JP5472188B2 - Method for determining air intrusion into working gas circulation engine and apparatus using the same - Google Patents

Description

  The present invention relates to a method for determining air intrusion into a working gas circulation engine and an apparatus using the method. More particularly, the present invention relates to a method for determining the intrusion of air into a circulation path of burned gas of a working gas circulation engine and an apparatus using the method.

Conventionally, a fuel (for example, hydrogen), an oxidant (for example, oxygen), and a working gas (for example, an inert gas) are supplied to the combustion chamber to burn the fuel, and the exhaust gas discharged from the combustion chamber has been conventionally used. There has been proposed a working gas circulation engine that circulates working gas in fuel gas through the circulation passage to the combustion chamber. The working gas is preferably inert and has a large specific heat ratio to increase the thermal efficiency of the engine. Accordingly, examples of the working gas include helium, neon, and argon, which are monoatomic gases belonging to rare gases. In reality, argon is widely used as the engine working gas. The burned gas of such an engine contains H ₂ O (water vapor) and argon gas. Therefore, the engine is interposed in the circulation passage for circulating (re-supplying) the burned gas discharged from the combustion chamber to the combustion chamber, and H ₂ O ( It is common to have a condenser that condenses and separates and removes (water vapor).

  The working gas circulation engine is a kind of so-called “closed cycle engine”, and a circulation passage for circulating (re-supplying) the burned gas discharged from the combustion chamber to the combustion chamber is sealed. Need to be. When leakage occurs in the circulation passage, the circulation gas including the working gas leaks into the atmosphere, and conversely, air in the atmosphere flows into the circulation passage. Nitrogen (and oxygen), which is the main component of air, has a lower specific heat ratio than an inert monoatomic gas (for example, argon) used as a working gas, so when air flows into the circulation passage, The specific heat ratio of the circulating gas as a whole is lowered, the temperature and pressure in the combustion chamber near the top dead center (TDC) are lowered, and the thermal efficiency of the engine may be lowered.

  Therefore, in a working gas circulation engine, it is necessary to quickly and accurately determine the intrusion of air into the burned gas circulation passage. In this technical field, for example, air contamination in a gas phase portion in a fuel tank of a liquefied gas internal combustion engine is monitored during operation based on the oxygen concentration. Attempts have been made to eliminate the deviation of the air-fuel ratio by adjusting the injection amount of the gas-phase fuel (see, for example, Patent Document 1).

  However, in a working gas circulation engine, since the oxygen concentration in the circulation gas varies depending on the operating conditions, it is difficult to determine the air contamination based on the oxygen concentration during operation as in the prior art.

  As described above, in this technical field, there is a continuous demand for a technique for quickly and accurately determining the intrusion of air into the circulation path of burned gas in a working gas circulation engine.

JP 2004-76665 A

  As described above, there is a continuing need in the art for a technique for quickly and accurately determining the intrusion of air into the circulation path of burned gas in a working gas circulation engine. The present invention has been made to meet such a demand. More specifically, an object of the present invention is to provide a method for quickly and accurately determining the intrusion of air into a circulation path of burned gas in a working gas circulation engine, and an apparatus using the method. To do.

The above object of the present invention is to
A working gas circulation engine that obtains power by directing fuel, oxidant, and working gas to a combustion chamber, and burning the fuel in the combustion chamber;
A circulation passage for circulating the burned gas released from the combustion chamber to the combustion chamber;
Oxygen concentration detection means for detecting the oxygen concentration in the circulation passage, and air intrusion determination means for judging whether air has entered the circulation passage based on the oxygen concentration detected by the oxygen concentration detection means,
In a working gas circulation engine comprising:
A first oxygen concentration detecting step in which the oxygen concentration detecting means detects a first oxygen concentration which is an oxygen concentration in the circulation passage at a time point after the predetermined period 1 has elapsed after the engine is stopped and before the engine is started;
A second oxygen concentration detector for detecting a second oxygen concentration that is an oxygen concentration in the circulation passage after a predetermined period 2 longer than the predetermined period 1 has elapsed after the engine is stopped and before the engine is started; A concentration detecting step; and the circulation passage when the air intrusion determining means has an oxygen concentration difference that is a difference obtained by subtracting the first oxygen concentration from the second oxygen concentration is equal to or greater than a predetermined value A. An air intrusion determination step that determines that there is air intrusion into the air and determines that there is no air intrusion into the circulation passage when the oxygen concentration difference is less than the predetermined value A;
Is achieved by an air intrusion determination method for a working gas circulation engine.

Also, the above object of the present invention is to
A working gas circulation engine that obtains power by directing fuel, oxidant, and working gas to a combustion chamber, and burning the fuel in the combustion chamber;
A circulation passage for circulating the burned gas released from the combustion chamber to the combustion chamber;
Oxygen concentration detection means for detecting the oxygen concentration in the circulation passage, and air intrusion determination means for judging whether air has entered the circulation passage based on the oxygen concentration detected by the oxygen concentration detection means,
In a working gas circulation engine comprising:
The oxygen concentration detecting means detects a first oxygen concentration that is an oxygen concentration in the circulation passage at a time point when a predetermined period 1 has elapsed after the engine is stopped and before the engine is started;
The oxygen concentration detecting means detects a second oxygen concentration which is an oxygen concentration in the circulation passage at a time point that is longer than the predetermined period 1 after the engine is stopped and before the engine is started, and the air If the oxygen concentration difference, which is a difference obtained by subtracting the first oxygen concentration from the second oxygen concentration, is greater than or equal to a predetermined value A, the intrusion determination means has air intrusion into the circulation passage. It is determined that there is no oxygen intrusion into the circulation passage when the oxygen concentration difference is less than the predetermined value A,
That is structured as
It is also achieved by an air intrusion determination device for a working gas circulation engine characterized by the above.

  As described above, according to the present invention, the oxygen concentration in the circulation passage after the engine is stopped and before the restart is detected by the oxygen concentration detection means, and the air flow into the circulation passage is determined based on the difference between these oxygen concentrations. The presence or absence of intrusion is determined. Thereby, according to this invention, the penetration | invasion of the air to the circulation path of the burned gas in a working gas circulation type engine can be determined rapidly and with high precision.

It is the schematic showing the structure of the system containing the working gas circulation engine to which the air intrusion determination method to the working gas circulation engine which concerns on one embodiment of this invention is applied. It is a flowchart showing a series of processes performed in the air intrusion determination method to the working gas circulation engine which concerns on one embodiment of this invention. It is a flowchart showing a series of processes performed in the air intrusion determination method to the working gas circulation engine which concerns on another embodiment of this invention.

  As described above, an object of the present invention is to provide a method for quickly and accurately determining the intrusion of air into the circulation passage of burned gas in a working gas circulation engine and a device using the method. .

  As a result of earnest research to achieve the above object, the present inventor detects the oxygen concentration in the circulation passage after the engine is stopped and before the restart by the oxygen concentration detecting means, and based on the difference between these oxygen concentrations, the circulation passage By determining whether or not air has entered the interior, it has been conceived that air intrusion into the circulation path of burned gas in a working gas circulation engine can be determined quickly and with high accuracy.

That is, the first aspect of the present invention is:
A working gas circulation engine that obtains power by directing fuel, oxidant, and working gas to a combustion chamber, and burning the fuel in the combustion chamber;
A circulation passage for circulating the burned gas released from the combustion chamber to the combustion chamber;
Oxygen concentration detection means for detecting the oxygen concentration in the circulation passage, and air intrusion determination means for judging whether air has entered the circulation passage based on the oxygen concentration detected by the oxygen concentration detection means,
In a working gas circulation engine comprising:
A first oxygen concentration detecting step in which the oxygen concentration detecting means detects a first oxygen concentration which is an oxygen concentration in the circulation passage at a time point after the predetermined period 1 has elapsed after the engine is stopped and before the engine is started;
A second oxygen concentration detector for detecting a second oxygen concentration that is an oxygen concentration in the circulation passage after a predetermined period 2 longer than the predetermined period 1 has elapsed after the engine is stopped and before the engine is started; A concentration detecting step; and the circulation passage when the air intrusion determining means has an oxygen concentration difference that is a difference obtained by subtracting the first oxygen concentration from the second oxygen concentration is equal to or greater than a predetermined value A. An air intrusion determination step that determines that there is air intrusion into the air and determines that there is no air intrusion into the circulation passage when the oxygen concentration difference is less than the predetermined value A;
An air intrusion determination method for a working gas circulation engine.

