Volume Dynamics Propulsion System Modeling for Supersonics Vehicle Research

Abstract

Under the NASA Fundamental Aeronautics Program the Supersonics Project is working to overcome the obstacles to supersonic commercial flight. The proposed vehicles are long slim body aircraft with pronounced aero-servo-elastic modes. These modes can potentially couple with propulsion system dynamics; leading to performance challenges such as aircraft ride quality and stability. Other disturbances upstream of the engine generated from atmospheric wind gusts, angle of attack, and yaw can have similar effects. In addition, for optimal propulsion system performance, normal inlet-engine operations are required to be closer to compressor stall and inlet unstart. To study these phenomena an integrated model is needed that includes both airframe structural dynamics as well as the propulsion system dynamics. This paper covers the propulsion system component volume dynamics modeling of a turbojet engine that will be used for an integrated vehicle Aero-Propulso-Servo-Elastic model and for propulsion efficiency studies.

Quasi One-Dimensional Unsteady Modeling of External Compression Supersonic Inlets

“…With the inlet by itself, this problem can be mitigated by establishing a finite dynamic volume at the inlet exit that accepts the mass flow rate, similar to the way fluidic volumes are modeled in Ref. [4]. By utilizing this latter approach, the mass flow demand at the inlet can be used with Eq.…”

“…Thus, the leakage mass flow rate as a function of back pressure also becomes a boundary condition for the external CFD cells. The remaining states at the exit boundary can be computed by utilizing the following characteristic equation: 2 (12) To integrate the inlet to the existing engine simulations, 4,5,6 the mass flow rate demand of the engine needs to be specified as a boundary condition. However, it is not possible to directly use this boundary condition for the inlet model by itself.…”

“…3 Thus, this modeling effort is considered to be a first step towards the development of a more comprehensive dynamic external compression inlet model, which potentially could be integrated with the rest of the propulsion system model, currently under development. 4,5,6 Recently, the modeling approaches developed and lessons learned in these efforts progressed to developing the first version of a Variable Cycle Engine (VCE) 6 model, which is considered to be a more appropriate propulsion system concept for future supersonic vehicles.…”

Turbofan Volume Dynamics Model for Investigations of Aero-Propulso-Servo-Elastic Effects in a Supersonic Commercial Transport

“…However, due to a lack of detailed non-proprietary information for turbofan engines the modeling effort done previously under the APSE task was for a turbojet engine, the GE J-85 (Ref. 4). The J-85 has undergone extensive testing at NASA Glenn, and has been used in supersonic vehicles.…”

“…4). However, a turbofan engine is identified by the High Speed Research (HSR) program as the optimal propulsive system for supersonic flight (Ref.…”