Overview

Test Case

This test simulates the closed cycle combustion in a small-bore direct injection diesel engine. The engine has a 7-hole injector and here it is modeled as a (360/7)⁰ sector with a stepped-lip piston bowl and no valve cutouts as shown in Figure 209: Geometry sector and dimensions.

Figure 209: Geometry sector and dimensions

The case is labeled on the ECN website as conventional diesel combustion at part load (9bar IMEPg), CDC9_SL_SSEp17b. It operates with a pilot-main injection strategy applied with a single profile and the spray targeting data, shown in Figure 210: Spray targeting data, can be found on the ECN site at this link:

The file contains both the re-entrant and the stepped-lip piston bowl data.

Figure 210: Spray targeting data

The table below lists the setup parameters, and results are compared against the experimental data. Data for the pressure trace can be found in the form of a Microsoft Excel file on the ECN site at the following link:

The file is named CDC9 InjRate Pcyl PIntake Fired and the worksheet it references is named CDC9_SL_SSEp17b. Notice that the engine has a piston pin offset of 1.5875 mm and the minimum volume occurs at -0.43 ATDC. Forte’s convention is to define piston TDC as crank angle= 0⁰, therefore the experimental curve is shifted by +0.43 degrees forward for a consistent comparison (see Slider Crank Motion in the Ansys Forte User's Guide). In addition, it is presented as the apparent heat release rate with constant gamma (𝛄=1.35) derived from the pressure trace (see Spatially averaged variables that are always output to the .csv files in the Ansys Forte User's Guide) according to:

Results Comparison for Ansys Forte

Figure 211: Pressure and apparent heat release rate