JP2000154770A - Water-cooled engine and small planing boat furnished with it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lower engine speed without depending on partial flame-out driving in the case when cooling water does not normally flow to a water-cooled engine. SOLUTION: Engine speed is detected by a tachometer 34 and pressure of cooling water W in the inside of a cooling water passage is detected by a pressure sensor 35 on a water-cooled engine 4 furnished with the cooling water passage 20 having an intake port 23 to take in the cooling water W from outside and a discharge port to discharge the cooling water after engine cooling outside. Ignition timing of an ignition plug is lagged by a lag means 38 at the time when detected cooling water pressure is lower than an allowable value to change in accordance with engine speed. Consequently, engine speed is automatically lowered when the cooling water W does not smoothly flow to the engine 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-cooled engine having a cooling water passage having an inlet for taking in cooling water from outside and an outlet for discharging cooling water after cooling the engine to the outside, and a water-cooled engine provided with the same. A small planing boat.

[0002]

2. Description of the Related Art In a personal watercraft, a water-cooled engine is usually used because the engine is housed in an engine room. The water cooling method of this engine is generally a direct cooling method having a simple structure. For example, a part of the pressurized water is introduced into an engine water jacket through a pipe from an opening provided in a water jet propulsion machine and used as cooling water. It is configured as follows. Further, the water after cooling the engine is discharged outboard via an exhaust device having the following configuration. That is, the exhaust device includes an exhaust pipe connected to an exhaust manifold of an engine cylinder, a muffler connected to a downstream portion of the exhaust pipe, a muffler connected to an outlet of the muffler, and a stern. The exhaust pipe and the muffler each have an outer wall having a double structure, a cooling water passage between the double outer walls, and a cooling water flowing out of the engine. After passing through the cooling water passage, the exhaust gas is discharged outboard through the muffler and the tail pipe together with the exhaust gas.

On the other hand, in a water-cooled engine, when the temperature of cooling water rises, the engine speed is reduced by performing a partial misfire operation (thinning operation) or an operation with a delayed ignition timing (retarded operation). There is known a control device for reducing the heat load of the engine. That is, some of the control devices delay the ignition timing by a predetermined value when the temperature of the engine coolant reaches or exceeds a predetermined temperature. Japanese Patent Application Laid-Open No. Hei.
No. 65 is known.

[0004]

However, in a water-cooled engine incorporating a control device having the above-described functions, control responsiveness is low because the cooling water temperature rises later than the engine temperature rise. Further, in the partial misfire operation method, when a catalytic converter for purifying exhaust gas is mounted in the exhaust pipe of the exhaust device, unburned gas due to partial misfire is burned by the catalytic converter and becomes high temperature.
A large heat load may be applied to the catalytic converter.

[0005] The present invention has been made in view of the above-described circumstances, and when the flow of cooling water to the engine is not smooth, a water-cooled type that can quickly reduce the engine speed. It is an object of the present invention to provide an engine and a personal watercraft equipped with the engine.

[0006]

In order to achieve the above object, a water-cooled engine according to a first aspect of the present invention has an intake for taking in cooling water from outside and a cooling water after cooling the engine to outside. A cooling water passage having a discharge port for detecting the rotation speed of the engine, a pressure sensor for detecting the pressure of the cooling water in the cooling water passage, and a driving device driven by the engine. Pumping means for pumping the cooling water from the inlet to the cooling water passage, storage means for storing a relationship between an engine speed and an allowable value of the pressure of the cooling water, and a detected cooling water pressure is detected. Retarding means for retarding the ignition timing of the ignition plug when the engine speed is equal to or less than the allowable value at the engine speed.

According to the water-cooled engine, the retarding means retrieves the allowable value of the cooling water pressure corresponding to the engine speed detected by the tachometer from the storage means, and detects the cooling water pressure detected by the pressure sensor. Is smaller than the permissible value found, the retarding means retards the ignition timing of the ignition plug, so that even if the cooling water is not smoothly pumped into the cooling water passage by the pumping means, the engine speed is higher than normal. And the heat load of the engine is prevented from increasing.
In addition, in the open-circuit type cooling water system that takes in the cooling water from the outside and discharges it to the outside, the flow rate of the cooling water is different from that of a closed-circuit type cooling water system such as for an automobile that circulates the cooling water. When the pressure decreases, the pressure of the cooling water immediately decreases, so that the responsiveness of the retard control is excellent.

