Cooled Gas Turbine Research Articles

Techno-Economic Feasibility Study of Earth Air Heat Exchangers for Gas Turbine Inlet Air Cooling

In response to pressing energy crises and environmental concerns, enhancing the performance of existing energy conversion systems, such as gas turbines, and tapping into renewable resources have become critical imperatives. Escalating ambient temperatures poses a notable challenge, hampering the efficiency of gas turbines. This study rigorously explores the feasibility of earth-to-air heat exchangers (EAHEs) as a pragmatic solution to cool gas turbine inlet air. The primary objective is an exhaustive techno-economic analysis evaluating the long-term operational viability of EAHE systems. Employing the Taguchi method, the study optimizes the system geometry and pipe arrangement, focusing on four key control factors: pipe diameter, spacing, length, and depth. The pivotal optimization criterion is the levelized cost of energy (LCOE), encompassing thermal performance and economic viability. The net present value (NPV) and Discounted Payback Period provide supplementary insights into the economic prospects. Integral to the study is a novel and intricate hybrid analytical-numerical model that simulates the long-term transient operation of EAHE. Findings from a detailed case study unveil an optimized scenario yielding an LCOE amounting to 0.071 $/kWh, accompanied by a substantial NPV of 4.5 million dollars.

Calculated and Experimental Substantiation of Increasing the Interval between Repairs of the SGT5-2000E Gas Turbine Cooled Blades

Calculated and Experimental Substantiation of Increasing the Interval between Repairs of the SGT5-2000E Gas Turbine Cooled Blades

Action Mechanism of Film Extraction on Channel Impingement Cooling for Blade Leading Edge Using Large Eddy Simulation

Abstract Various internal cooling techniques combined with external film cooling are applied to cool gas turbine blades, and the coolant extraction can cause variations in internal flow structures and cooling effectiveness. Effects of film extraction under different film hole diameters and coolant mass flow ratio on heat transfer and flow characteristics of channel impingement cooling are presented using large eddy simulation (LES) in this article. The current work was undertaken based on turbine blade dimensions and turbine operating conditions. The results indicate that film extraction coupled with the curvature-induced instability dominates flow patterns and heat transfer in the channel impingement cooling structure with a film hole, especially in the bend region corresponding to the leading edge of turbine blades. Film coolant extraction can disrupt the streamwise counterrotating flow circulation pair. The latter is caused by the curvature-induced instability and is also the major driver of multilongitudinal vortices. The hole edge vortex generated by coolant bleed amplifies heat transfer at the leading edge, and the effect is more significant as the film hole diameter increases. Conversely, heat transfer coefficient downstream of the cooling channel decreases due to a reduction in cooling air. The increasing film bleed flow increases overall total pressure loss, while flow loss in the cooling channel decreases because of the weakened flow circulations and reduced coolant mass flow. This work provides an in-depth insight into the cooling performance of channel impingement cooling with film extraction, contributing to designing film cooling for turbine blades with multichannel wall jet cooling.

Special Issue: Richard J. Goldstein Memorial Issue—Transformative and Innovative Advancements in Heat and Mass TransferA Lifetime of Path-Breaking Scholarship That Spans Gas-Turbine Cooling to Transport Processes and Critical Diagnostic Tools for Convective Heat Transfer and More

Abstract Professor Richard J. Goldstein was perhaps one of the "tallest" colleagues in our field with a career spanning over seven decades, and during which he contributed extensively to a gamut of heat and mass transfer topics and his work has impacted nearly all areas of thermal science. He was a pioneering innovator and his scholarship influenced the way scientists and engineers solve the world's contemporary engineering and technological challenges. This has been particularly evident in thermal science frontiers relating to novel diagnostics in temperature measurements, cooling technologies for high-performance gas turbines, innovative evaluation techniques for thermal convection, and visionary leadership on the global stage in energy engineering.

