scholarly journals Performance Analysis and Optimization for Irreversible Combined Carnot Heat Engine Working with Ideal Quantum Gases

Entropy ◽  
2021 ◽  
Vol 23 (5) ◽  
pp. 536
Author(s):  
Lingen Chen ◽  
Zewei Meng ◽  
Yanlin Ge ◽  
Feng Wu
Keyword(s):  
Power Output ◽  
Thermal Efficiency ◽  
Combined Cycle ◽  
Quantum Gases ◽  
Carnot Cycle ◽  
Leakage Loss ◽  
Optimal Power ◽  
Heat Leakage ◽  
Working Medium ◽  
Ideal Quantum

An irreversible combined Carnot cycle model using ideal quantum gases as a working medium was studied by using finite-time thermodynamics. The combined cycle consisted of two Carnot sub-cycles in a cascade mode. Considering thermal resistance, internal irreversibility, and heat leakage losses, the power output and thermal efficiency of the irreversible combined Carnot cycle were derived by utilizing the quantum gas state equation. The temperature effect of the working medium on power output and thermal efficiency is analyzed by numerical method, the optimal relationship between power output and thermal efficiency is solved by the Euler-Lagrange equation, and the effects of different working mediums on the optimal power and thermal efficiency performance are also focused. The results show that there is a set of working medium temperatures that makes the power output of the combined cycle be maximum. When there is no heat leakage loss in the combined cycle, all the characteristic curves of optimal power versus thermal efficiency are parabolic-like ones, and the internal irreversibility makes both power output and efficiency decrease. When there is heat leakage loss in the combined cycle, all the characteristic curves of optimal power versus thermal efficiency are loop-shaped ones, and the heat leakage loss only affects the thermal efficiency of the combined Carnot cycle. Comparing the power output of combined heat engines with four types of working mediums, the two-stage combined Carnot cycle using ideal Fermi-Bose gas as working medium obtains the highest power output.

Optimum Performance Improvements of the Combined Cycle Based on an Intercooler–Reheated Gas Turbine

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Thamir K. Ibrahim ◽  
M. M. Rahman
Keyword(s):  
Gas Turbine ◽  
Power Output ◽  
Thermal Efficiency ◽  
Power Plants ◽  
Combined Cycle ◽  
Inlet Temperature ◽  
Optimum Level ◽  
Simulation Code ◽  
Operation Conditions ◽  
Turbine Inlet

The performance enhancements and modeling of the gas turbine (GT), together with the combined cycle gas turbine (CCGT) power plant, are described in this study. The thermal analysis has proposed intercooler–reheated-GT (IHGT) configuration of the CCGT system, as well as the development of a simulation code and integrated model for exploiting the CCGT power plants performance, using the matlab code. The validation of a heavy-duty CCGT power plants performance is done through real power plants, namely, MARAFIQ CCGT plants in Saudi Arabia with satisfactory results. The results from this simulation show that the higher thermal efficiency of 56% MW, while high power output of 1640 MW, occurred in IHGT combined cycle plants (IHGTCC), having an optimal turbine inlet temperature about 1900 K. Furthermore, the CCGT system proposed in the study has improved power output by 94%. The results of optimization show that the IHGTCC has optimum power of 1860 MW and thermal efficiency of 59%. Therefore, the ambient temperatures and operation conditions of the CCGT strongly affect their performance. The optimum level of power and efficiency is seen at high turbine inlet temperatures and isentropic turbine efficiency. Thus, it can be understood that the models developed in this study are useful tools for estimating the CCGT power plant's performance.

Performance of a Novel Semiclosed Gas-Turbine Refrigeration Combined Cycle

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Joseph J. Boza ◽  
William E. Lear ◽  
S. A. Sherif
Keyword(s):  
High Pressure ◽  
Ambient Temperature ◽  
Gas Turbine ◽  
Power Output ◽  
Thermal Efficiency ◽  
Combined Cycle ◽  
Water Mixture ◽  
Absorption Refrigeration ◽  
Ambient Conditions ◽  
Large Engine

