Non-Tight Flap Valve for Closed Loop Brayton Cycle Control
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Solution Overview
Problem
The existing closed loop Brayton cycle power plants face inefficiencies due to sensitivity to pressure drop and slow gas flow adjustments, leading to potential rotor damage during sudden grid load decreases, as the inventory system is too slow to balance turbine and generator torques.
Innovation Solution
The implementation of a non-tight flap valve arrangement between the heater and turbine, which can be self-closing and electronically controlled, to rapidly adjust the mass flow of working fluid and minimize pressure drop, thereby reducing the driving torque of the turbine and preventing over-speeding during generator disconnection from the grid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the inventory system is used to adjust gas flow during sudden grid load decreases, then the gas mass in the closed loop can be changed, but the response time is too slow to prevent turbine over-speeding
Solution Approach 1:
The invention segments the gas flow control function into two independent parts: the inventory system handles slow gas mass adjustments, while the new flap valve arrangement handles fast gas flow rate adjustments. This segmentation allows each subsystem to operate in its optimal response range, with the flap valve providing immediate protection against over-speeding within milliseconds without requiring changes to the inventory system.
Solution Approach 2:
The flap valve arrangement acts as an intermediary device between the heater and turbine, providing a rapid response mechanism that bridges the gap between the slow inventory system and the fast turbine dynamics. This intermediary component enables fast gas flow modulation without directly modifying the inventory system or turbine structure.
2Reliability
If the bypass control arrangement is opened to reduce turbine torque during generator disconnection, then the shaft line acceleration can be controlled, but the pressure drop in the cycle increases significantly
Solution Approach 1:
The invention extracts the fast response control function from the bypass arrangement and places it at the turbine inlet via the flap valve. This separates the protective function (rapid torque reduction) from the bypass path, allowing the bypass to remain closed or partially open, thereby maintaining cycle pressure and efficiency while still providing over-speed protection.
Solution Approach 2:
The flap valve arrangement effectively copies the protective function of the bypass system but implements it at a different location (turbine inlet rather than compressor bypass) with superior response characteristics. This copied function achieves the same safety objective with minimal impact on cycle efficiency.
3Ease of operation
If a tight valve arrangement is used to control gas flow to the turbine, then the mass flow can be precisely controlled, but the pressure drop across the valve increases reducing cycle efficiency
Solution Approach 1:
The invention changes the operational parameters of the valve by designing it to operate in a partially open position rather than fully open or closed. This partial opening position allows sufficient gas flow control precision for protective actions while minimizing the pressure drop across the valve, thus maintaining cycle efficiency.
Solution Approach 2:
The flap valve is designed to provide partial action by opening only enough to allow controlled gas flow during normal operation and closing rapidly when protection is needed. This partial action approach provides adequate control precision for safety functions without the excessive pressure drop that would result from a tightly closed valve configuration.
Data Source
AI summary
An improved closed loop Brayton cycle for a power plant is provided that includes a heater, at least one turbine, a recuperator, at least one cooler, at least one compressor, a bypass line and a flap valve arrangement in a closed circuit in which working fluid is circulated to produce electricity via a generator. Depending upon the requirement, such as, in case of gird load disconnection, speed of a shaft-line to which the turbine, the compressor and the generator are configured is also required to be reduced without any impact on the pressure drop in the cycle. For that the non-tight flap valve arrangement is configured on each conduit between the heater and the at least one turbine in a closest possible proximity to each turbine inlet.