A Novel Brayton Cycle With the Integration of Liquid Hydrogen Cryogenic Exergy Utilization

2005 ◽  
Author(s):  
Na Zhang ◽  
Noam Lior
Keyword(s):  
Energy Efficiency ◽  
Gas Turbine ◽  
Liquid Hydrogen ◽  
Utilization Efficiency ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Brayton Cycle ◽  
Evaporation Process ◽  
Impact Reduction ◽  
Gas Turbine Cycle

Stored or transported liquid hydrogen for use in power generation needs to be vaporized before combustion. Much energy was invested in the H2 liquefaction process, and recovery of as much of this energy as possible in the re-evaporation process will contribute to both the overall energy budget of the hydrogen use process, and to environmental impact reduction. A new gas turbine cycle is proposed with liquefied hydrogen (LH2) cryogenic exergy utilization. It is a semi-closed recuperative gas turbine cycle with nitrogen as the working fluid. By integration with the liquid H2 evaporation process, the inlet temperature of the compressor is kept very low, and thus the required compression work could be reduced significantly. Internal-fired combustion is adopted which allows a very high turbine inlet temperature, and a higher average heat input temperature is achieved also by internal heat recuperation. As a result, the cycle ha ry attractive thermal performance with the predicted energy efficiency over 79%. The choice of N2 as the working fluid is to allow the use of air as the oxidant in the combustor. The oxygen in the air combines with the fuel H2 to form water, which is easily separated from the N2 by condensation, leaving the N2 as the working fluid. The quantity of this working fluid in the system is maintained constant by continuously evacuating from the system the same amount that is introduced with the air. The cycle is environmentally friendly because no CO2 and other pollutant are emitted. An exergy analysis is conducted to identify the exergy losses in the components and the potential for further system improvement. The biggest exergy destruction is found occurring in the LH2 evaporator due to the relatively higher heat transfer temperature difference. The energy efficiency and exergy efficiency are 79% and 52%, respectively. The system has a back-work ratio only 1/4 of that in a Brayton cycle with ambient as the heat sink, and thus can produce 30.14 MW (53.9%) more work, with the LH2 cryogenic exergy utilization efficiency of 54%.

Novel Gas Turbine Cycle With Integration of CO2 Recovery and LNG Cryogenic Exergy Utilization

2002 ◽  
Author(s):  
Shimin Deng ◽  
Hongguang Jin ◽  
Ruixian Cai ◽  
Rumou Lin
Keyword(s):  
Gas Turbine ◽  
Greenhouse Gas Emission ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Average Temperature ◽  
Co2 Recovery ◽  
Gas Turbine Cycle ◽  
Cycle Efficiency ◽  
Very High ◽  
Turbine Exhaust

In this paper we propose a new gas turbine cycle, which employs a semi-closed recuperative gas turbine with LNG utilization. Nitrogen is selected as working fluid with air induced at the inlet of compressor. The inlet temperature of the compressor is kept pretty low with LNG cooling, and turbine inlet temperature can be very high because of internal combustion, and higher average temperature of heat absorption of the cycle is achieved due to recuperation. As a result, the cycle efficiency can reach as high as 70% (TIT=1250°C). Furthermore, along the process of LNG vaporization, turbine exhaust is cooled down; CO2 in the mixture is solidified and separated without extra power consumption. Two different natural gas sendout pressures (7.0 and 3.0 MPa) are considered. Their performances are simulated and a comprehensive analysis is carried out. The performance of the new cycle, CO2 recovery, and heat transfer in LNG vaporizer are discussed in detail. The new cycle proposed here is based on the integration of carbon dioxide recovery and LNG cryogenic exergy utilization, and it will contribute to both improvement on power generation efficiency and reduction of greenhouse gas emission.

