Diesel engine waste heat graded utilization system and control method thereof

Abstract

The invention relates to a diesel engine waste heat grading utilization system which mainly comprises a diesel engine, a control unit, an air inlet supercharger and a turbine expansion power generation all-in-one machine. The air inlet supercharger is arranged on an air inlet pipeline of the diesel engine; the turbine expansion power generation all-in-one machine is arranged in the organic working medium circulation pipeline system; a first air inlet heat exchanger and a second air inlet heat exchanger are arranged on a downstream air inlet pipeline of the air inlet supercharger; the organic working medium circulating pipeline system further comprises a condenser, a working medium pump, a preheating heat exchanger, a cooling water heat exchanger and a high-temperature heat exchanger which are connected in sequence; an outlet pipeline of the high-temperature heat exchanger is connected with inlets of the first expansion turbine and the second expansion turbine through a first branch pipeline and a second branch pipeline respectively, and outlet pipelines of the first expansion turbine and the second expansion turbine are converged and then connected with an inlet of the condenser. According to the diesel engine waste heat graded utilization system and the control method thereof, the heat recovery efficiency of supercharged inlet air of the diesel engine can be improved through graded waste heat utilization, meanwhile, through a corresponding control strategy, the waste heat utilization efficiency is improved, and stable operation and high-efficiency output of the diesel engine under different working conditions are guaranteed.

Description

Technical Field

[0001] The present invention relates to the field of diesel engines, and in particular to a diesel engine waste heat graded utilization system and a control method thereof, which improves the energy consumption utilization rate of the diesel engine through efficient waste heat recovery. Background Art

[0002] The development and utilization of energy is a global issue, which is directly related to the survival and development of mankind. Since the birth of diesel engines, driven by the market, diesel engines have been developing towards high power, high reliability, low emissions, and low fuel consumption. Many new technologies have been applied to diesel engines, such as turbocharging and intercooling, high-pressure injection, electronic control, combustion chamber structure optimization, exhaust gas recirculation, exhaust gas post-treatment, structural optimization design, etc. With the reduction of oil resources and the improvement of environmental protection requirements, the requirements for diesel engine economy and emission performance have become more stringent. Although the application of the above new technologies helps to improve the performance of diesel engines, their high costs have also led to the continuous increase in diesel engine production costs and maintenance costs.

[0003] The exhaust gas energy of diesel engines accounts for about 18% of the total heat of fuel, and the usable part is about 12%, which is about 1 / 4 of the effective power of diesel engines. How to improve the utilization rate of energy, reduce the emission of diesel engine exhaust gas, and protect the environment on which human beings depend for survival is still the focus of development. At present, the utilization of waste heat of diesel engine exhaust gas is mainly that the exhaust gas turbocharger converts the exhaust gas energy into the pressure of scavenging air to improve the power and efficiency of diesel engines. This makes the utilization of waste heat of diesel engines not only insufficient but also unreasonable.

[0004] The existing waste heat utilization usually utilizes the cooling water and exhaust waste heat of the diesel engine. For example, the Chinese patent with publication number CN105587427A discloses an engine waste heat recovery power generation system based on the organic Rankine cycle. It includes: an endothermic subsystem, a turbine generator subsystem and a recovery subsystem; wherein the endothermic subsystem sequentially exchanges heat with the engine cylinder jacket water and the flue gas, absorbs the waste heat of the engine cylinder jacket water and the flue gas, and generates superheated organic working fluid vapor; the turbine generator subsystem, whose air inlet is connected to the air outlet of the endothermic subsystem, the turbine generator subsystem receives the superheated organic working fluid vapor generated by the endothermic subsystem, and uses the superheated organic working fluid vapor to generate electricity; the recovery subsystem, whose air inlet is connected to the air outlet of the turbine generator subsystem, receives the organic working fluid vapor after work, cools the organic working fluid vapor after work into liquid organic working fluid, and provides the liquid organic working fluid to the endothermic subsystem. Although the waste heat recovery power generation system of the above patent can utilize the waste heat of the engine, with high energy utilization rate, good recovery effect, and reduced irreversible loss of the system, most existing diesel engines use turbocharging systems, and the temperature of the intake air is high after being supercharged. Intercoolers are usually used for short-term cooling. At this time, the heat of the intake air after supercharging is lost in vain, resulting in energy waste.

[0005] However, the temperature and heat of the supercharged intake air are relatively small compared to the temperature and heat of the exhaust gas, making it difficult to utilize and fully recover. In addition, the operating conditions of the diesel engine are complex. In the process of waste heat utilization, waste heat recovery is usually performed directly without considering the operating conditions of the diesel engine. In this case, the waste heat recovery system will affect the operating conditions of the diesel engine, making the operating conditions of the diesel engine unstable, reducing the efficiency of the diesel engine, and affecting the power output of the diesel engine.

