JP6200464B2 - EGR unit and marine engine system - Google Patents

Description

  The present invention relates to an EGR unit that recirculates part of exhaust gas to an engine, and more particularly to an EGR unit of a marine engine system that includes a cleaning device that cleans exhaust gas to be recirculated.

  As a technique for reducing the amount of NOx discharged from the engine, there is exhaust gas recirculation (hereinafter referred to as “EGR”) in which a part of the exhaust gas is extracted and recirculated to the engine. In particular, in a marine engine system, exhaust gas to be recirculated (hereinafter referred to as “EGR gas”) includes suspended particulate matter (hereinafter referred to as “SPM”) such as carbon and sulfur oxide (SOx). In the case where a large amount of is contained, it is common to clean the EGR gas using a wet cleaning device (scrubber) in the EGR unit.

  In an EGR unit having a cleaning device, a mist-like cleaning liquid generated in the cleaning device (hereinafter referred to as “cleaning liquid mist”) is carried downstream from the cleaning device, or further from a cooler located downstream from the cleaning device. The phenomenon of “carry over” that is carried over downstream may occur. When carry-over occurs and as a result, the cleaning liquid mist enters the engine or auxiliary equipment, there is a possibility that problems such as seizure occur due to a sliding failure of the sliding portion. In addition, since the EGR gas that has passed through the cleaning device is in a saturated state, water droplets may be generated by condensation on the downstream side of the mist removing unit or the cooler even if carryover does not occur. However, there are few water droplets generated by condensation, and this alone does not cause a problem in the engine or the like.

  As described above, carryover is a very dangerous phenomenon, and if it can be detected only by whether carryover has occurred or not, the reliability of the EGR unit and the engine system including the same is improved. However, there has never been an EGR unit that can detect carryover. Since carry-over is a phenomenon in which water droplets are included in the EGR gas, if a device capable of detecting water droplets in the air is used, it should be possible to determine whether or not carry-over has occurred. Although it is away from the technical field of EGR, as a device for detecting water droplets in the air, a device that uses a current change caused by the water droplets adhering to the insulating portion (see Patent Document 1), scattering when light is applied to the water droplets There is one that utilizes the generation of light (see Patent Document 2) and one that detects water droplets by image processing.

JP-A-6-154654 JP 2011-27741 A

  However, among the devices described above, a device that detects a water droplet by the attachment of a water droplet also reacts to a water droplet generated by condensation, and therefore cannot be used to determine whether or not a carry-over has occurred. In addition, since an apparatus that uses scattered light also detects light reflected by a pipe wall through which EGR gas passes, this apparatus cannot be used to determine whether carryover has occurred. Furthermore, the image processing apparatus cannot be used in an environment where vibration occurs at a high temperature near the engine. Thus, it is very difficult to determine whether or not carry-over has occurred using a conventional apparatus for detecting water droplets. Therefore, the inventors have examined a method other than directly detecting a water droplet as a method for determining whether or not carry-over has occurred.

This invention is made in view of such a situation, and provides the EGR unit of the marine engine system which can determine whether the carry over has occurred , or can perform a predetermined | prescribed process at the time of a carry over occurrence. The purpose is that.

  An EGR unit of a marine engine system according to an embodiment of the present invention includes: a cleaning device that collects cleaning liquid contained in EGR gas by a mist removing unit after cleaning EGR gas using a cleaning liquid; and the mist removing unit An arithmetic control unit that obtains a differential pressure between the upstream side and the downstream side and determines that a carry-over has occurred when the differential pressure exceeds a threshold value.

  Here, it has been found by the inventors' tests that the differential pressure between the upstream side and the downstream side of the mist removing unit rapidly increases when a carry-over occurs such that the cleaning liquid mist is carried downstream from the cleaning device. Therefore, if it is determined that carryover has occurred when the differential pressure exceeds the threshold as described above, the occurrence of carryover can be reliably detected.

  In the EGR unit, the threshold value may be set based on an engine load and an EGR rate, or an engine load and an exhaust gas circulation ratio. According to such a configuration, an appropriate threshold value can be set.

  An EGR unit of a marine engine system according to another embodiment of the present invention includes a cleaning device that cleans EGR gas using a cleaning liquid, and a consumption amount of the cleaning liquid in the cleaning device is larger than an evaporation amount of the cleaning liquid in the cleaning device. And an arithmetic and control unit that determines that carry-over sometimes occurs.

  When a carry-over that causes the cleaning liquid mist to be carried downstream from the cleaning apparatus occurs, not only the water vapor contained in the EGR gas but also the mist-like cleaning liquid flows downstream from the cleaning apparatus. It will exceed the amount of evaporation. Therefore, as described above, when the consumption amount of the cleaning liquid is larger than the evaporation amount, it can be determined that carry-over has occurred.

  In the EGR unit, the evaporation amount may be calculated based on a difference between an amount of water vapor contained in the EGR gas before cleaning and an amount of water vapor contained in the EGR gas after cleaning. According to such a configuration, the evaporation amount can be reliably calculated, and as a result, it can be determined whether or not carry-over has occurred.

  An EGR unit of a marine engine system according to still another embodiment of the present invention includes a cleaning device that cleans EGR gas using a cleaning liquid, a cooler that is disposed downstream of the cleaning device and cools EGR gas, An arithmetic and control unit that determines that a carry-over has occurred when the amount of drain from the cooler is a predetermined amount greater than the amount of condensed water generated by cooling the EGR gas with the cooler. Yes.

  When a carry-over that causes the cleaning liquid mist to be carried downstream from the cleaning device occurs, not only the condensed water but also the cleaning liquid mist is collected in the cooler, so that the amount of drain becomes larger than the amount of condensed water. Therefore, as described above, when the drain amount is larger than the amount of condensed water by a predetermined amount, it can be determined that carry-over has occurred.

  An EGR unit of a marine engine system according to still another embodiment of the present invention includes a cleaning device that cleans EGR gas using a cleaning liquid, a cooler that is disposed downstream of the cleaning device and cools EGR gas, Compared with the reservoir portion for storing the liquid generated or captured by the cooler for use as a cleaning solution, and the amount of water in the EGR gas reduced when the EGR gas passes through the cleaning device and the cooler, An arithmetic and control unit that determines that carry-over has occurred when the increase in the amount of cleaning liquid stored in the liquid storage portion is small.

  Usually, since the EGR gas is cooled when passing through the cleaning device and the cooler, the moisture contained in the EGR gas is condensed and condensed water is generated. For this reason, when this condensed water is supplied to the liquid storage part in which the cleaning liquid is stored, the cleaning liquid in the liquid storage part increases by the amount of the generated condensed water. However, when a carry-over occurs in which the cleaning liquid mist is carried over to the downstream of the cooler, a part of the cleaning liquid does not return to the reservoir portion, and thus the amount of increase in the cleaning liquid is reduced compared to the amount of condensed water generated. Therefore, when the increase amount of the cleaning liquid stored in the liquid storage portion is smaller than the amount of water reduced when the EGR gas passes through the cleaning device and the cooler, it is determined that a carry-over has occurred. it can.

  In the above EGR unit, the arithmetic and control unit may decrease the flow rate of the EGR gas passing through the cleaning device when it is determined that carry-over has occurred. According to such a configuration, the amount of the cleaning liquid mist can be suppressed to an amount that can be processed by the mist removing unit, or the flow rate of the cleaning liquid mist flowing to the downstream side of the cleaning device can be reduced. For this reason, for example, when the EGR unit has a mist removing unit, it is possible to use a mist removing unit that has a reduced processing capacity compared to the conventional case and to avoid this when a carry-over occurs. Therefore, the mist removing unit can be reduced in size.

