Catalyst Temperature Control via Reformate Injection
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Solution Overview
Problem
Diesel engines face challenges in maintaining after-treatment device temperatures within the operating window, especially during cold starts and low speed/load conditions, leading to untreated emissions due to existing methods' inefficiencies and potential drawbacks such as high fuel consumption, complex hardware requirements, and energy penalties.
Innovation Solution
A system that monitors catalyst temperature and uses reformate injection, either directly into the catalyst or upstream and igniting it, to maintain or increase the temperature within the operating range, employing a controller, temperature sensor, and igniter in conjunction with a reformer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If post injection of fuel in cylinder is used to create exotherm, then exhaust gas temperature is raised, but fuel consumption increases significantly
Solution Approach 1:
An oxidation catalyst is introduced as an intermediary substance in the exhaust stream to facilitate exothermic oxidation of hydrocarbons. This mediator enables temperature increase without direct fuel combustion in the cylinder, thereby avoiding the high fuel consumption penalty while still achieving the desired thermal effect for emission control.
2Temperature
If post injection of fuel in cylinder is used, then exhaust gas temperature is raised, but cylinder wall wetting occurs causing oil dilution
Solution Approach 1:
The oxidation catalyst serves as an intermediary that enables exothermic reactions in the exhaust stream rather than in the combustion chamber. This eliminates direct fuel injection into the cylinder, preventing cylinder wall wetting and oil dilution while maintaining the ability to raise exhaust temperature for emission control.
3Temperature
If burner type systems are used for heating, then catalyst temperature is maintained, but system complexity increases
Solution Approach 1:
The system utilizes the exhaust stream itself as the heating medium and fuel source. Hydrocarbons already present in the exhaust gas are oxidized exothermically on the catalyst surface, making the system self-sufficient without requiring external burners, ignition systems, or complex control mechanisms. The exhaust gas automatically provides both the fuel and the reaction environment.
4Temperature
If electrically heated catalyst systems are used, then catalyst temperature is maintained, but fuel economy penalty increases
Solution Approach 1:
The system converts the harmful unburned hydrocarbons in the exhaust stream into a beneficial heat source through exothermic oxidation. These hydrocarbons, which would otherwise be wasted emissions, are oxidized on the catalyst surface to generate the heat needed to maintain catalyst temperature, eliminating the need for external electrical heating and its associated fuel economy penalty.
5Power
If larger engine size is used, then power output increases, but exhaust flow rate increases requiring even higher energy to heat exhaust gas
Solution Approach 1:
The exhaust stream from larger engines, which produces more heat due to higher power output, is utilized to heat the catalyst. The increased exhaust flow rate and temperature from larger engines naturally provide sufficient thermal energy for catalyst heating without requiring additional external energy input, making the system scalable to different engine sizes.
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
Effectively maintains catalyst temperature within the operating window, enhancing emission treatment during cold starts and low load conditions, reducing catalyst loading and improving overall performance without significant fuel economy penalties.
Implementation Method 1
If the catalyst temperature is high enough for exothermic reaction to occur, reformate is injected into the catalyst
Implementation Method 2
If the catalyst not high enough for exothermic reaction to occur, reformate is injected upstream of the catalyst and ignited
Data Source
AI summary
A method for controlling temperature of a catalyst. The method includes monitoring temperature of the catalyst and determining that the catalyst is outside of a catalyst operating temperature window. If the catalyst temperature is high enough for exothermic reaction to occur, reformate is injected into the catalyst. If the catalyst not high enough for exothermic reaction to occur, reformate is injected upstream of the catalyst and ignited.