Turbojet Compressor Shroud Ramps for Flow Control
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Solution Overview
Problem
Current turbojet compressors face challenges in increasing the compression and pumping efficiency of the low-pressure compressor while avoiding harmful effects on the aerodynamic behavior of blade root sections, particularly in the recompression zone, due to modifications in the air flow duct.
Innovation Solution
A fan shroud design with suction-side and pressure-side ramps that form a twisted projection, directing the gas stream to pass around the blade root via the suction-side, accelerating it and deflecting it towards the pressure-side of adjacent blades, thereby enhancing compression and pumping efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the duct is deepened in the shroud by forming flutes between the blade roots, then the Mach number at the inlet of the fan is reduced and air compression is improved, but the aerodynamic behavior of the blade root sections is adversely affected, particularly in the recompression zone
Solution Approach 1:
The shroud is segmented into multiple zones with different geometric characteristics: a first zone with a first radius of curvature and a second zone with a second radius of curvature. This segmentation allows each zone to be optimized independently - the first zone manages flow entry while the second zone protects the blade root aerodynamics, resolving the contradiction between improving compression efficiency and maintaining blade root aerodynamic performance.
Solution Approach 2:
Different regions of the shroud are given different local geometric properties. The first zone has specific curvature characteristics optimized for flow entry and compression, while the second zone has different curvature characteristics optimized for protecting the blade root suction-side surface. This local differentiation allows simultaneous optimization of both compression efficiency and aerodynamic performance without compromise.
2Weight of moving object
If the number of low-pressure compressor stages is reduced, then the size and weight of the compressor are reduced, but the compression and pumping efficiency of the fan is penalized
Solution Approach 1:
The invention changes the geometric parameters of the shroud, specifically the radius of curvature in different zones. By optimizing these parameters, the single-stage compressor achieves improved compression and pumping efficiency, allowing the design to maintain high performance with reduced number of stages, thereby reducing weight while preserving productivity.
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
The proposed design improves the compression and pumping efficiency of the low-pressure compressor by optimizing the air flow path, reducing aerodynamic losses, and ensuring efficient air compression without penalizing the turbojet's performance.
Implementation Method 1
the suction-side ramp presenting, between the leading edge and the trailing edge of the blade, a profile that is inclined relative to the outside surface of the shroud so as to deflect the gas stream flowing in the corresponding flow passage from the suction-side surface of the blade towards the pressure-side surface of the adjacent blade
Implementation Method 2
the pressure-side and suction-side ramps joining together upstream from the leading edge of the blade to form a projection, said projection presenting a profile that is twisted about the axis of the shroud so as to force the gas stream flowing in each flow passage to go round the blade root essentially via the suction-side thereof
Data Source
AI summary
The invention relates to a turbojet compressor comprising a shroud and a plurality of blades, each fixed via its root to the shroud. Level with each blade root, the shroud presents a suction-side ramp and a pressure-side ramp extending from the trailing edge of the blade to beyond its leading edge. The pressure-side and suction-side ramps join together upstream from the leading edge of the blade to form a projection presenting a profile that is twisted about the axis of the shroud so as to force the gas stream flowing in each flow passage to go round the blade root essentially on the suction-side thereof, and the suction-side ramp presents a profile that is inclined relative to the outside surface of the shroud so as to deflect the gas stream flowing in the corresponding flow passage from the suction-side surface of the blade towards the pressure-side surface of the adjacent blade.