[0006] Therefore, it is urgent to invent a diesel engine waste heat graded utilization system and its control method to solve the above-mentioned technical problems, make full use of the waste heat of the diesel engine, improve the waste heat utilization efficiency, and at the same time adjust the waste heat utilization control strategy according to the operating conditions of the diesel engine, so as to ensure the stable operation and high-efficiency output of the diesel engine on the basis of making full use of the waste heat. Summary of the invention

[0007] The present invention provides a diesel engine waste heat graded utilization system and a control method thereof, which can improve the heat recovery efficiency of the diesel engine's supercharged intake air through graded waste heat utilization, and at the same time improve the waste heat utilization efficiency through corresponding control strategies, thereby ensuring stable operation and high-efficiency output of the diesel engine under different working conditions.

[0008] To achieve the above object, the technical solution adopted by the present invention is: A diesel engine waste heat graded utilization system mainly comprises: a diesel engine, a control unit, an intake supercharger, and a turbine expansion generator; wherein the turbine expansion generator comprises a first expansion turbine, a second expansion turbine and a generator; the diesel engine has an intake pipeline and an exhaust pipeline, and the intake supercharger is arranged on the intake pipeline of the diesel engine; the turbine expansion generator is arranged in an organic working medium circulation pipeline system; a first intake air heat exchanger and a second intake air heat exchanger are arranged on the intake pipeline downstream of the intake supercharger; the organic working medium circulation pipeline system also comprises a condenser, a working medium pump, a preheating heat exchanger, a cooling water heat exchanger and a high-temperature heat exchanger, and the condenser, the working medium pump, the preheating heat exchanger, the cooling water heat exchanger and the high-temperature heat exchanger are connected in sequence along the circulation direction of the organic working medium; the outlet pipeline of the high-temperature heat exchanger passes through the first sub- The branch pipeline and the second branch pipeline are respectively connected to the inlet of the first expansion turbine and the second expansion turbine, and the outlet pipelines of the first expansion turbine and the second expansion turbine are merged and connected to the inlet of the condenser; a high-temperature intake air heat exchange pipeline is arranged between the first intake air heat exchanger and the high-temperature heat exchanger, a low-temperature intake air heat exchange pipeline is arranged between the second intake air heat exchanger and the preheating heat exchanger, and a cooling water heat exchange pipeline is arranged between the cooling water heat exchanger and the diesel engine water jacket; a first heat exchange valve is arranged on the high-temperature intake air heat exchange pipeline, a second heat exchange valve is arranged on the low-temperature intake air heat exchange pipeline, and a third heat exchange valve is arranged on the cooling water heat exchange pipeline. The first branch pipeline and the second branch pipeline are respectively provided with a first control valve and a second control valve, and the first heat exchange valve, the second heat exchange valve, the third heat exchange valve, the first control valve and the second control valve are all connected to the control unit.

[0009] Furthermore, the first expansion turbine, the second expansion turbine and the generator of the turbine expansion generator are integrated into one to form an integrated turbine generator set; the first expansion turbine and the second expansion turbine are symmetrical to each other.

[0010] Furthermore, the generator is a magnetic levitation permanent magnet generator, which includes: a first radial permanent magnet levitation bearing, a second radial permanent magnet levitation bearing, a permanent magnet motor winding, a rotating shaft, and a permanent magnet motor rotor; the two ends of the rotating shaft are respectively connected to the first expansion turbine and the second expansion turbine, and the permanent magnet motor rotor is arranged on the rotating shaft and located between the first expansion turbine and the second expansion turbine; a first radial permanent magnet levitation bearing is arranged on the rotating shaft between the permanent magnet motor rotor and the first expansion turbine, and a second radial permanent magnet levitation bearing is arranged on the rotating shaft between the permanent magnet motor rotor and the second expansion turbine.

[0011] Furthermore, an exhaust heat exchanger is arranged on the exhaust pipe of the diesel engine, an overheat heat exchanger is arranged downstream of the high-temperature heat exchanger and upstream of the first branch pipe and the second branch pipe, an overheat heat exchange pipe is arranged between the exhaust heat exchanger and the overheat heat exchanger, a fourth heat exchange valve is arranged on the overheat heat exchange pipe, and the fourth heat exchange valve is connected to the control unit.

[0012] Furthermore, a heat recovery heat exchanger is arranged between the confluence point of the outlet pipelines of the first expansion turbine and the second expansion turbine and the condenser, a residual temperature heat exchanger is arranged on the organic working fluid pipeline between the working fluid pump and the preheating heat exchanger, a heat recovery heat exchange pipeline is arranged between the heat recovery heat exchanger and the residual temperature heat exchanger, a fifth heat exchange valve is arranged on the heat recovery heat exchange pipeline, and the fifth heat exchange valve is connected to the control unit.

