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1
Бушнов, Валерий Васильевич. "Усовершенствование процессов сгорания и систем топливоподачи энергетических установок, работающих на металлизированных борсодержащих топливах." Thesis, Харьковский национальный автомобильно-дорожный университет, 2017. http://repository.kpi.kharkov.ua/handle/KhPI-Press/26557.
Full textAbstract:
Диссертация на соискание научной степени кандидата технических наук по специальности 05.05.03 – Двигатели и энергетические установки. – Национальный технический университет "Харьковский политехнический институт". – Харьков, 2017.
Диссертация посвящена решению вопросов улучшения характеристик и параметров систем топливоподачи металлизированных топлив на основе выявления физико-технических закономерностей предпламенного окисления и горения таких топлив, а также разработке алгоритма структурно-параметрической оптимизации систем топливоподачи энергетических установок для обеспечения их высокой эффективности. Перспективным направлением создания новых образцов техники является разработка энергетических установок, которые используют высокоэффективные энергоемкие металлизированные топливные композиции. При их создании очень важным является знание соответствующих аспектов взаимодействия реагирующих топливных композиций и методологии структурно-параметрической оптимизации систем топливоподачи. Поэтому актуальными направлениями исследований являются: изучение физико-технических закономерностей горения таких композиций, разработка алгоритма оптимизации систем топливоподачи высокоэнергетичных металлизированных топливных композиций и создание новых методов для их исследования. В диссертационной работе выявлены порог воспламенения в гетерофазных разветвленно-цепных процессах и смена характеристик горения бора в зависимости от его аллотропных модификаций, определена их энергия активации; установлена зависимость уровня сложности структур топливоподачи в соответствии с уровнем технизации; разработан алгоритм структурно-параметрической оптимизации систем топливоподачи энергетических установок, работающих на металлизированном топливе. Предложен метод экспериментального бесконтактного количественного измерения продуктов сложных химических реакций с высокой чувствительностью за счет применения резонансно-флуоресцентной спектроскопии. Для экспериментального исследования макрокинетических характеристик топливных компонентов энергетических установок использован термогравиметрический метод. Усовершенствован химический состав топлив за счет ввода в него аллотропных модификаций бора и других компонентов металлизированных топливных композиций. Разработана многомерная классификация указанных систем и экспериментально оценена их эффективность. Синтезированы системы подачи металлизированых топлив с разными уровнями регулирования. Экспериментальная проверка синтезированных систем показала: рост функциональных возможностей в 2–3 раза, увеличение количества элементов структур до 18, повышение полноты сгорания на 11 %, рост скорости сгорания и удельной объемной теплоты сгорания, соответственно на 33% и 2,7%, а также снижение энергии активации на 71% и температуры загорания на 22%.Thesis for obtaining the degree of Candidate of Technical Sciences in Specialty 05.05.03 – Engines and Power Plants. – National Technical University "Kharkov Polytechnic Institute". – Kharkiv, 2017. The thesis presents the issues of development of features and parameters of metal-backer fuel supply systems for power plants on the basis of detection of physical and technical patterns of metal-backer fuel burning and elaboration of the structural and parametric algorithm of power plant efficiency. The study of kinetic features of metal-backer fuels of different composition has been conducted and the main patterns of metal-backer fuel burning have been found. Physical and chemical process of metal-backer boron fuel burning has been explored. The method of structural and parametric optimization of metal-backer fuel supply systems has been elaborated. The metal-backer fuel supply systems with different levels of fuel supply regulation have been synthesized. Operating parameters have been experimentally determined and efficiency of the synthesized fuel supply systems has been assessed.
2
Бушнов, Валерій Васильович. "Вдосконалення процесів згоряння та систем паливоподачі енергетичних установок, що працюють на металізованих боромістких паливах." Thesis, НТУ "ХПІ", 2017. http://repository.kpi.kharkov.ua/handle/KhPI-Press/26489.
Full textAbstract:
Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.05.03 – Двигуни та енергетичні установки. – Національний технічний університет "Харківський політехнічний інститут". – Харків, 2017.
Дисертація присвячена питанням покращення характеристик та параметрів СППМП на основі виявлення фізико-технічних закономірностей горіння металізованих палив і розробки алгоритму структурно-параметричної оптимізації енергетичних установок для забезпечення їх високої ефективності. Проведено дослідження кінетичних характеристик металізованих палив різного складу та виявлені основні закономірності горіння металізованих палив. Досліджено фізико-хімічний процес горіння боромістких металізованих палив. Розроблено метод структурно-параметричної оптимізації систем паливоподачі металізованих палив. Синтезовані системи СППМП з різними рівнями регулювання процесів паливоподачі. Експериментально визначені експлуатаційні характеристики та оцінена ефективність роботи синтезованих систем паливоподачі.Thesis for obtaining the degree of Candidate of Technical Sciences in Specialty 05.05.03 – Engines and Power Plants. – National Technical University "Kharkov Polytechnic Institute". – Kharkiv, 2017. The thesis presents the issues of development of features and parameters of metal-backer fuel supply systems for power plants on the basis of detection of physical and technical patterns of metal-backer fuel burning and elaboration of the structural and parametric algorithm of power plant efficiency. The study of kinetic features of metal-backer fuels of different composition has been conducted and the main patterns of metal-backer fuel burning have been found. Physical and chemical process of metal-backer boron fuel burning has been explored. The method of structural and parametric optimization of metal-backer fuel supply systems has been elaborated. The metal-backer fuel supply systems with different levels of fuel supply regulation have been synthesized. Operating parameters have been experimentally determined and efficiency of the synthesized fuel supply systems has been assessed.
3
Naeem, Muhamma. "Implications of aero-engine deterioration for a military aircraft's performance." Thesis, Cranfield University, 1999. http://hdl.handle.net/1826/3397.
