In addition, the fuel injection timing was diversely changed to carry out similar experiments.
The suction air temperature was set to 40℃ by adjusting the outlet valve and the bypass valve of the cooling water of the intercooler. The temperature and the relative humidity in the room were 31℃ and 69% respectively during the experiment
3. Experimental Results
3.1 Characteristics of NOx Emission
Fig. 4 shows the cylinder pressure, the pressure in the fuel injection pipe, and the needle lift with BFO and GO at the normal injection timing. The curves show the mean value at 200 cycles at the load factor of 75% on the marine characteristics. The pressure in the fuel injection pipe and the needle lift were measured by the piezo type pressure gage (manufactured by Kistler) and the non-contact type gap sensor, respectively. In the figure, the injection timing of the fuel was when the needle is started to rise, and the ignition delay was obtained as the difference between the time when the fuel injection was started and the steep rise timing (ignition) of the cylinder pressure.
Fig. 5 shows the relationship between the fuel injection timing and the ignition delay. In this figure, the ignition delay was longer with BFO by about 0.3 ms in either fuel injection timing.
Fig. 6 shows comparison of the heat release rate and the proportion of heat release with BFO and GO. The proportion of heat release (Q/Gf・Hu) is the ratio of the measured integrated heat generation(Q) to the calorie (Gf・Hu) generated by the fuel (Gf) injected in one cycle. Fig. 6(a) shows the normal injection timing with both fuels, and Fig. 6(b) shows the delay of the injection timing with GO by 0.3 ms (4 degrees in terms of the crank angle) so that the ignition timings of both fuels are same.
Fig. 4 In-cylinder pressure, fuel injection pressure and needle lift at BFO and GO
Fig. 5 Relationship between fuel injection timing and ignition delay
Fig. 6 Heat release rate and proportion of heat release
