JP2020070781A - Gas cooling system and control method for the same - Google Patents

Abstract

To provide a gas cooling system which controls generation of condensate water when cooling gas in an engine and to provide a control method for the gas cooling system.SOLUTION: A gas cooling system 10 comprises a gas cooler 11, a coolant radiator 12 and a coolant pump 13. The gas cooling system also has a temperature control device 14, a control temperature acquisition device 20, parameter acquisition devices (21 to 27) and a control device 28. The control device 28 is adapted to perform control to cool intake air A3, on the basis of a saturation temperature Tw of water included in the intake air A3 passing through the gas cooler 11 estimated in accordance with parameters acquired through the parameter acquisition devices (21 to 27) and a temperature Tx of a coolant W1 acquired through the control temperature acquisition device 20, with the temperature Tx adjusted to be higher than the saturation temperature Tw by the temperature control device 14.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a gas cooling system and a control method thereof, and more particularly, to a gas cooling system and a control method thereof for improving fuel economy performance and exhaust gas performance in an engine.

  As a system for cooling the gas in the engine, a cooling water passage that allows the refrigerant to flow from the pump to the radiator via the intercooler, and a bypass passage that allows the refrigerant to bypass the radiator and then return to the pump after passing through the intercooler A device has been proposed (for example, see Patent Document 1). The device described in Patent Document 1 adjusts the flow rate of the cooling water flowing through each of the cooling water passage and the bypass passage to keep the intake air temperature after passing through the intercooler within a predetermined range.

JP, 2013-104314, A

  By the way, in the intercooler of the device described in Patent Document 1, condensed water may be generated inside when the temperature of intake air falls below the saturation temperature. The condensed water generated inside the intercooler is a factor that corrodes the inside of the intercooler.

  An object of the present disclosure is to provide a gas cooling system that suppresses generation of condensed water when cooling gas in an engine, and a control method thereof.

  A gas cooling system according to an aspect of the present invention that achieves the above object is a gas cooler for cooling a gas in an engine, a radiator for a refrigerant through which a refrigerant of the gas cooler passes, and a refrigerant for circulating the refrigerant. In a gas cooling system including a pump, a temperature adjusting device that adjusts the temperature of the refrigerant supplied to the gas cooler, and the temperature of the gas cooled by the gas cooler or the gas cooler. A control temperature acquisition device that acquires one of the temperatures of the refrigerant as a control temperature, and a parameter that acquires a parameter related to the estimation of the saturation temperature of water contained in the gas passing through the gas cooler. Acquisition device, temperature control device, control temperature acquisition device, and control device connected to the parameter acquisition device , Based on the saturation temperature and the control temperature acquired by the control temperature acquisition device estimated according to the parameter acquired by the parameter acquisition device, by the control device, the temperature adjustment device to the It is characterized in that the temperature of the refrigerant supplied to the gas cooler is adjusted so that the control temperature is higher than the saturation temperature and the gas is controlled to be cooled.

  A method for controlling a gas cooling system according to one aspect of the present invention that achieves the above object is to circulate a refrigerant by a refrigerant pump, and to cool a gas in an engine by a gas cooler that supplies a refrigerant cooled by a refrigerant radiator. In a method for controlling a gas cooling system for cooling, a control temperature comprising either one of a temperature of the gas cooled by the gas cooler or a temperature of the refrigerant supplied to the gas cooler, and The parameter relating to the estimation of the saturation temperature of the water contained in the gas passing through the gas cooler is acquired, the saturation temperature is estimated based on the acquired parameter, and the acquired control temperature and the estimated saturation temperature are acquired. Based on the above, the temperature of the refrigerant supplied to the gas cooler is adjusted by the temperature adjusting device to obtain the control temperature. Characterized by cooling the gas to a temperature higher than the saturation temperature.

  According to one aspect of the present invention, it is possible to suppress generation of condensed water when cooling gas in an engine.

It is a block diagram which illustrates 1st embodiment of the gas cooling system. It is a part of the flowchart which illustrates the control method of the gas cooling system. It is a flowchart which branches from S170 of FIG. FIG. 4 is a relationship diagram illustrating the relationship between the temperature of the refrigerant and the flow rate of the refrigerant flowing through the radiator flow path in the first embodiment of the gas cooling system. FIG. 3 is a relationship diagram illustrating the relationship between water vapor pressure, temperature, and saturated water vapor pressure line in the first embodiment of the gas cooling system. It is a block diagram which illustrates 2nd embodiment of the gas cooling system.

