Measurement of air flowrate by using an integration type ultrasonic flow meter applicable for spark ignition engine control

Abstract

An integration type air flow meter (IFM), composed of an ultrasonic sensor with an integration circuit, is tested for the air flowrate measurement in a pulsating flow condition. An accurate air flowrate measurement is essential to control the fuel injection rate of a fuel injection spark ignition (SI) engine. The difficulty comes from the pulsating and reverse flow characteristics of the induction pipe. The IFM integrates the instantaneous flowrate signal during the quarter cycle corresponding to an intake period of a four-stroke four-cylinder engine in order to identify and account for the flow direction. The IFM has significantly improved the accuracy of flowrate measurement compared with a hot wire type flow meter in certain conditions where a flow reversal exists. The sampling method is also easier when using the IFM compared with other techniques.