JPH10299578A - Operating method of diesel type turbo supercharging type double fuel internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the possibility of natural ignition so as to sufficiently utilize the heating value of fuel by directly injecting water in an air/gas mixture in a cylinder clearance between a piston and a cylinder cover in a downward spray condition. SOLUTION: Air and gas are supplied with a mixture ratio in a cylinder 2, and they are compressed on compression stroke. Ignition is carried out by ignition from an outside, and a diesel type turbo supercharging type compound fuel internal combustion engine is operated. Even if an air/fuel ratio is few, an excessive air ratio is set to λ=1.3, and it is injected through multiple injection nozzles 9 per cylinder in at least one part of a crank angle clearance in the compression stroke of 20 deg. to 150 deg. after a bottom dead point. Water is directly injected into an air/gas mixture in a cylinder clearance between a piston 15 which is moved upward and a cylinder cover 11 in a downward spray condition. It is thus possible to carry out an operation of a diesel engine in association with a good performance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diesel type in which air and gas are supplied at a mixing ratio in a cylinder, and then the air and gas are compressed during a compression process and ignited by external ignition. The present invention relates to a method for operating a turbocharged dual fuel internal combustion engine.

[0002]

2. Description of the Related Art US Pat. No. 4,527,516 discloses that
A plurality of cylinders, each of which has a row of scavenging ports formed in a lower portion of the cylinder, and at least one scavenging valve provided on a cylinder cover; Described is a method used for a diesel-type turbocharged dual fuel internal combustion engine with a valve-controlled gas supply having a single gas port formed as a single pipe extending from a distribution pipe to one. Have been. The engine of this U.S. patent is a high speed, two-stroke automobile engine with a speed of about 1800 rpm. A disadvantage identified with this high speed engine is that the speed of propagation across the flame is limited by the rate at which diesel oil burns. This is only one-third of the speed of the gas, and there is almost no time for the gas to burn.

US Pat. No. 5,035,206 describes a similar two-stroke diesel engine with a gas supply and a pilot oil igniter. Also in this engine, gas is supplied in the area around the scavenging port, and the gas is supplied to the cylinder through a single tube opening into the cylinder wall at a relatively short distance above the row of scavenging ports. Supplied. This specification states that the injection of gas continues after the piston shuts off the scavenging port. The amount of this gas is controlled by changing the start time, not the end time of the injection.

From US Pat. No. 4,924,822 it is known to supply gas from an LNG tank to a diesel engine, the remaining of the evaporated gas being about 2%.
It is compressed to 50 bar to a high pressure and, while being injected through a high pressure nozzle, a portion of the evaporated gas is compressed to a relatively low pressure and premixed with the intake air of the engine. Although some compression work is avoided by injecting some of the gas into the intake air of the engine, in this patent only a small part of the evaporated gas can be supplied to the intake air, because Otherwise, it is stated that the temperature rise during the adiabatic compression stroke may cause an abnormal combustion condition.

[0005] WO 96/08641 describes an Otto-type engine supplied with premixed air / fuel and ignited by a spark plug.
Water is injected into the cylinder during the combustion stroke to increase engine efficiency and reduce NO _X emissions. Also,
It is particularly preferable to supply a flow of intake air having a high oxygen concentration.

[0006]

All of the above diesel engines, which supply a low pressure gas into the cylinder before the start of compression, have a gas / air mixture that ignites spontaneously during the compression stroke, or There is a condition that must not explode. If spontaneous ignition occurs, the pressure in the cylinder significantly exceeds the highest combustion pressure during normal operation, and if spontaneous ignition occurs frequently, the cylinder elements may be overloaded. Normally, spontaneous ignition leads to insufficient utilization of the heat of the fuel.

For this reason, whether a diesel engine can use gas supplied at low pressure as fuel depends on how close the gas / air mixture supplied to the cylinder is to the limit value of spontaneous ignition. It depends on what you can control.
For any given fuel, the limit value for spontaneous ignition is small, that is, spontaneous ignition is more likely to occur in the following cases. That is, slow engine speed, large cylinder diameter,
This is when the large compression ratio, the high supply pressure, and the excess air ratio are close to one. Furthermore, when a gas is represented by a methane number, a lower value of the methane number means that the fuel is more easily ignited spontaneously, and thus the limit value of the spontaneous ignition largely depends on the current fuel.

The above factors will determine which of the following designs the diesel engine will have: That is, designed as a high speed running diesel engine with a relatively small cylinder bore, or a significant portion of the gas is compressed to high pressure and injected after that compression,
It determines whether the engine should be designed to keep the cylinder lean so that there is no possibility of spontaneous ignition during compression.