According to a second aspect of the present invention, there is provided a water-cooled engine according to the first aspect, wherein the retarding operation control means activates the retarding means only when the detected engine speed is equal to or higher than a predetermined value. It has.

[0009] According to the water-cooled engine, even when the engine is operated in a normal state in a state where the amount of cooling water of the engine is insufficient, the retarded operation is not performed at a low engine speed at which a load is not applied to the engine. Therefore, it is possible to prevent the engine speed from decreasing due to unnecessary retard operation.

A water-cooled engine according to a third aspect of the present invention is provided with a cooling water passage having an inlet for taking in cooling water from outside and an outlet for discharging cooling water after cooling the engine to the outside. A tachometer for detecting the number of revolutions of the engine, a pressure sensor for detecting the pressure of the coolant in the coolant passage, and the detected coolant when the number of revolutions of the engine is equal to or higher than a predetermined value. When the pressure is below a certain value,
Retarding means for retarding the ignition timing of the spark plug.

According to the water-cooled engine, when the engine speed detected by the tachometer is equal to or higher than a predetermined value, the flow of the cooling water in the cooling water passage is not smooth, and the cooling detected by the pressure sensor is performed. When the water pressure falls below a certain value, the retarding means retards the ignition timing of the spark plug, so that even if the amount of cooling water is reduced, the engine speed will be lower than normal and the engine heat load will be reduced. Is prevented from increasing. Moreover, when the flow rate of the cooling water is reduced, the pressure of the cooling water is immediately reduced, so that the responsiveness of the retard control is excellent.

According to a fourth aspect of the present invention, in the water-cooled engine according to the first, second, or third aspect, a catalyst for purifying exhaust gas is disposed in the exhaust passage.

According to the water-cooled engine, since the engine speed is reduced by retarding the engine, the unburned gas due to the partial misfire is burned by the catalyst as in the conventional partial misfire operation (thinning operation). This prevents a large heat load from being applied to the catalyst.

A personal watercraft according to a fifth aspect of the present invention includes an engine having any one of the first to fourth aspects, and a water jet propulsion device connected to the engine. The water jet thruster is also used as a pumping means for the cooling water by opening to the high pressure part of the thruster.

According to the personal watercraft, since the cooling water can be pumped into the cooling water passage by the water jet propulsion device, there is no need to provide any special pumping means, so that the cost can be reduced and the engine of the personal watercraft can be installed. A wide space can be used.

In the personal watercraft according to a sixth aspect of the present invention, in the configuration of the fifth aspect, the pressure sensor branches a part of the cooling water after passing through the engine body from the cooling water passage. It is provided in a water sampling passage for discharging air from the side of the hull.

According to the personal watercraft, the pilot can visually check the water discharge from the side of the hull in the air. It can be confirmed that the operation has shifted to the retard operation. Moreover,
Since the water passage extends to the side of the hull away from the engine, there is ample space near the water passage, so that the pressure sensor can be easily installed without interfering with the engine.

[0018]

Preferred embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a side view of a personal watercraft equipped with a water-cooled engine according to a first embodiment of the present invention. In FIG. 1, the hull 2 of the personal watercraft 1 is configured by joining a deck 2b on a hull 2a, and the deck 2b is provided with a seat 2c and a deck floor 2d serving as a footrest. Have. At the bottom of the hull, a duct 30 is opened at the bottom and stern 2f.
The water jet type propulsion device 3 is mounted in the duct 30. The shaft 7 of the propulsion device 3
It is connected to a rotating shaft 5 of a two-stroke engine 4 in the ship via a coupling 6. A tachometer 34 (FIG. 2) for detecting the number of revolutions of the engine 4 is arranged in a control section provided with the handle 2e. The engine 4 is disposed substantially at the center of the hull 2 with its rotation axis aligned with the front-rear direction of the hull 2 and fixed to a mount 9 (FIG. 2) on the bottom of the hull. An exhaust device 10 for discharging exhaust gas of the engine 4 outboard is provided in a portion extending from the engine 4 to the stern.
Is provided. The propulsion unit 3 is driven by the engine 4, and the hull 2 is propelled.

