CERES :: Browsing by Author "Singh, R."

Browsing by Author "Singh, R."

Now showing 1 - 20 of 54

Open Access
Aero engine life evaluated for combined creep and fatigue, and extended by trading-off excess thrust
(Cranfield University, 1994-01) Wu, F-E.; Singh, R.
This thesis investigates the concept of thrust rating as a means towards reducing the life cycle costs of engine ownership. Towards this end, this thesis has discussed the concept of thrust rating, developed computer programs for mechanical load type failures, which include creep, LCF, and combinations thereof, and conducted simulations of improving life usage and reducing life cycle costs. A study was performed on a military engine, under an original design mission mix, that showed significant gains in creep-LCF life of the HPT blade could be achieved, especially With the recently proposed and presumably more accurate criterion- ductility exhaustion, by thrust rating. The savings were expressed in terms of an approximate reduced life accumulation rates and life cycle costs. The net result was a 50% increase in creep-LCF life with a savings of $ 50.4 million. These calculations were based on a Feet of 300 engines having the designed lifetime of 8,000 operating hours per engine. Throughout the thesis, mention is also made of employing the thrust rating concept on other engines. To this end, the thesis will also give a blueprint for conducting a feasibility study to employ thrust rating as a maintenance tool. In addition to the technical aspects, the role of maintenance and aircraft operations policy will also be studied to determine the interrelationships that exist between thrust rating technology and its practical application.
Open Access
Civil aero-propulsion application: effect of thrust rating change on engine time on-wing
(Cranfield University, 2015-11) Shafi, Syed Atif; Singh, R.; Laskaridis, Panagiotis
Engine fleet management has always been one of the most challenging tasks in any airline as it requires assuring reliability and cost effectiveness of engine operation at all times. The engine maintenance expenses are quite significant and accounts for about one third of the total aircraft maintenance costs. For all airlines with “Labour & Material” type of contractual arrangement with respective OEM / MRO provider, maximizing engine’s Time On-Wing (TOW) is extremely crucial to face lower maintenance costs, while at the same time abiding by governing airworthiness standards. Engine’s TOW is generally limited due to at least one of the following reasons: performance degradation reflected by lower Exhaust Gas Temperature (EGT) margin, hot section hardware life monitored by regular borescope inspections and Life Limited parts (LLP) expiry enforced by OEM or regulatory authority. After introducing relevant aero engine maintenance concepts and terminology, this thesis will serve to provide both qualitative and quantitative assessment of how certain operational factors of flight profile influence engine performance deterioration and maintenance costs. One such factor is the thrust rating of the engine. Higher thrust gives rise to higher internal temperatures, exposing engine hardware to greater mechanical and thermal stresses and therefore leading to faster rate of degradation and earlier engine removal. This thesis will be of interest to airlines having at least two different types of aircraft models in their fleet with different average flight profiles but powered by the same engine model with the required thrust variant. A particular engine may spend some time first on the aircraft that requires higher thrust rating before being switched to the aircraft that requires lower thrust rating or vice versa. This thesis will look into the feasibility of such an operational strategy through different aspects and discuss its effectiveness in retaining the engine performance for a longer time, thereby affecting the operating fuel costs and restoration costs per flying hour expected at the time of shop visit.
Open Access
Combined gas/steam cycle power generation from a user’s viewpoint
(1990-05) Wright, M. R.; Singh, R.
Gas turbines have been used since the 1940's to provide electric power at times of peak demand, but this is due to low initial cost and short starting times. Historically low efficiency and a higher quality fuel requirement has kept the gas turbine on the high end of the load curve. The combined cycle uses a gas turbine as the prime engine, then uses an exhaust heat recovery boiler to raise steam for a steam turbine cycle. High efficiencies are achievable and the gas turbines can now b u m fuels from natural gas through to crude oil and coal via gasification. High efficiency, short construction time,, competitive installation costs and smaller plant power ratings, has led to increasing and extensive use of the combined cycle. During the next two decades large numbers of gas turbines will be purchased for all load curve requirements with combined cycles in the mid to base load range. Gas turbines and combined cycles are studied in a holistic way, from performance theory to issues of procurement and maintenance. Gas turbines are discussed more fully than steam turbines as they are a less mature technology and dictate the operation of the combined cycle. A mathematical, model of a hypothetical engine is used to find performance trends. This model includes the gas turbine, single pressure boiler and steam turbine. Off design of the gas turbine is studied using the Cranfield program Turbomatch. A mathematical model of the off design of the boiler is developed to give off design trends for the combined cycle. Other issues discussed are applications, fuels, rating, operation, maintenance and various configurations. Past development, current state-of-the-art and future prospects are also discussed.
