Fuel Gas Turbine Research Articles

The Development of a Model for the Assessment of Biofouling in Gas Turbine System

A significant problem encountered in the gas turbine industry with fuel products is the degradation of fuel and fuel systems by micro-organisms, which are largely bacteria, embedded in biofilms. These micro-organisms cause system fouling and other degradatory effects, extending often to sudden failure of components with cost implications. Current methods of assessment are only postimpact evaluation and do not necessarily quantify the effects of fuel degradation on engine performance and emission. Therefore, effective models that allow predictive condition monitoring are required for engine's fuel system reliability, especially with readily biodegradable biofuels. The aim of this paper is to introduce the concept of biofouling in gas turbines and the development of a biomathematical model with potentials to predict the extent and assess the effects of microbial growth in fuel systems. The tool takes into account mass balance stoichiometry equations of major biological processes in fuel biofouling. Further development, optimization, and integration with existing Cranfield in-house simulation tools will be carried out to assess the overall engine performance and emission characteristics. This new tool is important for engineering design decision, optimization processes, and analysis of microbial fuel degradation in gas turbine fuels and fuel systems.

Using Hydrogen as Gas Turbine Fuel: Premixed Versus Diffusive Flame Combustors

This work aims at estimating the efficiency gain resulting from using lean premixed combustors in hydrogen-fired combined cycles with respect to diffusive flame combustors with significant inert dilution to limit NOx emissions. The analysis is carried out by considering a hydrogen-fired, specifically tailored gas turbine whose features are representative of a state-of-the-art natural gas–fired F-class gas turbine. The comparison between diffusion flame and lean premixed combustion is carried out considering nitrogen and steam as diluents, as well as different stoichiometric flame temperatures and pressure drops. Results show that the adoption of lean premixed combustors allows us to significantly reduce the efficiency decay resulting from inert dilution. Combined cycle efficiency slightly reduces from 58.5%–57.9% when combustor pressure drops vary in the range 3%–10%. Such efficiency values are comparatively higher than those achieved by diffusive flame combustor with inert dilution. Finally, the study investigated the effects of decreasing the maximum operating blade temperature so as to cope with possible degradation mechanisms induced by hydrogen combustion.

Alternative Microturbine Fuels Feasibility Study Through Thermal Stability, Material Compatibility, and Engine Testing

Historically, gas turbine fuels have been procured based on availability and low cost criteria. However,in the past few decades, with the growing concern over the negative environmental impacts produced by emissions, alternative fuels have been developed and tested under the objective of reducing such negative effects. The physical properties and broad chemical composition of fuels, including trace elements, may result in engine performance issues found only after extensive operation. This, in turn, results in higher maintenance and operation costs. This paper studies the feasibility of several renewable fuels for microturbine application, identifying key relationships between the physical and chemical properties, thermal stability, materials compatibility, and turbine performance.

Using coolant modulation and pre-cooling to avoid turbine blade overheating in a gas turbine combined cycle power plant fired with low calorific value gas

Overheating of turbine blades is one of the major concerns in using low calorific value fuels in gas turbines. In this work, we examined the deviation of operating conditions of a gas turbine fired with a low calorific value gas fuel, with a focus on the turbine blade temperatures. Several measures to suppress blade overheating were compared in terms of the power output and efficiency of the gas turbine combined cycle plant. Blade overheating can be prevented by decreasing the firing temperature without the need for hardware modifications, but the accompanying power reduction is considerable. As a remedy to this large reduction in power, modulation of the coolant supply to each blade row was simulated, and a much lower power penalty was observed. Moreover, pre-cooling of the coolant enhances the power output further by reducing the coolant supply. Pre-cooling recovers 80% of the available maximum augmentation of the combined cycle by simply switching the fuel from natural gas to low calorific value gas. Pre-cooling also provides higher overall combined cycle efficiency compared to under-firing.

Thermo-economic assessment of externally fired micro-gas turbine fired by natural gas and biomass: Applications in Italy

This paper proposes a thermo-economic assessment of small scale (100kWe) combined heat and power (CHP) plants fired by natural gas and solid biomass. The focus is on dual fuel gas turbine cycle, where compressed air is heated in a high temperature heat exchanger (HTHE) using the hot gases produced in a biomass furnace, before entering the gas combustion chamber. The hot air expands in the turbine and then feeds the internal pre-heater recuperator, Various biomass/natural gas energy input ratios are modeled, ranging from 100% natural gas to 100% biomass. The research assesses the trade-offs between: (i) lower energy conversion efficiency and higher investment cost of high biomass input rate and (ii) higher primary energy savings and revenues from bio-electricity feed-in tariff in case of high biomass input rate. The influence of fuel mix and biomass furnace temperature on energy conversion efficiencies, primary energy savings and profitability of investments is assessed. The scenarios of industrial vs. tertiary heat demand and baseload vs. heat driven plant operation are also compared. On the basis of the incentives available in Italy for biomass electricity and for high efficiency cogeneration (HEC), the maximum investment profitability is achieved for 70% input biomass percentage. The main barriers of these embedded cogeneration systems in Italy are also discussed.