A thermodynamic performance analysis was performed on a novel cooling and power cycle that combines a semiclosed gas turbine called the high-pressure regenerative turbine engine (HPRTE) with an absorption refrigeration unit. Waste heat from the recirculated combustion gas of the HPRTE is used to power the absorption refrigeration cycle, which cools the high-pressure compressor inlet of the HPRTE to below ambient conditions and also produces excess refrigeration depending on ambient conditions. Two cases were considered: a small engine with a nominal power output of 100kW and a large engine with a nominal power output of 40MW. The cycle was modeled using traditional one-dimensional steady-state thermodynamics, with state-of-the-art polytropic efficiencies and pressure drops for the turbomachinery and heat exchangers, and curve fits for properties of the LiBr-water mixture and the combustion products. The small engine was shown to operate with a thermal efficiency approaching 43% while producing 50% as much 5°C refrigeration as its nominal power output (roughly 50tons) at 30°C ambient conditions. The large engine was shown to operate with a thermal efficiency approaching 62% while producing 25% as much 5°C refrigeration as its nominal power output (roughly 20,000tons) at 30°C ambient conditions. Thermal efficiency stayed relatively constant with respect to ambient temperature for both the large and small engines. It decreased by only 3–4% as the ambient temperature was increased from 10°Cto35°C in each case. The amount of external refrigeration produced by the engine sharply decreased in both engines at around 35°C, eventually reaching zero at roughly 45°C in each case for 5°C refrigeration. However, the evaporator temperature could be raised to 10°C (or higher) to produce external refrigeration in ambient temperatures as high as 50°C.

Genetic Optimization of Steam Injected Gas Turbine Power Plants

2002 ◽  
Author(s):  
Ibrahim Sinan Akmandor ◽  
O¨zhan O¨ksu¨z ◽  
Sec¸kin Go¨kaltun ◽  
Melih Han Bilgin
Keyword(s):  
Gas Turbine ◽  
Power Output ◽  
Thermal Efficiency ◽  
Gas Turbines ◽  
Power Plants ◽  
Pressure Ratio ◽  
Steam Injection ◽  
Combined Cycle ◽  
Inlet Temperature ◽  
Compressor Pressure Ratio

A new methodology is developed to find the optimal steam injection levels in simple and combined cycle gas turbine power plants. When steam injection process is being applied to simple cycle gas turbines, it is shown to offer many benefits, including increased power output and efficiency as well as reduced exhaust emissions. For combined cycle power plants, steam injection in the gas turbine, significantly decreases the amount of flow and energy through the steam turbine and the overall power output of the combined cycle is decreased. This study focuses on finding the maximum power output and efficiency of steam injected simple and combined cycle gas turbines. For that purpose, the thermodynamic cycle analysis and a genetic algorithm are linked within an automated design loop. The multi-parameter objective function is either based on the power output or on the overall thermal efficiency. NOx levels have also been taken into account in a third objective function denoted as steam injection effectiveness. The calculations are done for a wide range of parameters such as compressor pressure ratio, turbine inlet temperature, air and steam mass flow rates. Firstly, 6 widely used simple and combined cycle power plants performance are used as test cases for thermodynamic cycle validation. Secondly, gas turbine main parameters are modified to yield the maximum generator power and thermal efficiency. Finally, the effects of uniform crossover, creep mutation, different random number seeds, population size and the number of children per pair of parents on the performance of the genetic algorithm are studied. Parametric analyses show that application of high turbine inlet temperature, high air mass flow rate and no steam injection lead to high power and high combined cycle thermal efficiency. On the contrary, when NOx reduction is desired, steam injection is necessary. For simple cycle, almost full amount of steam injection is required to increase power and efficiency as well as to reduce NOx. Moreover, it is found that the compressor pressure ratio for high power output is significantly lower than the compressor pressure ratio that drives the high thermal efficiency.

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.

Performance Potential Analysis of Heavy-Duty Gas Turbines in Combined Cycle Power Plants

2015 ◽  
Author(s):  
Carl Georg Seydel
Keyword(s):  
Co2 Emissions ◽  
Power Output ◽  
Thermal Efficiency ◽  
Gas Turbines ◽  
Power Plants ◽  
Combined Cycle ◽  
Operational Flexibility ◽  
Heavy Duty ◽  
Performance Potential ◽  
Further Development