Open Access
Comparison of unconventional aero engine architectures
(Cranfield University, 2011-04-30) Noppel, F. G.; Singh, R.
In the light of global warming, the associated socio economical consequences, and the projected shortage of natural energy resources and ever rising oil prices, this thesis examines the potential for unconventional aero engine architectures to reduce fuel consumption of passenger aircraft. Current aircraft engines are based on the Brayton cycle, where the working fluid successively experiences isentropic compression, isobaric combustion, and isentropic expansion. Deviations from the ideal cycle in real engines occur through component inefficiencies. The maximum achievable thermodynamic efficiency of the Brayton cycle increases hand in hand with its peak cycle temperature. Since the peak cycle temperature is limited by material properties of the turbine, the maximum cycle efficiency of current jet engines is limited by the laws of thermodynamics. Hence, efficiency improvements of jet engines beyond what is possible with conventional turbofan designs are only feasible through unconventional engine architecture. Several technologies enabling unconventional engine architectures for aircraft propulsion have been identified. They include wave rotor, pulse detonation and internal combustion. These technologies are merged with conventional jet engine technology to form hybrid designs. A one dimensional engine performance model was developed to calculate the performance and allow a comparison of the hybrid cycles with a conventional turbofan cycle. Gradient optimisation techniques were applied to the allow comparison of the best possible designs. Results suggest that of the examined cycles, the hybrid internal combustion cycle has the best potential for fuel savings compared to conventional turbofan cycles.
Open Access
Contrail and cirrus cloud avoidance technology
(Cranfield University, 2007-10) Noppel, F. G.; Singh, R.
Civil aviation, providing transport to connect people, cultures and economies, is situated at the heart of globalisation. Since its earliest days, it has grown along with every other part of the industrialised society and experienced growth rates exceeding that of global GDP. Projections suggest that future air traffic emissions will play an increasingly important role in the contribution to global warming, which is regarded to be a serious threat to earth’s socio-ecological systems. Air traffic contributes to the overall anthropogenic radiative forcing, a metric denoting perturbations in the earth’s radiation budget, by the emission of greenhouse gases and aerosols, and also by the generation of high ice clouds, commonly known as contrails. Recent studies suggest that the radiative forcing resulting from contrails is potentially higher than that of all other air-traffic pollutants combined. In light of this, contrail avoidance is attracting increasing interest from the aeronautical community. An important contribution to the understanding of the problem in a wider context is made in this thesis, alongside proposals for short, mid and long term strategies for contrail avoidance. These are in particular the optimisation of the aircraft for contrail avoidance, the application of remotely induced heat to suppress contrail formation, and a novel engine concept that exhibits the potential for a reduction of all emissions simultaneously. Aircraft optimisation deals with the adaptation of existing technology for more environmentally compatible air transport, whereas the latter two approaches are breakthrough technologies of a more disruptive character covered by several patents resulting from this research. Short and mid term strategies are accompanied by an increase in carbon dioxide emissions. A study examining the long-term impact of aviation carbon dioxide emissions relative to that of contrails suggests that in order to achieve more sustainable air transport, the avoidance of contrails is inevitable. However, as the short-term impact of contrails is less severe, postponing contrail avoidance until the associated increase in carbon dioxide emissions is less significant could be a better way to deal with the problem.
Open Access
Design and engineering methods for open-rotor nacelle shaping
(Cranfield University, 2010-04) Zanenga, Erminio Samuele; Singh, R.
Due to the growing transport needs in emerging economies and recent success of the low-cost airlines, the demand for short/medium-haul aeroplanes is increasing. Within the next twenty years, the existing single-aisle aircraft are likely to be replaced by new models mounting new propulsion systems. One promising con- figuration being considered is the open-rotor, which is a revision of the propfan. However, further progress has to be done in order to transform propfan engines, whose technology dates back to the 1980s, into viable and feasible open-rotor con- cepts. Among the aspects yet to be investigated in su ficient depth is the de finition of a methodology for the open-rotor nacelle design. The aim of the present research is to help enhance the knowledge in this area. Even if there are a number of important fields of investigation for open-rotor designs, this work is limited to the analysis of the pusher architecture with no exhaust impingement through rotors. The research is initially performed combining both a graphical and a compu- tational approach, investigating the mathematical and physical aspects involved in the de finition of appropriate nacelle pro files, boundary conditions for the CFD analysis and simplifi ed rotor modelling. The first simulations are mainly focused on a typical propfan nacelle, which is taken as a reference model: the computations provide useful results for evaluating its aerodynamic features ... [cont.].
