JPH0688523A - Waste heat recovery system - Google Patents

Abstract

PURPOSE:To feed an expander with an amount of sufficient energy as preventing any knocking from occurring, in the waste heat recovery system of an internal combustion engine converting its waste heat into mechanical energy. CONSTITUTION:A water jacket 7 for cooling the peripheral part of an intake port 2 and another water jacket 8 for cooling each peripheral part of a combustion chamber and an exhaust port 3 both are separately installed in an internal combustion engine 21. A cooling medium circulating route combining a Rankine cycle system is composed of a feed pump 13, the water jacket 8, a heater 16 using exhaust heat as a heat source, an expander 17 converting steam's expansion energy into the mechanical one and a condenser 22. Likewise, this cooling medium circulating route preventing the overheat of fuel gas is composed of the feed pump 13, a pressure regulating valve 15, the water jacket 7 and the condenser 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waste heat recovery system for an internal combustion engine, and more particularly to converting waste heat energy into mechanical energy by an expander operating with a cooling medium vaporized by the heat generated in the internal combustion engine. The present invention relates to a waste heat recovery device for an internal combustion engine.

[0002]

2. Description of the Related Art An internal combustion engine is provided with a cooling mechanism for preventing the internal combustion engine itself from overheating due to combustion heat or frictional heat generated between mechanical members. As a typical cooling method, a water cooling method is known in which cooling water is circulated in a water jacket provided in the body of an internal combustion engine.

Generally, in the water cooling system, the cooling water, which has been heated by removing heat from the internal combustion engine in the water jacket, is cooled by air cooling in the middle of circulation, and is then fed again into the water jacket. . That is, in the generally widely used internal combustion engine,
Of the energy generated by the combustion performed in the combustion chamber, most of the heat energy is radiated into the atmosphere as waste heat and is not effectively used.

Therefore, conventionally, a mechanism for effectively utilizing the waste heat discharged from the internal combustion engine has been proposed. For example, Japanese Utility Model Laid-Open No. 61-140120 discloses an extract which is operated by steam in a circulation path of cooling water while steaming the cooling water in a water jacket in order to cool the internal combustion engine with heat of vaporization of the cooling water. Disclosed is a device that provides a panda to extract mechanical energy.

According to the apparatus described in the above publication, the condenser for cooling and liquefying the steam flowing out from the water jacket is air-cooled by the cooling fan driven by the expander. The expander is provided between the condenser and the water jacket.

That is, in the internal combustion engine equipped with this device, the waste heat energy is reused as the driving force for the cooling fan, and it is not necessary to separately supply power for driving the cooling fan. Therefore, the efficiency of the internal combustion engine as a whole is improved, and the fuel consumption can be improved.

[0007]

However, in order to drive the expander in the above-mentioned conventional apparatus, it is required that the vapor supplied to the expander has a large amount of energy. That is, it is required that the steam of the cooling water be sufficiently heated in the water jacket of the internal combustion engine. Therefore, in the above device, the temperature of the internal combustion engine in the steady state is set to the boiling temperature of the cooling water or higher.

By the way, the temperature of the internal combustion engine, particularly the temperature in the vicinity of the intake port, greatly affects the characteristics of the internal combustion engine. That is, when the temperature is relatively low, the temperature of the fuel gas supplied to the combustion chamber of the internal combustion engine is suppressed low, which leads to an increase in output. Conversely, when the temperature of the fuel gas is relatively high, not only the output decreases. It also causes knocking.

The present invention has been made in view of the above points, and by independently providing a cooling medium circulation path that maintains a relatively low temperature in the vicinity of the intake port, it is possible to prevent knocking while being sufficient for an expander. It is an object of the present invention to provide a waste heat recovery device for an internal combustion engine that can provide various energy.

[0010]

SUMMARY OF THE INVENTION The above-mentioned problem is caused by supplying a cooling medium which is vaporized by heat generated in the internal combustion engine into a cooling medium circulation path of the internal combustion engine to generate energy of the heat. In a waste heat recovery device for an internal combustion engine, comprising: an expander for converting the above into mechanical energy, the cooling medium circulation path includes a first cooling medium circulation path for cooling the vicinity of an intake port of the internal combustion engine, and the internal combustion engine A second cooling medium circulation path that cools a predetermined part, the first cooling medium circulation path bypasses the expander, and the internal pressure is lower than that of the second cooling medium circulation path. It is solved by the waste heat recovery device of the internal combustion engine set to.

