Fig.4 The comparison of calculated result with experimental result for combustion flame in engine
3-2. CALCULATION FOR OBSERVATION TEST
Combustion calculation was conducted in accordance with the observation test, and a comparison of the temperature distribution obtained by calculation with actual measurement photographs is shown in Fig.4. It can be seen from this that, during the TDC〜10ATDC period, the measured flame distribution corresponds quite well with the simulated distribution of the high temperature domain. However, it will also be noticed that, in comparison during the 20ATDC period, there is too much flow due to swirl in the high temperature domain calculation as opposed to the measured flame. This difference is considered to be caused by a lack of precision in terms of predicting flame flow on the wall surface. As indicated in Fig.3, the structure of the combustion chamber and the direction of fuel injection mean that the flame easily collides with the bottom of the piston. Flame thus flows on the wall surface, and the prediction accuracy of this phenomenon needs to be improved.
4. CALCULATION FOR LOW SPEED 2-STROKE DIESEL ENGINE
Combustion calculation was performed for the requisite low speed 2-stroke diesel engine. Analysis was undertaken corresponding to a UEC85LS II engine produced by Mitsubishi Heavy Industries, Ltd., and comparison was carried out between measured combustion chamber wall heat and the estimated amount of heat transfer.
4-1. CALCULATION CONDITIONS
Calculation conditions are presented in Table 3. The method employed here did not calculate the exhaust scavenging process, such that only the compression and combustion processes from after scavenging port closure to before exhaust valve opening were analyzed. It was necessary to provide the velocity. distribution in the cylinder at the time of calculation commencement. So the velocity measured in acrylic model using LDV was used as the initial velocity. Also, fuel injection speed was obtained by converting the pressure differential between measured fuel injection pressure and cylinder pressure to speed. Three different types of calculations were performed: the STD type, featuring the standard direction of fuel injection; the +3 type, indicating the standard type +3｡?utside; and the +6｡?ype, indicating the standard type +6｡?utside.
4-2. PREDICTION OF COMBUSTION
A comparison of the measured cylinder pressure history with calculated values is shown in Fig.5. Although calculated combustion speed is seen to be higher than for the actual data, combustion quite close to reality has been calculated. Next, Fig.6 indicates the equivalent temperature area distribution in the high temperature domain of 2200K and over in the cylinder for the three types of fuel injection valves that were calculated. Fig.6 shows that the piston and cylinder cover approach the high temperature domain of 2200 and over as the direction of fuel injection is increasingly towards the outside (i.e., in the order of +3, +6).
