JP2014092072A - Diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a diesel engine capable of improving a reliability in collision between fuel and water within a combustion chamber and reducing generation amount of NOx.SOLUTION: A diesel engine comprises a cylinder having a combustion chamber formed therein, a piston sliding within the cylinder, a fuel injection part 126 having one or a plurality of fuel injection ports 126a opened into the combustion chamber and injecting fuel F through the fuel injection ports, and a water injection part 128 having one or a plurality of water injection ports 128a formed to enclose the fuel injection ports to inject water from the water injection ports into the combustion chamber to generate a water layer L of water flow, the fuel injection part injects fuel in a direction where it passes through the water layer L generated by the water injection part.

Description

  The present invention relates to a diesel engine that injects fuel and water into a combustion chamber to burn the fuel.

  Diesel engines are classified into two-stroke and four-stroke methods. The two-stroke method is installed in ships and the like, and the four-stroke method is widely used in automobiles. The structure differs between the 2-stroke and 4-stroke systems. For example, in a 2-stroke diesel engine, an exhaust port is provided at one end of the cylinder in the stroke direction of the piston. A scavenging port is provided. Then, when the active gas is sucked into the combustion chamber from the scavenging port during the intake (supply) stroke, the exhaust gas generated by the combustion action is exhausted by being pushed out of the exhaust port by the sucked active gas. At this time, a combustion action is obtained by injecting fuel into the sucked active gas, and the piston reciprocates in the cylinder by the explosion pressure generated by this combustion action.

  In such a diesel engine, in any of the above systems, if the oxygen concentration in the combustion chamber becomes too high, harmful NOx (nitrogen oxide) is generated and discharged together with the exhaust gas. Therefore, Patent Document 1 describes a configuration in which, in the combustion chamber, water is injected before fuel is injected to add water vapor, thereby reducing the oxygen partial pressure and reducing the amount of NOx produced. . It is also known that when water is injected into the combustion chamber, the combustion chamber is cooled, the combustion temperature of the fuel is lowered, and the amount of NOx produced is reduced. In particular, when the fuel injected into the combustion chamber collides with water, water intervenes in the combustion reaction, so that the combustion speed of the fuel is reduced, which is effective in reducing the amount of NOx produced.

JP 2010-96133 A

  As described above, when the fuel and the water collide in the combustion chamber, a portion where the water does not collide with the injected fuel is generated simply by intersecting the fuel injection direction and the water injection direction. And if a combustion reaction takes place from the portion of the fuel where water does not collide, the combustion temperature will rise, and the amount of NOx produced may not be reduced much.

  In view of such a problem, an object of the present invention is to provide a diesel engine capable of improving the certainty of collision of fuel and water in a combustion chamber and reducing the amount of NOx generated.

  In order to solve the above problems, a diesel engine according to the present invention includes a cylinder in which a combustion chamber is formed, a piston that slides in the cylinder, and one or more fuel injection ports that open in the combustion chamber. A fuel injection unit that injects fuel from the fuel injection port, and one or a plurality of water injection ports formed to surround the fuel injection port, and injects water into the combustion chamber from the water injection port And a water injection unit that generates a layer of water by the water flow, wherein the fuel injection unit injects the fuel in a direction that passes through the water layer generated by the water injection unit. It is characterized by that.

  The fuel injection unit may include a plurality of the fuel injection ports, and may inject the fuel in a direction that intersects with the water injection direction and is different for each fuel injection port.

  The fuel injection unit may inject the fuel radially with respect to the centers of the plurality of fuel injection ports.

  According to the diesel engine of the present invention, it is possible to improve the certainty of collision between fuel and water in the combustion chamber and reduce the amount of NOx produced.

