Gas engine power generation system

Abstract

To create a highly efficient power generation system that operates using fuel generated from organic matter heated in an oxygen-free environment, such as food residues and animal waste, and that effectively burns the combustible materials in the fuel. [Configuration] The system comprises a main fuel gas container 11 for a bio-based main fuel gas G1, a support gas container 21 for a non-bio-based support gas G2, a gas engine 7, and a mixer 3 that supplies a mixed fuel gas G3, which is a mixture of the main fuel gas G1 and the support gas G2, to the gas engine 7. The gas engine 7 has two spark plugs 81, 82, an intake valve 84, and two exhaust valves 85, 85 arranged inside a cylinder 71. A flame sensor 9 that detects the degree of flame strength K is mounted on the inner circumferential wall surface 71a inside the cylinder 71 at a predetermined distance from both spark plugs 81, 82. The flame sensor 9 is in communication with an ECU 4, and when the explosive force of the flame K in the cylinder 71 is below a predetermined level, the ECU 4 supplies the support gas G2 into the cylinder 71.

Description

[Technical Field]

[0001] The present invention relates to a gas engine power generation system with extremely high operating efficiency that operates using fuel generated from organic matter heated in an oxygen-free state, such as food residue and animal excrement, and that can operate by effectively burning the combustible materials in the fuel. [Background technology]

[0002] Generally, animal waste such as manure, urine, or food scraps and residues is disposed of by solidifying it by simmering it in an oxygen-free environment before landfilling. However, the gases generated during this process are released into the atmosphere, leading to environmental pollution. Therefore, in recent years, engines that operate using gases (also called bio-fuels) generated from organic matter such as animal manure, urine, urine, or food scraps and residues have come into use for power generation or general power. Patent document 1 (Japanese Patent Application Publication No. 2009-174392) describes a conventional technology using such bio-fuels. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2009-174392 [Overview of the project] [Problems that the invention aims to solve]

[0004] The fermentation of food residues and the reduction of volume of industrial waste through oxygen-free steaming processes generate gases containing flammable gases. For convenience, these gases will be referred to as S gas (main fuel gas G1). Although the proportion of flammable gas in S gas (main fuel gas G1) is small, it is 20 Mj per cubic meter, or 20 Mj / m³. 3 If there is any of it, it would be a waste to just throw it away. However, this gas contains more carbon dioxide (CO2) than combustible gases.

[0005] CO2 inhibits combustion, as it is also used in fire extinguishers. Theoretically, if the aforementioned S gas (main fuel gas G1) could be burned in the engine cylinder and its energy could be converted into power to drive a generator, it would greatly contribute to energy conservation. The combustible gases in S gas (main fuel gas G1) include carbon monoxide (CO), hydrogen (H2), and methane (CH4), but these gases have high ignition temperatures and cannot be ignited by compression heat like in a diesel engine.

[0006] Furthermore, there are the following problems when using crude gas derived from bio-based gas fuels in gas engines. First, as mentioned above, crude gas is a so-called artificial gas made from livestock manure or food residue. In addition, crude gas may contain inorganic substances such as CO and H2. Therefore, the amount of crude gas produced is small compared to natural gas (propane or methane). Consequently, it is difficult to secure enough for use in large gas turbines. Thus, the Stirling engine disclosed in Patent Document 1 is an external combustion engine, and it is extremely difficult and unsuitable to directly apply the aforementioned crude gas to a Stirling engine.

[0007] Next, in the process of roasting or fermenting livestock manure or food residue in an oxygen-free environment, a combustible gas (referred to as crude gas) is generated and used as fuel for gas engines. However, this crude gas often contains a large amount of carbon dioxide (CO2). Typically, in technologies such as those described in Patent Document 1, gas turbines or Stirling engines undergo continuous combustion, and combustion is possible even if a certain amount of carbon dioxide is present in the fuel. However, in spark-ignition engines, combustion is intermittent, involving repeated intake, compression, ignition expansion, and exhaust. Carbon dioxide in the fuel can interfere with ignition, flame kernel formation, and flame propagation. In this respect, the technology disclosed in Patent Document 1 is difficult to apply to spark-ignition engines.

[0008] However, some of the components that make up crude gas are flammable. If we can thoroughly utilize the energy of these flammable components instead of discarding them, and use this less flammable gas as fuel for spark-ignition engines of 200kW or less, and then use that power to drive a generator and convert it into electrical energy, it would be an effective use of recycled resources and would greatly contribute to environmental protection.

[0009] The object of the present invention is to provide a gas engine power generation system that can make the most effective use of bio-based crude gas consisting of livestock manure or food residue in a spark-ignition engine, thereby contributing to the effective use of recycled resources and environmental conservation. [Means for solving the problem]

[0010] Therefore, the inventor diligently conducted research to solve the above problems, and as a result, solved the above problems by providing the invention of claim 1 as a gas engine power generation system comprising a main fuel gas container for storing a bio-based main fuel gas, a support gas pressure container for storing a non-bio-based support gas, a gas engine, and a mixer for supplying a mixed gas fuel, which is a mixture of the main fuel gas and the support gas, to the gas engine, wherein the gas engine has two spark plugs, an intake valve and an exhaust valve arranged in the cylinder, two flame sensors for detecting the degree of flame strength are mounted on the inner circumferential wall surface inside the cylinder at a predetermined distance from both spark plugs, both flame sensors are in communication with an ECU, and when the explosive force of the flame in the cylinder is below a predetermined level, the ECU supplies the support gas into the cylinder.

[0011] The invention of claim 2 solves the above problem by providing a gas engine power generation system according to claim 1, wherein both flame sensors are provided at contact points between a virtual second line perpendicular to the center of a virtual first line connecting both spark plugs and the inner circumferential wall surface of the cylinder.

