Directed Secondary Air Injection for Uniform Exhaust Catalyst Heating
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Solution Overview
Problem
Existing secondary air injection methods for internal combustion engines result in non-uniform air flow distribution and potential overheating of catalysts, particularly when using electrically heatable honeycomb bodies, leading to inefficient heating and potential damage.
Innovation Solution
A device for directed secondary air supply into the exhaust tract, featuring an injection pipe outside the flow path that allows precise control of air flow velocity, direction, and distribution, with a swirl-generating element and a chamber to precondition the air flow, ensuring homogeneous distribution and avoiding backpressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If secondary air is injected into the exhaust tract using conventional methods, then the catalyst heating process is accelerated, but the air flow distribution becomes non-uniform causing local overheating of the honeycomb body
Solution Approach 1:
The injection device divides the secondary air flow into multiple separate injection channels or nozzles that distribute air uniformly across the exhaust tract cross-section. This segmentation prevents concentrated jets from causing local overheating while maintaining overall heating efficiency.
Solution Approach 2:
The injection device is designed with varying nozzle characteristics (angle, diameter, position) to create locally optimized air distribution patterns. Each injection point is tailored to achieve uniform overall distribution, preventing non-uniform flow patterns that cause localized overheating of the honeycomb body.
2Temperature
If an electrically heated catalytic converter is used to preheat exhaust gases, then the light-off temperature is reached faster, but the heat distribution may be inefficient without directed air flow
Solution Approach 1:
The injection device uses controlled pneumatic injection of secondary air to enhance heat transfer from the electrically heated catalytic converter to the exhaust gases. The directed air flow creates turbulence and improves convective heat transfer, reducing energy losses and accelerating the heating of downstream catalysts.
Solution Approach 2:
The injection device modifies the physical parameters of the exhaust flow (velocity, turbulence, temperature distribution) by introducing secondary air. These parameter changes enhance the efficiency of heat transport from the preheating catalyst to subsequent catalysts, improving overall system performance.
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
Achieves uniform air distribution and efficient heating of catalysts, reducing the risk of overheating and accelerating the catalyst's light-off temperature, particularly effective with electrically heatable honeycomb bodies.
Implementation Method 1
the internal combustion engine is driven with an increased proportion of fuel to increase the fuel content of the exhaust gas blown into the exhaust port. As a result, an exothermic reaction occurs in the exhaust tract, which leads to heating of the catalysts.
Implementation Method 2
A heating disk of the catalyst is heated by utilizing the electrical resistance.
Implementation Method 3
the heat from the electrically heated catalytic converter will be transported by the secondary air flow via convection to the following catalytic converters
Data Source
AI summary
A device for supplying a quantity of secondary air into the exhaust tract of an internal combustion engine, having a flow path which is arranged downstream of the gas outlet of the internal combustion engine in the direction of flow of the exhaust gas, having an injection device which is designed to supply a quantity of secondary air at a supply point into the flow path. The supply of the secondary air takes place upstream of a first honeycomb body), the secondary air being introduced into the flow section through an injection pipe of the injection device, the injection pipe being arranged outside the flow section and opening into the flow section.