Study of Gas Film Cooling under Large Eddy Simulation: Effect of Forward and Backward Injection on Gas Turbine Cooling Efficiency and Stability

In the design of advanced gas turbines, improving thermal efficiency and power output is crucial achieve energy saving and emission reduction goals. This necessitates raising the inlet temperature, thereby highlighting the importance developing efficient cooling technologies to ensure the longevity of hot components. Gas film cooling, as a widely used traditional cooling method, is subject to the influence of fluid dynamic characteristics, especially in unstable operating environments such as pressure fluctuations in the upstream combustion chamber and interactions between stators and rotors. This study utilized large eddy simulation to analyze the effectiveness of trench film cooling under such unstable conditions, with a specific focus on the time-averaged and transient characteristics of forward and backward injection of cooling air. The study investigated the efficacy of film cooling under pulsating flow conditions, with a blowing ratio of 1.5 under steady-state conditions, utilizing cosine and square waves as pulse boundaries, and a Strouhal number of 0.254. The research findings reveal that: 1) Contrary to the results under steady-state conditions, pulsating reverse injection led to a reduction of over 15% in time-averaged cooling efficiency and a noticeable decrease in the film coverage area compared to forward injection; this phenomenon is determined by the different flow mechanisms under steady-state and pulsating states. 2) Under a certain blowing ratio, the instability of gas film cooling is induced by the temporal fluctuations of near-wall vortices, which could result in rapid temperature changes and component failures. For pulsating forward injection, additional high film cooling unsteadiness outside the slot membrane orifices was observed. In the case of backward injection, pulsations did not lead to a significant increase in instability. These research findings provide a deeper understanding of the impact of gas film cooling on the cooling efficiency and stability of gas turbines, enabling gas film cooling technology to meet the inlet temperature requirements of advanced gas turbines, thereby reducing carbon emissions and contributing to the achievement of China's dual carbon goals.

Overall cooling characteristics of double-wall effusion system considering material selections and hole arrangements

Enhancing thermal protection of hot components in gas turbines can be accomplished using advanced materials with various thermal conductivities and optimized cooling structures that exhibit high internal-external cooling efficiency. The double-wall effusion system (DWES) stands out as a promising solution for effectively cooling gas turbine hot components. However, its thermal response to new materials remains inadequately explored, and the combined effect of hole arrangement and thermal conductivity within the DWES system has not been thoroughly investigated. In this study, the impacts of material selection and hole arrangement on the overall cooling characteristics of the impingement-pinfin-effusion based DWES were thoroughly investigated. Three different materials with varying thermal conductivities were selected to control Biot number, and various hole arrangements, including effusion-only or impingement-effusion, as well as forward or backward film injection, were compared to quantify the contributions of internal and film cooling on the overall cooling performance. The results showed that the stainless-steel scheme achieves the highest overall cooling effectiveness due to its superior thermal conductivity, while the polycarbonate scheme obtains the lowest overall cooling effectiveness. Compared to the corresponding effusion-only schemes, the area-averaged overall cooling effectiveness of the stainless-steel impingement-effusion scheme demonstrates a remarkable increase of up to 29%. Notably, employing backward film injection yields remarkable improvements in overall cooling effectiveness, with the stainless-steel impingement-effusion scheme exhibiting an increment of up to 16% compared to the forward film injection configuration. Furthermore, the correlations that establish the relationship between the overall cooling effectiveness, Biot number, and blowing ratio were developed for various configurations. These correlations can serve as valuable design tools for the development of next-generation gas turbines that incorporate the DWES technology.

Peculiarities of the Calculations of the Gas Turbine Cooling Systems

Gas turbine cooling systems have the branched networks of various channels whose hydraulic and heat exchange capabilities define the air flow required for the cooling of turbine parts and, thus, directly influence the efficiency of gas turbines. Cooling system elements are, in particular, the throttles, diaphragms, seals, openings that act as regulating parts or elements to maintain pressure in the system. As a rule, the channels of this type have a significant pressure drop, and therefore during the calculations it is necessary to very carefully consider a change in air density along the channel. Therefore, we present in this paper the method developed by the authors for determining the hydraulic resistance in the openings, and the data obtained by it perfectly agree with the experimental data. It is shown how to take into account the effect of the air compressibility on the coefficient of hydraulic resistance in the cooling channels that allows for the use of the numerous experimental dependencies for the coefficients of hydraulic resistance of incompressible liquids. A method of calculating hydraulic resistances of the openings by defragmenting their total hydraulic resistance into separate components has been proposed. A generalized dependence was established for the hydraulic resistance of the discharge openings in the discs and in the mounting gaps between the shanks of the blades and the discs, taking into account the transverse air flows.

