JP2015078664A - Rotary piston engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotary piston engine which can enhance combustion stability of fire retardant gas containing large amount of inactive component.SOLUTION: A rotary piston engine includes a rotor 5 having a recess 20 formed on an outer peripheral surface. The recess 20 is constituted of a first concave portion 21 located in a trailing side in the rotational direction of the rotor 5, and a second concave portion 22 formed continuously to the first concave portion 21 and located in a leading side in the rotational direction of the rotor 5. The cross section of the first concave portion 21 orthogonal to the circumferential direction of the rotor 5 is smaller than the cross section of the second concave portion 22 orthogonal to the circumferential direction of the rotor 5.

Description

  The present invention relates to a rotary piston engine, and more particularly to a combustion chamber structure of a rotary piston engine suitable for burning a flame-retardant gas (fermented methane gas, syngas, ammonia gas, etc.).

  In recent years, the use of biofuel, which is renewable energy, has attracted attention for the purpose of reducing global environmental problems and fossil fuel consumption, reducing the environmental burden and creating a recycling society. As biofuel, for example, fermented methane gas produced from livestock manure, food waste, and the like is known. However, fermented methane gas generally contains a large amount of carbon dioxide of about 40 to 60%, and since carbon dioxide acts as an inert component, it has good combustion stability when used as engine fuel. Cannot be obtained.

  Here, using a compressed natural gas (hereinafter, referred to as CNG) fuel containing methane gas as a main component, the combustion stability (Coefficient of the engine) when the carbon dioxide concentration in the fuel is increased. FIG. 11 shows the measurement result of “Variation: hereinafter referred to as COV”. Here, the COV is a variation of the indicated mean effective pressure for each combustion cycle. The lower the COV, the more stable the combustion, and the higher the COV, the more unstable the combustion. Yes. FIG. 11 shows a COV target line. As the COV exceeds this target line, the combustion becomes unstable and the engine output becomes unstable. For example, it cannot be used for an engine as a generator that requires a constant output.

  As shown by a chain line in FIG. 11, in a general reciprocating engine, when the carbon dioxide concentration exceeds 20%, the combustion stability is remarkably deteriorated and exceeds the COV target line. For this reason, in order to use fermented methane gas, it is necessary to remove carbon dioxide below a certain level. However, removing carbon dioxide from the fermentation methane gas requires a great deal of energy, which increases the cost. As a result, in small and medium-sized factories and the like, from the profit side, the fermentation methane gas is not used as fuel for the reciprocating engine so much, that is, the fermentation methane gas is not effectively used as energy.

  By the way, the inventor of the present application has found that a rotary piston engine has a higher allowable limit of carbon dioxide concentration that can be operated while maintaining good combustion stability than a reciprocating engine. As shown by the solid line in FIG. 11, in the rotary piston engine, the allowable limit of the carbon dioxide concentration in the CNG fuel is about 50%, which is higher than about 20% of the reciprocating engine. This is because the expansion stroke of the rotary piston engine is usually about 270 ° in crank angle, and about 1.5 times longer than the expansion stroke of the reciprocating engine is about 180 ° in crank angle. This is because the volume of the combustion chamber after the top dead center expands slowly, so that the pressure in the combustion chamber does not drop rapidly.

  That is, the rotary piston engine is an engine having high combustion stability because it is easy to maintain the combustion after the top dead center for a long time, and so-called afterburning, as compared with the reciprocating engine. Therefore, the inventor of the present application has devised effective use of flame retardant gas such as fermented methane gas and biogas as fuel for the rotary piston engine.

  However, the content of carbon dioxide in the fermented methane gas varies greatly depending on the production environment of the fermented methane gas, and may exceed 50% as described above. When the content of carbon dioxide in the fermented methane gas exceeds 50%, even if it is a rotary piston engine, the combustion stability is remarkably deteriorated, so that stable operation is difficult. That is, there is a problem in using a flame retardant gas containing a large amount of an inert component as a fuel.

