The work presented herein describes thesis research in an on-going camshaft grinding evaluation study, initially under the sole sponsorship of Ford Motor Company, and subsequently under the auspices of the National Science Foundation, with industrial participation from American Stress Technologies, Ford Motor Company, G.E. Superabrasives and Litton Automotive Services. Six mechanically assembled camshafts were ground with each of their eight induction hardened lobes receiving a different depth of cut per pass. X-ray residual stress measurements made with depth identified significant near-surface tensile residual stresses in abusively ground regions of the lobes. Acid etching at the time of grinding and subsequent microhardness measurements were employed to verify the x-ray depth results. The grinding operation was further characterized with use of profile and roughness measurements. Burn (defined as a localized tempering of the cam lobe as a result of the grinding operation) appeared in those lobes that received the larger depth of cut, and was concentrated along the ramps and base circle. Several non-destructive examination techniques were then compared with each other to discover which best detected burn. Intercomparison involved evaluating the strength and consistency of the measurement signal. Background noise occurred in all cases due to the measurement technique, instrument error, and human error. Measurement of grinding forces and x-ray diffraction line width analysis were found to be suitable for rapidly and reliably detecting grinding burn in the induction-hardened carbon steel cam lobes. In this regard, it may now be possible to have reliable, quantitative, and non-destructive cam lobe examination in place of the traditional acid etching. / Master of Science

During the course of the experimental work included in this investigation, it was found that certain adjustments and conditions had a major effect on the performance of the tested engine, whereas certain others had a very minor effect. In order of decreasing importance, the conditions which affected the engine's operation were: (1) restriction of the air supply to the carburetor; (2) restriction of the flow of exhaust products from the engine; (3) a change in the carburetor float level; (4) a variation of the ignition timing within five degrees of that recommended; (5) the use of spark plugs which had been run a larger mileage than that recommended by the manufacturer; and (6) a change of the distributor breaker point gap within 0.007" limits of that recommended by the manufacturer. Restricting the air supply to the engine had a very large adverse effect on the economy of the engine, and a smaller effect on the power. Restriction of the exhaust line had approximately the same effect on the power and economy of the engine. Raising the carburetor float level decreased economy characteristics markedly, and power characteristics to a much smaller extent. Lowering the carburetor float level increased both the power and economy of the engine. A five degree advance in the ignition timing resulted in a slight increase in power and economy in the low speed range, this increase being at the expense of violent detonation. The performance in the high speed range was adversely affected. Retarding the spark timing five degrees had a detrimental effect on both power and economy, although this effect was comparatively small. The use of spark plugs beyond the recommended mileage limit showed a decrease in power and economy when this effect was not counteracted by the increase in the size of the gap due to normal usage. Spark plugs which had been cleaned at frequent intervals showed up much better on test than did those which had not. A change in the spacing of the distributor breaker points through a 0.014” range showed an effect of less than three percent when the natural effect of this change on the ignition timing was corrected. Things such as air cleaner and muffler restrictions, changes in the carburetor float level, and fouled spark plugs caused enough effect on the engine's performance to indicate the advisability of checking these things often. Other conditions which would normally be checked in a minor engine tune-up do not have an appreciable effect on the performance of the engine, providing that their effect is not sufficient to make the engine miss. / M.S.

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

University of Macau / Faculty of Science and Technology / Department of Electromechanical Engineering

Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: See PDF for abstract. / AFRIKAANSE OPSOMMING: Sien die PDF vir die opsomming.

