Gas Turbine Thermal Efficiency Research Articles

Thermo-economic Impact from Using Exhaust Gases Heat Lost for Power Generation

The heat lost from gas turbine power plants with exhaust gases represents the most important source for lowering its thermal efficiency. Also, the gas turbine thermal efficiency affected significantly with the ambient surrounding temperature. Al-Najybia gas-turbine power plant in Basrah, Iraq is choosing as a case study. The power plant consists of four units with a capacity of 125 MW for each unit. In the present study, all the calculations are performed for one unit only. Firstly the thermal impact is studied in terms of energy analysis for Al-Najybia gas turbine power plant (GTPP) for different ambient temperature for twelve months. Also, the economic loss a companied the heat lost with exhaust gases for different ambient temperature are estimated. Secondly, the thermo-economic improvement from coupling the GTPP with a heat recovery system is studied. For gas-steam combined cycle, the performance and economic analysis are performed. The results show that, the output power and thermal efficiency are decreased by 0.97 MW and 0.0726% respectively for each unit temperature rise of the ambient temperature. For the combined gas-steam power plant the percentage increasing of the thermal efficiency is approximately 46.4%. The results indicate the combined cycle power plant (CCPP) is very important to increase electrical capacity. From the economic analysis, the economic gain due to using HRB is 75757 $ per month

Advanced Cooling in Gas Turbines 2016 Max Jakob Memorial Award Paper

Gas turbines have been extensively used for aircraft engine propulsion, land-based power generation, and industrial applications. Power output and thermal efficiency of gas turbines increase with increasing turbine rotor inlet temperatures (RIT). Currently, advanced gas turbines operate at turbine RIT around 1700 °C far higher than the yielding point of the blade material temperature about 1200 °C. Therefore, turbine rotor blades need to be cooled by 3–5% of high-pressure compressor air around 700 °C. To design an efficient turbine blade cooling system, it is critical to have a thorough understanding of gas turbine heat transfer characteristics within complex three-dimensional (3D) unsteady high-turbulence flow conditions. Moreover, recent research trend focuses on aircraft gas turbines that operate at even higher RIT up to 2000 °C with a limited amount of cooling air, and land-based power generation gas turbines (including 300–400 MW combined cycles with 60% efficiency) burn alternative syngas fuels with higher heat load to turbine components. It is important to understand gas turbine heat transfer problems with efficient cooling strategies under new harsh working environments. Advanced cooling technology and durable thermal barrier coatings (TBCs) play most critical roles for development of new-generation high-efficiency gas turbines with near-zero emissions for safe and long-life operation. This paper reviews basic gas turbine heat transfer issues with advanced cooling technologies and documents important relevant papers for future research references.

Energy and Exergy Analysis of a Simple Gas Turbine Cycle with Wet Compression

A thermodynamic model of the wet compressor in a simple gas turbine cycle was investigated in this paper. A suitable quantity of water was injected into the compressor-stages where it evaporated. Subsequently, the steam and air were heated in the combustion chamber and expanded in the turbine. The wet compressor (WC) has become a reliable way to reduce gas emissions and increase gas turbine efficiency. In this study, the operational data of the simple gas turbine and the maximum amount of water that can be injected into the compressor were assessed, as well as a comparison between the dry compression, the wet compression and the isentropic compression. The performance variation due to water spray in the compressor and the effect of varying ambient temperature on the performance of gas turbine (thermal efficiency, power) was investigated, and the results are compared to the results of the same cycle with a dry compressor. The analytical formula of exergy destruction and results show that exergy destruction increases with water injection. The programming of the performance model for the gas turbine was developed utilizing the software IPSEpro. The results of the gas turbine with a wet compressor demonstrates a 12% reduction in the compressor exit temperature up to isentropic temperature. The compressor work decreased by 11% when using a wet compressor, this lead to an improvement in power output and efficiency However, the wet compressor increases the specific fuel consumption and heat rate of the gas turbine. There are limitations in the amount of steam that can be injected, 0.4 kg/s of water was the optimum amount injected into the compressor.

