Partial-Perimeter Wall for BPF Noise Suppression in Automotive Blower
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Centrifugal blower systems in automotive HVAC systems generate objectionable high-pitched whistle noise due to the interaction of air flow with fan blades, known as Blade Passing Frequency (BPF) noise, which is not effectively mitigated without reducing air flow in existing designs.
Innovation Solution
A partial-perimeter wall extending upstream from the inlet throat, spanning between 120° and 180° of the circumference, is integrated into the blower housing to modify airflow patterns and suppress BPF noise without significantly reducing air flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a typical throat arrangement is used in a centrifugal blower, then air flow is effectively directed to the fan blades, but BPF noise is generated at a high-pitched whistle frequency
Solution Approach 1:
The inlet throat is segmented into multiple sections with different geometric characteristics. The first section has a larger cross-sectional area while the second section has a smaller cross-sectional area, creating zones of different flow characteristics that reduce blade-passing frequency noise while maintaining air flow capacity.
Solution Approach 2:
Different sections of the inlet throat are given different local geometric qualities - the first section has larger cross-sectional area to reduce flow velocity and noise, while the second section has smaller cross-sectional area to maintain the venturi effect and air flow acceleration toward the fan blades.
2Object-generated harmful factors
If the throat cross-sectional area is reduced to suppress BPF noise, then noise is reduced, but air flow capacity is reduced
Solution Approach 1:
The inlet throat is divided into two sections with different cross-sectional areas. The first section has larger area to suppress noise by reducing flow velocity, while the second section has smaller area to maintain the venturi effect and ensure sufficient air flow capacity is preserved.
Solution Approach 2:
Instead of uniformly reducing the entire throat cross-sectional area, the invention applies partial reduction only in the second section while maintaining larger area in the first section, achieving noise suppression without excessive reduction of overall air flow capacity.
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 partial-perimeter wall effectively reduces BPF noise while maintaining nearly full air flow capacity, preventing degradation of air conditioning performance.
Implementation Method 1
The throat is usually ring-shaped having an inward arc and/or other features to create a venturi effect that increases air flow into the blower
Data Source
AI summary
A noise tone occurring at a blade passing frequency in a blower for an automotive HVAC system is suppressed. The blower includes a centrifugal fan and a scroll body disposed around the fan. An outlet extends from the scroll body to conduct an air flow from a cutoff point of the scroll body. An inlet is coupled to the scroll body defining an inlet throat comprising an arcuate ring extending between a base and an annular end coaxially disposed over the fan. A partial-perimeter wall extends upstream from the arcuate ring having a height between about 4% and about 6.5% of an inner diameter of the annular end. The wall spans a perimeter portion of the circumference of the throat between about 120° and about 180°. As a result, noise at the blade passing frequency is suppressed without any significant reduction in air flow.