Estimating Fuel Injector Flow Rate via Common Rail Pressure Change
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Solution Overview
Problem
The effective steady state flow rate of fuel injectors in fuel injection systems can change due to factors like spray hole coking, cavitation, erosion, and debris, leading to reduced engine efficiency, increased emissions, and inaccurate fuel metering, necessitating an accurate method for estimating this flow rate.
Innovation Solution
A method involving a processor that calculates the pressure change rate of a common rail in a fuel injection system, using pressure measurements from a pressure sensor, to estimate the effective steady state flow rate of injectors, and adjusts these estimates for error using an average flow rate calculation, which can be used in an injector control algorithm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional fuel injection systems are used without continuous monitoring, then the system structure remains simple, but the effective steady state flow rate changes due to spray hole coking, cavitation, erosion, and debris, leading to inaccurate fuel metering and reduced engine efficiency
Solution Approach 1:
The patent implements a feedback mechanism where the processor continuously monitors pressure changes in the common rail during injection events and uses this information to estimate the effective steady state flow rate of each injector. This feedback loop enables real-time detection of flow rate changes due to spray hole coking, cavitation, erosion, or debris, allowing the system to maintain accurate fuel metering without requiring physical modifications to the injectors themselves.
Solution Approach 2:
The patent replaces complex mechanical monitoring systems with a computational approach. Instead of using mechanical sensors directly on the injectors to measure flow rate, the system uses pressure sensors in the common rail combined with processor-based calculations to estimate the effective steady state flow rate. This substitution reduces mechanical complexity while achieving the desired measurement precision.
2Reliability
If the effective steady state flow rate is not accurately estimated, then the system operation remains unchanged, but fuel metering accuracy deteriorates and emissions increase
Solution Approach 1:
The patent performs preliminary estimation of the effective steady state flow rate before actual injection events by analyzing pressure changes during dedicated measurement windows. The processor calculates the pressure change rate during controlled injection events and uses this information to establish baseline flow rates for each injector. This preliminary action enables the system to detect and compensate for flow rate changes before they significantly impact fuel metering accuracy and emissions performance.
Solution Approach 2:
The system uses its own existing pressure sensing capability and injection events to self-diagnose and monitor injector performance. Rather than requiring external testing equipment or separate measurement systems, the patent leverages the normal operation of the fuel injection system itself to generate the data needed for flow rate estimation. The pressure sensor already present in the common rail is utilized to detect flow rate changes, making the system self-monitoring without additional hardware.
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 accurate estimation of the effective steady state flow rate, reducing errors and improving engine efficiency and emission control by enabling precise fuel metering and injector control.
Implementation Method 1
receiving, by the processor, pressure measurements of the common rail from the pressure sensor before and during an injection event
Data Source
AI summary
Provided are methods and fuel injection systems implemented with a plurality of injectors coupled with a common rail, the common rail coupled with a pressure sensor, and the pressure sensor coupled with a processor. The method includes: identifying, by the processor, one of the injectors to calculate a pressure change rate of the common rail associated therewith; receiving, by the processor, pressure measurements of the common rail from the pressure sensor before and during an injection event within a measurement window; using, by the processor, a pre-injection mean pressure of the common rail to determine a rail pressure drop range that is specific to the identified injector; and calculating, by the processor, the pressure change rate associated with the identified injector based on the pressure measurements of the common rail taken during the rail pressure drop range.