Parametric Performance of Ultra-light Gas Turbine Power Plant for Heavy Lift Multicopters Flight Systems Using Astra - Russian Aviation Engine Optimization Software

A detailed parametric analysis was performed on entire performance cycle model of micro gas turbine power plant. The parametric analysis was studied using Russian Software named ASTRA. Evaluation of parameters on both design and operation condition was performed. The parameters focused here are power output, compression work, specific fuel consumption and thermal efficiency. Various stages such as use of Intercooler, Pre-heater and their optimal influence on thermodynamics were performed. The task was to optimize the maximum output in free turbine power by simulating various cycles of compressor pressure ratios for centrifugal compressor, ambient temperature in various altitude; air-fuel mix ratio and turbine inlet temperature. The results are analysed and presented in this article, the Analysis known as on-design analysis. The compressor uses 66% of turbine work output. The research analysis focuses on reducing the use of power output by compressor and maximizes the power output by free turbine. The results could be summarized as increase in gas turbine thermal efficiency does not always improve the gas turbine efficiency. Optimum power increase of up to 3% was improved and improvement in fuel efficiency improved about 4%.

Effect of V-shaped Ribs on Internal Cooling of Gas Turbine Blades

Thermal efficiency and power output of gas turbines increase with increasing turbine rotor inlet temperature. The rotor inlet temperatures in most gas turbines are far higher than the melting point of the blade material. Hence the turbine blades need to be cooled. In this work, simulations were carried out with the leading edge of gas turbine blade being internally cooled by coolant passages with V-shaped ribs at angles of 30°, 45° or 60° and at three aspect ratios (1:1, 1:2 and 2:3). The trailing edge of the blade was cooled by cylindrical and triangular pin-fin perforations in staggered and inline arrangements. Numerical analyses were carried out for each configuration of the cooling passages. The best cooling passages for leading edge and trailing edge were deduced by comparing the results of these analyses. It was found that using V-shaped ribs and fins induces a swirling flow, which in turn increases the velocity gradient and hence produces an improvement in heat transfer. The results show that under real time flow conditions, the application of V-shaped ribs and pin-fin perforations is a very promising technique for improving blade life.

Energy and exergy analysis of air-film cooled gas turbine cycle: Effect of radiative heat transfer on blade coolant requirement

Gas turbine blade cooling is critical to continuous reliable operation of gas turbines. Literature suggests that air-film cooling is one of the most widely used blade cooling techniques. This paper compares previously developed blade cooling models which are relevant to film cooling technique and it also proposes a gas turbine blade cooling model for the estimation of blade coolant mass fraction, considering radiative heat transfer from hot combustion gases to gas turbine blade surface. The proposed model gives an enhanced coolant mass fraction (≈5–6% over a wide range of TIT) as compared to previously developed models while analyzing gas turbine cycle. Gas turbine cycle performance has been evaluated based on two blade cooling models to compare blade coolant flow mass fraction, gas turbine plant specific work which are function of both compressor-pressure ratio and turbine inlet temperature. Both the blade cooling models closely follow each other with radiative cooling model. For the proposed blade cooling model, gas turbine specific work is around 417.39 kJ/kg (rpc = 22 and TIT = 1650 K) and gas turbine thermal cycle efficiency has been found to be 41.25% at (rpc = 22 and TIT = 1550 K). Exergy analysis of gas turbine cycle has also been done which shows combustor to be main source of exergy destruction (≈29%).

CFD ANALYSIS ON RADIALCOOLING OF GAS TURBINE BLADE

Gas turbines are extensively used for air craft propulsion, land based power generation and industrial applications. Thermal efficiency of gas turbine improved by increasing turbine rotor inlet temperature. The current rotor inlet temperature in advanced gas turbine is for above the melting point of blade material. A sophisticated cooling scheme must be developed for continuous safe operation of gas turbines with high performance. Gas turbines are cooled externally and internally. Several methods have been suggested for the cooling of blades and vanes. The techniques that involve to cool the blades and vanes by using cooling methods is to have radial holes to pass high velocity cooling air along the blade span. In this thesis, a turbine blade is designed and modelled in CATIA v5and ICEM CFDsoftware. The turbine blades are designed using cooling holes. The turbine blade is designed with 12 holes. CFD analysis is done to determine the pressure distribution, velocity, temperature distribution and heat transfer rate by applying the inlet velocities. Thermaland Structural analysis is done to determine the heat transfer rates and strength of the blade. The present used material for blade is chromium steel. In this thesis, itis replaced with Titanium aluminium alloy. The better material for blade is analyzed

Numerical Analysis of Helical Grooved Channels Near the Leading Edge Region in Gas Turbine Blade