  As described above, the working gas circulation engine supplies fuel, oxidant, and working gas to the combustion chamber to burn the fuel, and the working gas in the burned gas discharged from the combustion chamber is used. It is circulated through the circulation passage to the combustion chamber. The burned gas includes combustion products generated with the combustion of fuel. Therefore, the working gas circulation engine is generally provided with means for separating and removing combustion products contained in the burned gas.

The combustion products vary depending on the type of substance used as the fuel. Therefore, a means for separating and removing the combustion products is also required according to the type of substance used as the fuel. For example, when hydrogen is used as the fuel, the burned gas contains H ₂ O (water vapor). In this case, the engine is interposed in the circulation passage for circulating (re-supplying) the burned gas discharged from the combustion chamber to the combustion chamber, and H ₂ O contained in the burned gas. It is common to provide a condenser that condenses (steam) to separate and remove. Alternatively, instead of the condenser or in addition to the condenser, an adsorbent that adsorbs H ₂ O (water vapor) may be disposed in the circulation passage.

For example, when using a hydrocarbon-based fuel, not only H ₂ O (water vapor) but also CO ₂ (carbon dioxide) is included in the burned gas. In this case, the engine separates and removes CO ₂ (carbon dioxide) as well as means (for example, a condenser, an adsorbent, etc.) for separating and removing H ₂ O (water vapor) as described above. The means for this is also generally arranged in the circulation passage. The means for separating and removing such a CO 2 _(carbon dioxide), for example, CO 2 zeolite for absorbing and adsorbing the monoethanolamine solution or CO 2 absorb by dissolving _(carbon dioxide) _(CO) And system adsorbents.

  The oxygen concentration detection means is not limited to a specific configuration as long as the oxygen concentration in the circulation passage can be detected. For example, the oxygen concentration detection means may be a so-called “oxygen concentration sensor” that sends a signal corresponding to the concentration of oxygen existing around the sensor element as a current or voltage. The oxygen concentration sensor is generally of a type that detects the oxygen concentration around the sensor using oxygen ion conductivity of stabilized zirconia (ceramics) heated to a high temperature, for example. The oxygen concentration detection means sends a measurement signal (detection signal) corresponding to the detected oxygen concentration.

  Further, the oxygen concentration detecting means does not select the installation location as long as the oxygen concentration in the circulation passage can be detected. Incidentally, in an engine that is an internal combustion engine, for the purpose of air-fuel ratio control or the like, for example, an oxygen concentration sensor is often disposed near the exhaust manifold of the engine, for example. Therefore, such an existing oxygen concentration sensor may be used as oxygen concentration detection means in the air intrusion determination method for the working gas circulation engine according to the present invention.

  As described above, the air intrusion determining means determines whether air has entered the circulation passage based on the oxygen concentration detected by the oxygen concentration detecting means. For example, the air intrusion determining means determines whether air has entered the circulation passage based on a measurement signal (detection signal) corresponding to the oxygen concentration sent from the oxygen concentration detecting means. It is common to have an algorithm. The algorithm may be implemented as software (for example, a program) or may be implemented as hardware (for example, an arithmetic circuit).

  For example, in general, the algorithm is, for example, a ROM (Read Only Memory) or a RAM (RAM) included in an electronic control unit (ECU) for performing various controls related to the system including the working gas circulation engine. Processing stored in a storage device such as a random access memory (Random Access Memory) as a program and defined by the central processing unit (CPU: Central Processing Unit) included in the ECU (determining whether air has entered the circulation passage) Is implemented to be executed. In addition, the ECU may include, for example, a communication port for receiving the detection signal or sending an instruction signal (control signal) for causing other means to execute processing based on the determination result. it can. Incidentally, the ECU refers to an electronic device mainly composed of a well-known microcomputer including a CPU, a storage device such as a ROM, a RAM, an HDD, or a nonvolatile memory, and an interface. However, the above description regarding the air intrusion determination means and the electronic control device is merely an example, and the configurations of the air intrusion determination means and the electronic control device are not limited to the above description.

As described above, the air intrusion determination method for the working gas circulation engine according to the present embodiment is applied to the working gas circulation engine as described above.
A first oxygen concentration detecting step in which the oxygen concentration detecting means detects a first oxygen concentration which is an oxygen concentration in the circulation passage at a time point after the predetermined period 1 has elapsed after the engine is stopped and before the engine is started;
A second oxygen concentration detector for detecting a second oxygen concentration that is an oxygen concentration in the circulation passage after a predetermined period 2 longer than the predetermined period 1 has elapsed after the engine is stopped and before the engine is started; A concentration detecting step; and the circulation passage when the air intrusion determining means has an oxygen concentration difference that is a difference obtained by subtracting the first oxygen concentration from the second oxygen concentration is equal to or greater than a predetermined value A. An air intrusion determination step that determines that there is air intrusion into the air and determines that there is no air intrusion into the circulation passage when the oxygen concentration difference is less than the predetermined value A;
including.

  First, in the first oxygen concentration detection step, as described above, the oxygen concentration detection means has a first oxygen concentration that is the oxygen concentration in the circulation passage when the predetermined period 1 elapses after the engine is stopped and before the engine is started. Is detected. Here, as the first oxygen concentration, the oxygen concentration in the circulation passage detected immediately after the engine is stopped can be applied. In other words, as the predetermined period 1, a very short period after the engine is stopped can be set unless there is a specific reason. Specifically, in the predetermined period 1, for example, in a system including the above-described working gas circulation engine, an instruction to stop the engine is issued, the engine is actually stopped, and the oxygen concentration distribution in the circulation gas in the circulation passage is approximately The oxygen concentration in the circulation passage immediately after becoming uniform can be set so as to be detected by the oxygen concentration detecting means as the first oxygen concentration.

  Next, in the second oxygen concentration detection step, as described above, the oxygen concentration detection means detects that the oxygen in the circulation passage has passed the predetermined period 2 longer than the predetermined period 1 after the engine is stopped and before the engine is started. The second oxygen concentration which is the concentration is detected. Here, in the predetermined period 2, when it is assumed that air has entered the circulation path of burned gas of the working gas circulation engine, the oxygen concentration in the circulation path shows a significant change. A sufficiently long period is desirable. However, when the engine is started (again), the oxygen concentration in the circulation passage varies depending on the operating conditions of the engine. Therefore, during the predetermined period 2, the second oxygen concentration before the oxygen concentration detecting means restarts the engine. Need to be set to detect.

  In other words, the predetermined period 2 is before the engine is restarted, and when the predetermined period 1 has elapsed since the previous engine stop and a sufficiently long period has elapsed since the first oxygen concentration was detected. Is set so that the second oxygen concentration is detected. Here, as described above, the “sufficiently long period” is a period that is sufficiently long to show a significant change in the oxygen concentration in the circulation passage. For example, the detection accuracy of the oxygen concentration detection means and the oxygen in the circulation passage It can be set in consideration of factors such as concentration fluctuation. Specifically, the second oxygen concentration may be detected immediately after a predetermined period 2 has elapsed since the previous engine stop, or after the predetermined period 2 has elapsed, an instruction to start the engine is issued. It may be detected at a time point before the engine is actually started (that is, immediately before the engine is restarted). Note that the length of the period from when the engine is stopped to when it is restarted varies, but the predetermined period 2 may not be a fixed value as long as it does not violate the above concept.

  Furthermore, in the air intrusion determination step, as described above, the air intrusion determination means has an oxygen concentration difference that is a difference obtained by subtracting the first oxygen concentration from the second oxygen concentration equal to or greater than a predetermined value A. In some cases, it is determined that air has entered the circulation passage. When the oxygen concentration difference is less than the predetermined value A, it is determined that air has not entered the circulation passage. Here, the oxygen concentration difference is a difference between the first oxygen concentration and the second oxygen concentration. In other words, the oxygen concentration difference is that the oxygen concentration in the circulation passage is before the engine is restarted and the predetermined period 1 is elapsed after the engine is stopped and before the engine is restarted and the predetermined period 2 is elapsed after the engine is stopped. This corresponds to the increase in the oxygen concentration in the circulation passage during the period up to this point. That is, the air intrusion determining means determines that there is air intrusion into the circulation passage when the increase in oxygen concentration in the circulation passage during the same period is equal to or greater than the predetermined value A, and When the increase in oxygen concentration is less than the predetermined value A, it is determined that there is no air intrusion into the circulation passage.

