Prediction of some performance characteristics of shale oil in the gas turbine combustor

Measurements of radiation, smoke and temperature in a developed experimental combustor at various air pressures, inlet temperatures and air-fuel ratios have shown the effects of such fuel properties as volatility, boiling range and H percentage mass content on ignition, lean blow-out, liner temperature and exhaust smoke. This study has been extended to cover some of these performance characteristics for shale oil.     

Thermoeconomic impact on combined cycle performance of advanced blade cooling systems

In this work the thermoeconomic features of two different combined cycles using air “open loop” and steam “closed loop” cooled gas turbines are presented and compared in depth. In order to properly estimate both thermodynamic and thermoeconomic performance of the different combined cycles an analytical model of the blade cooling system has been developed in details and outlined in the paper. Internal Thermoeconomic functional analysis is not performed here, as only economic results are shown and discussed. The blade cooling detailed model, originally developed by TPG researchers, has been integrated into the web based modular code WTEMP, already validated for GT based cycles, developed in the last ten years by TPG. It is shown that the closed loop blade cooling configuration has the greatest potential in terms of thermodynamic efficiency and economic competitivity in the mid-term.     

Characteristics and economics of high-efficiency gas turbine cogeneration systems using low BTU gas

Characteristics of high-efficiency gas turbine cogeneration systems using low Btu gas (LBG) are first analysed. Raising the turbine inlet temperature and incorporating a regenerator are both investigated as methods to improve the efficiency of the cogeneration system (CGS). Taking a gas obtained by pyrolyzing municipal refuse as an example of an LBG, various thermodynamic characteristics of the CGS are analysed using a simulation model developed by the authors. Secondly, authors investigate the economics of a CGS for district heating and cooling using the pyrolysis gas, making use of the estimated characteristics. It is shown that the CGS is estimated to be economically feasible, whereas a CGS using conventional high Btu fuel gas (methane gas) is estimated to be economically infeasible under assumed conditions. The impacts of changes in various parameters which determine the economics of the CGS are also investigated, and it is shown that the economics of the system using refuse-recovered LBG can be expected to be further improved owing to future developments in the technology of generating and refining pyrolysis gas.     

Rich-Quench-Lean model comparison for the clean use of humidified ammonia/hydrogen combustion systems

Ammonia and hydrogen are examples of zero-carbon fuels of high interest for implementation in gas turbine technologies. However, large emissions of nitrogen oxides are still a major detrimental for the implementation of these technologies. Therefore, various techniques have been presented as potential solutions to mitigate this problem. Rich-Quench-Lean systems combined with humidified atmospheres are amongst the most promising with the reduction of emissions as a consequence of recombinations of species and lower combustion temperatures. However, limited scrutiny exists around the chemical progression of species in systems like these whilst being fuelled with ammonia blends. Furthermore, any chemical study currently faces a challenge for the selection of a chemical kinetic mechanism due to the great variety of available mechanisms for ammonia combustion, each with different characteristics for the resolution of this fuel. Thus, a Chemical Reactor Network (CRN) has been developed to numerically assess an industry scale humidified Rich-Quench Lean system, utilising five of the most used chemical kinetic models in humidified ammonia combustion whilst informing developers of the differences between those selected. The results displayed significant differences between the mechanisms as the flame progresses. Sensitivity analyses of [OH] and [NH₃] displayed similar reactions having opposing effects for these two species at various points of the burner. Quantitative Reaction Path Diagrams (QRDP) for NO showed both similarities and differences between the mechanisms in terms of paths taken and rates of production.     

Comparison between externally fired gas turbine and gasifier-gas turbine system for the olive oil industry

The olive oil industry generates during the extraction process several solid wastes as olive tree leaves and prunings, exhausted pomace and olive pits. These renewable wastes could be used for power and heat applications. The aim of this paper is to compare the performance of two small-scale CHP systems: a gasification- gas turbine system and an EFGT (externally fired gas turbine system). For this reason, several parameters have been calculated: generated heat and power, electric and overall efficiencies, biomass consumption, exergy efficiency, optimum pressure ratio, etc. These systems provide 30 kW_e and about 60kW_th. Simulation results show that the electrical and overall efficiencies achieved in EFGT system (19.1% and 59.3%, respectively) are significantly higher than those obtained in the gasification plant (12.3% and 45.4%). The proposed CHP systems have been modeled using Cycle-Tempo^® software.     

