Estimating Combustion Chamber Mass Using Pressure and Thermodynamic Models
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Solution Overview
Problem
Current methods for estimating nitrogen oxides (NOx) emissions in internal combustion engines lack precision due to the absence of a mass sensor in the combustion chamber, relying on imprecise filling maps and costly pollutant emission sensors, which are not economically viable or robust enough to meet current pollution control standards.
Innovation Solution
A method that estimates the mass enclosed in the cylinder using a cylinder pressure sensor, crankshaft angle measurement, and coolant temperature, employing a nonlinear zero-dimensional model and sliding observer to determine the temperature and NOx production, allowing for precise estimation of NOx emissions without the need for expensive sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a mass sensor is installed in the combustion chamber to directly measure enclosed mass, then measurement precision would be improved, but device complexity and manufacturing cost would increase significantly
Solution Approach 1:
The patent uses pressure as an intermediary parameter to indirectly determine enclosed mass. Instead of directly measuring mass with a complex sensor, a simple pressure sensor measures cylinder pressure, which is then used through thermodynamic relationships to calculate enclosed mass. This intermediary approach avoids the complexity of direct mass measurement while achieving the desired measurement precision.
2Measurement precision
If expensive pollutant emission sensors are installed on exhaust systems to accurately measure NOx emissions, then measurement precision would be improved, but manufacturing cost would increase making it economically unviable
Solution Approach 1:
The patent creates a computational model that copies the physical measurement process. Instead of using expensive physical NOx sensors, the system uses a mathematical model that replicates the relationship between enclosed mass, temperature, and NOx formation. This virtual copy provides accurate NOx emission estimates without the high cost of physical emission sensors.
Solution Approach 2:
The patent replaces the mechanical/chemical sensing system (expensive NOx sensors) with a computational/mathematical system. By substituting physical measurement with calculation based on pressure data and thermodynamic models, the system achieves the same measurement precision without the high manufacturing cost and complexity of specialized emission sensors.
3Device complexity
If filling maps are used to estimate enclosed mass, then device complexity is kept simple, but measurement precision is insufficient for estimating polluting emissions
Solution Approach 1:
The patent transitions from using static filling maps to using dynamic pressure-based parameters. By measuring real-time cylinder pressure and using thermodynamic relationships to calculate enclosed mass, the system changes from relying on pre-defined lookup tables to using actual measured parameters. This parameter change significantly improves measurement precision while maintaining relative system simplicity.
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 method provides a robust and precise estimation of NOx emissions, improving the accuracy of pollution control in internal combustion engines by determining the enclosed mass and temperature using available sensors, thus meeting stringent pollution standards without the need for costly additional equipment.
Implementation Method 1
The temperature (T) of a gas mixture can be determined as a first approximation by applying the ideal gas law (P
Implementation Method 2
calibration parameters related to heat losses at the walls are determined as a function of a map based on the engine rotation speed
Implementation Method 3
the modeled temperature in the cylinder is determined by a zero-dimensional nonlinear pressure model
Data Source
AI summary
Method of estimating the mass enclosed in the combustion chamber of a cylinder of a motor vehicle internal combustion engine, equipped with a means of measuring the pressure in the cylinder, with a means of measuring the angle of the crankshaft with respect to a reference position and of measuring the temperature of the combustion chamber cooling liquid. The method comprising steps during which the rotational speed of the engine is determined from the measurement of the crankshaft angle and the engine load is determined. The method also comprises the following steps: when the valves of the cylinder are completely closed and before fuel is first injected, the volume of the cylinder is determined as a function of the angle of the crankshaft, calibration parameters connected with the heat losses at the walls are determined from a map dependent on engine rotational speed, the temperature modelled in the cylinder is determined using a non-linear dimensionless model of the pressure and the temperature in the combustion chamber as a function of the measured pressure in the cylinder, of the specific gas constant for the gases in the cylinder, of the specific heat capacity at constant volume of the gases in the cylinder, of the volume of the combustion chamber, and of calibration parameters connected with the heat losses at the walls, and the mass enclosed in the cylinder is determined.