Thesis (Ph.D.)--Montana State University--Bozeman, 2007. / Typescript. Chairperson, Graduate Committee: Walter B. Knighton. Includes bibliographical references (leaves 131-145).

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An experimental investigation of highly underexpanded exhaust jets impinging in a direction normal to a curved surface was conducted in the NASA-Langley Research Center 55-foot vacuum cylinder. The investigation included measurements of impingement pressures and measurements of various normal shock characteristics. Variables of the investigation were the size of the jet, jet-exit Mach number, exhaust gas, distance of the jet from the impingement surface, curvature of the surface, and jet-exit to ambient pressure ratio. The experimental data are presented and compared with available theory. / Master of Science

Kiekvienasis metais vis didėjant autotransporto kiekiui keliuose, didėja ir jų į aplinką išmetamų teršalų kiekiai. Todėl galime numanyti, jog Lietuvoje autotransportui išaugus 2,5 karto per paskutinį dešimtmetį tiek kartų išaugo ir į aplinką išmetamų kenksmingų deginių kiekiai, kurie labiausiai jaučiami didžiuosiuose miestuose ar miesteliuose. Greta Kelmės miesto yra keli dideli cheminės oro taršos šaltiniai: kelias Ryga-Kaliningradas, Kelmė – Raseiniai ir pagrindinė miesto sankryža, kur susidaro didžiausi teršalų kiekiai. Šiais keliais nuolat juda intensyvūs autotransporto srautai, kurių dalis patenka į Kelmės miestą. Todėl buvo atliktas autotransporto srautų įtakos Kelmės miesto aplinkos orui tyrimas: ištirti autotransporto srautai Kelmėje; išmatuota anglies monoksido kiekiai ore; teoriškai apskaičiuoti autotransporto amžiaus ir jo eksploatacinių parametrų įtaka deginių kiekiui ir jų sudėčiai; eksperimentiškai ištirta autotransporto cheminė tarša. / The volume of vehicle traffic, growing every year, increases the emissions of toxic substances and pollutes the environment. Consequently, the road traffic in Lithuania has increased by 2.5 times over the last decade. Big cities and small towns have noticed the effect of harmful exhaust emissions on the environment and people health most. A large number of chemical sources of air pollution are located near Kelme city: road Riga – Kaliningrad, Kelme – Raseiniai and the main city crossroads, which produces the most significant contaminants. These roads are constantly moving the intense flows of motor vehicles, the part of which falls within the town of Kelme. Therefore the aim of our research was to study the impact of the road traffic on the air quality in Kelme city, to investigate the traffic flows, to measure the concentration of carbon monoxide in the air, theoretically calculate the impact of vehicle age and its operating parameters on the exhaust emissions and its composition. The experimental research revealed the chemical pollution of the vehicles .

Os regulamentos de controle de emissões de exaustão de motores pequenos fora de estrada, recentemente introduzidos nos EUA e na Europa, exigem a realização de ensaios em motores, conhecidos como PLT – Production Line Testing. O presente trabalho apresenta uma sistemática para implantação deste programa de ensaios na linha de produção pelo fabricante. Neste trabalho foi identificada a oportunidade de utilizar métodos complementares para monitoramento e melhoria da qualidade, considerando requisitos do usuário e regulamentos. A sistemática proposta foi aplicada em uma empresa fabricante de motores durante a introdução de uma linha de produção e possibilitou a implantação do PLT com sucesso. O monitoramento da qualidade permitiu a identificação de informações adicionais, como tendências de afastamento do ajuste, que passariam despercebidas pelos métodos exigidos pelos regulamentos, e assim ajudou a prevenir a produção de unidades não-conformes. Finalmente, foi realizada uma otimização baseada em dados de testes compulsórios, que resultou em melhoria da qualidade sem custos adicionais. / Regulations for engine exhaust emissions control, recently introduced in the USA and Europe, demand engine testing, known as PLT – Production Line Testing. The present work suggests a systematic approach for implementation of such a manufacturer production line testing. The opportunity of integrating complementary methods for quality monitoring and improvement, considering both, regulations and user requirements, was identified. The proposed approach was applied for an engine manufacturer during introduction of a production line, allowing a successful implementation of PLT. The complementary quality monitoring allowed the identification of additional information, such as adjustment offset trends, that would have been unnoticed by only applying the methods as demanded by the regulations, and thus helped to prevent production of non-conforming products. An optimization based on data from compulsory tests was performed, resulting in quality improvements at no additional costs.

