Screw Expander Liquid Pump for ORC Systems
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Solution Overview
Problem
Existing liquid pumps in ORC systems face issues such as gear wear due to low viscosity, efficiency reduction due to evaporative losses, and refrigerant leakage, leading to low power generation efficiency and reliability concerns.
Innovation Solution
A semi-sealed or fully sealed shell liquid pump with a screw expander unit and pump unit, where the screw rotors of both units are fixedly connected, allowing the pump rotor to rotate driven by the expander rotor, with isolated cavities and seal rings to prevent leakage and reduce wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a gear pump is used, then the pump can pressurize the liquid refrigerant, but the gears wear easily due to low liquid viscosity
Solution Approach 1:
The patent combines the expander and liquid pump into a single integrated unit where the expander rotor directly drives the pump rotor through a shared shaft connection. This merging eliminates the need for separate drive mechanisms and reduces component wear by using the expander's rotational motion directly to drive the pump, thereby improving reliability while maintaining power generation efficiency.
2Reliability
If a centrifugal pump is used, then the pump can pressurize the liquid refrigerant, but the liquid evaporates easily during suction causing efficiency decrease
Solution Approach 1:
The patent replaces the centrifugal pump's suction-based mechanical system with a positive displacement screw pump mechanism. The screw rotors create sealed cavities that mechanically transport liquid from inlet to outlet, eliminating the suction process that causes pressure drops and evaporation. This substitution maintains high pump efficiency while preventing liquid evaporation.
3Reliability
If an open-type liquid pump is used, then the pump can pressurize the liquid refrigerant, but the refrigerant leaks easily through the shaft seal
Solution Approach 1:
The patent merges the expander and pump into a sealed integrated unit where both rotors share common shafts and bearings housed within a single sealed casing. This consolidation eliminates external shaft seals that are prone to leakage, as the entire assembly operates as a closed system with internal bearing support, thereby preventing refrigerant leakage while reducing overall structural complexity.
4Reliability
If a motor-driven pump is used, then the pump can pressurize the liquid refrigerant, but power is consumed, decreasing power generation efficiency
Solution Approach 1:
The pump is designed to be self-driven by the expander rotor through direct mechanical coupling via shared shafts. The expander's rotational motion, generated from the refrigerant expansion process, directly drives the pump rotors without requiring external motor power. This self-service mechanism eliminates additional power consumption and maximizes the overall power generation efficiency of the ORC system.
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 enhances reliability by minimizing rotor wear and improving power generation efficiency while preventing refrigerant leakage, thus addressing the limitations of existing pumps.
Implementation Method 1
the rotor of the expander unit is fixedly connected to the rotor of the liquid pump unit, and the rotor of the liquid pump unit rotates under driving of the rotor of the expander unit
Implementation Method 2
A semi-sealed or fully sealed shell, wherein an expander unit and a liquid pump unit are disposed in the shell
Data Source
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AI summary
A liquid pump of a screw expander is disclosed, applicable to an Organic Rankin Cycle (ORC). The liquid pump of a screw expander includes a semi-sealed or fully sealed shell. An expander unit and a liquid pump unit are disposed in the shell. The expander unit includes a screw rotor, and the liquid pump unit includes a screw rotor, The rotor of the expander unit is fixedly connected to the rotor of the liquid pump unit. The rotor of the liquid pump unit rotates under driving of the rotor of the expander unit. In the liquid pump of a screw expander applied to the ORC, since a resistance torque of the female rotor is small, the liquid pump does not wear even when the liquid viscosity is low, contributing to high reliability of the liquid pump. Meanwhile, the liquid pump is driven by the screw expander, thereby further improving power generation efficiency of the ORC. In addition, the semi-sealed or fully sealed shell can effectively prevent leakage of a refrigerant.