Fixed Displacement Pump Dosing with Pressure Sensor Calibration
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Solution Overview
Problem
Current selective catalytic reduction (SCR) systems for internal combustion engines face challenges in accurately dosing reductants, such as anhydrous ammonia or urea, due to variations in pressure and flow rates, which affect the efficiency of NOx emission reduction.
Innovation Solution
A reductant dosing system that includes a fixed displacement pump, a pressure sensor assembly, and a controller, which calculates the flow rate based on detected pressure and a calibration value, allowing for precise dosing by interpreting offsets at zero pressure or decoding multiplexed signals from the pressure sensor assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed displacement pump is used to dose reductant, then the dosing system is simpler and more reliable, but the flow rate varies with pressure changes reducing dosing accuracy
Solution Approach 1:
The system uses a pressure sensor assembly to continuously monitor reductant pressure and feeds this information back to the controller. The controller calculates the actual flow rate based on the measured pressure and calibration values, enabling closed-loop control that compensates for pressure variations and maintains accurate dosing with a simple fixed displacement pump
Solution Approach 2:
The patent replaces complex mechanical flow control mechanisms (such as variable displacement pumps or flow control valves) with a simpler fixed displacement pump配合pressure sensing and electronic control. The mechanical simplicity of the pump is maintained while using electronic feedback to achieve precise flow rate control
2Device complexity
If pressure sensor assembly with multiplexed signal is used, then calibration data is integrated without additional components, but signal decoding complexity increases
Solution Approach 1:
The calibration values are merged into the pressure sensor assembly itself, specifically integrated into the analog voltage output signal as multiplexed data. This combines the pressure sensing function and calibration data storage into a single component, eliminating the need for separate calibration memory or additional sensors while providing all necessary information through the existing signal line
Solution Approach 2:
The analog voltage output of the pressure sensor assembly serves multiple functions: it provides the pressure measurement signal for flow rate calculation and simultaneously carries the calibration values embedded in the multiplexed signal. This multi-functionality reduces the need for separate components and simplifies the overall system architecture
Data Source
AI summary
A reductant dosing system includes an injector, a fixed displacement pump in fluid communication with the injector, a reductant source in fluid communication with the fixed displacement pump, a pressure sensor assembly that detects a pressure of a reductant and stores a calibration value, and a controller communicatively coupled to the fixed displacement pump and the pressure sensor assembly. The controller receives data that includes the detected pressure of the reductant and the calibration value. The controller, in response to the calibration value being within a predetermined calibration value range, calculates a flow rate of the fixed displacement pump based on at least the detected pressure and the calibration value, and, in response to the calibration value being outside the predetermined calibration value range, calculates the flow rate of the fixed displacement pump based on at least the detected pressure and a pre-determined calibration value different from the calibration value.