  Hereinafter, an embodiment of the gas cooling system 10 will be described with reference to the drawings. In the figure, W1 represents a refrigerant, W2 represents engine cooling water, A1 represents fresh air, A2 represents intake air before supercharging, A3 represents intake air after supercharging and before cooling, A3 indicates intake after cooling, G1 indicates exhaust, and G2 and G3 indicate recirculated gas. In addition, the state in which the cooling water is flowing in the flow path is indicated by a thick line to distinguish it from the state in which the cooling water flow is stopped.

  As illustrated in FIG. 1, the gas cooling system 10 of the first embodiment is a water-cooled system that cools the supercharged intake air A3 after the fresh air A1 and the recirculation gas G2 are mixed. The gas cooling system 10 is exemplified by one that uses the same cooling water as the engine cooling water W2 used in the engine cooling system 3 as the refrigerant W1.

  The gas cooling system 10 is a system independent of the engine cooling system 3 that cools the engine 1, and includes a gas cooler 11, a refrigerant radiator 12, a refrigerant pump 13, and a temperature adjusting device 14. Further, the gas cooling system 10 includes a control temperature acquisition device 20, a humidity sensor 21, a flow rate sensor 22, a fuel injection amount acquisition device 23, an exhaust concentration sensor 24, an intake concentration sensor 25, which functions as a parameter acquisition device, A pressure sensor 26, a gas temperature sensor 27, and a controller 28 connected to these sensors are provided.

  The gas cooler 11 is a cooler that is arranged at a midway position of the intake passage 4 and cools the intake air A3 flowing through the intake passage 4 by flowing the refrigerant W1 therein. As the intake air A3 cooled by the gas cooler 11, fresh air A1 introduced from the outside into the intake passage 4 via an air cleaner (not shown), or a low-pressure exhaust gas recirculation system 6A from the exhaust passage 5 to the fresh air A1 is introduced. An example is illustrated in which either one of the intake air A2 mixed with the recirculated gas G2 recirculated through the intake passage 4 is supercharged.

  The refrigerant radiator 12 cools the refrigerant W1 passing through the inside thereof by using the vehicle speed air and the subsequent cooling air from the engine cooling fan 3A. The refrigerant radiator 12 is configured to cool the refrigerant W1 flowing therein to a temperature lower than that of the engine cooling water W2 flowing inside the engine radiator 3B of the engine cooling system 3. Specifically, the refrigerant radiator 12 is arranged in front of the engine radiator 3B in the front-rear direction of the vehicle, or in parallel with the left-right direction or the vertical direction of the vehicle, and after heat exchange with the engine radiator 3B. It is preferable not to hit the wind.

  The coolant pump 13 is connected to an electric motor 15 that is driven by electric power supplied from a battery (not shown), and is driven by the rotational power output from the electric motor 15 to circulate the coolant W1. The coolant pump 13 is connected to the crankshaft 7A via a power transmission mechanism 7B such as an endless belt or chain, similarly to the pump 3C of the engine cooling system 3, and is driven by the rotational power output from the engine 1. A mechanical pump for driving is also exemplified.

  The temperature adjustment device 14 is a device that adjusts the temperature of the refrigerant W1 supplied to the gas cooler 11, and has a radiator flow path 16, a bypass flow path 17, and a flow rate adjustment device 18. The radiator flow path 16 is a flow path in which the gas cooler 11, the refrigerant radiator 12, and the refrigerant pump 13 are annularly arranged by piping. The bypass passage 17 is branched from between the downstream side of the gas cooler 11 and the upstream side of the refrigerant radiator 12 in the radiator flow path 16 to branch between the upstream side of the gas cooler 11 and the downstream side of the refrigerant radiator 12. It is a flow path that merges and bypasses the radiator 12 for the refrigerant. The flow rate adjusting device 18 is a device that adjusts the flow rates of the refrigerant W1 flowing through the radiator flow path 16 and the bypass flow path 17, respectively. An example of the flow rate control device 18 is an electromagnetically controlled three-way valve. Note that the flow rate control device 18 blocks the bypass passage 17 and opens only the radiator passage 16 to block the passage of the refrigerant W1 in the gas cooling system 10, and shuts off the radiator passage 16 to bypass the bypass passage. Either only 17 is opened, or both channels are opened.

  The control temperature acquisition device 20 is a sensor that acquires the temperature Tx of the refrigerant W1 supplied to the gas cooler 11 as the control temperature. The control temperature acquisition device 20 only needs to be able to acquire the temperature Tx of the refrigerant W1 immediately before being supplied to the gas cooler 11, and if it is provided in the flow path between the gas cooler 11 and the flow rate control device 18. Good.

