This thesis contains the specific description of Group Design Project (GDP) and Individual Research Project (IRP) that are undertaken by the author and form part of the degree of Master of Science. The target of GDP is to develop a novel and unique commercial flying wing aircraft titled FW-11. FW-11 is a three-year collaborative civil aircraft project between Aviation Industry Corporation of China (AVIC) and Cranfield University. According to the market analysis result conducted by the author, 250 seats capacity and 7500 nautical miles were chosen as the design targets. The IRP is the further study of GDP, which is to enhance the competitive capability by deploying prognostics and health management (PHM) technology to the fuel system of FW-11. As a novel and brand-new technology, PHM enables the real-time transformation of system status data into alert and maintenance information during all ground or flight operating phases to improve the aircraft reliability and operating costs. Aircraft fuel system has a great impact on flight safety. Therefore, the development of fuel system PHM concept is necessary. This thesis began with an investigation of PHM, then a safety and reliability analysis of fuel system was conducted by using FHA, FMEA and FTA. According to these analyses, fuel temperature diagnosis and prognosis were chosen as a case study to improve the reliability and safety of FW-11. The PHM architecture of fuel temperature had been established. A fuel temperature prediction model was also introduced in this thesis.

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Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Regulators and designers of nuclear reactors regard knowledge of the pebble fuel temperature as important, due to the role that it plays in maintaining structural integrity and the production of neutrons. By using special fuel assemblies fitted with measuring equipment it is possible to measure the fuel temperature in stationary fuel reactors. This, however, is not possible in the pebble bed modular reactor due to its dynamic core. Designers of the pebble bed modular reactor have reserved special inspection channel borings inside the center reflector for fuel temperature measurement. By means of optical fibers and interferometry, the temperature can be measured inside such a channel. Currently the only way to control the fuel surface and core temperature is by measuring the gas inlet and outlet temperatures. This thesis attempts to determine the pebble temperature by measuring the temperature in a reflector channel. This is done by constructing an electrically heated pebble bed experimental setup simulating a cutout section of a pebble bed modular reactor core. An additional computational fluid dynamics simulation of the experimental setup was also performed. This thesis also attempts to determine if there is a measureable temperature peak that can indicate where a pebble was in contact with the reflector surface. This could then be used in future studies to determine the pebble fuel velocity as it moves down the reactor core. The computational fluid dynamics results were validated by experimental measurements. In the computational fluid dynamics model and experimental setup, it was found that there was indeed a measureable temperature difference on the temperature gradient along the reflector wall. The heat being conducted away from the pebble through the contact area can explain this. These differences were only observed when the channel was moved closer to the pebbles and it is therefore advised that some redesigning of the channel should be done if the in-core temperature is to be accurately interpreted by the designers at PBMR (Pty) Ltd. / AFRIKAANSE OPSOMMING: Reguleerders en ontwerpers van kern reaktore beskou die kennis van die korrel brandstof temperatuur as belangrik. Dit is weens die rol wat die brandstof temperatuur speel met die behoud van strukturele integriteit en die produksie van neutrone binne-in die reaktor. Met behulp van spesiale brandstof montasies toegerus met die meetings instrumentasie, is dit moontlik om die brandstof temperatuur in stilstaande brandstof reaktore te meet. Dit is egter nie moontlik in die korrel bed modulêre reaktor nie, as gevolg van sy dinamiese kern. Ontwerpers van die korrel bed modulêre reaktor het spesiale kanale in die binnekant van die middel reflektor vir brandstof temperatuur meeting gereseveer. Deur middel van optiese vesel en interferometrie, kan die temperatuur binne so 'n kanaal gemeet word. Tans is die enigste manier om die brandstof-oppervlak temperatuur te berekern, net moontlik deur gebruik te maak van die gemete gas inlaat-en uitlaat temperature van die reaktor. Hierdie tesis poog om vas te stel of die korrel brandstof temperatuur deur die meet van die oppervlak temperatuur in 'n reflektor-kanaal bepaal kan word. Dit word gedoen deur 'n elektriese verhitte korrel bed eksperimentele opstelling te bou wat 'n gedeelte van 'n korrel bed modulêre reaktor simuleer. 