JPWO2014054080A1 - Combustion stabilization device for sub-chamber gas engine - Google Patents

Abstract

The combustion stabilization device (100) includes a main chamber fuel supply device (21) that supplies gas fuel to the main chamber (33), a sub chamber fuel supply device (22) that supplies gas fuel to the sub chamber (34), and , A property detector (55) for detecting the property of the gas fuel, a theoretical air amount calculating unit (61) for calculating a theoretical air amount corresponding to the detected property of the gas fuel, and the air in the sub chamber (34) A target sub-chamber excess air ratio setting unit (62) for setting a target value of the excess rate, a sub-chamber fuel amount calculation unit (65) for calculating the amount of air and gas fuel supplied to the sub-chamber (34), A sub-chamber excess air ratio measurement unit (63) that calculates the excess air ratio in the sub-chamber (34) from the calculated air amount, gas fuel amount, and theoretical air amount, and the calculated value of the sub-chamber excess air ratio is the target value. The target subchamber fuel supply amount, which is the target value of the gas fuel supply amount to the subchamber (34), is set to Comprising auxiliary chamber fuel supply control unit which gas fuel of the target auxiliary combustion chamber fuel supply amount to control the auxiliary chamber fuel supply device (22) as supplied (67), the.

Description

  The present invention relates to a combustion stabilizing device applied to a sub-chamber gas engine having a main chamber and a combustion chamber having a sub-chamber communicating with the main chamber, and more particularly, to stabilize the combustion state regardless of the properties of gas fuel. TECHNICAL FIELD The present invention relates to a combustion stabilization device that achieves the above.

  The gas engine is an internal combustion engine that uses gas fuel as the main fuel. It can reduce nitrogen oxides in exhaust gas compared to a diesel engine and has a low CO2 emission. For example, the expectation for the power generation system which drives a generator with a gas engine is increasing. In recent years, a movement to apply a gas engine to a power generation system in an industrial plant, both domestically and abroad, and a movement to apply a gas engine to a marine propulsion and power generation system have become active.

  Conventionally, various combustion chamber structure modes, combustion methods, and combinations thereof have been proposed for gas engines. As a main example of this combination, so-called sub-chamber type spark ignition and so-called sub-chamber type pilot ignition are known. In these sub-chamber type gas engines, the combustion chamber has a main chamber and a sub-chamber communicating with the main chamber, and a communication hole is provided in a partition wall that divides the main chamber from the sub-chamber. In the sub chamber type gas engine, first, the air-fuel mixture in the sub chamber is ignited. Then, the combustion gas in the sub chamber is ejected from the sub chamber to the main chamber through the communication hole, and the ejected torch becomes a fire type to ignite the air-fuel mixture in the main chamber. Since the ignition power of the torch that is injected from the sub chamber is strong, misfiring is unlikely to occur even if the excess air ratio in the main chamber is increased, and higher efficiency and lower NOx can be achieved.

  Thus, the mainstream of gas engines in recent years is the lean burn type. Combustion control is particularly important to achieve high efficiency in lean burn gas engines. In order to achieve high efficiency, it is effective to advance the ignition timing and bring the combustion state to the limit where knocking occurs or near the limit. On the other hand, it is possible to improve the thermal efficiency by increasing the excess air ratio. However, if the excess air ratio becomes too high, misfire tends to occur. Therefore, in the lean burn type gas engine, the excess air ratio and ignition timing are adjusted, and the combustion control is executed so as to be stably within a narrow range surrounded by the knocking limit and the misfire limit. It is required to achieve both stabilization and high efficiency.

  As mentioned above, the range of application of gas engines tends to expand both locally and across the field. For example, when a gas engine is mounted on a ship, it is assumed that gas fuel is replenished at a docked port. However, the nature of gas fuel varies from country to country and from gas supplier to gas supplier. Even the properties of gas fuel supplied from the same gas supplier in the same country may vary over time.

  The properties of the gas fuel affect the ignitability. Then, even if the combustion control is optimized for a gas fuel having a certain property, the combustion state cannot always be stabilized when a gas fuel having a property different from this is supplied, The target output and efficiency may not be achieved. In some situations, the combustion state may become unstable such that knocking occurs beyond an acceptable range. Therefore, as disclosed in Patent Documents 1 and 2, techniques for coping with fluctuations in the properties of gas fuel have been proposed.

Patent Document 1 discloses an apparatus and a method for purifying natural gas used in a gas engine. In this method and apparatus, relatively heavy hydrocarbons such as propane (C ₃ H ₈ ), butane (C ₄ H ₁₀ ) and pentane (C ₅ H ₁₂ ) are separated from the natural gas mixture. The remaining natural gas mixture is used as gas fuel in the gas engine.

  Patent document 2 is disclosing the apparatus and method for adjusting the administration time of the pilot oil of a subchamber type pilot ignition gas engine. In this method and apparatus, for the purpose of stabilizing the combustion state in the main chamber, the composition of the gas fuel is measured, and the higher the concentration of the resulting inert gas, the more advanced the administration timing and the hydrogen gas concentration. The higher the value, the more retarded the timing of administration.

JP 2009-167411 A JP 2005-315177 A

  The method and apparatus of Patent Document 1 relies on the concept that the quality of the gas fuel may be adjusted before being supplied to the gas engine when the properties of the gas fuel fluctuate. However, if this method and apparatus are prepared by the engine supplier and the engine user, the entire facility becomes large, and the introduction cost and maintenance cost of the entire facility increase. If the gas supplier prepares this method and apparatus, the price of gas fuel may rise, and the operating cost of the gas engine may increase.

  However, at present, the combustion control technology corresponding to the change in the properties of the gas fuel does not necessarily realize stabilization of the combustion state. Combustion control was designed with the challenge of how to make the combustion state in the main chamber near the knock limit when it was allowed to assume that gas fuel with stable properties or quality was supplied. A reasonable result was obtained. As suggested in Patent Document 2, even in the combustion control to cope with the fluctuation of the properties of the gas fuel, it is the main room that is emphasized as an object of stabilizing the combustion state. The sub-chamber is the place where the fire type for igniting the air-fuel mixture in the main chamber is formed, but if the properties of the gas fuel fluctuate, the stability of the combustion state of the sub-chamber cannot be ensured as before. There is a risk that the fire will not form as usual. If the combustion state in the sub chamber is abnormal, it is very difficult to ensure the stability of the combustion state in the main chamber. However, a combustion control technique for stabilizing the combustion state in the sub chamber in response to fluctuations in the properties of the gas fuel has not yet been established.

