132 research outputs found
Full Load Testing Of A 12.5 MW Vertical High Speed Subsea Motorcompressor
Lecturepg. 79-92In late 2006 Authors’ company was awarded a contract for the motorcompressor for the Ormen Lange Subsea Compression Pilot. This Pilot represents the first subsea motorcompressor unit ever built in a fully marinized version and tested in a water pit, which was developed specifically for the project at the customer’s site (Nhyamna, Norway). The prototype unit is a 12.5MW (16763HP) integrated motorcompressor, which runs up to 10.5krpm in a vertical configuration with the following features: Single casing; High-speed motor rigidly coupled to a multistage centrifugal compressor (3 journal bearings shaft line); Canned Active Magnetic Bearings (AMBs); Process gas used as cooling fluid for the Electric Motor; Internal separation system (to protect the bearings and the electric motor from the intrusion of solid and liquid materials); Fully marinized AMBs control system; The design and validation plan for this complex equipment were developed through a four years program where many challenging milestones were achieved. The Ormen Lange Subsea Compression Pilot motorcompressor has successfully completed an intensive full load testing campaign in the Authors’ Company plant including the following: Static-dynamic tuning of the AMBs; Mechanical Running Test; Compressor Performance Test (ASME PTC-10 Type 2 + Full Load test); Electric Motor Performance Test; Overall cooling system check; Landing test (partial landing and full speed delevitation test). The test campaign has fully demonstrated the functionality of this prototype unit capable of operation in the service conditions. The Next step will be the shipment to the costumer site where the submerged testing will be conducted. This paper will provide a detailed description of the main test results of the subsea motorcompressor covering all aspects of the test program including rotordynamic behaviour, compressor thermodynamic performance, axial load variation versus operating conditions (monitored thanks to the thrust AMB), electric motor cooling system behaviour, electric motor performance, AMBs and control system operability. Of special interest is the rotor delevitation test from full speed consisting in the two ton rotor running at 10.5krpm dropping onto the mechanical emergency bearings until the machine reached a complete stop condition. This test, which was repeated 5 times, provided a full-scale verification of the landing numerical simulation developed by the authors (Ransom et al., 2009)
Flexible Micro Gas Turbine Rig for Tests on Advanced Energy Systems
The Thermochemical Power Group (TPG) of the University of Genoa, Italy, has developed a new flexible laboratory to study advanced energy systems based on micro gas turbine technology. In the laboratory a general-purpose experimental rig, based on a modified commercial 100 kW recuperated micro gas turbine, was installed and fully instrumented.
The main objectives of the laboratory is to perform experimental activities related to gas turbine based cycles in both steady-state and transient conditions. The rig layout was defined to include the effects of interaction between the turbomachines (especially the compressor) and further components. This approach is extremely significant for innovative cycle analyses, such as recuperated, humid air, and hybrid (with high temperature fuel cells) configurations.
The facility was partially funded by two Integrated Projects of the EU VI Framework Program (Felicitas and Large-SOFC) and the Italian Government (PRIN project). It was designed with a high flexibility approach including: flow control management, co-generative applications, downstream compressor volume variation, grid-connected or stand-alone operations, recuperated or simple cycles, and room temperature control. In the new EU VII Framework (E-HUB Project), the test rig has been improved with the installation of an absorption cooler to operate the system in tri-generative configuration.
The layout of the whole system, including connection pipes, valves, and instrumentation (in particular mass flow meter locations) was carefully designed to measure all the significant properties with high accuracy performance. Particular attention was devoted to component design, using CFD tools (Fluent), to perform emulation tests on high temperature fuel cell hybrid systems. For this reason, the facility was equipped with a modular cathodic vessel, an anodic recirculation loop (including a vessel and an ejector), and a steam injection system for chemical composition emulation.
To compare tests affected by a significant influence of the ambient temperature variation, such as the performance tests on the machine maximum electrical power and electrical efficiency or on the recuperator effectiveness, the rig was integrated with a compressor inlet temperature control system. This equipment is composed of three air/water heat exchangers located at the air intake, controlled valves and a variable speed pump operating in a closed loop. This circuit was designed to couple the machine air inlet with the absorption cooler.
The large number of experimental data available for the high flexibility test rig design is also used to validate both steady-state (design and off-design) and transient (also real-time) theoretical models. A good level of consistency can be achieved thanks to the complete knowledge of the test rig dimensions, volumes, masses, shaft inertia, thermal capacitances, and operating procedure. Such completeness is difficult to obtain in industrial plants, where details about equipment are often missing or confidential.