'n Bykomende numeriese simulasie van die eksperimentele opstelling was ook uitgevoer. Hierdie werk het ook probeer om vas te stel of daar 'n meetbare temperatuur piek op die temperatuur profiel aandui kan word waar 'n korrel in kontak is met die reflektor se oppervlak. Dit kan dan in toekomstige studies gebruik word om te bepaal wat die korrel brandstof spoed was soos dit in die reaktor beweeg. Die numerise simulasie uitslae was deur eksperimentele metings bevestig. In die numerise simulasie model en die eksperimentele opstelling, is daar gevind dat daar inderdaad 'n meetbare temperatuur verskil op die temperatuurgradiënt teen die reflektor oppervlak is. Dit kan verduidelik word as gevolg van die hitte wat weg van die korrel gelei word deur middel van die kontak area. Hierdie verskille was slegs waargeneem wanneer die kanaal nader aan die korrels geskuif is en dit word as n aanbeveling aan PBMR (Pty) Ltd gemaak om sommige herontwerpe aan die kanaal te doen indien die in-kerntemperatuur gemeet wil word en akkuraat geinterpreteer wil word.

The effect of uncertainty in gas composition on the accuracy of gas-phase thermometry using Laser-Induced Thermal Grating Spectroscopy, LITGS, is studied. Temperatures are obtained from measurements of the sound speed derived from the frequency of oscillations ƒ_OSC imposed upon the LITGS signal arising from the transit of acoustic waves across the density modulation feature. The dependence of the sound speed, c_s on √γ/m, where γ is the ratio of specific heats and m is the mean molecular mass leads to a dependence upon gas composition. LITGS signals were generated in acetone vapour in a variety of gas mixtures in a temperature controlled cell at 4 bar total pressure using pump pulses from a frequency quadrupled Q-switched Nd:YAG laser at 266 nm and a cw diode pumped solid state probe laser at 671 nm. Studies were undertaken of the variation in ƒ_OSC with gas composition using gas mixtures of O₂ and N₂ with component concentrations in the range 0-100 %, and was found to agree with theoretical predictions. Measurement precision of the data (one standard deviation in 50 measurements) was found to be typically ± 1.7 % for measurements at 4 bar total pressure. The effect of varying concentrations in exhaust gas residuals (EGR) typical of pre-ignition gases in a spark ignition internal combustion engine were studied using synthetic air (N₂/ O₂ mixtures) containing variable amounts of simulated EGR components, CO₂ and H₂O. The effect of variation in CO₂ concentration in dry synthetic air was measured at 4 bar and 30°C and found to agree with theoretical predictions. Experiments conducted at 30°C, with the addition of a saturated vapour pressure of water indicate that the effect of a saturated vapour pressure of water on the oscillation frequency in synthetic EGR is on the borderline of resolution. The effect of variable amounts of typical hydrocarbon fuel vapour on ƒ_OSC was studied using 2,2,4-trimethyl-pentane in gas mixtures composed of synthetic air and variable amounts of EGR and water vapour at 80°C. Kinetic theory was used in order to model the dependence of the oscillation frequency ƒ_OSC on various gas compositions containing fuel and EGR, in order to construct an error surface for comparison with experimental measurements. Experimental data were found to agree with the model predictions to within experimental error for a representative data set within the range of calculated values. The results indicate that uncertainties in temperature values derived from LITGS thermometry can be estimated with confidence within reasonable estimates of composition variations in an internal combustion engine, and should lead to absolute temperature accuracy of within 2-3 %.

