The aim of master’s thesis was to put forward calculation methodology of wastegate turbocharger bypass channel discharge coefficient. Designed methodology was based on discharge coefficient analysis conducted utilizing CFD simulations of turbocharger turbine-side parametric model. It was achieved to propose a calculation, which differentiates relatively in average 1,4% from CFD data. New methodology improves the accuracy bypass channel design and helps to choose appropriate wastegate valve actuator.

This diploma thesis is focused on the concept of threaded connection of the turbine wheel and shaft. At the beginning are described current welding methods of the turbine wheel and shaft connections as well as methods of the compressor wheel and shaft connections. Four possible concepts were designed and evaluated, and the best concept was chosen. For this concept was calculated tightening torque and concept was evaluated in terms of turbocharger operating conditions.

This research investigates the effects of both a Hybrid Energy Storage System and an Electrified Turbocharger in a consumer performance vehicle. This research also attempts to support the development of a prototype vehicle containing a Hybrid Energy Storage System currently being developed at McMaster University. Using a custom simulation tool developed in Matlab Simulink, Simulink models of each of the technologies were developed to predict the behavior of these subsystems across multiple physical domains. Control modeling, optimization and testing was completed for both systems. In addition, controls modeling for the Hybrid Energy Storage System was integrated with the development effort for a prototype vehicle considering the specifics of real world components. To assess the impact of these technologies on a performance vehicle platform, the simulation tool tested each technology using multiple vehicle variations. Three vehicle variants were developed, representing: a conventional performance hybrid design, a hybrid vehicle containing an electrified turbocharger, and a vehicle containing a Hybrid Energy Storage System. Electrical system peak output power was the vehicle specification held constant between each vehicle variant. Each vehicle variant was simulated against a number of traditional drive cycles representing everyday driving scenarios in an attempt to compare fuel economy while identifying each technologies individual impact on the vehicles performance. Finally, each vehicle variant was simulated using a custom performance drive cycle in a virtual race. Both technologies as assessed and in comparison to a larger battery variant, did not result in improved fuel economies during conventional vehicle driving. Both the Hybrid Energy Storage System and electrified turbocharger demonstrated improved vehicle performance in particular scenarios. / Thesis / Master of Applied Science (MASc) / Electrified vehicles have not typically been viewed as performance vehicles. A recent trend has seen a growing number of manufacturers turn to hybrid and electric powertrains to produce high performing vehicles. However, a performance vehicle's electrical power is conventionally limited by the size and power of its battery, adding weight and cost. Two technologies offer the ability to increase the power of these electrified components without the need for a large battery. First, Hybrid Energy Storage System combines ultra-capacitors and batteries to increase the power density of the system. Second, an Electrified Turbocharger improves the turbo lag of a turbocharged engine and also recovers waste heat energy from the exhaust gases which is then used to propel the vehicle. This research identifies and demonstrates the potential impact these two technologies have when included in an American Muscle Car.

No description available.

