JPH0286941A - Nitrogen oxide abating method and device for internal combustion engine - Google Patents

Abstract

PURPOSE:To enhance an abating effect of nitrogen oxide by cooling heat of a flame produced by main injection with the fuel spray of sub injection, suppressing its generation in the midway where the nitrogen oxide(NO) is generated by combustion, and abating the extent of exhaust of the nitrogen oxide. CONSTITUTION:At time of driving a diesel engine E1, main injection is performed in the turning downflow direction of intake air by feeding oil to an injection nozzle 8 from a main injection pump at about 15 deg.-0 deg. before a top dead center at the last period of compression strokes. The, firing of fuel subjected to the main injection is produced at a tip or both sides of spray, expanding it on an air vortex. At this time, there is a high temperature area in and around a flame tip, whereby a gas temperature is high and nitrogen oxide(NO) is produced in bulk. Next, sub injection is performed at the flame tip at about 5-20 deg. after the top dead center, and with this spray, fuel spray is fed to the high temperature area in and around the flame tip instantaneously at a high injection rate, and flame temperature is lowered by dint of heat of vaporization of the fuel spray. With this constitution, generation of the nitrogen oxide(NO) is effectively controlled.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to internal combustion engines, and in particular, to nitrogen oxides (hereinafter referred to as NO) in the combustion chamber of diesel engines and gasoline engines.
This invention relates to a method for reducing engine thermal efficiency without decreasing it, and a specific device that can achieve this.

[Prior art]

Methods for reducing NO in internal combustion engines, mainly piston engines, are divided into external after-treatment represented by three-way catalysts, and in-cylinder treatment represented by EGR (exhaust gas recirculation), ignition retardation, or injection retardation. It will be done.

■ Places a three-way catalyst near the engine's exhaust manifold and NO
It is applied to premixed spark ignition engines that operate near the stoichiometric mixture. N.

The reduction rate is very large, reaching over 70%, but it is hardly effective except around the stoichiometric mixture (air-fuel ratio around 14.5 (gasoline)), and leaded fuel is used because the catalyst is covered with lead. Can not. Furthermore, it cannot be applied to diesel engines that generate soot, as the catalyst will deteriorate if it becomes clogged.

■EGR mixes exhaust gas into the cylinder to lower the combustion temperature, but the soot in the exhaust tends to stain parts, causing deterioration of lubricating oil and accelerating wear on moving parts.

In the method (2), the reduction of No. is explained by the Zeldovich mechanism.

N+NO 〇-p N2 + O (1) N〇, 〇〇, N〇〇 (2) N+
OH calyx N O+ H (3) As shown in the above equations (1), (2), and (3), NO is generated in the high temperature part due to combustion by nitrogen and oxygen in the air. In each of these equations (1), (2), and (3), as the temperature increases, the process proceeds to the No generation side, and when the temperature increases from 2000 to 2200
It becomes more noticeable. Therefore, combustion is effective in keeping the temperature as low as possible, and EGR, ignition retardation, and injection retardation are performed to keep the combustion temperature low.

However, if the temperature is lowered, the thermal efficiency of the internal combustion engine deteriorates, so at present it is difficult to reduce NO without reducing engine performance other than NO reduction using a three-way catalyst. Particularly in diesel engines, it is impossible to use catalysts because the exhaust contains soot, and no method or device has yet been found that can effectively significantly reduce NOx levels without impairing engine performance, durability, etc. Not served.

Furthermore, in the method disclosed in Japanese Patent Application No. 62-82080, the fuel injection is divided into two or more times, and when the flame generated by the previous injection is extinguished, the subsequent injection is performed and the generated NO is transferred to CH3.
This method attempts to reduce NO by reducing NO by acting in an atmosphere of 1,000 to 2,000 with radicals, and its technical idea is different from that of the present invention.

[Problem to be solved by the invention]

As explained by the above-mentioned Zeldovich mechanism, No production has a strong temperature dependence, and No production increases rapidly as the temperature rises. Therefore, the inventors predicted that during combustion in an engine, the temperature is particularly high for a short time near top dead center, and that the high temperature part of the flame will be the main source of NO. It was considered that lowering the temperature of the high temperature flame section would be effective in reducing No.