  The predetermined value A is a threshold value for determining whether air has entered the circulation passage. The predetermined value A is based on, for example, the detection accuracy of the oxygen concentration detection means, for example, before the engine is restarted and after the predetermined period 1 has elapsed after the engine is stopped, before the engine is restarted, and after the engine is stopped, the predetermined period 2 The increase in oxygen concentration in the circulation passage during the period up to the point of time can be determined in consideration of the minimum value that can be regarded as significant. The air intrusion determining means determines the presence or absence of air intrusion into the circulation passage based on the predetermined value A as the threshold value, and the determination result is, for example, a warning that informs the air intrusion into the circulation passage; It can be used for conditional branching of whether or not to execute other processing such as prohibition of engine restart and purging of air that has entered the circulation passage.

  The predetermined period 1, the predetermined period 2, and the predetermined value A are similar to the algorithm for determining whether air has entered the circulation passage, for example, a ROM or RAM provided in the ECU, etc. Is stored in the storage device as data, and the CPU provided in the ECU defines the processing corresponding to the algorithm (for example, detection of the first oxygen concentration and the second oxygen concentration, detection of air intrusion into the circulation passage). It may be referred to when the presence / absence determination or the like is executed.

By the way, as the fuel used in the working gas circulation engine according to the present invention, various fuels such as gasoline, light oil, natural gas, propane, and hydrogen can be used. However, as described above, an object of the present invention is to quickly and accurately determine the intrusion of air into the circulation passage of burned gas in a working gas circulation engine. In a working gas circulation engine, it is necessary to remove combustion products generated as a result of fuel combustion in the combustion chamber from the burned gas. From this point of view, it is desirable that the above-mentioned fuel produce only combustion products that can be easily removed from burned gas. Specifically, hydrogen is desirable as the fuel. The use of hydrogen as a fuel is desirable because it produces only water (H ₂ O) as a combustion product.

The oxidizer may be any oxidizer as long as it can oxidize fuel in the combustion chamber of the engine to generate heat and expand the working gas to generate power. However, the oxidizer also produces its own reductant in addition to the oxidant of the fuel as a result of oxidizing (burning) the fuel. In a working gas circulation engine, it is necessary to remove such oxidant and reductant from burnt gas. From this point of view, it is desirable that the oxidant generates only an oxidant of the fuel and a reductant of the oxidant that can be easily removed from the burned gas. Specifically, oxygen is desirable as the oxidizing agent. When oxygen as an oxidizer is used in combination with hydrogen as the above-mentioned desirable fuel, only water (H ₂ O), which is an oxidant of combustion (hydrogen) and a reductant of oxidant (oxygen), is produced by combustion. This is desirable because it occurs as a product.

  Furthermore, as the working gas, for example, various gases such as air and nitrogen can be used. From the viewpoint of improving the thermal efficiency of the engine, it is desirable to use a gas having a large specific heat ratio. In addition, it is desirable to use an inert gas from the viewpoint of preventing generation of harmful substances accompanying the combustion of fuel in the combustion chamber. Specifically, it is desirable to use an inert monoatomic gas such as argon, neon, or helium as the working gas. When a gas having such a large specific heat ratio is used as the working gas, the engine can be operated with higher thermal efficiency than when a gas having a relatively small specific heat ratio (for example, air, nitrogen, etc.) is used as the working gas. it can. Further, since these are inert rare gases, they are desirable because they do not generate harmful substances such as nitrogen oxides (NOx) generated when air is used as a working gas. Among these, argon is widely used as a working gas in a working gas circulation engine.

Therefore, the second aspect of the present invention is:
An air intrusion determination method for a working gas circulation engine according to the first aspect of the present invention,
The fuel, oxidant, and working gas are hydrogen, oxygen, and argon, respectively.

As described above, when hydrogen, oxygen, and argon are used as the fuel, oxidant, and working gas, respectively, only water (H ₂ O) is produced as a combustion product, and the combustion product from the burned gas. Because it is easy to remove and the specific heat ratio of the working gas is high, the thermal efficiency of the engine is increased, and furthermore, the working gas is inert and does not generate harmful substances as the fuel burns. , And working gas combinations are highly desirable.

  By the way, as described above, the determination result on the presence or absence of air intrusion into the circulation passage made by the air intrusion determination means is, for example, a warning notifying the invasion of air into the circulation passage, prohibition of engine restart , And conditional branching of whether or not to execute other processing such as purging of air that has entered the circulation passage.

  For example, when it is determined by the air intrusion determining means that air has entered the circulation passage, for example, by issuing some warning, for example, air intrusion into the circulation passage has occurred. The driver and the vehicle inspector can be informed that the airtightness of the circulation passage is inspected and the air intrusion is repaired.

Therefore, the third aspect of the present invention is
An air intrusion determination method for a working gas circulation engine according to either the first aspect or the second aspect of the present invention,
The working gas circulation engine further includes warning means, and an air intrusion determination method for the working gas circulation engine includes:
A warning step, wherein the warning means issues a warning if the oxygen concentration difference is greater than or equal to the predetermined value A, and does not issue a warning if the oxygen concentration difference is less than the predetermined value A;
Further including
An air intrusion determination method for a working gas circulation engine.

  The warning means is connected to, for example, an ECU (electronic control unit) mentioned in the description relating to the configuration of the air intrusion determining means, and issues a warning by the control of the ECU based on the determination result by the air intrusion determining means. The warning means configured as described above may be used. Further, the warning issued by the warning means need not be limited to a specific method, for example, a vehicle equipped with an engine to which the air intrusion determination method for the working gas circulation engine according to the present embodiment is applied. It may be a method (for example, warning lamp, alarm sound, voice, etc.) that appeals to the sight and hearing of the driver or vehicle inspector. However, the above description regarding the warning means is merely an example, and the configuration of the warning means is not limited to the above description.

  As described above, in the present embodiment, when the air intrusion determination unit determines that there is air intrusion into the circulation passage, for example, to the working gas circulation engine according to the present embodiment, By lighting of warning lamps arranged on dashboards such as instrument panels (instrumental panels) of vehicles equipped with engines to which the air intrusion detection method is applied, by sounding alarm sounds and voices via the audio system, etc. A warning is issued to the driver and vehicle inspector of the vehicle. As a result, the driver or vehicle inspector, for example, detects that air has entered the circulation passage of the engine mounted on the vehicle, and checks the airtightness of the circulation passage or checks the air flow. It is possible to start repairing the intrusion site quickly.

  By the way, as a modification of the present embodiment, a plurality of predetermined values A that are threshold values for determining whether air has entered the circulation passage may be set, and a plurality of warnings corresponding to each may be issued. . For example, a second predetermined value larger than a predetermined value A used as a threshold value when determining whether air has entered the circulation passage in the air intrusion determination method for the working gas circulation engine according to this embodiment. A is set, and the air intrusion determination method for the working gas circulation engine according to the modified example has a second warning step in which the second warning means has a second predetermined value A to which an oxygen concentration difference is applied. If this is the case, a second warning may be issued, and if the oxygen concentration difference is less than the second predetermined value A, a second warning may not be issued.

  In this case, when the oxygen concentration difference is equal to or larger than the second predetermined value A larger than the predetermined value A, the second warning is issued by the second warning step. By this second warning, the driver or vehicle inspector of the vehicle equipped with the engine to which the air intrusion determination method for the working gas circulation engine according to the modified example is applied, for example, Intrusion of air into the circulation passage is a more serious situation, and if the airtightness of the circulation passage is checked without repairing the air intrusion point immediately, the engine will eventually stop. It is possible to detect that there is a high risk of a serious situation.

  When a plurality of warnings are issued as in the above modification, a plurality of warning means are not provided, but the warning means in the method for determining air intrusion into the working gas circulation engine according to the present embodiment is provided. It may also serve as a warning means. That is, the warning means in the air intrusion determination method for the working gas circulation engine according to the present embodiment may issue a plurality of warnings based on a plurality of threshold values.

