Roots-type Blower Rotor Alignment for Noise Reduction
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Solution Overview
Problem
Roots-type blowers experience significant noise due to pulsations in leakback, which are not uniformly controlled in previous helical-rotor designs, leading to inconsistent output and noise levels.
Innovation Solution
The method involves precise alignment of rotors using a paired drive and idler rotor setup with an extended lever arm, measuring displacement, and adjusting the angular position to achieve uniform leakback, reducing noise through improved alignment and verification techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If helical-rotor designs are used to achieve effectively constant displaced volume, then output consistency is improved, but pulsating leakback causes non-constant net delivered flow and increased noise
Solution Approach 1:
The patent applies preliminary action by pre-aligning the rotors to specific angular positions before operation. The alignment apparatus positions rotors at predetermined angles where leakback is minimized and uniform, ensuring that when the blower operates, the leakback pulsations are already optimized to reduce noise. This pre-positioning of critical components resolves the contradiction by establishing favorable conditions before the harmful effect (noise from pulsating leakback) manifests during operation.
2Ease of manufacture
If rotor alignment is not precisely controlled, then manufacturing is simpler, but leakback pulsations increase causing inconsistent output and higher noise levels
Solution Approach 1:
The patent introduces an intermediary alignment apparatus that mediates between the simple act of assembling rotors and the requirement for precise angular alignment. This apparatus includes alignment pins, reference surfaces, and adjustment mechanisms that serve as intermediaries to transfer and establish precise angular relationships between rotors without requiring complex measurement and adjustment procedures during final assembly. The intermediary tooling absorbs the complexity of achieving precision, leaving the manufacturing process itself relatively simple.
3Object-generated harmful factors
If uniform leakback is achieved through precise rotor alignment, then noise is reduced, but alignment complexity and measurement requirements increase
Solution Approach 1:
The alignment apparatus applies self-service by incorporating reference surfaces and alignment features directly into the blower housing and rotor assemblies. During assembly, components self-align through machined reference surfaces that guide rotor positioning, eliminating the need for external measurement instruments or complex adjustment procedures. The system serves itself by having the housing and rotors contain built-in alignment cues that automatically establish the correct angular relationships when properly assembled, reducing noise through uniform leakback without requiring complex external alignment equipment.
Data Source
AI summary
Roots-type blowers with helical cycloidal rotors exhibit variation in leakback flow with angular position intrinsic to these rotor geometries. Calibration of individual blowers using a combination of high-resolution alignment and enhanced detection of residual noise phenomena permits noise in as-produced blowers to be significantly attenuated. Intrinsic lower limits of noise induced by leakback variation are associated with manufacturing tolerances, necessary clearances, and particular geometric considerations. Gross alignment errors (excluding contact between rotors) produce a characteristic noise pulse rate that is three times the shaft rate. Proper alignment suppresses this and reveals a pulse sequence at double this rate and at about half of the amplitude of faulty alignment. The novel process explains the error mechanisms and defines repeatable calibration methods for a mass-production environment, introducing appropriate gauges and methods for the task.