Steam Injected Gas Turbine Research Articles

Sensitivity analysis and thermo-economic optimisation of Steam Injected Gas Turbine cycle design parameters

The purpose of the present work is to apply thermo-economic concepts to a Steam Injected Gas Turbine (STIG) electricity generation system and optimise it to indicate its economical advantages over a simple gas turbine. The system incorporates a combustion chamber, gas turbine, a compressor and a Heat Recovery Steam Generator (HRSG). A detailed sensitivity analysis was also performed to examine the impacts of the variation of the operating parameters. Genetic algorithm and direct search methods were used to find optimum values. The system is optimised, using thermo-economic concepts. The results demonstrate that the steam injected system shows a better thermodynamic and thermo-economic performance.

Two new high-performance cycles for gas turbine with air bottoming

The objective of this research is to model steam injection in the gas turbine with Air Bottoming Cycle (ABC). Based on an exergy analysis, a computer program has been developed to investigate improving the performance of an ABC cycle by calculating the irreversibility in the corresponding devices of the system. In this study, we suggest two new cycles where an air bottoming cycle along with the steam injection are used. These cycles are: the Evaporating Gas turbine with Air Bottoming Cycle (EGT-ABC), and Steam Injection Gas turbine with Air Bottoming Cycle (STIG-ABC). The results of the model show that in these cycles, more energy recovery and higher air inlet mass flow rate translate into an increase of the efficiency and output turbine work. The EGT-ABC was found to have a lower irreversibility and higher output work when compared to the STIG-ABC. This is due to the fact that more heat recovery in the regenerator in the EGT-ABC cycle results in a lower exhaust temperature. The extensive modeling performed in this study reveals that, at the same up-cycle pressure ratio and turbine inlet temperature (TIT), a higher overall efficiency can be achieved for the EGT-ABC cycle.

A Parametric Thermodynamic Evaluation of High Performance Gas Turbine Based Power Cycles

This paper discusses the gas turbine performance enhancement approach that has gained a lot of momentum in recent years in which modified Brayton cycles are used with humidification or water/steam injection, termed “wet cycles,” or with fuel cells, obtaining “hybrid cycles.” The investigated high performance cycles include intercooled steam-injected gas turbine cycle, recuperated water injection cycle, humidified air turbine cycle, and cascaded humidified advanced turbine cycle, Brayton cycle with high temperature fuel cells (molten carbonate fuel cells or solid oxide fuel cells), and their combinations with the modified Brayton cycles. Most of these systems, with a few exceptions, have not yet become commercially available as more development work is required. The results presented show that the cycle efficiency achievable with the aforementioned high performance systems can be comparable or better than a combined cycle system, a currently commercially available power generation system having maximum cycle efficiency. The main emphasis of this paper is to provide a detailed parametric thermodynamic cycle analysis, using uniform design parameters and assumptions, of the above mentioned cycles and discuss their comparative performance including advantages and limitations. The performance of these cycles is also compared with the already developed and commercially available gas turbines without water/steam injection features, called “dry cycles.” In addition, a brief review of the available literature of the identified high performance complex gas turbine cycles is also included in this paper.

Cogeneration in Sugar Industries: Technology Options and Performance Parameters—A Review

ABSTRACT This article presents a review of different technological options that are presently being practiced by sugar mills, and technological options that are identified as potentially promising future technologies. Different indices used to gauge the thermodynamic performance of cogeneration plants and facilitate the comparison of alternative systems are discussed. The most important performance parameters used to assess the steam turbine cogeneration plants in general and sugar mill cogeneration plants in particular are defined and developed. Criteria such as energy utilization factor, heat-to-power ratio, fuel energy savings ratio, exergetic efficiency and power generated per tonne of cane (tc) prove to be more important and relevant. Biomass-integrated gasifier/gas turbine cogeneration (BIG-GT) and biomass gasifier combined with steam injected gas turbine cogeneration (BIG-STIG) are considered as potentially promising future technologies. The existing modern, high pressure, high efficiency, steam turbine cogeneration plants generate 115–120 kWh/tc, while BIG-GT and BIG-STIG are potentially capable of generating up to 270–275 kWh/tc. Cogeneration plants using backpressure and condensing steam turbines perform with energy (First Law) and exergetic (Second Law) efficiency of approximately 60–70 % and 22–25%, respectively. The steam consumption in sugar mills at present varies from 480–550 kg/tc, while electricity consumption ranges between 16–22 kWh/tc (32–40 kWh/tc for electrified mills). These performance indices will help plant designers and engineers in improving their choice of system configuration and developing alternative schemes.