  Therefore, an object of the present invention is to stabilize the combustion state in the sub chamber in response to fluctuations in the properties of the gas fuel in the sub chamber type gas engine.

  The present invention has been made to achieve the above object. A combustion stabilization device according to the present invention is a combustion stabilization device applied to a sub-chamber type gas engine having a main chamber and a combustion chamber having a sub-chamber communicating with the main chamber. A main chamber fuel supply device for supplying fuel, a sub chamber fuel supply device for supplying gas fuel to the sub chamber, a property detector for detecting the property of the gas fuel, and a theory corresponding to the detected property of the gas fuel A theoretical air amount calculation unit for calculating the air amount, a target sub chamber excess air ratio setting unit for setting a target value of the excess air ratio in the sub chamber, and an air amount and a gas fuel amount introduced into the sub chamber A sub-chamber fuel amount calculation unit, an air amount and a gas fuel amount calculated by the sub-chamber fuel amount calculation unit, and a theoretical air amount calculated by the theoretical air amount calculation unit. Sub-room excess air ratio calculation unit that calculates the rate, and calculated excess air ratio A target sub-chamber fuel supply amount that is a target value of the supply amount of gas fuel to the sub chamber is set so as to be the target value, and the sub fuel is supplied so that the gas fuel of the target sub-chamber fuel supply amount is supplied. A sub-chamber fuel supply control unit that controls the chamber fuel supply device.

  According to the above configuration, the excess air ratio in the sub chamber is calculated from the theoretical air amount calculated according to the properties of the gas fuel, and the amount of gas fuel supplied to the sub chamber so that the calculated value becomes the target value. Is set. As long as the target value of the excess air ratio in the secondary chamber is set to an appropriate value to ensure stabilization of the combustion state, even if the theoretical air volume varies due to fluctuations in the properties of the gas fuel, By adjusting the fuel supply amount introduced into the, the excess air ratio in the sub chamber can be controlled to an appropriate value that ensures the stabilization of the combustion state. As a result, even if the properties of the gas fuel fluctuate, the air-fuel mixture in the sub chamber is normally ignited, thereby making it easier to stabilize the combustion state in the main chamber.

  The sub-chamber fuel amount calculation unit is introduced into the sub-chamber based on the amount of gas fuel supplied from the sub-chamber fuel supply device to the sub-chamber and the amount of air-fuel mixture entering the sub-chamber from the main chamber. The amount of air and the amount of gas fuel may be calculated.

  According to the above configuration, since the excess air ratio in the sub chamber can be calculated in consideration of the amount of gas fuel entering the sub chamber from the main chamber, the calculation accuracy of the excess air ratio in the sub chamber is improved. Therefore, the combustion state in the sub chamber can be controlled with higher accuracy.

  The sub-chamber fuel amount calculation unit may calculate the main chamber excess air ratio using the supply air pressure, the supply air temperature, and the main chamber supply gas amount.

  According to the said structure, a main chamber excess air ratio can be estimated without using a flowmeter, and a combustion stabilization apparatus can be comprised simply. Of course, it is also possible to directly measure the intake air amount using an air flow sensor or the like and calculate the excess air ratio of the main chamber using the measured value and the amount of gas fuel.

  The sub-chamber fuel amount calculation unit uses the differential pressure between the inlet pressure and the outlet pressure of the sub-chamber fuel supply device and the gas fuel supply amount of the sub-chamber fuel supply device to output from the sub-chamber fuel supply device. A gas fuel amount may be calculated, and a gas fuel amount introduced into the sub chamber may be calculated based on the gas fuel amount.

  According to the above configuration, the amount of gas fuel supplied from the sub chamber fuel supply device can be calculated without actually detecting or measuring the amount of gas fuel itself.

  The target value may be set to a constant value near stoichiometry, and the excess air ratio in the main chamber may be set to lean.

  According to the above configuration, the combustion state in the sub chamber can be kept stable even when the property of the gas fuel varies in the combustion state in the sub chamber, and the efficiency of the entire gas engine can be kept high.

  The property detector detects gas fuel components, gas chromatography, methane number sensor for detecting the methane number of the gas fuel, calorimeter for detecting the calorific value of the gas fuel, oxygen concentration in the combustion exhaust gas from the combustion chamber It may include at least one of oxygen concentration sensors for detecting.

  According to the above configuration, it is possible to obtain properties useful for calculating the theoretical air amount such as the composition of the gas fuel and the methane number, and it is possible to accurately calculate the excess air ratio in the sub chamber.

  As is apparent from the above description, in the sub-chamber gas engine, the combustion state in the sub-chamber can be stabilized in response to fluctuations in the properties of the gas fuel.

It is a conceptual diagram which shows the whole structure of the subchamber type gas engine to which the combustion stabilization apparatus which concerns on embodiment of this invention is applied. It is a conceptual diagram which shows the structure of the combustion stabilization apparatus which concerns on embodiment of this invention with the structure of the cylinder of the gas engine 1 shown in FIG. It is a block diagram which shows the structure of the controller shown in FIG. It is the graph which expressed the map which defined the correspondence of the property of gas fuel, and the theoretical air quantity, and the map which defined the correspondence of the property of gas fuel, and the target subchamber excess air ratio in the Cartesian coordinate system. .

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same or corresponding elements are denoted by the same reference numerals throughout all the drawings, and detailed description thereof is omitted.

(Overall configuration of gas engine)
FIG. 1 is a conceptual diagram showing an overall configuration of a gas engine 1 according to an embodiment of the present invention. The gas engine 1 shown in FIG. 1 is a four-stroke reciprocating engine that uses gas fuel, adopts the “sub-chamber type” as the combustion chamber structure, and adopts the “spark ignition type” as an example of the combustion method. ing. The gas engine 1 burns an air-fuel mixture containing gas fuel and generates a rotational output at the output shaft 2. As shown in FIG. 1, the output shaft 2 is connected to, for example, an AC generator 3. As described above, the power generation system in which the gas engine 1 is applied to the drive source of the AC generator 3 may be introduced into an industrial plant or may be mounted on a ship. When the gas engine 1 is mounted on a ship, the output shaft 2 may be replaced with the AC generator 3 and connected to the propulsion device of the ship.

