Research on the surface temperature compensation model of rotary kiln based on polynomial fitting and piecewise correction function

Abstract

Infrared scanning temperature measurement is applied more and more widely in rotary kiln, however, the less and less radiation energy can be received by the infrared scanner with the change in scanning angle (kiln head or kiln tail) of the monitoring system, which is one of the main factors that lead to temperature measurement error. The most common method is compensating based on cosine theorem, however, with the distance from the vertical point increasing, the error of temperature compensation is bigger. It's easy to appear the phenomenon of excessive compensation. According to the principle of temperature monitoring, this paper analyzes the reason for inadequate and excessive compensation, the real temperature of target is between the data after inadequate and excessive compensation by experimenting with different compensation methods. By observing the data distribution of the target temperature, it can be found a boundary point in the trend of temperature change (without any compensation), that means the temperature is approximately same when the angle change is very small. Therefore, this paper proposes piece-wise correction model which includes two parts, the first is constant which represents the part where the temperature is unchanged, the second is to apply temperature compensation factor formula acquired by polynomial fitting to original data. Experimental results show that the correction model proposed in this paper can not only describe the relationship between angle and measure error accurately, but also reduce the relative error of temperature measurement to 0.275% successfully.