CN108894834B - Automatic monitoring expander oil supply and return system - Google Patents

Abstract

The invention discloses an automatic monitoring expander oil supply and return system, which comprises a work circulation subsystem and an oil supply and return subsystem, wherein the work circulation subsystem comprises an expander, a condenser, a working medium pump and an evaporator which are sequentially and circularly connected, the oil supply and return subsystem comprises an oil-gas separator, an oil storage tank, an oil filter, an oil return pump, a heat regenerator, a first flow regulating valve and a second flow regulating valve which are sequentially connected, an inlet of the oil-gas separator is connected with an outlet of the expander, an outlet of the heat regenerator is connected with an inlet of the expander, one end of the first flow regulating valve is connected between an outlet of the heat regenerator and an inlet of the expander, the other end of the first flow regulating valve is connected with an inlet of the oil storage tank, and the second flow regulating valve is arranged at two ends of the heat regenerator in parallel. The invention has the advantages of simple structure, high degree of automation, simple and efficient design, small occupied space, low economic cost and great application prospect.

Description

Expander oil supply and return system with automatic monitoring

Technical field

The invention relates to the technical field of waste heat recovery, specifically an expander oil supply and return system that can be automatically monitored.

Background technique

As energy demand and energy prices continue to rise, and the environment continues to deteriorate, energy conservation and energy recovery have become national development strategies. Organic Rankine cycle (ORC), as a key technology for medium and low temperature waste heat recovery, has become a research hotspot among scholars. Among them, the expander is a key equipment of the organic Rankine cycle. Its operating performance greatly affects the cycle thermal efficiency of the system. The expander operates at high speed during the working process and requires sufficient lubricating oil to maintain its friction pair. Lubricating, cooling and taking away debris generated during the friction process. The oil supply and return system of the expander determines the working efficiency and working life of the expander to a large extent, and will also affect the operating performance and cycle thermal efficiency of the entire ORC system. Make an impact. The quality of the expander lubrication system directly determines the operating efficiency of the expander, which in turn affects the cycle efficiency of the system. The current oil supply and return system of the expander cannot accurately control the oil supply pressure, oil supply temperature and oil supply volume of the expander, and there is no special oil recovery system, resulting in poor lubrication effect of the expander. In addition, it also affects The heat exchange efficiency of the heat exchange equipment in the system is improved.

However, there is currently a lack of research on the expander oil supply and return system, and the traditional expander oil supply and return system is often relatively simple and cannot accurately monitor and control the oil supply temperature, oil supply pressure, and oil supply flow. Furthermore, affected by the separation efficiency of the oil and gas separator, after the traditional oil supply and return system of the expander reaches a certain operating time, a large amount of lubricating oil will enter and remain in other components of the ORC system (mainly the condenser, (in heat exchange components such as evaporators), which not only reduces the heat exchange efficiency of each heat exchange component, but also causes insufficient oil supply to the expander, thereby reducing the operating efficiency of the entire ORC system. When a serious oil leak occurs in the system, the traditional expander oil supply and return system cannot recycle and reuse the lubricating oil in the system loop. It can only replace the working fluid and replenish the lubricating oil, which will increase the operating cost of the ORC system. , and as the running time accumulates, the cycle efficiency of the system will gradually decrease.

