Thermodynamics of an Isothermal Gas Turbine Combined Cycle

1984 ◽  
Vol 106 (4) ◽  
pp. 743-749 ◽  
Author(s):  
M. A. El-Masri ◽  
J. H. Magnusson
Keyword(s):  
Gas Turbine ◽  
Pressure Ratio ◽  
Extraction Process ◽  
Combined Cycle ◽  
Peak Temperature ◽  
Combined Cycles ◽  
Isothermal Gas ◽  
Technological Constraints ◽  
Cycle Efficiency ◽  
Steam Cycle

The isothermal (or multiple-reheat) gas turbine performs the combustion/work extraction process at a sustained, elevated temperature. This has distinct thermodynamic advantages in combined cycles for given peak temperature constraints. A thermodynamic model for this cycle is developed. Although based on a simple CO/CO2/O2 chemcial system the results are applicable to other reactants and dilutants. Combined cycle efficiency is reported for different gas turbine pressure ratios, peak temperatures, reactant dilution and steam cycle conditions. The range of parameters investigated starts from present-day advanced technologies and examines the potential of higher pressures and temperatures. Balances of thermodynamic availability are used to interpret the results. They show that for a given steam cycle and gas turbine pressure ratio, increasing peak temperature beyond a certain value provides sharply diminishing return. This is because the reduction in combustion irreversibility is offset by increased heat transfer irreversibility. Higher pressure ratios or steam cycle temperatures can raise this optimum peak temperature. In view of the various technological constraints, the authors’ conclusion is that an isothermal gas turbine with a peak temperature and pressure-ratio of about 1600K and 100:1, respectively, represents the most promising next step in technology. Coupled with existing advanced steam cycles this should provide efficiencies in the 60 percent range.

Effect of Bottoming Cycle Alternatives on the Performance of Combined Cycle

2003 ◽  
Author(s):  
R. Yadav
Keyword(s):  
Gas Turbine ◽  
Pressure Ratio ◽  
Positive Influence ◽  
Combined Cycle ◽  
Exhaust Temperature ◽  
Compressor Pressure Ratio ◽  
Topping Cycle ◽  
Steam Parameters ◽  
Cycle Efficiency ◽  
Steam Cycle

The increase in efficiency of combined cycle has mainly been caused by the improvements in gas turbine cycle efficiency. With the increase in firing temperature the exhaust temperature is substantially high around 873 K for moderate compressor pressure ratio, which has positive influence on steam cycle efficiency. Minimizing the irreversibility within the heat recovery steam generator HRSG and choosing proper steam cycle configuration with optimized steam parameters improve the steam cycle efficiency and thus in turn the combined cycle efficiency. In this paper, LM9001H gas turbine, a state of art technology turbine with modified compressor pressure ratio has been chosen as a topping cycle. Various bottoming cycles alternatives (sub-critical) coupled with LM9001H topping cycle with and without recuperation such as dual and triple pressure steam cycles with and without reheat have been chosen to predict the performance of combined cycle.

Optimization of Advanced Liquid Natural Gas-Fuelled Combined Cycle Machinery Systems for a High-Speed Ferry

2012 ◽  
Author(s):  
Kari Anne Tveitaskog ◽  
Fredrik Haglind
Keyword(s):  
Gas Turbine ◽  
High Speed ◽  
Dynamic Network ◽  
Combined Cycle ◽  
Working Fluid ◽  
Power Requirement ◽  
Pressure Steam ◽  
Combined Cycles ◽  
Liquid Natural Gas ◽  
Steam Cycle

