Engine waste heat utilization device

Abstract

The invention belongs to the technical field of engines, and relates to an engine waste heat utilization device which comprises an air cylinder, a radiator and a heat absorber, a compression cavity and an expansion cavity are formed in the air cylinder, the radiator and the heat absorber are connected with the compression cavity and the expansion cavity respectively, and the engine waste heat utilization device further comprises a discharger used for driving a working medium to flow back and forth between the expansion cavity and the compression cavity; the bypass pipe is connected with the heat absorber in parallel, a switching valve is arranged to switch a flow path of a working medium passing through the heat absorber or the bypass pipe when the working medium returns to and fro the expansion cavity, the compression cavity is provided with a one-way liquid inlet valve and a one-way liquid outlet valve, and liquid is contained in the compression cavity; the control working medium flows into the expansion cavity and flows through the heat absorber, and flows out of the expansion cavity and flows through the bypass pipe. The problems that an existing waste heat recovery system is large in size, low in conversion efficiency, poor in dynamic adaptability and high in cost are solved, efficient heat exchange and energy transfer of a working medium are achieved through the circulating design of the compression cavity and the expansion cavity and cooperative control of the bypass pipeline and the switching valve, and the waste heat utilization rate is increased.

Description

Technical Field

[0001] The present invention belongs to the technical field of engines, and more particularly, relates to an engine waste heat utilization device. Background Art

[0002] In the fields of modern commercial vehicles and construction machinery, the engine is the core component that provides power. Its main working principle is to generate heat energy by burning fuel and convert part of the heat energy into mechanical energy to drive the vehicle or equipment. However, the thermal efficiency of existing internal combustion engines is restricted by many factors. On a test bench, the maximum thermal efficiency can usually reach about 50%, but under actual operating conditions, affected by load fluctuations, environmental conditions, and the transmission system, etc., its thermal efficiency is usually only 20% - 30%.

[0003] During the combustion process, the chemical energy of the fuel is mainly consumed in the forms of mechanical energy, cooling loss, and exhaust loss, etc. Among them, the engine exhaust gas temperature is usually as high as 200 - 400°C, accounting for 30% - 40% of the total fuel energy. The heat energy carried by these exhaust gases is usually directly discharged into the environment, which not only causes a large amount of energy waste, but also increases the fuel consumption and emission pollution of the vehicle.

[0004] In order to improve the thermal efficiency of the engine and reduce fuel consumption, the prior art has proposed various waste heat recovery solutions, such as:

[0005] 1. Waste heat boiler: Some commercial vehicle and ship engines adopt waste heat boilers. The high-temperature exhaust gas is introduced into a heat exchanger, and the heat is absorbed through a water or oil medium and then used for heating or an auxiliary power system. However, this system has a complex structure and a large installation space requirement, and is not suitable for small and medium-sized vehicles.

[0006] 2. Secondary utilization of turbochargers: In some high-performance vehicles, an additional turboexpander is added to recover the exhaust gas kinetic energy and convert it into mechanical work or electrical energy. However, this solution has a low efficiency under low-load conditions, and the additional mechanical structure increases the system complexity and maintenance cost.

[0007] 3. Rankine cycle (ORC) system: Using organic working fluids (such as R245fa, R134a, etc.) for phase change heat transfer to convert the exhaust gas heat energy into power output. Although this system has been applied in some industrial fields, its application in vehicles is restricted by factors such as equipment volume, condensation heat dissipation, and economic cost.

[0008] In addition, CN103470352A discloses an automobile exhaust gas waste heat recovery device based on a Stirling engine. This device adopts the Stirling cycle principle to convert the exhaust gas waste heat into mechanical energy. However, this device still has the following problems in actual application:

[0009] 1. Complex structure and large space occupation: The Stirling engine outputs electrical energy and requires a complex system.

[0010] 2. Poor performance: The heat exchanger of the Stirling engine is approximately isothermal, while the waste heat of the exhaust gas is a variable temperature heat source. Therefore, the recovered energy is low.

[0011] 3. High manufacturing and maintenance costs: Due to the high requirements of the Stirling engine for materials and processing accuracy, the manufacturing cost is relatively high. At the same time, the repair and maintenance are relatively complex, which is not conducive to large-scale popularization and application.

[0012] In summary, the existing waste heat recovery technology solutions still have problems such as low energy conversion efficiency, large equipment volume, high cost, and poor performance in vehicle applications, which limit their wide application. Therefore, how to develop a more compact, efficient, and low-cost waste heat recovery system to further improve the thermal utilization efficiency of the engine and reduce fuel consumption is an important problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0013] In view of the above problems, the present invention provides an engine waste heat utilization device, which solves the problems of low energy conversion efficiency, large equipment volume, high cost, etc. existing in the existing waste heat recovery technology in vehicle applications. Through the cyclic design of the compression chamber and the expansion chamber and the cooperation of the bypass pipeline and the switching valve, efficient heat exchange and energy transfer of the working medium are realized, and the work output is directly provided to the cooling water flow path or the fuel supply flow path of the engine, avoiding problems such as large volume and high cost caused by the crankshaft and the motor.

[0014] The present invention provides an engine waste heat utilization device, including a cylinder, a radiator, an absorber, an ejector, a bypass pipe, and a switching valve;

[0015] A compression chamber and an expansion chamber are provided inside the cylinder, and the ejector is arranged in the cylinder for driving the working medium to flow reciprocally between the compression chamber and the expansion chamber;

[0016] The absorber is arranged in parallel with the bypass pipe;

[0017] The switching valve is arranged between the expansion chamber, the absorber, and the bypass pipe for selectively controlling the working medium to flow through the absorber or the bypass pipe;

[0018] The radiator has a first end and a second end. Its first end is in fluid communication with the compression chamber, and the second end is directly connected to the bypass pipe. The working medium enters the bypass pipe from the expansion chamber;

[0019] The absorber has a first end and a second end. Its first end is in fluid communication with the compression chamber, and the second end is in fluid communication with the expansion chamber. The working medium enters the expansion chamber from the absorber;

[0020] The bypass pipe includes a first end and a second end, the first end of which is in fluid communication with the expansion chamber, and the second end of which is in fluid communication with the compression chamber;

[0021] The compression chamber contains liquid and includes a liquid inlet valve and a liquid outlet valve, both of which are one-way valves.