In the existing technology, there is a lack of literature related to the expander lubricating oil system. The publication number is CN105888731A, and the Chinese invention patent application titled "An organic Rankine cycle single-screw expander lubrication system" discloses an organic Rankine cycle single-screw expander lubrication system, which utilizes organic Rankine refrigerant and lubrication The oil mixture can be divided into gaseous working fluid and liquid lubricating oil in the evaporator to complete the lubrication system of the organic Rankine cycle single-screw expander. The publication number is CN101194084A, and the Chinese invention patent application titled "Expander Lubrication in Steam Power System" discloses a steam power generation system for generating power by using heat from a heat source. The system includes a closed loop for a working fluid and includes: a heat exchanger assembly for heating the fluid under pressure using heat from the source; and a separator for separating the vapor phase of the heated fluid from its liquid phase. Separation; an expander for expanding steam to generate power; a condenser for condensing the discharge fluid from the expander; a feed pump for returning the condensed fluid from the condenser to the heater; and a return path for returning the liquid phase from the separator to the heater. The liquid phase of the working fluid includes a lubricant that is soluble in or miscible with the liquid phase, and a bearing feed passage is arranged for delivering the liquid phase pressurized by the feed pump to the expander. at least one bearing of the rotating element. The common shortcomings of the above-mentioned existing technologies include: 1. The lubricating oil is directly dissolved in the working fluid, and the lubricating oil runs with the working fluid in the entire ORC system, which will cause part of the lubricating oil to be retained in each heat exchanger. It not only reduces the heat transfer coefficient of each heat exchange component, but also greatly increases the amount of lubricating oil used; 2. The oil-gas separator is set between the evaporator outlet and the expander inlet, which will cause the lubricating oil to be absorbed in the evaporator. The heat rises, and then the oil cooler is used to cool down the lubricating oil. One cold and one heat cancel each other out, resulting in a waste of energy; 3. The system lacks a lubricating oil monitoring system and cannot accurately detect whether the expander is short of oil; 4. Circulating oil pump The inability to adjust the oil supply pressure according to the inlet pressure of the expander may cause the oil pressure to be too low or too high, leading to oil supply failure; 5. The inability to control the oil supply volume of the expander will result in the expander being rich in oil or lacking oil.

Contents of the invention

In order to overcome the shortcomings mentioned in the prior art, the present invention provides an expander oil supply and return system that can be automatically monitored, which can be mainly used in the organic Rankine cycle to accurately supply oil to the expander and control the lubricating oil of the system. Monitor the volume and switch to oil recovery mode when necessary, ensuring the safe and efficient operation of the expander and improving the cycle thermal efficiency of the system.

The technical solution adopted by the present invention to solve the technical problem is: an automatically monitored expander oil supply and return system, which includes a working cycle subsystem and an oil supply and return subsystem. The working cycle subsystem includes an expander and an oil and gas separator. , condenser, working fluid pump and evaporator, the expander is connected to the oil and gas separator, the oil and gas separator is connected to the condenser, the condenser is connected to the working fluid pump, the working fluid pump is connected to the evaporator The evaporator is connected to the expander, and a recuperator is provided between the working fluid pump and the evaporator; the oil supply and return subsystem includes an oil and gas separator, an oil storage tank, an oil filter, and an oil return pump. , regenerator, first flow regulating valve and second flow regulating valve, the oil and gas separator is connected to the oil storage tank, the oil storage tank is connected to the oil filter, the oil filter is connected to the oil return pump, so The oil return pump is connected to the regenerator and the expander. The first flow regulating valve is installed at one end to be connected to the pipeline between the regenerator and the expander, and the other end is connected to the oil and gas separator and oil storage. On the pipeline branch connecting the tanks, the second flow regulating valve is installed on the pipeline branch connecting both ends of the regenerator.

It also includes a control unit, the control unit includes a controller, a photoelectric liquid level sensor, a first temperature sensor, a second temperature sensor, a first pressure sensor, a second pressure sensor, a first thermocouple and a second thermocouple; The photoelectric liquid level sensor is installed in the oil storage tank, the first temperature sensor and the first pressure sensor are installed at the inlet of the expander, and the second temperature sensor and the second pressure sensor are installed at the outlet of the expander. , the first thermocouple is installed at the bottom of the oil pool of the expander, and the second thermocouple is installed at the intersection of the first flow control valve and the regenerator; the photoelectric liquid level The sensor, the first temperature sensor, the second temperature sensor, the first pressure sensor, the second pressure sensor, the first thermocouple and the second thermocouple are connected to the controller for data control, and the controller controls the connection to the oil return pump. , the first flow regulating valve and the second flow regulating valve.

It also includes an oil leakage recovery control unit. The oil leakage recovery control unit includes a first stop valve, a second stop valve and a third stop valve. The second stop valve is installed on the evaporator and the expander. The third stop valve is installed between the expander and the oil and gas separator, and the first stop valve is installed in parallel between the inlet end of the second stop valve and the third stop valve. At the outlet end, the controller controls the connection of the first stop valve, the second stop valve and the third stop valve.

