Browsing by Author "Pilidis, Pericles"
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Item Open Access Abating CO2 and non-CO2 emissions with hydrogen propulsion(Cambridge University Press (CUP), 2024-04-02) Mourouzidis, Christos; Singh, G.; Sun, X.; Huete, Jon; Nalianda, Devaiah; Nikolaidis, Theoklis; Sethi, Vishal; Rolt, Andrew Martin; Goodger, E.; Pilidis, PericlesThis contribution focuses on the abatement with hydrogen of CO2 and non-CO2 emissions. It is agenda-setting in two respects. Firstly, it challenges the globally accepted hydrocarbon sustainable aviation fuel (SAF) pathway to sustainability and recommends that our industry accelerates along the hydrogen pathway to ‘green’ aviation. Secondly, it reports a philosophical and analytical investigation of appropriate accuracy on abatement strategies for nitrogen oxides and contrails of large hydrogen airliners. For the second contribution, a comparison is made of nitrogen oxide emissions and contrail avoidance options of two hydrogen airliners and a conventional airliner of similar passenger capacity. The hydrogen aircraft are representative of the first and second innovation waves where the main difference is the weight of the hydrogen tanks. Flights of 1000, 2000, 4000 and 8000 nautical miles are explored. Cranfield’s state of the art simulators for propulsion system integration and gas turbine performance (Orion and Turbomatch) were used for this. There are two primary contributions to knowledge. The first is a new set of questions to be asked of SAF and hydrogen decarbonising features. The second is the quantification of the benefits from hydrogen on non-CO2 emissions. For the second generation of long-range hydrogen-fuelled aircraft having gas turbine propulsion, lighter tanks (needing less thrust and lower gas temperatures) are anticipated to reduce NOx emissions by over 20%; in the case of contrails, the preliminary findings indicate that regardless of the fuel, contrails could largely be avoided with fuel-burn penalties of a few per cent. Mitigating action is only needed for a small fraction of flights. For conventional aircraft this penalty results in more CO2, while for hydrogen aircraft the additional emission is water vapour. The conclusion is that our research community should continue to consider hydrogen as the key ‘greening’ option for aviation, notwithstanding the very significant costs of transition.Item Open Access Advanced low-carbon power plants - the TERA approach(Cranfield University, 2010-04) Di Lorenzo, G.; Pilidis, PericlesIt is widely accepted that climate change is a very serious environmental concern facing the world today. Levels of carbon dioxide (CO2) in the global atmosphere have risen by more than a third since the industrial revolution and are now rising faster than ever before. Power generation accounts for a large proportion of GHGs emissions. Many different options are being proposed for CO2 emissions mitigation from the power generation sector. They have been extensively investigated in the scientific literature, but selection of better candidates for future investments is difficult and uncertain. Cont/d.Item Open Access Aerodynamic investigation of fluid injection in an axial compressor(Cranfield University, 2005-03) Mustafa, Z.; Pilidis, PericlesThe main objective of the investigation is to provide a physically realistic model describing the movement of liquid phase in an industrial axial compressor during online washing. ln order to achieve this objective, CFD simulations were developed for predicting the water particle trajectories inside an industrial axial compressor, the rate of evaporation of water droplets on axial compressor blades by inertial impaction, turbulent diffusion, pressure and temperature increments. Simulation of water droplet trajectories and evaporation of water droplet content in designed 260MW gas turbine engine were undertaken. Two types of boundary conditions have been considered for a droplet. The first is the inlet boundary condition, which describes the properties of a droplet at the entry/inlet position. It was assumed that the droplets are evenly distributed at the inlet face. For the droplet inlet boundary, there were 4 main factors considered, namely droplet initial temperature, droplet flow rate, droplet axial slip velocity and droplet average initial diameter. Each factor has at least two levels, namely the base line level and some deviation or deviations to the base-line level. The second boundary condition is the wall boundary condition, which models what happens when a droplet interacts with a solid wall. For this second type boundary condition, all simulations in this study, the coefficient of restitution of all solid walls was set at very low number, coefficient of restitution = 0.0005. It is assumed that a droplet that hits a solid wall will undergo a non-perfect rebound. Other than mechanical effects due to the impact of particulates during online washing, the main aero thermal effects are due to the flow changes occurring on account of the two phase nature of the working fluid, heat and mass transfer among the two phases, modification in thermal and transport properties, and changes in chemical action and