  In the above EGR unit, when the arithmetic and control unit determines that carry-over has occurred, the arithmetic and control unit may reduce the amount of cleaning liquid that the EGR gas contacts during cleaning. Even in such a configuration, the amount of the cleaning liquid mist can be suppressed to an amount that can be processed by the mist removing unit, or the flow rate of the cleaning liquid mist flowing to the downstream side of the cleaning device can be reduced.

  In the above EGR unit, the arithmetic and control unit may decrease the flow rate of the EGR gas discharged from the EGR unit when it is determined that carry-over has occurred. According to such a configuration, at least the flow rate of the cleaning liquid mist flowing to the downstream side of the cleaning device can be reduced.

  An EGR unit of a marine engine system according to still another embodiment of the present invention includes a cleaning device that cleans EGR gas using a cleaning liquid and an arithmetic and control unit, and the cleaning device includes a cleaning liquid included in the EGR gas. A mist removing unit that collects the mist removing unit, and a cleaning device that operates to clean the mist removing unit, wherein the arithmetic control unit is configured such that the differential pressure between the upstream side and the downstream side of the mist removing unit is a predetermined threshold value. And the cleaning device is operated to clean the mist removing portion when the consumption of the cleaning solution in the cleaning device is not larger than the evaporation amount of the cleaning solution in the cleaning device.

  In the case where the cleaning device has a mist removing unit, when carry-over occurs, the differential pressure between the upstream side and the downstream side of the mist removing unit rapidly increases. Therefore, it is possible to determine that carry-over has occurred when the differential pressure exceeds a threshold value. However, as a factor that increases the differential pressure between the upstream side and the downstream side of the mist removing unit, clogging of the mist removing unit due to foreign matters can be considered in addition to the occurrence of carryover. Even if the differential pressure between the upstream side and the downstream side of the mist removing unit exceeds a predetermined threshold, if the consumption of the cleaning liquid in the cleaning device is not larger than the evaporation amount of the cleaning solution in the cleaning device, the mist removing unit is clogged. The possibility is high. In the above configuration, when the differential pressure between the upstream side and the downstream side of the mist removing unit exceeds a predetermined threshold and the consumption amount of the cleaning liquid in the cleaning device is not larger than the evaporation amount of the cleaning solution in the cleaning device, the mist removing unit Therefore, the clogging of the mist removing portion is eliminated, and stable carryover can be determined.

  An EGR unit of a marine engine system according to still another embodiment of the present invention includes a cleaning device that cleans EGR gas using a cleaning liquid, a cooler that is disposed downstream of the cleaning device, and cools EGR gas, A control device, and the cleaning device includes a mist removing unit that collects the cleaning liquid contained in the EGR gas, and a cleaning device that operates to clean the mist removing unit, and the arithmetic control unit Is based on the amount of condensed water generated when the differential pressure between the upstream side and the downstream side of the mist removing unit exceeds a predetermined threshold and the drain amount from the cooler is cooled by the cooler. If the predetermined amount is not larger, the cleaning device is operated to clean the mist removing portion.

  Even if the differential pressure between the upstream side and the downstream side of the mist removing unit exceeds a predetermined threshold, the amount of drain from the cooler is larger than the amount of condensed water generated by cooling the EGR gas with the cooler. If not, there is a high possibility that clogging has occurred in the mist removing section. According to the above configuration, since the mist removing unit is cleaned in such a case, the clogging of the mist removing unit can be eliminated, and stable carryover can be determined.

  An EGR unit of a marine engine system according to still another embodiment of the present invention includes a cleaning device that collects cleaning liquid contained in EGR gas by a mist removing unit after cleaning EGR gas using cleaning liquid, and the mist removal An arithmetic and control unit that obtains a differential pressure between the upstream side and the downstream side of the unit and performs a predetermined process when the differential pressure exceeds a threshold value.

  An EGR unit of a marine engine system according to still another embodiment of the present invention includes a cleaning device that cleans EGR gas using a cleaning liquid, and a consumption amount of the cleaning liquid in the cleaning device is larger than an evaporation amount of the cleaning liquid in the cleaning device. And an arithmetic and control unit that performs predetermined processing when it is large.

  An EGR unit of a marine engine system according to still another embodiment of the present invention includes a cleaning device that cleans EGR gas using a cleaning liquid, a cooler that is disposed downstream of the cleaning device and cools EGR gas, An arithmetic and control unit that performs a predetermined process when the amount of drain from the cooler is larger by a predetermined amount than the amount of condensed water generated by cooling the EGR gas by the cooler.

  An EGR unit of a marine engine system according to still another embodiment of the present invention includes a cleaning device that cleans EGR gas using a cleaning liquid, a cooler that is disposed downstream of the cleaning device and cools EGR gas, Compared with the reservoir portion for storing the liquid generated or captured by the cooler for use as a cleaning solution, and the amount of water in the EGR gas reduced when the EGR gas passes through the cleaning device and the cooler, And an arithmetic and control unit that performs a predetermined process when the increase amount of the cleaning liquid stored in the liquid storage part is small.

  The marine engine system which concerns on a certain form of this invention is equipped with said EGR unit.

  As described above, according to the above EGR unit, it is possible to determine the occurrence of carryover.

FIG. 1 is a block diagram of an engine system according to an embodiment of the present invention. FIG. 2 is a diagram showing the relationship between the flow rate of EGR gas and the differential pressure across the front and back. FIG. 3 is a flowchart of the first determination method. FIG. 4 is a diagram in which threshold curves and the like used for the above control are superimposed on FIG. FIG. 5 is a graph illustrating an example of a threshold setting method. FIG. 6 is a flowchart of the second determination method. FIG. 7 is a flowchart of the third determination method. FIG. 8 is a flowchart of the fourth determination method. FIG. 9 is a flowchart of the fifth determination method. FIG. 10 is a flowchart of the sixth determination method. FIG. 11 is a block diagram of an engine system according to a first modification. FIG. 12 is a block diagram of an engine system according to a second modification. FIG. 13 is a block diagram of an engine system according to a third modification. FIG. 14 is a block diagram of an engine system according to a fourth modification.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Below, the same code | symbol is attached | subjected to the element which is the same or it corresponds through all the drawings, and the overlapping description is abbreviate | omitted.

<Engine system>
First, the overall configuration of the engine system 100 will be described with reference to FIG. FIG. 1 is a block diagram of an engine system 100 according to the present embodiment. A thick broken line in FIG. 1 indicates the flow of the supply gas supplied to the engine 10, and a thick solid line indicates the flow of the exhaust gas discharged from the engine 10. As will be described later, since the engine 10 of the present embodiment is a two-stroke engine, the “supply gas” is a so-called “scavenging gas”. However, when the engine 10 is a four-stroke engine, it is a so-called “air supply gas”.

  As shown in FIG. 1, the engine system 100 according to the present embodiment is a marine engine system, and includes an engine 10, a supercharger 20, and an EGR unit 30. The engine 10 of this embodiment is a two-stroke diesel engine for ships. However, the engine 10 may be other engines. The supercharger 20 compresses the atmospheric air taken in from the outside by the compressor unit 21 and supplies the compressed air to the engine 10 as a supply gas. The compressor unit 21 is connected to the turbine unit 22 and rotates as the turbine unit 22 rotates using exhaust gas as a drive source. The EGR unit 30 is a unit that extracts part of the exhaust gas discharged from the engine 10 and returns the extracted exhaust gas (EGR gas) to the engine 10 for recirculation. By returning the already burned exhaust gas to the engine 10, the oxygen concentration of the supply gas decreases, and the combustion temperature in the engine 10 decreases. As a result, the amount of NOx discharged from the engine 10 can be reduced.

