The work described in this thesis was carried out to investigate the application of variable valve actuation (VVA) to light-duty diesel engines for use in passenger vehicles. The background to this was that there was little published on the subject and with advanced turbochargers, exhaust gas re-circulation systems and high pressure fuel injection systems reaching maturity it seemed likely that further enhancement of the air management in this type of engine, through VVA would receive greater interest. The first section of this thesis discusses the external pressures on engine manufacturers, from legislation and from the customer expectations, which could be expected to influence the adoption of VVA, while looking at the criteria on which they would assess a VVA system prior to adoption. Section two provides an overview of the effects of VVA and how they may be used to improve engine operation by highlighting the specific features of diesel engines, i.e. cold starting and compression ratio, part load fuel economy, full load torque and transient torque rise, that can be influenced by air management and what characteristics are required from the VVA system in order to provide improvements in these areas. Having identified the key features of a VVA system that would be suitable for use in light duty diesel engines section three presents a brief literature review and discusses the family of non-constant angular velocity VVA systems that were identified as having the correct characteristics and relative simplicity necessary for any system that might be made in high volume production. This section also provides a detailed analysis of one system of this type to highlight its behaviour and impact on valve train design. Software was written to model the selected mechanism and produce the valve lift characteristics for use in simulating the engine's behaviour. Section four provides an overview of engine simulation techniques and some detail of the model constructed for this investigation. It also discusses the additional code and methodologies required to model the turbine, compressor and combustion processes, which required special treatment, and presents data to compare the behaviour of the model with the baseline of known engine behaviour. Section five presents simulation results that show the following possible improvements: a) a 23% increase in torque, b) light part-load fuel economy improvements of 13% and c) transient rise to maximum torque times reduced from 2.3 seconds to 1.6 seconds. It also discusses the features of engine operation with VVA that provide the potential for these improvements in engine operation, quantifies the benefits that might be expected at a large number of operating conditions and discusses the interactions between the VVA and other systems such as the turbo-charger and EGR system. Section six presents conclusions which beside the enumeration of the potential benefits and description of the key effects of VVA, highlights the need for test data to verify the extent to which the benefits can be realised in real engines and suggests areas for future research.

No description available.

The simulation of vehicle engine cooling validation in a Climatic chamber will benefit all vehicle manufacturers that are responsible for the design or the localization of parts used in a vehicle's engine cooling system. The ability to test the vehicle in-house allows testing at any time of the year; it provides repeatable and comparative data, and accelerates component level approval, which in itself reduces program timing and cost. For this dissertation road level testing was conducted in Upington using a TD1200 Superflow towing dynamometer, while the in-house testing was performed on a ROTOTEST chassis dynamometer in a Climatic chamber. All tests were conducted according to GENERAL MOTORS SOUTH AFRICA global testing standards. Statistical analyses of the test data were used to determine the relationship between parameters measured and results obtained. The major contributors to the simulation process was identified and implemented to improve measurement quality and test results. The result was an accurate simulation between road and chamber testing, hence the possibility of moving away from road testing and conduct simulated chamber testing. The presented dissertation is useful for the understanding of basic vehicle cooling testing and the methodology of simulated testing in an environmentally controlled chamber.

M.Ing. / The purpose of this thesis was to gather experimental data of a stainless steel sleeve being formed into a convoluted tube. This convoluted tube, made from stainless steel ASTM 240 type 321 and with a wall thickness of 0,4mm, is the main part of an automotive exhaust bellow. The automotive exhaust bellow fits into a motor vehicle exhaust system. One of the functions of this bellow is to compensate for engine movement. The bellow is also used to damp the engine vibration to the vehicle chassis. Typical failures that occur during the production of a convoluted tube are identified. The data gathered are listed and the forming process, typical conditions and its effects discussed. The actual data and graphs are presented in the annexures at the end of this report. Plasticity theory for shells and cylinders is summarized in Annexure A and the solution of a related problem discussed. Experimental data were used to verify the result of a finite element model. The calculated values of the model compare well with the values of the experimental data. The model must still be developed further and the experimental data can be used to verify this developed model. Possible aspects, related to the forming and life-cycle prediction of an automotive exhaust bellow, that still need to be studied are identified and presented at the end of this report.