  The humidity sensor 21, the flow rate sensor 22, the fuel injection amount acquisition device 23, the exhaust concentration sensor 24, the intake concentration sensor 25, the pressure sensor 26, and the gas temperature sensor 27, which function as the parameter acquisition device, are the gas cooler 11 This is a device for acquiring a parameter relating to estimation of the saturation temperature Tw of water (water vapor) contained in the intake air A3 passing through. The parameter relating to this estimation is a parameter capable of estimating the pressure (water vapor pressure) Pw of water contained in the intake air A3, and more specifically, the substance amount n1 (mol) of water contained in the fresh air A1 and the recirculation gas. Material amount n2 of water contained in G2 (material amount of water mixed with fresh air A1 by recirculation by the low pressure exhaust gas recirculation system 6A among water generated by combustion of fuel in the engine 1), all substances of intake air A2 The amount n3 and the pressure Pa of the intake air A3.

  The humidity sensor 21 is a sensor that acquires the humidity Xa of the fresh air A1 introduced into the intake passage 4 from the outside, and may be a sensor that acquires the humidity of the outside air. Examples of the humidity Xa include volume absolute humidity, mass absolute humidity, and relative humidity. The flow rate sensor 22 is a sensor that acquires the fresh air flow rate Qa of the fresh air A1 introduced into the intake passage 4 from the outside. As the fresh air flow rate Qa, a volume flow rate and a mass flow rate are exemplified.

  The fuel injection amount acquisition device 23 is a device that acquires the fuel injection amount Qe injected from the fuel injection device 8 of the engine 1 into the cylinder 2. An example of the fuel injection amount acquisition device is an engine control device that controls the fuel injection device 8 by calculating the fuel injection amount Qe from the depression amount of an accelerator pedal (not shown). The fuel injection amount acquisition device 23 may be any device that can acquire the fuel injection amount Qe, and may be a device that acquires the depression amount of the accelerator pedal.

  The exhaust gas concentration sensor 24 is a sensor that acquires the exhaust gas concentration ρg, which is the concentration of carbon dioxide contained in the exhaust gas G1, and is arranged on the upstream side of the turbine 9A of the turbocharger 9 with respect to the flow of the exhaust gas G1 in the exhaust passage 5. To be done. The intake air concentration sensor 25 is a sensor that acquires the intake air concentration ρa, which is the concentration of carbon dioxide contained in the intake air A2, and is located at the confluence point of the low pressure exhaust gas recirculation system 6A in the intake passage 4 and the compressor 9B of the turbocharger 9. Intervenes between.

  The pressure sensor 26 is a sensor that acquires the pressure Pa of the intake air A3 passing through the gas cooler 11, and is interposed between the compressor 9B and the gas cooler 11 in the intake passage 4. The gas temperature sensor 27 is a sensor that acquires the temperature Ta of the intake air A2, and is interposed between the confluence of the low pressure exhaust gas recirculation system 6A and the compressor 9B in the intake passage 4.

  The control device 28 includes a central processing unit (CPU) that performs various types of information processing, an internal storage device that can read and write programs used to perform the various types of information processing, and information processing results, and various interfaces. Is. The control device 28 includes a flow rate control device 18, a control temperature acquisition device 20, a humidity sensor 21, a flow rate sensor 22, a fuel injection amount acquisition device 23, an exhaust concentration sensor 24, an intake concentration sensor 25, a pressure sensor 26, and It is electrically connected to the gas temperature sensor 27. In this embodiment, the control device 28 exemplifies a device separate from the engine control device that functions as the fuel injection amount acquisition device 23 that acquires the fuel injection amount Qe, but the control device 28 and the engine control device are It may be configured as an integrated device.

  The control device 28 has an estimation unit 29, a first control unit 30, and a second control unit 31 as functional elements. Each functional element is stored in the internal storage device as a program and is executed by the central processing unit at appropriate times. In addition to the program, each functional element may be configured by a programmable controller (PLC) or an electric circuit that functions independently.

  The estimation unit 29 estimates the saturation temperature Tw of the water contained in the intake air A3 passing through the gas cooler 11 when the parameters acquired by the parameter acquisition device are input, and the estimated saturation temperature Tw is used as the first control unit 30. Is a functional element to be output to. The estimation unit 29 has a first substance amount estimation unit 29a, a second substance amount estimation unit 29b, a water vapor pressure estimation unit 29c, and a saturation temperature estimation unit 29d as individual functional elements.

  The first substance amount estimation unit 29a inputs the humidity Xa acquired by the humidity sensor 21 and the fresh air flow rate Qa acquired by the flow rate sensor 22, and estimates and estimates the substance amount n1 of water contained in the fresh air A1. It is a functional element that outputs the substance amount n1 to the water vapor pressure estimation unit 29c.