Open Access
Design of a decision support system for combined cycle schemes
(1998-01) Gayraud, S.; Singh, R.
The growing desire for sponsors of power generation projects to share risk with the lenders has promoted the use of computational tools, simulating and evaluating from a techno-economic viewpoint long-term, high-risk projects. Such models need to include reliable engine diagnostics, life cycle costing and risk analysis technique. This work consisted in designing a Decision Support System (DSS) for the assessment of power generation projects using industrial gas turbines in combined cycle. The software, programmed in Visual Basic in Excel in a windows-frame, runs an external application named Pythia, which has been developed by the Department of Propulsion, Power; Energy and Automotive Engineering at Cranfield University. It can perform gas turbine performance simulations, including off-design conditions, with or without degradation effects providing thus reliable engine diagnostics. Steam cycle models including different heat recovery steam generator configurations have been developed to simulate steam turbine design and off-design performance. Plant performance simulation takes into account off-design conditions, part-load governing strategies and degradation effects. Besides a robust economic mode and a life cycle costing model including maintenance planning assessments offer a wide range of possible operating and economic scenarios. The degree of uncertainty relating to technical and economic factors is assessed using normal distributions, and the level of risk is then evaluated using a risk analysis, technique based upon the Monte Carlo method. The DSS provides all sorts of charts and techno-economic figures in order to support the decision making through an effective user-friendly window-oriented interface.
Open Access
Design space exploration and performance modelling of advanced turbofan and open-rotor engines
(Cranfield University, 2013) Giannakakis, Panagiotis; Laskaridis, Panagiotis; Singh, R.
This work focuses on the current civil engine design practice of increasing overall pressure ratio, turbine entry temperature and bypass ratio, and on the technologies required in order to sustain it. In this context, this thesis contributes towards clarifying the following gray aspects of future civil engine development: the connection between an aircraft application, the engine thermodynamic cycle and the advanced technologies of variable area fan nozzle and fan drive gearbox. the connection between the engine thermodynamic cycle and the fuel consumption penalties of extracting bleed or power in order to satisfy the aircraft needs. the scaling of propeller maps in order to enable extensive open-rotor studies similar to the ones carried out for turbofan engines. The rst two objectives are tackled by implementing a preliminary design framework, which comprises models that calculate the engine uninstalled performance, dimensions, weight, drag and installed performance. The framework produces designs that are in good agreement with current and near future civil engines. The need for a variable area fan nozzle is related to the fan surge margin at take-o , while the transition to a geared architecture is identi ed by tracking the variation of the low pressure turbine number of stages. The results show that the above enabling technologies will be prioritised for long range engines, due to their higher overall pressure ratio, higher bypass ratio and lower speci c thrust. The analysis also shows that future lower speci c thrust engines will su er from higher secondary power extraction penalties. A propeller modelling and optimisation method is created in order to accomplish the open-rotor aspect of this work. The propeller model follows the lifting-line approach and is found to perform well against experimental data available for the SR3 prop-fan. The model is used in order to predict the performance of propellers with the same distribution of airfoils and sweep, but with di erent design point power coe cient and advance ratio. The results demonstrate that all the investigated propellers can be modelled by a common map, which separately determines the ideal and viscous losses.
Open Access
Design space exploration of distributed propulsion HALE UAVs burning liquid hydrogen.
(Cranfield University, 2015-11) Gallo, Luca; Laskaridis, Panagiotis; Singh, R.
High altitude long endurance (HALE) unmanned aerial vehicles (UAV) could serve as a platform to promote disruptive aircraft technologies in addition to set the stage to sustain week-long flights with electronic equipment. Hydrogen fuel is essential to meet the long-endurance requirement of low-speed HALE UAVs due to its high energy content per unit mass—2.8 times greater than that of kerosene. Hydrogen fuel could also be used to cryogenically cool the electric transmission system in a turbo-electric and/or hybrid-electric distributed propulsion system. This advanced propulsion system has the potential to affect all the aspects of a HALE UAV, from how much power is required to sustain flight to how power is produced, managed and distributed. However, in the literature there are no indications or design rules about how an integrated airframe/distributed propulsion system should be designed to maximise the integration synergies. The aim of this research was to identify a multi-disciplinary and multi-fidelity methodology for design space exploration studies of distributed propulsion low-speed HALE UAVs burning liquid hydrogen. The purpose of this methodology was to assess how the aircraft power requirement, production, management, and distribution are affected by the airframe selection, the distributed propulsion system and the energy management system. The results indicate that the slipstream-wing interaction of distributed propellers could increase the maximum endurance by nearly 60% on a tube-and-wing airframe for a given engine cycle. Superconductivity was assumed for the hydrogen-cooled electric transmission system that links the core engine to the distributed propulsors. These endurance benefits were three to four times greater than that of the series hybrid energy management strategy and of the wave rotor hybrid cycles. As such, the distributed propellers technology should be furthered investigated for both low-speed HALE UAVs and other low-Mach applications.
