Aftertreatment Exhaust Mass-Flow Estimation via Differential Pressure
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Solution Overview
Problem
Existing aftertreatment systems for internal combustion engines face challenges in accurately estimating exhaust air mass-flow, which is crucial for robust control and emissions reduction, especially when engine-side mass-flow sensors become unreliable.
Innovation Solution
The system employs a controller communicatively coupled with differential pressure, temperature, and ambient pressure sensors to estimate exhaust air mass-flow using calculated flow coefficients and density, allowing for continued optimal operation and diagnostic functions even without direct mass-flow sensor data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If engine-side mass-flow sensors are removed to reduce costs, then system cost is reduced, but the ability to accurately estimate exhaust air mass-flow deteriorates
Solution Approach 1:
The patent introduces intermediary measurement devices (differential pressure sensor and temperature sensor) that indirectly measure exhaust mass-flow through physical relationships. The differential pressure sensor measures pressure drop across the SCR catalyst, and the temperature sensor measures exhaust gas temperature, both of which serve as intermediaries to estimate mass-flow without requiring direct mass-flow sensors on the engine side.
Solution Approach 2:
The patent replaces mechanical mass-flow sensors with a measurement system based on pressure and temperature sensing combined with computational estimation. Instead of using mechanical sensors that directly measure mass-flow, the system uses pressure sensors and temperature sensors with algorithms to calculate and estimate the exhaust air mass-flow, substituting mechanical measurement with a sensor-computation hybrid approach.
2Reliability
If differential pressure and temperature sensors are used to estimate mass-flow, then dependency on engine-side mass-flow sensors is reduced, but system complexity increases
Solution Approach 1:
The patent makes existing sensors serve multiple functions. The differential pressure sensor, originally intended for monitoring SCR catalyst health, is also used for estimating exhaust mass-flow. The temperature sensor, used for monitoring exhaust gas temperature for SCR operation, is also utilized for mass-flow estimation. This multi-functionality reduces the need for dedicated mass-flow sensors and minimizes additional system complexity.
Solution Approach 2:
The system uses its own existing sensor infrastructure to provide mass-flow estimation functionality. Rather than requiring external or additional dedicated mass-flow measurement devices, the aftertreatment system leverages its own differential pressure and temperature sensors to self-estimate the exhaust air mass-flow, making the system self-sufficient.
3Adaptability or versatility
If mass-flow estimation algorithms are implemented, then diagnostic capabilities are enhanced, but computational requirements and control complexity increase
Solution Approach 1:
The patent implements feedback mechanisms where the estimated mass-flow information is fed back into the control system to monitor sensor consistency and detect faults. The controller compares the estimated mass-flow with expected values based on operating conditions, and when discrepancies exceed thresholds, it generates diagnostic alerts. This feedback-based diagnostic approach enhances versatility while keeping the control algorithm relatively simple and rule-based.
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 enables continued normal operation of aftertreatment functions, reduces costs by potentially removing engine-side mass-flow sensors, and enhances diagnostic capabilities for detecting sensor errors, while maintaining overall system performance and emissions reduction.
Implementation Method 1
The dP sensor is configured to measure a value of a differential pressure across the SCR system
Implementation Method 2
The first temperature output value from the temperature sensor is indicative of a temperature of the SCR system
Implementation Method 3
The controller is further configured to estimate an exhaust air mass-flow output from the aftertreatment system using the first output value from the dP sensor and the first temperature output value from the temperature sensor
Data Source
AI summary
An aftertreatment system includes: a selective catalytic reduction (SCR) system including at least one catalyst; a particulate filter fluidly coupled to the SCR; a particulate filter out pressure sensor operatively coupled to an outlet of the particulate filter, the particulate filter out pressure sensor configured to measure a value of a pressure at the outlet of the particulate filter; a temperature sensor; an ambient pressure sensor; and a controller communicatively coupled with the particulate filter out pressure sensor, the controller configured to estimate an exhaust air mass-flow output from the aftertreatment system using a first output value from a particulate filter out pressure sensor, a first temperature output value from a temperature sensor, and a second output value from an ambient pressure sensor.