Full textAbstract:
World developments have led the armed forces of many countries to become more
aware of how their increasingly stringent financial budgets are spent. Major expenditure
for military authorities is upon aero-engines. Some in-service deterioration in any
mechanical device, such as an aircraft's gas-turbine engine, is inevitable. However, its
extent and rate depend upon the qualities of design and manufacture, as well as on the
maintenance/repair practices followed by the users. Each deterioration has an adverse
effect on the performance and shortens the reliable operational life of the engine thereby
resulting in higher life cycle costs. The adverse effect on the life-cycle cost can be reduced
by determining the realistic fuel and life-usage and by having a better knowledge of the
effects of each such deterioration on operational performance. Subsequently improvements
can be made in the design and manufacture of adversely-affected components as well as
with respect to maintenance / repair and operating practices.
For a military aircraft's mission-profiles (consisting of several flight-segments),
using computer simulations, the consequences of engine deterioration upon the aircraft's
operational-effectiveness as well as fuel and life usage are predicted. These will help in
making wiser management decisions (such as whether to remove the aero-engines from the
aircraft for maintenance or to continue using them with some changes in the aircraft's
mission profile), with the various types and extents of engine deterioration. Hence
improved engine utilization, lower overall life-cycle costs and the optimal mission
operational effectiveness for a squadron of aircraft can be achieved.
4
Ulizar, Alvarez J. I. "Simulation of multi fluid gas turbines." Thesis, Cranfield University, 1998. http://hdl.handle.net/1826/3537.
Full textAbstract:
This work focuses on two main subjects: first, the development and validation
of a robust generic performance code for industrial gas turbines (GTSI) and, second,
the study of an innovative carbon dioxide/argon semi-closed cycle burning low
calorific gas coming from coal gasification. GTSI will be able to simulate open,
closed and semi-closed cycles at design and off-design conditions.
A comprehensive thermodynamic study of the properties of the most common
working fluids has been carried out, introducing the results in GTSI for a wide range
of temperatures and pressures, being easy to add other gases.
To make the code very general, in addition to gas turbines conventional
components, such as inlet, compressor,, intercooler, regenerator, combustor, turbine
and exhaust system, GTSI can model evaporative intercooler, steam injection and
reheat. The possibility of variable geometry was introduced in the compressor, steam
injector and turbine modules. Given the high temperatures in modem and future
turbines, a detailed cooling system modeling has been developed, being able to
predict cooling flow requirements according to different technology levels. The
control of the complete power plant has also been considered in detail, allowing the
user to select among different options. The code incorporates a simple steam turbine
bottoming cycle for a preliminary analysis of the combined cycle arrangement. In
addition to the conventional off-design simulations it is possible to carry out studies
involving engine deterioration and modification, or substitution, of components.
A validation process was carried out using different gas turbine arrangements.
The result has been satisfactory, although additional configurations should be
examined when more data is available.
As a direct application of GTSI, the conceptual design of the carbon
dioxide/argon semi-closed cycle was conducted. Several key performance factors
were considered in this study, such as the working fluid composition, the gas turbine
arrangement and the cooling technology. Other main parameters were selected
according to the state-of-the-art technology. Advanced concepts such as cryogenic
precooling and turbine stator internal cooling, together with improved component
efficiencies and higher temperatures were contemplated for a mid-long term future
design. The results obtained for the conventional cycles have not been very
promising, with slightly better values for the advanced cycles. Five of the most
interesting cycles were selected for off-design studies, evaluating the part-power
behaviour, the variable geometry requirement, etc. To complete the investigation, the
starting sequence of one of them was performed. Also, considering the possibility of
using existing turbomachinery, designed for air, in a semi-closed cycle pilot plant, the
operation of several gas turbine configurations was analysed.
5
Engelbrecht, Geoffrey E. "Modelling of premixed combustion in a gas turbine." Thesis, Cranfield University, 1998. http://hdl.handle.net/1826/3987.
Full textAbstract:
Three steady state combustion models, two turbulence models and a model for tK'6
prediction of NO., were implemented and investigated on a simple backward facing
step experiment as well as an experimental lean prevaporised premixed (LPP)
combustor. The three combustion models included the simple Eddy Break-up model
as well as a presumed probability density function (pdf) model and a form of the BML
crossing frequency flamelet model. These models were adapted to consider a
variable mixture fraction to account for a non-homogeneous fuel air mixture. The
two turbulence models used were the k-e and second moment models.
Despite being unable to capture the flame front spreading in the case of the
backward facing step, these predictions provided insight into the performance and
implementation of the models. All three of the combustion models, after appropriate
tuning, worked well for the LPP test combustor. This illustrates that such time
averaged models are useful for flows which do not contain large transient coherent
structures, such as that of the LPP test combustor and most practical engine
combustors designed today. The second moment closure turbulence model was
found to have the greatest impact on the flame front through the flow field predictions
rather than through counter gradient diffusion. The Eddy Break-up and BML
crossing frequency models both performed very well, qualitatively predicting the
correct trends. The additional consideration of flame front straining in the BML
crossing frequency model did not appear to significantly influence the flame front.
This is because the type of model adopted to predict this effect had a relatively
uniform influence everywhere in the flow. The presumed pdf model also performed
well and was additionally found to self ignite without the existence of hot products
when the inlet temperature was high enough. The NO., model faired well for a simple
experimental geometry. However, it considerably over predicted the NO., formed
within the LIPP test combustor, which was most probably due to poor boundary
conditions. Despite this overprediction, the results give insight into how to improve
the NQ, emissions for the experimental combustor.
6
Matthews, Alexander J. "Scramjet intakes." Thesis, University of Oxford, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.400217.
