Assignment 4
- As we have run both the cases (SI single cylinder and CI single cylinder) at the same rpm i.e. 3600, these two models have different specifications and outputs. Some of them are listed below:
As we have seen here the Bore and the Stroke are different, in case of CI engine it is 100 mm while in case of SI engine it's 86 mm. Also the compression ratios are different, in CI engine it's 16.5 while in SI engine it's 9.5.
Here we can see the difference in power and torque.
In case of CI engine the power is 36.3 kW, while in SI engine it's 16.7 kW.
Also the torque is different, in case of CI engine it's 96.2 Nm while in SI engine it's 44.3 Nm.
A/F Ratio: CI engine = 20.78 - SI engine = 14.51
The exhaust temperature in CI engine is 1039 K while in SI engine 1209 K.
The amount of NOx produced in CI engine is quite high that is 1110.21 ppm while in case of SI engine it's 180.72 ppm.
But the amount of CO and CO2 in CI engine is smaller than of SI engine.
The amount of CO produced in the CI engine is negligible or tends to zero.
2. CI engine SI engine
BSFC: 238.2 241.8 (g/kW*h)
Exh. Temp.: 1039 1209 (K)
A/F Ratio: 20.78 14.51 (-)
3. Change the value for MFB50 and observe the impact on the parameters:
Different cases are made by putting Main Burn Duration as a parameter as [main].
Three different cases are made that are:
The obtained values are listed below:
As we can see here is that the brake power and torque are maximum when we allow a less duration to burn the fuel that is our first case. Also in BSFC it required less amount of time when main duration is least.
Some other results are listed below:
From here we can also see that the NOx, CO and CO2 production are almost the same and thus didn't affect by the burn duration.
Also the Exhaust Temperature was more or less the same, with a small gap of approx 50/60 K.
Some useful graphs are listed below:
aIt's possible to detect that the in-cylinder pressure is maximum when the burn duration is minimum, and thus gradually increasing.
Similarly the cylinder's temperature is max in case 1 and minimum in the case 3.
Conclusion:
The basic CI engine calibration is understood in this assignment. It has been observed that the small duration for burning is suitable and the ignition delay must be balanced as to early burning of fuel produces more CO and NOx because of improper mixing of fuel and air and to much delay impacts the power output and torque.