JPS6321313A - Method and equipment for recovering exhaust gas energy in internal combustion engine - Google Patents

Abstract

PURPOSE:To eliminate the discontinuity of the engine performance, by providing a valve between the scavenging part and a power turbine in an internal combustion engine and constituting the system in such a manner that the valve is kept full open for the output lower than the normal output, while it is gradually opened for the range of output higher than the normal output by the predetermined value. CONSTITUTION:A turbine 6 of a supercharger 3 and a power turbine 7 are connected in parallel to the scavenging part of an internal combustion engine 1. A by-pass valve 8 is provided between the scavenging part and the power turbine 7. The by-pass valve 8 is kept full open for the output lower than the normal output. The opening of the by-pass valve 8 is gradually varied in the range of output higher than the normal output by the predetermined value. With this contrivance, discontinuity of the engine performance caused by the on-off operation of the power turbine 7 can be eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and apparatus for recovering exhaust gas energy by connecting a supercharger and a power turbine in parallel to the exhaust section of an internal combustion engine.

[Prior Art] In internal combustion engines such as diesel engines, it has been widely practiced to provide a supercharger to recover exhaust energy. Power is also recovered using axial or centrifugal turbines (herein referred to as power turbines).

FIG. 5 is a block diagram illustrating a conventional exhaust gas energy recovery method and device for an internal combustion engine in which a supercharger and a power turbine are connected in parallel to the exhaust section. A compressor section 4 of a supercharger 3 is connected to the scavenging receiver 2 . Further, the exhaust receiver 5 of the diesel engine body 1 is connected in parallel with a turbine section 6 of the supercharger 3 and a power turbine 7, and a valve (bypass valve) is connected between the exhaust receiver 5 and the power turbine 7. 8) is installed. Reference numeral 9 indicates a propeller screw connected to the diesel engine main body 1.

In such a conventional example, the bypass valve 8 is fully open when the output state of the engine is equal to or higher than a predetermined engine output (hereinafter, this output is referred to as a reference output), and is fully closed when it is lower than the reference output. , so-called on-off opening/closing control was performed.

That is, when the engine output exceeds the reference output, the engine exhaust gas from the scavenging receiver is supplied to both the turbine section 6 and the power turbine section 7, and the power recovered by the power turbine 7 is used as backup power for the propeller screw 9. The energy is transmitted to the output shaft of the engine via gears (or after being converted into electrical energy and via a backup electric motor), reducing fuel consumption accordingly.

Hereinafter, the operation of such a power recovery system will first be explained in detail.

The turbine efficiency ηt of the supercharger is a function of the turbine population/outlet pressure ratio πt, and generally has a characteristic that has a maximum value at a certain pressure ratio, as shown in FIG.

For example, the output of the engine is 14160 at 100% load.
Suppose psxl 17 rpm is requested. In this case, unless a power turbine is installed, the engine itself must generate an output of 14,160 ps, and the fuel consumption rate S FOC (g/p s - h) of the engine is 8
It will look like the solid line in the figure.

On the other hand, if a power turbine is installed, in order to obtain a shaft output of 14,160 ps, the engine itself will need 136 ps.
60 ps is enough, remaining 500 ps (approximately 37 of engine output)
%) can be supplemented with a power turbine.

Therefore, the smaller the net average effective pressure (which is proportional to the output/rotational speed), the better the fuel consumption rate.
Since 3660PSL/ is not required, the fuel consumption rate becomes even smaller in terms of shaft output.

However, as the load decreases, the effective output that can be extracted by the power turbine rapidly decreases as shown by the broken line in FIG. 8, and when the output becomes smaller than a certain level, the power turbine becomes unable to extract power.

