NOx Estimation in Internal Combustion Engines Using Cylinder Pressure
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Solution Overview
Problem
Current methods for estimating and regulating internal combustion engine output parameters, such as nitrogen oxides, carbon dioxide, carbon monoxide, unburned fuels, and particles, are complex and costly, requiring numerous sensors and calculations, which increases vehicle manufacturing costs and fails to account for engine variations.
Innovation Solution
A system that estimates engine output parameters using minimal direct measurements and calculations by measuring temporal variations of the crankshaft angle and internal pressure, calculating combustion parameters, and applying a weighted sum estimation method, with optional measurements of oxygen, fuel, and fresh air flow, to regulate engine output parameters through closed-loop control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complex chemical kinetic models are used for NOx estimation, then estimation accuracy is improved, but system complexity and cost increase
Solution Approach 1:
The patent extracts only the essential combustion parameters needed for NOx estimation from the complete chemical kinetic model. Instead of implementing the full complex model, it selectively uses measured combustion parameters (pressure, temperature, oxygen concentration, fuel flow, air flow) that have the most significant impact on NOx formation, thereby simplifying the system while maintaining adequate estimation accuracy.
Solution Approach 2:
The patent creates a simplified computational model that copies the essential behavior of the complex chemical kinetic model without replicating its full complexity. The estimation system uses a reduced-order model that reproduces the key relationships between combustion parameters and NOx emissions, achieving acceptable accuracy with significantly lower computational requirements.
2Measurement precision
If multiple sensors are embedded for measurement, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent makes the combustion parameters measured by sensors serve multiple functions. The same pressure, temperature, and flow measurements used for engine control and monitoring are also utilized for NOx estimation, eliminating the need for additional dedicated sensors and reducing overall system cost while maintaining measurement precision.
Solution Approach 2:
The estimation system uses data already collected by the engine's existing sensor network for control purposes. The system serves itself by reusing available measurement data rather than requiring separate dedicated measurement infrastructure, thereby avoiding additional manufacturing costs while achieving the required estimation precision.
3Reliability
If safety margins are increased for emissions compliance, then reliability is improved, but device size and cost increase
Solution Approach 1:
The patent implements real-time feedback control by continuously estimating actual NOx emissions and using this information to adjust engine operation and after-treatment system activation. This feedback mechanism allows the system to operate closer to emission limits with high confidence, reducing the need for oversized safety margins and enabling more compact after-treatment system design.
Data Source
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AI summary
System for estimating at least one output parameter (PSe) of an internal combustion engine (1) comprising at least one cylinder (2), one moving piston (3) driven by a crankshaft (5), means (20, 21) for measuring the temporal variations of the crank angle and of the internal pressure of said cylinder, a calculating means (23) for calculating a plurality of combustion parameters (Xi), such as internal cylinder pressures characteristic of the combustion, variations in the pressure inside the cylinder and engine strokes, from said crank angle measurements and internal cylinder pressures, and an estimating means (24) for estimating at least one engine output parameter (PSe) from said combustion parameters (Xi), the estimating means (24) estimating at least one engine output parameter (PSe) from a weighted sum of said combustion parameters (Xi).