Reheat Gas Turbine Research Articles

Combustion stage configurations for intercooled regenerative reheat gas turbine systems

Low-power gas turbines have been widely used for decades as combined heat and power. In the recent years, they received increasing interest with respect to applications such as range extenders in the automotive sector and for alternative fuels use.In this framework, the present work analyzes the combustion stages optimization of an intercooled regenerative reheat gas-turbine system, for a low power gas turbine. In particular, a thorough analysis was carried out to identify the optimal combustion system configuration in order to ensure suitable turbine inlet temperature and global efficiency of the thermodynamic cycle higher than 40%. Starting from the typical intercooled regenerative reheat gas turbine system, several configurations were analyzed. In particular, air bypass systems were introduced as suitable strategy able to tune the combustion chamber working temperatures and turbine inlet ones, according to operating requirements and combustion unit specifications. Furthermore, different bypass ratios were considered, analyzing the effectiveness of air bypass systems in terms of efficient combustion and reduced pollutant emissions (CO and NOx).An innovative cyclonic flow burner, assumed to operate under MILD (Moderate or Intense Low oxygen Dilution) combustion conditions, was considered as main combustion unit and in the reheat process. In this respect, the choice was motivated by the well-established high fuel flexibility and very low pollutants emission typical of such a combustion unit and the MILD process.Analyses were performed considering methane as fuel, which is currently the most used fuel in land-based applications. However, results here reported have general validity and may be directly applied with respect to the use of innovative energy vectors.

Advanced design, parameter optimization, and thermodynamic analysis of integrated air-blown IGCC power plants

With the increasing energy demand, it is essential to improve the utilization of traditional energy sources. Coal is still the mainstay of the Chinese energy market, especially in power generation. The IGCC offers significant advantages in terms of power efficiency and environmental protection. However, conventional IGCC uses oxygen as the gasification medium, posing serious economic challenges. To address this challenge, in this study, the overall system process for the IGCC systems using air-blown gasification is constructed by Aspen Plus. To explore the potential of the thermal performance of the air-blown gasification IGCC system, the operating parameters and process flows are improved. The energy and exergy analysis of the whole system using the advanced process is carried out and compared with the oxygen gasification IGCC. Optimal operating parameters and technical parameters are determined, and the gasifier is optimized. The results show that the system efficiency increased by 3.17%, and the exergy efficiency increased by 3.09%. Although the integrated gas turbine process does not offer obvious advantages, it is more compatible with the current gas turbine in terms of flow rate. The utilization of a high-pressure reheat gas turbine results in a 2.52% increase in system efficiency. The implementation of high-pressure reheat gas turbines and hot gas desulfurization can improve the thermal performance of the system. The air-blown gasification IGCC with this process has the highest power supply efficiency of 52.80%. It presents an improvement of 3.69% compared with oxygen gasification. The exergy loss in the cooling and cleaning module and the gas turbine module is significantly reduced. The heat efficiency of the air-blown gasification IGCC is 3.60% higher, and the effective energy in the system is fully utilized. It provides some heuristic ideas for the clean and efficient utilization of coal resources.

The Impact of Compressor Degradation on The Optimized Fleet Compositions, Optimized Thermal Efficiencies, and The Operations & Maintenance Cost of Fleets of a Reheat Engine Running on Associated Gas Fuel

