Gaseous Fuel Post-Injection for Catalytic Converter Heating
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Solution Overview
Problem
Gaseous fuels, particularly natural gas with methane as a main component, pose challenges in exhaust-gas treatment due to lower conversion rates and higher process temperatures required for catalytic converters, especially during cold starts, leading to inefficient emissions reduction.
Innovation Solution
A method involving direct injection of gaseous fuel into the combustion chamber, including a main injection followed by two post-injections, with the second post-injection occurring after ignition and combustion to increase exhaust-gas temperature, and simultaneous opening of the discharge valve for enhanced catalytic converter heating, while maintaining low uncombusted hydrocarbons and particles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If gaseous fuel is used in internal combustion engines, then CO2 emissions are reduced, but exhaust-gas treatment becomes more complex due to lower conversion rates and higher process temperatures required
Solution Approach 1:
The patent applies preliminary action by performing a post-injection of gaseous fuel after the main combustion event. This post-injection occurs when the combustion chamber temperature is still high, enabling the additional fuel to burn and generate high-temperature exhaust gases that preheat the catalytic converter before the vehicle starts moving, ensuring the converter reaches its light-off temperature for effective emissions treatment
2Productivity
If catalytic converter temperature is increased to required process temperature quickly, then exhaust-gas treatment efficiency is improved, but raw emissions of uncombusted hydrocarbons and particles worsen
Solution Approach 1:
The patent applies dynamics by using a two-stage injection strategy with different fuel quantities at different times. The main injection uses a larger fuel quantity for primary combustion, while the subsequent post-injection uses a smaller fuel quantity to generate high-temperature exhaust for catalytic converter heating. This dynamic adjustment of fuel injection timing and quantity allows the system to balance the need for rapid converter heating with the need to minimize uncombusted hydrocarbon emissions
3Temperature
If post-injection is carried out after combustion to increase exhaust-gas temperature, then catalytic converter heating is improved, but the complexity of controlling injection timing and quantity increases
Solution Approach 1:
The patent applies periodic action by implementing a structured two-stage injection cycle: first a main injection for primary combustion, then a post-injection after combustion completion. This periodic injection pattern, with the post-injection occurring at a specific phase in the combustion cycle (when the combustion chamber temperature is still high but the main combustion is complete), simplifies control by using naturally occurring combustion phases as timing references rather than requiring complex external control systems
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
This method rapidly heats the catalytic converter, significantly reducing emissions during cold starts and ensuring smoother engine operation by increasing exhaust-gas temperature and enthalpy, while minimizing NOx and particle emissions.
Implementation Method 1
The first post-injection generates additional turbulence around the spark plug and thereby enriches the fuel-air mixture with fuel in this region shortly before the ignition. This facilitates a flame development, and the flame core formation, and thus a subsequent combustion, are stabilized.
Implementation Method 2
a second post-injection of gaseous fuel into the combustion chamber is carried out following the ignition and following the end of the combustion in the combustion chamber. With the aid of the second post-injection, another combustion following the actual main combustion is able to be realized, thereby significantly increasing an exhaust-gas temperature.
Implementation Method 3
In conjunction with the high charge temperature in the combustion chamber, this facilitates the oxidation of the quantity of gaseous fuel introduced with the aid of the second post-injection. The additional conversion generates a higher temperature of the exhaust-mass flow, and thus its enthalpy
Data Source
AI summary
A method for injecting gaseous fuel directly into a combustion chamber of an internal combustion engine in order to heat a catalytic converter, the method including: carrying out a main injection of gaseous fuel directly into the combustion chamber; carrying out a first post-injection following the main injection but prior to an ignition, and following the ignition and preferably following the end of combustion in the combustion chamber, carrying out a second post-injection of gaseous fuel into the combustion chamber.