1984-10-01

Estimation of Hot Gas Reingestion for a VTOL Aircraft at the Conceptual Design Stage 841555

A methodology has been computerized to allow for a rapid first order estimation of inlet temperature rise due to near and far field exhaust gas reingestion from a VTOL aircraft. A computer interactive graphics package has also been developed in conjunction with the reingestion code to display planform aircraft configurations with ground plane and undersurface stagnation lines superimposed. This allows for the rapid visual assessment of the location of the upwash flow with respect to the aircraft inlets. In addition to the stagnation lines, the ground plane wall jets can be characterized, for axisymmetric nozzles, and isocontour lines of the wall jet temperature can be displayed superimposed over the aircraft configuration. The code is based on empirical relationships and simplified analytical approximations. It was designed as a rapid evaluation tool and provides reasonable estimates of inlet temperature rise from exhaust gas reingestion over a wide range of configurations and conditions. The code has been exercised, with reasonable success, against several aircraft models for which average inlet temperature rise data was available. As it presently exists, the code is based on a rather limited data base but can be modified as the flow fields are better defined and a more substantial data base is generated.

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