Premix Burner Mixture Control with Variable Intake Cross Section
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Solution Overview
Problem
Existing control devices for premix gas burners face challenges in achieving precise air/gas ratio control across a wide range of thermal flow rates with reduced energy consumption, leading to high head losses and excessive noise at high flow rates, and are prone to shutter blockages due to complex construction and limited operating ranges.
Innovation Solution
A device with a control unit that regulates the gas flow rate using an electrically-controlled solenoid valve and a second regulator with a movable shutter, varying the intake duct's cross section as a function of fan speed to maintain constant head losses and reduce noise, while minimizing construction complexity and shutter blockage risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the fan speed is increased to handle high flow rates, then the thermal power output is improved, but the head losses increase and noise becomes excessive
Solution Approach 1:
The shutter is made movable rather than fixed, allowing it to dynamically adjust the cross-sectional area of the intake duct based on operating conditions. This dynamic adjustment optimizes airflow characteristics across different fan speeds, reducing head losses at high flow rates while maintaining productivity.
Solution Approach 2:
The cross-sectional area of the intake duct is changed by moving the shutter to different positions. This parameter change allows the system to adapt to varying flow rates, reducing turbulence and head losses when the fan operates at high speeds for maximum thermal power output.
2Adaptability or versatility
If a hinged shutter is used to vary the intake duct cross section, then the operating range is improved, but the device complexity increases and shutter blockages occur
Solution Approach 1:
The hinge mechanism is removed from the shutter design. Instead of being hinged to the duct wall, the shutter is designed to move freely within the duct cross-section, supported only at its ends by guide elements. This extraction of the hinge simplifies the construction and eliminates the complexity and blockage risks associated with hinged mechanisms.
Solution Approach 2:
The shutter design is simplified by copying only the essential function (varying cross-sectional area) without the complex hinged mechanism. The shutter is a simple movable element that can be positioned at different locations, replicating the adaptive function with minimal structural complexity.
3Device complexity
If the gas valve is designed as a passive follower element, then the device complexity is reduced, but the air/gas ratio control precision deteriorates
Solution Approach 1:
The control system incorporates feedback by continuously monitoring the actual gas flow and comparing it with the desired flow corresponding to the fan speed. The gas valve is actively adjusted based on this feedback to maintain the correct air/gas ratio, achieving precision control while maintaining relatively simple device architecture.
Solution Approach 2:
The passive mechanical follower mechanism is replaced with an actively controlled valve system that responds to control signals based on operating conditions. This substitution allows for more precise control of the air/gas ratio while maintaining simplicity through electronic or pneumatic actuation rather than complex mechanical linkages.
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
The solution enables precise control of the air/gas ratio across a wide range of flow rates, reducing energy consumption and noise, and increases the flexibility and reliability of the burner by maintaining constant head losses and minimizing maintenance needs.
Implementation Method 1
the gas valve (7) is an electrically-controlled solenoid valve
Implementation Method 2
The mixing system determines the negative pressure to which the air passing through is subjected to and hence the pressure in the mixing zone
Implementation Method 3
The fan generates an operating flow in a direction of flow, oriented from the inlet to the outlet, and an operating pressure
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
Described is a device (1) for controlling a fuel-oxidizer mixture for a premix gas burner (100), comprising an intake duct (2), which defines a cross section for the passage of a fluid inside the duct (2) and includes an inlet (201), a mixing zone (202) and an outlet (203), an injection duct (3), connected to the intake duct (2) in the mixing zone (202), a monitoring device (4), configured for generating a control signal (401), representing a combustion state in the burner (100), a gas regulating valve (7), positioned along the injection duct (3), a fan (8), positioned in the intake duct (2) for generating therein an operating flow in an inflow direction (V), a control unit (5), configured to control the rotation speed of the fan, a regulator (9), coupled with the intake duct (2) for varying the cross section. The control unit (5) is configured for controlling the gas regulating valve (7) in real time.