Air conditioner including indoor unit
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Solution Overview
Problem
The existing indoor units for air conditioners with centrifugal fans suffer from poor blowing performance and noise due to recirculating flow, which occurs when air leaks back into the inlet through a gap between the shroud and the bell mouth, leading to increased windage losses and potential damage during transportation and operation.
Innovation Solution
The design incorporates an annular member with a smooth curved protrusion on its outer surface, spaced apart from the inlet portion of the shroud, creating an S-shaped flow path for recirculating air, which reduces the recirculating flow and prevents contact-induced damage, while also minimizing fluid frictional losses and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a gap is formed between the shroud and bell mouth to allow air flow, then air circulation is enabled, but recirculating flow occurs causing poor blowing performance and noise
Solution Approach 1:
The patent introduces a bell mouth as an intermediary component between the shroud and the air intake port. The bell mouth with its specific inner diameter configuration (gradually increasing toward upstream) acts as a flow guide that prevents recirculating air from directly re-entering the centrifugal fan inlet, thereby eliminating the harmful recirculating flow while maintaining proper air circulation through the gap.
Solution Approach 2:
The patent addresses the recirculating flow problem by transitioning from a simple radial gap configuration to a three-dimensional bell mouth structure with varying inner diameter along the axial direction. This dimensional change creates a flow path that directs air away from the fan inlet, preventing recirculation while maintaining the necessary gap for air circulation.
2Ease of manufacture
If the bell mouth inner diameter is constant, then manufacturing is simple, but recirculating flow increases causing noise and poor performance
Solution Approach 1:
The patent applies parameter changes by varying the inner diameter of the bell mouth along its axial length. Specifically, the inner diameter gradually increases toward the upstream side, creating an optimized flow path that reduces recirculating flow and associated noise. This gradual parameter change balances manufacturing complexity with performance improvement.
3Device complexity
If the shroud and bell mouth are placed close together, then structural compactness is achieved, but contact damage occurs during transportation and operation
Solution Approach 1:
The patent incorporates a predetermined gap between the shroud and bell mouth that serves as a protective buffer. This gap is designed in advance to prevent direct contact between these components during transportation and operation, thereby protecting them from damage while maintaining structural compactness. The gap acts as a cushioning space that absorbs mechanical stresses before they can cause damage.
4Device complexity
If recirculating flow is allowed, then air circulation path is simplified, but windage losses increase reducing efficiency
Solution Approach 1:
The bell mouth serves as an intermediary flow control element that redirects recirculating air away from the centrifugal fan inlet. By positioning the bell mouth with its specific geometry between the gap and the fan inlet, it acts as a mediator that prevents the short-circuiting of air flow, thereby reducing windage losses and improving energy efficiency while maintaining a relatively simple air circulation path.
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
This configuration effectively reduces recirculating flow, prevents damage to the shroud and bell mouth, and decreases windage losses, thereby enhancing the blowing performance and reducing noise by increasing flow resistance and suppressing turbulence.
Implementation Method 1
The bell mouth has an inner diameter that gradually increases toward the upstream side of the recirculating flow
Implementation Method 2
a protrusion formed on an outer circumferential portion of a surface of the annular flat plate portion facing the shroud, the protrusion having an outer surface that is curved
Implementation Method 3
a centrifugal fan to suck in air through an air intake port and discharge the air through an air discharge port
Implementation Method 4
a heat exchanger to exchange heat with an air flow generated by the centrifugal fan
Data Source
AI summary
An indoor unit for an air conditioner including a centrifugal fan. The centrifugal fan includes a main plate connectable to a rotation shaft of a motor, a plurality of blades, with one respective end to be bonded to the main plate and arrangeable at equal intervals from each other along a circumferential direction, a shroud, to be bonded to another respective end of the plurality of blades, to face the main plate, and a bell mouth arrangeable inside the shroud. An annular member arrangeable on an outer circumferential portion of the bell mouth with an inlet portion at the gap between the shroud and the bell mouth. The annular member including an annular flat plate portion spaced apart from and face the inlet portion, and a protrusion formed on an outer circumferential portion of a surface of the annular flat plate portion facing the shroud and being curved.