It is explanatory drawing which shows the whole structure of a diesel engine. It is an enlarged view of the broken-line part of FIG. It is explanatory drawing for demonstrating the injection form of a fuel and water. It is explanatory drawing which shows operation | movement of each control part.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating the understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

  FIG. 1 is an explanatory diagram showing the overall configuration of the diesel engine 100, and FIG. 2 is an enlarged view of a broken line portion of FIG. The diesel engine 100 of this embodiment is used for a ship etc., for example. Specifically, the diesel engine 100 includes a cylinder 110 (cylinder head 110a, cylinder block 110b), a piston 112, a pilot injection valve 114, an exhaust port 116, an exhaust valve driving device 118, an exhaust valve 120, a scavenging air. The port 122, the scavenging chamber 124, the fuel injection unit 126, the water injection unit 128, the rotary encoder 130, and the combustion chamber 140 are configured to include a governor (regulator) 150, an injection control unit 152, It is controlled by a control unit such as the exhaust control unit 154.

  In the diesel engine 100, a piston 112 connected to a crosshead (not shown) reciprocates in a slidable manner in a cylinder 110 through four consecutive strokes such as intake (supply), compression, combustion, and exhaust. In such a cross head type piston 112, the stroke in the cylinder 110 can be formed relatively long, and the side pressure acting on the piston 112 can be received by the cross head. Can be achieved. Further, since the cylinder 110 and a crank chamber (not shown) in which the crosshead is accommodated are isolated, deterioration of contamination can be prevented even when using low quality fuel oil.

  The pilot injection valve 114 is provided in the cylinder head 110a above the top dead center of the piston 112, which is one end of the cylinder 110 in the stroke direction, and injects an appropriate amount of fuel oil at a desired point in the engine cycle. Such fuel oil is spontaneously ignited by the heat of the combustion chamber 140 surrounded by the cylinder head 110a, the cylinder liner in the cylinder block 110b, and the piston 112, and burns in a short time, so that the temperature of the combustion chamber 140 is extremely reduced. Since it is made high, the fuel can be surely burned at a desired timing.

  The exhaust port 116 is an opening provided at one end of the cylinder 110 in the stroke direction of the piston 112, that is, at the top of the cylinder head 110 a above the top dead center of the piston 112. It is opened and closed to exhaust the exhaust gas. The exhaust valve driving device 118 opens and closes the exhaust port 116 by sliding the exhaust valve 120 up and down at a predetermined timing. The exhaust gas exhausted through the exhaust port 116 in this manner is supplied to the turbine side of a turbocharger (not shown) and then exhausted to the outside.

  The scavenging port 122 is a hole that penetrates from the inner peripheral surface (the inner peripheral surface of the cylinder block 110b) on the other end side in the stroke direction of the piston 112 in the cylinder 110 to the outer peripheral surface. Is provided. The scavenging port 122 sucks the active gas into the cylinder 110 according to the sliding motion of the piston 112. Such an active gas includes an oxidizing agent such as oxygen and ozone, or a mixture thereof (for example, air). The scavenging chamber 124 is filled with active gas (for example, air) pressurized by a compressor of a supercharger (not shown), and the active gas is sucked from the scavenging port 122 with a differential pressure in the scavenging chamber 124 and the cylinder 110. Is done. The pressure in the scavenging chamber 124 can be substantially constant, but when the pressure in the scavenging chamber 124 changes, a pressure gauge is provided in the scavenging port 122, and the fuel injection amount, etc., according to the measured value, etc. The parameters may be controlled.

  As shown in FIG. 2, an exhaust member 116a forming the exhaust port 116 is fixed to the cylinder head 110a. Further, an injection member 110c that forms each injection section (a fuel injection section 126 and a water injection section 128) to be described later is fixed to the cylinder head 110a.

  The fuel injection unit 126 has a plurality of fuel injection ports 126a that open to the combustion chamber 140, and a communication passage 126b that forms at least a part of a path that connects the fuel injection ports 126a to a fuel tank (not shown).

