Engine Power Boost via Segmented Cylinder Air-Fuel Ratios
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Solution Overview
Problem
Typical spark ignition engines face challenges in increasing power output while maintaining low vehicle emissions, as global enrichment strategies can degrade exhaust system components and violate stringent emission standards.
Innovation Solution
A method involving responsive engine torque adjustments, including increasing boost without EGR until a threshold torque is reached, then increasing EGR rate over engine cycles, and gradually adjusting air-fuel ratios between cylinder sets to maintain stoichiometry, thereby cooling exhaust components and reducing emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If global enrichment strategy is used to increase engine power, then engine power output increases, but exhaust system component temperature increases causing heat-related degradation
Solution Approach 1:
The engine cylinders are divided into two separate sets (first set and second set) with different air-fuel ratios. The first set operates at stoichiometry while the second set operates enriched, allowing selective EGR extraction from the stoichiometric set to cool exhaust components without compromising overall power output.
Solution Approach 2:
Different regions of the engine (different cylinder sets) are given different air-fuel ratio qualities. The stoichiometric cylinders provide cool EGR gas for exhaust system cooling, while the enriched cylinders provide the power benefit, allowing local optimization of both cooling and power objectives.
2Power
If global enrichment strategy is used to increase engine power, then more air flow is achieved, but vehicle emissions increase due to decreased three-way catalyst efficiency
Solution Approach 1:
The exhaust stream is segmented from two different cylinder sets with different air-fuel ratios. By maintaining one set at stoichiometry, the exhaust from that set has the proper composition for three-way catalyst efficiency, while the enriched set provides power benefits.
Solution Approach 2:
Different cylinder sets produce exhaust with different qualities (stoichiometric vs. enriched). The stoichiometric exhaust maintains catalyst efficiency for emission control, while the enriched operation provides the power increase, allowing both emission control and power gains simultaneously.
3Temperature
If EGR rate is increased to cool exhaust components, then exhaust system component temperature decreases, but engine vibrations increase due to abrupt changes
Solution Approach 1:
The air-fuel ratio adjustments and EGR rate changes are implemented gradually over multiple engine cycles rather than abruptly. This preliminary gradual adjustment allows the engine control system to smooth out transitions and minimize vibrations while still achieving the desired exhaust component cooling.
Solution Approach 2:
The EGR rate and air-fuel ratios are dynamically adjusted over multiple engine cycles rather than held constant. This dynamic adjustment allows the system to adaptively cool exhaust components while minimizing vibrations through controlled, gradual changes.
4Object-generated harmful factors
If air-fuel ratio difference between cylinder sets is increased to maintain stoichiometry, then emissions are reduced, but engine power may be compromised
Solution Approach 1:
The air-fuel ratio parameter is changed differently for two separate cylinder sets. By enriching one set and maintaining stoichiometry in the other, the system achieves both emission reduction (through stoichiometric exhaust for catalyst efficiency) and power maintenance (through enriched operation in the other set).
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 enhances engine power while minimizing vibrations and protecting exhaust system components from heat-related degradation, achieving increased power with reduced emissions compared to conventional enrichment strategies.
Implementation Method 1
the EGR may provide temperature relief to exhaust system components to increase engine air flow without increasing vehicle emissions
Implementation Method 2
Operating at stoichiometry increases an efficiency of a three-way catalyst positioned in an exhaust system of the engine, thereby reducing vehicle emissions
Implementation Method 3
some engines are equipped with a turbocharger to harness heat from the exhaust gas to supply more air to the engine to increase engine power
Data Source
AI summary
Methods and systems are provided for increasing engine power while reducing vehicle emissions and engine system degradation. In one example, a method may include, responsive to an engine load reaching a threshold load, increasing engine torque by increasing an amount of boost without providing exhaust gas recirculation (EGR), and, responsive to the engine torque reaching a first threshold torque, increasing the engine torque by increasing an EGR rate over a plurality of engine cycles while further increasing the amount of boost. In this way, cooling effects from the EGR enable engine air flow, and thus engine power, to be increased while engine vibrations and heat-related exhaust component degradation are decreased.