Associated gas is a viable source of fuel for industrial gas turbines. Flaring of this fuel resource has not only resulted in environmental pollution and deterioration but also huge energy and economic loss. TURBOMATCH, a Cranfield University performance simulation software was used in modeling a hypothetical but realistic 296MW reheat gas turbine engine.The study was carried out using one clean fleet and three degraded fleets – the optimistic, medium, and pessimistic. Optimization of the fleet compositions and thermal efficiencies were achieved using Genetic algorithm. Detailed operations and maintenance costs analysis for the various fleets were carried out. .Results from the optimization show the optimized fleet compositions, from the various fleets and their turbine entry temperatures for 20 years life span of the project. the result from the 11th to the 20th year of the project, only one unit of engine was left due to engine divestment. Results of the optimized efficiencies for all the fleets show a gradual reduction in optimized efficiencies over the years of the project. Similarly, for all the scenarios considered, from the 11th to the 20th year of the project, with only one unit of engine left, the optimized efficiency trend is observed to be Clean > Optimistic > Medium > Pessimistic.Results from the fleets operations and maintenance costs show that the clean, optimistic, medium, and pessimistic degraded fleets have total operations and maintenance costs to be 1.224, 1.242, 1.265, and 1.297 billion US dollars respectively. Engine degradation resulted to 1.4%, 3.3%, and 5.9% increase in the operations and maintenance costs of the optimistic, medium, and pessimistic degraded fleets respectively.The results, approach and methodology presented in this paper would be a very useful decision-making tool for investors and governments who would want to invest in the economic utilization of associated gas using gas turbines.

Techno-Economic Assessment of Associated Gas Fueled Fleets of Reheat Gas Turbine Plants

Techno-Economic Assessment of Associated Gas Fueled Fleets of Reheat Gas Turbine Plants

Observation of reactive shear layer modulation associated with high-frequency transverse thermoacoustic oscillations in a gas turbine reheat combustor experiment

This paper presents the investigation of high-frequency thermoacoustic oscillations and associated flame dynamics in an experimental gas turbine reheat combustor at atmospheric pressure. Examination of dynamic pressure measurements reveals bursts of high-frequency periodic oscillations which appear randomly amidst stochastic fluctuations in the reheat combustor. Analysis of the flame dynamics during these bursts of periodic behaviour reveals that increased heat release in the reactive shear layers of the reheat flame is associated with greater thermoacoustic driving potential. This redistribution of heat release is likely due to the stochastic nature of auto-ignition kernel formation. To determine the underlying flame-acoustic coupling mechanism behind the driving potential, phase-resolved flame dynamics over the acoustic cycle are investigated which reveal the presence of an oscillatory heat release pattern associated with the first transverse eigenmode. An in-phase interaction between the acoustic field and these heat release oscillations in the shear layer regions indicates that this phenomenon likely constitutes a thermoacoustic driving mechanism. This is an important step towards the development of models for high-frequency thermoacoustic driving mechanisms relevant to reheat combustion systems, which will allow accurate prediction and mitigation of thermoacoustic instabilities in future designs.

Energy and exergy analysis of hybridization of solar, intercooled reheated gas turbine trigeneration cycle

PurposeThis paper aims to analyze energy and exergy analysis of solar-based intercooled and reheated gas turbine (GT) trigeneration cycle using parabolic trough solar collectors (PTC) with the use of MATLAB 2018.Design/methodology/approachIn the first section of this paper, the solar-based GT is validated with the reference paper. According to the reference paper, the solar field is comprising 30 modules in series and 35 modules in parallel series, where a total of 1,050 modules of PTC are taken into consideration. In the second part of this paper, the hybridization of the solar, GT trigeneration cycle is analyzed and optimized. In the last section of this paper, the hybridization of solar, intercooled and reheated GT trigeneration systems is examined and compared.FindingsThe results examined the first section, the power produced by the cycle will be 37.34 MW at 0.5270 kg/s mass flow rate of the natural gas consumption and the efficiencies of energy and exergy will be 38.34% and 39.76%, respectively. The results examined in the second section, the power produced by the cycle will be 38.4 MW at 0.5270 kg/s mass flow rate of the natural gas consumption and accordingly the efficiency of energy and exergy is found to be 40.011% and 41.763%. Where in the last section, the power produced by the cycle will be 41.43 MW at 0.5270 kg/s mass flow rate of the natural gas consumption and the energy and exergy efficiencies will be 39.76% and 40.924%, respectively.Originality/valueThe author confirms that this study is original and has neither been published elsewhere nor it is currently under consideration for publication elsewhere.