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Kim, Sogkyun. "Fuzzy modelling and control for gas turbine altitude relighting." Thesis, University of Sheffield, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.421225.
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8
Castres, Fabrice. "Mode detection in turbofan inlets." Thesis, University of Southampton, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.438539.
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9
Reveille, T. "Study of fuel injection and mixture formation for a gasoline direct injection engine." Thesis, Cranfield University, 2005. http://hdl.handle.net/1826/4288.
Full textAbstract:
Future requirements for lower automotive emissions have lead to the development of
new internal combustion (IC) engine technologies. Gasoline Direct Injection (GDI), for
example, is one of these promising new IC engine concepts. It offers the opportunity of
increased efficiency through unthrottled operation. However, the realisation of this
concept is critically dependent on the in-cylinder mixture formation, especially in the
late injection/lean operation mode. Ideally, this would require a precise stratification of
the in-cylinder fuel-air mixture in 3 distinct zones: an ignitable pocket located at the
spark plug, surrounded by a stoichiometric mixture of fuel and air, encompassed by air.
To enable this stratification, the GDI concept utilises advanced injector technology.
Phase Doppler Anemometry (PDA), Planar Laser-Induced Fluorescence (PLIF) and the
combination of PLIF and Mie scattering in the Laser-Sheet Dropsizing (LSD)
technique, have been applied to sprays in the past to obtain dropsize information and
study the mixture formation process. These new GDI sprays are denser, their droplet
sizes are smaller and they evaporate faster, and as such, place us at the limit of the
validity of these measurements techniques.
The diagnostics were applied to a GDI spray in a pressure vessel for realistic in-cylinder
conditions, ranging from supercooled to superheated environments. Tracer evaporation
issues in the PLIF technique were resolved by using a dual tracer system. The study
showed that the LSD technique provided good quantitative data in low evaporation
regimes. In highly evaporating regimes, the technique still gave reliable dropsize data
for the early stages of the injection, but was limited afterwards by vapour-phase
contribution to the fluorescence signal. Variations between PDA data and LSD results
also suggested a deviation of the Mie scattering signal from the assumed d2 dependence.
This was further investigated and was found to be true for small droplets (d/?. <0.2). This
source of error might be improved by using a different observation angle. High density
seriously compromises the accuracy of PDA, whilst its effect through multiple
scattering is of second order for the LSD technique. In low evaporating regimes, LSD has the overall advantage of being a 2-D measurement
technique, and will yield data with a maximum error of 30% in dense parts of the spray
where PDA data is totally unreliable. If the spray evaporates quickly, PLIF by itself is
an appropriate tool for following the air-fuel mixture, because short droplet lifetimes
limit the 2-phase flow behaviour of the spray.
Particle Image Velocimetry (PIV), the LSD technique and equivalence ratio LIF
measurements were applied to a BMW single cylinder optical GDI engine. The early
injection operation showed no particular issues. However, the results obtained in the late
injection highlighted the poor mixing and inappropriate stratification.
10
Karaiskos, Ilias-Efstratios. "Spray structure and mixture distribution in direct-injection gasoline engines." Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.417137.
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Cao, Li. "Numerical study of controlled auto-ignition combustion in port and direct fuel injection gasoline engines." Thesis, Brunel University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.422419.
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WyszynÌski, Åukasz P. "Investigation of combustion processes in a direct injection spark ignition engine." Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398260.
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Ashurst, Colin. "Realising benefits from IS/IT : exploring the practices and competences required to succeed." Thesis, Loughborough University, 2007. https://dspace.lboro.ac.uk/2134/10727.
Full textAbstract:
The primary driver for this research was the continuing high failure rate of investments in IS/IT which has stayed at around 70-80% for over 30 years. The aim of this research was to explore the extent to which organisations have adopted benefits driven practices when undertaking investments in IS/IT. An initial phase of the research was primarily based on detailed documentation on 25 projects taken from the knowledge management database of an IS/IT consultancy. A second phase comprised in-depth case studies at three organisations. This phase explored the practices adopted on three or four projects at each organisation and importantly the wider organisational context in which the projects took place. An important contribution from this research has been the development of a framework of competences and practices for the realisation of benefits from investments in IS/IT. The empirical elements of the study then go well beyond recent survey-based research, by providing in-depth insights into the practice of benefits realisation, across a variety of organisations. The empirical study showed that benefits-related practices are very rarely adopted. The research has also provided evidence of the value of the practices 'lens', which is shown to provide a valuable way to operationalise competences, as it fits very well with how people think and work. The thesis provides some concrete suggestions as to how the practice of benefits realisation might best be improved.
14
Kalian, Navin. "Investigation of CAI/SI operations ina a four-cylinder direct injection gasoline engine." Thesis, Brunel University, 2006. http://bura.brunel.ac.uk/handle/2438/5482.
Full textAbstract:
A four-cylinder, four-stroke, gasoline engine with direct injection fuel was commissioned and used to achieve CAI combustion. CAI combustion was achieved by employing short-duration, low-lift camshafts and early exhaust valve closure. Trapping sufficient volumes of exhaust residual provided the necessary thermal energy needed to initiate auto-ignition. The effects of valve opening durations on the CAI operation range were investigated at different air/fuel ratios, valve timings and injection timings. Furthermore the effect on engine performance, exhaust emissions, fuel consumption and combustion characteristics were also investigated. Methods which could be used for CAI combustion region enlargement were also studied. These included spark-assisted CAI at different EVC timings and valve durations, CAI operation at 2000 rpm and CAI combustion at late fuel injection timings
15
Fleck, B. J. "Computer simulation and evaluation of design parameters in a high performance two-stroke engine." Thesis, Queen's University Belfast, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.411227.
