Turbochargers are used on many automotive internal combustion engines to increase power density. The broad operating range of the engine also requires a wide range of the turbocharger compressor. At low mass flows, however, turbo compressor operation becomes unstable and eventually enters surge. Surge is characterized by large oscillations in mass flow and pressure. Due to the associated noise, control problems, and possibility of mechanical component damage, this has to be avoided. Different indicators exist to classify compressor operation as stable or unstable on a gas stand. They are based on pressure oscillations, speed oscillations, or inlet temperature increase. In this thesis, a new stability indicator is proposed based on the Hurst exponent of the pressure signal. The Hurst exponent is a number between zero and one that describes what kind of long-term correlations are present in a time series. Data from three cold gas stand experiments are analyzed using this criterion. Results show that the Hurst exponent of the compressor outlet pressure signal has good characteristics. Stable operation is being indicated by values larger than 0.5. As compressor operation moves towards the surge line, the Hurst exponent decreases towards zero. An additional distinction between the long-term correlations of small and large amplitude fluctuations by means of higher order Hurst exponents can be used as an early warning indicator. Further tests using compressor housing accelerometers show that the Hurst exponent is not a good choice for real-time surge detection on the engine. Reasons are the long required sampling time compared to competing methods, and the fact that other periodically repeating oscillations lead to Hurst exponents close to zero independent of compressor operation. / Turboladdare används ofta på förbränningsmotorer för att öka motorns effekttäthet. Motorns breda driftområde ställer krav på ett brett driftområde för turboladdarens kompressor. Vid låga massflöden blir kompressordriften dock mindre stabil, och surge kan uppträda. Surge innebär stora oscillationer i tryck och massflöde genom kompressorn. På grund av oljud, reglerproblem och risken för mekaniska skador vill man undvika surge. Det finns indikatorer för att bedöma kompressorns stabilitet på ett gas stand. Indikatorerna är baserade på tryckoscillationer, varvtalsoscillationer, eller temperaturökning i gasen i kompressorinloppet. I denna avhandling presenteras en ny indikator baserad på Hurst-exponenten, beräknad på trycksignalen. Hurst-exponenten är ett tal mellan noll och ett som beskriver vilka typer av långtidskorrelationer det finns i signalen. Mätningar från tre gas-stand-experiment har analyserats på detta sätt. Analyserna visar att Hurst-exponenten baserad på kompressorutloppstrycket fungerar bra som som surgeindikator. Stabil drift av kompressorn indikeras av att Hurst-exponenten är större än 0.5. När kompressordriftpunkten närmar sig surgelinjen faller Hurst-exponenten mot noll. En distinktion mellan oscillationer med små och stora amplituder kan används för att få en tidig varning. Analyser av vibrationsmätningar på kompressorhuset vid motorapplikation visar att Hurst-exponenten inte är lämplig som realtidsindikator på en motor. Detta kommer sig dels av att data behöver samlas in under en längre tid än med andra tänkbara indikatorer, dels av att andra periodiska oscillationer i signalen kopplade till motorns naturliga beteende leder till Hurst-exponenter nära noll även vid stabil kompressordrift. / <p>QC 20170510</p> / CCGEx - Compressor off-Design

Turbocharging is used as a means to downsize petrol engines, thereby, producing more power for a lower engine size, when compared with a naturally aspirated engine. Due to the presence of a throttle valve in the intake system in petrol engines, flow is restricted at the outlet pipe of the compressor during low load engine operation. For example, during transient tip out tip in maneuvers. Hence, there is a chance of the turbocharger operating in near surge or surge conditions and, thus, generating surge noise. This Thesis describes an experimental and simulation method to predict and measure the turbocharger surge noise. Initially, experimental transient tip-in and tip-out maneuver was performed on a non turbocharged car with a petrol engine. The measured noise level in the intake manifold, at a low frequency of up to 1200 Hz, was analysed and was shown not to represent surge noise. Next, a one dimensional simulation method was applied to simulate the noise of the engine and this demonstrated an increase in the acoustic pressure level in the intake manifold during the tip in and tip out maneuver. However, a surge noise pattern was not observed in the analysis of acoustic pressure signals in the intake system using Short Time Fourier Transform (STFT). The simulation procedure was also used to inform the design of an experimental rig to recreate the surge noise under laboratory conditions. An experimental turbocharger noise rig, designed and built for this purpose, is explained in the Thesis. Important component parts likely to be involved in the surge noise generation such as the intake system, compressor, throttle body, compressor recirculation valve and measurement and control systems were integrated into the test rig. Background noise contributions from the electric motor, AC mains, supercharger pulley, throttle body, inverter fan, throttle body gearing and structural vibration of the supporting structure were identified from the analysed frequency components of the signals from surface microphone measurements taken at the intake system. This helped to clearly identify the surge noise frequency components (3250 Hz) in the STFT analysis. The fundamental mechanism of noise generation was identified using an analysis of the experimental results and a frequency calculation for vortex shedding and the radial acoustic resonances. One of the main conclusions of the Thesis is that the compressor recirculation valve (CRV) open or close position, the CRV delay time and the throttle position are major contributing factors to the cause of the surge noise. Another major conclusion is that the radial acoustic resonance may be a mechanism of surge noise generation. Finally, a passive solution to reduce the surge noise is proposed. A pipe with cross ribs is designed as a passive solution using the radial acoustic resonance calculation and the corresponding nodal patterns. This solution demonstrated a measured intake system noise reduction of up to 10dB under compressor surge conditions.