[0013] A control method for a diesel engine waste heat graded utilization system, characterized in that it comprises the following steps: S1: measuring the working environment temperature of the diesel engine or the intake air temperature upstream of the intake supercharger, and controlling the opening or closing of the first heat exchange valve and the second heat exchange valve according to the working environment temperature of the diesel engine or the intake air temperature upstream of the intake supercharger; S2: judging whether the diesel engine is in the starting and warming-up condition. If the diesel engine is in the starting and warming-up condition, the control unit controls the third heat exchange valve to close, and at the same time controls the first control valve or the second control valve to close, so that only one of the first expansion turbine and the second expansion turbine is involved in the operation; S3: judging whether the diesel engine is in an idle or low-load condition. If the diesel engine is in an idle or low-load condition, the control unit controls the first control valve or the second control valve to close, so that only one of the first expansion turbine and the second expansion turbine is involved in the operation; S4: judging whether the diesel engine is in a medium load or high load condition. If the diesel engine is in a medium load or high load condition, the control unit controls all heat exchange valves and control valves to open; Steps S1 to S5 are repeated at regular intervals.

[0014] Further, if the ambient temperature or the intake air temperature upstream of the intake supercharger is greater than or equal to 10 degrees Celsius, the control unit controls the first control valve or the second control valve to be opened; if the ambient temperature or the intake air temperature upstream of the intake supercharger is between -5 and 10 degrees Celsius, the control unit controls the first control valve to be opened and the second control valve to be closed; if the ambient temperature or the intake air temperature upstream of the intake supercharger is less than or equal to -5 degrees Celsius, the control unit controls both the first control valve and the second control valve to be closed.

[0015] Further, in step S1, the control unit controls both the first control valve and the second control valve to be closed, and at the same time, the control unit controls the first control valve or the second control valve to be closed, so that only one of the first expansion turbine and the second expansion turbine is involved in the operation.

[0016] Further, in step S2, it is determined whether the diesel engine is in a starting and warming-up condition according to the diesel engine cooling water temperature. If the diesel engine cooling water temperature is lower than 80 degrees Celsius, it is determined that the diesel engine is in a starting and warming-up condition.

[0017] Further, in step S3, if the load of the diesel engine is lower than 30%, it is determined that the diesel engine is in a low load condition.

[0018] Further, if an exhaust heat exchanger is provided on the exhaust pipe of the diesel engine, a superheat heat exchanger is provided downstream of the high-temperature heat exchanger and upstream of the first branch pipe and the second branch pipe, a superheat heat exchange pipe is provided between the exhaust heat exchanger and the superheat heat exchanger, a fourth heat exchange valve is provided on the superheat heat exchange pipe, and the fourth heat exchange valve is connected to the control unit; then the control method is replaced by executing only the S1-S2 cycle.

[0019] Compared with the prior art, the present invention has the following advantages and technical effects: The present invention provides a first intake heat exchanger and a second intake heat exchanger on the downstream intake pipe of the intake supercharger, thereby realizing the graded utilization of the heat of the pressurized air. On the one hand, it improves the utilization rate of waste heat, and on the other hand, it further reduces the temperature of the pressurized air, which can increase the intake volume of the diesel engine and improve the combustion efficiency and power output of the diesel engine.

[0020] The first expansion turbine, the second expansion turbine and the generator of the turbine expansion generator are integrated into one to form an integrated turbine generator set. At the same time, magnetic bearings are used to integrate the permanent magnet motor and the impeller, eliminating the gearbox and eliminating the dynamic sealing problem.

[0021] The present invention adopts two expansion turbines, a first expansion turbine and a second expansion turbine, which can be controlled according to the specific working environment and working conditions of the diesel engine, so that only one of the first expansion turbine and the second expansion turbine is involved in the work, which can avoid the energy loss caused by the simultaneous operation of two turbo expanders under low waste heat or low load, improve the working efficiency of the turbo expander, and effectively improve the waste heat utilization efficiency.

[0022] The present invention provides a control method for a diesel engine waste heat graded utilization system, which controls the heat exchange of waste heat utilization according to the specific working environment and working conditions of the diesel engine, ensures the normal operation of the diesel engine while utilizing the waste heat, and ensures the stable operation and high-efficiency output of the diesel engine under different environments and working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific implementation methods or the description of the prior art. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 It is a structural schematic diagram of a first embodiment of a diesel engine waste heat classification utilization system of the present invention; Figure 2 It is a structural schematic diagram of a second embodiment of the diesel engine waste heat classification utilization system of the present invention; Figure 3 It is a structural schematic diagram of a third embodiment of the diesel engine waste heat classification utilization system of the present invention; Figure 4 It is a structural schematic diagram of a turbine expansion power generation integrated machine of the present invention; Figure 5 It is a flow chart of the control method of the diesel engine waste heat graded utilization system of the present invention.