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Wang, Shiwei. "Advanced air fuel ratio control of automotive si engines." Thesis, Liverpool John Moores University, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.438766.
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17
Alrefae, Waleed H. "Combustion studies in an optically accessed gasoline direct injection engine." Thesis, University of Leeds, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.439607.
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Suyabodha, Apiwat. "Simulation of cyclic variability in gasoline engine under cold start conditions." Thesis, University of Bath, 2012. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.555749.
Full textAbstract:
Emissions from gasoline engines remain an important issue worldwide as they are both harmful to health and contribute to green house effects especially under cold start conditions. A major challenge of the automotive industry is to reduce harmful emissions as much as possible whilst continuing to reduce CO2 emissions. Three-way-catalytic converters have been used very successfully to convert the harmful gases before release to the environment but these devices have to reach their light-off temperature in order to activate the chemical reactions. Therefore, the conversion time is delayed and during the pre light-off period, high levels of emissions are released. An investigation into methods capable of increasing catalyst temperature under cold start conditions has been carried out. The most beneficial technique used in this research was the secondary air method. The method introduced extra air into the exhaust manifold which allowed the engine to run rich and then the residual unburned fuel to be oxidised in the exhaust before approaching the converter. An experiment following a Box- Behnken design was used to study the effect of engine speed, spark angle, load, relative air/fuel ratio (lambda) and secondary air flow on pre-catalyst temperature. The study suggested the best result for the engine studied was to achieve fast catalytic light-off time was to run engine at 1225 rpm, spark angle of 0 degree BTDC, lambda of 0.82 and load of 0.5 bar BMEP. These settings allowed the remaining fuel to be burned with 5.87 kg/hr of secondary air in the exhaust manifold to achieve a pre-catalytic temperature of 631.1 QC and achieve light-off for all emissions within 17.2 seconds. The results were also used to build a temperature prediction model using the Matlab MBC toolbox and the best available model gave an R2 of 0.9997 by using radial base functions (RBF). However, the optimum conditions still produced cyclic variation in the combustion, giving an average COVimep of 14.8% during the pre-catalytic heating period which caused problems concerning engine smoothness. To derive a greater insight into the mechanisms governing the cyclic variability observed a simulation study was undertaken. The study used a simulation using Ricardo WAVE and Matlab Simulink to allow a detailed representation of some of the principle mechanisms giving rise to cyclic variability under cold start conditions. The study included combustion under rich and lean mixtures and considered the effect of variations of air/fuel ratios and residual gas fraction. As a result, the simulation showed a similar characteristic variability of heat release to that observed experimentally. The validation of the model for heat release showed that the predictions were under estimated by 0.49 % while under lean combustion, there was an under estimation of 2.07%. Both predictions had normally distributed residuals. The model suggested that the residual gas fractions were higher than the limit of 8.8% (under rich fuelling) or 8.0% (under lean fuelling) that was predicted to cause ignition delay to increase significantly and therefore contribute to high cyclic variability. ' An optimisation was carried out by varying camshaft angle in the simulation. The results suggest that retarding the exhaust camshaft position by 4 degrees (EVC 12 degrees BTDC) could reduce COVimep by 63.2% under rich combustion. In contrast, advancing the intake camshaft position suggested that the COVmep can be reduced but more experimental data is required to validate the results because variation of intake camshaft positions had a larger impact on pumping work than varying exhaust camshaft positions. These additional pumping losses result in higher air and fuel flow requirements. In summary, this thesis describes a detailed investigation into the effects of engine calibration on catalyst heating performance. One of the limiting factors in achieving rapid light-off is combustion variability. Extensions have been introduced to an industry standard ID engine simulation to allow realistic cyclic variability to represented and developed. These tools could allow cyclic variability to be considered more rigorously during a calibration exercise.
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Bale, Christopher J. C. "The application of advanced spark-ignition engine combustion systems for high-performance and a better environment." Thesis, Loughborough University, 2007. https://dspace.lboro.ac.uk/2134/36018.
Full textAbstract:
This is a thesis that brings together work conducted over a thirty year period concerning the research, development and knowledge management of high perfonnance and low exhaust emission engines. The thesis includes nine published and refereed works that are discussed and appended. Internal combustion engines translate the chemical energy of a fuel into mechanical work by burning the fuel with air in a combustion chamber. It is demonstrated that this process can be improved beneficially with respect to power output, fuel economy and exhaust emissions, by efficient cylinder filling and the generation of enhanced charge motion characteristics at the point of ignition. The advantages of multivalve engines, particularly with 5-valves per cylinder, and the methods of producing and measunng good air flow and beneficial amounts of tumble or barrel swirl, are described. Two patents and three novel research techniques for air flow and air motion are presented and discussed. The combustion developments carried out by the author for competition and high-perfonnance road cars are presented as examples of the application of the theory and research.
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Twiney, Benjamin W. G. "Investigation of combustion robustness in catalyst heating operation on a spray guided DISI engine." Thesis, University of Oxford, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.558407.