  The gas engine 1 includes an engine body 5 having a plurality of cylinders 4. The number and arrangement of the cylinders 4 are not particularly limited. The gas engine 1 includes an air supply line 6 that supplies air to each cylinder 4, an exhaust line 7 that exhausts exhaust from each cylinder 4, and a supercharger connected to the air supply line 6 and the exhaust line 7 ( Turbocharger) 8 is provided. The air supply line 6 includes a common portion 11 common to the plurality of cylinders 4 and a plurality of branch portions 12 (see FIG. 2) that connect the common portion 11 to the corresponding cylinders. The exhaust line 7 also includes a common portion 13 common to the plurality of cylinders 4 and a plurality of branch portions 14 that connect the corresponding cylinders 4 to the common portion 13. A downstream end portion of the branching portion 12 of the air supply line 6 is an air supply port 12a formed in the engine body 5 and communicates with the combustion chamber 32 (specifically, the main chamber 33) of the corresponding cylinder 4 ( (See FIG. 2). The upstream end portion of the branch portion 14 of the exhaust line 7 is an exhaust port 14a formed in the engine body 5 and communicates with the corresponding combustion chamber 32 (specifically, the main chamber 33) of the cylinder 4 (FIG. 2). See). The supercharger 8 includes a turbine 9 on the common part 13 of the exhaust line 7 and a compressor 10 on the common part 11 of the air supply line 6. The supercharger 8 is driven by the exhaust gas flowing through the exhaust line 7 and supercharges the air flowing through the air supply line 6. An exhaust bypass line 15 that bypasses the turbine 9 is connected to a common portion of the exhaust line 7, and an exhaust bypass valve 16 having a variable opening degree is provided on the exhaust bypass line 15. By adjusting the opening degree of the exhaust bypass valve 16, the flow rate of exhaust gas supplied to the turbine 9 can be adjusted, whereby the supply air pressure can be adjusted.

  The gas engine 1 is provided with a fuel line 25 that supplies gas fuel to each cylinder 4. The fuel line 25 extends from a fuel supply source (not shown), branches from the common portion 26 common to the plurality of cylinders 4, branches from the common portion 26, and guides gas fuel from the common portion 26 to the corresponding cylinder 4. A plurality of branch portions 27. Each cylinder 4 is provided with a main chamber fuel supply device 21, a sub chamber fuel supply device 22, and an ignition device 23. Since the two fuel supply devices 21 and 22 are provided in one cylinder 4 in this way, the main branch for guiding the gas fuel from the common portion 26 to the main chamber fuel supply device 21 is provided at the branch portion 27 of the fuel line 25. A part 28 and a sub-branch part 29 for guiding the gas fuel from the common part 26 to the sub-chamber fuel supply device 22 are included.

  FIG. 2 is a conceptual diagram showing the configuration of the combustion stabilizing device 100 according to the embodiment of the present invention together with the configuration of the cylinder 4 of the gas engine 1 shown in FIG. Although FIG. 2 shows the configuration of only one cylinder 4, the other cylinders 4 have the same configuration. As shown in FIG. 2, a piston 31 is inserted into each cylinder 4 so as to be reciprocally movable. The piston 31 is connected to the output shaft 2 via a connecting rod (not shown).

  Each cylinder 4 is provided with a combustion chamber 32 for burning the air-fuel mixture. The combustion chamber 32 includes a main chamber 33 formed on the upper surface side of the piston 31 and a sub chamber 34 communicating with the main chamber 33. The sub chamber 34 is partitioned from the main chamber 33 via a partition wall 35 provided in the upper portion of the main chamber 33, and spatially communicates with the main chamber 33 via a communication hole 36 formed in the partition wall 35. Yes. The volume of the sub chamber 34 is smaller than the volume of the main chamber 33.

  The engine body 5 has the above-described air supply port 12a and exhaust port 14a. The air supply port 12a constitutes the branch portion 12 of the air supply line 6 and communicates with the main chamber 33 at the downstream end thereof. The exhaust port 14 a constitutes the branch portion 14 of the exhaust line 7 and communicates with the main chamber 33 at the upstream end thereof. Each cylinder 4 is provided with an air supply valve 37 and an exhaust valve 38. The air supply valve 37 opens and closes the downstream end of the air supply port 12a, and the exhaust valve 38 opens and closes the upstream end of the exhaust port 14a.

  The main chamber fuel supply device 21 is provided on the main branch portion 28 of the fuel line 25 or provided at the end of the main branch portion 28, and supplies gas fuel to the branch portion 12 of the air supply line 6. The main chamber fuel supply device 21 according to the present embodiment is attached to the engine body 5 and supplies gas fuel to the air supply port 12a. The sub chamber fuel supply device 22 is provided on the sub branch portion 29 of the fuel line 25 or provided at the end of the sub branch portion 29, and supplies gas fuel into the sub chamber 34.

  In the present embodiment, each cylinder 4 is provided with a sub-chamber forming member 39 that has the above-described partition wall 35 and forms the sub-chamber 34, and the sub-chamber forming member 39 has the partition wall 35 in the sub-chamber forming member 39. It extends along the cylinder axis so as to form the lower end of the cylinder. The sub branching portion 29 of the fuel line 25 extends into the sub chamber forming member 39 above the sub chamber forming member 39 and opens on the inner upper surface of the sub chamber 34. The sub chamber fuel supply device 22 is disposed outside the sub chamber forming member 39 and is interposed on the sub branch portion 29 of the fuel line 25. Note that a check valve 40 is provided on the sub-branch portion 29 between the sub-chamber fuel supply device 22 and the opening to the sub-chamber 34. Thereby, it is possible to prevent the gas from flowing backward from the sub chamber 34 toward the sub chamber fuel supply device 22.

