Date of Award

2008

Publication Type

Doctoral Thesis

Degree Name

Ph.D.

Department

Mechanical, Automotive, and Materials Engineering

Keywords

Applied sciences, Diesel engines, Premixed combustion

Supervisor

Ming Zheng

Rights

info:eu-repo/semantics/openAccess

Abstract

Three different combustion modes for simultaneous low-nitrogen oxides (NOx) and low-particulate-matter (PM) called enhanced-premixed combustion (EPC) are described in this thesis for diesel engines.

a) Multi-pulse EPC: This combustion mode was implemented with multi-pulse fuel-injection events early during the compression stroke and a heavy use of EGR. This type of combustion was characterized by a short combustion duration which increased the rate-of-pressure rise and maximum pressures in comparison to the conventional diesel combustion mode. The combustion phasing for this mode was kinetics controlled and this combustion mode was largely applicable to mid-load engine operating conditions.

b) EGR enabled EPC with single injection: This combustion mode was implemented with a single-injection close to top-dead center and a heavy use of EGR. The use of closed-loop control on combustion phasing via a cylinder pressure based control was found to be an important enabler for stabilizing this type of combustion. This combustion mode was applied mainly at low-load engine operating conditions.

c) Combustion mode with a split heat-release characteristic: This combustion mode consisted of a part of the fuel delivery very early during the compression stroke and a part of the fuel delivery close to the top-dead-centre (TDC). The part of fuel injected close to TDC experienced conventional high-temperature combustion and oxidized the carbon-monoxide produced earlier in the cycle, thereby improving combustion efficiency. The split nature of the combustion limited the rate-of-pressure rise associated with the multi-pulse EPC combustion.

The implementation of EPC were associated with fuel-efficiency penalty either due to off-phasing of combustion event, UHC and carbon-monoxide or oil-dilution. Specific strategies have been presented to overcome each of these limitations.

A production version of 2.0 Liter, 4-cylinder FORD common-rail diesel engine was modified for the EPC experiments to run in a single-cylinder mode using a prototype intake and exhaust manifold and using independent fuel-injection strategies.

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