History, Philosophy, Physics, and Future Directions of Aircraft Propulsion System/Inlet Integration

Abstract

This work provides a historical perspective of the developments of propulsion system inlet/engine integration. The flow physics of inlet distortion are discussed, along with the stability effects on the engine compression systems. Throughout the document, both commercial and military applications are considered. Developments in analyses from the original works characterizing inlet distortion, the use of distortion descriptors and early modeling concepts, and the modeling and simulation required today are reviewed. The special requirements and testing techniques necessary to adequately describe inlet distortion and the effects on the propulsion system are summarized. The aspects of pressure distortion, temperature distortion, and swirl are addressed and the physics of interaction described. The compression system response to different types of distortion is discussed with the interaction with various compression system components and designs explained. Axial and centrifugal compressors are covered, as the resulting physics of the inlet distortion effects on each has a different characteristic. An overview of the necessary flow physics to consider in the integration of compression systems in both low and high-Mach number applications is presented.

Parametric Analysis and Design for Embedded Engine Inlets

“…The inlet design will thus need to satisfy multiple competing objectives driven by the inlet-propulsion system integration [9] and the new N 2 requirements [1]. These objectives include minimizing inlet total pressure losses and inflow distortion, optimizing inflow profiles and swirl distributions, and achieving a compact aft-mounted airframe-integrated design that maximizes the BLI portion of the cycle benefit while minimizing inlet/nacelle weight and drag.…”

“…7, which shows contour plots of inlet total pressure loss, the first two distortion harmonics, the distortion intensity ΔPc∕P av as described by the ARP1420 [14], and mass flow imbalance between the top half of the inlet and the bottom half. These objectives capture the inlet performance and its impact on the fan/engine stability and operability [9]. The simulations that provided these results modeled only the internal duct.…”

Jet Engine Inlet Distortion Screen and Descriptor Evaluation

“…The total pressure distortions may appear during aircraft operations as a result of an S-shaped inlet duct [1][2][3][4], flow separation or wake initiated by a high angle of attack or by a shock wave. A variety of methods can be used for creation of such distortions for compressor and engine rig testing.…”

An Air Jet Distortion Generation System

“…This method avoids the otherwise cumbersome representation of the total pressure distribution by polynomial, spline. or Fourier curve fit and results in consistently good correlations to an acceptable degree of accuracy (see Cousins [22]). With the new distortion descriptors defined, now the flow case example can be considered.…”