The turbocharger industry is booming recently, and there is an urgent need for new evaluations of the overall design. As the oil prices continue to rise, along with the new emissions regulations strictly enforced for the in-road as well as the off-road vehicles, the transition to turbocharged engines, and especially for diesel engines, has become irresistible. Higher power, smaller engines, reduced emissions, and overall better efficiency are the main concerns. By means of the recent development in the computational tools, a new era of the product development has emerged. Most diesel engine turbochargers incorporate floating-ring bearings that use the engine's oil for lubrication. The high-speed turbocharger is known to have subsynchronous vibrations at high amplitudes for a wide speed range that could reach 150,000 rpm. The bearing fluid-film whirl instability is the main source of the subsynchronous vibration. The nonlinear reaction forces inside the bearings are usually causing the rotor to whirl in a limit cycle but may become large enough to cause permanent damages. Additionally, the lubrication oil may leak at higher rates through the seals into the engine or the exhaust emissions. This dissertation investigates methods for improving the dynamic stability of the high-speed automotive turbochargers, especially designed for heavy-duty diesel engines that are used for example in heavy machinery, trucks, tractors, etc. The study utilizes the available modern computational tools in rotor-dynamics in addition to the locally developed supportive computer codes. This research is a major part of the turbocharger dynamic analysis supporting the current extensive experimental tests in the Virginia Tech Rotor Dynamics Laboratory for the product development of different high-speed diesel engine turbochargers. The study begins with the method of enhanced-performance hydrodynamic bearings. The aim is to modify the inner surface of the bearing for better dynamic characteristics. The finite-element model of the turbocharger rotor shaft with linearized bearing dynamic coefficients is developed. The system is solved for eigenvalues and eigenvectors in order to evaluate the dynamic stability. The first phase of the study demonstrated that there are two modes of instability that persist during much of the operating speed range, and one of the modes exhibits serious subsynchronous vibration levels at the higher speeds. The first unstable mode builds up at very low speeds forming a conical shape, where both rotor shaft ends whirl forward out-of-phase. The second unstable mode has a cylindrical shape with slight bending, where both rotor ends whirl forward in-phase. The outcome of the study is that the inner surface of the bearing has direct influence on the turbocharger dynamic stability. However, a fixed hydrodynamic bearing may not give total linear stability of the system if it is used without additional damper. The second method is to analytically design flexible damped bearing-supports in order to improve the dynamic characteristics of the rotor-bearing system. The finite-element model of the turbocharger rotor with linearized bearing dynamic coefficients is used to solve for the logarithmic decrements and hence the stability map. The design process attempts to find the optimum dynamic characteristics of the flexible damped bearing-support that would give best dynamic stability of the rotor-bearing system. The method is successful in greatly improving the dynamic stability of the turbocharger and may also lead to a total linear stability throughout the entire speed range when used besides the enhanced-performance hydrodynamic bearings. The study also presents a new method for improving the dynamic stability by inducing the turbocharger rotor unbalance in order to suppress the subsynchronous vibrations. The finite-element model of the turbocharger rotor with floating-ring bearings is numerically solved for the nonlinear time-transient response. The compressor and the turbine unbalance are induced and the dynamic stability is computed. The turbocharger model with linearized floating-ring bearings is also solved for eigenvalues and eigenvectors to predict the modes of instability. The linear analysis demonstrates that the forward whirling mode of the floating-ring at the compressor end becomes also unstable at the higher turbocharger speeds, in addition to the unstable forward conical and cylindrical modes. The numerical predictions are also compared to the former experimental results of a typical turbocharger. The results of the study show that the subsynchronous frequency amplitude of the dominant first mode is reduced when inducing either the compressor or the turbine unbalance at a certain level. In addition to the study of the stability improvement methods, the dissertation investigates the other internal and external effects on the turbocharger rotor-bearing system. The radial aerodynamic forces that may develop inside the centrifugal compressor and the turbine volutes due to pressure variation of the circulating gas are numerically predicted for magnitudes, directions, and locations. The radial aerodynamic forces are numerically simulated as static forces in the turbocharger finite-element model with floating-ring bearings and solved for nonlinear time-transient response. The numerical predictions of the radial aerodynamic forces are computed with correlation to the earlier experimental results of the same turbocharger. The outcomes of the investigation demonstrated a significant influence of the radial aerodynamic loads on the turbocharger dynamic stability and the bearing reaction forces. The numerical predictions are also compared to the former experimental results for validation. The external effect of the engine-induced vibration on the turbocharger dynamic stability is studied. The engine-induced excitations are numerically simulated as time-forcing functions on the rotor-bearings of the turbocharger finite-element model with floating-ring bearings in order to solve for the nonlinear time-transient response. The compressor radial aerodynamic forces are combined to the engine-induced excitations to numerically predict the total nonlinear transient response. The results of the study show that there are considerable amplitudes at the engine-excitation frequency in the subsynchronous region that may also have similar amplitude at the second harmonic. Additionally, the magnitudes of the engine-induced vibration have an effect on the turbocharger dynamic stability. The numerical predictions are compared to the former experimental tests for turbocharger dynamic stability. / Ph. D.

