Emissions have for long been a matter of concern for different governmental and private agencies including manufacturers and regulatory bodies. A matter of concern for all the stakeholders has always been the fact that emissions come from various sources and in various forms. There is no one size fits all solution for an industry combatting the issue of emissions. In this study, the focus is on the automotive industry, however even within automotive industry there are variety of vehicles running on different fuel types and thus producing variety of emissions. Over years, many technological advancements have been made in tackling these emissions with different methods being developed for different pollutants. Not only have various methods been designed for emission control, but a variety of solutions have also been developed for each type of pollutant with continuous advancements in each technology. The damage to the environment has been driving this constant advancement and technology development has advanced as the regulations have become more stringent. Sometimes two different technologies are coupled to provide even more efficient results. However, whilst doing this, it is always a primary concern for manufacturers to maintain the efficiency and power requirements of the vehicle. This study takes inspiration from this ongoing issue of emissions and continuous efforts to work on reduction techniques. In this work, a different approach has been taken towards emission reduction wherein the formation of the emissions has been targeted. Specifically, this work focusses on NOx emissions produced by heavy duty vehicles. The source of NOx emissions is presence of Nitrogen and Oxygen in the high temperature and high-pressure environment which is present in a diesel engine. An attempt, therefore, has been made to reduce the temperature and pressure of the charge air before entering the intake manifold using novel turbomachinery technology, the ACT (Air Cycle Technology) turboexpander. Reduction in temperature has been achieved by a second stage of cooling being introduced in a turbocharged engine. The consequent effect on NOx emissions and power demand has been studied. It was found that the turboexpander reduced the temperature of the intake charge air by about 30℃, which in turn led to a reduction in the NOx emissions. A reduction in the power by approximately 8% was also noticed throughout the range of operation. Further in this work, an attempt at controlling the amount of cooling has also been made and hence the effects of such control been studied. During the mixing trials, it was noticed that with the increase in the percentage of cold air going into the system, temperature of the intake charge air was becoming cooler followed by subsequent dip in NOx emissions. NOx emissions start to increase initially with the increase in the percentage of warm air until reaching a peak around 60% warm air and 40% cold air mixture. The graph shows slight decrease in NOx before plateauing by further mixing beyond this stage. Various steps have been undertaken including theoretical assessment, experimental testing and validation followed by simulating the more complex problem to establish the feasibility and reliability of the work. This study aims to revolutionise the automotive industry particularly those dealing heavy-duty diesel vehicles by providing a retrofittable solution to make their vehicles more reliable, emissions standards conforming and longer running on the road.
| Date of Award | 9 Apr 2026 |
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| Original language | English |
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| Supervisor | John Allport (Main Supervisor) & Helen Miao (Co-Supervisor) |
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