JPH0647937B2 - Turbo Compound Engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a turbo compound engine.

[Prior Art] A combustion chamber of an adiabatic engine is made of ceramic, and a turbocharger and a turbine are connected to an exhaust manifold,
A turbo compound engine is generally known as a device for efficiently recovering exhaust gas energy.

This turbo compound engine aims to recover the exhaust gas energy by the diesel engine cycle and the Brighton cycle that drive the turbocharger and the turbine by the heat energy transferred to the exhaust gas by insulating as much as possible during the heat generation period of the engine. is there.

By the way, the preceding example of turbo compound engine is No. 7
"Two-stage supercharged internal combustion engine" as shown in the figure
Issue).

According to this proposal, the high-pressure exhaust valve a is opened before the low-pressure exhaust valve b and the high-pressure exhaust valve is closed before the low-pressure exhaust valve b. , The high-pressure turbocharger d is activated first, and then the high-pressure turbocharger d
The engine E supplied to the downstream side of the high-pressure stage turbocharger d and the upstream side of the low-pressure stage turbocharger e, bypassing the exhaust gas via the high-pressure stage turbocharger d
The low pressure turbocharger e is configured to operate by the static pressure of the exhaust gas that merges with the exhaust gas, and the exhaust gas energy is effectively recovered to reduce the pumping loss of the engine E. .

[Problems to be Solved by the Invention] However, as proposed, at all rotation speeds and loads,
When the high pressure exhaust valve is opened before the low pressure exhaust valve and the high pressure exhaust valve is closed before the low pressure exhaust valve, the high pressure turbocharger and the low pressure turbocharger are provided even when the flow rate of exhaust gas is low. However, there is a problem in that exhaust gas cannot be supplied at a sufficient flow rate and an appropriate boost pressure cannot be obtained.

SUMMARY OF THE INVENTION An object of the present invention is to provide a turbo compound engine configured so that a turbocharger operates well and an appropriate supercharging pressure is obtained even when the exhaust gas flow rate is small.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a cylinder head with a main exhaust passage opened and closed by a main exhaust valve and a sub exhaust passage opened and closed by a sub exhaust valve. In a turbo compound engine in which a turbocharger turbine is provided in the exhaust passage and a turbine is separately provided on the downstream side of the turbine, the downstream end of the auxiliary exhaust passage is separated from the turbine of the turbocharger in the main exhaust passage and another turbine. The auxiliary exhaust valve is set to be opened and closed later than the main exhaust valve and to be closed at the same time as the main exhaust valve. An opening / closing valve that adjusts the opening degree of the sub exhaust passage according to the exhaust gas flow rate of the engine is provided on the downstream side of the.

[Operation] The on-off valve fully opens the sub exhaust passage when the exhaust gas flow rate is sufficient, for example, at high speed and high load. At this time, if the sub exhaust valve is opened later than the main exhaust valve, the exhaust gas that has been left in the cylinder in the past is discharged from the sub exhaust passage without remaining. For this reason, the pressure in the cylinder decreases, the work amount in the exhaust process of the engine decreases, and the work amount in the intake stroke decreases.

Further, the on-off valve adjusts the opening degree of the sub exhaust passage to an opening degree according to the exhaust gas flow rate when the exhaust gas flow rate is low. Therefore, the amount of exhaust gas supplied from the sub exhaust passage to the main exhaust passage is limited. Therefore, even when the exhaust gas flow rate is low, the turbine of the turbocharger is rotated well and an appropriate supercharging pressure is secured (for example, when the exhaust gas flow rate is the minimum amount for the engine, the on-off valve is fully closed, The exhaust gas in the cylinder is not supplied from the auxiliary exhaust passage to the main exhaust passage, but is supplied to the turbocharger turbine through the main exhaust passage).

[Embodiment] A preferred embodiment of the turbo compound engine of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a schematic cross section of a turbo compound engine.

In the figure, 1 is a cylinder body, 2 is a cylinder liner,
3 is a piston, 4 is a cylinder head, and 7 is a main exhaust valve.

The cylinder liner 2 is made of highly heat-insulating ceramic, and the piston 3 is reciprocally housed in the cylinder liner 2. A cylinder chamber 5 is defined by the cylinder head 4, the cylinder liner 2, and the piston 3 which are seated on the cylinder body 1 and integrally joined thereto. Inside the cylinder head 4, a main exhaust passage 6 communicating with the cylinder chamber 5 is formed.
It is adapted to be opened and closed by a main exhaust valve 7 which is reciprocally provided therein. 8a is a valve seat on which the valve face 7a of the main exhaust valve 7 is seated. Also,
A sub-exhaust passage 9 communicating with the cylinder chamber 5 is formed in the cylinder head 4 at a position parallel to the main exhaust passage 6, and the sub-exhaust passage 9 is reciprocally movable in the cylinder head 4. It is adapted to be opened and closed by the auxiliary exhaust valve 10 provided. 8b is a valve seat on which the valve face 10a of the auxiliary exhaust valve 10 is seated. An exhaust system is constructed by connecting an exhaust manifold to each of the main exhaust passage 6 and the auxiliary exhaust passage 9.