On-road remote sensing has the ability to operate in real-time, and under real world conditions, making it an ideal candidate for detecting gross polluters on major freeways and thoroughfares. In this study, remote sensing was employed to detect carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxide (NO). On-road remote sensing data taken from measurements performed in six states, (Arizona, California, Colorado, Illinois, Texas, and Utah) were cleaned and analyzed. Data mining and exploration were first undertaken in order to search for relationships among variables such as make, year, engine type, vehicle weight, and location. Descriptive statistics were obtained for the three pollutants of interest. The data were found to have non-normal distributions. Applied transformations were ineffective, and nonparametric tests were applied. Due to the extremely large sample size of the dataset (508,617 records), nonparametric tests resulted in "p" values that demonstrated "significance." The general linear model was selected due to its ability to handle data with non-normal distributions. The general linear model was run on each pollutant with output producing descriptive statistics, profile plots, between-subjects effects, and estimated marginal means. Due to insufficient data within certain cells, results were not obtained for gross vehicle weight and engine type. The "year" variable was not directly analyzed in the GLM because "year" was employed in a weighted least squares transformation. "Year" was found to be a source of heteroscedasticity; and therefore, the basis of a least-squares transformation. Grouped-years were analyzed using medians, and the results were displayed graphically. Based on the GLM results and descriptives, Japanese vehicles typically had the lowest CO, HC, and NO emissions, while American vehicles ranked high for the three. Illinois, ranked lowest for CO, while Texas ranked highest. Illinois and Colorado were lowest for HC emissions, while Utah and California were highest. For NO, Colorado ranked highest with Texas and Arizona, lowest.

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2005. / This study involved the modeling and verification of the finger follower valve train arrangement with the focus on the non-linear behaviour of high speed valve springs. The project was divided into three phases namely; the measuring of valve train dynamics, modeling of the valve train and the verification of the dynamic models by comparing the results from the two aforementioned two phases. Acceleration and force were measured on a running engine. A force transducer was specially developed for this purpose. Digital signal processing was used in the analysis and implementation of all measured data. The spring model was developed systematically from a solid model, into a finite element model, and finally into a dynamic model. All development steps were continually checked with experiments and calculations. The primary concept used in the spring modeling lends itself to modal analysis theory in conjunction with the superimposing of non-linearities onto a linear model. The dynamic model was verified and good correlations were found, especially at high engine speeds where valve train dynamics play an important role. Parameter adjustments could be made in the dynamic model and the effect that some engine mechanisms, such as engine oil aeration, had on the valve train dynamics were identified. The project was concluded with a case study of a cam profile optimisation project. Dynamic problems were found that would normally not have been identified without the dynamic model.

Thesis (MScEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: This thesis is concerned with unsteady, one-dimensional flow, which closely mimics those found in the manifolds of internal combustion engines. The physical equations describing problems of this nature are presented and some of the important concepts introduced. These equations and concepts were verified by comparison to published results. The Method of Characteristics (MaC) for unsteady one-dimensional flow with friction and heat transfer was used to analyse the gas flow through the inlet and exhaust systems of an engine. The theoretical derivation of unsteady gas dynamic boundary conditions is presented and the integration with the unsteady pipe flow explained. A simulation flow model was developed to analyse the flow by using the Mae. Thisflow model was then incorporated into an engine simulation program, ESA,to simulate internal combustion engines and to predict the performance of a specific engine. A cam-profile model and an in-cylinder thermodynamic model are used to complete the ESAsoftware. Experimental work was done on a modified Nissan Z24/NA20 engine to evaluate the simulation model. The manifolds of the Nissan Z24/NA20 were modified to isolate one of the cylinders for a proper single cylinder model. More experimental work was done on a Volkswagen 1.6£ 8-valve and a 1.6£ 20-valve engine to obtain performance data on two inlet manifolds developed using the ESAsoftware. Performance data and pressure traces in the inlet manifold of the Nissan Z24/NA20 were recorded for comparison with the ESA software. Good correspondence was found between tested and modelled data and the differences varied between ±5% on engine performance data and pressure wave frequency predictions, and ± 10% on pressure pulse amplitudes. / AFRIKAANSE OPSOMMING: Hierdie tesis handeloor bestendige, eendimensionele vloei, wat die gasvloei in spruitstukke van binnebrandenjins naboots. Die nodige vergelykings wat hierdie tipe probleme beskryf asook van die belangrikste konsepte, word bespreek. Hierdie vergelykings en konsepte is met behulp van gepubliseerde data geverifieer. Die Metode van Karakteristieke (MVK) vir bestendige, eendimensionle vloei met wrywing en warmte oordrag, is gebruik om die gasvloei deur inlaat en uitlaat sisteme van 'n enjin te analiseer. Die teoretiese afleiding van bestendige gasdinamiese randvoorwaardes asook hul integrasie met die bestendige pypvloei, word verduidelik. 'n Simulasie vloeimodel is ontwikkelom die vloei met behulp van die metode van karakteristieke te analiseer. Hierdie vloeimodel is deel van 'n omvattende enjinsimulasie program, ESA. Dit word gebruik om binnebrandenjins te simuleer en enjinwerkverrigting te voorspel. 'n Nokprofielmodel en 'n termodinamiese ontbrandingsmodel word gebruik om die enjinsimulasie program af te rond. Eksperimentele toetse op 'n gemodifiseerde Nissan Z24/NA20 enjin is gebruik om die simulasie model te evalueer. Die spruitstukke van die Nissan Z24/NA20 is aangepas om een van die silinders te isoleer om so 'n geskikte enkelsilindermodel te skep. Verdere eksperimentele toetse is gedoen op Volkswagen 1.6£8- klep en 1.6£ 20-klep enjins. Werkverrigtingsdata is verkry op twee nuwe inlaatspruitstukke wat met behulp van die ESAsagteware ontwerp is. Werkverrigtingsdata en drukverdelingsdata in die inlaatspruitstuk van die Nissan Z24/NA20is aangeteken om te vergelyk met die resultate van die ESAsagteware. Goeie ooreenstemming is verkry tussen toets- en gemoduleerde data. Die verskille varieer tussen ±5% op enjin werkverrigtingsdata en drukpulsfrekwensie voorspellings, en ± 10%op drukpuls-amplitudes.

