CN114370354A - Waste heat recovery system and method suitable for variable working conditions of engine - Google Patents
Waste heat recovery system and method suitable for variable working conditions of engine Download PDFInfo
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- CN114370354A CN114370354A CN202111656802.4A CN202111656802A CN114370354A CN 114370354 A CN114370354 A CN 114370354A CN 202111656802 A CN202111656802 A CN 202111656802A CN 114370354 A CN114370354 A CN 114370354A
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- 239000002918 waste heat Substances 0.000 title claims abstract description 49
- 238000011084 recovery Methods 0.000 title claims abstract description 41
- 238000000034 method Methods 0.000 title claims abstract description 22
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims abstract description 73
- 239000003546 flue gas Substances 0.000 claims abstract description 73
- 239000007789 gas Substances 0.000 claims abstract description 30
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 29
- 239000007788 liquid Substances 0.000 claims description 54
- 238000001704 evaporation Methods 0.000 claims description 15
- 230000008020 evaporation Effects 0.000 claims description 15
- 239000012071 phase Substances 0.000 claims description 14
- 230000009471 action Effects 0.000 claims description 5
- 230000001105 regulatory effect Effects 0.000 claims description 4
- 230000017525 heat dissipation Effects 0.000 claims description 3
- 239000007791 liquid phase Substances 0.000 claims description 3
- 238000011017 operating method Methods 0.000 claims 1
- 238000006243 chemical reaction Methods 0.000 abstract description 2
- 230000003044 adaptive effect Effects 0.000 abstract 1
- 238000010521 absorption reaction Methods 0.000 description 9
- 230000008569 process Effects 0.000 description 7
- 238000001816 cooling Methods 0.000 description 5
- 238000005516 engineering process Methods 0.000 description 4
- 239000002253 acid Substances 0.000 description 3
- 230000006978 adaptation Effects 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 239000000110 cooling liquid Substances 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 238000004781 supercooling Methods 0.000 description 1
- 230000001502 supplementing effect Effects 0.000 description 1
- 239000002912 waste gas Substances 0.000 description 1
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02G—HOT GAS OR COMBUSTION-PRODUCT POSITIVE-DISPLACEMENT ENGINE PLANTS; USE OF WASTE HEAT OF COMBUSTION ENGINES; NOT OTHERWISE PROVIDED FOR
- F02G5/00—Profiting from waste heat of combustion engines, not otherwise provided for
- F02G5/02—Profiting from waste heat of exhaust gases
- F02G5/04—Profiting from waste heat of exhaust gases in combination with other waste heat from combustion engines
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
- F01D15/00—Adaptations of machines or engines for special use; Combinations of engines with devices driven thereby
- F01D15/10—Adaptations for driving, or combinations with, electric generators
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
- F01K17/00—Using steam or condensate extracted or exhausted from steam engine plant
- F01K17/06—Returning energy of steam, in exchanged form, to process, e.g. use of exhaust steam for drying solid fuel or plant
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/12—Improving ICE efficiencies
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Engine Equipment That Uses Special Cycles (AREA)
- Control Of Steam Boilers And Waste-Gas Boilers (AREA)
Abstract
The invention provides a waste heat recovery system and method suitable for variable working conditions of an engine. The system is a single-stage waste heat recovery system based on organic Rankine cycle, can simultaneously recover waste heat of engine cylinder sleeve water and waste heat of engine tail gas, and particularly can realize the conversion heat area of a cycle working medium and the engine tail gas by a flue gas evaporator exchanging heat with the engine tail gas, so that the adaptive adjustment of the variable working condition of an engine is realized.
Description
Technical Field
The invention relates to a waste heat recovery system and method suitable for variable working conditions of an engine, and belongs to the technical field of engines.
Background
The engine waste heat recovery technology is a circulating device which recovers waste heat sources such as engine tail gas, cooling liquid, waste gas recirculation heat, supercharged intercooled air and the like, converts the waste heat sources into useful work through an expander and outputs the useful work. The heavy-duty commercial vehicle diesel engine can improve the thermal efficiency of the engine by 3-4% by using a waste heat recovery technology, has the technical potential of saving oil by 6-8%, and is a necessary technical means for realizing an engine with 55% thermal efficiency.