Therefore, the present inventors measured and analyzed in detail the temperature distribution within the combustion chamber and the changes in the temperature distribution over time. As a result, when fuel is injected into the combustion chamber, it ignites and burns after a slight delay near the tip of the spray in a compression ignition engine or near the spark plug in a spark ignition engine, and then the flame develops rapidly. The pressure rise is large due to the fact that it is close to top dead center and the piston speed is slow and the change in combustion chamber volume is small, so the initially generated flame is adiabatically compressed and its temperature rises further, making it the highest temperature of all flames. It turned out to be a big part.

Based on the above analysis results, the present inventors have determined that by effectively and locally cooling the high-temperature flame portion and suppressing No generation, the temperature of other flame portions will not be lowered unnecessarily. They came up with the idea of reducing NO emissions while avoiding a decrease in thermal efficiency.

The present invention focuses on cooling the above-mentioned high-temperature flame portion, and differs from the conventional technology in that it cools the high-temperature portion of the flame while NO is being generated by combustion to suppress No generation. However, it is an object of the present invention to provide a method and apparatus for reducing nitrogen oxide in an internal combustion engine, which can reduce the amount of NO released.

[Description of the invention]

(Structure) The method for reducing nitrogen oxide in an internal combustion engine according to claim (1) of the present invention provides a combustion chamber of a reciprocating internal combustion engine formed by a piston, a cylinder head, and a cylinder block, which communicates with a fuel supply source, and injects fuel into the combustion chamber of the internal combustion engine. A fuel supply device consisting of a valve performs main injection (hereinafter referred to as main injection) to supply a predetermined amount of fuel during a predetermined process of the internal combustion engine, ignites combustion, and temporarily reduces the injection rate, and then, following the above injection, Then, the injection rate is increased again to perform a secondary injection (hereinafter referred to as a sub-injection) in which a predetermined amount of fuel is injected at a predetermined time from the fuel supply device, and the flame generated by the main injection is transferred to the sub-injection. This configuration reduces the emission of nitrogen oxide by cooling with fuel spray and suppressing the generation of nitrogen oxide during combustion.

(Function) Since the structure is as described above, the method for reducing nitrogen oxide in an internal combustion engine of the present invention has the following function.

At the end of the compression stroke, when the piston rises and approaches top dead center, pressure and temperature rise due to compression, and a swirling flow of air is formed in the combustion chamber. At that time, main injection is performed from the fuel injection valve facing the combustion chamber, and fuel is injected and supplied.

Thereafter, the spray is flowed by the swirling flow, ignites and burns while swirling, and a flame develops. Since the pressure increases as the flame develops, the flame generated immediately after ignition becomes even hotter due to adiabatic compression, and as this becomes the hottest part of the flame, NO is actively produced. When the high-temperature flame part swirls again to the position of the fuel injection valve nozzle due to the swirling flow, the injection rate is temporarily lowered to reduce the generation of flame near the nozzle and lower the temperature of this part. After that, sub-injection is performed targeting the high-temperature flame area, instantaneously supplying a large amount of fuel spray at a high injection rate, cooling the high-temperature flame area, and rapidly lowering the temperature of this area. .

(Effects) The method for reducing nitrogen oxide in an internal combustion engine according to the present invention has the effects described above, and therefore has the following effects. In other words, the high-temperature flame generated by the main injection is rapidly cooled by the fuel spray supplied by the sub-injection, lowering its temperature.
NO generated from the high temperature flame portion can be suppressed.

Since this part is at a high temperature and NO is most actively generated, the NO reduction effect is remarkable.

Further, the flame is cooled locally, and the temperature of other flame parts does not decrease, so there is no decrease in thermal efficiency. Furthermore, fuel is supplied at a high injection rate by the sub-injection, the injection energy is large, and air is actively introduced into the spray, so the mixing of fuel and air is sufficient and the generation of soot is suppressed. Subsequent combustion is also more efficient and fast, with no deterioration in fuel efficiency and less unburned fuel being emitted.