As shown in FIGS. 1 and 2, the exhaust manifold 11 connected to the main exhaust passage 6 is connected to the turbine scroll introduction portion 12 a of the turbocharger 12 as one collecting pipe, and is connected to the exhaust portion 14 of the turbocharger 12. The connected exhaust manifold 18 is connected to the turbine scroll introducing portion 16 of the turbine 15 for recovering exhaust gas energy. The exhaust part 15a of the turbine 15 is connected to an exhaust manifold 17 having a muffler. Therefore, the turbocharger 12 and the turbine 15 are sequentially provided in the exhaust manifolds 11, 18, and 17, which are part of the main exhaust passage 6, in the downstream direction. The turbine 15 for recovering exhaust gas energy is connected to an energy recovery device 30 that is directly or indirectly operated by this and recovers exhaust gas energy as energy that can be reused. As the energy circuit device 30, for example, an alternator that recovers exhaust gas energy as electric power is adopted.

On the other hand, the auxiliary exhaust passage 9 is connected to an exhaust manifold 18 between the connecting portions of the turbocharger 12 and the turbine 15 via an auxiliary exhaust manifold 19, and the auxiliary exhaust passage 9 is connected to the exhaust gas flow rate of the engine E. An on-off valve means is provided whose opening is adjusted accordingly. The on-off valve means includes an on-off valve 20, a controller 21 for adjusting the opening degree of the on-off valve 20, an actuator 22 for operating the on-off valve 20 according to a command from the controller 21, an exhaust gas flow rate of the engine, and the controller 21 for detecting the exhaust gas flow rate. It is composed of a sensor (not shown) for inputting a detection value. Any sensor may be used as long as it can detect the exhaust gas flow rate of the engine, and specifically, a load sensor, a rotation speed sensor, a boost pressure sensor, or the like is provided.

In FIG. 2, 25 is an intake passage, 26 is an intake manifold, and the intake passage 25 is connected to the compressor 27 of the turbocharger 12 and the turbine 15 via the intake manifold 26.

FIG. 3 shows the opening and closing timings of the main and auxiliary exhaust valves 7 and 10.

As shown in the figure, the main exhaust valve 7 is designed to be opened before bottom dead center (BDC) and closed at a position beyond the top dead center (TDC), while the sub exhaust valve 10 is The main exhaust valve 7 is opened at the maximum lift and closed at the same time as the main exhaust valve 7.

The operation of the turbo compound engine of the present invention will be described below with reference to the accompanying drawings.

As shown in FIGS. 1 and 2, when the engine E is started and the rotation speed and load are small, the exhaust gas flow rate is small. At this time, the controller 21 causes the actuator 2 to close the on-off valve 20 according to the flow rate of the exhaust gas.
Adjust the movement amount of 2. Therefore, since the opening degree of the sub exhaust passage 9 becomes small, most of the exhaust gas flows into the main exhaust passage 6, and this exhaust gas sequentially operates the turbocharger 12 and the turbine 15. Of course, when the exhaust gas flow rate is the minimum amount for the engine E, the on-off valve 20 is fully closed. Therefore, even at the time of low rotation and low load where the exhaust gas flow rate tends to be insufficient, the turbocharger 12 is driven well, an appropriate supercharging pressure is obtained, and the exhaust energy is effectively recovered by the operation of the turbine 15.

When the exhaust gas flow rate is high and the load is high, the controller 21 controls the actuator 22 to fully open the open / close valve 20 and fully open the sub exhaust passage 9. At this time, the main exhaust valve 7
When the auxiliary exhaust valve 10 is opened after the delay, the conventional cylinder chamber 5
The exhaust gas left inside is discharged from the auxiliary exhaust passage 9 without remaining. For this reason, the pressure in the cylinder chamber 5 decreases, and the work amount during the exhaust stroke and the work amount during the intake stroke of the engine decrease.

FIG. 4 is a p-v diagram showing a comparison between the turbo compound engine of the embodiment of the present invention and a conventional turbo compound engine.

In the figure, the solid line a indicates the embodiment of the present invention, and the broken line b indicates the conventional example.

In this p-v diagram, the diesel cycle D of the engine
S and the turbine cycle TS of the turbocharger 12 and the turbine 15 are represented as a composite. In the figure, in the diesel cycle DS, a begins to compress and b the compression end,
C is the heat generation period, N is the expansion stroke, W is the blowdown period, HEAT is the exhaust stroke, and CH is the intake stroke. Further, PB indicates supercharging pressure.

First, the case where the exhaust gas energy is sufficient as in the case of high speed and high load will be described.