Turbocharger performance maps are vital components used in an engine-turbocharger matching process, a 1D engine performance development stage and a day-to-day operation of a turbocharged vehicle. The main aim of this thesis is the investigation of the turbocharger compressor performance when operating with an alternative to air substitute gas. This occurs, for instance, when turbocharging and low pressure exhaust gas recirculation (LP EGR) technologies are combined. To conduct the experimental study of the turbocharger performance with substitute gas a steady-state turbocharger test facility with a compressor closed-loop mode has been designed and built within this thesis by the author. Also, for the most accurate performance map determination an uncertainty analysis of a selected turbocharger performance map and an extensive study on surge have also been carried out. The sensor based uncertainty analysis has been a key aspect to help to understand the links between the accuracy of measured quantities and the overall uncertainty of the performance parameters. Such knowledge allowed for a selection of sensors targeting the most accurate data measurement. While investigating the uncertainty of the turbocharger performance maps heat transfer related efficiency uncertainty was also studied. Namely, a series of a semi-adiabatic tests were performed in the low turbocharger speed region which highlighted the issues related to a work and heat transfer separation and uncertainty of the extrapolated performance data. Also, a contribution to the turbocharger heat transfer modelling has been made by supporting the in-house lumped capacitance thermal node model with the 3D CHT (conjugate heat transfer) simulations [1, 2]. Finally, a study of a literature based compressor heat estimation method was performed as an alternative way of separating work and heat transfer (with low speed adiabatic mapping). The experimental surge study was conducted in phases and included the analysis and comparison of the low and high frequency pressure data gathered at various locations downstream and upstream from the compressor and temperature data collected at close distance from impeller eye. It has been concluded that the post-compressor located pressure measurement is preferable (than the pre-compressor pressure measurement) as the FFT (Fast Fourier Transform) magnitude of the peak frequency associated with surge is independent on the distance of the sensor from the compressor. The useage of the temperature sensor installed at the closest distance from the compressor entry allowed an observation of the near surge temperature rise (a result of the air recirculation). However, due to the inconsistent rate of the temperature rise across the various speed lines along with the poor response it offers no benefit from the surge avoidance point of view. The comparison of the available surge metrics revealed that the resultant surge lines were drawn at different operating points especially at the higher turbocharger speed lines where the surge development investigated by the rise of the low frequency FFT magnitude peaks was much more visible. The experimental tests performed in steady-state and pulsating flow conditions have indicated larger surge margin availability for the latter case [3]. Development of a turbocharger rig and gaining the confidence in turbocharger performance map generation allowed the author to carry out the investigation over compressor performance with a substitute gas. The study covered two cases of homogeneous and non-homogeneous gas introduction representing a well and a poorly mixed gases respectively. The substitute gas included various mixtures of CO2 and air and pure CO2. It has been highlighted that when comparing turbomachinery performance maps working with substitute gas non-dimensional speed and mass flow parameters shall be introduced. These parameters allow for the map corrections with respect to individual gas constant (R) and ratio of specific heats (γ). The experimentally obtained compressor performance maps with low CO2 concentration in CO2-air mixtures (3%, 5% and 10%) were successfully corrected with the use of non-dimensional speed and mass flow parameters. However, the compressor performance map obtained for the pure CO2 has revealed significant offsets in pressure ratio, efficiency, surge and choke flow locations. This is due to a significantly different γ. In the attempt of the further performance correction a method proposed by Roberts and Sjolander has been followed. As a result of such, a poor match between the measured and predicted values of compressor efficiency was achieved (n exponent = 0.8). A closer correlation was obtained if the n exponent was made a speed dependent variable. This observation has suggested that the measurement of compressor efficiency was affected by the heat transfer between the uninsulated turbomachinery components. Due to the time limitations this assertion has not been investigated experimentally. Realising this limitation, therefore, a series of adiabatic CFD simulations have been performed instead. These simulations have shown that for the case of pure CO2 a reasonable match between the simulated and predicted values of efficiency and pressure ratio was achieved. The experimental and numerical comparison of the compressor performance for homogeneously and non-homogeneously introduced substitute gas did not show any significant compressor performance changes. Finally, experimental study of selected configurations of the intake pipework and EGR mixing valve has shown that complex flow regimes can be developed within the LP EGR system affecting the compressor’s surge margin, efficiency and width of the map. This demonstrates that the aerodynamic disturbances of an EGR mixing valve may have the largest influence on the compressor map compared to all other factors.