[Description of other inventions]

(Structure) Furthermore, the nitrogen oxide reduction device for an internal combustion engine according to the present invention according to claim (2) has a combustion chamber for a reciprocating internal combustion engine formed by a piston, a cylinder head, and a cylinder block,
A first fuel supply means that communicates with a fuel supply source in the combustion chamber and performs a main injection, a second fuel supply means that performs a secondary injection, and a position of the first and second fuel supply means. A fuel supply device consisting of a phase control means for controlling a phase difference and a fuel injection valve is provided, and the flame generated by the main injection based on the first fuel supply means is transferred to a secondary fuel injection based on the second fuel supply means. This is a configuration in which the fuel is cooled by the fuel spray of the injection, and the generation of nitrogen oxides is suppressed while they are being generated by combustion, thereby reducing the emission of nitrogen oxides.

The fuel supply device may include a fuel injection valve, two cams that drive a plunger that pumps fuel, and a phase control device that changes the phase of both cams, or may include an electrically driven fuel injection valve. It is composed of a valve, a drive circuit that drives the fuel injection valve and generates a drive signal for main injection, and a drive signal for sub-injection whose phase relationship is controlled with respect to the drive signal for main injection.

(Function) The nitrogen oxide reduction device for an internal combustion engine of the present invention performs main injection to inject and supply a predetermined amount of fuel by the first fuel supply means, ignites combustion, and first reduces the injection rate. Following the main injection, the injection rate is increased again, and a secondary injection is performed in which a predetermined amount of fuel is injected and supplied from the second fuel supply means. Furthermore, by controlling the phase difference between the first and second fuel supply means by a phase control means, the flame generated by the main injection is cooled by the fuel spray of the secondary injection. .

(Effects) The nitrogen oxide reduction method for an internal combustion engine of the present invention is characterized in that the flame generated by the first fuel supply means is transferred to the second fuel supply means whose phase difference with respect to the first fuel supply means is controlled. The fuel spray supplied by the above can selectively and rapidly cool the high-temperature portion of the flame, thereby effectively suppressing the generation of NO and locally cooling the high-temperature flame portion. Since the temperature of the other flame parts does not decrease, there is no decrease in thermal efficiency. In addition, the second
In the sub-injection based on the fuel supply means, fuel is supplied at a high injection rate, the injection energy is large, and air is actively introduced into the spray, so the mixing of fuel and air is sufficient and soot generation is suppressed. This has excellent effects in that there is no deterioration in fuel efficiency and less unburned fuel is emitted.

〔Example〕

The method and apparatus of the present invention will be explained based on an example in which it is applied to a diesel engine and a gasoline engine.

The first embodiment is an IDI diesel engine E having a combustion chamber as a swirl chamber 2 in a cylinder head 1 as shown in FIG.
It is. This diesel engine E has a recess 4 in the piston 3, and a main combustion chamber 5 is formed by the recess 4, the cylinder head 1, and the cylinder block 7. The cylinder head 1 has a torpedo-shaped swirl chamber 2, which communicates with the main combustion chamber 5 through a communication hole 6.

In such a diesel engine E, as the piston 3 rises during the compression process, air in the main combustion chamber 5 flows into the swirl chamber 2 through the communication hole 6, generating a swirling flow in the direction of the arrow in the figure.

In this diesel engine E1, as shown in FIGS. 3 and 4, only one injection nozzle 8 serving as a fuel injection valve of a fuel supply device is disposed in the swirl chamber 2.

This diesel engine E has an injection system as shown in FIG. 4 in order to perform the above-mentioned sub-injection before the main injection (regular normal injection) by the injection nozzle 8 is completed. In other words, the injection pump 9.10 has two sets of plungers (not shown), one plunger is for main injection and the other plunger is for sub-injection, and the sub-injection plunger is set by a timer to determine when to start oil supply. change. The plunger outlet high pressure fuel pipe 11 is connected to the injection nozzle 8.
It is designed to guide high pressure fuel to. In the diesel engine E1, two sets of plunger-type injection pumps 9 and 10 are drivably connected to a pump drive shaft 12 that is driven at two speeds by its crankshaft. Adjustment of each main or auxiliary injection amount is performed by a rack, similar to a normal diesel engine. Each injection pump 9, 10 has a built-in timer, and the main injection pump 9 is operated in a range of 15° to 0° before the top dead center at the start of discharge (injection start) depending on the operating conditions (load, rotation speed). It has been adjusted. Also, the timer of the sub-injection pump 10 starts from 5 degrees past the top dead center to 20 degrees.
The same is adjusted to the range of °. Furthermore, since there are some parts where the fuel injection period of main injection and sub-injection overlaps with each other,
Fuel injection from the injection nozzle 8 is performed continuously.

