波导内飞灰灰位与折射率的微波测量方法

为了进一步提高微波波导法对飞灰含碳量检测的准确性,提出了一种利用微波在波导内不同介质分界面的反射作用,通过时域变换找到微波到达不同介质分界面的时间,再结合微波在波导内不同介质中的传输速度,计算得到波导内飞灰的灰位及相对群折射率的方法。本文使用规格为7.9 mm×15.8 mm×100 mm的矩形波导,在12.4～18 GHz频段下利用上述方法对质量为0～12 g,含碳量为1%～10%的一系列灰样的灰位与相对群折射率进行测试。结果表明在测量过程中,存在一个临界点,即当波导内实际灰位大于47.3 mm时,测得的灰位与实际灰位误差基本在±2 mm以内,且波导内灰样的相对群折射率与飞灰含碳量呈正相关,而不随飞灰质量的变化而变化。

A microwave measuring method of the level and refractive index of fly ash in the waveguide

To further improve the accuracy of the microwave waveguide method for detecting the unburned carbon content of fly ash, a method is proposed to calculate the ash level and relative group refractive index of fly ash in the waveguide. Through time domain transformation, the time of microwave reaching the interface of different media is achieved. Then, by combining with the transmission speed of microwave in different media in the waveguide, the reflection of microwave on the interface of different media in the waveguide is obtained. This paper uses a rectangular waveguide with a specification of 8 mm×15 mm×100 mm. Under the 12. 4-18 GHz frequency band, the above method tests the level and relative group refractive index of a series of ash samples with a mass of 0-12 g and a carbon content of 1% -10% . Results show that there is a critical point in the measurement process. When the actual ash level in the waveguide is larger than 47. 3 mm, the error between the measured level and the actual gray level is basically within ±2 mm. And the relative group refractive index of the ash sample in the waveguide is positively correlated with the carbon content of the fly ash. It does not vary with the mass of fly ash.