CAGE User's Guide

Filling Key Operating Points

You now fill the key operating points in the lookup table for spark angle.

The upper pane displays the lookup table, and the lower pane displays the behavior of the torque and NOx emissions models with each variable.

You maximize the torque and restrict NOx emissions to below 250 g/hr.

To fill an operating point:

1. Select the operating point N = 4500 and L = 0.5 in the lookup table.
2. Find the spark angle that gives the maximum torque and restricts NOx emissions to below 250 g/hr. There are detailed instructions on how to do this tradeoff following.

Determining the Value of Spark

At each operating point, the behavior of the model alters. The following display shows the behavior of the models over the range of the input variables.

Graphs of the Models When N = 4500 and L = 0.5

The top three graphs show how the torque model varies with the spark angle, the AFR (labeled A), and the EGR (E), respectively. The lower panes show how the NOx emissions model varies with these variables, respectively.

Looking at the Spark table, the two spark (SPK) graphs are green, indicating that these graphs are directly linked to the lookup table.

You can change the value of spark by dragging the red line on the SPK graphs or typing values into the edit box. The following graph shows the behavior of the two models when the spark angle is 26.4458.

3. Select Find Global Maximum from the right-click menu of the SPK - TQ_Model graph. This calculates the value of spark that gives the maximum value of torque.

At this operating point, the maximum torque that is generated is 48.136 when the spark angle is 26.4485. However, the value of NOx is 347.7861, which is greater than the restriction of 250 g/hr. Clearly you have to look at another value of spark angle.

4. Enter 21.5 as the value of SPK in the edit box at the top of the SPK column.

The value of the NOx emissions model is now 249.1542. This is within the restriction, and the value of torque is 47.2478.

At this operating point, this value of 21.5 degrees is acceptable for the spark angle lookup table, so you want to apply this point to your table.

5. Press Ctrl+T or click  (Add Point) in the toolbar to apply that value to the spark table.

1. This automatically adds the selected value of spark to the table and turns this cell yellow. It is pink when selected, yellow if you click elsewhere.

6. Now repeat this process of finding acceptable values of spark at four more operating points listed in the table following. In each case,
• Select the cell in the spark table at the specified values of speed and load.
• Enter the value of spark given in the table (the spark angles listed all satisfy the requirements).
• Press Ctrl+T or click  (Add Point) in the toolbar to apply that value to the spark table.
  
  

  Speed, N	Load, L	Spark Angle, SPK
  2500	0.3	25.75
  3000	0.8	10.7
  5000	0.7	8.3
  6000	0.2	41.3

After you enter these key operating points, you can fill the table by extrapolation. This is described in the next section.

Setting Values for Other Variables

Filling the Table by Extrapolation