[0012] The invention of claim 3 is a gas engine power generation system according to claim 1 or 2, wherein the flame sensor has a first electrode and a second electrode whose tips protrude from the insulator portion within the insulator portion, a gap is formed between the first electrode and the second electrode, when flame particles sufficiently reach the gap a current is generated in the gap and the ECU determines that the flame is stable, when flame particles do not sufficiently reach the gap no current is generated in the gap and the ECU determines that the flame is unstable and the ECU supplies the support gas, thereby solving the above problems.

[0013] The invention of claim 4 solves the above problem by providing a gas engine power generation system according to claim 1 or 2, wherein an O2 sensor and a ternary angle catalyst are arranged in the exhaust system, and the O2 sensor and the ternary angle catalyst are provided. [Effects of the Invention]

[0014] The invention of claim 1 comprises a main fuel gas container for storing a bio-based main fuel gas, a support gas pressure container for storing a non-bio-based support gas, a gas engine, and a mixer for supplying a mixed gas fuel, which is a mixture of the main fuel gas and the support gas, to the gas engine, wherein the gas engine has two spark plugs, an intake valve, an exhaust valve, and two flame sensors arranged in the cylinder.

[0015] Both flame sensors are mounted on the inner circumferential wall surface inside the cylinder at a predetermined distance from both spark plugs, and their role is to detect the degree of flame intensity during the combustion of gaseous fuel inside the cylinder. The flame sensors are connected to the ECU (Engine Control Unit), and when the explosive force of the flame inside the cylinder is below a predetermined level, the ECU supplies the support gas into the cylinder.

[0016] With the above configuration, the concentration of the bio-based main fuel gas in the mixed gas supplied to the cylinder becomes high, and if the combustion state of the mixed gas flame from the spark plug deteriorates, the flame sensor detects this condition and sends a signal from the flame sensor to the ECU, which then supplies an appropriate amount of auxiliary gas to the mixer, enabling a good mixed gas to be supplied to the cylinder of the gas engine via the mixer.

[0017] Thus, in this invention, with an extremely simple configuration in which a flame sensor is installed inside the cylinder, the ECU (Engine Control Unit) determines the state of the flame of the fuel ignited by the spark plug, maintains a good ratio of main fuel gas to auxiliary gas in the mixed fuel drawn into the cylinder via the mixer, and maintains the smooth operation of the gas engine.

[0018] In the invention of claim 2, the flame sensor is provided at both contact points between a virtual second line perpendicular to the center of a virtual first line connecting both spark plugs and the inner circumferential wall surface of the cylinder. As a result, the flame sensor is located at an equal distance from both spark plugs, and the flame sensor can detect (perceive) the flames ignited from both spark plugs with even greater accuracy. This information is transmitted to the ECU, which then determines whether or not to supply support gas to the gas fuel. By providing two flame sensors, the accuracy of detecting (perceiving) the flames ignited from both spark plugs can be further improved, thereby enabling the maintenance of an even better combustion state inside the cylinder.

[0019] In the invention of claim 3, the flame sensor has a first electrode and a second electrode with tips protruding from the insulator portion within the insulator portion, a gap is provided between the first electrode and the second electrode, and when flame particles sufficiently reach the gap, a current is generated in the gap and the ECU determines that the flame is stable. When flame particles do not sufficiently reach the gap, no current is generated in the gap and the ECU determines that the flame is unstable. With the ECU configured to supply the auxiliary gas, the flame sensor can have a very simple structure and can detect (sense) the state of the gas fuel in the cylinder with high accuracy.

[0020] In the invention of claim 4, in the gas engine power generation system according to claim 1 or 2, with a configuration in which an O2 sensor is disposed in the exhaust system, by using the O2 sensor in combination with the flame sensor, the mixing ratio of the main fuel gas and the auxiliary gas of the mixed gas fuel in the gas fuel (mixed gas fuel and air) in the cylinder via the mixer can be maintained well, that is, maintained at the theoretical air-fuel ratio or approximately the theoretical air-fuel ratio, and a good combustion state in the cylinder can be maintained.

Brief Description of the Drawings

[0021] [Figure 1] It is a schematic configuration diagram for explaining the overall configuration of the present invention. [Figure 2] It is a process diagram (flowchart diagram) showing the operation of the present invention. [Figure 3] (A) is a cross-sectional view of the main part showing the position of the flame sensor of the cylinder and the cylinder head of the gas engine in the present invention, (B) is a cross-sectional view taken along the Y1-Y1 arrow of (A), (C) is a cross-sectional view taken along the X1-X1 arrow of (B), and (D) is an enlarged cross-sectional view of the (α) part of (C). [Figure 4] (A) is a front view of a partial cross-section of the flame sensor, (B) is a longitudinal front view of the flame sensor, and (C) to (E) are enlarged views of each state in the (β) part of (B). [Figure 5] (A) is a graph showing the state of the flame, and (B) and (C) are state diagrams of the flame and the flame sensor. [Figure 6](A) is a graph showing the state of the flame, and (B) and (C) are diagrams showing the state of the flame and the flame sensor. [Figure 7] (A) is a front cross-sectional view of the mixer, (B) is a top view of the mixer, and (C) is a front cross-sectional view of the main fuel gas low-pressure control valve and the support gas low-pressure control valve. [Figure 8] (A) and (B) are graphs showing the duty cycle in the present invention, and (C) is a graph showing the duty cycle and stoichiometric air-fuel ratio in the present invention. [Modes for carrying out the invention]

[0022] Embodiments of the present invention will now be described based on the drawings. The gas engine power generation system of the present invention mainly comprises a main fuel gas container 11, a main fuel gas shut-off valve 12, a main fuel gas low-pressure regulating valve 13, and a main fuel gas pressure sensor 14 as the main fuel gas system, and a support gas container 21, a support gas shut-off valve 22, and a support gas low-pressure regulating valve 23 as the support gas system, and also comprises a mixer 3, an ECU (engine control unit) 4, and a gas engine 7 (see Figure 1). Furthermore, a flame sensor 9 is provided in the cylinder 71 that constitutes the gas engine 7 (see Figure 3). The main fuel gas container 11 is filled with main fuel gas G1, and the support gas container 21 is filled with support gas G2.

