RICARDO WAVE Port Modelling Now that the data is collected experimentally, the pressure loss within the ports due to the flow over the port surface and changes in flow momentum from the port geometry can be modelled into WAVE. Either coefficients discussed in section 7.7.2 can be entered into the flow coefficients profile but WAVE preferably uses as internally, Cd if is used, WAVE converts the values to using the valve reference diameter Cf Cd specified by the user within the valve lift editor. To accurately model the effects of reverse flow, the reverse flow coefficient is recorded, calculated and entered by the same means of achieving the forward flow coefficients with the flow direction reversed. To eliminate the effects of the pressure loss within the model, the ducts “duplicating” and junctions used to simulate the ports should not contribute any additional pressure losses and therefore all friction and pressure loss multipliers should be set to 0 and discharge coefficients set to 1. Any duct bend angles should be set to 0 since the pressure loss due to the ports geometries have been accounted for from the port flow tests. Flow Coefficients Coefficients Combustion Modelling SI Wiebe Friction WAVE’s friction model is defined by the modified Chen Flynn (1965) correlation seen in EQUATION. Where are the Chen Flynn coefficients Acf, Bcf, Ccf, Qcf inputted by the user, is the peak cylinder pressure, is the speed factor, Pmax Sfact is the engine speed and is the cylinder stroke. RPM stroke
RICARDO WAVE Port Modelling Now that the data is collected experimentally, the pressure loss within the ports due to the flow over the port surface and changes in flow momentum from the port geometry can be modelled into WAVE. Either coefficients discussed in section 7.7.2 can be entered into the flow coefficients profile but WAVE preferably uses Cd as internally, if Cf is used, WAVE converts the values to Cd using the valve reference diameter specified by the user within the valve lift editor. To accurately model the effects of reverse flow, the reverse flow coefficient is recorded, calculated and entered by the same means of achieving the forward flow coefficients with the flow direction reversed. To eliminate the effects of “duplicating” the pressure loss within the model, the ducts and junctions used to simulate the ports should not contribute any additional pressure losses and therefore all friction and pressure loss multipliers should be set to 0 and discharge coefficients set to 1. Any duct bend angles should be set to 0 since the pressure loss due to the ports geometries have been accounted for from the port flow tests. Flow Coefficients Coefficients Combustion Modelling SI Wiebe Friction WAVE’s friction model is defined by the modified Chen Flynn (1965) correlation seen in EQUATION. Where Acf, Bcf, Ccf, Qcf are the Chen Flynn coefficients inputted by the user, Pmax is the peak cylinder pressure, Sfact is the speed factor, RPM is the engine speed and stroke is the cylinder stroke.
20080617.docx