Steam Injected Gas Turbine Research Articles

Analytical Off-design Characteristics of Gas Turbine-Based CCHP System

Grounded on the typical analytical off-design performances of some basic CCHP (combined cooling, heating and power) components, off-design characteristics of a gas turbine-based CCHP system were analyzed and summarized. The results and discussion show that, at full power load of the gas turbine, the CCHP relative cold output Qrc varies from 0∼1.2, and the corresponding relative heat output Qrh from 1∼0. The CCHP system supplies 23.7% of the design cold capacity or 22.7% of the design heat capacity at empty power load. CCHP economic exergy efficiency and thermal efficiency both rise with the increase of power output, and trend towards a slight decline at a near-full cooling load of chiller. In a wide operation range of CCHP, economic exergy efficiency and thermal efficiency both rise with the increase of cooling load. Higher ambient temperature results in lower relative capacity of cold, heat and power. It is proposed that renovation technologies such as gas turbine inlet air cooling, steam injected gas turbine and HRSG supplementary firing be applied to weaken the effect of the ambient temperature on CCHP system. The quantitative results are meaningful for optimal configuration and economical operation of the energy systems.

Thermoeconomic Analyses of Steam Injected Gas Turbine Cogeneration Cycles

Thermoeconomic Analyses of Steam Injected Gas Turbine Cogeneration Cycles

Performance Comparison between Steam Injected Gas Turbine and Combined Cycle during Frequency Drops

Single-shaft gas turbine and its cycles are sensitive to frequency drops and, therefore, sudden change loads or large frequency dips might affect their stability. This phenomenon is related to the reduction of the air mass flow passing through the machine during the frequency dips, which might lead to an interaction between governor and temperature control loop. In this paper, the performance of the combined cycle and steam-injected gas turbine are studied during frequency dips and transient maneuvers. For this purpose, two similar units are developed based on these cycles and their performances are studied in different scenarios. The simulation results show that the steam injected gas turbine has a better performance during frequency drops and it can handle relatively larger change loads.

Performance of the solar hybrid STIG cycle with latent heat storage

Abstract The solar hybrid Steam Injection Gas turbine (STIG) cycle uses both recuperated heat and solar heat in order to generate steam at a low temperature and pressure, and inject it into the cycle in order to augment the power output. This work addresses the addition of thermal energy storage to allow operation from solar energy beyond the daylight hours. An annual performance analysis of the Solar STIG cycle with latent heat phase change material (PCM) storage is presented for the climatic conditions of Sede Boqer, Israel. We show that the heat transfer limitation present in a real PCM storage leads to a slight performance penalty only compared to an ideal storage. We also analyze the impact of shifting electricity generation from daytime to evening, which can lead to a surprisingly high contribution of the thermal storage. Results show annual solar fraction of up to 35.2%. The annual solar to electricity efficiency was 20.1% when using the recuperated Brayton cycle as reference, and 13.9% for an optimal conventional STIG cycle as reference. These values are similar to or higher than the annual efficiency of current solar thermal power technologies, even though the hybrid STIG cycle uses low-grade solar heat at 200–280 °C.

Thermodynamic Analysis of a Power Plant Integrated with Fogging Inlet Cooling and a Biomass Gasification

Biomass energy and especially biofuels produced by biomass gasification are clean and renewable options for power plants. Also, on hot days the performance of gas turbines decreases substantially, a problem that can be mitigated by fog cooling. In the present paper, a biomass-integrated fogging steam injected gas turbine cycle is analyzed with energy and exergy methods. It is observed that (1) increasing the compressor pressure ratio raises the air flow rate in the plant but reduces the biomass flow rate; (2) increasing the gas turbine inlet temperature decreases the air and biomass flow rates; (3) increasing the compressor pressure ratio raises the energy and exergy efficiencies, especially at lower pressure ratios; (4) increasing the gas turbine inlet temperature raises both efficiencies; and (5) overspray increases the energy efficiency and net cycle power slightly. The gas turbine exhibits the highest exergy efficiency of the cycle components and the combustor the lowest. A comparison of the cycle with similar cycles fired by natural gas and differently configured cycles fueled by biomass shows that the cycle with natural gas firing has an energy efficiency 18 percentage points above the biomass fired cycle, and that steam injection increases the energy efficiency about five percentage points relative to the cycle without steam injection. Also, the influence of steam injection on energy efficiency is more significant than fog cooling.

