Organic Rankine cycle system for fully recycling waste heat of marine diesel engine

Abstract

The invention relates to an organic Rankine cycle system for fully recovering waste heat of a marine diesel engine. The organic Rankine cycle system comprises a high-pressure working medium pump; a low-pressure working medium pump; an ejector; a mixing tank; an inlet of the mixing tank is communicated with an outlet of the ejector; a gas inlet of the expansion machine is communicated with a gas outlet of the mixing tank; the condenser is provided with a cooling water pipe and a condensation working medium pipeline, one end of the condensation working medium pipeline is communicated with an air outlet of the expansion machine, and a liquid inlet of the high-pressure working medium pump and a liquid inlet of the low-pressure working medium pump are respectively connected with the condensation working medium pipeline; a first high-pressure evaporator; a second high-pressure evaporator; and a low-pressure evaporator. According to the marine three-evaporator organic Rankine cycle system with the ejectors, the problems that in the prior art, waste heat of different temperature grades cannot be recycled, the structure is complex, and the occupied space is large are solved, full recycling of waste heat of three different temperature grades of a marine diesel engine is achieved, the waste heat utilization efficiency of the marine diesel engine is improved, and the cost is reduced. And the space occupied by the system is reduced as much as possible.

Description

Technical Field

[0001] The present invention relates to the technical field of waste heat utilization of marine diesel engines, and in particular to an organic Rankine cycle system for fully recovering waste heat of marine diesel engines. Background Art

[0002] Diesel engines will continue to be the main type of ship propulsion power unit, especially large ocean-going ships. The thermal efficiency of marine diesel engines, especially large low-speed two-stroke diesel engines, is only about 50%, and a large part of the energy contained in the consumed fuel is released in the form of waste heat. According to the thermal balance analysis report of MAN Turbo & Diesel on a representative diesel engine (model MAN 12k98ME / MC), under the condition of 100% maximum continuous power (SMCR), the output shaft work of the diesel engine only accounts for 49.3% of the total thermal energy of the consumed fuel, while the energy contained in the exhaust gas waste heat accounts for 25.5%, the energy released by the charge air cooling waste heat accounts for 16.5%, the energy released by the cylinder liner cooling water waste heat accounts for 5.2%, and other ways (lubricating oil cooling, surface radiation) account for 3.5%; it can be seen that the exhaust gas waste heat accounts for about 50% of the total waste heat of the diesel engine. The temperature grade of exhaust gas waste heat is high and easy to recover. Traditionally, marine diesel engines use turbochargers for waste heat recovery to achieve intake supercharging. The exhaust gas temperature after the turbocharger can still reach 250℃ to 300℃ for two-stroke low-speed diesel engines, and as high as 300-350℃ for four-stroke medium-speed diesel engines. The temperature grade of the supercharged air cooling waste heat varies widely. Usually, when the diesel engine is working at full load, the scavenging temperature at the outlet of the turbocharger can reach more than 200℃, but when the diesel engine is under partial load, the scavenging temperature will drop sharply; usually at 50% partial load, the scavenging temperature can still reach 130-150℃, but when the diesel engine load further drops to 40% or 25% and below, the scavenging supercharging is usually achieved by the supercharger fan, and the scavenging temperature at this time is only about 45-50℃. The quantity and temperature grade of the cylinder liner cooling water waste heat are relatively stable, and the cooling water temperature at the cylinder liner outlet is usually maintained at 70-90℃. It can be seen from the above that the waste heat released by ship diesel engines through the three channels of flue gas emission, charge air cooling and cylinder liner cooling water is large in quantity and high in temperature, and should be recycled. Summary of the invention

[0003] The present invention provides an organic Rankine cycle system with three evaporators for use on a ship with an ejector, which solves the problem in the prior art that waste heat of different temperature grades cannot be recovered and the structure is complex and occupies a large space. The organic Rankine cycle system is used to fully recover three types of waste heat of different temperature grades of a ship diesel engine, thereby improving the waste heat utilization efficiency of the ship diesel engine and minimizing the space occupied by the system.

