Date of Award

2016

Degree Type

Dissertation

Degree Name

Ph.D.

Department

Mechanical, Automotive, and Materials Engineering

First Advisor

Zheng, Ming

Second Advisor

Chen, Xiang

Keywords

Clean combustion, Dual-fuel, Dynamic combustion control, Emissions versus efficiency, Ethanol, Exhaust gas recirculation

Rights

CC BY-NC-ND 4.0

Abstract

The primary objective of this dissertation is to develop combustion control strategies, that can reduce the thermal efficiency penalty associated with clean combustion in modern compression ignition engines. The clean combustion targets of simultaneously low oxides of nitrogen (NOX) and smoke emissions are selected as the platforms for demonstrating the dynamic control strategies on a single cylinder research engine. First, parametric analyses, including exhaust gas recirculation (EGR) calculations, are performed using a zero-dimensional engine cycle simulation model. Thereafter, two combustion strategies are experimentally investigated, namely the single-shot diesel strategy and the dual-fuel strategy. The single-shot diesel combustion strategy employs a single direct injection of diesel with the use of moderate levels of EGR. In the dual-fuel combustion strategy, port injection of ethanol is utilized in addition to the direct injection of diesel and the application of EGR. The results of parametric analyses and engine experiments provide guidelines for the development of a systematic control strategy. Closed-loop combustion control systems are implemented for regulating the fuel injection commands, by which the combustion phasing is effectively controlled on a cycle-by-cycle basis in both the diesel and dual-fuel combustion strategies. The fuel injection control is integrated into the systematic control strategy for simultaneously controlling the air and fuel systems. The intake boost pressures, EGR rates, and fuelling strategies are dynamically selected, depending on the engine load level. By implementing the systematic control, both the NOX and smoke targets are achieved over a wide engine load range, while retaining the thermal efficiency of conventional diesel combustion.

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