Exergy analysis and annual exergetic performance evaluation of solar hybrid STIG (steam injected gas turbine) cycle for Indian conditions

The STIG (steam injected gas turbine) cycle offers a way for increasing the power, efficiency and NOx reduction in gas turbines by injecting steam into the combustor. The present exergetic study is to investigate the influence of compressor PR (pressure ratio), TIT (turbine inlet temperature) and SAR (steam to air ratio) on the solar hybrid STIG cycle. Exergy analysis was performed for four cases based on the parameters of real gas turbines. Annual exergetic performance is also presented for the sites Indore and Jaipur in India under constant and variable power modes. The analysis suggests that the steam injection does not affect the performance of compressor. The total exergy destruction in the cycle increases with SAR and TIT. The exergetic efficiency also increases in the range of 40%–54.2% with SAR up to 0.9. The magnitude of exergy destruction in all components in the cycle (except compressor) increases by increasing SAR. Nevertheless, largest component of exergy destruction in the combustion chamber increases with SAR and TIT about 53% at SAR 0.9. The exergetic efficiency of combustor increases from 74.5% to 81.8% with increasing SAR from 0.3 to 0.9. The exergy destruction in the turbine increases considerably with compressor pressure ratio, sparingly with SAR and independent of TIT. The exergy destruction in the SH (super heater) is less compared to the economiser in the HRSG (heat recovery steam generator). The contribution of solar energy (exergetic solar fraction) is more sensitive to TIT and SAR than PR. It is noticed that increase in turbine outlet temperature, led by PR and TIT, decreases the exergetic solar fraction, and the cycle exergetic efficiency improves as the exergetic solar fraction increases, which leads to an improved performance device. The second largest percentage of exergy destruction is in the flue gas condenser to recover water for recycling, and the heat removed from the condenser is lost to the surroundings by cooling air. The annual values of exergetic solar fraction and exergetic efficiency at Indore are higher than Jaipur in both constant and variable power modes of operation.

An economic analysis of solar hybrid steam injected gas turbine (STIG) plant for Indian conditions

Steam injection for power augmentation is one of the significant modifications of gas turbines that has been commercialized for natural gas-fired applications. The primary objective of this work is to demonstrate that the installation of a solar hybrid steam injected gas turbine plant (STIG) for power generation could have a lower installed cost and lower solar levelized tariff compared to the solar-only thermal power plant while producing a comparable energy output. An economic evaluation is presented for the locations Indore and Jaipur in India under constant, variable power and mixed power scenarios. The levelized tariff (LT) of solar hybrid STIG plant ranges 0.24–0.26 $/kWh, and the levelized tariff (solar only) or solar levelized tariff (SLT) of solar STIG plant ranges from 0.29 to 0.4 $/kWh in constant power (CP) and variable power (VP) scenarios. In case of mixed power (MP) scenario, the range of LT varies from 0.16 to 0.21 $/kWh for CP and VP modes basis. In this analysis, size of the solar STIG plant varies from 48 MW to 212 MW based on the steam to air ratio. The IRR and payback period varies between 12%–17% and 6.3–8 years for both CP and VP scenarios at Jaipur and Indore. Sensitivity analysis reports that the performance of the power plants depends, to a large degree, on boundary conditions such as fuel and equipment costs.

Using compressor discharge air bypass to enhance power generation of a steam-injected gas turbine for combined heat and power

In gas turbine combined heat and power systems, steam injection is a good way to cope with seasonal variations in electricity and heat demands. However, even though thermal energy demand decreases considerably in cooling seasons, the surplus exhaust heat cannot be fully utilized for steam injection in conventional operation because of a reduction in compressor surge margin. This study suggests a modified operation to increase power output without damaging the minimum allowable surge margin. This can be realized by extracting some of the compressor discharge air and supplying it to the turbine exhaust side. This paper shows that the modified operation allows for more steam to be injected in comparison to conventional steam-injected operation while maintaining the same compressor surge margin. The modified operation provides another merit of modulating the heat-to-power-generation ratio by controlling both the amount of air bypass and the steam injection rate. In particular, pure power generating operation, where generated steam is fully injected such that no heat output is available, is possible without decreasing the surge margin below a desired minimum value. The impact of the air bypass is demonstrated for a sample ambient temperature condition and the trend with ambient temperature variation is also illustrated.