This project was initiated to more fully understand the dynamic stability of an automotive turbocharger rotor-bearing system using both linear and nonlinear analyses. The capabilities of a commercial Finite Element Analysis (FEA) code (computer program) were implemented in the investigation process. Several different hydrodynamic journal bearings were employed in the study of the turbocharger linearized dynamic stability. The research demonstrates how the linear analysis of a turbocharger rotordynamics can be very beneficial for the design evaluation and maintenance purposes. / Master of Science

No description available.

Heat transfer plays an important role in affecting an on-engine turbocharger performance. However, it is normally not taken into account for turbocharged engine simulations. Generally, an engine simulation based on one-dimensional gas dynamics uses turbocharger performance maps which are measured without quantifying and qualifying the heat transfer, regardless of the fact that they are measured on the hot-flow or cold-flow gas-stand. Since heat transfer situations vary for on-engine turbochargers, the maps have to be shifted and corrected in the 1-D engine simulation, which mass and efficiency multipliers usually do for both the turbine and the compressor. The multipliers change the maps and are often different for every load point. Particularly, the efficiency multiplier is different for every heat transfer situation on the turbocharger. The heat transfer leads to a deviation from turbocharger performance maps, and increased complexity of the turbocharged engine simulation. Turbochargers operate under different heat transfer situations while they are installed on the engines. The main objectives of this thesis are: heat transfer modeling of a turbocharger to quantify and qualify heat transfer mechanisms, improving turbocharged engine simulation by including heat transfer in the turbocharger, assessing the use of two different turbocharger performance maps concerning the heat transfer situation (cold-measured and hot-measured turbocharger performance maps) in the simulation of a measured turbocharged engine, prediction of turbocharger walls’ temperatures and their effects on the turbocharger performance on different heat transfer situations. Experimental investigation has been performed on a water-oil-cooled turbocharger, which was installed on a 2-liter GDI engine for different load points of the engine and different heat transfer situations on the turbocharger by using insulators, an extra cooling fan, radiation shields and water-cooling settings. In addition, several thermocouples have been used on accessible surfaces of the turbocharger to calculate external heat transfers. Based on the heat transfer analysis of the turbocharger, the internal heat transfer from the bearing housing to the compressor significantly affects the compressor. However, the internal heat transfer from the turbine to the bearing housing and the external heat transfer of the turbine housing mainly influence the turbine. The external heat transfers of the compressor housing and the bearing housing, and the frictional power do not play an important role in the heat transfer analysis of the turbocharger. The effect of the extra cooling fan on the energy balance of the turbocharger is significant. However, the effect of the water is more significant on the external heat transfer of the bearing housing and the internal heat transfer from the bearing housing to the compressor. It seems the radiation shield between the turbine and the compressor has no significant effect on the energy balance of the turbocharger. The present study shows that the heat transfer in the turbocharger is very crucial to take into account in the engine simulations. This improves simulation predictability in terms of getting the compressor efficiency multiplier equal to one and turbine efficiency multiplier closer to one, and achieving turbine outlet temperature close to the measurement. Moreover, the compressor outlet temperature becomes equal to the measurement without correcting the map. The heat transfer situation during the measurement of the turbocharger performance influences the amount of simulated heat flow to the compressor. The heat transfer situation may be defined by the turbine inlet temperature, oil heat flux and water heat flux. However, the heat transfer situation on the turbine makes a difference on the required turbine efficiency multiplier, rather than the amount of turbine heat flow. It seems the turbine heat flow is a stronger function of available energy into the turbine. Of great interest is the fact that different heat situations on the turbocharger do not considerably influence the pressure ratio of the compressor. The turbine and compressor efficiencies are the most important parameters that are affected by that. The component temperatures of the turbocharger influence the working fluid temperatures. Additionally, the turbocharger wall temperatures are predictable from the experiment. This prediction enables increased precision in engine simulations for future works in transient operations. / QC 20120504

