Indirect EGR Flow Measurement Using Turbocharger Data
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Solution Overview
Problem
Existing methods for measuring exhaust gas recirculation (EGR) flow in engine systems are costly, prone to malfunction, and impose restrictions that affect fuel economy, while direct measurement techniques are unreliable.
Innovation Solution
A method using turbo speed, inlet pressure, and boost pressure measurements to calculate EGR flow indirectly, employing existing engine system components like turbochargers and sensors, without direct EGR flow measurement, and adjusting EGR flow to control emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct measurement techniques (orifice plate, lambda sensor, venturi, delta P sensor) are used to measure EGR flow, then measurement precision is improved, but device complexity and cost increase, reliability decreases, and fuel economy deteriorates
Solution Approach 1:
The patent uses an intermediary calculation approach where EGR flow is determined indirectly through a balance equation involving air mass flow measurement (using MAF sensor) and exhaust mass flow calculation (based on fuel injection rate and stoichiometric ratio), rather than direct EGR measurement. This intermediary method avoids complex direct measurement equipment while achieving accurate EGR flow determination.
Solution Approach 2:
The patent replaces mechanical direct measurement systems (orifice plates, venturi tubes, delta P sensors) with a computational approach using existing engine management sensors and calculations. The EGR flow is derived through software-based mass balance calculations rather than physical measurement devices, reducing hardware complexity and improving reliability.
2Measurement precision
If direct measurement equipment (venturi, orifice plate, delta P sensor) is installed in the EGR circuit, then EGR flow can be measured, but the EGR circuit is restricted and fuel economy diminishes
Solution Approach 1:
The patent introduces an intermediary calculation method that determines EGR flow as the difference between calculated exhaust mass flow and measured air mass flow. This approach requires no physical intervention in the EGR circuit, avoiding flow restrictions and maintaining optimal fuel economy while achieving accurate measurement.
Solution Approach 2:
The patent extracts the measurement function from the EGR circuit itself by using separate measurements (air mass flow via MAF sensor, fuel injection rate via injector timing/duration) to calculate EGR flow externally. This removes any restrictive elements from the EGR path, preserving fuel economy while enabling measurement.
3Measurement precision
If direct measurement equipment (lambda sensor, delta P sensor) is used to measure EGR flow, then measurement data is obtained, but the equipment is unreliable and prone to malfunction
Solution Approach 1:
The patent makes the existing engine management system serve the dual purpose of controlling fuel injection and measuring EGR flow. The MAF sensor and injector data, already used for air-fuel ratio control, are additionally utilized for EGR calculation, eliminating the need for separate unreliable measurement equipment and improving overall system reliability.
Solution Approach 2:
The patent enables existing sensors and control systems to perform multiple functions: the MAF sensor serves both air-fuel ratio control and EGR measurement, the injector timing/duration data serves both fuel delivery control and exhaust mass flow calculation. This multi-functionality reduces component count and improves reliability by using proven, redundant systems.
Data Source
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AI summary
A method is provided for measuring exhaust gas recirculation (EGR) flow in. an engine system wherein turbo speed of a torbocharger, inlet pressure upstream of a compressor., boost pressure upstream of an engine, and engine intake temperature upstream of the engine are measured. Air mass flow into the engine system is calculated as a function of the turbo speed, inlet pressure, and boost pressure, exhaust mass flow is calculated as a function of the boost pressure, the engine intake temperature, volumetric efficiency of the engine, and engine size, and EGR flow is determined, by subtracting air mass flow from exhaust mass flow. A method for controlling emissions from an engine system, and an. engine system are also provided.