Air mass flow sensor is based upon thermal conduction and convection, provided the laminar flow conditions prevail in the whole measurement range. Due to the turbulence in the manifold, an especially small channel has been designed inside the manifold, and the laminar flow condition has been maintained throughout the measurement range in this small channel. The velocity distribution throughout the channel has been predicted. An ideal Re≈12-110 is obtained throughout the small channel. A fixed velocity ratio between the flow in whole manifold and in small channel is obtained. The air intake will be obtained though measuring the flow rates in the small channel. At the constant temperature of heater, temperature field around the heater under different flow conditions were simulated by finite volume method (FVM). The relationships of dt, the measuring distance and flow rate are obtained. There is the highest dt for increasing of the measurement distance, and the corresponding measurement distance is 140-210 m. By placing two pairs of thermistors, the highest precision of flow velocity can reach 0. 02 m/s.
|Number of pages||5|
|Journal||Chinese Journal of Sensors and Actuators|
|Publication status||Published - 1 Jul 2007|