Exhaust Valve Timing for Catalyst Light-Off
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Solution Overview
Problem
Catalytic converters in internal combustion engines require significant time to reach effective operating temperatures, leading to untreated pollutant emissions during the heat-up phase, and existing solutions like pre-heating or secondary air injection increase energy consumption and system complexity.
Innovation Solution
The system advances the exhaust valve timing to open earlier in the engine cycle, retaining excess sensible heat in exhaust gases to accelerate catalyst heating, and optionally uses chemical processes to generate hydrogen and oxygen for additional heat, while adjusting compression ratios to optimize energy retention and combustion stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the exhaust valve opens at conventional timing, then work is extracted from combustion efficiently, but the catalyst does not receive enough heat to reach light-off temperature quickly
Solution Approach 1:
The exhaust valve is opened earlier in the combustion cycle than conventional timing, specifically opening before the piston reaches bottom dead center during the power stroke. This preliminary action allows the exhaust valve to remain open longer, retaining hot exhaust gases in the cylinder longer and delivering them to the catalyst at higher temperatures, thereby accelerating catalyst heating to light-off temperature.
Solution Approach 2:
The exhaust valve timing is made variable rather than fixed, allowing dynamic adjustment based on operating conditions. The controller adjusts the exhaust valve opening timing to optimize the balance between work extraction and heat delivery to the catalyst, enabling the system to adapt to different engine states and catalyst temperature requirements.
2Loss of time
If pre-heating methods (electrolysis, secondary air injection) are used to heat the catalyst, then the catalyst reaches light-off temperature faster, but energy consumption and system complexity increase
Solution Approach 1:
The system uses the exhaust gases themselves as the heating medium for the catalyst, eliminating the need for external pre-heating systems. The hot exhaust gases naturally flowing from the combustion chamber are directed to the catalyst through optimized valve timing and exhaust manifold design, allowing the catalyst to heat up using its own operational byproducts rather than requiring separate heating apparatus.
Solution Approach 2:
The invention extracts and utilizes the thermal energy already present in the exhaust gases that would otherwise be wasted. By opening the exhaust valve earlier and retaining the hot gases longer in the cylinder, the system extracts maximum thermal energy from the exhaust stream to deliver to the catalyst, converting what would be waste heat into a useful heating function without adding external energy input 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 approach reduces the time to reach effective catalyst temperature, decreases energy consumption, and enhances pollutant removal efficiency by utilizing retained heat and chemical reactions, thereby minimizing untreated emissions during engine start-up and operation.
Implementation Method 1
exhaust gases with the excess sensible heat being delivered to the catalyst to cause accelerated heating of the catalyst
Implementation Method 2
hydrogen gas (H2) in the effluent passing to the catalyst under low temperature operations. The resulting hydrogen gas reacts with the catalyst and available oxygen (O2) at a relatively low temperature, and the resulting oxidation reaction releases energy and heat
Implementation Method 3
combustion of a fuel-air mixture in the cylinder
Data Source
AI summary
Energy to speed heating of a catalyst associated with an internal combustion engine can be provided in the form of sensible energy (heat) via hot combustion products. In some variations, timing of opening and/or closing of an exhaust valve can be manipulated to increase sensible heat delivered to the catalyst in the exhaust gases.