JPS61212629A - Exhaust apparatus for 2-cycle engine - Google Patents

Abstract

PURPOSE:To improve charging efficiency by blasting-in the uncombusted gas into the small-diameter pipe part of an exhaust pipe consisting of a small-diameter pipe part, spread part, and a contracted-diameter part which are installed into the exhaust hole of a 2-cycle engine and recombusting said uncombusted gas, thus controlling the speed of the pressure waves by adjusting the temperature inside the exhaust pipe. CONSTITUTION:An exhaust pipe 11 consisting of a small-diameter pipe part 4, diffuser part 6 as spread part 6, and a contracted diameter part 9 is installed into the exhaust hole 2 of a 2-cycle engine 1. Each gas is supplied into the small diameter pipe part 4 through the pipes 12 and 14 from an uncombusted-gas feeding part 12 and a high- temperature steam feeding part 14. In the engine 1, the max. scavenging efficiency can be obtained with the inside-scavenging-pipe pressure waves in case of the engine revolution speed corresponding to each set value of the length and capacity of the exhaust pipe. Further, the temperature of the exhaust can be adjusted arbitrarily by feeding the uncombusted gas from the uncombusted-gas feeding part into the exhaust pipe and recombusting said gas or feeding the high-temperature steam form a high-temperature steam feeding part 14 and heating the exhaust, and therefore, the exhaust can be varied arbitrarily according to the revolution speed, since the speed of the pressure wave varies according to the temperature variation.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an exhaust system for a two-stroke engine that improves output by utilizing pressure waves generated by blowing exhaust gas into an exhaust pipe.

2. Description of the Related Art Conventionally, as a typical exhaust system used for two-stroke engines, there is one shown in FIG. , small diameter pipe 4. A small diameter tube 5 slidably fitted into the small diameter tube 4, a diffuser 6 that gradually expands, a rear cone 8 that gradually reduces the diameter of the large diameter tube 71. It consists of a small diameter tail pipe 9, and a muffler 10 is connected to the tip of the tail pipe 9.

Here, the pressure waves generated by the exhaust blowing from the exhaust port 2 into the exhaust pipe 3 are decelerated and depressurized within the diffuser 6 and the large diameter pipe 7. At this time, a negative pressure wave (reflected negative pressure wave) is applied to the exhaust port 2 to bring the exhaust port 2 into a negative pressure state and promote scavenging in the cylinder. Further, the advancing pressure wave is collected in the cylinder cone 8 and becomes a high pressure state, and a positive pressure wave (reflected positive pressure wave) is exerted on the exhaust port 2, thereby increasing the filling ratio of unburned gas in the cylinder. The output of the two-stroke engine 1 is improved by promoting scavenging by nine reflected negative pressure waves and by increasing the filling ratio of fresh unburned gas in the cylinder by one reflected positive pressure wave.

By the way, in order to improve the output by using reflected negative pressure waves and reflected positive pressure waves, the timing of applying the reflected negative pressure waves to the exhaust port 2 is adjusted to the period from when the scavenging port opens to when the scavenging port is closed. It is necessary to match the timing of applying the pressure wave to the period from when the scavenging port is closed to when the exhaust hole 2 is closed. The opening/closing timing of the exhaust port 2, scavenging port, etc. changes as the engine speed changes, and the timing at which reflected negative pressure waves etc. reach the exhaust port 2 changes depending on the dimensions of each member of the exhaust pipe 3 and the speed of the pressure wave. It is something.

Note that the speed of the pressure wave is determined by the exhaust temperature when the exhaust gas enters the exhaust pipe 3, the temperature inside the exhaust pipe 3, the medium inside the exhaust pipe 3 that transmits the pressure wave, and the like.

For this reason, we focused on the differences in the dimensions of each member of the exhaust pipe 3 among the factors that affect the timing at which reflected negative pressure waves etc. reach the exhaust port 2, and we focused on the differences in the dimensions of each member of the exhaust pipe 3. For each 2-stroke engine 1, we designed a design that matches the required rotation speed range of the engine. Exhaust pipes 3 of various member sizes are used. Therefore, when the engine is operated at a rotational speed outside the required number of rotations, it is not possible to improve the output by one reflected negative pressure wave, etc., and the one reflected negative pressure wave acts to impede scavenging, resulting in a decrease in output. Sometimes it brings.

Therefore, as shown in Fig. 4, the small diameter pipe 5 is made slidable and the timing at which the reflected negative pressure waves reach the exhaust port 2 is adjusted by sliding the small diameter pipe 5 according to changes in engine speed. The rotation speed range in which output can be improved by pressure waves, etc. has been expanded.

