Two-Stroke Engine Air Flow Rate Determination
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Solution Overview
Problem
Existing methods for determining the air flow rate in two-stroke engines, such as using absolute pressure at the intake manifold, are inaccurate due to nonlinearity with engine load, especially at light loads, and are costly when using air flow meters.
Innovation Solution
A method that measures absolute pressure at specific crankshaft angles to calculate the air flow rate using linear relationships and quotients, eliminating the need for flow meters and adapting to varying engine loads by selecting appropriate models based on load thresholds and atmospheric pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If absolute pressure at the intake manifold is used to determine air flow rate, then the measurement is simple and accessible, but the accuracy deteriorates at light loads due to nonlinearity with engine load
Solution Approach 1:
The patent applies dynamics by making the measurement approach adaptive rather than static. The system dynamically selects between different calculation methods (first calculation method for light loads, second calculation method for medium/heavy loads) based on real-time engine operating conditions. This dynamic adaptation resolves the contradiction by maintaining measurement simplicity while improving accuracy across varying load conditions.
Solution Approach 2:
The patent changes the parameter used for air flow rate calculation based on engine load. At light loads, it uses the relationship between atmospheric pressure, manifold pressure, and throttle angle. At medium and heavy loads, it switches to a different calculation method. This parameter change allows the system to maintain measurement simplicity while achieving accurate air flow rate determination across all operating conditions.
2Measurement precision
If an air flow meter is used to evaluate the mass of air delivered to a two-stroke engine, then the measurement accuracy is improved, but the cost increases significantly
Solution Approach 1:
The patent creates a computational model that copies the function of an expensive air flow meter. Instead of using a physical flow meter, the system uses electronic sensors (pressure sensors and throttle angle sensor) combined with calculation algorithms to replicate the air mass measurement function. This copying approach achieves similar measurement accuracy without the high cost of dedicated flow meters.
Solution Approach 2:
The patent replaces the mechanical air flow meter with an electronic calculation system. Instead of using a mechanical device to physically measure air flow, the system uses electronic sensors to measure pressure and throttle angle, then computes the air mass using predefined relationships and algorithms. This substitution eliminates the need for expensive mechanical flow meters while maintaining measurement accuracy.
3Device complexity
If a single calculation method is used for all engine loads, then the system simplicity is maintained, but the reliability deteriorates due to nonlinearity at light loads
Solution Approach 1:
The patent segments the engine operating range into two distinct zones: light load and medium/heavy load. Each zone has its own optimized calculation method. The system divides the overall air flow rate determination task into separate handling for different operating conditions, improving reliability without significantly increasing system complexity. This segmentation allows each calculation method to be optimized for its specific operating range.
Solution Approach 2:
The patent makes the calculation system dynamic by automatically selecting the appropriate calculation method based on real-time engine load conditions. The system monitors engine operating parameters and dynamically switches between the first calculation method (for light loads) and the second calculation method (for medium and heavy loads). This dynamic adaptation ensures reliable air flow rate determination across all operating conditions while maintaining reasonable system simplicity.
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 and efficient air flow rate estimation for two-stroke engines, applicable across all loads without the need for expensive flow meters, and can detect combustion instability and malfunctions.
Implementation Method 1
acquiring a first absolute pressure at the manifold in the intake manifold at a first predetermined crankshaft angle of rotation around top dead center; acquiring a second absolute pressure at the manifold in the intake manifold at a second predetermined crankshaft angle of rotation around bottom dead center
Data Source
AI summary
A method for measuring the flow rate MAF of cool air entering an intake manifold of a two-stroke engine, the intake manifold being located between a throttle body and an intake system. The method uses a specific prediction model depending on whether the two-stroke engine is subject, on the one hand, to a light load and, on the other hand, to a medium or heavy load. The model suitable for the load is selected using a predetermined threshold and two absolute pressure measurements taken at the intake manifold at crankshaft angles of rotation around top dead center and bottom dead center. Next, a pressure quotient is formed for each model which will be used to deduce the flow rate of cool air entering the intake manifold.