[0023] Each piece of equipment is connected to the others by pipelines (main fuel gas pipeline 51 and support gas pipeline 52). The main fuel gas G1 in the main fuel gas container 11 and the support gas G2 in the support gas container 21 are sent to the mixer 3, with their respective pressures adjusted as needed. In the mixer 3, the main fuel gas G1 and support gas G2 are mixed to produce mixed gas fuel G3, which is then sent towards the gas engine 7 while mixing with air G0.

[0024] With this configuration, the main fuel gas G1, which is a crude biomass gas, and the support gas G2, such as city gas, are mixed by the mixer 3 and supplied to the gas engine 7 as a mixed gas fuel G3, which is then used to operate the gas engine 7 together with separately supplied air G0 (see Figure 2). In this invention, the main fuel gas G1 is a gas generated by heating the manure or urine of livestock such as cattle and pigs or food waste in an oxygen-free state, and is sometimes referred to as crude gas. The support gas G2 is a general gas such as city gas.

[0025] The configuration of the gas engine power generation system in the present invention is shown in a schematic diagram in Figure 1. Figure 2 is a process diagram (also called a flowchart) showing the operation of the gas engine power generation system in the present invention. The process from when the main fuel gas G1 in the main fuel gas container 11 and the support gas G2 in the support gas container 21 are mixed in the mixer 3 to produce mixed gas fuel G3, and when this mixed gas fuel G3 is supplied to the gas engine 7, is shown in Figure 2.

[0026] The main fuel gas container 11 and the support gas container 21 are connected to the mixer 3 by separate, independent main fuel gas pipelines 51 and support gas pipelines 52, respectively. The main fuel gas G1 in the main fuel gas container 11 and the support gas G2 in the support gas container 21 are sent to the mixer 3 via the separate main fuel gas pipelines 51 and support gas pipelines 52, where the main fuel gas G1 and support gas G2 are mixed for the first time, generating a mixed gas fuel G3 inside the mixer 3.

[0027] The gas engine 7 comprises a cylinder 71 and a cylinder head 72, and has a structure in which one or more cylinders 71 and cylinder heads 72 are arranged in series (see Figure 3). A piston is housed in the cylinder 71 so as to be able to move up and down, and the cylinder head 72 is provided on the upper part of the cylinder 71, with the lower surface of the cylinder head 72 formed as the inner top wall surface 72a of the head. The inner top wall surface 72a of the head has a substantially spherical shape, and more specifically, a flattened spherical concave surface (see Figure 3(B)). The cylinder head 72 is provided with an intake port 73 and an exhaust port 74, and the openings for the intake port 73 and the exhaust port 74 are formed in the inner top wall surface 72a of the head, respectively. The horizontal cross-section of the cylinder 71 is a perfect circle.

[0028] The cylinder head 72 is provided with two spark plugs 81 and 82, an intake valve 84, and an exhaust valve 85 (see Figures 3(A) and 3(B)). The two spark plugs 81 and 82, and the intake valve 84 and exhaust valve 85 are arranged in a way that allows them to be viewed in plan from the top side of the cylinder head 72 (or the cylinder 71). Specifically, the two spark plugs 81 and 82, the intake valve 84, and the exhaust valve 85 are arranged around the circumference at equal intervals, dividing the cylinder into four equal parts (see Figure 3(C)). The intake valve 84 opens and closes the opening of the intake port 73, and the exhaust valve 85 opens and closes the opening of the exhaust port 74.

[0029] The two spark plugs 81 and 82 are identical and are mounted so that their respective gaps 81a and 82a protrude from the top wall surface 72a inside the cylinder head (see Figure 3(B)). For the sake of clarity, one of the two spark plugs 8 will be referred to as the first spark plug 81 and the other as the second spark plug 82. Here, the first spark plug 81 is the first to receive the injection jet of gaseous fuel (a mixture of mixed gaseous fuel G3 and air G0) flowing into the cylinder 71 from the intake port 73 of the cylinder head 72.

[0030] Next, the flame sensor 9 will be explained. The role of the flame sensor 9 is to detect the state of the flame caused by the explosion of the fuel mixture G3 and air G0, which is the fuel gas in the cylinder 71. The signal from the flame sensor 9, which detects the strength of the flame, is sent to the ECU (engine control unit) 4, and the ECU 4 uses this to determine whether the mixture of fuel G3 and air G0 is good or bad, and to decide whether or not to supply support gas G2 to the mixer 3 (see Figures 1 and 2).

[0031] The flame sensor 9 is mounted on the circumferential inner wall surface 71a of the cylinder 71 at a predetermined distance from the first spark plug 81 and the second spark plug 82 inside the cylinder 71 [see Figures 3(C), 5(B), (C), 6(B), (C)]. The predetermined distance is approximately a long distance; specifically, it is mounted on the inner wall surface 71a of the cylinder 71 at a position far from the first spark plug 81 and the second spark plug 82 inside the cylinder 71. By mounting the flame sensor 9 inside the cylinder 71 as far away as possible from the first spark plug 81 and the second spark plug 82, it becomes easier to detect (perceive) the overall combustion state of the fuel gas (mixed gas fuel G3 and air G0) inside the cylinder 71, and it becomes easier to accurately detect the combustion state of the fuel gas and send more accurate information to the ECU 4.

[0032] To elaborate on the installation of the flame sensor 9 inside the cylinder 71, a virtual first line L1 is set within the cylinder 71, connecting the first spark plug 81 and the second spark plug 82. Furthermore, a virtual second line L2 is set horizontally, perpendicular to the center of the virtual first line L1 [see Figure 3(C)]. Both the virtual first line L1 and the virtual second line L2 pass through the center Q of the diameter of the circumference of the cylinder 71. Also, the virtual first line L1 and the virtual second line L2 differ in the height direction and do not intersect.