  As a prior art that uses a flame retardant gas containing carbon dioxide as an inert component as a fuel for an engine, for example, Patent Document 1 estimates the carbon dioxide concentration contained in CNG fuel in a reciprocating engine, and estimates It is disclosed that the ignition timing and the air-fuel ratio are controlled in accordance with the carbon dioxide concentration. Further, in Patent Document 2, in a rotary piston engine, a turbulent flow is generated by a projection for generating a turbulent flow provided in a recess portion of a rotor surface, thereby promoting mixing and diffusion of the mixed gas, A rotary piston engine capable of suppressing combustion delay is disclosed.

JP 2011-214568 A JP2013-050040A

  However, in Patent Document 1, the ignition conditions and the air-fuel ratio are changed to suppress the deterioration of the engine performance, and the combustion itself is not improved. Furthermore, the carbon dioxide as an inactive component is not improved. The allowable limit of content cannot be expanded. That is, it is difficult to use a flame retardant gas such as CNG fuel containing a large amount of carbon dioxide as a fuel. Patent Document 2 is directed to hydrogen gas having a high combustion rate, and cannot improve the combustion stability of a flame retardant gas containing an inert component having a low combustion rate.

  The present invention has been made to solve the above-described problems, and it is an object of the present invention to provide a rotary piston engine capable of improving combustion stability even with a flame-retardant gas containing a large amount of inert components. Objective.

  In order to solve the above problems, the present invention is configured as follows.

  The invention according to claim 1 of the present application includes a rotor having a recess formed on an outer peripheral surface, and the recess is continuous with the first recess located on the trailing side in the rotation direction of the rotor, and the first recess. And the second concave portion located on the leading side in the rotational direction of the rotor, and the cross-sectional area of the first concave portion perpendicular to the circumferential direction of the rotor is the rotor of the second concave portion. The cross-sectional area perpendicular to the circumferential direction is smaller.

  According to a second aspect of the present invention, in the first aspect of the present invention, the dimension of the first recess in the width direction of the rotor is smaller than the dimension of the second recess in the same direction. And

  The invention according to claim 3 is characterized in that, in the invention according to claim 1, the depth of the first recess is shallower than the depth of the second recess.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the rotor is positioned at a top dead center in a rotor housing that rotatably accommodates the rotor. A trailing-side spark plug is disposed corresponding to the first recess when the leading-side spark plug is disposed corresponding to the second recess when the rotor is located at the top dead center. And

  The invention according to claim 5 is the invention according to claim 4, wherein a plurality of the leading spark plugs are arranged in parallel in the width direction of the rotor.

  The invention according to claim 6 is the invention according to any one of claims 1 to 5, further comprising a guide groove formed continuously with the first recess, wherein the guide groove A plurality of the concave portions are formed so as to extend obliquely from the side portion of the first concave portion toward the trading side.

  According to the invention of each claim of the present application, the following effects can be obtained by the above configuration.

  First, according to the first aspect of the present invention, the flow of the air-fuel mixture from the trailing side to the leading side generated with the volume expansion on the leading side of the working chamber by the rotor rotating beyond the top dead center, It is easy to generate a turbulent flow at the connection from the first recess to the second recess where the cross-sectional area of the recess changes. Thereby, mixing and diffusion of the air-fuel mixture are promoted, the combustion speed of the air-fuel mixture is improved, and initial combustion can be activated. Then, the trailing side air-fuel mixture is reliably supplied to the activated combustion area of the initial combustion by the squish flow generated through the recess, so that the diffusion as the second stage combustion follows the initial combustion. Combustion can occur.

  In addition, by improving the combustion speed of the initial combustion, it is easy to activate the initial combustion before the flow velocity of the squish flow becomes maximum, and the squish flow is brought into the activated combustion region of the initial stage of the first stage. Easy to supply. In addition, the volume difference between the first and second recesses can be increased by configuring the cross-sectional area of the first recess to be smaller than the cross-sectional area of the second recess. As a result, the first and second recesses in the first and second recesses are rotated. A squish flow from the first recess to the second recess can be further enhanced by effectively generating a pressure difference. Thereby, the second stage diffusion combustion can be performed more stably.