However, in the existing design method of the waste heat recovery system, the matching design of a single fixed working condition point is often performed only by selecting a common working condition point or a highest thermal efficiency point of an engine, and the sizes and heat exchange areas of heat exchangers such as an evaporator, a preheater, a condenser and the like of the designed waste heat recovery system are also fixed therewith, so that the design parameters of the waste heat recovery system can often only realize high-efficiency operation at the selected design working condition point, and the efficiency of the whole system deviating from the design working condition point can be greatly reduced or cannot meet the operation requirement. For heavy commercial vehicles, the common working condition point of the engine is medium load, the large-load waste heat is more and is basically about twice of the medium load, if the engine is matched with a waste heat recovery system according to the medium load, the redundant heat is discharged when the engine runs under the large load, and the system is prevented from running beyond indexes; if the waste heat recovery system is designed according to a large load, the problem that the operation parameters deviate from the design requirements also exists in the system operation of the medium load, and the common operation working condition of the vehicle is not in the high-efficiency operation area of the system. For example, two main considerations are given to design parameters of the flue gas evaporator, one is that the outlet temperature of the circulating working medium, namely the cold source, is not too high, the working medium is easily decomposed and deteriorated, the other is that the outlet temperature of the heat source, namely the tail gas, of the flue gas evaporator is not lower than the acid dew point temperature of 120 ℃, otherwise, sulfur-containing liquid drops are easily generated, and the tail pipe and the flue gas evaporator are corroded. The following table 1 shows the result of the heat exchange area of the flue gas evaporator designed according to the large-load working condition of the engine when the heat exchange area is operated under the medium-load working condition, the outlet temperature of the large-load tail gas is 120 ℃, the requirement of an acid dew point is met, the outlet temperature of a working medium is 130 ℃, and the maximum allowable temperature of the working medium in operation is reached at the same time, so that the heat of the tail gas can be fully utilized when the engine is under the large load; however, when the engine runs to a medium load, the heat exchange between the tail gas and the working medium is excessive because the area of the heat exchanger is overlarge, so that the outlet temperature of the tail gas is only 89 ℃, the acid dew point temperature is lower than 120 ℃, and the temperature of the working medium is overhigh and is higher than the maximum allowable temperature of the working medium. Therefore, if the flue gas evaporator is designed according to a large load, the heat exchange of the medium load is excessive, and if the flue gas heat exchanger is designed according to the medium load, the heat exchange area is insufficient during the large load, and the heat cannot be fully utilized.
TABLE 1 temperature values of cold and hot source inlet and outlet of flue gas heat exchanger with different loads
The waste heat recovery system and parts thereof are designed according to a single operation working condition point, and the problem that the waste heat recovery system cannot be compatible with the variable working conditions of the heavy diesel engine exists, so that the waste heat recovery system which can be simultaneously suitable for medium and large loads of the engine is designed, and the method has important significance for expanding the application range of the waste heat recovery technology and popularizing the technology.
Disclosure of Invention
The invention aims to provide a waste heat recovery system and a waste heat recovery method suitable for variable working conditions of an engine, which can realize the heat area conversion of a circulating working medium and engine tail gas, and further realize the adaptation to the variable working conditions of the engine.
In order to achieve the purpose, the invention is realized by the following technical scheme:
a waste heat recovery system suitable for engine variable working conditions comprises a preheater, a three-way valve, a flue gas evaporator, an expander, a heat regenerator, a condensing fan, a working medium pump, a liquid storage tank and a condenser;
the working medium inlet of the preheater is connected with the outlet of the low-temperature working medium of the heat regenerator through a pipeline, the working medium outlet of the preheater is connected with the inlet of the three-way valve, and the cylinder liner water inlet and outlet of the preheater are connected with the cylinder liner water pipeline of the engine; two outlets of the three-way valve are respectively connected with a working medium edge inlet and a middle inlet of the flue gas evaporator; a working medium outlet of the flue gas evaporator is connected with a working medium inlet of the expansion machine, and a flue gas inlet and a flue gas outlet of the flue gas evaporator are connected with an exhaust pipeline of the engine; the working medium outlet of the expander is connected with the high-temperature working medium inlet of the heat regenerator; the high-temperature working medium outlet of the heat regenerator is connected with the inlet of the condenser, and the low-temperature working medium inlet of the heat regenerator is connected with the outlet of the working medium pump; the inlet of the working medium pump is connected with the outlet of the liquid storage tank; the inlet of the liquid storage tank is connected with the outlet of the condenser; the condensing fan is installed at one side of the condenser.