As in the diesel cycle shown in the conventional example b, the gate charge during the intake / exhaust stroke becomes a negative work for the engine when the boost pressure PB is taken as a reference, and becomes a heavy burden.
On the other hand, in the embodiment a of the present invention, when the exhaust gas energy is sufficiently high speed and high load, the actuator 22 fully opens the on-off valve 20 according to the command of the controller 21, so that not only the main exhaust passage 6 but also the auxiliary exhaust passage 6 is opened. Since the exhaust gas is supplied to the exhaust passage 9, the exhaust gas does not remain in the cylinder chamber 5. Therefore, the cylinder chamber 5
The pressure of is dropped from the re-position in FIG. 4 to the n-position. Even if the exhaust stroke is completed in this state, if the exhaust gas from the main exhaust passage 6 has sufficient exhaust gas energy to drive the turbocharger 12, the boost pressure is maintained at PB. Therefore, the internal pressure of the cylinder chamber 5 can be lowered during the exhaust stroke, and fresh air can be smoothly introduced into the cylinder chamber 5 during the intake stroke. That is, the exhaust stroke shown by the number in FIG. 4 becomes lower than the supercharging pressure PB, and the reach-wheel during the intake-exhaust stroke is reduced as a work to make the positive one-wheel reach. Can be a job. Since the energy of the exhaust gas that drives the turbine 15 is recovered by the energy recovery device 30, this recovered energy is effectively used again as power and electric energy. Further, exhaust gas can be exhausted without being left inside the cylinder chamber 5, which prevents the temperature inside the cylinder chamber 5 from rising and suppresses heating of the intake air. Therefore, intake efficiency of intake air is stabilized and decrease in output is suppressed. be able to. In the embodiment, the auxiliary exhaust valve 1
The reposition for opening 0 is set to an appropriate position in the middle of the exhaust stroke in consideration of exhaust gas energy and engine friction.

These results also positively affect the diesel cycle and turbine cycle (= Brighton cycle). That is, the work of the turbocharger 12 is reduced in the expansion stroke as shown in the tare, and the turbine work of the turbine 15 is increased to the laser. This shows that the turbine work can be increased and the exhaust gas energy recovery efficiency can be improved. This means that the energy recovery device 30
It means that the amount of work of the turbine 15 that drives the engine increases, and the recovered energy that can be reused increases with this increase. In this embodiment, the energy recovery device 30
As the alternator is driven, electric power can be obtained according to the increase of turbine work. The electric power obtained here is reused for power again.

Next, the case where the exhaust gas energy, that is, the exhaust gas flow rate is small, as in the case of low speed and low load, will be described. in this case,
The auxiliary exhaust valve 10 is opened at the reposition, but the controller 21 controls the actuator 22 to operate the auxiliary exhaust passage 9 to the fully closed side. Therefore, even if the auxiliary exhaust valve 10 is opened later than the main exhaust valve 7, the exhaust gas is not supplied from the auxiliary exhaust passage 9 to the main exhaust passage 6, and the exhaust gas in the cylinder chamber 5 is entirely in the main exhaust passage 6. Is supplied to. Therefore,
Even when the exhaust gas flow rate is small, the turbocharger 12 turbine rotates well and an appropriate boost pressure can be obtained.

Therefore, the energy of the exhaust gas can be effectively used by the two turbines as in the turbo compound engine, and the energy recovery at the time of high speed and high load where the change of the air volume increases quadratically like the rotating machine and It is possible to achieve both energy recovery at low speed and low load.

As shown in FIGS. 5 and 6, a second turbocharger 15b is provided instead of the turbine 15 downstream of the turbocharger 12 in the main exhaust passage 6 so as to supercharge the engine. Of course it is possible.

[Effects of the Invention] As is apparent from the above description, the turbo compound engine of the present invention can exhibit the following excellent effects.

The work of the exhaust stroke and the intake stroke at high speed and high load can be reduced, and an appropriate boost pressure can be obtained even when the exhaust gas flow rate is small.

[Brief description of drawings]

FIG. 1 is a schematic view showing a first embodiment of a turbo compound engine of the present invention, FIG. 2 is an overall view of the turbo compound engine of FIG. 1, and FIG. 3 is a view showing opening / closing timings of main and auxiliary exhaust valves. FIG. 4 is a p-v diagram showing a diesel cycle and a turbine cycle, FIG. 5 is a schematic diagram showing a second embodiment of the turbo compound engine of the present invention, and FIG. 6 is a turbo compound engine of FIG. An overall view and FIG. 7 are schematic views showing a conventional two-stage supercharged internal combustion engine. In the figure, 6 is a main exhaust passage, 9 is an auxiliary exhaust passage, 12 is a turbocharger, 15 is a turbine for collecting exhaust gas energy, 20 is an opening / closing valve, and E is an engine.

Claims (1)

[Claims] 1. A cylinder head is provided with a main exhaust passage opened and closed by a main exhaust valve and a sub exhaust passage opened and closed by a sub exhaust valve, a turbine of a turbocharger is provided in the main exhaust passage, and a downstream of the turbine. In a turbo compound engine in which a turbine is separately provided on the side, the downstream end of the auxiliary exhaust passage is connected to be connected between the turbine of the turbocharger of the main exhaust passage and another turbine,
The opening / closing timing of the auxiliary exhaust valve is set to be opened later than the main exhaust valve and to be closed at the same time as the main exhaust valve, and the engine exhaust gas is provided in the auxiliary exhaust passage downstream of the auxiliary exhaust valve. A turbo compound engine having an on-off valve for adjusting the opening of the auxiliary exhaust passage according to the gas flow rate.