[0022] In a preferred implementation, further, a tail gas heat exchanger is further included. The tail gas heat exchanger is arranged on the tail gas emission side of the engine, and the heat of the tail gas is transferred to the heat absorber through a heat transfer medium.

[0023] In a preferred implementation, further, the liquid inlet valve of the compression chamber is in communication with the oil pan of the engine to receive and guide the engine oil from the oil pan into the compression chamber. The liquid outlet valve of the compression chamber, its fluid outlet end is in communication with the engine's fuel supply pipeline to control the delivery of the liquid in the compression chamber to the fuel supply pipeline.

[0024] In a preferred implementation, further, both the heat absorber and the tail gas heat exchanger are provided with a liquid inlet and a liquid outlet, and heat exchange occurs between the heat absorber and the tail gas heat exchanger through the liquid; the liquid outlet of the heat absorber is connected to the inlet valve of the compression chamber via a fluid passage, and the liquid inlet of the tail gas heat exchanger is connected to the outlet valve of the compression chamber via a fluid passage.

[0025] In a preferred implementation, further, a bypass valve is further included. The bypass valve is configured to have at least three fluid interfaces for adjusting the distribution ratio of the liquid between different circuits, where:

[0026] The first fluid interface of the bypass valve is in fluid communication with the liquid inlet valve or the liquid outlet valve of the compression chamber to control the liquid flow path entering or exiting the compression chamber;

[0027] The second fluid interface of the bypass valve is in fluid communication with the liquid inlet of the tail gas heat exchanger for guiding the liquid into the tail gas heat exchanger for heat exchange;

[0028] The third fluid interface of the bypass valve is in fluid communication with the engine's fuel supply pipeline or the engine oil circuit of the oil pan to control the liquid entering the engine lubrication system or returning to the oil pan;

[0029] The bypass valve is also configured to dynamically adjust the flow rate ratio of the liquid passing through the second fluid interface and the third fluid interface.

[0030] In a preferred implementation, further, the heat absorber adopts a variable temperature heat absorption structure. The temperature difference between the liquid at the liquid outlet end and the liquid at the liquid inlet end of the tail gas heat exchanger is ≥150°C.

[0031] In a preferred implementation, further, a heat exchanger is further included, where the heat exchanger is configured with two independent fluid passages, namely a first flow path and a second flow path, for heat exchange and circulation of the liquid.

[0032] In a preferred implementation manner, further, the first flow path is connected to the liquid outlet of the heat absorber and the liquid inlet valve of the compression chamber, and is used to convey the thermal energy released from the heat absorber to the compression chamber to improve the preheating of the liquid inside the compression chamber;

[0033] The second flow path is connected to the liquid outlet valve of the compression chamber and the liquid inlet of the tail gas heat exchanger, and is used to introduce the liquid discharged from the compression chamber into the tail gas heat exchanger to perform heat exchange with the waste heat of the tail gas.

[0034] In a preferred implementation manner, further, a diaphragm is further included, and the diaphragm is disposed inside the compression chamber and is used to form a first fluid chamber and a second fluid chamber inside the compression chamber;

[0035] The first fluid chamber is used to accommodate the liquid, and the fluid inlet and outlet are realized through the liquid inlet valve and the liquid outlet valve;

[0036] The second fluid chamber is used to accommodate the working medium, and is connected to the expansion chamber through a pipeline to realize the circulating flow of the working medium between the expansion chamber and the compression chamber.

[0037] In a preferred implementation manner, further, a hydraulic motor is further included. The hydraulic motor is in fluid communication with the liquid outlet valve through a pipeline and is in fluid communication with the liquid inlet valve through a pipeline;

[0038] An engine cooling water pump is further included. The hydraulic motor is mechanically connected to the engine cooling water pump and is used to drive the engine cooling water pump to operate by using the hydraulic energy generated by the liquid flow;

[0039] And / or, a motor is further included. The motor is power-connected to the ejector and is used to drive the ejector to reciprocate inside the cylinder.

[0040] The beneficial effects of the present invention are:

[0041] First, the engine waste heat utilization device of the present invention realizes the variable-temperature heat absorption of the working medium and the precise heat exchange with the waste heat of the exhaust gas by setting a compression chamber and an expansion chamber in the cylinder and using an ejector to drive the working medium to flow reciprocally between the two, thereby improving the waste heat recovery efficiency. Moreover, the pressure potential energy generated after the working medium absorbs heat is transmitted to the cooling water flow path or the fuel supply flow path of the engine through a liquid, realizing the direct utilization of the potential energy, further enhancing the engine performance. In addition, it avoids problems such as large volume and high cost caused by the structure of recovering energy through the crankshaft and the motor output. Compared with the existing waste heat boilers and ORC systems, this design effectively improves the waste heat recovery efficiency, and the structure is more compact, facilitating integration into the vehicle power system with limited space. Through the bypass pipe design and the regulation of the switching valve, the working medium can precisely exchange heat with the external heat source in the heat absorber, thereby reducing heat exchange losses and improving the heat exchange efficiency. In addition, by setting a liquid in the compression chamber and equipping with a liquid inlet valve and a liquid outlet valve, the pressure potential energy generated after the working medium absorbs heat can be transmitted to the cooling water flow path or the fuel supply flow path of the engine through a liquid, realizing the direct utilization of the potential energy and further enhancing the engine performance. Compared with the prior art, the present invention significantly reduces energy losses, improves the waste heat utilization rate of the engine, and at the same time reduces additional energy consumption, making the system more economical. Compared with traditional solutions such as the Rankine cycle system and the Stirling engine, the device of the present invention has a simpler structure, reduces the dependence on high-precision manufacturing and special materials, reduces the manufacturing cost and maintenance complexity, and is more suitable for large-scale popularization and application.

[0042] Second, in a preferred implementation manner, the present invention sets a waste gas heat exchanger between the engine exhaust gas emission side and the heat absorber, enabling the effective recovery of the high-temperature waste gas emitted by the engine and transferring it to the heat absorber for heat exchange with the working medium, thereby improving the waste heat utilization efficiency.