Study on Flow and Heat Transfer Characteristics and Anti-Clogging Performance of Tree-Like Branching Microchannels

In this paper, a tree-like branching microchannel with bifurcating interconnections is designed for gas turbine blade cooling. A theoretical analysis, experimental study, and numerical simulation of the heat transfer and hydrodynamic characteristics of the tree-like branching microchannel is performed, and the influence of the total number of branching levels m on the anti-clogging performance is also studied. The results indicate that the total heat transfer ratio and pressure drop ratio are closely related to the structur ne parameters. The comprehensive thermal performance increase with an increase in the ratio of Lb/L0 and fractal dimension D. Nu/Nus, f/fs, and η are increased as m increases from 3 to 5. Furthermore, the tree-like microchannel network exhibits robustness for cooling gas turbine blades. A greater total number of branching levels and a higher Re number are advantageous for enhancing the anti-clogging performance of the tree-like branching microchannel.

Advanced Gas Turbine Cooling for the Carbon-Neutral Era

In the coming carbon-neutral era, industrial gas turbines (GT) will continue to play an important role as energy conversion equipment with high thermal efficiency and as stabilizers of the electric power grid. Because of the transition to a clean fuel, such as hydrogen or ammonia, the main modifications will lie with the combustor. It can be expected that small and medium-sized gas turbines will burn fewer inferior fuels, and the scope of cogeneration activities they are used for will be expanded. Industrial gas turbine cycles including CCGT appropriate for the carbon-neutral era are surveyed from the viewpoint of thermodynamics. The use of clean fuels and carbon capture and storage (CCS) will inevitably increase the unit cost of power generation. Therefore, the first objective is to present thermodynamic cycles that fulfil these requirements, as well as their verification tests. One conclusion is that it is necessary to realize the oxy-fuel cycle as a method to utilize carbon-heavy fuels and biomass and not generate NOx from hydrogen combustion at high temperatures. The second objective of the authors is to show the required morphology of the cooling structures in airfoils, which enable industrial gas turbines with a higher efficiency. In order to achieve this, a survey of the historical development of the existing cooling methods is presented first. CastCool® and wafer and diffusion bonding blades are discussed as turbine cooling technologies applicable to future GTs. Based on these, new designs already under development are shown. Most of the impetus comes from the development of aviation airfoils, which can be more readily applied to industrial gas turbines because the operation will become more similar. Double-wall cooling (DWC) blades can be considered for these future industrial gas turbines. It will be possible in the near future to fabricate the DWC structures desired by turbine cooling designers using additive manufacturing (AM). Another conclusion is that additively manufactured DWC is the best cooling technique for these future gas turbines. However, at present, research in this field and the data generated are scattered, and it is not yet possible for heat transfer designers to fabricate cooling structures with the desired accuracy.

A comparison of oscillating sweeping jet and steady normal jet in cooling gas turbine leading edge: Numerical analysis

Impinging jets have emerged as a prominent cooling technology in the gas turbine industry. With the addition of fluidic oscillators as heat removal devices, steady-state impinging jets can be converted to sweeping impinging jets, presenting an opportunity to improve the heat transfer performance of current impinging jets by covering a larger cooling surface area on the leading edge of a gas turbine blade. Sweeping jets are self-oscillating devices that operate based on the Coanda effect, making them self-sustaining. In this study, the flow and heat transfer performance of an array of seven steady and sweeping impinging jets were investigated using the unsteady Reynolds-averaged Navier-Stokes turbulent SST k-ω model. The sweeping jet impingement improved the heat removal performance by cooling a larger surface area of the leading edge with a constant heat flux and by improving the overall time-averaged cooling effectiveness. Compared with the steady jet case, the sweeping jet case shows an improvement in heat transfer of 12.2%. Further, the use of fluidic oscillators (sweeping jets) produced a more uniform mass flow rate distribution from all jets compared with a simple jet.