This facility is also essential to introduce undergraduate students to micro gas turbine technology, and Ph.D.s to advanced experimental activities in the same field. With this experimental rig, in addition to learning about the thermodynamic cycles and plant layouts, students can also become familiar with their materials, piping, gaskets, technology for auxiliaries, and instrumentation
High capacity heat pump development for sanitary hot water production
Heat pumps have been identified as an efficient alternative to traditional boilers for the production of sanitary hot water (SHW). The high water temperature lift (usually from 10ºC to 60ºC) involved in this application has conditioned the type of used solutions. On the one hand, transcritical cycles have been considered as one of the most suitable solutions to overcome the high water temperature lift. Nevertheless, the performance of the transcritical CO2 heat pump is quite dependent on the water inlet temperature, which in many cases is above 10ºC. Furthermore, performance highly depends on the rejection pressure, which needs to be controlled to work at the optimum point in any condition. On the other hand, for the subcritical systems, subcooling seems to be critical for the heat pump performance when working at high temperature lifts, but there is not any published work that optimizes subcooling in the SHW application for these systems. Therefore, the subcritical cycle should require a systematic study on the subcooling that optimizes COP depending on the external conditions, in the same way as it has been done for the rejection pressure in the transcritical cycle.
The aim of this thesis is to investigate the role of subcooling in the performance of a Propane water-to-water heat pump for SHW production, in the application of heat recovery from any water source. Two different approaches to overcome the high degree of subcooling were designed and built to test them in the laboratory:
1) Subcooling is made at the condenser: The active refrigerant charge of the system is controlled by a throttling valve. Subcooling is controlled independently at any external condition.
2) Subcooling is made in a separate heat exchanger, the subcooler. Subcooling is not controlled, it depends on the external condition and the heat transfer at the subcooler.
The heat pumps were tested at different water temperatures at the evaporator inlet (10ºC to 35ºC) and condenser inlet (10ºC to 55ºC), while the water production temperature was usually fixed to 60¿C. The obtained results have shown that COP depends strongly on subcooling. In the nominal condition (20¿C/15¿C for the inlet/outlet water temperature at the evaporator and 10ºC/60ºC for the inlet/outlet water temperature in the heat sink), the optimum subcooling was about 43 K with a heating COP of 5.61, which is about 31% higher than the same cycle working without subcooling. Furthermore, the system with subcooling has been proved experimentally as being capable of producing water up to 90¿C and has shown a higher COP than some CO2 commercial products (catalog data reference).Las bombas de calor han sido identificadas como una alternativa eficaz a las calderas tradicionales para la producción de agua caliente sanitaria (ACS). El elevado salto de temperatura del agua que normalmente tiene lugar en esta aplicación (por lo general de 10ºC a 60ºC) ha condicionado el tipo de soluciones que se utilizan. Por un lado, los ciclos transcríticos han sido considerados como una de las mejores soluciones para trabajar con los elevados saltos de temperatura del agua. Sin embargo, el rendimiento de la bomba de calor transcrítica con CO2 es bastante dependiente de la temperatura de entrada del agua, que en muchos casos está por encima de los 10¿C. Además, el rendimiento depende en gran medida de la presión de descarga, la cual necesita ser controlada con el fin de trabajar en el punto óptimo en cualquier condición externa. Por otra parte, para los sistemas subcríticos, el subenfriamiento parece ser crítico para el buen funcionamiento de la bomba de calor cuando se trabaja con elevados saltos de temperatura del agua, pero no hay ningún trabajo publicado en el que optimicen el subenfriamiento para la aplicación de ACS en estos sistemas. Por lo tanto, los sistemas subcríticos requieren de un estudio sistemático para buscar el subcooling óptimo y maximizar el COP en función de las condiciones externas, de la misma forma que se ha hecho para la presión de descarga en los ciclos transcríticos.
El objetivo de esta tesis es investigar el papel del subenfriamiento en el rendimiento de una bomba de calor trabajando con Propano para la producción de ACS, en la aplicación de recuperación de calor de cualquier fuente de agua (agua- agua). Dos enfoques diferentes para superar el alto grado de subenfriamiento fueron diseñados y construidos para ponerlos a prueba en el laboratorio:
1) El subenfriamiento se hace en el condensador: La carga activa de refrigerante del sistema se controla con una válvula de estrangulación. De esta manera, el subenfriamiento puede ser controlado de forma independiente a cualquier condición externa.
2) El subenfriamiento se hace en un intercambiador de calor separado, el subenfriadador. El subenfriamiento no se controla, este depende de la condición externa y de la transferencia de calor en el subenfriadador.
