Dafang Wu

High-speed and accurate non-linear calibration of temperature sensors for transient aerodynamic heating experiments

Transient aerodynamic heating experiments with high-speed aircraft require temperature sensors that can carry out rapid and accurate electromotive force (EMF)–temperature conversions. A fast, high-precision non-linear EMF–temperature conversion method is proposed. In this method, the temperature values to be converted were pre-positioned using a non-linear mathematical model. Then, they were accurately positioned using an efficient binary search algorithm with a small scope. Thus, this method has rapid conversion speed and high calibration precision. This conversion precision is enhanced by one order of magnitude over that of the normal reference table, and the conversion time is 1% of that of the traditional piecewise linearization method. This method was employed in a transient aerodynamic heating experimental simulation system with high-speed aircraft. The experiment results show that, in the case of a high change rate of temperature and heat flux, accurate dynamic tracking can still be realized, and the experimental simulation results agree well with the pre-set environment. The developed temperature sensor calibration method is necessary for high-speed and high-precision aerodynamic heating experiments with hypersonic aircraft.

Insulation Performance of Heat-Resistant Material for High-Speed Aircraft Under Thermal Environments

Lightweight insulation materials are widely used to thermally protect high-speed aircraft, such as missiles. Thermal conductivity is an important parameter used to evaluate the efficiency of a material’s thermal insulation performance. Since thermal conductivities provided from material handbooks or manufacturers are discrete data for different temperature ranges, there is a deviation between those and actual parameters in terms of continuous nonlinear variations. Therefore, this study measures the thermal conductivities of lightweight thermal insulation materials at high temperatures, and the relationship between the thermal conductivity and temperature is obtained. A finite element model of the thermal insulation materials is also established and applied to numerically calculate the thermal insulation properties for high-temperature ceramic fiber insulation materials using the experimentally obtained nonlinear relationship between thermal conductivity and temperature. Additionally, a transient aerodynamic heating experiment simulation system is used to thermally test the same materials; the calculated and experimental results for the same materials are compared, which exhibit good consistency that demonstrates that accurate results can be obtained from the numerical computation using the relationship established from the experimentally measured conductivity and temperature.

Study on the thermal protection performance of superalloy honeycomb panels in high-speed thermal shock environments

The thermal protection performance of superalloy honeycomb structure in high-temperature environments are important for thermal protection design of high-speed aircrafts. By using a self-developed transient aerodynamic thermal simulation system, the thermal protection performance of superalloy honeycomb panel was tested in this paper at different transient heating rates ranging from 5°C/s to 30°C/s, with the maximum instantaneous temperature reaching 950°C. Furthermore, the thermal protection performance of superalloy honeycomb structure under simulated thermal environments was computed for different high heating rates by using 3D finite element method, and a comparison between calculational and experimental results was carried out. The results of this research provide an important reference for the design of thermal protection systems comprising superalloy honeycomb panel.

Experimental study and numerical simulation of active vibration control on high order mode of piezoelectric flexible beam

To reduce effective load and lower the launch cost, many light-weight flexible structures are employed in spacecraft. The research of active control on flexible structural vibration is very important in spacecraft design. Active vibration control on a flexible beam with piezoelectric pieces bonded in surface is investigated experimentally using independent modal space control method, which is able to control the first three modes independently. A comparison between the system responses before and after control indicates that the modal damping of flexible structure is greatly improved after active control is performed, indicating remarkable vibration suppression effect. Dynamic equation of the flexible beam is deducted by Hamilton principle, and numerical simulation of active vibration control on the first three order vibration modes is also conducted in this paper. The simulation result matches experimental result very well. Both experimental and numerical results indicate that the independent modal control method using piezoelectric patch as driving element is a very effective approach to realize vibration suppression, which has promising applications in aerospace field.

