Measurement and Uncertainty Analysis of Transonic Fan Response to Total Pressure Inlet Distortion


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Virginia Tech


Distortion tolerant fans represent the enabling technology for the successful implementation of highly integrated airframe propulsion system vehicles. This investigation extends the study of fan-distortion interactions to an actual turbofan engine with a total pressure distortion profile representative of a boundary-layer ingesting (BLI) embedded engine. The goal was to make a series of flow measurements that contribute to the overall physical understanding of this complex flow situation.

Proper uncertainty analysis is critical to extracting meaning from the data measured in this study. The important information in the measurements is contained in small differences that lead to large impacts on the fan performance. In some cases, these differences were measured to a useful degree of accuracy, while in others they were not. One important application of the uncertainty analysis techniques developed in this work is the identification of the dominant error sources that resulted in unacceptable uncertainties.

This dissertation presents an experimental study of transonic fan response to inlet total pressure distortion. A Pratt and Whitney JT15D-1 turbofan engine was subjected to a total pressure distortion representative of a boundary layer ingesting serpentine inlet. A 5-hole probe measured the aerodynamic response of the fan rotor in terms of flow angles, total pressure, and static pressure. A thermocouple embedded in the probe measured the rotor outlet total temperature. These measurements enabled the full characterization of the flow condition at each measurement point. The results indicate that a trailing edge separation and reattachment cycle experienced by the blades caused variations in the work input to the flow and resulted in a non-uniform rotor outlet flow profile. The details of the aerodynamic process and several means for improving distortion response are presented in this context.

As a second theme, the modern measurement and uncertainty analysis techniques required to obtain useful information in this situation are developed and explored. Uncertainty analysis is often treated as a less glamorous afterthought in experimental research. However, as technology develops along lines of ever increasing system-level integration, simply suggesting the solution to a single flow situation does not repre- sent closure to the larger problem. In addition to frameworks for developing distortion tolerant fans, frameworks for developing frameworks are required. Uncertainty-drivenexperimental techniques represent the enabling methodology for the discovery and un- derstanding of the subtle phenomena associated with such coupled performance. These considerations are required to extend the usefulness of the results to the overarching issue of integrating the complex performance of individual components into an overall superior system. The experimental methods and uncertainty analysis developed in this study are presented in this context.



Fan, Distortion, Total Pressure, Uncertainty, Monte Carlo, Jacobian