The Thrust Measurement System Research For Combined Nozzle In Small Space

The nozzle is an important component of the thrust chamber which is widely used in aircraft engine and rocket engine.It is not only used to provide the thrust,but also to control the position and posture of aircraft through the combination of several nozzles.With the development of aerospace technology,many fields such as aeroengine,missiles,and satellites will be promoted by the measurement of the nozzle thrust.At present,as for the measurement of the nozzle thrust,there are mainly two test methods to build the thrust measurement system.On this basis,the thrust measuring devices of different kinetics configurations arise at the historic moment.The combined nozzle used in small space was researched as the main object in this paper,and their thrust forces were unable to be measured on the ground by the momentum balance when they were in the satellite attitude adjustment capsule.Thus,the test method that the nozzle directly sprays on the load baffle was adopted.Based on this method,a set of complete and automatic nozzle thrust measurement system,which provides a convenient measurement way for the thrust measurement,was designed.This method also combined with the numerical calculation technology and the digital signal processing technology.Firstly,the FLUENT software was used to calculate the flow field of the Laval nozzles with the outlet diameters of respectively ?2.3 mm and ?5.1 mm.The influence of the load baffle applied on the flow field of nozzles and their extension was analyzed.Thus,the suitable position scopes of the load baffles were determined,which was the theoretical basis for providing the measurement of the nozzle thrust.Meanwhile,the size of theoretical value of the different dimensional nozzle thrusts were obtained by the numerical calculation,and the range of the thrust was less than 10 N.Secondly,the hardware and software platform of the thrust measurement system of the combined nozzle were built.The hardware system was made up of the data acquisition function module and the sensor installation platform.It converts force signal into electrical signal which was processed by computer.Furthermore,the amplification and digitization of the signal were implemented by the data acquisition function module.The installation of sensors and other devices,the position fixation in small space of the measurement system and the positioning of the load baffle were realized by the sensor installation platform.The acquisition and processing of the signal,data display,error evaluation and other functions were implemented by the software system.The subsequent processing and control of the hardware system was realized,and the measurement results were obtained.Finally,a thrust calibration experiment was finished for the thrust measurement system of the combined nozzle.The thrust measurement experiments were carried out after the calibration.The load surface locations of the sensors for the different types of nozzles were determined by the calibration experiment.The load surface locations of sensors of nozzle ?,?,? were respectively set at the distance of 4 mm,6 mm,10 mm between the load baffles and the nozzles.Meanwhile the validity of the numerical calculation of Laval nozzles was demonstrated.Afterwards,the correction coefficients of thrust forces for all channels of the measurement system were determined according to the actual test condition.The uncertainty of the measurement system was evaluated by using type A uncertainty component and type B uncertainty component on the basis of the thrust measurement data.The analysis of error sources met the test requirement with the accuracy of 0.1 N.