Fuel Heater Startup Control Reducing Emissions
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Solution Overview
Problem
Existing control methods for fuel-operated heaters result in increased exhaust gas emissions during the transitional phase due to a constant air mass introduction, which cools components and prolongs the heating process, leading to inefficient combustion and emissions.
Innovation Solution
A control method that varies the air mass supplied to the combustion chamber based on a fixed time sequence, reducing the air/fuel ratio during the transitional phase and increasing it to the steady-state value, allowing components to heat up quickly and reducing emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a constant air mass equal to the continuous operation value is supplied to the burner chamber during startup, then the lambda value for continuous operation is achieved, but the components remain cool and exhaust gas emissions increase during the transitional phase
Solution Approach 1:
The air mass supplied to the burner chamber is made dynamic rather than constant. During the transitional phase, a reduced air mass is supplied to allow components to heat up, and then the air mass is increased to the continuous operation value once steady state is reached. This dynamic adjustment resolves the contradiction by adapting the air supply to the operational phase.
Solution Approach 2:
The air mass parameter is changed based on the operational phase. The control unit supplies a first air mass value during the transitional phase that is lower than the second air mass value supplied during continuous operation. This parameter change allows components to reach operating temperature faster, reducing exhaust gas emissions while maintaining proper lambda control.
2Quantity of substance
If a large air mass is supplied during the transitional phase, then mixture formation occurs, but the components are cooled down and the transition to steady state is prolonged
Solution Approach 1:
The air mass supply is dynamically adjusted based on the operational phase. During the transitional phase, a reduced air mass is supplied to minimize cooling of components and accelerate heating. Once steady state is detected, the air mass is increased to the continuous operation value. This dynamic control reduces the duration of the transitional phase.
Solution Approach 2:
The control unit prepares for the transition to continuous operation by monitoring component temperatures and detecting when steady state has been reached. This preliminary detection allows timely adjustment of the air mass from the reduced first value to the higher second value, minimizing the time spent in the transitional phase.
3Quantity of substance
If the air mass is increased to the continuous operation value immediately, then steady state lambda is achieved, but fuel atomization and vaporization are insufficient due to cool components
Solution Approach 1:
The air mass supply is dynamically controlled to match the thermal state of components. During the transitional phase when components are cool, a reduced air mass is supplied to allow proper fuel atomization and vaporization. Once components reach operating temperature, the air mass is increased to ensure proper lambda control. This dynamic adjustment ensures reliable combustion throughout the startup process.
Solution Approach 2:
The air mass parameter is changed based on component temperature. The control unit supplies a first air mass value during the transitional phase that is lower than the second air mass value for continuous operation. This parameter change ensures that fuel atomization and vaporization are sufficient during startup while maintaining proper lambda control once steady state is reached.
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
Significantly reduces exhaust gas emissions during the transitional phase, shortens the duration to reach steady state, and maintains low emissions in steady state without increasing fuel consumption or diluting exhaust gases.
Implementation Method 1
a fan (13) which conveys air (1.2) into the burner chamber (11)
Implementation Method 2
If the fuel is in liquid form, it is atomized and mixed with the air that is still being conveyed by the fan
Implementation Method 3
The fuel-air mixture supplied to the combustion chamber is ignited by one or more ignition sparks generated in rapid succession
Implementation Method 4
liquid or gaseous fuels are mixed with air and burned in a burner chamber to generate heat
Implementation Method 5
a heat exchanger (16) which is supplied with a coolant (1.5) and conveys the heated coolant to the engine (2) or to the passenger compartment
Data Source
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AI summary
In a control procedure for the start-up sequence of a fuel-operated heating appliance, this comprises the following time periods: a pre-run phase (VPh) beginning with the switching on of the heating appliance, during which only outside air but no fuel is supplied to the combustion chamber for purging and which is ended after a predefinable period by the start (S) of combustion, a transition phase (ÜPh) immediately following the start (S) of combustion and a steady-state operating condition (BBZ) following the transition phase (ÜPh), during which an air mass with a value mLnormal required to achieve the desired lambda value and a corresponding amount of fuel are supplied to the combustion chamber.To improve the exhaust emissions of such a heating appliance, it is provided that a reduced air mass is supplied to the combustion chamber at least during part of the transition phase (ÜPh), the value of which mLTransition is smaller than the value mLnormal of the air mass supplied to the combustion chamber during the steady-state operating condition (BBZ).