In the first embodiment having the above configuration, when the diesel engine E reaches 15° to 0° before top dead center at the end of the compression stroke, oil is sent from the main injection pump 9 to the injection nozzle 8, as shown in FIG. The main injection is performed in the forward direction of the swirling direction of the intake air.

Ignition of the main injected fuel occurs at the tip or both sides of the spray, as shown in Figure 6, and spreads along with the air vortex. There is a high temperature area near the flame tip, and the gas temperature is high <N
Generates a large amount of O. This NO generation mechanism is explained by the above-mentioned Zeldovich reaction equation (1), (
This can be explained in 2) and (3). Then, as time passes, the flame spreads as shown in Figure 7, and is carried away by the vortex, and when it passes the top dead center, the flame makes almost one revolution. As a result of the increase in combustion pressure accompanying the main injection, gas has begun to be ejected from the communication hole 6 into the main combustion chamber 5, but since fuel injection continues, the flame further develops.

Next, sub-injection is performed at the flame tip 5 to 20 degrees past the top dead center. This injection momentarily supplies fuel spray at a high injection rate to the high-temperature region near the tip of the flame, and the flame temperature can be lowered by the heat of vaporization of the fuel spray.

In other words, since the NO generation mechanism strongly depends on the flame temperature as shown by the above-mentioned Zeldovich reaction equation, the sub-injection can effectively suppress the generation of No by cooling the high temperature part of the flame.

The spray from the sub-injection evaporates instantly and mixes with high-temperature oxygen and chemically active unburned gas, and the strong mixing energy of the sub-injection promotes the introduction of air into the flame, causing the high-temperature flame of the main injection to Immediately after the flame disappears, a new flame appears and burns quickly. At this time, the piston is descending and its speed is gradually increasing, so
The volumetric expansion suppresses the temperature rise of the flame, and even though it burns quickly, the temperature rise is small and NO is produced. As described above, the high-temperature part of the flame generated by the main injection is cooled by the sub-injection, and then the fuel in the sub-injection is efficiently combusted through rapid combustion, reducing smoke emissions and increasing fuel consumption and unburned hydrocarbon emissions. It has the excellent effect of reducing NO without any problems.

FIG. 2 shows an example of the results obtained by applying the method to a swirl chamber type diesel engine and confirming its effectiveness. The engine has a bore of 83mm and a stroke of 85cm, and the injection amount per stroke at full load is approximately 40cm3. The illustrated state shows a state of approximately % load. Normal injection (main injection) starts 6 degrees before top dead center and ends at TDC, and the injection amount is 10++++n”
/ st. The amount of secondary injection is 5mm for 2 of the main injection.
'/st, and the total injection amount is 15+nn+3/st. At this time, the timing of the secondary injection is changed to increase or decrease NO (
Reduction rate) and mean effective pressure (Pe
) and changes in smoke concentration (S). The horizontal axis shows the timing of sub-injection, the vertical axis shows the increase and decrease of N01S and Pe,
The line 1.0 corresponds to the same operation as a normal diesel engine with only main injection.

A reduction in No occurs when the secondary injection timing is 3 to 5 degrees past top dead center,
NO is at a minimum between 10'' and 15°. This is because the flame cooling mentioned above is effectively performed.

Although the timing of the secondary injection has passed the top dead center, the gas temperature at this time is higher than the gas temperature of 700 to 800 at the beginning of the main injection.
Since the temperature is 2000 to 2500K, the ignition delay is short, and in addition, mixing with highly reactive combustion products progresses, so combustion progresses rapidly and there is almost no decrease in Pe.

