CERES :: Browsing by Author "Nikolaidis, Theoklis"

Browsing by Author "Nikolaidis, Theoklis"

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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, Pericles
This 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.
Open Access
Advanced constraints management strategy for real-time optimization of gas turbine engine transient performance
(MDPI, 2019-12-06) Nikolaidis, Theoklis; Jafari, Soheil; Li, Zhuo
Motivated by the growing technology of control and data processing as well as the increasingly complex designs of the new generation of gas turbine engines, a fully automatic control strategy that is capable of dealing with different aspects of operational and safety considerations is required to be implemented on gas turbine engines. An advanced practical control mode satisfaction method for the entire operating envelope of gas turbine engines is proposed in this paper to achieve the optimal transient performance for the engine. A constraint management strategy is developed to generate different controller settings for short-range fighters as well as long-range intercontinental aircraft engines at different operating conditions by utilizing a model predictive control approach. Then, the designed controller is tuned and modified with respect to different realistic considerations including the practicality, physical limitations, system dynamics, and computational efforts. The simulation results from a verified two-spool turbofan engine model and controller show that the proposed method is capable of maneuverability and/or fuel economy optimization indices while satisfying all the predefined constraints successfully. Based on the parameters, natural frequencies, and dynamic behavior of the system, a set of optimized weighting factors for different engine parameters is also proposed to achieve the optimal and safe operation for the engine at different flight conditions. The paper demonstrates the effects of the prediction length and control horizon; adding new constraints on the computational effort and the controller performance are also discussed in detail to confirm the effectiveness and practicality of the proposed approach in developing a fully automatic optimized real-time controller for gas turbine engines.
Open Access
Advanced control algorithm for FADEC systems in the next generation of turbofan engines to minimize emission levels
(MDPI, 2022-05-23) Aghasharifian Esfahan, Majid; Namazi, Mohammadmehdi; Nikolaidis, Theoklis; Jafari, Soheil
New propulsion systems in aircrafts must meet strict regulations and emission limitations. The Flightpath 2050 goals set by the Advisory Council for Aviation Research and Innovation in Europe (ACARE) include reductions of 75%, 90%, and 65% in CO2, NOx, and noise, respectively. These goals are not fully satisfied by marginal improvements in gas turbine technology or aircraft design. A novel control design procedure for the next generation of turbofan engines is proposed in this paper to improve Full Authority Digital Engine Control (FADEC) systems and reduce the emission levels to meet the Flightpath 2050 regulations. Hence, an Adaptive Network–based Fuzzy Inference System (ANFIS), nonlinear autoregressive network with exogenous inputs (NARX) techniques, and the block-structure Hammerstein–Wiener approach are used to develop a model for a turbofan engine. The Min–Max control structure is chosen as the most widely used practical control algorithm for gas turbine aero engines. The objective function is considered to minimize the emission level for the engine in a pre-defined maneuver while keeping the engine performance in different aspects. The Genetic Algorithm (GA) is applied to find the optimized control structure. The results confirm the effectiveness of the proposed approach in emission reduction for the next generation of turbofan engines.
Open Access
Advanced optimization of gas turbine aero-engine transient performance using linkage-learning genetic algorithm: Part Ⅰ, Building blocks detection and optimization in runway
(Elsevier, 2020-08-15) Liu, Yinfeng; Jafari, Soheil; Nikolaidis, Theoklis
This paper proposes a Linkage Learning Genetic Algorithm (LLGA) based on the messy Genetic Algorithm (mGA) to optimize the Min-Max fuel controller performance in Gas Turbine Engine (GTE). For this purpose, a GTE fuel controller Simulink model based on the Min-Max selection strategy is firstly built. Then, the objective function that considers both performance indices (response time and fuel consumption) and penalty items (fluctuation, tracking error, overspeed and acceleration/deceleration) is established to quantify the controller performance. Next, the task to optimize the fuel controller is converted to find the optimization gains combination that could minimize the objective function while satisfying constraints and limitations. In order to reduce the optimization time and to avoid trapping in the local optimums, two kinds of building block detection methods including lower fitness value method and bigger fitness value change method are proposed to determine the most important bits which have more contribution on fitness value of the chromosomes. Then the procedures to apply LLGA in controller gains tuning are specified stepwise and the optimization results in runway condition are depicted subsequently. Finally, the comparison is made between the LLGA and the simple GA in GTE controller optimization to confirm the effectiveness of the proposed approach. The results show that the LLGA method can get better solution than simple GA within the same iterations or optimization time. The extension applications of the LLGA method in other flight conditions and the complete flight mission simulation will be carried out in part II
