thermoflex software was used to simulate the GE 7001EA gas turbine using different TIAC systems including evaporative, two-stage evaporative, hybrid absorption refrigeration evaporative and hybrid vapor-compression refrigeration evaporative cooling systems. Comparisons of different performance parameters of gas turbines were conducted. The added annual profit and payback period were estimated for different TIAC systems.

Evaluation of Numerical Methods to Predict Temperature Distributions of an Experimentally Investigated Convection-Cooled Gas-Turbine Blade

2017 ◽  
Author(s):  
E. Findeisen ◽  
B. Woerz ◽  
M. Wieler ◽  
P. Jeschke ◽  
M. Rabs
Keyword(s):  
Heat Transfer ◽  
Numerical Methods ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Gas Turbines ◽  
Cooling System ◽  
Fe Model ◽  
Gas Turbine Blade ◽  
Transfer Coefficients ◽  
Temperature Distributions

This paper presents two different numerical methods to predict the thermal load of a convection-cooled gas-turbine blade under realistic operating temperature conditions. The subject of the investigation is a gas-turbine rotor blade equipped with an academic convection-cooling system and investigated at a cascade test-rig. It consists of three cooling channels, which are connected outside the blade, so allowing cooling air temperature measurements. Both methods use FE models to obtain the temperature distribution of the solid blade. The difference between these methods lies in the generation of the heat transfer coefficients along the cooling channel walls which serve as a boundary condition for the FE model. One method, referred to as the FEM1D method, uses empirical one-dimensional correlations known from the available literature. The other method, the FEM2D method, uses three-dimensional CFD simulations to obtain two-dimensional heat transfer coefficient distributions. The numerical results are compared to each other as well as to experimental data, so that the benefits and limitations of each method can be shown and validated. Overall, this paper provides an evaluation of the different methods which are used to predict temperature distributions in convection-cooled gas-turbines with regard to accuracy, numerical cost and the limitations of each method. The temperature profiles obtained in all methods generally show good agreement with the experiments. However, the more detailed methods produce more accurate results by causing higher numerical costs.

Heat Transfer Associated With Air-Water Spray Cooling of Forgings From High Temperatures

2001 ◽  
Author(s):  
J. Ward ◽  
M. de Oliveira ◽  
D. R. Garwood ◽  
R. A. Wallis
Keyword(s):  
Heat Transfer ◽  
Water Flow ◽  
Gas Turbines ◽  
Spray Cooling ◽  
Solution Temperature ◽  
Air Cooling ◽  
Water Spray ◽  
Transfer Rates ◽  
Wide Range ◽  
Water Spray Cooling

Abstract The desired mechanical properties of the nickel-based or titanium forgings used in gas turbines for aircraft and power generation applications can be controlled by varying the rate of cooling from the so-called solution temperature during an initial heat treatment process. The use of dilute air-water spray cooling of these forgings is a technique which can provide heat transfer rates lying between those associated with conventional oil quenching or convective air-cooling. Air assisted atomisation can result in fine sprays over a wide range of water flow rates and it has a further advantage in that the air “sweeps” the surface and hence helps to prevent the build up of deleterious vapour films at high surface temperatures. The paper presents experimental data for the heat transfer rates associated with the use of these sprays to cool surfaces from temperatures of approximately 800°C. Many forgings contain surface recesses, which can lead to build up or “pooling” of the water so that the effect of variations in surface geometry is also reported. Periodic interruption of the water flow is a technique which can be employed to provide additional control of the heat transfer rate, particularly at temperatures below 500°C so that data is also presented for pulsed sprays.

Thermal Influences in Gas Turbine Transients: Effects of Changes in Compressor Characteristics

1979 ◽  
Author(s):  
N. R. L. Maccallum
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Transient Response ◽  
Gas Turbines ◽  
Axial Flow ◽  
Transient Heat Transfer ◽  
Shaft Speed ◽  
Delivery Pressure ◽  
Surge Line ◽  
Transfer Parameters

During transients of axial-flow gas turbines, the characteristics of the compressor are altered. The changes in these characteristics (excluding surge line changes) have been related to transient heat transfer parameters, and these relations have been incorporated in a program for predicting the transient response of a single-shaft aero gas turbine. The effect of the change in compressor characteristics has been examined in accelerations using two alternative acceleration fuel schedules. When the fuel is scheduled on compressor delivery pressure alone. there is no increase in predicted acceleration times. When the fuel is scheduled on shaft speed alone, the predicted acceleration times are increased by about 5 to 6 percent.