combustion. Practically, it is not possible, in general, to assure that all of the washing fluid, which entered the engine during online washing, would always be converted to the gas phase by the time the working fluid leaves the high pressure compressor, or even the combustor. Thus, both the state of the fluid and the cross-sectional distribution of washing fluid are of concern throughout the engine flow path, especially the first 3 front stages of the axial compressor. It must be noted that the preceding statements take no account of the presence and effects of bypass doors, vents, and valves. This is a set of devices for which there are no reliable data for air-fluid mixture operation, and thus, no guidance in design or installation. They can introduce major changes in the amount and distribution of the discrete phases of fluid along the flow path in compressors. Finally, however there is a need for at least one set of definitive tests on selected components and engines. At the moment, there is neither clear view nor experimental data available to validate those said objectives. On one hand, there is no validated computational model available to assist with understanding the complex relationship between the injection parameters and the resultant flow pattern and trajectories of the droplet as well as there is no information regarding the droplet build up on the blade surface in a multistage axial compressor during online washing. Nevertheless, even though without experimental validation, this investigation is very important as advancing tools to further understand the axial compressor online washing phenomenon which is still not fully understood even today. Therefore, post-axial-compressor fluid motion is important in understanding the role of air/fluid mixing and fluid evaporations and will be analysed and presented in this study. More precisely, this investigation tries to quantify the effect of injected droplet parameters on generic multistage axial compressor. As this work is focused on the model (droplet parameter) sensitivities rather than the CFD model itself, presented in this investigation herewith are only the main features of the generic droplet trajectories flow pattern in a multistage industrial axial compressor.Item Open Access Analyses of a high pressure ratio intercooled direct Brayton helium gas turbine cycle for Generation IV reactor power plants(ASME, 2016-12-20) Gad-Briggs, Arnold; Pilidis, Pericles; Nikolaidis, TheoklisThe intercooled cycle (IC) as an alternative to the simple cycle recuperated (SCR) and intercooled cycle recuperated (ICR) is yet to be fully analyzed for the purpose of assessing its viability for utilization within Generation IV nuclear power plants (NPPs). Although the benefits are not explicitly obvious, it offers the advantage of a very high overall pressure ratio (OPR) in the absence of a recuperator. Thus, the main objective of this study is to analyze various pressure ratio configurations, the effects of varying pressure ratio including sensitivity analyses of component efficiencies, ambient temperature, component losses and pressure losses on cycle efficiency, and specific work of the IC, including comparison with the SCR and ICR. Results of comparison between the IC and the SCR and ICR derived that the cycle efficiencies are greater than the IC by ∼4%∼4% (SCR) and ∼6%∼6% (ICR), respectively. However, the pressure losses for IC are lower when compared with the SCR and ICR. Nonetheless, heat from the turbine exit temperature of the IC can be used in a processing plant including the possibility of higher turbine entry temperatures (TETs) to significantly increase the cycle efficiency in a bid to justify the business case. The analyses intend to bring to attention an alternative to current cycle configurations for the gas-cooled fast reactors (GFRs) and very-high-temperature reactors (VHTRs), where helium is the coolant. The findings are summarized by evaluating the chosen pressure ratio configurations against critical parameters and detailed comparison with the SCR and ICR.Item Open Access Analyses of long term off-design performance strategy and operation of a high pressure ratio intercooled Brayton helium gas turbine cycle for generation IV nuclear power plants(ASME, 2018-05-23) Gad-Briggs, Arnold; Pilidis, Pericles; Nikolaidis, TheoklisThe Intercooled Cycle (IC) is a simplified novel proposal for Generation IV Nuclear Power Plants (NPP) based on studies demonstrating efficiencies of over 45%. As an alternative to the Simple Cycle Recuperated (SCR) and the Intercooled Cycle Recuperated (ICR), the main difference in configuration is no recuperator, which reduces its size. It is expected that the components of the IC will not operate at optimum part power due to seasonal changes in ambient temperature and grid prioritisation for renewable sources. Thus the ability to demonstrate viable part load performance becomes an important requirement. The main objective of this study is to derive Off-Design Points (ODPs) for a temperature range of -35 to 50°C and COTs between 750 to 1000°C. The ODPs have been calculated using a tool designed for this study. Based on results, the intercooler changes the mass flow rate