Automotive turbochargers (TCs) increase internal combustion engine power and efficiency in passenger and commercial vehicles. TC rotors are usually supported on floating ring bearings (FRBs) or semi-floating ring bearings (SFRBs), both of which are inexpensive to manufacture. However, fluid film bearings are highly nonlinear components of TC units and contribute to the complex behavior (i.e. bifurcations and frequency jumps between a first whirl frequency and a second whirl frequency) of the entire rotor-bearing system (RBS). The frequency jump phenomenon concerns the TC manufacturing industry due to increased levels of noise generation. This thesis presents progress on assessing the effects of some bearing parameters and operating conditions on the RBS dynamic forced performance and the frequency jump phenomenon. A fluid film bearing model is integrated into a finite element rotordynamics computational model for numerical prediction of the TC linear and nonlinear (time transient) forced response. Since automotive TCs operate with variable rotational speed, predictions are conducted with shaft acceleration/deceleration. Over most of its operating speed range, TC rotor nonlinear response predictions display two subsynchronous whirl frequencies w1 and w 2 representing a conical mode and a cylindrical bending mode, respectively. At low shaft speeds w1 is present up to a shaft speed (Omega bifurcation), where there is a frequency jump from w1 to w 2. The second whirl frequency may persist up to the highest shaft speeds (depending on operating conditions). Results show during rotor deceleration the Omega bifurcation may be different from the one during rotor acceleration (hysteresis). Predictions show the following factors delay the Omega bifurcation: increasing oil supply pressure, decreasing oil supply temperature, and increasing shaft acceleration. Also, rotor imbalance distribution greatly affects Omega bifurcation and the shaft amplitude of total motion. Overall, this study shows the sensitivity of bifurcations and frequency jump phenomenon in TC nonlinear response due to various bearing parameters and operating conditions. Further analysis is required to generalize these findings and to assess the effect of other bearing parameters (i.e. clearances, outer film length, ring rotation, etc.) on this phenomenon. In addition further validation of the predictions against test data is required for refinement of the predictive tool.

With huge demands for potable water in regions lacking fresh water sources such as surface or ground water, various potential technologies have been explored for eliminating water shortage. Seawater emerged as a potential source and a major lifeline for such water-deprived areas. The development of seawater reverse osmosis (SWRO) technology proved to be a groundbreaking innovation, making it easier to extract pure water from seawater. Ever since its inception, SWRO technology has taken many leaps towards the development of energy efficient and high yielding systems. The reduction in energy consumption of desalination plants that were based on the SWRO technology emerged as a major driver of the technology revolution in this field. The improvement of membrane life and salt rejection, increase in recovery, and decrease in energy consumption has been the primary criteria for sifting through available technologies for incorporation in desalination plants. Many developments have, ever since, occurred in this direction. The membrane life has multiplied and the Total Dissolved Solids in the product are now as low as 100 mg/L. In addition, recoveries of 40-50% have been achieved. By recycling energy, many SWRO desalination plants have significantly lowered their total energy consumption. With the help of energy recovery devices (ERDs), it is now possible to decrease power consumption and increase efficiency of the seawater reverse osmosis desalination plant. The first large-scale municipal SWRO plant was installed in 1980 in Jeddah, Saudi Arabia. This plant consumed 8 kilowatt-hours energy per cubic meter of water produced. This consumed energy was less than half of what was usually consumed by other conventional distillation processes. However, the SWRO desalination technology has one disadvantage. The seawater, which is to be desalinated, is pressurized with the help of high-pressure pumps. A large amount of energy is consumed during this process. Once the desalination is complete, the remaining reject water has to be eliminated as waste. Since the brine reject produced in this process has a high pressure, simply dumping it back into the sea is a waste of energy. This pressure can be reused and thus, the energy could be recycled. This idea led to the innovation of energy recovery devices (ERDs) that prevent the wastage of energy in the SWRO process. The hydraulic energy in the highly pressurized reject brine can be re-used with the help of ERDs, and energy consumption can thus be reduced by significant high amounts. The development of ERDs helped in the set-up and operation of large-scale SWRO plants, and facilitated the economic viability of the desalination process. The energy requirements of conventional SWRO plants are presently as low as 1.6 kWh/m3, making the process more cost effective and energy efficient than other technologies. About 80% of the total cost of desalinated water is due to energy consumption and capital amortization. The remaining costs are associated with other maintenance operations such as replacement of membranes and other components, labor associated costs etc. Since energy consumption is the main determinant of final costs of the product, increasing energy efficiency of the plants is of primary concern. This paper deals with various energy recovery devices such as the Francis turbine, Pelton wheel, turbocharger, Recuperator, DWEER and Pressure Exchanger, used in SWRO desalination plants along with case studies associated with each of these. Special focus is given to the energy efficiency and costs associated with these devices. A brief discussion of the devices that are currently under investigation is also provided in the conclusion. An analysis of isobaric versus centrifugal devices is also conducted in this work. A comparison between the energy recovery turbine (ERT) manufactured by Pump Engineering Inc. (PEI) and the pressure exchanger (PX) manufactured by Energy Recovery Inc. (ERI) energy recovery systems is performed using collected data from provided water analyses and respective manufacturers' device specifications. The different configurations used for this comparison were applied to the Jeddah SWRO desalination plant for a total productivity of 240,000 m³/day. As a result of this analysis, the specific energy consumption of the ERT and PX configurations were 2.66 kWh/m3 and 2.50 kWh/m3 respectively. Analysis shows however that although the PX configuration achieved the best specific energy consumption, the ERT was favored over it due to its lower capital and maintenance costs. Therefore, the final conclusion of this work, in this special case, is that the ERT configuration is more economical than the PX configuration.