  That is, the two-stage combustion including the first stage initial combustion and the second stage diffusion combustion can be stably performed, and the combustion stability of the air-fuel mixture can be improved. Thereby, even if it is a flame-retardant gas containing a large amount of an inert component, combustion stability can be improved.

  According to the second aspect of the present invention, a corner portion is formed between the first recess portion and the second recess portion so that a dimension in the width direction suddenly increases. It is easy to generate turbulent flow in the air-fuel mixture supplied to the two recesses, and the invention according to claim 1 can be suitably implemented. In addition, by making the width of the second recess larger than the width of the first recess, the air-fuel mixture supplied to the second recess can be easily diffused in the width direction, and the flame propagation in the width direction of the rotor in the initial combustion is promoted. it can. Further, the second stage diffusion combustion can be stably burned over the width direction of the rotor. Therefore, the combustion stability of the flame retardant gas can be further improved.

  According to the invention described in claim 3, the step portion in which the dimension in the depth direction suddenly changes is formed between the first recess portion and the second recess portion, and in the step portion, from the first recess portion. It is easy to generate turbulent flow in the air-fuel mixture supplied to the second recess, and the invention according to claim 1 can be suitably implemented.

  According to the fourth aspect of the present invention, the spark is supplied to the turbulent flow of the air-fuel mixture generated at the connecting portion with the first recess in the second recess by the leading side spark plug to stabilize the initial combustion. Can be done. Further, in the rotary piston engine, it is difficult to propagate the flame to the trailing side due to the flow of the air-fuel mixture to the leading side. However, by providing the trailing-side spark plug, it is possible to supply a spark to the air-fuel mixture that is closer to the trailing side than the leading-side spark plug and burn it. Thereby, while being able to suppress the production | generation of unburned gas, a combustion speed can be raised and the combustion stability of initial stage combustion can be improved.

  Further, according to the invention described in claim 5, turbulent flow of the air-fuel mixture generated at the connecting portion with the first recess in the second recess is caused by a plurality of leading-side spark plugs arranged in parallel in the width direction of the rotor. Sparks can be supplied over the width direction of the rotor. As a result, the growth of flame propagation in the width direction of the rotor in the initial combustion can be promoted and a combustion region extending in the width direction can be formed, so that the second stage diffusion combustion can be stably performed in the width direction of the rotor. Can be generated. Therefore, the combustion stability of the flame retardant gas can be further improved.

  According to the sixth aspect of the present invention, the air-fuel mixture on the side of the first recess can be efficiently supplied into the first recess by the guide groove. Thereby, the squish flow from the first recess to the second recess can be further strengthened, and the second stage diffusion combustion can be burned more efficiently. In addition, since the unburned gas in the combustion chamber can be effectively supplied to the second stage diffusion combustion, the generation of unburned gas can be suppressed and the combustion stability of the air-fuel mixture can be further enhanced. That is, the combustion stability of the flame retardant gas can be further improved.

  That is, according to the rotary piston engine of the present invention, the combustion stability can be improved, and a flame-retardant gas containing a large amount of inert components can be used as the fuel.

It is a perspective view showing a schematic structure of a rotary piston engine concerning a 1st embodiment. It is a front view of the rotary piston engine by A arrow view of FIG. It is a side view of the rotor by B arrow view of FIG. It is IV-IV sectional drawing of FIG. It is VV sectional drawing of FIG. It is a graph which shows transition for every crank angle of the heat release rate at the time of making the flame-retardant gas whose carbon dioxide concentration is 55% into a fuel. It is a graph which shows the relationship between a carbon dioxide concentration and combustion stability. It is a side view of the rotor similar to FIG. 3 based on 2nd Embodiment. It is a side view of the rotor similar to FIG. 3 based on 3rd Embodiment. It is XX sectional drawing of FIG. It is a graph which shows the relationship between the carbon dioxide concentration and combustion stability in the engine of a prior art example.

[First Embodiment]
(Overall configuration of engine 1)
Hereinafter, the overall configuration of the engine 1 according to the first embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a perspective view showing a schematic configuration of the engine 1 according to the first embodiment, and FIG. 2 is a front view of the engine 1 as viewed in the direction of arrow A in FIG. 1, the front side (right side in FIG. 1) rotor housing 3 and side housing 4 are partially cut away to show the inside, and the rear side (left side in FIG. 1) side housing 4 is shown. Shown separately. In FIG. 2, the side housing 4 is omitted.