Performance and environment as objectives in multi-criterion optimization of steam injected gas turbine cycles

Rapidly growing demand for gas turbines promotes research on their performance improvement and reducing their exhaust pollutants. Even small increments in net power or thermal efficiency and small changes in pollutant emissions have become significant concerns for both new designs and cycle modifications. To fulfill these requirements an accurate performance evaluation method which enables to see the effects on the exhaust gas composition is an important necessity. To fill this gap, a thermo-ecologic performance evaluation approach for gas turbine cycles with chemical equilibrium approximation which enables performance and environmental aspects to be considered simultaneously, is presented in this work. Steam injection is an effective modification to boost power and limit NOx emissions for gas turbine systems. Steam injection also increases thermal efficiency so less fuel is burnt to maintain the same power output. Because of its performance related and environmental advantages, presented approach is applied on the steam injected gas turbine cycle and a precise multi-criterion optimization is carried out for varying steam injection, as well as equivalence and pressure ratios. Irreversibilities and pressure losses are also considered. Effects of each parameter on the net work and thermal efficiency as well as non-equilibrium NOx and CO emissions are demonstrated. Precision improvement of the presented thermo-ecological model is shown and two main concerns; constant turbine inlet condition for higher net work output and constant net work output condition for lower fuel consumption are compared.

Annual performance of the solar hybrid STIG cycle

The solar hybrid Steam Injection Gas turbine (STIG) cycle uses both recuperated heat and solar heat in order to generate steam at a low temperature and pressure, and inject it into the cycle in order to augment the power output. An annual performance analysis of the Solar STIG cycle is presented for sites in Israel and India, with moderate and high annual direct insolation. The cycle operation was simulated in two modes: constant power output and variable power output following the variation of solar input. The solar contribution to the electricity production of the hybrid cycle and the solar to electricity efficiency were calculated, where the conventional reference system was either a conventional STIG or a conventional recuperated Brayton cycle. Results show annual solar fraction of up to 31% in constant power mode and up to 33% in variable power mode. The annual solar to electricity efficiency was in the range of 22–26% when the reference efficiency was based on the recuperated Brayton cycle, and 12–16% when the reference efficiency was based on an optimal conventional STIG cycle. These values are similar to or higher than the annual efficiency of current solar thermal power technologies, even though the hybrid STIG cycle uses low-grade solar heat at only 200°C.

Impact of Steam-Dilution on the Flame Shape and Coherent Structures in Swirl-Stabilized Combustors

Humidified gas turbines and steam-injected gas turbines are promising technologies to lower the emissions and increase the efficiency and fuel flexibility of gas turbines. In the current study, the influence of steam-dilution on swirl-stabilized methane and hydrogen-fired flames is experimentally investigated at Reynolds numbers in the range of 22,000 to 32,000. Velocity fields and flame positions were measured using high-speed particle image velocimetry and OH* chemiluminescence. An extension of the quantitative light sheet technique was employed to estimate the temperature fields. The combined results reveal strong changes in the flame position, the velocity field, and the temperature field with increasing rates of steam dilution. In particular, three different flow and flame patterns are encountered: At dry conditions, a V-shaped flame stabilizes in a broad inner recirculation zone with low local turbulent kinetic energy; at moderate steam content, the flame changes into a trumpet-like shape; and at very high rates of steam-dilution, the flame detaches and shows an annular shape. The associated coherent flow structures are extracted from the particle image velocimetry data employing proper orthogonal decomposition. The isothermal flow is dominated by a helical instability arising near the combustor inlet. This structure is completely suppressed for the dry flame and reappears for the heavily steam-diluted detached flame with a similar shape and frequency as for the isothermal case. The flow field of the trumpet-like flame at intermediate to high steam dilution rates features a helical instability of lower frequency that is located further downstream than in the isothermal and very wet case. A conceptional explanation is presented that relates the suppression of the helical instability to the specific encountered temperature fields and flame shapes.