FIG. 2 shows a control system of the engine 4 and a side view in which a part of the exhaust device 10 is cut away. The exhaust device 10 is connected to an exhaust port 12a that opens upward at an end of the exhaust manifold 12 provided in the cylinder 11 of the engine 4 facing the bow (left side), and extends from above the engine 4 toward the stern 2f. Pipe 13 and this exhaust pipe 13
And a tail pipe 16 connecting the muffler 14 to the discharge port 15 opened in the duct 30 in FIG.

The exhaust pipe 13 shown in FIG. 2 has a double structure consisting of an inner pipe and an outer pipe, and is divided into an exhaust pipe upstream section 13A and an exhaust pipe downstream section 13B, which are integrally connected by a clamp 17. A catalytic converter 18 for purifying the exhaust gas G is detachably attached to this connection portion. Exhaust pipe downstream 13
B extends from a position directly above the engine 4 toward the stern 2f. Further, a muffler portion 21 bulging in the radial direction is formed at a rear portion of the upstream portion 13A and a front portion of the downstream portion 13B.

The exhaust pipe downstream section 13B is connected to the muffler 14 by inserting the inner pipe 13Ba of the exhaust pipe downstream section 13B into the muffler 14, and connecting the exhaust pipe to the outer periphery of the collar member 31 fixed to the muffler 14. This is performed by fitting the outer tube 13Bb of the downstream portion 13B and tightening the outer periphery of the fitting portion with the clamp 32. The silencer 14 is fixed to a mount 19 on the bottom of the ship.

The exhaust pipe upstream section 13A and the exhaust pipe downstream section 1
Each of the inner pipes 13Aa and 13Ba of 3B is provided with an exhaust passage 33 inward.
Are formed of a metal such as an aluminum casting, an aluminum sheet metal, or a stainless sheet metal in order to increase heat resistance to the exhaust gas G. The outer pipes 13 of the exhaust pipe upstream section 13A and the exhaust pipe downstream section 13B are also provided.
Ab and 13Bb are pipes forming an annular passage 20 for the cooling water between the inner pipes 13Aa and 13Ba. The outer pipe 13Bb of the exhaust pipe downstream portion 13B reduces the weight of the exhaust pipe 13 and suppresses vibration. In order to enhance the effect, it is formed of a flexible member such as rubber or resin.

The cooling water introduction passage 24 shown in FIG. 2 takes in cooling water W from an inlet 23 opened to the high-pressure section 3a of the propulsion unit 3 and supplies the cooling water W to a water jacket (not shown) of the engine 4 to cool the engine 4. It is a passage and consists of pipes. After passing through the cylinder 11 and the exhaust manifold 12 of the engine 4, the cooling water W introduced through the cooling water introduction passage 24 is supplied from the water jacket to the annular passage 20 of the exhaust pipe 13. The cooling water W that has entered the silencer 14 through the annular passage 20 is mixed with the exhaust gas G here and contributes to the temperature reduction and silencing of the exhaust gas. Released into water. Thus, a cooling water passage including the cooling water introduction passage 24, the water jacket, the annular passage 20, the muffler 14, and the tail pipe 16 is formed.

The propulsion unit 3 is connected to the annular passage 20 through the inlet 23.
And also serves as a pumping means for pumping the cooling water W. In this example, the high-pressure portion 3a of the propulsion device 3 is a portion of a stationary blade 26 located behind an impeller 25 that is a moving blade fixed to the shaft 7. As described above, since the cooling water W is pressure-fed to the annular passage 20 by the propulsion device 3, it is not necessary to provide a special pressure-feeding means, so that the cost can be reduced, and the engine installation space of the personal watercraft 1 can be widely used. it can.

In the upstream part of the annular passage 20, a part of the cooling water W after passing through the engine body is filled with the annular passage 20.
A water detection passage 27 that branches off from the hull 2 and discharges into the air from the side of the hull 2 is connected. Opening 27a of water detection passage 27
Is provided on the side portion 2bg of the deck 2b in front of the seat 2c of the hull 2 so that the operator can visually recognize the cooling water W discharged into the air from the water detection passage 27. The water detection passage 27 is provided with a pressure sensor 35 for detecting the pressure of the cooling water W in the water detection passage 27.

