MEEM 4220 - I.C. Engines

MEEM 4220 - I.C. Engines

GT-POWER Assignment#4

Objectives:

1.  Run the 4-cylinder engine model at 4000RPM for various spark timings by using Case Setup.

2.  (a) Plot bmep vs. timing. This will give you an idea of what the best timing is.

(b) Examine P-V diagram for each timing.

3.  Determine the best timing for maximum bmep by turning on the “Optimizer” feature.

Procedure:

1.  The 4-cylinder engine model required for Assignment#4 (“assign4-model.gtm”) can be found at www.me.mtu.edu/~smathur. Save the model as “4cyl-assignment4.gtm” in your home directory.

2.  Go to Case-Setup and enter the crankangle values for 50%_BURN_ANGLE as -20, -10, 0, 10 and 20 for case#1, 2, 3, 4, and 5 respectively.

3.  Run the model and obtain the plot of bmep vs. CAD at 50% burn from GT-POST by using Plot RLT. To obtain a combined plot of P-V diagrams for each case, use Plot Case Combine. Refer to instructions for Assignment# 1 if you are having trouble using Plot Case Combine.

4.  Go to Case Setup and uncheck cases 1, 2, 4 and 5 so that only case#3 is left checked. Click Ok. The reason for doing so is explained in step 5.

5.  Go to Optimizer from the Run menu. Choose “OptimumMax” for the Optimization Type. Right click on line for “RLT Variable to be Optimized” and choose RLT Selector. Scroll down to the EngineCrankTrain part and click on Main folder. Choose “BMEP” from the list and click OK.

Click on Opt-Arrays tab at the bottom of the Optimizer window. Right click in the “Parameter to be Varied” column of line one and choose Value Selector. In the list, double click on 50 %_BURN_ANGLE. Remove the square brackets from the text that appears. In the “Parameter Range” column enter 40. This is the total range that the 50% Burn angle will be varied. The range will be centered on the value entered in Case Setup for 50%_BURN_ANGLE. Since we have case#3 checked, the range will be centered around the corresponding value of 50%_BURN_ANGLE, which is 0. In the “Resolution” column enter 1. Click Ok.

6.  Run the model and open GT-POST. The first plot in the plot tree should be called Targeting/Optimization Results. Click the plus sign to the left of the plot name and it should expand into two plots. The second plot shows the value of dependent variable (bmep) vs. the independent variable (CAD at 50% burn). Print out this plot. Expand the second plot and right click on the item that is expanded out. Choose View Data. The last values in the data set are the optimum CAD at 50% burn and the bmep produced for conditions in that particular case.

(Remember to turn the Optimizer to OFF before attempting to do normal (non-optimizing) runs again.)

DUE DATE: Wednesday, Nov. 2, beginning of class.