Las bombas de calor se ensayaron a diferentes temperaturas del agua a la entrada del evaporador (10ºC a 35ºC) y entrada del condensador (10ºC a 55ºC), mientras que la temperatura de producción de agua, normalmente, se fija a 60¿C. Los resultados obtenidos han demostrado que el COP depende mucho del subenfriamiento. En las condiciones nominales (20ºC/15ºC para la temperatura del agua de entrada/salida en el evaporador y 10ºC/60ºC para la temperatura del agua de entrada/salida en el condensador), el subenfriamiento óptimo fue aproximadamente de 43 K con un COP de calentamiento de 5,61, que es alrededor del 31% más alto que el mismo ciclo trabajando sin subenfriamiento. Además, el sistema con subenfriamiento ha probado de forma experimental, que es capaz de producir agua hasta los 90ºC, y ha mostrado un COP más alto que algunos productos comerciales que trabajan con CO2 (datos de referencia del catálogo).Les bombes de calor han estat identificades com una alternativa eficaç a les calderes tradicionals per a la producció d'aigua calenta sanitària (ACS). L'elevat salt de temperatura de l'aigua que normalment té lloc en aquesta aplicació (en general de 10ºC a 60ºC) ha condicionat el tipus de solucions que s'utilitzen. Per una banda, els cicles transcrítics s'han considerat com una de les millors solucions per tal de treballar amb els elevats salts de temperatura de l'aigua. No obstant això, el rendiment de la bomba de calor transcrítica amb CO2 és bastant dependent de la temperatura d'entrada de l'aigua, que en molts casos està per damunt de 10¿C. A més, el rendiment depèn en gran mesura de la pressió de descarrega, la qual necessita ser controlada per tal de treballar en el punt òptim a qualsevol condició externa. Per altra banda, per als sistemes subcrítics, el sub-refredament sembla ser crític per al funcionament de la bomba de calor quan es treballa amb elevats salts de temperatura de l'aigua, però no hi ha cap treball publicat en el qual optimitzen el sub-refredament per a l'aplicació d'ACS en aquests sistemes. Per tant, els sistemes subcrítics requereixen d'un estudi sistemàtic per tal de buscar el subcooling òptim i maximitzar el COP en funció de les condicions externes, en la mateixa forma que s'ha fet per la pressió de descarrega en els cicles transcrítics.
L'objectiu d'aquesta tesi és investigar el paper del sub-refredament en el rendiment d'una bomba de calor treballant amb Propà per a la producció d'ACS, en l'aplicació de recuperació de calor de qualsevol font d'aigua (aigua-aigua). Dos enfocaments diferents per tal de superar l'alt grau de sub-refredament van ser dissenyats i construïts per posar-los a prova en el laboratori:
1) El sub-refredament es fa en el condensador: La càrrega activa de refrigerant del sistema es controla amb una vàlvula d'estrangulació. D'aquesta manera, el sub-refredament pot ser controlat de forma independent en qualsevol condició externa.
2) El sub-refredament es fa en un intercanviador de calor separat, el sub-refredador. El sub-refredament no es controla, este depèn de la condició externa i de la transferència de calor al sub-refredador.
Les bombes de calor es van assajar a diferents temperatures de l'aigua a l'entrada de l'evaporador (10ºC a 35ºC) i a l'entrada del condensador (10ºC a 55ºC), mentre que la temperatura de producció d'aigua, normalment, es fixa a 60¿C. Els resultats obtinguts han demostrat que el COP depèn molt del sub-refredament. En les condicions nominals (20ºC/15ºC per a la temperatura de l'aigua d'entrada/eixida a l'evaporador i 10ºC/60ºC per a la temperatura de l'aigua d'entrada/eixida en el condensador), el sub-refredament òptim és aproximadament de 43 K amb un COP d'escalfament de 5,61, que és al voltant del 31% més alt que el mateix cicle treballant sense sub-refredament. A més, el sistema amb sub-refredament ha provat de forma experimental, que és capaç de produir aigua fins als 90ºC, i ha mostrat un COP més alt que alguns productes comercials que treballen amb CO2 (dades de referència del catàleg).Pitarch I Mocholí, M. (2017). High capacity heat pump development for sanitary hot water production [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/81858TESI
Design, Development, and Testing of a Low Cost, Additively-Manufactured, Centrifugal Compressor
The three objectives of this research were to: 1.) design, build, and test AM compressors to substitute into COTS micro-gas turbine engines, 2.) provide initial correlations between FEA and compressor failure speed, and 3.) characterize the effects of AM on compressor performance. These goals improved the design cycle cost and the design-validation time cycle. ULTEM 9085, 300-AMB, and Onyx-Kevlar temperature-dependent tensile properties were measured. FEA-predicted failure speeds of stock compressor designs led design improvements, potentially fulfilling the original compressor requirements. Physical testing of the stock and ULTEM 9085 compressors occurred. Comparing these compressors\u27 performances demonstrated that low cost, AM materials are viable alternatives for certain micro-turbine applications. An improved Onyx-Carbon Fiber compressor was tested to failure. These results provide a proof of concept supporting AM compressors, improving the development time cycle. This approach enables high-risk yet low-cost research and development. Additionally, with proper mission planning, low-cost AM compressors could provide significant improvements to engine cost and weight for limited-life applications
Approximate Nonlinear Modeling of Aircraft Engine Surge Margin Based on Equilibrium Manifold Expansion
AbstractStable operation of aircraft engine compressions is constrained by rotating surge. In this paper, an approximate nonlinear surge margin model of aircraft engine compression system by using equilibrium manifold is presented. Firstly, this paper gives an overview of the current state of modeling aerodynamic flow instabilities in engine compressors. Secondly, the expansion form of equilibrium manifold is introduced, and the choosing scheduling variable method is discussed. Then, this paper also gives the identification procedure of modeling the approximate nonlinear model. Finally, the modeling and simulations with high pressure (HP) compressor surge margin of the aircraft engine show that this real-time model has the same accuracy with the thermodynamic model, but has simpler structure and shorter computation time
Analysis and Optimization of the Transient Operation of Gasoline Turbocharged Direct Injection Engines Under High EGR Conditions
[ES] El transporte por carretera es uno de los sectores que más contribuyen al cambio climático. Por ello, muchos gobernantes a nivel mundial están promoviendo una transición hacia medios de transporte sostenibles que no dependan de combustibles fósiles. Sin embargo, debido a la falta de competitividad de las alternativas actuales, no parece factible, en el corto plazo, reducir significativamente el uso de los motores de combustión. Así pues, es probable que los motores de gasolina (MEP) mantengan su papel dominante en el sector automotriz durante los próximos años. De ahí que sea crucial seguir mejorando estos motores a fin de reducir su huella de carbono.
