Physics-Based Charge Air Temperature Model for Engine Control
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Solution Overview
Problem
Current algorithms for estimating charge air temperature in automobile vehicle engines are inadequate, as they do not accurately account for factors like exhaust gas mixing, engine operating states, and vehicle speed, leading to inaccurate fuel calculations and engine timing adjustments.
Innovation Solution
A physics-based charge temperature model that uses multiple variables such as engine speed, cam position, firing fraction, engine coolant temperature, and air intake temperature, along with lookup tables to calculate charge air temperature for individual intake strokes, accounting for factors like cylinder gas backflow and scavenging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If present algorithms use vehicle speed to estimate charge air temperature, then the algorithm simplicity is maintained, but the estimation accuracy deteriorates because air flow through the engine bay does not vary substantially with vehicle speed in newer aerodynamically designed vehicles
Solution Approach 1:
The patent replaces vehicle speed as an input parameter with engine bay air flow rate, which directly correlates with heat transfer to the charge air. This parameter change improves estimation accuracy by using a variable that actually influences the thermal process, rather than relying on vehicle speed which has become decoupled from air flow due to aerodynamic design improvements.
Solution Approach 2:
The patent substitutes a physics-based thermal model for the empirical correlation-based algorithm. Instead of using simple lookup tables or regression equations based on vehicle speed, the system employs fundamental heat transfer equations that model the actual physical processes occurring in the engine bay, improving accuracy across diverse operating conditions.
2Measurement precision
If present algorithms do not account for exhaust gas mixing at intake ports, then the algorithm simplicity is maintained, but the charge air temperature estimation accuracy deteriorates
Solution Approach 1:
The patent combines the estimation of charge air temperature from two distinct sources: ambient air heating in the engine bay and exhaust gas mixing at the intake ports. By merging these two thermal processes into a single comprehensive model, the system captures the total heat transfer to the charge air, improving accuracy without requiring complex separate algorithms.
Solution Approach 2:
The patent introduces exhaust gas temperature and exhaust flow rate as additional input parameters to account for exhaust gas mixing effects. These parameter additions enable the model to calculate the thermal contribution of exhaust gases to the charge air, directly addressing the previously unmodeled phenomenon.
3Measurement precision
If direct temperature measurement within piston chamber is implemented, then measurement accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent uses easily measurable parameters (ambient air temperature, engine bay air flow rate, coolant temperature, exhaust gas temperature) as intermediaries to indirectly determine charge air temperature. Rather than directly measuring the difficult-to-access piston chamber temperature, the system uses these intermediary measurements combined with physics-based calculations to infer the charge air temperature, achieving high accuracy without complex instrumentation.
Solution Approach 2:
The patent replaces direct physical temperature measurement in the piston chamber with a computational thermal model. Instead of installing temperature sensors in difficult-to-reach locations, the system uses a virtual sensor approach where software calculations based on fundamental heat transfer principles provide the temperature estimate, eliminating the need for complex hardware installation.
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 provides a more accurate estimation of charge air temperature, improving fuel calculation precision and engine timing adjustments by considering various engine operating conditions and airflow dynamics.
Implementation Method 1
heat transferred to the charge air volume
Implementation Method 2
exhaust gas mixing that occurs at engine intake ports
Implementation Method 3
delta coolant charge, wherein the delta coolant charge is equal to the engine coolant temperature minus the air intake temperature
Data Source
AI summary
A physics-based charge temperature model to calculate a charge air temperature for an automobile vehicle includes multiple variables. The multiple variables include: a first variable defining an engine speed of an engine defining revolutions per minute of a crankshaft of the engine; a second variable defining a cam position; a third variable defining an engine coolant temperature; a fourth variable defining an air intake temperature; a fifth variable defining an engine air flow; and a sixth variable defining a firing fraction of the engine. A controller provides multiple lookup tables. The controller controls operation of the engine using the multiple variables and data in the multiple lookup tables to calculate a charge air temperature for individual intake strokes of at least one cylinder of the engine.