Thesis (MScEng)--Stellenbosch Universit, 2004. / ENGLISH ABSTRACT: The requirements regarding the quality of engines and vehicles have increased constantly, requiring more and more sophisticated engine testing. At the same time, there is a strong demand to reduce lead time and cost of development. For many years steady state engine testing was the norm using standard principles of power absorption. Since the mid 1980's increasing importance has been attached to the optimisation of transient engine characteristics and the simulation of dynamic real world driving situations on engine test stands. This has led to the use of bi-directional DC or AC regenerative dynamometers a practice now known as dynamic engine testing. Interfacing a computer with vehicle simulation software to an engine on a dynamic test stand and using "hardware in the loop" techniques, enables the simulation of real world driving situations in a test facility. In dynamic engine testing a distinction can be made between simulation testing and transient testing. In simulation testing the set point values are predetermined whereas in transient testing a model generates set point values in real time. Speeds and loads are calculated in real time on the basis of real time measurements. The model can be in the form of a human or driver simulation. This project involved the application of dynamic engine testing to simulating a racing application. It is termed Real Time Full Circuit Driving Simulation System due to the simulation of a race car circling a race track, controlled by a driver model and running the engine on a dynamic test bench in real time using "hardware in the loop" techniques. By measuring the simulated lap times for a certain engine configuration on the test bench in real time, it is possible to select the optimal engine set-up for every circuit. The real time nature of the simulation subjects the engine on the test bench to similar load and speed conditions as experienced by its racing counterpart in the race car yielding relevant results. The racing simulation was achieved by finding a suitable dynamic vehicle model and a three dimensional race track model, developing a control strategy, programming the software and testing the complete system on a dynamic test stand. In order to verify the simulation results it was necessary to conduct actual track testing on a representative vehicle. A professional racing driver completed three flying laps of the Killarney racing circuit in a vehicle fitted with various sensors including three axis orientation and acceleration sensors, a GPS and an engine control unit emulator for capturing engine data. This included lap time, vehicle accelerations, engine speed and manifold pressure, an indicator of driver input. The results obtained from the real time circuit simulation were compared to actual track data and the results showed good correlation. By changing the physical engine configuration in the hardware and gear ratios in the software, comparative capabilities of the system were evaluated. Again satisfactory results were obtained with the system clearly showing which configuration was best suited for a certain race track. This satisfies the modem trend of minimizing costs and development time and proved the value of the system as a suitable engineering tool for racing engine and drive train optimisation. The Real Time Full Circuit Driving Simulation System opened the door to further development in other areas of simulation. One such area is the driveability of a vehicle. By expanding the model it would be possible to evaluate previously subjective characteristics of a vehicle in a more objective manner. / AFRIKAANSE OPSOMMING: Die vereistes om die kwaliteit van enjins en voertuie te verhoog, word daagliks hoër. Meer gesofistikeerde enjintoetse word daarom vereis. Terselfdertyd is dit 'n groot uitdaging om die tydsduur en koste van ontwikkeling so laag as moontlik te hou. Gestadigde toestand enjintoetse, wat op die prinsiep van krag absorpsie werk, was vir baie jare die norm. Vanaf die middel tagtigerjare het die optimering van dinamiese enjinkarakteristieke en die simulasie van werklike bestuursituasies op enjintoetsbanke van al hoe groter belang geword. Die gevolg was die gebruik van twee rigting wisselof gelykstroomdinamometers en staan vandag bekend as dinamiese enjintoetsing. Deur 'n rekenaar met simulasiesagteware aan 'n enjin op 'n dinamiese toetsbank te koppel, word die moontlikheid geskep om enige werklike bestuursituasies van 'n voertuig te simuleer in die enjintoetsfasiliteit. Dinamiese enjintoetse kan opgedeel word in simulasietoetse en oorgangstoestandtoetse. By laasgenoemde genereer 'n "bestuurdersmodel" die beheerwaardes intyds deur te kyk na intydse metings terwyl by simulasietoetse die beheerwaardes vooraf bepaal word. Die "bestuurder" kan in die vorm van 'n persoon of rekenaarsimulasie wees. Die projek behels die toepassing van dinamiese enjintoetse vir renbaansimulasie en staan bekend as'n Intydse, Volledige Renbaansisteem weens die simulasie van 'n renmotor om 'n renbaan, onder die beheer van 'n bestuurdersmodel. Dit geskied terwyl die enjin intyds op 'n dinamiese enjintoetsbank loop en gekoppel is aan die simulasie. Deur die intydse, gesimuleerde rondtetye te analiseer, word die moontlikheid geskep om die enjinkonfigurasie te optimeer vir 'n sekere renbaan. Dit is bereik deur die keuse van 'n gepaste dinamiese voertuigmodel, 'n driedimensionele renbaanmodel, ontwikkeling van 'n beheermodel, programmering van die sagteware en integrasie van die dinamiese enjintoetsstelsel. Die simulasieresultate verkry is gestaaf deur werklike renbaantoetse. 'n Professionele renjaer het drie rondtes van die Killarney renbaan voltooi in 'n verteenwoordigende voertuig wat toegerus was met verskeie sensors o.a. drie as versnellings- en orientasiesensors, GPS en 'n enjinbeheereenheidemmuleerder vir die verkryging en stoor van enjindata. Die sensors het data versamel wat insluit rondtetyd, voertuigversnellings, enjinspoed en inlaatspruitstukdruk. Die korrelasie tussen die simulasie waardes en werklik gemete data was van hoë gehalte. Deur die fisiese enjinkonfigurasie te verander in die hardeware en ratverhoudings in die sagteware, is die vergelykbare kapasiteite van die renbaansimulasie geevalueer. Die resultate was weer bevredigend en die simulasie was in staat om die beste enjinkonfigurasie vir die renbaan uit te wys. Dit bevredig die moderne neiging om koste en ontwikkelingstyd so laag as moontlik te hou. Sodoende is bewys dat die stelsel waarde in die ingenieurswêreld het. 'n Intydse, Volledige Renbaansisteem die skep die geleentheid vir verdere ontwikkeling op verskeie terreine van simulasie. Een so 'n veld is die bestuurbaarheid van 'n voertuig. Deur die model verder te ontwikkel word die moontlikheid geskep om voorheen subjektiewe karakteristieke van 'n voertuig meer wetenskaplik te analiseer.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / by Seyed Hossein Mansouri. / Ph.D.