Open Access
Development of gas turbine combustor preliminary design methodologies and preliminary assessments of advanced low emission combustor concepts
(Cranfield University, 2012-07) Khandelwal, Bhupendra; Singh, R.; Sethi, Vishal
It is widely accepted that climate change is a very serious environmental concern. Levels of carbon dioxide (CO2) and other emissions in the global atmosphere have increased substantially since the industrial revolution and now increasing faster than ever before. There is a thought that this has already led to dangerous warming in the Earth’s atmosphere and relevant changes around. Emissions legislations are going to be stringent as the years will pass. Hydro carbon fuel cost is also increasing substantially; more over this is non- renewable source of energy. There is an urgent need for novel combustor technologies for reducing emission as well as exploring alternative renewable fuels without effecting combustor performance. Development of novel combustors needs comprehensive understanding of conventional combustors. The design and development of gas turbine combustors is a crucial but uncertain part of an engine development process. At present, the design process relies upon a wealth of experimental data and correlations. Some major engine manufacturers have addressed the above problem by developing computer programs based on tests and empirical data to assist combustor designers, but such programs are proprietary. There is a need of developing design methodologies for combustors which would lead to substantial contribution to knowledge in field of combustors. Developed design methodologies would be useful for researchers for preliminary design assessments of a gas turbine combustor. In this study, step by step design methodologies of dual annular radial and axial combustor, triple annular combustor and reverse flow combustor have been developed. Design methodologies developed could be used to carry out preliminary design along with performance analysis for conventional combustion chambers. In this study the author has also proposed and undertaken preliminary studies of some novel combustor concepts. A novel concept of a dilution zone less combustor has been proposed in this study. According to this concept dilution air would be introduced through nozzle guide vanes to provide an optimum temperature traverse for turbine blades. Preliminary study on novel dilution zone less combustor predicts that the length of this combustor would be shorter compared to conventional case, resulting in reduced weight, fuel burn and vibrations. Reduced fuel burn eventually leads to lower emissions. Another novel concept of combustor with hydrogen synthesis from kerosene reformation has been proposed and a preliminary studies has been undertaken in this work. Addition of hydrogen as an additive in gas turbine combustor shows large benefits to the performance of gas turbine engines in addition to reduction in NOx levels. The novel combustor would have two stages, combustion of ~5% of the hydrocarbon fuel would occur in the first stage at higher equivalence ratios in the presence of a catalyst, which would eventually lead to the formation of hydrogen rich flue gases. In the subsequent stage the hydrogen rich flue gases from the first stage would act as an additive to combustion of the hydrocarbon fuel. It has been preliminary estimated that the mixture of the hydrocarbon fuel and air could subsequently be burned at much lower equivalence ratios than conventional cases, giving better temperature profiles, flame stability limits and lower NOx emissions. The effect of different geometrical parameters on the performance of vortex controlled hybrid diffuser has also been studied. It has been predicted that vortex chamber in vortex controlled hybrid diffuser does not play any role in altering the performance of diffuser. The overall contribution to knowledge of this study is development of combustor preliminary design methodologies with different variants. The other contribution to knowledge is related to novel combustors with a capability to produce low emissions. Study on novel combustor and diffuser has yielded application of two patent applications with several other publications which has resulted in a contribution to knowledge. A list of research articles, two patents, awards and achievements are presented in Appendix C.
Open Access
Discretized Miller approach to assess effects on boundary layer ingestion induced distortion
(Elsevier, 2016-12-21) Valencia, Esteban; Hidalgo, Víctor; Nalianda, Devaiah; Laskaridis, Panagiotis; Singh, R.