The present invention uses oil temperature superheat as the basis for determining the oil supply situation of the expander. The oil temperature superheat is defined as the lubricating oil temperature in the expander minus the saturation temperature of the working fluid under the working pressure (the high-pressure cavity expander takes the suction air pressure, the low-pressure chamber expander takes the exhaust pressure), and the oil temperature superheat is a relative value that represents the degree to which the lubricating oil exceeds its initial state. The preset oil temperature superheat degrees under different working conditions are also different. The oil temperature superheat degrees under different working conditions can be determined through the following cycle experiment method:

S1. Set up the expander air extraction device to extract the working medium/lubricating oil mixture in the expander, separate the working medium and lubricating oil, and calculate the actual solubility of the lubricating oil under this working condition;

S2. According to the operating temperature and pressure of the expander, check the solubility-pressure/temperature diagram to obtain the theoretical solubility of the lubricating oil during normal oil supply;

S3. Compare the theoretical solubility and actual solubility to determine whether the two are close (the proximity range can be determined based on the actual working medium conditions);

S4. If the two are close, calculate the oil temperature superheat, and use this as the preset oil temperature superheat of the expander under this working condition, proceed to S5; if the deviation between the two exceeds the preset value, adjust the supply voltage The amount of oil is close to the theoretical solubility, and then returns to S1;

S5. Change the operating pressure and operating temperature of the expander, return to S1, conduct a cycle experiment, and finally draw the preset oil temperature superheat-pressure/temperature diagram under each working condition.

Working process of the present invention:

1. Normal oil supply mode of the expander: When the photoelectric liquid level sensor detects that the liquid level in the oil storage tank exceeds the preset minimum liquid level, the working cycle subsystem and the oil supply and return subsystem work normally; the lubricating oil is It flows out of the oil storage tank and enters the oil pump after passing through the oil filter. The oil pump provides circulating flow force for the lubricating oil. The controller controls the oil supply pressure by changing the operating frequency of the oil pump according to the first pressure sensor (expander inlet pressure); subsequently, The lubricating oil that reaches the preset oil supply pressure is divided into two paths, one path enters the regenerator for cooling, and the other path passes through the first flow regulating valve and is mixed with the cooled lubricating oil at the outlet of the regenerator. The temperature value fed back by the second thermocouple adjusts the opening of the second flow control valve to control the flow of lubricating oil participating in heat exchange, thereby controlling the oil supply temperature; the controller is based on the preset oil temperature superheat-pressure/temperature diagram. The amount of oil supply is determined, so part of the excess lubricating oil returns to the oil storage tank through the first flow control valve, and the other part of the lubricating oil is transported to the inlet of the expander, mixed with the working fluid, and then enters the main bearing and friction of the expander. Vice; finally, the lubricating oil/working fluid mixture after lubrication enters the oil-gas separator for separation, the separated gaseous working fluid enters the condenser, and the liquid lubricating oil returns to the oil storage tank to start a new cycle;

2. Oil leakage recovery mode: When the photoelectric liquid level sensor detects that the liquid level in the oil storage tank is lower than the preset minimum liquid level, the system switches to oil leakage recovery mode: at this time, the controller controls the oil pump. When shutting down, at the same time, the first stop valve is controlled to open, the second stop valve and the third stop valve are controlled to close, and the stroke of the working medium pump is increased to increase the flow rate of the working cycle subsystem. The working fluid carrying lubricating oil passes through the condenser, working fluid pump, regenerator and evaporator in sequence at a high flow rate, and then enters the oil and gas separator after passing through the first stop valve, and the separated lubricating oil returns to the oil storage tank, and the gaseous working fluid enters the condenser and enters the next cycle. Since the expander is in a circuit-breaker state, the lubricating oil remaining in the oil supply and return subsystem will be slowly recovered into the oil storage tank.

Compared with the existing technology, the beneficial effects of the present invention are: it realizes precise control of the lubricating oil supply temperature, oil supply pressure and oil supply quantity, and ensures that the expander operates smoothly and efficiently under the appropriate oil supply quantity. , while maintaining the oil leakage at a low level; in addition, the lubricating oil remaining in other components outside the expander can be effectively recovered, which not only reduces operating costs but also improves cycle thermal efficiency; the equipment structure is simple, It has a high degree of automation, saves electricity, the entire design is simple and efficient, has good craftsmanship, takes up little space, has low economic costs, and has great engineering application prospects.

