Evaluation of a Phenomenological Spray-Combustion Model for Two Open-Chamber Diesel Engines

The predictive capability of a phenomenological spray-combustion model was evaluated for diesel engine performance, combustion, and emissions. The data used for comparisons with the predictions resulted from tests on two single-cylinder research-type open-chamber diesel engines -- a 2.0-L per cylinder heavy-duty engine and a 0.52-L per cylinder light-duty engine. The data covered wide ranges of speed and overall air-fuel ratio.

Such global performance quantities as indicated mean effective pressure and indicated thermal efficiency predicted by the model agreed with experimental results from both engines within 5%. Pressure-time and heat-release rate predictions agreed within 5-15%. However, further improvements are needed before the model can be used reliably for emissions predictions. Specifically, predictions of nitric oxide (NO) and non-volatile particulate (soot) were in poor agreement with the measurements, especially for the light-duty engine. Inadequate modeling of the spray-wall impingement could be the reason for the observed disagreement.