Review of the State of the Art for Radial Rotating Heat Pipe Technology Potentially Applicable to Gas Turbine Cooling

Improvements in the efficiency of gas turbine engines over the decades have led to increasing turbine inlet temperatures. This, in turn, has resulted in the need to cool the turbine blades themselves to avoid damage to them. While air-cooling and film-cooling methods have been adopted as the primary methods of gas turbine blade cooling, the heat pipe cooling method shows greater potential in terms of temperature uniformity, maximum allowable gas temperature, reliability, and durability. This paper reviews the state-of-the-art research activities on the radial rotating heat pipes (RRHP) potentially applicable to gas turbine cooling. The emergence of the heat-pipe-cooled turbine blade concept, designs, and variants will be described at the beginning. Then the paper will review the literature addressing the heat transfer performance of RRHPs, and the effects on them of rotational forces, working fluid properties, and geometry, as well as operational limits they may be subject to. Additionally, the effects of secondary flow and numerical simulation of RRHPs will be reviewed and discussed. It can be concluded that fundamental studies are still needed for the understanding of the RRHP, as well as the improvement of numerical models.

Thermodynamic sensitivity analysis of SOFC integrated with blade cooled gas turbine hybrid cycle

In the area of clean energy production along with higher efficiency, integrated combine power system, specifically gas turbine (GT) cycle with solid oxide fuel (SOFC) system, is gaining the attention of researchers. Thermodynamic modeling for the SOFC-GT hybrid cycle has been presented in this paper. For the proposed hybrid cycle, a high-temperature SOFC has successfully integrated with the recuperated-blade cooled gas turbine cycle. The gas turbine outlet waste heat has perfectly utilized the recuperator to power the fuel cell system. However, to maintain the temperature of the gas turbine blade within the permissible limit, air–film blade cooling scheme has been used. The SOFC-GT hybrid cycle has been operated under steady-state conditions, and a developed MATLAB program has been used to solve the governing equations for the components of the hybrid cycle. The impact of main operating parameters such as the temperature intake turbine (TIT), compression ratio (rpc), fuel utilization ratio (UF), and recirculation ratio are examined. From the obtained result, it can be revealed that the integration of the SOFC has seen significant improves overall hybrid cycle efficiency. The performance of fuel cell (SOFC) increases notably as the level of recuperation increases. To check the influence of main operating parameters, a sensitivity analysis has been performed for the hybrid cycle, and the maximum efficiency of 73% has been achieved. Moreover, to extend this research, an exclusive performance map has been plotted for power plant designers.

Investigation into femtosecond based laser ablation and morphology of micro-hole in titanium alloy

Creating good surface quality micro holes for cooling gas turbine blades made of titanium alloy is still challenging for manufacturers of aerospace engine components. Therefore, the goal of this work is to comprehend how an ultra-short pulse laser interacts with titanium alloy and to explore the effect of laser fluence, pulse overlap and pulse repetition rate on hole diameter, depth, heat affected zone and recast layer. The threshold for femtosecond laser ablation is determined for different laser fluence, pulse repetition rates, and hole sizes. By using a 3D profilometer and field emission scanning electron microscopy, the ablated micro hole features are determined. Regardless of laser fluence or hole size, better micro hole shape is seen at a threshold repetition rate of 10 kHz. Better hole geometry is obtained at fluence of 0.44 J/cm2, 10 kHz repetition rate and 85% of pulse overlap. At higher pulse overlap, micro-cracks, heat-affected zones, and recast layers are more prominent, which is related to higher heat accumulation since titanium alloy has a low thermal conductivity.

Coupled aerothermal-mechanical analysis in single crystal double wall transpiration cooled gas turbine blades with a large film hole density

