Optical measurement of droplet dimensions in real gas-droplet flows

Abstract

In this paper, the optical methods for studying the gas-droplet flows are analyzed and compared. The analysis has shown that the Interferometric Particle Imaging (hereinafter IPI) and Glare Point Technique (hereinafter GPT) are most effective for studying the atomization process in fuel injectors. These methods have been used to measure the size of fuel droplets in the spray cone of the air-blast atomizer.  Measurements of atomization characteristics of the fuel atomizer under different operating conditions made by both methods (IPI and GPT) have shown that the IPI technique is more effective for small particles (5-100 µm) and GPT technique – for larger particles (20 - 200 µm) for this scheme of measurements. To computerize the GPT method, a special software product, incorporating the wavelet transform –based procedure for validation of liquid droplets, has been developed. The size and velocity distributions of droplets determined by the GPT method have been used to construct the relative flowrate characteristic curve for the fuel atomizer. Therefore, the application of both methods essentially extends the range of measurable droplet dimensions. In practical applications, the use of only one method can lead to significant errors. Thus, Sauter’s diameter D32 evaluated with the use of IPI data was ~40 µm, whereas the use of GPT method gives the value of about  80  µm.