Blade cooling optimisation in humid-air and steam-injected gas turbines

Humidified gas turbine cycles such as the humidified air turbine (HAT) and the steam-injected gas turbine (STIG) present exciting new prospects for industrial gas turbine technology, potentially offering greatly increased work outputs and cycle efficiencies at moderate costs. The availability of humidified air or steam in such cycles also presents new opportunities in blade and disk cooling architecture. Here, the blade cooling optimisation of a HAT cycle and a STIG cycle is considered, first by optimising the choice of coolant bleeds for a reference cycle, then by a full parametric optimisation of the cycle to consider a range of optimised designs. It was found that the coolant demand reductions which can be achieved in the HAT cycle using humidified or post-aftercooled coolant are compromised by the increase in the required compression work. Furthermore, full parametric optimisation showed that higher water flow-rates were required to prevent boiling within the system. This corresponded to higher work outputs, but lower cycle efficiencies. When optimising the choice of coolant bleeds in the STIG cycle, it was found that bleeding steam for cooling purposes reduced the steam available for power augmentation and thus compromised work output, but that this could largely be overcome by reducing the steam superheat to give useful cycle efficiency gains.

A Systematic Comparison and Multi-Objective Optimization of Humid Power Cycles—Part I: Thermodynamics

The steam injected gas turbine (STIG), humid air turbine (HAT), and TOP Humid Air Turbine (TOPHAT) cycles lie at the center of the debate on which humid power cycle will deliver optimal performance when applied to an aeroderivative gas turbine and, indeed, when such cycles will be implemented. Of these humid cycles, it has been claimed that the TOPHAT cycle has the highest efficiency and specific work, followed closely by the HAT, and then the STIG cycle. In this study, the systems have been simulated using consistent thermodynamic and economic models for the components and working fluid properties, allowing a consistent and nonbiased appraisal of these systems. Part I of these two papers focuses purely on the thermodynamic performance and the impact of the system parameters on the performance; Part II will study the economic performance. The three humid power systems and up to ten system parameters are optimized using a multi-objective Tabu Search algorithm, developed in the Cambridge Engineering Design Centre.

A Systematic Comparison and Multi-Objective Optimization of Humid Power Cycles—Part II: Economics

The steam injected gas turbine (STIG), humid air turbine (HAT), and TOP Humid Air Turbine (TOPHAT) cycles lie at the center of the debate on which humid power cycle will deliver optimal performance when applied to an aeroderivative gas turbine and, indeed, when such cycles will be implemented. Of these humid cycles, it has been claimed that the TOPHAT cycle has the highest efficiency and specific work, followed closely by the HAT and then the STIG cycle. In this study, the systems have been simulated using consistent thermodynamic and economic models for the components and working fluid properties, allowing a consistent and nonbiased appraisal of these systems. Part I of these two papers focused on the thermodynamic performance and the impact of the system parameters on the performance, Part II studies the economic performance of these cycles. The three humid power systems and up to ten system parameters are optimized using a multi-objective Tabu Search algorithm, developed in the Cambridge Engineering Design Centre.

Exergy based performance analysis of a solid oxide fuel cell and steam injected gas turbine hybrid power system

This paper presents exergy analysis of a hybrid solid oxide fuel cell and gas turbine (SOFC/GT) system in comparison with retrofitted system with steam injection. It is proposed to use hot gas turbine exhaust gases heat in a heat recovery steam generator to produce steam and inject it into gas turbine. Based on a steady-state model of the processes, exergy flow rates are calculated for all components and a detailed exergy analysis is performed. The components with the highest proportion of irreversibility in the hybrid systems are identified and compared. It is shown that steam injection decreases the wasted exergy from the system exhaust and boosts the exergetic efficiency by 12.11%. Also, 17.87% and 12.31% increase in exergy output and the thermal efficiency, respectively, is demonstrated. A parametric study is also performed for different values of compression pressure ratio, current density and pinch point temperature difference.