Recognising the Viability of Cooling Gas Turbine Inlet Air in Colder Regions by Using Low Pressure Fogging Techniques

2002 ◽  
Author(s):  
John Confurius
Keyword(s):  
Ambient Temperature ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Cooling System ◽  
Low Pressure ◽  
Air Cooling ◽  
Turbine Inlet ◽  
The World

The profits that can be gained by use of inlet air cooling on gas turbines has been recognised for quite some time now and the systems installed throughout the world have shown the users in the gas turbine field that cooling indeed can be used to boost power at times when the ambient temperature reaches or exceeds the ISO rating temperature of the gas turbine. Drawback however being that the initial investment asked of the gas turbine user is rather large thus only justifying a cooling system in regions where the outdoor temperatures exceed the ISO rating time and again due to the climate in that region. Lately gas turbine users in colder climates have become interested in power augmentation during their short summer, however there is no justification for an investment like necessary when installing one of the presently available systems on the market. As the question reached us from more and more of our clients it stimulated us to go out and search for a low-investment solution to this problem. This resulted in the world’s first low pressure gas turbine inlet cooling system.

Performance Assessment of Steam Injection Gas Turbine With Inlet Air Cooling

1997 ◽  
Author(s):  
Carlo M. Bartolini ◽  
Danilo Salvi
Keyword(s):  
Ambient Temperature ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Heat Recovery ◽  
Power Plants ◽  
Waste Heat ◽  
Cooling System ◽  
Steam Injection ◽  
Maximum Efficiency ◽  
Air Cooling

The steam generated through the use of waste heat recovered from a steam injection gas turbine generally exceeds the maximum mass of steam which can be injected into steam injection gas turbine. The ratio between the steam and air flowing into the engine is not more than 10–15%, as an increase in the pressure ratio can cause the compressor to stall. Naturally, the surplus steam can be utilized for a variety of alternative applications. During the warmer months, the ambient temperature increases and results in reduced thermal efficiency and electrical capacity. An inlet air cooling system for the compressor on a steam injection gas turbine would increase the rating and efficiency of power plants which use this type of equipment. In order to improve the performance of steam injection gas turbines, the authors investigated the option of cooling the intake air to the compressor by harnessing the thermal energy not used to produce the maximum quantity of steam that can be injected into the engine. This alternative use of waste energy makes it possible to reach maximum efficiency in terms of waste recovery. This study examined absorption refrigeration technology, which is one of the various systems adopted to increase efficiency and power rating. The system itself consists of a steam injection gas turbine and a heat recovery and absorption unit, while a computer model was utilized to evaluate the off design performance of the system. The input data required for the model were the following: an operating point, the turbine and compressor curves, the heat recovery and chiller specifications. The performance of an Allison 501 KH steam injection gas plant was analyzed by taking into consideration representative ambient temperature and humidity ranges, the optimal location of the chiller in light of all the factors involved, and which of three possible air cooling systems was the most economically suitable. In order to verify the technical feasibility of the hypothetical model, an economic study was performed on the costs for upgrading the existing steam injection gas cogeneration unit. The results indicate that the estimated pay back period for the project would be four years. In light of these findings, there are clear technical advantages to using gas turbine cogeneration with absorption air cooling in terms of investment.

The Transpiration-Cooled Gas Turbine

1970 ◽  
Vol 92 (4) ◽  
pp. 351-358 ◽  
Author(s):  
F. J. Bayley ◽  
A. B. Turner
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Turbulent Boundary Layers ◽  
Transpiration Cooling ◽  
Combustion System ◽  
Transfer Rates ◽  
Thermodynamic Performance ◽  
Porous Surfaces ◽  
Analytical Research ◽  
High Temperature Gas

This paper describes a program of experimental and analytical research designed to evaluate the aerodynamic and thermodynamic performance of transpiration-cooled porous surfaces in the high-temperature gas turbine. The aerodynamic penalties of effusing coolant through a set of nozzle blades are shown to be small, particularly when compared with the thermodynamic advantages which accrue from the effective cooling obtained. Although the effusing coolant can in certain circumstances increase gas to blade heat transfer rates by destabilizing a laminar boundary layer, in the turbulent boundary layers which predominate in turbine practice there is inevitably a reduction in heat transfer which can be satisfactorily predicted theoretically. In the combustion system of the gas turbine, transpiration cooling appears also to be very attractive, but much work remains to be done on heat transfer rates in the flame-tube.