<EGR unit>
Next, the configuration of the EGR unit 30 according to the present embodiment will be described with reference to FIG. As shown in FIG. 1, the EGR unit 30 includes a cleaning device 40, an EGR blower 60, a cooler 70, a replenishment tank 80, and an arithmetic control device 90. Hereinafter, each of these components will be described in order.

  The cleaning device (scrubber) 40 is a device for cleaning EGR gas. Since the engine 10 of the present embodiment uses heavy oil as fuel, the EGR gas contains a large amount of SPM and SOx (hereinafter referred to as “SPM or the like”). If the EGR gas is returned to the engine 10 without cleaning, SPM or the like contained in the EGR gas adversely affects the engine 10. Therefore, the EGR gas is supplied to the engine 10 after removing SPM and the like from the EGR gas by the cleaning device 40. The cleaning device 40 of the present embodiment is an injection type cleaning device, and includes an injection unit 41 that injects a cleaning liquid. When EGR gas flows into the cleaning device 40, cleaning water is injected from the injection unit 41. As a result, the cleaning liquid captures the SPM in the EGR gas, the cleaning liquid having a large particle diameter falls by its own weight, and the cleaning liquid having a small particle diameter is conveyed to the mist removing unit 43 described later together with the EGR gas.

  The cleaning liquid is reused in the cleaning device 40, and the cleaning liquid sprayed from the injection unit 41 is obtained by pumping the cleaning liquid collected at the bottom of the container of the cleaning device 40 by the cleaning liquid pump 42. Therefore, by adjusting the rotational speed of the cleaning liquid pump 42, the amount of the cleaning liquid ejected from the injection unit 41, and hence the amount of the cleaning liquid that comes into contact with the EGR gas during cleaning (hereinafter referred to as “the amount of liquid contact”) is adjusted. Can do. In addition, although the cleaning apparatus 40 of this embodiment is an injection type cleaning apparatus, the cleaning apparatus 40 may be other types of cleaning apparatuses such as a stored water type. In the case of a stored water type cleaning device, EGR gas is sent to the bottom of the container in which the cleaning liquid is stored, and the EGR gas and the cleaning liquid are brought into contact with each other while the EGR gas floats on the surface of the cleaning liquid. Remove. In this case, the amount of wetted liquid can be adjusted by raising or lowering the level of the cleaning liquid stored in the container.

  The cleaning device 40 includes a mist removing unit 43 that collects cleaning liquid mist. The mist removing portion 43 of the present embodiment is a so-called demister and is formed by weaving thin metal wires. However, the mist removing unit 43 may be a mist catcher or a baffle plate. When the EGR gas containing the cleaning liquid mist tries to pass through the mist removing unit 43, the cleaning liquid mist is captured by the mist removing unit 43. When the captured cleaning liquid mist collects and becomes large to some extent, it falls to the bottom on the cleaning device 40 side by its own weight. In this way, the collected cleaning liquid mist is returned to the cleaning device 40. If an amount of cleaning liquid mist exceeding the processing capability of the mist removing unit 43 is about to pass, the mist removing unit 43 is water-sealed and a carry-over occurs. In the cleaning device 40 of the present embodiment, the mist removing unit 43 is provided at one place, but it may be provided at a plurality of places in the EGR gas flow direction.

  In addition, the cleaning device 40 includes a cleaning device 44 for cleaning the mist removing unit 43. The mist removing unit 43 may be clogged due to accumulation of SPM in the EGR gas inside the mist removing unit 43. In such a case, the clogging can be eliminated by the cleaning device 44. The cleaning device 44 of the present embodiment is a cleaning type cleaning device configured to spray purified water on the mist removing unit 43. However, the cleaning device 44 may be one that blows high-pressure air, or may be configured to vibrate the mist removing unit 43 to remove substances that cause clogging. The cleaning device 44 is electrically connected to the calculation control device 90, and the cleaning device 44 is activated by a control signal transmitted from the calculation control device 90. The timing for operating the cleaning device 44 will be described later.

The cleaning device 40 is provided with a differential pressure gauge 45 that acquires pressure from both the upstream side and the downstream side of the mist removing unit 43. Differential pressure gauge 45 upstream and downstream of the differential pressure of the mist removal unit 43 (hereinafter, referred to as "differential pressure") to measure P _d. In addition, when the mist removal part 43 is arrange | positioned in multiple places, it is desirable to provide the differential pressure gauge 45 corresponding to each mist removal part 43, However, Corresponding to any one mist removal part 43 A differential pressure gauge 45 may be provided. Further, instead of the differential pressure gauge 45 described above, pressure gauges are provided on the upstream side and the downstream side of the mist removing unit 43, respectively, and the arithmetic control device 90 is operated based on the measurement signal transmitted from these pressure gauges. May be calculated (obtained). Further, the cleaning device 40 is provided with a first liquid level meter 46 for measuring the liquid level height H ₁ of the cleaning liquid accumulated in the cleaning device 40.

A first pressure gauge 47, a first thermometer 48, and a gas flow meter 49 are provided at the inlet of the cleaning device 40. The first pressure gauge 47 measures the pressure P ₁ of the EGR gas before cleaning, the first thermometer 48 measures the temperature T ₁ of the EGR gas before cleaning, and the gas flow meter 49 flows into the cleaning device 40. for measuring the flow rate _{Q g} of (dry gas). Further, a second pressure gauge 50 and a second thermometer 51 are provided on the downstream side of the mist removing unit 43 in the cleaning device 40. The second pressure gauge 50 is a pressure _{P 2} of the EGR gas is measured after the washing, the second thermometer 51 measures the temperature _{T 2} of the EGR gas after cleaning. The differential pressure gauge 45, the first liquid level gauge 46, the first pressure gauge 47, the first thermometer 48, the gas flow meter 49, the second pressure gauge 50, and the second thermometer 51 described above are respectively connected to the arithmetic control device 90. It is electrically connected and transmits a measurement signal to the arithmetic and control unit 90.

  The EGR blower 60 is a device that boosts the EGR gas. The EGR blower 60 can adjust the flow rate of the EGR gas by increasing or decreasing the rotational speed. The EGR blower 60 of this embodiment is a positive displacement blower in which the rotational speed and the flow rate of EGR gas are in a proportional relationship, and is driven by the electric motor 61. The electric motor 61 is electrically connected to the arithmetic and control unit 90, and the rotational speed of the electric motor 61 and thus the flow rate of EGR gas are set by the control signal transmitted from the arithmetic and control unit 90.

  The cooler (gas cooler) 70 is a device that cools the EGR gas. In the present embodiment, the cooler 70 is disposed on the downstream side of the EGR blower 60. Note that the EGR blower 60 may be disposed on the downstream side of the cooler 70. The cooler 70 includes a cooler main body 71 and a condensed water collecting unit 72. The cooler body 71 can reduce the EGR gas to the temperature of the supply gas. The EGR gas is lowered to the saturation temperature by the cleaning, but by further reducing the EGR gas to the temperature of the supply gas by the cooler main body 71, it is prevented that condensed water is generated when the EGR gas merges with the supply gas, Water mixing into the engine 10 can be prevented. When the EGR gas is cooled by the cooler body 71, the water vapor contained in the EGR gas is condensed to become condensed water. Since this condensed water is reused as a cleaning liquid, it is discharged from the drain port of the cooler body 71 and collected. When carry-over has occurred, not only the condensed water but also the cleaning liquid mist contained in the EGR gas is discharged from the drain port of the cooler body 71.