[0043] Third, in a preferred implementation manner, the present invention realizes the direct introduction of engine oil by connecting the liquid inlet valve of the compression chamber to the oil sump of the engine, and connects it to the engine fuel supply pipeline through the liquid outlet valve, so that the pressure potential energy generated after the working medium absorbs heat is directly transferred to the engine oil, eliminating the energy conversion loss of other energy conversion methods.

[0044] Fourth, in a preferred implementation manner, the present invention sets a bypass valve to enable the dynamic adjustment of the flow rate distribution of the liquid between different circuits according to the system requirements, thereby optimizing the waste heat utilization efficiency. The multi-fluid interface design of the bypass valve enables it to flexibly control the flow path of the liquid between the compression chamber, the waste gas heat exchanger, and the engine lubrication system. When the system needs to improve the heat exchange efficiency, the liquid can be preferentially introduced into the waste gas heat exchanger for waste heat recovery, thereby increasing the liquid temperature and improving the heat exchange effect; when the engine lubrication demand increases, the bypass valve can adjust the liquid flow direction to the fuel supply pipeline to ensure stable engine oil supply and reduce the dependence on additional heat sources.

[0045] Fifth, in the preferred implementation, the heat absorber of the present invention adopts a variable-temperature heat absorption structure, reducing the heat exchange loss between the working fluid and the heat source and improving the efficiency of heat transfer. At the same time, the temperature difference between the liquid at the liquid outlet end and the liquid at the liquid inlet end of the tail gas heat exchanger is ≥150 °C, ensuring that the waste heat of the tail gas is fully recovered, improving the heat utilization rate of the heat exchanger and reducing waste heat loss.

[0046] Sixth, in the preferred implementation, the present invention improves the heat energy recovery rate, reduces energy waste and optimizes the overall performance of the engine waste heat utilization system by setting up a heat exchanger to enable the liquid to conduct efficient heat exchange and circulation in different circuits.

[0047] Seventh, in the preferred implementation, the diaphragm provided in the compression cavity of the present invention can effectively isolate the liquid from the working fluid, forming independent first and second fluid cavities, enabling the liquid and the working fluid to flow in their respective independent flow channels, avoiding the influence of the liquid on the heat exchange performance of the heat exchanger and also eliminating the problem of working fluid leakage through the liquid.

[0048] Eighth, in the preferred implementation, the present invention is mechanically connected to the engine cooling water pump by setting a hydraulic motor, enabling the hydraulic motor to directly drive the engine cooling water pump to operate by using the hydraulic energy generated during the liquid flow process, thereby realizing the drive of the cooling system without additional energy input and improving the energy utilization efficiency. At the same time, the introduction of the hydraulic motor can reduce the dependence on the mechanical energy of the engine and reduce the engine load. In addition, the driving mode of the ejector can be selected to be powered by an electric motor, enabling the ejector to perform stable reciprocating motion along the cylinder. This structure not only optimizes the power transmission mode of the waste heat utilization system but also simplifies the mechanical transmission structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 is a schematic structural diagram of the engine waste heat utilization device of Embodiment 1 of the present invention;

[0050] Figure 2 is a schematic structural diagram of the engine waste heat utilization device of Embodiment 2 of the present invention with a heat exchanger installed;

[0051] Figure 3 is a schematic structural diagram of the engine waste heat utilization device of Embodiment 3 of the present invention with a hydraulic motor and a cooling water pump installed;

[0052] Figure 4 is a schematic structural diagram of the compression cavity of the engine waste heat utilization device of Embodiment 3 of the present invention with a diaphragm installed.

[0053] Among them, 1 - cylinder; 2 - compression chamber; 3 - radiator; 4 - ejector; 5 - heat absorber; 6 - switching valve; 7 - expansion chamber; 8 - exhaust gas heat exchanger; 9 - liquid inlet valve; 10 - liquid outlet valve; 11 - engine; 12 - bypass valve; 13 - heat exchanger; 14 - hydraulic motor; 15 - bypass pipe; 16 - diaphragm; 17 - cooling water pump. Specific embodiments

[0054] In order to enable those skilled in the art to better understand the technical solutions of the present application, the following will further elaborate on the present invention in conjunction with the drawings and embodiments.

[0055] The orientation terms such as up, down, left, right, front, and back in the present application document are based on the positional relationship shown in the drawings. If the drawings are different, the corresponding positional relationships may also change accordingly. Therefore, it should not be understood as a limitation of the protection scope.

[0056] In the present application, terms such as "installed", "connected", "joined", "connected", "fixed", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, an integral connection, a mechanical connection, an electrical connection or a connection that can communicate with each other, a direct connection, or an indirect connection through an intermediate medium. It can be the connection inside two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0057] The present invention provides an engine waste heat utilization device. As a heat engine, the heat absorption end of this waste heat utilization device adopts a variable temperature heat absorption method to recover the waste heat of the engine in the form of sensible heat, thereby improving the thermal energy conversion efficiency. At the same time, the waste heat utilization device outputs high-pressure liquid without mechanical structures such as pistons and crankshafts, reducing the volume, weight, and manufacturing cost. In addition, the high-pressure liquid output by the waste heat utilization device can be directly used in the engine fuel supply flow path, eliminating the oil pump, and realizing the direct drive of the fuel supply system by the pressure potential energy of the waste heat utilization device; it can also directly exchange heat with the engine exhaust gas heat exchanger without additionally setting a liquid pump for exhaust gas heat exchange. Therefore, the engine waste heat utilization device of the present invention has the advantages of compact structure, low cost, excellent performance, and small occupied space.

[0058] It should be noted that sensible heat release refers to the heat released by a substance during the process of temperature reduction, but its phase state (solid, liquid, gas) does not change. In other words, the characteristic of sensible heat release is that sensible heat release only affects the temperature. When a substance releases sensible heat, its temperature will decrease, and the substance remains in its original state without causing phase changes such as melting, solidification, evaporation, or condensation of the substance. Common forms of sensible heat release include the heat released when a metal block cools, the heat released when high-temperature air cools in a heat exchanger, and the heat released when hot water cools down.