The performance of propulsion configurations with boundary layer ingestion (BLI) is affected to a large extent by the level of distortion in the inlet flow field. Through flow methods and parallel compressor have been used in the past to calculate the effects of this aerodynamic integration issue on the fan performance; however high-fidelity through flow methods are computationally expensive, which limits their use at preliminary design stage. On the other hand, parallel compressor has been developed to assess only circumferential distortion. This paper introduces a discretized semi-empirical performance method, which uses empirical correlations for blade and performance calculations. This tool discretizes the inlet region in radial and circumferential directions enabling the assessment of deterioration in fan performance caused by the combined effect of both distortion patterns. This paper initially studies the accuracy and suitability of the semi-empirical discretized method by comparing its predictions with CFD and experimental data for a baseline case working under distorted and undistorted conditions. Then a test case is examined, which corresponds to the propulsor fan of a distributed propulsion system with BLI. The results obtained from the validation study show a good agreement with the experimental and CFD results under design point conditions.
Open Access
Effect of Combustor Geometry on Performance of Airblast Atomizer under Sub- Atmospheric Conditions
(2012-06-30T00:00:00Z) Grech, N.; Mehdi, A.; Zachos, Pavlos K.; Pachidis, Vassilios; Singh, R.
Open Access
Enabling alternate fuels for commercial aircraft
(Cranfield University, 2010-01) Daggett, D.; Singh, R.
The following reports on the past four years of work to examine the feasibility, sustainability and economic viability of developing a renewable, greenhouse-gas-neutral, liquid biofuel for commercial aircraft. The sharp increase in environmental concerns, such as global warming, as well as the volatile price fluctuations of fossil fuels, has ignited a search for alternative transportation fuels. However, commercial aircraft can not use present alternative fuels that are designed for ground transportation. Aircraft also have much longer service lives, are capital intensive to purchase, require a complex refueling infrastructure, and are specifically designed to use petroleum-type liquid jet fuels. Synthetic jet fuel, manufactured using a Fischer-Tropsch process from coal, is currently the only alternative jet fuel commercially available to aviation, but it presently experiences environmental challenges. Biojet fuels are currently not commercially available for aviation, but have the potential to become quite acceptable If passenger growth increases at 5%/year, it appears the only way that the aviation industry can meets its environmental goals of reducing CO2 emissions would be through commercialization of carbon-neutral fuels. This research shows that biojet fuels can be developed that do not compete with food or fresh water resources, will not lead to deforestation and will not cause other adverse environmental or social impacts. The approach of using a “drop in” jet fuel replacement, which would consist of a blend of kerosene and up to 50% biofuel will be possible for use in existing and future aircraft. A 60-80% lifecycle CO2 emission reduction is calculated for the biofuel portion with no performance degradation. New biofuel processing techniques (i.e. hydroprocessing, isomerization & distillation) and next generation feedstock sources (e.g. halophyte and algal biomass) appear to be the best pathways to enable the large scale deployment of sustainable and economically competitive biojet fuels in the near future.
Open Access
Evaluation and optimisation of environmentally friendly aircraft propulsion systems
(Cranfield University, 2010-04) Celis, Cesar; Sethi, Vishal; Singh, R.; Pilidis, Pericles
In this globalised world where the efficient transportation of people and goods greatly contributes to the development of a given region or country, the aviation industry has found the ideal conditions for its development, thereby becoming in one of the fastest growing economic sectors during the last decades. The continuing growth in air traffic and the increasing public awareness about the anthropogenic contribution to global warming have meant that environmental issues associated with aircraft operations are currently one of the most critical aspects of commercial aviation. Several alternatives for reducing the environmental impact of aircraft operations have been proposed over the years, and they broadly comprise reductions in the number of aircraft operations, changes in the type of aircraft, and changes in the aircraft operational rules and procedures. However, since the passenger traffic is expected to increase over the next years, only the last two options seem to be the most feasible solutions to alleviate the problem. Accordingly, the general aim of this research work is to develop a methodology to evaluate and quantify aircraft/engines design trade-offs originated as a consequence of addressing conflicting objectives such as low environmental impact and low operating costs. More specifically, it is an objective of this work to evaluate and optimise both aircraft flight trajectories and aircraft