  By the way, as described above, when the intrusion of air into the circulation passage of the working gas circulation engine becomes a more serious situation, the inspection of the sealing of the circulation passage and the repair of the intrusion portion of the air are promptly performed. If left unattended, even if the engine is allowed to start, the engine may stop due to misfire or the like.

  In consideration of the above-described problems, it is desirable to prohibit the start of the engine when the air intrusion into the circulation passage of the working gas circulation engine becomes more serious.

Therefore, the fourth aspect of the present invention is:
An air intrusion determination method for a working gas circulation engine according to any one of the first to third aspects of the present invention,
The working gas circulation engine is
Start prohibition means for prohibiting engine start,
And a method for determining air intrusion into the working gas circulation engine,
The start prohibiting means prohibits engine start when the oxygen concentration difference is equal to or greater than a predetermined value B that is larger than the predetermined value A, and when the oxygen concentration difference is less than the predetermined value B. Start prohibition step that does not prohibit engine start,
Further including
An air intrusion determination method for a working gas circulation engine.

  The start prohibiting means is configured such that even when the driver or the like gives an instruction to start the engine when the increase in oxygen concentration (oxygen concentration difference) in the circulation passage in the predetermined period is equal to or greater than the predetermined value B, This is means for prohibiting starting of the engine. Specifically, the start prohibiting means can prohibit the start of the engine, for example, by shutting off power supply to an engine start motor (so-called “cell motor”).

  The predetermined value B is a threshold value for determining whether or not the degree of air intrusion into the circulation passage is at a level at which engine start should be prohibited. The predetermined value B is, for example, in the circulation passage in a period from when the predetermined period 1 has elapsed after the engine has stopped and before the engine has been restarted until before the engine has been restarted and the predetermined period 2 has elapsed after the engine has stopped. It can be determined in consideration of whether or not the increase in the oxygen concentration is such as to cause problems such as unintentional engine stop as described above.

  The starting prohibiting means prohibits starting of the engine based on the predetermined value B as the threshold when the oxygen concentration difference is equal to or larger than the predetermined value B which is larger than the predetermined value A, and the oxygen concentration difference is When it is less than the predetermined value B, the engine start is not prohibited. Thereby, according to the air intrusion determination method for the working gas circulation engine according to the present embodiment, when it is determined that the air intrusion into the circulation passage is extremely large (that is, the oxygen concentration difference is equal to or greater than the predetermined value B). In such a case, since the start of the engine is forcibly prohibited, problems such as the unintended engine stop as described above can be prevented in advance.

  As is well known, the main components of air are nitrogen and oxygen. Therefore, when air enters the burned gas circulation passage of the working gas circulation engine, oxygen contained in the entered air may be consumed and reduced as an oxidant during fuel combustion in the engine. However, since nitrogen does not contribute to the combustion of fuel, it is accumulated in the circulation passage without being consumed. As described above, the specific heat ratio of nitrogen is low compared to the specific heat ratio of a working gas (for example, an inert monoatomic gas) generally used in a working gas circulation engine.

  As a result, when air enters into the burned gas circulation passage of the working gas circulation engine, nitrogen having a relatively low specific heat ratio is accumulated in the circulation passage of the engine. A specific heat ratio will fall and the thermal efficiency of the said engine will fall. In other words, in a working gas circulation engine in which air has entered the circulation passage, in order to maintain the thermal efficiency of the engine at a good level, the nitrogen accumulation amount in the circulation passage has a substantial influence on the engine thermal efficiency. It is necessary to maintain it below the level that does not affect

Accordingly, the fifth aspect of the present invention provides
An air intrusion determination method for a working gas circulation engine according to any one of the first to fourth aspects of the present invention,
The working gas circulation engine is
A nitrogen accumulation amount estimating means for estimating a nitrogen accumulation amount, which is an accumulation amount of nitrogen that has entered the circulation passage, based on a fluctuation history of the oxygen concentration detected by the oxygen concentration detection means; and the operation in the circulation passage. Working gas filling means for filling the gas,
And a method for determining air intrusion into the working gas circulation engine,
The nitrogen accumulation amount estimation means estimates the nitrogen accumulation amount based on the fluctuation history of the oxygen concentration detected by the oxygen concentration detection means, and the working gas filling means includes the nitrogen accumulation amount When the amount is equal to or larger than a predetermined value C, the working gas is additionally filled in the circulation passage, and when the nitrogen accumulation amount is less than the predetermined value C, the operation is performed in the circulation passage. Working gas filling step, no additional gas filling,
Further including
An air intrusion determination method for a working gas circulation engine.

  As described above, the nitrogen accumulation amount estimation means estimates the nitrogen accumulation amount that is the accumulation amount of nitrogen that has entered the circulation passage based on the fluctuation history of the oxygen concentration detected by the oxygen concentration detection means. More specifically, the nitrogen accumulation amount estimation means, for example, stores the oxygen concentration difference calculated every time the above-described air intrusion determination step is executed, for example, a storage device (for example, ROM, RAM, The concentration of nitrogen (intrusion amount) corresponding to each oxygen concentration difference is calculated on the basis of the ratio of the known constituents of air. The nitrogen accumulation amount estimating means can estimate the nitrogen accumulation amount by calculating the total value of the amounts of nitrogen that have entered the circulation passage thus calculated.

  Note that the above-described processing algorithm executed by the nitrogen accumulation amount estimating unit may be implemented as software (for example, a program or the like) or as hardware (for example, an arithmetic circuit or the like), for example. It may be. For example, in general, such an algorithm is stored as a program in a storage device (for example, ROM, RAM, HDD, or nonvolatile memory) provided in the ECU, and is defined by the program by a CPU provided in the ECU. It is mounted so that the process (calculation of nitrogen accumulation amount) is executed.

  The working gas filling means is means for filling the working gas into the circulation passage. For example, the working gas filling means includes a working gas storage section (for example, a tank, a cylinder, etc.) for storing the working gas, a working gas supply path for communicating the working gas storage section and the circulation passage, and the working gas supply path. And a working gas flow rate adjusting means (for example, a variable throttle valve) that adjusts the flow rate of the working gas. In this case, the working gas filling means may be of a type that supplies the working gas into the circulation passage by the pressure of the working gas itself stored in the working gas storage section, or is interposed in the working gas supply path. It may be of the type that increases the pressure of the working gas by a compressor (for example, a compressor, a pump, etc.) and supplies the working gas into the circulation passage.

  Further, the predetermined value C is a threshold value for determining whether or not the accumulated amount of nitrogen that has entered the circulation passage is at a level at which the working gas filling means should be activated to add working gas to the circulation passage. It is. As the predetermined value C, for example, the nitrogen accumulation amount (nitrogen accumulation amount) in the circulation passage estimated based on the fluctuation history of the oxygen concentration in the circulation passage by the nitrogen accumulation amount estimation means is thus accumulated. It can be determined in consideration of whether the specific heat ratio of the working gas including nitrogen as a whole is lowered and the thermal efficiency of the engine is substantially affected.

  The working gas filling means additionally fills the circulating gas with the working gas based on the predetermined value C as the threshold when the nitrogen accumulation amount is not less than a predetermined value C. When the nitrogen accumulation amount is less than the predetermined value C, the working gas is not additionally filled in the circulation passage. Thereby, according to the air intrusion determination method for the working gas circulation engine according to the present embodiment, when it is determined that the accumulated amount of nitrogen that has entered the circulation passage (nitrogen accumulated amount) is extremely large (that is, nitrogen When the accumulated amount is equal to or greater than the predetermined value C), the working gas is additionally filled in the circulation passage, so that the specific heat ratio as a whole of the working gas containing nitrogen accumulated as described above is reduced, and as a result As a result, the problem that the thermal efficiency of the engine is reduced can be avoided.

  By the way, the amount of working gas additionally filled in the circulation passage by the working gas filling means when the nitrogen accumulation amount estimated by the nitrogen accumulation amount estimating means is equal to or larger than a predetermined value C is set in the present embodiment. It can be determined as appropriate according to the configuration of the system including the engine to which the air intrusion determination method for the working gas circulation engine according to the aspect is applied.