Therefore, in the conventional exhaust gas energy recovery method and apparatus for an internal combustion engine shown in FIG. 5, when the output is lower than the reference output, the valve 8 is fully closed and the power turbine is stopped. In other words, in the case of the conventional exhaust gas energy recovery method and device for an internal combustion engine, a part of the exhaust gas is flowed toward the power turbine, and the rest is guided to the supercharger for the engine main body, and the total amount of exhaust gas is GT the amount of gas to the feeder,
If the amount of gas to the power turbine is GP, then G=GT
+GP, and the optimal supercharger is selected (matching) for the gas flow rate GT. This is designated as π1 point in FIG. In this case, when the load decreases, the amount of waste gas decreases and the pressure ratio decreases, resulting in a decrease in turbine efficiency. Therefore, the work done by the supercharger decreases, and fuel efficiency also deteriorates (π2 points).

However, if the valve 8 is fully opened and the exhaust gas ftGP, which has been flowing towards the power turbine, is now also allowed to flow towards the supercharger, the pressure ratio will increase by the amount of gas increased. Turbine efficiency also increases, the workload of the supercharger increases, and fuel efficiency improves (π3).

[Problem to be Solved by the Invention 1] As described above, in the conventional exhaust gas energy recovery method and device for an internal combustion engine in which a supercharger and a power turbine are installed in parallel, the bypass valve opening shown in FIG. As shown in the figure, the flow rate of exhaust gas flowing into the power turbine 7 is controlled by opening and closing the bypass 8 (fully open or fully closed) at a load where the fuel consumption rate and other conditions are considered optimal. Therefore, as shown in the fuel consumption rate 5FOC etc. in Figure 6, the performance curve looks like a dashed line on the low load side at full throttle, and like a broken line on the high load side at full throttle, and there is a gap between the two. A discontinuous portion (thick solid line) occurs, resulting in wasteful fuel consumption, and there is a risk that engine operation may become unstable during this full-close/fully-open switching.

[Means for Solving the Problems] The exhaust gas energy recovery method and device for an internal combustion engine of the present invention connects a turbine section of a supercharger and a power turbine in parallel to a scavenging section of an internal combustion engine. In an exhaust gas energy recovery system that has a valve (bypass valve) between the It was designed to increase the number of people.

[Examples] Hereinafter, the present invention will be described in more detail with reference to examples shown in the drawings.

FIG. 1 is a block diagram showing the configuration of an exhaust gas energy recovery method and device for an internal combustion engine according to an embodiment of the present invention, and FIG. 2 is a characteristic diagram thereof. Moreover, FIG. 3 is a sectional view showing the structure of the bypass valve.

In the present invention, a valve whose opening degree can be gradually changed is adopted as the bypass valve 8.
A separator control device 10 is provided for adjusting the opening degree of the separator according to the engine output rotation speed and the like. Reference numeral 11 is a detector for the engine rotation speed, and 12 is a detector for the scavenging air pressure of the scavenging section receiver, and the detected values can be manually input to the separator device 10, respectively. In this embodiment, it is also possible to input the temperature, engine room pressure, and temperature of seawater, which is the cooling source for the supercharged air cooler (not shown) provided in the path supplied from the compressor 4 to the scavenging section 2. has been done.

Further, the bypass valve 8 is equipped with a pulse motor 8a, and a pulse signal is sent as a control output signal, and the pulse motor 8a rotates by the number of rotations corresponding to the number of pulses, thereby adjusting the valve opening degree. It has become.

The configuration of the bypass valve 8 will be explained with reference to FIG. Reference numeral 20 denotes a valve housing, which is provided with a valve seat 22 and a valve body 23 so as to be able to shut off an internal passage 21. The valve body 23 is provided at the tip of the valve spindle 24, and has a streamlined shape with conical upper and lower sides.
A seat portion 23a that contacts the valve seat 22 is provided on the upper side surface.

The housing 20 is provided with a sleeve 25 that slidably supports the spindle 24. The spindle 24 is inserted through the sleeve 25, and the tip of the spindle 24 extends to come into contact with a guide 26.

As shown in FIG. 4, which is a sectional view taken along the line IV-rV in FIG. 3, this guide 26 has a female screw hole bored in the axial direction, and a key 27 protruding from the side. key 27
is engaged with a keyway 28 provided in the housing 20, and the female screw hole is screwed into a female screw 29 fixed to the rotating shaft of the pulse motor 8a.