engine cycles taking into account multidisciplinary aspects such as performance, gaseous emissions, and economics. In order to accomplish the objectives proposed in this project, a methodology for optimising aircraft trajectories has been initially devised. A suitable optimiser with a library of optimisation algorithms, Polyphemus, has been then developed and/or adapted. Computational models simulating different disciplines such as aircraft performance, engine performance, and pollutants formation, have been selected or developed as necessary. Finally, several evaluation and optimisation processes aiming to determine optimum and ‘greener’ aircraft trajectories and engine cycles have been carried out and their main results summarised. In particular, an advanced, innovative gaseous emissions prediction model that allows the reliable calculation of emissions trends from current and potential future aircraft gas turbine combustors has been developed. When applied to a conventional combustor, the results showed that in general the emission trends observed in practice were sufficiently well reproduced, and in a computationally efficient manner for its subsequent incorporation in optimisation processes. For performing the processes of optimisation of aircraft trajectories and engine cycles, an optimiser (Polyphemus) has also been developed and/or adapted in this work. Generally the results obtained using Polyphemus and other commercially available optimisation algorithms presented a satisfactory level of agreement (average discrepancies of about 2%). It is then concluded that the development of Polyphemus is proceeding in the correct direction and should continue in order to improve its capabilities for identifying and efficiently computing optimum and ‘greener’ aircraft trajectories and engine cycles, which help to minimise the environmental impact of commercial aircraft operations. The main contributions of this work to knowledge broadly comprise the following: (i) development of an environmental-based methodology for carrying out both aircraft trajectory optimisation processes, and engine cycle optimisation-type ones; (ii) development of both an advanced, innovative gas turbine emissions prediction model, and an optimiser (Polyphemus) suitable to be integrated into multi-disciplinary optimisation frameworks; and (iii) determination and assessment of optimum and ‘greener’ aircraft trajectories and aircraft engine cycles using a multi-disciplinary optimisation tool, which included the computational tools developed in this work. Based on the results obtained from the different evaluation and optimisation processes carried out in this research project, it is concluded that there is indeed a feasible route to reduce the environmental impact of commercial aviation through the introduction of changes in the aircraft operational rules and procedures and/or in the aircraft/engine configurations. The magnitude of these reductions needs to be determined yet through careful consideration of more realistic aircraft trajectories and the use of higher fidelity computational models. For this purpose, the computations will eventually need to be extended to the entire fleet of aircraft, and they will also need to include different operational scenarios involving partial replacements of old aircraft with new environmentally friendly ones.
Open Access
Experimental and numerical investigation of a compressor cascade at highly negative incidence
(2011-03-31T00:00:00Z) Zachos, Pavlos K.; Grech, N.; Charnley, B.; Pachidis, Vassilios; Singh, R.
The performance prediction of axial flow compressors and turbines still relies on the stationary testing of blade cascades. Most of the blade testing studies are done for operating conditions close to the design point or in off-design areas not too far from it. However, blade-and consequently engine-performance remain unexplored at relatively far off-design conditions, such as windmilling or sub-idle. Such regimes are dominated by blade operation under extremely low mass flows and rotational speeds that imply highly negative values of incidence angle, thus totally separated flows on the pressure side of the blades. Those flow patterns are difficult to be measured and even more difficult to be numerically predicted as the current modelling capability of separated internal flows is of limited reliability. In this paper, the performance of a 3- dimensional linear compressor cascade at highly negative incidence angle is initially experimentally investigated. The main objective of the study is to derive the total pressure loss and outlet flow angle through the blades and use the data for the validation-calibration of a numerical solver enhancing its capability to predict highly separated flows. The development of the CFD model and the simulation strategy followedare also presented.The numerical results are compared against the derived test data demonstrating a good agreement. In addition, most trends of the properties of interest have been captured sufficiently, therefore the physical phenomena are considered to be well captured, allowing the numerical tool to be used for further studies on similar test cases.
Open Access
Experimental Study of Radiation From Coated Turbine blades
(Cranfield University, 1990-03) Husain Al-taie, Arkan Khilkhal; Singh, R.