A Supercritical CO2 Gas Turbine Power Cycle for Next-Generation Nuclear Reactors

2002 ◽  
Author(s):  
Vaclav Dostal ◽  
Michael J. Driscoll ◽  
Pavel Hejzlar ◽  
Neil E. Todreas
Keyword(s):  
Gas Turbine ◽  
Oil Recovery ◽  
Supercritical Co2 ◽  
Power Plants ◽  
Ideal Gas ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Brayton Cycle ◽  
Pinch Point ◽  
Good Efficiency

Although proposed more than 35 years ago, the use of supercritical CO2 as the working fluid in a closed circuit Brayton cycle has so far not been implemented in practice. Industrial experience in several other relevant applications has improved prospects, and its good efficiency at modest temperatures (e.g., ∼45% at 550°C) make this cycle attractive for a variety of advanced nuclear reactor concepts. The version described here is for a gas-cooled, modular fast reactor. In the proposed gas-cooled fast breeder reactor design of present interest, CO2 is also especially attractive because it allows the use of metal fuel and core structures. The principal advantage of a supercritical CO2 Brayton cycle is its reduced compression work compared to an ideal gas such as helium: about 15% of gross power turbine output vs. 40% or so. This also permits the simplification of use of a single compressor stage without intercooling. The requisite high pressure (∼20 MPa) also has the benefit of more compact heat exchangers and turbines. Finally, CO2 requires significantly fewer turbine stages than He, its principal competitor for nuclear gas turbine service. One disadvantage of CO2 in a direct cycle application is the production of N-16, which will require turbine plant shielding (albeit much less than in a BWR). The cycle efficiency is also very sensitive to recuperator effectiveness and compressor inlet temperature. It was found necessary to split the recuperator into separate high- and low-temperature components, and to employ intermediate recompression, to avoid having a pinch-point in the cold end of the recuperator. Over the past several decades developments have taken place that make the acceptance of supercritical CO2 systems more likely: supercritical CO2 pipelines are in use in the western US in oil-recovery operations; 14 advanced gas-cooled reactors (AGR) are employed in the UK at CO2 temperatures up to 650°C; and utilities now have experience with Rankine cycle power plants at pressures as high as 25 MPa. Furthermore, CO2 is the subject of R&D as the working fluid in schemes to sequester CO2 from fossil fuel combustion and for refrigeration service as a replacement for CFCs.

The Parameter Analysis on the Gas Turbine Cycle in a High Temperature Gas-Cooled Reactor

2010 ◽  
Author(s):  
Huisheng Zhang ◽  
Jiancheng Zhang ◽  
Ming Su ◽  
Shilie Weng
Keyword(s):  
High Temperature ◽  
Gas Turbine ◽  
High Efficiency ◽  
Temperature Limit ◽  
Parameter Analysis ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Efficient Production ◽  
Gas Turbine Cycle ◽  
High Temperature Gas

The high-temperature gas-cooled reactor (HTGR) technology is the only nuclear technology capable of achieving coolant temperatures as high as 950 °C and at the same time ensuring safe and efficient production of electricity, process steam and hydrogen. HTGR can be combined with a gas turbine to be gas turbine cycle with HTGR. This cycle can make use of high temperature (750–950°C) gas heated by HTGR to generate electricity with high efficiency. Because it breaks through the temperature limit of steam cycle and incorporates the inter-cooling and recuperating, so the gas turbine cycle with HTGR is expected to be a competing candidate for future concepts of high efficiency power generation. The performance of direct gas turbine with HTGR coupled with recuperating, inter-cooling and pre-cooling process was investigated. Considering the selection of working fluid, the thermal efficiency of gas turbine with HTGR with helium, nitrogen, carbon dioxide and their mixtures as the working fluid was compared. Then, the influence of different parameters such as turbine inlet temperature, pressure loss coefficient and recuperation effectiveness on cycle efficiency was analyzed. Some useful conclusions were drawn on the system performance.

Modelling and Simulation of Transient Performance of the Semi-Closed O2/CO2 Gas Turbine Cycle for CO2-Capture

2003 ◽  
Author(s):  
Ragnhild E. Ulfsnes ◽  
Olav Bolland ◽  
Kristin Jordal
Keyword(s):  
Water Vapor ◽  
Specific Heat ◽  
Gas Turbine ◽  
Transient Behavior ◽  
Cycle Performance ◽  
Working Fluid ◽  
Transient Event ◽  
Co2 Gas ◽  
Specific Heat Ratio ◽  
Gas Turbine Cycle