A spring presser 30 is provided in the middle of the spindle 24 so as not to protrude sideways, and a coil spring 32 is provided between it and a flange portion 31 provided on the casing 20.
The spindle 24 is urged upward in the figure.

Reference numeral 33 indicates a flange for attaching the bypass valve 8 to the scavenging section of the engine.

In such a configuration, when the pulse motor 8a is rotated in the forward direction, the guide 26 is pushed downward in the figure, and the spindle 2
4 descends against the repulsive force of the spring 32, and the valve body 23
is separated from the valve seat 22, the passage 21 is gradually opened, and eventually reaches a fully open state. When the pulse motor 8a is reversed, the elastic force stored in the spring 32 pulls the spindle 24 upward in the figure, gradually reducing the amount of airflow in the passage 21, and eventually the valve body 23 is brought into contact with the valve seat 22. When the person is seated, the passage 21 reaches a fully closed state.

In this way, this pulse motor bypass valve converts the rotational motion of the pulse motor 8a into vertical motion by the screw engagement between the male screw 29 and the guide 26 and by the spring 32. Also, spring 3
2 ensures airtightness when seated. Furthermore, the exhaust gas that is about to flow through the passage 21 (bypass line) has a high pressure and a high flow velocity. Therefore, it is necessary to adjust the opening degree sensitively depending on the scavenging pressure, so it is necessary to reduce the resistance of the pulp spindle and make the valve easy to open and close.In this example, the valve spindle The valve body 23 at the tip of the valve body 24 has a streamlined shape as shown in the figure, and corresponds to this. Note that the tip shape does not necessarily have to be streamlined, but may be a pointed shape, or a shape in which rod-shaped protrusions are connected downward to a flat tip portion.

Note that in the present invention, a known computer or the like can be employed as the control device 10.

As is well known, this computer is equipped with a ROM that stores control programs, a RAM that temporarily stores various data, a central processing unit, an input/output device, a data bus that connects these, etc. Temperature, seawater temperature, etc. are converted into digital signals by an A/D converter and input manually.

The above control is performed, for example, according to the flowchart (steps 91 to 96) shown in FIG. Next, the operation of the above embodiment device will be explained.

In the present invention, by continuously opening and closing the bypass valve 8 from fully open to fully closed, the discontinuous part (Fig. 6) in the output characteristics is eliminated and the output characteristics are smoothly continuous. be. To that end, first, as shown in Figure 2,
Point A at which the bypass valve is fully opened and point B at which the bypass valve is fully opened are determined from engine performance such as fuel consumption rate when the bypass valve 8 is fully open and when it is fully closed. Therefore, points A and B of the scavenging pressure PS of the engine are smoothly connected, and a curve CABD representing the relationship between the engine speed and the scavenging pressure is set as the set scavenging pressure curve for the engine (step 92.93). However, the scavenging pressure is under standard conditions (e.g. 20°C, 760mmHg,
(Seawater temperature: 10° C.) (corrected based on the engine pressure, temperature, and seawater temperature read in step 91).

Then, this set scavenging pressure curve is stored in the storage device of the bypass valve opening control device 10 (step 94).

The scavenging pressure ps and engine speed Ne during operation are used as the main input signals of the bypass valve opening control device (step 95), and the opening of the bypass valve is determined from the deviation from the set scavenging pressure curve and output (step 96). ). Steps 91 to 96 are repeated to adjust the scavenging pressure while giving feedback.

In addition, for standard state conversion, the engine room pressure, temperature, and seawater inlet temperature are also used as input signals for correction (step 91
).

Based on these input data, the valve opening calculated by the bypass valve opening control device is transmitted to the pulse motor 8a as an electric signal (pulse signal).

Then, the pulse motor 8a rotates at a required number of rotations, and the valve body is controlled to continuously adjust the opening between fully open and fully closed.
As shown in FIG. 2, the output characteristics are smoothly continuous over the entire output range.