Thesis (MScEng)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Stellenbosch University participated in a project to re-design the compressor section of a diesel locomotive turbocharger. Tests conducted on the prototype compressor showed possible rotating stall in the diffuser section before the designed higher pressure ratio could be achieved. When approaching the higher pressure ratio, the compressor inlet trunk started to rhythmically collapse (due to suction), the engine shook and bellows of black smoke were exhausted by the engine. It was decided to simulate the prototype compressor's operation by using the 1-D theory of Aungier (2000) and to perform a 3-D CFD analysis of the compressor using FINE/Turbo of NUMECA International. A veri cation process was followed to show the accuracy of the 1-D and 3-D modelling methods using two well-known centrifugal compressor test cases found in the literature, namely the O-Rotor by Eckardt (1975, 1976, 1980) and the "Radiver" open CFD test case by Ziegler et al. (2003c). Results from the models were compared to available experimental results and the accuracy was found to be su cient to investigate the prototype compressor's impeller and diffuser. Both prediction methods con rmed separation in the vaned di user across the entire operating ow range of the prototype compressor at the design impeller speed. The 3-D method identi ed supersonic ow at the vaned diffuser inlet at the operating point and also predicted a smaller operating range than originally anticipated. Both the 1-D and 3-D methods also predicted impeller blade stall over the entire operating ow range at the design impeller speed. A recommendation was made to redesign the impeller and diffuser of the prototype compressor. / AFRIKAANSE OPSOMMING: Die Universiteit van Stellenbosch het deel geneem aan 'n projek om die kompressor gedeelte van 'n diesel lokomotief se turbo-aanjaer te herontwerp. Toetse uitgevoer op die prototipe kompressor het moontlike roterende wegbreking in die diffuser seksie uitgewys voordat die ontwerpte hoër drukverhouding bereik kon word. Toe die hoër drukverhouding genader is, het die kompressor inlaatpyp begin ritmies inmekaar vou (as gevolg van die suig aksie), die enjin het geskud en wolke swart rook is deur die enjin uitgeblaas. Die besluit is geneem om die prototipe kompressor se werking te simuleer met behulp van die 1-D teorie van Aungier (2000) en om ook 'n 3-D berekenings vloeimeganika (BVM) analise op die kompressor uit te voer met behulp van FINE/Turbo van NUMECA Internasionaal. 'n Veri kasieproses is gevolg om die akkuraatheid van die 1-D en 3-D modelle te illustreer met behulp van twee welbekende sentrifugaal kompressor toetsgevalle beskikbaar in die literatuur, naamlik die O-Rotor deur Eckardt (1975, 1976, 1980) en die "Radiver" oop BVM toetsgeval deur Ziegler et al. (2003c). Resultate van die modelle is vergelyk met beskikbare eksperimentele resultate en die bevinding is gemaak dat die akkuraatheid genoegsaam is om die prototipe kompressor se rotor en diffuser te ondersoek. Beide voorspellingsmetodes het wegbreking bevestig in die gelemde diffuser oor die hele werksbestek van die prototipe kompressor teen die ontwerp rotorspoed. Die 3-D metode het supersoniese vloei by die gelemde diffuser se inlaat by die bedryfspunt geïdenti seer en het ook 'n kleiner werksbestek voorspel as wat vroeër verwag is. Beide die 1-D en 3-D metodes het ook wegbreking in die rotor oor die hele werksbestek teen die ontwerp rotorspoed voorspel. 'n Voorstel is gemaak om die rotor en diffuser van die prototipe kompressor te herontwerp.

This thesis covers the reconstruction and the redesign of the modeling library VehProLib,which is constructed in the modeling language Modelica with help of the modeling toolWolfram SystemModeler. The design choices are discussed and implemented. This thesisalso includes the implementation of a turbocharger package and an initial study of the justificationof the ideal gas law in vehicle modeling. The study is made with help of Van derWaals equation of states as a reference of non-ideal gas model. It will be shown that for themean-value-engine-model, the usage of ideal gas law is justified.