JP2008196379A - Exhaust heat recovering device and engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To supply cooling water to an engine having high pressure and circulate a sufficient amount of cooling water to each part of the engine equipped with a Rankine cycle. <P>SOLUTION: This exhaust heat recovering device (1) is equipped with a first cooling water path (12) extending from a lower part of a water jacket (3), a three-way valve (16) disposed downstream of the first cooling water path (12), a second cooling water path (17) extending downstream from the three-way valve (16), a second cooling water path (17) connecting the three-way valve (16) to a catch tank (11), and a steam path (6) branched at a downstream part of an outlet of the water jacket (3), into a power collecting path (6a) and its bypass path (6b). The bypass path (6b) is provided with an opening/closing valve (20) and its terminal end is connected to the catch tank (11). When supplying cooling water inside the catch tank (11) into the water jacket (3), steam pressure is applied inside the water jacket (3), and differential pressure between the outlet and inlet of a water pump (5) is made small. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a waste heat recovery apparatus that recovers waste heat in an engine via steam.

  2. Description of the Related Art Conventionally, there is known a waste heat recovery device that recovers waste heat generated by driving an internal combustion engine (engine) using a Rankine cycle. In such a waste heat recovery device, for example, the water cooling cooling system of the engine has a sealed structure, and the expander (turbine) is driven by cooling water vaporized by the waste heat in the engine, that is, steam, and the heat of the steam There is one that converts energy into electrical energy and recovers it. For example, Patent Document 1 discloses an improved version of such a waste heat recovery apparatus.

JP 2000-345835 A

  In such a water-cooled cooling system for an engine in a waste heat recovery apparatus, the engine is cooled by latent heat absorbed from the engine when the cooling water evaporates. As described above, in cooling the engine using the latent heat at the time of evaporation of the cooling water, the amount of cooling water required for cooling is much smaller than when the engine is cooled in the liquid state. However, since the water-cooled cooling system of the engine that is filled with evaporated cooling water, that is, steam, has a high pressure, the water pump requires a very high discharge pressure to supply the cooling water from outside the low pressure. Is done.

  As described above, the waste heat recovery device requires a high pressure of the cooling water to supply the cooling water into the water cooling cooling system of the engine. On the other hand, the indoor heater or the throttle mechanism that uses the cooling water for warming up is required. A large amount of cooling water may need to be supplied in order to immediately perform such functions. Thus, the waste heat recovery apparatus has two requirements with different properties. In order to satisfy these requirements, it is conceivable to equip two types of water pumps, but it is difficult to install two types of water pumps in consideration of the space of the vehicle.

  Therefore, the present invention has an object to propose a waste heat recovery device that enables the supply of cooling water into the engine at a high pressure and circulates a sufficient amount of cooling water to each part of the engine. And

  In order to achieve such a problem, a waste heat recovery apparatus of the present invention includes a power recovery path in which an expander and a condenser are arranged, a bypass path of the power recovery path, the power recovery path, and the bypass path. And a steam flow path switching means for switching and changing a steam flow path (Claim 1). By adopting such a configuration, when supplying the cooling water into the high pressure system, the steam is circulated to the bypass path, and the pressure of the steam acts on the cooling water supplied into the system. Cooling water can be easily supplied into the system. Such a waste heat recovery apparatus should just be provided with one water pump. The water pump itself may not have a high discharge pressure. That is, since the steam pressure acts on the cooling water itself sucked by the water pump, the cooling water can be supplied into the high-pressure system. The capacity of the water pump is not limited as long as the cooling water is supplied around the indoor heater and the throttle mechanism so that the functions of these devices can be immediately demonstrated.

  Such a waste heat recovery apparatus includes a water pump, and a cooling water supply path that switches between a cooling water supply path that uses a water jacket or the condenser as a cooling water supply source and a cooling water supply source in the cooling water supply path. The original switching means may be further provided (claim 2).

  The steam flow path switching means in such a waste heat recovery apparatus switches between the power recovery path and the bypass path according to the remaining amount of cooling water in the water jacket. Further, the cooling water supply source switching means switches the cooling water supply source according to the remaining amount of the cooling water in the water jacket. Thus, by switching each path | route, a cooling water can be supplied in a water jacket and the quantity of the cooling water in a water jacket can be maintained.

  Furthermore, in such a waste heat recovery apparatus, the power recovery path may be configured to include a cooling water backflow prevention means on the downstream side of the condenser (Claim 5). This cooling water backflow prevention means suppresses the backflow of cooling water that has received this pressure to the condenser side in consideration of the high pressure in the bypass path when the steam flow path is switched to the bypass path. Is for.

  By incorporating these waste heat recovery devices into the engine, the engine of the present invention can be obtained (claim 6).