The condensed water collecting unit 72 is a so-called mist catcher disposed downstream of the cooler main body 71 and is a device that collects condensed water (cleaning liquid) generated in the cooler main body 71. The condensed water collecting unit 72 originally collects condensed water, but also collects the cleaning liquid mist contained in the EGR gas when carryover has occurred. The collected cleaning liquid is discharged from the drain port of the condensed water collecting unit 72. The cleaning liquid discharged from the condensed water collecting unit 72 merges with the cleaning liquid discharged from the cooler main body 71 through the drain pipe 77 and flows to the replenishing tank 80. A drain flow meter 78 is disposed in the drain pipe 77. The drain flow meter 78 can measure the amount (hereinafter referred to as “drain amount”) Q _d of the cleaning liquid discharged from the cooler 70 (the cooler main body 71 and the condensed water collecting unit 72). The cooler 70 of the present embodiment has the condensed water collecting unit 72. However, if the cooler main body 71 is configured to collect all condensed water, the condensed water collecting unit 72 is provided. May be omitted.

A third pressure gauge 73 and a third thermometer 74 are provided at the EGR gas inlet of the cooler 70. The third pressure gauge 73 measures the pressure P ₃ of the EGR gas before being cooled by the cooler 70, and the third thermometer 74 measures the temperature T ₃ of the EGR gas before being cooled by the cooler 70. Further, a fourth pressure gauge 75 and a fourth thermometer 76 are provided at the outlet of the EGR gas of the condensed water collecting unit 72. The fourth pressure gauge 75 measures the pressure P ₄ of the EGR gas after being cooled by the cooler 70, and the fourth thermometer 76 measures the temperature T ₄ of the EGR gas after being cooled by the cooler 70. The third pressure gauge 73, the third thermometer 74, the fourth pressure gauge 75, and the fourth thermometer 76 are each electrically connected to the calculation control device 90, and the measurement signal is sent to the calculation control device 90. And send.

The replenishment tank 80 is a tank that stores the liquid generated or captured by the cooler 70 for use as a cleaning liquid in the cleaning device 40. The cleaning liquid discharged from the cooler 70 flows into the supply tank 80. On the downstream side of the replenishing tank 80, a supply pump 81 for sending the stored cleaning liquid to the cleaning device 40 is provided. The supply pump 81 is electrically connected to the arithmetic control device 90 and is controlled by a control signal transmitted from the arithmetic control device 90. Further, on the downstream side of the feed pump 81, the supply flow rate meter 82 is provided for measuring the flow rate Q _f of the cleaning liquid supplied to the cleaning device 40. The supply flow meter 82 is electrically connected to the arithmetic and control unit 90 and transmits a measurement signal to the arithmetic and control unit 90. Further, the replenishment tank 80 is provided with a second liquid level gauge 83 for measuring the liquid level height H ₂ of the cleaning liquid stored in the replenishment tank 80. The second liquid level gauge 83 is electrically connected to the calculation control device 90 and transmits a measurement signal to the calculation control device 90.

In the present embodiment, control such that the liquid level of the cleaning liquid stored in the washing device 40 the height H ₁ constant is performed. First, the arithmetic and control unit 90 acquires the liquid level height H ₁ based on the measurement signal of the first liquid level gauge 46 provided in the cleaning device 40. Then, the arithmetic control device 90, the acquired liquid level H ₁ is determined to be lower than a predetermined height, and drives the supply pump 81 to the liquid level H ₁ becomes a predetermined height. In this embodiment, since the control is performed as described above, the amount of the cleaning liquid supplied from the replenishing tank 80 to the cleaning device 40, that is, the flow rate of the cleaning liquid measured by the supply flow meter 82 is the consumption amount of the cleaning liquid in the cleaning device 40. Can be considered. Unlike the present embodiment, when control is performed such that the cleaning liquid is not supplied to the cleaning device 40 even if the liquid level is lowered, the liquid level height H ₁ measured by the first liquid level meter 46 is used. By acquiring the fluctuation amount, the consumption amount of the cleaning liquid in the cleaning device 40 can be calculated.

  The arithmetic control device 90 is a device that controls the entire EGR unit 30 and is constituted by a CPU, a ROM, a RAM, and the like. As described above, the arithmetic and control unit 90 is electrically connected to each instrument, and acquires information on EGR gas, information on the cleaning liquid, and the like based on measurement signals transmitted from these instruments. And the arithmetic and control unit 90 performs various calculations based on such information. The arithmetic and control unit 90 is also electrically connected to each device other than the instrument, and transmits a control signal to these devices.

<First determination method>
Next, the first carryover determination method will be described. Here, when the carryover occurs such that the cleaning liquid mist is carried downstream from the cleaning device 40, the inventors have lost the pressure in the mist removing unit 43, that is, the differential pressure between the upstream side and the downstream side of the mist removing unit 43. It was discovered by a test that (the differential pressure before and after) increases rapidly. FIG. 2 is a graph showing the relationship between the flow rate of EGR gas and the differential pressure across the front and back. If the flow rate of the EGR gas is large, the amount of cleaning liquid mist that passes through the mist removing unit 43 increases. In FIG. 2, the EGR gas flow rate increases as the process proceeds to the right side of the drawing, and the amount of cleaning liquid mist passing through the mist removing unit 43 increases. In FIG. 2, when the speeds are V _A and V _B , no carryover has occurred. At this time, the front-rear differential pressure is maintained at a low value. On the other hand, when the speed is V _C, carryover occurs. Differential pressure across at this time, the rate is significantly higher than when the V _A and V _B.

The first carry-over determination method uses the above characteristics. As an example, carry-over determination is performed according to the procedure shown in FIG. FIG. 3 is a flowchart showing a control method of the EGR unit 30 including the first carryover determination method. The calculation and control described below are performed by the calculation control device 90. First, when the processing is started, the arithmetic and control unit 90 reads measurement signals from the first pressure gauge 47, the first thermometer 48, and the gas flow meter 49, and based on these signals, the pressure P _{1 of the} EGR gas. , the temperature _{T 1} of the EGR gas, and obtains the information of the flow rate _{Q g} of EGR gas (step S1).

  Subsequently, the arithmetic and control unit 90 calculates the pressure loss of the mist removing unit 43 in an ideal state (differential pressure before and after the mist removing unit 43) by calculation (step S2). That is, the pressure loss (hereinafter referred to as “theoretical value”) of the EGR gas generated when the EGR gas passes through the mist removing unit 43 in a normal state where no water seal or the like has occurred. The theoretical value ΔP can be obtained by the following equation.

In the above formula, “g” is the gravitational acceleration. “X”, “ε”, and “D” are the thickness, the space ratio, and the wire diameter of the mist removing unit 43, respectively, and are values specific to the mist removing unit 43. “F”, “v”, and “ρ” are the friction coefficient of EGR gas, the speed of EGR gas, and the density of EGR gas with respect to the mist removing unit 43, respectively. it can be calculated based on information of the pressure _P 1, the temperature _{T 1} of the EGR gas, and EGR gas flow rate _{Q g.}

  Subsequently, the arithmetic and control unit 90 sets a threshold value based on the above theoretical value (step S3). The threshold is set to a value slightly higher than the theoretical value (for example, a value 30% higher than the theoretical value). Thus, the reason why the threshold value is set higher than the theoretical value is that the contamination of the mist removing unit 43 and exhaust pulsation are taken into consideration. Note that how much higher the threshold value is than the theoretical value is determined by a prior test. Here, FIG. 4 is a diagram in which a curve (one-dot chain line) indicating the calculated theoretical value and a curve (two-dot chain line) indicating the threshold are superimposed on FIG. As shown in FIG. 4, the threshold is set to increase as the speed increases. Note that a different threshold may be set depending on conditions as in the present embodiment, but the threshold may always be set to a constant value.