Open Access
Advanced optimization of gas turbine aero-engine transient performance using linkage-learning genetic algorithm: Part Ⅱ, Optimization in flight mission and controller gains correlation development
(Elsevier, 2020-08-15) Liu, Yinfeng; Jafari, Soheil; Nikolaidis, Theoklis
This paper proposes a Linkage Learning Genetic Algorithm (LLGA) based on the messy Genetic Algorithm (mGA) to optimize the Min-Max fuel controller performance in Gas Turbine Engine (GTE). For this purpose, a GTE fuel controller Simulink model based on the Min-Max selection strategy is firstly built. Then, the objective function that considers both performance indices (response time and fuel consumption) and penalty items (fluctuation, tracking error, overspeed and acceleration/deceleration) is established to quantify the controller performance. Next, the task to optimize the fuel controller is converted to find the optimization gains combination that could minimize the objective function while satisfying constraints and limitations. In order to reduce the optimization time and to avoid trapping in the local optimums, two kinds of building block detection methods including lower fitness value method and bigger fitness value change method are proposed to determine the most important bits which have more contribution on fitness value of the chromosomes. Then the procedures to apply LLGA in controller gains tuning are specified stepwise and the optimization results in runway condition are depicted subsequently. Finally, the comparison is made between the LLGA and the simple GA in GTE controller optimization to confirm the effectiveness of the proposed approach. The results show that the LLGA method can get better solution than simple GA within the same iterations or optimization time. The extension applications of the LLGA method in other flight conditions and the complete flight mission simulation will be carried out in part II
Open Access
Aircraft thermal management: Practices, technology, system architectures, future challenges, and opportunities
(Elsevier, 2021-11-12) van Heerden, Albert S. J.; Judt, David M.; Jafari, Soheil; Lawson, Craig P.; Nikolaidis, Theoklis; Bosak, D.
The provision of adequate thermal management is becoming increasingly challenging on both military and civil aircraft. This is due to significant growth in the magnitude of onboard heat loads, but also because of their changing nature, such as the presence of more low-grade, high heat flux heat sources and the inability of some waste heat to be expelled as part of engine exhaust gases. The increase in the use of composites presents a further issue to address, as these materials are not as effective as metallic materials in transferring waste heat from the aircraft to the surrounding atmosphere. These thermal management challenges are so severe that they are becoming one of the major impediments to improving aircraft performance and efficiency. In this review, these challenges are expounded upon, along with possible solutions and opportunities from the literature. After introducing relevant factors from the ambient environment, the discussion of the challenges and opportunities is guided by a simple classification of the elements involved in thermal management systems. These elements comprise heat sources, heat acquisition mechanisms, thermal transport systems, heat rejection to sinks, and energy conversion and storage. Heat sources include both those from propulsion and airframe systems. Heat acquisition mechanisms are the means by which thermal energy is acquired from the sources. Thermal transport systems comprise cooling loops and thermodynamic cycles, along with their associated components and fluids, which move the heat from the source to the sinks over potentially large distances. The terminal aircraft heat sinks include atmospheric air, fuel, and the aircraft structure. In addition to the discussions on these different elements of thermal management systems, several topics of particular priority in aircraft thermal management research are deliberated upon in detail. These are thermal management for electrified propulsion aircraft, ultra-high bypass ratio geared turbofans, and high power airborne military systems; environmental control systems; power and thermal management systems; thermal management on supersonic transport aircraft; and novel modelling and simulation processes and tools for thermal management.
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, Theoklis
The 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.
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, Theoklis
The 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).
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, Theoklis
The 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.
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, Theoklis
Previous 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.
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, Pericles
Nuclear 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.
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, Theoklis
The 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.
Open Access
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.
