1. Kul-14.4400 Simulation of Internal Combustion Engines Learning exercise 4 solutions

2. Running instructions Click Start and digit ”gt ” Or prompt/windows and type cmd In the windows prompt type gtise - console Copy all the files in a folder in your network space \\home.org.aalto.fi\username Make all the modifications needed and tick the results you want to see. Check carefully To see the results open again the windows prompt and type gtpost – console If you need to make modifications in your model you might need to close GT-Post

3. Troubleshooting What if simulations cannot run? Map Z-drive with MapNetworkDrive support@gtisoft.com

4. Analysis Performance values: - earlier injection and higher CR produce more extreme cylinder conditions in terms of temperature and pressure - the performance values will be better as the timing of gas expansion is more beneficial with earlier injection and higher CR - nitrous oxide emissions will be higher when the combustion temperatures increase -Local vs. average

5. Cooling capacity - the needed cooling capacity depends on the amount of heat transfer - the differences in heat transfer are small but still effective - cooling capacity should be taken into account when during engine design

6. Friction model & cylinder temperatures Friction - fmep around 2.2bar  a bit high or in the upper limit Cylinder wall temperature - 450K is a bit higher than in GT- Power Engine Performance- manual (400K)

7. Plotting examples (indicated work)

8. Plotting examples (NOx vs. in-cyl temp.)

9. CR 15.5, in-cylinder conditions

10. Initialization The initialization can be performed - by creating customized initial conditions for each simulation case - by beginning the simulation from the results of the previous case Good initialization always reduces the computational time as the model converges more rapidly.

11. Two-temperature model Burned & unburned - two-temperature model divides the cylinder contents simply to burned and unburned - burn rate transfers fuel and air from the unburned zone to the burned zone (exhaust gases)