Particulate matter emissions characteristics, dynamics and control in compression ignitions engines

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Dharmadhikari, Aawishkar (2020). Particulate matter emissions characteristics, dynamics and control in compression ignitions engines. University of Birmingham. Ph.D.

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Abstract

Combustion engines’ exhaust emissions have impacted the environment with greenhouse gas emissions on a large scale and this will reach a global catastrophe limit in the coming decades. It has been an important issue of consideration for many years and substituting fossil fuels to decarbonise the environment has been of utmost importance. With the increase in knowledge and research to understand and control particulate matter emissions, the fundamental research still holds unanswered questions.

The study carried out in the following thesis is primarily focussed on the particulate matter’s inception, evolution, control and its characterisation from a compression ignition engine. The thesis proceeds with the initial study on the evolution and course of particulate matter inside the exhaust tailpipe using a zero-dimensional numerical model. The model aims to investigate the nucleation of water and sulphuric acid from the engine out, and its impact on the particulate matter as it is transported autonomously along a 3.5-metre exhaust pipe. The research is also concerned with explaining the effects of exhaust temperatures on particulate matter and gas emissions, by characterising them into size, mass, and concentrations at consecutive testing positions. The simulated and analysed data are used for a comparative analysis with empirical results acquired from similar exhaust temperature and particulate matter conditions that were confirmed as the assumptions were established.

Further, the research is based on an empirical investigation of particulate matter evolution and the impact of the external cooling of an exhaust tailpipe. The cooling was produced using copper coil tube windings with a decreasing pitch along the length of the pipe and supplied with an ice water and antifreeze mixture solution. The external cooling of the exhaust tailpipe was an important parameter to study the effects of external cooling on the particulate matter flowing through the internal space of the tailpipe. The evolution of the particulates and the impact of the reduction in temperature gradient provided agreeable results. The objective was achieved in understanding and contributing to the knowledge of particulate behaviour inside the tailpipe under various engine operating conditions.

In consideration of the previous studies mentioned above, it is critical to research the control of particulate matter and gas emissions at this stage. Hence, a diesel particulate filter is equipped as an exhaust after-treatment system for the abatement and oxidation of toxic gases and particulate matter. A catalyst is developed to be coated on the filter substrate with a novel nano-fibrous morphology using a rare-earth metal catalyst. The conceptualisation of the research was to investigate the morphological effects on particle trapping and the oxygenated catalytic effect on soot burn at low exhaust temperatures. Tests were performed at laboratory scale and test bench scale, where the filter substrate was coated with the catalyst; and the results acquired depicted an increased filtration efficiency consistent at 95–99%, and a high oxidation and continuous regeneration rate at reduced local exhaust temperatures, contributing to overall lower back pressure on the particulate filter and engine. Finally, the thesis provides details of the research findings and conclusions to provide a valuable contribution to the knowledge of exhaust emissions’ characteristics and their control.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):