This thesis details an experimental and computational investigation of the relationship between exhaust system geography, the exhaust port pressure history and the gas exchange process in reciprocating four-stroke engines. The study was conducted in four phases. In the first phase, an extensive experimental programme was undertaken, during which key engine performance indicators together with exhaust and intake system manifold pressure and temperature data were recorded on a Rover 1.4 litre 16-valve K series engine. Measured data from each test were used to validate computational predictions. In the second phase the effect of the phasing of pressure waves at the exhaust port was systematically studied using a modified version of the validated model. The relationships between key engine performance indicators and the pressure at the exhaust port during specific periods of the exhaust event were identified. In the third phase, exhaust system gas dynamics were studied and the effect of exhaust system junctions and components on the transmitted and reflected characteristics of pressure waves were investigated. A method was identified by which the dynamic pressure history at the exhaust port could be broken down into its principal incident and reflected pressure wave components.

Thesis (M.S.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains xi, 101 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 72-76).

Thesis (M.S.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains xiv, 143 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 123-129).

The present thesis aims to study the effect of human movements on local exhaust ventilation. In its simplest terms, local exhaust ventilation is a system which has the function of extracting contaminated air situated close to the contaminant source, protecting a working person from exposure to hazardous substances by containing or capturing them locally, at the emission point. As an important security measure referred to terms of health, it is crucial for the healthiness of workers to control and prevent them from the exposure to vapour, mist, dust or other airborne contaminants. Additionally, to a lesser degree of significance, it can be stressed an expected increase in worker performance due to an improvement of the working conditions. There is an existing necessity for well-defined and appropriate methods to test the performance of local exhaust devices in order to reach standard efficiency values. The lack of an international standardization led to the realization of this study, which, ultimately, has the purpose of obtaining relevant results that can be utilized for future normalized test procedures. The study entails full scale experimental measurements that include air velocity measurements in 3 dimensions, a local exhaust ventilation device with circular hood and a flat flanged plate and a controlled generation of air turbulence through physical movements of a human-sized cylinder, simulating a walking person. The present study extends previous similar studies at the University of Gävle, where the controlled air turbulence was generated by a moving plate. After meaningful results obtained in that study, one of the considerations was to better simulate a walking person, by replacing the plate for a movable cylinder. The present study points at a larger similarity occurring with a cylinder than with a plate, as regards the air flow pattern produced by a real walking person. As in the previous study, the Percentage of Negative Velocities, PNV, has been used as the main measure of turbulence induced risk of contaminant spread. The PNV represents the fraction of the time when the flow is directed opposite to the suction air stream in front of the local exhaust hood. The obtained results conclude that the use of the cylinder as a moving object has been an improvement to simulate the effect of the movement of a human being on a relaxed walking pace. The present study was carried out in parallel with the thesis work by Leyre Catalán Ros, which complements this study by analyzing the effect of an added heated dummy, simulating a person seated in front of the local exhaust device.

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In occupational and public health there is a need for measurement and speciation of chemicals in ambient air to achieve control of air pollution and minimize health risks. In this work two methods of analysis are developed for the analysis of polycyclic aromatic hydrocarbons (PAHs) and volatile organic compounds (VOCs) under ambient air conditions. Both methods involve the use of thermal desorption techniques with gas chromatography-mass spectrometry (GC-MS). For the measurement of polycyclic aromatic hydrocarbons (PAHs) airborne particulate samples are obtained by collection on small glass fibre filters. The volatile materials from these are thermally desorbed in two stages and transferred to a Gas Chromatograph-Mass Spectrometer analytical system. Results from studies of particulate samples obtained from sites in the region of Uxbridge, Middlesex are reported for eight selected polycyclic aromatic hydrocarbons (PAHs). Measurements on samples obtained directly from vehicle emission sources with the engine used under different running conditions are also reported. In the method of analysis of volatile organic compounds in air, samples are absorbed into 4mm Carbotrap 300 tubes and thermally desorbed and passed into a gas chromatography-mass spectrometry (GC/MS) or gas chromatography (GC) using helium as carrier gas. The Carbotrap absorbers used, show complete absorb/desorb reversibility, are thermally stable and do not react chemically with injected hydrocarbon standards. To demonstrate the value of the method analytical results obtained under ambient air conditions on the Brunel University campus (Uxbridge, Middlesex) are reported. Six selected low molecular weight aromatic hydrocarbons namely benzene, toluene, ethyl benzene and m-, p- and o-xylene are investigated in detail. The concentrations of these compounds were measured and results related to traffic flow rates and meteorological conditions to establish the fact that vehicle exhaust emissions are the main sources of the volatile organic compounds (VOCs) pollution at the collection sites. A study of volatile organic compounds (VOCs) levels in ambient air in Tehran (Iran) in which 55 hydrocarbons are identified is reported. A detailed study is made of the concentrations of the six hydrocarbons benzene, toluene, ethyl benzene and m-, p- and o-xylene because high concentrations of these pollutants can produce potential health problems. It is shown that the nature of the geographical location and the day time temperature play an important part in determining the composition of the mixture of pollutants in Tehran. Samples obtained directly from internal combustion engines with and without catalytic converters are also analysed using the method developed and the results show that there is a large depletion in aromatic hydrocarbons when toluene is reduced to a greater extent than benzene. The analytical method is also used to compare vehicle emissions from engines under cold start and hot start conditions.

The need for a catalytic converter within the exhaust system of automotive engines in order to meet emission regulations and the associated costs of its design and testing have meant that a computational model is highly desirable. A number of models have been developed with increasing completeness and versatility. Each model has used approximations and simplifications to reduce the computation time and to enable their use as a design tool to be viable. The present project utilises a commercial Computational Fluid Dynamics (CFD) code STAR-CD to model the initial stages of a catalytic converter in a motor vehicle starting from cold. The ultimate aim is to be able to use the model to improve the efficiency of a catalytic converter by reducing the time taken for light-off. A detailed single channel study is utilised to provide the geometric versatility of the model and to assess the feasibility of using a thin film approach (with heat transfer coefficient as a function of distance down the monolith) which can be utilised in a full equivalent continuum model. The results of this unique study show that the heat transfer from the gas to the monolith can be reliably quantified for a given geometry under common input variables. For typical ceramic substrate monoliths the heat transfer towards the rear of the channels was given by a Nusselt number of approximately 3.5 with elevated heat transfer in the developing region near the channel entrance. Sinusoidal metallic substrate monoliths had a fully developed heat transfer of 2.4.

Thesis (M.S.)--West Virginia University, 2008. / Title from document title page. Document formatted into pages; contains ix, 135 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 52-53).

Thesis (M.S.)--West Virginia University, 2009. / Title from document title page. Document formatted into pages; contains x, 97 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 73-74).