Piston Expander Transfer Valve Assembly
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Solution Overview
Problem
Free piston expanders in Rankine cycle systems face challenges in precisely metering high pressure gas into the expansion chamber due to the difficulty in accurately timing the inlet valve event, leading to inefficiencies and non-isentropic expansion losses, especially around the piston's turnaround position where pressure variations are significant.
Innovation Solution
A piston expander with a transfer valve assembly that moves within the cylinder, allowing precise metering of high pressure gas into the expansion chamber without the need for piston position measurement, utilizing pressure differentials to control the valve's open and closed positions, thus eliminating the need for independent pressure sensing and actuation means.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If independent pressure sensing and inlet valve actuation means are used to achieve precise timing of the inlet event, then the timing accuracy is improved, but the device complexity and cost increase significantly
Solution Approach 1:
The inlet valve actuation is achieved through self-service by utilizing the existing pressure differentials within the expander system. The pressure differential between the inlet manifold and expansion chamber naturally drives the inlet event, eliminating the need for independent pressure sensing and actuation means while maintaining precise timing control
Solution Approach 2:
The patent introduces an intermediary mechanism that couples the inlet valve actuation to the piston motion profile. This intermediary allows the valve to respond to pressure changes in sync with piston position without requiring direct position sensing, thus reducing complexity while preserving timing accuracy
2Quantity of substance
If the inlet event occurs early to ensure sufficient gas quantity, then the gas quantity is improved, but the expansion efficiency decreases due to high expansion chamber pressure
Solution Approach 1:
The system employs feedback through pressure differential sensing that responds to the actual state of the expansion chamber. The inlet valve actuation is triggered when the pressure differential reaches a threshold that indicates optimal timing, ensuring both sufficient gas quantity and expansion efficiency by preventing premature opening
Solution Approach 2:
The inlet valve timing is made dynamic rather than fixed, allowing it to adapt to varying operating conditions. The valve responds to real-time pressure differential changes, automatically adjusting the inlet event timing to optimize both gas quantity and expansion efficiency for each cycle
3Loss of energy
If the inlet event occurs late to maintain expansion chamber pressure, then the expansion efficiency is improved, but the gas quantity admitted decreases significantly
Solution Approach 1:
The feedback mechanism monitors the pressure differential and triggers the inlet event at the precise moment when expansion efficiency is maximized while ensuring adequate gas quantity. The system detects when the pressure differential indicates optimal timing and actuates the valve accordingly
4Loss of energy
If a free piston expander is used to reduce friction and heat losses, then the energy efficiency is improved, but the difficulty in determining piston position increases
Solution Approach 1:
The patent replaces mechanical position sensing with a pressure-based sensing system. By monitoring pressure differentials that correlate with piston position and velocity, the system determines the optimal inlet event timing without requiring direct mechanical measurement of piston position, thus maintaining the energy efficiency benefits of the free piston design
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 solution enables precise and efficient metering of high pressure gas, reducing system complexity and cost, improving efficiency by integrating a liquid phase pump and allowing for efficient hydrogen and oxygen combustion, thereby enhancing energy recovery and storage capabilities.
Implementation Method 1
utilizing pressure differentials to control the valve's open and closed positions
Implementation Method 2
a heat to power conversion device employing a rankine thermodynamic cycle and a free piston expander
Implementation Method 3
a liquid phase working fluid is raised to a high pressure by a liquid displacement pump
Implementation Method 4
allowing for efficient hydrogen and oxygen combustion
Data Source
Figure 1
Figure 1a
Figure 1b
AI summary
A piston expander and transfer valve for the controlled metering of a pressurised working fluid into an expansion chamber as part of an energy conversion device, and in particular as part of a heat to power conversion device employing a rankine thermodynamic cycle. The piston expander comprising a cylinder having an inlet manifold connected to an aperture in the cylinder's inlet aperture, a piston movable within the cylinder, and a transfer valve assembly movable under the action of changing gas pressure in the main chamber of the piston expander.