  According to the present invention, when cooling water is supplied into the water jacket, the steam pressure is applied to the cooling water, so that the cooling water can be easily supplied into the system.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  Embodiments of the present invention will be described with reference to the drawings. 1 and 2 are explanatory diagrams showing a schematic configuration of the waste heat recovery apparatus 1 of the present embodiment. FIG. 1 shows a state in which the engine is in a warm-up state and in a “circulation state” in which the cooling water in the water jacket 3 is circulated, and FIG. 2 supplies cooling water from the catch tank 11 side. It shows the situation when it is in the “water supply state”.

  The waste heat recovery apparatus 1 is incorporated in an engine 2 that is a combustion engine. The waste heat recovery apparatus 1 includes a water jacket 3 formed from the cylinder block 2a to the cylinder head 2b, and a cooling water injection nozzle 4 installed in the cylinder head 2b. Cooling water as a cooling medium is supplied into the water jacket 3. Specifically, the waste heat recovery apparatus 1 includes a first cooling water path 12 extending from a lower portion of the water jacket 3, a three-way valve 16 disposed downstream of the first cooling water path 12, and a downstream side of the three-way valve 16. The 2nd cooling water path 17 extended to is provided. A water pump (W / P) 5 is disposed in the middle of the second cooling water path 17, and the cooling water injection nozzle 4 is mounted on the tip side thereof. Through such a cooling water supply path, the cooling water pumped up from the lower portion of the water jacket 3 by the water pump 5 is supplied to the cooling water injection nozzle 4. The injected cooling water is vaporized when the hot engine 2 is cooled, and fills the upper portion of the water jacket 3.

  Such a second cooling water path 17 is branched downstream of the water pump 5 so that the cooling water circulates around the vehicle interior heater 18 and the throttle 19. Thereby, heat exchange can be performed in the heater 18, and the throttle 19 can be warmed up. The path circulating around the heater 18 and the throttle 19 is returned to the first cooling water path 12 again.

  The waste heat recovery apparatus 1 further includes a vaporized cooling medium, that is, a vapor path 6 through which the vapor flows. This steam path 6 is branched downstream of the outlet of the water jacket 3 into a power recovery path 6a and a bypass path 6b.

  A superheater 7 and a turbine 8 are arranged in this order from the upstream side in the power recovery path 6 a, and their ends are connected to the upper part 9 a of the condenser 9. An exhaust path 14 connected to the exhaust port 13 of the engine body 2 is drawn into the superheater 7. The superheater 7 recovers heat from the exhaust gas in the exhaust path 14 and further gives heat to the steam passing through the power recovery path 6, and improves the recovery efficiency of waste heat. The turbine 8 is driven by high-temperature and high-pressure steam flowing in through the power recovery path 6a. The turbine 8 includes a drive shaft 8 a that is common to the generator 15. For this reason, when the turbine 8 is driven, the generator 15 converts the thermal energy of the steam into electrical energy and recovers it. The steam that has passed through the turbine 8 is condensed by the condenser 9 and returned to the cooling water. A catch tank 11 is disposed on the downstream side of the condenser 9, and the cooling water returned to the liquid by the condenser 9 is stored in the catch tank 11. In the passage 6a1 connecting the condenser 9 and the catch tank 11, a one-way valve 10 corresponding to the cooling water backflow prevention means in the present invention is disposed. The one-way valve 10 prevents the cooling water from flowing backward from the catch tank 11 to the condenser 9 side.

  On the other hand, the end of the bypass path 6b is connected to the catch tank 11, and an opening / closing valve 20 corresponding to the steam flow path switching means in the present invention is provided between the branch point and the catch tank 11. When the on-off valve 20 is opened, steam pressure acts in the catch tank 11.

  A third cooling water path 23 is connected to the lower end of the catch tank 11. The other end side of the third cooling water passage 23 is connected to the three-way valve 16. The third cooling water path 23 forms the cooling water supply path in the present invention together with the first cooling water path 12 and the second cooling water path 17, and the three-way valve 16 is the cooling water supply / source switching means in the present invention. It corresponds to. That is, if the first cooling water path 12 and the second cooling water path 17 are connected by switching the three-way valve 16, the cooling water in the water jacket 3 is supplied to the water pump 5. Further, if the third cooling water path 23 and the second cooling water path 17 are connected, the cooling water returned to the liquid in the condenser 9, that is, in the condenser 9, is supplied to the water pump 5. Water is supplied.

  The waste heat recovery apparatus 1 includes an ECU (Electronic Control Unit) 21. The ECU 21 is electrically connected to the three-way valve 16 and the opening / closing valve 20, and the opening / closing of the three-way valve 16 and the opening / closing valve 16 is controlled by the ECU 21. The ECU 21 is electrically connected to a water temperature sensor 22 installed in the cylinder block 2a and other various sensors (not shown). The one valve 10 disposed in the passage 6a1 opens and closes due to the pressure balance in the passage 6a1, but the one valve 10 may be connected to the ECU 21 so that the ECU 21 controls the opening and closing.