Parametric Analysis of Solar-Biomass Based Intercooled and Reheated Gas Turbine Trigeneration Cycle

Parametric Analysis of Solar-Biomass Based Intercooled and Reheated Gas Turbine Trigeneration Cycle

Direct Numerical Simulation of hydrogen combustion at auto-ignitive conditions: Ignition, stability and turbulent reaction-front velocity

Direct Numerical Simulations (DNS) are performed to investigate the process of spontaneous ignition of hydrogen flames at laminar, turbulent, adiabatic and non-adiabatic conditions. Mixtures of hydrogen and vitiated air at temperatures representing gas-turbine reheat combustion are considered. Adiabatic spontaneous ignition processes are investigated first, providing a quantitative characterization of stable and unstable flames. Results indicate that, in hydrogen reheat combustion, compressibility effects play a key role in flame stability and that unstable ignition and combustion are consistently encountered for reactant temperatures close to the mixture’s characteristic crossover temperature. Furthermore, it is also found that the characterization of the adiabatic processes is also valid in the presence of non-adiabaticity due to wall heat-loss. Finally, a quantitative characterization of the instantaneous fuel consumption rate within the reaction front is obtained and of its ability, at auto-ignitive conditions, to advance against the approaching turbulent flow of the reactants, for a range of different turbulence intensities, temperatures and pressure levels.

Combined cycle gas turbine system optimization for extended range electric vehicles

In order to meet the Corporate Average Fuel Economy standards for passenger vehicles in 2025, car manufacturers are exploring several alternative energy converters to replace the Internal Combustion Engine, which has demonstrated limited efficiency improvement. Recent studies explored the use of a Gas Turbine as the primary vehicle driver in a hybrid powertrain; however, none evaluated the implementation of a Combined Cycle Gas Turbine, which offers higher efficiency. This study presents a methodology for the design and optimization of the most optimal combined cycle system configuration, suitable to replace the engine in a series-hybrid extended-range electric vehicle, and investigates its potential fuel savings. The two-steps methodology consists of conducting first an exergo-technological analysis using a Non-dominated Sorting Genetic Algorithm to identify the best suitable combined cycle configuration for integration in a series hybrid powertrain. Second, a series-hybrid extended range vehicle model is developed, to assess the consumption savings of the prioritized combined cycle on the Worldwide Harmonized Light Vehicle Test Cycle. The Reheat Gas Turbine combined to a Turbine Reheat Steam Rankine Cycle system is prioritized, for offering the highest efficiency and an acceptable vehicle integration complexity among the other investigated systems. Consumption results show fuel savings up to 23.6% with the prioritized system as compared to a reference extended-range electric vehicle equipped with an engine and savings up to 17% compared to other gas-turbine systems presented in the literature, depending on the battery size, the trip length, and the maximum turbine inlet temperature. Consequently, combined-cycle gas-turbine systems present a serious alternative to replacing internal combustion engines on series hybrid electrified vehicles if the cost-effectiveness of these systems was proven.

Thermodynamic investigation of intercooled reheat gas turbine combined cycle with carbon capture and methanation

In this work an intercooled reheat gas/steam combined power cycle with CO2 capture and methanation is studied. CO2 capture and methanation unit is integrated to capture CO2 from the exhaust of gas/steam combined cycle plant and converted it into methane (CH4) so that this methane can be used as additional fuel and hence reduces the amount of carbon emission into the atmosphere. An organic Rankine cycle is integrated between the high-pressure compressor and low-pressure compressor to utilize the heat extraction during the intercooling process. Suitable working fluids for the Organic Rankine cycle have been chosen taking thermophysical properties into consideration such as lower boiling point, critical temperature & pressure and global warming potential. The energy and the mass balance equations have been developed to analyse thermodynamic performance of the proposed combined cycle system. Parametric analysis of the cycle has been performed to evaluate the impact of several cycle variables such as cycle pressure ratio, turbine inlet temperature, condenser temperature, vapor turbine inlet pressure, etc. on the system performance. The study reveals that higher cycle pressure ratio of topping cycle results in less formation of steam in HRSG which further advocates that cycle pressure ratio might be kept low to achieve the high rate of steam generation which again results in increased work output of the cycle. The study reveals that the overall work output of combined system is increased from 220.9 MW to 370 MW by including carbon capture unit at a turbine inlet temperature (TIT) of 1475 K and a cycle pressure ratio of 20.