Gas turbines are greatly operative engineered prime movers for transforming energy from thermal form (combustion stage) to mechanical form which is widely used for propulsion and power generation systems. The power output and thermal efficiency of gas turbine can be increased with increase in turbine inlet temperature of the hot gases. The modern gas turbines operating presently, the entry temperature of the hot gases at the inlet of the turbine are as high as 1723 K but this temperature surpasses the melting point of the turbine blade material. Since the present day gas turbines are functioning at very high temperatures, it is essential to implement effective cooling techniques, so the gas turbine vanes and blades sustain in the path of the hot fluid. Sufficient cooling cannot be achieved by passing the cool air through the blade, consequently it is essential to implement cooling methods that will additionally augment the heat transfer from the blade walls. It is seen that the blade can be cooled efficiently by adding in helical grooved channels near the leading edge region which promotes turbulence and higher flow rates through the channels. Based on the investigation better cooling of turbine blade is achieved by helical grooved channels with diameter five millimetre, pitch of helix: 50 millimetre and 8 starts resulting best thermal performance. Copyright © 2017 Praise Worthy Prize S.r.l. - All rights reserved

Exergy Analysis for Brayton and Inverse Brayton Cycles with Steam Injection

Global economic and social development has led to the growth in demand for electrical power. Gas turbines play an essential role in many societies, and as the requirements for power generation increase, the power output and thermal efficiency of gas turbines must also increase. This paper presents one of the ways to improve the performance of the gas turbine with a study of exergy analysis of combined Brayton and inverse Brayton cycles with steam injected into the combustion chamber. The effect of variation of operating conditions (compression ratio and ambient temperature) on the performance of gas turbine (thermal efficiency, power) were investigated, the results were compared with the same cycle, but without injection with the analytical formulae of exergy and exergy destruction. The programming of performance model for gas turbine was developed utilizing the commercially available software IPSEpro. The analysis shows that the highest exergy destruction occurs in the combustion chamber. In addition, the performance has been improved by using steam injection by 11% in efficiency and 57% in power output and decrease linearly with the increase of the ambient temperature. However, steam injection increases the specific fuel consumption and heat rate. Thus, the thermodynamic parameters on cycle performance are economically feasible and beneficial for the gas turbine operations.

Thermodynamic analysis of alternative marine fuels for marine gas turbine power plants

The marine shipping industry faces challenges to reduce engine exhaust emissions and greenhouse gases (GHGs) from ships, and in particular, carbon dioxide. International regulatory bodies such as the International Maritime Organization and National Environmental Agencies of many countries have issued rules and regulations to drastically reduce GHG and emissions emanating from marine sources. This study investigates the possibility of using natural gas and hydrogen as alternative fuels to diesel oil for marine gas turbines and uses a mathematical model to assess the effect of these alternative fuels on gas turbine thermodynamic performance. Results show that since natural gas is categorized as a hydrocarbon fuel, the thermodynamic performance of the gas turbine cycle using natural gas was close to that of the diesel case. However, the gas turbine thermal efficiency was found to be slightly lower for natural gas and hydrogen fuels compared to diesel fuel.

CHT Analysis of Trailing Edge Region Cooling In HP Stage Turbine Blade

Gas turbines play a vital role in the today’s industrialized society, and as the demands for power increase, the power output and thermal efficiency of gas turbines must also increase. Modern high-speed aero-engines operate at elevated temperatures about 2000 K to achieve better cycle efficiencies. The internal cooling techniques of the gas turbine blade includes: jet impingement, rib turbulated cooling, and pin-fin cooling which have been developed to maintain the metal temperature of turbine blades within acceptable limits. Cooling passages having fins are incorporated into the trailing edge regions which are modelled and analysed to achieve maximum thermal performance in terms of cooling. It is seen that fins provide an augmented convective area for better heat dissipation. The shape and orientation of fins plays a major role in air flow patterns and greatly affects the heat dissipation rate.

Enhancement of gas turbine power output using earth to air heat exchanger (EAHE) cooling system

The application of earth to air heat exchanger (EAHE) as an inlet air cooling system on gas turbine performance has been investigated. Transient, one-dimensional model was developed for predicting the thermal performance of EAHE. Gas turbine output power, efficiency and specific fuel consumption are assessed with application of EAHE. MATLAB program is developed for solving the discrete numerical equations. Damietta power plant is selected as case study. The output power and thermal efficiency of gas turbine increases by 9% and 4.8%; respectively. In addition the annual revenue will increase by 1.655∗106$ with payback period of 1.2year.