[0033] Next, the points where both ends of the virtual second straight line L2 meet the inner circumferential wall surface 71a of the cylinder 71 are designated as the installation positions for the flame sensors 9 [see Figure 3(C)]. The flame sensors 9 are provided at the points where the inner circumferential wall surface 71a of the cylinder 71 intersects with the virtual second straight line L2. There are two such intersection points, and therefore two flame sensors 9 are provided. Alternatively, a flame sensor 9 may be provided at only one of the two intersection points. In this case, there is one flame sensor 9. Furthermore, the position where the flame sensors 9 are placed on the inner circumferential wall surface 71a of the cylinder 71 is not limited to the above conditions, and they may be placed at any position on the inner circumferential wall surface 71a. In this case, the number of flame sensors 9 may be three or more.

[0034] In this invention, we will explain the invention assuming that there are two flame sensors 9, and that the two flame sensors 9 are mounted on the inner circumferential wall surface 71a of the cylinder 71. As mentioned above, the inner top wall surface 72a of the cylinder head 72 is a spherical concave surface, and the spherical outer shape of this surface is circular, having the same diameter as the circumference of the inner circumferential wall surface 71a of the cylinder 71. The virtual first straight line L1 connecting the first spark plug 81 and the second spark plug 82 mounted on the cylinder head 72 passes through the diameter center Q of the cylinder 71 in principle, as mentioned above, and the position of the center of the virtual first straight line L1 is the position of the diameter center Q of the cylinder 71. Therefore, the virtual second straight line L2, which is perpendicular to the center of the virtual first straight line L1 in the horizontal direction, also passes through the diameter center Q of the cylinder 71 [see Figure 3(C)].

[0035] As a result, the flame sensor 9 is positioned at the maximum distance and equidistant from the gaps 81a and 82a of the first spark plug 81 and the second spark plug 82, respectively (see Figure 3(C)). One or two flame sensors 9 are provided for each cylinder 71. In practice, the flame sensor 9 is positioned on the inner circumferential wall surface 71a of the cylinder 71, equidistant from the gaps 81a and 82a of the first spark plug 81 and the second spark plug 82, respectively.

[0036] The flame sensor 9 consists of an insulator portion 91, a case portion 92, connector portions 93a and 93b, a first electrode 94a, a second electrode 94b, and connecting wires 95a and 95b that connect the connector portion 93a to the first electrode 94a and the connector portion 93b to the second electrode 94b, respectively [see Figures 3(D), 4(A), and 4(B)]. In other words, the connector portion 93a and the first electrode 94a are electrically connected by the connecting wire 95a, and the connector portion 93b and the second electrode 94b are electrically connected by the connecting wire 95b. A gap is provided between the two first electrodes 94a and the second electrode 94b, and this gap is referred to as the gap 94s between the first electrode 94a and the second electrode 94b [see Figures 4(A) and 4(B)].

[0037] Regarding the mounting of the flame sensor 9 to the inner circumferential wall surface 71a of the cylinder 71, the flame sensor 9 is mounted so as to be embedded in the inner circumferential wall surface 71a [see Figures 3(C) and (D)]. Specifically, an external thread 92a is formed on a part of the case portion 92 of the flame sensor 9 [see Figure 4(A)], and a mounting hole 71b for the flame sensor 9 is formed on the inner circumferential wall surface 71a of the cylinder 71. An internal thread 71c is formed in the mounting hole 71b. The external thread 92a of the flame sensor 9 and the internal thread 71c of the mounting hole 71b are screwed together, and the flame sensor 9 is mounted to the inner circumferential wall surface 71a of the cylinder 71 [see Figures 3(C) and (D)].

[0038] As mentioned above, the flame sensor 9 is responsible for detecting the degree of intensity of the flame K caused by the explosion of gas fuel in the cylinder 71. By transmitting the state of the flame to the ECU 4, which is connected to the flame sensor 9, the ECU 4 is instructed to decide whether or not to supply support gas G2 into the mixer 3 (see Figures 5 and 6).

[0039] The following describes the process by which the flame sensor 9 and the ECU 4 determine whether or not to supply support gas G2 within the mixer 3. First, when the gas engine 7 is in operation, the gas fuel explodes in the cylinder 71 due to the first spark plug 81 and the second spark plug 82, and the flame particles ka of the flame K from this explosion surround the first electrode 94a and the second electrode 94b of the flame sensor 9 [see Figures 4(C) and 5(B)]. When a sufficient number of flame particles ka reach both the first electrode 94a and the second electrode 94b, an ion current is generated in the gap 94s between the first electrode 94a and the second electrode 94b, and the ECU 4 determines that the flame K is stable and does not supply support gas G2 [see Figures 5(B) and 4(C)].

[0040] The situation at this time is in the normal combustion region of the explanatory diagram showing the flame state in Figure 5(A), specifically part (1). Furthermore, when the force of the gaseous fuel explosion weakens and the number of flame particles ka reaching the gap 94s between the first electrode 94a and the second electrode 94b begins to decrease, the ECU4 determines that the explosion can be maintained, and the supply of support gas G2 is not performed [see (2) in Figure 5(A) and Figure 5(C)].

[0041] Next, if the flame particles ka from the explosion of the gaseous fuel do not sufficiently reach the first electrode 94a and the second electrode 94b, no current is generated in the gap 94s between the first electrode 94a and the second electrode 94b, and the ECU4 determines that the state of the flame K is unstable [see Figures 6(B) and 4(D)]. When the ECU4 determines that the state of the flame K is unstable, it means that the number of flame particles ka reaching the gap 94s between the first electrode 94a and the second electrode 94b of the flame sensor 9 is extremely small.

