Diesel Dubbelbränsle Teknologi

Sammanfattning

The work covered in this report includes a literature study of the diesel dual fuel technology

(hereinafter referred to as DDF). The literature study covers earlier work that has been done

regarding the use of compressed natural gas (CNG) and diesel in a DDF system. Moreover a one

cylinder research diesel engine was fitted with a CNG fuel system for experimental testing. The

installation of the engine and the test cell is described. Results from the tests are presented

covering emissions, heat release and pressure traces from the DDF-concept.

During the literature study it was found that most research was related to heavy duty diesel

engines. The research papers covered in this report describes the main areas of interests in DDF

engines including injection strategies, amount of diesel fuel ratio, low load performance,

knocking, emission levels and the effect of the injector geometry. When looking at the concept

of DDF engines, the main problems are poor low load characteristics and proneness to knock at

high loads and emission levels. A major concern is the ability to handle the high levels of

hydrocarbon emissions especially at low loads associated with low exhaust gas temperatures.

The main focus of the work presented in this report has been on completing the installation of a

CNG system and making it work. Although, experimental testing was performed and an injection

sweep and an attempt to increase load was tested. Results from the injection sweep showed that

the choice of SOI (start of injection) and the injection strategy could most likely be improved at

low loads. Looking at a single injection strategy moving from SOI at 5

oBTDC to 55o

BTDC

lowered the nitrous oxide emissions by more than 90 % and at the same time increasing net

torque. However, this is just an example of what influence the SOI has on one emission. It is

believed that a multi-injection strategy could reduce the engine out emissions and at the same

time improving combustion efficiency at low loads.

For further work recommendations and theories of the author are presented at the end of the

report.