It is an object of the present invention to provide a method of operating a dual fuel diesel engine with better performance than in prior art engines, using gas supplied at low pressure to meet fuel requirements. It is to be.

[0010]

SUMMARY OF THE INVENTION In view of the above, the method according to the present invention provides a method of air / fuel ratio which results in at least λ
= 1.3 excess air ratio, 20 ° to 1 after bottom dead center
During at least a part of the compression stroke consisting of a crank angle in the range of 50 °, the water in the cylinder gap between the upwardly moving piston and the cylinder cover is introduced into the air ^/ gas mixture through a number of injection nozzles per cylinder. Being sprayed directly in a downward spraying state,
The water is supplied to the injection nozzle at a pressure of bar.

An excess air ratio of at least λ = 1.3 means that, in order to burn accurately, it is essential to operate on the principle of lean burn, in which the absolute condition of the air / gas mixture is extremely homogeneous. Means for the engine being done. If the mixture is excessively inhomogeneous, the area near the combustion chamber will have a very high excess air rate, and as a result, the heat of the fuel cannot be used effectively, and The emissions will cause an explosion in the exhaust system, leading to undesirable environmental effects due to the form of unburned hydrocarbon emissions. In another area of the combustion chamber, the concentration of the mixture is so high that spontaneous ignition occurs. The problem of obtaining a sufficiently homogeneous mixture of gas and air is particularly pronounced when the gas is supplied to the intake at a relatively short distance from the cylinder or only inside the cylinder.

The principle of lean burn is not sufficient to improve the possibility of using a gas supplied at low pressure by a diesel engine to the desired extent, and also as a result of the variables that occur during actual mixing. However, it is difficult to realize this principle in a diesel engine.

Injecting water directly into the gas ^/ air mixture during the compression stroke has a number of effects, each of which separates the gas / air mixture from the limits of auto-ignition. And at the same time reduce or solve the problems arising from the principle of lean burn. One major effect is that the injection of water has a physical effect on the gas / air mixture, and the water injected in its atomized state entrains the gas in the cylinder, causing the gas and air to flow when the cylinder is loaded. Causes a flow that differs from the flow generated by the inflow, which results in more homogeneous mixing in the cylinder and prevents local spontaneous ignition in the rich mixture region. Injection performed by injecting high-pressure water supplied at a pressure of at least 50 bar downward into a spray state, even when the piston is far away from the cylinder cover, starts the injection of the cylinder from the start of injection. Enhances mixing of the contents of the cylinder throughout.

Furthermore, after bottom dead center, the water injection performed in the range of crank angles between 20 ° and 150 ° intervenes in a chemical reaction which determines the rate at which a given lean gas / air mixture ignites spontaneously. . Evaporation of the water injected during the compression stroke cools the gas / air mixture, lowering the temperature during compression,
And the low end temperature at the end of the compression stroke,
It acts enough to block chemical reactions. Another independent factor in this reaction is the current pressure in the cylinder. Since the pressure drop associated with cooling is about five times greater than the pressure increase associated with evaporation, the water injection will result in low pressure levels, resulting in a delayed chemical reaction. The combined action of these factors significantly reduces the risk of spontaneous ignition. Injecting water at the above interval
This is done before the mixture of air and gas is ignited by external ignition means.

This may be due to the use of low methane number gas in an engine whose basic structure is invariable, or the use of a low excess air rate, ie, a higher concentration gas / air mixture. Utilizes low-pressure gas supplied to the air supply to primarily meet engine fuel requirements and eliminates the need for costly methods of compressing gas to high pressure And many other advantages.

A significant advantage of the method according to the invention is that it has a large bore with a bore of more than 400 mm, a speed at full load of less than about 200 rpm and a compression ratio of more than 1:14,
This makes it possible to use gas injected at low pressure in a low speed and high compression ratio diesel engine.

Preferably, the water is supplied to the injection nozzle at a pressure in the range from 150 to 500 bar. In order to effectively "stir" the contents of the cylinder, there must be more than one jet nozzle for the water, and to the extent that it is very effective in obtaining a homogeneous mixture of gas and air. The injection pressure must be high. The water pressure can be above 500 bar, but this requires significant compression work. In a very efficient form, the jet of water can create at least one swirl in the cylinder contents by the gas flowing downward near the cylinder wall and upward near the cylinder axis. it can. This swirl flow cooperates with a circular cylindrical swirl flow formed by the incoming air and coaxial with the axis of the cylinder, resulting in a very effective and homogeneous mixing of the gas in the cylinder. Leads to.