  The communication passage 126b includes a hole formed in the injection member 110c, and a hemispherical hollow member 126c is formed on the plane side of the hollow member 126c at the outlet end of the communication passage 126b on the combustion chamber 140 side. The openings to the inside are fixed so as to face each other.

  A plurality of holes penetrating from the inside to the curved surface side are formed in the hollow member 126c, and the fuel injection port 126a is configured by an end portion on the curved surface side of the hole formed in the hollow member 126c.

  The fuel injection unit 126 injects fuel from the fuel injection port 126a by opening a fuel injection valve (not shown) that can open and close the communication path between the fuel injection port 126a and the fuel tank.

  A plurality of water injection ports 128a are provided around the fuel injection port 126a of the fuel injection unit 126 so as to surround the fuel injection port 126a. In FIG. 2, two water injection ports 128a are shown. Four or more water injection ports 128a are arranged at equal intervals, for example, in the circumferential direction of the cylinder 110 with the opening of the hollow member 126c as the center.

  The positional relationship between the fuel injection port 126a and the water injection port 128a will be described in detail. A plurality of water injection ports 128a are arranged around the fuel injection port 126a in the bottom view from the vertically lower side of the cylinder head 110a. That is, the fuel injection port 126a is located on the center side of the plurality of water injection ports 128a.

  The water ejection unit 128 includes a plurality of water ejection ports 128a and a communication path 128b that forms at least a part of a path that connects the water ejection ports 128a to a water tank (not shown). The communication path 128b includes a hole formed in the injection member 110c, and the water injection port 128a is an outlet end of the communication path 128b.

  In FIG. 2, for easy understanding, the communication path 126 b of the fuel injection unit 126 and the communication path 128 b of the water injection unit 128 are shown intersecting each other. However, actually, both the communication paths 126 b and 128 b intersect each other. It is assumed that they are not in communication with each other.

  The water injection unit 128 injects (sprays) water into the combustion chamber 140 from the communication path 128b by opening a water injection valve (not shown) that can open and close the communication path between the water injection port 128a and the water tank. . In the present embodiment, the water to be ejected is liquid.

  Here, the water injection amount by the water injection unit 128 is, for example, about 30 to 50% of the fuel injection amount. Further, the optimum value of the water injection amount varies depending on the number of water injection ports 128a, and it is desirable to reduce the ratio of the water injection amount to the fuel injection amount as the number of water injection ports 128a increases.

  Further, the water injection unit 128 is assumed to inject water almost simultaneously with the fuel injection by the fuel injection unit 126. However, if the water injection pressure is substantially constant and the fuel injection pressure by the fuel injection unit 126 is high, the water injection timing may be advanced by about 1 millisecond (ms) at the maximum from the fuel injection timing. desirable.

  FIG. 3 is an explanatory diagram for explaining a fuel and water injection mode. In FIG. 3, the communication paths 126b and 128b are indicated by broken lines, and the water layer L formed by the flow of water jetted by the water jetting part 128 is indicated by gray fill.

  As shown in FIG. 3, in this embodiment, the water injection part 128 injects water in the direction slightly inclined from the vertical direction. Further, the fuel injection unit 126 injects fuel in a direction inclined by about 45 degrees with respect to the water injection direction. Here, the water injection direction is slightly inclined from the vertical direction, and the fuel injection direction is inclined 45 degrees with respect to the water injection direction, but the water injection direction may be vertically downward, May be the direction. The fuel injection direction is not limited to 45 degrees as long as the fuel injection direction is inclined with respect to the water injection direction. However, the inclination angle of the fuel injection direction with respect to the water injection direction is preferably at least 45 degrees or more.

  Since the water injection port 128a is disposed so as to surround the fuel injection port 126a, the water layer L generated by the flow of water injected by the water injection unit 128 is a cylinder surrounding the fuel injection port 126a. It becomes a shape.

