Numerical Study and Performance Analyses of Mems-Based Particle Velocity Sensor with Combined Inclined Rib Pair

The combined inclined rib pair(CIRP)is the first time proposed to improve the sensor performance of particle velocity sensor(PVS)by using a three-dimensional numerical method.The method is verified by the experiment results in the literature.The optimal plain channel parameters are determined as the basic sensor structure.In comparison of plain channel,both heat transfer characteristics and sensor performance are enhanced effectively by arranging the CIRP.The reason is that the high flow rate region caused by the CIRP can maintain strongly in the whole fluid field if there are enough rib pairs.Furthermore,the produced longitudinal vortex pair can get a better fluid mix,which is more conductive to heat transfer.The increasing height and number of the CIRP can improve the heat transfer characteristics,but the flow resistance will increase as well.For the purpose of finding the best overall performance,the effects of the parameters including the geometric sizes and the position of the CIRP have been investigated.The results show that PVS will get the best sensitivity when the rib length and width are 0.2 mm and 0.03 mm respectively,and the distance between rib pair and between ribs in the same pair are 0.15 mm and 0.3 mm respectively.Besides,the most suitable crossing angle is 45°.Thus,the performance of PVS can be significantly improved by this novel structure.

Effect of particle degradation on electrostatic sensor measurements and flow characteristics in dilute pneumatic conveying

Vigorous particle collisions and mechanical processes occurring during high-velocity pneumatic con- veying often lead to particle degradation. The resulting particle size reduction and particle number increase will impact on the flow characteristics, and subsequently affect the electrostatic type of flow measurements. This study investigates this phenomenon using both experimental and numerical meth- ods. Particle degradation was induced experimentally by recursively conveying the fillite material within a pneumatic pipeline. The associated particle size reduction was monitored. Three electrostatic sensors were embedded along the pipeline to monitor the flow. The results indicated a decreasing trend in the electrostatic sensor outputs with decreasing particle size, which suggested the attenuation of the flow velocity fluctuation. This trend was more apparent at higher conveying velocities, which suggested that more severe particle degradation occurred under these conditions. Coupled computational fluid dynamics and discrete element methods （CFD-DEM） analysis was used to qualitatively validate these experimental results. The numerical results suggested that smaller particles exhibited lower flow velocity fluctua- tions, which was consistent with the observed experimental results. These findings provide important information for the accurate aoolication of electrostatic measurement devices in oneumatic conveyors.

Three-dimensional analysis of relationship between relative orientation and motion modes

Target motion modes have a close relationship with the relative orientation of missile-totarget in three-dimensional highly maneuvering target interception. From the perspective of relationship between the sensor coordinate system and the target body coordinate system, a basic model of sensor is stated and the definition of relative angular velocity between the two coordinate systems is introduced firstly. Then, the three-dimensional analytic expressions of relative angular velocity for different motion modes are derived and simplified by analyzing the influences of target centroid motion, rotation around centroid and relative motion. Finally, the relationships of the relative angular velocity directions and values with motion modes are discussed. Simulation results validate the rationality of the theoretical analysis. It is demonstrated that there are significant differences of the relative orientation in different motion modes which include luxuriant information about motion modes. The conclusions are significant for the research of motion mode identification,maneuver detection, maneuvering target tracking and interception using target signatures.