This thesis describes an experimental program covering the development of certain simple combustion chamber modifications to alleviate smoke emissions from the Allison T56 turboprop engines operated by the Royal Australian Air Force. The work includes a literature survey, smoke emission tests on two variants of the T56 engine, flow visualisation studies of the combustion system in a water tunnel and combustion rig tests of a standard combustor and four possible modifications. The rig tests showed that reductions in smoke emissions of 80% were possible by simple modifications that reduced the primary zone equivalence ratio and improved mixing in that zone.

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In response to the increasingly widespread use of catalytic converters for meeting automotive exhaust emission regulations considerable attention is currently being directed towards improving their performance. Experimental analysis is costly and time consuming. A desirable alternative is computational modelling. This thesis describes the development of a fully integrated computational model for simulating monolith type automotive catalytic converters. Two commercial CFD codes, PHOENICS and STAR-CD, were utilised to implement established techniques for modelling the flow field in catalyst assemblies. To appraise the accuracy of the flow field predictions an isothermal steady flow rig was designed and developed. A selection of axisymmetric inlet diffusers and 180o expansions were tested, with the velocity profile across the monolith, the wall static pressure distribution along the inlet section and the total pressure drop across the assembly being measured. These datum sets were compared with predictions using a variety of turbulence models and solution algorithms. The closest agreement was achieved with a two-layer near wall approach, coupled to the fully turbulent version of the RNG k-ε model, and a nominally second order differencing scheme. Even with these approaches the predicted velocity profiles were too flat, the maximum velocity being as much as 17.5% too low. Agreement on pressure drops was better, the error being consistently less than 10%. These results illustrate that present modelling techniques are insufficiently reliable for accurate predictions. It is suggested that the major reason for the relatively poor performance of these techniques is the neglecting of channel entrance effects in the monolith pressure drop term. Despite these weaknesses it was possible to show that the model reproduces the correct trends, and magnitude of change, in pressure drop and velocity distributions as the catalyst geometry changes. The PHONETICS flow field model was extended to include the heat transfer, mass transfer and chemical reactions associated with catalysts. The methodology is based on an equivalent continuum approach. The result is a reacting model capable of simulating the three-dimensional distribution of solid and gas temperatures, species concentrations and flow field variables throughout the monolith mat and the effects that moisture has on the transient warm-up of the monolith. To assess the reacting model’s accuracy use was made of published light-off data from a catalyst connected to a test bed engine. Comparison with predicted results showed that the model was capable of reproducing the correct type, and time scales, of temperature and conversion efficiency behaviour during the warm-up cycle. From these predictions it was possible to show that the flow distribution across the monolith can significantly change during light-off. Following the identification, and subsequent modelling, of the condensation and evaporation of water during the warm-up process it was possible to show that, under the catalyst conditions tested, these moisture effects do not affect light-off times. Conditions under which moisture might affect light-off have been suggested. Although the general level of model accuracy may be acceptable for studying many catalyst phenomena, known deficiencies in the reaction kinetics used, errors in the flow field predictions, uncertainty over many of the physical constants and necessary model simplifications mean that accurate quantitative predictions are still lacking. Improving the level of accuracy will require a systematic experimental approach followed by model refinements.

The main purpose of this dissertation is to develop a process to improve actual policy-making procedures in terms of aviation environmental effects. This research work expands current practices with physics based publicly available models. The process herein proposed provides information regarding the interdependencies between the environmental effects of aircraft. These interdependencies are also tied to the actual physical parameters of the aircraft and the engine, making it more intuitive for decision-makers to understand the impacts to the vehicle due to different policy scenarios. These scenarios involve the use of fleet analysis tools in which the existing aircraft are used to predict the environmental effects of imposing new stringency levels. The aircraft used are reduced to a series of coefficients that represent their performance, in terms of flight characteristics, fuel burn, noise, and emissions. These coefficients are then utilized to model flight operations and calculate what the environmental impacts of those aircraft are. If a particular aircraft does not meet the stringency to be analyzed, a technology response is applied to it, in order to meet that stringency. Depending on the level of reduction needed, this technology response can have an effect on the fuel burn characteristic of the aircraft. The proposed alternative is to create a fleet of replacement aircraft to the current fleet that does not meet stringency. These replacement aircraft represent the achievable physical limits for state of the art systems. In addition, the replacement aircraft show the linkage between environmental effects and fundamental aircraft and engine characteristics, something that has been neglected in previous policy making procedures. Another aspect that has been ignored is the creation of the coefficients used for the fleet analyses. In current literature, a defined process for the creation of those coefficients does not exist, but this research work develops a process to do so and demonstrates that the characteristics of the aircraft can be propagated to the coefficients and to the fleet analysis tools.

Thesis (LL.M.). / Written for the Institute of Air and Space Law. Title from title page of PDF (viewed 2009/06/17). Includes bibliographical references.