Novel dilution sampling method for gas analysis with a low sampling rate

Abstract

The characterization of the product gas of flames is important not only in the design of combustors but also to provide a fundamental understanding of the phenomenon of combustion. To prevent the disturbance of the flow field during gas sampling, the flow rate of the sampled gas must be kept low. However, some gas analyzers require a relatively large flow rate of several liters per minute for gas sampling to increase the response of the gas analysis. In this study, to enable analysis with a low net sampling rate, a method for the dilution of the sampled gas was developed. Although a dilution sampling method has already been proposed, it is difficult to measure the species of interest with this existing method when a tracer species is included in the object mixture. To address this problem, the newly proposed dilution sampling method is appropriate for object gases containing tracer species. In the proposed dilution sampling method, sampling is carried out twice using two dilution gases with different mole fractions of the tracer species. The mole fraction of the target species can be then calculated by solving simultaneous equations. Uncertainty analysis was also conducted for this method, and demonstrations of the dilution sampling method were successfully carried out. In addition, it is suggested that the selection of the dilution gas, i.e., the mole fraction of the tracer species in the dilution gas, is important to reduce the experimental uncertainty in the dilution sampling method.

Keywords

• gas analysis
• low flow rate sampling
• dilution
• uncertainty analysis
• dilution ratio