Browsing by Author "Osigwe, Emmanuel O."

Now showing 1 - 13 of 13
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    Analysis of control-system strategy and design of a small modular reactor with different working fluids for electricity and hydrogen production as part of a decentralised mini grid
    (MDPI, 2022-03-18) Gad-Briggs, Arnold; Osigwe, Emmanuel O.; Jafari, Soheil; Nikolaidis, Theoklis
    Hydrogen is increasingly being viewed as a significant fuel for future industrial processes as it offers pathways to zero emission. The UK sees hydrogen as one of a handful of low-carbon solutions for transition to net zero. Currently, most hydrogen production is from steam reforming of natural gas or coal gasification, both of which involve the release of carbon dioxide. Hydrogen production from mini decentralised grids via a thermochemical process, coupled with electricity production, could offer favourable economics for small modular reactors (SMRs), whereby demand or grid management as a solution would include redirecting the power for hydrogen production when electricity demand is low. It also offers a clean-energy alternative to the aforementioned means. SMRs could offer favourable economics due to their flexible power system as part of the dual-output function. This study objective is to investigate the critical performance parameters associated with the nuclear power plant (NPP), the cycle working fluids, and control-system design for switching between electricity and hydrogen demand to support delivery as part of a mini grid system for a reactor power delivering up to approximately 600 MWth power. The novelty of the work is in the holistic parametric analysis undertaken using a novel in-house tool, which analyses the NPP using different working fluids, with a control function bolt-on at the offtake for hydrogen production. The results indicate that the flow conditions at the offtake can be maintained. The choice of working fluids affects the pressure component. However, the recuperator and heat-exchanger effectiveness are considered as efficiency-limiting factors for hydrogen production and electricity generation. As such, the benefit of high-technology heat exchangers cannot be underestimated. This is also true when deciding on the thermochemical process to bolt onto the plant. The temperature of the gas at the end of the pipeline should also be considered to ensure that the minimum temperature-requirement status for hydrogen production is met.
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    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 Amaral
    Numerous 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.
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    Economic optimization from fleets of aero-derivative gas turbines utilising flared associated gas
    (Elsevier, 2020-10-18) Obhuo, M.; Aziaka, Duabari S.; Osigwe, Emmanuel O.; Emmanuel, O. A.; Pilidis, Pericles
    Associated gas is been wasted to flaring in some parts of the world. The use of these flared gases for both industrial and economic purposes would be very beneficial. This paper presents the development of a model for optimizing the economic return of fleets of gas turbines utilizing flared associated gas. The paper further analyzed the impact of gas turbine degradation on the optimized divestment times of the redundant engines and the economic use of associated gas. Hypothetical but realistic gas turbines were modeled using the Cranfield University performance simulation tool, TURBOMATCH. In furtherance with the investigation, the Techno-Economic and Environmental Risk Assessment (TERA) framework has been adopted for a broad and multi-dimensional optimization of the economic return from the fleets. The results were employed in three degradation scenarios (optimistic, medium, and pessimistic) within the TERA framework to generate economic models. Genetic Algorithm (GA) in MATLAB was used in carrying out optimization to maximize the economic benefit. The result showed that an increase of 1.0% and 1.6% in the energy and net present value (NPV) respectively of the optimized clean fleet as against the baseline were achieved. The economic performance of the fleets shows the optimized fleet (clean) having the highest NPV of $2.84b and the pessimistic degraded fleet having the least NPV of $2.39b. More results revealed that degradation reduced the NPV of the project by 4.0%, 9.1%, and 15.8% for the three different degradation scenarios. This paper has proposed a model that can be used for the profitable economic utilization of associated gas which would be useful to gas turbine operators and investors
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    Effect of working fluid on selection of gas turbine cycle configuration for Gen-IV nuclear power plant system
    (JSME, 2019-05-31) Osigwe, Emmanuel O.; Gad-Briggs, Arnold; Pilidis, Pericles; Nikolaidis, Theoklis; Sampath, Suresh
    The cycle configuration of the energy conversion system in a nuclear power plant tends to have a governing effect on the overall performance and acquisition cost. Interestingly, one factor that could greatly affect the design choice of the cycle configuration which may not have been explored extensively in many literatures reviewed is the choice of the working fluid. This paper presents a technical analysis on the effect of working fluid on selection of the cycle arrangement for a Generation IV nuclear power plant. It provides insight on potential performance gains that justifies the benefit for an additional cost of a complex cycle, and how the working fluid can influence this choice. The study identifies candidate working fluid that may be suitable for simple, inter-cooled-recuperated, recuperated and other complex cycles. The results obtained shows that for fluid like carbon dioxide, its optimal performance is achieved above it critical points which will require pressurizing the system or operating at high pressure ratio, hence, it would be suitable for a re-compressed inter-cooled cycle configuration. Similar, for fluid like helium with low molecular weight and high gas properties, the simple cycle configuration seem more realistic for its highest cycle efficiency of 41% and turbomachinery design.