  For example, the system includes a working gas filling port that is filled with a new working gas by the working gas filling means, and an existing existing in the circulation passage according to a new working gas filling amount when the working gas is filled. An existing gas discharge port for discharging gas from the circulation passage, and a space in the corresponding circulation passage between the working gas filling port and the existing gas discharge port (hereinafter referred to as “purge space”). When the existing gas that is present is replaced by the working gas that is additionally filled into the circulation passage by the working gas filling means, the nitrogen contained in the gas that exists in the circulation passage other than the purge space is replaced. In the purge space, the amount of nitrogen is, for example, the amount obtained by subtracting the amount of nitrogen that is not replaced from the amount of nitrogen that is allowed to remain from the viewpoint of the thermal efficiency of the engine, for example. Until also reduced, existing gas must be replaced by a new working gas.

  Alternatively, in the configuration in which the mixed gas is discharged from the circulation passage after the working gas newly filled by the working gas filling means is mixed with the existing gas in the circulation passage, as described above, Compared to a configuration in which the existing gas is replaced by a new working gas, more working gas needs to be additionally filled.

  As mentioned above, although several embodiments of the method for determining air intrusion into the working gas circulation engine according to the present invention have been described, the scope of the present invention is not limited to these methods, and these methods are realized. An apparatus for determining air intrusion into a working gas circulation engine is also included in the scope of the present invention. The details of these devices are clear from the description of the method for determining the air intrusion into the working gas circulation engine according to each of the embodiments described so far, and will not be described here again. Only the configuration requirements of the air intrusion determination device for the circulation engine are listed below.

That is, the sixth aspect of the present invention is
A working gas circulation engine that obtains power by directing fuel, oxidant, and working gas to a combustion chamber, and burning the fuel in the combustion chamber;
A circulation passage for circulating the burned gas released from the combustion chamber to the combustion chamber;
Oxygen concentration detection means for detecting the oxygen concentration in the circulation passage, and air intrusion determination means for judging whether air has entered the circulation passage based on the oxygen concentration detected by the oxygen concentration detection means,
In a working gas circulation engine comprising:
The oxygen concentration detecting means detects a first oxygen concentration that is an oxygen concentration in the circulation passage at a time point when a predetermined period 1 has elapsed after the engine is stopped and before the engine is started;
The oxygen concentration detecting means detects a second oxygen concentration which is an oxygen concentration in the circulation passage at a time point that is longer than the predetermined period 1 after the engine is stopped and before the engine is started, and the air If the oxygen concentration difference, which is a difference obtained by subtracting the first oxygen concentration from the second oxygen concentration, is greater than or equal to a predetermined value A, the intrusion determination means has air intrusion into the circulation passage. It is determined that there is no oxygen intrusion into the circulation passage when the oxygen concentration difference is less than the predetermined value A,
That is structured as
An air intrusion determination device for a working gas circulation engine.

The seventh aspect of the present invention is
An air intrusion determination device for a working gas circulation engine according to the sixth aspect of the present invention,
The fuel, oxidant, and working gas are hydrogen, oxygen, and argon, respectively.

Furthermore, the eighth aspect of the present invention provides
An apparatus for determining air intrusion into a working gas circulation engine according to either the sixth aspect or the seventh aspect of the present invention,
The working gas circulation engine further includes warning means, and the warning means issues a warning when the oxygen concentration difference is equal to or greater than the predetermined value A, and the oxygen concentration difference is less than the predetermined value A. If you do not warn,
That is structured as
An air intrusion determination device for a working gas circulation engine.

In addition, the ninth aspect of the present invention provides:
An apparatus for determining air intrusion into a working gas circulation engine according to any one of the sixth to eighth aspects of the present invention,
The working gas circulation engine is
Start prohibition means for prohibiting engine start,
And the start prohibiting means prohibits engine start when the oxygen concentration difference is greater than or equal to a predetermined value B that is greater than the predetermined value A, and the oxygen concentration difference is less than the predetermined value. If it is less than B, do not prohibit starting the engine.
That is structured as
An air intrusion determination device for a working gas circulation engine.

Still further, the tenth aspect of the present invention provides
An apparatus for determining air intrusion into a working gas circulation engine according to any of the sixth to ninth aspects of the present invention,
The working gas circulation engine is
A nitrogen accumulation amount estimating means for estimating a nitrogen accumulation amount, which is an accumulation amount of nitrogen that has entered the circulation passage, based on a fluctuation history of the oxygen concentration detected by the oxygen concentration detection means; and the operation in the circulation passage. Working gas filling means for filling the gas,
And the nitrogen accumulation amount estimation means estimates the nitrogen accumulation amount based on the fluctuation history of the oxygen concentration detected by the oxygen concentration detection means,
The working gas filling means additionally fills the circulation passage with the working gas when the nitrogen accumulation amount is greater than or equal to a predetermined value C, and the nitrogen accumulation amount is less than the predetermined value C. In some cases, the working gas is not additionally filled in the circulation passage.
That is structured as
An air intrusion determination device for a working gas circulation engine.

  As described above, according to the air intrusion determination method and the air intrusion determination device for the working gas circulation engine according to the various embodiments of the present invention, the oxygen concentration in the circulation passage after the engine is stopped and before the restart is determined. Detection is performed by the detection means, and the presence or absence of air intrusion into the circulation passage is determined based on the difference between these oxygen concentrations. Thereby, according to this invention, the penetration | invasion of the air to the circulation path of the burned gas in a working gas circulation type engine can be determined rapidly and with high precision. As a result, according to the present invention, it is possible to prevent problems such as a decrease in the thermal efficiency of the engine due to the intrusion of air into the circulation passage.

  Hereinafter, an air intrusion determination method and an air intrusion determination device for a working gas circulation engine according to some embodiments of the present invention will be described with reference to the accompanying drawings. However, the following description is for illustrative purposes only, and the scope of the present invention should not be construed as being limited to the following description.

1) Configuration of a system including a working gas circulation engine As described above, FIG. 1 illustrates a working gas circulation engine to which an air intrusion determination method for a working gas circulation engine according to one embodiment of the present invention is applied. 1 is a schematic diagram illustrating a configuration of a system including The system includes a main body 110 of a working gas circulation engine, a fuel supply unit 130, an oxygen supply unit 140, a working gas supply unit (working gas filling unit) 150, a circulation passage unit 160, and a condensing unit 170. As shown in FIG. 1, this engine supplies oxygen as an oxidant and argon gas as a working gas to a combustion chamber, and compresses the gas to generate high-temperature and high-pressure hydrogen as fuel. This is an engine of a type that diffuses and burns fuel by injecting gas. 1 shows only a cross section of a specific cylinder of the engine main body 110, but in the case of an engine including a plurality of cylinders, the other cylinders have the same configuration.

  The engine main body 110 is not limited to a specific configuration, but in this embodiment, the cylinder head 111, the cylinder 112 formed by the cylinder block, the piston 113 reciprocating in the cylinder, and the crankshaft 114, a piston reciprocating motion comprising a connecting rod 115 for connecting the piston 113 and the crankshaft 114 to convert the reciprocating motion of the piston 113 into a rotational motion of the crankshaft 114, and an oil pan 116 connected to the cylinder block. Type engine.

  In this case, a piston ring is disposed on the side surface of the piston 113 (not shown), and a space formed by the cylinder head 111, the cylinder 112, and the oil pan 116 is formed by the piston 113 into a combustion chamber on the top surface side of the piston. 117 and a crankcase 118 for accommodating the crankshaft.

  The cylinder head 111 is formed with an intake port communicating with the combustion chamber 117 and an exhaust port communicating with the combustion chamber 117 (none is shown). An intake valve 121 that opens and closes the intake port is disposed at the intake port, and an exhaust valve 122 that opens and closes the exhaust port is disposed at the exhaust port. Further, the cylinder head is provided with a fuel injection valve 123 that directly injects hydrogen gas as fuel into the combustion chamber 117.

  The fuel supply unit 130 includes a fuel tank 131 (hydrogen gas tank), a fuel gas passage 132, a fuel gas pressure regulator (not shown), a fuel gas flow meter (not shown), a surge tank (not shown), and the like. be able to. The oxidant supply unit 140 includes an oxidant tank 141 (oxygen gas tank), an oxygen gas passage 142, an oxygen gas pressure regulator (not shown), an oxygen gas flow meter (not shown), and an oxygen gas mixer (not shown). ). Further, a working gas supply unit (working gas filling means) 140 includes a working gas tank 141 (argon gas tank), a working gas passage 142, a working gas pressure regulator (not shown), a working gas flow meter (not shown), and a working gas tank. A gas mixer (not shown) can be provided.