  As shown in FIG. 1, the engine 1 is a two-rotor type rotary piston engine, and a rotor housing 3 and a side housing 4 are sequentially laminated on both sides of the intermediate housing 2 so as to be integrated. It is constituted by being made. In the rotor housing 3, a substantially triangular rotor 5 that divides the rotor housing 3 into three working chambers 30 is accommodated rotatably. Recesses 20 are respectively formed on the outer peripheral surface of the rotor 5.

  As shown in FIG. 2, the rotor 5 is eccentrically rotated about the eccentric shaft 6 in the rotation direction X, whereby the volume of each working chamber 30 is changed, and the intake process, the compression process, the expansion process, the exhaust process is changed. The steps are performed in order. The intermediate housing 2 and the side housing 4 (see FIG. 1) are respectively formed with an intake port 11 facing the working chamber 31 for the intake stroke and an exhaust port 12 facing the working chamber 32 for the exhaust stroke. .

  A trailing-side spark plug 7a and a leading-side spark plug 7b are provided at a position facing the working chamber 33 formed by the rotor 5 positioned substantially at the top dead center. Further, the rotor housing 3 is provided with an injector 8 for injecting a flame-retardant gas into the working chamber 30 at a position that opens to the working chamber 30 from the intake stroke to the compression stroke. The injector 8 is configured so that a flame retardant gas is supplied from a gas tank (not shown) through a fuel supply passage.

(Recess 20)
Next, the recess 20 will be described with reference to FIGS. FIG. 3 is a side view of the rotor 5 as viewed in the direction of arrow B in FIG. 2, and the trailing side spark plug 7a and the leading side spark plug 7b are indicated by chain lines. 4 is a cross-sectional view taken along the line IV-IV in FIG. 3, showing a cross-sectional view perpendicular to the rotation axis of the rotor 5, and FIG. 5 is a cross-sectional view taken along the line VV in FIG. 3 to 5, a recess 200 having a conventional structure as a comparative example is indicated by a chain line.

  For convenience of explanation, the rotation axis direction of the rotor 5 is the width direction of the rotor 5, the direction along the outer peripheral surface of the rotor 5 perpendicular to the width direction is the circumferential direction of the rotor 5, and the rotation of the rotor 5 in the circumferential direction is The leading side of the direction is called the leading side, and the lagging side is called the trailing side.

  As shown in FIG. 3, the recess 20 adjusts the compression ratio of each working chamber (combustion chamber) and generates a squish flow from the trailing side to the leading side. The first concave portion 21 is formed on the trailing side, and the second concave portion 22 is formed on the leading side continuously to the first concave portion 21.

  The first recess 21 is a side view shown in FIG. 3 and is arranged at a substantially central portion in the width direction of the rotor 5 and has a substantially rectangular shape with a circumferential length 21b longer than the width 21a. doing. As shown in FIG. 4, the first recess 21 is formed to a depth 21c. The first recess 21 is formed with a smaller width 21a (see FIG. 3) and a shallower depth 21c (see FIG. 4) than the recess 200 having the conventional structure.

  The second concave portion 22 is a side view shown in FIG. 3 and is arranged at a substantially central portion in the width direction of the rotor 5 and has a vertex on the leading side and a rectangular portion on the trailing side. It has a pentagonal shape. As shown in FIG. 4, the second recess 22 is formed to a depth 22c. The second recess 22 has a width 22a (see FIG. 3) and a depth 22c (see FIG. 4) deeper than the recess 200 having the conventional structure.

  That is, the first recess 21 is formed to have a smaller width and a smaller depth than the second recess 22. For this reason, as shown in FIG. 5, the longitudinal sectional area of the first recess 21 is configured to be smaller than the same sectional area of the second recess. In other words, the longitudinal sectional area of the first recess 21 is smaller than the sectional area of the recess 200 having the conventional structure, and the longitudinal sectional area of the second recess 22 is larger than the sectional area of the recess 200 having the conventional structure.

