Novel Air Flow Meter for an Automobile Engine Using a Si Sensor with Porous Si Thermal Isolation

Abstract

An air flow meter for measuring the intake air of an automobile engine is presented. It is based on a miniaturized silicon thermal mass flow sensor using a thick porous Si (Po-Si) layer for local thermal isolation from the Si substrate, on which the sensor active elements are integrated. The sensor is mounted on one side of a printed circuit board (PCB), on the other side of which the readout and control electronics of the meter are mounted. The PCB is fixed on a housing containing a semi-cylindrical flow tube, in the middle of which the sensor is situated. An important advantage of the present air flow meter is that it detects with equal sensitivity both forward and reverse flows. Two prototypes were fabricated, a laboratory prototype for flow calibration using mass flow controllers and a final demonstrator with the housing mounted in an automobile engine inlet tube. The final demonstrator was tested in real life conditions in the engine inlet tube of a truck. It shows an almost linear response in a large flow range between –6,500 kg/h and +6,500 kg/h, which is an order of magnitude larger than the ones usually encountered in an automobile engine.

Adaptive sliding mode observer for updating maps with an application to mass air flow sensors in diesel engines

“…A possible solution to satisfying the strict emissions requirement is the accurate detection and precise control of engine operating parameters. The accurate control of the exhaust gas recirculation rate control and air-fuel ratio control depend on their precise calculation; this can be improved using a hot-wire (or film) mass air flow (MAF) sensor installed between the air filter and the intake manifold (Grimes et al, 2005;Ho¨ckerdal et al, 2008;Zheng et al, 2004).These MAF sensors are widely used in commercial automobiles to measure the air mass flow into the engine; a sensor element is heated to a fixed temperature, and the difference in temperature attributed to heat transfer from the heating element to the air flow is taken as a measure of the air mass flow (Bosch, 2009;Hourdakis et al, 2012). However, there are many different local flow fields within the inlet piping due to the three-dimensional (3D) turbulence flow, leading to measurement biases in the MAF sensor.…”

An LPV Adaptive Observer for Updating a Map Applied to an MAF Sensor in a Diesel Engine

“…Accurate exhaust gas recirculation (EGR) rate control and air-fuel ratio (AFR) control are important technologies to satisfy the increasingly stringent emission regulations, which are dependent on the precise calculation of the EGR rate and AFR [ 1 , 2 ]. The accuracy of the EGR rate and AFR can be improved by a mass air flow (MAF) sensor, in which a sensor element is heated to a fixed temperature, and the difference in temperature attributed to heat transfer from the heating element to the air flow is a measure of the air mass flow [ 3 , 4 , 5 ]. However, there are many different local flow fields within the inlet piping due to the three-dimensional turbulence flow, leading to measurement biases in the MAF sensor installed between the air filter and the intake manifold.…”

Temperature Effects on the Wind Direction Measurement of 2D Solid Thermal Wind Sensors

“…According to whether thermal insulation is present or not, calorimetric flow sensors can be divided into two categories. One type is those with thermal insulation, which are usually fabricated on silicon dioxide membranes [ 6 , 8 , 9 , 10 , 11 , 12 ], thin crystalline silicon membranes [ 13 , 14 , 15 ], or on porous silicon layers [ 16 , 17 ]. The thermal insulation is so effective that the total power consumption of some thermal flow sensors can be decreased to the milliwatt or even sub-milliwatt range [ 11 , 15 ], which is attractive for some applications, such as biological and medical applications.…”