The controller 36 shown in FIG. 2 is a control device for controlling the driving of the engine 4. The controller 36 includes a storage unit 37, a retarding unit 38, and a retarding operation control unit 39.

The storage means 37 stores, as a data map, the relationship between the engine speed and the allowable value of the cooling water pressure as shown in FIG. 3, for example. In normal times, the cooling water pressure increases with the engine speed, that is, the propulsion device speed. For example, a pressure lower than the normal value by a fixed pressure width irrelevant to the engine speed is set as the allowable value. When the pressure of the cooling water W detected by the pressure sensor 35 is equal to or less than an allowable value corresponding to the engine speed detected by the tachometer 34,
This is a means for judging that the flow of the cooling water is not smooth and delaying the ignition timing of the ignition plug from a regular ignition timing (ignition before top dead center) by a certain angle (for example, to 10 ° after top dead center).

The retarding operation control means 39 is a means for operating the retarding means 38 only when the detected engine speed is a predetermined value or more (for example, 2500 rpm or more). When the cooling water passage including the annular passage 20 and the cooling water introduction passage 24 is clogged with foreign matter and the supply amount of the cooling water W to the engine 4 is reduced, the controller 36 is shown in a flow chart in FIG. The engine 4 is controlled as described above. Hereinafter, the control operation will be described with reference to FIG.

The retard operation control means 39 shown in FIG.
4 is a predetermined value (for example, 2500).
rpm) or not (step S in FIG. 4).
1) When the engine speed is equal to or higher than a predetermined value, the retarding means 3
8 is ready for operation. The retarding means 38 searches the storage means 37 for an allowable value of the cooling water pressure corresponding to the engine speed detected by the tachometer 34, and determines whether the cooling water pressure detected by the pressure sensor 35 is equal to or less than the allowable value. It is determined whether or not it is (step S2).

If the flow of the cooling water W to the engine 4 is not smooth, the pressure of the cooling water W discharged through the water detection passage 27 decreases, so that a pressure sensor 35 for detecting the water pressure is used.
Is less than or equal to the allowable value. Thereby, the retarding means 38 retards the ignition timing of the ignition plug by a known method for adjusting the ignition circuit (step S3). as a result,
Even if the throttle is in the high rotation range, the engine speed will be lower than in normal operation, and even if the supply amount of cooling water W to the engine 4 decreases, the increase in the heat load of the engine 4 will be suppressed. it can.

In addition, the conventional partial misfire operation (thinning operation)
Therefore, it is possible to prevent the unburned exhaust gas G from burning in the catalytic converter 18 and applying a large heat load to the catalytic converter 18.

As described above, when the operation shifts from the normal operation to the retard operation, the engine speed decreases even if the throttle opening is set to a large value. Therefore, it is necessary to notify the operator that the operation has shifted to the retard operation mode. In this embodiment, the amount of the cooling water W discharged from the side of the hull in the air during normal operation is reduced or eliminated when the operation is shifted to the retarded operation. You can see that you have entered.

Further, since the water detection passage 27 extends to the side of the hull 2 away from the engine 4, there is a space in the vicinity of the water detection passage 27. Therefore, by providing the pressure sensor 35 provided in the water detection passage 27, the installation becomes easy without interference with the engine 4.

If the engine speed is equal to or higher than the predetermined value (2500 rpm) even after the retard operation is started, the retard operation control means 39 keeps the retard means 38 operable. Continue as it is. However, when the engine speed falls below the predetermined value (step S4), the retard operation control means 39 deactivates the retard means 38, so that the retard operation of the engine 4 is canceled and the operation returns to the normal operation. (Step S5).

As described above, the retarded operation is not performed under a low engine speed at which the engine 4 is not normally cooled down and the normal operation is performed without imposing a great load on the engine 4. It is possible to prevent the engine speed from excessively lowering due to unnecessary retard operation.