• Double wall transpiration cooling protects turbine blades against high heat flux. • A high film hole density can benefit both the aerothermal and mechanical response. • The wall spacing influences the cooling effectiveness and aerothermal response. • The wall thickness ratio influences thermal stresses and the mechanical response. • Stresses tend to apply along secondary crystallographic directions around features. The ambition for increasing gas turbine efficiency beyond current levels through the elevation of gas temperatures demands substantial progress in turbine blade cooling technology. Double wall transpiration cooling (DWTC) is an emerging technology which offers enhanced thermal protection at only modest coolant flows, thanks to a combination of impingement jets and densely packed arrays of film cooling holes. This paper presents a coupled aerothermal-mechanical investigation of a transpiration cooled double wall turbine blade design, by employing Computational Fluid Dynamics (CFD), heat transfer theory as well as stress analysis based on plate theory and Finite Element (FE) analysis. In comparison to previously explored systems with modest outer wall porosity, a system with high porosity is found to display enhanced cooling effectiveness and to reduce the temperature difference across the two walls that drives thermal stresses. This difference can be decreased further by reducing the wall spacing, H , or the inner-outer wall thickness ratio, t c / t h , at the cost of higher overall metal temperatures. A lower bound for H should be used to avoid undesirable poor coolant flow distribution and hot gas ingestion effects, whereas the t c / t h ratio does not impose any aerothermal constraints. Thermal stresses associated with a fixed temperature field are invariant with H but they vary drastically with t c / t h . From a design perspective, the above suggest that H is primarily determined by aerothermal requirements, whereas t c / t h by the mechanical performance. The single crystal orientation and elastic anisotropy of Nickel alloys are shown to have a profound impact on the stress concentration around cooling holes, with secondary crystallographic directions, such as 〈 110 〉 and 〈 111 〉 , playing a prominent role in the local stress state. Our study provides a framework for optimising the aerothermal and mechanical performance in a range of high temperature components and highlights key areas where more elaborate analysis is needed.

Numerical investigation of crack initiation in high-pressure gas turbine blade subjected to thermal-fluid-mechanical low-cycle fatigue

A thermo-fluid-structural analysis procedure was proposed in this study to investigate the lifespan of a realistic cooling gas turbine blade. The temperature and pressure data extracted from computational fluid dynamics simulations were applied as the loading force to calculate the strain and stress using the finite element (FE) method. Subsequently, a fatigue analysis was conducted to estimate the blade life and predict the position of cracks. Here, the fatigue model used to calculate the blade life and damage was based on the strain-life model. The results showed that although the cooling film covered the entire blade surface, inefficient cooling was still observed in some regions, such as the tip and platform, which lead to blade overheating. A high pressure distribution of approximately 1.374 MPa was formed primarily on the leading tip (LT) of the pressure side (PS) blade; this pressure decreased toward the suction side. The FE simulations revealed that temperature caused a high stress at the tip and platform regions, whereas pressure caused stress at the leading edge fillet and trailing edge (TE) root slot. Thermal stress accounted for a greater amount of stress on the blade in comparison to the pressure force. Moreover, the combination of thermal and pressure stresses increased the stress at the TE root slot. Although the maximum stress in almost all the regions was lower than the ultimate strength, cracks still appeared under low-cycle start–stop loading. According to the fatigue life predictions, cracks would appear on the TE root slot, middle-tip, trailing tip, LT, and on the PS edge platform after approximately 150, 484, 701, 673, and 374 start–stop cycles, respectively. These fatigue life estimations showed good agreement with the blade crack patterns.

Mixed-dimensional geometric coupling of port-Hamiltonian systems

We propose a new interconnection relation for infinite-dimensional port-Hamiltonian systems that enables the coupling of ports with different spatial dimensions by integrating over the surplus dimensions. To show the practical relevance, we apply this interconnection to a model system of an actively cooled gas turbine blade. We also show that this interconnection relation behaves well with respect to a discretization in finite element space, ensuring its usability for practical applications.

Application of Sine Cosine Egret Swarm Optimization Algorithm in Gas Turbine Cooling System

Gas turbine cooling system is a typical multivariable, strongly coupled, nonlinear, and uncertain MIMO system. In order to solve the control problem of pressure, flow, and temperature of the system, an intelligent approach is necessary and more appropriate. The current system control mainly depends on the experience of the staff, which exists problems such as high labor intensity, low work efficiency and low control accuracy. Lack of accurate models make parameters tune difficultly, and ordinary control methods are difficult to control complex gas turbine cooling system. In this paper, the system transfer function model is built based on the field data obtained under different working conditions and system identification method. The diagonal matrix decoupling method is used to weaken the correlation between variables and achieve independent control among variables. When optimizing the parameters of the controller, Sine Cosine Egret Swarm Optimization Algorithm is proposed. Egret Swarm Optimization Algorithm is composed of Sit-And-Wait strategy, random walk, and encirclement strategy. The sit-and-wait strategy is prone to premature convergence, which makes the optimized parameters unsuitable for gas turbine cooling system. Sine Cosine Algorithm is introduced to randomly use the sine-cosine function for the pseudo-gradient of the weights of the observation equation, thus expanding the search range of the population. Friedman tests prove that the deviation of SE-ESOA is within the allowable range. The results show that the result of Sine Cosine Egret Swarm Optimization Algorithm is more stable and accurate, and it is more suitable for gas turbine cooling system, which solve the pressure, flow, and temperature control problems of complex systems.

