2,152 research outputs found
Small Engine Flash Vapor JP-8 Fuel Injector Testing, Simulation and Development
Following U.S. Army’s single fuel initiative, Wankel rotary engines used in U.S. Army’s shadow unmanned aerial vehicles (UAVs) need to be retrofitted from running on aviation gasoline (AVGAS) to JP-8. The feasibility of retrofitting the engine with a flash vapor direct fuel injector was investigated. A commercial off-the-shelf direct fuel injector was used in the study. A photo detector measurement tool was developed to measure high frequency (>100 Hz) injection event. A coupled electrical-electomagnetics-fluid-mechanical system was simulated to understand the pintle dynamics during an injection event. Optimal injector power drive was revealed to be a multi-stage current profile. A flash heater was designed and tested to be capable of heating up JP-8 from room temperature to its vaporization temperature (>310F) under one tenth of a second at the required flow rate. An ignition test rig was built to compare ignition behavior between AVGAS and heated JP-8. Test result showed that the 550F pre-heated JP-8 had equal or superior ignition pressure rise / ignition delay time than AVGAS
Thermal effects influence on the Diesel injector performance through a combined 1D modelling and experimental approach
[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 asà 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 termofÃsicas 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 lÃmites 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 balÃstica para la mayorÃa 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 varÃa de manera importante una vez se alcanzan condiciones estacionarias. No obstante, un calentamiento significativo puede tener lugar para temperaturas de entrada tÃpicas de las condiciones de arranque en frÃo.[CA] 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, aixà 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 importà ncia 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 termofÃsiques del combustible més relevants en el sistema d'injecció també ha de ser avaluada, degut al seu impacte en la dinà mica 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 hidrà ulica 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 grà cies a la hipòtesi de flux adiabà tic, per la qual cosa també s'ha hagut de dur a terme una caracterització experimental de les propietats del combustible a alta pressió. Els lÃmits 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 balÃstica 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 dinà mica 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 estacionà ries. No obstant això, un escalfament significatiu pot tenir lloc per a temperatures d'entrada tÃpiques 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/10251/73066TESI
Ytterbium ion trapping and microfabrication of ion trap arrays
Over the past 15 years ion traps have demonstrated all the building blocks required of a
quantum computer. Despite this success, trapping ions remains a challenging task, with
the requirement for extensive laser systems and vacuum systems to perform operations on
only a handful of qubits. To scale these proof of principle experiments into something that
can outperform a classical computer requires an advancement in the trap technologies that
will allow multiple trapping zones, junctions and utilize scalable fabrication technologies.
I will discuss the construction of an ion trapping experiment, focussing on my work
towards the laser stabilization and ion trap design but also covering the experimental
setup as a whole. The vacuum system that I designed allows the mounting and testing of
a variety of ion trap chips, with versatile optical access and a fast turn around time.
I will also present the design and fabrication of a microfabricated Y junction and a 2-
dimensional ion trap lattice. I achieve a suppression of barrier height and small variation of
secular frequency through the Y junction, aiding to the junctions applicability to adiabatic
shuttling operations. I also report the design and fabrication of a 2-D ion trap lattice.
Such structures have been proposed as a means to implement quantum simulators and to
my knowledge is the first microfabricated lattice trap.
Electrical testing of the trap structures was undertaken to investigate the breakdown
voltage of microfabricated structures with both static and radio frequency voltages. The
results from these tests negate the concern over reduced rf voltage breakdown and in
fact demonstrates breakdown voltages significantly above that typically required for ion
trapping. This may allow ion traps to be designed to operate with higher voltages and
greater ion-electrode separations, reducing anomalous heating.