Since the effect of water injection on the limit of spontaneous ignition is significant, it is advantageous to be able to inject a very large amount of water during the compression stroke. The amount of water injected may be, for example, at least 0,4 per 42.7 MJ of the amount of heat supplied.
75 kg, preferably 0.85 kg to 2.0 kg
Or it can be set to 4.0 kg. In this case, 1kg
Of oil is about 42.7 MJ, which means that, in terms of weight, the amount of water supplied will be supplied if the engine is running on fuel oil at that engine load. It should be appreciated that the amount of brazing oil can be approximately equal to or greater than the amount. The calorific value of a gas may vary slightly depending on the type of gas and its composition. If the amount is 0.75 kg or less, it is difficult to avoid spontaneous ignition in a large low-speed engine. By setting the amount of water in the range of 1.0 to 2.0 kg per 42.7 MJ of heat, a large compression ratio is possible and ^/ or it is possible to operate in a state where the methane number of the gas fluctuates remarkably. A very homogeneous and lean gas / air mixture and a very humid combustion gas with a high heat capacity are obtained. It also has the environmental advantage of avoiding the energy consumption associated with high pressure compression of the gas, and the present invention provides for manufacturing gas driven diesel engines with minimal environmental impact. Is what makes it possible.

After bottom dead center, ie, after the scavenging port is closed and during the first part of the compression stroke, at least the compression stroke consisting of a crank angle in the range of about 20 ° to 90 °. In some cases, it is advantageous to inject water. The temperature drop due to the evaporation of water at the beginning of the compression stroke will itself reduce the final temperature at the end of the compression stroke accordingly, but in addition to this complete cooling effect, Since the degree of temperature rise is small, the final temperature can be reduced correspondingly. Injecting water at the start of the compression stroke in this way has two effects.

Replenishment of the method of injecting water at the start of the compression stroke, or as an alternative, 120 ° to 15 ° after bottom dead center
Water can be injected at least at a part thereof comprising a crank angle in the range of 0 °, preferably 90 ° to 150 °. In this angular range, the compression raises the temperature level and causes the injected water to evaporate rapidly, so that a large amount of water does not adhere to the surface of the cylinder element, and at the same time From a point of view, there is also no injection of water at such a low speed that the action of water injection cannot be realized during the compression stroke. It is of course possible for the water injection to start earlier and / or end later and also to be done intermittently.

[0021] A gas is supplied in a region around a scavenging port of a cylinder provided in a lower cylinder portion, the gas port having an exhaust valve arranged on the cylinder cover.
If the two-stroke uniflow scavenging engine was a dual fuel engine, preferably located in the scavenging port, with the gas port opening much slower than the scavenging port,
The method of the invention is particularly advantageous. In such a uniflow scavenging engine, by arranging the gas port in a region corresponding to the scavenging port, the gas is supplied directly into the cylinder, and the supplied gas is prevented from flowing out into the exhaust system during scavenging of the cylinder. Is known. A preferred arrangement of providing a gas port in the scavenging port is that the incoming gas is directly discharged into the incoming air and mixed with the incoming air immediately after being discharged, so from a mixing point of view, Brings significant benefits.

Once the components of the overall engine have been determined, a number of factors that contribute to the chemical reaction that causes spontaneous ignition are also determined. However, the operation of the engine can be continuously adapted to other factors of the chemical reaction process, such as fluctuations in the quality of the fuel and / or external conditions. That is, when the gas / air mixture is very close to its spontaneous ignition limit before being ignited by external ignition, by adjusting the closing timing of the exhaust valve, the effective compression ratio is reduced, Conversely, the effective compression ratio can be increased as the distance from the spontaneous ignition limit increases. This continuous and rapid operation adjustment of the effective compression ratio does not significantly affect the efficiency of the engine since the expansion ratio during the effective stroke is not affected by the timing of closing the exhaust valve during the compression stroke. Allows the gas / air mixture to be kept close to the limit of spontaneous ignition in changing operating conditions.

In consideration of engine safety, it is preferable that the gas supply pipe to the cylinder engine be designed as follows. That is to say, during a cycle, when the piston cuts off flow communication between the scavenging port and the cylinder air gap above the piston, it may be provided with a flow meter to determine whether there is an absolute gas flow. It is preferable to design the gas supply pipe. Monitoring the overall flow during periods when there is no absolute gas flow is due to slight leaks in the otherwise normally functioning control valve seats in the gas supply line. If any gas leaks, it is possible to detect the leak, and immediately detect that the normal shutoff function of the control valve suddenly becomes defective.