[0059] Example 1

[0060] Refer to the attached Figure 1 , a waste heat utilization device for an engine. The waste heat utilization device includes a cylinder 1, an ejector 4 located inside the cylinder 1, a radiator 3, and an absorber 5. A compression chamber 2 and an expansion chamber 7 are provided inside the cylinder 1, and the working fluid is located in the compression chamber 2 and the expansion chamber 7. The ejector 4 is used to drive the working fluid to flow reciprocally between the compression chamber 2 and the expansion chamber 7. The compression chamber 2 and the expansion chamber 7 of the cylinder 1 are respectively connected by two parallel bypass pipes. One of them is the bypass pipe 15, and a radiator 3 is provided on the bypass pipe 15. An absorber 5 is provided on the other bypass pipe. Specifically, the intake port of the expansion chamber 7 of the expansion chamber 7 is connected to the outlet of the absorber 5, so that the working fluid enters the expansion chamber 7 after being heated by the absorber 5; the outlet of the expansion chamber 7 is connected to the intake port of the radiator 3 through the bypass pipe 15, so that the working fluid flows out of the expansion chamber 7 to the radiator 3 for heat dissipation. A switching valve 6 is provided between the expansion chamber 7, the absorber 5, and the bypass pipe 15. The switching valve 6 is used to select whether the working fluid passes through the absorber 5 when flowing into the expansion chamber 7 and whether it passes through the bypass pipe 15 when flowing out of the expansion chamber 7 according to the cycle requirement during the reciprocating process of the working fluid between the compression chamber 2 and the expansion chamber 7. The outlet of the radiator 3 is connected to the intake port of the compression chamber 2, so that after the working fluid completes expansion in the expansion chamber 7, it is cooled by the radiator 3 and then enters the compression chamber 2; the intake port of the absorber 5 is connected to the outlet of the compression chamber 2, so that the working fluid flows from the compression chamber 2 into the absorber 5 to be heated and then enters the expansion chamber 7, and the working fluid flowing out of the expansion chamber 7 enters the radiator 3 to be cooled and then returns to the compression chamber 2 to achieve cyclic flow.

[0061] The compression chamber 2 further includes a liquid inlet and a liquid outlet. The liquid inlet valve 9 is respectively connected to the liquid inlet of the compression chamber 2 and the outlet of the absorber 5, and the liquid outlet is connected to the liquid outlet valve 10.

[0062] Liquid only exists in the compression chamber 2, and there is no liquid in the expansion chamber 7, only the working fluid (gas). The pressure of the liquid always remains balanced with the pressure of the working fluid in the compression chamber 2. When the pressure of the working fluid increases, the liquid is extruded out of the compression chamber 2 and flows out through the liquid outlet valve 10; when the pressure of the working fluid decreases, the external liquid flows into the compression chamber 2 through the liquid inlet valve 9. Therefore, the flow of the liquid is driven by the change in the pressure of the working fluid in the compression chamber 2, and the expansion chamber 7 is only used for the expansion and flow of the working fluid.

[0063] The waste heat utilization device further includes a motor, which is power-connected to the ejector 4 and is used to drive the ejector 4 to reciprocate inside the cylinder 1.

[0064] In the implementation of this application, the working fluid is a gas. Preferably, it is a gas such as helium, nitrogen, argon, air, CO2, etc., and the liquid is oil, water, ethylene glycol solution, etc., to adapt to the waste heat utilization in different scenarios.

[0065] The working principle of the system is based on the gas thermodynamic cycle and the liquid pressure balance. Since the ejector 4 reciprocates in the cylinder 1, it drives the working fluid to circulate between the compression chamber 2 and the expansion chamber 7 through the bypass pipeline, resulting in periodic changes in the temperature and pressure of the working fluid in the chamber. The temperature of the working fluid entering the expansion chamber is close to the outlet temperature of the heat absorber 5, and the working fluid entering the compression chamber is close to the outlet temperature of the radiator 3. Therefore, the temperature of the working fluid in the compression chamber 2 and the expansion chamber 7 will change, and the working fluid in the system continuously undergoes a dynamic process of working fluid absorbing heat and rising in temperature → liquid discharging → working fluid cooling → liquid supplementing. This process can be described by the ideal gas state equation and the first law of thermodynamics. The behavior of the working fluid (gas) conforms to the ideal gas state equation:

[0066] PV = mRT

[0067] Where: P is the pressure of the working fluid; V is the volume of the chamber (changing with the movement of the piston); m is the amount of substance of the working fluid (assumed to be constant); R is the gas constant; T is the temperature of the working fluid.

[0068] The pressure and temperature of the working fluid in the expansion chamber 7 and the compression chamber 2 are different:

[0069] P 2 V 2 = mRT 2

[0070] P 7 V 7 = mRT 7

[0071] Where: P 2 、V 2 、T 2 are the pressure, volume and temperature of the compression chamber 2 respectively; P 7 、V 7 、T 7 are the pressure, volume and temperature of the expansion chamber 7 respectively.

[0072] Due to the volume change caused by the movement of the ejector 4, ignoring the volume of the heat exchanger and the parallel pipes, the pressure of the working fluid is:

[0073]

[0074] Due to the volume change caused by the movement of the ejector 4, fluctuations in pressure and temperature will occur. The temperature of the working fluid in the expansion chamber is higher than that in the compression chamber. When the volume of the expansion chamber 7 increases, the overall temperature of the working fluid rises and the pressure increases; when the volume of the compression chamber 2 increases, the overall temperature of the working fluid decreases and the pressure decreases. The liquid pressure P in the compression chamber 2 L is affected by the working fluid pressure P 2 and follows Pascal's principle P L =P 2 .

[0075] Specifically, when the working fluid flows from the compression chamber 2 into the expansion chamber 7, it needs to be heated in the heat absorber 5:

[0076] Q in =nC v (T 7 -T 2 )

[0077] In the formula: Q in represents the heat absorbed by the working fluid in the heat absorber 5; C v is the specific heat capacity at constant volume of the gas.