[0025] Reference numerals in the figures: Diesel engine 1, control unit 2, intake supercharger 3, first expansion turbine 4, second expansion turbine 5, generator 6, condenser 7, working fluid pump 8, first intake heat exchanger 11, second intake heat exchanger 12, high temperature heat exchanger 13, preheating heat exchanger 14, cooling water heat exchanger 15, exhaust heat exchanger 16, superheating heat exchanger 17, residual heat exchanger 18, regenerative heat exchanger 19, first control valve 21, second control valve 22, first heat exchange valve 23, second heat exchange valve 24, third heat exchange valve 25, fourth heat exchange valve 26, fifth heat exchange valve 27, first radial permanent magnetic suspension bearing 61, second radial permanent magnetic suspension bearing 62, rotating shaft 63, permanent magnet motor rotor 64. DETAILED DESCRIPTION

[0026] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0027] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the present invention.

[0028] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on the present invention, it should be understood by those skilled in the art that an aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number and aspect described herein can be used to implement the device and / or practice the method. In addition, other structures and / or functionalities other than one or more of the aspects described herein can be used to implement this device and / or practice this method.

[0029] It should also be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention. The drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0030] Additionally, in the following description, specific details are provided to facilitate a thorough understanding of the examples. However, it will be understood by those skilled in the art that the examples can be practiced without these specific details.

[0031] At the same time, in this specification, descriptions involving orientations, such as up, down, left, right, front, back, inside, outside, longitudinal, lateral, vertical, horizontal, etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the drawings and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. Example

[0032] like Figure 1 As shown, the diesel engine waste heat graded utilization system of the present invention mainly includes: a diesel engine 1, a control unit 2, an intake supercharger 3, and a turbine expansion generator integrated machine; wherein the turbine expansion generator integrated machine includes a first expansion turbine 4, a second expansion turbine 5 and a generator 6.

[0033] The diesel engine 1 has an intake pipeline and an exhaust pipeline, and the intake supercharger 3 is arranged on the intake pipeline of the diesel engine 1. A first intake heat exchanger 11 and a second intake heat exchanger 12 are arranged on the intake pipeline downstream of the intake supercharger 3. The turbine expansion power generation integrated machine is arranged in an organic working fluid circulation pipeline system, and the organic working fluid circulation pipeline system also includes a condenser 7, a working fluid pump 8, a preheating heat exchanger 14, a cooling water heat exchanger 15 and a high-temperature heat exchanger 13. The condenser 7, the working fluid pump 8, the preheating heat exchanger 14, the cooling water heat exchanger 15 and the high-temperature heat exchanger 13 are connected in sequence along the circulation direction of the organic working fluid. The outlet pipeline of the high-temperature heat exchanger 13 is connected to the inlet of the first expansion turbine 4 and the second expansion turbine 5 respectively through the first branch pipeline and the second branch pipeline, and the outlet pipelines of the first expansion turbine 4 and the second expansion turbine 5 are connected to the inlet of the condenser after merging.

[0034] A high-temperature intake heat exchange pipeline is provided between the first intake heat exchanger 11 and the high-temperature heat exchanger 13, a low-temperature intake heat exchange pipeline is provided between the second intake heat exchanger 12 and the preheating heat exchanger 14, and a cooling water heat exchange pipeline is provided between the cooling water heat exchanger 15 and the diesel engine water jacket. A first heat exchange valve 23 is provided on the high-temperature intake heat exchange pipeline, a second heat exchange valve 24 is provided on the low-temperature intake heat exchange pipeline, a third heat exchange valve 25 is provided on the cooling water heat exchange pipeline, a first branch pipeline and a second branch pipeline are provided with a first control valve 21 and a second control valve 22 respectively, and the first heat exchange valve 23, the second heat exchange valve 24, the third heat exchange valve 25, the first control valve 21 and the second control valve 22 are all connected to the control unit 2.

[0035] Normally, the temperature of the compressed air at the outlet of the air intake supercharger 3 is about 200 degrees Celsius, and the temperature of the cooling water of the diesel engine water jacket is about 90 degrees Celsius. The temperature of the compressed air at the outlet of the air intake supercharger 3 will drop to about 60 degrees Celsius after one heat exchange, and the compressed air at this time still has a certain amount of heat. Therefore, the present invention adopts the first air intake heat exchanger 11 and the second air intake heat exchanger 12 to perform graded heat exchange on the compressed air, and further heat exchanges the compressed air at the outlet of the first air intake heat exchanger 11 through the second air intake heat exchanger 12, which improves the waste heat utilization rate on the one hand, and further reduces the temperature of the compressed air on the other hand, which can increase the intake volume of the diesel engine and improve the combustion efficiency and power output of the diesel engine.