Security of supply, energy spillage control and peaking options within a 100% renewable electricity system for New Zealand

Abstract In this paper, issues of security of supply, energy spillage control, and peaking options, within a fully renewable electricity system, are addressed. We show that a generation mix comprising 49% hydro, 23% wind, 13% geothermal, 14% pumped hydro energy storage peaking plant, and 1% biomass-fuelled generation on an installed capacity basis, was capable of ensuring security of supply over an historic 6-year period, which included the driest hydrological year on record in New Zealand since 1931. Hydro spillage was minimised, or eliminated, by curtailing a proportion of geothermal generation. Wind spillage was substantially reduced by utilising surplus generation for peaking purposes, resulting in up to 99.8% utilisation of wind energy. Peaking requirements were satisfied using 1550 MW of pumped hydro energy storage generation, with a capacity factor of 0.76% and an upper reservoir storage equivalent to 8% of existing hydro storage capacity. It is proposed that alternative peaking options, including biomass-fuelled gas turbines and demand-side measures, should be considered. As a transitional policy, the use of fossil-gas–fuelled gas turbines for peaking would result in a 99.8% renewable system on an energy basis. Further research into whether a market-based system is capable of delivering such a renewable electricity system is suggested.

Using MCFC for high efficiency CO2 capture from natural gas combined cycles: Comparison of internal and external reforming

In recent years, several research groups have proposed the combination of Molten Carbonate Fuel Cells (MCFCs) and gas turbine cycles for the application to CO2 capture. One of the most promising configuration relies on the use of MCFCs as “active CO2 concentrator” in combined cycles (CCs): the fuel cell is placed downstream the gas turbine and ahead the heat recovery steam generator (HRSG), to concentrate the CO2 from the gas turbine exhaust feeding the cathode, to the anode (where CO2 is transferred together with oxygen) and generate electricity; while exhaust heat released by the cell effluents is recovered by the steam cycle. It has been shown that such plant configuration can capture 70–85% of CO2 with small efficiency penalties compared to the combined cycle, and increasing by about 20% the overall power output (mainly given by the MCFC section); hence, this configuration could have relevant advantages with respect to competitive carbon capture technologies.This work presents a comprehensive discussion of the results of a modeling activity developed at Politecnico di Milano regarding the possible use of MCFCs for high efficiency CO2 capture from combined cycles. The work discusses different types of MCFC–CC cycles, focusing on the comparison of two families of MCFC and corresponding power plants which have been discussed only separately in the past. The MCFC can be fed with natural gas according to an internal reforming (IR) or external reforming (ER) process, according to the technological proposals of different MCFC manufacturers. Then, the anode exhaust stream of the MCFC, where is concentrated the majority of CO2, is sent to a CO2 purification section which can be based on (i) a cryogenic CO2 separation section, or (ii) an oxy-combustion of residual fuel components, followed by cooling, condensation of water and separation of CO2. In both cases, a high purity CO2 stream is obtained and pumped to liquid form for storage.Detailed results are presented in terms of energy and mass balances of the different proposed cycles, evidencing pros and cons of the different layout and pointing out the role of relevant FC operating parameters (CO2 utilization, operating current density and voltage) on the overall balances. Moreover, it is presented a comparison between the best proposed cycles and conventional NGCC–CCS systems.

Integration of a municipal solid waste gasification plant with solid oxide fuel cell and gas turbine

An interesting source of producing energy with low pollutants emission and reduced environmental impact are the biomasses; particularly using Municipal Solid Waste (MSW) as fuel, can be a competitive solution not only to produce energy with negligible costs but also to decrease the storage in landfills. A Municipal Solid Waste Gasification Plant Integrated with Solid Oxide Fuel Cell (SOFC) and Gas Turbine (GT) has been studied and the plant is called IGSG (Integrated Gasification SOFC and GT). Gasification plant is fed by MSW to produce syngas by which the anode side of an SOFC is fed wherein it reacts with air and produces electricity. The exhausted gases out of the SOFC enter a burner for further fuel combusting and finally the off-gases are sent to a gas turbine to produce additional electricity. Different plant configurations have been studied and the best one found to be a regenerative gas turbine. Under optimized condition, the thermodynamic efficiency of 52% is achieved. Variations of the most critical parameters have been studied and analyzed to evaluate plant features and find out an optimized configuration.