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    Feasibility of a helium closed-cycle gas turbine for UAV propulsion
    (MDPI, 2020-12-22) Osigwe, Emmanuel O.; Gad-Briggs, Arnold; Nikolaidis, Theoklis
    When selecting a design for an unmanned aerial vehicle, the choice of the propulsion system is vital in terms of mission requirements, sustainability, usability, noise, controllability, reliability and technology readiness level (TRL). This study analyses the various propulsion systems used in unmanned aerial vehicles (UAVs), paying particular focus on the closed-cycle propulsion systems. The study also investigates the feasibility of using helium closed-cycle gas turbines for UAV propulsion, highlighting the merits and demerits of helium closed-cycle gas turbines. Some of the advantages mentioned include high payload, low noise and high altitude mission ability; while the major drawbacks include a heat sink, nuclear hazard radiation and the shield weight. A preliminary assessment of the cycle showed that a pressure ratio of 4, turbine entry temperature (TET) of 800 °C and mass flow of 50 kg/s could be used to achieve a lightweight helium closed-cycle gas turbine design for UAV mission considering component design constraints.
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    GT-ACYSS: gas turbine arekret-cycle simulation modelling for training and educational purposes
    (ASME, 2019-05-08) Osigwe, Emmanuel O.; Pilidis, Pericles; Nikolaidis, Theoklis; Sampath, Suresh
    This paper presents the modelling approach of a multi-purpose simulation tool called GT-ACYSS; which can be utilized for simulation of steady-state and pseudo transient performance of closed-cycle gas turbine plants. The tool analyses the design point performance as a function of component design and performance map characteristics predicted based on multi-fluid map scaling technique. The off-design point is analyzed as a function of design point performance, plant control settings and a wide array of other off-design conditions. GT-ACYSS can be a useful educational tool since it allows the student to monitor gas path properties throughout the cycle without laborious calculations. It allows the user to have flexibility in selection of four different working fluids, and the ability to simulate various single-shaft closed-cycle configurations, as well as the ability to carry out preliminary component sizing of the plant. The modelling approach described in this paper has been verified with case studies and the trends shown appeared to be reasonable when compared with reference data in the open literature, hence, can be utilized to perform independent analyses of any referenced single-shaft closed-cycle gas turbine plants. The results of case studies presented herein demonstrated that the multi-fluid scaling method of components and the algorithm of the steady state analysis were in good agreement for predicting cycle performance parameters (such as efficiency, and output power) with mean deviations from referenced plant data ranging between 0.1% and 1% over wide array of operations.