  The specific configurations and operations of the engine main body 110, the fuel supply unit 130, the oxidant supply unit 140, and the working gas supply unit 150 are well known in the art with respect to, for example, a working gas circulation hydrogen engine. Therefore, the detailed description in this specification is omitted.

  The circulation passage portion 160 includes first and second passage portions (first and second flow path forming pipes) 161 and 162, and an inlet portion and an outlet portion are provided between the first passage portion 161 and the second passage portion 162. A condensing means 170 having a portion is interposed. The circulation passage portion 160 constitutes a “circulation passage of burned gas (circulation gas)” that connects the exhaust port and the intake port outside the combustion chamber 117.

  The first passage portion 161 connects the exhaust port and the inlet portion of the condensing means 170. The second passage portion 162 connects the outlet portion of the condensing means 170 and the intake port, and the oxygen supply portion 140 and the working gas supply are provided in the middle of the second passage portion 162 via an oxygen gas mixer and a working gas mixer (not shown). Part 150 is joined.

  As described above, the condensing unit 170 includes an inlet portion and an outlet portion of burned gas (circulated gas). Further, the condensing means 170 includes a refrigerant inlet 171, a refrigerant outlet 172, and a condensed water outlet 173, and the refrigerant circulation section connecting the refrigerant inlet 171 and the refrigerant outlet 172 is used for cooling the refrigerant. A radiator 174 to be used is interposed. For example, water can be used as the refrigerant.

  Condensing means 170 introduced moisture (water vapor) contained in burned gas (circulated gas) introduced from the inlet and discharged from the outlet through the refrigerant inlet 171 and passed through the inside of the condenser 170. It is cooled and condensed by the refrigerant discharged from the refrigerant outlet 172 later. The condensed water once accumulates at the bottom of the condensing means 170 and is discharged out of the system through the condensed water discharge port 173 when a valve body (not shown) for opening and closing the condensed water discharge port 173 is opened. In other words, in the present embodiment, the bottom of the condensing means 170 functions as a condensate reservoir, and the condensate discharge port 173 and the valve body constitute a draining means. On the other hand, the gas from which moisture has been removed (separated) is discharged from the outlet of the condensing means 170 to the circulation passage 160 (second passage 162).

  As described above, in this embodiment, the condensing unit 170 uses a water-cooled condenser that can use cooling water as a refrigerant, but the condensing unit 170 uses a refrigerant other than water. It may also be provided with an air-cooled condensing unit that condenses the moisture of the gas passing through the inside by air (air blowing).

  Next, in the present embodiment, an oxygen concentration detection unit 180 (oxygen concentration detection unit) is disposed in the circulation passage unit 160 (first passage unit 161) upstream of the condensing unit. The oxygen concentration detection unit 180 detects an oxygen concentration in the first passage unit 161, and an oxygen concentration detection that sends a measurement signal (detection signal) corresponding to the oxygen concentration detected by the oxygen concentration sensor 181. A signal transmission line 182 is provided.

  As described above, the measurement signal (detection signal) corresponding to the oxygen concentration detected by the oxygen concentration sensor 181 included in the oxygen concentration detection unit 180 is, for example, sent to an ECU (not shown) by the oxygen concentration detection signal transmission line 182. Based on a program stored in a storage device (for example, ROM) provided in the ECU, the ECU determines whether or not air has entered the circulation passage (in the air intrusion determination step). It is used when the CPU provided is executed.

  In the present embodiment, as described above, the oxygen concentration detection means 180 is the oxygen concentration in the circulation passage portion 160 when the predetermined period 1 elapses after the engine 110 is stopped and before the engine 110 is restarted. 1 oxygen concentration is detected, and then the second oxygen concentration, which is the oxygen concentration in the circulation passage portion 160 at the time before the engine 110 is started, after a predetermined period 2 longer than the predetermined period 1 has elapsed after the engine 110 is stopped. If the oxygen concentration difference, which is a difference obtained by subtracting the first oxygen concentration from the second oxygen concentration, is greater than or equal to a predetermined value A detected by the air intrusion determination means (not shown). It is determined that there is air intrusion into the portion 160, and when the oxygen concentration difference is less than the predetermined value A, it is determined that there is no air intrusion into the circulation passage portion 160. A series of processes executed in the air intrusion determination method for the working gas circulation engine will be described in detail below with reference to the drawings.

2) Specific example of air intrusion determination method for working gas circulation engine (1)
As described above, in the air intrusion determination method for the working gas circulation engine according to the present invention, the first oxygen which is the oxygen concentration in the circulation passage at the time when the predetermined period 1 elapses after the engine is stopped and before the engine is started. Next, after the engine is stopped, a predetermined period 2 longer than the predetermined period 1 elapses, and a second oxygen concentration that is an oxygen concentration in the circulation passage at a time before the engine is started is detected. When the oxygen concentration difference, which is a difference obtained by subtracting the first oxygen concentration from the gas, is equal to or greater than a predetermined value A, it is determined that air has entered the circulation passage, and the oxygen concentration difference is determined to be a predetermined value. When it is less than A, it is determined that there is no air intrusion into the circulation passage. As described above, various actions (for example, issuing a warning) can be controlled based on the determination result thus obtained.

  Such a series of processes will now be described with reference to FIG. FIG. 2 is a flowchart showing a series of processing executed in the air intrusion determination method for the working gas circulation engine according to one embodiment of the present invention as described above. The series of processes shown in the flowchart can be started at an appropriate timing, for example, using a stop of the engine as a trigger.

  As shown in FIG. 2, in this embodiment, first, in step S201, the working gas circulation engine is stopped. Thereafter, when the predetermined period 1 elapses after the engine is stopped (step S202: Yes), the first oxygen concentration C1, which is the oxygen concentration in the circulation passage at this time, is detected by the oxygen concentration detecting means. For example, the storage device provided in the ECU (Eg, RAM, HDD, etc.) (step S203). However, as described above, in the predetermined period 1, in the system including the working gas circulation engine according to this embodiment, the oxygen concentration in the circulation passage immediately after the engine is stopped is the oxygen concentration as the first oxygen concentration C1. In general, a very short period is set so as to be detected by the detecting means. If the predetermined period 1 has not elapsed since the engine was stopped (step S202: No), the process waits in step S202 until the predetermined period 1 has elapsed.

  In the present embodiment, after the first oxygen concentration C1 is acquired in step S203, for example, an engine start instruction is given by a driver of a vehicle equipped with the engine (step S204). However, this step is not always essential. In any case, when the predetermined period 2 has elapsed since the engine stopped (step S205: Yes), the second oxygen concentration C2, which is the oxygen concentration in the circulation passage at this time, is detected by the oxygen concentration detecting means, for example, It is stored in a storage device provided in the ECU (step S206). However, as described above, the predetermined period 2 is longer than the predetermined period 1, and when it is assumed that air has entered the circulation path of the engine, the oxygen concentration in the circulation path is It is set as a period long enough to show a significant change. If the predetermined period 2 has not elapsed since the engine stopped (step S205: No), the process waits in step S205 until the predetermined period 2 elapses.

  As described above, the second oxygen concentration C2 may be detected immediately after the predetermined period 2 has elapsed since the engine was stopped in step S201, or after the predetermined period 2 has elapsed, An instruction may be issued and detected at a time point before the engine is actually started (that is, immediately before the engine is restarted). Note that the length of the period from when the engine is stopped to when it is restarted varies, but the predetermined period 2 may not be a fixed value as long as it does not violate the above concept.

  The series of processes in steps S201 to S203 described above correspond to the first oxygen concentration detection step in the air intrusion determination method for the working gas circulation engine according to the present invention, and the series of processes in steps S205 and S206 are: This corresponds to the second oxygen concentration detection step in the air intrusion determination method for the working gas circulation engine according to the present invention. As described above, in the air intrusion determination method for the working gas circulation engine according to the present invention, the change in the oxygen concentration in the circulation passage during the period in which the engine is stopped is detected, and the circulation is performed based on the change. Since air intrusion into the path is determined, it is difficult to be influenced by engine operating conditions, and the determination accuracy can be improved.