  The first recess 21 is formed in the first recess 21 by making the vertical cross-sectional area of the second recess 22 larger than the cross-sectional area of the conventional recess 200 while making the vertical cross-sectional area of the first recess 21 smaller than the same cross-sectional area of the recess 200 of the conventional structure. The difference in cross-sectional area between the squish flow channel formed and the squish flow channel formed in the second recess 22 can be increased. Thereby, the flow of the air-fuel mixture from the trailing side to the leading side generated by the rotor rotating beyond the top dead center with the expansion of the volume on the leading side of the working chamber, that is, the first concave portion 21 to the second concave portion 22. The squish flow can be strengthened as compared with the recess 200 having the conventional structure.

  At the connection portion between the first recess 21 and the second recess 22, a corner portion 23 in which the dimension of the recess 20 in the width direction suddenly expands and a step portion 24 in which the depth suddenly increases are formed. . As shown in FIG. 3 and FIG. 4, the corner 23 and the stepped portion 24 are preferably formed in an acute angle state in which the corners are not chamfered and the corners are sharp.

  By configuring the connecting portion between the first concave portion 21 and the second concave portion 22 in this way, the flow path of the squish flow from the first concave portion 21 to the second concave portion 22 in the recess 20 is changed to the corner portion 23 and the step portion. 24 can be changed rapidly, and it is easy to generate turbulent flow in the squish flow passing through the corner 23 and the stepped portion 24. In addition, the other corners of the first and second recesses 21 and 22 are rounded to smooth the flow of the air-fuel mixture in the first and second recesses 21 and 22 and to the corners. The mixture is prevented from staying and unburned fuel remains in the recess 20.

(Trailing side, leading side spark plugs 7a, 7b)
The rotor housing 3 is provided with a trailing-side spark plug 7a corresponding to the first recess 21 when the rotor 5 is located at the top dead center, and the second recess 22 when the rotor 5 is located at the top dead center. A leading side spark plug 7b is arranged corresponding to the above. Preferably, the leading side spark plug 7b is disposed in the second recess 22 in correspondence with the turbulent flow generation position of the air-fuel mixture in the vicinity of the connection portion with the first recess 21.

(Operation of engine 1)
The operation of the engine 1 according to this embodiment will be described with reference to FIG. As described above, when the rotor 5 rotates eccentrically around the eccentric shaft 6 in the X direction, the volume of each working chamber 30 changes, and the intake process, the compression process, the expansion process, and the exhaust process are sequentially performed. It has become. Each process will be described below.

  In FIG. 2, the upper left working chamber 31 is an intake stroke. In the intake stroke, the volume of the working chamber 31 increases as the rotor 5 rotates, and air is sucked into the working chamber 31 via the intake port 11. Thereafter, when the rotor 5 further rotates, the volume of the working chamber 31 changes from expansion to reduction and shifts to the compression stroke. In the compression stroke, the sucked air and the flame-retardant gas injected from the injector 8 are mixed to form an air-fuel mixture.

  When the rotor 5 further rotates and the rotor 5 is located at the top dead center, the air is compressed into the working chamber 33 as shown on the right side in FIG. 2, and the air-fuel mixture becomes the most compressed state in the working chamber 33. . The compressed air-fuel mixture is ignited by the trailing-side spark plug 7a and the leading-side spark plug 7b, and shifts to the expansion stroke.

  By the way, in the rotary piston engine, during the compression stroke to the expansion stroke, the flow of the air-fuel mixture toward the leading side is generated with the volume expansion on the leading side of the working chamber 30 due to the rotation of the rotor 5. In the present embodiment, since the recess 20 including the first recess 21 and the second recess 22 is provided, the squish flow of the air-fuel mixture flows along the recess 20, that is, from the first recess 21 toward the second recess 22. Generated.