Furthermore, if the timing of the sub-injection is delayed, the high-temperature part of the flame will not be properly cooled, and the tendency for No. to decrease will worsen. Pe also decreases due to afterburning. Further, the decreasing tendency of the smoke concentration S also decreases.

When the engine is not loaded, the amount of fuel injected is small, the excess air ratio λ is large, and the combustion temperature is low, so the amount of sub-injected fuel is reduced so that the gas temperature does not drop more than necessary due to combustion of the sub-injected fuel.

On the other hand, even when the load is full, the timing of the sub-injection may be approximately the same as when the load is light. This is because the high temperature portion of the main injection flame moves to the injection valve nozzle position at approximately the same time regardless of the load. In this case, although the sub-injection amount increases, the subsequent combustion is rapid, so the smoke concentration S is reduced and Pe does not decrease much.

The sub-injection amount (the fuel injection amount after the time when the injection rate becomes minimum) and the sub-injection timing (the time when the injection rate becomes minimum) at no-load are as follows: 0.05<q, /q, , <0.1 (q, sub-injection amount m
m'/st, qi, full load injection amount at full load 11
1111''/s t ) t, (sub-injection timing) is valid in the range of 3° to 10° after top dead center.

For full load, the range is valid and the optimal value is 0.08<qs/q, X<0
．． 2. ts is between 10'' and 15''.

The method and apparatus of the present invention are applicable to IDI diesel, DI diesel, and direct injection spark ignition engines, as long as the engine type has an injection nozzle in the combustion chamber.

The timing and injection amount of the sub-injection are means for adjusting the location and degree of flame cooling, and the optimum adjustment range is as described above.

With this new method and device for combustion, it is possible to reduce NO, reaching a reduction rate of over 30%, and the smoke concentration is also reduced by over 30% at the same time, which is remarkable. It has great effects.

The first embodiment is an extremely effective method and device without increasing the fouling, smoke, and wear associated with conventional EGR. In addition, it is well known that the combustion noise of the diesel engine EI of the first embodiment is correlated with the pattern of heat generation over time of the fuel in the combustion chamber. In other words, the lower the peak of heat generation, the lower the noise. In this embodiment, by creating two peaks (maximum values) in the fuel injection rate, the heat generation peak is reduced and noise is reliably reduced. This is especially noticeable at low speeds and low loads, where the proportion of the sub-injection amount to the total injection amount is large. 8th
The figure shows the heat generation progress dQ/ based on the pressure measurement results in the main combustion chamber 5.
This is the calculated value of dθ.

The amounts of main injector and sub-injection are the same in the case of normal regular injection and in the case of sub-injection. When sub-injection is performed, the peak of dQ/dθ becomes lower, and dQ/dθ becomes larger in the latter half, and as a result, the area in FIG. 8, that is, the amount of heat generated, hardly changes.

Next, diesel engines generally have higher compression ratios, higher maximum combustion pressures, and sharper dQ/dθ curves than gasoline engines, so torque fluctuations during one cycle are large. In the case of a vehicle engine such as an engine body or a transmission, this causes vibrations in the drive system.

FIG. 9 shows torque fluctuations during one cycle.

Compared to gasoline engines, diesel engines have larger fluctuations within the same average torque (so-called shaft torque). When sub-injection is performed, heat generated by the sub-injection is added to the latter half of combustion and the peak becomes low, as explained in Figure 8.
Torque fluctuations are closer to those of gasoline engines, resulting in lower noise, which has a practical effect.

The injection system as a fuel supply device is provided inside the injection nozzle 8 as shown in FIG. In addition to the mechanical type that demonstrates the
0 Even if it is an electric type, such as a pressure accumulating type electromagnetic injection valve, which activates the electromagnetic solenoid 13 in response to the operating state of the internal combustion engine and lifts the needle valve using electromagnetic force to inject fuel as shown in the figure. The same effects as described above can be obtained.

Note that 14 in FIG. 10 is a fuel pipe, one end of which communicates with the fuel passage of the electromagnetic injection valve 15, and the other end of which communicates with the hydraulic pump P via a pressure accumulator 16 and a check valve 17.

