Application of Specific Entropy Generation to Enhance Thermal Efficiency of a Combined Cycle

2018 ◽  
Author(s):  
Yousef Haseli
Keyword(s):  
Heat Exchanger ◽  
Power Plant ◽  
Gas Turbine ◽  
Entropy Generation ◽  
Thermal Efficiency ◽  
Combined Cycle ◽  
Flue Gases ◽  
Specific Entropy ◽  
Topping Cycle ◽  
Gas Turbine Cycle

The method of specific entropy generation (SEG) is employed to show how the thermal efficiency of a combined cycle power plant can be improved. SEG is defined as the total entropy generation rate associated with the operation of a power plant per unit flowrate of the fuel burnt in the combustor. In a recent article published in Journal of Energy Resources and Technology, it is shown that the thermal efficiency of a gas turbine cycle inversely correlates with SEG. In this work, we extend the analysis to show that the same relation between the thermal efficiency and SEG is also valid for a combined cycle. The topping cycle consists of a compressor, a combustor and a gas turbine, whereas the bottoming cycle includes a heat recovery steam generator, a steam turbine, a condenser, a deaerator, a condensate pump and a feed water pump. It is shown that the minimization of SEG is identical to the maximization of thermal efficiency. An illustrative example is presented using the SEG method to improve the efficiency of the combined cycle. The results reveal that 89% of the inefficiencies takes place in the gas turbine cycle. A modified design is then proposed to reduce the efficiency losses in the topping cycle. In the modified design, the thermal energy of the flue gases is first used in a heat exchanger to preheat the air before the combustor. The flue gases leaving the heat exchanger is then directed to the HRSG for producing steam. With this modification, the thermal efficiency and the power output of the combined cycle increase 2.7 percentage points and 20.9 kW per unit molar flowrate of the fuel. Recovering the thermal energy of the flue gases for both preheating the air and producing the steam appears to be more efficient than just producing the steam. Despite the net power production of the bottoming cycle decreases in the modified design, the overall efficiency of the combined cycle increases due to the improvement in the efficiency of the topping cycle.

scholarly journals Energetic and Exergetic Investigation of Regenerative Gas Turbine Air-Bottoming/Steam -Bottoming Combined Cycle

Mechanika ◽  
2021 ◽  
Vol 27 (3) ◽  
pp. 251-258
Author(s):  
Mohammad Nadeem KHAN
Keyword(s):  
Heat Exchanger ◽  
Gas Turbine ◽  
Fuel Consumption ◽  
Thermal Efficiency ◽  
Combined Cycle ◽  
Specific Fuel Consumption ◽  
Exergy Loss ◽  
Exhaust Gases ◽  
Topping Cycle ◽  
Gas Turbine Cycle

The present study is a thermodynamic analysis of a Regenerative Air-Bottoming combined (RABC) cycle /Steam bottoming combined (RABC) cycle operated by the exhaust gases the topping gas turbine cycle. The fractional mass of exhaust gases passes through the first heat exchanger where it exchanges heat with the compressed air from the air compressor of topping cycle and remaining amount of exhaust gasses passes through a second heat exchanger where it uses to supply heat to RABC cycle or third heat exchanger where it uses to supply heat to RSBC cycle. The energetic and exergetic performance of RABC cycle and RSBC cycle is investigated using turbine inlet temperature (1000 K⩽ TIT⩽1500 K) and mass fraction of exhaust gas (0⩽x⩽1) of the topping cycle as the input variables.  The work net output attained its peak value at x=0 which is 22.1 % to 27.3 % for RABC cycle and 22.7 % to 21.5 % for RSBC cycle whereas the maximum thermal efficiency and minimum specific fuel consumption is observed at x=1. Also exergy loss by exhaust gases is minimum at x=0 for both RABC cycle and RSBC cycle. Finally, it is concluded that for the maximum work net output and minimum exergy loss by exhaust gases, RABC cycle is the best option followed by RSBC cycle but for optimum thermal efficiency and minimum specific fuel consumption purely regenerative gas turbine cycle have no comparison with RABC cycle and RSBC cycle.

scholarly journals Thermodynamic analysis of high temperature nuclear reactor coupled with advanced gas turbine combined cycle