  At this time, the corner portion 23 (see FIG. 4) and the step portion 24 (see FIG. 4) are formed at the connecting portion between the first recess 21 and the second recess 22 as described above. A turbulent flow is generated in the squish flow passing through the connecting portion. As a result, mixing and diffusion of the air-fuel mixture are promoted, the combustion speed of the air-fuel mixture is improved, and the initial combustion of the air-fuel mixture is activated. Further, due to the strong squish flow toward the leading side, the flame propagation in the initial combustion promotes the growth toward the leading side.

  Next, as the rotor 5 further rotates, the air-fuel mixture on the trailing side is sent to the leading side by a squish flow. As a result, the squish flow from the trailing side is efficiently supplied to the combustion region by the initial combustion, and diffusion combustion as the second stage combustion occurs. In this embodiment, since the cross-sectional area of the 1st recessed part 21 is comprised smaller than the cross-sectional area of the normal recess 200, a stronger squish flow can be produced | generated.

  In addition, the recess 20 is divided into a first recess 21 and a second recess 22, and the second recess 22 located on the leading side is configured to be larger than the first recess 21 located on the trading side. It is easy to increase the difference between the pressure in the first recess 21 and the pressure in the second recess 22 due to the rotation, whereby the squish flow from the first recess 21 toward the second recess 22 can be further increased. Thereby, the diffusion combustion in the second stage can be further stabilized. Furthermore, since the width 22a of the second recess 22 is larger than the width 21a of the first recess 21, the turbulent flow of the air-fuel mixture generated at the joint between the first recess 21 and the second recess 22 in the width direction. Diffusion is promoted, and thereby the flame propagation in the initial combustion is promoted to grow in the width direction of the rotor 5 and the combustion stability can be enhanced.

  Further, by causing the first stage initial combustion to grow in the width direction of the second recess 22, the squish flow supplied from both sides of the first recess 21 to the leading side is also burned by the first stage initial combustion. Thus, the second stage diffusion combustion can be suitably realized.

  The result of evaluating the recess 20 according to the present embodiment and the conventional recess 200 as a comparative example using CNG containing carbon dioxide is shown in FIGS. FIG. 6 is a graph showing the heat generation rate (dQ / dθ) with respect to the crank angle, and shows the analysis result in CNG where the carbon dioxide concentration is 55%. FIG. 7 is a graph showing the analysis result of calculating the relationship between the carbon dioxide concentration and COV. In FIG. 6 and FIG. 7, the case of the recess 20 is indicated by a solid line, and the case of the recess 200 is indicated by a broken line.

  First, referring to FIG. 6, in the conventional recess 200, only one peak of the heat generation rate is seen, and the boundary between the first stage initial combustion and the second stage diffusion combustion is not seen. . This indicates that since the carbon dioxide content is high, the combustion rate is slow, the initial combustion in the first stage is delayed, and it is integrated with the diffusion combustion in the second stage. Furthermore, since the initial combustion in the first stage is delayed, a squish flow having a peak flow velocity is supplied before the peak of the initial combustion. As a result, the squish flow cannot be effectively supplied to the fuel region, indicating that the second diffusion combustion is slow. That is, in the recess 200 having the conventional structure, the first stage initial combustion is delayed, and therefore, the second stage diffusion combustion becomes slow, so the combustion stability is poor.

  On the other hand, in the recess 20 according to the present embodiment, two peaks of the heat generation rate are seen. As described above, the initial combustion is activated by the recess 20, and the peak of the initial combustion in the first stage occurs at a timing earlier than the peak position of the flow velocity of the squish flow, and the squish flow is generated in the combustion region by the initial combustion. It is supplied efficiently. Therefore, the second stage diffusion combustion is stably performed. That is, in the recess 20 according to the present embodiment, the first stage initial combustion can be activated, the second stage diffusion combustion can be performed stably, and the combustion stability is good.

  Next, referring to FIG. 7, in the conventional recess 200, the COV exceeds the target line when the carbon dioxide content exceeds 50%, but in the recess 20 according to the present embodiment, the carbon dioxide content. Even if the value exceeds 50%, the COV does not deteriorate rapidly and does not exceed the target line. That is, in the rotary piston engine according to the present invention, the combustion stability of the flame retardant gas containing a large amount of inert components is improved.