  The second substance amount estimation unit 29b uses the fresh air flow rate Qa acquired by the flow rate sensor 22, the fuel injection amount Qe acquired by the fuel injection amount acquisition device 23, the exhaust gas concentration ρg acquired by the exhaust gas concentration sensor 24, and the intake air concentration. The intake concentration ρa acquired by the sensor 25 is input, the substance amount n2 of water contained in the recirculation gas G2 is estimated, and the estimated substance amount n2 is a functional element that outputs it to the water vapor pressure estimation unit 29c.

  Specifically, the second substance amount estimation unit 29b uses the fuel injection amount Qe and the chemical reaction model that the fuel injected from the fuel injection device 8 is considered to be completely combusted, from the cylinder 2 to the exhaust passage 5. The substance amount n4 of the water contained in the discharged exhaust gas G1 is estimated. Then, the second substance amount estimating unit 29b uses the exhaust gas concentration ρg and the intake air concentration ρa and the known carbon dioxide concentration ρo of the air to calculate the ratio Re of the recirculated gas G2 in the intake air A2. To estimate. In the present disclosure, the proportion Re of the recirculated gas G2 in the intake air A2 does not include the recirculated gas G3 recirculated by the high pressure exhaust gas recirculation system 6B, but is recirculated by the low pressure exhaust gas recirculation system 6A. The ratio of only the circulating gas G2 is shown. Next, the second substance amount estimation unit 29b estimates the recirculation flow rate Qg, which is the flow rate of the recirculation gas G2, based on the fresh air flow rate Qa and the ratio Re of the recirculation gas G2 in the intake air A2. Next, the second substance amount estimation unit 29b estimates the substance amount n2 of water contained in the recirculation gas G2 based on the estimated substance amount n4 of water contained in the exhaust gas G1 and the estimated recirculation flow rate Qg. To do.

  The water vapor pressure estimation unit 29c estimates the fresh air flow rate Qa acquired by the flow rate sensor 22, the pressure Pa acquired by the pressure sensor 26, the temperature Ta acquired by the gas temperature sensor 27, and the first substance amount estimation unit 29a. The substance amount n1, the substance amount n2 and the recirculation flow rate Qg estimated by the second substance amount estimating unit 29b are input. The water vapor pressure estimation unit 29c is a functional element that estimates the water vapor pressure Pw of the intake air A3 based on the input value and outputs the estimated water vapor pressure Pw to the saturation temperature estimation unit 29d.

  Specifically, the water vapor pressure estimation unit 29c is based on the fresh air flow rate Qa, the recirculation flow rate Qg, the temperature Ta, and the preset standard pressure (1013 hPa (1 atm)) before being supercharged by the compressor 9B. Estimate the total amount n3 of intake air A2. Next, the water vapor pressure estimation unit 29c estimates the mole fraction of water ((n1 + n2) / n3) in the intake air A2 (intake air A3) using the estimated total amount of substances n3. Next, the water vapor pressure estimation unit 29c multiplies the water Pa in the intake air A3 by the pressure Pa to estimate the water vapor pressure Pw of the intake air A3 passing through the gas cooler 11.

  The saturation temperature estimator 29d receives the water vapor pressure Pw estimated by the water vapor pressure estimator 29c, and uses the preset saturation water vapor pressure line Lw to set the saturation temperature Tw of water in the intake air A3 passing through the gas cooler 11. Is a functional element that outputs the estimated saturation temperature Tw to the first control unit 30. The saturated water vapor pressure line Lw is a line represented by a known approximation formula in the relation between the temperature and the water vapor pressure, and as the known approximation formulas, the Tetens formula, the Wagner formula, the Sonntag formula (Japanese Industrial Standard JIS Z 8806). Is exemplified.

