Dedicated EGR Engine Reformate Estimation via Chemical Modeling
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Solution Overview
Problem
Current dedicated-EGR systems lack an efficient method to determine the mass and composition of the EGR stream without relying on costly gas composition sensors, particularly during engine load transients when reformate levels deviate from desired levels.
Innovation Solution
A method and system that provide a rich air-fuel mixture to a dedicated cylinder, model combustion using chemical reaction models, estimate the composition of combustion products, and control engine parameters like fuel injection timing, spark timing, and EGR bypass valve based on estimated mass fractions of reformate and burned gas to maintain optimal combustion in non-dedicated cylinders.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a gas composition sensor is used to measure the composition of the EGR stream, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces the mechanical/sensor-based measurement system with a computational modeling approach. Chemical reaction models are used to calculate the composition of the EGR stream based on fuel composition and combustion conditions, eliminating the need for physical gas composition sensors while maintaining measurement capability.
Solution Approach 2:
The patent introduces an intermediary computational model that mediates between the combustion process and the control system. Instead of directly measuring gas composition, the model processes fuel composition and combustion parameters to derive EGR stream composition, serving as an intermediary calculation layer.
2Measurement precision
If a gas composition sensor is installed in the intake manifold, then measurement precision is improved, but cost increases
Solution Approach 1:
The patent replaces expensive, complex gas composition sensors with a low-cost computational model that runs on existing engine control units. The 'sensor' is effectively replaced by software algorithms that calculate composition based on readily available data from the combustion process, dramatically reducing system cost.
3Ease of operation
If reformate levels are not properly controlled, then engine operation is simplified, but combustion stability deteriorates
Solution Approach 1:
The patent implements a feedback control system where the computational model continuously calculates EGR stream composition based on current combustion conditions, and this information feeds back to the engine control unit. The control unit then adjusts fuel injection and ignition timing to maintain optimal reformate levels, ensuring combustion stability.
Solution Approach 2:
The patent makes the engine control dynamic by continuously adjusting fuel injection timing and ignition timing based on real-time combustion conditions and modeled EGR composition. This dynamic adaptation allows the system to maintain optimal combustion stability across varying operating conditions without complex manual intervention.
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 allows for effective control of combustion in non-dedicated cylinders, improving EGR tolerance and stability without the need for a dedicated gas composition sensor, enhancing engine efficiency and knock resistance.
Implementation Method 1
combusting the rich air-fuel mixture in the dedicated cylinder
Data Source
AI summary
A method of operating a dedicated-EGR engine includes providing a rich air-fuel mixture to a dedicated cylinder; combusting the rich air-fuel mixture in the dedicated cylinder; modeling the combustion of the rich air-fuel mixture in the dedicated cylinder; estimating the composition of the combustion products in the dedicated cylinder based on interpolation of chemical reaction models of stoichiometric and rich combustion. The method further includes mixing the combustion products from the dedicated cylinder with air to produce an intake mixture; estimating a mass fraction of reformate and a mass fraction of burned gas in the intake mixture; providing the intake mixture to the intake ports of all of the cylinders of the dedicated-EGR engine; combusting an air-fuel mixture in a non-dedicated cylinder of the engine; and controlling an engine control parameter based on the estimated mass fractions of reformate and burned gas in the intake mixture.