Thermo-economic analysis of combined cycle configurations with intercooling and reheating

Combined cycles have integration of different cycles for the effective utilization of heat energy. Among different measures the intercooling and reheating are the commonly used techniques for improving the performance of thermal power cycles. Here, the study of combined cycle configurations having gas turbine, steam turbine and ammonia-water turbine with intercooling and reheating has been undertaken. The present paper analyzes the different configurations of intercooled reheat gas turbine cycle based combined cycle configurations using steam and/or ammonia-water mixture as coolant to gas turbine blades for fixed design condition - turbine inlet temperature of 2000K, cycle pressure ratio 40 and ambient condition of 303K. The comparison of different configurations shows that the work output of 1789.39 kJ/kg of air is obtained. First law and second law efficiencies of 62.50% and 60.7% is maximum for triple pressure heat recovery generator having ammonia-water turbine at each pressure level. The cost of electricity production is minimum for maximum work output and corresponds to 0.06727USD/kWh.

Technological analysis and fuel consumption saving potential of different gas turbine thermodynamic configurations for series hybrid electric vehicles

Gas turbine systems are among potential energy converters to substitute the internal combustion engine as auxiliary power unit in future series hybrid electric vehicle powertrains. Fuel consumption of these auxiliary power units in the series hybrid electric vehicle strongly relies on the energy converter efficiency and power-to-weight ratio as well as on the energy management strategy deployed on-board. This paper presents a technological analysis and investigates the potential of fuel consumption savings of a series hybrid electric vehicle using different gas turbine–system thermodynamic configurations. These include a simple gas turbine, a regenerative gas turbine, an intercooler regenerative gas turbine, and an intercooler regenerative reheat gas turbine. An energetic and technological analysis is conducted to identify the systems’ efficiency and power-to-weight ratio for different operating temperatures. A series hybrid electric vehicle model is developed and the different gas turbine–system configurations are integrated as auxiliary power units. A bi-level optimization method is proposed to optimize the powertrain. It consists of coupling the non-dominated sorting genetic algorithm to the dynamic programming to minimize the fuel consumption and the number of switching ON/OFF of the auxiliary power unit, which impacts its durability. Fuel consumption simulations are performed on the worldwide-harmonized light vehicles test cycle while considering the electric and thermal comfort vehicle energetic needs. Results show that the intercooler regenerative reheat gas turbine–auxiliary power unit presents an improved fuel consumption compared with the other investigated gas turbine systems and a good potential for implementation in series hybrid electric vehicles.

Thermoeconomic analysis of SOFC-GT-VARS-ORC combined power and cooling system

The integration of the gas turbine cycle and organic Rankine cycle with the solid oxide fuel cell for power generation is quite prevalent. However, the need is also felt for systems capable of providing power with cooling. Therefore, it is proposed to integrate solid oxide fuel cell with gas turbine cycle, vapour absorption refrigeration system and organic Rankine cycle through the heat available with fluid in the cycle. Here intercooled and reheat gas turbine cycle is integrated with solid oxide fuel cell. Heat rejected in intercooling is used in vapour absorption refrigeration system for cooling. This paper presents thermoeconomic analysis. Results show that the combination of solid oxide fuel cell-gas turbine-vapour absorption refrigeration system-organic Rankine cycle yields increase in efficiency to 68.79% as compared to 58.88% from combined solid oxide fuel cell-gas turbine cycle. The cost of electricity per unit power output is found as 1939.93 $/kW.