As a result, the fuel consumption is reduced by the area S shown with a comparison hatch in the prior art, and the instability of engine operation when switching between fully open and fully closed, which was seen in the prior art, is eliminated.

Note that the engine room pressure, engine room temperature, and seawater temperature are processed as correction factors as follows.

(a) When the engine room pressure increases, it acts to increase the force attributable to the scavenging section, so when the engine room pressure increases, the valve opening of the bypass valve is increased.

(b) When the engine room temperature rises, it acts to lower the scavenging force, so when the engine room temperature falls, the opening degree of the bypass valve is reduced.

(c) When the seawater temperature rises, it acts to increase the scavenging force, so when the seawater temperature rises, the valve opening of the bypass valve is increased.

(In addition, in (a) to (c), when the engine room pressure, temperature, and seawater temperature change in the opposite direction, the valve opening degree is adjusted in the opposite direction to the above.) [Effect] As described above, In the present invention, since the opening degree of the valve between the engine scavenging section and the power turbine is gradually increased or decreased,
The conventional discontinuity in engine performance caused by fully opening and closing the valve, that is, turning the power turbine on and off, is eliminated, improving fuel consumption and stabilizing machine-related motion in the valve opening switching range.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the configuration of an exhaust gas energy recovery method and device for an internal combustion engine according to an embodiment of the present invention, Fig. 2 is an output characteristic diagram thereof, Fig. 3 is a sectional view of a flow rate regulating valve, and Fig. 4 is a sectional view taken along the TV-rV line in FIG. 3, FIG. 5 is a block diagram showing the configuration of a conventional example, FIG. 6 is an output characteristic diagram of the same, and FIGS. 7 and 8 are explanatory diagrams of characteristics of the power turbine. It is. 9th
The figure is a flowchart showing a control program in an embodiment. 1...Diesel engine body, 2...Scavenging air receiver,
3...Supercharger, 4...Compressor, 5...Exhaust receiver, 6...Turbine,
7... Power turbine, 8... Bypass valve,
8a...Pulse motor, 22...Valve seat, 23
... Valve body, 26... Guide.

Claims (5)

[Claims] (1) A supercharger whose turbine section is connected to the exhaust section of the internal combustion engine and whose compressor section is connected to the scavenging section of the internal combustion engine, and connected to the exhaust section in parallel with the supercharger through a valve. In the method for recovering exhaust gas energy of an internal combustion engine, the valve is fully closed at below the reference output, and the valve is fully closed at below the reference output, and the valve is opened at an output above the reference output capable of energy recovery. A method for recovering exhaust gas energy from an internal combustion engine, characterized in that the valve is fully opened at a predetermined output on the high output side by a required output, and the opening degree of the valve is gradually changed between the reference output and the predetermined output. (2) The method according to claim 1, wherein the predetermined output is an output at which the scavenging pressure when the valve is fully open is approximately equal to the scavenging pressure at the reference output when the valve is fully closed. (3) A supercharger whose turbine section is connected to the exhaust section of the internal combustion engine and whose compressor section is connected to the scavenging section of the internal combustion engine, and connected to the exhaust section in parallel with the supercharger through a valve. a power turbine which has been stored, a storage means for a reference output capable of energy recovery, and a valve that is fully closed when the output is below the reference output and fully opened from the reference output by a required output to the high output side, and in which the valve opening degree is adjusted. An exhaust gas energy recovery device for an internal combustion engine, comprising a gradually changing valve control device. (4) The valve control device further includes a means for detecting the engine output of the internal combustion engine, a means for detecting the pressure of the scavenging section, a means for storing the pressure Pa at the fully closed state at the reference output, and an output equal to or higher than the reference output. Comparison means for comparing the scavenging pressure Px and the Pa, and scavenging pressure P between when the valve is fully closed and when the valve is fully opened
4. The device according to claim 3, further comprising means for adjusting the valve opening degree based on the comparison result of the comparison means so that x becomes approximately equal to Pa. (5) The device according to claim 3 or 4, wherein the valve includes a valve body having a streamlined shape in the gas flow direction.