  The engine 1 according to the present embodiment described above can exhibit the following effects.

(1) The cross-sectional area of the recess 20 changes due to the flow of the air-fuel mixture from the trailing side to the leading side that occurs as the volume of the working chamber on the leading side increases due to the rotation of the rotor 5 rotating beyond the top dead center. It is easy to generate a turbulent flow at the connecting portion from the first recess 21 to the second recess 22. Thereby, mixing and diffusion of the air-fuel mixture are promoted, the combustion speed of the air-fuel mixture is improved, and initial combustion can be activated. Then, the trailing-side air-fuel mixture is reliably supplied to the activated combustion region of the initial combustion by the squish flow generated through the recess 20, so that the second-stage combustion is performed following the initial combustion. Diffusion combustion can be generated stably.

(2) By improving the combustion speed of the initial combustion, it is easy to activate the initial combustion before the flow velocity of the squish flow reaches the maximum, and the squish flow is activated in the first-stage initial combustion combustion region. Easy to supply. In addition, by configuring the cross-sectional area of the first recess 21 to be smaller than the cross-sectional area of the second recess 22, the volume difference between the first and second recesses 21 and 22 can be increased. The pressure difference in the 1st, 2nd recessed parts 21 and 22 can be produced effectively, and the squish flow which goes to the 2nd recessed part 22 from the 1st recessed part 21 can be strengthened further. Thereby, the second stage diffusion combustion can be performed more stably.

(3) The two-stage combustion consisting of the first stage initial combustion and the second stage diffusion combustion can be stably generated, and the combustion stability of the air-fuel mixture can be improved. Thereby, even if it is a flame-retardant gas containing a large amount of inert components, combustion stability can be improved.

(4) A corner 23 is formed between the first recess 21 and the second recess 22 so that the dimension in the width direction suddenly increases. The corner 23 is supplied from the first recess 21 to the second recess 22. It is easy to generate turbulent flow in the air-fuel mixture. In addition, by configuring the width of the second recess 22 to be larger than the width of the first recess 21, the air-fuel mixture supplied to the second recess 22 can be easily diffused in the width direction, and the width of the rotor 5 in the initial combustion can be increased. Can promote flame propagation. Furthermore, the second stage diffusion combustion can also be stably burned across the width direction of the rotor 5. Therefore, the combustion stability of the flame-retardant gas containing a large amount of inert components can be further improved.

(4) A step portion 24 whose dimension in the depth direction changes abruptly is formed between the first recess portion 21 and the second recess portion 22, and in the step portion 24, from the first recess portion 21 to the second recess portion 22. It is easy to generate turbulent flow in the supplied air-fuel mixture. Thereby, as mentioned above, the combustion stability of the flame-retardant gas containing a large amount of inert components can be further enhanced.

(5) The leading side spark plug 7b can stably supply initial sparks by supplying a spark to the turbulent flow of the air-fuel mixture generated at the connecting portion of the second concave portion 22 with the first concave portion 21. Further, in the rotary piston engine, it is difficult to propagate the flame to the trailing side due to the flow of the air-fuel mixture to the leading side. However, by providing the trailing-side spark plug 7a, it is possible to supply a spark to the air-fuel mixture that is closer to the trailing side than the leading-side spark plug 7b and burn it. Thereby, while being able to suppress the production | generation of unburned gas, a combustion speed can be raised and the combustion stability of initial stage combustion can be improved.

[Second Embodiment]
FIG. 8 is a side view similar to FIG. 3 of the rotor 50 according to the second embodiment. As shown in FIG. 8, the second embodiment is different from the first embodiment in that a plurality of leading side spark plugs 7b are arranged in parallel in the width direction. In the second embodiment, the leading side spark plugs 7b are arranged in the rotor housing 3 so as to be arranged in parallel so that two leading side spark plugs 7b are arranged in the width direction. Other configurations are the same as those of the first embodiment.