One of the concepts proposed for capture of CO2 in power production from gaseous fossil fuels is the semi-closed O2/CO2 gas turbine cycle. The semi-closed O2/CO2 gas turbine cycle has a near to stoichiometric combustion with oxygen, producing CO2 and water vapor as the combustion products. The water vapor is condensed and removed from the process, the remaining gas, primarily CO2, is mainly recycled to keep turbine inlet temperature at a permissible level. A model for predicting transient behavior of the semi-closed O2/CO2 gas turbine cycle is presented. The model is implemented in the simulation tool gPROMS (Process System Enterprise Ltd.), and simulations are performed to investigate two different issues. The first issue is to see how different cycle performance variables interact during transient behavior; the second is to investigate how cycle calculations are affected when including the gas constant and the specific heat ratio in compressor characteristics. The simulations show that the near to stoichiometric combustion and the working fluid recycle introduce a high interaction between the different cycle components and variables. This makes it very difficult to analytically predict the cycle performance during a transient event, i.e. simulations are necessary. It is also found that, except for the shaft speed calculation, the introduction of gas constant and specific heat ratio dependence on the compressor performance map will have only a minor influence on the process performance.

Second Law Efficiency of an Intercooled-Reheated-Regenerative-Brayton Cycle With Variable Temperature Heat Reservoirs

2012 ◽  
Author(s):  
Vishal Anand ◽  
Krishna Nelanti ◽  
Kamlesh G. Gujar
Keyword(s):  
Gas Turbine ◽  
Variable Temperature ◽  
Pressure Ratio ◽  
Working Fluid ◽  
Thermodynamic Efficiency ◽  
Second Law ◽  
Brayton Cycle ◽  
Cooling Fluid ◽  
Turbine Engine ◽  
Temperature Heat

The gas turbine engine works on the principle of the Brayton Cycle. One of the ways to improve the efficiency of the gas turbine is to make changes in the Brayton Cycle. In the present study, Brayton Cycle with intercooling, reheating and regeneration with variable temperature heat reservoirs is considered. Instead of the usual thermodynamic efficiency, the Second law efficiency, defined on the basis of lost work, has been taken as a parameter to study the deviation of the irreversible Brayton Cycle from the ideal cycle. The Second law efficiency of the Brayton Cycle has been found as a function of reheat and intercooling pressure ratios, total pressure ratio, intercooler, regenerator and reheater effectiveness, hot and cold side heat exchanger effectiveness, turbine and compressor efficiency and heating capacities of the heating fluid, the cooling fluid and the working fluid (air). The variation of the Second law efficiency with all these parameters has been presented. From the results, it can be seen that the Second law efficiency first increases and then decreases with increase in intercooling pressure ratio and increases with increase in reheating pressure ratio. The results show that the Second law efficiency is a very good indicator of the amount of irreversibility of the cycle.

The Heat Transfer Performance of Porous Gas Turbine Blades

1968 ◽  
Vol 72 (696) ◽  
pp. 1087-1094 ◽  
Author(s):  
F. J. Bayley ◽  
A. B. Turner
Keyword(s):  
Gas Turbine ◽  
Turbine Blades ◽  
Engine Performance ◽  
Operating Conditions ◽  
Maximum Temperature ◽  
Specific Power ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Turbine Inlet ◽  
Compression And Expansion

It is well known that the performance of the practical gas turbine cycle, in which compression and expansion are non-isentropic, is critically dependent upon the maximum temperature of the working fluid. In engines in which shaft-power is produced the thermal efficiency and the specific power output rise steadily as the turbine inlet temperature is increased. In jet engines, in which the gas turbine has so far found its greatest success, similar advantages of high temperature operation accrue, more particularly as aircraft speeds increase to utilise the higher resultant jet velocities. Even in high by-pass ratio engines, designed specifically to reduce jet efflux velocities for application to lower speed aircraft, overall engine performance responds very favourably to increased turbine inlet temperatures, in which, moreover, these more severe operating conditions apply continuously during flight, and not only at maximum power as with more conventional cycles.

Advanced High Temperature Gas-Cooled Reactor Systems

2008 ◽  
Author(s):  
Yasuyoshi Kato
Keyword(s):  
Gas Turbine ◽  
Power Conversion ◽  
Inlet Temperature ◽  
Turbine Inlet Temperature ◽  
Co2 Gas ◽  
Flow Channels ◽  
Turbine Inlet ◽  
Conversion System ◽  
Gas Turbine Cycle ◽  
Cycle Efficiency