As an alternative to or in addition to monitoring the flow rate, during operation of the engine, a sample of air may be taken from the scavenging box of each engine cylinder and the hydrocarbons of the sample measured and / or the exhaust temperature, or cylinder. At least one cylinder parameter representative of cylinder output, such as pressure, can be measured and compared to a predetermined load-independent limit for at least one cylinder parameter. It can be determined by measuring the hydrocarbon whether gas is leaking to the air supply outside the cylinder, that is, whether gas is leaking into the scavenging box surrounding the lower part of the cylinder. If there is a leak, the gas content in the air will be higher than the intended gas supply,
That is, because the gas / air mixture becomes more concentrated, any leakage will result in an increase in exhaust gas temperature and / or turbulence in combustion, for example, in the form of auto-ignition. Such a condition can be detected as a sudden and very sharp rise in cylinder pressure. Thus, gas leakage can be detected by sensors that measure pressure and temperature. Such sensors are well known and have been thoroughly tested on diesel engines operated in a conventional manner. Using known sensors to detect gas leaks, for example,
It is possible to perform a quick recovery operation by detecting gas leakage and shutting off supply of gas to a malfunctioning cylinder or the entire engine.

The supply amount of gas depending on the engine load is:
It can be appropriately adjusted by the discharge pressure of the gas. In contrast to known supply methods, by adapting to the injection period, supply under pressure control conditions can be achieved, for example, in a substantially constant crank angle range corresponding to about 2/3 of the angle range in which the scavenging port is open. Allows fuel to be supplied in time. When only a relatively small amount of gas is injected, the injection of the gas takes a significantly longer time, so that the gas and air can be more uniformly mixed in the cylinder. This effect is particularly important in the case of very lean mixtures, which may result in a risk of incombustibility in the region of the cylinder contents.

Further, the present invention has a large number of cylinders,
A valve-controlled gas having a plurality of gas ports, each of the cylinders having a row of scavenging ports formed in a lower portion of the cylinder and at least one exhaust valve provided in the cylinder cover; It also relates to a diesel turbocharged dual fuel internal combustion engine having an exhaust valve with a supply. In order to meet the fuel requirements by the gas supplied at low pressure and to meet the requirements of larger sized engines with lower speeds than motor vehicle engines, the engine according to the invention requires that each of the cylinders provided with gas ports be Having at least one water injection device for injecting water at high pressure into the cylinder gap between the piston and the cylinder cover, and a pressure higher than the current cylinder pressure;
Preferably, a water supply device for supplying extremely high-pressure water to the water injection device is provided. The injection of water offers the advantages described above.

In one embodiment, the nozzle holes of the water injection device are oriented so that water is injected downward toward the piston and is suitably spaced from the inner surface of the cylinder. As described above, as a result of spraying water in a state of spraying downward, the entire contents of the cylinder are strongly circulated downward and upward, so that an excellent mixing state is obtained. If the nozzle holes are located at appropriate radial distances within the cylinder wall, the injection direction will be substantially parallel to the longitudinal axis of the cylinder. If the nozzle hole is located close to the inner surface, the injection can be appropriately directed in a direction away from the inner surface of the cylinder, i.e., away from the inner surface. This means that water directly impacts the running surface of the cylinder against the piston ring, such that the sprayed water breaks the lubricant film and causes unacceptable cylinder wear. Bring the advantage of not.

Water injection can reduce the risk of spontaneous ignition to such an extent that a two-stroke crosshead engine with a speed of 250 rpm or less and a cylinder bore of at least 230 mm can be obtained. Apart from the calorie of the pilot fuel, it is possible to meet the fuel requirements of the engine with the gas injected at low pressure, at least at full load.

In one preferred embodiment, the gas port opens into the scavenging port and gas is supplied to the gas port from an annular chamber extending around the cylinder and communicating with the gas supply tube containing the shut-off valve. Is done. This means that the gas is discharged directly into the air flowing into the cylinder, with the gas port located higher than the scavenging port, resulting in a very homogeneous mixing state. Bring benefits. Also, using an annular chamber to distribute gas to multiple gas ports per cylinder facilitates distribution of gas in the air.

The hydrocarbon meter described above may be economically advantageous in that it may be common to several cylinders, while the cylinder may be used to transfer a gaseous sample to the hydrocarbon meter. To supply.

[0031]

BRIEF DESCRIPTION OF THE DRAWINGS An embodiment of the invention will now be described in more detail with reference to schematic drawings.

FIG. 1 illustrates a diesel-type two-stroke crosshead engine 1 for propelling a ship or generating electricity in a stationary power plant. When the engine drives a generator or is connected to an adjustable pitch propeller, the engine is typically operated at a predetermined constant speed independent of the engine load. This is because speed does not affect the spontaneous ignition limit in various ways.
This is considered an advantage for the present invention. The engine can also be connected directly to a ship propeller, not shown, whose speed varies with the engine load.