Dynamic Modeling and Fuel Consumption Potential of an Intercooled Regenerative Reheat Gas Turbine Auxiliary Power Unit on Series Hybrid Electric Vehicle

Abstract Gas turbine systems are among potential energy converters to substitute the internal combustion engine in future series hybrid electric vehicle. Fuel consumption of these powertrains strongly relies on the energy converter efficiency, the energy management strategy deployed on-board as well as on the transient operation during start-up phase. This paper presents a dynamic modeling and the fuel consumption calculation of an intercooled regenerative reheat gas turbine system used as an auxiliary power unit on a series hybrid electric vehicle. A vehicle model is developed and an optimization method is proposed to optimize the powertrain operation. It consists of using the dynamic programing as an energy management strategy in order to minimize the fuel consumption and the number of switching On/Off of the power unit. Fuel consumption simulations are performed on the worldwide-harmonized light vehicles test cycle while considering the electric and the thermal comfort vehicle energetic needs. Then, a gas turbine dynamic model is developed, where turbomachinery and heat exchanger components are modeled by taking into account their dynamic inertias. The efficiency, the power, and the fuel consumption are calculated during transient operations. Based on the optimization results of switching ON and OFF the system, the fuel consumption dynamic simulation results are considered instead of the dynamic programming results. A constant power start-up strategy and a constant fuel strategy were investigated. Results show an increase in fuel consumption between 2.4% and 3.8% with the first start-up scenario and between 5.7% and 6.4% with the second scenario, compared with static model.

Regimes of premixed turbulent spontaneous ignition and deflagration under gas-turbine reheat combustion conditions

We address the problem of turbulent spontaneous ignition vs. deflagration propagating against a mean residence time gradient, particularly relevant to the stabilization of quasi-steady diesel flames and gas-turbine reheat combustion, by performing a large series of statistically one-dimensional premixed turbulent flame DNS. An autoignitve mixture of hydrogen-vitiated air representative of gas-turbine reheat combustion is considered. First, we demonstrate that turbulence can trigger the transition from spontaneous ignition to a deflagration. We then construct a spontaneous ignition vs. deflagration regime diagram based on inflow velocity, turbulent velocity fluctuations and integral length scale and identify the mechanism that governs the transition from one propagation mode to the other. Finally, we propose a theoretical model that captures accurately this transition and assess the validity of a proxy based on chemical explosive mode analysis to determine the local propagation mode in complex configurations.

Reference natural gas flames at nominally autoignitive engine-relevant conditions

Laminar natural gas flames are investigated at engine-relevant thermochemical conditions where the ignition delay time τ is short due to very high ambient temperatures and pressures. At these conditions, it is not possible to measure or calculate well-defined values for the laminar flame speed sl, laminar flame thickness δl, and laminar flame time scale τl=δl/sl due to the explosive thermochemical state. Here, the corresponding reference values, sR, δR, and τR=δR/sR, that account for the effects of autoignition, are numerically estimated to investigate the enhancement of flame propagation, and the competition with autoignition that arises under nominally autoignitive conditions (characterised here by the number τ/τR). Large values of τ/τR indicate that autoignition is unimportant, values near or below unity indicate that flame propagation is not possible, and intermediate values indicate that a combination of both flame propagation and autoignition may be important, depending upon factors such as device geometry, turbulence, stratification, et cetera. The reference quantities are presented for a wide range of temperatures, equivalence ratios, pressures, and hydrogen concentrations, which includes conditions relevant to stationary gas turbine reheat burners and boosted spark ignition engines. It is demonstrated that the transition from flame propagation to autoignition is only dependent on residence time, when the results are non-dimensionalised by the reference values. The temporal evolution of the reference values are also reported for a modelled boosted SI engine. It is shown that the nominally autoignitive conditions enhance flame propagation, which may be an ameliorating factor for the onset of engine knock. The calculations are performed using a recently-developed, detailed 177 species mechanism for C0–C3 chemistry that is derived from theoretical chemistry and is suitable for a wide range of thermochemical conditions as it is not tuned or optimised for a particular operating condition.

