基于复合热膜技术的低风速及湍流测量

Low speed and turbulence measurements based on composite hot-film technology

针对复合热膜应用于低风速和湍流强度测量方法进行了研究。风洞在进行低风速测量时普遍存在输出灵敏度不高的问题,采用增加热膜与环境温度差的方法,提高了热膜敏感探头在低速范围的输出灵敏度,实现了2m/s内的风速和湍流准确测量。考虑到气体温度对热膜探头输出信号的影响,对温度补偿方法和补偿电路进行了研究,通过对电路的合理设计,实现了温差的精确控制。对热膜结构、尺寸和器件进行合理匹配,实现了复合热膜敏感探头的微型化设计。采用MEMS技术,通过最大限度减小加热电阻和测量电阻的尺寸,达到了较好的响应频率。测试结果表明,该复合热膜敏感探头可以满足低风速和湍流度的测试需求。

The paper studies the composite hot-film test method used to measure the air veloc-ity and turbulence at low speed.The output sensitivity of the air velocity measurement is general-ly low in wind tunnel tests.In order to improve the sensitivity of the hot-film sensitive probe when the velocity is very slow,the temperature difference between the hot-film and the airflow is enhanced.The velocity and turbulence of the low speed airflow can be accurately measured even when it is under 2m/s.In order to correct the output of the hot-film sensitive probe influenced by the gas temperature,the methods of temperature compensation and compensation circuit are studied.A special circuit is designed to obtain the accurate control of temperature difference.By matching the structune,size and components of the hot film reasonably,the hot film sensitive probe is miniaturized.Using the MEMS technology,good frequency response of the probe is achieved by reducing the size of the thermal resistances and measurement resistances.Test results show that the composite hot-film sensitive probe can satisfy the requirement of the low speed and turbulence measurement.