The Influence of Recovering Wasted Energy and Air Coolers on Gas Turbine Cycle Performance

ABSTRACT This article studies the performance enhancement of a gas turbine power plant by using many proven technologies, such as inlet air cooling, intercooling, regeneration, and steam injection gas turbine. The temperature of exhaust gases from a gas turbine cycle is usually very high, and plenty of useful energy is expelled to the atmosphere. The exhaust gases of the gas turbine can be used to produce steam by a heat recovery steam generator (HRSG). The generated steam injects to a combustion chamber to increase both output power and cycle efficiency. Mass flow of the exhaust gases is more than the required quantity of the HRSG, so the remaining quantity can be used for regeneration processes and to supply required heat for an absorption chiller. In this study, two types of air coolers are used. An absorption inlet air cooler increases the mass flow rate of inlet air of the gas turbine and boosts output power and cycle efficiency independent of relative humidity and the temperature of ambient air. Intercooled compression, achieved through an indirect evaporative intercooler that reduces the temperature of the air between two compressors to reduce the compression work and increasing net output power. The results of using the above methods under consideration are presented and discussed.

Combustion Chamber Steam Injection for Gas Turbine Performance Improvement During High Ambient Temperature Operations

The gas turbines are generally used for large scale power generation. The basic gas turbine cycle has low thermal efficiency, which decreases in the hard climatic conditions of operation, so the cycles with thermodynamic improvement is found to be necessary. Among several methods shown their success in increasing the performances, the steam injected gas turbine cycle (STIG) consists of introducing a high amount of steam at various points in the cycle. The main purpose of the present work is to improve the principal characteristics of gas turbine used under hard condition of temperature in Algerian Sahara by injecting steam in the combustion chamber. The suggested method has been studied and compared to a simple cycle. Efficiency, however, is held constant when the ambient temperature increases from ISO conditions to 50°C. Computer program has been developed for various gas turbine processes including the effects of ambient temperature, pressure ratio, injection parameters, standard temperature, and combustion chamber temperature with and without steam injection. Data from the performance testing of an industrial gas turbine, computer model, and theoretical study are used to check the validity of the proposed model. The comparison of the predicted results to the test data is in good agreement. Starting from the advantages, we recommend the use of this method in the industry of hydrocarbons. This study can be contributed for experimental tests.

Gas Turbine Performances Improvement using Steam Injection in the Combustion Chamber under Sahara Conditions

Gas turbines are generally used for large scale power generation. The basic gas turbine cycle has low thermal efficiency which decreases in the hard climatic conditions of operation, so it is important to look for improved gas turbine based cycles. Among several methods shown their success in increasing the performances, the steam injected gas turbine cycle (STIG) consists to introduce a high amount of steam at various points in the cycle. The objective of the present work is to improve the performances of gas turbine used under Sahara conditions by injecting suitable quantities of steam in the upstream of combustion chamber. The suggested method has been studied and compared with a simple cycle. Efficiency, however, is held constant when the ambient temperature increases from iso conditions to 50C. Computer program has been developed for various gas turbine processes including the effect of ambient temperature. This is achieved by studying the effect of steam injection on the gas turbine performances. Data from the performance testing of an industrial gas turbine, computer model and theoretical study are used to check the validity of the proposed model. The comparison of the prediction results to the test data is in good agreement.

Sensitivity analysis of STIG based combined cycle with dual pressure HRSG

Thermodynamic evaluation has been carried out for a combined cycle with STeam Injected Gas Turbine (STIG) having dual pressure heat recovery steam generator (HRSG). Steam from high-pressure steam turbine is injected into the combustion chamber at a pressure higher than the combustion pressure to improve the exergy efficiency of combined cycle. The effect of steam injection mass ratio, deaerator pressure (or temperature ratio), steam reheat pressure ratio, HP steam turbine pressure, compressor pressure ratio and combustion temperature on combined cycle exergy efficiency has been investigated. It has been found that advantage from steam injection to combined cycle is obtained at high steam reheat pressure and high steam turbine inlet pressure. At this condition, the increasing effect of gas cycle output exceeds the decreasing effect of steam cycle output. The major exergetic loss that occurs in combustion chamber decreases with introduction of steam injection in to the combustion.