  The main chamber fuel supply device 21 and the sub chamber fuel supply device 22 are, for example, normally closed electromagnetic on-off valves, and open during a period when a valve opening command is given. While the main chamber fuel supply device 21 is open, gas fuel is supplied to the air supply port 12a. Gas fuel is supplied to the sub chamber 34 while the sub chamber fuel supply device 22 is open. The ignition device 23 is attached to the sub chamber forming member 39, and for example, a portion that generates a spark is disposed in the sub chamber 34. The ignition device 23 is, for example, an ignition plug having an electrode that generates a spark when energized.

  In the gas engine 1 configured as described above, in the air supply stroke in which the piston 31 moves downward, the air supply valve 37 is opened and the main chamber fuel supply device 21 supplies gas fuel to the air supply port 12a. Thereby, the air-fuel mixture of the air supply from the supercharger 8 and the gas fuel from the main chamber fuel supply device 21 is supplied from the air supply port 12a to the main chamber 33. In the compression stroke in which the piston 31 moves upward, the air supply valve 37 is closed and the air-fuel mixture is compressed in the main chamber 33. At this time, the compressed air-fuel mixture in the main chamber 33 is supplied into the sub chamber 34 through the communication hole 36. The sub chamber fuel supply device 22 injects gaseous fuel into the sub chamber 34 during the air supply stroke. As a result, the excess air ratio of the air-fuel mixture in the sub chamber 34 becomes smaller than the excess air ratio of the air-fuel mixture in the main chamber 33.

  The ignition device 23 operates near the time when the compression stroke ends, and a spark is generated in the sub chamber 34. As a result, the air-fuel mixture in the sub chamber 34 is ignited, and a flame is generated in the sub chamber 34. The flame in the sub chamber 34 is ejected into the main chamber 33 through the communication hole 36, and the ejected torch ignites the air-fuel mixture in the main chamber 33, and the flame propagates in the main chamber 33. . In this way, the air-fuel mixture in the sub chamber 34 and the main chamber 33 is combusted, and the piston 31 moves downward (expansion stroke). In the exhaust stroke after the expansion stroke, the exhaust valve 38 is opened, and the gas in the main chamber 33 and the sub chamber 34 is discharged to the exhaust line 7. At this time, the action of the check valve 40 can prevent the combustion exhaust gas from flowing back to the sub-branch portion 29.

(Combustion stabilization device)
A combustion stabilizing device 100 is applied to the gas engine 1. The combustion stabilizing device 100 performs combustion control for the purpose of stabilizing the combustion state in the sub chamber 34 in response to fluctuations in the properties of the gas fuel. The combustion stabilization apparatus 100 includes the main chamber fuel supply device 21, the sub chamber fuel supply device 22, and the ignition device 23 described above. Further, the combustion stabilization apparatus 100 includes a supply air pressure sensor 51, a supply air temperature sensor 52, a gas flow meter 53, a sub chamber inlet pressure sensor 54, a property sensor 55, and a controller 60. The controller 60 includes a CPU, a ROM, a RAM, and an input / output interface. The input side of the controller 60 is connected to the air pressure sensor 51, the air temperature sensor 52, the gas flow meter 53, the sub chamber inlet pressure sensor 54, and the property sensor 55, and the output side of the controller 60 is the main chamber fuel supply device 21. The sub chamber fuel supply device 22 and the ignition device 23 are connected.

  The air pressure sensor 51 and the air temperature sensor 52 are provided on the downstream side of the supercharger 8 in the air supply line 6. The air pressure sensor 51 detects the pressure of the air supplied from the supercharger 8 to the cylinder 4, and the air temperature sensor 52 detects the temperature of the air supplied from the supercharger 8 to the cylinder 4. To do. The gas flow meter 53 detects the flow rate of the gas fuel flowing through the fuel line 25. The air pressure sensor 51 and the air temperature sensor 52 may be provided in the common part 11 of the air supply line 6, and the gas flow meter 53 may be provided in the common part 26 of the fuel line 25. The sub chamber inlet pressure sensor 54 is provided for each cylinder 4 and detects the pressure of the gas fuel flowing through the sub branch portion 29 of the fuel line 25.

  The properties of gas fuel vary locally or temporally. Even if the property of the gas fuel fluctuates in this way, the property sensor 55 can detect the property of the gas fuel after the variation. The property sensor 55 detects an index or index that can be used for calculating the theoretical air amount, such as the composition of the gas fuel, as the property of the gas fuel. Therefore, a gas chromatography that detects the composition of the gas fuel in the fuel line 25 may be applied to the property sensor 55. Further, the methane number can be suitably applied as an index for calculating the theoretical air amount of the gas fuel. As a general tendency, a large methane number indicates a high concentration of light hydrocarbons, and a small methane number indicates a high concentration of heavy hydrocarbons. From such a viewpoint, a methane number sensor that detects the methane number of the gas fuel in the fuel line 25 can be suitably applied to the property sensor 55.

  Moreover, as a general tendency, when the concentration of light hydrocarbons increases, the calorific value per unit volume of the gas fuel decreases, and when the concentration of heavy hydrocarbons increases, the opposite is true. When the properties of the gas fuel fluctuate during operation with the same load and the same intake air amount, and the calorific value per unit volume changes accordingly, the concentration of oxygen contained in the combustion exhaust gas changes according to the change. That is, it is possible to estimate the properties of the gas fuel by measuring the residual oxygen concentration under conditions where the operating state is limited. For this reason, the calorific value and the residual oxygen concentration per unit volume of the gas fuel can be suitably applied as an index for calculating the theoretical air amount of the gas fuel.

  From such a viewpoint, a calorimeter that detects the calorific value per unit volume of the gas fuel in the fuel line 25 may be applied to the property sensor 55, or the residual oxygen concentration in the exhaust line 7 is detected. An oxygen concentration sensor may be applied. The methane number sensor, gas chromatography, and calorimeter are preferably provided in the common part 26 of the fuel line 25, and the oxygen concentration sensor is provided in the common part 13 of the exhaust line 7. preferable. The combustion stabilization apparatus 100 may include two or more types of detectors among the four types illustrated above as the property sensor 55.

  The controller 60 according to the present embodiment calculates a theoretical air amount corresponding to the detected property of the gas fuel in response to the change in the property of the gas fuel. Then, the excess air ratio in the sub chamber is calculated using the calculated theoretical air amount, and a target value for the excess air ratio in the sub chamber is set. Then, the sub chamber fuel supply device 22 is controlled so that the calculated excess air ratio in the sub chamber becomes the target value.

