Free-Piston Device Scavenging Control via Adjustable Bottom Dead Center
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Solution Overview
Problem
Existing free-piston devices lack the ability to set their operating point in a versatile manner, limiting the adjustment of the scavenging process and the ratio of fresh gas to exhaust gas for optimized combustion.
Innovation Solution
The free-piston device allows for control of the scavenging process by adjusting the opening duration and cross-sectional area of the inlet and outlet openings, enabling flexible operation between external ignition with low residual gas and self-ignition with high residual gas, without the need for additional scavenging channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If additional openings are provided on the piston receptacle for different scavenging channels, then the versatility of operating points is improved, but the device complexity increases
Solution Approach 1:
The invention applies dynamics by making the bottom dead center position of the piston adjustable rather than fixed. This allows the opening cross-section of the inlet opening to be varied dynamically by changing the piston position, enabling versatile operation without adding structural complexity. The control device adjusts the bottom dead center position to optimize scavenging for different operating conditions.
Solution Approach 2:
The invention changes the parameter of piston position (bottom dead center location) to control the opening cross-section of the inlet opening. By varying this parameter, the system can adjust the amount of fresh gas and exhaust gas flow without modifying the physical structure or adding openings, thus resolving the contradiction between versatility and complexity.
2Quantity of substance
If the opening duration of the inlet opening is increased, then the amount of fresh gas supplied is improved, but the residual gas content increases which may lead to unfavorable operating points
Solution Approach 1:
The control device monitors the operating conditions and adjusts the bottom dead center position and opening duration accordingly. This feedback mechanism ensures that the amount of fresh gas supplied is optimized while maintaining appropriate residual gas content for stable combustion, preventing unfavorable operating points.
Solution Approach 2:
The system dynamically adjusts both the opening duration and the bottom dead center position based on operating conditions. This dynamic control allows the system to optimize fresh gas supply while simultaneously managing residual gas content to maintain combustion stability, resolving the contradiction between quantity and reliability.
3Productivity
If the bottom dead center position is adjusted to optimize scavenging, then the gas exchange efficiency is improved, but the timing of combustion events may be affected
Solution Approach 1:
The control device uses feedback to monitor both gas exchange efficiency and combustion timing. When the bottom dead center position is adjusted to optimize scavenging, the control device compensates for timing shifts by adjusting other parameters such as injection timing or ignition timing, ensuring that combustion events occur at the optimal moment.
Solution Approach 2:
The system performs preliminary adjustment of the bottom dead center position and opening duration before combustion occurs. This allows the gas exchange to be optimized in advance, and the control device can then coordinate combustion events to occur at the correct timing, preventing time loss.
Data Source
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AI summary
Free-piston device and method for operation, having a piston (24) which is arranged so as to be movable linearly to an fro, and having a combustion chamber (40) which is delimited by a wall (38) and in which there are formed a first opening (42) and a second opening (44) which comprise an inlet opening (46) and an outlet opening (48), wherein the movement of the at least one piston device (18) can be controlled by means of a control device (78). To ensure that an operating point of the free-piston device can be set in a more versatile manner, the bottom dead centre of the piston (24) is adjustable, wherein, when the piston (24) assumes the bottom dead centre, the at least one first opening (42) is partially freed and partially blocked in order to set a free cross-sectional area. Alternatively, an opening period (112, 114) can be set while the piston (24) at least partially frees the at least one first opening (42) when passing through the bottom dead centre, also with maintaining of the position of the bottom dead centre.