Fuel allocation in a combined steam-injected gas turbine and thermal seawater desalination system

Fuel allocation in a combined steam-injected gas turbine (STIG) power generation and multi-effect thermal vapor compression (METVC) desalination system is studied, using seven methods: (1) Products Energy Method, (2) Products Exergy Method, (3) Power-Generation-Favored Method, (4) Heat-Production-Favored Method, (5) Basic Exergetic Cost Theory, (6) Functional Approach and (7) Splitting Factor Method. The latter three are thermoeconomics-based. Two sample cases are calculated. The methods and results are compared and discussed. The main conclusions are: it is important to carefully choose suitable methods to perform fuel allocation in a dual purpose desalination systems (here a combined STIG-METVC system) since different methods produce very different results; The results obtained from Methods (1) and (5) are unreasonable, and those from Methods (3) and (4) set the range within which the fuel allocation values must reside; Although thermoeconomic methodologies are considered to be the most rational for cost attribution of multi-product systems, false results could be reached if they are not suitably used; When sufficient information is unavailable for performing a thermoeconomic analysis, Method (2) can be taken as an approximation for fuel allocation, as well as for the distribution of fuel cost and combustion pollutant emission, between power and water in a STIG-METVC system. A recommended fuel allocation analysis procedure, based on this study and with some generality for other gas-turbine power plant dual purpose thermal desalination systems, was outlined.

Performance analysis of combined humidified gas turbine power generation and multi-effect thermal vapor compression desalination systems: Part 2: The evaporative gas turbine based system and some discussions

This is Part 2 of the paper “Performance analysis of combined humidified gas turbine power generation and multi-effect thermal vapor compression desalination systems — Part 1: The desalination unit and its combination with a steam-injected gas turbine power system”. A combined power and water system based on the evaporative gas turbine (EvGT) is studied, and major features such as the fuel saving, power-to-water ratio, energy and exergy utilization, and approaches to performance improvement, are presented and discussed in comparison with STIG- and EvGT- based systems, to further reveal the characteristics of these two types of combined systems. Some of the main results of the paper are: the fuel consumption of water production in STIG-based combined system is, based on reference-cycle method, about 45% of a water-only unit, and that in an EvGT-based system, it is 31–54%; compared with the individual power-only and water-only units, the fuel savings of the two combined systems are 12%–28% and 10%–21%, respectively; a water production gain of more than 15% can be obtained by using a direct-contact gas-saline water heat exchanger to recover the stack heat; and the combined system are more flexible in its power-to-water ratio than currently used dual-purpose systems. Further studies on aspects such as operation, hardware cost, control complexity, and environmental impact, are needed to determine which configuration is more favorable in practice.

Parametric simulation of steam injected gas turbine combined cycle

In the current work, thermodynamic analysis has been conducted for a steam injected gas turbine (STIG) in the combined cycle system with the dual pressure heat-recovery steam generator. Effect of operating variables such as low-pressure (LP) steam temperature ratio, steam reheat pressure ratio, steam turbine inlet pressure, gas cycle pressure ratio and combustion chamber temperature on the efficiency of the combined cycle has been investigated. Exergy efficiency of the cycle is compared with and without the steam injection with respect to the above-mentioned parameters. Maximum mass ratio of steam injection to fuel has been examined as 6 kg/kg fuel with the complete combustion of the fuel due to excess air supply in the combustion chamber and gas reheater. Results are plotted from the case of without steam injection to the maximum possible steam ratio. LP temperature ratio is identified as a dominant parameter having impact on the efficiency of the combined cycle as the steam is injected at this pressure. Component exergetic losses of the combined cycle as a fraction of exergy of fuel are compared with and without the steam injection. The results showed that the major exergetic loss in the combustion chamber decreased with the steam injection.

Simulation of Producer Gas Fired Power Plants with Inlet Fog Cooling and Steam Injection