Three systems have been proposed for advanced high temperature gas-cooled reactors (HTGRs): a supercritical carbon dioxide (S-CO2) gas turbine power conversion system; a new MicroChannel Heat Exchanger (MCHE); and a once-through-then-out (OTTO) refueling scheme with burnable poison (BP) loading. An S-CO2 gas turbine cycle attains higher cycle efficiency than a He gas turbine cycle due to reduced compression work around the critical point of CO2. Considering temperature lowering at the turbine inlet by 30°C through the intermediate heat exchange, the S-CO2 indirect cycle achieves efficiency of 53.8% at turbine inlet temperature of 820°C and turbine inlet pressure of 20 MPa. This cycle efficiency value is higher by 4.5% than that (49.3%) of a He direct cycle at turbine inlet temperature of 850°C and 7 MPa. A new MCHE has been proposed as intermediate heat exchangers between the primary cooling He loop and the secondary S-CO2 gas turbine power conversion system; and recuperators of the S-CO2 gas turbine power conversion system. This MCHE has discontinuous “S”-shape fins providing flow channels with near sine curves. Its pressure drop is one-sixth reference to the conventional MCHE with zigzag flow channel configuration while the same high heat transfer performance inherits. The pressure drop reduction is ascribed to suppression of recirculation flows and eddies that appears around bend corners of zigzag flow channels in the conventional MCHE. An optimal BP loading in an OTTO refueling scheme eliminates the drawback of its excessively high axial power peaking factor, reducing the power peaking factor from 4.44 to about 1.7; and inheriting advantages over the multi-pass scheme because of the lack of fuel handling and integrity checking systems; and reloading. Because of the power peaking factor reduction, the maximum fuel temperatures are lower than the maximum permissible values of 1250°C for normal operation and 1600°C during a depressurization accident.

Off-Design Performance Investigation of a Low Calorific Value Gas Fired Generic-Type Single-Shaft Gas Turbine

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Raik C. Orbay ◽  
Magnus Genrup ◽  
Pontus Eriksson ◽  
Jens Klingmann
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Pressure Ratio ◽  
Calorific Value ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Flammability Limits ◽  
Generic Type ◽  
Wobbe Index ◽  
The Impact

When low calorific value gases are fired, the performance and stability of gas turbines may deteriorate due to a large amount of inertballast and changes in working fluid properties. Since it is rather rare to have custom-built gas turbines for low lower heating value (LHV) operation, the engine will be forced to operate outside its design envelope. This, in turn, poses limitations to usable fuel choices. Typical restraints are decrease in Wobbe index and surge and flutter margins for turbomachinery. In this study, an advanced performance deck has been used to quantify the impact of firing low-LHV gases in a generic-type recuperated as well as unrecuperated gas turbine. A single-shaft gas turbine characterized by a compressor and an expander map is considered. Emphasis has been put on predicting the off-design behavior. The combustor is discussed and related to previous experiments that include investigation of flammability limits, Wobbe index, flame position, etc. The computations show that at constant turbine inlet temperature, the shaft power and the pressure ratio will increase; however, the surge margin will decrease. Possible design changes in the component level are also discussed. Aerodynamic issues (and necessary modifications) that can pose severe limitations on the gas turbine compressor and turbine sections are discussed. Typical methods for axial turbine capacity adjustment are presented and discussed.

A Solar Gas Turbine Cycle With Super-Critical Carbon Dioxide as a Working Fluid

2006 ◽  
Author(s):  
Motoaki Utamura ◽  
Yutaka Tamaura
Keyword(s):  
Carbon Dioxide ◽  
Heat Exchanger ◽  
Molten Salt ◽  
Gas Turbine ◽  
Thermal Power ◽  
Working Fluid ◽  
Regenerative Heat ◽  
Operation Conditions ◽  
Gas Turbine Cycle ◽  
Cycle Efficiency

Solar thermal power generation system equipped with molten salt thermal storage offers continuous operation at a rated power independent of the variation of insolation. A gas turbine cycle for solar applications is studied which works in a moderate temperature range (600–850K) where molten salt stays as liquid stably. It is found that a closed cycle with super-critical state of carbon dioxide as a working fluid is a promising candidate for solar application. The cycle featured in smaller compressor work would achieve high cycle efficiency if cycle configuration and operation conditions are chosen properly. The temperature effectiveness of a regenerative heat exchanger is shown to govern the efficiency. Under the condition of 98% temperature effectiveness, the regenerative cycle with pre- and inter-cooling provides cycle efficiency of as much as 47%. A novel heat exchanger design to realize such a high temperature effectiveness is also presented.

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