Numerical investigation on heat transfer in an advanced new leading edge impingement cooling configuration

It is known that the leading edge has the most critical heat transfer area of a gas turbine blade. The highest heat transfer rates on the airfoil can always be found on the stagnation region of the leading edge. In order to further improve the gas turbine thermal efficiency the development of more advanced internal cooling configurations at leading edge is very necessary. As the state of the art leading edge cooling configuration a concave channel with multi inline jets has been widely used in most of the blades. However, this kind of configuration also generates strong spent flow, which shifts the impingement off the stagnation point and weakens the impingement heat transfer. In order to solve this problem a new internal cooling configuration using double swirl chambers in gas turbine leading edge has been developed and introduced in this paper. The double swirl chambers cooling (DSC) technology is introduced by the authors and contributes a significant enhancement of heat transfer due to the generation of two anti-rotated swirls. In DSC-cooling, the reattachment of the swirl flows always occurs in the middle of the chamber, which results in a linear impingement effect. Compared with the reference standard impingement cooling configuration this new cooling system provides a much more uniform heat transfer distribution in the chamber axial direction and also provides a much higher heat transfer rate. In this study, the influences of different geometrical parameters e.g. merging ratio of two cylinder channels, the jet inlet hole configurations and radius of blunt protuberances in DSC have been investigated numerically. The results show that in the DSC cooling system the jet inlet hole configurations have large influences on the thermal performance. The rectangular inlet holes, especially those with higher aspect ratios, show much better heat transfer enhancement than the round inlet holes. However, as the price for it the total pressure drop is increased. Using blunt protuberances instead of sharp edges in the DSC cooling can improve the heat transfer enhancement and reduce the total pressure drop.

Innovative inlet air cooling technology for gas turbine power plants using integrated solid desiccant and Maisotsenko cooler

Gas turbine thermal efficiency has significant dependency on climatic conditions. Evaporative cooling is commonly utilized as an inlet air cooling technique in hot and dry climates though an increase in atmospheric humidity will considerably diminish its performance. Implementing desiccants to dehumidify air will enhance evaporative inlet cooling effectiveness. Furthermore, a recently commercialized cooler named Maisotsenko cooler can be integrated in gas turbine inlet air cooling to replace conventional evaporative coolers. In this paper, four different inlet air cooling systems employing turbine waste heat are proposed for gas turbine power augmentation in hot and humid climates such as UAE. Detailed sensitivity analysis is performed to investigate the impact of ambient air conditions and regeneration temperature on the inlet air cooling systems' effectiveness. Recommended inlet air cooling techniques are evaluated against more commonly used inlet air cooling systems under UAE climatic conditions. Finally, economic and transient analysis are accomplished to signify the most economical inlet air cooling system that is most suitable for UAE gas turbine power augmentation. Maisotsenko evaporative desiccant inlet air cooling with life savings of 31.882 MUS$ is the most economically justified inlet cooling technique for a 50 MWe gas turbine power plant in UAE with life span of 25 years.

Thermal conductivity and mechanical properties of YSZ/LaPO4 composites

High temperature gas turbine sealing is an important issue for increasing the thermal efficiency of gas turbine. In this purpose, layered structured LaPO4 has been selected as the soft phase to add into the commercialized thermal barrier coating material 7 wt% yttria stabilized zirconia (7YSZ). The consequent thermal conductivities and mechanical properties versus the content of LaPO4 have been researched systemically in this paper. Phase composition and microstructure of the high-temperature sintered LaPO4/7YSZ composites were characterized. The thermal conductivity decreases significantly due to the second phase effects and the interface thermal resistance was also strongly involved according to the composite model. The hardness decreased by composed LaPO4 phase so that to reduce attrition of the vanes at high temperature. The slight increase of fracture toughness and bending strength in the results were also favored in operation. The experimental results demonstrate that the LaPO4/7YSZ composite will be an excellent candidate abradable sealing material for high temperature gas turbine.