[0036] Since the temperature of the supercharged air after heat exchange in the first air intake heat exchanger 11 is lower than the temperature of the diesel water jacket cooling water, the heat exchange between the second air intake heat exchanger 12 and the preheating heat exchanger 14 in the organic working fluid circulation pipeline system preliminarily preheats the organic working fluid output from the working fluid pump. The preheated organic working fluid enters the cooling water heat exchanger 15 to exchange heat with the cooling water at a higher temperature to further increase the temperature. The organic working fluid whose temperature is further increased after heat exchange with the cooling water enters the high-temperature heat exchanger 13 to receive the heat transferred by the high-temperature supercharged air, and then enters the turbine expansion generator to expand and do work and drive the generator to generate electricity. The expanded organic working fluid enters the condenser 7 to condense, cools down in the condenser 7 to become a liquid organic working fluid, and then enters the working fluid pump 8. The working fluid pump 8 pressurizes the liquid organic working fluid and then transports the organic working fluid to the preheating heat exchanger 14 for the next cycle.

[0037] Preferably, the first expansion turbine 4, the second expansion turbine 5 and the generator 6 of the turbine expansion power generator are integrated into one to form an integrated turbine generator set. The first expansion turbine 4 and the second expansion turbine 5 are symmetrical to each other. The generator 6 is a magnetic levitation permanent magnet generator, which includes: a first radial permanent magnet suspension bearing 61, a second radial permanent magnet suspension bearing 62, a permanent magnet motor winding (not shown), a rotating shaft 63, and a permanent magnet motor rotor 64. The two ends of the rotating shaft 63 are respectively connected to the first expansion turbine 4 and the second expansion turbine 5, and the permanent magnet motor rotor 64 is arranged on the rotating shaft 63 and located between the first expansion turbine 4 and the second expansion turbine 5. A first radial permanent magnet suspension bearing 61 is arranged on the rotating shaft 63 between the permanent magnet motor rotor 64 and the first expansion turbine 4, and a second radial permanent magnet suspension bearing 62 is arranged on the rotating shaft 63 between the permanent magnet motor rotor 64 and the second expansion turbine 5.

[0038] The first expansion turbine, the second expansion turbine and the generator of the turbine expansion generator are integrated into one to form an integrated turbine generator set. At the same time, magnetic bearings are used to integrate the permanent magnet motor and the impeller, eliminating the gearbox and eliminating the dynamic sealing problem.

[0039] The organic working medium expands and performs work in the first expansion turbine 4 and the second expansion turbine 5, and drives the rotating shaft 63 and the permanent magnet motor rotor 64 to rotate through the first expansion turbine 4 and the second expansion turbine 5. The permanent magnet motor winding cuts the magnetic field lines of the rotating permanent magnet motor rotor to generate electrical energy for power generation, which drives the first expansion turbine 4 and the second expansion turbine 5 to rotate and perform work. The organic working medium is discharged from the outlets of the first expansion turbine 4 and the second expansion turbine 5. Example

[0040] like Figure 2As shown, on the basis of embodiment 1, in order to further improve the waste heat utilization rate and the working capacity of the organic working fluid, an exhaust heat exchanger 16 is arranged on the exhaust pipe of the diesel engine, and an overheating heat exchanger 17 is arranged downstream of the high-temperature heat exchanger 13 and upstream of the first branch pipe and the second branch pipe. An overheating heat exchange pipeline is arranged between the exhaust heat exchanger 16 and the overheating heat exchanger 17, and a fourth heat exchange valve 26 is arranged on the overheating heat exchange pipeline, and the fourth heat exchange valve 26 is connected to the control unit 2.

[0041] The organic working fluid steam heated by the high-temperature heat exchanger 13 enters the superheat heat exchanger 17, and is further heated into superheated organic working fluid steam in the superheat heat exchanger 17 by utilizing the heat of the diesel engine exhaust. The superheated organic working fluid steam enters the first expansion turbine 4 and the second expansion turbine 5 through the first branch pipeline and the second branch pipeline to perform work, thereby driving the turbine expansion generator to generate electricity.

[0042] In this embodiment, the exhaust heat exchanger 16 and the superheat heat exchanger 17 are provided to fully utilize the exhaust waste heat of the diesel engine, and the organic working fluid steam is further heated into superheated organic working fluid steam in the organic working fluid cycle, thereby improving the waste heat utilization rate and the working capacity of the organic working fluid. Example

[0043] like Figure 3 As shown, on the basis of the second embodiment, a heat recovery heat exchanger 19 is arranged between the confluence point of the outlet pipelines of the first expansion turbine 4 and the second expansion turbine 5 and the condenser 7, a residual temperature heat exchanger 18 is arranged on the organic working fluid pipeline between the working fluid pump 8 and the preheating heat exchanger 14, a heat recovery heat exchange pipeline is arranged between the heat recovery heat exchanger 19 and the residual temperature heat exchanger 18, a fifth heat exchange valve 27 is arranged on the heat recovery heat exchange pipeline, and the fifth heat exchange valve 26 is connected to the control unit 2.