Actualmente, es habitual fabricar motores MEP de pequeña cilindrada ("downsizing") con sistemas de sobrealimentación e inyección directa, a fin de reducir el consumo de combustible y las emisiones de CO2. Además, en la última década, se ha demostrado que la recirculación de gases de escape (EGR) puede mejorar la eficiencia de los motores MEP entre un 3 % y un 6 %, dependiendo del grado de carga. Como desventaja, para poder extraer todo el potencial de la estrategia EGR, es necesario trabajar con altas tasas de EGR, lo que puede causar ciertos problemas en condiciones transitorias. En esta tesis, se ha demostrado que el uso de altas tasas de EGR a través de sistemas de baja presión en motores MEP turboalimentados puede ralentizar la respuesta del motor y provocar fallos de encendido durante maniobras de aceleración y desaceleración, respectivamente.
Con la entrada en vigor de nuevos procedimientos de homologación de vehículos, como el WLTP (Worldwide harmonized Light vehicle Test Procedure), donde las operaciones transitorias tienen un peso importante, los fabricantes buscan que sus motores consuman y emitan menos en un amplio rango de condiciones de operación, tanto estacionarias como transitorias. Por ello, el objetivo principal de esta tesis es analizar y optimizar el funcionamiento, en condiciones transitorias, de los motores MEP que operan con altas tasas de EGR. Para ello, se ha empleado un motor de gasolina (Euro 6) de 1.3l turboalimentado con inyección directa, distribución variable y turbina de geometría variable. Se ha desarrollado un modelo unidimensional (1D) del motor para el estudio de la fluidodinámica y los fenómenos de transporte en su interior. Por otro lado, se ha ensayado el motor para calibrar el modelo 1D y evaluar aspectos difícilmente predecibles con dicho modelo, como las emisiones contaminantes y la estabilidad de la combustión.
Previo al estudio en condiciones transitorias, el motor fue calibrado con EGR, y se realizaron simulaciones para determinar el consumo de un vehículo convencional y otro híbrido, ambos con EGR, durante un ciclo WLTP. Finalmente, se concluyó que ciertas estrategias orientadas a mejorar el proceso de renovación de la carga pueden resolver la problemática del uso del EGR en condiciones transitorias. Eso sí, implementar dichas estrategias conllevaría un aumento en complejidad y costes.[CA] El transport per carretera és un dels sectors que més contribueixen al canvi climàtic. Per això, molts governants a nivell mundial estan promovent una transició cap a mitjans de transport sostenibles que no depenguen de combustibles fòssils. No obstant això, a causa de la falta de competitivitat de les alternatives actuals, no sembla factible, en el curt termini, reduir significativament l'ús dels motors de combustió. Així doncs, és probable que els motors de gasolina (MEP) mantinguen el seu paper dominant en el sector automotriu durant els pròxims anys. D'ací ve que siga crucial continuar millorant aquests motors a fi de reduir la seua petjada de carboni. Actualment, és habitual fabricar motors MEP de xicoteta cilindrada ("downsizing") amb sistemes de sobrealimentació i injecció directa, a fi de reduir el consum de combustible i les emissions de CO2. A més, en l'última dècada, s'ha demostrat que la recirculació de gasos d'escapament (EGR) pot millorar l'eficiència dels motors MEP entre un 3% i un 6%, depenent del grau de càrrega. Com a desavantatge, per a poder extraure tot el potencial de l'estratègia EGR, és necessari treballar amb altes taxes de EGR, la qual cosa pot causar uns certs problemes en condicions transitòries. En aquesta tesi, s'ha demostrat que l'ús d'altes taxes de EGR a través de sistemes de baixa pressió en motors MEP turboalimentats pot alentir la resposta del motor i provocar fallades d'encesa durant maniobres d'acceleració i desacceleració, respectivament. Amb l'entrada en vigor de nous procediments d'homologació de vehicles, com el WLTP (Worldwide harmonized Light vehicle Test Procedure), on les operacions transitòries tenen un pes important, els fabricants busquen que els seus motors consumisquen i emeten menys en un ampli rang de condicions d'operació, tant estacionàries com transitòries. Per això, l'objectiu principal d'aquesta tesi és analitzar i optimitzar el funcionament, en condicions transitòries, dels motors MEP que operen amb altes taxes de EGR. Per a això, s'ha emprat un motor de gasolina (Euro 6) de 1.3l turboalimentat amb injecció directa, distribució variable i turbina de geometria variable. S'ha desenvolupat un model unidimensional (1D) del motor per a l'estudi de la fluidodinàmica i els fenòmens de transport en el seu interior. D'altra banda, s'ha assajat el motor per a calibrar el model 1D i avaluar aspectes difícilment predictibles amb aquest model, com les emissions contaminants i l'estabilitat de la combustió. Previ a l'estudi en condicions transitòries, el motor va ser calibrat amb EGR, i es van realitzar simulacions per a determinar el consum d'un vehicle convencional i un altre híbrid, tots dos amb EGR, durant un cicle WLTP. Finalment, es va concloure que unes certes estratègies orientades a millorar el procés de renovació de la càrrega poden resoldre la problemàtica de l'ús del EGR en condicions transitòries. Això sí, implementar aquestes estratègies comportaria un augment en complexitat i costos.[EN] Road transport is a major contributor to climate change. However, given the lack of competitiveness of fossil fuel-free alternatives, it does not seem possible to reduce the dependence on the internal combustion engine (ICE) as rapidly as planned by the authorities. Advanced gasoline engines will therefore hold a high market share in the automobile industry in the following years, at least during the next decade, either working in conventional or hybrid powertrains. Hence it is essential to keep improving these engines to reduce the negative impact of light-duty vehicles on the environment.