[0078] The high-temperature and high-pressure working fluid enters the expansion chamber 7, resulting in an increase in the internal temperature T 7 and pressure P 7 in the expansion chamber 7.

[0079] Due to the increase in the working fluid pressure in the compression chamber 2, the liquid pressure in the compression chamber 2 rises synchronously P L =P 2 . When the liquid pressure P L is higher than the opening pressure of the liquid outlet valve 10, the liquid is squeezed out of the compression chamber 2, that is, P L >P outlet , and the liquid outlet valve 10 opens, and the liquid flows out of the compression chamber 2 and into the external pipeline.

[0080] After the ejector 4 moves towards the expansion chamber 7, the volume of the expansion chamber 7 shrinks, the volume in the compression chamber 2 increases, and the pressure drops. Due to P L =P 2 , the liquid pressure in the compression chamber 2 decreases accordingly. When the liquid pressure P L in the compression chamber 2 is lower than the opening pressure P inlet of the liquid inlet valve 9, that is, P L <P inlet , external liquid flows into the compression chamber 2 to supplement the liquid.

[0081] After the liquid enters the compression chamber 2, the liquid pressure in the compression chamber 2 gradually rises P L =P 2 ↑. When the liquid pressure in the compression chamber 2 rises to near the equilibrium state, that is, PL ≈P inlet The liquid inlet valve 9 is closed to prevent excessive inflow, and this process ensures that the compression chamber 2 always maintains an appropriate amount of liquid.

[0082] Furthermore, the engine waste heat utilization device further includes an exhaust gas heat exchanger 8. The exhaust gas heat exchanger 8 is in fluid communication with the exhaust gas emission system of the engine 11. The intake end of the exhaust gas heat exchanger 8 is connected to the exhaust gas outlet of the engine 11, and the exhaust end of the exhaust gas heat exchanger 8 is in communication with the exhaust pipe to ensure that the engine exhaust gas can smoothly enter the exhaust gas heat exchanger 8 for waste heat exchange. The heat exchange side of the exhaust gas heat exchanger 8 exchanges heat with the heat absorber 5 through a heat transfer medium, so that the high-temperature exhaust gas discharged from the engine 11 releases heat in the exhaust gas heat exchanger 8 and exchanges heat with the working fluid in the waste heat utilization device through the heat transfer medium, improving the temperature of the working fluid and the waste heat recovery efficiency.

[0083] Since the heat exchange area of the heat absorber 5 is small, to achieve compact and efficient heat exchange, the heat absorber 5 has a liquid inlet and a liquid outlet, and the exhaust gas heat exchanger 8 also has a liquid inlet and a liquid outlet. The heat absorber 5 and the exhaust gas heat exchanger 8 are connected through a liquid heat exchange loop to form an independent liquid heat exchange channel. The liquid outlet of the heat absorber 5 is in communication with the liquid inlet valve 9 of the compression chamber 2 for introducing the heated liquid into the compression chamber 2. The liquid inlet of the exhaust gas heat exchanger 8 is in communication with the liquid outlet valve 10 of the compression chamber 2 for receiving the liquid from the compression chamber 2 and heating it using the waste heat of the exhaust gas. The liquid absorbs the waste heat of the exhaust gas in the exhaust gas heat exchanger 8 and then flows into the heat absorber 5, transferring the heat to the working fluid, thereby further increasing the temperature of the working fluid. In addition, the flow of the liquid in the exhaust gas heat exchanger 8 and the heat absorber 5 is driven by the waste heat utilization device itself, eliminating the need for an additional liquid pump, reducing the volume of the device and the manufacturing cost. Since the liquid flow directly depends on the potential energy of the liquid in the compression chamber 2 rather than being driven by an external power pump, the overall heat exchange efficiency and energy utilization rate of the system are further improved.

[0084] Further, the liquid inlet valve 9 of the compression chamber 2 is connected to the engine oil in the oil pan of the engine 11, and the liquid outlet valve 10 is connected to the oil supply pipeline of the engine 11, so as to realize the circulating transportation of the engine oil by using the pressure fluctuation of the working medium. The liquid inlet valve 9 is used to allow the engine oil to flow from the oil pan of the engine 11 into the compression chamber 2 when the pressure in the compression chamber 2 is lower than the engine oil pressure in the oil pan. The liquid outlet valve 10 is used to allow the engine oil to flow from the compression chamber 2 into the oil supply pipeline of the engine 11 when the pressure in the compression chamber 2 is higher than the pressure in the oil supply pipeline. During the working process, when the ejector 4 moves towards the compression chamber 2, the volume of the compression chamber 2 decreases, the pressure in the chamber increases, pushing the engine oil to flow out through the liquid outlet valve 10 and enter the oil supply pipeline of the engine 11; when the ejector 4 moves towards the expansion chamber 7, the volume of the compression chamber 2 increases, resulting in a decrease in the pressure in the compression chamber 2, causing the engine oil to flow into the compression chamber 2 through the liquid inlet valve 9 under the action of the oil pan pressure, thereby realizing the circulating transportation of the engine oil. Through the above structure, the function of the oil pump is realized by the reciprocating motion of the ejector 4, and the transportation of the engine oil is completed by using the natural fluctuation of the working medium pressure, reducing the need for an independent oil pump, realizing the direct utilization of the liquid potential energy in the waste heat recovery device, improving the system energy efficiency, and at the same time reducing the installation requirement of additional power equipment and optimizing the structural design of the engine oil circuit system.

[0085] Further, the engine waste heat recovery device further includes a bypass valve 12. The bypass valve 12 has a first port, a second port, and a third port, and is used to adjust the flow distribution of the liquid between the exhaust gas heat exchanger 8 and the engine oil supply pipeline or the engine oil circuit of the oil pan, so as to optimize the liquid flow path of the waste heat recovery device, reduce the flow loss, and improve the system efficiency. Specifically, the first port is connected to the liquid inlet valve 9 or the liquid outlet valve 10 of the compression chamber 2, so that the liquid in the compression chamber 2 can enter the external circuit through the bypass valve 12. The second port is connected to the liquid inlet of the exhaust gas heat exchanger 8, so that the liquid can be heated through the exhaust gas heat exchanger 8 to improve the heat energy recovery efficiency. The third port is connected to the engine oil supply pipeline or the engine oil circuit of the oil pan of the engine 11, so that part of the liquid can directly enter the lubrication system of the engine 11, reducing the additional pipeline loss.