Analysis of the benefits of carbon credits to hydrogen addition to midsize gas turbine feedstocks

The addition of hydrogen to the natural gas feedstocks of midsize (30–150 MW) gas turbines was analyzed as a method of reducing nitrogen oxides (_NOx)$({\mathrm{NO}}_x)$ and _CO2${\mathrm{CO}}_2$ emissions. In particular, the costs of hydrogen addition were evaluated against the combined costs for other current _NOx${\mathrm{NO}}_x$ and _CO2${\mathrm{CO}}_2$ emissions control technologies for both existing and new systems to determine its benefits and market feasibility. Markets for _NOx${\mathrm{NO}}_x$ emissions credits currently exist in California and the Northeast States and are expected to grow. Although regulations are not currently in place in the United States, several other countries have implemented carbon tax and carbon credit programs. The analysis thus assumes that the United States adopts future legislation similar to these programs. Therefore, potential sale of emissions credits for volunteer retrofits was also included in the study. It was found that hydrogen addition is a competitive alternative to traditional emissions abatement techniques under certain conditions. The existence of carbon credits shifts the system economics in favor of hydrogen addition.     

Integrated solar combined cycle system with steam methane reforming: Thermodynamic analysis

The present paper considers an integrated solar combined cycle system (ISCCS) with an utilization of solar energy for steam methane reforming. The overall efficiency was compared with the efficiency of an integrated solar combined cycle system with the utilization of solar energy for steam generation for a steam turbine cycle. Utilization of solar energy for steam methane reforming gives the increase in an overall efficiency up to 3.5%. If water that used for steam methane reforming will be condensed from the exhaust gases, the overall efficiency of ISCCS with steam methane reforming will increase up to 6.2% and 8.9% for β = 1.0 and β = 2.0, respectively, in comparison with ISCCS where solar energy is utilized for generation of steam in steam turbine cycle. The Sankey diagrams were compiled based on the energy balance. Utilization of solar energy for steam methane reforming increases the share of power of a gas turbine cycle: two-thirds are in a gas turbine cycle, and one-third is in a steam turbine cycle. In parallel, if solar energy is used for steam generation for a steam turbine cycle, than the shares of power from a gas and steam turbine are almost equal.     

Aerodynamic performance prediction of a 30 kW counter-rotating wind turbine system

In the present work, the aerodynamic performance prediction of a unique 30 kW counter-rotating (C/R) wind turbine system, which consists of the main rotor and the auxiliary rotor, has been investigated by using the quasi-steady strip theory. The near wake behavior of the auxiliary rotor that is located upwind of the main rotor is taken into consideration in the performance analysis of the turbine system by using the wind tunnel test data obtained for scaled model rotors. The relative size and the optimum placement of the two rotors are investigated through use of the momentum theory combined with the experimental wake model. In addition, the performance prediction results along with the full-scale field test data obtained for C/R wind turbine system are compared with those of the conventional single rotor system and demonstrated the effectiveness of the current C/R turbine system.     

Optimum generation capacities of micro combined heat and power systems in apartment complexes with varying numbers of apartment units

A dynamic simulation of micro combined heat and power (micro-CHP) systems that includes the transient behavior of the system was developed by modeling the generation of electricity and recovery of heat separately. Residential load profiles were calculated based on statistical reports from a Korean government agency, and were used as input data to select the optimum capacities of micro-CHP systems based on the number of apartment units being served, focusing on both economic and energetic criteria. The capacity of internal combustion engine (ICE) based micro-CHP was assumed to be in the range 1–500 kW, and the dependence of the efficiency of the generator unit on the capacity was included. It was found that the configuration (i.e., the capacity and number of generator units) that maximized the annual savings also had favorable energetic performance. Additionally, the statistical mode calculated from the annual electrical load distribution was verified as a suitable indicator when deciding the optimum capacity of a micro-CHP system.     