Orientador: Milton Dias Júnior / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-25T09:48:12Z (GMT). No. of bitstreams: 1 Nomura_PaulaWatanabe_M.pdf: 4842075 bytes, checksum: fb2b3e20baadde947cb7b9aad16227d8 (MD5) Previous issue date: 2014 / Resumo: As novas legislações de emissões demandam das montadoras de veículos automotores, o desenvolvimento de tecnologias para melhorar o consumo de combustível e emissão de poluentes. Seguindo esta tendência, os sistemas de turbocompressores inovam junto e lançam ao mercado novas arquiteturas de turbos. Uma delas é o turbocompressor regulado de dois estágios, que otimiza a eficiência em um intervalo de rotação mais amplo. Neste sistema, há dois turbocompressores: o estágio de baixa pressão e de alta pressão. O primeiro tem maior influência nas baixas rotações, enquanto o segundo nas altas rotações do motor. Entre os dois estágios, existe uma válvula bypass que controla a passagem do gás de escape para o estágio de baixa pressão, evitando assim, sobrecarregar o estágio de alta pressão. Esta válvula bypass é composta por um eixo rotativo e uma bucha fixa, e exatamente entre estes dois componentes foi detectado desgaste, aumentando as folgas e causando vazamento de gás. Com o objetivo de diminuir este vazamento e resolver o problema, uma investigação sobre este desgaste prematuro foi iniciada dentro da empresa onde a autora da presente dissertação trabalha. Neste trabalho a análise de forças das condições estática e dinâmica que envolve a bucha e o eixo, as forças e momentos para abrir e fechar o prato da válvula, e as equações de movimento são apresentadas. A análise experimental inclui medições feitas em dois motores reais: um deles conectado a um dinamômetro e o outro instalado em um veículo usado na mesma aplicação onde o desgaste excessivo foi observado. Além disso, a análise de desgaste de dez pares bucha-eixo que retornaram de testes de durabilidade é apresentado. A comparação do desgaste entre dois sistemas de bucha e eixo foi realizada. Ambos os sistemas rodaram na mesma condição, exceto pela frequência de operação da válvula de controle, assim a influência desta frequência pôde ser analisada. Ao final, todo este dado foi coletado e usado para o cálculo de taxa de desgaste que avalia a influência de diferentes parâmetros de design sobre a taxa de desgaste / Abstract: The new emission legislations demand, from vehicle manufactures the development of technologies to improve fuel consumption and pollutants emission. Following this trend, the turbocharging systems innovate together and release new turbocharger architectures in the market. One of them is the regulated-two-stages turbocharger, which optimizes the efficiency in a broader engine speed range. In this system, there are two turbochargers, the high and low pressure stages. The former has a bigger influence on the low engine speeds, and the latter in the higher engine speeds. Between both stages there is a bypass valve that controls the gas flow to the low pressure stage, avoiding overpressure in the high pressure stage. This bypass valve is composed by a rotating shaft and a fixed bushing, and exactly between these two components it was detected wear, increasing the clearances and causing gas leakage. In order to reduce this leakage and solve the problem, an investigation about this premature wear has started inside the company where the author of the present dissertation works. In the present work the force analysis of the static and dynamic conditions that involve the shaft and bushing, the forces and momentum to open and close the valve plate, and the equations of motion are presented. The experimental analysis includes measurements made on two real engines: one of them connected to a dynamometer and the other installed on a vehicle used on the same application where the excessive wear was observed. Also, the wear analysis of ten shafts and bushings returned from durability tests is presented. The wear comparison between two shaft-bushing systems was performed. Both systems run in the same condition except for the control valve operational frequency, so the influence of this frequency could be evaluated. In the end, this entire data base collected could be used as input to a wear rate calculation that evaluates the influence of different design parameters on the wear rate / Mestrado / Mecanica dos Sólidos e Projeto Mecanico / Mestra em Engenharia Mecânica

Tato diplomová práce se zabývá turbodmychadly a CFD simulací turbodmychadla s integrovaným přepouštěcím ventilem pro benzínový motor. Cílem je poskytnout všeobecný přehled o přeplnování a konstrukci turbodmychadel. Práce popisuje proces tvorby 3-rozměrného virtuálního modelu sestavy turbínové skříně, extrakci negativního objemu plynů, tvorbu meshe a nastavení počítačové CFD simulace, která je v závěru práce vyhodnocena. Výsledky simulace slouží pro návrh odlišného provedení turbínové skříně za účelem zlepšení rozložení teplot výfukových plynů na výstupu a zkrácení aktivační doby výfukového katalyzátoru.

