FlexVent – EGR Valve Integrated EGR Mass Flow Metering for Heavy-Duty Engines

Authors

Dr.-Ing. Christian Antoni, Dr.-Ing. Berthold Franz, Dr.-Ing. Stojan Cucuz, Dipl.-Ing. Franz Dellen,
Pierburg GmbH, Neuss

Summary

The development of heavy-duty Diesel engines is closely linked to the optimization of engine-out particulate and nitrogen oxide emissions. Most recent challenge OEMs are facing is the emissions legislation restricting and nowadays also monitoring real drive emissions under all engine operating conditions. Since introduction of emission legislations stage EURO IV and in contrast to passenger car engines truck engines have to comply the emission limits within a challenging dynamic test cycle. Nevertheless there still remain gaps between real drive emissions and legislative expectations, which may be reduced by further improvements like the FlexVent EGR valve.

To achieve lowest engine-out NO_x emissions EGR is one of the main enablers. Pierburgs innovative FlexVent EGR valve is dedicated to heavy-duty Diesel engines, where a Venturi EGR mass flow sensor is already state of the art. These engines emit, supported by means of a precise EGR mass flow sensor accurately predictable engine-out NO_x emissions even under transient conditions. FlexVent EGR integrates the well-known Venturi EGR mass flow rate sensing principle with the EGR valve in one housing. Two robust technologies are combined, applied in one final product. System complexity and package requirements are reduced to only one component with one electrical connector. The term FlexVent was chosen as the integrated Venturi mass flow sensor covers a flexible range of Venturi diameters, depending on the actual valve position. Functional effect of this flexible Venturi diameter is a higher signal resolution at low EGR mass flow rates passing by, increasing the prediction precision of the engine-out NO_x mass flow rate.

FlexVent technology enables the full control of the EGR mass flow rate within the engine component EGR valve by means of integration of the components EGR valve, pressure and temperature sensors and extended EGR control electronics with a fast PCB. Intention is to change the EGR control architecture of future engines. These engines may request the EGR mass flow rate set-value from the EGR valve instead of requesting only an EGR valve position. Closed loop EGR mass flow rate control will be transferred from engine ECU to the smart FlexVent EGR valve. Sensed EGR mass flow, absolute pressure p3 and exhaust gas temperature T3 will be return values to the engine ECU. Remaining task for the engine ECU will be the model based calculation of the required set-value for EGR mass flow rate to keep engine-out NO_x emissions.

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