  Subsequently, an oxygen concentration difference ΔC is calculated from the first oxygen concentration C1 and the second oxygen concentration C2 acquired as described above (step S207). Specifically, the oxygen concentration difference ΔC can be obtained by subtracting the first oxygen concentration C1 from the second oxygen concentration C2. As described above, this process can be performed by causing the CPU to execute a program stored in a storage device included in the ECU, for example. The oxygen concentration difference ΔC is a value that is strongly related to the amount of air that has entered the inspection passage from the time when the predetermined period 1 has elapsed after the engine stop until the time when the predetermined period 2 has elapsed.

  Next, in step S208, it is determined whether or not the oxygen concentration difference ΔC obtained as described above is equal to or greater than a predetermined value A. Here, the predetermined value A is a threshold for determining whether or not air has entered the circulation passage, as described above. The predetermined value A is, for example, an increase in the oxygen concentration in the circulation passage in a period from the time when the predetermined period 1 has elapsed after the engine stop to the time when the predetermined period 2 has elapsed, based on the detection accuracy of the oxygen concentration detecting means. The threshold value is determined in consideration of the minimum value that can be considered significant. The predetermined value A takes into consideration whether or not the increase in the oxygen concentration in the circulation passage during the period from when the predetermined period 1 elapses after the engine stops until when the predetermined period 2 elapses is significant. It can be predetermined.

  In step S208, whether or not air has entered the circulation passage is determined based on the predetermined value A as the threshold value. Specifically, in step S208, if the oxygen concentration difference ΔC is greater than or equal to the predetermined value A (step S208: Yes), it is determined that air has entered the circulation passage (step S209). On the other hand, when the oxygen concentration difference ΔC is less than the predetermined value A (step S208: No), it is determined that there is no air intrusion into the circulation passage (step S210), and the series of processes shown in this flowchart is completed. Is done.

  The series of processes from step S207 to S210 described above correspond to the air intrusion determination step in the air intrusion determination method for the working gas circulation engine according to the present invention. In this embodiment, if it is determined in this air intrusion determination step that air has entered the circulation passage (step S208: Yes → step S209), a warning is issued in step S211. This step corresponds to the warning step described above. As described above, the warning need not be limited to a specific method. For example, a warning lamp, an alarm sound, a voice, etc., a method of appealing to the visual or auditory sense of the driver or vehicle inspector. Even so, it may appeal to the tactile sense of a vibrator or the like. By giving a warning in this way, for example, the driver or vehicle inspector is informed that air has entered the circulation passage, and the sealing of the circulation passage is checked or the air entry point is repaired. Etc. can be encouraged.

  Further, in the present embodiment, in step S212, it is determined whether or not the oxygen concentration difference ΔC calculated in step S207 is equal to or greater than a predetermined value B that is a value larger than the predetermined value A described above. As described above, the predetermined value B is a threshold value for determining whether or not the degree of air intrusion into the circulation passage is at a level at which engine start should be prohibited. Here, the level at which starting of the engine should be prohibited is, for example, an unintended engine as described above due to misfire in the combustion chamber due to a large amount of air entering the circulation passage. This corresponds to a significant decrease in the airtightness of the circulation passage so as to cause a problem such as a stop.

  In step S212, based on the predetermined value B as the threshold value, when the oxygen concentration difference ΔC is equal to or larger than the predetermined value B (which is a value larger than the predetermined value A) (step S212: Yes), the engine is started. If it is prohibited (step S213) and the oxygen concentration difference ΔC is less than the predetermined value B (step S212: No), the series of processing shown in this flowchart is terminated without prohibiting the engine start. This step corresponds to the start prohibition step described above.

  As a result, according to the air intrusion determination method for the working gas circulation engine according to the present embodiment, when the oxygen concentration difference ΔC is equal to or larger than the predetermined value B (step S212: Yes), air enters the circulation passage. Is determined to be extremely large, and even when an instruction to start the engine is issued by the driver or the like, the starting of the engine is forcibly prohibited. Therefore, problems such as the unintended engine stop as described above can be prevented in advance.

3) Specific example of air intrusion determination method for working gas circulation engine (2)
According to the air intrusion determination method for the working gas circulation engine according to the embodiment shown in the specific example (1), the period from the time when the predetermined period 1 has elapsed after the engine is stopped to the time when the predetermined period 2 has elapsed. The oxygen concentration difference ΔC corresponding to the increase in the oxygen concentration in the circulation passage is evaluated and determined using threshold values such as the predetermined value A and the predetermined value B. Based on the determination result, for example, to the driver or the like Various actions such as warnings of the engine and prohibition of engine restart are controlled.

  By the way, as described above, since nitrogen, which is the main component of air, does not contribute to the combustion of fuel, nitrogen contained in the air that has entered the circulation passage of the working gas circulation engine is not consumed and is not consumed in the circulation passage. Will be accumulated. Since the specific heat ratio of nitrogen is lower than the specific heat ratio of a working gas (for example, inert monoatomic gas such as argon) generally used in a working gas circulation engine, the specific heat ratio of the working gas as a whole is low. And the thermal efficiency of the engine is reduced. In other words, in a working gas circulation engine in which air has entered the circulation passage, in order to maintain the thermal efficiency of the engine at a good level, the nitrogen accumulation amount in the circulation passage has a substantial influence on the engine thermal efficiency. It is necessary to maintain it below the level that does not affect

  Such a series of processes will now be described with reference to FIG. FIG. 3 is a flowchart showing a series of processes executed in the air intrusion determination method for the working gas circulation engine according to another embodiment of the present invention as described above. The series of processes shown in the flowchart can be started at an appropriate timing, for example, using a stop of the engine as a trigger.

  As shown in FIG. 3, in this embodiment as well, as in the embodiment shown in the specific example (1), the step (S301) in which the working gas circulation engine is stopped triggers a series of processes. Each process from this step S301 to the step (S307) in which the oxygen concentration difference ΔC is calculated is the process from step S201 to step S207 in the embodiment shown in the above specific example (1). Since this is the same as the process, the description of this part is omitted in this embodiment.

As shown in FIG. 3, when the oxygen concentration difference ΔC is calculated in step S307, the nitrogen increase ΔN ₂ in the circulation path to the working gas circulation engine is estimated based on the oxygen concentration difference ΔC ( Step S308). Further, the nitrogen increase ΔN ₂ estimated this time is added to the nitrogen accumulation amount ΣN ₂ (previous update), which is the total value of the nitrogen increase ΔN ₂ estimated in the past, and new nitrogen accumulation is performed. An amount ΣN ₂ (updated this time) is obtained (step S309).

Next, in step S310, it is determined whether or not the latest nitrogen accumulation amount ΣN ₂ (updated this time) updated in this way is equal to or greater than a predetermined value C. When it is determined that the latest nitrogen accumulation amount ΣN ₂ is equal to or greater than the predetermined value C (step S310: Yes), the circulation gas is additionally filled with a working gas (Ar in this embodiment), and the circulation channel The concentration of nitrogen in the inside is reduced (step S311).

By the way, as described above, the predetermined value C is a level at which the accumulated amount of nitrogen ΣN ₂ (updated this time) that has entered the circulation passage should be added to the circulation passage by operating the working gas filling means. It is a threshold value when determining whether or not. That is, the predetermined value C is determined in advance in consideration of, for example, the minimum concentration of nitrogen that lowers the specific heat ratio of the entire working gas including nitrogen accumulated in the circulation passage and substantially affects the thermal efficiency of the engine. Determined.

In this embodiment, the working gas filling means is based on the predetermined value C as the threshold value, and when the nitrogen accumulation amount ΣN ₂ is equal to or larger than a predetermined value C, the working gas (Ar) is present in the circulation passage. Additional filling. Thereby, according to the air intrusion determination method for the working gas circulation engine according to the present embodiment, when it is determined that the accumulation amount (ΣN ₂ ) of nitrogen that has entered the circulation passage is extremely large (that is, nitrogen accumulation). When the amount ΣN ₂ is equal to or greater than the predetermined value C), the working gas is additionally filled in the circulation passage, so that the specific heat ratio as a whole of the working gas including the accumulated nitrogen is lowered, resulting in the thermal efficiency of the engine. Can be avoided.