Low fuel consumption is one of the main requirement for current internal combustion engines for passenger car applications. One of the most used strategies to achieve this goal is to use downsized engines (smaller engines while maintaining power) what implies the usage of turbochargers. The coupling between both machines (the turbocharger and the internal combustion engines) presents many difficulties due to the different nature between turbomachines and reciprocating machines. These difficulties make the optimal design of the turbocharged internal combustion engines a complicated issue. In these thesis a strong effort has been made to improve the global understanding of different physical phenomena occurring in turbochargers and in turbocharged engines. The work has been focused on the 1D modelling of the phenomena since 1D tools currently play a major role in the engine design process. Both experimental and modelling efforts have been made to understand the heat transfer and gas flow processes in turbochargers. Previously to the experimental analysis a literature review has been made in which the state of the art of heat transfer and gas flow modelling in turbochargers have been analysed. The experimental effort of the thesis has been focused on measuring different turbochargers in the gas stand and the engine test bench. In the first case, the gas stand, a more controlled environment, has been used to perform tests at different conditions. Hot tests with insulated and not insulated turbocharger have been made to characterise the external heat transfer. Moreover, adiabatic tests have been made to compare the effect of the heat transfer on different turbocharger variables and for the validation of the turbine gas flow models. In the engine test bench full and partial load tests have been made for model validation purposes. For the models development task, the work has been divided in heat flow models and gas flow models. In the first case, a general heat transfer model for turbochargers has been proposed based on the measured turbochargers and data available from previous works of the literature. This model includes a procedure of conductive conductances estimation, internal and external convection correlations and radiation estimation procedure. In the case of the gas flow modelling, an extended model for VGT performance maps extrapolation for both the efficiency and the mass flow has been developed as well as a model for discharge coefficient prediction in valves for two stage turbochargers. Finally, the models have been fully validated coupling them with a 1D modelling software simulating both the gas stand and the whole engine. On the one hand, the results of the validation show that compressor and turbine outlet temperature prediction is highly improved using the developed models. This results prove that the turbocharger heat transfer phenomena are important not only for partial load and transient simulation but also in full loads. On the other hand, the VGT extrapolation model accuracy is high even at off-design conditions. / El bajo consumo de combustible es uno de los principales requerimientos de los motores de combustión interna actuales para aplicaciones de coches de pasajeros. Una de las estrategias más usadas para conseguir ese fin es el uso de motores "downsized" (motores más pequeños con la misma potencia) lo que implica el uso de turbocompresores. El acoplamiento entre ambas máquinas (el turbocompresor y el motor de combustión alternativo) presenta muchas dificultades debido a la diferente naturaleza entre las turbomáquinas y las máquinas alternativas. Estas dificultades convierten el diseño óptimo de los motores de combustión interna sobrealimentados en un asunto complicado. En esta tesis se ha realizado un importante esfuerzo para mejorar el entendimiento global de los diferentes fenómenos físicos que ocurren en los turbocompresores y en los motores sobrealimentados. El trabajo se ha centrado en el modelado 1D de los fenómenos puesto que las herramientas 1D juegan actualmente un papel principal en el proceso de diseño del motor. Se han realizado tanto esfuerzos experimentales como de modelado para el entendimiento de los procesos de transmisión de calor y de flujo de gases en turbocompresores. Previamente al análisis experimental se ha realizado una revisión de la literatura disponible en la que se ha analizado el estado del arte del modelado de transmisión de calor y flujo de gases en turbocompresores. El esfuerzo experimental de la tesis se ha centrado en la medida de diferentes turbocompresores en el banco de gas y en el banco motor. En el primer caso, se ha utilizado el banco de gas, un ambiente más controlado, para realizar ensayos en diferentes condiciones. Se han realizado ensayos calientes con y sin aislamiento del turbocompresor para caracterizar el flujo de calor externo. Además, se han realizado ensayos adiabáticos para comparar el efecto de la transmisión de calor sobre diferentes variables del turbocompresor y para la validación de los modelos de flujo de gases de la turbina. En el banco motor se han realizado ensayos a plena carga y a cargas parciales para usarlos en la validación. Para la tarea del desarrollo de los modelos, el trabajo se dividió en modelos de flujo de calor y modelos de flujo de gases. En el primer caso, se ha propuesto un modelo general de transmisión de calor para turbocompresores basado en los turbocompresores