[0086] The bypass valve 12 can adjust the flow ratio between the second port and the third port, specifically including: when the waste heat recovery demand is high, the bypass valve 12 increases the flow of the second port, so that more liquid flows into the exhaust gas heat exchanger 8 to improve the waste heat recovery capacity. When the engine lubrication demand increases or the heat exchange demand decreases, the bypass valve 12 increases the flow of the third port, so that more liquid flows to the engine oil supply pipeline or the oil pan of the engine 11 to optimize the lubrication effect and reduce the liquid flow resistance. When the system operating condition changes, the bypass valve 12 can dynamically adjust the liquid flow distribution to achieve the optimal balance between waste heat recovery and engine lubrication and improve the overall system efficiency.

[0087] The bypass valve 12 can dynamically adjust the flow distribution of the liquid between the second port (the exhaust gas heat exchanger 8) and the third port (the engine oil circuit) according to the system operating conditions and external control signals. Specifically, it includes dynamic adjustment through a temperature sensor, feedback of the flow demand through a pressure sensor, and precise adjustment through an electric control valve. The temperature sensor T1 is arranged on the liquid inlet pipeline of the exhaust gas heat exchanger 8. When it detects that the exhaust gas temperature is relatively high and the heat exchange demand increases, the bypass valve 12 increases the flow rate of the second port, allowing more liquid to flow to the exhaust gas heat exchanger 8 to improve the heat exchange capacity. When the exhaust gas temperature is relatively low or the heat exchange capacity of the heat exchanger is saturated, the bypass valve 12 reduces the flow rate of the second port, decreasing the proportion of the liquid flowing through the exhaust gas heat exchanger. The temperature sensor T2 is arranged in the engine 11 oil circuit. When the engine oil temperature is too high and the heat dissipation demand of the lubrication system increases, the bypass valve 12 increases the flow rate of the third port, increasing the liquid flowing to the engine oil circuit to enhance the cooling effect. When the engine oil temperature is relatively low or the lubricating oil demand decreases, the bypass valve 12 reduces the flow rate of the third port to avoid excessive cooling.

[0088] The pressure sensor P1 is arranged at the first port of the bypass valve 12 (the liquid passage from the compression chamber 2). When the liquid pressure is relatively high, the bypass valve 12 dynamically adjusts the opening degree to balance the flow distribution between the second port and the third port. When the liquid pressure drops below the set value, the bypass valve 12 can preferentially ensure the critical lubrication demand and increase the engine fuel supply ratio. The pressure sensor P2 is arranged at the liquid outlet of the exhaust gas heat exchanger 8. If the pressure is too high, it indicates that the flow resistance is relatively large. The flow rate of the second port can be appropriately reduced to optimize the flow path and reduce the liquid flow loss.

[0089] In the preferred implementation mode of this application, the bypass valve 12 can adopt an electro-hydraulic proportional valve or a stepper motor control valve, receive signals from the temperature and pressure sensors, and perform dynamic adjustment in combination with the flow demand calculated by the ECU (electronic control unit) or PLC (programmable logic controller).

[0090] Through the above configuration, the bypass valve 12 can flexibly control the liquid flow direction, realize the reasonable distribution of the mass flow rate of the liquid outlet of the waste heat utilization device between the exhaust gas heat exchanger 8 and the engine oil circuit, reduce the liquid flow loss, and improve the system thermal management performance.

[0091] In a preferred implementation of the present application, the heat absorber 5 adopts a variable-temperature heat absorption method to achieve efficient heat exchange of the waste heat from the exhaust gas. To further enhance heat exchange, multiple heat exchange tube bundles or finned tubes are provided inside the heat absorber 5 to achieve temperature-stratified heat exchange. By optimizing the heat transfer coefficient in different regions, the heat exchange efficiency is optimized. Structures such as corrugated fins, perforated plates, or spiral flow channels are used to enhance the turbulence effect, extend the heat transfer path, and improve the heat transfer capacity. The system design is based on the engine exhaust gas temperature range of 200 - 300 °C, and through an inlet and outlet temperature difference ≥ 150 °C, the effective recovery of the waste heat from the exhaust gas is ensured. The temperature of the heat absorber 5 changes in a gradient along the flow direction, causing the working fluid to form a temperature slip in the expansion chamber 7.

[0092] The waste heat utilization device of the present invention adopts a high pressure ratio design, enabling the working fluid to form a large temperature slip in the expansion chamber 7 and optimizing the heat exchange efficiency. For example, the average temperature of the working fluid flowing out of the expansion chamber 7 is at least 100 °C lower than the average temperature of the working fluid flowing into the expansion chamber 7, ensuring that the waste heat utilization device has a high thermal efficiency.

[0093] To further optimize the heat exchange process, the heat absorber 5 is provided with a parallel bypass pipe 15, and the flow direction of the working fluid is adjusted through a control valve 6: the working fluid entering the expansion chamber 7 flows through the heat absorber 5 to achieve large temperature slip heat exchange; the working fluid flowing out of the expansion chamber 7 passes through the bypass pipe.

[0094] Compared with the prior art, mechanical work is usually output through a piston, crank, and connecting rod mechanism, which increases the system cost and volume. Especially for commercial vehicles and construction machinery, the space available for arranging the waste heat utilization device is small, restricting its application. To address the above problems, the present invention directly uses the pressure potential energy generated by the waste heat from the exhaust gas to drive the engine oil, replacing the traditional mechanical work output method:

[0095] 1. Reduce components such as pistons and cranks, simplify the system structure, and reduce the cost and volume.

[0096] 2. Avoid the layout limitations caused by the crankshaft connection and improve the system adaptability.

[0097] 3. Eliminate the efficiency conversion loss of the liquid pump and improve the engine oil pumping efficiency. For example, the efficiency of a traditional liquid pump is usually less than 70%, while this device directly uses the pressure potential energy to improve the overall energy efficiency.