[0044] Since the organic working fluid steam still has a certain amount of heat after doing work in the first expansion turbine 4 and the second expansion turbine 5, directly entering the condenser 7 for condensation will result in a waste of this heat. Therefore, a heat recovery heat exchanger 19 and a residual heat exchanger 18 are set to transfer the residual heat in the organic working fluid steam after doing work in the first expansion turbine 4 and the second expansion turbine 5 to the organic working fluid at the outlet of the working fluid pump 8. The organic working fluid output by the working fluid pump 8 can be subjected to preliminary residual heat treatment, and then the organic working fluid after the preliminary residual heat treatment is transported to the preheating heat exchanger 14 for preheating.

[0045] In this embodiment, the waste heat utilization rate is further improved by providing the heat recovery heat exchanger 19 and the waste heat exchanger 18 . Example

[0046] Since the working environment and operating conditions of diesel engines vary, it is necessary to adjust the waste heat utilization control strategy according to the different working environments and operating conditions of diesel engines in order to ensure stable operation and high-efficiency output of the diesel engine while making full use of the waste heat.

[0047] To this end, the present invention provides a control method for a diesel engine waste heat graded utilization system, and the specific control is as follows: S1: measuring the working environment temperature of the diesel engine or the intake air temperature upstream of the intake supercharger, and controlling the opening or closing of the first heat exchange valve 23 and the second heat exchange valve 24 according to the working environment temperature of the diesel engine or the intake air temperature upstream of the intake supercharger.

[0048] S2: Determine whether the diesel engine is in the starting and warming-up condition. If the diesel engine is in the starting and warming-up condition, the control unit controls the third heat exchange valve 25 to close, and at the same time controls the first control valve 21 or the second control valve 22 to close.

[0049] S3: Determine whether the diesel engine is in an idle or low-load condition. If the diesel engine is in an idle or low-load condition, the control unit controls the first control valve 21 or the second control valve 22 to close.

[0050] S4: Determine whether the diesel engine is in a medium load or high load condition. If the diesel engine is in a medium load or high load condition, the control unit controls all heat exchange valves and control valves to open.

[0051] S1-S5 are repeated at regular intervals.

[0052] Preferably, in step S1, if the ambient temperature or the intake air temperature upstream of the intake supercharger is greater than or equal to 10 degrees Celsius, the control unit controls the first control valve 21 or the second control valve 22 to open; if the ambient temperature or the intake air temperature upstream of the intake supercharger is between -5 and 10 degrees Celsius, the control unit controls the first control valve 21 to open and the second control valve 22 to close; if the ambient temperature or the intake air temperature upstream of the intake supercharger is less than or equal to -5 degrees Celsius, the control unit controls the first control valve 21 or the second control valve 22 to close. When the control unit controls the first control valve 21 and the second control valve 22 to close, the control unit controls the first control valve 21 or the second control valve 22 to close, so that only one of the first expansion turbine 4 and the second expansion turbine 5 is involved in the operation. Preferably, in step S2, whether the diesel engine is in the starting and warming-up condition is determined according to the diesel engine cooling water temperature. If the diesel engine water temperature is lower than 80 degrees Celsius, it is determined that the diesel engine is in the starting and warming-up condition.

[0053] Preferably, in step S3, if the load of the diesel engine is lower than 30%, it is determined that the diesel engine is in a low-load condition.

[0054] Preferably, if an exhaust heat exchanger (16) is provided on the exhaust pipe of the diesel engine, a superheat heat exchanger (17) is provided downstream of the high-temperature heat exchanger (13) and upstream of the first branch pipe and the second branch pipe, a superheat heat exchange pipe is provided between the exhaust heat exchanger (16) and the superheat heat exchanger (17), a fourth heat exchange valve (26) is provided on the superheat heat exchange pipe, and the fourth heat exchange valve (26) is connected to the control unit (2); then the control method is replaced by executing only the S1-S2 cycle.