Description of the drawings

Figure 1 is an overall structural block diagram of the automatically monitored expander oil supply and return system of the present invention;

Figure 2 is a connection block diagram of the control unit of the expander oil supply and return system that can be automatically monitored according to the present invention;

Figure 3 is a flow chart of a method for determining the oil temperature superheat in the expander oil supply and return system that can be automatically monitored according to the present invention;

Figure 4 is a working schematic diagram of the normal oil supply mode of the automatically monitored expander oil supply and return system of the present invention;

Figure 5 is a schematic diagram of the operation of the oil recovery mode of the automatically monitored expander oil supply and return system of the present invention.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings, in which arrows indicate media processing directions.

The automatically monitored expander oil supply and return system of the present invention is mainly used in the organic Rankine cycle to accurately supply oil to the expander, monitor the lubricating oil amount of the system, and switch to the oil leakage recovery mode when necessary, ensuring Safe and efficient operation of the expander while improving the cycle thermal efficiency of the system. It includes a working cycle subsystem and an oil supply and return subsystem. The working cycle subsystem includes an expander 13, an oil and gas separator 2, a condenser 5, a working fluid pump 8 and an evaporator 11. The expander 13 separates oil and gas. The oil and gas separator 2 is connected to the condenser 5, the condenser 5 is connected to the working fluid pump 8, the working fluid pump 8 is connected to the evaporator 11, and the evaporator 11 is connected to the expander. 13 connections, the above components are connected in series to form a basic ORC system. A regenerator 9 is provided between the working fluid pump 8 and the evaporator 11 . The oil supply and return subsystem includes an oil and gas separator 2, an oil storage tank 3, an oil filter 6, an oil return pump 7, a regenerator 9, a first flow regulating valve FV1 and a second flow regulating valve FV2. The oil storage tank 3 is connected to the oil filter 6, the oil filter 6 is connected to the oil return pump 7, and the oil return pump 7 is connected to the regenerator 9. The expander 13 is connected, and the first flow regulating valve FV1 is installed at one end to be connected to the pipeline between the regenerator 9 and the expander 13, and at the other end to be connected to the pipeline between the oil and gas separator 2 and the oil storage tank 3. On pipe branches where pipes are connected. The second flow regulating valve FV2 is installed on the pipeline branch connected to both ends of the regenerator 9 . The regenerator 9 has a heat exchanger. The regenerator 9 is provided with a working medium channel and a lubricating oil channel. The two ends of the lubricating oil channel are connected to the oil return pump 7 and the expander 13 respectively. The two ends of the working medium channel are connected to the working fluid channel respectively. Mass pump 8 and evaporator 11. The oil return pump 7 is a variable frequency oil pump and is equipped with a frequency converter V/F. The oil supply pressure can be controlled by changing the frequency of the frequency converter. The oil-gas separator 2 is installed at the outlet of the expander 13 and is used to separate gaseous working fluid and liquid lubricating oil. The oil storage tank 3 is located after the oil and gas separator 2 and is used to store the lubricating oil of the system. The outlet of the regenerator 9 is connected to the inlet of the expander 13, and one end of the first flow regulating valve FV1 is connected between the outlet of the regenerator 9 and the inlet of the expander 13, so The other end of the first flow regulating valve FV1 is connected to the inlet of the oil storage tank 3 . The second flow regulating valve FV2 is installed in parallel at both ends of the regenerator 9 to control the amount of oil entering the regenerator 9 .

Wherein, the oil and gas separator 2 is provided with a working medium outlet and a lubricating oil outlet. The working medium outlet is connected to the condenser 5 through a working medium pipeline, and the lubricating oil outlet is connected to the oil storage tank 3; the return The heater 9 is also provided with a working medium channel and a lubricating oil channel. The two ends of the lubricating oil channel are respectively connected to the oil return pump 7 and the expander 13. The two ends of the working medium channel are respectively connected to the working medium pump. 8 and evaporator 11, the high-temperature lubricating oil enters the lubricating oil channel of the regenerator 9 and exchanges heat with the low-temperature working fluid in the working medium channel to reduce the oil temperature.