medidos y en datos disponibles de trabajos previos de la literatura. Este modelo incluye un procedimiento para la estimación de las conductancias conductivas, correlaciones de convección interna y externa y un procedimiento de estimación de la radiación. En el caso del modelado de flujo de gases, se ha desarrollado un modelo extendido para la extrapolación de mapas de funcionamiento de TGV tanto para el rendimiento como para el gasto másico además del modelo de predicción de coeficientes de descarga en válvulas de turbocompresores de doble etapa. Finalmente, los modelos han sido completamente validados con su acoplamiento a un software de modelado 1D simulando tanto el banco de turbos como el motor completo. Por un lado, los resultados de la validación señalan que la predicción de las temperaturas de salida de compresor y turbina mejora notablemente usando los modelos desarrollados. Este resultado demuestra que los fenómenos de transmisión de calor son importantes no sólo en simulaciones de cargas parciales y de transitorios sino también en plenas cargas. Por otro lado, la precisión del modelo de extrapolación de TGV es alta incluso en condiciones fuera de diseño. / El baix consum de combustible és un dels principals requeriments dels motors de combustió interna actuals per a aplicacions de cotxes de passatgers. Una de les estratègies més usades per a aconseguir eixe fi és l'ús de motors "downsized" (motors més xicotets amb la mateixa potència) el que implica l'ús de turbocompressors. L'adaptament entre ambdues màquines (el turbocompressor i el motor de combustió alternatiu) presenta moltes dificultats degut a la diferent naturalesa entre les turbomàquines i les màquines alternatives. Estes dificultats convertixen el disseny òptim dels motors de combustió interna sobrealimentats en un assumpte complicat. En esta tesi s'ha realitzat un important esforç per a millorar l'enteniment global dels diferents fenòmens físics que ocorren en els turbocompressors i en els motors sobrealimentats. El treball s'ha centrat en el modelatge 1D dels fenòmens ja que les ferramentes 1D juguen actualment un paper principal en el procés de disseny del motor. S'han realitzat tant esforços experimentals com de modelatge per a l'enteniment dels processos de transmissió de calor i de flux de gasos en turbocompressors. Prèviament a l'anàlisi experimental s'ha realitzat una revisió de la literatura disponible en què s'ha analitzat l'estat de l'art del modelatge de transmissió de calor i flux de gasos en turbocompressors. L'esforç experimental de la tesi s'ha centrat en la mesura de diferents turbocompressors en el banc de gas i en el banc motor. En el primer cas, s'ha utilitzat el banc de gas, un ambient més controlat, per a realitzar assajos en diferents condicions. S'han realitzat assajos calents amb i sense aïllament del turbocompressor per a caracteritzar el flux de calor extern. A més, s'han realitzat assajos adiabàtics per a comparar l'efecte de la transmissió de calor sobre diferents variables del turbocompressor i per a la validació dels models de flux de gasos de la turbina. En el banc motor s'han realitzat assajos a plena càrrega i a càrregues parcials per a usar-los en la validació. Per a la tasca del desenvolupament dels models, el treball es va dividir en models de flux de calor i models de flux de gasos. En el primer cas, s'ha proposat un model general de transmissió de calor per a turbocompressors basat en els turbocompressors mesurats i en dades disponibles de treballs previs de la literatura. Este model inclou un procediment per a l'estimació de les conductàncies conductivas, correlacions de convecció interna i externa i un procediment d'estimació de la radiació. En el cas del modelatge de flux de gasos, s'ha desenvolupat un model estés per a l'extrapolació de mapes de funcionament de TGV tant per al rendiment com per al gasto màssic a més del model de predicció de coeficients de descàrrega en vàlvules de turbocompressors de doble etapa. Finalment, els models han sigut completament validats amb el seu adaptament a un software de modelatge 1D simulant tant el banc de turbos com el motor complet. D'una banda, els resultats de la validació assenyalen que la predicció de les temperatures d'eixida de compressor i turbina millora notablement usant els models desenrotllats. Este resultat demostra que els fenòmens de transmissió de calor són importants no sols en simulacions de càrregues parcials i de transitoris sinó també en plenes càrregues. D'altra banda, la precisió del model d'extrapolació de TGV és alta inclús en condicions fora de disseny. / Dombrovsky, A. (2017). Synthesis of the 1D modelling of turbochargers and its effects on engine performance prediction [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/82307 / TESIS