Open Access
Assessment of numerical radiation models on the heat transfer of an aero-engine combustion chamber
(Elsevier, 2020-11-02) Gamil, Abdelaziz A. A.; Nikolaidis, Theoklis; Lelaj, Indrit; Laskaridis, Panagiotis
Thermal radiation is the most dominant type of heat transfer inside the combustion chamber, which can directly affect the temperature distributions at the combustor walls. This paper provides a comprehensive analysis of the effects of two radiation models on the flame and liner-walls temperatures. A combustion chamber used in the Rolls-Royce-RB-183 turbofan engine was examined in this study by integrating a solid combustor model with the numerical fluid domain. The results indicated that the implementation of radiation models shrinks the flame peak-temperature and altered temperature distribution across the liner. The Discrete Ordinates Method (DOM) estimated a 10% higher temperature at the front part of the liner compared to the non-radiation model and 15% less than the P-1 radiation method. After the dilution zone, the DOM and P-1 models estimated respectively 15% and 25% reduction in the liner temperature compared to the non-radiation combustor. The radiation models have also down predicted the flame temperature by 200 K and more than 200 K for DOM and P-1 case respectively. The results also showed that the emissivity value had minimal effects on the combustor temperature distribution. The DOM considered being more accurate to estimate the combustor wall and flow temperatures compared to the P-1 radiation method
Open Access
Assessment of surface roughness effects on micro axial turbines
(ASME, 2021-01-11) Gamil, Abdelaziz A. A.; Nikolaidis, Theoklis; Teixeira, Joao Amaral; Madani, S. H.; Izadi, Ali
Surface roughness significantly affects the aerodynamics and heat transfer within micro-scale turbine stages. It results in a considerable increment in the blade profile loss and leads consequently to sizeable performance reductions. The provision of low roughness surfaces in micro gas turbine stages presents challenges on account of the small (mm scale) sizes, manufacturing complexity and associated costs. The axial turbine investigated in this study is fitted to Samad Power’s TwinGen domestic micro combined heat and power unit. The micro gas turbine has a compressor pressure ratio of 3, 1200K turbine inlet temperature and a rotational speed of 170,000 rpm. This paper presents a numerical assessment of the effects of varying the surface roughness on the performance and heat transfer of the micro turbine. The surface roughness was uniformly distributed on the NGV and rotor blades. The results showed that increasing the surface roughness from 3 microns to 6, 20, and 100 microns resulted in a reduction in stage total efficiency of 0.8%, 4% and 12% respectively as well as a comparable decrease in output power (0.7%, 3.6%, and 11% respectively). The turbine temperature was also observed to be very sensitive to surface roughness and a temperature increase of some 5% at the rotor hub and over 4% increment in the blade tip surface was observed for 100 microns when compared to the 3 microns surface roughness case. The findings of this paper highlight the adverse effects of the surface roughness on the micro-turbine performance and temperature distribution as well as the importance of careful consideration of wall roughness during the design and manufacturing stages
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 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.
Open Access
A combined technique of Kalman filter, artificial neural network and fuzzy logic for gas turbines and signal fault isolation
(Elsevier, 2020-06-18) Togni, Simone; Nikolaidis, Theoklis; Sampath, Suresh
The target of this paper is the performance-based diagnostics of a gas turbine for the automated early detection of components malfunctions. The paper proposes a new combination of multiple methodologies for the performance-based diagnostics of single and multiple failures on a two-spool engine. The aim of this technique is to combine the strength of each methodology and provide a high success rate for single and multiple failures with the presence of measurement malfunctions. A combination of KF (Kalman Filter), ANN (Artificial Neural Network) and FL (Fuzzy Logic) is used in this research in order to improve the success rate, to increase the flexibility and the number of failures detected and to combine the strength of multiple methods to have a more robust solution. The Kalman filter has in his strength the measurement noise treatment, the artificial neural network the simulation and prediction of reference and deteriorated performance profile and the fuzzy logic the categorization flexibility, which is used to quantify and classify the failures. In the area of GT (Gas Turbine) diagnostics, the multiple failures in combination with measurement issues and the utilization of multiple methods for a 2-spool industrial gas turbine engine has not been investigated extensively. This paper reports the key contribution of each component of the methodology and brief the results in the quantification and classification success rate. The methodology is tested for constant deterioration and increasing noise and for random deterioration. For the random deterioration and nominal noise of 0.4%, in particular, the quantification success rate is above 92.0%, while the classification success rate is above 95.1%. Moreover, the speed of the data processing (1.7 s/sample) proves the suitability of this methodology for online diagnostics.
Open Access
Combustor development and performance analysis for recuperated microturbine application
(AIAA, 2021-07-28) Liu, Yize; Nikolaidis, Theoklis; Gamil, Abdelaziz; Madani, Seyed Hossein; Sarkandi, Mohammad
In recent years, increased attention is paid to the microturbine MGT as a promising technology for combined heat and power (CHP) applications. An MGT has advantages of high reliability, high efficiency, lower manufacturing and maintenance costs, reduced vibration and noise levels, and clean emissions. Recuperation can further increase efficiency by recycling the heat from the turbine exhaust and preheating the air for combustion via a heat exchanger. Such a system will be realized by designing a combustion chamber that can meet various design and operability requirements. This paper presents an overview of the combustor development and provides CFD analysis on combustor performance and emissions. A single tubular combustor is designed, and the direct injection mode is applied to mitigate the autoignition and flashback risks resulting from the high preheating temperature. Heat transfer and cooling analysis indicate that ceramic liner is capable of tolerating high temperature using effusion cooling. Studies of flow characteristics, temperature field, pressure loss, and pattern factor are provided in detail. The effects of design parameters and methods (i.e., fuel-air mixture strength, cooling hole angles, dilution hole design approaches) are also discussed. Finally, the use of biomass is investigated and shows that it has the potential to achieve a high combustion efficiency and low emissions for the recuperated microturbine application.