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    Integrated gas turbine system diagnostics: components and sensor faults quantification using artificial neural networks
    (International Society for Air Breathing Engines (ISABE), 2017-09-11) Osigwe, Emmanuel O.; Li, Yi-Guang; Suresh, Sampath; Jombo, Gbanaibolou
    The role of diagnostic systems in gas turbine operations has changed over the past years from a single support troubleshooting maintenance to a more proactive integrated diagnostic system. This has become so, because detecting and fixing fault(s) on one gas turbine sub-system can trigger false fault(s) indication, on other component(s) of the gas turbine system, due to interrelationships between data obtained to monitor not only the GT single component, but also the integrated components and sensors. Hence, there is need for integration of gas turbine system diagnostics. The purpose of this paper is to present artificial neural network diagnostic system (ANNDS) as an integrated gas turbine system diagnostic tool capable of quantifying gas turbine component and sensor fault. A model based approach which consists of an engine model, and an associated parameter estimation algorithm that predicts the difference between the real engine data and the estimated output data is described in this paper. The ANNDS system was trained to detect, isolate and assess component(s) and sensor fault(s) of a single spool industrial gas turbine GT-PG9171ER. The ANN model was construed with multi-layer feed-forward back propagation network for component fault(s) and auto associative network for sensor fault(s). The diagnostic methodology adopted was a nested network structure, trained to handle specific objective function of detecting, isolating or quantifying faults. The data used for training, and testing purposes were obtained from a non-linear aero-thermodynamic model using PYTHIA; a Cranfield University in-house software. The data set analyzed in this paper represent samples of clean and faulty gas turbine components caused by fouling (0.5% - 6% degradation) and sensor fault(s) due to bias (±1% - ±7%). The results show the capability of ANN to detect, isolate (classification) and quantify multiple faults if properly trained.
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    Inventory control systems for nuclear powered closed-cycle gas turbine: technical studies on effect of working fluid options
    (Unknown, 2019-05-24) Osigwe, Emmanuel O.; Gad-Briggs, Arnold; Pilidis, Pericles; Nikolaidis, Theoklis; Sampath, Suresh
    The Inventory Control System (ICS) offer unique characteristics when modulating the gas turbine output power to match the required load demand. The unique opportunities it offers have made it to be widely used in most nuclear powered closed-cycle gas turbine plant design and operations. This paper presents a technical study on how the different working fluid options affect the design and performance characteristics of the inventory control system. The results from this study shows that using helium as cycle working fluid offers an advantage in terms of Reynolds effect on cycle efficiency and also enable the design for compact inventory tank size and weight which could have a direct effect on the capital cost, due to its thermodynamic characteristics. However, the long term operational cost of helium compared with other working fluid utilized in this study provides a reasonable argument to justify any investment decision.
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    Performance analyses and evaluation of CO2 and N2 as coolants in a recuperated Brayton gas turbine cycle for a Generation IV nuclear reactor power plant
    (ASME, 2019-04-24) Osigwe, Emmanuel O.; Gad-Briggs, Arnold; Nikolaidis, Theoklis; Pilidis, Pericles; Sampath, Suresh
    As demands for clean and sustainable energy renew interests in nuclear power to meet future energy demands, Generation IV nuclear reactors are seen as having the potential to provide the improvements required for nuclear power generation. However, for their benefits to be fully realised, it is important to explore the performance of the reactors when coupled to different configurations of closed-cycle gas turbine power conversion systems. The configurations provide variation in performance due to different working fluids over a range of operating pressures and temperatures. The objective of this paper is to undertake analyses at the design and off-design conditions in combination with a recuperated closed-cycle gas turbine and comparing the influence of carbon dioxide and nitrogen as the working fluid in the cycle. The analysis is demonstrated using an in-house tool, which was developed by the authors. The results show that the choice of working fluid controls the range of cycle operating pressures, temperatures and overall performance of the power plant due to the thermodynamic and heat properties of the fluids. The performance results favored the nitrogen working fluid over CO2 due to the behavior CO2 below its critical conditions. 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).