2019 ◽  
Vol 23 (Suppl. 4) ◽  
pp. 1187-1197 ◽  
Author(s):  
Marek Jaszczur ◽  
Michal Dudek ◽  
Zygmunt Kolenda
Keyword(s):  
High Temperature ◽  
Power Plant ◽  
Gas Turbine ◽  
Thermodynamic Analysis ◽  
Thermal Efficiency ◽  
Nuclear Power ◽  
Coal Gasification ◽  
Nuclear Reactor ◽  
Combined Cycle ◽  
Oil Processing

One of the most advanced and most effective technology for electricity generation nowadays based on a gas turbine combined cycle. This technology uses natural gas, synthesis gas from the coal gasification or crude oil processing products as the energy carriers but at the same time, gas turbine combined cycle emits SO2, NOx, and CO2 to the environment. In this paper, a thermodynamic analysis of environmentally friendly, high temperature gas nuclear reactor system coupled with gas turbine combined cycle technology has been investigated. The analysed system is one of the most advanced concepts and allows us to produce electricity with the higher thermal efficiency than could be offered by any currently existing nuclear power plant technology. The results show that it is possible to achieve thermal efficiency higher than 50% what is not only more than could be produced by any modern nuclear plant but it is also more than could be offered by traditional (coal or lignite) power plant.

Analysis of Intermediate Temperature Combined Cycles With a Carbon Dioxide Topping Cycle

2008 ◽  
Author(s):  
R. Chacartegui ◽  
D. Sa´nchez ◽  
F. Jime´nez-Espadafor ◽  
A. Mun˜oz ◽  
T. Sa´nchez
Keyword(s):  
Carbon Dioxide ◽  
Power Plant ◽  
Gas Turbine ◽  
High Efficiency ◽  
Solar Power ◽  
Combined Cycle ◽  
Inlet Temperature ◽  
Pressure Drops ◽  
Combined Cycles ◽  
Topping Cycle

The development of high efficiency solar power plants based on gas turbine technology presents two problems, both of them directly associated with the solar power plant receiver design and the power plant size: lower turbine intake temperature and higher pressure drops in heat exchangers than in a conventional gas turbine. To partially solve these problems, different configurations of combined cycles composed of a closed cycle carbon dioxide gas turbine as topping cycle have been analyzed. The main advantage of the Brayton carbon dioxide cycle is its high net shaft work to expansion work ratio, in the range of 0.7–0.85 at supercritical compressor intake pressures, which is very close to that of the Rankine cycle. This feature will reduce the negative effects of pressure drops and will be also very interesting for cycles with moderate turbine inlet temperature (800–1000 K). Intercooling and reheat options are also considered. Furthermore, different working fluids have been analyzed for the bottoming cycle, seeking the best performance of the combined cycle in the ranges of temperatures considered.

Advanced Gas Turbine and High Performance Gas-Steam Combined Cycle Plant With Blade Cooling Air Controlling

2006 ◽  
Author(s):  
Tadashi Tsuji
Keyword(s):  
Power Generation ◽  
Heat Exchanger ◽  
Gas Turbine ◽  
Thermal Efficiency ◽  
Gas Turbines ◽  
Combined Cycle ◽  
Hot Water ◽  
Blade Cooling ◽  
Combined Cycle Plant ◽  
Cooling Air

Air cooling blades are usually applied to gas turbines as a basic specification. This blade cooling air is almost 20% of compressor suction air and it means that a great deal of compression load is not converted effectively to turbine power generation. This paper proposes the CCM (Cascade Cooling Module) system of turbine blade air line and the consequent improvement of power generation, which is achieved by the reduction of cooling air consumption with effective use of recovered heat. With this technology, current gas turbines (TIT: turbine inlet temperature: 1350°C) can be up-rated to have a relative high efficiency increase. The increase ratio has a potential to be equivalent to that of 1500°C Class GT/CC against 1350°C Class. The CCM system is designed to enable the reduction of blade cooling air consumption by the low air temperature of 15°C instead of the usual 200–400°C. It causes the turbine operating air to increase at the constant suction air condition, which results in the enhancement of power and thermal efficiency. The CCM is installed in the cooling air line and is composed of three stage coolers: steam generator/fuel preheater stage, heat exchanger stage for hot water supplying and cooler stage with chilled water. The coolant (chilled water) for downstream cooler is produced by an absorption refrigerator operated by the hot water of the upstream heat exchanger. The proposed CCM system requires the modification of cooling air flow network in the gas turbine but produces the direct effect on performance enhancement. When the CCM system is applied to a 700MW Class CC (Combined Cycle) plant (GT TIT: 135°C Class), it is expected that there will be a 40–80MW increase in power and +2–5% relative increase in thermal efficiency.