This thesis describes an investigation into the spatial species conversion profiles of a Cu-zeolite SCR under engine conditions at low exhaust gas temperatures; this was then compared with a CFD model that models the catalyst via a porous medium measuring 5 x 5 x 91 cells assuming a uniform cross-sectional flow distribution. Species conversion rates were sampled at fixed points in the axial direction. The analysis of the spatial conversion profiles is a more rigorous method in assessing the ability of a mathematical model to predict the experimental data. It can also assist in the optimisation of the catalyst size, minimising packaging requirements and manufacturing costs. The experiments were undertaken on a light-duty diesel engine at a speed of 1500rpm, and at a load of 6bar BMEP; this provided exhaust gas temeraqtures between 200 and 220°C. NO2:NOx ratios were controlled by changing the size and position of the diesel oxidation catalyst, the inlet NH3: NOx ratio was also also varied, ammonia gas was used instead of urea for the purposes of simlicity. The advantage of testing on an actual engine over lab-babed studies is that the conditions such as exhaust gas composition are more realistic. A 1D CFD model was constructed using the ‘porous medium approach’ with kinetics obtained from open literature. Results from the simulations were then compared with the experimental data for the same engine conditions. It was observed that the majority of the NOx conversion took place in the first half of the brick for all NH3: NOx ratios investigated, and that the formation of N2O via NO2 and ammonia had the same influence as the ‘fast’ SCR reaction just after the inlet, which the CFD model failed to predict for the base case analyses. The influence of the inlet ammonia on the model was also noticed to be greater than in the experiments. Simple transient analyses were also undertaken on the short SCR bricks for NO2: NOx ratios of 0.6 and 0.07, and it was observed that the response time to steady-state was noticeably higher in the experiments than in the model. Modifications made to the model, including decreasing the influence of the ‘fast’ SCR reaction, and the addition of an empirical term onto the ammonia adsorption provided a noticeably better agreement for different NH3: NOx injection ratios. The desorption kinetics in the model were also altered by increasing the strength of the bonding of the ammonia onto the adsorption sites. This improved the transient agreement between the model and the experiments, but reduced the steady-state concentrations at the exit of the brick for all NH3:NOx ratios investigated.

Thesis (PhD (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2006. / The research described in this dissertation examined the effects that fuel formulation can have on the regulated exhaust emissions produced by spark ignition engines in a South African context. Typical South African engine technology, and fuels representative of available fuels were investigated. To broaden the scope and provide information on as many fuel parameters as possible, fuel formulations other than typical retail fuels were also investigated. In order to gain insight into the mechanisms taking place, combustion analysis was performed on measured cylinder pressure traces