Brayton or Brayton-Rankine Combined Cycle With Hot-Gas Recirculation and Inverse Mixing Ejector

2002 ◽  
Author(s):  
Branko Stankovic
Keyword(s):  
Gas Turbine ◽  
Thermal Efficiency ◽  
Combined Cycle ◽  
Necessary Condition ◽  
Carnot Cycle ◽  
Gas Velocity ◽  
Hot Gas ◽  
Gas Recirculation ◽  
Gas Turbine Cycle ◽  
Cycle Efficiency

An open/closed gas-turbine simple Brayton cycle or Brayton-Rankine gas- and steam-turbine combined-cycle power-producing system is proposed, with the gas turbine recirculating a large portion of partly expanded high-temperature gas into an inverse mixing ejector. The inverse mixing ejector uses injected-gas velocity that is necessarily greater than jet-gas velocity to increase the hot-gas pressure up to the compressor-discharge level. This is a necessary condition for achieving very high cycle thermal efficiency. Maximum combined-cycle thermal efficiency can be expected to reach up to about 80%, up to an appropriate temperature-level Carnot-cycle efficiency. The inverse mixing ejector can operate in either subsonic or supersonic (necessary for higher cycle thermal efficiencies) regions of gas velocity. The gas turbine cycle can operate in either simple-cycle, single-intercooled-cycle or multi-intercooled-cycle mode.

scholarly journals Thermodynamic Analysis of Different Configurations of Combined Cycle Power Plants

2015 ◽  
Vol 5 (2) ◽  
pp. 89
Author(s):  
Munzer S. Y. Ebaid ◽  
Qusai Z. Al-hamdan
Keyword(s):  
Gas Turbine ◽  
Power Plants ◽  
Combined Cycle ◽  
Cycle Performance ◽  
Maximum Efficiency ◽  
Specific Work ◽  
Slight Effect ◽  
Turbine Engine ◽  
Gas Turbine Cycle ◽  
Cycle Efficiency

<p class="1Body">Several modifications have been made to the simple gas turbine cycle in order to increase its thermal efficiency but within the thermal and mechanical stress constrain, the efficiency still ranges between 38 and 42%. The concept of using combined cycle power or CPP plant would be more attractive in hot countries than the combined heat and power or CHP plant. The current work deals with the performance of different configurations of the gas turbine engine operating as a part of the combined cycle power plant. The results showed that the maximum CPP cycle efficiency would be at a point for which the gas turbine cycle would have neither its maximum efficiency nor its maximum specific work output. It has been shown that supplementary heating or gas turbine reheating would decrease the CPP cycle efficiency; hence, it could only be justified at low gas turbine inlet temperatures. Also it has been shown that although gas turbine intercooling would enhance the performance of the gas turbine cycle, it would have only a slight effect on the CPP cycle performance.</p>

Pulsed Impingement Turbine Cooling and its Effect on the Efficiency of Gas Turbines With Pressure Gain Combustion

2020 ◽  
Author(s):  
Nicolai Neumann ◽  
Dieter Peitsch ◽  
Arne Berthold ◽  
Frank Haucke ◽  
Panagiotis Stathopoulos
Keyword(s):  
Gas Turbine ◽  
Thermal Efficiency ◽  
Gas Turbines ◽  
Turbine Blades ◽  
Impingement Cooling ◽  
Turbine Cooling ◽  
Pressure Gain Combustion ◽  
Cooling Air ◽  
Gas Turbine Cycle ◽  
Cycle Efficiency

Abstract Performance improvements of conventional gas turbines are becoming increasingly difficult and costly to achieve. Pressure Gain Combustion (PGC) has emerged as a promising technology in this respect, due to the higher thermal efficiency of the respective ideal gas turbine cycle. Previous cycle analyses considering turbine cooling methods have shown that the application of pressure gain combustion may require more turbine cooling air. This has a direct impact on the cycle efficiency and reduces the possible efficiency gain that can potentially be harvested from the new combustion technology. Novel cooling techniques could unlock an existing potential for a further increase in efficiency. Such a novel turbine cooling approach is the application of pulsed impingement jets inside the turbine blades. In the first part of this paper, results of pulsed impingement cooling experiments on a curved plate are presented. The potential of this novel cooling approach to increase the convective heat transfer in the inner side of turbine blades is quantified. The second part of this paper presents a gas turbine cycle analysis where the improved cooling approach is incorporated in the cooling air calculation. The effect of pulsed impingement cooling on the overall cycle efficiency is shown for both Joule and PGC cycles. In contrast to the authors’ anticipation, the results suggest that for relevant thermodynamic cycles pulsed impingement cooling increases the thermal efficiency of Joule cycles more significantly than it does in the case of PGC cycles. Thermal efficiency improvements of 1.0 p.p. for pure convective cooling and 0.5 p.p. for combined convective and film with TBC are observed for Joule cycles. But just up to 0.5 p.p. for pure convective cooling and 0.3 p.p. for combined convective and film cooling with TBC are recorded for PGC cycles.