Biomass can be converted to energy via direct combustion or thermochemical conversion to liquid or gas fuels. This study focuses on burning producer gases derived from gasifying biomass wastes to produce power. Since the producer gases are usually of low calorific values (LCV), power plant performance under various operating conditions has not yet been proven. In this study, system performance calculations are conducted for 5MWe power plants. The power plants considered include simple gas turbine systems, steam turbine systems, combined cycle systems, and steam injection gas turbine systems using the producer gas with low calorific values at approximately 30% and 15% of the natural gas heating value (on a mass basis). The LCV fuels are shown to impose high compressor back pressure and produce increased power output due to increased fuel flow. Turbine nozzle throat area is adjusted to accommodate additional fuel flows to allow the compressor to operate within safety margin. The best performance occurs when the designed pressure ratio is maintained by widening nozzle openings, even though the turbine inlet pressure is reduced under this adjustment. Power augmentations under four different ambient conditions are calculated by employing gas turbine inlet fog cooling. Comparison between inlet fog cooling and steam injection using the same amount of water mass flow indicates that steam injection is less effective than inlet fog cooling in augmenting power output. Maximizing steam injection, at the expense of supplying the steam to the steam turbine, significantly reduces both the efficiency and the output power of the combined cycle. This study indicates that the performance of gas turbine and combined cycle systems fueled by the LCV fuels could be very different from the familiar behavior of natural gas fired systems. Care must be taken if on-shelf gas turbines are modified to burn LCV fuels.

Performance analysis of combined humidified gas turbine power generation and multi-effect thermal vapor compression desalination systems — Part 1: The desalination unit and its combination with a steam-injected gas turbine power system

Humidified gas turbines (HGT) have been identified as a promising way of producing power. The use of the steam-injected gas turbine (STIG) HGT cycle in a combined power and water desalination system was analyzed using energy and exergy performance criteria. A brief description and rationale of the background of HGT cycles and dual-purpose power and water systems is given. A thermal desalination unit was modeled and analyzed, and the results led to the selection of a multi-effect thermal vapor compression (METVC) unit for producing fresh water from seawater for both general use and humidification; then the performance of a STIG-based combined system was investigated. The analysis performed improved the understanding of the combined STIG power and water desalination process and of ways to improve and optimize it. Some specific conclusions are that: (1) a METVC desalination system is preferred to a multieffect evaporation one when the pressure of the motive steam is high enough, >∼3 bar, to run a steam jet ejector; (2) the steam injection rate in the STIG cycle has a strong effect on water and power production, offering good flexibility for design and operation; (3) higher pressure ratios and higher steam injection rates in the STIG cycle increase power generation, but decrease water production rates, and higher turbine inlet temperatures increased both power and water production; (4) a distinct water production gain can be obtained by recovering the stack gas energy. The results indicate that such dual-purpose systems have good synergy, not only in fuel utilization, but also in operation and design flexibility.

Cascade utilization of chemical energy of natural gas in an improved CRGT cycle

In this paper three advanced power systems: the chemically recuperated gas turbine (CRGT) cycle, the steam injected gas turbine (STIG) cycle and the combined cycle (CC), are investigated and compared by means of exergy analysis. Making use of the energy level concept, cascaded use of the chemical exergy of natural gas in a CRGT cycle is clarified, and its performance of the utilization of chemical energy is evaluated. Based on this evaluation, a new CRGT cycle is designed to convert the exergy of natural gas more efficiently into electrical power. As a result, the exergy efficiency of the new CRGT cycle is about 55%, which is 8 percentage points higher than that of the reference CRGT cycle. The analysis gave a better interpretation of the inefficiencies of the CRGT cycle and suggested improvement options. This new approach can be used to design innovative energy systems.

A thermodynamic analysis of a biogas-fired integrated gasification steam injected gas turbine (BIG/STIG) plant

A thermodynamic analysis considering both the first and the second laws of thermodynamics has been made on a 53 MW (net) biogas-fired integrated gasification steam injected gas turbine (BIG/STIG) plant. The energy utilization diagrams (EUDs) for the plant and for the reaction subsystems have also been considered, revealing both problems and potentials for improvement. The analysis indicates a thermal efficiency of about 41% (power based) and 45% (power and recovered heat based) but that the exergy loss in the combustion chamber is largest at about 79% of the total system exergy loss.

A Study of Humidified Gas Turbines for Short-Term Realization in Midsized Power Generation—Part I: Nonintercooled Cycle Analysis

Humidified Gas Turbine (HGT) cycles are a group of advanced gas turbine cycles that use water-air mixtures as the working media. In this article, three known HGT configurations are examined in the context of short-term realization for small to midsized power generation: the Steam Injected Gas Turbine, the Full-flow Evaporative Gas Turbine, and the Part-flow Evaporative Gas Turbine. The heat recovery characteristics and performance potential of these three cycles are assessed, with and without intercooling, and a preliminary economic analysis is carried out for the most promising cycles.