Adjustable Iris Burner Nozzle for High Turndown Ratio
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Solution Overview
Problem
Conventional burner nozzles have limited turndown ratio, leading to inefficient heat control, increased noise, and emissions due to fixed port sizes, resulting in suboptimal combustion stability and frequent shutdowns at low heat demand.
Innovation Solution
A mechanically adjustable iris port burner nozzle with a cylindrical extension and laminar flow insert, allowing for adjustable port sizes and internal recirculation of exhaust gases to maintain optimal exit velocity and flame stability across a range of firing rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed port size is used in the burner nozzle, then the structure is simple, but the turndown ratio is limited and the burner must shutdown at low heat demand
Solution Approach 1:
The patent applies the dynamics principle by replacing the fixed port size with a variable port size that can be dynamically adjusted. The nozzle includes an adjustable iris mechanism that changes the port opening based on heat demand, enabling continuous modulation from high to low firing rates without shutdown. This dynamic adjustment resolves the contradiction by allowing high adaptability (turndown ratio >20:1) while maintaining reasonable structural complexity through the use of standard iris mechanisms.
Solution Approach 2:
The patent applies parameter changes by varying the port size parameter in response to changing heat demand conditions. The control system adjusts the iris position to change the effective port area, thereby changing the gas flow rate and maintaining optimal combustion parameters across a wide turndown range. This resolves the contradiction by making the port size a variable parameter rather than a fixed value.
2Productivity
If the air/gas mixture velocity is increased to improve combustion, then the flame speed increases, but the flame lifts off from the nozzle causing noise
Solution Approach 1:
The patent applies the intermediary principle by introducing a recirculation zone that acts as a mediator between the high-velocity gas flow and the flame. The recirculation zone creates a low-velocity region where the flame can be anchored stably, while the main gas flow continues at high velocity for efficient combustion. This resolves the contradiction by decoupling the gas velocity from the flame anchoring condition, allowing high productivity without noise.
3Reliability
If the air/gas mixture velocity is decreased to maintain flame anchoring, then the flame stays at the nozzle, but combustion efficiency decreases
Solution Approach 1:
The patent applies segmentation by dividing the nozzle flow into two distinct zones: a high-velocity main flow path for efficient combustion and a low-velocity recirculation zone for flame anchoring. This segmentation allows each zone to operate at optimal velocities for its specific function, resolving the contradiction by enabling both high productivity (through main flow velocity) and high reliability (through recirculation zone velocity).
4Loss of energy
If on-off control is used at low heat demand, then the burner shuts down completely, but additional heat losses occur due to safety purge requirements
Solution Approach 1:
The patent applies continuity of useful action by enabling the burner to operate continuously at reduced firing rates through variable port adjustment, rather than shutting down completely. The iris mechanism allows the port size to be reduced to match low heat demand while maintaining continuous combustion, thereby eliminating the periodic shutdowns and safety purges that cause heat losses. This resolves the contradiction by maintaining continuous useful action (combustion) at all heat demand levels.
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
Enables stable combustion and reduced emissions across a broader range of firing rates, eliminating shutdowns and heat losses, and achieving turndown ratios greater than 20:1 with improved flame control and operational efficiency.
Implementation Method 1
The laminar flow insert desirably produces laminar flow of the combustible gas flowing therethrough
Implementation Method 2
The recirculation ports desirably serve to allow internal recirculation of at least a portion of exhaust gas produced by operation of the gaseous fuel burner nozzle
Implementation Method 3
In normal burner operation, the speed of the air/gas mixture is somewhat higher than the flame speed
Data Source
AI summary
High turndown ratio gaseous fuel burner nozzles and the control thereof are provided. High turndown ratio gaseous fuel burner nozzles include a mechanically adjustable nozzle port, such as in the form of an iris port, for expanded turndown control. A nozzle extension longitudinally extending from the mechanical adjustable nozzle port can be included to assist in shaping the flow of combustible gas from the nozzle port. A laminar flow insert can be housed within the nozzle extension to assist in producing laminar flow of the combustible gas flowing therethrough. A burner nozzle controller in control communication with the mechanically adjustable nozzle port can adjust the size of the nozzle port to selectively maintain exit velocity of the gaseous fuel from the nozzle port for one or more of combustion stability and flame stability.