Thermo-economic analysis of a solid oxide fuel cell and steam injected gas turbine plant integrated with woodchips gasification

This paper presents a thermo-economic analysis of an integrated biogas-fueled solid oxide fuel cell (SOFC) system for electric power generation. Basic plant layout consists of a gasification plant (GP), an SOFC and a retrofitted steam-injected gas turbine (STIG). Different system configurations and simulations are presented and investigated. A parallel analysis for simpler power plants, combining GP, SOFC, and hybrid gas turbine (GT) is carried out to obtain a reference point for thermodynamic results. Thermodynamic analysis shows energetic and exergetic efficiencies for optimized plant above 53% and 43% respectively which are significantly greater than conventional 10 MWe plants fed by biomass. Thermo-economic analysis provides an average cost of electricity for best performing layouts close to 6.4 and 9.4 c€/kWe which is competitive within the market. A sensitivity analysis of the influence of SOFC stack cost on the generation cost is also presented. In order to discuss the investment cost, an economic analysis has been carried out and main parameters such as Net Present Value (NPV), internal rate of return (IRR) and Time of Return of Investment (TIR) are calculated and discussed.

Annual Thermodynamic Analysis of Solar Power with Steam Injection Gas Turbine (STIG) Cycle for Indian Conditions

Solar thermal energy is now being widely utilized to meet the world's energy demand due to its huge potential. Power generation from solar is varying and high cost of solar thermal energy systems that makes sense only in regions with high solar insolation. In order to overcome these practical issues, low cost solar hybrid steam injection gas turbine (STIG) cycle is adapted. Both gas turbine exhaust stream and solar heat are used for steam generation, and then it is injected into the combustor. The steam injection reduces NOX and CO2 emission in addition to increased power output and plant efficiency compared to the simple cycle. It offers a path for high conversion efficiency without the requirement of operating at high temperature and high pressure in the solar components. The objective of the proposed work is to investigate a conversion method for solar radiation that offers potentially high conversion efficiency and for increased competitiveness against fossil fuels. The annual performance of the cycle for sites in India with local climatic conditions such as ambient temperature, relative humidity and availability of direct normal irradiance to the solar concentrators under two modes of constant and variable power is presented in this paper. The results reveal that the solar to electricity efficiency of solar hybrid STIG plant with a simple Parabolic Trough Collector (PTC) is similar to existing solar thermal technologies and higher solar share is obtained. The study also reveals that the annual CO2 emission is similar to combined cycle plants and lower than gas turbine technologies.

Feasibility study and performance assessment for the integration of a steam-injected gas turbine and thermal desalination system

This study proposes a systematic approach for retrofitting a steam-injection gas turbine (SIGT) with a multi-effect thermal vapor compression (METVC) desalination system. The retrofitted unit's product cost of the fresh water (RUPC) was used as a performance criterion, which comprises the thermodynamic, economic, and environmental attributes when calculating the total annual cost of the SIGT–METVC system. For the feasibility study of retrofitting the SIGT plant with the METVC desalination system, the effects of two key parameters were analyzed using response surface methodology (RSM) based on a central composite design (CCD): the steam air ratio (SR) and the temperature difference between the effects of the METVC system (∆TMETVC) on the fresh water production (Qfreshwater) and the net power generation (Wnet) of the SIGT–METVC system. Multi-objective optimization (MOO) which minimizes the modified total annual cost (MTAC) and maximizes the fresh water flow rate was performed to optimize the RUPC of the SIGT–METVC system. The best Pareto optimal solution showed that the SIGT–METVC system with five effects is the best one among the systems with 4–6 effects. This system under optimal operating conditions can save 21.07% and 9.54% of the RUPC, compared to the systems with four and six effects, respectively.

Solar steam reforming of natural gas integrated with a gas turbine power plant

This paper shows a hybrid power plant wherein solar steam reforming of natural gas and a steam injected gas turbine power plant are integrated for solar syngas production and use. The gas turbine is fed by a mixture of natural gas and solar syngas (mainly composed of hydrogen and water steam) from mid-low temperature steam reforming reaction whose heat duty is supplied by a parabolic trough Concentrating Solar Power plant.A comparison is made between a traditional steam injected gas turbine and the proposed solution to underline the improvements introduced by the integration with solar steam reforming of the natural gas process.The paper also shows how solar syngas can be considered as an energy vector consequent to solar energy conversion effectiveness and the natural gas pipeline as a storage unit, thus accomplishing the idea of a smart energy grid.