Direct numerical simulation of flame stabilization assisted by autoignition in a reheat gas turbine combustor

A three-dimensional direct numerical simulation (DNS) is performed for a turbulent hydrogen-air flame, represented with detailed chemistry, stabilized in a model gas-turbine combustor. The combustor geometry consists of a mixing duct followed by a sudden expansion and a combustion chamber, which represents a geometrically simplified version of Ansaldo Energia’s GT26/GT36 sequential combustor design. In this configuration, a very lean blend of hydrogen and vitiated air is prepared in the mixing duct and convected into the combustion chamber, where the residence time from the inlet of the mixing duct to the combustion chamber is designed to coincide with the ignition delay time of the mixture. The results show that when the flame is stabilized at its design position, combustion occurs due to both autoignition and flame propagation (deflagration) modes at different locations within the combustion chamber. A chemical explosive mode analysis (CEMA) reveals that most of the fuel is consumed due to autoignition in the bulk-flow along the centerline of the combustor, and lower amounts of fuel are consumed by flame propagation near the corners of the sudden expansion, where the unburnt temperature is reduced by the thermal wall boundary layers. An unstable operating condition is also identified, wherein periodic auto-ignition events occur within the mixing duct. These events appear upstream of the intended stabilization position, due to positive temperature fluctuations induced by pressure waves originating from within the combustion chamber. The present DNS investigation represents the initial step of a comprehensive research effort aimed at gaining detailed physical insight into the rate-limiting processes that govern the sequential combustor behavior and avoid the insurgence of the off-design auto-ignition events.

Comparative exergoeconomic analysis of basic and reheat gas turbine with air film blade cooling

In power plant industry, it is always desirable that the performance of the plant should be as high as possible with the lowest possible investment. In this regard exergoeconomic analysis is a tool which combines thermodynamic analysis and economic principles to provide information that is helpful to predict thermodynamic performance and total cost of the plant. In this work an exergoeconomic approach is applied to the gas turbine based power plant cycles. In present work comparative exergoeconomic analysis of basic and reheat air-film blade cooled gas turbine cycles have been performed with exergy analysis as the basis. Average cost theory of exergoeconomic analysis has been carried out, in order to estimate the thermodynamic performance, thermoeconomics and electricity cost for power utility based on the cycle. Present work also represents the behavior of key parameters with cycle operating parameters (compressor pressure ratio and turbine inlet temperature) of proposed cycle. The comparative analysis result for base case (TIT = 1500 K, rpc = 26, ηAC=88%, ηGT=90%) being total cost rate = 20.172 $/h and 29.156 $/h, plant specific work = 422.49 kJ/kg and 576.40 kJ/kg and cost of electricity = 3.31 cents/kWh and 3.45 cents/kWh for basic and reheat gas turbine cycle based power utility respectively.

Looking Back 40 Years—The Reheat Gas Turbine Applied to Energy Storage

The article presents an overview of the compressed air energy storage gas turbines (CAES GT). The CAES GT works at low turbine inlet temperatures and is capable of fast start and loading 10 minutes to full load. It is characterized by high ramp rates up or down with minimum load as low as 10%, and flat heat rate for most of the load range. With exceptional low fuel input efficiency of 85%, the kW/hr equivalent Btu input to the compression cycle must be added, resulting in an overall efficiency of close to 55%, impressive versus a 300 MW GTCC plant that is required to load follow when integrating renewable energy source. The metamorphosis from that of a “peak shaving” unit to that of a grid support and renewable energy enabler is now complete. Advanced Reheat Gas Turbines such as the GT24/26 with higher operating temperatures offer further potential development for CAES.

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

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.