Diesel Dubbelbränsle Teknologi
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 doneregarding the use of compressed natural gas (CNG) and diesel in a DDF system. Moreover a onecylinder research diesel engine was fitted with a CNG fuel system for experimental testing. Theinstallation of the engine and the test cell is described. Results from the tests are presentedcovering 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 dieselengines. The research papers covered in this report describes the main areas of interests in DDFengines 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 conceptof DDF engines, the main problems are poor low load characteristics and proneness to knock athigh loads and emission levels. A major concern is the ability to handle the high levels ofhydrocarbon 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 aCNG system and making it work. Although, experimental testing was performed and an injectionsweep and an attempt to increase load was tested. Results from the injection sweep showed thatthe choice of SOI (start of injection) and the injection strategy could most likely be improved atlow loads. Looking at a single injection strategy moving from SOI at 5oBTDC to 55oBTDClowered the nitrous oxide emissions by more than 90 % and at the same time increasing nettorque. However, this is just an example of what influence the SOI has on one emission. It isbelieved that a multi-injection strategy could reduce the engine out emissions and at the sametime improving combustion efficiency at low loads.For further work recommendations and theories of the author are presented at the end of thereport.