However, the adjustable range by sliding the small diameter tube 5 is narrow, and it is not possible to improve the output over a wide range of rotation speeds.In addition, gas leakage from the sliding part and pressure Wave leakage occurs, which can easily cause engine trouble.

The present invention was made in view of these points.

The purpose of the present invention is to provide an exhaust system for a two-stroke engine that can improve output over a wide rotational speed range by controlling the speed of pressure waves.

Means for Solving the Problem An exhaust pipe 11 having a small-diameter pipe 41, a diffuser 6 that gradually expands, and a rear cone 8 that gradually decreases in diameter is connected to the exhaust port 2 of the two-stroke engine 1. The exhaust pipe 11 is provided with a speed adjustment mechanism 12,14 for adjusting the speed of the pressure wave generated by the exhaust air blowing to the exhaust pipe 11.

The acting pressure wave is decelerated and depressurized by the diffuser 6, thereby exerting a negative pressure wave (reflected negative pressure wave) on the exhaust port 2 and promoting scavenging in the cylinder. Moreover, the pressure waves are converged at the rear cone 8, resulting in a high pressure state.

This exerts a positive pressure wave (reflected positive pressure wave) on the exhaust port 2, increasing the filling ratio of new unburned gas in the cylinder, and increasing the filling ratio of this new unburned gas and promoting scavenging, resulting in two cycles. The output of the engine 1 is improved. The opening/closing timing of the exhaust port 2 and the scavenging port changes as the engine speed changes, but in that case, the speed adjustment mechanism 12.1
The speed of the pressure wave is adjusted by 4, and the reflected negative pressure wave 1 is applied to the exhaust port 2 at a timing corresponding to the engine speed.

Embodiment An embodiment of the present invention will be described with reference to FIGS. 1 to 3. In addition, the 41st! The same parts as those explained in 1 are indicated by the same reference numerals, and the explanation will be omitted.

One end of the small diameter pipe 4 is connected to the exhaust port 2 of the two-stroke engine 1, and a diffuser 6 is connected to the other end of the small diameter pipe 4, which are connected in sequence. Diffuser 6, large diameter pipe 7. Rear cone8. The tail pipe 9 constitutes an exhaust pipe 11. In the exhaust pipe 11.

An injection nozzle 13 that is part of a speed adjustment mechanism 12 that injects new unburned gas into the exhaust pipe 11 is connected.

The speed adjustment mechanism 12 includes an engine rotation speed detection section, an exhaust pipe humidity temperature detection section, and a control section that controls the injection amount of new unburned gas based on the detection results from these detection sections. ing. Further, an injection nozzle 15 is connected to the exhaust pipe 11 and is part of a second speed adjustment mechanism 14 that injects a gas (for example, water vapor) that can change the pressure wave velocity into the exhaust pipe 11. has been done.

The speed adjustment mechanism 14, like the speed adjustment mechanism 12, includes a detection section that detects the engine rotation speed, a control section that controls the amount of gas to be injected based on the detection result from the detection section, and the like.

In such a configuration, the length of each member (small diameter pipe 4, diffuser 6, etc.) of the exhaust pipe 1 is always constant,
This length dimension is set so that reflected negative pressure waves and reflected positive pressure waves reach the exhaust port 2 in accordance with the opening/closing timing of the exhaust port 2, scavenging port, etc. in the required rotational speed range of the two-cycle engine 1.

Therefore, when operating at a rotation speed outside the required rotation speed range, the opening/closing timing of the exhaust port 2, etc. and the timing at which reflected negative pressure waves, etc. reach the exhaust port 2 will be different, and the reflected positive pressure waves will interfere with scavenging. Otherwise, the reflected negative pressure wave may also act to scavenge new unburned gas, leading to a decrease in output.

Therefore, the speed adjustment mechanism 12.14 is used alone or in combination to adjust the speed of the pressure wave according to the number of rotations, and the timing when the 1 reflected negative pressure wave etc. reaches the exhaust port 2 is adjusted to the opening/closing timing of the exhaust port 2, etc. Match.

That is, this method focuses on the fact that the speed of the pressure wave changes depending on the temperature inside the exhaust pipe 11 and the medium inside the exhaust pipe 11 that transmits the pressure wave. By this, the temperature inside the exhaust pipe 11 is adjusted, and the gas injected from the injection nozzle 15 adjusts the properties of the medium inside the exhaust pipe 11, and thereby the speed of the pressure wave is adjusted.

The graph in FIG. 2 shows an equivalent pipe length curve due to temperature change with temperature as a variable. for example.