This engine 1 has a large number of cylinders 2 projecting from an engine frame box 3. A common supply line 4 for pilot fuel, such as oil, supplies pilot fuel to a fuel pump 5, which may be a piston pump, and at a desired adjustable point in the engine cycle, this pump In accordance with the well-known dual fuel principle, pilot fuel can be injected into the cylinder 2 via at least one fuel injector 5 'to initiate combustion. Instead of being externally ignited by pilot fuel, the engine according to the present invention may be designed to be externally ignited by another heat source, such as an electric igniter. This electric ignition device
As such, it can be arranged in a known pre-combustion chamber.
The pre-combustion chamber is supplied with a higher concentration of a gas / air mixture than the combustion chamber 6 of the cylinder.

During the compression stroke before the pilot fuel is injected, the air in the cylinder is supplied with the main fuel in the form of a gas which is advantageously discharged at a low pressure during the injection. The pressure of this gas is, for example, 15 bar or less,
It is often less than 10 bar. This pressure requires little compression work and requires less complex compression machines. As described in more detail below, the pressure of the gas can be variable.

The engine 1 has a water supply comprising a source of fresh water or another suitable type of water (not shown). These waters are supplied via a pipe 7 to a high-pressure generator 8 which is periodically filled with water and compressed air to a pressure corresponding to the desired feed pressure to the water injector 9. Pressurized. If it is desired to keep the water and air separated from each other in any other way than by a membrane in the tank, the tank may be air-floating, floating above the water and transmitting air pressure to the water. Some type of float, such as a filling ball, can be provided. In this way, it is possible to generate a very high water pressure and to discharge a large amount of water to the cylinder without taking into account the lubrication state in the pump cylinder, in which the piston moves partially in the water. It is possible to do. This water can be supplied to the water injector 9 of the cylinder by opening and closing a time-controlled control valve according to the engine cycle.
This control valve can be electronically controlled by a control device that receives a signal for the current angular position of the crankshaft. The water pressure can be changed and increased during the compression stroke to account for the increase in compression pressure.

In a known manner, each of the water injection devices 9
A valve housing having an interior seat is provided, and a movable slider pressed against the seat by a spring to break the connection between the water supply and the spray nozzle. The slider is displaced away from the seat when the valve is actuated to initiate water injection. This operation can be performed by, for example, a control valve. The control valve opens due to the effect of hydraulic pressure on the lower surface of the slider, thereby causing the hydraulic pressure to change the slider away from the seat. Another possibility is to use control oil to displace the slider away from the seat. In this case, the opening and closing function of the valve can be independent of the hydraulic pressure. The spray nozzle near the lower end of the injector is directed downward, so that the injected water does not directly hit the cylinder wall. The water jet (spray) emitted by the spray nozzle can be directed downward, for example, at an angle in the range of 0 ° to 20 ° with respect to the longitudinal direction of the cylinder. The various angles of the injection nozzle distribute the water relatively evenly within the cylinder contents, and also generate at least one swirling flow that flows downward, in part, near the cylinder wall, and at the center of the cylinder. Different directions can be oriented to produce an upward flow near the axis. When the piston is in a position that completely blocks the scavenging port, it is desirable to orient the atomizer nozzle so that the direction of the jet extends within the outer circumference of the piston. Depending on the amount of water to be sprayed and the desired distribution, one or more water jets 9 can be provided.

The engine is supplied with scavenging air and supply air at a pressure that varies with the engine load. When the engine is operating at partial load, i.e. low load, scavenging and charge can be provided by one or more turbochargers, augmented by driven auxiliary blowers.

This engine can be a medium-speed or high-speed engine. An exhaust valve 10 formed at the top of the cylinder in a cylinder cover 11 and a scavenging box 1
Preferably, it is a low speed engine having a row of scavenging ports 12 formed in a lower cylinder surrounded by 3. This scavenging box 13 communicates with a pressurized scavenging supply, such as a scavenging receiver 30, via an opening 14. This scavenging receiver can be a long pressure vessel common to several cylinders. This scavenging box 13 can be separate for each cylinder. That is, the cylinders can be separated from each other by a transverse wall, and a boundary is set down by an intermediate bottom portion 14 in the engine frame box in order to effectively separate the crank housing and the air supply body. Can be done. The piston 15 in the cylinder is attached to a piston rod 16 that passes through the middle bottom in a piston rod packing box 17.
In another embodiment, the scavenging box may be common to some or all cylinders.