[0011]

In the waste heat recovery device for the internal combustion engine having the above structure,
The cooling water flowing through the first cooling medium circulation path is kept at a relatively low pressure, and neither compression temperature rise nor boiling point rise occurs. Therefore, the vicinity of the intake port of the internal combustion engine is kept at a relatively low temperature, and the temperature rise of the fuel gas supplied to the combustion chamber of the internal combustion engine is prevented.

On the other hand, the cooling water flowing through the second cooling medium circulation passage is kept at a higher pressure than the cooling water flowing through the front first cooling medium circulation passage, and the boiling point rises as the temperature rises due to compression. Therefore, high temperature, that is, high-energy steam is generated in the first cooling medium circulation path.

Therefore, high-energy steam is supplied to the expander while maintaining a proper temperature in the vicinity of the intake port of the internal combustion engine, and it is highly efficient without knocking in the combustion chamber of the internal combustion engine. Waste heat is converted into mechanical energy.

[0014]

Next, preferred embodiments will be described in order to further clarify the structure of the waste heat recovery system for an internal combustion engine according to the present invention.

FIG. 1 is a block diagram showing an example in which the device of this embodiment is incorporated in an internal combustion engine. In FIG. 1, reference numeral 1 indicates an internal combustion engine in which the device of this embodiment is incorporated. Reference numerals 2 and 3 denote an intake port and an exhaust port of the internal combustion engine 1, respectively, the intake valve 4 and the exhaust valve 5
Through the combustion chamber of the internal combustion engine 1.

A cylinder block 6 constituting the main body of the internal combustion engine 1 is provided with a water jacket for circulating cooling water to prevent the internal combustion engine 1 from overheating. In the apparatus of this embodiment, the water jacket 7 is provided around the intake port 2 as a part of the first cooling medium circulation path, and the water jacket 7 is provided around the combustion chamber and the exhaust port 3 as a part of the second cooling medium circulation path. A jacket 8 is provided.

The water jackets 7 and 8 are completely separated in the cylinder block 6, and circulate the cooling water through independent paths. That is, as shown in FIG. 1, in the case of the water jacket 7, the cooling water is supplied from the inflow passage 9 and flows to the outflow passage 10, and in the case of the water jacket 8, the cooling water is supplied from the inflow passage 11. Goes from the vicinity of the combustion chamber to the vicinity of the exhaust port 3 and flows into the outflow passage 12. The inflow passages 9 and 11 are both branched from the circulation passage 14 communicating with the outlet side of the supply pump 13, and the inflow passage 9 has a valve 15 for pressure adjustment.
Is provided.

The outflow passage 12 of the water jacket 8 communicates with a heater 16 which uses the heat of the exhaust gas discharged from the exhaust port 3 as a heat source, and the heater 16 further expands the expander 1.
7 is in communication with the steam inlet. This expander 17
Has a function of converting expansion energy of superheated steam into mechanical energy. For example, an impeller that rotates by introducing steam and a reduction gear that transmits the rotation of the impeller to the outside are provided. It is configured.

The vapor outlet of the expander 17 communicates with the outflow passage 10 of the water jacket 7 and the circulation passage 18. A condenser 20 is provided between the circulation path 18 and a circulation path 19 communicating with the inlet side of the supply pump 13 to cool and condense the vapor into a liquid.

The above-mentioned supply pump 13, water jacket 8 and heater 16, expander 17, condenser 2
0 constitutes a Rankine cycle system known as a device for converting heat energy into mechanical energy. The operation of the apparatus of this embodiment will be described below along the flow of cooling water.

Supply pump 1 cooled by condenser 20
The cooling water given the flow velocity in 3 advances through the circulation passage 14 to the inflow passages 9 and 11 of the respective water jackets 7 and 8. Next, the cooling water diverted to the inflow passage 9 enters the water jacket 7 via the valve 15 for pressure adjustment, and the cooling water diverted to the inflow passage 11 directly enters the water jacket 8.

Therefore, the internal pressure of the water jacket 7 is always kept lower than the internal pressure of the water jacket 8. The supply pump 13 has a higher output than a pump installed in a normal internal combustion engine that does not have a waste heat recovery device, and the adjusting valve 15 controls the internal pressure of the water jacket 7 of the present embodiment device. Is set to the same level as the internal pressure of the water jacket in a normal internal combustion engine.