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America’s energy crunch— something new for a country that has been used to great affluence. America’s smog— an eye stinging, lung burning situation which the Environmental Protection Agency has "promised" to rectify. These are two outstanding problems that face the engineer and scientist of today. The end of the era of cheap gasoline has brought the beginnings of a quiet revolution to Detroit: an improvement in the efficiency, economy and emission level of the American automobile. Word has penetrated to the automotive engineers that the emissions level, fuel economy and automobile safety are the prime design considerations for the automobile of the future.

The 3/4-race cam and dual carburetors tested in this investigation provided moderate increases in maximum power output at speeds above 3000 rpm, The fuel consumption was reduced by the use of the racing type cam and increased with the use of two standard carburetors. However in the latter case it is possible that the economy would have been improved had the proper carburetor jets been installed. The maximum power afforded by the dual carburetors occurred at about the same speed as that for the stock engine whereas the maximum power afforded by the 3/4-race cam occurred at 250 rpm higher than that of the stock engine. Large increases in maximum power output and increase in the speed for maximum power were provided by a combination of a 3/4-race cam and dual carburetors. However the gain in speed and power was obtained at the expense of fuel consumption. The above modifications in engine equipment were beneficial for high speed operation, the only advantage at low speeds being an increase in the accelerating ability of the engine. / Master of Science

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