Evaluation of the Compression-Intercooled Reheat-Gas-Turbine-Combined Cycle

1984 ◽  
Author(s):  
Ivan G. Rice
Keyword(s):  
Gas Turbine ◽  
Thermodynamic Analysis ◽  
Pressure Range ◽  
Pressure Ratio ◽  
Combined Cycle ◽  
Time Increase ◽  
Efficiency Loss ◽  
Gas Turbine Cycle ◽  
Cycle Efficiency ◽  
Turbine Output

Interest in the reheat-gas turbine (RHGT) as a way to improve combined-cycle efficiency is gaining momentum. Compression intercooling makes it possible to readily increase the reheat-gas-turbine cycle-pressure ratio and at the same time increase gas-turbine output; but at the expense of some combined-cycle efficiency and mechanical complexity. This paper presents a thermodynamic analysis of the intercooled cycle and pinpoints the proper intercooling pressure range for minimum combined-cycle-efficiency loss. At the end of the paper two-intercooled reheat-gas-turbine configurations are presented.

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.

Semi-Closed Gas Turbine/Combined Cycle With Water Recovery and Extensive Exhaust Gas Recirculation

1996 ◽  
Author(s):  
Bruno Facchini ◽  
Daniele Fiaschi ◽  
Giampaolo Manfrida
Keyword(s):  
Gas Turbine ◽  
Water Injection ◽  
Combined Cycle ◽  
Point Of View ◽  
Exhaust Gas ◽  
Water Recovery ◽  
Gas Treatment ◽  
High Level ◽  
Gas Recirculation ◽  
Gas Turbine Cycle

This innovative gas turbine cycle can offer several advantages over conventional cycles from the point of view of environmental friendship. The basic idea of SCGT/CC (Semi-Closed Gas Turbine/Combined Cycle with water recovery) is to cool down the exhaust temperatures to allow full condensation of the water vapor, and recirculate a large part of the exhaust gases to the compressor. The condensed water can then be reinjected by means of a pump at compressor delivery. The working gas composition is thus close to that corresponding to stoichiometric combustion, which opens the possibility of applying techniques for CO2 recycling and general exhaust gas treatment. An increase in work output is connected to water injection, while a high level of efficiency is maintained as the compressor work is reduced and the cycle parameters are tuned for the exhaust of this turbine.

Review of a Combined Steam and Gas Turbine Cycle for Pipeline Service

1975 ◽  
Author(s):  
T. C. Heard
Keyword(s):  
Ambient Temperature ◽  
Gas Turbine ◽  
Combined Cycle ◽  
Drive System ◽  
Paper Briefly ◽  
Preliminary Study ◽  
Gas Turbine Cycle ◽  
Cycle Efficiency ◽  
Standard Gas ◽  
Regenerative Cycle

The combined steam and gas turbine cycle provides the highest efficiency turbine system available today. In view of the rapidly escalating value of fuel the combined cycle therefore merits a review for pipeline applications. Such a review reveals the combined cycle has a number of advantages. First, the combined cycle efficiency is significantly higher than the efficiency of a standard regenerative cycle gas turbine. Second, and contrary to the characteristics of a standard gas turbine, the efficiency at a given load improves significantly as the ambient temperature increases, so that the combined cycle would be applicable in hot climates. Third, the adjustable speed capability of the combined cycle meets the usual pipeline service requirements. This paper briefly presents the results of a preliminary study of a combined cycle single drive system as it might be utilized in a gas pipeline station.

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 Steam and Gas Turbine Combined Cycle Equipment Currently Available for Natural Gas Pipelines

1979 ◽  
Author(s):  
R. P. Lang ◽  
D. L. Chase
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Thermal Efficiency ◽  
Combined Cycle ◽  
Gas Pipeline ◽  
Gas Pipelines ◽  
Equipment Selection ◽  
Natural Gas Pipelines ◽  
Attractive Candidate ◽  
Gas Turbine Cycle

The high thermal efficiency of the combined steam and gas turbine cycle makes it an attractive candidate for gas pipeline drivers. This paper discusses some aspects of the performance which can be achieved, and the economics associated with this cycle using currently available equipment. One equipment selection has an output capability of over 20,000 hp with a net thermal efficiency of approximately 40 percent. A second equipment selection has an output capability of over 35,000 hp with a net thermal efficiency of approximately 47 percent.

Assessing the Potential of Gas-Recuperation in Reheated Gas Turbines Within Combined Gas-Steam Power Plants

2014 ◽  
Author(s):  
Adam Doligalski ◽  
Luis Sanchez de Leon ◽  
Pavlos K. Zachos ◽  
Vassilios Pachidis
Keyword(s):  
Gas Turbine ◽  
Thermal Efficiency ◽  
Gas Turbines ◽  
Power Plants ◽  
Current Approach ◽  
Combined Cycle ◽  
Variable Position ◽  
Power Turbine ◽  
Power Generation Systems ◽  
Gas Turbine Cycle

This paper presents a comparative analysis between two different gas turbine configurations for implementation within combined cycle power plants, aiming to downselect the most promising one in terms of thermal efficiency at design point. The analysed gas turbines both feature the same dual-pressure steam bottoming cycle, but differ in the gas turbine cycle itself: the first configuration comprises a single-shaft reheated gas turbine with variable position of the reheater (representative of the current approach of the industry to combined cycle power plants), whilst the second configuration comprises a dual-shaft reheated-recuperated engine with free power turbine. Comparison of the two competing gas turbine configurations is conducted by means of systematic exploration of the combined cycle design space. The analysis showed that the reheated-recuperated configuration delivers higher thermal efficiency than the more conventional reheated (non-recuperated) gas turbine and is identified, therefore, as a competitive option for future combined cycle power generation systems.

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