Research On Dynamic Pressure Sensor For Unstable Combustion Measurement Of Rocket Motor

As the core component of carrier rocket,the engine plays a crucial role in the success of rocket launch,and the combustion process of the combustion chamber of the engine has a great impact on the smooth operation of the rocket,so every rocket engine needs to conduct combustion stability test before it is put into use.In general tests,the dynamic pressure signal of the rocket combustion chamber is used to characterize its internal combustion process.Based on the engineering practice of the rocket engine unsteady combustion scale test,a dynamic pressure sensor is designed to monitor the combustion process of the engine combustion chamber in the test.Due to the harsh operating environment,a capacitive pressure-sensitive structure with strong environmental adaptability is adopted in the design,and a signal conditioning circuit is designed to work with the sensitive structure,and the output performance of the sensor is calibrated.Capacitive sensitive structure has superior adaptability to the environment.The sensitive structure designed in this paper expands the linear working range of the sensitive structure by adopting the double-moving plate structure.An innovative differential capacitance structure is designed to further enhance the linearity of the sensitive structure based on the contact capacitance pressure sensitive structure.The structure consists of two contact capacitive pressure sensitive diaphragms made of different dielectric materials,and the capacitive values of the two sensitive diaphragms are subtracted in the subsequent signal conditioning circuit.The structure and output performance simulation of the sensitive structure is carried out by ANSYS,which proves that the strength of the sensitive structure can meet the requirements of use.The output data shows that the linearity of the contact differential capacity pressure sensitive structure is improved by about 50% compared with the traditional contact capacitance pressure sensitive structure.At the same time,the impact of parasitic capacitance and edge capacitance on the sensitive structure can be restrained.The signal conditioning circuit of the sensor adopts the diode double T type AC bridge as the signal detection circuit,and then designs a square wave generation circuit matching the signal detection circuit.An 8-order Butterworth low-pass filter is designed for low-pass filtering,and the output signal of signal detection circuit is averaged.All the designed circuits are simulated by Multisim,and the simulation data basically agree with the theoretical calculation value.At the end of the paper,the performance of the pressure sensor is calibrated according to the calculation method of static performance uncertainty of QJ-28A-1998 pressure sensor and the verification regulation of JJG 624-2017 dynamic pressure sensor.The final nonlinearity of the contact differential tolerance dynamic pressure sensor designed in this paper is 0.697%,and the in-band unevenness of the first 90% of the passband is not more than 1d B.The differential tolerance pressure sensitive structure provides a new idea for improving the poor linearity of capacitive pressure sensor,and has universal applicability.There are 101 figures and 13 tables in the paper,and the design process and structural parameters of the sensor are described in detail.There are 153 references.