Therefore, the water jacket 8 has a higher internal pressure than the internal pressure in a normal internal combustion engine, and the boiling point of the cooling water circulating inside increases. For this reason, the temperature of the cooling water circulating in the water jacket 8 rises, and the steam generated there becomes high-energy steam of high temperature and high pressure.

On the other hand, the internal pressure of the water jacket 7 is not as high as the internal pressure of the water jacket 8 as described above, and is almost the same level as that of the internal combustion engine without the waste heat recovery device. Therefore, the temperature of the cooling water circulating in the water jacket 7 is maintained at a level at which the internal combustion engine can be cooled appropriately. Therefore, the steam flowing out from the water jacket 7 becomes low-temperature and low-pressure steam.

Therefore, in the internal combustion engine equipped with the device of this embodiment, the vicinity of the intake port 2 is sufficiently cooled and the fuel gas supplied to the combustion chamber is not overheated in the intake port 2. Absent. Therefore, unlike the internal combustion engine in which the waste heat recovery device having the conventional configuration is incorporated, knocking does not occur frequently.

By the way, the high-energy steam flowing out from the water jacket 8 is further heated by the heater 16,
It is supplied to the expander 17 with higher energy. That is, a high pressure difference occurs between the steam inlet and the steam outlet of the expander 17. Therefore, the impeller provided in the expander 17 rotates vigorously and a large amount of mechanical energy is generated.

The steam flowing out of the heater 16 with high energy loses energy and becomes low-pressure steam.
The low-pressure steam flowing out of the water jacket 7 flows into the condenser 20.

The low-pressure steam that has flowed into the condenser 20 is cooled and condensed here again, and then proceeds to the supply pump 13.
After that, the cooling water repeats the above circulation to efficiently supply the high pressure steam to the expander 17 while efficiently cooling the periphery of the intake port 2.

As described above, the apparatus of this embodiment is provided with the cooling medium circulation path for cooling the periphery of the intake port 2 and the cooling medium circulation path for cooling the periphery of the exhaust port 3 and the periphery of the combustion chamber in parallel. It is possible to provide a difference in the internal pressure of both cooling medium circulation paths. Therefore, the high-pressure steam can be supplied to the expander 17 while appropriately cooling the periphery of the intake port 2. Therefore, the waste heat can be recovered as mechanical energy with high efficiency without suffering from overheating around the intake port as in the conventional waste heat recovery device.

In the above embodiment, the temperature of the cooling water circulating through the water jacket 7 is adjusted so as to be substantially the same as the temperature of the cooling water in a general internal combustion engine without a waste heat recovery device. However, the temperature is not limited to this, and may be set to a lower temperature.

In this case, the temperature around the intake port 2 becomes lower, and low temperature fuel gas is supplied to the combustion chamber. Therefore, in addition to the effect of the above-described embodiment apparatus, the effect of improving the output of the internal combustion engine is also obtained.

[0032]

As described above, according to the present invention, it is possible to supply the expander with steam having a pressure higher than that of the conventional waste heat recovery device while maintaining the proper temperature around the intake port. Therefore, the temperature rise of the fuel gas sucked into the combustion chamber of the internal combustion engine is suppressed, the occurrence of knocking is prevented, and the waste heat of the internal combustion engine is recovered with higher efficiency than the waste heat recovery device of the conventional configuration. It has the feature of being able to

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of a waste heat recovery device for an internal combustion engine according to the present invention.

[Explanation of symbols]

 1 Internal Combustion Engine 2 Intake Port 3 Exhaust Port 7,8 Water Jacket 9,11 Inflow Path 10,12 Outflow Path 13 Supply Pump 14,18,19 Circulation Path 15 Valve 16 Heater 17 Expander 20 Condenser

Claims (1)

[Claims] 1. An expander that operates by supplying a cooling medium vaporized by heat generated in the internal combustion engine into a cooling medium circulation path of the internal combustion engine to convert the heat energy into mechanical energy. In the waste heat recovery device for an internal combustion engine, the cooling medium circulation path includes a first cooling medium circulation path for cooling a vicinity of an intake port of the internal combustion engine and a second cooling medium circulation path for cooling a predetermined portion of the internal combustion engine. And a cooling medium circulation path, wherein the first cooling medium circulation path bypasses the expander and the internal pressure is set to be lower than that of the second cooling medium circulation path. Waste heat recovery device for internal combustion engine.