A Homogenous Combustion Catalyst For Fuel Efficiency Improvements In Diesel Engines Fuelled With Diesel And Biodiesel

[Truncated abstract] The ferrous picrate based homogeneous combustion catalyst has been claimed to promote diesel combustion and improve fuel efficiency in diesel engines. However, the reported fuel savings were controversial. Moreover, a lack of understanding of the working mechanism of the catalyst in diesel combustion processes so far has hindered its widespread applica-tion. On the other hand, the effect of the catalyst on biodiesel combustion has never been scientifically studied and presents a new area regarding the application of the catalyst. The present research aims to systematically study the effect of the catalyst on the fuel efficiency of diesel and biodiesel in diesel engines and to understand its working mechanisms. The specific objectives of this research include a systematic study on the effect of the catalyst on fuel efficiency and combustion characteristics of diesel and biodiesel in diesel engines, an investigation into the working mechanisms of the catalyst in diesel and bio-diesel combustion processes through both experimental and mathematical modelling studies on single droplets, and a study on the chemical kinetic effect of iron atoms on the diesel combustion processes. To accomplish these objectives, the influence of the catalyst on fuel efficiency of diesel and biodiesel as a function of engine speed, load and catalyst dosing ratio was first studied using both a laboratory small single cylinder engine and a large industrial scale four cylinders engine. Then both mathematical modelling and experi-mental studies on the combustion characteristics, including ignition delay periods, burnout time, burning rates and flame temperature, of single droplets of diesel and biodiesel were performed. Lastly, a kinetic modelling study of the effect of iron on the ignition and combustion characteristics of diesel was carried out using CHEMKIN PRO. Diesel engine tests have shown that the use of the catalyst reduced the brake specific fuel consumption (BSFC). Up to 4.2% fuel saving in the small laboratory diesel engine and up to 5.6% in the large industrial scale diesel engine under tested conditions were achieved. The reduction of the BSFC was greater at light loads. In addition, the use of the catalyst reduced the BSFC of the biodiesel up to 2.8% under the tested conditions. It has been found that the addition of the catalyst shortened the ignition delay and combustion duration of diesel and biodiesel in the engine, resulting in slightly higher peak cylinder pressures and faster heat release rates. The study of combustion characteristics of single droplets has indicated that the catalyst shortened the burnout time, increased the burning rate and flame temperature of the drop-lets of both diesel and biodiesel. At the catalyst dosing ratio of 1:10000 (by volume) in the diesel and biodiesel, the flame temperatures of the catalyst dosed droplets were about 40K-50K higher than those of the droplets without the catalyst while the burning rate was 0.05-0.1 mm2s-1 higher. With the assistance of flame emissions spectroscopy, iron atoms were detected to present in the flame of the combustion of the catalyst and it was found that the pure ferrous picrate decomposed at approximately 523K using thermogravimetric analysis...