Further, when the amount of the cooling water W decreases, the cooling water pressure immediately decreases, so that the retard control can be quickly performed. That is, the responsiveness of the retard control is good. Here, the premise of the present invention is that the cooling water passage of the engine 4 is an open circuit type. In a closed circuit type that circulates cooling water, such as an engine for an automobile, etc., even if the cooling water passage is clogged, the pressure of the cooling water does not drop so much as long as the water pump continues to operate. Is not easy to apply.

In the above embodiment, the detected engine speed is not less than a predetermined value (for example, not less than 2500 rpm).
Only in the case of, the retarding operation control means 39 enables the retarding means 38, but the retarding operation control means 39 is omitted, and the detected cooling water pressure is reduced to the detected rotation speed. When the cooling water pressure becomes equal to or less than the allowable value of the cooling water pressure corresponding to the number, the retarding means 38 may always be operated.

In the first embodiment, the case of the water-cooled engine 4 mounted on the personal watercraft 1 has been described. However, the present invention is not limited to this, and a land-based water-cooled engine such as the second embodiment shown in FIG. It may be. In the second embodiment, a land-based water-cooled engine having an open-circuit type cooling water passage having an intake for taking in cooling water W from the outside and an outlet 15 for discharging cooling water after cooling the engine to the outside. And
A water source 4 is provided by a water pump 40 directly attached to the engine 4.
The cooling water W is taken in from 1. In this case, the water pump 40 serves as a pumping unit that pumps the cooling water W from the inlet 23 to the annular passage 20.

In the control system for retarding operation in such a water-cooled engine, the retarding means 47 uses a data map to represent the relationship between the engine speed and the allowable value of the cooling water pressure, as in the above-described embodiment. The engine speed detected by the tachometer 34 is not less than a predetermined value (for example, 25) without going through a procedure such as searching for an allowable value of the coolant pressure corresponding to the detected engine speed from the storage means 37 for storing.
If the cooling water pressure (water pressure in the annular passage 20) detected by the pressure sensor 35 is equal to or less than a predetermined value, the ignition timing of the ignition plug is retarded. No means 39 is provided. That is, in this example, when the engine speed and the coolant pressure are in the hatched region in FIG. 6 showing the relationship between the engine speed and the coolant pressure, the retard operation is started immediately. Other configurations are almost the same as those of the previous embodiment.

As a result, when the supply of the cooling water to the engine 4 is not smooth, the normal operation is automatically shifted to the retard operation, and the engine speed is lower than that in the normal operation. Can be prevented from increasing in heat load.

In the water-cooled engine 4 of the second embodiment, for example, tap water may be used as the cooling water W. In this case, a pumping means for pumping the cooling water W to the cooling water passage is unnecessary.

[0042]

As described above, according to the water-cooled engine of the first aspect of the present invention, the retarding means stores the allowable value of the cooling water pressure corresponding to the engine speed detected by the tachometer. When the cooling water pressure detected by the pressure sensor is equal to or less than the searched allowable value, the retarding means delays the ignition timing of the ignition plug, so that the cooling water smoothly flows into the cooling water passage by the pressure feeding means. Even if the pumping is not performed, the engine speed will be lower than normal, and an increase in the thermal load of the engine can be prevented.

According to the water-cooled engine of the second aspect of the present invention, when the cooling water does not flow smoothly through the cooling water passage and the cooling water pressure detected by the pressure sensor falls below a certain value, the tachometer is rotated. When the engine rotation speed detected by the above becomes a predetermined value or more, the retarding means delays the ignition timing of the spark plug, so that even if the cooling water amount decreases, the engine rotation speed becomes lower than normal. As a result, an increase in the heat load of the engine can be prevented. Further, when the amount of cooling water decreases, the pressure of the cooling water immediately decreases, so that the responsiveness of the retard control is good.

According to the personal watercraft of claim 5 of the present invention, the cooling water can be pumped into the cooling water passage by the water jet propulsion device, so that there is no need to provide a special pumping means and the cost can be reduced. The engine installation space of the personal watercraft can be widely used.

[Brief description of the drawings]

FIG. 1 is a side view showing a personal watercraft equipped with a water-cooled engine according to a first embodiment of the present invention.