This paper is aimed at designing and optimizing combined cycles for marine applications. For this purpose, an in-house numerical simulation tool called DNA (Dynamic Network Analysis) and a genetic algorithm-based optimization routine are used. The top cycle is modeled as the aero-derivative gas turbine LM2500, while four options for bottoming cycles are modeled. Firstly, a single pressure steam cycle, secondly a dual-pressure steam cycle, thirdly an ORC using toluene as the working fluid and an intermediate oil loop as the heat carrier, and lastly an ABC with inter-cooling are modeled. Furthermore, practical and operational aspects of using these three machinery systems for a high-speed ferry are discussed. Two scenarios are evaluated. The first scenario evaluates the combined cycles with a given power requirement, optimizing the combined cycle while operating the gas turbine at part load. The second scenario evaluates the combined cycle with the gas turbine operated at full load. For the first scenario, the results suggest that the thermal efficiencies of the combined gas and steam cycles are 46.3% and 48.2% for the single pressure and dual pressure steam cycles, respectively. The gas ORC and gas ABC combined cycles obtained thermal efficiencies of 45.6% and 41.9%, respectively. For the second scenario, the results suggest that the thermal efficiencies of the combined gas and steam cycles are 53.5% and 55.3% for the single pressure and dual pressure steam cycles, respectively. The gas ORC and gas ABC combined cycles obtained thermal efficiencies of 51.0% and 47.8%, respectively.

Evolution and Future Trend of Large Frame Gas Turbines: A New 1600 Degree C, J Class Gas Turbine

2012 ◽  
Author(s):  
Satoshi Hada ◽  
Masanori Yuri ◽  
Junichiro Masada ◽  
Eisaku Ito ◽  
Keizo Tsukagoshi
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Pressure Ratio ◽  
Standard Condition ◽  
Development Program ◽  
Combined Cycle ◽  
Component Technology ◽  
Extensive Experience ◽  
National Project ◽  
Cycle Efficiency

MHI recently developed a 1600°C class J-type gas turbine, utilizing some of the technologies developed in the National Project to promote the development of component technology for the next generation 1700°C class gas turbine. This new frame is expected to achieve higher combined cycle efficiency and will contribute to reduce CO2 emissions. The target combined cycle efficiency of the J type gas turbine will be above 61.5% (gross, ISO standard condition, LHV) and the 1on1 combined cycle output will reach 460MW for 60Hz engine and 670MW for 50Hz engine. This new engine incorporates: 1) A high pressure ratio compressor based on the advanced M501H compressor, which was verified during the M501H development in 1999 and 2001. 2) Steam cooled combustor, which has accumulated extensive experience in the MHI G engine (> 1,356,000 actual operating hours). 3) State-of-art turbine designs developed through the 1700°C gas turbine component technology development program in Japanese National Project for high temperature components. This paper discusses the technical features and the updated status of the J-type gas turbine, especially the operating condition of the J-type gas turbine in the MHI demonstration plant, T-Point. The trial operation of the first M501J gas turbine was started at T-point in February 2011 on schedule, and major milestones of the trial operation have been met. After the trial operation, the first commercial operation has taken place as scheduled under a predominantly Daily-Start-and-Stop (DSS) mode. Afterward, MHI performed the major inspection in October 2011 in order to check the mechanical condition, and confirmed that the hot parts and other parts were in sound condition.

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.

The Reheat Gas Turbine With Steam-Blade Cooling—A Means of Increasing Reheat Pressure, Output, and Combined Cycle Efficiency

1982 ◽  
Vol 104 (1) ◽  
pp. 9-22 ◽  
Author(s):  
I. G. Rice
Keyword(s):  
Gas Turbine ◽  
Pressure Ratio ◽  
Pressure Rise ◽  
Expansion Ratio ◽  
Combined Cycle ◽  
Gas Generator ◽  
Exhaust Temperature ◽  
Blade Cooling ◽  
Cycle Efficiency ◽  
Turbine Blading

The reheat (RH) pressure can be appreciably increased by applying steam cooling to the gas-generator (GG) turbine blading which in turn allows a higher RH firing temperature for a fixed exhaust temperature. These factors increase gas turbine output and raise combined-cycle efficiency. The GG turbine blading will approach “uncooled expansion efficiency”. Eliminating cooling air increases the gas turbine RH pressure by 10.6 percent. When steam is used (injected) as the blade coolant, additional GG work is also developed which further increases the RH pressure by another 12.0 percent to yield a total increase of approximately 22.6 percent. The 38-cycle pressure ratio 2400° F (1316° C) TIT GG studied produces a respectable 6.5 power turbine expansion ratio. The higher pressure also noticeably reduces the physical size of the RH combustor. This paper presents an analysis of the RH pressure rise when applying steam to blade cooling.