Superimposition of Elementary Thermodynamic Cycles and Separation of the Heat Transfer Section in Energy Systems Analysis

In a wide variety of thermal energy systems, the high integration among components derives from the need to correctly exploit all the internal heat sources by a proper matching with the internal heat sinks. According to what has been suggested in previous works to address this problem in a general way, a “basic configuration” can be extracted from the system flowsheet including all components but the heat exchangers, in order to exploit the internal heat integration between hot and cold thermal streams through process integration techniques. It was also shown how the comprehension of the advanced thermodynamic cycles can be strongly facilitated by decomposing the system into elementary thermodynamic cycles which can be analyzed separately. The advantages of the combination of these approaches are summarized in this paper using the steam injected gas turbine (STIG) cycle and its evolution towards more complex system configurations as an example of application. The new concept of “baseline thermal efficiency” is introduced to combine the efficiencies of the elementary cycles making up the overall system, which demonstrates to be a useful reference to quantify the performance improvement deriving from heat integration between elementary cycles within the system.

터빈 블레이드 온도 변화를 고려한 증기분사 가스터빈 열병합발전 시스템의 성능해석

ABSTRACT This study simulated the operation of a steam injected gas turbine combined heat and power (CHP) system. A full off-design analysis was carried out to examine the change in the turbine blade temperature caused by steam injection. The prediction of turbine blade temperature was performed for the operating modes suggested in the previous study where the limitation of compressor surge margin reduction was analyzed in the steam injected gas turbine. It was found that both the fully injected and partially injected operations suggested in the previous study would cause the blade temperature to exceed that of the pure CHP operation and the under-firing operation would provide too low blade temperature. An optimal operation was proposed where both the turbine inlet temperature and the injection amount were modulated to keep both the reference turbine blade temperature and the minimum compressor surge margin. The modulation was intended to maintain a stable compressor operation and turbine life. It was shown that the optimal operation would provide a larger power output than the under-firing operation and a higher efficiency than the original partially injected operation.

Performance and Water Consumption of the Solar Steam-Injection Gas Turbine Cycle

Solar heat at moderate temperatures around 200 °C can be utilized for augmentation of conventional steam-injection gas turbine power plants. Solar concentrating collectors for such an application can be simpler and less expensive than collectors used for current solar power plants. We perform a thermodynamic analysis of this hybrid cycle, focusing on improved modeling of the combustor and the water recovery condenser. The cycle's water consumption is derived and compared to other power plant technologies. The analysis shows that the performance of the hybrid cycle under the improved model is similar to the results of the previous simplified analysis. The water consumption of the cycle is negative due to water production by combustion, in contrast to other solar power plants that have positive water consumption. The size of the needed condenser is large, and a very low-cost condenser technology is required to make water recovery in the solar STIG cycle technically and economically feasible.

Effects of Water and Steam Injection on Thermodynamic Performance of Gas-Turbine Systems

The water and steam injection gas-turbine systems are comparatively investigated. Thermodynamic performances of the regenerative after-fogging gas-turbine (RAF) system, steam-injection gas-turbine (STIG) system, and the regenerative steam-injection gas-turbine (RSTIG) system are analyzed parametrically. Using the analytic model, the important system variables such as thermal efficiency, fuel consumption, specific power, and specific emission of CO2 gas are evaluated in terms of pressure ratio and water or steam injection ratio. The numerical results show that water or steam injection results in a notable enhancement of thermal efficiency and specific power.

Solar hybrid steam injection gas turbine (STIG) cycle

Abstract Solar heat at moderate temperatures around 200 °C can be utilized for augmentation of conventional steam-injection gas turbine power plants. Solar concentrating collectors for such an application can be simpler and less expensive than collectors used for current solar power plants. We perform a thermodynamic analysis of this hybrid cycle. High levels of steam-to-air ratio are investigated, leading to high power augmentation compared to the simple cycle and to conventional STIG. The Solar Fraction can reach up to 50% at the highest augmentation levels. The overall conversion efficiency from heat to electricity (average over fuel and solar contributions) can be in the range of 40–55% for typical candidate turbines. The incremental efficiency (corresponding to the added steam beyond conventional STIG) is in the range of 22–37%, corresponding to solar-to-electricity efficiency of about 15–24%, similar to and even exceeding current solar power plants using higher temperature collectors. The injected water can be recovered and recycled leading to very low water consumption of the cycle, but a very low cost condenser is required to make water recovery feasible.