Burner Unit Coanda Profile for Low Emission Drying
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Solution Overview
Problem
Existing burner units for tempering objects, such as drying vehicle bodies, face challenges in achieving low CO and NOx emission values, particularly when using exhaust air as burner air, which affects the efficiency and environmental impact of the drying process.
Innovation Solution
The burner unit incorporates a Coanda profile in the through-flow space and an annular Venturi nozzle design, along with a swirl device, to enhance flow velocities and mixing efficiency, effectively recirculating flue gases and optimizing the combustion process to reduce emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If exhaust air is used as burner air, then gas consumption is reduced, but CO and NOx emission values increase
Solution Approach 1:
The burner air is divided into two separate streams: primary air and secondary air. The primary air is mixed with fuel gas to form a primary air/fuel gas mixture that enters the combustion chamber. The secondary air is mixed with flue gases in an annular space to form a secondary air/flue gas mixture that is then fed to the primary air/fuel gas mixture in the combustion chamber. This segmentation allows different air streams to serve different combustion functions, enabling low emission operation while using exhaust air.
Solution Approach 2:
The patent changes the physical parameters of the air streams by creating velocity differences through the Coanda effect and Venturi effect. The primary air/fuel gas mixture and secondary air/flue gas mixture are introduced at different velocities and positions, creating optimal mixing conditions that reduce CO and NOx emissions while maintaining efficient combustion with exhaust air.
2Object-generated harmful factors
If flue gas recirculation is increased to reduce emissions, then combustion efficiency decreases, but temperature control capability is improved
Solution Approach 1:
The patent introduces a tertiary air stream that acts as an intermediary between the primary and secondary air streams. This tertiary air is mixed with the secondary air/flue gas mixture in the annular space before being introduced to the primary air/fuel gas mixture in the combustion chamber. This intermediary mixing stage allows for better control of the combustion process, maintaining efficiency while achieving low emissions through optimized flue gas recirculation.
3Object-generated harmful factors
If mixing zone is enlarged to improve combustion, then device complexity increases, but emission control is improved
Solution Approach 1:
The patent utilizes the annular space surrounding the core area of the mixing zone to introduce secondary air and flue gases. This annular configuration adds a spatial dimension to the mixing process, allowing secondary air/flue gas mixture to be introduced circumferentially around the primary air/fuel gas mixture. This dimensional approach enables effective emission control without significantly increasing device complexity, as the annular structure is integrated into the existing burner geometry.
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 design achieves significant reductions in CO and NOx emissions, with CO values below 8 mg/m³ and NOx values less than 50 mg/m³, while improving the overall efficiency and reducing noise and gas consumption, resulting in a more environmentally friendly and effective drying process.
Implementation Method 1
the inner lateral surfaces of the through-flow space form a Coanda profile in the direction of flow; Due to the Coanda effect, there are high flow velocities and thus an effective negative pressure at the inlet of the through-flow space, so that the flue gas in turn flows into and through the through-flow space at high speed
Implementation Method 2
the annular space forms an annular Venturi nozzle, the device by means of which the secondary air/flue gas mixture is supplied to the primary air/fuel gas mixture in the combustion chamber comprising this Venturi nozzle
Implementation Method 3
a swirl device, by means of which primary air can be caused to swirl before it enters the core region and/or by which secondary air can be caused to swirl before it enters the annular space
Implementation Method 4
a combustion chamber in which flue gases are produced; a gas burner, to which fuel gas can be fed via a fuel gas line
Data Source
Figure 1
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AI summary
Flue gases are produced in a combustion chamber (62) of a burner unit (40), in particular for the combustion of exhaust air. Combustion gas can be supplied to a gas burner (42) via a combustion gas line (52) and feed air, in particular exhaust air that can be used as feed air, is supplied to said burner via a feed air line (44). The feed air is divided into primary air and secondary air by a device (96). The primary air is mixed with the combustion gas, in a mixing zone (72), to form a primary air/combustion gas mixture, said primary air/combustion gas mixture being supplied to the combustion chamber (62). A flue gas re-circulation system comprises a through-flow chamber which is connected to the combustion chamber (62) and in which the secondary air is mixed with the flue gases occurring in the combustion chamber (62) to form a secondary air/flue-gas mixture. The secondary air/flue-gas mixture is supplied to the primary air/combustion gas mixture in the combustion chamber (62) by means of a device. At least one internal cylindrical surface of the through-flow chamber forms a Coanda profile (103a, 103b) in the direction of flow. A device for the temperature control of objects, in particular for drying painted vehicle bodies, comprises a temperature-control tunnel that is accommodated in a housing and that defines at least one tunnel section (T) comprising at least one air outlet and at least one air inlet. A heating assembly (20), in which a hot primary gas can be generated by means of a burner unit (40) of this type, is associated with the tunnel section.