Optimization of MHD Generator Based Combined Cycle Efficiency

2005 ◽  
Author(s):  
M. H. Saidi ◽  
A. A. Mozafari ◽  
H. D. Rezaei ◽  
A. J. Dehkordy
Keyword(s):  
Pressure Ratio ◽  
Combined Cycle ◽  
Second Law ◽  
Exergy Destruction ◽  
Mhd Generator ◽  
Pros And Cons ◽  
Combined Cycles ◽  
Power Generation Systems ◽  
Gas Turbine Cycle ◽  
Cycle Efficiency

Energy crisis has directed scientific efforts to increase the efficiency of power generation systems. Thermodynamic optimization of MHD (Magneto Hydrodynamic) generator based combined cycles due to their high operating temperatures may seriously reduce exergy, destruction and improve the second law efficiency. In this research a combined cycle, comprising of MHD cycle as topping and gas turbine cycle as bottoming cycle has been simulated and analyzed and its pros and cons have been exposed. The first and second law efficiencies have been estimated from the operating pressures and temperatures of the system. To calculate the second law efficiency, the entropy generation of all components of the combined cycle has been parametrically calculated. Furthermore, the optimal pressure ratio and working temperature for both cycles are represented. The influence of pressure loss in pipeline and the effect of heat exchanger performance on the cycle efficiency have been considered as well.

Using Hydrogen as Gas Turbine Fuel: Premixed Versus Diffusive Flame Combustors

2014 ◽  
Vol 136 (5) ◽  
Author(s):  
Matteo Gazzani ◽  
Paolo Chiesa ◽  
Emanuele Martelli ◽  
Stefano Sigali ◽  
Iarno Brunetti
Keyword(s):  
Gas Turbine ◽  
State Of The Art ◽  
Combined Cycle ◽  
Efficiency Gain ◽  
Degradation Mechanisms ◽  
Lean Premixed Combustion ◽  
Pressure Drops ◽  
Lean Premixed ◽  
Combined Cycles ◽  
Cycle Efficiency

This work aims at estimating the efficiency gain resulting from using lean premixed combustors in hydrogen-fired combined cycles with respect to diffusive flame combustors with significant inert dilution to limit NOx emissions. The analysis is carried out by considering a hydrogen-fired, specifically tailored gas turbine whose features are representative of a state-of-the-art natural gas–fired F-class gas turbine. The comparison between diffusion flame and lean premixed combustion is carried out considering nitrogen and steam as diluents, as well as different stoichiometric flame temperatures and pressure drops. Results show that the adoption of lean premixed combustors allows us to significantly reduce the efficiency decay resulting from inert dilution. Combined cycle efficiency slightly reduces from 58.5%–57.9% when combustor pressure drops vary in the range 3%–10%. Such efficiency values are comparatively higher than those achieved by diffusive flame combustor with inert dilution. Finally, the study investigated the effects of decreasing the maximum operating blade temperature so as to cope with possible degradation mechanisms induced by hydrogen combustion.