  At this time, the fuel injection unit 126 injects the fuel F in a direction crossing the water injection direction by the water injection unit 128. That is, the fuel injection unit 126 injects the fuel F in a direction inclined with respect to the vertical direction. The fuel injection unit 126 injects fuel F in different directions for each of the plurality of fuel injection ports 126a.

  In detail, the fuel injection part 126 injects the fuel F radially with respect to the center of the some fuel injection port 126a. That is, when viewed from the vertical upper side, the plurality of fuel injection ports 126a are located at equal intervals in the circumferential direction on the virtual circle, and the fuel F is injected in a direction away from the center of the plurality of fuel injection ports 126a. The

  For example, when the fuel injection direction and the water injection direction are simply crossed, a portion where water does not collide with the injected fuel is generated. When a combustion reaction occurs from a portion of the fuel that does not collide with water, the combustion temperature may rise and NOx may be generated.

  In the present embodiment, as described above, the water layer L is formed so as to surround the fuel injection port 126a. The fuel injection unit 126 injects the fuel F in the direction passing through the water layer L generated by the water injection unit 128, that is, the direction inclined with respect to the water injection direction. It is possible to improve the certainty of the collision and reduce the amount of NOx produced.

  Further, since the water layer L is formed so as to surround the fuel injection port 126a, a situation has occurred in which the fuel F is injected from the fuel injection port 126a in a direction slightly deviated from the direction aimed at the time of design. However, the possibility of collision between the fuel F and water can be increased.

  Returning to FIG. 1, the rotary encoder 130 is provided in a crank mechanism (not shown) and detects a crank angle signal (hereinafter referred to as a crank angle signal).

  The governor 150 derives the fuel injection amount based on the engine output command value input from the host controller and the engine speed based on the crank angle signal from the rotary encoder 130, and outputs the fuel injection amount to the injection control unit 152.

  The injection control unit 152 controls the fuel injection valve based on the information indicating the fuel injection amount input from the governor 150 and the crank angle signal from the rotary encoder 130. Further, the injection control unit 152 derives a water injection amount based on the fuel injection amount, and controls the water injection valve based on the crank angle signal from the rotary encoder 130.

  The exhaust control unit 154 outputs an exhaust valve operation signal to the exhaust valve driving device 118 based on the signal related to the fuel injection amount from the injection control unit 152 and the crank angle signal from the rotary encoder 130.

  Hereinafter, the operation of each control unit in the engine cycle of the diesel engine 100 described above will be described.

  FIG. 4 is an explanatory diagram showing the operation of each control unit. As shown in FIG. 4, in the exhaust stroke after the combustion stroke, the exhaust port 116 and the scavenging port 122 are in a closed state, and the combustion chamber 140 (inside the cylinder 110) is filled with exhaust gas.

  When the piston 112 descends and approaches the bottom dead center due to the explosion pressure generated by the combustion action of the combustion chamber 140, the exhaust control unit 154 opens the exhaust valve 120 through the exhaust valve driving device 118 (t1 shown in FIG. 4). Subsequently, the scavenging port 122 is opened according to the sliding motion of the piston 112 (t2 shown in FIG. 4). Then, the active gas is sucked from the scavenging port 122. The active gas rises in the cylinder 110 and pushes the exhaust gas in the combustion chamber 140 (in the cylinder 110) from the exhaust port 116.

  Then, in the compression stroke in which the piston 112 rises from the bottom dead center toward the top dead center, the scavenging port 122 is closed and the suction of the active gas is stopped.

  At this time, the exhaust control unit 154 maintains the exhaust valve 120 in an open state, and the exhaust gas in the combustion chamber 140 (inside the cylinder 110) continues to be exhausted from the exhaust port 116 as the piston 112 rises. .

  Thereafter, when the piston 112 further rises, the exhaust control unit 154 closes the exhaust valve 120 and closes the exhaust port 116 (t3 shown in FIG. 4).