[0042] At this point, the ECU4 decides to supply support gas G2 and delivers it to the mixer 3. The situation at this time corresponds to the area labeled "Flame is present but weak" in the explanatory diagram of the flame state in Figure 6(A), specifically to part (3). Furthermore, if the flame particles ka from the explosion of the gaseous fuel do not fully reach the first electrode 94a and the second electrode 94b, a misfire occurs [see Figures 6(C) and 4(E)].

[0043] Furthermore, to elaborate on the state of flame K, although flame K propagates, the outer periphery of flame K, where the molecules are activated, is ionized and conductive. High-speed imaging results from model experiments show that flame K, resulting from the explosion of a mixed gas fuel G3 and air G0 ignited by the spark of the first spark plug 81 (or second spark plug 82), spreads concentrically. However, the two flames K, K, which grow and expand starting from the gaps 81a and 82a of the first and second spark plugs 81 and 82 respectively, come into contact and spread vertically [see Figure 5(B)]. This is thought to be because the front surfaces (tip portions) of flame K are both positively charged and repel each other.

[0044] The flame sensor 9 is installed at the point where the flame K arrives furthest from the first spark plug 81 and the second spark plug 82, and detects this condition and sends the information to the ECU 4. If the ECU 4 determines via the flame sensor 9 that the arrival of the flame K is deteriorating, it increases the outlet pressure of the support gas low-pressure regulating valve 23 to increase the flow rate of the support gas G2. In other words, if a misfire is likely to occur in the cylinder 71, the ECU 4 issues a command to the support gas low-pressure regulating valve 23 to increase the flow rate of the support gas G2, thereby controlling the pressure P2 of the support gas G2 to be slightly higher.

[0045] Next, we will explain the state of the flame K of the explosion of the mixed gas fuel G3 and air G0 ignited by the first spark plug 81 and the second spark plug 82 inside the cylinder 71, and the state of the flame sensor 9. First, as shown in Figure 5, the flame K spreads concentrically from the gaps between the first spark plug 81 and the second spark plug 82. At this time, since the flame K is charged, the flames K, K generated from the gaps 81a, 82a of the first spark plug 81 and the second spark plug 82 repel each other as their flame fronts (also called "flame fronts") approach each other, and the flame fronts spread out so that they become longer along a virtual second line L2 that is perpendicular to a virtual first line L1 connecting the first spark plug 81 and the second spark plug 82. Therefore, the two flames K, K generated by the first spark plug 81 and the second spark plug 82 have a predetermined time after the explosion until they spread out and reach the flame sensor 9.

[0046] The main fuel gas G1 contains a large amount of CO2, and in order to burn the main fuel gas G1, it is necessary to add support gas G2 to create a mixed gas fuel G3, regardless of whether the air-fuel ratio is stoichiometric or not. In the cylinder 71, as the flame K spreads due to the mixed gas fuel G3 and air G0, when the front of the flame reaches the positions of both first electrodes 94a and second electrodes 94b of the flame sensor 9, a sufficient ion current flows in the gap 94s between the two first electrodes 94a and second electrodes 94b [see Figure 4(C)], indicating that stable combustion is achieved [see Figures 5(A) and (B)].

[0047] If the combustion state is poor, the ion current will be small even if the front of the flame reaches both the first electrodes 94a and the second electrodes 94b of the flame sensor 9 [see Figure 4(D)]. Here, even if the intensity of the flame K weakens somewhat, and even if the amount of flame particles ka reaching the first electrodes 94a and the second electrodes 94b decreases, the system will continue to operate in the same state [see Figure 5(C)]. Furthermore, if the flame K does not reach the flame sensor 9, no ion current will flow in the gap 94s between the first electrode 94a and the second electrode 94b of the flame sensor 9 [see Figure 4(E)], and the ECU 4 will issue a command to increase the amount of support gas G2 [see Figures 6(A) and (B)]. Note that Figure 6(C) shows a state of complete misfire.

[0048] Next, for reference, let's consider how long it takes for the flame K generated by the first spark plug 81 and the second spark plug 82 to reach the entire cylinder 71. For the engine to operate stably regardless of engine speed, the crankshaft rotation angle must be within 120 degrees during the expansion stroke. Converting this to time, at 2500 rpm, it is 60 s / 2500 r × 120 degrees / 360 degrees = 0.008 s. In other words, the time it takes for the flame K generated by the first spark plug 81 and the second spark plug 82 to reach the entire cylinder 71 is 8 ms.

[0049] Additionally, an O2 sensor 54 may be installed in the exhaust system of the gas engine 7 (e.g., the exhaust pipe on the exhaust port 74 side) (see Figure 1). The air-fuel ratio is then controlled by the ECU 4, which uses a signal from the O2 sensor 54 installed in the exhaust system to adjust the pressure of the gas fuel supplied to the mixer 3 using a support gas low-pressure regulating valve 23, so that the air-fuel ratio is stoichiometric. A three-way catalytic converter 55 is installed downstream of the exhaust system to neutralize HC / CO / NOx in the exhaust. To achieve this, the engine must be operated at the stoichiometric air-fuel ratio so that there is no excess oxygen or combustible material (fuel) after combustion in the cylinder 71.

[0050] To achieve this, the O2 sensor 54 detects the O2 concentration in the exhaust gas, and the ECU 4 performs feedback control to adjust the air-fuel ratio to the stoichiometric ratio. Specifically, if the air-fuel ratio detected by the O2 sensor 54 is determined to be leaner than the stoichiometric ratio, the flow rate of the support gas G2 is increased. The air-fuel ratio is adjusted not by the main fuel (main fuel gas G1), whose combustible components are not clear, but by increasing or decreasing the flow rate of the support gas G2. In this way, by using the O2 sensor 54 and the flame sensor 9 in combination, the mixing ratio of the main fuel gas G1 and the support gas G2 in the gas fuel (mixed gas fuel G3 and air G0) in the cylinder 71 via the mixer 3 can be maintained at a good level, that is, at the stoichiometric ratio or approximately the stoichiometric ratio, thereby maintaining a good combustion state in the cylinder 71.