and compressor pressure ratio. However, a drop of ~9% in plant efficiency, in comparison to the ICR (6%) was observed for pressure losses of up to 5% . The reactor pressure losses for IC has the lowest effect on plant cycle efficiency in comparison to the SCR and ICR. Characteristic maps are created to support first order calculations. It is also proposed to consider the intercooler pressure loss as a handle for ODP performance. The analyses brings attention to the IC an alternative cycle and aids development of cycles for Generation IV Nuclear Power Plants specifically Gas Cooled Fast Reactors (GFRs) and Very High Temperature Reactors (VHTRs).Item Open Access Analyses of simple and intercooled recuperated direct Brayton helium gas turbine cycles for Generation IV reactor power plants(ASME, 2016-12-20) Gad-Briggs, Arnold; Pilidis, PericlesAs a nongreenhouse gas-emitting source, the benefits of nuclear as a main power-generation alternative are yet to be fully explored; part of the reason is due to the significant implementation costs. However, with cycle efficiencies of 45–50% in current studies, it can be argued that the long-term benefits outweigh the initial costs, if developed under the Generation-IV (Gen-IV) framework. The main objective of this study is to analyze the effects of pressure and temperature ratios (TRs) including sensitivity analyses of component efficiencies, ambient temperature, component losses and pressure losses on cycle efficiency and specific work. The results obtained indicate that pressure losses and recuperator effectiveness have the greatest impact on cycle efficiency and specific work. The analyses intend to aid development of the simple cycle recuperated (SCR) and intercooled cycle recuperated (ICR) cycles, applicable to gas-cooled fast reactors (GFRs) and very-high-temperature reactors (VHTRs), in which helium is the coolant.Item Open Access Analyses of the associated technical and economic risks of the simple and intercooled Brayton helium recuperated gas turbine cycles for Generation IV nuclear power plants(ASME, 2018-11-30) Gad-Briggs, Arnold; Pilidis, Pericles; Nikolaidis, TheoklisThe Simple Cycle Recuperated (SCR) and Intercooled Cycle Recuperated (ICR) are highly efficient Brayton helium gas turbine cycles, designed for the Gas-cooled Fast Reactor (GFR) and Very-High-Temperature Reactor (VHTR) Generation IV (Gen IV) Nuclear Power Plants (NPPs). This paper documents risk analyses which considers technical and economic aspects of the NPP. The sensitivity analyses are presented that interrogate the plant design, performance and operational schedule and range from component efficiencies, system pressure losses, operating at varied power output due to short term load-following or long term reduced power operations to prioritise other sources such as renewables. The sensitivities of the economic and construction schedule are also considered in terms of the discount rates, capital and operational costs and increased costs in Decontamination and Decommissioning (D&D) activity due to changes in the discount rates. This was made possible by using a tool designed for this study to demonstrate the effect on the ‘non-contingency’ baseline Levelised Unit Electricity Cost (LUEC) of both cycles. The SCR with a cycle efficiency of 50%, has a cheaper baseline LUEC of $58.41/MWh in comparison to the ICR (53% cycle efficiency), which has a LUEC of $58.70 /MWh. However, the cost of the technical and economic risks is cheaper for the ICR resulting in a final LUEC of $70.45/MWh (ICR) in comparison to the SCR ($71.62/MWh) for the year 2020 prices.Item Open Access Analyses of the control system strategies and methodology for part power control of the simple and intercooled recuperated Brayton helium gas turbine cycles for generation IV nuclear power plants(The American Society of Mechanical Engineers, 2017-05-15) Gad-Briggs, Arnold; Pilidis, Pericles; Nicolaidis, TheoklisAn important requirement for Generation IV Nuclear Power Plant (NPP) design is the control system, which enables part power operability. The choices of control system methods must ensure variation of load without severe drawbacks on cycle performance. The objective of this study is to assess the control of the NPP under part power operations. The cycles of interest are the Simple Cycle Recuperated (SCR) and the Intercooled Cycle Recuperated (ICR). Control strategies are proposed for NPPs but the focus is on the strategies that result in part power operation using the inventory control method. Firstly, results explaining the performance and load limiting factors of the inventory control method are documented; subsequently, the transient part power performances. The load versus efficiency curves were also derived from varying the load to understand the efficiency penalties. This is carried out using a modelling and performance simulation tool designed for this study. Results show that the ICR takes ~102% longer than the SCR to reduce the load to 50% in Design Point (DP) performance conditions for similar valve flows, which correlates to the volumetric increase for the ICR inventory tank. The efficiency penalties are comparable for both cycles at 50% part power, whereby a 