Exhaust Catalyst Light-Off via Water Injection
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Solution Overview
Problem
Existing engine systems face challenges in reducing cold-start emissions due to the slow heating of exhaust catalysts below light-off temperature, which can be exacerbated by additional heating systems that increase manufacturing costs and complexity.
Innovation Solution
Injecting water into the engine intake during cold-start to accumulate water in the exhaust catalyst, where it generates heat through momentum conversion and increased capacitance, thereby reducing the time to reach light-off temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If heater pumps or catalyst heaters are added to preheat the exhaust catalyst during cold-start, then the catalyst light-off time is reduced, but the manufacturing cost increases
Solution Approach 1:
The water injection system is designed to perform multiple functions: during normal operation it controls knock and exhaust temperature, and during cold-start it accelerates catalyst light-off by injecting water into the intake manifold. This eliminates the need for separate heating systems while reducing cold-start emissions.
Solution Approach 2:
The system uses the engine's own water injection system to heat the catalyst during cold-start, rather than requiring external heating equipment. The water injected into the combustion chamber undergoes phase change and chemical reactions that generate heat directly within the exhaust stream, warming the catalyst without additional components.
2Loss of time
If heater pumps or catalyst heaters are added to preheat the exhaust catalyst during cold-start, then the catalyst light-off time is reduced, but the system complexity increases
Solution Approach 1:
The water injection system is designed to perform multiple functions: during normal operation it controls knock and exhaust temperature, and during cold-start it accelerates catalyst light-off by injecting water into the intake manifold. This eliminates the need for separate heating systems while reducing cold-start emissions.
Solution Approach 2:
The patent combines the catalyst heating function with the existing water injection system, merging two functions into one system. The water injection system simultaneously handles knock control, exhaust temperature management, and catalyst warming, reducing overall system complexity.
3Loss of time
If additional heaters are added to preheat the exhaust catalyst, then the catalyst light-off time is reduced, but the exhaust backpressure increases
Solution Approach 1:
The patent replaces mechanical heating systems (heaters, heat pumps) with a chemical/thermal process using water injection and phase change. Water injected into the combustion chamber undergoes evaporation, combustion, and chemical reactions that generate heat directly in the exhaust stream, avoiding the need for mechanical heating components that would increase backpressure.
Solution Approach 2:
The system exploits phase transitions of water (liquid to vapor during evaporation, and chemical reactions) to generate heat. When water is injected into the hot exhaust gases and combustion chamber, it rapidly evaporates and undergoes chemical reactions that release significant heat energy, warming the catalyst without mechanical heaters that would restrict exhaust flow.
Data Source
AI summary
Methods and systems are provided for controlling exhaust catalyst temperature during an engine cold-start by water injection. In one example, a method may include during the engine cold-start, injecting water into an intake of an engine based on the exhaust catalyst temperature and accumulating water molecules within an exhaust catalyst to generate heat within the exhaust catalyst. In this way, by generating and storing heat within the exhaust catalyst, the exhaust catalyst may be heated up rapidly, thus reducing catalyst light-off time.