Full textAbstract:
The cold start catalyst warm-up operation is seen as one of the most important modes in Direct Injection Spark Ignition (DISI) Engine operation. When the catalyst is cold the engine out emissions become the tailpipe out emissions, so it is vital for the catalyst to obtain its working temperature as quickly as possible. A very high exhaust temperature can be achieved with a very retarded ignition - the engine can be made to operate at no load with a close to wide open throttle. With a retarded ignition, a split injection strategy has been shown to improve combustion stability which is critical for the trade-off between tailpipe emissions and vehicle idle stability. The spray guided DISI engine has a multi- hole injector centrally located in the chamber with the spark plug. For catalyst heating operation, the first injection occurs during induction, which forms a relatively well mixed but lean mixture in the cylinder before ignition, and the second injection occurs close to a retarded ignition, which produces a stratified fuel rich mixture in the central region of the combustion chamber near the spark plug. Combustion initialization is found to be sensitive to spark plug protrusion and orientation, injector orientation and 2nd injection timing relative to ignition. High tension current and voltage measurements have been taken in order to characterize the effect of the 2nd injection timing on both the breakdown and the glow phase of the arc discharge. Both phases are shown to be influenced by the timing of the 2nd injection. The richer mixture causes the breakdown voltage to increases while the airflow entrained in the 2nd injection has been shown to stretch the spark and in the worst case extinguish it prematurely. In-cylinder spray imaging by Mie scattering has been taken with frame rates up to 6000 fps, with high speed video photography of chemiluminescence and soot thermal radiation. Tests have studied the effect of the spark plug orientation and injector orientation, with timing sweeps for the phasing of the second injection. The images show interaction of a fuel jet with the earth electrode, stretching of the arc, variable location for the start of combustion and significant cycle-by-cycle variations with the same operating point leading to normal combustion, slow combustion and misfiring cycles. Spectroscopic measurements have confirmed the presence of OH *, CH * and C2*; emissions lines, and their relative magnitude compared to soot radiation. Filtering for CH * has been used with a photo-multiplier tube. These signals show the arc discharge, the delay between the arc and the kernel growth and (depending on the timing of the 2nd injection) small kernels which do not subsequently fully develop and can cause misfiring cycles. Unburned hydrocarbon emissions have been measured with a fast-response FID, so that emissions can be related to: misfiring cycles, slow burning cycles (0 < GMEP <0.5), and normal cycles. These measurements show that only the misfiring cycles lead to significant unburnt hydrocarbon emissions. The misfire mechanism depends on the timing of the 2nd injection. When the 2nd injection ends at the spark, no kernel is seen for a misfiring cycle. However, a kernel is shown to grow in the lean background mixture indicating that the misfire mechanism, when the 2nd injection ends close to the spark, is that the local air/fuel ratio is too rich for the onset of combustion. However, when the 2nd injection is significantly retarded from the spark a different misfire mechanism is present. A small kernel is shown to exist between the spark and the arrival of the fuel from the 2nd injection. For the misfiring cycle, this kernel is extinguished early, possibly due to an interaction between the kernel and the 2nd injection.
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Smith, Oliver Mark Edward. "In-cylinder fuel and lubricant effects on gasoline engine friction." Thesis, University of Leeds, 2007. http://etheses.whiterose.ac.uk/4716/.
Full textAbstract:
The purpose of the research reported in this thesis was to investigate the viability and quantify the potential gains of improving fuel economy of the gasoline engine through strategic application of additives. An increased awareness of the link between greenhouse gas emissions and global warming means that there is a desire to reduce carbon dioxide emissions from transportation. There is therefore a growing emphasis on improving the fuel economy performance of vehicles. The addition of friction modifier additives to the fuel is one way to achieve this. Using bespoke in-cylinder sampling techniques, an understanding of the operation of the piston assembly, a system responsible for much of the power loss in the internal combustion engine, is developed. Validation is given to the hypothesis that fuel economy gains can be achieved through the application of friction modifier administered to the engine via the gasoline. Results show gasoline administered friction modifier additive can accumulate in the piston assembly lubricant at levels 77 times greater than the initial fuel treatment level. The performance of a large number of friction modifier additives were uniquely screened in a novel bench-top test which simulated the arduous in-cylinder conditions found in a firing gasoline engine. The test generated vast amounts of information which led to high performance formulations capable of reducing the friction coefficient in both the boundary and mixed lubrication regimes by around 50% when compared with the result for the base oil alone. Surface analysis techniques were also employed 0!l engineering surfaces coated with friction modifier additives and add to the knowledge of their mechanism of action. Finally a series of engine tests were conducted which prove the effectiveness of friction modifier administered to the engine via the gasoline. A fuel economy improvement of approximately 2% was seen where friction modifier gasoline was employed. Application of successful technology such as this is shown to correspond to the projected saving of around 502 million litres of gasoline and 388,000 tonnes of carbon (C02) per year in the UK alone.
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Mufti, Riaz Ahmad. "Total and component friction in a motored and firing engine." Thesis, University of Leeds, 2004. http://etheses.whiterose.ac.uk/5354/.
Full textAbstract:
Engine developers and lubricant formulators are constantly improving the performance of internal combustions engines by reducing the power losses and emissions. The majority of the mechanical frictional losses generated in an engine can be attributed to the main tribological components of an engine, the valve train, piston assembly and engine bearings. However no single method has been developed to measure the friction loss contribution of each component simultaneously in a firing engine. Such results would be invaluable to the automotive/lubricant industries, research institutions and for validating predictive mathematical models for engine friction. The main focus of the research reported in this thesis was to validate an engine friction mathematical model called FLAME, developed in a separate study at Leeds. The validation was achieved by experimentally characterising the frictional losses generated from the major tribological components of a single cylinder gasoline engine. A novel experimental system was developed to evaluate experimentally, frictional losses in all the three main tribological components of an engine under fired conditions. A specially designed pulley torque transducer was used to measure valve train friction whereas improved IMEP method was adopted to measure piston assembly friction. For the very first time bearing friction was determined experimentally in a fired engine indirectly by measuring total engine friction. The FLAME engine friction model predicted valve train friction of the same order as the experimental data at engine speeds of 1500rpm and above. However, there was a much-reduced sensitivity to engine speed and temperature in the predictions. The piston assembly predicted results correlated very well with the measured data especially at lubricant inlet temperature of 80°C whereas for the bearing friction, the predicted results obtained with the short bearing approximation for the 1t film case were very close to the measured values. Overall the predicted total engine power loss results showed a good correlation with the experimental data especially at high lubricant inlet temperatures and engine speeds. It was concluded that the predicted results were in good agreement with the experimental results and the comparison validated the FLAME engine friction model.