[0098] Through this optimization scheme, the waste heat utilization device not only improves the engine performance but also reduces the intermediate links of mechanical work output in the traditional waste heat utilization method, achieving a more efficient and compact system design.

[0099] Embodiment 2

[0100] Refer to the attached drawings of the specification Figure 2, This embodiment includes all the structures of Embodiment 1, and the engine waste heat utilization device further includes a heat exchanger 13. The heat exchanger 13 has two independent flow paths, which are respectively used for heat exchange of liquids to optimize the heat recovery efficiency of the system. The first flow path of the heat exchanger 13 is connected to the liquid outlet of the heat absorber 5 and the liquid inlet valve 9 of the compression chamber 2 to ensure that the liquid is heat-exchanged before entering the compression chamber 2, reducing its temperature. The second flow path is connected to the liquid outlet valve 10 of the compression chamber 2 and the liquid inlet of the tail gas heat exchanger 8, so that the liquid discharged from the compression chamber 2 is preheated by the heat exchanger 13 before entering the tail gas heat exchanger 8, increasing the temperature of the liquid at the inlet of the tail gas heat exchanger 8, thereby improving the utilization efficiency of the tail gas waste heat.

[0101] Furthermore, the liquid inlet valve 9 and the liquid outlet valve 10 adopt one-way valves to fix the liquid flow direction, prevent backflow, and improve the stability of the system. At the same time, due to the characteristics of the one-way valve, automatic flow direction adjustment can be achieved without complex control strategies, thereby reducing the complexity of the control system and improving the system reliability.

[0102] Embodiment 3

[0103] Refer to the attached drawings of the specification Figure 3 , On the basis of Embodiment 1, the engine waste heat utilization device further includes a hydraulic motor 14 and a cooling water pump 17. The hydraulic motor 14 is used to convert the pressure energy of the liquid flow into mechanical energy. The first end of the hydraulic motor 14 is connected to the liquid outlet valve 10 through a pipeline, and the second end is connected to the liquid inlet valve 9 through a pipeline to form a closed hydraulic circuit.

[0104] When the liquid is discharged from the liquid outlet valve 10, it flows through the pipeline and the hydraulic motor 14 in sequence, driving the rotor of the hydraulic motor 14 to rotate during the flow process, thereby outputting mechanical work. After the liquid passes through the hydraulic motor 14, its pressure decreases, and finally it flows into the liquid inlet valve 9 and returns to the system to complete the cycle.

[0105] Preferably, the hydraulic motor 14 is connected to the engine cooling water pump 17, and the rotation of the hydraulic motor 14 is used to drive the cooling water pump 17 to operate, realizing the power substitution of the engine cooling water pump. This design can reduce the dependence of the engine waste heat utilization device on the crankshaft - connecting rod mechanism, reduce the complexity of the engine transmission system, improve the energy utilization efficiency, reduce additional power loss at the same time, and optimize the overall performance of the engine.

[0106] Embodiment 4

[0107] Refer to the attached drawings of the specification Figure 4, on the basis of Embodiment 1, in order to prevent liquid from entering the heat absorber and radiator and avoid the leakage of the working medium caused by the dissolution of the working medium in the liquid, a diaphragm 16 is arranged in the compression chamber 2 of the present invention. The diaphragm 16 can be a thin film or a corrugated pipe, which is used to isolate the working medium from the liquid, ensure the stable operation of the system, and improve the heat exchange efficiency. The design of the diaphragm 16 needs to meet the requirements of high sealing performance, corrosion resistance, and deep contraction, etc., so as to adapt to the dynamic pressure change and fluid environment of the working medium.

[0108] Specifically, the diaphragm 16 is arranged in the compression chamber 2, forming a sealed space with the cavity, effectively preventing the direct contact between the working medium and the liquid. One side of the diaphragm is in contact with the working medium, and the other side is in contact with the liquid, and it adapts to the pressure change in the cavity through elastic deformation. The diaphragm 16 is made of plastic or metal. When the pressure of the working medium increases, the diaphragm expands towards the liquid side; when the pressure of the liquid increases, the diaphragm retracts, thereby dynamically balancing the pressure between the working medium and the liquid.

[0109] During the operation of the system, the working medium and the liquid are located on both sides of the diaphragm 16 respectively, ensuring their physical separation. Its working process includes: pushing the ejector 4 towards the compression chamber 2, the volume of the expansion chamber increases, the pressure of the working medium rises, the pressure of the liquid rises synchronously, pushing the liquid outlet valve 10 to open, and the liquid flows out of the compression chamber 2. Pushing the ejector 4 towards the expansion chamber 7, the volume of the expansion chamber decreases, the pressure drops, the liquid inlet valve 9 opens, and the external liquid enters the compression chamber 2. During the whole cycle process, the diaphragm 16 isolates the working medium from the liquid, ensures that the working medium and the liquid do not come into direct contact, prevents the dissolution and loss of the working medium, and maintains the sealing performance and pressure stability of the system working medium.

[0110] The present invention realizes the recycling of the working medium and improves the waste heat recovery efficiency by arranging a compression chamber and an expansion chamber in the cylinder and using an ejector to drive the reciprocating flow of the working medium between the two. Through the parallel design of the bypass pipeline and the switching valve, the heat exchange loss is reduced. In addition, the setting of the liquid inlet valve and the liquid outlet valve enables the liquid in the compression chamber to form a pressure balance mechanism with the working medium, effectively improving the energy transfer efficiency. Preferably, the combination of the exhaust gas heat exchanger and the heat absorber recovers the discharged high-temperature exhaust gas and effectively transfers the heat to the working medium, improving the waste heat utilization efficiency. The liquid inlet valve in the compression chamber is connected to the engine oil pan, reducing the energy consumption. The setting of the bypass valve enables the flexible adjustment of the liquid flow distribution, improving the heat exchange efficiency and system adaptability. The present invention also isolates the liquid from the working medium through a diaphragm, ensuring their independent flow and improving the system stability. The hydraulic motor directly drives the cooling water pump through the hydraulic energy generated by the liquid flow, reducing the mechanical load and improving the energy efficiency.