Actual vA (a) is an exhaust pipe whose length is set to 3000 revolutions, and the temperature inside the exhaust pipe is changed by the speed adjustment mechanism 12. As the temperature rises, the speed of the pressure wave also increases. By raising the temperature inside the exhaust pipe to 1000°C, it becomes equivalent to an exhaust pipe with a length dimension in which the required rotation speed range is set to 6000 rotations. That is, by appropriately adjusting the temperature inside the exhaust pipe using this exhaust pipe, 30
In a wide rotation speed range from 00 rotations to 6000 rotations, it is possible to improve output through reflected negative pressure waves and the like. Similarly,
The solid line (b) shows an exhaust pipe whose length is set to 5,000 rpm, and whose length is set to 9,000 rpm by raising the temperature inside the exhaust pipe to 1,000°C. This is equivalent to , and it is possible to improve the output by reflecting negative pressure waves, etc. in a wide rotation speed range from 500 rotations to 9000 rotations. In addition, the broken line (C) shows the combination of two speed adjustment mechanisms 12 and 14, which increases the temperature in the exhaust pipe due to combustion of unburned gas injected from the injection nozzle 13 and increases the temperature of the gas (heated) from the injection nozzle 15. The velocity of the pressure wave further increases due to the injection of water vapor).

Then, as shown by the broken line (c), the required rotation speed range is 40
In an exhaust pipe with a length set at 00 rpm, the temperature inside the exhaust pipe is raised to 1000°C while injecting a predetermined amount of heated steam.
By increasing the number of revolutions to 10,000 revolutions, it becomes equivalent to an exhaust pipe whose length dimension is set to 10,000 revolutions. Therefore, by using this exhaust pipe and injecting heated steam and adjusting the temperature within the exhaust pipe at node m, it is possible to improve the output through reflected negative pressure waves and the like in a wider rotational speed range from 4,000 rotations to 10,000 rotations.

Next, the broken lines in the graph of Figure 3 indicate the required rotation speed ranges of 3000 rotations, 4000 rotations, 5000 rotations, and 60 rotations.
In an engine using an exhaust pipe with a length dimension set at 00 rpm and 7000 rpm.

This is an engine output curve showing a state in which the engine output decreases significantly when the engine is operated at a rotation speed outside the required rotation speed range.

Also, the solid line in this graph is.

Speed adjustment mechanism 1 according to the number of revolutions using one exhaust pipe
This shows the engine output when 2.14 is activated. As can be seen from this graph, the solid line shows the continuous peak value of the output shown by the broken line, and since the same exhaust pipe is used, the maximum output can be obtained at all rotation speeds (3000 to 7000 rpm).

In this embodiment, as a means to adjust the temperature inside the exhaust pipe 11, unburned gas is injected into the exhaust pipe 11 and is combusted. It may be heated.

Effects of the Invention The present invention adjusts the speed of the pressure waves in the exhaust pipe using the speed adjustment mechanism as described above, so that reflected negative pressure waves etc. can be applied to the exhaust port in accordance with the timing of opening and closing of the exhaust port, etc. Therefore, even if the opening/closing timing of the exhaust port, etc. changes due to a change in the number of revolutions, the speed of the pressure wave can be adjusted accordingly, promoting scavenging by the reflected negative pressure wave, and removing new unburned gas by the reflected positive pressure wave. By improving the filling ratio, it is possible to improve the output, and it has the effect that the output can be improved in a wide rotation speed range from low speed rotation to high speed rotation.

[Brief explanation of the drawing]

Fig. 1 is a side view showing an embodiment of the present invention, Fig. 2 is a graph showing equivalent pipe length due to temperature change, Fig. 3 is a graph showing engine output, and Fig. 4 is a side view showing a conventional example. . 1...2-cycle engine, 2...Exhaust port, 4...
・Small diameter pipe, 6... Diffuser, 8... Rear cone, 11... Exhaust pipe, 12... Speed adjustment mechanism, 14...
...Speed adjustment mechanism Applicant: Ishikawajima Shibaura Machinery Co., Ltd. N (ram) Js required

Claims (1)

[Claims] An exhaust pipe is provided which has a small diameter pipe, a diff user located on the distal end side of the small diameter pipe and gradually expands, and a rear cone located on the distal end side of the diff user whose diameter gradually decreases. An exhaust system for a two-cycle engine, characterized in that the exhaust pipe is provided with a speed adjustment mechanism that is connected to an exhaust port of the cycle engine and adjusts the speed of pressure waves generated by blowing exhaust gas from the exhaust port into the exhaust pipe. .