The most used strategy to reduce fuel consumption and CO2 emissions in current spark-ignition (SI) gasoline engines is downsizing combined with direct injection (DI). Besides, downsizing must go hand in hand with turbocharging to maintain peak power. It is also proven that exhaust gas recirculation (EGR) can improve fuel economy in SI engines by 3-6% at medium and high loads. As a disadvantage, extracting the full benefit from EGR requires operating with high recirculation rates (close to the EGR dilution limit), leading to some issues under transient conditions. In this thesis, it is demonstrated that high EGR operation through long-route systems in turbocharged engines can potentially originate combustion instabilities and poor engine response during load-decrease (tip-out) and load-increase (tip-in) maneuvers, respectively.
Transient operations are especially important for manufacturers since the implementation of the Worldwide harmonized Light vehicle Test Procedure (WLTP). The present thesis is therefore devoted to analyzing and optimizing the gasoline engine performance under high EGR conditions during relevant transient maneuvers. To this end, a Euro-6 1.3L turbocharged DI SI gasoline engine with a variable geometry turbine was employed. A 1D model of this ICE was developed to assess fluid dynamics and transport phenomena. Engine tests were also performed to validate the 1D model and evaluate torque response, combustion stability, and raw exhaust emissions.
Before addressing the study of transient maneuvers, the engine calibration with EGR was carried out, and 0D conventional and hybrid vehicle simulations were done to determine the EGR benefit in fuel economy under WLTP driving conditions. Finally, tip-in and tip-out results revealed that some air management strategies are effective in meeting the transient EGR challenges in SI engines, but at the expense of increased complexity and costs.González Domínguez, D. (2023). Analysis and Optimization of the Transient Operation of Gasoline Turbocharged Direct Injection Engines Under High EGR Conditions [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/19385
Contribution to the Experimental Characterization and 1-D Modelling of Turbochargers for IC Engines
At the end of the 19th Century, the invention of the Internal Combustion Engine
(ICE) marked the beginning of our current lifestyle. Soon after the first ICE
patent, the importance of increasing air pressure upstream the engine cylinders was
revealed. At the beginning of the 20th Century turbo-machinery developments (which
had started time before), met the ICE what represented the beginning of turbocharged
engines. Since that time, the working principle has not fundamentally changed. Nevertheless,
stringent emissions standards and oil depletion have motivated engine developments;
among them, turbocharging coupled with downsized engines has emerged
as the most feasible way to increase specific power while reducing fuel consumption.
Turbocharging has been traditionally a complex problem due to the high rotational
speeds, high temperature differences between working fluids (exhaust gases,
compressed air, lubricating oil and cooling liquid) and pulsating flow conditions. To
improve current computational models, a new procedure for turbochargers characterization
and modelling has been presented in this Thesis. That model divides turbocharger
modelling complex problem into several sub-models for each of the nonrecurring
phenomenon; i.e. heat transfer phenomena, friction losses and acoustic
non-linear models for compressor and turbine. A series of ad-hoc experiments have
been designed to aid identifying and isolating each phenomenon from the others. Each
chapter of this Thesis has been dedicated to analyse that complex problem proposing
different sub-models.
First of all, an exhaustive literature review of the existing turbocharger models
has been performed. Then a turbocharger 1-D internal Heat Transfer Model (HTM)
has been developed. Later geometrical models for compressor and turbine have been
proposed to account for acoustic effects. A physically based methodology to extrapolate
turbine performance maps has been developed too. That model improves
turbocharged engine prediction since turbine instantaneous behaviour moves far from
the narrow operative range provided in manufacturer maps. Once each separated
model has been developed and validated, a series of tests considering all phenomena
combined have been performed. Those tests have been designed to check model
accuracy under likely operative conditions.
