Temperature Measurements of Diesel Fuel Combustion With Multicolor Pyrometry

Optical diagnostics techniques to measure diesel combustion flame temperatures are useful for evaluation and control of combustion processes. In this paper, diesel combustion flame temperatures are measured based on a multicolor pyrometry method respectively adopting an optical fiber spectrometer and a color charge coupled device (CCD). The intensity ratios for various wavelengths/wavebands are utilized as the analytical variables to deduce the temperatures to avoid the need to calibrate each system for the specific geometry conditions. The measured multicolor data can determine the temperature T and the soot factor KL. Extra data collected at many wavelengths is used to reduce the noise and random fluctuations in the measurements. To improve the solving precision, a data-processing method based on the least-squares technique is proposed to fit the data for approximate solutions. Verification experiments using the multicolor pyrometry were conducted in a 54-120 kW test furnace with diesel fuel. Data for 16 wavelengths detected by a fiber optic spectrometer from a diesel flame is analyzed to determine how to choose a suitable combination of three wavelengths for three-color pyrometry. The CCD-based three-color measurements, which would be much more practical in field measurements, are compared with the spectrometer-based results.