Design of Gas Turbine Cooling System Based on Improved Jumping Spider Optimization Algorithm

The gas turbine cooling system is a complex MIMO system with a strong coupling, nonlinear, time-varying and large disturbance amplitude. In order to automatically control the target flow, target temperature and pipeline pressure, in this paper, the decoupler and regulator of a gas turbine cooling system are designed. Firstly, the working principle of a gas turbine cooling system and the coupling between the controlled variables of the system are analyzed. The decoupler of the system is designed by using the diagonal matrix decoupling method. The transfer function models of the coupling system are built through system identification, and the decoupling matrix of the system is calculated according to the diagonal matrix decoupling method and transfer function models. Then, the engine cooling control system simulation model is constructed and an improved jumping spider optimization algorithm is proposed. The parameters of the controller are optimized by the improved jumping spider optimization algorithm. Finally, the control system simulation is done and compared with the jumping spider optimization algorithm and the particle swarm optimization algorithm. The simulation results show that the improved jumping spider optimization algorithm is more suitable for the multivariable strong coupling nonlinear engine cooling system. For the flow and pressure control, the transient time and overshoot are reduced, and the steady-state error is less than 1%. For the temperature control, the result of the improved jumping spider optimization algorithm is more smooth, without overshoot, and almost does not exceed the set inlet water temperature. The overshoot, steady-state errors and transient time of the system have been improved, which proves the feasibility and significance of the improved jumping spider optimization algorithm by comparing the control performance and optimization time.

Research and Development of Trinary Power Cycles

The most effective and environmentally safe fossil fuel power production facilities are the combined cycle gas turbine (CCGT) ones. Electric efficiency of advanced facilities is up to 58% in Russia and up to 64% abroad. The further improvement of thermal efficiency by increase of the gas turbine inlet temperature (TIT) is limited by performance of heat resistance alloys that are used for the hot gas path components and the cooling system efficiency. An alternative method for the CCGT efficiency improvement is utilization of low potential heat of the heat recovery steam generator (HRSG) exhaust gas in an additional cycle operating on a low-boiling heat carrier. This paper describes a thermodynamic analysis of the transition from binary cycles to trinary ones by integration of the organic Rankine cycle (ORC). A mathematical model of a cooled gas turbine plant (GT) has been developed to carry out calculations of high-temperature energy complexes. Based on the results of mathematical modeling, recommendations were made for the choice of the structure and parameters of the steam turbine cycle, as well as the ORC, to ensure the achievement of the maximum thermal efficiency of trinary plants. It is shown that the transition from a single pressure CCGT to a trinary plant allows the electric power increase from 213.4 MW to 222.7 MW and the net efficiency increase of 2.14%. The trinary power facility has 0.45% higher efficiency than the dual pressure CCGT.

Sensitivity of transpiration cooled gas turbine cycle efficiency and coolant requirement to changes in cooling parameters

The maximum temperature at the gas turbine inlet gets restricted due to metallurgical constraints, which can be increased using blade cooling. Among different techniques for cooling blades in the gas turbine, the transpiration cooling of blades permits quite a high temperature at the turbine inlet. The objective of this study is to analyse the sensitivity of transpiration cooled gas turbine cycle performance for cooling parameterssuch as allowable blade material temperature, film cooling effectiveness, and internal cooling efficiency, so that the most important cooling parameters may be focused upon for the improvement of gas turbine cycle performance. In this study, it is found that the cycle efficiency is more sensitive to allowable blade material temperature followed by film cooling effectiveness and to internal cooling efficiency only a little bit. This study shows that with the use of cooling, for an increase in allowable blade temperature by 50 K, the gas turbine cycle efficiency increases by 0.15% . Also, the increase in film cooling effectiveness from 0.4 to 0.5 increases the cycle efficiency by 0.13% . Furthermore, with an increase in cooling efficiency from 0.7 to –0.8 the cycle efficiency increases by 0.03% only.