The gas source 18 supplies gas to the gas system of the engine. The pressure regulator 19 controls the supply pressure of gas in the distribution pipe 20, and the distribution pipe 20 is connected to each cylinder 2 via a branch pipe 21 having a shutoff valve. If the gas evaporates from the tank at low pressure or is discharged from an external supply tube, the device 19 can compress the gas in an adjustable manner. It is also possible to supply gas from the supply at a somewhat higher gas pressure, in which case the device 19 can be an adjustable throttle.

As shown in FIG.
In the case of a stroke uniflow scavenging diesel engine, the scavenging air supplied during the first part of the scavenging process is applied before the exhaust valve 10 closes and the cylinder is filled with air for the next combustion. Because it flows directly into the exhaust system, it is unacceptable to premix gases in the intake air of the engine. For this reason, this gas is supplied directly to the cylinder, one preferred embodiment of a gas supply for the cylinder is illustrated in FIGS.

Along the side of the cylinder, the branch pipe 21
It has a central shut-off valve, that is, a control valve 22. The control valve 2
2 opens and closes a gas supply to an annular chamber 23 formed in the cylinder wall as a groove closed outward by a cover ring 24 at an appropriate point in the engine cycle. From the annular chamber 23, several nozzle tubes 2
5 allows the gas to flow to the gas port formed in the scavenging port. The number of nozzle tubes may be four to six evenly distributed along the circumference. To obtain the most uniform gas / air mixture, each of the scavenging ports is 1
It can have two gas ports. In a simple embodiment, this gas port is the outlet opening of the nozzle tube, but a non-return valve is provided in the nozzle tube to prevent hot gas backflow (ketching) into the annular chamber 23 at the end of the expansion stroke. It can be built in. Instead of disposing the nozzle tube in the bore, the bore is formed in a simple manner from the annular chamber 23 and the upper wall of the scavenging port,
Alternatively, the scavenging port may be formed diagonally downward and inward at a corner corresponding to the inner surface of the cylinder. In this case, the opening constitutes a gas port.

In another embodiment (not shown), several gas injection valves are arranged near positions above the scavenging ports. The number and arrangement of the gas injection valves is formed as described above, such that the gas is supplied from a common tube extending around the cylinder. The supply of gas to this tube is controlled by an electronic control valve located near the cylinder. The gas injection valve is arranged in the bore of the cylinder wall, and is formed in a countersink shape with respect to the inner surface of the cylinder,
Also, it can be a simple nozzle having one or two holes and provided with a non-return valve to prevent backflow at the start of the evacuation period.

On the supply side of the control valve 22, the branch 21 can be equipped with a flow meter capable of measuring a small absolute gas flow during a specific time interval. The flow meter has an orifice and may have an associated sensor for detecting a pressure drop at the orifice. The flow meter can measure the average value of the pressure change during a particular time interval.

The supply of gas to the cylinders can take place during specific and substantially constant intervals of the engine cycle. If the period during which the scavenging port is open, usually expressed as a specific crank rotation angle, is divided into 100 parts, the gas supply is advantageously performed during a period of about 30 to about 95 parts. be able to. Since the gas supply is stopped immediately before the scavenging port is closed by the upwardly moving piston, the residual gas is discharged from the annular chamber by the effect of the ejector, and therefore, the gas may leak into the gap below the piston. Is minimal.

The adjustment of this amount can be appropriately performed by adjusting the gas discharge pressure by the pressure adjusting device 19 so as to be higher than or lower than the scavenging pressure at the current engine load. . Surplus air rate is usually about λ
= 2, the amount of fuel in the cylinder depends on the amount of air while the amount of air depends on the scavenging pressure. Since the scavenging pressure of an engine with an exhaust driven turbocharger changes with the engine load, the scavenging air is blown out after the compressor at a specific engine load or when the load changes suddenly, and the output changes suddenly. It is necessary to control the output of the engine, including the following.

FIG. 5 shows the spontaneous ignition limits for different engine sizes as a function of the excess air ratio λ. The solid curve shows the ratio for a medium speed engine at 600 rpm. If the excess air ratio λ = 2, spontaneous ignition occurs when the piston reaches the top dead center, but theoretically, if the gas / air mixture is made leaner (larger value of λ), the spontaneous ignition occurs. It is understood that the limit value of ignition increases. However, in practice, leaner mixtures cannot be used, since the leaner the mixture, the more unstable and incomplete the combustion. Since external ignition usually occurs within a range of 5 ° before and after top dead center, the limit of spontaneous ignition is
Should not be less than 5 °.

