Solenoid injector system

Solenoid injector system

In order to run this example you will need access to an Simcenter Amesim license with the Hydraulic, Hydraulic Component Design and Electromechanical libraries.

You will start from an existing demo model. Go to the Help menu and select Get demo then look for solenoid. Copy and open the model as in the following screenshot.

Figure 91: Getting the solenoid model

In order to highlight the use of the Performance Analyzer you are going to alter the model with a bad parameter. Go to Parameter mode and double-click the vertical pipe joining the two volumes as shown in the following figure. Change the pipe length from 0.025 m to 2.5e- 7 m. We will assume that for some reason the length was badly parameterized. Then forget about it!

Figure 92: Changing the pipe length

Run a simulation, take a break, and when you come back open the Performance Analyzer.

Figure 93: Performance Analyzer of the modified model

Now, go to the Frequencies tab and notice the 9.9 MHz undamped frequency.

Figure 94: Frequencies in the Performance Analyzer

In order to identify where it is coming from, switch to the State contributions pane. Select the most active variable and double-click the corresponding line.

Figure 95: State contribution in the Performance Analyzer

Plotting this flow rate highlights the issue.

Figure 96: Flow rate oscillations in the pipe

Some severe oscillation occurs in the pipe (the previous plot was made with a very fine Print interval of 3e-8 seconds.

Modes of hydraulic lines depend on their length (L), their boundary conditions (open or closed) and on the fluid properties (bulk modulus β, fluid density ρ). The exact modes without taking friction into account can be approximated using following equations.

Figure 97: Pulsations of hydraulic lines

Since the frequency of each mode is proportional to the inverse of the length (which is very small here), increasing that length will lower the frequency. In our case, change the length back to 25 mm and run a new simulation.

The solving time is now under 6 seconds instead of 120 seconds and the maximal frequency is now 31 kHz instead of 9.9 MHz.

Figure 98: New frequencies after modification

Next we plot a comparison between the flow rate in the pipe and the CPU time for the two lengths.

Figure 99: Comparison of flow rate and CPU time

We can observe fewer oscillations with an impressive CPU speed-up of 20 %.

The performance of a simulation model can be greatly influenced by a single parameter and the Performance Analyzer helps you to identify such issues.