Gas Engine Air Mass Flow Calculation via Intercooler Pressure Drop
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Solution Overview
Problem
Internal combustion engines with exhaust gas recirculation, particularly gas engines, face challenges in accurately determining air mass flow without expensive and fault-prone hot film air mass meters, which are sensitive to dirt and fail to account for recirculated exhaust gas in calculations.
Innovation Solution
A method using a sensor system to measure pressure loss across a charge air cooler or throttle valve, with a computing unit calculating air mass flow based on intercooler or throttle valve models, eliminating the need for hot film air mass meters and accounting for recirculated exhaust gas by determining the EGR rate through intake manifold pressure and lambda control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a hot-film air mass meter (HFM) is used to measure air mass flow, then measurement precision is improved, but device cost increases and reliability deteriorates due to sensitivity to dirt and failure
Solution Approach 1:
The patent replaces the expensive and unreliable hot-film air mass meter with a combination of inexpensive pressure sensors and a charge air cooler that acts as a geometrically constant throttle. The pressure sensors measure pressure loss across the throttle, and the air mass flow is calculated using a stored model, eliminating the need for costly replacement-prone HFM sensors
Solution Approach 2:
The patent substitutes the mechanical hot-film air mass meter with a measurement system based on pressure differential measurement and mathematical calculation. Pressure sensors measure the pressure loss across the charge air cooler, and a computing unit calculates air mass flow based on stored models, replacing direct mechanical measurement with a calculation-based approach
2Measurement precision
If a hot-film air mass meter (HFM) is used to measure air mass flow, then measurement precision is improved, but device cost increases
Solution Approach 1:
The patent replaces the expensive hot-film air mass meter with inexpensive pressure sensors and utilizes the existing charge air cooler as a measurement element. The system calculates air mass flow using pressure differential measurements and stored models, significantly reducing hardware costs while maintaining measurement accuracy
3Device complexity
If traditional air mass flow calculation methods are used in engines with exhaust gas recirculation, then device complexity is reduced, but measurement precision deteriorates because recirculated exhaust gas is not accounted for
Solution Approach 1:
The patent incorporates feedback from multiple sensors including pressure sensors measuring pressure loss across the charge air cooler, lambda sensors for air-fuel ratio monitoring, and EGR rate determination. The computing unit continuously adjusts air mass flow calculations based on these feedback signals, accounting for recirculated exhaust gas and maintaining precision without excessive complexity
Solution Approach 2:
The charge air cooler serves dual functions: it cools the charge air to improve engine performance and acts as a geometrically constant throttle for air mass flow measurement. This multi-functionality reduces device complexity by eliminating separate measurement components while maintaining measurement precision through pressure differential measurement
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
Provides a cost-effective and reliable air mass flow determination, improving fuel metering accuracy and reducing the susceptibility to failure, especially in gas engines with exhaust gas recirculation, by using pressure loss measurements and intercooler or throttle valve models to calculate air mass flow.
Implementation Method 1
the charge air cooler forms a geometrically constant throttle for the air mass flow passing through
Implementation Method 2
a sensor system for measuring a pressure loss across the intercooler
Implementation Method 3
with which the air mass flow can be calculated at least from the pressure loss measured by the sensor system in a charge air cooler model stored therein
Data Source
Figure 1
Figure 2
AI summary
The invention relates to an internal combustion engine (1), in particular a gas engine, for a motor vehicle, with an intercooler (6) arranged upstream of a fuel mixture device (8) in an air mass flow supply, and with a measuring device for determining the air mass flow (3). According to the invention, a sensor system (19, 20) for measuring a pressure drop across the intercooler (6) is included, wherein the measuring device further includes a processing unit (21) as an evaluation unit, with which, in an intercooler model stored therein, in which the intercooler (6) forms a geometrically constant throttle for the flowing air mass flow (3), the air mass flow (3) can be calculated, or is calculated, at least from the pressure drop measured by means of the sensor system. The invention further relates to a corresponding method.