The main contributions of this Thesis are the development of a 1-D heat transfer
model to account for internal heat fluxes of automotive turbochargers; the development
of a physically-based turbine extrapolation methodology; the several tests
campaigns that have been necessary to study each phenomenon isolated from others
and the integration of experiments and models in a comprehensive characterization
procedure designed to provide 1-D predictive turbocharger models for ICE calculation.Reyes Belmonte, MÁ. (2013). Contribution to the Experimental Characterization and 1-D Modelling of Turbochargers for IC Engines [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/34777TESI
A numerical approach for predicting flow-induced acoustics at near-stall conditions in an automotive turbocharger compressor
Se realiza un modelo CFD-3D de un compresor centrífugo. Se determina la configuración numérica adecuada para simular puntos de funcionamiento cercanos a bombeo. Se validan los resultados frente a ensayos experimentales realizados en cámara anecoica. Se analizan los resultados, justificando las características del ruido emitido por el compresor a partir de los patrones de flujo encontrados. En particular, se analiza el flujo en la holgura entre los álabes y la carcasa del compresor y en la parte posterior del rodete. Por último, se analiza la influencia de las geometrías aguas arriba del compresor en el ruido producido por éste.Navarro García, R. (2014). A numerical approach for predicting flow-induced acoustics at near-stall conditions in an automotive turbocharger compressor [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/44114TESISPremios Extraordinarios de tesis doctorale
Performance analysis and dynamics of innovative SOFC hybrid systems based on turbocharger-derived machinery
La crescente consapevolezza su temi quali il cambiamento climatico e l\u2019inquinamento atmosferico ha portato a politiche nazionali ed internazionali mirate allo sviluppo di sistemi energetici innovativi e sostenibili. Tra di essi, le fuel cell sono uno dei pi\uf9 promettenti, essendo caratterizzate da alte efficienze e basse emissioni. In particolare, i sistemi ibridi basati sull\u2019integrazione di fuel cell ad alta temperatura con dispositivi derivati da turbocompressori hanno attirato l\u2019attenzione del mondo accademico e dell\u2019industria negli ultimi decenni. Tuttavia, la complessit\ue0, la fragilit\ue0 e l\u2019alto costo di questi impianti ha rallentato il loro sviluppo, e solo poche grandi aziende sono state in grado di realizzare prototipi completi. Le difficolt\ue0 tecniche affrontate dalla comunit\ue0 scientifica hanno messo in luce l\u2019importanza delle simulazioni per progettare, testare, controllare e analizzare i sistemi ibridi a fuel cell.
Sulla base di tale esperienza, questa tesi mira ad espandere la attuale conoscenza sui sistemi ibridi a fuel cell a ossidi solidi, ponendo una particolare attenzione su un innovativo sistema turbocompresso di piccola taglia, alimentato con biogas e recentemente introdotto all\u2019interno del progetto europeo Bio-HyPP. Lo scopo principale della tesi \ue8 determinare se questo tipo di sistema possa essere una valida alternativa ai sistemi basati su microturbine a gas, analizzando il suo comportamento in relazione a diversi scenari, sia stazionari, sia transitori. Per fare ci\uf2, \ue8 necessario definire i vincoli operativi del sistema e sviluppare un sistema di controllo in grado di rispettarli, ottimizzando al tempo stesso le prestazioni dell\u2019impianto. Inoltre, l\u2019affidabilit\ue0 dei sistemi ibridi pu\uf2 essere migliorata grazie all\u2019implementazione di strumenti diagnostici e di procedure per prevenire il pompaggio del compressore. La parte finale della tesi \ue8 mirata allo studio di tali strumenti, al loro sviluppo e alla loro integrazione con il sistema di controllo.
Tutte le attivit\ue0 presentate in questa tesi sono state svolte facendo affidamento su strumenti di simulazione. Ci\uf2 \ue8 stato possibile grazie alla collaborazione tra il Laboratorio di Matematica Applicata, Simulazione e Modellistica Matematica e il Thermochemical Power Group dell\u2019Universit\ue0 degli Studi di Genova.
Dopo aver presentato il layout del sistema a fuel cell con turbocompressore, un dettagliato modello stazionario dell\u2019impianto sviluppato in Matlab\uae-Simulink\uae \ue8 stato utilizzato per progettare una strategia, basata sul controllo di valvole installate sull\u2019impianto, in grado di rispettare tutti i suoi vincoli operativi. Successivamente, \ue8 stata svolta un\u2019analisi di prestazioni in off-design, considerando allo stesso tempo diverse condizioni di carico di potenza e di temperatura ambiente. Tale analisi \ue8 stata utilizzata per confermare l\u2019efficacia della strategia di controllo proposta, e per valutare le capacit\ue0 del sistema con turbocompressore.
Successivamente \ue8 stato creato un modello dinamico utilizzando lo strumento TRANSEO, in modo da studiare il comportamento del sistema durante i transitori. Avendo adottato una strategia di controllo basata sulla valvola di cold bypass, \ue8 stata analizzata la risposta del sistema ad una sua apertura a gradino, al fine di progettare un sistema di controllo efficace e reattivo, in grado di mantenere la massima temperatura di cella costante e, allo stesso tempo, di rispettare i vincoli del sistema. Sono stati progettati quattro diversi controllori, che successivamente sono stati testati su due diversi scenari di variazione di carico e confrontati sulla base di vari parametri operativi.
