Automatic pairing measurement of servo valve nozzles and experimental research

The twin nozzle-flapper valve of symmetric structure is the pilot stage of servo valve. Nozzles are the key parts of a twin nozzle-flapper valve. A pair of nozzles fixed in a twin nozzle-flapper valve is called paired nozzles which has strictly consistent fluid performances. Fluid performances are influenced by the shape and size of the round throttle orifices on the head of the nozzles. It is so difficult to ensure the consistencies of fluid performances only by machining, that there should be a hydraulic testing experiment to select the performances-closest nozzles from one batch of machined nozzles to compose paired nozzles separately, and the testing method is called pairing measurement. This paper proposed a measuring method based on differential pressure-flow measuring and pressure measuring. This paper also proposed a sort-based paring algorithm according to the differential pressure-flow feature of nozzles, and the paired success ratio can be increased by the algorithm. Experimental research has been done on the SPCT-II servo valve nozzle flow testing system which is developed by ourselves and the results had proved the correctness of the measuring method and the proposed sort-based paring algorithm.