  In particular, in the present embodiment, since the controller 60 brings the calculated value of the excess air ratio in the sub chamber 34 close to the target value, the valve opening period of the sub chamber fuel supply device 22 in one engine cycle (that is, one engine) The amount of fuel supplied from the sub chamber fuel supply device 22 to the sub chamber 34 in the cycle is controlled. The “excess air ratio” is a ratio of the actual fuel / air mixture ratio (that is, air / fuel ratio) supplied to the cylinder 4 and the stoichiometric air / fuel ratio, and theoretically represents the air / fuel ratio of the air / fuel mixture supplied to the cylinder 4. Divided by the air-fuel ratio. In other words, it is the ratio of the amount of air actually supplied to the theoretical amount of air that is the amount of air that burns fuel without excess or deficiency. The stoichiometric air-fuel ratio and the stoichiometric air amount change stoichiometrically depending on the properties (particularly the composition) of the fuel. In the following description, the “excess air ratio” may be abbreviated as “λ” for simplification.

  FIG. 3 is a block diagram showing the configuration of the combustion stabilization apparatus 100 shown in FIG. As shown in FIG. 3, the controller 60 includes a theoretical air amount calculation unit 61, a target sub chamber λ setting unit 62, a sub chamber λ calculation unit 63, and a sub block as functional blocks for executing the above combustion control. A chamber fuel amount calculation unit 65, a constant storage unit 66, and a sub chamber fuel supply control unit 67 are included.

  The theoretical air amount calculation unit 61 calculates a theoretical air amount corresponding to the property of the gas fuel detected by the property sensor 55. When gas chromatography is applied to the property sensor 55, the theoretical air amount can be calculated from the detailed composition of the detected gas fuel. When a methane number sensor, a calorimeter, and an oxygen concentration sensor are applied to the property sensor 55, the controller 60 has a theoretical air amount map that defines the correspondence between the properties of the gas fuel and the theoretical air amount, as shown in FIG. Referring to 81, the theoretical air amount is calculated from the detected property of the gas fuel. For example, when the methane number is high, the calorific value of the gas fuel per unit volume is small, and the residual oxygen concentration is low, a relatively large value is calculated as the theoretical air amount according to the theoretical air amount map 81. As described above, the methane number, the calorific value of the gas fuel, and the residual oxygen concentration generally correlate with the carbon number of hydrocarbons contained in the gas fuel. For this reason, a map 81 that defines the correspondence between these indexes and the theoretical air amount is created, and the excess air ratio (sub-volume) in the sub chamber 34 is calculated from the theoretical air amount calculated according to the index using the map 81. It is significant to calculate chamber λ). When the methane number sensor, calorimeter, and oxygen concentration sensor are applied, the theoretical air amount can be calculated more quickly than when gas chromatography is applied, so that it is possible to quickly cope with changes in the properties of gas fuel.

  The target sub chamber λ setting unit 62 sets a target value of the excess air ratio (sub chamber λ) in the sub chamber 34. As shown by the solid line 82 parallel to the horizontal axis in FIG. 4, the target value of the sub chamber λ may be a constant value regardless of the properties of the gas fuel. In this case, for example, 1 that is a λ value when the air-fuel ratio is the stoichiometric air-fuel ratio may be applied as the constant value. The target value of the sub chamber λ may be variably set according to the properties of the gas fuel such as the methane number, the calorific value of the gas fuel, or the residual oxygen concentration.

  The sub chamber fuel amount calculation unit 65 calculates the amount of air and the amount of fuel introduced into the sub chamber 34. The sub-chamber fuel amount calculation unit 65 is introduced into the sub-chamber 34 based on the amount of fuel supplied from the sub-chamber fuel supply device 22 to the sub-chamber 34 and the air-fuel mixture amount entering the sub-chamber 34 from the main chamber 33. Calculate the amount of air and fuel. As an example, the sub chamber fuel amount calculation unit 65 calculates the fuel amount V1 introduced into the sub chamber 34 using the following equation (1), and the air introduced into the sub chamber 34 using the following equation (2). The amount V2 is calculated.

ここで、Ｖｐは副室３４の容積、Ｖは副室燃料供給装置２２から副室３４に供給される燃料量、ｘはガス燃料に対応した理論空気量、λｍは主室３３の空気過剰率、εは圧縮比である。副室３４の容積Ｖｐ及び圧縮比εはガスエンジン１の設計パラメータであって定数であり、定数記憶部６６に予め記憶されている。副室燃料量算出部６５は、定数記憶部６６に記憶された容積Ｖｐ及び圧縮比εのデータを参照して、燃料量Ｖ１及び空気量Ｖ２を算出することができる。

Here, Vp is the volume of the sub chamber 34, V is the amount of fuel supplied from the sub chamber fuel supply device 22 to the sub chamber 34, x is the theoretical air amount corresponding to the gas fuel, and λm is the excess air ratio of the main chamber 33. , Ε is a compression ratio. The volume Vp and the compression ratio ε of the sub chamber 34 are design parameters of the gas engine 1 and are constants, and are stored in the constant storage unit 66 in advance. The sub-chamber fuel amount calculation unit 65 can calculate the fuel amount V1 and the air amount V2 by referring to the data of the volume Vp and the compression ratio ε stored in the constant storage unit 66.

  In the above formulas (1) and (2), it is assumed that the sub-chamber fuel supply device 22 has completed the supply of gas fuel to the sub-chamber 34 near the bottom dead center of the compression stroke. In addition, it is assumed that no gas contributing to combustion in the next cycle remains in the sub chamber 34 after ignition combustion.

  When gas fuel is supplied from the sub-chamber fuel supply device 22 to the sub-chamber 34, the sub-chamber 34 has a fuel amount V of gas fuel, and a combustion exhaust gas amount subtracting the gas fuel amount V from the sub-chamber volume Vp. (That is, the amount of combustion exhaust gas is Vp-V).

