Roots Fluid Machine Rotor Design Reducing Dead Volume
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Solution Overview
Problem
Conventional roots type fluid machines experience significant power loss and noise due to fluid leakage and reexpansion, resulting in inefficient operation and reduced thermal efficiency.
Innovation Solution
The design incorporates rotors with a four or more lobe configurations, featuring an arc, involute curve, and envelope curve outlines, with a torsional angle greater than 360/n degrees, which reduces dead volume and minimizes fluid leakage, enhancing volumetric and thermal efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the rotor outline is formed by an involute curve and envelope curve with a six-lobe configuration, then the rotor can be driven easily to rotate at high speed with reduced space, but a large dead volume is formed between rotors causing significant power loss and noise
Solution Approach 1:
The patent changes the geometric parameters of the rotor outline by introducing a specific torsional angle β (greater than 360/n degrees) to the lobe portions. This parameter modification alters the spatial arrangement of the lobes, reducing the dead volume between rotors while maintaining the pumping function, thereby decreasing power loss from fluid leakage
Solution Approach 2:
The patent introduces asymmetry in the rotor design by applying a torsional angle to the lobe portions, making them non-uniformly distributed around the rotor axis. This asymmetric configuration optimizes the fluid chamber volume changes and reduces dead volume, improving volumetric efficiency and reducing energy loss
2Speed
If the rotor outline is formed by an involute curve and envelope curve with a six-lobe configuration, then the rotor can be driven easily to rotate at high speed, but noise is generated by reexpansion of fluid in the dead volume
Solution Approach 1:
By modifying the geometric parameters of the rotor lobes through the introduction of torsional angle β, the patent changes the volume characteristics of fluid chambers during rotation. This parameter change minimizes dead volume where fluid reexpansion occurs, thereby reducing noise generation while allowing high-speed operation
3Productivity
If the number of lobe portions is increased to four or more with a torsional angle, then dead volume is reduced and volumetric efficiency is improved, but the rotor design becomes more complex
Solution Approach 1:
The patent employs parameter changes by defining the rotor outline using a torsional angle β applied to the lobe portions. This mathematical parameter approach allows for systematic optimization of the rotor geometry to reduce dead volume and improve volumetric efficiency while providing a clear design methodology that manages complexity
Data Source
AI summary
A roots type fluid machine includes suction and discharge ports, rotary shafts and a pair of rotors. The rotor has a number n of lobe and valley portions with apex and bottom ends. The lobe portions are located on imaginary lines extending radially from an axis of the rotary shaft. The outer surface of each one of the rotors is generated by rotating an outline of the rotor including an arc and involute and envelope curves around and moving the outline in the direction of the axis. The arc has a radius R and a center located on the imaginary line. The involute curve is formed by an imaginary base circle having a radius r and a center located on the axis. The envelope curve is formed by an arc having a radius R. The number n is four or more. A torsional angle β is over 360/n degrees.