Non-axisymmetric Compressor Bleed Slots for Turbine Engines
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Solution Overview
Problem
Prior art turbomachinery compressors experience non-uniformity in mass flow rate and static pressure around the compressor casing due to the presence of a single offtake pipe, which acts as a pressure sink, leading to reduced stall margin and operability characteristics.
Innovation Solution
A compressor bleed apparatus with non-axisymmetric bleed slots and plenums is designed to distribute air flow uniformly, using varying aperture sizes and shapes, or plenum volumes to compensate for the presence of a single offtake pipe, ensuring consistent static pressure across the compressor casing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single chamber offtake pipe is used to collect bleed air, then the parts count, weight, and complexity are reduced, but the static pressure becomes non-uniform around the compressor casing
Solution Approach 1:
The patent applies asymmetry by configuring the bleed slots with non-uniform circumferential spacing and/or varying cross-sectional areas around the compressor casing. This asymmetric arrangement compensates for the asymmetric influence of the single offtake pipe, distributing bleed air extraction more evenly and maintaining uniform static pressure around the entire compressor casing perimeter.
Solution Approach 2:
The patent implements local quality by varying the properties of bleed slots at different circumferential locations. Specifically, bleed slots closer to the offtake pipe connection may have different spacing or cross-sectional areas compared to those farther away, creating locally optimized extraction characteristics that collectively achieve global pressure uniformity.
2Stress or pressure
If multiple chamber offtake pipes are provided to minimize non-uniformity, then the static pressure uniformity improves, but the parts count, weight, and complexity increase
Solution Approach 1:
The patent uses asymmetric bleed slot configuration to compensate for the asymmetric flow pattern created by a single offtake pipe. By strategically varying the spacing and/or cross-sectional area of bleed slots around the compressor, the system achieves pressure uniformity equivalent to multiple offtake pipes while maintaining the simplicity of a single pipe connection.
Solution Approach 2:
The patent changes the parameters of the bleed slots (spacing between slots, cross-sectional area of slots) to optimize air extraction distribution. These parameter variations allow the system to achieve uniform static pressure around the compressor casing while using only a single offtake pipe, avoiding the complexity of multiple pipes.
3Reliability
If uniform mass flow rate and static pressure are maintained around the compressor casing, then the compressor operability and stall margin improve, but the design complexity of the bleed system increases
Solution Approach 1:
The patent applies local quality by configuring bleed slots with non-uniform properties at different circumferential locations. This localized variation in bleed slot characteristics (spacing, cross-sectional area) enables uniform mass flow rate and static pressure distribution around the compressor, improving operability and stall margin without requiring complex active control systems.
Solution Approach 2:
The patent uses asymmetric bleed slot arrangement to counterbalance the asymmetric influence of the single offtake pipe. This asymmetric configuration achieves uniform compressor performance characteristics while maintaining a relatively simple passive bleed system design.
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 solution achieves substantially uniform static pressure and mass flow rate around the compressor casing, enhancing operability and stall margin by mitigating the effects of the offtake pipe's pressure sink.
Implementation Method 1
the mass flow through the bleed slots is generally greater near the location of the chamber offtake pipe, and the static pressure is generally lower near the location of the chamber offtake pipe. This inverse relationship of flow and static pressure is due to the basic Bernoulli relation.
Data Source
AI summary
A compressor bleed apparatus includes: a compressor comprising one or more rotors mounted for rotation about a central axis and enclosed in a compressor casing; a bleed slot passing through the compressor casing; an outer wall defining, in cooperation with the compressor casing, a plenum surrounding the compressor casing; at least one offtake pipe communicating with the plenum; and wherein at least one of the plenum and the bleed slot has a non-axisymmetric structure.