Masters Theses

Date of Award

8-1982

Degree Type

Thesis

Degree Name

Master of Science

Major

Aerospace Engineering

Major Professor

John E. Caruthers

Abstract

Criteria for the design of conical transition ducts for typical direct connect engine testing installations have been developed. Parametric studies of the effects of Mach number, Reynolds number, duct divergence angle, duct diameter ratio, and flow disturbance dissipation duct length were conducted to develop these criteria. Criteria were developed for both diverging and converging conical ducts.

Diverging conical ducts were found to be limited by conical duct entrance Mach number and by boundary layer growth. The duct Mach number at the entrance of the conical duct must be below M = 0.8 to avoid local flow acceleration reaching sonic flow at the duct entrance. The boundary layer was limited to a blockage of eight percent, and a correlation was derived to predict the allowable duct diameter ratio as a function of Mach number, Reynolds number, and duct half angle. An optimum value of duct half angle was determined.

Converging ducts were limited by the uncertainty they would produce in thrust calculations. Since this uncertainty is installation peculiar, it must be investigated on a case-by-case basis if convergent conical ducts are to be employed.

Labyrinth seal operation was investigated for both convergent and divergent ducts. It was found that labyrinth seal operation will not be impaired by either configuration if the previously mentioned criteria are satisfied. It was found that an L / D = 0.5 duct will dissipate flow disturbances generated by the exit or entrance of a conical transition duct.

Two computer codes were developed and demonstrated in the pursuit of these criteria. A computer code for predicting boundary layer growth, including separation, for two-dimensional subsonic flows in ducts with or without centerbodies was developed to establish the boundary layer criterion. A second-order accurate subsonic compressible two-dimensional full potential solver was developed to evaluate dissipation duct length requirements at the entrance and exit of the conical transition duct.

This thesis serves to point out guidelines for identifying factors which must be considered in the application of conical transition ducts to turbine engine testing. The criteria developed are restrictive to ensure the criteria will hold in typical turbine engine installations. Attempts have been made to point out possible means of circumventing these criteria when they cannot be met for a specific engine installation.

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