Next, a second embodiment is an example in which the present invention is applied to a direct injection diesel engine E2 as shown in FIG.

This diesel engine E2 has a combustion chamber 20 having a recess 19 of a predetermined volume in the piston 18, and the injection nozzle 21 is a Hall valve having multiple injection holes. The injection system is of the same type as that of the first embodiment, but is different from the first embodiment, which is a single-hole bottle valve or throttle valve. Inside the combustion chamber 20, as shown by the arrow in the figure, a swirl remains during intake and there is a swirling flow. In this case, the main injection of four to five fuel sprays injected from the injection nozzle 21 is performed radially into the recess 19, and then, after the sub-injection, each one of the fuel sprays is injected radially into the recess 19, as in the first embodiment described above. The high temperature flame is cooled down.

In other words, the four to five radially injected fuel sprays are ignited and burned, and then flowed in the circumferential direction of the recess by the swirling flow formed inside the recess 19, and are mixed with other sprays downstream of the swirling flow. Rotate to the position of interference. The flame that has rotated to this position is a flame generated by combustion immediately after ignition, and, as described in the first embodiment, has a higher temperature and more active generation of NO than other flames. Therefore, sub-injection is performed to this high-temperature flame to instantaneously and locally supply fuel at a high injection rate to rapidly lower the temperature of the high-temperature flame portion and suppress the generation of NO. In addition, since the injection energy of the sub-injection can generate turbulence and promote the introduction of air into the flame, it is possible to suppress the production of soot, and since there is no delay in combustion due to the sub-injection, there is no deterioration in fuel efficiency. In this way, the second embodiment can be effectively implemented in the direct injection diesel engine E2, and provides substantially the same effects as the first embodiment.

Considering the case of the diesel engine shown in the first and second embodiments, it is theoretically possible to inject fuel according to the degree of flame cooling, but if the injection amount of sub-injection is too small, atomization will occur. It is bad, and it is dripping as if it is dripping from behind.
Causes soot generation.

- For boat fishing, to ensure atomization, 2 mm per injection is required.
Requires 3 or more. Furthermore, when the engine speed is low, the pressure of the injection pump is low and atomization is poor, so the minimum injection amount to ensure atomization increases somewhat.

In the case of a diesel engine, main injection is performed at 15° to 5° before top dead center, and sub-injection is subsequently started approximately at top dead center, although this varies depending on operating conditions (load, rotation speed).

The ignition of the fuel supplied into the combustion chamber by the main injection occurs several degrees later than the start of injection, and combustion begins, with a temperature of 150°C.
Reaches 0-2500K. The secondary injection that follows the main injection cools the high-temperature part of the flame, and the temperature decreases as the piston expands as it descends. In order to supply the fuel of the sub-injection to the high-temperature part of the flame of the main injection, the timing of the sub-injection should be approximately 5° to 20° after top dead center. Since the speed at which the high-temperature part of the main injection flame moves differs depending on the fuel injection, the timing of the sub-injection must be changed somewhat accordingly.

Next, as another embodiment, as shown in FIGS. 12 and 13, an in-cylinder fuel injection system in which gasoline directly metered by a fuel injection valve 28 is injected into a recess 24 of a combustion chamber 23 as a main injection and a sub-injection is provided. This is a type internal combustion engine E3, and the differences from the above-mentioned embodiment will be mainly described, and the same parts will be given the same reference numerals and the explanation will be omitted.

The fuel supply device 26 of the piston type gasoline engine E3 of this embodiment has a so-called impingement injection system that penetrates through the cylinder head 1, has an injection hole 27 exposed in the combustion chamber 23, and is equipped with the injection system shown in FIG. type injection valve 28 and intake passage 29'
Based on the air flow meter that detects the intake air amount in the engine, the tachometer that detects the engine rotation speed, and the signals of the intake air amount and engine rotation speed, the engine cooling water temperature is taken into consideration. It consists of a control unit that outputs a signal to control the amount of gasoline to be injected according to operating conditions, and a fuel supply device that supplies an amount of pressurized gasoline to the injection valve according to the control signal.