As shown in Figure 2, it also includes a control unit, which includes a controller 1, a photoelectric liquid level sensor 4, a first temperature sensor 18, a second temperature sensor 16, a first pressure sensor 15, and a second pressure sensor. 17. The first thermocouple 12 and the second thermocouple 10. The photoelectric liquid level sensor 4 is installed in the oil storage tank 3, and the photoelectric conversion principle of the photoelectric liquid level sensor 4 is used to determine whether the oil level in the oil storage tank 3 reaches the preset minimum oil level. The first temperature sensor 18 and the first pressure sensor 15 are installed at the inlet of the expander 13, and the second temperature sensor 16 and the second pressure sensor 17 are installed on the working fluid pipeline at the outlet of the expander 13. The first thermocouple 12 is installed at the bottom wall of the oil pool of the expander 13, and the second thermocouple 10 is installed at the connection intersection between the first flow regulating valve FV1 and the regenerator 9 (expander 13 (oil supply place); the photoelectric liquid level sensor 4, the first temperature sensor 18, the second temperature sensor 16, the first pressure sensor 15, the second pressure sensor 17, the first thermocouple 12 and the second thermocouple 10. The controller 1 is connected to the controller 1 through an encoder (data collector) 14. The controller 1 controls and connects the oil return pump 7, the first flow regulating valve FV1 and the second flow regulating valve FV2.

Among them, the photoelectric oil level sensor 4 is set at the preset minimum liquid level of the oil storage tank 3 and consists of an infrared transmitter and a receiving board. When the oil level is lower than the preset minimum oil level (i.e., the installation of the photoelectric oil level sensor position), the emitted light of the infrared emitter directly penetrates the air instead of the lubricating oil. This change will generate an electrical signal, indicating that the liquid level in the oil storage tank 3 is too low, and the electrical signal will be transmitted to the encoder (data collector) 14. As a starting basis for the system oil running mode; the oil return pump 7 is installed in front of the regenerator 9, and based on the pressure at the inlet of the expander 13, by changing the operating frequency of the oil return pump 7, the outlet of the oil return pump 7 can be realized The pressure at the working fluid pump changes to adapt to different working conditions; the regenerator 9 serves as a cooling heat exchanger for the lubricating oil, cooling the lubricating oil by utilizing the coldness of the working fluid at the outlet of the working fluid pump, and the heat of the lubricating oil can be used as waste heat part of it is recycled.

It also includes an oil leakage recovery control unit. The oil leakage recovery control unit includes a first stop valve SV1, a second stop valve SV2 and a third stop valve SV3. The second stop valve SV2 is installed on the evaporator 11 The third stop valve SV3 is installed on the working medium pipeline between the expander 13 and the oil and gas separator 2, and the first stop valve SV1 It is installed between the inlet end of the second stop valve SV2 and the outlet end of the third stop valve SV3, and is arranged in parallel with the second stop valve SV2 and the third stop valve SV3. The controller 1 is connected to the first stop valve SV1, the second stop valve SV2 and the third stop valve SV3. The first stop valve (which may be an electric stop valve) SV1, the second stop valve SV2 and the third stop valve (It can be a bypass valve for the working fluid circuit) SV3, oil and gas separator 2, oil storage tank 3 with photoelectric oil level sensor 4, working fluid pump 8, evaporator 11, and condenser 5 constitute the oil leakage of the entire system. Recycling subsystem.

As shown in Figure 3, the present invention uses oil temperature superheat as the basis for determining the oil supply situation of the expander. The oil temperature superheat is defined as the lubricating oil temperature in the expander minus the saturation temperature of the working medium under the working pressure (high pressure The chamber expander takes the suction pressure, and the low-pressure chamber expander takes the exhaust pressure). The oil temperature superheat is a relative value that represents the degree to which the lubricating oil exceeds its initial state. The preset oil temperature superheat degrees under different working conditions are also different. The oil temperature superheat degrees under different working conditions can be determined through the following cycle method:

S1. Set up the expander air extraction device to extract the working medium/lubricating oil mixture in the expander, separate the working medium and lubricating oil, and calculate the actual solubility of the lubricating oil under this working condition;

