Turbofan Radial Arms Intermediate Stream Air Supply
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Solution Overview
Problem
The existing air supply to the radial arms of an exhaust casing in turbofan engines is insufficient due to pressure losses caused by protruding elements, leading to inadequate flow and potential turbulence in the secondary flow.
Innovation Solution
A dual-flow turbojet engine design that collects air directly downstream of the low-pressure compressor, utilizing the increased static pressure combined with dynamic pressure to supply pressurized air through radial arms, which are equipped with pierced liners for enhanced cooling, while minimizing turbulence and pressure losses by routing the intermediate flow through these arms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If air is collected from the secondary stream along the casings, then the radial arms can be supplied with air, but protruding elements cause significant pressure losses that reduce flow efficiency
Solution Approach 1:
The invention extracts the air supply function from the secondary stream path and relocates it to the intermediate stream. By collecting air from the intermediate stream at a location upstream of the high-pressure compressor, the system removes the harmful interaction with protruding elements that cause pressure losses in the secondary stream, while still providing adequate air flow to the radial arms.
Solution Approach 2:
The intermediate stream acts as an intermediary air supply path between the low-pressure compressor outlet and the radial arms. This intermediate pathway mediates the conflict between needing air for the radial arms and avoiding pressure losses, by providing a dedicated collection zone that is not affected by the protruding elements on the outer casings.
2Quantity of substance
If a scoop is used to collect air radially from the casings, then air supply to radial arms is improved, but turbulence is introduced that is detrimental to the secondary stream flow
Solution Approach 1:
The invention removes the scoop structure from the design entirely and replaces it with a collection opening in the intermediate fairing. This extraction of the harmful scoop element eliminates the turbulence it generates in the secondary stream, while the intermediate stream collection opening provides the necessary air supply function without introducing harmful flow disturbances.
3Stress or pressure
If air is collected from the secondary stream, then the bearing can be pressurized and cooled, but the pressure at collection openings becomes insufficient due to pressure losses
Solution Approach 1:
The invention performs preliminary air collection from the intermediate stream before the air enters regions with high pressure losses. By positioning the collection opening in the intermediate fairing upstream of the high-pressure compressor and utilizing the higher pressure region, the system proactively secures adequate pressure for radial arm supply, preventing pressure deficiencies before they occur.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design maintains sufficient pressure and reduces turbulence, ensuring efficient air supply to the radial arms, effectively pressurizing the lubrication enclosure and cooling the arms, while minimizing interference with the secondary flow.
Implementation Method 1
radial arms starting from this external shell, at least one of these radial arms collecting air coming from the intermediate stream to supply pressurized air to a central region of this exhaust casing
Implementation Method 2
the pressure prevailing at the inlet of the radial supply arms of the casing corresponds to the static pressure increased by the dynamic pressure at the outlet of the low pressure compressor
Data Source
Figure 1
Figure 2~3
AI summary
The invention relates to a turbofan (1) comprising a low-pressure compressor (3); a series of housings (9, 10) arranged downstream of said low-pressure compressor (3) for defining a primary stream, and comprising an upstream edge (19) defining an inlet (23); a high-pressure compressor (24) in the primary stream; a shroud (11) surrounding the series of housings (9, 10) for defining a stream of circulation of an intermediate flow (7), and having an upstream edge (19) defining a circular inlet (21) arranged upstream of the high-pressure compressor (24); a secondary stream housing (12) surrounding the shroud (11) for defining a secondary stream; and an exhaust housing (38) comprising radial arms (39) that collect the air from the intermediate stream.