[0051] The main fuel gas container 11 is filled with main fuel gas G1, which is a crude gas. The main fuel gas container 11 is also equipped with a primary pressure reducing valve 11a. The main fuel gas container 11 and the mixer 3 are connected by a main fuel gas pipeline 51. In addition, a main fuel gas shut-off valve 12, a main fuel gas low-pressure regulating valve 13, and a main fuel gas pressure sensor 14 are installed in series in the main fuel gas pipeline 51 between the main fuel gas container 11 and the mixer 3 (see Figure 1).

[0052] The main fuel gas G1 discharged from the main fuel gas container 11 is reduced in pressure to approximately 50 kPa by the primary pressure reducing valve 11a installed in the main fuel gas container 11, and then further reduced in pressure to approximately 3 kPa, close to atmospheric pressure, by the main fuel gas low-pressure regulating valve 13. In this case, if the primary pressure reducing valve 11a can reduce the main fuel gas G1 discharged from the main fuel gas container 11 to approximately 3 kPa, close to atmospheric pressure, in one go, then the main fuel gas low-pressure regulating valve 13 does not need to be provided and can be considered unnecessary.

[0053] Support gas container 21 is filled with support gas G2. Support gas container 21 is equipped with a primary pressure reducing valve 21a. Support gas container 21 and mixer 3 are connected by a support gas pipeline 52. In addition, a support gas shut-off valve 22 and a support gas low-pressure regulating valve 23 are installed in series in the support gas pipeline 52 between support gas container 21 and mixer 3. The support gas G2 discharged from support gas container 21 is reduced to approximately 50 kPa by the primary pressure reducing valve 21a installed in support gas container 21, and then further reduced to a pressure close to atmospheric pressure of approximately 3 kPa by the support gas low-pressure regulating valve 23.

[0054] In particular, the main fuel gas G1 contains combustible gases such as carbon monoxide (CO), hydrogen (H2), and methane (CH4). These gases have high ignition temperatures and cannot be ignited by compression heat like in a diesel engine. Therefore, it is possible to use a spark ignition engine system in which readily available propane (C3H8) is pre-mixed with the main fuel gas G1 as a support gas to help the flame spread after ignition with an electric spark.

[0055] Mixer 3 comprises a mixer body 31 and a throttle 32. The mixer body 31 has a first inlet 31a, a second inlet 31b, and an introduction pipe 31c. A venturi section 31d is formed inside the introduction pipe 31c, and an annular space 31e is formed on the outer circumference of the venturi section 31d via a partition wall 31f (see Figures 7(A) and (B)). An annular slit 31g is formed in the partition wall 31f, and the annular space 31e and the inside of the venturi section 31d are connected via the annular slit 31g.

[0056] Furthermore, both the first inlet 31a and the second inlet 31b are in communication with the annular space 31e. In other words, the first inlet 31a and the second inlet 31b are in communication via the annular space 31e. A throttle 32 is provided on the discharge side of the venturi section 31d. The first inlet 31a of the mixer 3 is in communication with the main fuel gas pipeline 51 of the main fuel gas system and serves as the inlet for the main fuel gas G1. The second inlet 31b is in communication with the support gas pipeline 52 of the support gas system and serves as the inlet for the support gas G2. The mixer 3 is drawn from the intake manifold through the intake valve into the cylinder of the two-point ignition gas engine 7.

[0057] Next, the main fuel gas low-pressure regulating valve 13 and the support gas low-pressure regulating valve 23 will be described. The main fuel gas low-pressure regulating valve 13 and the support gas low-pressure regulating valve 23 have the same structure and differential, and the main fuel gas low-pressure regulating valve 13 will be described primarily [see Figure 7(C)]. Note that the symbols in parentheses are symbols related to the support gas low-pressure regulating valve 23. When there is no signal from the low-pressure controller or ECU 4, the sealing member 13c(23c) at the tip of the armature 13a(23a) is pushed back by the spring 13b(23b) and blocks the nozzle 13d(23d).

[0058] When a pulse signal is received from ECU4, the magnetic force generated by coil 13h (23h) pulls up the armature 13a (23a), creating a gap ks, and the main fuel gas G1 from the main fuel gas container 11 (and its primary pressure reducing valve 11a) flows into the small chamber 13f (23f) partitioned by the diaphragm 13e (23e). The main fuel gas G1 then flows out to the shut-off valve or mixer 3, so the pressure inside the small chamber 13f (23f) decreases. The main fuel gas low-pressure regulating valve 13 and the support gas low-pressure regulating valve 23 have through holes that release to the atmosphere. These are atmospheric vents 13g (23g) and serve to improve the movement of the diaphragm 13e (23e).

[0059] Coil 13h (23h) receives a square wave signal from ECU4 that drives the armature 13a (23a). Figure 8(A) shows the form of this signal. When the engine is running, current is supplied for t (S) with a period of to (s) (frequency is 1 / to). While current is supplied, a magnetic field is generated, and the armature 13a (23a) is pulled up, overcoming the force of the spring 13b (23b), forming a gap ks, through which the main fuel gas G1 (support gas G2) flows. However, in a separate visualization experiment, the sealing member 13c (23c) does not flap around, and the gap ks increases as the duty cycle increases. This is due to the inertia and hysteresis of the movable part.

[0060] Furthermore, reference numeral 13j indicates the inlet of the main fuel gas low-pressure regulating valve 13, which communicates with the main fuel gas container 11 and the main fuel gas shut-off valve 12 via the main fuel gas pipeline 51, and serves to supply the main fuel gas G1 into the main fuel gas low-pressure regulating valve 13 via the main fuel gas container 11 and the main fuel gas shut-off valve 12. Reference numeral 13k indicates the outlet of the main fuel gas low-pressure regulating valve 13, which communicates with the mixer 3, and serves to supply the main fuel gas G1 to the mixer 3.