[0004] The organic Rankine cycle system for fully recovering waste heat from a marine diesel engine of the present invention comprises:

[0005] High-pressure working fluid pump;

[0006] Low pressure working fluid pump;

[0007] Ejector;

[0008] A mixing tank; the inlet of the mixing tank is connected to the outlet of the ejector;

[0009] an expander, wherein an air inlet of the expander is communicated with an air outlet of the mixing tank;

[0010] A condenser, wherein the condenser has a cooling water pipe and a condensing working fluid pipeline, one end of the condensing working fluid pipeline is connected to the gas outlet of the expander, and the liquid inlet of the high-pressure working fluid pump and the liquid inlet of the low-pressure working fluid pump are respectively connected to the condensing working fluid pipeline;

[0011] A first high-pressure evaporator, wherein the first high-pressure evaporator is provided with a first heat source pipeline and a first working fluid pipeline, wherein the first heat source pipeline is communicated with an air outlet of a flow turbocharger of a diesel engine, an inlet of the first working fluid pipeline is communicated with the high-pressure working fluid pump, and an outlet of the first working fluid pipeline is communicated with the mixing tank, wherein the high-pressure working fluid pump, the first high-pressure evaporator, the mixing tank, the expander and the condenser constitute a first high-pressure working fluid circuit;

[0012] A second high-pressure evaporator, wherein the second high-pressure evaporator is provided with a second heat source pipeline and a second working fluid pipeline, wherein the second heat source pipeline is connected to the high-temperature steam outlet of the exhaust gas boiler of the diesel engine, the inlet of the second working fluid pipeline is connected to the high-pressure working fluid pump, and the outlet of the second working fluid pipeline is connected to the working fluid inlet of the ejector, and the high-pressure working fluid pump, the second high-pressure evaporator, the mixing tank, the expander and the condenser constitute a second high-pressure working fluid circuit;

[0013] A low-pressure evaporator, wherein the low-pressure evaporator is provided with a third heat source pipeline and a third working fluid pipeline, wherein the third heat source pipeline is connected to the cooling water outlet of the cylinder liner of the diesel engine, the inlet of the third working fluid pipeline is connected to the low-pressure working fluid pump, and the outlet of the third working fluid pipeline is connected to the ejected fluid inlet of the ejector, and the low-pressure working fluid pump, the low-pressure evaporator, the mixing tank, the expander and the condenser constitute a low-pressure working fluid circuit.

[0014] Preferably, the first high-pressure working fluid circuit further includes a pressure regulating valve arranged between the outlet of the first working fluid pipeline and the inlet of the mixing tank.

[0015] Preferably, the expander is a single-stage or multi-stage expander; or a group of expanders is formed by connecting multiple expanders in parallel.

[0016] Preferably, the system further comprises a generator set, which generates electricity under the action of the expander.

[0017] Preferably, the cooling water pipe of the condenser is connected to cooling seawater.

[0018] Compared with the prior art, the present invention has the following beneficial effects: the system of the present invention can not only utilize the waste heat of the high-temperature steam generated by the exhaust gas boiler, but also utilize the waste heat of the compressed gas after turbocharging and the cooling water of the cylinder liner. Compared with the existing diesel engine waste heat utilization equipment, the efficiency of waste heat utilization can be further improved, and the three working fluid circuits are connected in parallel and act on the same expander together for power generation or other functions. It has a simple structure and a small size, which can reduce the occupied space. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The structure diagram of an organic Rankine cycle system with three evaporators for use on a ship and an ejector according to an embodiment of the present invention is shown.

[0020] Reference numerals

[0021] 1 high-pressure working fluid pump, 2 low-pressure working fluid pump, 3 low-pressure evaporator, 31 third heat source pipeline, 32 third working fluid pipeline, 4 first high-pressure evaporator, 41 first heat source pipeline, 42 first working fluid pipeline, 5 second high-pressure evaporator, 51 second heat source pipeline, 52 second working fluid pipeline, 6 ejector, 7 expander, 8 generator, 9 condenser, 10 mixing tank, 11 pressure regulating valve, 12 compressor, A ship diesel engine, A1 exhaust manifold, A2 scavenge air box, A3 cylinder liner, B turbocharger, C exhaust gas boiler. DETAILED DESCRIPTION

[0022] The present invention provides an organic Rankine cycle system with three evaporators for use on a ship with an ejector 6, such as Figure 1 As shown, the system includes: a high-pressure working fluid pump 1, a low-pressure working fluid pump 2, an ejector 6, a mixing tank 10, an expander 7, a condenser 9, a first high-pressure evaporator 4, a second high-pressure evaporator 5 and a low-pressure evaporator 3.

[0023] The inlet of the mixing tank 10 is connected to the outlet of the ejector 6, the air inlet of the expander 7 is connected to the air outlet of the mixing tank 10, the condenser 9 has a cooling water pipe and a condensing working fluid pipeline, one end of the condensing working fluid pipeline is connected to the air outlet of the expander 7, and the liquid inlet of the high-pressure working fluid pump 1 and the liquid inlet of the low-pressure working fluid pump 2 are respectively connected to the condensing working fluid pipeline.