Within the last decades heavy-duty gas turbines have become more relevant for the energy sector, especially due to the changing requirements on fossil power plants. In combination with high fluctuating renewables, such as wind and solar energy, combined cycle power plants provide the needed operational flexibility along with high thermal efficiency. In order to meet the ambitious reduction targets for future CO2 emissions, the extension of renewable power solutions is mandatory. Meanwhile further development of fossil power plants is important, to ensure a secure energy supply at all conditions and to back up the worldwide increasing power demand. Enhancements for heavy-duty gas turbines focus on higher thermal efficiency and increasing power output, whilst providing a high operational flexibility. This study analyzes the future performance potential for heavy-duty gas turbines in combined cycle power plants, by further development of the main gas turbine components: compressor, combustion chamber and turbine, including the cooling system. The performance potential will be evaluated separately for each component and in combination for on- and off-design operation. The thermodynamic power plant design will be calculated with the performance software GTlab of the German Aerospace Center. Furthermore the fuel and CO2 savings for different levels of component technology development will be quantified. Concluding a potential evolution timeline for combined cycle power plants until the year 2050 will be given. The results show that there is a high potential regarding to thermal efficiency and power output, by conventional component improvements of heavy-duty gas turbines. Also the improved components lead to a significant reduction of fuel consumption and CO2 emissions.

scholarly journals Energy and exergy analyses of a combined cycle power plant with inlet fuel heating

2021 ◽  
pp. 296-296
Author(s):  
Ting Chen ◽  
Anping Wan ◽  
Ke Li ◽  
Xingwei Xiang ◽  
Qinglong Zhou ◽  
...  
Keyword(s):  
Power Plant ◽  
Ambient Temperature ◽  
Power Output ◽  
Thermal Efficiency ◽  
Combined Cycle ◽  
Combined Cycle Power Plant ◽  
Plant System ◽  
Heating Source ◽  
Power Load ◽  
Energy And Exergy

By using exhaust gas as heating source, a combined cycle power plant with inlet fuel heating is investigated experimentally. Energy analysis and exergy analysis are carried out under different power load and ambient temperature. The results reveal that the thermal efficiency of the power plant system increases as power load increases. The thermal efficiency and power output at 5?C are 54.15% and 412 MW, respectively; while when the ambient temperature is 35?C, the thermal efficiency and power output are 52.3% and 330 MW, respectively. Under the same conditions, the combustion chamber has the highest irreversibility rate, while the air compressor has the lowest. The irreversibility rate of the power plant system increases in line with power load. The second-law efficiency increases from 37.08% to 50.12% when the power load changes from 30% to 100%.

Performance of a Novel Semi-Closed Gas Turbine Refrigeration Combined Cycle

2003 ◽  
Author(s):  
Joseph J. Boza ◽  
William E. Lear ◽  
S. A. Sherif
Keyword(s):  
High Pressure ◽  
Ambient Temperature ◽  
Gas Turbine ◽  
Power Output ◽  
Thermal Efficiency ◽  
Combined Cycle ◽  
Water Mixture ◽  
Absorption Refrigeration ◽  
Ambient Conditions ◽  
Large Engine

A thermodynamic performance analysis was performed on a novel cooling and power cycle that combines a semi-closed gas turbine called the High Pressure Regenerative Turbine Engine (HPRTE) with an absorption refrigeration unit. Waste heat from the recirculated combustion gas of the HPRTE is used to power the absorption refrigeration cycle, which cools the high-pressure compressor inlet of the HPRTE to below ambient conditions and also produces excess refrigeration depending on ambient conditions. Two cases were considered: a small engine with a nominal power output of 100kW, and a large engine with a nominal power output of 40 MW. The cycle was modeled using traditional one-dimensional steady-state thermodynamics, with state-of-the-art polytropic efficiencies and pressure drops for the turbo-machinery and heat exchangers, and curve-fits for properties of the LiBr-water mixture and the combustion products. The small engine was shown to operate with a thermal efficiency approaching 43% while producing 50% as much 5°C refrigeration as its nominal power output (roughly 50 tons) at 30 °C ambient conditions. The large engine was shown to operate with a thermal efficiency approaching 62% while producing 25% as much 5°C refrigeration as its nominal power output (roughly 20,000 tons) at 30 °C ambient conditions. Thermal efficiency stayed relatively constant with respect to ambient temperature for both the large and small engine. It decreased by only 3–4% as the ambient temperature was increased from 10 to 35 °C in each case. The amount of external refrigeration produced by the engine decreased sharply in both engines at around 35 °C, eventually reaching zero at roughly 45°C in each case for 5°C refrigeration. However, the evaporator temperature could be raised to 10°C (or higher) to produce external refrigeration in ambient temperatures as high as 50°C.