Lastly I present my work towards the implementation of magnetic fields gradients and
microwaves on chip. This may allow coupling of the ions internal state to its motion using
microwaves, thus reducing the requirements for the use of laser systems
Advanced Sensors for Real-Time Monitoring Applications
It is impossible to imagine the modern world without sensors, or without real-time information about almost everything—from local temperature to material composition and health parameters. We sense, measure, and process data and act accordingly all the time. In fact, real-time monitoring and information is key to a successful business, an assistant in life-saving decisions that healthcare professionals make, and a tool in research that could revolutionize the future. To ensure that sensors address the rapidly developing needs of various areas of our lives and activities, scientists, researchers, manufacturers, and end-users have established an efficient dialogue so that the newest technological achievements in all aspects of real-time sensing can be implemented for the benefit of the wider community. This book documents some of the results of such a dialogue and reports on advances in sensors and sensor systems for existing and emerging real-time monitoring applications
Diesel engine performance comparisons of high temperature and low temperature combustion with conventional and biodiesel fuels
The main objective of the work underlying the dissertation was in-cylinder simultaneous reduction of nitrogen oxides (NOx) and particulate matter (PM) in diesel-/biodiesel-fuelled engines. Empirical investigations were performed for comparisons between (1) engine cycle performance of conventional diesel high and low temperature combustion processes (HTC and LTC), and (2) the use of neat commercial biodiesel and conventional diesel in the HTC and LTC modes. A four-cylinder common-rail direct-injection (DI) diesel engine and a single-cylinder DI engine with mechanical injection configuration were employed. The tests were conducted under independently controlled single- and multi-event injections, exhaust gas recirculation (EGR), boost and backpressure to achieve the LTC mode. Furthermore, engine cycle, chemical kinetics and multi-dimensional simulations were performed primarily as tools facilitating the explanation of empirical results. Deduced from extensive empirical analyses, the exhaust emissions and fuel efficiency of the diesel engines employed characterised strong resilience to biodiesel fuels when the engines were operated in conventional HTC cycles. The results offered a promising perspective of the neat biodiesel fuels. As the engine cycles approached the LTC, dissimilar engine performance between the use of conventional diesel and biodiesel fuels was observed. In the late single-shot strategy with heavy EGR rates (EGR-incurred LTC), which could be utilised to improve the fuel efficiency of diesel/biodiesel LTC cycles at low loads, the biodiesel was found to sustain a broader range of loads than the diesel fuel. This was mainly attributable to the biodiesel\u27s higher Cetane number (CN) and combustion-accessible fuel oxygen. At high load LTC, the diesel fuel early-multiple injections with EGR facilitated mixture homogeneity that is more difficult to generate with a single pulse injection. Conversely, the biodiesel early-injection strategy presented numerous challenges apropos of the homogeneous fuel/air mixture formation, especially at medium-to-high load conditions. This was attributed to the low volatility and high viscosity and CN of the investigated biodiesel fuel. The empirical analyses, especially involving the EGR-incurred LTC, presented a platform for model-based control with an improved ignition delay correlation. The new correlation, which considered the CN and oxygen concentrations in the fuel and intake air, captured the ignition delay trends with good agreement
Modern Applications in Optics and Photonics: From Sensing and Analytics to Communication
Optics and photonics are among the key technologies of the 21st century, and offer potential for novel applications in areas such as sensing and spectroscopy, analytics, monitoring, biomedical imaging/diagnostics, and optical communication technology. The high degree of control over light fields, together with the capabilities of modern processing and integration technology, enables new optical measurement systems with enhanced functionality and sensitivity. They are attractive for a range of applications that were previously inaccessible. This Special Issue aims to provide an overview of some of the most advanced application areas in optics and photonics and indicate the broad potential for the future
Design and investigation of a diesel engine operated on pilot ignited LPG
This thesis explores the idea of igniting LPG in a compression ignition diesel engine
using pilot diesel injection as spark ignition medium. The main advancement in using
this technology on current diesel engines is the establishment of a better balance
between NOx and PM emissions without losing too much of the CO2 benefits of diesel.
With the advent of common rail diesel engines, it is now possible to get control of pilot
diesel injection and make the LPG and diesel control systems work together.
Combined diesel and LPG operation is a new subject for engine research, so the thesis
moves on to consider the results from detailed engine simulation studies that explore the
potential benefits of the mix. Subsequent simulations of a modern four cylinder dCi
engine suggest that with closer control over the pilot diesel injection, diesel like
performance can be obtained, hopefully with less emissions than currently expected
from diesel only operation.
A single cylinder variable compression ratio research engine was developed to explore
diesel /LPG dual fuel operation. A second generation common rail injection rig was also
developed for the engine and for fuel spray characterisation.
Engine experiments proved the concept of using a modest charge of pilot injected diesel
for igniting a larger dose of port injected LPG. The experimental work results suggest
that combining diesel common rail injection technology with the state of the art LPG
injection systems, it is possible to establish a better balance between NOx/ PM
emissions without losing too much of the CO2 benefits from the diesel operation
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