Scroll casing of centrifugal fan, centrifugal fan, air-conditioning apparatus and refrigeration cycle apparatus including the scroll casing

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Solution Overview

Problem

The scroll casing in air-conditioning apparatuses experiences insufficient airflow pressure rise due to structural restrictions, limiting the enlargement of the discharge port and resulting in inefficient heat exchange and assembly challenges.

Innovation Solution

The scroll casing features a discharge portion with a cross-sectional area that gradually enlarges toward the discharge port, an extended plate inclined relative to the housing inner wall, and a change point that increases the enlargement ratio downstream, optimizing airflow pressure and assembly ease.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the discharge port is enlarged to improve airflow passage, then the heat exchange efficiency is improved, but the structural restrictions inside the apparatus prevent sufficient enlargement

Engineering Contradiction:

Improveheat exchange efficiencyVSAvoiddischarge port size

Core Design Contradiction:

ProductivityVSVolume of stationary object

Solution Approach 1:

The patent introduces an extended plate that protrudes in the axial direction from the discharge portion, creating a new spatial dimension for airflow expansion. This allows the flow passage cross-sectional area to be increased without enlarging the discharge port opening itself, thereby resolving the contradiction between heat exchange efficiency and structural space constraints.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The discharge portion is segmented into multiple functional zones: a first portion with a gradual expansion angle (θ1) for stable airflow, and a second portion with a larger expansion angle (θ2) for enhanced flow area. This segmentation allows optimized airflow control while adapting to structural space limitations.

Inventive Principle:

Principle #1Segmentation

2Reliability

If the discharge port is enlarged to allow broader airflow passage, then drift flow is reduced, but structural restrictions prevent sufficient enlargement

Engineering Contradiction:

Improvedrift flow suppressionVSAvoiddischarge port size

Core Design Contradiction:

ReliabilityVSVolume of stationary object

Solution Approach 1:

The extended plate protruding in the axial direction provides additional flow passage area without increasing the discharge port opening size. This enables broader airflow passage for drift flow suppression while maintaining the same structural footprint.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The flow passage cross-sectional area gradually increases from the first portion to the second portion, creating a dynamic expansion that adapts the airflow path to the structural constraints while ensuring stable flow without drift.

Inventive Principle:

Principle #15Dynamics

3Stress or pressure

If the scroll casing structure is modified to improve pressure rising effect, then the assembly workability deteriorates

Engineering Contradiction:

Improveairflow pressure riseVSAvoidassembly workability

Core Design Contradiction:

Stress or pressureVSEase of manufacture

Solution Approach 1:

The discharge portion is divided into a first portion and a second portion with different expansion characteristics. The first portion connects to the scroll portion with a gradual angle for stable pressure rise, while the second portion extends axially for assembly compatibility. This segmentation allows optimized pressure rising while maintaining ease of assembly.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different portions of the discharge structure have different geometric properties: the first portion has a gradual expansion angle (θ1) for pressure stabilization, while the second portion has a larger expansion angle (θ2) and axial protrusion for assembly workability. This local differentiation resolves the contradiction between pressure rising and assembly ease.

Inventive Principle:

Principle #3Local quality

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 achieves a pressure rising effect, suppresses drift flow for efficient heat exchange, and improves workability in assembly by ensuring proper fitment without interference.

Implementation Method 1

an area of a cross section crossing orthogonally to a flow direction of the airflow gradually enlarges toward the discharge port

Methodology Applied

Scientific EffectPressure gradient: Pressure Gradient

Data Source

PatentUS12286977B2Scroll casing of centrifugal fan, centrifugal fan, air-conditioning apparatus and refrigeration cycle apparatus including the scroll casing

Publication Date: 2025.04.29 MITSUBISHI ELECTRIC CORP

AI summary

A scroll casing has a scroll portion, a discharge portion provided with a discharge port, and a tongue portion. An extended plate has, in a cross section obtained by cutting in a thickness direction, a change point, at which an enlargement ratio of an area of the cross section is enlarged so as to be larger on a downstream side than that on an upstream side due to a change of inclination. In the extended plate, an angle θ1, and an angle θ2 satisfy a relationship of either 0≤θ2<θ1 or 0<θ2≤θ1. A distance L1 and a distance L2 satisfy a relationship of L2<L1.