Subsequently, the arithmetic and control unit 90 determines whether or not the measured front-rear differential pressure Pd is greater than a threshold value (step S4). Specifically, the arithmetic and control unit 90 determines that the actual front-rear differential pressure P _d (hereinafter referred to as “actually measured value”) acquired based on the measurement signal received from the differential pressure gauge 45 is greater than the threshold set in step S3. It is determined whether or not it is larger. The arithmetic and control unit 90 determines that carry-over has occurred when the measured value is greater than the threshold (step S5), and determines that carry-over has not occurred when the measured value is less than the threshold. (Step S6). If the arithmetic and control unit 90 determines that no carryover has occurred (step S6), the process ends. On the other hand, when it is determined that carryover has occurred (step S5), carryover is avoided (step S7), and the subsequent processing ends. A specific method for avoiding carryover will be described later.

  In addition, when the mist removal part 43 is provided in two places of the flow direction of EGR gas in the washing | cleaning apparatus 40 and the differential pressure gauge 45 is provided corresponding to each mist removal part 43, the following control is carried out. Is possible. That is, when the differential pressure (actual value) of the upstream mist removing unit 43 among the mist removing units 43 provided at two locations exceeds a threshold value, the arithmetic and control unit 90 issues a warning, and then the downstream side. When the differential pressure (measured value) before and after the mist removing unit 43 exceeds a threshold value, control to avoid carryover may be performed.

  In the above description, a value slightly higher than the theoretical value is set as the threshold value. However, the threshold value may be set by a method other than this. For example, a threshold value can be set based on the engine load and the EGR rate. Specifically, the arithmetic and control unit 90 stores map data or mathematical expressions corresponding to the graph as shown in FIG. 5 in advance, and sets a threshold using the map data and the calculated engine load and EGR rate. May be. The EGR rate refers to the ratio of the mass flow rate of EGR gas to the entire intake gas. In the example shown in FIG. 5, the threshold value increases as the engine load increases, and the threshold value increases as the EGR rate increases. Further, the exhaust gas circulation rate may be used in place of the EGR rate. The exhaust gas circulation rate refers to the ratio of the mass flow rate of exhaust gas extracted as EGR gas out of exhaust gas discharged from the engine. Even if the exhaust gas circulation rate is used instead of the EGR rate, the tendency of the threshold change is the same.

  As described above, according to the present embodiment, a special sensor is not required to determine whether or not carryover has occurred based on the pressure loss (front-rear differential pressure) of the mist removing unit 43. Therefore, a system for detecting carryover can be constructed at a low cost.

<Second determination method>
Next, the second carryover determination method will be described. FIG. 6 is a flowchart showing a control method of the EGR unit 30 including the second carryover determination method. The calculation and control described below are performed by the calculation control device 90. First, when the process is started, the arithmetic and control unit 90 acquires EGR gas information (step S11). Specifically, the arithmetic and control unit 90 reads measurement signals from the first pressure gauge 47, the first thermometer 48, the gas flow meter 49, the second pressure gauge 50, and the second thermometer 51. Then, based on these signals, the pressure P ₁ [kPa abs] of the EGR gas before cleaning, the temperature T ₁ [° C.] of the EGR gas before cleaning, the flow rate Q _g [kg / min] of the EGR gas, and the cleaning, respectively. Information on the pressure P ₂ [kPa abs] of the later EGR gas and the temperature T ₂ [° C.] of the EGR gas after cleaning is acquired.

Subsequently, the arithmetic and control unit 90 calculates the evaporation amount of the cleaning liquid in the cleaning device 40 based on the information acquired in step S11 (step S12). The amount of evaporation of the cleaning liquid can be obtained by subtracting the amount of water vapor contained in the EGR gas before washing from the amount of water vapor contained in the EGR gas after washing. Specifically, the evaporation amount [kg / min] of the cleaning liquid can be obtained by the following equation. Note that RH ₁ [%] in the following equation is the relative humidity of the EGR gas before cleaning, and can be calculated from the humidity of the supply gas supplied to the engine 10 and the fuel injection amount in the engine 10. RH ₂ [%] is the relative humidity of the EGR gas after cleaning, and can be calculated as 100 [%].

  Subsequently, the arithmetic control device 90 acquires the consumption amount of the cleaning liquid in the cleaning device 40 (step S13). As described above, in the present embodiment, the water level of the cleaning liquid stored in the cleaning device 40 is controlled to be constant. Therefore, the arithmetic and control unit 90 can acquire the supply amount of the cleaning liquid to the cleaning device 40 based on the measurement signal of the supply flow meter 82, and can use this supply amount as the consumption amount of the cleaning liquid in the cleaning device 40.

  Subsequently, the arithmetic and control unit 90 determines whether or not the consumption amount of the cleaning liquid in the cleaning device 40 is larger than the evaporation amount of the cleaning liquid in the cleaning device 40 (step S14). The arithmetic and control unit 90 determines that a carry-over has occurred when the consumption amount is larger than the evaporation amount (step S15), and a carry-over has occurred when the consumption amount is less than or equal to the evaporation amount. It is determined that it is not present (step S16). When the arithmetic and control unit 90 determines that no carryover has occurred (step S16), the process ends. On the other hand, when it is determined that carry-over has occurred (step S15), carry-over is avoided (step S17), and the subsequent processing ends.

  As described above, when the consumption amount is larger than the evaporation amount, it can be determined that the carry-over has occurred for the following reason. That is, when the EGR gas dried at high temperature flows into the cleaning device 40, a part of the cleaning liquid evaporates and becomes water vapor and is contained in the EGR gas. In a normal state, the evaporation amount of the cleaning liquid matches the consumption amount of the cleaning liquid. However, when a carry-over occurs such that the cleaning liquid mist is carried downstream from the cleaning device 40, not only the water vapor but also the cleaning liquid mist flows to the downstream side of the cleaning device 40. Therefore, the consumption of the cleaning liquid exceeds the evaporation amount. End up. Therefore, when the consumption amount is larger than the evaporation amount, it can be determined that carry-over has occurred.

  According to the second carry-over determination method, since it is determined whether or not carry-over has occurred based on the evaporation amount and consumption amount of the cleaning liquid in the cleaning device 40, it is possible to reliably detect the occurrence of carry-over. it can. In addition, since this carry-over determination method does not require a special sensor, a system for determining carry-over can be constructed at low cost. Further, unlike the first carry-over determination method, the cleaning device 40 can be used even when the mist removing unit 43 is not provided.

<Third determination method>
Next, a third carryover determination method will be described. FIG. 7 is a flowchart showing a control method of the EGR unit 30 including the third carryover determination method. The calculation and control described below are performed by the calculation control device 90. First, when the process is started, the arithmetic and control unit 90 acquires information on EGR gas (step S21). Specifically, the arithmetic and control unit 90 reads the measurement signals of the gas flow meter 49, the third pressure gauge 73, the third thermometer 74, the fourth pressure gauge 75, and the fourth thermometer 76. Based on these signals, EGR gas flow rate Q _g [kg / min], EGR gas pressure P ₃ [kPa abs] before cooling by cooler 70, and EGR gas temperature T ₃ [before cooling] [ ₃ ] C], EGR gas pressure P ₄ [kPa abs] after cooling, and EGR gas temperature T ₄ [° C.] after cooling.