La parte finale della tesi ha riguardato lo sviluppo di innovativi strumenti che possano aumentare l\u2019affidabilit\ue0 dei sistemi ibridi a fuel cell a ossidi solidi, in particolare tecniche di prevenzione del pompaggio e sistemi di diagnostica basati su reti Bayesiane. Un modello semplificato del sistema con turbocompressore \ue8 stato sviluppato in TRANSEO e sono state testate diverse tecniche di prevenzione del pompaggio: condizionamento del flusso d\u2019aria, iniezione di acqua, ricircolo e bleed, installazione di un eiettore all\u2019imbocco del compressore. Le soluzioni pi\uf9 efficaci sono state integrate con il controllore del sistema ibrido e sono state testate durante un transitorio per evitare che il punto operativo del compressore si avvicinasse al pompaggio.
Infine, grazie ad una collaborazione tra l\u2019Universit\ue0 degli Studi di Genova e la M\ue4lardalens H\uf6gskola di V\ue4ster\ue5s, in Svezia, sono state sviluppate delle reti Bayesiane per la diagnostica di sistemi ibridi a fuel cell a ossidi solidi con microturbina a gas. Questa attivit\ue0 \ue8 stata svolta simulando il sistema su Matlab\uae-Simulink\uae e creando le reti Bayesiane su Hugin Expert. Due sistemi di diagnostica, uno per la microturbina e uno per la fuel cell, sono stati sviluppati e testati in condizioni stazionarie. Il secondo \ue8 stato anche testato in condizioni dinamiche e integrato con il sistema di controllo per prevenire l\u2019usura della cella.
In conclusione, questa tesi ha messo in luce il grande potenziale dei sistemi ibridi SOFC-turbocompressore, mostrando la loro alta efficienza in un ampio intervallo di condizioni operative in termini di carico elettrico e temperatura ambiente. La tesi ha anche dimostrato che \ue8 possibile garantire il corretto funzionamento di questi sistemi durante diversi scenari transitori, implementando controllori a cascata progettati per agire sulla valvola di bypass freddo per controllare la massima temperatura della cella. Per quanto riguarda la possibilit\ue0 di migliorare l\u2019affidabilit\ue0 di tali sistemi, le tecniche basate sul ricircolo del compressore sono risultate essere le pi\uf9 efficaci per allontanare il sistema da una condizione di pompaggio. I risultati delle simulazioni mostrano come la loro integrazione con strumenti di monitoraggio possa prevenire diverse situazioni di pericolo. La parte finale della tesi ha mostrato come il deterioramento dei sistemi ibridi a SOFC possa essere limitato grazie a reti Bayesiane, che sono state utilizzate per diagnosticare accuratamente le condizioni di un sistema SOFC-microturbina a gas, ma potrebbero ugualmente essere applicate su impianti con turbocompressore.The growing awareness on climate change and pollution has brought to national and international policies aimed at promoting the development of innovative and environmentally sustainable energy systems. Among these systems, fuel cells are one of the most promising technologies, characterized by high energy conversion efficiencies and low emissions. In particular, hybrid systems based on the integration of a high temperature fuel cell with turbocharger-derived machinery have drawn the interest of academia and industry over the past decades. However, the complexity, fragility and high cost of these plants have slowed down their development, and only a few big companies were able to build complete prototypes. The technological challenges faced by the scientific community have highlighted the importance of simulations to design, test, control and analyse fuel cell hybrid systems.
Based on this experience, this thesis wants to expand the current knowledge on solid oxide fuel cell hybrid systems, with a particular focus on an innovative small-scale biofueled turbocharged layout, which was introduced recently within the Bio-HyPP European project. The main goal of this thesis is to determine if this kind of system can be a viable alternative to micro gas turbine-based systems, analysing its steady-state and transient behaviour in various operating conditions. To do this, it is necessary to define the system operative constraints, and to develop a control system capable of ensuring their compliance, while optimizing the plant performance. The possibility of increasing the reliability of solid oxide fuel cell hybrid systems is finally investigated, considering the implementation of surge prevention techniques and diagnostic tools.
All these activities strongly relying on simulation tools. This was possible thanks to the collaboration between the Laboratory of Applied Mathematics, Simulation and Mathematical Modelling with the Thermochemical Power Group of the University of Genoa.
After introducing the layout of the turbocharged fuel cell system, a detailed steady-state model of the plant is developed in Matlab\uae-Simulink\uae and used to design a strategy, based on the control of valves installed on the plant, able to comply with its many operative constraints. Then, an off-design performance analysis of the system is performed, considering simultaneously various conditions of power load and ambient temperature. This analysis is used to confirm the effectiveness of the proposed control strategy and to assess the capabilities of the turbocharged system.
A dynamic model is created using the TRANSEO tool to study the transient behaviour of the system. Having adopted a control strategy based on the cold bypass valve, the response of the system to a valve opening step change is analysed in order to design an effective and responsive control system, able to keep the fuel cell maximum temperature constant while complying with the system constraints. Four different controllers are designed, tested on two different load variation scenarios and compared on the basis of many parameters.
