Roots Rotor Profile Design for Interference Prevention
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Solution Overview
Problem
Existing roots type fluid machines face issues with phase shift during operation or assembly, leading to rotor interference and noise due to the need for large clearance to prevent fluid leakage, which compromises performance.
Innovation Solution
The design incorporates rotors with lobe and well portions defined by convex and concave arcs, along with an involute curve, where the base radius and radius are set within specific ranges to ensure gradual clearance change during rotation, preventing rapid interference and enhancing compression performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large clearance is provided between rotors to prevent interference due to phase shift, then rotor interference is prevented, but fluid leakage through clearance increases thereby reducing compressor performance
Solution Approach 1:
The patent changes the geometric parameters of the rotor profile by introducing a specific curvature radius R at the lobe portion and a corresponding concave arc with radius R/2 in the well portion. This parameter modification creates a gradual clearance change mechanism that prevents rapid interference while maintaining small clearance for high performance
Solution Approach 2:
The patent applies curved surfaces by forming the lobe portion with a convex arc of radius R and the well portion with a concave arc of radius R/2. This curvature design ensures smooth clearance variation during rotor engagement, preventing sudden interference while maintaining compact clearance dimensions
2Quantity of substance
If the lobe portion and well portion are formed with circular arc shapes, then trapping of large volume of fluid is ensured, but a space is formed between lobe portion and well portion causing noise generation
Solution Approach 1:
The patent applies different curvature characteristics to different regions: the lobe portion uses a convex arc with radius R while the well portion uses a concave arc with radius R/2. This localized quality differentiation eliminates the space between lobe and well portions while maintaining fluid trapping capability
Solution Approach 2:
By carefully selecting the curvature radii R and R/2 for the convex and concave arcs respectively, the patent creates a seamless transition between lobe and well portions, eliminating gaps that would otherwise generate noise while preserving the volume needed for fluid trapping
Data Source
AI summary
A roots type fluid machine includes a housing, a pair of parallel rotary shafts and two-lobe rotors. Each rotor includes two lobe portions and two well portions. Each lobe portion has a profile of convex arc with a radius R and each well portion has a profile of concave arc which is an envelope of the convex arc of the lobe portion. The rotor has a configuration defined by a curve which includes the convex arc, the concave arc and further an involute curve with a base radius r between the convex and concave arcs. The base radius r is set in a range L/(2√{square root over ( )}2)<r<0.3(√{square root over ( )}2)L where distance between axes of the rotary shafts is L, and the radius R is set in a range {(√{square root over ( )}2)/16}πL<R<{(27−5√{square root over ( )}2)/56}L.