Optimal design of the structure and settings of nuclear HTR thermodynamic cycles

A thermal integration method has been used by Framatome-ANP since 2001 in order to optimize thermodynamic cycles (cogeneration and combined cycles) coupled to new nuclear high temperature reactors. This method allows the design of complex thermodynamic cycles that comply to a large number of industrial constraints, without any a priori assumption on the structure of the internal heat exchanger network.This paper briefly recalls the principles of the method and shows how accurate and rigorous exergy analyses can be carried out quite easily in an industrial context. It details on an example how industrial constraints and thermodynamical considerations interact to lead to an optimal cycle structure and settings. The efficiencies obtained are presented and discussed. In particular we discuss what we mean by optimal design. It is shown that this method is well suited to build optimal complex heat exchanger networks. The differences with other methods like the thermoeconomic ones are also briefly discussed.     

Design and performance evaluation of an innovative small scale combined cycle cogeneration system

This paper deals with an innovative natural gas (NG) combined cycle cogeneration system (150-kW_e, 192 kW_t). The system is made up of a combination of two interconnected combined heat and power (CHP) systems: a reciprocating internal combustion engine cogenerator (ICE CHP) as the topping cycle and a Rankine cycle cogenerator (RC CHP) which operates as the bottoming cycle on the exhaust gases from the ICE. The expander technology chosen for the Rankine cycle prime mover is a reciprocating single expansion steam engine with three cylinders in a radial architecture. The ICE is an automotive derived internal combustion engine with a high part-load electrical efficiency, due to a variable speed operation strategy and reduced emissions.     

An analysis of SOFC/GT CHP system based on exergetic performance criteria

In this study, we first consider developing a thermodynamic model of solid oxide fuel cell/gas turbine combined heat and power (SOFC/GT CHP) system under steady-state operation using zero-dimensional approach. Additionally, energetic performance results of the developed model are compared with the literature concerning SOFC/GT hybrid systems for its reliability. Moreover, exergy analysis is carried out based on the developed model to obtain a more efficient system by the determination of irreversibilities. For exergetic performance evaluation, exergy efficiency, exergy output and exergy loss rate of the system are considered as classical criteria. Alternatively, exergetic performance coefficient (EPC) as a new criterion is investigated with regard to main design parameters such as fuel utilization, current density, recuperator effectiveness, compressor pressure ratio and pinch point temperature, aiming at achieving higher exergy output with lower exergy loss in the system. The simulation results of the SOFC/GT CHP system investigated, working at maximum EPC conditions, show that a design based on EPC criterion has considerable advantage in terms of entropy-generation rate.     

Exergetic evaluation of methods for improving power generation efficiency of a gas turbine cogeneration system

A cogeneration system generating both heat and power for district heating and cooling is required to be more efficient to improve its economy. In this paper, three typical methods for improving the power generation efficiency of a gas turbine cogeneration system are evaluated by examining exergy flow at various points of the system. The three methods investigated are: (a) to raise turbine inlet temperature, (b) to incorporate a regenerative cycle, and (c) to introduce a dual-fluid cycle. Exergy flows at various points of each cogeneration system have been evaluated. It has been shown through quantitve analyses of exergy flows (1) what kind of energy loss of the system can be reduced by introducing each efficiency-improving method, (2) that the method of incorporating a regenerative cycle is highly useful in improving exergy efficiency of the cogeneration system. © 1997 by John Wiley & Sons, Ltd.     

Energy and exergy analyses of a combined molten carbonate fuel cell - Gas turbine system

This study deals with the thermodynamic analysis of molten carbonate fuel cell combined with a gas turbine, based on the first- and second-law of thermodynamics. The mass, energy, entropy and exergy balance equations are written and applied to the system and its components. Some parametric studies are performed to investigate the change of system performance through energy and exergy efficiencies with the change of operating conditions. The irreversibilities occuring in different devices of the integrated system are also investigated through the exergy destruction analysis in these devices. The maximum output work of the MCFC is estimated to be 314.3 kW for an operating temperature of 650 °C. The overall energy and exergy efficiencies achieved for this system are 42.89% and 37.75%, respectively.     