Influence of Steam Injection on Thermal Efficiency and Operating Temperature of GE-F5 Gas Turbines Applying VODOLEY System

2005 ◽  
Author(s):  
Mohsen Ghazikhani ◽  
Nima Manshoori ◽  
Davood Tafazoli
Keyword(s):  
Power Plant ◽  
Ambient Temperature ◽  
Gas Turbine ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Thermal Efficiency ◽  
Gas Turbines ◽  
Steam Injection ◽  
Gas Turbine Cycle

An industrial gas turbine has the characteristic that turbine output decreases on hot summer days when electricity demand peaks. For GE-F5 gas turbines of Mashad Power Plant when ambient temperature increases 1° C, compressor outlet temperature increases 1.13° C and turbine exhaust temperature increases 2.5° C. Also air mass flow rate decreases about 0.6 kg/sec when ambient temperature increases 1° C, so it is revealed that variations are more due to decreasing in the efficiency of compressor and less due to reduction in mass flow rate of air as ambient temperature increases in constant power output. The cycle efficiency of these GE-F5 gas turbines reduces 3 percent with increasing 50° C of ambient temperature, also the fuel consumption increases as ambient temperature increases for constant turbine work. These are also because of reducing in the compressor efficiency in high temperature ambient. Steam injection in gas turbines is a way to prevent a loss in performance of gas turbines caused by high ambient temperature and has been used for many years. VODOLEY system is a steam injection system, which is known as a self-sufficient one in steam production. The amount of water vapor in combustion products will become regenerated in a contact condenser and after passing through a heat recovery boiler is injected in the transition piece after combustion chamber. In this paper the influence of steam injection in Mashad Power Plant GE-F5 gas turbine parameters, applying VODOLEY system, is being observed. Results show that in this turbine, the turbine inlet temperature (T3) decreases in a range of 5 percent to 11 percent depending on ambient temperature, so the operating parameters in a gas turbine cycle equipped with VODOLEY system in 40° C of ambient temperature is the same as simple gas turbine cycle in 10° C of ambient temperature. Results show that the thermal efficiency increases up to 10 percent, but Back-Work ratio increases in a range of 15 percent to 30 percent. Also results show that although VODOLEY system has water treatment cost but by using this system the running cost will reduce up to 27 percent.

Development of Key Technologies for the Next Generation High Temperature Gas Turbine

2011 ◽  
Author(s):  
Eisaku Ito ◽  
Ikuo Okada ◽  
Keizo Tsukagoshi ◽  
Junichiro Masada
Keyword(s):  
Global Warming ◽  
High Temperature ◽  
Power Plant ◽  
Gas Turbine ◽  
Thermal Efficiency ◽  
Reducing Power ◽  
Combined Cycle ◽  
National Project ◽  
Key Technologies ◽  
High Temperature Gas

Global warming is being “prevented” by reducing power plant CO2 emissions. We are contributing to the overall solution by improving the gas turbine thermal efficiency for gas turbine combined cycle (GTCC). Mitsubishi Heavy Industries, Ltd. (MHI) is a participant in a national project aimed at developing 1700°C gas turbine technology. As part of this national project, selected component technologies are investigated in detail. Some technologies which have been verified through component tests have been applied to the design of the newly developed 1600°C J-type gas turbine.

Outline of Plan for Advanced Reheat Gas Turbine

1981 ◽  
Vol 103 (4) ◽  
pp. 772-775 ◽  
Author(s):  
Akifumi Hori ◽  
Kazuo Takeya
Keyword(s):  
Power Plant ◽  
Gas Turbine ◽  
Thermal Efficiency ◽  
Gas Turbines ◽  
Axial Flow ◽  
Combined Cycle ◽  
Research Association ◽  
Major Objective ◽  
Engineering Research ◽  
Set Up

A new reheat gas turbine system is being developed as a national project by the “Engineering Research Association for Advanced Gas Turbines” of Japan. The machine consists of two axial flow compressors, three turbines, intercooler, combustor and reheater. The pilot plant is expected to go into operation in 1982, and a prototype plant will be set up in 1984. The major objective of this reheat gas turbine is application to a combined cycle power plant, with LNG burning, and the final target of combined cycle thermal efficiency is to be 55 percent (LHV).