22% drop in cycle efficiency was observed and indicates limiting time at very low part power. The analyses intend to aid the development of cycles for Generation IV NPPs specifically Gas Cooled Fast Reactors (GFRs) and Very High Temperature Reactors (VHTRs), where helium is the coolant.Item Open Access Analyses of the costs associated with very high turbine entry temperatures in helium recuperated gas turbine cycles for Generation IV nuclear power plants(ASME, 2018-08-27) Gad-Briggs, Arnold; Pilidis, Pericles; Nikolaidis, TheoklisPrevious analyses of Generation IV (GEN IV) helium gas turbine cycles indicated the possibility for high Turbine Entry Temperatures (TETs) up to 1200°C in order to improve cycle efficiency, using improved turbine blade material and optimum turbine cooling fractions. The purpose of this paper is to understand the effect on the Levelised Unit Electricity Cost (LUEC) of the Nuclear Power Plant (NPP), when the TET is increased to 1200°C from an original TET of 950°C and when an improved turbine blade material is used to reduced the turbine cooling fraction. The analyses focus on the Simple Cycle Recuperated (SCR) and the Intercooled Cycle Recuperated (ICR). The baseline LUECs of the NPPs were calculated as $61.84/MWh (SCR) and $62.16/MWh for a TET of 950°C. The effect of changing the turbine blades improved the allowable blade metal temperature by 15% with a reduction in the LUEC by 0.6% (SCR) and 0.7% (ICR). Furthermore, increasing the TET to 1200°C has a significant effect on the power output but more importantly it reduces the LUECs by 22.7% (SCR) and 19.8% (ICR). The analyses intends to aid development of the SCR and ICR including improving the decision making process on choice of cycles applicable to the Gas-cooled Fast Reactors (GFRs) and Very High-Temperature Reactors (VHTRs), where helium is the coolant.Item Open Access Analyses of the effect of cycle inlet temperature on the precooler and plant efficiency of the simple and intercooled helium gas turbine cycles for generation IV nuclear power plants(MDPI, 2017-03-24) Gad-Briggs, Arnold; Nikolaidis, Theoklis; Pilidis, PericlesNuclear Power Plant (NPP) precooler coolant temperature is critical to performance because it impacts the work required to increase the coolant pressure. Variation of the coolant temperature results in varied precooler hot gas temperatures, which are cooled before re-entry. For recirculation, the heat sink (usually sea water), could exit the precooler at unfavourable temperatures and impact the re-entering coolant, if not recirculated properly at the source. The study objective is to analyse the effects of coolant inlet temperature on the heat sink and cycle efficiency. The cycles are Simple Cycle Recuperated (SCR), Intercooler Cycle Recuperated (ICR), and Intercooled Cycle without Recuperation (IC). Results show that the co-current precooler provides favourable outlet heat sink temperatures but compromises compactness. For a similar technology level, the counter-current precooler yields excessive heat sink outlet temperatures due to a compact, robust, and efficient heat transfer design, but could be detrimental to precooler integrity due to corrosion, including the cycle performance, if not recirculated back into the sea effectively. For the counter-current, the ICR has the best heat sink average temperature ratio of 1.4; the SCR has 2.7 and IC has 3.3. The analyses aid the development of Gas Cooled Fast Reactors (GFRs) and Very High Temperature Reactors (VHTRs), where helium is used as the coolant.Item Open Access Analyses of the load following capabilities of Brayton Helium gas turbine cycles for generation IV nuclear power plants(ASME, 2017-06-09) Gad-Briggs, Arnold; Pilidis, Pericles; Nikolaidis, TheoklisThe control system for Generation IV Nuclear Power Plant (NPP) design must ensure load variation when changes to critical parameters affect grid demand, plant efficiency and component integrity. The objective of this study is to assess the load following capabilities of cycles when inventory pressure control is utilised. Cycles of interest are Simple Cycle Recuperated (SCR), Intercooled Cycle Recuperated (ICR) and Intercooled Cycle without recuperation (IC). Firstly, part power performance of the IC is compared to results of the SCR and ICR. Subsequently, the load following capabilities are assessed when the cycle inlet temperature is varied. This was carried out using a tool designed for this study. Results show that the IC takes ~2.7% longer than the ICR to reduce the power output to 50% when operating in Design Point (DP) for similar valve flows, which correlates to the volumetric increase for the IC inventory storage tank. However, the ability of the IC to match the ICR’s load following capabilities is severely hindered because the IC is most susceptible to temperature variation. Furthermore, the IC takes longer than the SCR and ICR to regulate the reactor power by a factor of 51 but this is severely reduced, when regulating NPP power output. However, the IC is the only cycle that does not compromise reactor integrity and cycle efficiency when regulating the power. The analyses intend to aid the development of cycles specifically Gas Cooled Fast