[ES] Está fuera de toda duda que la industria del automóvil está viviendo una profunda transformación que, durante los últimos años, ha progresado a un ritmo acelerado. Debido a la crecientemente estricta regulación sobre emisiones contaminantes y la necesidad de satisfacer la siempre creciente demanda de movilidad sostenible, es necesario que los motores de combustión modernos reduzcan su consumo y emisiones manteniendo el rendimiento del motor. Para enfrentarse a este desafío, los ingenieros de investigación y desarrollo han redoblado sus esfuerzos a la hora de diseñar y mejorar los modelos unidimensionales, hasta el punto en el que el desarrollo de modelos 1D así como la simulación juegan un papel fundamental en los primeras etapas de diseño de nuevos motores y tecnologías. Al mismo tiempo, la tecnología de turbosobrealimentación se ha consolidado como una de las más efectivas a la hora de construir motores de alta eficiencia, lo que ha hecho evidente la importancia de comprender y modelar correctamente los efectos asociados a los turbogrupos. Particularmente, los fenómenos que ocurren en la turbina en condiciones de flujo fuertemente pulsante han demostrado ser complicadas de modelar y sin embargo decisivas, ya que los códigos de simulación son especialmente útiles cuando son diseñados para trabajar en condiciones realistas. Este trabajo se centra en mejorar los modelos unidimensionales actuales así como en desarrollar nuevas soluciones con el objetivo de contribuir a una mejor predicción del comportamiento de la turbina sometida a condiciones de flujo pulsante. Tanto los esfuerzos realizados en los trabajos experimentales como en los de modelado se han producido para poder proporcionar métodos que sean fáciles de adaptar a las diferentes configuraciones de turbogrupo usadas en la industria, por ello, pueden ser aplicados por ejemplo en turbinas de entrada simple y también en las cada vez más usadas turbinas de entrada doble. En cuanto al trabajo de modelado en la parte de turbina de entrada simple, el foco se ha puesto en presentar una versión mejorada de un código quasi-2D. La validación del modelo se basa en los datos experimentales que están disponibles de trabajos enteriores de la literatura, proporcionando una comparación completa entre los modelos quasi-2D y el clásico modelo 1D. La presión a la entrada y salida de la turbina se ha descompuesto en ondas que viajan hacia delante y hacia atrás por medio de la descomposición de presiones, empleando la componente reflejada y transmitida para verificar la bondad del modelo. El trabajo experimental de esta tesis se centra en desarrollar un nuevo método para ensayar cualquier turbina de doble entrada sometida a condiciones de flujo fuertemente pulsante. La configuración del banco de gas se ha diseñado para ser suficientemente flexible como para realizar pulsos en las dos ramas de entrada por separado, así como para usar condiciones de flujo caliente o condiciones ambiente con mínimos cambios en la instalación. La campaña experimental se usa para validar un modelo integrado unidimensional de turbina tipo twin scroll con especial foco en las componentes reflejada y transmitida para analizar el desempeño del modelo su capacidad de predicción de la acústica no lineal. Finalmente, después de desarrollar el trabajo experimental y de modelado, se presenta un procedimiento para caracterizar el sonido y ruido de la turbina por medio de matrices de transferencia acústica que es comparado con el código unidimensional completo. En este sentido, el método proporciona una herramienta útil y fácil de implementar para simulaciones en tiempo real que aplica de una manera práctica el trabajo de modelado expuesto a lo largo de esta tesis. / [CAT] Està fora de tot dubte que la indústria de l'automòbil està vivint una profunda transformació que, durant els últims anys, ha progressat a un ritme accelerat. A causa de la creixentment estricta regulació sobre emissions contaminants i la necessitat de satisfer la sempre creixent demanda de mobilitat sostenible, és necessari que els motors de combustió moderns reduïsquen el seu consum i emissions mantenint el rendiment del motor. Per a enfrontar-se a aquest desafiament, els enginyers de recerca i desenvolupament han redoblat els seus esforços a l'hora de dissenyar i millorar els models unidimensionals, fins al punt en el qual el desenvolupament de models 1D així com la simulació juguen un paper fonamental en les primeres etapes de disseny de nous motors i tecnologies. Al mateix temps, la tecnologia de turbosobrealimentación s'ha consolidat com una de les més efectives a l'hora de construir motors d'alta eficiència, la qual cosa ha fet evident la importància de comprendre i modelar correctament els efectes associats als turbogrupos. Particularment, els fenòmens que ocorren en la turbina en condicions de flux fortament polsant han demostrat ser complicades de modelar i no obstant això decisives, ja que els codis de simulació són especialment útils quan són dissenyats per a treballar en condicions realistes. Aquest treball se centra en millorar els models unidimensionals actuals així com a desenvolupar noves solucions amb l'objectiu de contribuir a una millor predicció del comportament de la turbina sotmesa a condicions de flux polsant. Tant els esforços realitzats en els treballs experimentals com en els de modelatge s'han produït per a poder proporcionar mètodes que siguen fàcils d'adaptar a les diferents configuracions de turbogrupo usades en l'indústria, per això, poden ser aplicats per exemple en turbines d'entrada simple i també en les cada vegada més usades turbines d'entrada doble. Pel que fa al treball de modelatge en la part de turbina d'entrada simple, el focus s'ha posat a presentar una versió millorada d'un codi quasi-2D. La validació del model es basa en les dades experimentals que estan disponibles de treballs anteriors de la literatura, proporcionant una comparació completa entre els models quasi-2D i el clàssic model 1D. La pressió a l'entrada i eixida de la turbina s'ha descompost en ones que viatgen cap avant