Effect of Water-Cooling Turbine Blades on Advanced Gas Turbine Power Systems

1977 ◽  
Author(s):  
B. V. Johnson ◽  
A. J. Giramonti ◽  
S. J. Lehman
Keyword(s):  
Power Systems ◽  
Gas Turbine ◽  
Pressure Ratio ◽  
Turbine Blades ◽  
Combined Cycle ◽  
Air Cooling ◽  
Water Cooling ◽  
Gas Turbine Blades ◽  
And Performance ◽  
Cycle Efficiency

A study was conducted to determine what benefits in cycle efficiency and performance could be obtained with water-cooled gas turbine blades. Water cooling was compared against various degrees of air cooling and the ultimate limit of no cooling. Performance studies were conducted for both combined gas turbine-steam cycles and simple gas turbine cycles with temperatures at the inlet to the first turbine blade row from 1478 K (2200 F) to 1922 (3000 F) and compressor pressure ratios from 12 to 28. Results for both types of cycles indicated that absolute efficiencies 1 to 3 percentage points greater and power output per unit airflow 5 to 25 percent greater than could be obtained with water-cooled blades compared to air-cooled blades. For a given cooling scheme and pressure ratio, highest efficiencies were obtained at 1700 K (2600 F) for the simple cycle and 1922 K for the combined cycle.

Efficiency Entitlement for Bottoming Cycles

2006 ◽  
Author(s):  
Douglas C. Hofer ◽  
S. Can Gulen
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Power Plants ◽  
Combined Cycle ◽  
New Method ◽  
Working Fluid ◽  
Generating Capacity ◽  
Topping Cycle ◽  
Cycle Efficiency ◽  
Steam Cycle

A significant portion of the new electrical generating capacity installed in the past decade has employed heavy-duty gas turbines operating in a combined cycle configuration with a steam turbine bottoming cycle. In these power plants approximately 1/3 of the power is generated by the bottoming cycle. To ensure that the highest possible combined cycle efficiency is realized it is important to optimize the bottoming cycle efficiency and doing so requires a solid understanding of the efficiency entitlement. This paper describes a new technique for calculating the theoretical efficiency entitlement for a bottoming cycle that corresponds to the maximum possible bottoming cycle work and maximized combined cycle work and efficiency. This new method accounts for the decrease in ideal efficiency as the gas turbine exhaust is cooled as it transfers heat energy to the working fluid in the bottoming cycle. The new definition is compared to conventional definitions, including that of Carnot and an Exergy based second law efficiency, and shown to provide a simple and accurate analytical expression for the entitlement efficiency in a bottoming cycle. For representative cycle conditions, the entitlement efficiency for the bottoming cycle is calculated to be ∼45% compared to the Carnot efficiency for the same conditions of ∼67%. Although the new method is applicable to any power cycle obtaining its heat input from the exhaust stream of a topping cycle, special attention is given to the steam bottoming cycle traditionally used in modern gas turbine combined cycle power plants. Comparisons are made between the ideal bottoming cycle and variants of a steam cycle including a single pressure non-reheat and a three pressure reheat cycle. These comparisons explore the unavoidable loss in efficiency associated with constant temperature heat addition that occurs in the steam cycle.

scholarly journals Gas Turbine and Combined Cycle Technologies for Power and Efficiency Enhancement in Power Plants

1994 ◽  
Author(s):  
Meherwan P. Boyce ◽  
Cyrus B. Meher-Homji ◽  
A. N. Lakshminarasimha
Keyword(s):  
Gas Turbine ◽  
Power Plants ◽  
Pressure Ratio ◽  
Combined Cycle ◽  
Inlet Temperature ◽  
Specific Work ◽  
Efficiency Enhancement ◽  
Turbine Inlet Temperature ◽  
Cycle Efficiency ◽  
Original Equipment Manufacturers

A wide variety of gas turbine based cycles exist in the market today with several technologies being promoted by individual Original Equipment Manufacturers. This paper is focused on providing users with a conceptual framework within which to view these cycles and choose suitable options for their needs. A basic parametric analysis is provided to show the interdependency of Turbine Inlet Temperature (TIT) and Pressure Ratio on cycle efficiency and specific work.

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