Reactors (GFRs) and Very High Temperature Reactors (VHTRs), where helium is the coolant.Item Open Access Analysis of a 115MW, 3 shaft, helium Brayton cycle(Cranfield University, 2002-07) Pradeepkumar, K. N.; Pilidis, Pericles; Tourlidakis, A.This research theme is originated from a development project that is going on in South Africa, for the design and construction of a closed cycle gas turbine plant using gas-cooled reactor as the heat source to generate 115 MW of electricity. South African Power utility company, Eskom, promotes this developmental work through its subsidiary called PBMR (Pebble Bed Modular Reactor). Some of the attractive features of this plant are the inherent and passive safety features, modular geometry, small evacuation area, small infrastructure requirements for the installation and running of the plant, small construction time, quick starting and stopping and also low operational cost. This exercise is looking at the operational aspects of a closed cycle gas turbine, the finding of which will have a direct input towards the successful development and commissioning of the plant. A thorough understanding of the fluid dynamics in this three-shaft system and its transient performance analysis were the two main objectives of this research work. A computer programme called GTSI, developed by a previous Cranfield University research student, has been used in this as a base programme for the performance analysis. Some modifications were done on this programme to improve its control abilities. The areas covered in the performance analysis are Start-up, Shutdown and Load ramping. A detailed literature survey has been conducted to learn from the helium Turbo machinery experiences, though it is very limited. A critical analysis on the design philosophy of the PBMR is also carried out as part of this research work. The performance analysis has shown the advantage, disadvantage and impact of various power modulation methods suggested for the PBMR. It has tracked the effect of the operations of the various valves included in the PBMR design. The start-up using a hot gas injection has been analysed in detail and a successful start region has been mapped. A start-up procedure is also written based on this. The analysis on the normal and emergency load rejection using various power modulation devices has been done and it stress the importance of more control facilities during full load rejection due to generator faults. A computational fluid dynamics (CFD) analysis, using commercial software, has been carried out on some geometry of the PBMR design to find out whether its flow characteristic will have any serious impact on the performance on the cycle during the load control of the plant. The analysis has demonstrated that there will not be much impact on the performance, during load control using pressure level changes, from this geometry. However, some locations in the geometry have been identified as areas where the flow is experiencing comparatively high pressure losses. Recommendations, which include modification in the physical design, were made to improve this. The CFD analysis has extended to a cascade to compare the flow behaviour of Air and Helium with an objective of using air, being inexpensive, to test the helium flow characteristic in a test rig to simulate the behavioural pattern of helium in the PBMR pressure vessel. The specification of a hypothetical test rig and the necessary scaling parameters has been derived from this exercise. This will be useful for designing test rigs during the developmental and operational stage of the PBMR project.Item Open Access Analysis of gas turbine compressor fouling and washing on line(Cranfield University, 2007) Vigueras Zuniga, Marco Osvaldo; Pilidis, PericlesThis work presents a model of the fouling mechanism and the evaluation of compressor washing on line. The results of this research were obtained from experimental and computational models. The experimental model analyzed the localization of the particle deposition on the blade surface and the change of the surface roughness condition. The design of the test rig was based on the cascade blade arrangement and blade aerodynamics. The results of the experiment demonstrated that fouling occurred on both surfaces of the blade. This mechanism mainly affected the leading edge region of the blade. The increment of the surface roughness on this region was 1.0 μm. This result was used to create the CFD model (FLUENT). According to the results of the CFD, fouling reduced the thickness of the boundary layer region and increased the drag force of the blade. The model of fouling was created based on the experiment and CFD results and was used to calculate the engine performance in the simulation code (TURBOMATCH). The engine performance results demonstrated that in five days fouling can affect the overall efficiency by 3.5%. The evaluation of the compressor washing on line was based on the experimental tests and simulation of the engine performance. This system demonstrated that it could recover 99% of the original blade surface. In addition, this system was evaluated in a study case of a Power Plant, where it proved itself to be a techno-economic way