  The fuel amount V supplied from the sub chamber fuel supply device 22 to the sub chamber 34 is obtained by using the differential pressure between the inlet pressure and the outlet pressure of the sub chamber fuel supply device 22 and the fuel supply period of the sub chamber fuel supply device 22. Is calculated. The sub chamber inlet pressure is the pressure of the gas fuel at the inlet of the sub chamber fuel supply device 22 and is detected by the sub chamber inlet pressure sensor 54. The sub chamber outlet pressure is the pressure on the outlet side of the sub chamber fuel supply device 22. The outlet side communicates with the air supply port 11a through the communication hole 36 and the main chamber 33, and is a portion where the supply air pressure acts. Therefore, the sub-chamber outlet pressure includes the detection value of the supply air pressure sensor 51 or The correction value can be applied. The sub-chamber fuel amount calculation unit 65 transfers the sub-chamber inlet pressure and the sub-chamber outlet pressure from the sub-chamber fuel supply period to the sub-chamber 34 in the sub-chamber fuel supply period. Calculate the amount of fuel supplied.

  Both the gas fuel amount V1 in the above equation (1) and the air amount V2 in the above equation (2) represent values when the sub chamber 34 is compressed at the compression ratio ε. The gas fuel supplied from the sub-chamber fuel supply device 22 is compressed to V / ε, and the combustion exhaust gas is compressed to (Vp−V) / ε. When these are added, Vp / ε is obtained, and the sum of the added value and the amount of air-fuel mixture entering the sub chamber 34 from the main chamber 33 becomes Vp. That is, the amount of air-fuel mixture that has entered the sub chamber 34 from the main chamber 33 is Vp (1-1 / ε). The above formulas (1) and (2) include a factor Vp (1-1 / ε), and the amount of air-fuel mixture that has entered the sub chamber 34 from the main chamber 33 when calculating the gas fuel amount V1 and the air amount V2. Is considered.

  As shown in the above formulas (1) and (2), if the excess air ratio λm of the main chamber 33 and the theoretical air amount x corresponding to the gas fuel are used, it is based on the air-fuel mixture amount Vp (1-1 / ε). The amount of fuel and the amount of air contained in the air-fuel mixture entering from the main chamber 33 can be respectively determined. Since the controller 60 has a theoretical air amount calculation unit 61 that calculates the theoretical air amount according to the properties of the gas fuel, the sub-chamber fuel amount calculation unit 65 outputs the calculation result by the theoretical air amount calculation unit 61. Referring to, the fuel amount and the air amount in the air-fuel mixture entering from the main chamber 33 can be obtained respectively.

  The excess air ratio λm of the main chamber 33 can be calculated using the amount of fuel supplied to the main chamber 33 and the amount of air supplied to the main chamber 33. The amount of fuel supplied to the main chamber 33 is obtained based on the differential pressure between the inlet pressure and the outlet pressure of the main chamber fuel supply device 21 and the fuel supply period of the main chamber fuel supply device 21, as in the sub chamber 34. . Alternatively, a value obtained by subtracting the amount of fuel supplied from the sub chamber fuel supply device 22 to the sub chamber 34 from the detected value of the gas flow meter 53 may be used. Conversely, the amount of fuel supplied from the sub chamber fuel supply device 22 to the sub chamber 34 may be a value obtained by subtracting the amount of fuel from the main chamber fuel supply device 21 from the detected value of the gas flow meter 53. The amount of air supplied to the main chamber 33 may be directly detected by an air flow sensor (not shown) provided in the air supply line 6. Moreover, you may calculate using a speed density method according to an engine speed and gas density.

  The excess air ratio is obtained by dividing the air amount by the fuel amount and multiplying the divided value by the reciprocal of the theoretical air amount. Therefore, the excess air ratio is multiplied by the theoretical air amount to be the divided value. . For this reason, in the equation (1), 1 / (λm × x + 1) is equal to the ratio of the fuel amount in the mixture to the mixture amount. In equation (2), [1-1 / (λm × x + 1)] is equal to the ratio of the air amount in the mixture to the amount of the mixture. Therefore, the equation for calculating V1 and V2 does not necessarily include the excess air ratio λx and the theoretical air amount x of the main chamber 33 as factors. If the ratio between the amount of fuel and the amount of air contained in the air-fuel mixture supplied to the main chamber 33 is known, this ratio is used to determine the amount of fuel in the air-fuel mixture that has entered the sub-chamber 34 from the main chamber 33 and Each air amount can be calculated.

  The sub chamber fuel amount calculation unit 65 calculates the amount of air supplied to the sub chamber 34 based on the air-fuel mixture amount supplied to the sub chamber 34 via the main chamber 33 in this way. Further, the sub chamber fuel amount calculation unit 65 is based on the fuel amount supplied to the sub chamber 34 via the main chamber 33 and the fuel amount directly supplied from the sub chamber fuel supply device 22 to the sub chamber 34. Thus, the amount of fuel supplied to the sub chamber 34 is calculated.

  The sub chamber λ calculating unit 63 actually calculates the air amount and fuel amount supplied to the sub chamber 34 calculated by the sub chamber fuel amount calculating unit 65 and the theoretical air amount calculated by the theoretical air amount calculating unit 61. The sub-chamber λ is calculated. The sub chamber λ can be obtained by dividing the amount of air supplied to the sub chamber 34 by the amount of fuel supplied to the sub chamber 34 and multiplying the divided value by the inverse of the theoretical air amount. When calculating the amount of fuel and the amount of air supplied to the sub chamber 34 using the above formulas (1) and (2), the excess air ratio λp of the sub chamber 34 is obtained from the following formula (3).

本実施形態に係る制御器６０においては、前述した副室燃料量算出部６５により算出される空気量及び燃料量からわかるとおり、副室３４に供給された空気量が、設計パラメータである副室容積、圧縮比はもちろん、圧縮行程において主室３３から副室３４へと連通穴３６を介して入り込む空気量を考慮に入れて算出される。副室３４に供給された燃料量が、副室燃料供給装置２２から副室３４へと供給されたガス燃料量と、圧縮行程において主室３３から副室３４へと連通穴３６を介して入り込む燃料量とを考慮に入れて算出される。副室λ算出部６３は、このようにして算出された副室３４に供給される空気量及び燃料量と、理論空気量算出部６１により算出された理論空気量とから、副室λを算出する。

In the controller 60 according to the present embodiment, as can be seen from the air amount and the fuel amount calculated by the sub-chamber fuel amount calculation unit 65 described above, the air amount supplied to the sub-chamber 34 is a design parameter. Of course, the volume and compression ratio are calculated in consideration of the amount of air entering the main chamber 33 from the main chamber 33 into the sub chamber 34 through the communication hole 36 in the compression stroke. The amount of fuel supplied to the sub chamber 34 enters from the main chamber 33 to the sub chamber 34 through the communication hole 36 in the compression stroke, and the amount of gas fuel supplied from the sub chamber fuel supply device 22 to the sub chamber 34. It is calculated taking into account the fuel amount. The sub chamber λ calculating unit 63 calculates the sub chamber λ from the air amount and fuel amount supplied to the sub chamber 34 calculated in this way and the theoretical air amount calculated by the theoretical air amount calculating unit 61. To do.