Open Access
Comparing different schemes in a combined technique of Kalman filter, artificial neural network and fuzzy logic for gas turbines online diagnostics
(American Society of Mechanical Engineers, 2022-10-28) Togni, Simone; Nikolaidis, Theoklis; Sampath, Suresh
The paper presents research on the online performance-based diagnostics by implementing a novel methodology, which is based on the combination of Kalman Filter, Artificial Neural Network, Neuro-Fuzzy Logic and Fuzzy Logic. These methods are proposed to improve the success rate, increase the flexibility, and allow the detection of single and multiple failures. The methodology is applied to a 2-shaft industrial gas turbine engine for the automated early detection of single and multiple failures with the presence of measurement noise. The methodology offers performance prediction and the possibility of utilizing multiple schemes for the online diagnostics. The architecture leads to three possible schemes. The first scheme includes the base methodology and enables Kalman Filter for data filtering, Artificial Neural Network for the component efficiency prediction, the Neuro-Fuzzy logic for the failure quantification and the Fuzzy Logic for the failure classification. For this scheme, a performance simulation tool (Turbomatch) is used to calculate the thermodynamic baseline. The second scheme replaces Turbomatch with the Artificial Neural Network, that is used to calculate the deteriorated efficiencies and the reference efficiencies. The third scheme is identical to the first one but excludes the shaft power measurements, which are not available in aero engines or might not be usable for some power plant configurations. The paper compares the performance of the three methodologies, with the presence of measurement noise (0.4% reference noise and 2.0% reference noise), and 24 types of random single and multiple failures, with variable magnitude. The first methodology has been already presented by Togni et al. [10], whereas the other two methodologies and results are part of the PhD thesis presented by Togni [18] and they extend the applicability of the method. The success rate, targeting the correct detection of the of the failure magnitude ranges between 92% and 100% without measurement noise and ranges between 66% and 83% with measurement noise. Instead, the success rate of the classification, targeting the correct detection of the type of failure ranges between 93% and 100% without measurement noise and between 85% and 100% with measurement noise.
Open Access
Comparison of sodium sulphate deposition rate models based on operational factors influencing hot corrosion damage in aero-engines
(American Society of Mechanical Engineers, 2021-01-11) Pontika, Evangelia; Laskaridis, Panagiotis; Nikolaidis, Theoklis; Koster, Max
Hot corrosion is defined as the accelerated oxidation/sulphidation in the presence of alkali metal molten salts. It is a form of chemical attack that causes good metal loss. Current lifing models in aircraft engines focus on creep, fatigue and oxidation while hot corrosion damage has been overlooked as being of secondary importance. However, the absence of hot corrosion lifing models for aircraft engines often leads to unexpected and unexplained hot corrosion findings by aircraft engine operators and Maintenance, Repair and Overhaul (MRO) providers during inspections. Although hot corrosion does not cause failure on its own, the interaction with other damage mechanisms can reduce component life significantly, consequently, there is a requirement for including hot corrosion in the damage prediction process of aircraft engines. In both theoretical and experimental studies in literature, deposition of molten salts is identified as one of the primary conditions for hot corrosion to occur and an increased amount of deposited liquid salts accelerates the attack. Currently, most hot corrosion studies are limited to experimental testing of superalloys which are pre-coated with a controlled layer of salts. Such experimental studies are disconnected from gas turbine operating conditions during service. The present paper analyses two deposition rate models applicable to gas turbine operating conditions using Design of Experiments. Design space exploration is presented by taking into account gas turbine operating parameters which vary during a flight as well as temperature ranges where hot corrosion can occur. Analysis of variance is presented for 6 input parameters using Box-Behnken 3-level factorial design. Results from the Analysis of Variance indicate that the deposition rate models are sensitive to pressure and salt concentration in the gas flow. Finally, the saturation point of sodium sulphate has been investigated within the operating range of gas turbine and it was found that it can vary significantly under different conditions.