to recover the power of the engine due to fouling. The model of the fouling mechanism presented in this work was validated by experimental tests, CFD models and information from real engines. However, for further applications of the model, it would be necessary to consider the specific conditions of fouling in each new environment.Item Open Access ARES: aircraft propulsion integration(Cranfield University, 2013-02) Tsentseris, Michail; Pilidis, PericlesThe combat aircraft and the gas turbine engine interact with one another. These interactions have become of even greater significance than previously due to the fact that the modern aircraft have increased requirements in terms of thrust, efficiency, reliability and ease of maintenance. Issues that affect the performance and operational capability of combat aircraft are the aircraft aerodynamic characteristics, propulsion system performance and the airframe/engine matching. This study focuses on the evaluation of the propulsion system of modern jet powered combat aircraft and combines computations with the existing integration methodology. The main objective of this study is the update of ARES method (aircraftengine performance tool for combat aircraft) so as to be feasible the incorporation of new data in the calculations of the program. The update contains: • the establishment of a procedure that can be used for the calculation of the additional drag that a external load (tanks, bombs, missiles, pods) contribute in the total aircraft drag, • the modification of ARES method in order to integrate the additional drag of the external loads in the program calculations, • the creation of a procedure that will be used for the calculation of the thrust deductions due to installation effects. The information that can be received from this study are valuable because can be used in the evaluation of the engine performance, can give the opportunity for further engine studies such as the structural and thermal analysis, component sizing and geometry, life consumption and of course can make apparent if a specific aircraftengine system is capable of accomplishing a demanded operating requirement. The final results of the study led to the general conclusion that the total aircraft drag and the demanded uninstalled net thrust increased with the addition of external tanks in the aircraft. The fuel consumption was higher for the configuration with the two tanks and was noticed an increase of the TET which is proportional to the number of the used external tanks (max TET increases at least 0.8% per tank). Additionally was extracted the conclusion that the addition of an external wing tank increases the amount of the consumed fuel at least 3.5%.Item Open Access Assessing biomass-fired gas turbine power plants: a techno-economic and environmental perspective(Cranfield University, 2013-07) Ihiabe, Daniel; Di Lorenzo, Giuseppina; Pilidis, PericlesFossil fuels continue to deplete with use as they are irreplaceable. In addition, the environmental impact with the continuous use of these conventional fuels has generated global concern due to the production of harmful emission gases. An alternative source of energy has become inevitable. Technological advancements in the area of biomass use for both aviation and power generation are at different levels of development. There is however the need for an integrated approach to assess gas turbine engine behaviour in terms of performance, emission and economics when they are running on biofuels. The current research work is concerned with finding alternative fuel resources for use on stationary gas turbine engines for power generation with the necessary identification of suitable biofuels using a multidisciplinary approach. A techno-economic, environmental and risk assessment (TERA) model comprising the performance, emissions, economics and risk modules has been developed. There had been several simulations of two gas turbine engines (GTEs) to ascertain the effects of both ambient and operating conditions and the effect of fuel types on the engines. These simulations were done with the use of an in-house code-the Turbomatch and a code developed for the steam cycle which is employed for the combined cycle simulation. Cont/d.Item Open Access Assessment of an energy-efficient aircraft concept from a techno-economic perspective(Elsevier, 2018-04-17) Goldberg, Chana; Nalianda, Devaiah; Sethi, Vishal; Pilidis, Pericles; Singh, Riti; Kyprianidis, KonstantinosAn increase in environmental awareness in both the aviation industry and the wider global setting has led to large bodies of research dedicated to developing more sustainable technology with a lower environmental impact and lower energy usage. The goal of reducing environmental impact has necessitated research into revolutionary new technologies that have the potential to be significantly more energy efficient than their predecessors. However, for innovative technologies in any industry, there is a risk that adoption will be prohibitively expensive for commercial application. It is therefore important to model the economic factors of the new technology or policy at an early stage of development. This research demonstrates the application