Research On Hydraulic Measurment And Experimentsof Laval Nozzle Throat Diameter

Laval nozzle is an important component of many power facilit ies, and widely applied in power and other fields. With the geometries of expansion after shrinking, it can produce powerful thrust. The process ing qualit y of Laval nozzle throat greatly impact the nozzle performance, and is the core of the nozzle processing qualit y. According to its manufacturing process, the precision of nozzle throat is limited by both high-precision processing technology and it s measurement accuracy. Based on the special structure, hydraulic measurement measuring throat diameter is proposed. On the basis of flow characterist ics, hydraulic measurements measure the size of throat diameter by measuring the flow, which has with the characterist ics of non-contact, high accuracy, good stabilit y.In this dissertat ion, research on the hydraulic measurement of the Laval nozzle throat has been done on the base of theoret ical analysis of the orifice flow characterist ics. The principle of the hydraulic measuring system is demonstrated and the standard mandrel model of this system was established. Then the t ype and the size of the standard mandrel are displayed. Finally, the range of pressure drop is determined which is very important to the measuring system.The physical model is developed on Fluent platform to simulate the flow o f the measurement model. On the base of the simulat ion, the relationship between the pressure drop and flowrate has been defined, as well as the relat ion ship between the throat diameter and flowrate to optimize the parameters of the measurement model. Analysis the error factors which affect measuring throat diameter, simulate the flowrate with the error factors, and then analysis the error caused by the error factors on the measurement res ult.An automat ion measurement program is developed. The oil circuit was designed to achieve closed-loop control of pressure drop and automat ic temperature control, as well as the mechanical structure of the measuring fixture. In addit ion, the measurement software, which meets the automat ic requirement, is programmed on Visual Studio.The last part of this dissertat ion are the experiments. First ly, the essent ial calibration experiments of the pressure sensors and the flow sensors are taken. Then the size of the standard mandrel, the pressure drop and the measuring fixture are defined to meet the measuring requirement by several experiments. The calibration experiments of the measurement platform were also carried out, on the base of which, the repeatabilit y measurements and the error factors impact experiments were taken. Results show that this hydraulic measurement platform has higher accuracy and better repeatabilit y.