Investigation of Spray Angle Measurement Techniques

Abstract

The in-cylinder fluid-dynamic processes of fuel injection and air entrainment influence the structure and shape of evolving fuel sprays, which can subsequently alter the ignition, combustion, and pollutant formation processes in diesel engines. Different spray angle detection methods have been used in the literature to investigate the global and local spray characteristics. In this paper, the five most widely used diesel spray angle detection methods were identified and used to evaluate the characteristic features of each detection method: methods with a detection range based on the spray penetration length, methods with a fixed detection range in the near- and far-field spray regions, triangular-based methods, and methods based on averaging local data points. The sprays were acquired from our spray chamber and processed with different thresholding techniques to explore the differences between the spray angle detection methods. All five methods generated a similar global trend of spray angle variation for temporally evolving sprays over the complete injection period. However, the actual spray angle values detected by each method were not always comparable. The differences in spray angle values between the different detection methods were larger during the early start of injection, and these differences systematically decreased as the spray approached a steady state. The methods that detected the angle in the far field demonstrated lower spatio-temporal variability when compared with the methods that detected the angle in the near field. An assessment of the comparability between angle detection methods was made, and the outcome provides guidance for the selection of the spray angle detection method.