[0024] The first high-pressure evaporator 4 is provided with a first heat source pipeline 41 and a first working fluid pipeline 42. The first heat source pipeline 41 is connected to the outlet of the flow turbocharger B of the diesel engine, the inlet of the first working fluid pipeline 42 is connected to the high-pressure working fluid pump 1, and the outlet of the first working fluid pipeline 42 is connected to the mixing tank 10. The high-pressure working fluid pump 1, the first high-pressure evaporator 4, the mixing tank 10, the expander 7 and the condenser 9 constitute a first high-pressure working fluid circuit. In the present invention, the high-temperature exhaust gas of the ship diesel engine A first enters the turbocharger after passing through the exhaust manifold A1. Driven by the high-temperature exhaust gas, the impeller of the turbine rotates to drive the compressor 12 to compress the input air. The compressed air finally enters the diesel engine. Before entering the diesel engine, the temperature of the compressed air is increased by the high-temperature exhaust gas, so that the compressed air passes through the first heat source pipeline 41 of the first high-pressure evaporator 4. At the same time, the high-pressure working medium pump 1 sends the liquid working medium into the first working medium pipeline 42 of the first high-pressure evaporator 4. The working medium and the compressed air exchange heat. After the compressed air releases heat and cools down, it enters the scavenging box A2 of the diesel engine. The working medium absorbs the heat of the compressed air and becomes gaseous. The working medium enters the mixing tank 10 and then enters the expander 7 to work. The exhaust steam after work enters the condenser 9 and cools to become liquid. The above cycle constitutes the first high-pressure working medium circuit, which utilizes the waste heat of the air after the turbocharger is pressurized.

[0025] The second high-pressure evaporator 5 is provided with a second heat source pipeline 51 and a second working fluid pipeline 52, the second heat source pipeline 51 is connected to the high-temperature water vapor outlet of the exhaust gas boiler C of the diesel engine, the inlet of the second working fluid pipeline 52 is connected to the high-pressure working fluid pump 1, and the outlet of the second working fluid pipeline 52 is connected to the working fluid inlet of the ejector 6, and the high-pressure working fluid pump 1, the second high-pressure evaporator 5, the mixing tank 10, the expander 7 and the condenser 9 constitute a second high-pressure working fluid circuit. The high-pressure working fluid pump 1, the mixing tank 10, the expander 7 and the condenser 9 in the first high-pressure circuit and the second high-pressure circuit are shared. After passing through the turbocharger B, the high-temperature exhaust gas enters the exhaust gas boiler C to heat the water to form high-temperature water vapor. Part of the high-temperature water vapor can be used for domestic heat or to heat oil products, and the other part enters the second heat source pipeline 51 of the second high-pressure evaporator 5. At the same time, the high-pressure working fluid pump 1 sends the liquid working fluid into the second working fluid pipeline 52 of the second high-pressure evaporator 5. The working fluid exchanges heat with the high-temperature water vapor. The high-temperature water vapor is cooled and becomes liquid water. The working fluid absorbs heat and becomes gaseous. After passing through the ejector 6, it enters the mixing tank 10 and mixes with the working fluid gas generated by the first high-pressure working fluid circuit, and then the expander 7 performs work, and then enters the condenser 9 for cooling.

[0026] The low-pressure evaporator 3 is provided with a third heat source pipeline 31 and a third working fluid pipeline 32. The third heat source pipeline 31 is connected to the cooling water outlet of the cylinder liner A3 of the diesel engine. The inlet of the third working fluid pipeline 32 is connected to the low-pressure working fluid pump 2. The outlet of the third working fluid pipeline 32 is connected to the ejected fluid inlet of the ejector 6. The low-pressure working fluid pump 2, the low-pressure evaporator 3, the mixing tank 10, the expander 7 and the condenser 9 constitute a low-pressure working fluid circuit. The first high-pressure evaporator 4, the second high-pressure evaporator 5 and the low-pressure evaporator 3 are connected in parallel. The low-pressure working fluid circuit is shared with the mixing tank 10, the expander 7 and the condenser 9 in the first high-pressure circuit and the second high-pressure circuit. The cooling water outlet of the cylinder liner A3 (heated after heat exchange with the cylinder liner A3) enters the third heat source pipeline 31 of the low-pressure evaporator 3, and the low-pressure working fluid pump 2 delivers the working fluid into the third working fluid pipeline 32 of the low-pressure evaporator 3. The working fluid exchanges heat with the cooling water outlet, and the cooling water releases heat and returns to the cylinder liner A3. The working fluid absorbs heat and becomes steam and enters the ejector 6 for pressure increase, and then enters the mixing tank 10 to mix with the working fluid gases of the other two circuits, and then the expander 7 performs work, and then enters the condenser 9 for cooling.