The curves shown apply to a particular gas.
It has a 350 mm bore and a corresponding speed of 209
If the same methane number gas is used in a large engine with a low rpm and autonomous speed, the limit value of the auto-ignition is represented by the curve b
The state shown by. It is clearly seen that the effect of increasing λ is significantly less at low speeds, and that the limit of spontaneous ignition is very small for reasonable engine operation. Therefore, a speed of 123 rpm and a bore of 60
Curve c for 0 mm engine and speed 94 rpm
The curve d for an engine with a bore of 900 mm shows that the condition gets worse for larger engines.

Based on an engine with a bore of 350 mm and a speed of 209 rpm, FIG. 6 schematically shows a change in the operating state of the engine. In this case, the curve b is a solid line. Curve e shows the effect of lowering the cylinder pressure by 10 bar, this pressure drop being, for example, by keeping the exhaust valve somewhat longer so that compression does not start until later in the engine cycle. This can be achieved by reducing the compression ratio of the engine. This spontaneous ignition limit is considered to be improved, but far from sufficient. Therefore, for example, in order to continuously finely adjust the limit value of spontaneous ignition in order to correct even a slight change in the methane number of the fuel, changing the effective compression ratio is the only appropriate measure.

The effect of injecting water according to the present invention is much more pronounced, as illustrated by curves f and g, where 10 parts by weight of an equal amount of fuel oil are each used.
Inject the amount of water corresponding to 0% and 125%. That is,
1.0kg for each 42.7MJ of fuel supplied
And 1.25 kg of water are injected. With larger amounts of water, water injection would have a significantly greater effect.

FIG. 7 shows a 350 mm bore and a 209r bore.
cylinder pressure P during the compression stroke in an engine at pm speed
_cyl and the cylinder temperature T _cyl are shown, which are curves h and i respectively when water is not injected and when water corresponding to 100% of the same amount of fuel oil is injected. This is indicated by a pressure curve j and a temperature curve k. It can be seen that a significant effect of the water jet occurs during the last 90 ° rotation before top dead center. For example, injecting intermittently,
Or by changing the water injection pressure (amount per hour) during the compression stroke by changing the water injection pressure,
It is preferable that the maximum injection amount is obtained in an angle range of 90 ° to 150 ° after the bottom dead center.

By injecting water directly and strongly into the entire cylinder during the compression stroke in an amount equal to or greater than the amount of fuel, the present invention provides for the gas injected at low pressure as the main fuel. It also makes it possible to operate even large, two-stroke diesel engines that burn, so that only fuel injected at high pressure is used as ignition promoter. The present invention can also be applied to use low methane gas in small gas / diesel engines operating at higher speeds.

[Brief description of the drawings]

FIG. 1 is a side view of a diesel engine according to the present invention.

FIG. 2 is a longitudinal sectional view taken along a cylinder in the engine of FIG. 1;

FIG. 3 is a partial view of a lower region of the cylinder.

FIG. 4 is a larger scale partial view of the gas port of one preferred embodiment.

FIG. 5 is a schematic diagram showing the limits of spontaneous ignition for gas in the engine as a function of excess air rate and for certain operating parameters.

FIG. 6 is a schematic diagram illustrating a limit value of spontaneous ignition illustrated for an operation parameter different from that of FIG. 5;

FIG. 7 is a diagram showing processes of pressure and temperature changes in respective cylinders when water injection is performed and when water injection is not performed.

[Explanation of symbols]

Reference Signs List 1 2 stroke crosshead engine 2 cylinder 3 engine frame box 4 supply pipe 5 fuel pump 5 'fuel injection device 6 fuel chamber 7 pipe 8 high pressure generator 9 water injection device 10 exhaust valve 11 cylinder cover 12 scavenging port 13 scavenging box 14 opening Part 15 Piston 16 Piston rod 17 Piston rod storage box 18 Gas source 19 Pressure regulator 20 minute pipe 21 Branch pipe 22 Central shut-off valve / control valve 23 Annular chamber 24 Covering 25 Nozzle pipe 30 Scavenging receiver

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁶ Identification symbol FI F02M 25/02 S (71) Applicant 594140904 Center Syd, 161 Staholmen, DK-2650 HVIDOVR E, Denmark (72) Inventor Maz. Ragilt Dekkok, Denmark-2860 Servo A, Hoywangen 1

Claims (15)