[EN] The injection system is one of the topics that has been paid most attention to by researchers in the field of direct injection diesel engines, due to its key role on fuel atomization, vaporization and air-fuel mixing process, which directly affect fuel consumption, noise irradiation and pollutant emissions. The increasing injection pressures in modern engines have propitiated the need of studying phenomena such as cavitation, compressible flow or the effect of changes in the fuel properties along the process, whose relative importance was lower in early stages of the reciprocating engines development. The small dimensions of the injector ducts, the high velocities achieved through them and the transient nature of the process hinder the direct observation of these facts. Computational tools have then provided invaluable help in the field. The objective of the present thesis is to analyse the influence of the thermal effects on the performance of a diesel injector. To this end, the fuel temperature variation through the injector restrictions must be estimated. The influence of these changes on the fuel thermophyisical properties relevant for the injection system also needs to be assessed, due to its impact on injector dynamics and the injection rate shape. In order to give answer to the previous objectives, both experimental and computational techniques have been employed. A dimensional and a hydraulic experimental characterization of a solenoid-actuated Bosch CRI 2.20 injector has been carried out, including rate of injection measurements at a wide range of operating conditions, with special attention to the fuel temperature control. A 1D computational model of the injector has been implemented in order to confirm and further extend the findings from the experiments. Local variations of fuel temperature and pressure are considered by the model thanks to the assumption of adiabatic flow, for which the experimental characterization of the fuel properties at high pressure also had to be performed. The limits of the validity of this assumption have been carefully assessed in the study. Results show a significant influence of the fuel temperature at the injector inlet on injection rate and duration, attributed to the effect of the variation of the fuel properties and to the fact that the injector remains in ballistic operation for most of its real operating conditions. Fuel temperature changes along the injector control orifices are able to importantly modify its dynamic behaviour. In addition, if the fuel at the injector inlet is at room temperature or above, the temperature at the nozzle outlet has not been proved to importantly change once steady-state conditions are achieved. However, a significant heating may take place for fuel temperatures at the injector inlet typical of cold-start conditions. / [ES] El sistema de inyección es uno de los elementos que más interés ha despertado en la investigación en el campo de los motores diésel de inyección directa, debido a su papel clave en la atomización y vaporización del combustible así como en el proceso de mezcla, que afectan directamente al consumo y la generación de ruido y emisiones contaminantes. Las crecientes presiones de inyección en motores modernos han propiciado la necesidad de estudiar fenómenos como la cavitación, flujo compresible o el efecto de los cambios de las propiedades del combustible a lo largo del proceso, cuya importancia relativa era menor en etapas tempranas del desarrollo de los motores alternativos. Las pequeñas dimensiones de los conductos del inyector, las altas velocidades a través de los mismos y la naturaleza transitoria del proceso dificultan la observación directa en estas cuestiones. Por ello, las herramientas computacionales han proporcionado una ayuda inestimable en el campo. El objetivo de la presente tesis es analizar la influencia de los efectos térmicos en el funcionamiento de un inyector diésel. Para tal fin, se debe estimar la variación de la temperatura del combustible a lo largo de las restricciones internas del inyector. La influencia de estos cambios en las propiedades termofísicas del combustible más relevantes en el sistema de inyección también debe ser evaluada, debido a su impacto en la dinámica del inyector y en la forma de la tasa de inyección. Para dar respuesta a estos objetivos, se han utilizado técnicas experimentales y computacionales. Se ha llevado a cabo una caracterización dimensional e hidráulica de un inyector Bosch CRI 2.20 actuado mediante solenoide, incluyendo medidas de tasa de inyección en un amplio rango de condiciones de operación, para lo que se ha prestado especial atención al control de