Preferably, the working medium side of the flue gas evaporator is provided with two inlets and one outlet, wherein one working medium inlet is arranged at the edge of the flue gas evaporator, and one working medium inlet is arranged in the middle of the flue gas evaporator.
A waste heat recovery method suitable for engine variable working conditions comprises the following steps:
1) the working medium pump sucks liquid low-pressure working medium in the liquid storage tank, and evaporation pressure is established according to the evaporation temperature requirement of the preheater, and the pressure is the same as the outlet pressure of the working medium pump; the working medium pump pumps the flow of the working medium, and the flow of the working medium is adjusted according to the residual heat of the cylinder sleeve water of the engine and the tail gas, namely the flow of the working medium is adjusted to meet the requirement that the residual heat of the preheater and the flue gas evaporator can be completely absorbed by the working medium;
2) high-pressure liquid working medium from the working medium pump flows into the cold side of the heat regenerator to exchange heat with high-temperature exhaust steam working medium flowing out of the expander, and the liquid working medium flows into the preheater after being heated;
3) the liquid working medium flows into the cold side of the preheater and exchanges heat with the engine cylinder liner water flowing into the hot side of the preheater, the liquid working medium is heated in the preheater, the temperature is gradually increased, partial evaporation is carried out after the temperature reaches the evaporation temperature, and the liquid working medium flows out of the preheater in a gas-liquid two-phase mode; the proportion of gas phase and liquid phase of the working medium is adjusted according to the heat of the water in the engine cylinder sleeve, when the water heat of the engine cylinder sleeve is low, the proportion of the gaseous working medium is reduced, and when the water heat of the engine cylinder sleeve is high, the proportion of the cylinder sleeve water is increased;
4) after working media on the two sides of the gas and the liquid flow out of the preheater, flow distribution is carried out on a three-way valve;
5) gas-liquid two-phase working media flowing in from the two working medium inlets of the flue gas evaporator exchange heat with engine tail gas at the hot side, and the gas-liquid two-phase working media completely evaporate into a gas state after absorbing heat and then flow into the expander;
6) the working medium expands in the expander to do work, the working medium steam is changed into a low-pressure state and still keeps a gas state, and the working medium flows into the heat regenerator to be used as a heat source to continuously heat the liquid working medium on the cold side of the heat regenerator;
7) the high-temperature working medium gas flowing out of the heat regenerator enters a condenser, is blown by an external condensing fan to dissipate heat, and flows out after being cooled, condensed and supercooled in the condenser to enter a liquid storage tank.
Preferably, the calculation formula for adjusting the gas-liquid two-phase ratio of the working medium according to the heat of the cylinder liner water of the engine is as follows:
in the formula, m is the flow of the working medium, Q is the heat dissipation capacity of the water in the cylinder sleeve of the engine,
is the enthalpy value of the working medium outlet of the preheater,
is the inlet enthalpy of the preheater.
Preferably, the evaporation temperature of the working medium in the preheater is lower than the temperature of the cylinder sleeve of the engine by adjusting the outlet pressure of the working medium pump, so that the partial evaporation of the working medium in the preheater is ensured; meanwhile, the dryness of the working medium at the outlet of the preheater is adjusted, so that the preheater can adapt to the variable working conditions of the engine.