  In addition, the series of processes in step S308 and step S309 in the present embodiment correspond to the above-described nitrogen accumulation amount estimation step. In addition, the series of processing in step S310 and step S311 in the present embodiment corresponds to the above-described working gas filling step.

  In the foregoing, for the purpose of illustrating the present invention, several embodiments having specific configurations and combinations of execution procedures have been described, but the scope of the present invention is limited to these exemplary embodiments. Instead, modifications can be appropriately made within the scope of the matters described in the claims and the specification.

  DESCRIPTION OF SYMBOLS 110 ... Engine main part, 111 ... Cylinder head, 112 ... Cylinder, 113 ... Piston, 114 ... Crankshaft, 115 ... Connecting rod, 116 ... Oil pan, 117 ... Combustion chamber, 118 ... Crankcase, 121 ... Intake valve, 122 DESCRIPTION OF SYMBOLS ... Exhaust valve, 123 ... Fuel injection valve, 130 ... Fuel supply part, 131 ... Fuel tank, 132 ... Fuel gas passage, 140 ... Oxidant supply part, 141 ... Oxidant tank, 142 ... Oxidant passage, 150 ... Working gas Supply part (working gas filling means), 151 ... working gas storage tank, 152 ... working gas passage, 160 ... circulation passage part, 161 ... first passage part (first flow path forming pipe), 162 ... second passage part ( (Second flow path forming pipe), 170 ... condensing means, 171 ... refrigerant inlet, 172 ... refrigerant outlet, 173 ... condensed water outlet, 174 ... radiator (radiator) , 180 ... oxygen concentration detection unit, 181 ... oxygen sensor, and 182 ... oxygen concentration sensing signal transmission line.

Claims (10)

A working gas circulation engine that obtains power by directing fuel, oxidant, and working gas to a combustion chamber, and burning the fuel in the combustion chamber;
A circulation passage for circulating the burned gas released from the combustion chamber to the combustion chamber;
Oxygen concentration detection means for detecting the oxygen concentration in the circulation passage, and air intrusion determination means for judging whether air has entered the circulation passage based on the oxygen concentration detected by the oxygen concentration detection means,
In a working gas circulation engine comprising:
A first oxygen concentration detecting step in which the oxygen concentration detecting means detects a first oxygen concentration which is an oxygen concentration in the circulation passage at a time point after the predetermined period 1 has elapsed after the engine is stopped and before the engine is started;
A second oxygen concentration detector for detecting a second oxygen concentration that is an oxygen concentration in the circulation passage after a predetermined period 2 longer than the predetermined period 1 has elapsed after the engine is stopped and before the engine is started; A concentration detecting step; and the circulation passage when the air intrusion determining means has an oxygen concentration difference that is a difference obtained by subtracting the first oxygen concentration from the second oxygen concentration is equal to or greater than a predetermined value A. An air intrusion determination step that determines that there is air intrusion into the air and determines that there is no air intrusion into the circulation passage when the oxygen concentration difference is less than the predetermined value A;
An air intrusion determination method for a working gas circulation engine. An air intrusion determination method for a working gas circulation engine according to claim 1,
The method for determining air intrusion into a working gas circulation engine, wherein the fuel, the oxidant, and the working gas are hydrogen, oxygen, and argon, respectively. An air intrusion determination method for a working gas circulation engine according to any one of claims 1 and 2,
The working gas circulation engine further includes warning means, and an air intrusion determination method for the working gas circulation engine includes:
A warning step, wherein the warning means issues a warning if the oxygen concentration difference is greater than or equal to the predetermined value A, and does not issue a warning if the oxygen concentration difference is less than the predetermined value A;
Further including
An air intrusion determination method for a working gas circulation engine. An air intrusion determination method for a working gas circulation engine according to any one of claims 1 to 3,
The working gas circulation engine is
Start prohibition means for prohibiting engine start,
And a method for determining air intrusion into the working gas circulation engine,
The start prohibiting means prohibits engine start when the oxygen concentration difference is equal to or greater than a predetermined value B that is larger than the predetermined value A, and when the oxygen concentration difference is less than the predetermined value B. Start prohibition step that does not prohibit engine start,
Further including
An air intrusion determination method for a working gas circulation engine. An air intrusion determination method for a working gas circulation engine according to any one of claims 1 to 4,
The working gas circulation engine is
A nitrogen accumulation amount estimating means for estimating a nitrogen accumulation amount, which is an accumulation amount of nitrogen that has entered the circulation passage, based on a fluctuation history of the oxygen concentration detected by the oxygen concentration detection means; and the operation in the circulation passage. Working gas filling means for filling the gas,
And a method for determining air intrusion into the working gas circulation engine,
The nitrogen accumulation amount estimation means estimates the nitrogen accumulation amount based on the fluctuation history of the oxygen concentration detected by the oxygen concentration detection means, and the working gas filling means includes the nitrogen accumulation amount When the amount is equal to or larger than a predetermined value C, the working gas is additionally filled in the circulation passage, and when the nitrogen accumulation amount is less than the predetermined value C, the operation is performed in the circulation passage. Working gas filling step, no additional gas filling,
Further including
An air intrusion determination method for a working gas circulation engine. A working gas circulation engine that obtains power by directing fuel, oxidant, and working gas to a combustion chamber, and burning the fuel in the combustion chamber;
A circulation passage for circulating the burned gas released from the combustion chamber to the combustion chamber;
Oxygen concentration detection means for detecting the oxygen concentration in the circulation passage, and air intrusion determination means for judging whether air has entered the circulation passage based on the oxygen concentration detected by the oxygen concentration detection means,
In a working gas circulation engine comprising:
The oxygen concentration detecting means detects a first oxygen concentration that is an oxygen concentration in the circulation passage at a time point when a predetermined period 1 has elapsed after the engine is stopped and before the engine is started;
The oxygen concentration detecting means detects a second oxygen concentration which is an oxygen concentration in the circulation passage at a time point that is longer than the predetermined period 1 after the engine is stopped and before the engine is started, and the air If the oxygen concentration difference, which is a difference obtained by subtracting the first oxygen concentration from the second oxygen concentration, is greater than or equal to a predetermined value A, the intrusion determination means has air intrusion into the circulation passage. It is determined that there is no oxygen intrusion into the circulation passage when the oxygen concentration difference is less than the predetermined value A,
That is structured as
An air intrusion determination device for a working gas circulation engine. An apparatus for determining air intrusion into a working gas circulation engine according to claim 6,
An apparatus for determining air intrusion into a working gas circulation engine, wherein the fuel, the oxidant, and the working gas are hydrogen, oxygen, and argon, respectively. An apparatus for determining air intrusion into a working gas circulation engine according to any one of claims 6 and 7,
The working gas circulation engine further includes warning means, and the warning means issues a warning when the oxygen concentration difference is equal to or greater than the predetermined value A, and the oxygen concentration difference is less than the predetermined value A. If you do not warn,
That is structured as
An air intrusion determination device for a working gas circulation engine. An apparatus for determining air intrusion into a working gas circulation engine according to any one of claims 6 to 8,
The working gas circulation engine is
Start prohibition means for prohibiting engine start,
And the start prohibiting means prohibits engine start when the oxygen concentration difference is greater than or equal to a predetermined value B that is greater than the predetermined value A, and the oxygen concentration difference is less than the predetermined value. If it is less than B, do not prohibit starting the engine.
That is structured as
An air intrusion determination device for a working gas circulation engine. An apparatus for determining air intrusion into a working gas circulation engine according to any one of claims 6 to 9,
The working gas circulation engine is
A nitrogen accumulation amount estimating means for estimating a nitrogen accumulation amount, which is an accumulation amount of nitrogen that has entered the circulation passage, based on a fluctuation history of the oxygen concentration detected by the oxygen concentration detection means; and the operation in the circulation passage. Working gas filling means for filling the gas,
And the nitrogen accumulation amount estimation means estimates the nitrogen accumulation amount based on the fluctuation history of the oxygen concentration detected by the oxygen concentration detection means,
The working gas filling means additionally fills the circulation passage with the working gas when the nitrogen accumulation amount is greater than or equal to a predetermined value C, and the nitrogen accumulation amount is less than the predetermined value C. In some cases, the working gas is not additionally filled in the circulation passage.
That is structured as
An air intrusion determination device for a working gas circulation engine.

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