  When the piston 112 approaches top dead center (t4 shown in FIG. 4), the injection control unit 152 is derived by information indicating the fuel injection amount input from the governor 150 and the crank angle signal from the rotary encoder 130. The fuel injection valve is opened based on the engine speed and the like, and fuel F is injected from the fuel injection unit 126 into the combustion chamber 140.

  At the same time, the injection control unit 152 opens the water injection valve to inject water into the combustion chamber 140 from the water injection unit 128. Thereby, the fuel F collides with the water layer L formed by the injected water.

  Then, the injection control unit 152 closes the fuel injection valve and the water injection valve, and the fuel F and water injection from the fuel injection unit 126 and the water injection unit 128 into the combustion chamber 140 is stopped.

  As described above, the combustion of the fuel F in the combustion chamber 140 causes the exhaust, intake, compression, and combustion strokes to be repeated as described above.

  In the above-described embodiment, for example, seawater in the sea where the ship on which the diesel engine 100 is mounted is taken and stored in the water tank. As a result, the capacity of the water tank loaded on the ship can be reduced and the load of fresh water can be reduced. Moreover, the said seawater may be filtered with a filter, impurities, such as salt content, may be removed and stored in a water tank. Moreover, when storing seawater in a water tank and using the seawater stored in the water tank, it may be filtered with a filter.

  In the above-described embodiment, the case where the water ejection unit 128 ejects liquid water has been described. However, the water ejection unit 128 may eject, for example, gaseous water (water vapor).

  In the above-described embodiment, the case where a plurality of fuel injection ports 126a and water injection ports 128a are provided has been described. However, even if there is only one fuel injection port 126a and one water injection port 128a. Good. When one water injection port 128a is used, the water injection port 128a may be formed in a ring shape so as to surround the fuel injection port 126a.

  In the above-described embodiment, the fuel injection unit 126 injects the fuel F in a different direction for each of the plurality of fuel injection ports 126a. However, the fuel injection unit 126 has the same direction for all the fuel injection ports 126a. The fuel F may be injected into the fuel injection port, or the fuel F may be injected in the same direction only with respect to two or more fuel injection ports 126a that are smaller than the total number of the fuel injection ports 126a. However, by injecting the fuel F in a different direction for each of the plurality of fuel injection ports 126a, the fuel F can be easily dispersed in the combustion chamber 140, and the wide range of the water layer L is the fuel F. Thus, the injected water can collide with the fuel F efficiently.

  In the above-described embodiment, the fuel injection unit 126 has explained the case of injecting the fuel F radially. However, if the direction in which the fuel F is injected passes through the water layer L, it is not radial. May be. However, the fuel injection unit 126 injects the fuel F radially, so that the dispersion of the fuel F and the collision of the injected water with the fuel F are more efficiently performed.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to this embodiment. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Is done.

  The present invention can be used for a diesel engine in which fuel and water are injected into a combustion chamber to burn the fuel.

F ... Fuel L ... Water layer 100 ... Diesel engine 110 ... Cylinder 112 ... Piston 126 ... Fuel injection part 126a ... Fuel injection part 128 ... Water injection part 128a ... Water injection part 140 ... Combustion chamber

Claims (3)

A cylinder in which a combustion chamber is formed;
A piston sliding in the cylinder;
A fuel injection portion having one or a plurality of fuel injection ports opened in the combustion chamber and injecting fuel from the fuel injection ports;
A water injection unit that has one or a plurality of water injection ports formed around the fuel injection port, and injects water into the combustion chamber from the water injection port to generate a water layer by the flow of the water When,
With
The diesel engine, wherein the fuel injection unit injects the fuel in a direction passing through the water layer generated by the water injection unit. The fuel injection part is
A plurality of the fuel injection ports;
2. The diesel engine according to claim 1, wherein the fuel is injected in a direction intersecting with the water injection direction and different in each fuel injection port.   The diesel engine according to claim 2, wherein the fuel injection section injects the fuel radially with respect to the centers of the plurality of fuel injection ports.