The specific power (or specific thrust) of modern gas turbines is much influenced by the gas temperature at turbine inlet. Even with the use of the best superalloy available and the most advanced cooling configurations, there are competitive pressures to operate engines at even higher gas temperatures. Ceramic coatings operate as thermal barriers and can allow the gas temperature to be increased by 50 to 220 K over the operating gas temperature for an uncoated turbine . It is important that the surface temperature of the blade be determined as accurately as possible. Large uncertainties as to the surface temperature require significant margins for safe operation . Blade surface temperatures can be determined with an accuracy of 10 K using radiation pyrometry and about"30 to 40 K by calculating the blade temperature based on---gas temperature measurement of the exhaust gas plane. This'- makes pyrometry an attractive option for advanced high temperature gas turbines . However, there is little experience in measuring surface temperatures of blades coated with ceramic coatings. There is evidence that the. radiation signal picked up by the pyrometer will not only depend on the surface temperature but also on a number of optical properties of the coating. Important among these are the emissivity of the coating and whether the coating is translucent. Parameters affecting this are the coating material, coating surface finish, coating thickness and whether or not a bond coat is used . This work explores these variables in a rig that simulates the conditions within a turbine stage of a gas turbine engine. In which six thermal barrier coating systems were tested. These systems are of current interest to gas turbine manufacturers and users. They include the latest advances in coating technology. Four stabilized zirconia systems and two alumina based systems were tested. It was found experimentally that the surface emissivity of these coating systems was invariant over the range 873 to 1023 K surface temperature. It was found that the use of different stabilizers did not affect the surface spectral emissivity. In further experiments six turbine wheels were coated with these systems and tested at turbine entry temperatures of 973, 1073, and 1173 K. It was found that the blade surface temperature was function of the coating material, coating thickness and turbine entry temperature. The blade surface temperature was also function of the blade height being maximum at the blade tip and minimum at the blade root . It was found that the C-YPSZ was better insulator than the rest of the systems. Whilst the blades coated with zirconia based systems suffered minor loss near the edges, the two alumina based systems were lost from more than a blade during the test. This coating loss was picked up by. the pyrometer . Analysis shows that the measured blade surface temperature was within 10 K of that calculated. The use of 0.3 mm of C-YPSZ on air cooled turbine blades caused 250 K surface temperature increase and 270 K metal temperature decrease for turbine entry temperature of 1673 K. The metal temperature reduction was as high as 310 K for coating thickness of 0.5 mm.
Open Access
Fault diagnostics for advanced cycle marine gas turbine using genetic algorithm
(Cranfield University, 2003-08) Sampath, Suresh; Singh, R.
The major challenges faced by the gas turbine industry, for both the users and the manufacturers, is the reduction in life cycle costs , as well as the safe and efficient running of gas turbines. In view of the above, it would be advantageous to have a diagnostics system capable of reliably detecting component faults (even though limited to gas path components) in a quantitative marmer. V This thesis presents the development an integrated fault diagnostics model for identifying shifts in component performance and sensor faults using advanced concepts in genetic algorithm. The diagnostics model operates in three distinct stages. The rst stage uses response surfaces for computing objective functions to increase the exploration potential of the search space while easing the computational burden. The second stage uses the heuristics modification of genetics algorithm parameters through a master-slave type configuration. The third stage uses the elitist model concept in genetic algorithm to preserve the accuracy of the solution in the face of randomness. The above fault diagnostics model has been integrated with a nested neural network to form a hybrid diagnostics model. The nested neural network is employed as a pre- processor or lter to reduce the number of fault classes to be explored by the genetic algorithm based diagnostics model. The hybrid model improves the accuracy, reliability and consistency of the results obtained. In addition signicant improvements in the total run time have also been observed. The advanced cycle Intercooled Recuperated WR2l engine has been used as the test engine for implementing the diagnostics model.
Open Access
Gas turbine combustor modelling for design
(Cranfield University, 1988-02) Murthy, J. N.; Singh, R.
The design and development of gas turbine combustors is a crucial but uncertain part of an engine development process. Combustion within a gas turbine is a complex interaction of, among other things, fluid dynamics, heat and mass transfer and chemical kinetics. At present, the design process relies upon a wealth of experimental data and correlations. The proper use of this information requires experienced combustion engineers and even for them the design process is very time consuming. Some major engine manufacturers have attempted to address the above problem by developing one dimensional computer programs based on the above test and empirical data to assist combustor designers. Such programs are usually proprietary. The present work, based on this approach has yielded DEPTH, a combustor design program. DEPTH ( Design and Evaluation of Pressure, Temperature and Heat transfer in combustors) is developed in Fortran-77 to assist in preliminary design and evaluation of conventional gas turbine combustion chambers. DEPTH can be used to carry out a preliminary design along with prediction of the cooling slots for a given metal temperature limit or to evaluate heat transfer and temperatures for an existing combustion chamber. Analysis of performance parameters such as efficiency, stability and NOx based on stirred reactor theories is also coupled. DEPTH is made sufficiently interactive/user-friendly such that no prior expertise is required as far as computer operation is concerned. The range of variables such as operating conditions, geometry, hardware, fuel type can all be effectively examined and their contribution towards the combustor performance studied. Such comprehensive study should provide ample opportunity for the designer to make the right decisions. It should also be an effective study aid. Returns in terms of higher thermal efficiencies is an incentive to go for combined cycles and cogeneration. In such cases, opting for higher cycle pressures together with a second or reheat combustor promise higher thermal efficiencies and exhaust temperatures and hence such designs are likely to be of interest. The concepts that are needed for understanding a double or reheat combustor are also addressed using the programme. A specific application of the programme is demonstrated through the design of a double combustor.