23
Mohamed, Caroline. "Autoignition of hydrocarbons in relation to engine knock." Thesis, University of Leeds, 1997. http://etheses.whiterose.ac.uk/4197/.
Full textAbstract:
A single piston Rapid Compression Machine (RCM) has been used to investigate the autoignition of hydrocarbons under conditions of temperature and pressure similar to those which occur in the end-gas of a spark-ignition engine under knocking conditions. Extents of reactant consumption have been measured during the course of autoignition following rapid compression of hydrocarbon-air mixtures. Evidence for the occurrence of low temperature oxidation during the compression stroke has been found and its effect on the overall ignition delay has been determined by numerical methods. The influence of diethylamine on this reactivity during compression and on the overall ignition delay has been investigated experimentally. The amine was shown to exert an inhibiting influence on the low temperature oxidation of n-heptane and n-pentane. Measurements of autoignition delays have been made over a range of compressed gas temperatures for different hydrocarbons (C4-C8). The results illustrate the relationship between autoignition delay and octane rating and the effect of molecular structure on the reactivity of hydrocarbons in an RCM. In general, as the Research Octane Number (RON) increases the duration of the ignition delay following compression to 900 K increases, however, a quantitative correlation of the two could not be made. Spatial imaging techniques (schlieren imaging, image intensified Charge Coupled Device (CCD)), used in the investigation of the spatial development of autoignition in the RCM, confirm the existence of spatial temperature inhomogeneities within the combustion chamber during the post-compression period. These imaging techniques have also been used in the study of spark-ignition and “knock” in the RCM. The ignition of methane in the RCM has been studied. The experimental results suggest that the presence of higher alkanes (ethane, propane and n-butane) or carbonaceous particles enhances the initiation of ignition of methane-oxygen mixtures. The effects of pressure and temperature on this behaviour have been explored experimentally.
24
Murad, Ahmad E. M. A. "Flow and combustion in disc and pent-roof SI engines." Thesis, University of Leeds, 2006. http://etheses.whiterose.ac.uk/5392/.
Full textAbstract:
Reported in this thesis is a study of combustion in a disc-shaped combustion chamber spark ignition engine, and in-cylinder flow and combustion in an idealised pent-roof spark ignition engine. Both engines were skip fired, to remove residuals and ensure a welldefined in-cylinder fuel-air mixture. Other important parameters were also controlled, e.g. inlet temperature, inlet pressure, air mass flow, mixture strength, engine speed and spark timing. With the disc-shaped spark ignition engine, a shadowgraph technique was used to study early flame development. Simultaneous natural light and shadowgraph imaging techniques were adopted to validate the later use of the former method for monitoring flame propagation in the pent-roof engine. The disc-shaped engine flame images were processed to yield mean flame radius, flame centroid and to describe flame 'circularity'. Good agreement was obtained between flame radii obtained from natural light and shadowgraph images. No correlation was found between early flame development, centroid displacement, flame 'shape' and the rate of combustion as defined by the crank angle at which peak pressure was attained. The pent-roof engine was 'mapped' to determine optimum conditions, prior to flow and flame studies on the same engine. Flow was analysed using laser doppler and particle tracking velocimetry techniques. Mean and rms velocities were obtained. Observed flow patterns at the two engine speeds tested (750 and 1500 rpm) differed and were not as expected for the simplified geometry. Similar trends in rms velocity were observed at all locations tested, with similar magnitudes at all points and in all directions tested during the critical combustion period. Simultaneous top and side natural light flame images were generated using two high-speed digital cameras; in-cylinder pressure was also recorded. The top and side images were analysed in terms of top and side successive flame positions and top and side mean flame radius. Centroid displacements, from side flame views, were also determined. No correlation was found between initial flame developments and later flame development viewed from the side.
25
Fleck, R. "Predicting the performance characteristics of internal combustion engines." Thesis, Queen's University Belfast, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.431397.
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Loustalan, Paul William. "Experimental investigation of near-nozzle characteristics of gasoline sprays from pressure-swirl atomisers." Thesis, University College London (University of London), 2005. http://discovery.ucl.ac.uk/1444952/.
Full textAbstract:
This thesis presents an experimental investigation of the near-nozzle region of the fuel spray issuing from a pressure-swirl injector commonly found in a direct injection spark ignition engine. Specifically, the effects of the back pressure and impinging air flows were investigated. In addition to this the effect of fuel pressure was investigated. The literature survey reveals only limited published work on the near-nozzle characteristics of fuel sprays, and the requirement for more detailed knowledge of the area to aid in the general understanding of the topic and the development of mathematical models. Two separate experimental test rigs were designed and built to carry out the testing, firstly a static pressure chamber to identify the effects of back pressure on the fuel spray, and secondly a steady state flow rig, to investigate the effects of an impinging air flow. The steady state air flow rig was designed to simulate the air flow from the inlet valves of a direct injection spark ignition engine cylinder head. A novel void fraction technique was utilised to quantify the fuel spray break up process. It was found that there was a correlation between the void fraction and the fuel spray break-up length. The results from this analysis were compared to mathematical models currently available in the literature. It was found that the models do not compare well with the experimental results. A modified mathematical model was therefore proposed by the author, which can be easily integrated into existing computational codes. It was shown that impinging air flows do not affect the primary fuel spray break-up process, however they do affect the secondary break-up of the fuel spray from ligaments into droplets. Impinging air flows also affect the general fuel spray shape, and will determine the location of the fuel spray within the cylinder far downstream of the injector.