[0027] The system of the present invention can not only utilize the waste heat of the high-temperature steam generated by the exhaust gas boiler C, but also utilize the waste heat of the compressed gas after turbocharging and the cooling water of the cylinder liner A3. Compared with the existing diesel engine waste heat utilization equipment, the efficiency of waste heat utilization can be further improved. The three working fluid circuits are connected in parallel and act together on the same expander 7 for power generation or other functions. It has a simple structure and a small size, which can reduce the occupied space.

[0028] The working fluid used in the present invention is an organic working fluid. In this embodiment, the working fluid used is R245fa. The ejector 6 can pressurize the ejected fluid to the pressure of the mixing tank 10.

[0029] The first high-pressure working fluid circuit also includes a pressure regulating valve 11 disposed between the outlet of the first working fluid pipeline 42 and the inlet of the mixing tank 10. The pressure regulating valve 1 can achieve pressure balance in each working fluid circuit after entering the mixing tank to avoid backflow. The cooling water pipe of the condenser 9 is connected to cooling seawater.

[0030] The expander 7 is a single-stage or multi-stage expander 7, or a group of expanders 7 formed by connecting multiple expanders 7 in parallel. The system also includes a generator 8 group, and the generator 8 group generates electricity under the action of the expander 7.

[0031] The above embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention. The protection scope of the present invention is defined by the claims. Various modifications or equivalent substitutions made by those skilled in the art to the present invention within the essence and protection scope of the present invention also fall within the protection scope of the present invention.

Claims

1. An organic Rankine cycle system for fully recovering waste heat from a marine diesel engine, characterized in that: include: High-pressure working fluid pump; Low pressure working fluid pump; Ejector; A mixing tank; the inlet of the mixing tank is connected to the outlet of the ejector; an expander, wherein an air inlet of the expander is communicated with an air outlet of the mixing tank; A condenser, wherein the condenser has a cooling water pipe and a condensing working fluid pipeline, one end of the condensing working fluid pipeline is connected to the gas outlet of the expander, and the liquid inlet of the high-pressure working fluid pump and the liquid inlet of the low-pressure working fluid pump are respectively connected to the condensing working fluid pipeline; A first high-pressure evaporator, wherein the first high-pressure evaporator is provided with a first heat source pipeline and a first working fluid pipeline, wherein the first heat source pipeline is communicated with an air outlet of a flow turbocharger of a diesel engine, an inlet of the first working fluid pipeline is communicated with the high-pressure working fluid pump, and an outlet of the first working fluid pipeline is communicated with the mixing tank, wherein the high-pressure working fluid pump, the first high-pressure evaporator, the mixing tank, the expander and the condenser constitute a first high-pressure working fluid circuit; A second high-pressure evaporator, wherein the second high-pressure evaporator is provided with a second heat source pipeline and a second working fluid pipeline, wherein the second heat source pipeline is connected to the high-temperature steam outlet of the exhaust gas boiler of the diesel engine, the inlet of the second working fluid pipeline is connected to the high-pressure working fluid pump, and the outlet of the second working fluid pipeline is connected to the working fluid inlet of the ejector, and the high-pressure working fluid pump, the second high-pressure evaporator, the mixing tank, the expander and the condenser constitute a second high-pressure working fluid circuit; A low-pressure evaporator, wherein the low-pressure evaporator is provided with a third heat source pipeline and a third working fluid pipeline, wherein the third heat source pipeline is connected to the cooling water outlet of the cylinder liner of the diesel engine, the inlet of the third working fluid pipeline is connected to the low-pressure working fluid pump, and the outlet of the third working fluid pipeline is connected to the ejected fluid inlet of the ejector, and the low-pressure working fluid pump, the low-pressure evaporator, the mixing tank, the expander and the condenser constitute a low-pressure working fluid circuit.

2. The system according to claim 1, characterized in that The first high-pressure working fluid circuit also includes a pressure regulating valve disposed between the outlet of the first working fluid pipeline and the inlet of the mixing tank.

3. The system according to claim 1, characterized in that The expander is a single-stage or multi-stage expander; or a group of expanders is formed by connecting multiple expanders in parallel.

4. The system according to claim 1, characterized in that The system further comprises a generator set, which generates electricity under the action of the expander.

5. The system according to claim 1, characterized in that The cooling water pipe of the condenser is connected to cooling seawater.

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