la temperatura del combustible. Se ha implementado un modelo 1D del inyector para confirmar y extender las observaciones extra\'idas de los experimentos. El modelo considera variaciones locales de presión y temperatura del combustible gracias a la hipótesis de flujo adiabático, para lo cual también se ha tenido que llevar a cabo una caracterización experimental de las propiedades del combustible a alta presión. Los límites de la validez de esta hipótesis se han analizado cuidadosamente en el estudio. Los resultados muestran una influencia significativa de la temperatura del combustible a la entrada del inyector en la tasa y duración de inyección, atribuida al efecto de la variación de las propiedades del combustible y al hecho de que el inyector permanece en operación balística para la mayoría de sus condiciones de funcionamiento. Los cambios en temperatura del combustible a lo largo de los orificios de control del inyector son capaces de modificar su dinámica considerablemente. Además, si el combustible a la entrada del inyector se encuentra a temperatura ambiente o por encima, se ha observado que la temperatura a la salida de la tobera no varía de manera importante una vez se alcanzan condiciones estacionarias. No obstante, un calentamiento significativo puede tener lugar para temperaturas de entrada típicas de las condiciones de arranque en frío. / [CAT] El sistema d'injecció és un dels elements que més interés ha despertat en la investigació en el camp dels motors dièsel d'injecció directa, degut al seu paper clau en l'atomització i vaporització del combustible, així com en el procés de mescla, que afecten directament el consum i la generació de soroll i emissions contaminants. Les creixents pressions d'injecció en motors moderns han propiciat la necessitat d'estudiar fenòmens com la cavitació, flux compressible o l'efecte dels canvis de les propietats del combustible al llarg del procés, la importància relativa dels quals era menor en les primeres etapes del desenvolupament dels motors alternatius. Les menudes dimensions dels conductes de l'injector, les altes velocitats a través dels mateixos i la natura transitòria del procés dificulten l'observació directa en estes qüestions. Per això, les ferramentes computacionals han proporcionat una ajuda inestimable en el camp. L'objectiu de la present tesi és analitzar la influència dels efectes tèrmics en el funcionament d'un injector dièsel. Per a tal fi, es deu estimar la variació de la temperatura del combustible al llarg de les restriccions internes de l'injector. La influència d'estos canvis en les propietats termofísiques del combustible més relevants en el sistema d'injecció també ha de ser avaluada, degut al seu impacte en la dinàmica de l'injector i en la forma de la tasa d'injecció. Per tal de donar resposta a estos objectius, s'han utilitzat tècniques experimentals i computacionals. S'ha dut a terme una caracterització dimensional i hidràulica d'un injector Bosch CRI 2.20 actuat mitjançant solenoide, incloent mesures de tasa d'injecció en un ampli rang de condicions d'operació, per al que s'ha prestat especial atenció al control de la temperatura del combustible. S'ha implementat un model 1D de l'injector per tal de confirmar i estendre les observacions extretes dels experiments. El model considera variacions locals de pressió i temperatura del combustible gràcies a la hipòtesi de flux adiabàtic, per la qual cosa també s'ha hagut de dur a terme una caracterització experimental de les propietats del combustible a alta pressió. Els límits de la validesa d'esta hipòtesi s'han analitzat acuradament en l'estudi. Els resultats mostren una influència significativa de la temperatura del combustible a l'entrada de l'injector en la tasa i duració d'injecció, atribuïda a l'efecte de la variació de les propietats del combustible i al fet que l'injector roman en operació balística per a la majoria de les seues condicions de funcionament. Els canvis en temperatura del combustible al llarg dels orificis de control de l'injector són capaços de modificar la seua dinàmica considerablement. A més, si el combustible a l'entrada de l'injector es troba a temperatura ambient o per damunt, s'ha observat que la temperatura a l'eixida de la tobera no varia de manera important una vegada s'han assolit condicions estacionàries. No obstant això, un escalfament significatiu pot tenir lloc per a temperatures d'entrada típiques de les condicions d'arrancada en fred. / Carreres Talens, M. (2016). Thermal effects influence on the Diesel injector performance through a combined 1D modelling and experimental approach [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/73066 / TESIS