[0111] The above are only embodiments of the present invention, and common knowledge such as specific structures and characteristics known in the art are not described in detail herein. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be construed as limiting the claims involved.

Claims

1. An engine waste heat utilization device, characterized in that: It comprises a cylinder (1), a radiator (3), a heat absorber (5), an ejector (4), a bypass pipe (15) and a switching valve (6); The cylinder (1) is provided with a compression chamber (2) and an expansion chamber (7) inside, and the discharger (4) is arranged inside the cylinder (1) and is used to drive the working medium to flow back and forth between the compression chamber (2) and the expansion chamber (7); The heat absorber (5) and the bypass pipe (15) are arranged in parallel; The switching valve (6) is arranged between the expansion chamber (7), the heat absorber (5) and the bypass pipe (15), and is used to selectively control the working medium to flow through the heat absorber (5) or the bypass pipe (15); The radiator (3) has a first end and a second end, wherein the first end is in fluid communication with the compression chamber (2), and the second end is directly connected to a bypass pipe (15), and the working medium enters the bypass pipe (15) from the expansion chamber (7); The heat absorber (5) has a first end and a second end, wherein the first end is in fluid communication with the compression chamber (2), and the second end is in fluid communication with the expansion chamber (7), and the working medium enters the expansion chamber (7) from the heat absorber (5); The bypass pipe (15) comprises a first end and a second end, the first end is in fluid communication with the expansion chamber (7), and the second end is in fluid communication with the compression chamber (2); The compression chamber (2) contains liquid and comprises a liquid inlet valve (9) and a liquid outlet valve (10), both of which are one-way valves.

2. The engine waste heat utilization device according to claim 1, characterized in that: It also includes an exhaust gas heat exchanger (8), which is arranged on the exhaust gas discharge side of the engine, and the heat of the exhaust gas is transferred to the heat absorber (5) through a heat transfer medium.

3. The engine waste heat utilization device according to claim 1, characterized in that: The liquid inlet valve (9) of the compression chamber (2) is connected to the oil pan of the engine, so as to receive and guide the oil from the oil pan to flow into the compression chamber (2); the liquid outlet valve (10) of the compression chamber (2) has a fluid outlet end connected to the oil supply pipeline of the engine, so as to control the liquid in the compression chamber (2) to be transported to the oil supply pipeline.

4. The engine waste heat utilization device according to claim 2, characterized in that: The heat absorber (5) and the exhaust gas heat exchanger (8) are both provided with a liquid inlet and a liquid outlet, and heat is exchanged between the heat absorber (5) and the exhaust gas heat exchanger (8) through liquid; the liquid outlet of the heat absorber (5) is connected to the liquid inlet valve (9) of the compression chamber (2) via a fluid channel, and the liquid inlet of the exhaust gas heat exchanger (8) is connected to the liquid outlet valve (10) of the compression chamber (2) via a fluid channel.

5. The engine waste heat utilization device according to claim 2, characterized in that: The invention also comprises a bypass valve (12), wherein the bypass valve (12) is configured to have at least three fluid interfaces for adjusting the distribution ratio of the liquid between different circuits, wherein: The first fluid interface of the bypass valve (12) is fluidically connected to the liquid inlet valve (9) or the liquid outlet valve (10) of the compression chamber (2) to control the liquid flow path entering or exiting the compression chamber (2); The second fluid interface of the bypass valve (12) is fluidically connected to the liquid inlet of the exhaust gas heat exchanger (8) for guiding the liquid into the exhaust gas heat exchanger (8) for heat exchange; The third fluid interface of the bypass valve (12) is fluidically connected to the oil supply pipeline of the engine or the oil pan oil circuit of the engine to control the liquid to enter the engine lubrication system or return to the oil pan; The bypass valve (12) is also configured to dynamically adjust the flow ratio of the liquid passing through the second fluid interface and the third fluid interface.

6. The engine waste heat utilization device according to claim 2, characterized in that: The heat absorber (5) adopts a variable temperature heat absorption structure; The temperature difference between the liquid temperature at the liquid outlet end of the exhaust gas heat exchanger (8) and the liquid temperature at the liquid inlet end thereof is ≥150°C.

7. The engine waste heat utilization device according to claim 1, characterized in that: It also includes a heat exchanger (13), wherein the heat exchanger (13) is constructed with two independent fluid passages, namely a first flow passage and a second flow passage, for heat exchange and circulation of liquid.

8. The engine waste heat utilization device according to claim 7, characterized in that: The first flow path connects the liquid outlet of the heat absorber (5) and the liquid inlet valve (9) of the compression chamber (2), and is used for conveying the heat energy released from the heat absorber (5) to the compression chamber (2), so as to improve the preheating of the liquid inside the compression chamber (2); the second flow path connects the liquid outlet valve (10) of the compression chamber (2) and the liquid inlet of the exhaust gas heat exchanger (8), and is used for introducing the liquid discharged from the compression chamber (2) into the exhaust gas heat exchanger (8), so as to exchange heat with the waste heat of the exhaust gas.

9. The engine waste heat utilization device according to claim 1, characterized in that: The invention also includes a diaphragm (16), which is arranged in the compression chamber (2) and is used to form a first fluid chamber and a second fluid chamber in the compression chamber (2); the first fluid chamber is used to contain liquid, and the fluid enters and exits through a liquid inlet valve (9) and a liquid outlet valve (10); the second fluid chamber is used to contain a working medium, and is connected to the expansion chamber (7) through a pipeline, so as to realize the circulation of the working medium between the expansion chamber (7) and the compression chamber (2).

10. The engine waste heat utilization device according to claim 1, characterized in that: It also includes a hydraulic motor (14), which is in fluid communication with the liquid outlet valve (10) through a pipeline, and is in fluid communication with the liquid inlet valve (9) through a pipeline; it also includes an engine cooling water pump (17), which is mechanically connected to the engine cooling water pump and is used to drive the engine cooling water pump (17) to operate by utilizing hydraulic energy generated by the flow of liquid; And / or, it also includes a motor, which is connected to the ejector (4) in power and is used to drive the ejector (4) to reciprocate along the cylinder (1).

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