[0055] In S1, if the ambient temperature or the intake air temperature upstream of the intake supercharger is lower than 10 degrees Celsius, it means that the intake air temperature is low. At this time, the temperature of the air compressed by the intake compressor is usually not very high. The temperature of the compressed air after heat exchange by the first intake heat exchanger 11 is usually low, which can meet the intake needs and has little residual heat. At this time, it is not necessary to use the second intake heat exchanger for heat exchange. Therefore, the control unit controls the first heat exchange valve 23 to open and the second heat exchange valve 24 to close. If the ambient temperature or the intake air temperature upstream of the intake supercharger is lower than -5 degrees Celsius, it means that the ambient temperature is very low. If the boosted air is heat exchanged, the boosted air temperature may be too low, which is not conducive to the combustion efficiency in the diesel engine cylinder. Therefore, it is necessary to close the first heat exchange valve 23 and the second heat exchange valve 24. Due to the reduction in heat exchange, the heat of the organic working fluid that performs expansion work is less. At this time, using two turbo expanders to work will result in reduced efficiency. Therefore, the control unit controls the first control valve or the second control valve to close, so that only one of the first expansion turbine and the second expansion turbine is involved in the work.

[0056] In S2, if the diesel engine is in the starting and warming-up condition, it proves that the cooling water temperature in the diesel engine water jacket is low, and it is difficult to effectively heat the organic working fluid. In addition, the cooling water needs to keep warming during this process, and heat exchange is not suitable. Therefore, the control unit controls the third heat exchange valve 25 to close. Due to the lack of heat exchange of cooling water, the waste heat of compressed air is small, and the heat absorbed by the organic working fluid is difficult to drive two turbo expanders to work at the same time. Therefore, the control unit controls the first control valve 21 or the second control valve 22 to close, and the organic working fluid only drives one turbo expander to work, which can effectively improve the waste heat utilization efficiency.

[0057] In S3, if the diesel engine is in an idling or low-load condition, it means that the waste heat generated by the diesel engine is small, and one turbo expander is sufficient to utilize all the waste heat. Therefore, the control unit controls the first control valve 21 or the second control valve 22 to close, avoiding energy loss caused by the simultaneous operation of the two turbo expanders and improving the working efficiency of the turbo expander.

[0058] In S4, if the diesel engine is in a medium or high load condition, it means that the waste heat generated by the diesel engine is large. The control unit controls all heat exchange valves and control valves to open, so that the waste heat can be fully utilized.

[0059] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A diesel engine waste heat graded utilization system, mainly comprising: A diesel engine (1), a control unit (2), an air intake supercharger (3), and a turbine expansion generator; wherein the turbine expansion generator comprises a first expansion turbine (4), a second expansion turbine (5), and a generator (6); the diesel engine (1) has an air intake pipeline and an exhaust pipeline, and the air intake supercharger (3) is arranged on the air intake pipeline of the diesel engine (1); and the turbine expansion generator is arranged in an organic working fluid circulation pipeline system; Features: A first intake air heat exchanger (11) and a second intake air heat exchanger (12) are arranged on the intake pipeline downstream of the intake supercharger (3); the organic working fluid circulation pipeline system further comprises a condenser (7), a working fluid pump (8), a preheating heat exchanger (14), a cooling water heat exchanger (15) and a high-temperature heat exchanger (13); the condenser (7), the working fluid pump (8), the preheating heat exchanger (14), the cooling water heat exchanger (15) and the high-temperature heat exchanger (13) are connected in sequence along the circulation direction of the organic working fluid; the outlet pipeline of the high-temperature heat exchanger (13) is connected to the inlet of the first expansion turbine (4) and the second expansion turbine (5) respectively through a first branch pipeline and a second branch pipeline, and the outlet pipelines of the first expansion turbine (4) and the second expansion turbine (5) are connected to the inlet of the condenser after merging; A high-temperature intake heat exchange pipeline is provided between the first intake heat exchanger (11) and the high-temperature heat exchanger (13), a low-temperature intake heat exchange pipeline is provided between the second intake heat exchanger (12) and the preheating heat exchanger (14), and a cooling water heat exchange pipeline is provided between the cooling water heat exchanger (15) and the water jacket of the diesel engine; A first heat exchange valve (23) is provided on the high-temperature intake air heat exchange pipeline, a second heat exchange valve (24) is provided on the low-temperature intake air heat exchange pipeline, a third heat exchange valve (25) is provided on the cooling water heat exchange pipeline, a first control valve (21) and a second control valve (22) are provided on the first branch pipeline and the second branch pipeline, respectively, and the first heat exchange valve (23), the second heat exchange valve (24), the third heat exchange valve (25), the first control valve (21) and the second control valve (22) are all connected to the control unit (2).

2. A diesel engine waste heat graded utilization system according to claim 1, characterized in that: The first expansion turbine (4), the second expansion turbine (5) and the generator (6) of the turbine expansion generator are integrated into one body to form an integrated turbine generator set; the first expansion turbine (4) and the second expansion turbine (5) are symmetrical to each other.