  The first control unit 30 receives the saturation temperature Tw estimated by the estimation unit 29 and the temperature Tx acquired by the control temperature acquisition device 20, and the temperature of the refrigerant W1 supplied to the gas cooler 11 by the temperature adjustment device 14. It is a functional element that controls Tx to control the temperature Ty of the intake air A2 to a temperature higher than the saturation temperature Tw in the gas cooler 11. Specifically, the first control unit 30 controls the flow rate control device 18 to control the flow rate of the refrigerant W1 flowing through each of the radiator flow path 16 and the bypass flow path 17, and the temperature of the refrigerant W1 supplied to the gas cooler 11 is controlled. It is a functional element that controls the temperature Ty of the intake air A2 to a temperature higher than the saturation temperature Tw by setting the temperature Tx higher than the saturation temperature Tw. The first control unit 30 calculates a deviation ΔT (a value obtained by subtracting the saturation temperature Tw from the temperature Tx) of the temperature Tx, which is the control amount, with respect to the saturation temperature Tw that is the target value, and the calculation for increasing the temperature. It is a functional element that performs feedback control to bring the deviation ΔT closer to zero so as not to become zero or less. In this feedback control, the control condition is to set the deviation ΔT to a positive value, and it is preferable to set a dead zone (hysteresis) so that the deviation ΔT does not become a value of zero or less. For example, by setting the range from the saturation temperature Tw to a temperature higher by a predetermined temperature as the dead zone, when the temperature Tx falls within the dead zone, the feedback control is not performed and the temperature Tx that is the control amount is maintained. This makes it possible to bring the deviation ΔT close to zero so as not to become zero or less.

  The second control unit 31 has a timer 32 as an individual functional element, and when the deviation ΔT calculated by the first control unit 30 is input, the time tx when the deviation ΔT becomes zero or less is a predetermined determination time ta or more. It is a functional element that performs control to reduce the water vapor pressure Pw of the intake air A3 passing through the gas cooler 11 when the time has elapsed. As a control for reducing the water vapor pressure Pw, the second control unit 31 closes the flow rate control valve 6C of the low pressure exhaust gas recirculation system 6A to reduce the proportion Re of the recirculated gas G2 by the low pressure exhaust gas recirculation system 6A to reduce the high pressure exhaust gas. It is a functional element that performs control to open the flow rate control valve 6D of the recirculation system 6B and increase the proportion of the recirculation gas G3 by the high pressure exhaust gas recirculation system 6B.

  The timer 32 is a functional element that counts the time tx when the deviation ΔT becomes zero or less, and counts the elapsed time when the deviation ΔT becomes zero or less for each unit time, or the deviation ΔT becomes zero or less. An example is one that counts the number of cycles.

  The determination time ta is set to a time that can avoid the generation of condensed water inside the gas cooler 11. The determination time ta may be set according to the deviation amount of the deviation ΔT with respect to zero, and the determination time ta may be shortened when the deviation amount of the deviation ΔT with respect to zero is large.

  As illustrated in FIG. 2 and FIG. 3, the control method of the gas cooling system 10 is a method that is repeatedly performed at a predetermined cycle. In addition, the progress of one cycle in the flow chart is indicated by "return".

  Each of the humidity sensor 21, the flow rate sensor 22, the fuel injection amount acquisition device 23, the exhaust concentration sensor 24, the intake concentration sensor 25, the pressure sensor 26, and the gas temperature sensor 27 is included in the intake air A2 as the parameter acquisition device. A parameter relating to the estimation of the water saturation temperature Tx is acquired (S110).

  Next, the first substance amount estimation unit 29a estimates the substance amount n1 of water contained in the fresh air A1 based on the humidity Xa and the fresh air flow rate Qa (S120). Next, the second substance amount estimation unit 29b includes the recirculated gas G2 based on the fresh air flow rate Qa, the fuel injection amount Qe, the exhaust concentration ρg, the intake concentration ρa, and the carbon dioxide concentration ρo of the air. The substance amount n2 of the water to be stored is estimated (S130). Next, the water vapor pressure estimation unit 29c causes the intake air A2 passing through the gas cooler 11 based on the fresh air flow rate Qa, the recirculation flow rate Qg, the temperature Ta, the standard pressure P0, the substance amount n1, the substance amount n2, and the pressure Pa. The water vapor pressure Pw is estimated (S140). Next, the saturation temperature estimation unit 29d estimates the saturation temperature Tw of water in the intake air A2 passing through the gas cooler 11 based on the water vapor pressure Pw and the saturated water vapor pressure line Lw (S150).

  Next, the control temperature acquisition device 20 acquires the temperature Tx of the refrigerant W1 supplied to the gas cooler 11 (S160). Next, the first control unit 30 subtracts the temperature Tx from the saturation temperature Tw estimated by the estimation unit 29 to calculate the deviation ΔT (S170). Next, the first control unit 30 controls the temperature adjusting device 14 so as to bring it closer to the temperature controller 14 based on the deviation ΔT (S180), and returns to the start.

  As illustrated in FIG. 4, the correlation between the temperature Tx of the coolant W1 and the flow rate of the coolant W1 flowing through the radiator passage 16 is a negative correlation. Therefore, to decrease the temperature Tx of the refrigerant W1, the flow path of the refrigerant W1 flowing through the radiator flow path 16 is enlarged, and to increase the temperature Tx of the refrigerant W1 the flow path of the refrigerant W1 flowing through the radiator flow path 16 is decreased. do it.