FIG. 2 is a side view showing a control system of the engine and an exhaust device of the personal watercraft.

FIG. 3 is a characteristic diagram showing a relationship between a rotation speed of the engine and a cooling water pressure.

FIG. 4 is a flowchart showing retarded operation control of the engine.

FIG. 5 is a block diagram illustrating a control system of a water-cooled engine according to a second embodiment of the present invention.

FIG. 6 is a characteristic diagram showing a relationship between a rotation speed of the engine and a cooling water pressure.

[Explanation of symbols]

DESCRIPTION OF REFERENCE NUMERALS 1: small personal watercraft, 2: hull, 3: water jet type propulsion device (pressure feeding means), 3a: high pressure section, 4: water cooled engine, 2
0: annular passage, 23: intake, 27: water detection passage, 33:
Exhaust passage, 34: tachometer, 35: pressure sensor, 37, 4
7: retarding means, 38: storage means, 39: retarding operation control means, 40: water pump (pressure feeding means) 20, 24, 14, 1
6. Cooling water passage

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission Date] January 11, 2000 (2000.1.1)
1)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 1

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction contents]

[0006]

In order to achieve the above object, a water-cooled engine according to a first aspect of the present invention has an intake for taking in cooling water from outside and a cooling water after cooling the engine to outside. A cooling water passage having a discharge port for detecting the rotation speed of the engine, a pressure sensor for detecting the pressure of the cooling water in the cooling water passage, and a driving device driven by the engine. Pumping means for pumping the cooling water from the inlet to the cooling water passage; and increasing the engine speed and the engine speed of the cooling water pressure .
Storage means for storing a relationship with an allowable value lower than the normal value, and when the detected cooling water pressure is equal to or less than the allowable value at the detected engine speed, the ignition timing of the spark plug is retarded. Retarding means.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0040

[Correction method] Change

[Correction contents]

As a result, when the supply of the cooling water to the engine 4 is not smooth, the normal operation is automatically shifted to the retard operation, and the engine speed is lower than that in the normal operation. Can be prevented from increasing in heat load.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) F01P 3/20 B63H 21/24 F02P 5/15 B F term (reference) 3G022 BA01 DA02 EA01 EA06 FA06 FA08 GA00 GA05 3G091 AA04 AA17 AB01 BA04 BA08 BA21 CB05 DA07 DB10 DB11 EA00 EA01 FA07

Claims (6)

[Claims] 1. An engine provided with a cooling water passage having an inlet for taking in cooling water from outside and an outlet for discharging cooling water after cooling the engine to the outside, wherein the tachometer detects the engine speed. A pressure sensor for detecting a pressure of the cooling water in the cooling water passage; a pumping means driven by an engine to pump the cooling water from the intake to the cooling water passage; Storage means for storing a relationship between the pressure and an allowable value; and a delay means for delaying the ignition timing of the spark plug when the detected cooling water pressure is equal to or less than the allowable value at the detected engine speed. A water-cooled engine with a. 2. The water-cooled engine according to claim 1, further comprising a retarding operation control unit that activates the retarding unit only when the detected engine speed is equal to or higher than a predetermined value. 3. An engine provided with a cooling water passage having an inlet for taking in cooling water from the outside and an outlet for discharging cooling water after cooling the engine to the outside, wherein the tachometer detects the engine speed. A pressure sensor for detecting the pressure of the cooling water in the cooling water passage; and, when the detected engine speed is equal to or higher than a predetermined value and the detected cooling water pressure is equal to or lower than a predetermined value, the ignition timing of the ignition plug. Water-cooled engine provided with a retarding means for retarding the angle. 4. A water-cooled engine according to claim 1, wherein an exhaust purification catalyst is disposed in the exhaust passage. 5. An engine according to claim 1, further comprising a water jet propulsion device connected to the engine, wherein the intake port is opened to a high-pressure portion of the water jet propulsion device, and water is supplied to the water jet propulsion device. A small planing boat that also uses a jet propulsion unit as a means for pumping cooling water. 6. The pressure sensor according to claim 5, wherein:
A personal watercraft provided in a water inspection passage for branching part of the cooling water after passing through the engine body from the cooling water passage and discharging the air into the air from the side of the hull.