  The operation of the waste heat recovery apparatus 1 configured as described above will be described with reference to the flowchart shown in FIG. 3, which is an example of control performed by the ECU 21, and FIGS. 1 and 2. When the control is started, the ECU 21 determines in step S1 whether or not the engine speed Ne is Ne> 0, that is, whether or not the engine 2 is operating. When it is determined Yes in step S1, that is, when the engine 2 is operating, the process proceeds to step S2. On the other hand, when it is determined No in step S1, the process of step S1 is repeated.

  In step S2, it is determined whether or not the value acquired by the water temperature sensor 22 installed in the cylinder block 2a, that is, the water temperature or the steam temperature Tw (° C.) is higher than a preset temperature 120 ° C. Here, the temperature of 120 ° C. is a value for determining whether or not the engine 2 has been warmed up. When it is determined No in this step S2, that is, when the warm-up of the engine 2 has not yet been completed, the processing from step S1 is repeated again via step S3. In step S3, the ECU 21 performs control for setting the state of the waste heat recovery apparatus 1 to the “circulation state” shown in FIG. That is, the three-way valve 6 is brought into a state where the first cooling water passage 12 and the second cooling water passage 17 communicate with each other, and the on-off valve 20 is brought into a closed state. Thereby, the cooling water circulates in the water jacket 3 and around the heater 18 and the throttle 19. The cooling water circulating in this way gradually increases in temperature due to the combustion heat of the engine 2. The heated cooling water exchanges heat in the heater 18 and warms up the throttle 19.

  On the other hand, when it is determined Yes in step S2, the process proceeds to step S4. In step S4, the ECU 21 performs a warm-up end determination. When the condition of Tw> 120 ° C. is satisfied, the cooling water starts to vaporize and generation of steam starts. For this reason, ECU21 starts calculation of steam generation amount etc. after that. After finishing the process of step S4, the ECU 21 proceeds to step S5. In step S4, the ECU 21 issues a new command for maintaining the waste heat recovery apparatus 1 in the circulating state shown in FIG. After performing the process in step S5, the process proceeds to step S6.

In step S6, determination is made as to whether or not the accumulated amount of cooling water evaporation, that is, Gv (g), which is the cooling water decrease amount in the water jacket 3, exceeds Gw (g), which is the required water supply amount per time. I do. The evaporation amount integrated value Gv is expressed by the following equation:
Gv = ΣQw (Ne, H) / qw × dt
And it is required.
That is, it is calculated from the time integration of the cooling water heat receiving amount Qw (kw) which is a function of the engine speed Ne (rps) and the engine load H (Nm).
The cooling water heat receiving amount Qw (kw) and the evaporation amount Gs have a relationship of Gs = Qw / q (kj / g) as shown in FIG. 4 where the latent heat of evaporation is q (kj / g). Qw itself is a function of the engine speed Ne (rps) and the engine load H (Nm), and Qw = (Ne, H), as shown in FIG. 5, on the engine speed-engine load diagram. Can be obtained as equal Qw lines.
The ECU 21 repeats the processing from step S1 when Gv obtained by performing the above calculation is still smaller than Gw and it is determined No in step S6. On the other hand, if Yes is determined in step S6, the process proceeds to step S7.

  In step S7, the evaporation amount integrated value Gv used in step S6 is once reset. That is, Gv = 0 is set. After such processing in step S7, the process proceeds to step S8. In step S8, the ECU 21 performs control for setting the state of the waste heat recovery apparatus 1 to the “water supply state” shown in FIG. That is, the three-way valve 6 is brought into a state where the third cooling water passage 23 and the second cooling water passage 17 communicate with each other, and the on-off valve 20 is brought into an open state. As a result, the steam flows into the bypass path 6b, and the high pressure of the steam acts in the catch tank 11. The cooling water in the catch tank 11 is supplied to the cooling water injection nozzle 4 by the water pump 5 through the three-way valve 16. Thereby, the differential pressure between the inlet and outlet of the water pump 5 is reduced, and water is supplied into the water jacket 3. At this time, since the one-way valve 10 is closed by the pressure in the catch tank 11, the cooling water in the catch tank 11 does not flow backward to the condenser 9 side. In addition, the process of step S7 and the process of step S8 may be interchanged regardless of the order, and may be performed simultaneously. After performing the processing of step S7 and step S8, the process proceeds to step S9.

