Abstract
Detailed measurements within sprays are needed to understand the vaporization, transport, and combustion of liquid fuels. While diagnostics have been developed to characterize the structure of the spray droplets in great detail (e.g., phase Doppler interferometry), details regarding the gas phase (e.g., oxidizing media and fuel vapor) are more difficult to obtain. In the present study, measurement of gas phase vector properties are achieved in the spray field of a twin-fluid atomizer using phase Doppler interferometry. A gas phase scalar, the concentration of hydrocarbon vapor, is measured using an infrared extinction/scattering technique. When combined, the two measurements provide a direct measure of the vaporization characteristics of the spray. A methanol spray is studied which is produced by an atomizer operating at three conditions, (1) no atomizing air, (2) non-swirling atomizing air, and (3) swirling atomizing air. The injection mode alters the vaporization behavior of the spray. For the non-reacting cases, (1) the presence of non-swirling air-assist, while not strongly affecting the spatial vaporization history, enhances the temporal vaporization rate compared to the case without atomizing air; (2) the presence of swirling atomizing air greatly enhances the vaporization rate in both space and time; and (3) examination of the rate of change of vaporization reveals a correlation among all three injection modes, suggesting that the fundamental mechanism of vaporization in all three sprays is the same. For the reacting cases, swirling air increases the production of fuel vapor in both time and space compared to the non-swirling air case. The change in vaporization rate shows a trend similar to the non-reacting case, although the rate of change is negative in the region of the reaction zone due to competition between vaporization and consumption.
Highlights
IntroductionD ETAILED measurements of both the continuous and dispersed phases in liquid fuel sprays are necessary to develop 1) an understanding of the physical processes of evap· oration, mixing, and momentum and mass exchange, and 2) a data base for the verification and development of computational codes
D ETAILED measurements of both the continuous and dispersed phases in liquid fuel sprays are necessary to develop 1) an understanding of the physical processes of evap· oration, mixing, and momentum and mass exchange, and 2) a data base for the verification and development of computational codes.Further, measurements in both non-reacting and reacting sprays are of interest
Efforts are currently being directed at better understanding the role of the fluctuating drop velocities
Summary
D ETAILED measurements of both the continuous and dispersed phases in liquid fuel sprays are necessary to develop 1) an understanding of the physical processes of evap· oration, mixing, and momentum and mass exchange, and 2) a data base for the verification and development of computational codes. These studies have been useful in demonstrating the application of various optical techniques to the measurement of drop size in reacting sprays, the necessary gas phase data are not provided. The present study characterizes, in the absence and presence of reaction, the gas and drops in a spray produced by a production air-blast atomizer. The system provides a bulk air velocity of 1 m/s (with no atomizer flows) through the square duct in the present study. This will be discussed in more detail
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