Screw Compressor Rotor Profile Generation via Rack Enveloping
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Solution Overview
Problem
Screw compressor designs face challenges in constructing rotors with asymmetrical profiles using cutting tools that wear easily, particularly for the female rotor with reduced lobe thickness, which limits stress and efficiency, and result in suboptimal volumetric efficiency due to the blow hole area between the rotors and the casing.
Innovation Solution
The screw compressor employs a rack profile with specific curves to generate rotor profiles, maximizing the addendum and lobe thickness of the male rotor and optimizing the relation between rotor thicknesses, reducing tool wear and minimizing the blow hole area through a hyperbolic first curve and carefully defined arc lengths, allowing for easier manufacturing and improved volumetric efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the female rotor is designed with reduced lobe thickness to achieve asymmetrical profiles for improved volumetric efficiency, then the volumetric efficiency is improved, but the allowable stress during cutting of the lobes is limited and tool wear increases
Solution Approach 1:
The patent applies asymmetry by designing the female rotor with reduced lobe thickness compared to the male rotor, creating an asymmetrical profile that improves volumetric efficiency by optimizing the blow hole area and gas flow characteristics, while accepting the manufacturing challenge of cutting thinner lobes
Solution Approach 2:
The patent changes the geometric parameters of the rotor profiles by defining specific mathematical relationships between the male and female rotor dimensions, including the ratio of lobe thicknesses and the curvature radii, to optimize volumetric efficiency while maintaining structural integrity during manufacturing
2Productivity
If the rotor profiles are designed to minimize the blow hole area for maximized volumetric efficiency, then the volumetric efficiency is improved, but the complexity of profile generation and manufacturing increases
Solution Approach 1:
The patent establishes universal mathematical relationships that can generate both male and female rotor profiles from a single generating rack profile, making the design process more systematic and reducing the complexity of generating conjugate profiles that minimize blow hole area
Solution Approach 2:
The patent uses parameter changes by defining the rotor profiles through mathematical equations that relate the generating rack profile parameters to the final rotor geometry, allowing optimization of blow hole area through controlled variation of geometric parameters
Data Source
AI summary
Screw compressor (1) comprising: a male (2) and a female rotor (3) rotating respectively around a first axis (01) and second axis (02) of rotation, said rotors (2;3) showing, in cross section, meshing lobes (4) and valleys (6) and having profiles generated by enveloping a rack profile (p) including a first curve (z1) of the rack profile (p) extending between a first point (H) and a second point (Q) in a Cartesian reference frame (X, Y) and having a convexity in the positive direction of the axis of abscissa (X), said first point (H) lying on the axis of abscissa (X) at a distance from an origin (0) of the Cartesian reference frame (X, Y) equal to an addendum (hi) of the male rotor (2).