  FIG. 5 exemplifies the relationship between the temperature and the water vapor pressure in the gas cooling system 10. In the figure, the solid line arrow indicates the relationship between the temperature of the gas to be controlled and the water vapor pressure of the gas, and the dashed line indicates the relationship. The saturated steam pressure line L1 is shown. The shaded area indicates the dead zone.

  The fresh air A1 introduced from the outside into the intake passage 4 and the low-pressure exhaust gas recirculation system 6A mix the recirculated gas G2 recirculated from the exhaust passage 5 on the downstream side of the turbine 9A to the intake passage 4 and the compressor 9B. The intake air becomes A2 before being supercharged. The temperature Ta of the intake air A2 rises as the fresh air A1 is mixed with the recirculation gas G2. Further, the substance amount (n1 + n2) of water contained in the intake air A2 increases as compared with the fresh air A1, and the water vapor pressure becomes high.

  Next, when the intake air A2 is supercharged by the turbine 9A, it becomes intake air A3. The temperature Ty of the intake air A3 becomes higher than that of the intake air A2 due to the compression of the intake air A2, and the pressure Pa also increases. As the pressure Pa increases, the water vapor pressure Pw of the intake air A3 becomes higher.

  Next, the supercharged intake air A3 is cooled by the gas cooler 11 to become intake air A4. At this time, the temperature Tx of the refrigerant W1 supplied to the gas cooler 11 is higher than the saturation temperature Tw, and the temperature of the intake air A4 is lower than that of the supercharged intake air A3. Not below As a result, the intake air A3 is cooled in a state in which condensed water is not generated inside the gas cooler 11.

  When the deviation ΔT is calculated in step S170, the control flow of FIG. 3 is started. The second control unit 31 determines whether the calculated deviation ΔT is equal to or less than zero (S210). When the dead zone is set by the approach control by the first controller 30, the dead zone may be taken into consideration in this step.

  When it is determined that the deviation ΔT is larger than zero (S210: NO), the time tx counted by the timer 32 is reset (S220) and the process returns to step S210. One cycle also passes for this return.

  When it is determined that the deviation ΔT is less than or equal to zero (S210: YES), the timer 32 counts the time tx (S230). Next, the second control unit 31 determines whether or not the counted time tx has passed a predetermined determination time ta or more (S240). When it is determined that the time tx does not elapse until it reaches the determination time ta (S230: NO), the process returns to step S210.

  When it is determined that the time tx has reached the determination time ta (S230: YES), the second control unit 31 closes the flow rate control valve 6C as control for reducing the water vapor pressure Pw of the intake air A3 passing through the gas cooler 11. Then, the ratio Re of the recirculated gas G2 is reduced, the flow rate control valve 6D is opened to increase the ratio of the recirculated gas G3 (S240), and the process ends.

  As described above, in the gas cooling system 10, the temperature Tx of the refrigerant W1 supplied to the gas cooler 11 by the temperature control device 14 is equal to or lower than the saturation temperature Tw of water contained in the intake air A3 cooled by the gas cooler 11. It is possible to avoid the generation of condensed water inside the gas cooler 11 at the time of cooling by adjusting so as not to turn off.

  That is, according to the gas cooling system 10, the temperature Tx of the refrigerant W1 is prevented from becoming equal to or lower than the saturation temperature Tw even when the humidity or the temperature of the outside air changes or the cooling capacity of the refrigerant radiator 12 changes due to the vehicle speed wind. It is possible to cope with the generation of condensed water caused by these changes.

  As described above, according to the gas cooling system 10, even when the recirculation gas G2 is mixed with the intake air A3 and the water vapor pressure Pw is high, generation of condensed water is avoided during cooling. It is advantageous to expand the operating range in which the recirculation gas G2 can be recirculated by the low pressure exhaust gas recirculation system 6A. This reduces the frequency of recirculating the recirculation gas G2 by the high pressure exhaust gas recirculation system 6B and increases the frequency of recirculating the recirculation gas G2 by the low pressure exhaust gas recirculation system 6A, thereby increasing the efficiency of the turbocharger 9. Can be driven to. Along with this, it is possible to realize high supercharging by the turbocharger 9 while maintaining exhaust performance by recirculation of the recirculation gas G2 and improve fuel efficiency. In the present disclosure, the exhaust performance refers to the performance of reducing harmful components contained in the exhaust gas G1 discharged to the outside.