i cap enrere per mitjà de la descomposició de pressions, emprant la component reflectida i transmesa per a verificar la bondat del model. El treball experimental d'aquesta tesi se centra en desenvolupar un nou mètode per a assajar qualsevol turbina de doble entrada sotmesa a condicions de flux fortament pulsante. La configuració del banc de gas s'ha dissenyat per a ser prou flexible com per a realitzar polsos en les dues branques d'entrada per separat, així com per a usar condicions de flux calent o condicions ambient amb mínims canvis en la instal·lació. La campanya experimental s'usa per a validar un model integrat unidimensional de turbina tipus twin-scroll amb especial focus en les components reflectida i transmesa per a analitzar l'acompliment del model la seua capacitat de predicció de l'acústica no lineal. Finalment, després de desenvolupar el treball experimental i de modelatge, es presenta un procediment per a caracteritzar el so i soroll de la turbina per mitjà de matrius de transferència acústica que és comparat amb el codi unidimensional complet. En aquest sentit, el mètode proporciona una eina útil i fàcil d'implementar per a simulacions en temps real que aplica d'una manera pràctica el treball de modelatge exposat al llarg d'aquesta tesi. / [EN] It is beyond all doubt that the automotive industry is living a deep transformation that, during the last years, has progressed at an ever accelerating rate. Due to the increasingly stringent pollutant emission regulations and the necessity to fulfil an ever growing demand for sustainable mobility, the modern internal combustion engines are required to strongly reduce the fuel consumption and emissions, while keeping the engine performance. In order to confront this challenge, engine research and development engineers have redoubled their efforts in designing and improving one-dimensional codes, to the point that the development of 1D models and simulation campaigns play a major role in the early steps of designing new engines or technologies. At the same time as the turbocharging technology has arisen as one of the most effective and extended solutions for building high efficient engines, the importance of understanding and modelling correctly the turbocharger effects has become evident. In particular, the phenomena that occurs in the turbine under highly pulsating conditions have proven to be challenging to model and yet decisive, as simulation codes are especially useful when they are designed to work under realistic conditions. This work focusses on the improvement of current one-dimensional models as well as in the development of new solutions with the aim of contributing to a better prediction of the turbine performance under pulsating conditions. Both experimental and modelling efforts have been made in order to provide methods that are easily adaptable to different turbocharger configurations used in the industry, so they can be applied for example in single turbines and also in the increasingly used two-scroll turbine technology. Regarding the modelling work of the single entry turbine part, the work has been focused in presenting an improved version of a quasi-2D code. The validation of the model is based on the experimental data available from previous works of the literature, providing a complete comparison between the quasi-2D and a classic 1D model. By means of a pressure decomposition, the pressure at the turbine inlet and outlet has been split into forward and backward travelling waves, employing the reflected and transmitted components to verify the goodness of the model. The experimental work of the thesis is centred in developing a new method in order to test any two-scroll turbine under highly pulsating flow conditions. The gas stand setup has been designed to be flexible enough to perform pulses in both inlet branches separately as well as to use hot or ambient conditions with minimal changes in the installation. The experimental campaign is used to fully validate an integrated 1D twin-scroll turbine model with special focus in the reflected and transmitted components for analysing the performance of the model and its non-linear acoustics prediction capabilities. Finally, after the experiment and modelling work is developed, a procedure to characterise the turbine sound and noise by means of acoustic transfer matrices is presented and tested against the fully one-dimensional code. In this sense, this method provides a useful and easily-implementable tool for fast and real time simulations that applies in a practical way the modelling work exposed along this thesis. / Soler Blanco, P. (2020). Simulation and modelling of the performance of radial turbochargers under unsteady flow [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/141609 / TESIS

This master thesis deals with the design of the turbine housing of turbocharger VNT for supplying separated pressure pulses from the exhaust manifold. Subsequently, the work includes strength analysis of the designed turbine housing. The aim of the thesis is to create components for the supply of separate pressure pulses as close as possible to the turbine. Furthermore, the modification of the existing turbine housing and the assessment of the functionality of the VNT mechanism after this modification and strength analysis. The final aim of this thesis is the creation of 2D and 3D technical documentation of newly designed and modified parts.