This work presents an advanced cycle analysis of a naturally aspirated, four stroke, diesel engine with a swirl prechamber. For calculating the heat of exchange between gas and the walls in both main chamber and prechamber, the relevant characteristic velocities and lengths are calculated by setting-up a zero dimensional energy cascade turbulence model. Combustion in both the main chamber and the swirl prechamber is studied by proposing a two-zone combustion model, following the movement of the spray plume inside an air solid body rotation environment in the prechamber and its later progression into the main chamber. The concentration of the constituents in the exhaust gases is calculated by adopting a complete chemical equilibrium scheme for the C-H-O system of the eleven species considered, together with chemical rate equations for the calculation of nitric oxide (NO). A model for the evaluation of soot formation and oxidation rates is incorporated, in order to compute the net soot concentration in the exhaust. To validate the analysis, an extensive experimental investigation is undertaken in the laboratory on a flexible Ricardo, single cylinder, swirl chamber diesel engine, measuring its performance (load, specific fuel consumption, maximum pressures, etc) and emissions characteristics (NO,C) in a wide range of operating conditions. The experimental results are compared with the theoretical results obtained from the computer program implementing the analysis and the agreement of this comparison is found very satisfactory. (A)
Samenvatting