27
De, Zoysa Merrenna Manula. "Neural network estimation of air-fuel ratio in internal combustion engines." Thesis, University of Brighton, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.399048.
Full textAbstract:
This thesis presents an investigation into a novel method of estimating the air-fuel ratio of a gasoline-fuelled spark-ignition internal combustion engine. The measurement of the air-fuel ratio is important for controlling an engine to reduce exhaust emissions. In production vehicles, the air-fuel ratio is measured using an exhaust gas analyser and the exhaust emissions are reduced by using electronically controlled three-way catalytic converters, which are expensive and subject to operationallimitations such as, requiring the engine to operate with a stoichiometric air-fuel ratio. A micro-processor based engine management system monitors the engine performance and controls various engine parameters - the fuel pulse width, ignition timing, exhaust gas re-circulation etc. - to maintain strict control of the engine and ensure optimum engine performance. In the USA and UK the engine management system is also responsible for performing on-board diagnostics and warns the driver of any problems such as misfire, knocking combustion and failure of the catalytic converter. The method of measuring the air-fuel ratio presented in this thesis, termed Spark Voltage Characterization (SVC), uses neural networks to analyse the time varying spark voltage waveform to estimate the air-fuel ratio. The spark plug is in direct contact with the combustion itself, thus making it is an excellent candidate for use as a combustion sensor. As it is already installed in the engine, no modifications are required to the engine block itself. The method uses few external components making it cheaper to implement. Preliminary investigations on this method showed that it was possible to estimate the air-fuel ratio by neural network analysis of the spark voltage waveform. As different engines are equipped with different types of ignition systems, it is important that the sensor is independent of the ignition system thus ensuring that it is able to operate with any type of ignition system. The work presented in this thesis includes: i) an extensive review of other methods of measuring the air-fuel ratio, noting the advantages and disadvantages of each method and how the SVC sensor overcome these disadvantages; ii) a description of the theoretical operation of the sensor; iii) investigation of the effects of various engine parameters on the performance of the sensor; iv) suggestions for further work to improve the sensor performance.
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Attia, Osama Abdel Moniem Mohamied. "Finite element static, dynamic, and flutter analysis of rotating composite layered plates and shells." Thesis, Cranfield University, 1996. http://hdl.handle.net/1826/4052.
Full textAbstract:
This thesis introduces new conforming and non-conforming finite elements for the
static and dynamic analysis of rotating composite layered plates and shells. The
elements consider parabolic distributions of transverse shear stresses, and based on
Lagrangian and Hermitian shape functions. They can deal with variable thickness
distributions as well as uniform distributions, and they are fully capable to deal with
rotating plate and shell structures, i. e. centrifugal stiffening and Coriolis force effects
are considered. Natural frequency analysis, forced vibration analysis, and flutter
analysis of composite layered plate and shell structures, employing those elements,
have been investigated. A computer programming package based on the developed
theory was designed, and it is machine independent and user friendly. A modular
approach was adopted in the package structure to allow any further development to
be considered. Efficient frontal solvers were adopted in the package for different
types of analysis. The developed package has been successfully validated on a main
frame computer (VAX), Unix workstations, and personal computers. Several case
studies were investigated and the results obtained were compared with corresponding,
published theoretical and/or experimental work. The package has proved to be a very
useful tool for the design optimization of composite layered plates and shells by
means of using different fibre angles for different layers so as to achieve the required
strength and/or stiffness.
29
Fowler, Andrew. "A new advanced turbine-stage test facility : the concept, design, construction and commissioning." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386786.
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Nikpour, B. "Measurement of the performance of a radial inflow turbine." Thesis, University of Manchester, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282899.
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Robotham, William. "The elastic-plastic buckling behaviour of shafts." Thesis, University of Nottingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323611.
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Lucas, Simon Charles. "Higher specific speed impulse turbines." Thesis, University of Reading, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270200.
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Hughes, Adam William. "Investigation of tip-driven thruster and waterjet propulsion systems." Thesis, University of Southampton, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322015.
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Dunkley, Michael John. "The aerodynamics of intermediate pressure turbines." Thesis, University of Cambridge, 1998. https://www.repository.cam.ac.uk/handle/1810/272045.
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Dennis, C. W. "A Study of Rocket Exhaust Particles." Thesis, Cranfield University, 1996. http://hdl.handle.net/1826/3583.
Full textAbstract:
The exhaust -plumes generated by rocket motors are of significant military importance
for missile detection, recognition and communication due to their electromagnetic
emission and propagation properties. The plume is a high temperature, high velocity
stream of gas and particles, into which the surrounding air is entrained. With
improvements in the modelling of plume gas chemistry and turbulence, particles
present in the plume have become more important in the computational prediction of
the plume's flow field, and the subsequent prediction of plume emission and
propagation characteristics.
This thesis describes research on plume particles, including the measurement of their
physical characteristics and the addition of two phase coding (ie. particles) into current
plume prediction software. Particle collections were carried out in plumes produced by
rocket motors with double base and composite propellants (including aluminised). The
collected particles were analysed to establish their chemical composition and size
distribution. A laser Doppler anemometer system was successfully used to measure
particle velocities in the plumes of 1.5kN double base motors. Particle tracking
software was used to trace the paths of particles using a simplified prediction of the
plume and it was found that the predicted particle behaviour was analogous to that
measured experimentally.
Project management software was used during the research and its relevance was
assessed in respect to the project's size and nature. The management of experimental
trials was studied and a methodology formulated to help improve their future operation.
The costs and benefits of the research were assessed and compared to other research
projects. Many of the benefits gained, such as measurement techniques, require
marketing to ensure that they are exploited in the future. Recommendations for future
research are given that should enhance the present work.