Preferably, the flow distribution of the working medium edge inlet and the middle inlet of the flue gas evaporator is realized by utilizing the working medium shunting action of the three-way valve, and the flow distribution is as follows:
when the heat of the flue gas is larger, the three-way valve is only communicated with the working medium outlet of the preheater and the edge working medium inlet of the flue gas evaporator; when the heat of the flue gas is small, the three-way valve is only communicated with the working medium outlet of the preheater and the intermediate working medium inlet of the flue gas evaporator; when the heat of the flue gas is in the middle load, the three-way valve is simultaneously communicated with a working medium outlet of the preheater and a working medium middle inlet and an edge inlet of the flue gas evaporator; and distributing the working medium flow of the edge inlet and the middle inlet of the flue gas evaporator according to the opening of the working medium gas-liquid two-phase proportional regulating valve calculated in the step three and the heat exchange quantity of the flue gas heat source.
The invention has the advantages that:
1) the phase change of the working medium in the preheater is designed into two processes of preheating and evaporation, and the sufficient heat exchange quantity of the preheater can be ensured by utilizing the heat absorption of the evaporation of the working medium;
2) the flue gas evaporator has a structure of two inlets and one outlet on the working medium side, and the heat exchange area of the working medium and the flue gas can be realized by adjusting the proportion of the working medium flowing into the edge inlet and the middle inlet;
3) the dryness of a working medium outlet in the preheater and the proportion of the working medium flowing into an edge inlet and a middle inlet of the flue gas evaporator are regulated through a three-way valve, so that the heat absorption capacity of the waste heat recovery system can be regulated to the change of a waste heat source of the engine, and the waste heat recovery system can be further adapted to the variable working conditions of the engine;
4) the waste heat recovery system provided by the invention adopts a single-stage waste heat recovery system structure, can simultaneously absorb waste heat sources with different qualities of the engine through the preheater and the flue gas evaporator, and has the advantages of simple structure, few components and high system efficiency.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention.
FIG. 1 is a schematic diagram of the connection of components of a waste heat recovery system and a working method suitable for variable working conditions of an engine.
In the figure: 1. the system comprises a preheater, a three-way valve 2, a flue gas evaporator 3, an expander 4, a heat regenerator 5, a condensing fan 6, a working medium pump 7, a liquid storage tank 8 and a condenser 9.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention aims to provide a waste heat recovery system and a working method suitable for variable working conditions of an engine, aiming at solving the problem that the waste heat recovery system in the prior art cannot simultaneously take medium load and large load into consideration.
In order to achieve the purpose, the invention provides the following technical scheme: a waste heat recovery system suitable for engine variable working conditions comprises a preheater 1, a three-way valve 2, a flue gas evaporator 3, an expander 4, a heat regenerator 5, a condensing fan 6, a working medium pump 7, a liquid storage tank 8 and a condenser 9.
The system comprises the following components:
the preheater 1 is a heat exchanger for heat exchange between a circulating working medium of the waste heat recovery system and cylinder liner water of the engine, the working medium flows through the preheater 1 to realize heat absorption and temperature rise, and the cylinder liner water flows through the preheater 2 to realize heat release and temperature reduction.
The three-way valve 2 is a 'one-inlet two-outlet' proportional control valve, and the flow distribution of two outlets can be continuously adjusted, so that the flow distribution of different outlets of the working medium can be realized.
The flue gas evaporator 3 is a heat exchanger for heat exchange between a circulating working medium of a waste heat recovery system and engine tail gas, two working medium inlets are arranged, one inlet edge inlet is arranged at the edge of the flue gas evaporator 3, the working medium flows in from the inlet and can exchange heat in the largest area, the middle inlet of the other inlet is arranged at the middle position of the flue gas evaporator, and the working medium flows in from the inlet and can utilize half of the heat exchange area; the working medium outlet is provided with one working medium, and the working medium at the two inlets flows out from a common outlet after flowing through the flue gas evaporator 3. The working medium flows through the flue gas evaporator 3 to realize heat absorption and temperature rise, and the engine tail gas flows through the flue gas evaporator 3 to realize heat release and temperature reduction. The position of the middle inlet of the working medium can be adjusted according to the size of a heat exchange area required by the waste heat recovery system when the waste heat recovery system operates in an engine under load.