  According to the gas cooling system 10, generation of condensed water inside the gas cooler 11 is avoided, thereby expanding an operation region in which the low-pressure exhaust gas recirculation system 6A can recirculate the recirculation gas G2. You can That is, it is advantageous to recirculate the recirculation gas G2 by the low pressure exhaust gas recirculation system 6A even when the temperature Tx of the refrigerant W1 is low at the cold start of the engine 1 or at low ambient temperature.

  Further, according to the gas cooling system 10, when the temperature Tx of the refrigerant W1 as the control temperature is equal to or lower than the saturation temperature Tw for a predetermined time, the ratio Re of the recirculated gas G2 in the intake air A3 is reduced. The control for lowering the saturation temperature Tw is performed. Therefore, only by adjusting the temperature Tx of the refrigerant W1 by the temperature adjusting device 14, even in a situation where condensed water is generated inside the gas cooler 11, it is possible to avoid generation of condensed water during cooling. ..

  In addition, in the gas cooling system 10, the temperature Ty of the intake air A4 cooled by the gas cooler 11 does not exceed the temperature Tx of the refrigerant W1 supplied to the gas cooler 11. Therefore, as in this embodiment, by using the temperature Tx of the refrigerant W1 supplied to the gas cooler 11 as the control temperature, the temperature Ty of the intake air A4 cooled by the gas cooler 11 is made lower than the saturation temperature Tw. This is advantageous for raising the temperature to a higher level, and safer control is possible in avoiding the generation of condensed water.

  As illustrated in FIG. 6, the gas cooling system 10 of the second embodiment includes a control temperature acquisition device 33 as compared with the first embodiment, and the intake air cooled by the gas cooler 11 as the control temperature. The difference is that the temperature Ty of A4 is used.

  The control temperature acquisition device 33 is a sensor that acquires the temperature Ty of the intake air A4 cooled by the gas cooler 11 as the control temperature. The control temperature acquisition device 33 only needs to be able to acquire the temperature Ty of the intake air A4 immediately after being cooled by the gas cooler 11, and is preferably arranged near the outlet of the gas cooler 11.

  The first control unit 30 receives the saturation temperature Tw estimated by the estimation unit 29 and the temperature Ty acquired by the control temperature acquisition device 33, and the temperature of the refrigerant W1 supplied to the gas cooler 11 by the temperature adjustment device 14. It is a functional element that controls Tx to control the temperature Ty of the intake air A2 to a temperature higher than the saturation temperature Tw in the gas cooler 11. The first control unit 30 calculates a deviation ΔT (a value obtained by subtracting the saturation temperature Tw from the temperature Ty) of the temperature Ty that is the control amount with respect to the saturation temperature Tw that is the target value, and the calculation to increase the temperature. It is a functional element that performs feedback control to bring the deviation ΔT closer to zero so as not to become zero or less. In this feedback control, the control condition is to set the deviation ΔT to a positive value as in the first embodiment, and it is preferable to set a dead zone (hysteresis) so that the deviation ΔT does not become a value of zero or less. .. The correlation between the temperature Ty of the intake air A4 and the flow rate of the refrigerant W1 flowing through the radiator flow path 16 also has a negative correlation. Therefore, in order to lower the temperature Ty of the intake air A4, the flow path of the refrigerant W1 flowing through the radiator flow path 16 may be increased, and to increase the temperature Ty, the flow path of the refrigerant W1 flowing through the radiator flow path 16 may be decreased. ..

  In the gas cooling system 10, the intake air A4 cooled by the gas cooler 11 has a higher density as the temperature Ty is lower, and the number of oxygen molecules contained in the intake air A4 increases. Therefore, as in this embodiment, the temperature Ty of the intake air A4 cooled by the gas cooler 11 is used as the control temperature to bring the temperature Ty of the intake air A4 cooled by the gas cooler 11 close to the saturation temperature Tw. Therefore, it is advantageous to cool to a temperature at which the generation of condensed water can be avoided. As a result, the compression ratio of the intake air A4 can be increased, the output of the engine 1 can be increased, and the fuel consumption can be improved.

  The gas cooling system 10 may be recirculation gases G2 and G3 in which the gas to be cooled is discharged from the engine 1 and recirculated from the exhaust passage 5 to the intake passage 4.

  The gas cooling system 10 is preferably a system separate from the engine cooling system 3. By using a separate system, the influence of the engine cooling water W2 on the refrigerant W1 can be avoided, and it is advantageous to operate the temperature Tx of the refrigerant W1 in a lower temperature range than the engine cooling water W2. The gas cooling system 10 may be incorporated in the engine cooling system 3.