3. A diesel engine waste heat graded utilization system according to claim 2, characterized in that: The generator (6) is a magnetic suspension permanent magnet generator, comprising: a first radial permanent magnet suspension bearing (61), a second radial permanent magnet suspension bearing (62), a permanent magnet motor winding, a rotating shaft (63), and a permanent magnet motor rotor (64); the two ends of the rotating shaft (63) are respectively connected to the first expansion turbine (4) and the second expansion turbine (5); the permanent magnet motor rotor (64) is arranged on the rotating shaft (63) and located between the first expansion turbine (4) and the second expansion turbine (5); the first radial permanent magnet suspension bearing (61) is arranged on the rotating shaft (63) between the permanent magnet motor rotor (64) and the first expansion turbine (4), and the second radial permanent magnet suspension bearing (62) is arranged on the rotating shaft (63) between the permanent magnet motor rotor (64) and the second expansion turbine (5).

4. A diesel engine waste heat graded utilization system according to claim 1, characterized in that: An exhaust heat exchanger (16) is provided on the exhaust pipeline of the diesel engine, an overheat heat exchanger (17) is provided downstream of the high-temperature heat exchanger (13) and upstream of the first branch pipeline and the second branch pipeline, an overheat heat exchange pipeline is provided between the exhaust heat exchanger (16) and the overheat heat exchanger (17), a fourth heat exchange valve (26) is provided on the overheat heat exchange pipeline, and the fourth heat exchange valve (26) is connected to the control unit (2).

5. A diesel engine waste heat graded utilization system according to claim 1, characterized in that: A regenerative heat exchanger (19) is provided between the junction of the outlet pipelines of the first expansion turbine (4) and the second expansion turbine (5) and the condenser (7); a residual heat exchanger (18) is provided on the organic working fluid pipeline between the working fluid pump (8) and the preheating heat exchanger (14); a regenerative heat exchange pipeline is provided between the regenerative heat exchanger (19) and the residual heat exchanger (18); a fifth heat exchange valve (27) is provided on the regenerative heat exchange pipeline; and the fifth heat exchange valve (27) is connected to the control unit (2).

6. The control method of a diesel engine waste heat graded utilization system according to claim 1, characterized in that: The steps include: S1: measuring the working environment temperature of the diesel engine or the intake air temperature upstream of the intake supercharger, and controlling the opening or closing of the first heat exchange valve (23) and the second heat exchange valve (24) according to the working environment temperature of the diesel engine or the intake air temperature upstream of the intake supercharger; S2: determining whether the diesel engine is in a starting and warming-up condition; if the diesel engine is in a starting and warming-up condition, the control unit controls the third heat exchange valve (25) to close, and at the same time controls the first control valve (21) or the second control valve (22) to close, so that only one of the first expansion turbine (4) and the second expansion turbine (5) is put into operation; S3: determining whether the diesel engine is in an idling or low-load condition. If the diesel engine is in an idling or low-load condition, the control unit controls the first control valve (21) or the second control valve (22) to close, so that only one of the first expansion turbine (4) and the second expansion turbine (5) is put into operation; S4: determining whether the diesel engine is in a medium load or high load condition; if the diesel engine is in a medium load or high load condition, the control unit controls the first control valve (21), the second control valve (22), the first heat exchange valve (23), the second heat exchange valve (24), and the third heat exchange valve (25) to open; Steps S1 to S5 are repeated at regular intervals.

7. The control method of a diesel engine waste heat graded utilization system according to claim 6, characterized in that: In step S1, if the ambient temperature or the intake air temperature upstream of the intake supercharger is greater than or equal to 10 degrees Celsius, the control unit controls the first control valve (21) or the second control valve (22) to be opened; if the ambient temperature or the intake air temperature upstream of the intake supercharger is between -5 and 10 degrees Celsius, the control unit controls the first control valve (21) to be opened and the second control valve (22) to be closed; if the ambient temperature or the intake air temperature upstream of the intake supercharger is less than or equal to -5 degrees Celsius, the control unit controls the first control valve (21) and the second control valve (22) to be closed.

8. The control method of a diesel engine waste heat graded utilization system according to claim 7, characterized in that: In step S1, the control unit controls both the first control valve (21) and the second control valve (22) to be closed. At the same time, the control unit controls the first control valve (21) or the second control valve (22) to be closed, so that only one of the first expansion turbine (4) and the second expansion turbine (5) is put into operation.

9. The control method of a diesel engine waste heat graded utilization system according to claim 6, characterized in that: In step S2, whether the diesel engine is in the starting and warming-up condition is determined according to the diesel engine cooling water temperature. If the diesel engine cooling water temperature is lower than 80 degrees Celsius, it is determined that the diesel engine is in the starting and warming-up condition.

10. The control method of a diesel engine waste heat graded utilization system according to claim 6, characterized in that: In step S3, if the load of the diesel engine is lower than 30%, it is determined that the diesel engine is in a low load condition.

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