The expansion machine 4 is used for converting the thermal energy of the high-pressure gaseous working medium into effective work to be output, and the expansion machine 4 can be used for driving a generator to generate electricity or directly driving an engine crankshaft through gear transmission.
The heat regenerator 5 is used for exchanging heat between the low-temperature liquid working medium flowing out of the working medium pump 7 and the high-temperature working medium exhaust steam flowing out of the expander 4, continuously recovering the heat of the high-temperature exhaust steam at the outlet of the expander 4, and improving the efficiency of the waste heat recovery system.
The condensing fan 6 is used for dissipating heat and cooling the condenser 9, so that the gaseous working medium in the condenser 9 is condensed into liquid.
The working medium pump 7 is used for driving working medium circulation to establish evaporation pressure.
The liquid storage tank 8 is used for storing liquid working media and has the function of supplementing working media for the waste heat recovery system pipeline and the heat exchanger.
The condenser 9 is an air-cooled two-phase heat exchanger and is used for condensing gaseous working media into liquid working media.
The position relation is as follows:
a working medium inlet of the preheater 1 is connected with a low-temperature working medium outlet of the heat regenerator 5 through a pipeline, a working medium outlet of the preheater 1 is connected with an inlet of the three-way valve 2, and a cylinder liner water inlet and a cylinder liner water outlet of the preheater 1 are connected with a cylinder liner water pipeline of the engine; two outlets of the three-way valve 2 are respectively connected with a working medium edge inlet and a middle inlet of the flue gas evaporator 3; a working medium outlet of the flue gas evaporator 3 is connected with a working medium inlet of the expansion machine 4, and a flue gas inlet and a flue gas outlet of the flue gas evaporator 3 are connected with an exhaust pipeline of the engine; a working medium outlet of the expander 4 is connected with a high-temperature working medium inlet of the heat regenerator 5; a high-temperature working medium outlet of the heat regenerator 5 is connected with an inlet of the condenser 9, and a low-temperature working medium inlet of the heat regenerator 5 is connected with an outlet of the working medium pump 7; the inlet of the working medium pump 7 is connected with the outlet of the liquid storage tank 8; the inlet of the liquid storage tank 8 is connected with the outlet of the condenser 9; the condensing fan 6 is installed at one side of the condenser 9 for radiating heat to the condenser 9.
The working method comprises the following steps:
the invention provides a closed circulating system consisting of all the components of a waste heat recovery system suitable for the variable working conditions of an engine, wherein a working medium circularly absorbs heat and releases heat in the circulating system, and can push an expansion machine 4 to do work after being changed into high-temperature high-pressure steam, and the working process can be decomposed as follows:
1) the first heat absorption of the working medium: the liquid working medium is pumped into the heat regenerator 5 by the working medium pump 7, and carries out primary heat exchange with the high-temperature exhaust steam from the expander 4, so that the temperature of the liquid working medium is increased and still is liquid;
2) secondary heat absorption of the working medium: the liquid working medium from the heat regenerator 5 enters the preheater 1 to exchange heat with the water in the cylinder sleeve of the engine, the working medium in the preheater 1 is designed to be a preheating process and an evaporation process at the common working condition point of the load in the engine, and the adjustment of the heat exchange quantity is realized by adjusting the dryness of the working medium at the working medium outlet of the preheater 1, so that the adaptation of the preheater 1 to the variable working condition of the engine is realized;
