/ 109 Flow direction v sin α α v sin α v c c D T2,R1 T1,R2 T - Transmitter R - Receiver c - speed of sound v - flow media velocity α - inclination angle Differential pressure drop Orifice measurement pipe Blow-by flow Differential pressure transducer DIFFERENTIAL PRESSURE For the determination of blow-by flow the orifice measurement principle (differential pressure measurement procedure) is used. A neck (orifice) in the tube cross-section provokes a pressure drop that is measured by means of a differential pressure sensor. The shape of the orifice of the AVL Blow By Meter has been selected in a manner that it, on the one hand, ensures the accuracy in both flow directions and, on the other hand, prevents condensation at the orifice modifying the cross-section. The selected shape of the orifice allows for a broad dynamic range of 1:50. 6 GRAVIMETRIC (OIL CONSUMPTION METER) This measurement is based on the gravimetric principle. This means that oil is always sucked to a defined level or completely into a measurement tank by means of a modified dip stick or an oil drain plug. Afterwards, the weight is determined with the help of a highly precise pressure sensor. After the weight has been determined, the oil is pumped back into the oil pan of the engine. This measurement cycle consists of three steps: pumping (out) – weighing – pumping (back). The difference between two subsequent measurement cycles results in the oil consumption. ULTRASONIC TRANSIT DIFFERENTIAL TIME The measuring principle is based on the ultrasonic transit-time differential method. In this method, two ultrasonic pulses are sent simultaneously from Transmitter 1 (T1) and Transmitter 2 (T2) right through the flowing medium. One pulse is propagating in and the other one against flow direction. The interaction between the speed of sound c and the velocity of flow v accelerates the pulse on one of the paths and decelerates the pulse on the other path. This effective propagation velocity results in different transit times through the medium: The signal at Receiver 1 (R1) arrives faster than the signal arriving at Receiver 2 (R2). The device measures the speed of sound traveling either way, corresponding to t1 and t2. 1 2 3 4 5 7 8 1 - Oil dip stick 2 - Measuring tank 3 - Refilling tank 4 - Pump 5 - Drain plug 6 - Electronics 7 - PUMA CDH – Task 8 - Hybrid interface or serial interface via RS232
Solutions Katalog 2015_E
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