of a Techno-economic Environmental Risk Assessment framework that may be used to identify the economic impact of an energy-efficient aircraft concept and the impact that environmental policy would have on the viability of the concept. The framework has been applied to a case study aircraft designed to achieve an energy saving of 60% in comparison to a baseline 2005 entry-into-service aircraft. The model compares the green aircraft concept to a baseline conventional aircraft using a sensitivity analysis of the aircraft direct operating cost to changes in acquisition and maintenance cost. The research illustrates an economically viable region for the technology. Cost margins are identified where the increase in operating cost due to expensive novel technology is counterbalanced by the reduction in cost resulting from low energy consumption. Viability was found to be closely linked to fuel price, with a low fuel price limiting the viability of energy-efficient aviation technology. In contrast, a change in environmental taxation policy was found to be beneficial, with the introduction of carbon taxation incentivising the use of an environmentally optimised aircraft.Item Open Access Assessment of novel power generation systems for the biomass industry(Cranfield University, 1999-11) Codeceira Neto, Alcides; Pilidis, PericlesThe objective of this programme of research is to produce a method for assessing and optimising the performance of advanced gas turbine power plants for electricity generation within the Brazilian electric sector. With the privatisation of the Brazilian electric sector, interest has been given to the thermal plants and studies have been carried out along with the use of other alternative fuels rather than fossil fuels. Biomass is a fuel of increasing interest for power generation systems since it is clean and renewable. Essentially all biomass power plants in the Brazilian market today operate on a steam Rankine cycle, which has a poor efficiency. The Brazilian electricity market has paid attention on Biomass integrated gasification gas turbine (BIG/GT) combined cycle plants where solid biomass is gasified. A simple chemical model for representing the gasifier in the power plant is presented and optimisation of the gasification process has been applied. The method for assessing the performance of power plants takes into account not only energy, but it applies the exergy method, which uses the second law of thermodynamics and works out the destruction of energy inside plant components and energy losses rejected to atmosphere. A thermoeconomic model for assessing the power plant has also been described. The optimisation of the assessment method of power plants using exergy and thermoeconomics has been proposed based on genetic algorithms. This new technique has been fairly successful at solving optimisation problems and is easy to implement. The decision of applying genetic algorithms is due to the complexity of the mathematical model applied in the performance assessment of power plants. The assessment of combined cycles like gas / steam cycle, gas / air cycle, gas / steam / freon cycle, gas / air / freon cycle and chemically recuperated gas turbine have been investigated. The application of the overall assessment method helps to understand different and very expensive choices of power plants before making final decisions.Item Open Access Benefits, drawbacks, and future trends of Brayton helium gas turbine cycles for gas-cooled fast reactor and very-high temperature reactor Generation IV nuclear power plants(American Society of Mechanical Engineers, 2020-10-02) Gad-Briggs, Arnold; Osigwe, Emmanuel O.; Pilidis, Pericles; Nikolaidis, Theoklis; Sampath, Suresh; Teixeira, Joao AmaralNumerous studies are on-going on to understand the performance of generation IV (Gen IV) nuclear power plants (NPPs). The objective is to determine optimum operating conditions for efficiency and economic reasons in line with the goals of Gen IV. For Gen IV concepts such as the gas-cooled fast reactors (GFRs) and very-high temperature reactors (VHTRs), the choice of cycle configuration is influenced by component choices, the component configuration and the choice of coolant. The purpose of this paper to present and review current cycles being considered—the simple cycle recuperated (SCR) and the intercooled cycle recuperated (ICR). For both cycles, helium is considered as the coolant in a closed Brayton gas turbine configuration. Comparisons are made for design point (DP) and off-design point (ODP) analyses to emphasize the pros and cons of each cycle. This paper also discusses potential future trends, include higher reactor core outlet temperatures (COT) in excess of 1000 °C and the simplified cycle configurations.Item Open Access Combined Cycle Performance Deterioration Analysis(Cranfield University, 2002-01) Zwebek, A. I.; Pilidis, PericlesCombined cycles are subject to degradations and hence performance deterioration. According to the author's survey nothing was found in the open literature on this subject. Therefore, it was anticipated that it would be of great achievement if a tool for analysing and diagnosing the deterioration of combined cycle could be