Air-Fuel Ratio Control via Lambda Sensor Feedback
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Solution Overview
Problem
Existing systems for controlling air-fuel ratios in gas burners that vent combustion gases to the atmosphere, such as those used in flame treatment devices for packaging paper webs, face challenges in precision control and monitoring, especially when using gaseous fuels, due to the reliance on Bernoulli's law, which makes fine-tuning difficult and prone to drifts outside acceptable ratios, leading to costly production line shut-downs and inability to correct for variations in gas quality.
Innovation Solution
An air-fuel control system comprising a preheated reaction chamber with a lambda sensor connected to a controller that controls the amount of air bypassing a Venturi-pipe, utilizing a side-channel blower and uninsulated piping for cooling, allowing for precise monitoring and adjustment of the air-fuel ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a carburettor or Bernoulli-based mechanism is used to control air/fuel ratio, then the system structure is simple, but the air/fuel ratio control precision deteriorates and is difficult to fine-tune
Solution Approach 1:
The patent introduces a feedback control system using a lambda sensor to measure the actual air/fuel ratio and feed this information back to a controller. The controller adjusts the fuel gas flow based on the measured lambda value, enabling precise control and compensation for drifts that occur in Bernoulli-based systems. This closed-loop feedback mechanism resolves the precision problem while maintaining relative system simplicity.
Solution Approach 2:
The patent replaces the purely mechanical Bernoulli-based carburettor system with an electronically controlled system using a solenoid valve and lambda sensor. This substitution of mechanical control with electronic control and sensing enables precise measurement and adjustment of the air/fuel ratio, overcoming the limitations of mechanical fine-tuning.
2Manufacturing precision
If a lambda sensor is used to control air/fuel ratio, then the air/fuel ratio control precision is improved, but the device complexity increases
Solution Approach 1:
The patent introduces a preheated reaction chamber as an intermediary component between the combustion system and the lambda sensor. This reaction chamber preheats the combustion gases to a temperature suitable for lambda sensor operation, enabling the sensor to function in systems where combustion gases are too cool. This intermediary solution allows lambda sensor implementation without requiring complete system redesign.
Solution Approach 2:
The patent segments the combustion system into distinct functional zones: a combustion chamber, a preheated reaction chamber for temperature conditioning, and a measurement zone for the lambda sensor. This segmentation allows the lambda sensor to operate in optimized conditions while the rest of the system continues to function as before, reducing overall system complexity.
3Device complexity
If combustion gases are vented directly to atmosphere, then the system structure is simple, but the ability to monitor and control air/fuel ratio deteriorates
Solution Approach 1:
The patent applies preliminary action by preheating the combustion gases in a reaction chamber before they reach the lambda sensor. This preheating ensures the gases are at the appropriate temperature for accurate lambda measurement, enabling monitoring capability in systems that would otherwise lack it. The preliminary temperature conditioning resolves the measurement problem without complicating the overall venting structure.
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 continuous monitoring and control of air-fuel ratios, preventing sudden failures and accommodating variations in gas quality, thereby reducing production downtime and ensuring consistent operation.
Implementation Method 1
a Venturi-pipe for controlling an amount of fuel gas mixed into the combustion air
Implementation Method 2
a lambda sensor arranged in a probe chamber connected to the preheated reaction chamber
Implementation Method 3
a preheated reaction chamber with a lambda sensor
Data Source
AI summary
A system for controlling air/fuel ratio in an air/fuel mixture supplied to a premix burner for gaseous fuels includes a blower (310) for inducting and pressurising combustion air, a Venturi-pipe (330) for governing a rate of gas to be mixed into the combustion air, and a pressure regulator (230) interconnecting a source of gaseous fuel to a supply point in the Venturi pipe (330). A preheated reaction chamber (500) and a lambda sond (620) are connected to a controller (350) controlling an amount of air bypassing said Venturi-pipe (330).