Subsequently, the arithmetic and control unit 90 calculates the amount (condensation amount) of the cleaning liquid condensed by cooling the EGR gas by the cooler 70 based on the information acquired in step S21 (step S22). The amount of condensation can be determined by subtracting the amount of water vapor contained in the EGR gas after cooling from the amount of water vapor contained in the EGR gas before cooling. Specifically, the condensation amount [kg / min] can be obtained by the following equation. In the following formula, RH ₃ [%] is the relative humidity of the EGR gas before cooling, and RH ₄ [%] is the relative humidity of the EGR gas after cleaning, both of which are 100 [%]. Arithmetic can be performed.

  Subsequently, the arithmetic and control unit 90 sets a threshold value (step S23). The threshold is set based on the condensation amount calculated in step S22. Specifically, the threshold is set to a value that is higher than the condensation amount by a predetermined amount (for example, a value that is 10% higher than the condensation amount). It should be noted that how much the threshold value is set higher than the condensation amount is determined based on the result of a prior test.

  Subsequently, the arithmetic and control unit 90 acquires the amount (drain amount) of the cleaning liquid discharged from the cooler 70 (step S24). The arithmetic and control unit 90 can receive the measurement signal of the drain flow meter 78 and acquire (calculate) the drain amount based on the measurement signal. Alternatively, the drain amount may be calculated from the consumption amount obtained based on the measured value of the supply flow meter 82 and the liquid level fluctuation amount of the replenishing tank 80 obtained based on the measured value of the second liquid level meter 83.

  Subsequently, the arithmetic and control unit 90 determines whether or not the drain amount is larger than the threshold value (step S25). That is, it is determined whether the drain amount is larger than the aggregation amount by a predetermined amount (for example, an amount corresponding to 10% of the aggregation amount). The arithmetic and control unit 90 determines that carry-over has occurred when the drain amount is larger than the threshold (step S26), and determines that carry-over has not occurred when the drain amount is smaller than the threshold. (Step S27). If the arithmetic and control unit 90 determines that no carryover has occurred (step S27), the process ends. On the other hand, when it is determined that carry-over has occurred (step S26), carry-over is avoided (step S27), and the subsequent processing ends.

  Thus, when the drain amount is larger than the threshold value (when the predetermined amount is larger than the condensation amount), it can be determined that carry-over has occurred for the following reason. That is, when the saturated EGR gas flows in the cooler 70, the water vapor contained in the EGR gas is condensed and returned to the cleaning liquid. In the present embodiment, since all the condensed cleaning liquid is discharged, the drain amount and the condensation amount substantially coincide with each other in a normal state. However, when a carry-over that causes the cleaning liquid mist to be carried downstream from the cleaning device 40 occurs, not only the cleaning liquid that has become water vapor but also the cleaning liquid mist contained in the EGR gas is discharged from the cooler 70. As a result, the drain amount exceeds the condensation amount. Therefore, when the drain amount is larger than the condensation amount by a predetermined amount (when larger than the threshold value), it can be determined that carry-over has occurred.

  According to the third carry-over determination method, the condensation amount of the cleaning liquid generated by the cooling of the EGR gas is calculated, and a carry-over occurs depending on whether or not the drain amount of the cleaning liquid is larger than a threshold set based on the condensation amount. Therefore, it is possible to reliably detect the occurrence of carryover. In addition, since this carry-over determination method does not require a special sensor, a system for determining carry-over can be constructed at low cost. Furthermore, according to the third carryover determination method, similarly to the second carryover determination method, the cleaning device 40 can be used even when the mist removing unit 43 is not provided.

<Fourth determination method>
Next, a fourth carryover determination method will be described. The fourth carryover determination method is a combination of the first carryover determination method and the second carryover determination method. Here, a duplicate description is omitted. FIG. 8 is a flowchart showing a control method of the EGR unit 30 including the fourth carryover determination method. The calculation and control described below are performed by the calculation control device 90. First, when the process is started, the arithmetic and control unit 90 performs steps S1 to S3 performed by the first carryover determination method (acquisition of EGR gas information, calculation of pressure loss in the mist removing unit, and setting of a threshold value). It is determined whether or not the measured differential pressure (actual value) is larger than a threshold value (step S4). The arithmetic and control unit 90 determines that no carry-over has occurred when the actual measurement value is smaller than the threshold value (step S31). On the other hand, when the actual measurement value is larger than the threshold value (YES in step S4), unlike the first carryover determination method, it is not immediately determined that a carryover has occurred. This is because the cause of the increase in the differential pressure across the mist removing portion 43 is considered to be other than the occurrence of carry over.

  When the actual measurement value is larger than the threshold value, steps S11 to S13 (acquisition of EGR gas, calculation of the amount of condensed water, and setting of the threshold value) performed by the second carryover determination method are performed, and then the cleaning liquid It is determined whether or not the consumption amount is larger than the evaporation amount (step S14). Then, when the consumption amount of the cleaning liquid is smaller than the evaporation amount, the cleaning device 44 is operated to clean the mist removing unit 43. As a factor that increases the differential pressure across the mist removing unit 43, the mist removing unit 43 may be clogged due to the volume of the SPM. Even if the measured value of the differential pressure across the mist removing unit 43 is larger than the threshold value, if the consumption of the cleaning liquid is smaller than the evaporation amount, the mist removing unit 43 is likely to be clogged. Therefore, in the fourth carryover determination method, if the measured value of the differential pressure across the mist removing unit 43 is larger than the threshold value and the consumption of the cleaning liquid is smaller than the evaporation amount, the mist removing unit 43 is caused by foreign matter. Assuming that clogging has occurred, the mist removing unit 43 is cleaned.

  On the other hand, when the consumption amount of the cleaning liquid is larger than the evaporation amount, the arithmetic and control unit 90 determines that carry-over has occurred (step S33). That is, in the fourth carryover determination method, it is determined that carryover has occurred when the differential pressure across the mist removing unit 43 is greater than the threshold value and the consumption of the cleaning liquid is greater than the evaporation amount. . If it is determined that carry-over has occurred (step S33), carry-over is avoided (step S34), and the subsequent processing ends.

  As described above, in the fourth carryover determination method, a double check is performed on the occurrence of carryover, so that highly accurate determination is possible. In addition, when there is a possibility that the mist removing unit 43 is clogged, the mist removing unit 43 is cleaned, so that a highly accurate determination can be maintained.

<Fifth determination method>
Next, a fifth carryover determination method will be described. The fifth carryover determination method is a combination of the first carryover determination method and the third carryover determination method. Here, a duplicate description is omitted. FIG. 9 is a flowchart showing a control method of the EGR unit 30 including the fifth carryover determination method. The calculation and control described below are performed by the calculation control device 90. First, when the process is started, the arithmetic and control unit 90 performs steps S1 to S3 performed by the first carryover determination method (acquisition of EGR gas information, calculation of pressure loss in the mist removing unit, and setting of a threshold value). It is determined whether or not the measured differential pressure (actual value) is larger than a threshold value (step S4). If the measured value is smaller than the threshold value, the arithmetic and control unit 90 determines that no carryover has occurred (step S41).