Enhancing the performance of a high-pressure cogeneration boiler with waste hydrogen-rich fuel

The cogeneration boiler has been applied extensively for simultaneously supplying electrical power and high-pressure steam. In this study, the performance of a high-pressure cogeneration boiler (max 280 tons/h boiler capacity) that burnt fuel oil (FO) and natural gas (NG) in a full-scale petrochemical plant was enhanced by partially replacing the NG with a waste hydrogen-rich refinery gas (RG), a byproduct from catalytic reforming and catalytic cracking operations. The addition of RG does not influence the boiler efficiency; it results in saving the energy consumption and significantly decreasing the greenhouse gas emission. If the inlet FO/NG/RG volumetric flow rate ratio is maintained at 50:33:17, adding RG will save 14,500,000 m³/year of NG and reduce 12,900 tons/year of CO₂ emission. Therefore, the use of RG to partially replace NG has practical benefits for reducing energy consumption and greenhouse gas emission.     

Techno-economic analysis of a coal-fired CHP based combined heating system with gas-fired boilers for peak load compensation

Combined heat and power (CHP) plants dominate the heating market in China. With the ongoing energy structure reformation and increasing environmental concerns, we propose gas-fired boilers to be deployed in underperforming heating substations of heating networks for peak load compensation, in order to improve both energy efficiency and environmental sustainability. However, due to the relatively high price of gas, techno-economic analysis is required for evaluating different combined heating scenarios, characterized by basic heat load ratio (β). Therefore, we employ the dynamic economics and annual cost method to develop a techno-economic model for computing the net heating cost of the system, considering the current state of the art of cogeneration systems in China. The net heating cost is defined as the investment costs and operations costs of the system subtracted by revenues from power generation. We demonstrate the model in a real-life combined heating system of Daqing, China. The results show that the minimum net heating cost can be realized at β=0.75 with a cost reduction of 16.8% compared to coal heating alone. Since fuel cost is the dominating factor, sensitivity analyses on coal and gas prices are discussed subsequently.     

On the off-design of a natural gas-fired combined cycle with CO2 capture

During the last 15 years cycles with CO₂ capture have been in focus, due to the growing concern over our climate. Often, a natural gas fired combined cycle with a chemical absorption plant for CO₂ capture from the flue gases have been used as a reference in comparisons between cycles. Neither the integration of the steam production for regeneration of amines in the combined cycle nor the off-design behaviour of such a plant has been extensively studied before.     

Influence of multiple irreversible losses on the performance of a molten carbonate fuel cell-gas turbine hybrid system

In this study, a new molten carbonate fuel cell-gas turbine hybrid system, which consists of a fuel cell, three heat exchangers, a compressor, and a turbine, is established. The multiple irreversible losses existing in real hybrid systems are taken into account by the models of a molten carbonate fuel cell and an open Brayton cycle with a regenerative process. Expressions for the power outputs and efficiencies of the subsystems and hybrid system are derived. The maximum power output and efficiency of the hybrid system are numerically calculated. It is found that compared with a single molten carbonate fuel cell, both the power output and efficiency of the hybrid system are greatly enhanced. The general performance characteristics of the hybrid system are evaluated and the optimal criteria of the main performance parameters are determined. The effects of key irreversibilities on the performance of the hybrid system are investigated in detail. It is found that the use of a regenerator in the gas turbine can availably improve the power output and efficiency of the system. The results obtained here are significant and may be directly used to discuss the optimal performance of the hybrid system in special cases.     

Reduced models of doubly fed induction generator system for wind turbine simulations

This article compares three reduced models with a detailed model of a doubly fed induction generator system for wind turbine applications. The comparisons are based on simulations only. The main idea is to provide reduced generator models which are appropriate to simulate normal wind turbine operation in aeroelastic wind turbine models, e.g. for control system design or structural design of the wind turbine. The electrical behaviour such as grid influence will therefore not be considered. The work presented in this article shows that with an ideal, undisturbed grid the dynamics of the doubly fed induction generator system is very well represented by the dynamics due to the generator inertia and the generator control system, whereas the electromagnetic characteristics of the generator can be represented by the steady state relations. The parameters for the proposed models are derived from parameters typically available from the generator data sheet and from the controller settings. Thus the models are simple to apply in any case where the generator data sheet is available. Copyright © 2005 John Wiley & Sons, Ltd.