  According to the second embodiment, the turbulent flow of the air-fuel mixture generated at the connecting portion with the first concave portion 21 in the second concave portion 22 by the plurality of leading side spark plugs 7 b, 7 b arranged in parallel in the width direction of the rotor 5. Moreover, a spark can be supplied over the width direction of the rotor 5. As a result, the growth of flame propagation in the width direction of the rotor 5 in the initial combustion can be promoted, and a combustion region extending in the width direction can be formed, so that the second stage diffusion combustion can be stabilized over the width direction of the rotor 5. Can be generated. Therefore, the combustion stability of the flame retardant gas containing a large amount of inert components can be further improved.

[Third Embodiment]
FIG. 9 shows a side view similar to FIG. 3 of the rotor 50 according to the third embodiment, and FIG. 10 shows an XX cross section of FIG. As shown in FIG. 9, in the third embodiment, a plurality of guide grooves 25 extending obliquely toward the trading side are formed continuously to the side of the first recess 21. Unlike the first embodiment, the rest is the same as the first embodiment. As shown in FIG. 10, the guide groove 25 is formed at substantially the same depth as the first recess 21.

  According to the third embodiment, the air-fuel mixture on the side of the first recess 21 can be efficiently supplied into the first recess 21 by the guide groove 25. Thereby, the squish flow from the 1st recessed part 21 to the 2nd recessed part 22 can further be strengthened, and the diffusion combustion of the 2nd stage can be burned more efficiently. In addition, since the unburned gas in the combustion chamber can be effectively supplied to the second stage diffusion combustion, the generation of unburned gas can be suppressed and the combustion stability of the air-fuel mixture can be further enhanced. That is, the combustion stability of the flame retardant gas can be further improved.

[Other Embodiments]
In the above-described embodiment, the CNG gas containing carbon dioxide as an inert component has been described as an example of the flame retardant gas. It can also be applied to gasoline engines or diesel engines included in the above. That is, the present invention can be applied to an engine that uses a flame-retardant gas that is difficult to burn.

  In the above embodiment, the case where the flame retardant gas is directly injected into the working chamber 30 by the injector 8 has been described as an example. However, the present invention is not limited to this, and the intake port 11 or the intake pipe connected to the intake port 11 (illustrated) The injector 8 may be appropriately laid out so as to inject fuel.

  The present invention is not limited to the embodiment described above, and various modifications and changes can be made without departing from the spirit and scope of the present invention described in the claims.

  As described above, according to the present invention, the combustion stability can be improved, and the flame-retardant gas can be used as a fuel.

DESCRIPTION OF SYMBOLS 1 Engine 2 Intermediate housing 3 Rotor housing 4 Side housing 5 Rotor 6 Eccentric shaft 7a Trading side spark plug 7b Leading side spark plug 8 Injector 11 Intake port 12 Exhaust port 20 Recess 21 1st recessed part 22 2nd recessed part 23 Corner part 24 steps Part 25 Guide groove 30 Working chamber 200 Recess of conventional structure

Claims (6)

A rotor with a recess formed on the outer peripheral surface,
The recess is composed of a first recess located on the trailing side in the rotational direction of the rotor, and a second recess formed continuously from the first recess and located on the leading side in the rotational direction of the rotor. ,
The rotary piston engine characterized in that a cross-sectional area of the first recess perpendicular to the circumferential direction of the rotor is smaller than a cross-sectional area of the second recess perpendicular to the circumferential direction of the rotor. The width dimension of the rotor of the first recess is smaller than the dimension of the second recess in the same direction,
The rotary piston engine according to claim 1. The depth of the first recess is shallower than the depth of the second recess,
The rotary piston engine according to claim 1. A rotor housing that rotatably accommodates the rotor includes a trailing-side spark plug positioned corresponding to the first recess when the rotor is positioned at the top dead center, and the rotor is positioned at the top dead center. A leading-side spark plug positioned corresponding to the second concave portion at the time is arranged,
The rotary piston engine as described in any one of Claims 1-3. A plurality of the leading side spark plugs are juxtaposed in the width direction of the rotor,
The rotary piston engine according to claim 4. A guide groove formed continuously in the first recess,
A plurality of the guide grooves are formed so as to extend obliquely from the side of the first recess toward the trading side,
The rotary piston engine as described in any one of Claims 1-5.

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