Fundamental Gas Turbine Heat Transfer

Gas turbines are used for aircraft propulsion and land-based power generation or industrial applications. Thermal efficiency and power output of gas turbines increase with increasing turbine rotor inlet temperatures (RIT). Current advanced gas turbine engines operate at turbine RIT (1700 °C) far higher than the melting point of the blade material (1000 °C); therefore, turbine blades are cooled by compressor discharge air (700 °C). To design an efficient cooling system, it is a great need to increase the understanding of gas turbine heat transfer behaviors within complex 3D high-turbulence unsteady engine-flow environments. Moreover, recent research focuses on aircraft gas turbines operating at even higher RIT with limited cooling air and land-based gas turbines burn coal-gasified fuels with a higher heat load. It is important to understand and solve gas turbine heat transfer problems under new harsh working environments. The advanced cooling technology and durable thermal barrier coatings play critical roles for the development of advanced gas turbines with near zero emissions for safe and long-life operation. This paper reviews fundamental gas turbine heat transfer research topics and documents important relevant papers for future research.

Utilization of alternative marine fuels for gas turbine power plant onboard ships

Marine transportation industry is undergoing a number of problems. Some of these problems are associated with conventional marine fuel-oils. Many researchers have showed that fuel-oil is considered as the main component that causes both environmental and economic problems, especially with the continuous rising of fuel cost. This paper investigates the capability of using natural gas and hydrogen as alternative fuel instead of diesel oil for marine gas turbine, the effect of the alternative fuel on gas turbine thermodynamic performance and the employed mathematical model. The results showed that since the natural gas is categorized as hydrocarbon fuel, the thermodynamic performance of the gas turbine cycle using the natural gas was found to be close to the diesel case performance. The gas turbine thermal efficiency was found to be 1% less in the case of hydrogen compared to the original case of diesel.

Utilization of alternative marine fuels for gas turbine power plant onboard ships

Marine transportation industry is undergoing a number of problems. Some of these problems are associated with conventional marine fuel-oils. Many researchers have showed that fuel-oil is considered as the main component that causes both environmental and economic problems, especially with the continuous rising of fuel cost. This paper investigates the capability of using natural gas and hydrogen as alternative fuel instead of diesel oil for marine gas turbine, the effect of the alternative fuel on gas turbine thermodynamic performance and the employed mathematical model. The results showed that since the natural gas is categorized as hydrocarbon fuel, the thermodynamic performance of the gas turbine cycle using the natural gas was found to be close to the diesel case performance. The gas turbine thermal efficiency was found to be 1% less in the case of hydrogen compared to the original case of diesel.

On flow structure, heat transfer and pressure drop in varying aspect ratio two-pass rectangular channel with ribs at 45°

To increase the thermal efficiency of gas turbines, inlet temperature of gas is increased. This results in the requirement of cooling of gas turbine blades and vanes. Internal cooling of gas turbine blades and vanes is one of several options. Two-pass channels are provided with ribs to enhance heat transfer at the expense of an increased pressure drop. The space in the blade is limited and requires channels with small aspect ratios. Numerical simulations have been performed to investigate heat transfer, flow field and pressure loss in a two-pass channel equipped with 45° ribs with aspect ratio (Win/H) equal to 1:3 in the inlet pass and 1:1 in the outlet pass with both connected together with a 180° bend. The results are compared with a higher aspect ratio channel (Win/H = 1:2, inlet pass). In the ribbed channel, a decrease in pressure drop was observed with a decrease in the aspect ratio of the channel. The smaller aspect ratio channel not only allows using more cooling channels in the blade, but also results in more heat transfer enhancement. The divider-to-tip wall distance (Wel) has influence on the pressure drop, as well as on the heat transfer enhancement at the bend and outlet pass. Heat transfer decreases with decrease in aspect ratio of the inlet pass of the two-pass channel. With increase in divider-to-tip wall distance, heat transfer tries to attain a constant value.

Transient Analysis of Inlet Fogging Process for Gas Turbine Systems

Gas turbine inlet fogging is a method of cooling intake air by injecting demineralized water in the duct through the special atomizing nozzles. Gas turbine cycles with inlet fogging could offer enhanced efficiency with low complexity, so the inlet air-cooling is considered the most cost-effective way to increase the power output as well as thermal efficiency of gas turbines. In this work the inlet fogging process is modeled based on the evaporation of droplets. Transient behaviors of the process are investigated with analytic expressions obtained by considering heat and mass transfer and thermodynamic relations. Effects of water injection ratio on the transient behaviors of temperature of mixed air, mass of liquid droplets, mass flux and heat transfer from the droplets are thoroughly investigated. Results show also the dependencies of system parameters on the critical injection ratio and evaporation time.