Patent Publication Number: US-2013236334-A1

Title: Double-screw liquid pump

Description:
BACKGROUND OF THE PRESENT INVENTION 
     1. Field of Invention 
     The present invention relates to the field of Organic Rankin Cycle (ORC) technology, specifically to an ORC power generation system, and more specifically to a double-screw liquid pump of the ORC power generation system. 
     2. Description of Related Arts 
     Referring to  FIG. 1 ,  FIG. 1  is a typical ORC, which includes an expander  1 ′, a generator  2 ′, an evaporator  3 ′, a liquid pump  4 ′ and a condenser  5 ′. 
     A low-temperature and low-pressure liquid refrigerant is pressurized in the liquid pump  4 ′, and then enters the evaporator  3 ′ to be evaporated through heating until the refrigerant becomes an overheated gas (high temperature and high pressure). The overheated gas enters the expander  1 ′ to work through expansion, so as to drive the generator  2 ′ to generate power. After working, the low-temperature and low-pressure gas enters the condenser  5 ′ and is condensed to liquid, and then flows back into the liquid pump  4 ′, thus completing a cycle. 
     Most of the existing liquid pumps are open-type gear pumps or centrifugal pumps. The gear pump has the following defects: in the gear pump, one gear always drives another gear, and half of the consumed work is consumed during a driving process; meanwhile, in the ORC cycle, liquid viscosity is usually low, and the gear wears easily. The centrifugal pump has the following defect: after the centrifugal pump sucks the liquid, a pressure during the suction process is decreased, and the liquid evaporates easily, which causes efficiency of the centrifugal pump to decrease, thereby affecting efficiency of the entire ORC cycle. The open-type liquid pump has the following defect: the refrigerant leaks easily through a shaft seal. 
     SUMMARY OF THE PRESENT INVENTION 
     The technical problem to be solved by the present invention is to provide a double-screw liquid pump, in which a resistance torque of a female rotor is very small, and the liquid pump does not wear even when the liquid viscosity is very low, contributing to good reliability. 
     In order to solve the above technical problem, the present invention adopts the following technical solution. 
     A double-screw liquid pump is provided, comprising a semi-sealed or fully sealed shell, wherein the shell comprises a first cavity and a second cavity isolated from each other; a motor is disposed in the first cavity, and a main body part of a double-screw is disposed in the second cavity; at least one rotor of the double-screw is fixedly connected to a rotor of the motor, and the double-screw rotates through driving of the motor; a liquid refrigerant injection inlet and a refrigerant outlet are disposed on the first cavity, and the motor is cooled through evaporation of the liquid refrigerant; a liquid inlet and a liquid outlet are disposed on the second cavity. 
     As a preferential solution of the present invention, the double-screw comprises a male rotor and a female rotor, and a first end of the male rotor is fixedly connected to the rotor of the motor. 
     As a preferential solution of the present invention, the male rotor comprises a rotor part and a connection part which are integrally designed; the rotor part is disposed in the second cavity and coordinates with the female rotor; the connection part extends into the motor in the first cavity; the first cavity and the second cavity are isolated from each other through an isolation mechanism, so that a hole is formed between the first cavity and the second cavity; the connection part passes through the hole and enters the first cavity, and an end of the connection part away from the rotor part is fixedly connected to the rotor of the motor. 
     As a preferential solution of the present invention, a first male rotor bearing is disposed at a second end of the male rotor away from the motor, and female rotor bearings are separately disposed at two ends of the female rotor. 
     As a preferential solution of the present invention, a second male rotor bearing is disposed at the connection part and between the rotor part of the male rotor and the rotor of the motor. 
     As a preferential solution of the present invention, the connection part and an end of the second male rotor bearing close to the rotor of the motor are sealed through a shaft seal. 
     As a preferential solution of the present invention, the motor is an inverter motor or a motor with a fixed rotating speed. 
     The present invention has the following beneficial effects: in the double-screw liquid pump applied to the ORC provided in the present invention, since a resistance torque of the female rotor is very small, the liquid pump does not wear even when the liquid viscosity is very low, contributing to good reliability, and thereby improving power generation efficiency of the ORC. In addition, the semi-sealed or fully sealed shell can effectively prevent leakage of the refrigerant. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of composition of an ORC power generation system. 
         FIG. 2  is a schematic view of composition of an ORC power generation system using the present invention. 
         FIG. 3  is a sectional view of a double-screw liquid pump in a vertical direction consistent with the present invention. 
         FIG. 4  is a sectional view of a double-screw liquid pump in a horizontal direction consistent with the present invention. 
         FIG. 5  is a sectional view of the male and female motors of a double-screw liquid pump consistent with the present invention. 
     