Gas Turbines and Natural Gas Synergism

This article presents a study on new electric power gas turbines and the advent of shale natural gas, which now are upending electrical energy markets. Energy Information Administration (EIA) results show that total electrical production cost for a conventional coal plant would be 9.8 cents/kWh, while a conventional natural gas fueled gas turbine combined cycle plant would be a much lower at 6.6 cents/kWh. Furthermore, EIA estimates that 70% of new US power plants will be fueled by natural gas. Gas turbines are the prime movers for the modern combined cycle power plant. On the natural gas side of the recently upended electrical energy markets, new shale gas production and the continued development of worldwide liquefied natural gas (LNG) facilities provide the other element of synergism. The US natural gas prices are now low enough to compete directly with coal. The study concludes that the natural gas fueled gas turbine will continue to be a growing part of the world’s electric power generation.

합성천연가스의 수소함량 변화에 따른 가스터빈 연소특성 평가

Increasing demand for natural gas and higher natural gas prices in the recent decades have led many people to pursue unconventional methods of natural gas production. POSCO-Gwangyang synthetic natural gas (SNG) project was launched in 2010. As the market price of natural gas goes up, the increase of its price gets more sensitive due to the high cost of transportation and liquefaction. This project can make the SNG economically viable. In parallel with this project, KEPCO (Korea Electric Power Corporation) joined in launching the SNG Quality Standard Bureau along with KOGAS (Korea Gas Corporation), POSCO and so on. KEPCO Research Institute is in charge of SNG fueled gas turbine combustion test. In this research, several combustion tests were conducted to find out the effect of hydrogen contents in SNG on gas turbine combustion. The hydrogen in synthetic natural gas did not affect on gas turbine combustion characteristics which are turbine inlet temperature including pattern factor and emission performance. However, flame stable region in <TEX>${\Phi}$</TEX>-Air flow rate map was shifted to the lean condition due to autocatalytic effect of hydrogen.

Application of the Advanced Distillation Curve Method to the Variability of Jet Fuels

In this paper, we report the application of the advanced distillation-curve (ADC) approach to the gas turbine fuels Jet-A, JP-8, and JP-5, in order to obtain information about the variability of these gas turbine fuels. The measurements of the ADC derived temperatures Tk and Th provide volatility information as an approximation of the vapor–liquid equilibrium, VLE. The composition channel of the advanced distillation curve provides access to more detailed insight into the fluid behavior. Finally, we have shown how the composition channel allows the combination of thermochemical data with the temperature data of the distillation curve. The variability in distillation curves and calculated heat of combustion between jet fuels is significant. Understanding of this variability is critical information for a more effective and reliable thermophysical property modeling system.

Gas and steam combined cycles for low calorific syngas fuels utilisation

The utilisation of low-calorific syngas fuels in conventional gas turbines and gas and steam combined cycle equipments has been studied by the authors over the last years. In the present work, the effects of using different fuels of the referred type on the performance of a gas and steam combined cycle performance are assessed. The main bottle-necks found when trying to exploit the potential of the syngas fuels considered are also identified and some general rules with regard to the necessary modifications that need to be implemented in standard plants are provided.In continuation to this research line, the present work analyses the challenges that using syngas fuels have on the major equipment of a conventional combined cycle designed for natural gas operation. First, the most relevant constraints imposed by the new fuels onto the conventional power plant are identified. This leads to setting up a list of the bottle-necks that prevent the plant from fully exploiting the potential of the new fuels employed. A list of the necessary modifications of the existing pieces of equipment, selected according to their technical feasibility and economic viability, is developed accordingly. These design updates are then assessed by means of a performance analysis of the redesigned plant. The full analysis is based on commercial and in-house computer codes.The modifications proposed in this work can be regarded as general rules to redesign existing combined cycle power plants. The conclusions drawn from the paper permit to envisage the work that needs to be done if the present combined cycle plants are to be adapted to syngas fuels in a near future.

