| The surface temperature and temperature field distribution information of aerospace hot-end components are important parameters for the design and development of the structure and thermal protection system of hypersonic vehicles.Thin-film thermocouples have the advantages of small size,fast response time,and little interference to the measured environment.It is an advanced technology for accurate measurement of the surface temperature of aerospace hot-end components.This thesis takes the temperature test requirements of aerospace hot-end components as the research background,and mainly carries out research work on the design and preparation of probe-type thin-film thermocouples,the performance testing of thin-film thermocouples,and the design and implementation of integrated thin-film thermocouple temperature display systems.The main work of the thesis is as follows:First,the structure of the probe-type thin film thermocouple was designed and fabricated.The thermocouple was made of aΦ9 mm × 40 mm cylindrical rod as the base,and a thermocouple film was deposited on one end face of the cylindrical rod with a junction width of 1 mm.There are four through grooves with a diameter of 1 mm on the side of the thermocouple wire to fill the groove.The rods are made of alumina ceramics,nickel-based superalloy rods and C-C composite rods.Before depositing the thermocouple sensitive layer,it is necessary to deposit two kinds of rods with a thickness of about A 1 μm alumina insulating layer was used to deposit a Pt/Pt Rh10% film with a thickness of about 1 μm on the end face of the cylindrical rod as a temperature sensitive layer by magnetron sputtering.It is connected to the Pt wire and Pt Rh wire lead encapsulation with the side through-groove buried,and the encapsulation are thin film thermocouple samples.Secondly,the thermoelectric properties of the probe-type thin-film thermocouple samples were calibrated by static calibration method.The results showed that the annealing treatment can significantly improve the output response of the thin-film thermocouples and effectively improve the repeatability;The Seebeck coefficient of the ceramic substrate thin film thermocouple annealed at 900℃ is 10.12 μV in the range of0～1100 ℃,the sensitivity is 0.96,the repeatability is the best,and the temperature measurement accuracy is less than 4‰;The thin film thermocouples still have a good response in low temperature environment,the output thermoelectric potential increases regularly with the increase of temperature,and the low temperature calibration curve is in good agreement with the high temperature calibration curve.The dynamic performance of the thin-film thermocouples was calibrated by the method of pulsed laser dynamic calibration.The results show that the response time of the thin-film thermocouples is8.108 μs,which can meet the application requirements.Thirdly,the probe-type thermocouple samples wind tunnel test was carried out on the xxx aircraft test piece.The test results show that the maximum temperature of the surface of the aircraft nose cone measured by the developed thin-film thermocouples in the wind tunnel test is 163℃,which is close to the estimated value,and the samples were not damaged after the test and can be reused.The wind tunnel test results show that the thin-film thermocouples are feasible for the temperature measurement of the head of the hypersonic vehicle.Finally,an integrated thin-film thermocouple temperature display system is designed and implemented.The display system consists of a signal acquisition module,a calculation module and a display module.Operational amplifiers and analog-to-digital converters are used to collect thermoelectric signals,and FPGA is used to control the acquisition circuit and calculate the temperature.,after decoding,it will be displayed on the digital tube,and the displayed result will be kept to one decimal place.The integrated thin film thermocouple temperature display system can work normally,and the temperature display results are consistent with the actual situation. |
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