Measurements of Flow in Boundary Layer Ingesting Serpentine Inlets
Abstract
Highly integrated airframe-propulsion systems featuring ingestion of the airframe boundary
layer oer reduced noise, emissions, and fuel consumption. Embedded engine systems are
envisioned which require boundary layer ingesting (BLI) serpentine inlets to provide the
needed air
ow to the engine. These inlets produce distorted
ow proles that can cause
aeromechanical, stability, and performance changes in embedded engines. Proper design
of embedded engine systems requires understanding of the underlying
uid dynamics that
occur within serpentine inlets.
A serpentine inlet was tested in a specially designed wind tunnel that simulated boundary
layer ingestion in a full-scale realistic environment. The measured total pressure proles at
the inlet and exit planes of the duct, and the static pressure distributions along the walls
provided useful data related to the
ow in BLI serpentine inlet systems. A bleed
ow control
system was tested that utilized no more than 2% of the total inlet
ow. Two bleed slots
were employed, one near the rst bend of the S-duct and one near second. The bleed system
successfully reduced inlet distortions by as much as 30%, implying improvements in stall
margin and engine performance.
Analysis of the wake shape entering the S-duct showed that the airframe and inlet duct are
both important components of a wake-ingesting inlet/diusion system. Shape eects and
static pressure distributions determined
ow transport within the serpentine inlet. Flow
separation within the S-duct increased distortion at the engine inlet plane. Discussion
of airframe/inlet/engine compatibility demonstrates that embedded engine systems require
multi-disciplinary collaborative design eorts. An included fundamental analysis provides
performance estimates and design guidelines. The ideal airframe performance improvement
associated with wake-ingestion is estimated.
Collections
- Masters Theses [19687]