  On the other hand, when the actual measurement value is larger than the threshold value, steps S21 to S24 (EGR gas information acquisition, EGR gas information acquisition, Calculate the amount of condensed water, set the threshold value, and acquire the drain amount). Thereafter, the arithmetic and control unit 90 determines whether or not the drain amount is larger than the threshold value (step S25). When the drain amount is smaller than the threshold value, the cleaning device 44 is operated to clean the mist removing unit 43. For the same reason as described in the fourth carry-over determination method, when the measured value of the differential pressure across the mist removing unit 43 is larger than the threshold value, the mist removal is performed when the drain amount is smaller than the threshold value. This is because there is a high possibility that the portion 43 is clogged.

  On the other hand, when the drain amount is larger than the threshold value, the arithmetic and control unit 90 determines that carry over has occurred (step S42). That is, it is determined that a carry-over has occurred when the differential pressure across the mist removing unit 43 is greater than the threshold value and the drain amount is greater than the threshold value. If it is determined that carry-over has occurred (step S43), carry-over is avoided (step S44), and the subsequent processing ends.

<Sixth determination method>
Next, a sixth carryover determination method will be described. FIG. 10 is a flowchart showing a control method of the EGR unit 30 including the sixth carryover determination method. The calculation and control described below are performed by the calculation control device 90. First, when the process is started, the arithmetic and control unit 90 acquires EGR gas information (step S51). Specifically, the arithmetic and control unit 90 measures the measurement signals of the gas flow meter 49, the first pressure gauge 47, the first thermometer 48, the fourth pressure gauge 75, the fourth thermometer 76, and the second liquid level gauge 83. Is read. Based on these signals, EGR gas flow rate Q _g [kg / min], EGR gas temperature T ₁ [° C.] before cleaning, EGR gas pressure P ₁ [kPa abs] before cleaning, cooling Information about the pressure P ₄ [kPa abs] of the EGR gas after, the temperature T ₄ [° C.] of the EGR gas after cooling, and the amount of displacement of the liquid level in the replenishing tank 80 is acquired.

Subsequently, the arithmetic and control unit 90 calculates the water content (reduced water content) of the EGR gas that is reduced when the EGR gas passes through the cleaning device 40 and the cooler 70 based on the information acquired in step S51 ( Step S52). The amount of reduced water can be determined by subtracting the amount of water vapor contained in the EGR gas after cooling from the amount of water vapor contained in the EGR gas before cleaning. Specifically, the reduced water content [kg / min] can be obtained by the following equation. Note that RH ₅ [%] in the following equation is the relative humidity of the EGR gas before cleaning, and can be calculated from the humidity of the supply gas supplied to the engine 10 and the fuel injection amount in the engine 10. RH ₆ [%] is the relative humidity of the EGR gas after cleaning, and can be calculated as 100 [%].

  Subsequently, the arithmetic and control unit 90 acquires the amount of increase (amount of liquid increase) of the cleaning liquid in the replenishment tank 80 (step S53). The amount of liquid increase can be obtained from the amount of liquid level displacement in the replenishing tank 80. Although the cleaning liquid is also stored in the cleaning device 40, in this embodiment, the water level of the cleaning liquid in the cleaning device 40 is controlled to be constant. Therefore, the increase amount of the cleaning liquid in the replenishment tank 80 is the increase amount of the cleaning liquid in the entire portion of the replenishment tank 80 and the cleaning device 40 where the cleaning liquid is stored (these correspond to the “reservoir part” of the present invention). equal.

  Subsequently, the arithmetic and control unit 90 determines whether or not the liquid increase amount is smaller than the reduced water amount (step S54). The arithmetic and control unit 90 determines that a carry-over has occurred when the liquid increase amount is smaller than the reduced water amount (step S55), and when the liquid increase amount is not smaller than the reduced water amount. It is determined that no carryover has occurred (step S56). If the arithmetic and control unit 90 determines that no carryover has occurred (step S56), the process ends. On the other hand, when it is determined that carry-over has occurred (step S55), carry-over is avoided (step S57), and the subsequent processing ends.

  Thus, it can be determined that carry-over has occurred when the amount of liquid increase is smaller than the amount of reduced water for the following reason. Normally, since the EGR gas is cooled when passing through the cleaning device 40 and the cooler 70, the moisture contained in the EGR gas is condensed and condensed water is generated. Therefore, the cleaning liquid in the replenishment tank 80 increases by the amount of condensed water. However, when a carry-over that causes the cleaning liquid mist to be carried downstream of the cooler 70 occurs, a part of the cleaning liquid does not return to the replenishing tank 80, so that the amount of increase in the cleaning liquid is smaller than the amount of condensed water generated. . Therefore, when the amount of liquid increase is smaller than the amount of reduced water, it can be determined that carry-over has occurred.

  In the above description, the case where the replenishment tank 80 and the cleaning liquid storage part of the cleaning device 40 are separately formed has been described. However, when these are integrated as a shared tank, the shared tank The amount of liquid increase can be determined from the amount of displacement of the liquid level. This shared tank corresponds to the “reservoir part” of the present invention. Further, according to the sixth carry-over determination method, even when the cleaning device 40, the cooler 70, and the replenishment tank 80 are integrally formed and the temperature and pressure of the EGR gas in the inside cannot be measured, the carry Over can be determined. Note that the sixth determination method may be combined with other determination methods. Further, the amount of liquid increase in the liquid reservoir is not limited to the case of detecting by a liquid level gauge, and may be detected from the weight of each tank or the water pressure at the bottom of the tank, for example.

<First avoidance method>
As described above, in this embodiment, when it is determined that a carryover has occurred, the carryover is avoided. Hereinafter, a specific method for avoiding carryover will be described. When the cleaning device 40 includes the mist removing unit 43, carryover occurs when cleaning liquid mist exceeding the processing capability of the mist removing unit 43 attempts to pass through the mist removing unit 43. Therefore, carryover can be avoided by reducing the amount of the cleaning liquid mist that tries to pass through the mist removing unit 43. Therefore, in the first carryover avoidance method, the amount of the cleaning liquid mist that attempts to pass through the mist removing unit 43 is reduced by reducing the flow rate of the EGR gas that passes through the mist removing unit 43. Specifically, the arithmetic and control unit 90 transmits a control signal to the electric motor 61, reduces the rotational speed of the EGR blower 60 (gas passage adjusting device), and sets the flow rate of EGR gas passing through the mist removing unit 43. cut back. In the present embodiment, the EGR blower 60 is a positive displacement blower, and since the rotational speed and the flow rate of the EGR gas are in a proportional relationship, the flow rate adjustment of the EGR gas is relatively easy.

<Second avoidance method>
The second carry-over avoiding method is a method for reducing the amount of the cleaning liquid mist contained in the EGR gas, not reducing the amount of the EGR gas passing through the mist removing unit 43. Even if the flow rate of the EGR gas that passes through the mist removing unit 43 is the same, if the amount of the cleaning liquid mist contained in the EGR gas is reduced, the amount of the cleaning liquid mist that tries to pass through the mist removing unit 43 can be reduced. . Specifically, the amount of cleaning liquid that comes into contact with the EGR gas (the amount of liquid contact) is reduced, thereby reducing the amount of cleaning liquid mist contained in the EGR gas. In the present embodiment, the arithmetic and control unit 90 transmits a control signal to the cleaning liquid pump 42 to reduce the rotational speed of the cleaning liquid pump 42, thereby reducing the amount of liquid contact. In addition, when the washing | cleaning apparatus 40 is a stored water type, if the water level of the washing | cleaning liquid stored in the container is reduced, the amount of liquid contact can be reduced. Note that the second carryover avoidance method may be performed simultaneously with the first carryover avoidance method.