The impingement type injection valve 28 includes a member I inserted into the valve body VB.
Gasoline is injected from the injection hole 27 toward the collision part CP fixed to M via the rod member BM, and collides with the collision part CP.
It injects a thin film of gasoline with a wide injection angle by changing the direction.

A shroud 30 is formed on the intake valve 29 as an intake mechanism to form a swirling flow in the intake air.

By the way, the piston type gasoline engine E3 of this embodiment is as follows.
As shown in FIG. 13, a perfectly circular recess 32 is formed in the upper part 20 of the piston 31 in cross section, and an ignition device 25 is provided to ignite and burn the fuel spray mainly injected into the cylinder head l. .

Piston type gasoline engine E of this embodiment having the above configuration
In No. 3, fuel is injected in main and sub-injections earlier than the injection timing seen in the above-mentioned diesel engines E1 and E2, and an impingement-type injection valve with a relatively wide spread angle and good atomization is used, and the fuel is sprayed in a concave area. It spreads over almost the entirety of 32. Because of the intake swirl generated by the shroud 30 of the intake valve 29, the fuel spray associated with the main injection does not swirl, so when near TDC, a strong swirl of the mixture converges into the recess 32 at the top of the piston while vaporizing and mixing. be done.

The flame is ignited by the ignition device 25 near TDC, and the flame gradually spreads while being carried by the swirling flow within the recess 32.

In this case as well, the flame at the initial stage of combustion has the highest temperature and NO is actively produced. The sub-injection is performed when this high-temperature flame part swirls near the nozzle of the injection valve 28, and this high-temperature flame is instantaneously and locally cooled with fuel spray at a high injection rate. This suppresses the generation of NO and reduces the amount of NO discharged.

[Brief explanation of drawings]

Figure 1 is a diagram comparing the progress of high-temperature flame development in the internal combustion engines of the present invention and the prior art, in terms of the flame rate of 1900°C or higher, and Figure 2 is a swirl chamber type diesel engine that is an embodiment of the present invention. Figures 3 to 7 are schematic diagrams showing a diesel engine with a swirl chamber according to the first embodiment of the present invention, and Figures 8 and 9 are diagrams showing emissions of NO1 smoke and mean effective pressure. 10 is a schematic diagram showing another injection system of the fuel supply device, and FIGS.
FIG. 3 is a cross-sectional view showing an example and other examples, respectively. In the figure 8.15.21.28... Injection nozzle, 1...
・Cylinder head, 2... Vortex chamber, 3... Piston, 6... Communication hole, 7... Cylinder block, 9...
...Injection pump for main injection, 10...Injection pump for sub-injection, 11...Fuel pipe

Claims (2)

[Claims] (1) A predetermined amount of fuel is supplied into the combustion chamber of a reciprocating internal combustion engine formed by a piston, a cylinder head, and a cylinder block during a predetermined process of the internal combustion engine by a fuel supply device that communicates with a fuel supply source and consists of a fuel injection valve. A main injection is carried out to cause ignition and combustion, and the injection rate is once reduced, and then, following the main injection, the injection rate is increased again, and a predetermined amount of fuel is injected and supplied from the fuel supply device at a predetermined time. The flame generated by the main injection is cooled by the fuel spray of the secondary injection, and the production of nitrogen oxide is suppressed while it is being generated by combustion, thereby reducing the oxidation. A method for reducing nitrogen oxide in an internal combustion engine, characterized by reducing nitrogen emissions. (2) A reciprocating internal combustion engine has a combustion chamber formed by a piston, a cylinder head, and a cylinder block, and has a first fuel supply means communicating with a fuel supply source in the combustion chamber and performing main injection, and a secondary fuel supply means. a fuel supply device consisting of a second fuel supply means for performing an injection, a phase control means for controlling a phase difference between the first and second fuel supply means, and a fuel injection valve; The flame generated by the main injection based on the second fuel supply means is cooled by the fuel spray of the secondary injection based on the second fuel supply means, and the production of nitrogen oxide is suppressed while it is being generated by combustion, thereby reducing the oxidation. A nitrogen oxide reduction device for an internal combustion engine, characterized in that it reduces nitrogen emissions.