produced. So this thesis presents a procedure for combined cycle performance analysis and fault diagnostic by way of simulation. l order to accomplish this task successfully it was necessary to developed two pieces of software. These are STEAMOMATCH for steam cycle performance deterioration analysis, and GOTRESS for GPA of any system. STEAMOMATCH, which is built on the basics of combined cycle thermodynamics, can simulate up to three levels of pressure with reheat. On the other hand GOTRESS uses a Gas Path Analysis technique that enables the user the choice of conducting either linear or non-linear GPA at the same time. I both cases single or multiple fault can be diagnosed. GOTRESS was built in such a way that it makes it a generalised code that can be used not only for combined cycle but to diagnose a wide range of power cycle plants. The deterioration simulation results of the gas turbine power plant showed that the isentropic efficiency deterioration of the turbine unit has the uppermost sever effect on overall gas turbine power output and thermal efficiency. This is also the case with steam turbine (bottoming) cycle power and Rankine efficiency. Also, the simulation results obtained showed that the relationship between the gas turbine size and its performance deterioration is almost constant, i.e. performance deterioration follows the plant's size. Among the two major gas turbine parameters that affects the steam bottoming cycle performance of a CCGT power plant, the gas turbine exhaust temperature has a predominant effect on steam cycle efficiency over the exhaust mass flow.' As a general result, the obtained simulation results showed that the behaviour of CCGT power plant performance is more affected by gas turbine cycle conditions than by steam turbine cycle conditions. The obtained results showed that GPA can be successfully applied to either gas turbine cycle, steam turbine cycle, or the combination of the two in a form of combined cycle. The GPA diagnostic results obtained showed that it would be possible to detect some faults that might occur within the gas turbine that is a part of a combined cycle power plant by monitoring the dependent parameters of the steam turbine (bottoming) cycle such as live steam pressure and temperature and steam turbine power. In contrast, it would not been possible to detect the problems (implanted faults) that might occur within the steam turbine by monitoring the dependent parameters of the gas turbine unit.Item Open Access Contrail-free aero-engines.(2016-08) Qureshi, Sarah; Pilidis, PericlesThis thesis presents a contrail-free aero-engine designed to reduce the aviation induced global warming through the development of a condensation and containment mechanism for the exhaust water vapour content of an aero-engine. This mechanism intends to eliminate the source of contrail formation. A pressure-based turbomachinery defined as the water expeller is developed and introduced as a modular attachment to a standard aero-engine. It employs the use of centrifugal compression to generate pressure in the exhaust gas leading to a phase change that precipitates out the water content of the core exhaust gases. The water produced is drained out of the device and collected within the engine. The heat dissipated by water during condensation is absorbed by the remaining combustion gases. The design of the centrifugal water expeller is derived from a patented invention and evolved into a practical system. The theory of centrifugal extraction is explained and the underlying physics is established. This proceeds with a thermodynamic analysis whereby data for mechanical design is computed and advanced towards a prototype ready engineering model inclusive of structural design and structural analysis. The power requirements of this system are determined using thermodynamic data. In the preliminary design, the inclusion of the water expelling device results in a thirty percent increase in the length of the engine which has a likelihood of being reduced through optimization. The initial design parameters of the system are obtained from the performance analysis of a standard high-bypass three-spool turbofan engine and the study of atmospheric science and water physics. The design of the condensation device is validated through the study of the thermo-chemistry of the exhaust gases and a simple heat transfer analysis. The inter-gaseous exchange of energy at the molecular level during the process of condensation is also quantified. The performance of the standard engine with the integration of the centrifugal water expeller is analysed and progressed towards the performance evaluation of a standard wide body large aircraft with four contrail-free engines on board. Initial estimates indicate an increase in the weight of the engine by twenty five percent with the installation of the centrifugal water expeller onto the engines. This is merely a two percent increase in the overall weight of the aircraft. The integration of the mechanical device with the aero-engine results in an environmentally favourable engine-aircraft configuration with a three percent thrust penalty which is recognized as the acceptable trade-off for environmental benefits.