  The sub chamber fuel supply control unit 67 includes a comparator 68 and a regulator 69, and the comparator 68 calculates the calculated value of the sub chamber λ calculated by the sub chamber λ calculation unit 63 and the target sub chamber λ setting unit. The control value of the sub chamber λ is calculated by comparing with the target value of the sub chamber λ set in 62. The adjuster 69 performs PID adjustment according to the calculated control deviation, and supplies the target sub-chamber fuel supply that is the target value of the gas fuel supply period to the sub chamber 34 so that the calculated value of the sub chamber λ becomes the target value. Set the period. Then, the sub chamber fuel supply control unit 67 controls the sub chamber fuel supply device 22 so that the gas fuel is supplied in the target sub chamber fuel supply period in the next air supply and / or compression stroke.

  According to the combustion stabilization apparatus 100 configured as described above, the sub chamber λ is calculated using the theoretical air amount corresponding to the properties of the gas fuel, and the gas fuel to the sub chamber 34 is set so that the calculated value becomes the target value. The supply period is set. If the target value of the sub chamber λ is set to an appropriate value for ensuring the stabilization of the combustion state, even if the theoretical air amount fluctuates due to fluctuations in the properties of the gas fuel, it is supplied to the sub chamber 34. The amount of fuel is adjusted, so that the sub chamber λ can be controlled to have the appropriate value that ensures stabilization of the combustion state. Thereby, even if the properties of the gas fuel fluctuate, the air-fuel mixture in the sub chamber 34 is normally ignited, and as a result, the combustion state in the main chamber 33 is easily stabilized.

  If the target value is set to 1 and the sub chamber λ is controlled to be close to stoichiometry (theoretical air-fuel ratio), the combustion state in the sub chamber 34 is easily stabilized, which is beneficial. The combustion stabilization apparatus 100 according to the present embodiment copes with fluctuations in the excess air ratio by adjusting the fuel amount even if there is fluctuations in the properties of the gas fuel, so that the combustion state of the sub chamber 34 is effective. Can be stabilized. On the other hand, if the main chamber λ is set to be lean, the efficiency of the entire gas engine can be kept high regardless of fluctuations in the properties of the gas fuel.

  In the above combustion control, it is important to accurately calculate the sub chamber λ in order to control the sub chamber λ in response to fluctuations in the properties of the gas fuel. Therefore, in the combustion stabilization apparatus 100 according to the present embodiment, the sub chamber λ calculating unit 63 calculates the sub chamber λ based on the fuel amount and the air amount introduced into the sub chamber. Thus, in the sub-chamber gas engine 1, the sub-chamber λ can be calculated in consideration of the amount of air and the amount of fuel that enter the sub-chamber 34 from the main chamber 33 during the compression stroke. That is, the amount of air and the amount of fuel (air mixture amount) entering the sub chamber 34 from the main chamber 33 are calculated according to the supply air pressure and the supply air temperature. Since the amount of air-fuel mixture can be calculated without providing a flow meter near the cylinder, the combustion stabilizing device can be simplified. Further, in the combustion stabilization apparatus 100 according to the present embodiment, the sub chamber λ calculating unit 63 calculates the sub chamber λ with reference to the amount of fuel supplied from the sub chamber fuel supply device 22 to the sub chamber 34. . This fuel amount is calculated in consideration of the differential pressure between the sub chamber inlet pressure and the sub chamber outlet pressure. Therefore, the amount of fuel supplied to the sub chamber 34 can be accurately calculated, and the sub chamber λ is calculated with reference to the calculated value of the fuel amount, so that the calculation accuracy of the sub chamber λ is also improved. . As described above, since the calculation accuracy of the sub chamber λ is improved, the combustion state of the sub chamber 34 can be easily stabilized, thereby contributing to the stabilization of the combustion state of the main chamber 33.

  Although the embodiments of the present invention have been described so far, the above configuration can be appropriately changed within the scope of the present invention.

  The present invention has a remarkable effect that the combustion state in the sub chamber can be stabilized in response to fluctuations in the properties of the gas fuel, and includes a sub chamber fuel supply device that supplies gas fuel to the sub chamber. It is beneficial to apply to a sub-chamber gas engine.

DESCRIPTION OF SYMBOLS 1 Gas engine 4 Cylinder 6 Supply line 7 Exhaust line 15 Fuel line 21 Main chamber fuel supply device 22 Sub chamber fuel supply device 23 Ignition device 32 Combustion chamber 33 Main chamber 34 Sub chamber 51 Supply pressure sensor 52 Supply temperature sensor 53 Gas flow rate Total 54 Sub chamber inlet pressure sensor 55 Property sensor 60 Controller 61 Theoretical air amount calculation unit 62 Target sub chamber λ setting unit (target sub chamber excess air ratio setting unit)
63 Sub chamber λ calculator (sub chamber excess air ratio calculator)
65 Sub-chamber fuel amount calculation unit 66 Constant storage unit 67 Sub-chamber fuel supply control unit 100 Combustion stabilization device

The sub-chamber fuel amount calculation unit uses the differential pressure between the inlet pressure and the outlet pressure of the sub-chamber fuel supply device and the gas fuel supply period of the sub-chamber fuel supply device to output from the sub-chamber fuel supply device. A gas fuel amount may be calculated, and a gas fuel amount introduced into the sub chamber may be calculated based on the gas fuel amount.