3) shunting working media: the working medium flowing out of the preheater 1 is divided and shunted by the three-way valve 2, and when the medium load or the low load available for the waste heat recovery system is used, the working medium only enters the middle inlet of the flue gas evaporator 3 through the shunting action of the three-way valve 2, and heat exchange is carried out by utilizing the minimum heat exchange area; when the load is maximum, the working medium only enters the edge inlet of the flue gas evaporator 3 through the shunting action of the three-way valve 2, and the heat exchange is carried out by utilizing the maximum heat exchange area; in the working condition between the medium load and the large load, part of the working medium enters the middle inlet of the flue gas evaporator 3 through the shunting action of the three-way valve 2, part of the working medium enters the edge inlet of the flue gas evaporator 3, the flow distribution of the working medium at the two inlets can be continuously changed, the contact area of the working medium and the flue gas in the flue gas evaporator 3 is actually changed through the adjustment of the flow of the working medium at the different inlets, the equivalent is that the heat exchange area of the working medium and the tail gas of the engine can be continuously changed, and the flue gas evaporator 3 can adapt to the variable working condition of the engine;
4) the third heat absorption of the working medium: working media with different dryness enter the flue gas evaporator 3, continue to exchange heat with tail gas of the engine, and become complete gas state;
5) expansion work is done: the high-temperature and high-pressure working medium which is changed into a gaseous state through three times of heat absorption enters the expander 4 to be expanded to apply work, the expansion work is changed into shaft work of the expander 4 to be output, the expanded working medium, namely high-temperature exhaust steam, has higher temperature although the pressure is reduced, and flows out of the expander 4 to enter the heat regenerator 5;
6) the working medium exhaust steam releases heat for the first time: the high-temperature exhaust steam flowing out of the expander 4 exchanges heat with the low-temperature working medium flowing out of the working medium pump 7 in the heat regenerator 5, so that the heat release and cooling processes of the high-temperature exhaust steam are realized, and the state of the high-temperature exhaust steam working medium after heat release is still in a gaseous state;
7) and (3) secondary heat release of working medium exhaust steam: the exhaust steam of the gaseous working medium flowing out of the heat regenerator 5 enters a condenser 9, air cooling and cooling are carried out through a condensing fan 6, the gaseous working medium is subjected to cooling, condensing and supercooling processes in the condenser 9, the working medium is changed into a liquid state, and the liquid state flows into a liquid storage tank 8;
8) working medium pressurization: the working medium pump 7 pumps the liquid working medium in the liquid storage tank 8, pressurizes the working medium, then pumps the working medium to the heat regenerator 5, and continues the cycle process of heat absorption and heat release of the working medium.
Claims (6)
1. A waste heat recovery system suitable for engine variable working conditions comprises a preheater (1), a three-way valve (2), a flue gas evaporator (3), an expander (4), a heat regenerator (5), a condensing fan (6), a working medium pump (7), a liquid storage tank (8) and a condenser (9);
a working medium inlet of the preheater (1) is connected with a low-temperature working medium outlet of the heat regenerator (5) through a pipeline, a working medium outlet of the preheater (1) is connected with an inlet of the three-way valve (2), and a cylinder liner water inlet and a cylinder liner water outlet of the preheater (1) are connected with a cylinder liner water pipeline of the engine; two outlets of the three-way valve (2) are respectively connected with a working medium edge inlet and a middle inlet of the flue gas evaporator (3); a working medium outlet of the flue gas evaporator (3) is connected with a working medium inlet of the expansion machine (4), and a flue gas inlet and a flue gas outlet of the flue gas evaporator (3) are connected with an exhaust pipeline of the engine; a working medium outlet of the expander (4) is connected with a high-temperature working medium inlet of the heat regenerator (5); a high-temperature working medium outlet of the heat regenerator (5) is connected with an inlet of the condenser (9), and a low-temperature working medium inlet of the heat regenerator (5) is connected with an outlet of the working medium pump (7); the inlet of the working medium pump (7) is connected with the outlet of the liquid storage tank (8); the inlet of the liquid storage tank (8) is connected with the outlet of the condenser (9); the condensing fan (6) is arranged at one side of the condenser (9).
2. The waste heat recovery system suitable for the variable working conditions of the engine as claimed in claim 1, wherein the working medium side of the flue gas evaporator (3) is provided with two inlets and one outlet, wherein one working medium inlet is arranged at the edge of the flue gas evaporator (3) and one working medium inlet is arranged in the middle of the flue gas evaporator (3).
