Split Lambda Catalyst Heating for Engine Efficiency
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Solution Overview
Problem
Existing methods for increasing catalyst temperature in vehicle engines, such as spark retard, decrease engine efficiency and result in thermal energy loss, as the hot exhaust cools before reaching the catalyst.
Innovation Solution
Operating the engine in a split lambda catalyst heating mode, where the lambda split between rich and lean combustion events is adjusted based on soot formation and catalyst washcoat storage capacity, with differential spark timing and fuel injection strategies to maintain global stoichiometry and increase catalyst temperature without reducing engine efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If spark retard is used to increase exhaust gas temperature and catalyst temperature, then catalyst temperature is improved, but engine efficiency deteriorates
Solution Approach 1:
The engine cylinders are divided into two separate sets: a first set operating with spark retard to generate hot exhaust for catalyst heating, and a second set operating with normal or advanced spark timing to maintain engine efficiency. This segmentation allows each cylinder set to perform specialized functions without compromising overall system performance.
Solution Approach 2:
Different spark timing strategies are applied to different cylinder sets based on their specific functional roles. The first cylinder set uses spark retard locally to maximize exhaust temperature for catalyst heating, while the second cylinder set uses optimal spark timing locally to maintain combustion efficiency and torque production.
2Temperature
If spark retard is used to increase exhaust gas temperature, then catalyst temperature is improved, but thermal energy loss increases due to cooling before reaching catalyst
Solution Approach 1:
The first cylinder set generates hot exhaust gases in advance through spark retard operation, creating a thermal reservoir that pre-heats the catalyst before the second cylinder set's exhaust arrives. This preliminary heating action ensures the catalyst reaches optimal temperature faster, reducing thermal energy loss from cooling exhaust.
Solution Approach 2:
The exhaust streams from both cylinder sets are merged in the exhaust manifold, combining the hot exhaust from the first set (with spark retard) and the exhaust from the second set (with normal timing). This merging ensures continuous high-temperature exhaust flow to the catalyst, maintaining thermal energy and preventing cooling.
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 effectively increases catalyst temperature while maintaining engine efficiency by ensuring excess oxygen and hydrocarbons react exothermically at the catalyst, reducing thermal losses and minimizing soot formation, thus enhancing emission reduction capabilities.
Implementation Method 1
the excess O2, CO, and H2 may react exothermically, providing catalyst heating
Data Source
AI summary
Methods and systems are provided for increasing a temperature of a catalyst of an engine by operating the engine in a split lambda catalyst heating mode. In one example, a method may include, while operating an engine in a split lambda catalyst heating mode, adjusting a magnitude of a lambda split between a rich set of combustion events and a lean set of combustion events based on soot formation in the rich set of combustion events. In this way, catalyst temperature may be increased while maintaining engine efficiency and preventing soot formation in the cylinders.