A method for determining the horizontal impact load based on the rotational speed of the aircraft's wheel in a landing gear drop test

ABSTRACT The maximum horizontal impact load experienced by an aircrafts landing gear wheel during landing is an important parameter in the landing gears safety design and performance analysis. Using a noncontact photoelectric testing method, this paper experimentally obtained the temporally varying data of the instantaneous rotational speed for an aircraft wheel at the instant of its contact with the test platform. Moreover, the kinetic relationship between the transient rotational speed of the aircrafts wheel and the horizontal impact force was established. According to the temporally varying data measured from the transient rotational speed of the aircrafts wheel, the maximum horizontal impact load at the instant the aircraft contacted the platform was calculated. To verify the accuracy of this method in which changes in rotational speed of the aircrafts wheel determine the horizontal impact load, verification equipment without lateral constrains was designed and used for testing. The experimental results showed that the horizontal impact load determined based on the transient rotational speed of the aircrafts wheel are consistent with the results obtained using direct measurements obtained from custom-made equipment free of lateral constrains. This paper provides a new experimental method for measuring the horizontal impact load on the aircrafts wheel.

Experimental study on the thermal-vibration testing of the wing structure of high-speed vehicles

During long time and high speed flight, high-speed aircraft structures, such as the wings and rudders, bear not only prolonged serious vibration, but also harsh aerodynamic heating. The high temperatures caused by aerodynamic heating can significantly change the mechanical properties of the materials and structures, including the elastic modulus, stiffness, and so on. Meanwhile, the complex flight maneuver process will also produce high-temperature gradients, which affect the thermal stress field of the structures. Both of these impacts significantly affect the natural vibration characteristics of the high-speed aircraft. In this paper, the wing structure vibration characteristics were investigated in high temperature environments. A self-designed extension configuration withstanding high temperature was used to transfer the vibration signals to the non-high temperature zone for vibration data acquisition by using the regular acceleration sensors. Combined this novel method and the self-developed thermal-vibration test system, the thermalvibration joint testing was performed on the wing structure of high-speed flight vehicles under a thermal environment with the highest temperature up to 600 °C and the vibration characteristics of the wing structure (e.g., the natural frequency) at various temperatures were obtained. The experimental results can provide a reliable basis for the safety design of the wing structure of high speed vehicles under high-speed thermal vibration conditions.

Experimental research on thermal vibration characteristics of wing structure for high-speed flight vehicles in high-temperature environment

It is crucial for the safety design of high-speed vehicles to obtain the information on the parameters of the vibration characteristics of the wing structures of a long-range high-speed vehicle by an experimental method in a complex environment with high temperatures and intense vibrations. In this report, a high-temperature environment test system and vibration test system were combined to generate a controlled thermal environment for a hollow wing structure by applying infrared radiation heating while exerting vibration excitation on the wing. Furthermore, by transmitting the structural vibration signal of the hollow wing through a self-designed high-temperature extension device to the non-high temperature zone for data collection and analysis, we measured the relevant parameters of the vibration characteristics, such as natural frequency and vibration mode, in a force-heat complex environment with temperatures reaching 900°C. The results provide an important basis for the dynamic characteristics analysis and safe and reliable design of hollow wing structures for long-range, high-speed flight vehicles under a high-temperature and intense vibration environment.

Study on active vibration control for high order mode of flexible beam using smart material piezoelectric ceramic

In order to reduce effective load and lower the launch cost, many light-weight flexible structures are employed in spacecraft. The research of active control on flexible structural vibration is very important in spacecraft design. Active vibration control on a flexible beam with smart material piezoelectric pieces bonded in surface is investigated experimentally using independent modal space control method, which is able to control the first three modes independently. A comparison between the systems responses before and after control indicates that the modal damping of flexible structure is greatly improved after active control is performed, indicating remarkable vibration suppression effect. Dynamic equation of the flexible beam is deducted by Hamilton principle, and numerical simulation of active vibration control on the first three order vibration modes is also conducted in this paper. The simulation result matches experimental result very well. Both experimental and numerical results indicate that the independent modal control method using piezoelectric patch as driving element is a very effective approach to realize vibration suppression, which has promising applications in aerospace field.