The present invention has been made to achieve the above object. A combustion stabilization device according to the present invention is a combustion stabilization device applied to a sub-chamber type gas engine having a main chamber and a combustion chamber having a sub-chamber communicating with the main chamber. A main chamber fuel supply device that supplies fuel, a sub chamber fuel supply device that supplies gas fuel to the sub chamber, a constant storage unit that stores a compression ratio and a sub chamber volume of the sub chamber type gas engine, and gas fuel A property detector for detecting the property of the gas, a theoretical air amount calculation unit for calculating a theoretical air amount corresponding to the detected property of the gas fuel, and a target sub-chamber air for setting a target value of the excess air ratio in the sub-chamber An excess ratio setting unit, the amount of gas fuel supplied to the sub chamber from the sub chamber fuel supply device, the compression ratio and sub chamber volume stored in the constant storage unit, the excess air ratio in the main chamber, the theory Based on the theoretical air volume calculated by the air volume calculator, Air amount supplied to the auxiliary chamber from serial main chamber, said auxiliary chamber fuel supply system and the auxiliary combustion chamber fuel amount calculating unit for calculating a gas amount of fuel supplied to the auxiliary chamber from the main chamber, the sub A sub-chamber excess air ratio calculation unit that calculates an excess air ratio in the sub-chamber from the air amount and gas fuel amount calculated by the chamber fuel amount calculation unit and the theoretical air amount calculated by the theoretical air amount calculation unit If the calculated value of the excess air ratio of the secondary chamber set goals antechamber fuel supply amount is a target value of the supply amount of gaseous fuel into the precombustion chamber such that the target value, the target auxiliary combustion chamber fuel A sub-chamber fuel supply control unit that controls the sub-chamber fuel supply device so that a supply amount of gas fuel is supplied.

According to the above configuration, the excess air ratio in the sub chamber is calculated from the theoretical air amount calculated according to the properties of the gas fuel, and the amount of gas fuel supplied to the sub chamber so that the calculated value becomes the target value. Is set. Since the excess air ratio in the sub chamber is calculated in consideration of the amount of air and gas fuel that enter the sub chamber from the main chamber, the accuracy of calculating the excess air ratio in the sub chamber is improved. As long as the target value of the excess air ratio in the secondary chamber is set to an appropriate value to ensure stabilization of the combustion state, even if the theoretical air volume varies due to fluctuations in the properties of the gas fuel, By adjusting the fuel supply amount introduced into the, the excess air ratio in the sub chamber can be controlled to an appropriate value that ensures the stabilization of the combustion state. As a result, even if the properties of the gas fuel fluctuate, the air-fuel mixture in the sub chamber is normally ignited, thereby making it easier to stabilize the combustion state in the main chamber.

The amount of gas fuel supplied from the auxiliary chamber fuel supply device to the auxiliary chamber is V, the compression ratio is ε, the auxiliary chamber volume is Vp, the excess air ratio in the main chamber is λm, and the theoretical air amount is x. In this case, the sub-chamber excess air ratio calculating unit calculates the excess air ratio λp in the sub-chamber from λp = λm / [(V / Vp) {(λm × x + 1) / (ε−1)} + 1]. It may be calculated.

The sub-chamber fuel amount calculation unit uses the differential pressure between the inlet pressure and the outlet pressure of the sub-chamber fuel supply device and the gas fuel supply period of the sub-chamber fuel supply device to output from the sub-chamber fuel supply device. A gas fuel amount may be calculated, and a gas fuel amount supplied to the sub chamber may be calculated based on the gas fuel amount.

Claims (6)

A combustion stabilization device applied to a sub-chamber type gas engine having a main chamber and a combustion chamber having a sub chamber communicating with the main chamber,
A main chamber fuel supply device for supplying gas fuel to the main chamber;
A sub chamber fuel supply device for supplying gas fuel to the sub chamber;
A property detector for detecting the properties of the gas fuel;
A theoretical air amount calculation unit for calculating a theoretical air amount corresponding to the detected property of the gas fuel;
A target sub chamber excess air ratio setting unit for setting a target value of the excess air ratio in the sub chamber;
A sub-chamber fuel amount calculation unit for calculating the amount of air and gas fuel supplied to the sub-chamber;
Subchamber excess air ratio calculation for calculating the excess air ratio in the subchamber from the air amount and gas fuel amount calculated by the subchamber fuel amount calculation unit and the theoretical air amount calculated by the theoretical air amount calculation unit And
A target sub-chamber fuel supply amount that is a target value of the gas fuel supply amount to the sub chamber is set so that the calculated value of the excess air ratio becomes the target value. A combustion stabilization device for a sub-chamber gas engine, comprising: a sub-chamber fuel supply control unit that controls the sub-chamber fuel supply device to be supplied.   The sub-chamber fuel amount calculation unit supplies the sub-chamber based on the amount of gas fuel supplied from the sub-chamber fuel supply device to the sub-chamber and the amount of air-fuel mixture entering the sub-chamber from the main chamber. The combustion stabilizing device for a sub-chamber type gas engine according to claim 1, wherein the amount of air and the amount of gas fuel to be calculated are calculated.   The combustion stabilization device for a sub-chamber type gas engine according to claim 2, wherein the sub-chamber fuel amount calculation unit calculates the amount of air-fuel mixture entering the sub-chamber from the main chamber using a supply air pressure and a supply air temperature. .   The sub-chamber fuel amount calculation unit uses the differential pressure between the inlet pressure and the outlet pressure of the sub-chamber fuel supply device and the gas fuel supply amount of the sub-chamber fuel supply device to output from the sub-chamber fuel supply device. The combustion stability for a subchamber type gas engine according to any one of claims 1 to 3, wherein a gas fuel amount is calculated, and a gas fuel amount supplied to the subchamber is calculated based on the gas fuel amount. Device.   The sub-chamber gas engine according to any one of claims 1 to 4, wherein the target value is set to a constant value near stoichiometry, and the excess air ratio in the main chamber is set to lean. Combustion stabilization device.   The property detector detects gas fuel components, gas chromatography, methane number sensor for detecting the methane number of the gas fuel, calorimeter for detecting the calorific value of the gas fuel, oxygen concentration in the combustion exhaust gas from the combustion chamber The combustion stabilization device for a sub-chamber type gas engine according to any one of claims 1 to 5, comprising at least one of oxygen concentration sensors for detecting the above.

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