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    Performance modeling and analysis of a single-shaft closed-cycle gas turbine using different operational control strategy
    (ASME, 2019-07-18) Osigwe, Emmanuel O.; Gad-Briggs, Arnold; Igbong, Dodeye; Nikolaidis, Theoklis; Pilidis, Pericles
    In the last few years, one considerable factor for the viability and interest in closed-cycle gas turbine systems for nuclear or conventional power plant application is its potential to maintain high cycle performance at varying operating conditions. However, for this potential to be realised, more competitive analysis and understanding of its control strategy is importantly required. In this paper, the iterative procedure for three independent control strategies of a 40 MW single-shaft intercooled-recuperated closed-cycle gas turbine incorporated to a Generation IV nuclear reactor is been analysed and their performance at various operating conditions compared. The rationale behind this analysis was to explore the different control strategy and to identify potential limitations using each independent control. The inventory control strategy offered a more viable option for high efficiency at changes in ambient and part-load operations, however, operational limitations in terms of size and pressure of inventory tank, rotational speed for which the centrifugal forces acting on the blade tips could become too high, hence would affect the mechanical integrity and compressor performance. The bypass control responds rapidly to load rejection in event of loss of grid power. And more interestingly the results showed the need for a mixed or combined control instead of a single independent technique, which is limited in practice due to operational limits.
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    Performance simulation to understand the effects of multi-fluid scaling of gas turbine components for Generation IV nuclear power plants
    (ASME, 2019-08-05) Osigwe, Emmanuel O.; Gad-Briggs, Arnold; Nikolaidis, Theoklis; Pilidis, Pericles; Sampath, Suresh
    A significant hurdle in the development of performance simulation tools to analyse and evaluate nuclear power plants (NPP) is finding data relating to component performance maps. As a result, Engineers often rely on an estimation approach using various scaling techniques. The purpose of this study is to determine the component characteristics of a closed-cycle gas turbine NPP using existing component maps with corresponding design data. The design data is applied for different working fluids using a multi-fluid scaling approach to adapt data from one component map into another. The multi-fluid scaling technique described herein was developed as an in-house computer simulation tool. This approach makes it easy to theoretically scale existing maps using similar or different working fluids without carrying out a full experimental test or repeating the whole design and development process. The results of selected case studies show a reasonable agreement with available data. 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).
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    Techno-economic study on implementation of inventory control requirements for a nuclear powered closed-cycle gas turbine power plant
    (ASME, 2020-10-23) Osigwe, Emmanuel O.; Gad-Briggs, Arnold; Obhuo, Mafel; Pilidis, Pericles
    The use of an inventory control system offers a unique benefit of stable cycle thermal efficiency during part-load operation. This article focuses on the influence of initial inventory tank pressure on the control level using pressure differential as a driving force of the inventory control system. The study also considered the effects of using multiple tanks to increase the overall size of the inventory control tank and the use of insulation to reduce the impact of temperature variation between the compressor discharge temperature and the inventory tank temperature. The second part of this analysis is a cost comparison between the use of multiple tanks and the use of a transfer compressor to achieve high cycle efficiency at continuous part-load operation. The discussions in this paper accentuate the optimum benefit for utilizing an inventory control system for a single-shaft intercooled-recuperated closed-cycle gas turbine plant
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    Thermodynamic performance and creep life assessment comparing hydrogen- and jet-fueled turbofan aero engine
    (MDPI, 2021-04-25) Osigwe, Emmanuel O.; Gad-Briggs, Arnold; Nikolaidis, Theoklis; Jafari, Soheil; Sethi, Bobby; Pilidis, Pericles
    There is renewed interest in hydrogen as an alternative fuel for aero engines, due to their perceived environmental and performance benefits compared to jet fuel. This paper presents a cycle, thermal performance, energy and creep life assessment of hydrogen compared with jet fuel, using a turbofan aero engine. The turbofan cycle performance was simulated using a code developed by the authors that allows hydrogen and jet fuel to be selected as fuel input. The exergy assessment uses both conservations of energy and mass and the second law of thermodynamics to understand the impact of the fuels on the exergy destruction, exergy efficiency, waste factor ratio, environmental effect factor and sustainability index for a turbofan aero engine. Finally, the study looks at a top-level creep life assessment on the high-pressure turbine hot section influenced by the fuel heating values. This study shows performance (64% reduced fuel flow rate, better SFC) and more extended blade life (15% increase) benefits using liquefied hydrogen fuel, which corresponds with other literary work on the benefits of LH2 over jet fuel. This paper also highlights some drawbacks of hydrogen fuel based on previous research work, and gives recommendations for future work, aimed at maturing the hydrogen fuel concept in aviation.