Water Heater Fan Structure to Suppress Combustion Gas Backflow
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Solution Overview
Problem
In water heaters of the exhaust suction and combustion type, backflow of combustion gas can occur due to increased pressure within the fan casing, leading to instability in the suctioning capability and oscillating combustion, especially when the exhaust tube is smaller in diameter.
Innovation Solution
The design incorporates a fan case with a back surface wall and an impeller having specific blade configurations and a rotation shaft, allowing outside air to be suctioned and used to resist backflow of combustion gas, maintaining resistance pressure and cooling the fan while suppressing backflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If air flow passage is provided to cool the fan, then fan cooling is improved, but combustion gas backflow occurs causing instability in suctioning capability
Solution Approach 1:
The fan blade is segmented into a first blade and a second blade positioned on opposite sides of the rotation axis. The second blade specifically faces the back surface wall to create a dedicated air suction path, while the first blade handles combustion gas suction. This segmentation allows independent optimization of cooling function without affecting combustion gas suction stability.
Solution Approach 2:
The gap between the back surface wall and the main plate serves as an intermediary air passage that allows outside air to enter the fan case for cooling purposes. This intermediary path is distinct from the combustion gas flow path, enabling cooling function without compromising combustion gas suction capability.
2Adaptability or versatility
If exhaust tube diameter is decreased to maintain building appearance, then adaptability is improved, but combustion stability deteriorates due to backflow
Solution Approach 1:
The second blade is positioned to face the back surface wall in advance, creating a preliminary air flow path that generates negative pressure in the gap between the back surface wall and main plate. This preliminary anti-action prevents combustion gas backflow before it can occur, maintaining combustion stability even with smaller exhaust tube diameter.
Solution Approach 2:
The invention introduces a new spatial dimension for air flow by positioning the second blade on the back surface of the main plate to face the back surface wall. This creates a third-dimensional air suction path from the outside environment through the gap, adding a new flow dimension that does not interfere with the traditional combustion gas suction 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 cools the fan by inflowing air while preventing backflow of combustion gas, stabilizing combustion and maintaining efficient operation even with a smaller exhaust tube diameter.
Implementation Method 1
the negative pressure generated by the rotation of the impeller acts on the gap between the back surface wall and the main plate
Implementation Method 2
a heat exchanger heating water flowing through inside by heat exchange with combustion gas
Implementation Method 3
a burner generating combustion gas
Data Source
AI summary
A water heater capable of cooling a fan by inflow of air while suppressing backflow of combustion gas is provided. A fan includes: a fan case having a back surface wall; an impeller having a first blade and a second blade and housed in the fan case; a drive source rotating the impeller; and a rotation shaft coupling the impeller and the drive source through a through hole provided in the back surface wall. A gap through which air outside the fan case is suctioned into the fan case is provided between the rotation shaft and the back surface wall. The second blade faces the back surface wall without another member interposed therebetween throughout a range from an inner circumferential side to an outer circumferential side of the second plane.