Common Rail Fuel Injection Wave Speed Correction
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Solution Overview
Problem
Existing fuel injection systems for common rail diesel engines face inaccuracies in fuel quantity control due to variations in rail pressure, leading to deviations in injected fuel amounts and increased exhaust gases, requiring extensive and costly map preparation and verification tests.
Innovation Solution
A pressure wave correction logic using a wave speed correction map with fuel temperature and rail pressure as input variables, coupled with a time corrector and amplitude maps, to accurately adjust injection time differences and quantities, thereby reducing fuel quantity deviations and improving engine efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional correction logic using base map and amplitude map is used, then fuel injection can be controlled, but fuel quantity deviation increases due to rail pressure variations
Solution Approach 1:
The invention introduces wave speed as a dynamic correction parameter that changes based on rail pressure variations. By calculating wave speed using the formula c = sqrt(K/ρ) where K is bulk modulus and ρ is fuel density, the system adapts the correction factor to actual pressure conditions, thereby maintaining consistent fuel quantity delivery across different operating pressures.
Solution Approach 2:
The system implements a feedback mechanism where the actual rail pressure is measured and used to calculate the appropriate wave speed correction factor. This corrected wave speed then adjusts the fuel injection timing and quantity in real-time, creating a closed-loop control system that compensates for pressure variations and maintains precise fuel delivery.
2Productivity
If multiple fuel injections are performed, then combustion efficiency improves, but fuel quantity deviation increases due to pressure variations in rail and high-pressure pipe
Solution Approach 1:
The system performs preliminary calculation of the wave speed correction factor before each fuel injection event. By pre-calculating the correction based on current rail pressure and temperature conditions, the control system can accurately determine the required injection timing and quantity for each injection pulse in the multiple injection sequence, preventing cumulative errors.
Solution Approach 2:
The invention makes the correction system dynamic by continuously updating the wave speed calculation based on real-time rail pressure and temperature measurements. This dynamic adjustment allows the system to maintain precise fuel quantity control throughout the multiple injection process, adapting to pressure changes that occur between and during injection events.
3Measurement precision
If map preparation covers all pressure cases, then accuracy improves, but time and cost increase significantly
Solution Approach 1:
The invention extracts the pressure-dependent behavior from the static maps by isolating it into a separate wave speed calculation. Instead of creating separate maps for each pressure level, the system uses a single base map combined with a dynamic wave speed correction factor that accounts for pressure variations, dramatically reducing map preparation and verification requirements.
Solution Approach 2:
The wave speed correction factor serves as a universal solution that works across all rail pressure conditions. This single correction mechanism replaces the need for multiple pressure-specific maps, providing a multi-functional approach that maintains accuracy throughout the entire operating range while requiring minimal calibration data.
Data Source
AI summary
An apparatus for controlling the quantity of fuel over a common rail diesel engine includes a wave speed correction map correcting a wave speed and a time corrector, a first adder multiplying the corrected wave speed by an injection time difference, a base correction map using an output of the first adder and a former injection quantity as input variables, an amplitude map using a following injection quantity and a rail pressure as input variables, and a second adder multiplying a base correction map value of the base correction map by an amplitude map value of the amplitude map, and outputting a finally corrected value of the fuel quantity.