Simulations of Pressurized Fluidized Circulating Bed Based Combined Cycle (PFCB)

2014 ◽  
Author(s):  
Hossin Omar ◽  
Mohamed Elmnefi
Keyword(s):  
Steam Turbine ◽  
Gas Turbine ◽  
Compression Ratio ◽  
Steam Pressure ◽  
Combined Cycle ◽  
Flue Gases ◽  
First Case ◽  
Combined Cycle Plant ◽  
Gas Turbine Cycle ◽  
Cycle Efficiency

The Pressurized Fluidized Circulating Bed (PFCB) combined cycle was simulated. The simulations balance the energy between the elements of the unit, which consists of gas turbine cycle and steam turbine cycle. The PFCB is used as a combustor and steam generator at the same time. The simulations were carried out for PFCB combined cycle plant for two cases. In the first case, the simulations were performed for combined cycle with reheat in the steam turbine cycle. While in the second case, the simulations were carried out for the PFCB combined cycle with extra combustor and steam turbine cycle with reheat. For both cases, the effect of steam inlet pressure on the combined cycle efficiency was predicted. It was found that increasing of steam pressure results in increase in the combined cycle thermal efficiency. The effect of the inlet flue gases temperature on the gas turbine and on the combined cycle efficiencies was also predicted. The maximum PFCB combined cycle efficiency occurs at a compression ratio of 18, which is the case of utilizing an extra combustor. The simulations were carried out for only one fuel composition and for a compression ratio ranges between 1 to 40.

Study on Primary and Secondary Heat-Transport Systems for Sodium-Cooled Fast Reactor

2013 ◽  
Author(s):  
Alexey Dragunov ◽  
Eugene Saltanov ◽  
Igor Pioro ◽  
Glenn Harvel ◽  
Brian Ikeda
Keyword(s):  
Heat Exchanger ◽  
Gas Turbine ◽  
Heat Transport ◽  
Fast Reactor ◽  
Thermal Efficiency ◽  
Nuclear Power ◽  
Power Plants ◽  
Power Conversion ◽  
Gas Turbine Cycle ◽  
Steam Cycle

One of the current engineering challenges is to design next generation (Generation IV) Nuclear Power Plants (NPPs) with significantly higher thermal efficiencies (43–55%) compared to those of current NPPs to match or at least to be close to the thermal efficiencies reached at fossil-fired power plants (55–62%). The Sodium-cooled Fast Reactor (SFR) is one of the six concepts considered under the Generation IV International Forum (GIF) initiative. The BN-600 reactor is a sodium-cooled fast-breeder reactor built at the Beloyarsk NPP in Russia. This concept is the only one from the Generation IV nuclear-power reactors, which is actually in operation (since 1980’s). At the secondary side, it uses a subcritical-pressure Rankine-steam cycle with heat regeneration. The reactor generates electrical power in the amount of 600 MWel. The reactor core dimensions are 0.75 m (height) by 2.06 m (diameter). The UO2 fuel enriched to 17–26% is utilized in the core. There are 2 loops (circuits) for sodium flow. For safety reasons, sodium is used both in the primary and the intermediate circuits. Therefore, a sodium-to-sodium heat exchanger is used to transfer heat from the primary loop to the intermediate one. In this work major parameters of the reactor are listed. The actual scheme of the power-conversion heat-transport system is presented; and the results of the calculation of thermal efficiency of this scheme are analyzed. Details of the heat-transport system, including parameters of the sodium-to-sodium heat exchanger and main coolant pump, are presented. In this paper two possibilities for the SFR in terms of the power-conversion cycle are investigated: 1. a subcritical-pressure Rankine-steam cycle through a heat exchanger (current approach in Russian and Japanese power reactors); 2. a supercritical-pressure CO2 Brayton gas-turbine cycle through a heat exchanger (US approach). With the advent of modern super-alloys, the Rankine-steam cycle has progressed into the supercritical region of the coolant and is generating thermal efficiencies into the mid 50% range. Therefore, the thermal efficiency of a supercritical Rankine-steam cycle is also briefly discussed in this paper. According to GIF, the Brayton gas-turbine cycle is under consideration for future nuclear power reactors. The supercritical-CO2 cycle is a new approach in the Brayton gas-turbine cycle. Therefore, dependence of the thermal efficiency of this SC CO2 cycle on inlet parameters of the gas turbine is also investigated.

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