    
    
     LIST OF REFERENCE NUMERALS 
     
         
           1 ′ Expander 
           2 ′ Generator 
           3 ′ Evaporator 
           4 ′ Liquid pump  5 ′ Condenser 
           1  Expander 
           2  Generator 
           3  Evaporator 
           4  Liquid pump 
           5  Condenser 
           401  Motor 
           402  Male rotor 
           403  Female rotor 
           4041  First male rotor bearing 
           4042  Second male rotor bearing 
           405  Female rotor bearing 
           406  Seal ring 
           407  Liquid inlet 
           408  Liquid outlet 
           409  Refrigerant injection inlet 
           410  Refrigerant outlet 
           411  Shaft seal 
       
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Exemplary embodiments of the present invention are described in detail with reference to the accompanying drawings below. 
     Embodiment  1   
     Referring to  FIG. 2 ,  FIG. 2  shows an ORC power generation system using the present invention. The ORC power generation system includes a condenser  5 , a liquid pump  4 , an evaporator  3 , an expander  1 , and a generator  2 . The main improvement of the present invention is the liquid pump  4 . In this embodiment, the liquid pump  4  is a double-screw liquid pump  4 . 
     Referring to  FIG. 3  and  FIG. 4 , the double-screw liquid pump  4  includes a semi-sealed or fully sealed shell. The shell is formed of multiple components, and a seal ring  406  is disposed at each gap between components. The shell includes a first cavity and a second cavity isolated from each other. A motor  401  is disposed in the first cavity, and a main body part of a double-screw is disposed in the second cavity. At least one rotor of the double-screw is fixedly connected to a rotor of the motor. The double-screw rotates through driving of the motor  401 . A dynamic source of the motor  401  may be from electric energy generated by the ORC power generation system. A liquid refrigerant injection inlet  409  and a refrigerant outlet  410  are disposed on the first cavity, and the motor  401  is cooled through evaporation of the liquid refrigerant. A liquid inlet  407  and a liquid outlet  408  are disposed on the second cavity. The motor may be an inverter motor or a motor of a fixed rotating speed, and definitely may be an ordinary motor. 
     The double-screw liquid pump includes a male rotor  402 , and a female rotor  403 . A first end of the male rotor  402  is fixedly connected to the rotor of the motor  401 . The male rotor  402  includes a rotor part and a connection part which are integrally designed. The rotor part is disposed in the second cavity and coordinates with the female rotor  403 . The connection part extends into the motor  401  in the first cavity. The first cavity and the second cavity are isolated from each other through an isolation mechanism, so that a hole is formed between the first cavity and the second cavity; the connection part passes through the hole and enters the first cavity, and an end of the connection part away from the rotor part is fixedly connected to the rotor of the motor  401 . 
     A first male rotor bearing  4041  is disposed at a second end of the male rotor  402  away from the motor  401 . Female rotor bearings  405  are separately disposed at two ends of the female rotor  403 . A second male rotor bearing  4042  is disposed at the connection part and between the rotor part of the male rotor and the rotor of the motor. The connection part and an end of the second male rotor bearing  4042  close to the rotor of the motor are sealed through a shaft seal  411 . 
     In conclusion, in the fully sealed or semi-sealed double-screw liquid pump applied to the ORC power generation system provided in the present invention, since a resistance torque of the female rotor is very small, the liquid pump does not wear even when the liquid viscosity is very low, contributing to good reliability, and thereby improving power generation efficiency of the ORC. In addition, the semi-sealed or fully sealed shell can effectively prevent leakage of the refrigerant. 
     Herein, the description and application of the present invention are illustrative, and the scope of the present invention is not intended to be limited to the above embodiments. Variations and changes to the embodiments disclosed herein are possible. Replacement made to the embodiments and equivalent parts are well-known to persons skilled in the art. It should be known to persons skilled in the art that, the present invention can be implemented in other forms, structures, arrangements, ratios and through other components, materials, and parts without departing from the script or essential features of the present invention. Other variations and changes may be made to the embodiments disclosed herein without departing from the scope and script of the present invention.