Design and Performance Study of a Solid Oxide Fuel Cell and Gas Turbine Hybrid System Applied in Combined Cooling, Heating, and Power System

AbstractBecause of their high efficiency and very low emissions, fuel cells have been one of the choice areas of research in current energy development. The solid oxide fuel cell (SOFC) is a type of high-temperature fuel cell. It has the characteristic of a very high operating temperature of 1,027°C (1,300 K). The SOFC has the main advantage of very high performance efficiency (more than 50%) but also has very high exhaust temperatures. Current studies point out that the combination of the SOFC and gas turbine (GT) can produce efficiency of more than 60%. The exhaust temperature of this hybrid power system can be as high as 227–327°C (500–600 K). With this waste heat utilized, it is possible to further improve the overall efficiency of the system. A simulation program of the SOFC/GT system and the introduction of the concept of combined cooling, heating, and power (CCHP) system have been used in this study. The waste heat of the SOFC/GT hybrid power generation system was used as the heat source to drive a...

SPHERA project: Assessing the use of syngas fuels in gas turbines and combined cycles from a global perspective

The use of gasified fuels for electricity generation is gaining interest as an alternative to traditional fuels especially in regions with abundant biomass or coal resources. However their use in some of the most extended power generation technologies like gas turbines and combined cycles is not straightforward.The authors have studied the use of gasified fuels in the gas turbine and combined cycle technologies within a four year research project funded by the Spanish Government (SPHERA project). The main goals of the research were to identify the components and processes that limit the use of the syngas fuels (bottle-necks) and suggest the necessary modifications to be implemented in standard combined cycle power plants, selecting them according to their technical feasibility and economic viability.To this purpose, the research was divided in six tasks, each one was aimed at analysing the effects of syngas fuels on the performance of a particular component within the power plant or at assessing the impact of fuel composition at a particular level (from component level through system level and up to plant level). These tasks were focused essentially on the following topics: technology review, combustion system, turbine expansion and plant performance both for standard and redesigned equipment.This paper provides a global overview of the main steps and outcomes of this research showing the main results and conclusions obtained in each task. It is intended to show, from a global point of view and in a single document, a roadmap to adapt the existing combined cycle technology to syngas operation. It is therefore out of the scope of this project to provide a deep insight into particular issues or into models that have been covered in detail in other publications by the authors.

Design and Testing of a Micromix Combustor With Recuperative Wall Cooling for a Hydrogen Fueled μ-Scale Gas Turbine

For more than 1 decade up to now, there is an ongoing interest in small gas turbines downsized to microscale. With their high energy density, they offer a great potential as a substitute for today’s unwieldy accumulators found in a variety of applications such as laptops, small tools, etc. But microscale gas turbines could not only be used for generating electricity, they could also produce thrust for powering small unmanned aerial vehicles or similar devices. Beneath all the great design challenges with the rotating parts of the turbomachinery at this small scale, another crucial item is in fact the combustion chamber needed for a safe and reliable operation. With the so-called regular micromix burning principle for hydrogen successfully downscaled in an initial combustion chamber prototype of 10 kW energy output, this paper describes a new design attempt aimed at the integration possibilities in a μ-scale gas turbine. For manufacturing the combustion chamber completely out of stainless steel components, a recuperative wall cooling was introduced to keep the temperatures in an acceptable range. Also a new way of an integrated ignition was developed. The detailed description of the prototype’s design is followed by an in depth report about the test results. The experimental investigations comprise a set of mass flow variations, coupled with a variation of the equivalence ratio for each mass flow at different inlet temperatures and pressures. With the data obtained by an exhaust gas analysis, a full characterization concerning combustion efficiency and stability of the prototype chamber is possible. Furthermore, the data show full compliance with the expected operating requirements of the designated μ-scale gas turbine.

Examination of the Effect of System Pressure Ratio and Heat Recuperation on the Efficiency of a Coal-Based Gas Turbine Fuel Cell Hybrid Power Generation System With CO2 Capture

This paper examines two coal-based hybrid configurations that employ separated anode and cathode streams for the capture and compression of CO2. One configuration uses a standard Brayton cycle, and the other adds heat recuperation ahead of the fuel cell. Results show that peak efficiencies near 55% are possible, regardless of cycle configuration, including the cost in terms of energy production of CO2 capture and compression. The power that is required to capture and compress CO2 is shown to be approximately 15% of the total plant power.