Study of a Rich/Lean Staged Combustion Concept for Hydrogen at Gas Turbine Relevant Conditions

2013 ◽  
Author(s):  
Felipe Bolaños ◽  
Dieter Winkler ◽  
Felipe Piringer ◽  
Timothy Griffin ◽  
Rolf Bombach ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Carbon Capture ◽  
Flame Temperature ◽  
Nox Emissions ◽  
Hydrogen Fuel ◽  
Auto Ignition ◽  
Wide Range ◽  
The Rich

The combustion of hydrogen-rich fuels (> 80 % vol. H2), relevant for gas turbine cycles with “pre-combustion” carbon capture, creates great challenges in the application of standard lean premix combustion technology. The significant higher flame speed and drastically reduced auto-ignition delay time of hydrogen compared to those of natural gas, which is normally burned in gas turbines, increase the risk of higher NOX emissions and material damage due to flashback. Combustion concepts for gas turbines operating on hydrogen fuel need to be adapted to assure safe and low-emission combustion. A rich/lean (R/L) combustion concept with integrated heat transfer that addresses the challenges of hydrogen combustion has been investigated. A sub-scale, staged burner with full optical access has been designed and tested at gas turbine relevant conditions (flame temperature of 1750 K, preheat temperature of 400 °C and a pressure of 8 bar). Results of the burner tests have confirmed the capability of the rich/lean staged concept to reduce the NOx emissions for undiluted hydrogen fuel. The NOx emissions were reduced from 165 ppm measured without staging (fuel pre-conversion) to 23 ppm for an R/L design having a fuel-rich hydrogen pre-conversion of 50 % at a constant power of 8.7 kW. In the realized R/L concept the products of the first rich stage, which is ignited by a Pt/Pd catalyst (under a laminar flow, Re ≈ 1900) are combusted in a diffusion-flame-like lean stage (turbulent flow Re ≈ 18500) without any flashback risk. The optical accessibility of the reactor has allowed insight into the combustion processes of both stages. Applying OH-LIF and OH*-chemiluminescence optical techniques, it was shown that mainly homogeneous reactions at rich conditions take place in the first stage, questioning the importance of a catalyst in the system, and opening a wide range of optimization possibilities. The promising results obtained in this study suggest that such a rich/lean staged burner with integrated heat transfer could help to develop a new generation of gas turbine burners for safe and clean combustion of H2-rich fuels.

On Thermodynamics of Gas-Turbine Cycles: Part 3—Thermodynamic Potential and Limitations of Cooled Reheat-Gas-Turbine Combined Cycles

1986 ◽  
Vol 108 (1) ◽  
pp. 160-168 ◽  
Author(s):  
M. A. El-Masri
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Closed Loop ◽  
Elevated Temperatures ◽  
Pressure Ratio ◽  
Air Cooling ◽  
Full Potential ◽  
Evaporative Water ◽  
Combined Cycles ◽  
Cooling Technology

Reheat gas turbines have fundamental thermodynamic advantages in combined cycles. However, a larger proportion of the turbine expansion path is exposed to elevated temperatures, leading to increased cooling losses. Identifying cooling technologies which minimize those losses is crucial to realizing the full potential of reheat cycles. The strong role played by cooling losses in reheat cycles necessitates their inclusion in cycle optimization. To this end, the models for the thermodynamics of combined cycles and cooled turbines presented in Parts 1 and 2 of this paper have been extended where needed and applied to the analysis of a wide variety of cycles. The cooling methods considered range from established air-cooling technology to methods under current research and development such as air-transpiration, open-loop, and closed-loop water cooling. Two schemes thought worthy of longer-term consideration are also assessed. These are two-phase transpiration cooling and the regenerative thermosyphon. A variety of configurations are examined, ranging from Brayton-cycles to one or two-turbine reheats, with or without compressor intercooling. Both surface intercoolers and evaporative water-spray types are considered. The most attractive cycle configurations as well as the optimum pressure ratio and peak temperature are found to vary significantly with types of cooling technology. Based upon the results of the model, it appears that internal closed-loop liquid cooling offers the greatest potential for midterm development. Hybrid systems with internally liquid-cooled nozzles and traditional air-cooled rotors seem most attractive for the near term. These could be further improved by using steam rather than air for cooling the rotor.

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