  The parameter acquisition device is not limited to the above configuration as long as it can acquire the parameter related to the estimation of the saturation temperature Tw of the water (water vapor) contained in the intake air A3 passing through the gas cooler 11. For example, instead of the exhaust concentration sensor 24 and the intake concentration sensor 25, a device that acquires the opening degree of the flow control valve 6C of the low pressure exhaust gas recirculation system 6A is used, and the recirculation occupying in the intake air A2 from the opening degree is used. The ratio Re of the gas G2 may be estimated.

  Further, the parameter acquisition device may comply with the estimation method of the saturation temperature Tw of the water (water vapor) included in the intake air A3 passing through the gas cooler 11 in the estimation unit 29. As an estimation method, for example, a map in which the relationship between the parameter and the saturation temperature Tw is set by an experiment or test is created, and the saturation temperature Tw is estimated based on the map, or the operating state of the engine 1 or the outside air A method of estimating the saturation temperature Tw using a physical model including environmental changes and the like is exemplified.

  The gas cooling system 10 cools the gas cooler 11 when the deviation ΔT between the saturation temperature Tw and the temperature Tx of the refrigerant W1 or the temperature Ty of the intake air A4, which is the control temperature, continues for a certain period of time. The control may be performed so as to increase the water vapor pressure Pw of the intake air A3 passing through. This increasing control is a control that opens the flow rate control valve 6C to increase the proportion Re of the recirculation gas G2 and closes the flow rate control valve 6D to reduce the proportion of the recirculation gas G3.

1 Engine 10 Gas Cooling System 11 Gas Cooler 12 Refrigerant Radiator 13 Refrigerant Pump 13 Refrigerant Pump 14 Temperature Control Device 20 Controlling Temperature Acquisition Device 21-27 Parameter Acquisition Device 28 Control Device A3 Intake W1 Refrigerant Tx Temperature Tw Saturation Temperature

Claims (5)

In a gas cooling system including a gas cooler that cools gas in an engine, a refrigerant radiator through which a refrigerant of the gas cooler passes, and a refrigerant pump that circulates the refrigerant,
A temperature control device that controls the temperature of the refrigerant supplied to the gas cooler, and either the temperature of the gas cooled by the gas cooler or the temperature of the refrigerant supplied to the gas cooler. A control temperature acquisition device that acquires one as a control temperature, a parameter acquisition device that acquires a parameter related to estimation of the saturation temperature of water contained in the gas passing through the gas cooler, the temperature adjustment device, and the control For temperature acquisition device, and a control device connected to the parameter acquisition device,
Based on the saturation temperature and the control temperature acquired by the control temperature acquisition device estimated according to the parameter acquired by the parameter acquisition device, by the control device, the temperature adjuster to the gas cooler A cooling system for gas, characterized in that the temperature of the supplied refrigerant is adjusted to bring the control temperature to a temperature higher than the saturation temperature to perform control for cooling the gas.   The temperature control device adjusts a flow rate of the refrigerant flowing through each of the bypass flow path that bypasses the refrigerant radiator and the bypass flow path and the radiator flow path in which the refrigerant radiator exists at an intermediate position. The cooling system for gas according to claim 1, further comprising: The gas is intake air in which fresh air flowing into the intake passage of the engine from the outside and recirculated gas recirculated from the exhaust passage of the engine to the intake passage upstream of the gas cooler are mixed,
The parameter acquisition device, as the parameter, the substance amount of water contained in the fresh air, the substance amount of water contained in the recirculation gas, the total substance amount of the gas, and when passing through the gas cooler. The gas cooling system according to claim 1 or 2, which is a device for acquiring the pressure of the intake air in.   When the control temperature is equal to or lower than the saturation temperature for a predetermined period of time, the control device reduces the ratio of the recirculated gas in the gas to control to lower the saturation temperature. Item 4. A cooling system for gas according to Item 3. In the control method of the gas cooling system, which circulates the refrigerant by the refrigerant pump, cools the gas in the engine by the gas cooler supplied with the refrigerant cooled by the refrigerant radiator,
Included in the control temperature, which is either the temperature of the gas cooled by the gas cooler or the temperature of the refrigerant supplied to the gas cooler, and the gas passing through the gas cooler. Obtain the parameters related to the estimation of water saturation temperature,
Estimating the saturation temperature based on the obtained parameters,
Based on the acquired control temperature and the estimated saturation temperature, the temperature adjusting device adjusts the temperature of the refrigerant to be supplied to the gas cooler so that the control temperature is higher than the saturation temperature. A method for controlling a gas cooling system, comprising: cooling the gas.

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