[Claims] 1. A diesel type turbocharger in which air and gas are supplied at a mixing ratio in a cylinder (2), and then the air and gas are compressed during a compression process and ignited by external ignition. In the operating method of the supercharged dual fuel internal combustion engine (1), the air / fuel ratio becomes at least an excess air ratio of λ = 1.3, and after the bottom dead center, the crank angle interval of the compression stroke of 20 ° to 150 ° is obtained. Water passes directly down into the air / gas mixture in the cylinder gap between the upwardly moving piston (15) and the cylinder cover (11) through a number of injection nozzles per cylinder (9) during at least a portion. Operation of a diesel-type turbocharged dual fuel internal combustion engine, characterized in that the injection is carried out in a spray state and that the water is supplied to the injection nozzle at a pressure of at least 50 bar. Law. 2. The driving method according to claim 1, wherein
An operating method, characterized in that the water is supplied to the injection nozzle at a pressure in the range from 50 to 500 bar. 3. The operating method according to claim 1, wherein the water injection amount is a heat amount of the supplied fuel amount.
Operating method characterized by at least 0.75 kg per 7 MJ, preferably 0.85 kg to 2.0 kg or 4.0 kg thereof. 4. The method according to claim 1, wherein after the bottom dead center, water is injected in at least a part of a compression stroke having a crank angle in a range of 20 ° to 90 °. A driving method characterized by: 5. The operating method according to claim 1, wherein after the bottom dead center, at least a compression stroke consisting of a crank angle in the range from 120 ° to 150 °, preferably from 90 ° to 150 °. A driving method characterized in that water is partially injected. 6. The operating method according to claim 1, further comprising an exhaust valve (10) disposed on a cylinder cover (11), wherein the exhaust valve (10) is disposed on a lower cylinder portion. Gas is supplied in an area around the scavenging port (12), and the gas port is preferably located within the scavenging port so that the gas supply opens significantly slower than the scavenging port. An operating method comprising: a dual fuel engine (1). 7. The operating method according to claim 6, wherein, during operation, when the gas / air mixture is very close to its spontaneous ignition limit before being ignited by external ignition, the exhaust valve ( By adjusting the closing timing of 10), the effective compression ratio is reduced, and conversely, as the gas / air mixture moves away from the limit of spontaneous ignition,
An operation method characterized in that the effective compression ratio is increased. 8. The operating method according to claim 1, wherein the piston (15) blocks the flow communication between the scavenging port (12) and the cylinder gap above the piston during the cycle. Operating method, wherein the gas supply pipe to the cylinder is provided with a flow meter for measuring whether or not an absolute gas flow exists. 9. The operating method according to claim 1, wherein a sample of air is collected from a scavenging box (13) of each engine cylinder during operation of the engine, and the hydrocarbon of the sample is removed. Measuring and / or measuring at least one cylinder parameter representative of cylinder output, such as exhaust temperature or cylinder pressure, and comparing at least one cylinder parameter to a predetermined limit value independent of the load. How to drive. 10. The operating method according to claim 1, wherein a supply amount of the gas depending on an engine load is adjusted by a supply pressure of the gas. 11. A plurality of cylinders (2) each having a row of scavenging ports (12) formed in the lower portion of the cylinder and at least one scavenging port provided in a cylinder cover (11). Diesel turbocharged dual fuel internal combustion engine (1) having two exhaust valves (10) and a valve controlled gas supply having a number of gas ports formed therein
Wherein each of the cylinders in which the gas ports are formed comprises at least one water injection device (9) for injecting water at high pressure into the cylinder gap between the piston and the cylinder cover; A diesel turbocharged dual fuel internal combustion engine, comprising: a water supply device for supplying water having a higher pressure to the water injection device (9). 12. The turbocharged dual fuel internal combustion engine according to claim 11, wherein water is injected downward toward a piston (15) through a nozzle hole of the water injection device (9) and an inner surface of the cylinder is provided. A turbocharged dual fuel internal combustion engine characterized in that it is oriented so as to be appropriately separated from the engine. 13. The turbocharged dual fuel internal combustion engine according to claim 11, which is a two-stroke crosshead engine having a speed of 250 rpm or less and a cylinder bore of at least 230 mm. Dual fuel internal combustion engine. 14. The turbocharged dual fuel internal combustion engine according to claim 11, wherein a gas port opens into the scavenging port, extends around the cylinder with respect to the gas port, and shuts off. A turbocharged dual fuel internal combustion engine, wherein gas is supplied from an annular chamber communicating with a gas supply pipe containing a valve. 15. A turbocharged dual fuel internal combustion engine according to claim 11, wherein each scavenging port of said cylinder is surrounded by a respective scavenging box for said cylinder. Provides that scavenging and supply air is supplied from a scavenging receiver and that each of the scavenging boxes comprises an air sampler that supplies an air sample to a hydrocarbon meter common to several cylinders. Features a turbocharged dual fuel internal combustion engine.