Characteristic Time Model Validation
Abstract
An experimental program for validation of the semi-empirical characteristic time model (CTM) is described. A two-dimensional turbulent shear layer is generated in the experimental test section using a two-stream, vertically downflowing wind tunnel with a flat pre-filming airblast atomizer fitted along its centerline. This facility simulates the shear layer around the recirculation zone found in the primary zone of a gas turbine combustor. Experimental results are used to investigate CTM parameters for turbulent mixing and droplet lifetime and to examine current finite difference modeling techniques. Global mixing times evaluated at the origin of the shear layer and defined in terms of geometric macroscale and a reference velocity are compared with the locally measured values of turbulent mixing time. The results demonstrate that these global times, as defined for the CTM, do in fact accurately represent the events occurring on a local scale, as hypothesized. Modifications to the mixing time parameter to improve existing correlations are proposed. Due to restrictions imposed by the facility and instrumentation, validation of the droplet lifetime parameter was not possible. Measurements were restricted to mean spray diameters. These data and others demonstrate that current correlations for Sauter mean diameter do not adequately account for changes in atomizer geometry or liquid properties. In addition, the present measurements show that the presence of a shear layer at the atomizer tip significantly degrades atomization quality.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 1988
- Accession Number
- ADA201374
Entities
People
- A. M. Mellor
- K. V. Tallio
- R. C. Prior Jr.
Organizations
- Drexel University