scholarly journals Power and Efficiency Optimization for Open Combined Regenerative Brayton and Inverse Brayton Cycles with Regeneration before the Inverse Cycle

Entropy ◽  
2020 ◽  
Vol 22 (6) ◽  
pp. 677 ◽  
Author(s):  
Lingen Chen ◽  
Huijun Feng ◽  
Yanlin Ge
Keyword(s):  
Pressure Drop ◽  
Flow Rate ◽  
Power Output ◽  
Thermal Efficiency ◽  
Pressure Ratio ◽  
Plant Size ◽  
Combined Cycle ◽  
Brayton Cycle ◽  
Flow Resistances ◽  
Top Cycle

A theoretical model of an open combined cycle is researched in this paper. In this combined cycle, an inverse Brayton cycle is introduced into regenerative Brayton cycle by resorting to finite-time thermodynamics. The constraints of flow pressure drop and plant size are taken into account. Thirteen kinds of flow resistances in the cycle are calculated. On the one hand, four isentropic efficiencies are used to evaluate the friction losses in the blades and vanes. On the other hand, nine kinds of flow resistances are caused by the cross-section variances of flowing channels, which exist at the entrance of top cycle compressor (TCC), the entrance and exit of regenerator, the entrance and exit of combustion chamber, the exit of top cycle turbine, the exit of bottom cycle turbine, the entrance of heat exchanger, as well as the entrance of bottom cycle compressor (BCC). To analyze the thermodynamic indexes of power output, efficiency along with other coefficients, the analytical formulae of these indexes related to thirteen kinds of pressure drop losses are yielded. The thermodynamic performances are optimized by varying the cycle parameters. The numerical results reveal that the power output presents a maximal value when the air flow rate and entrance pressure of BCC change. In addition, the power output gets its double maximal value when the pressure ratio of TCC further changes. In the premise of constant flow rate of working fuel and invariant power plant size, the thermodynamic indexes can be optimized further when the flow areas of the components change. The effect of regenerator on thermal efficiency is further analyzed in detail. It is reported that better thermal efficiency can be procured by introducing the regenerator into the combined cycle in contrast with the counterpart without the regenerator as the cycle parameters change in the critical ranges.

Steam-Injected GT Cycles Offer More Power in a Hot Season

2003 ◽  
Author(s):  
Kirk Hanawa
Keyword(s):  
Ambient Temperature ◽  
Thermal Energy ◽  
Power Output ◽  
Thermal Efficiency ◽  
Gas Turbines ◽  
Combined Cycle ◽  
Inlet Temperature ◽  
Water Steam ◽  
Technology Application ◽  
Cycle Temperature

It is said that gas turbine generating plants on simple cycle reduce the power output by 3% in variation with 1% increase of ambient temperature change. When maintaining maximum cycle temperature, i.e., turbine inlet temperature (T4), the reduction of temperature ratio cannot be avoided by increasing minimum cycle temperature, i.e., ambient temperature (T2). Accordingly, the useful power output must be reduced and the thermal energy would be emitted into the atmosphere. The widely used combined cycle plant is an idea to recover the not-used thermal energy into the power, and it is still losing power by 2% in variation with 1% of the ambient temperature. In order to recover effectively such waste thermal energy into the power output, many ideas are adopted to mainly aim the thermal efficiency exceeding 60%, like “Steam-Cooled Combined Cycle”, “Kalina Cycle” etc. It was confirmed that the water/steam-injected WI/GAS3D GT version of modified LM6000 could produce 106 MW with 56% thermal efficiency at ISO conditions *6, and it is demonstrated, this time, that the power curve of the plant in variation with ambient temperature is very flat, comparing with those of conventional GT plants. It might be recommended to establish advantageous cycle plants using the more advanced gas turbines derived from like GE90, PW4000, and Trent800, in order to get exceeding 60% thermal efficiency in hot climate conditions, and it would be expected that such technology application might contribute to execute the worldwide COP3 agreement by saving the fossil fuel usage, resulting in minimal CO2 emissions.

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