Numerical simulation of a hydrogen fuelled gas turbine combustor

The interest for hydrogen-fuelled combustors is recently growing thanks to the development of gas turbines fed by high content hydrogen syngas. The diffusion flame combustion is a well-known and consolidated technology in the field of industrial gas turbine applications. However, few CFD analyses on commercial medium size heavy duty gas turbine fuelled with pure hydrogen are available in the literature. This paper presents a CFD simulation of the air-hydrogen reacting flow inside a diffusion flame combustor of a single shaft gas turbine. The 3D geometrical model extends from the compressor discharge to the gas turbine inlet (both liner and air plenum are included). A coarse grid and a very simplified reaction scheme are adopted to evaluate the capability of a rather basic model to predict the temperature field inside the combustor. The interest is focused on the liner wall temperatures and the turbine inlet temperature profile since they could affect the reliability of components designed for natural gas operation. Data of a full-scale experimental test are employed to validate the numerical results. The calculated thermal field is useful to explain the non-uniform distribution of the temperature measured at the turbine inlet.

Efficiency of a standard gas-turbine power generation cycle running on different fuels

This paper presents a study of second-law efficiency in a standard Brayton combined cycle power generation, using several paraffinic fuels ranging from methane to heptane. The main objective of the study was to identify a trend with the number of carbon atoms in the compound. In this way, a qualitative criterion can be built to evaluate the properties of poor-quality gas turbine fuels containing significant amounts of C2+ hydrocarbons from the point of view of exergy. This is important in the current energetic scenario, where new blends are being studied as alternative to natural gas for economic, environmental or availability reasons. The results show a decreasing trend in exergetic efficiency with heavier compounds.

Ethanol-Hydrocarbon Blend Vapor Prediction

In the volatile fuel price environment of today, the quest for alternative fuels has become a heavy and long term trend in power generation worldwide. Incorporating alternative fuels in gas turbine installations raises multiple engineering questions relating to combustion, emissions, on-base and auxiliary hardware capability, safety, etc. In 2008, GE carried out a field test aimed at characterizing the combustion of ethanol in a naphtha fuelled gas turbine plant. The testing strategy has been to locally prepare and burn ethanol-naphtha blends with a fraction of ethanol increasing from 0% to nearly 100%. During the engineering phase prior to this field test, it appeared necessary to develop a sufficient knowledge on the behavior of ethanol-hydrocarbon blends in order to establish the safety analysis and address in particular the risks of (i) potential uncontrolled ignition event in the air blanket of fuel tanks and (ii) flash vaporization of potential fuel pond in a confined environment. Although some results exist in the car engine literature for ethanol-gasoline blends, it was necessary to take into account the specificities of gas turbine applications, namely, (i) the much greater potential ethanol concentration range (from 0% to 100%) and (ii) the vast composition spectrum of naphtha likely to generate a much larger Reid vapor pressure envelope as compared with automotive applications. In order to fulfill the safety needs of this field test, the “Laboratoire de Thermodynamique des Milieux Polyphasés” of Nancy, France has developed a thermodynamic model to approach the vaporization equilibria of ethanol-hydrocarbons mixtures with variable ethanol strength and naphtha composition. This model, named PPR78, is based on the 1978 Peng–Robinson equation of state and allows the estimation of the thermodynamic properties of a multicomponent mixture made of ethanol and naphtha compounds by using the group contribution concept. The saturation equilibrium partial pressure of such fluids in the various situations of relevance for the safety analysis can thus be calculated. The paper reports the elaboration of this model and illustrates the results obtained when using it in different safety configurations.

P22 Kenyan children with cancer: Controlling Burkitt's lymphoma

Microorganisms are important in fuel deterioration and consequently in engine performance. To assess the impact of fuel deterioration on gas turbines, a bio-mathematical model, Bio-fAEG, was developed to simulate microbial fuel degradation and estimate hydrocarbon loss. Simulation of four conventional diesel fuels and a biodiesel fuel estimated hydrocarbon loss between 0.37 mg/L per day (diesel-type fuel) and 1.48 mg/L per day (biodiesel-type fuel), with nearly complete degradation of the bioavailable fraction of the fuels within 20–60 days. Assuming biodegradation of these fuels is not impeded and conditions for growth remained constant, the Bio-fAEG model predicted that significant degradation begins in four months for a less degradable fuel and two months for a more degradable fuel. Analysis carried out with this model provides insight into cumulative biodegradation of engine fuels and the importance of microbial characteristics, initial microbial population and residence time. The integration of this model in engine performance and emission tools could provide further information on the effect of fuel degradation on engine systems. This is a first step in quantifiable assessment of microbial fuel degradation towards predictive condition monitoring in gas turbine fuels and fuel systems.