The final part of the thesis regards the development of innovative tools aimed at improving the reliability of solid oxide fuel cell hybrid system, in particular surge prevention techniques and Bayesian belief network-based diagnosis systems.
A simplified dynamic model of the turbocharged SOFC system is developed in TRANSEO, and various surge prevention techniques are tested on it: intake air conditioning, water spray at compressor inlet, air bleed and recirculation, and installation of an ejector at the compressor intake. The most effective procedures are integrated with the controller of the hybrid system and tested during a transient scenario to prevent the compressor operative point from approaching a surge condition.
Bayesian belief networks aimed at diagnosing the status of SOFC hybrid systems are developed thanks to a collaboration between the University of Genoa and the M\ue4lardalens H\uf6gskola of V\ue4ster\ue5s, Sweden. A micro gas turbine \u2013 solid oxide fuel cell system is considered for this study, but the methodology could be easily extended to turbocharged plants. The activity is carried out simulating the system on Matlab\uae-Simulink\uae and designing the Bayesian networks on Hugin Expert. Two different diagnosis systems, one for the turbomachinery and one for the fuel cell stack, are developed and tested on stationary conditions. The second one is also tested during transients and integrated with the control system to prevent degradation of the fuel cells.
In conclusion, this thesis highlighted the great potential of turbocharged SOFC hybrid systems, showing high energy conversion efficiencies in a wide operative range in terms of load and ambient conditions. It also showed that the proper operation of the system is possible during various transient scenarios, implementing cascade controllers designed to act on a cold bypass valve to control the SOFC maximum temperature. Regarding the possibility of improving the reliability of these systems, surge prevention techniques based on compressor recirculation appeared as the most effective ones. Simulation results suggest that their integration with a surge precursors detection tool could avoid the occurrence of many potentially dangerous scenarios. The final part of this thesis showed that the durability of SOFC hybrid systems could be further improved thanks to Bayesian belief networks, which were proved to effectively diagnose the status of SOFC-MGT systems but could be applied to turbocharged plants as well
Study of Hybrid Solar Gas Turbine System: T100 Modeling and Dynamic Analysis of Thermal Energy Storage
Concentrated Solar Power (CSP) hybrid gas turbine systems particularly based on the micro Gas Turbines (mGT) will be of great importance in future power infrastructure where energy security, economic feasibility and clean and efficient power generation are the key concerns. Integration of Thermal Energy Storage (TES) in CSP hybrid gas turbine systems could be a viable solution to overcome the intermittent nature of solar power, and increase the dispatchability. Based on this perception, a comprehensive analysis of both mGT cycle and TES technology should be undertaken, in order to achieve a better understanding of the behavior of TES and its interaction with other components in a hybrid gas turbine system. The present work intends to contribute to this analysis through mGT and TES system modeling and testing. This thesis is framed in two main parts: first part deals with T100 mGT modeling and second part focuses on the study of thermal storage systems. Regarding TES, detailed dynamic analysis of sensible heat storage is provided, while a preliminary study of thermochemical storage is conducted.
The mGT performance diagnosis involves the development for steady-state simulation of T100, model validation, and application in real operating conditions at the Ansaldo Energia AE-T100 test rig. Furthermore, diagnostic application of the AE-T100 model for whole mGT cycle is discussed with the help of two case studies at AE-T100 test rig. AE-T100 model has also been applied in the real operating conditions of micro Humid Air Turbine (mHAT) system located at Vrije Universiteit Brussel (VUB), to highlight the modeling capability of AE-T100 tool as well as monitoring the recuperator performance in the VUB-mHAT cycle.
The second part of this work concerns the dynamic modeling and experimental validation of a sensible TES system at laboratory scale, which is part of the Hybrid Solar Gas Turbine (HSGT) system developed at the University of Genova. TES is modeled with the help of a two-dimensional CFD model based on the ANSYS-FLUENT code, and a one-dimensional TRANSEO model employing software designed by the Thermochemical Power Group (TPG) at the University of Genova. The experimental validation, modeling capability to present the actual thermal stratification and State of Charge (SoC) of the TES, and scope of each model are also discussed. This study also highlighted the potential of TES system based on the monolithic structures for hybrid gas turbine systems i.e. low pressure drop across the TES
which are acceptable for the whole gas turbine hybrid system, modular structure of the storage and very low thermal losses.
In addition to the sensible heat storage system, ThermoChemical Storage (TCS) based on the redox cycle of cobalt oxides pair Co3O4\CoO was finally studied by the candidate during research period at Zhejiang University, China. The mathematical model which has been developed in MATLAB is based on the mass and energy conservation and reaction kinetics of the redox cycle, and has been validated against the experimental data available from literature. This work was aimed to study the process of thermochemical storage and understand the reaction kinetics of cobalt oxides with less computational effort. This analysis will help in design and optimization of the actual TCS system at the Zhejiang University, China.
Overall, the knowledge and modelling capabilities developed for mGT cycle and TES systems in this study will be merged to develop a single simulation tool for mGT based CSP hybrid systems, in the future
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