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This study investigated neat n-butanol combustion, emissions and thermal efficiency characteristics in a compression ignition (CI) engine by using two fuelling techniques - port fuel injection (PFI) and direct injection (DI). Diesel fuel was used in this research for reference. The engine tests were conducted on a single-cylinder four-stroke DI diesel engine with a compression ratio of 18.2 : 1. An n-Butanol PFI system was installed to study the combustion characteristics of Homogeneous Charge Compression Ignition (HCCI). A common-rail fuel injection system was used to conduct the DI tests with n-butanol and diesel. 90 MPa injection pressure was used for the DI tests. The engine was run at 1500 rpm. The intake boost pressure, engine load, exhaust gas recirculation (EGR) ratio, and DI timing were independently controlled to investigate the engine performance.

In this study, impacts of neat n-butanol fuel injection parameters on direct injection (DI) compression ignition (CI) engine performance were investigated to gain knowledge for understanding the fuel injection strategies for n-butanol. The engine tests were conducted on a four-stroke single-cylinder DI CI engine with a compression ratio of 18.2:1. The effects of fuel injection pressure (40, 60 and 90 MPa) and injection timing in a single injection strategy were investigated. The results showed that an increase in injection pressure significantly reduced nitrogen oxides (NOx) emissions which is the opposite trend seen in conventional diesel combustion. The parallel use of a higher injection pressure and retarded injection timing was a proposed method to reduce NOx and cylinder pressure rise rate simultaneously. NOx was further reduced by using exhaust gas recirculation (EGR) while keeping near zero soot emissions.

Advances in engine technology in recent years have led to significant reductions in the emission of pollutants and gains in efficiency. As a facet of investigations into clean, efficient combustion, the homogenous charge compression ignition (HCCI) mode of combustion can improve upon the thermal efficiency and nitrogen oxides emission of conventional spark ignition engines. With respect to conventional diesel engines, the low nitrogen oxides and particulate matter emissions reduce the requirements on the aftertreatment system to meet emission regulations. In this paper, n-butanol, an alcohol fuel with the potential to be derived from renewable sources, was used in a light-duty diesel research engine in the HCCI mode of combustion. Control of the combustion was implemented using the intake pressure and external exhaust gas recirculation. The moderate reactivity of butanol required the assistance of increased intake pressure for ignition at the lower engine load range.

Dual fuel applications of alcohol fuels such as ethanol or butanol through port injection with direct injection of diesel can be effective in reduction of NOx. However, these dual fuel applications are usually associated with an increase in the incomplete combustion products such as hydrocarbons (HC), carbon monoxide (CO), and hydrogen (H2) emissions. An analysis of these products of incomplete combustion and the resulting combustion efficiency penalty was made in the diesel ignited alcohol combustion modes. The effect of EGR application was evaluated using ethanol and butanol as the port injected fuel, with varying alcohol fractions at the mid-load condition (10 -12 bar IMEP). The impact of varying the engine load (5 bar to 19 bar IMEP) in the diesel ignited ethanol mode on the incomplete combustion products was also studied. Emission measurements were taken and the net fuel energy loss as a result of the incomplete combustion was estimated.

The dual-fuel application using ethanol and diesel fuels can substantially improve the classical trade-off between oxides of nitrogen (NOx) and smoke, especially at moderate-to-high load conditions. However, at low engine load levels, the use of a low reactivity fuel in the dual-fuel application usually leads to increased incomplete combustion products that in turn result in a significant reduction of the engine thermal efficiency. In this work, engine tests are conducted on a high compression ratio, single cylinder dual-fuel engine that incorporates the diesel direct-injection and ethanol port-injection. Engine load levels are identified, at which, diesel combustion offers better efficiency than the dual-fuel combustion while attaining low NOx and smoke emissions. Thereafter, a cycle-to-cycle based closed-loop controller is implemented for the combustion phasing and engine load control in both the diesel and dual-fuel combustion regimes.

The study investigated the characteristics of the combustion, the emissions and the thermal efficiency of a direct injection diesel engine fuelled with neat n-butanol. Engine tests were conducted on a single cylinder four-stroke direct injection diesel engine. The engine ran at 6.5 bar IMEP and 1500 rpm engine speed. The intake pressure was boosted to 1.0 bar (gauge), and the injection pressure was controlled at 60 or 90 MPa. The injection timing and the exhaust gas recirculation (EGR) rate were adjusted to investigate the engine performance. The effect of the engine load on the engine performance was also investigated. The test results showed that the n-butanol fuel had significantly longer ignition delay than that of diesel fuel. n-Butanol generally led to a rapid heat release pattern in a short period, which resulted in an excessively high pressure rise rate. The pressure rise rate could be moderated by retarding the injection timing and lowering the injection pressure.