S2. According to the operating temperature and pressure of the expander, check the solubility-pressure/temperature diagram to obtain the theoretical solubility of the lubricating oil during normal oil supply;

S3. Compare the theoretical solubility and actual solubility and determine whether the two are close ();

S4. If the two are close, calculate the oil temperature superheat, and use this as the preset oil temperature superheat of the expander under this working condition, proceed to S5; if the deviation between the two exceeds the preset value, adjust the supply voltage The amount of oil is close to the theoretical solubility, and then returns to S1;

S5. Change the operating pressure and operating temperature of the expander, return to S1, conduct a cycle test, and finally draw the preset oil temperature superheat-pressure/temperature diagram under each working condition.

The working process of the present invention is as follows:

1. Normal oil supply mode of the expander: As shown in Figure 4, when the photoelectric liquid level sensor 4 detects that the liquid level in the oil storage tank 3 exceeds the preset minimum liquid level, the oil supply subsystem and the oil return subsystem The system works normally; the lubricating oil flows out from the oil storage tank 3 and enters the oil return pump 7 after passing through the oil filter 6. The oil return pump 7 provides circulating flow force for the lubricating oil. The controller 1 measures the expansion machine inlet according to the first pressure sensor 18. pressure) by changing the operating frequency of the oil return pump 7 to control the oil supply pressure; then, the lubricating oil reaching the preset oil supply pressure is divided into two channels, one channel enters the regenerator 9 for cooling, and the other channel passes through the first flow regulating valve FV1, And it is mixed with the cooled lubricating oil at the outlet of the regenerator 9. The controller 1 adjusts the opening of the second flow control valve FV2 according to the temperature value fed back by the second thermocouple 10, thereby controlling the lubricating oil participating in the heat exchange. flow, thereby controlling the oil supply temperature; the controller 1 determines the oil supply amount according to the preset oil temperature superheat-pressure/temperature diagram, so part of the excess lubricating oil returns to the oil storage tank 3 through the first flow control valve FV1 , the other part of the lubricating oil is transported to the entrance of the expander 13, mixed with the working fluid and then enters the main bearing and each friction pair of the expander 13; finally, the lubricating oil/working fluid mixture after completion of lubrication enters the oil and gas separator 2 for separation. , the separated gaseous working fluid enters the condenser 5, and the liquid lubricating oil returns to the oil storage tank 3 to start a new cycle.

During the operation of the expander 13 in the oil supply and return mode, the data collector 14 collects the thermocouple temperature value at the oil pool at the bottom of the expander 13 and the pressure value at the outlet/inlet of the expander (depending on the type of the expander 13, The high-pressure chamber expander 13 takes the suction pressure, and the low-pressure chamber expander 13 takes the inlet pressure) and transmits the signal to the controller 1. The controller 1 obtains the oil temperature superheat degree after calculation and processing, which is used as the basis for controlling the oil supply amount. , regulate the opening of the first flow regulating valve FV1; the oil return pump 7 uses the inlet pressure of the expander 13 as a control basis, adjust the operating frequency of the oil return pump 7 so that the oil supply pressure is slightly higher than the inlet pressure of the expander 13; the lubricating oil supply The oil temperature should be controlled between 30°C and 50°C, so the control system regulates the opening of the second flow control valve FV2 by analyzing the temperature values of the thermocouples (first thermocouple 12 and second thermocouple 10) at the oil supply point. , control the amount of lubricating oil entering the regenerator 9, and realize control of the oil supply temperature.

2. Oil leakage recovery mode: As shown in Figure 5, when the photoelectric liquid level sensor 4 detects that the liquid level in the oil storage tank 3 is lower than the preset minimum liquid level, the system switches to the oil leakage recovery mode and returns to the oil leakage recovery mode. The oil subsystem stopped working. At this time, the controller 1 controls the oil return pump 7 to stop. At the same time, it controls the first stop valve SV1 to open, the second stop valve SV2 and the third stop valve SV3 to close, and the stroke of the working medium pump 8 increases, so that the supply The flow rate of the oil subsystem increases. The working fluid carrying the lubricating oil passes through the condenser 5, the working fluid pump 8, the regenerator 9 and the evaporator 11 in sequence at a high flow rate, and then passes through the first stop valve SV1 and enters the oil and gas separator 2. The separated lubricating oil The oil returns to the oil storage tank 3, while the gaseous working fluid enters the condenser 5 and enters the next cycle. Since the expander 13 is in a disconnected state, the lubricating oil remaining in the working cycle subsystem will be slowly recovered into the oil storage tank 1 .