[0061] Furthermore, reference numeral 23j indicates the inlet of the support gas low-pressure regulating valve 23, which communicates with the support gas container 21 and the support gas shut-off valve 22 via the support gas pipeline 52, and serves to supply support gas G2 into the support gas low-pressure regulating valve 23 via the support gas container 21 and the support gas shut-off valve 22. Reference numeral 23k indicates the outlet of the support gas low-pressure regulating valve 23, which communicates with the mixer 3, and serves to supply support gas G2 to the mixer 3.

[0062] Next, for reference, we will discuss whether or not a main fuel gas (for convenience, referred to as S gas "main fuel gas G1") produced by fermenting livestock manure or by simmering food waste in an oxygen-free environment can be combusted in cylinder 71, assuming its composition by volume is 40% methane (CH4), 30% carbon monoxide (CO), and 30% carbon dioxide (CO2).

[0063] Determine the mass of each component in 1 mole of S gas (main fuel gas G1) (22.4 liters at standard conditions). The molecular weight of CH4 is 16, so the mass of 0.4 moles is 16 × 0.4 = 6.4 g. Since the molecular weight of CO is 28, the mass of 0.3 moles is 28 × 0.3 = 0.34 g. The molecular weight of CO21 is 44, so the mass of 0.3 moles is 44 × 0.3 = 13.2 g. Therefore, the mass of 1 mole of S gas (main fuel gas G1) is 25 g (approximately the same as air). Density of S gas (main fuel gas G1) (1m³ 3 The mass (in kg) is 28 g × 1000 / 22.4 = 1.25 kg / m 3

[0064] Next, we determine the calorific value of S gas (main fuel gas G1). The heat output of CH4 is 36.1 MJ / m³. 3 Therefore, 0.44m 3 So 36.1 × 0.4 = 14.44 The calorific value of CO is 12.66 MJ / m³. 3 Therefore, 0.3m 3 So 12.6 × 0.3 = 3.8 Since the calorific value of CO2 is 0, 0x0.3 = 0.

[0065] Therefore, the calorific value of 1 m 3 of S gas (main fuel gas G1) is 18.2 Mj / m 3 , which is about 20% of propane (C3H8) 90.7 Mj / m 3 . It is determined that there is significance in regeneration. However, since carbon dioxide (CO2), which is also used in fire extinguishers, accounts for 30% in the main fuel, the fact that it does not enter the flammable region in the cylinder 71 will be explained below. When the exhaust gas recirculation (EGR) amount is increased to the operating limit of the engine in a gasoline engine with two-point ignition, in the case of the theoretical air-fuel ratio, the CO2 concentration in the air-fuel mixture inhaled into the cylinder 71 was 10%, which was the limit of stable combustion.

[0066] Therefore, assuming that the engine can be operated using only S gas (main fuel gas G1), the theoretical air-fuel ratio of S gas (main fuel gas G1) is obtained. First, the mass of air required to burn 1 mole (28 g) of S gas (main fuel gas G1) is calculated.

[0067] CH4 + 2O2 = CO2 + 2H2O, that is, 2 moles of O2 are required. If CH4 is 0.4 moles, then 2 moles × 0.4 = 0.8 moles of O2 are required. CO + 1 / 2O2 = CO2, that is, 1 / 2 mole of O2 is required. If CO is 0.3 moles, then 0.5 mole x 0.3 = 0.15 moles of O2 are required. CO2 does not burn, so no O2 is required. To burn 1 mole of S gas (main fuel gas G1), 0.8 + 0.15 moles = 0.995 moles (30.4 g) of O2 are required.

[0068] [[ID=3))2]]On the other hand, since the mass of O2 in 1 mole (28.8 g) of air is 32 g × 0.21 = 6.72, (30.4 g / 6.72) × 28.8 = 130.3 g of air is required. Therefore, the theoretical air-fuel ratio of the main fuel gas G1 is 130.3 / 28 g = 4.64 A lower stoichiometric air-fuel ratio compared to 15.6 for propane and 14.7 for gasoline means that there are fewer combustible components.

[0069] We will consider whether combustion is possible in the cylinder, using 10% as a baseline. Omitting the chemical and mathematical formulas, 101.3 liters are needed to burn 1 mole (28g) of S gas (main fuel gas G1). This corresponds to 130.2g in 4.522 molar mass. The stoichiometric air-fuel ratio of main fuel gas G1 is 130.2g / 28g = 4.65. It's considerably lower than propane's 15.6 and gasoline's 14.7. This means there's less to burn.

[0070] Next, we will consider whether combustion is possible in the cylinder based on the aforementioned criterion of a CO2 concentration of 10% or less immediately before ignition. The volume ratio of the support gas to the S gas (main fuel gas G1) is determined such that the CCb concentration in the mixture drawn into the cylinder 71 is 10% or less. If X moles of propane are needed when adding a combustion support gas (hereafter referred to as support gas) to burn S gas (main fuel gas G1), which cannot be combusted on its own, then 0.1 ≥ (Number of moles of CO2 in 1 mole of S gas (main fuel gas G1)) / { (1 mole of S gas (main fuel gas G1) (X moles of propane and the number of moles of air needed to burn it) + (X moles of propane and the number of moles of air needed to burn it)} ... (1) This is what we get. If we plug in the values ​​we have calculated so far, 0.1 ≥ (0.3 moles) / {(1 + 4.52 moles) + (X + 23.7X) ... (1')} Solving this equation gives us X≧0.121, meaning that propane (C3 H8) is required in a volume proportion of 12.1% or more of the S (crude) gas (main fuel gas G1).