Open Access
Gas turbine engine and sensor fault diagnosis
(Cranfield University, 1999-11) Zedda, M.; Singh, R.
Substantial economic and even safety related gains can be achieved if effective gas turbine performance analysis is attained. During the development phase, analysis can help understand the effect on the various components and on the overall engine performance of the modifications applied. During usage, analysis plays a major role in the assessment of the health status of the engine. Both condition monitoring of operating engines and pass off tests heavily rely on the analysis. In spite of its relevance, accurate performance analysis is still difficult to achieve. A major cause of this is measurement uncertainty: gas turbine measurements are affected by noise and biases. The simultaneous presence of engine and sensor faults makes it hard to establish the actual condition of the engine components. To date, most estimation techniques used to cope with measurement uncertainty are based on Kalman filtering. This classic estimation technique, though, is definitely not effective enough. Typical Kalman filter results can be strongly misleading so that even the application of performance analysis may become questionable. The main engine manufactures, in conjunction with research teams, have devised modified Kalman filter based techniques to overcome the most common drawbacks. Nonetheless, the proposed methods are not able to produce accurate and reliable performance analysis. In the present work a different approach has been pursued and a novel method developed, which is able to quantify the performance parameter variations expressing the component faults in presence of noise and a significant number of sensor faults. The statistical basis of the method is sound: the only accepted statistical assumption regards the well known measurement noise standard deviations. The technique is based on an optimisation procedure carried out by means of a problem specific, real coded Genetic Algorithm. The optimisation based method enables to concentrate the steady state analysis on the faulty engine component(s). A clear indication is given as to which component(s) is(are) responsible for the loss of performance. The optimisation automatically carries out multiple sensor failure detection, isolation and accommodation. The noise and biases affecting the parameters setting the operating point of the engine are coped with as well. The technique has been explicitly developed for development engine test bed analysis, where the instrumentation set is usually rather comprehensive. In other diagnostic cases (pass off tests, ground based analysis of on wing engines), though, just few sensors may be present. For these situations, the standard method has been modified to perform multiple operating point analysis, whereby the amount of information is maximised by simultaneous analysis of more than a single test point. Even in this case, the results are very accurate. In the quest for techniques able to cope with measurement uncertainty, Neural Networks have been considered as well. A novel Auto-Associative Neural Network has been devised, which is able to carry out accurate sensor failure detection and isolation. Advantages and disadvantages of Neural Network-based gas turbine diagnostics have been analysed.
Open Access
Gas turbine engine control and performance enchancement with fuzzy logic
(Cranfield University, 1998-09) Keng, W.; Singh, R.
Gas turbine engine performance improvement has been requested continuously for both military and commercial applications due t various reasons. One of the issues is to save fuel and/or to increase the engine life to meet the multi-mission and operation cost economics requirements. I order to satisfy the customers' requirements, the engine manufacturers invested a lot of money and time if the gas turbine performance improvement. The most straight forward and simple approach is to trade the excess remained surge margins for performance. NASA has demonstrated the feasibility of this concept in their F-15 Highly Integrated Digital Electronic Control and Performance Seeking Control programs. It offers not only obvious benefits if the overall system performance improvement but also cost effective operations such a fuel saving and extended component life. Those were carried out with traditional control approaches which have to face the modelling difficulties. ' Due to successful control implementations of fuzzy logic if various environment of uncertainties, a proportional plus integral z logic controller if proposed. The fuzzy logic control system simulation results prove that the fuzzy logic controller is appropriate for gas turbine engine control. Basic fuzzy logic control concept is used with new approaches to simplifying the fuzzy logic controller. I order to enhance the engine performance, fuzzy logic control concept is used to optimize the engine performance parameters. A time function linear control scheme is proposed to the engine to a new operation location System simulation results prove the new methodology. It has to be understood that the engine model used if this research is not representative of a gas turbine, but it `is appropriate for the fuzzy logic control design analysis and simulation.

Browsing by Author "Singh, R."

Results Per Page

Sort Options