Compared with the existing technology, the present invention has the following advantages:

1. A regenerator is installed at the outlet of the oil return pump 5. By utilizing the cooling capacity of the working fluid at the outlet of the working fluid pump to cool down the lubricating oil, not only the oil cooler is eliminated, but also the heat released during the cooling process of the lubricating oil is It can also be recycled as part of the waste heat to preheat the working fluid before entering the evaporator, thus reducing the heat exchange area of the evaporator and improving the heat exchange efficiency;

2. The oil return pump adopts a variable frequency oil pump, which can automatically adjust the oil supply pressure and has strong adaptability to various ORC operating conditions, effectively preventing the oil supply pressure from being too low or too high due to changes in the expander inlet pressure;

3. A bypass circuit with a second flow regulating valve FV2 is installed on the regenerator, and the amount of lubricating oil entering the regenerator is controlled through the electric regulating valve on the circuit, thereby controlling the supply temperature of the lubricating oil (usually 30-50℃);

4. A bypass circuit with the first flow regulating valve FV1 is installed at the oil supply point of the expander. The controller determines the oil supply situation of the expander (rich oil/lack of oil) based on the data fed back by the data acquisition system, thereby adjusting The electric stop valve on it controls the oil supply;

5. A photoelectric oil level sensor is installed on the oil storage tank. When the oil level in the oil storage tank is lower than the set minimum oil level, the photoelectric oil level sensor will transmit the electrical signal generated to the data collector and trigger it. Call the police;

6. The oil temperature superheat is used as the basis for determining whether the expander is rich or short of oil. The oil temperature superheat is defined as the oil temperature minus the saturation temperature of the working fluid working under this pressure. It is used to indicate that the lubricating oil exceeds the initial state. temperature value. Oil temperature superheat can reasonably reflect the oil supply situation of the expander;

7. A bypass circuit with the first stop valve SV1 is installed on the expander, and oil leakage recovery is realized through three electric stop valves in the system. When the controller receives the electrical signal from the photoelectric oil level sensor, it will switch to the oil recovery mode, allowing the mixture of working fluid and lubricating oil to avoid the expander and pass directly through the bypass valve to improve lubricating oil recovery efficiency.

The above are only preferred embodiments of the present invention, and should not be used to limit the scope of the present invention. That is, all simple equivalent changes and modifications made in accordance with the patent scope of the present invention and the description of the invention are still applicable. It is within the scope covered by the patent of this invention.

Claims (5)

1. The automatic monitoring expander oil supply and return system is characterized by comprising a work circulation subsystem, an oil supply and return subsystem and a control unit, wherein the work circulation subsystem comprises an expander, an oil-gas separator, a condenser, a working medium pump and an evaporator, the expander is connected with the oil-gas separator, the oil-gas separator is connected with the condenser, the condenser is connected with the working medium pump, the working medium pump is connected with the evaporator, the evaporator is connected with the expander, and a heat regenerator is arranged between the working medium pump and the evaporator; the oil supply and return subsystem comprises an oil-gas separator, an oil storage tank, an oil filter, an oil return pump, a heat regenerator, a first flow regulating valve and a second flow regulating valve, wherein the oil-gas separator is connected with the oil storage tank, the oil storage tank is connected with the oil filter, the oil filter is connected with the oil return pump, the oil return pump is connected with the heat regenerator and the expansion machine, the first flow regulating valve is arranged on a pipeline branch connected with a pipeline between the heat regenerator and the expansion machine at one end and a pipeline between the oil-gas separator and the oil storage tank at the other end, and the second flow regulating valve is arranged on a pipeline branch connected with two ends of the heat regenerator; the control unit comprises a controller, a photoelectric liquid level sensor, a first temperature sensor, a first pressure sensor, a first thermocouple, a second thermocouple, a first stop valve, a second stop valve and a third stop valve, wherein the photoelectric liquid level sensor is arranged in the oil storage tank, the first temperature sensor and the first pressure sensor are arranged at an inlet of the expander, the first thermocouple is arranged at the bottom of an oil pool of the expander, and the second thermocouple is arranged at the joint of the first flow regulating valve and the heat regenerator; the photoelectric liquid level sensor, the first temperature sensor, the first pressure sensor, the first thermocouple and the second thermocouple are in data connection with the controller for control, the controller is in control connection with the oil return pump, the first flow regulating valve and the second flow regulating valve, the second stop valve is arranged between the evaporator and the expander, the third stop valve is arranged between the expander and the oil-gas separator, the first stop valve is arranged at the inlet end of the second stop valve and the outlet end of the third stop valve in parallel, and the controller is in control connection with the first stop valve, the second stop valve and the third stop valve;

