Rankine Cycle Bypass Flow Control via Temperature Differential Sensing
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Solution Overview
Problem
Rankine cycle apparatuses face challenges in adjusting the flow rate of working fluids in bypass paths, particularly due to the high cost of pressure sensors and the risk of liquid working fluids entering expanders, which can lead to reliability issues such as thinning and insufficient lubrication.
Innovation Solution
A Rankine cycle apparatus with a bypass flow path and a pair of temperature sensors that detect temperature differences to adjust the flow rate of the working fluid, allowing for the bypassing of the expander when necessary, thereby preventing liquid working fluids from entering the expander and improving reliability without the need for expensive pressure sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pressure sensors are used to detect working fluid pressure for bypass flow path control, then the flow rate adjustment accuracy is improved, but the device cost increases
Solution Approach 1:
The patent introduces temperature sensors as intermediary elements that indirectly measure working fluid pressure through temperature detection. The temperature difference between two points in the main circuit serves as a proxy indicator for pressure conditions, eliminating the need for direct pressure sensing while maintaining control accuracy
Solution Approach 2:
The patent replaces the mechanical pressure sensor system with a thermal measurement system. By substituting pressure detection with temperature difference measurement, the system achieves the same control function without the complexity and cost associated with pressure sensors
2Productivity
If the bypass valve is kept closed to maximize power generation, then the productivity is improved, but the reliability deteriorates due to risk of liquid working fluid entering the expander
Solution Approach 1:
The patent implements a feedback control mechanism where temperature sensors continuously monitor the working fluid state, and the bypass valve is dynamically adjusted based on the detected temperature difference. When liquid working fluid is detected (indicated by insufficient temperature difference), the bypass valve opens to protect the expander, and closes when vapor state is confirmed, maximizing power generation
Solution Approach 2:
The patent transforms the bypass valve from a static component to a dynamic control element that continuously adjusts its opening degree based on real-time temperature difference measurements. This dynamic adjustment allows the system to optimize between power generation and expander protection differentially
3Reliability
If the bypass valve is opened to prevent liquid working fluid from entering the expander, then the reliability is improved, but the productivity decreases due to reduced power generation
Solution Approach 1:
The patent applies partial action by opening the bypass valve only to the extent necessary to protect the expander from liquid working fluid, rather than fully opening it. The valve opening degree is precisely controlled based on temperature difference measurements, allowing partial bypass that maintains expander reliability while minimizing impact on power generation
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
The solution enables effective adjustment of the working fluid flow rate based on temperature differences, enhancing the reliability of the Rankine cycle apparatus by preventing liquid working fluids from entering the expander and reducing operational costs associated with pressure sensor usage.
Implementation Method 1
a pair of temperature sensors that detects temperatures of the working fluid at two positions spaced from each other in a flow direction
Implementation Method 2
a heat exchange portion located in the main circuit at a position between an outlet of the expander and an inlet of the pump
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A Rankine cycle apparatus (1A) of the present disclosure includes a main circuit (10), a heat exchange portion (HX), a bypass flow path (20), a flow rate-adjusting mechanism (3), and a pair of temperature sensors (7A). The main circuit (10) is formed by an expander (11), a condenser (13), a pump (14), and an evaporator (15) that are circularly connected in this order. The heat exchange portion (HX) is located in the main circuit (10) at a position between an outlet of the expander (11) and an inlet of the pump (14). The bypass flow path (20) branches from the main circuit (10) at a position between an outlet of the evaporator (15) and an inlet of the expander (11), and joins to the main circuit (10) at a position between the outlet of the expander (11) and an inlet of the heat exchange portion (HX). The flow rate-adjusting mechanism (3) adjusts the flow rate of the working fluid in the bypass flow path (20). The pair of temperature sensors (7A) detects temperatures of the working fluid at two positions spaced from each other in a flow direction of the working fluid.