[0071] Even if the engine is operating at the stoichiometric air-fuel ratio with the aforementioned support gas ratio, if the amount of support gas is insufficient, combustion in the cylinder 71 will become uneven, leading to large rotational fluctuations, and if these fluctuations increase further, the engine will stop. Before explaining the means of controlling co-combustion, Figure 8(C) shows the relationship between the output signal (electromotive force) of the platinum-zirconia O2 sensor 54 and the air-fuel ratio. The electromotive force changes significantly around the stoichiometric air-fuel ratio, but 0.5 V can be said to be the stoichiometric air-fuel ratio. As shown in the upper part of Figure 8(C), the outlet pressure P2 of the support gas low-pressure regulating valve 23 is adjusted to P50. Next, as explained, increasing the duty cycle t / t0 will decrease (richer) the air-fuel ratio.

[0072] Figure 7(C) illustrates the pressure control method for the main fuel gas G1 and auxiliary gas G2 entering the mixer 3. The coil 13h (23h) of the main fuel gas low-pressure control valve 13 (auxiliary gas low-pressure control valve 23) receives a signal from the battery 57 that drives the square wave armature 13a (23a). Figure 8(A) shows the form of this signal. When the engine is running, the system is energized for t(S) with a period of t0 and (s) (frequency is 1 / t0).

[0073] When energized, a magnetic field is generated, causing the armature 13a (23a) to overcome the force of the spring 13b (23b) and be pulled up, creating a gap 58 through which gas can flow. However, in a separate visualization experiment, the sealing member 13c (23c) does not flap around; rather, the gap increases as the duty cycle increases. This is due to the inertia and hysteresis of the movable part.

[0074] Even if the mixture of fuel G3 (a mixture of main fuel gas G1 and support gas G2) and air, calculated using equations (1) and (1'), is at the stoichiometric air-fuel ratio, CO2 in the main fuel can interfere with flame propagation. This disruption of combustion causes a disturbance in the signal from the flame sensor 9. The flame detection signal appears with a delay of t(s) from the ignition signal. This t is different from the t used in the explanation of the duty cycle in Figure 8(A).

[0075] In Figure 5(A), (1) shows that the flame K has correctly reached the gap 94s between the first electrode 94a and the second electrode 94b of the flame sensor 9. Figure 5(B) shows the state in Figure 5(A) (1). In Figure 5(A), (2) shows that a weak flame K has reached the gap 94s between the first electrode 94a and the second electrode 94b of the flame sensor 9. In Figure 6(A), (3) shows that the flame K has reached the gap 94s between the first electrode 94a and the second electrode 94b of the flame sensor 9 with a delay, and although weak, propagation has reached the gap.

[0076] Figure 6(A) (4) shows a misfire state in which the flame K does not reach the gap 94s between the first electrode 94a and the second electrode 94b of the flame sensor 9 at all. This phenomenon can occur even when operating at the stoichiometric air-fuel ratio due to the extinguishing effect of CO2 in the main fuel gas G1. When the ECU4 determines that there is a misfire, increasing the duty cycle as described above will increase P2 in Figures 1 and 8(C). For example, if pressure P1 in Figure 1 is 2.8 kPa, adjust pressure P2 to 4.5 kPa, and continue adjusting until no misfires are detected. As shown in Figure 8(C), P2 is always greater than P1. The pressure P1 of the main fuel gas G1 is not changed.

[0077] If ECU4 determines that a misfire has occurred, increasing the duty cycle as described above will increase P2 in Figure 1, 8(C). For example, if pressure P1 in Figure 1 is 2.8 kPa, adjust pressure P2 to 4.5 kPa, and continue adjusting until no misfire is detected. As shown in Figure 8(B), pressure P2 is always greater than pressure P1. The pressure P1 of the main fuel gas G1 is not changed.

[0078] In Figure 1, reference numeral 53 denotes the generator, reference numeral 54 denotes the O2 sensor, reference numeral 55 denotes the three-way catalytic converter, reference numeral 56 denotes the muffler, reference numeral 57 denotes the battery, reference numeral 58 denotes the crank sensor, reference numeral 59 denotes the flywheel, and reference numeral 14 denotes the main fuel gas pressure sensor. [Explanation of symbols]

[0079] 11…Main fuel gas container, 21…Support gas pressure vessel, 3…Mixer, 4…ECU 54...O2 sensor, 7...gas engine, 71...cylinder, 71a...inner circumferential wall surface, 81...First spark plug, 82...Second spark plug, 84...Intake valve 85...Exhaust valve, 9...Flame sensor, 91...Insulator section, 94a...First electrode, 94b...Second electrode, 94s...Gap, L1...Virtual first straight line, L2…Virtual second straight line, G1…Main fuel gas G1, G2…Support gas, G3... Mixed gas fuel, G0... Air, K... Flame, ka... Flame particle.

Claims

1. The system comprises a main fuel gas container for storing bio-based main fuel gas, a support gas pressure vessel for storing non-bio-based support gas, a gas engine, and a mixer for supplying a mixed gas fuel, which is a mixture of the main fuel gas and the support gas, to the gas engine. The gas engine power generation system is characterized in that the gas engine has two spark plugs, an intake valve and an exhaust valve arranged in the cylinder, two flame sensors that detect the degree of flame strength are mounted on the inner circumferential wall surface of the cylinder at a predetermined distance from both spark plugs, both flame sensors are in communication with an ECU, and when the explosive force of the flame in the cylinder is below a predetermined level, the ECU supplies the support gas into the cylinder.

2. A gas engine power generation system according to claim 1, characterized in that both flame sensors are provided at contact points between a virtual second line perpendicular to the center of a virtual first line connecting the two spark plugs and the inner circumferential wall surface of the cylinder.

3. A gas engine power generation system according to claim 1 or 2, wherein both flame sensors have a first electrode and a second electrode whose tips protrude from the insulator portion within the insulator portion, a gap between the first electrode and the second electrode, when flame particles sufficiently reach the gap a current is generated in the gap and the ECU determines that the flame is stable, when flame particles do not sufficiently reach the gap no current is generated in the gap and the ECU determines that the flame is unstable and supplies the support gas.

4. A gas engine power generation system according to claim 1 or 2, characterized in that an O2 sensor is provided in the exhaust system.

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