One of the research areas at the Institute of Jet Propulsion
focuses on the design and optimization of s-shaped engine inlet
configurations. The distortion being evoked within such inlet
ducts should be limited to ensure an optimal performance, stability,
and durability of the engine’s compression system.
Computational Fluid Dynamics (CFD) play a major role in
the design process of bent engine inlet ducts. The flow within
such ducts can be computed, distortion patterns can be visualized,
and related distortion coefficients are easily calculated. The
impact of a distortion on flow phenomena within the compressor
system can, however, only be computed with major computational
efforts and thus the quality of an s-duct design in development
is usually assessed by analyzing the evoked distortion with
suitable distortion coefficients without a true knowledge of the
duct’s influence on the downstream propulsion system.
The influence of inlet distortion on both the performance and
stability of the Larzac 04 jet engine was parameterized during
experimental investigations at the engine test bed of the Institute
of Jet Propulsion. Both pressure and swirl distortion patterns
as they typically occur in s-duct inlet configurations were
reproduced with distortion generators. Pressure distortion patterns
were generated using seven types of distortion screens. The
intensity of the distortion varies with the mesh size of the screen
whereas the extension of the distortion is defined by the dimensions
of the screen in radial and circumferential direction. A typical
counter rotating twin-swirl was generated with a delta-wing
installed upstream of the compressor system.
First, the development of flow distortion was analyzed for
several engine operating points (EOPs). A linear relation between
the total pressure loss in the engine inlet and the EOPs was
found. Secondly, the flow within the compressor system with an
inlet distortion was analyzed and unsteady flow phenomena were
detected for severe inlet distortions. Finally, the effect of both
pressure and swirl distortion on the performance and stability of
the test vehicle was parameterized. A loss in engine performance
with increasing inlet distortion is observable. The limiting inlet
distortion with respect to engine stability was found and moreover
it was shown that pressure distortion has a stronger influence
on the stability of the compressor system compared to a counter
rotating twin-swirl distortion. The presented parameterization is
essential for the s-duct design, which is under development for
an experimental set-up with the Larzac 04 jet engine.
«One of the research areas at the Institute of Jet Propulsion
focuses on the design and optimization of s-shaped engine inlet
configurations. The distortion being evoked within such inlet
ducts should be limited to ensure an optimal performance, stability,
and durability of the engine’s compression system.
Computational Fluid Dynamics (CFD) play a major role in
the design process of bent engine inlet ducts. The flow within
such ducts can be computed, distortion patterns can be visua...
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