In step S9, the integrated value of the cooling water supply amount, that is, the amount of cooling water Gf (g) supplied from the catch tank 11 into the water jacket 3 exceeds the required water supply amount Gw (g). Judge whether or not. The water supply integrated value Gf is expressed by the following equation as the specific gravity γw (g / L) of the cooling water:
Gf = ΣVw (Ne) × γw × dt
And it is required.
That is, it is calculated from the time integration of the discharge amount of the water pump 5 determined from the engine speed Ne (rps).
Note that there is a relationship as shown in FIG. 6 among the engine speed Ne, the discharge amount Vw of the water pump 5, and the water pump inlet / outlet differential pressure.
ECU21 continues water supply, when Gf obtained by performing the above calculations is still smaller than Gw, and it is judged No in step S9. On the other hand, if Yes is determined in step S9, the process proceeds to step S10.

  In step S10, the water supply amount integrated value Gf used in step S9 is once reset. That is, Gf = 0 is set. After the process of step S10 is performed, a return is returned. The control is returned, and again, the process proceeds to step S5, whereby the waste heat recovery apparatus 1 is controlled to return to the “circulation state” shown in FIG. 1, and the “water supply state” shown in FIG. .

  FIG. 7 shows an example of a state of switching between the “circulation state” and the “water supply state” in the waste heat recovery apparatus 1 that performs the control as described above. That is, when the engine 2 is in a warm-up state, it is in a “circulation state”, and when the warm-up is completed and steam is generated, a “water supply state” appears. This “water supply state” appears repeatedly while the engine 2 is operating, but the interval is long when the load of the engine 2 is low, and the interval is short when the load is high. Thereby, the amount of cooling water in the water jacket 3 is maintained.

  As described above, according to the waste heat recovery apparatus of the present invention, the catch tank is used when the amount of cooling water in the water jacket 3 is reduced, although only one water pump 5 is provided. By applying the pressure of the steam to the inside 11, the differential pressure between the inlet and outlet of the water pump 5 can be reduced, and the cooling water that has become liquid in the condenser 9 can be supplied again into the water jacket 3. Thereby, the amount of cooling water in the water jacket 3 can be maintained.

  The above-described embodiments are merely examples for carrying out the present invention, and the present invention is not limited thereto. Various modifications of these embodiments are within the scope of the present invention. It is apparent from the above description that various other embodiments are possible within the scope.

It is explanatory drawing which showed the mode when it is in the "circulation state" when an engine is in a warming-up state and circulating the cooling water in a water jacket. It is explanatory drawing which showed the mode when it is in the "water supply state" which supplies cooling water from the catch tank side. It is a flowchart which shows an example of control of a waste heat recovery apparatus. It is explanatory drawing which shows the relationship between the cooling water heat-receiving amount Qw and the evaporation amount Gs. It is explanatory drawing which shows the relationship between the engine speed Ne, the engine load H, and the cooling water heat receiving amount Qw. It is explanatory drawing which shows the relationship between engine speed Ne, discharge amount Vw of a water pump, and water pump inlet / outlet differential pressure. It is explanatory drawing which shows an example of the mode of switching between the "circulation state" and the "water supply state" in a waste heat recovery apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Waste heat recovery apparatus 2 Engine 2a Cylinder block 2b Cylinder head 3 Water jacket 4 Cooling water injection nozzle 5 Water pump 6a Power recovery path 6b Bypass path 7 Superheater 8 Turbine 9 Condenser 10 One-way valve 11 Catch tank 12 1st cooling water Path 13 Exhaust port 14 Exhaust path 15 Generator 16 Three-way valve 17 Second cooling water path 18 Heater 19 Throttle 20 On-off valve 21 ECU
22 Water temperature sensor

Claims (6)

A power recovery path in which an expander and a condenser are arranged;
A bypass path of the power recovery path;
A steam flow path switching means for switching between the power recovery path and the bypass path and changing a steam flow path;
A waste heat recovery device characterized by comprising: A power recovery path in which an expander and a condenser are arranged;
A bypass path of the power recovery path;
A steam flow path switching means for switching between the power recovery path and the bypass path and changing a steam flow path;
A cooling water supply path including a water pump, the water jacket or the condenser as a cooling water supply source,
Cooling water supply source switching means for switching the cooling water supply source in the cooling water supply path;
A waste heat recovery device characterized by comprising: In the waste heat recovery apparatus according to claim 1 or 2,
The waste heat recovery apparatus, wherein the steam flow path switching means switches between the power recovery path and the bypass path according to a remaining amount of cooling water in the water jacket. The waste heat recovery apparatus according to claim 1 or 2,
The waste water recovery apparatus, wherein the cooling water supply source switching means switches the cooling water supply source in accordance with a remaining amount of cooling water in the water jacket. The waste heat recovery apparatus according to claim 1 or 2,
The waste heat recovery apparatus according to claim 1, wherein the power recovery path includes a cooling water backflow prevention means on the downstream side of the condenser. An engine comprising the waste heat recovery device according to any one of claims 1 to 5.

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