36
Knife, S. "Propulsion system safety analysis methodology for commercial transport aircraft." Thesis, Cranfield University, 1997. http://hdl.handle.net/1826/4256.
Full textAbstract:
Airworthiness certification of commercial transport aircraft requires a
safety analysis of the propulsion system to establish that the probability of a
failure jeopardising the safety of the aeroplane is acceptably low. The
needs and desired features of such a propulsion system safety analysis are
discussed, and current techniques and assumptions employed in such
analyses are evaluated. It is concluded that current assumptions and
techniques are not well suited to predicting behaviour of the propulsion
system in service. The propulsion accident history of the high bypass ratio
commercial transport fleet is reviewed and an alternate approach to
propulsion system safety analysis is developed, based on this accident
history. Features of the alternate approach include quantified prediction of
propulsion related crew error, engine-level reliability growth modelling to
realistically predict engine failure rates, and quantified credit for design
features which mitigate the effects of propulsion system failures. The
alternate approach is validated by applying it to two existing propulsion
systems. It is found to produce forecasts in good agreement with service
experience. Use of the alternate approach to propulsion system safety
analysis during design and development will enable accurate prediction of
the expected propulsion related accident rate and identification of
opportunities to reduce the accident rate by incorporating mitigating
features into the propulsion system/ aeroplane design.
37
Robinson, Christopher J. "End-wall flows and blading design for axial flow compressors." Thesis, Cranfield University, 1991. http://dspace.lib.cranfield.ac.uk/handle/1826/6929.
Full textAbstract:
The flow in multistage axial flow compressors is
particularly complex in nature because of the proximity of
moving bladerows, the growth of end-wall boundary layers and
the presence of tip and seal leakages and secondary flow.
The problems associated with these phenomena are at their
most acute in the latter, subsonic stages of the core
compressor, where Reynolds numbers are modest and the
blading has low aspect ratio. Indeed, much of the
inefficiency of axial stages is believed to be associated
with the interaction between blading and end-wall flows.
The fact that the end-wall flow phenomena result in
conditions local to the blade which are quite different
from those over the major part of the annulus was
appreciated by many of the earliest workers in the axial
turbomachinery field. However, experiments on blading
designs aimed specifically at attacking the end-loss have
been sparse.
This thesis includes results from tests of conventional
and end-bent blading in a four-stage, low-speed, axial
compressor, built specifically for the task, at a scale
where high spatial measurement resolution could be readily
achieved within the flowpath. Two basic design styles are
considered: a zero a0 stage with DCA aerofoils and a
low-reaction controlled-diffusion design with cantilevered
stators.
The data gives insight into the flow phenomena present in
'buried' stages and has resulted in a much clearer
understanding of the behaviour of end-bent blading. A
3D Navier-Stokes solver was calibrated on the two
low-reaction stators and was found to give good agreement
with most aspects of the experimental results. An improved
design procedure is suggested based on the incorporation
of end-bends into the throughflow and iterative use of the
3D Navier-Stokes solver.
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Addison, John Stephen. "Wake-boundary layer interaction in axial flow turbomachinery." Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357704.
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Dorrington, Graham Edward. "Performance of earth-to-orbit transports breathing air." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.277797.
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Leontopoulos, Chris. "Vibration analysis for the design on a turbo-generator based powertrain for hybrid vehicles." Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284809.
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Brayton, Simon Nicholas. "Hot wire instrumentation for unsteady aerodynamic measurements in a rotating gas turbine stage." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390399.
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Kuk, Victor H. M. "An investigation of particle trajectories and particle impact points in turbine film cooling hole system." Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294380.
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Slater, J. T. D. "Three-dimensional aerodynamic studies of a turbine stage in a transient flow facility." Thesis, University of Oxford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358729.
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Nascimento, M. A. R. "The selective bleed variable cycle engine." Thesis, Cranfield University, 1992. http://dspace.lib.cranfield.ac.uk/handle/1826/7359.
Full textAbstract:
A new concept in aircraft propulsion is described in this work. In particular, variable jet engine is investigated for supersonic ASTOVL aircraft. This engine is a Selective Bleed Variable Cycle, twin shaft turbofan. At low flight speeds the engine operates as a medium bypass turbofan. At supersonic cruise it operates as low bypass turbofan without reheat. The performance of the engine and its components is analyzed using a novel matching procedure. Off-design engine performance characteristics are explained, compressor running lines are shown, and variable geometry requirements are described.
The performance analysis shows that fuel savings are significant, thus reducing aircraft take-off weight. The major advantage of this engine is that all the components are used continuously for all operating modes, thus incurring low weight penalties. The benefits predicted by this preliminary investigation indicate that further research on this engine should be carried out.
The matching procedure developed and described shows itself to be very effective for two-shaft engines with a fixed geometry LP turbine. The method can also be extended to three shaft cases with or without a variable geometry LP turbine.
Extensive development of compressor and turbine design and performance software has been undertaken.
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Rolston, Stephen Carson. "An application of passive control for supersonic sidewall intakes." Thesis, Queen's University Belfast, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359123.
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Al-Ajmi, Rashed. "Evaluation of vortex cooling systems for turbine blades." Thesis, Cardiff University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364475.
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Isaias, Loizos. "Performance simulation of a medium speed diesel engine under optimal and fault conditions." Thesis, University of Newcastle Upon Tyne, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388759.
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Zhou, Ji. "Intelligent fault diagnosis with applications to gas turbine engines." Thesis, University of Sheffield, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284354.
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Sellers, Jerry Jon. "Investigation into hybrid rockets and other cost-effective propulsion system options for small satellites." Thesis, University of Surrey, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309201.
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Zayed, Abdel-Nasser Abdel-Hamid. "Computed tomography applications in ballistics." Thesis, Cranfield University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282474.
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