Experimental data are divided into two groups corresponding to two different projects from recent years:

  1. Piston bowl geometry study
  2. Close-coupled pilot injection study

The piston bowl geometry study utilizes two different piston bowls that represent two competing approaches to swirl-supported diesel combustion chamber design: a conventional, re-entrant piston bowl and a stepped-lip (or chamfered-lip) bowl. The conventional, re-entrant piston resembles the production GM 1.9L piston geometry, while the stepped-lip bowl is a scaled version of a production Ford piston design. Neither piston has valve cutouts, so the squish height is set to avoid interference with valves. Experiments were performed with two operating points: a conventional, part-load operating point with a pilot-main injection strategy, and a highly dilute, highly premixed operating point (low temperature combustion). An injection timing sweep has been performed for both, and fueling is adjusted to maintain load. Thermodynamic, injection rate, and optically-derived data will be uploaded to this site to facilitate simulations and comparison with experimental data.

 

The close-coupled pilot injection study was performed using a fast-acting solenoid injector to enable very short dwells between a single pilot and a single main injection. This study involved a conventional, re-entrant piston that features valve cutouts, and a part-load, conventional diesel operating point. The pilot quantity is held constant while the dwell between the pilot and main is adjusted. The main injection quantity is adjusted to maintain a constant engine load, and both the pilot and main injections are block-shifted to maintain a nearly constant value of CA50 (the point at which half of the fuel energy has been released). Thermodynamic, injection rate, and optically-derived data will be uploaded to this site to facilitate simulations and comparison with experimental data.