3. A method for recovering waste heat suitable for engine variable working condition according to any one of claims 1-2, characterized by comprising the following steps:
1) the working medium pump (7) sucks the liquid low-pressure working medium in the liquid storage tank (8), and evaporation pressure is established according to the evaporation temperature requirement of the preheater (1), and the pressure is the same as the outlet pressure of the working medium pump (7); the working medium pump (7) pumps working medium flow, and the flow is adjusted according to the residual heat of the cylinder sleeve water of the engine and the tail gas, namely the working medium flow is adjusted to meet the requirement that the residual heat of the preheater (1) and the flue gas evaporator (3) can be completely absorbed by the working medium;
2) high-pressure liquid working medium from the working medium pump (7) flows into the cold side of the heat regenerator (5) and exchanges heat with high-temperature exhaust steam working medium flowing out of the expander (4), and the liquid working medium flows into the preheater (1) after being heated;
3) the liquid working medium flows into the cold side of the preheater (1) and exchanges heat with the engine cylinder liner water flowing into the hot side of the preheater (1), the liquid working medium is heated in the preheater (1), the temperature is gradually increased, partial evaporation is generated after the temperature reaches the evaporation temperature, and the liquid working medium flows out of the preheater (1) in a gas-liquid two-phase mode; the proportion of gas phase and liquid phase of the working medium is adjusted according to the heat of the water in the engine cylinder sleeve, when the water heat of the engine cylinder sleeve is low, the proportion of the gaseous working medium is reduced, and when the water heat of the engine cylinder sleeve is high, the proportion of the cylinder sleeve water is increased;
4) after working media on the two sides of the gas and the liquid flow out of the preheater (1), flow distribution is carried out on a three-way valve (2);
5) gas-liquid two-phase working media flowing in from two working medium inlets of the flue gas evaporator (3) exchange heat with engine tail gas at the hot side, and flow into the expander (4) after the gas-liquid two-phase working media absorb heat and are completely evaporated into a gas state;
6) the working medium expands in the expander (4) to do work, the working medium steam becomes a low-pressure state but still keeps a gas state, and flows into the heat regenerator (5) as a heat source to continuously heat the liquid working medium at the cold side of the heat regenerator (5);
7) high-temperature working medium gas flowing out of the heat regenerator (5) enters a condenser (9), air is blown by an external condensing fan (6) for heat dissipation, and the working medium flows out after being cooled, condensed and supercooled in the condenser (9) and enters a liquid storage tank (8).
4. The operating method of the waste heat recovery system suitable for the variable working condition of the engine as claimed in claim 3, wherein the calculation formula for adjusting the proportion of the working medium gas phase and the working medium liquid phase according to the heat of the cylinder liner water of the engine is as follows:
in the formula, m is the flow of the working medium, Q is the heat dissipation capacity of the water in the cylinder sleeve of the engine,
is the enthalpy value of the working medium outlet of the preheater,
is the inlet enthalpy of the preheater.
5. The working method of the waste heat recovery system applicable to the variable working conditions of the engine as claimed in claim 3, wherein the evaporation temperature of the working medium in the preheater (4) is lower than the temperature of the water in the cylinder sleeve of the engine by adjusting the outlet pressure of the working medium pump (7), so as to ensure that the working medium in the preheater (4) is partially evaporated; meanwhile, the dryness of the working medium at the outlet of the preheater (4) is adjusted, so that the preheater (4) can adapt to the variable working conditions of the engine.
6. The working method of the waste heat recovery system applicable to the variable working conditions of the engine as claimed in claim 3, wherein the flow distribution of the working medium edge inlet and the middle inlet of the flue gas evaporator (3) is realized by utilizing the working medium shunting action of the three-way valve (2), and the working method comprises the following specific steps:
when the heat of the flue gas is large, the three-way valve is only communicated with the working medium outlet of the preheater (1) and the edge working medium inlet of the flue gas evaporator (3); when the heat of the flue gas is small, the three-way valve is only communicated with the working medium outlet of the preheater (1) and the intermediate working medium inlet of the flue gas evaporator (3); when the heat of the flue gas is in the middle load, the three-way valve is communicated with the working medium outlet of the preheater (1) and the working medium middle inlet and the edge inlet of the flue gas evaporator (3) at the same time; and distributing the working medium flow of the edge inlet and the middle inlet of the flue gas evaporator (3) according to the opening of the working medium gas-liquid two-phase proportional regulating valve calculated in the step three and the heat exchange quantity of the flue gas heat source.
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