when the photoelectric liquid level sensor detects that the liquid level in the oil storage tank exceeds a preset minimum liquid level, the working circulation subsystem and the oil supply and return subsystem work normally; the lubricating oil flows out of the oil storage tank, enters the oil pump after passing through the oil filter, and provides circulating flow power for the lubricating oil, and the controller controls the oil supply pressure by changing the operating frequency of the oil return pump according to the pressure value fed back by the first pressure sensor; then, the lubricating oil reaching the preset oil supply pressure is divided into two paths, one path enters the heat regenerator to cool, the other path passes through the first flow regulating valve and is mixed with the cooled lubricating oil at the outlet of the heat regenerator, the controller regulates the opening degree of the second flow regulating valve according to the temperature value fed back by the second thermocouple so as to control the flow rate of the lubricating oil participating in heat exchange, the redundant lubricating oil returns to the oil storage tank through the first flow regulating valve, the other part of lubricating oil is conveyed to the inlet of the expander, the lubricating oil/working medium mixture after lubrication in the expander enters the oil-gas separator to be separated, the separated gaseous working medium enters the condenser, the liquid lubricating oil returns to the oil storage tank and starts a new cycle.

2. The automatic monitoring expander oil supply and return system according to claim 1, wherein the oil-gas separator is provided with a working medium outlet and a lubricating oil outlet, the working medium outlet is connected with the condenser, and the lubricating oil outlet is connected with the oil storage tank.

3. The automatic monitoring expander oil supply and return system according to claim 1, wherein a working medium channel and a lubricating oil channel are arranged in the heat regenerator, two ends of the lubricating oil channel are respectively connected with the oil return pump and the expander, and two ends of the working medium channel are respectively connected with the working medium pump and the evaporator.

4. The automatic monitoring expander oil supply and return system according to claim 1, wherein when the photoelectric liquid level sensor detects that the liquid level in the oil storage tank is lower than a preset minimum liquid level, the controller controls the oil pump to stop, simultaneously controls the first stop valve to be opened, controls the second stop valve and the third stop valve to be closed, working medium carrying lubricating oil in the working cycle subsystem sequentially passes through the condenser, the working medium pump, the regenerator and the evaporator, then enters the oil-gas separator after passing through the first stop valve, the separated lubricating oil returns to the oil storage tank again, and the gaseous working medium enters the condenser to enter the next cycle.

5. The automatically monitorable expander oil supply and return system of claim 4 wherein the superheat of the oil temperature under different conditions is determined by the method steps of:

s1, arranging an air extractor of an expander, extracting a working medium/lubricating oil mixture in the expander, separating the working medium from the lubricating oil, and calculating the actual solubility of the lubricating oil under the working condition;

s2, according to the running temperature and pressure of the expander, searching a solubility-pressure/temperature diagram to obtain the theoretical solubility of the lubricating oil during normal oil supply;

s3, comparing the theoretical solubility with the actual solubility, and judging whether the theoretical solubility and the actual solubility are close or not;

s4, if the two are close, calculating the oil temperature superheat degree, and taking the oil temperature superheat degree as the preset oil temperature superheat degree of the expander under the working condition; if the deviation exceeds the preset value, the oil supply amount is adjusted to be close to the theoretical solubility, and the process returns to S1.