<Third avoidance method>
The third carryover avoidance method is a method of reducing the flow rate of the EGR gas passing through the mist removing unit 43, as in the first carryover avoidance method. However, the third carryover avoidance method is performed when the EGR unit 30 is configured as shown in FIG. FIG. 11 is a block diagram of an engine system 101 according to a first modification of the present embodiment. In the EGR unit 30 shown in FIG. 11, a turbo blower is used as the EGR blower 60, and opening / closing valves 31 and 32 are provided on the inlet side (upstream side) of the cleaning device 40 and the outlet side (downstream side) of the EGR blower 60. Is provided. The opening degree of these open / close valves 31 and 32 is set by the arithmetic and control unit 90. As described above, when a turbo blower is used as the EGR blower 60, when the arithmetic and control unit 90 determines that a carry-over has occurred, not only the rotation speed of the EGR blower 60 but also the opening degrees of the on-off valves 31 and 32 are set. By adjusting, the flow rate of the EGR gas passing through the mist removing unit 43 is reduced. Thereby, carry over can be avoided.

<Fourth avoidance method>
The fourth carryover avoidance method is performed by configuring the EGR unit 30 as shown in FIG. FIG. 12 is a block diagram of an engine system 102 according to a second modification of the present embodiment. The EGR unit 30 shown in FIG. 12 has a bypass pipe 64 that connects the inlet side and the outlet side of the cleaning device 40, and a bypass valve 65 provided in the bypass pipe 64. The opening degree of the bypass valve 65 is set by the arithmetic and control unit 90. In the fourth carryover avoidance method, when the arithmetic and control unit 90 determines that a carryover has occurred, the bypass valve 65 is opened. Thereby, a part of the EGR gas bypasses the cleaning device 40 and is conveyed to the inlet side of the EGR blower 60. Therefore, the flow rate of the EGR gas that passes through the mist removing unit 43 is reduced, and the amount of liquid contact in the entire EGR gas is also reduced, so that the amount of cleaning liquid mist that attempts to pass through the mist removing unit 43 is reduced. As a result, carryover can be avoided. Note that, according to the fourth carryover avoidance method, the flow rate of the EGR gas passing through the mist removing unit 43 decreases, but the flow rate of the EGR gas supplied to the engine 10 can be maintained.

<Fifth avoidance method>
The fifth carryover avoidance method is performed by configuring the EGR unit 30 as shown in FIG. FIG. 13 is a block diagram of an engine system 103 according to a third modification of the present embodiment. The EGR unit 30 shown in FIG. 13 has a circulation pipe 66 that connects the outlet side of the cooler 70 and the inlet side of the EGR blower 60, and a circulation valve 67 provided in the circulation pipe 66. The opening degree of the circulation valve 67 is set by the arithmetic and control unit 90. In the fifth carryover avoidance method, when the arithmetic and control unit 90 determines that a carryover has occurred, the circulation valve 67 is opened. Thereby, a part of the EGR gas discharged from the cooler 70 is conveyed to the inlet side of the EGR blower 60. Therefore, the same effect as reducing the rotation speed of the EGR blower 60 is obtained, and the flow rate of the EGR gas passing through the mist removing unit 43 is reduced. As a result, carryover can be avoided. In FIG. 13, the cooler 70 is disposed on the downstream side of the EGR blower 60, but the EGR blower 60 may be disposed on the downstream side of the cooler 70.

  The above-described first to fifth carryover avoidance methods have been described on the assumption that the cleaning device 40 includes the mist removing unit 43. However, even if the cleaning device 40 does not have the mist removing unit 43, the downstream of the cleaning device 40 can be achieved by reducing the flow rate of the EGR gas or reducing the amount of liquid contact when carryover occurs. It is possible to reduce the amount of the cleaning liquid mist conveyed to. That is, carry over can be reduced. Further, if the amount of the cleaning liquid mist conveyed downstream of the cleaning device 40 can be reduced, a certain amount of the cleaning liquid mist can be collected by the cooler 70, so that the cleaning liquid mist can be prevented from flowing into the engine 10. .

<Sixth avoidance method>
The sixth carryover avoidance method is performed by configuring the EGR unit 30 as shown in FIG. FIG. 14 is a block diagram of an engine system 104 according to a fourth modification of the present embodiment. The EGR unit 30 shown in FIG. 14 has a circulation pipe 68 that connects the inlet side of the cleaning device 40 and the outlet side of the EGR blower 60, and a circulation valve 69 provided in the circulation pipe 68. The opening degree of the circulation valve 69 is set by the arithmetic and control unit 90. In the sixth carryover avoidance method, when the arithmetic and control unit 90 determines that a carryover has occurred, the circulation valve 69 is opened. As a result, part of the EGR gas discharged from the EGR blower 60 returns to the inlet side of the cleaning device 40, so that the flow rate of the EGR gas flowing to the cooler 70 can be reduced. As a result, the amount of cleaning liquid mist conveyed to the cooler 70 and the engine 10 can be reduced, and carryover can be avoided or reduced.

  The above is the description of the engine system 100 according to the present embodiment. In the EGR unit 30 according to the present embodiment, it is determined whether or not carryover has occurred, and control for avoiding carryover is performed. Therefore, damage that may occur to the engine 10 or the like can be prevented in advance. Further, according to the present embodiment, it is possible to perform an operation of suppressing the processing capability of the mist removing unit 43 and avoiding the occurrence of carryover. Therefore, excessive processing capability is not required for the mist removing unit 43, and the mist removing unit 43 can be made compact and inexpensive.

  As described above, the embodiments of the present invention have been described with reference to the drawings. However, the specific configuration is not limited to these embodiments, and even if there is a design change or the like without departing from the gist of the present invention. It is included in the present invention. For example, when the arithmetic and control unit 90 determines that a carry-over has occurred, the present invention includes a case in which the control for simply preventing the carry-over is performed without performing the control for avoiding the carry-over. It is. Even in this case, the reliability of the EGR unit 30 and the engine system 100 can be improved.

  With the EGR unit according to the present invention, it is possible to determine whether or not carryover has occurred. Therefore, it is useful in the technical field of the EGR unit.

DESCRIPTION OF SYMBOLS 10 Engine 30 EGR unit 40 Cleaning apparatus 43 Mist removal part 44 Cleaning apparatus 70 Cooler 80 Replenishment tank (reservoir part)
100, 101, 102, 103, 104 Engine system

Claims (6)

A cleaning apparatus for cleaning EGR gas using a cleaning liquid;
A cooler disposed downstream of the cleaning device and for cooling the EGR gas;
An arithmetic and control unit that determines that a carry-over has occurred when the amount of drain from the cooler is larger by a predetermined amount than the amount of condensate generated by cooling the EGR gas with the cooler. EGR unit for marine engine system. 2. The EGR unit according to claim 1 , wherein the arithmetic and control unit reduces the flow rate of EGR gas passing through the cleaning device when it is determined that carry-over has occurred. 2. The EGR unit according to claim 1 , wherein when it is determined that carry-over has occurred, the arithmetic and control unit reduces the amount of cleaning liquid that comes into contact with EGR gas during cleaning. 2. The EGR unit according to claim 1 , wherein the arithmetic and control unit reduces the flow rate of the EGR gas discharged from the EGR unit when it is determined that carry-over has occurred. A cleaning apparatus for cleaning EGR gas using a cleaning liquid;
A cooler disposed downstream of the cleaning device and for cooling the EGR gas;
A marine engine system comprising: an arithmetic and control unit that performs a predetermined process when the amount of drain from the cooler is larger by a predetermined amount than the amount of condensed water generated by cooling the EGR gas by the cooler. EGR unit. The marine engine system provided with the EGR unit as described in any one of Claims 1 thru | or 5 .

Images