Engine air supply system and method for determining egr rate

Abstract

The application belongs to the technical field of engine air supply, and discloses an engine air supply system and an EGR rate determination method, the engine air supply system comprising an engine, an air inlet pipe, an exhaust pipe and an EGR assembly, the engine having a plurality of cylinders, the air inlet pipe being communicated with air inlet ends of the plurality of cylinders, the exhaust pipe being communicated with exhaust ends of the plurality of cylinders, the EGR assembly comprising a gas storage tank, a main control valve, an EGR main pipe and a plurality of EGR branch pipes, the first end of the EGR main pipe being communicated with the exhaust pipe through the main control valve, the second end of the EGR main pipe being communicated with the gas storage tank, the gas storage tank being communicated with the air inlet ends of the plurality of cylinders through the plurality of EGR branch pipes, and each of the EGR branch pipes being provided with an EGR control valve; the EGR rate determination method is applied to the above engine air supply system. The engine air supply system provided by the application ensures that the exhaust pressure supplied into the engine cylinders subsequently does not fluctuate, and ensures the uniformity of the EGR rates of the cylinders.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of engine air supply, in particular to an engine air supply system and an EGR rate determination method. BACKGROUND

[0002] During the working process of the engine, each cylinder alternately works, and the pressure in the exhaust pipe fluctuates during the exhaust process. Therefore, after the EGR pipe takes gas from the exhaust pipe, the pressure in the EGR pipe also fluctuates, and the exhaust gas in the EGR pipe will enter the cylinder of the engine together with the fresh air. Due to the pressure fluctuation of the EGR pipe, the EGR rate of the mixed exhaust gas and fresh air changes at different times, which affects the reliability of the engine. SUMMARY

[0003] The purpose of the present application is to provide an engine air supply system, which can temporarily store the exhaust gas taken from the exhaust pipe, stabilize the pressure of this part of gas, and then supply it to each cylinder through the corresponding EGR branch pipe, ensuring that the exhaust gas pressure supplied to the engine cylinder is stable and does not fluctuate, and an EGR control valve is arranged on each EGR branch pipe to control the opening and closing of the corresponding EGR branch pipe to adjust the exhaust gas intake time of each cylinder, ensuring the uniformity of the EGR rate of each cylinder.

[0004] To achieve this purpose, the present application adopts the following technical scheme:

[0005] An engine air supply system, comprising:

[0006] an engine having a plurality of cylinders;

[0007] an intake pipe connected to the intake end of the plurality of cylinders;

[0008] an exhaust pipe connected to the exhaust end of the plurality of cylinders;

[0009] an EGR assembly comprising a gas storage tank, a main control valve, an EGR main pipe, and a plurality of EGR branch pipes, the first end of the EGR main pipe being connected to the exhaust pipe through the main control valve, the second end of the EGR main pipe being connected to the gas storage tank, the gas storage tank being connected to the intake end of the plurality of cylinders through the plurality of EGR branch pipes, and an EGR control valve being arranged on each EGR branch pipe.

[0010] Preferably, the EGR control valve is configured to unidirectionally guide the EGR branch pipe from the gas storage tank to the cylinder.

[0011] Preferably, a intercooler is arranged on the intake pipe, and an EGR cooler is arranged between the gas storage tank and the main control valve on the exhaust pipe.

[0012] As preferred, a turbine and a compressor are further included, the turbine is connected to the compressor, the turbine is arranged on the exhaust pipe, and the compressor is arranged on the intake pipe.

[0013] The application further provides an EGR rate determination method, which is applied to the engine air supply system and can effectively improve the uniformity of the EGR rate of each cylinder of the engine.

[0014] An EGR rate determination method is applied to the engine air supply system, and the EGR rate determination method comprises the following steps:

[0015] S100, an EGR rate is proposed, and a calculation value α of the EGR rate is assigned;

[0016] S200, according to α, a duration t0 that the pressure P1 in the gas tank is greater than the pressure P2 in the cylinder of the engine is obtained;

[0017] S300, the opening time t of the EGR control valve to be determined is obtained, and it is judged whether t < t0 is satisfied;

[0018] If yes, step S400 is performed;

[0019] If no, the pressure P1 in the gas tank and / or the cross-sectional area A of the injection hole of the fuel injector are adjusted, and then the step S200 is returned;

[0020] S400, performance index evaluation is performed, and it is judged whether the evaluation requirement is satisfied;

[0021] If yes, the EGR rate determination is completed;

[0022] If no, a new EGR rate is proposed, and then the step S200 is returned after the new EGR rate is assigned to α.

[0023] As preferred, in step S200, the duration t0 that the pressure P1 in the gas tank is greater than the pressure P2 in the cylinder is obtained by using GT-POWER software calculation.

[0024] As preferred, the pressure P1 in the gas tank and the pressure P2 in the cylinder are obtained by a pressure sensor.

[0025] As preferred, in step S300, the opening time t of the EGR control valve is specifically obtained as follows:

[0026] The mass m of the EGR gas of the cylinder e and the mass flow q m are obtained. Wherein,

[0027] m1 is the fresh air intake mass of the cylinder, m is the fresh air intake mass flow of the cylinder, and n is the rotating speed of the engine;

[0028] p is the gas density in the gas tank, T1 is the gas temperature in the gas tank, and R is the gas constant.

[0029] Preferably, step S400 is specifically judging whether the NOx value and the SOOT value in the exhaust pipe meet the requirements. X Preferably, step S400 is specifically judging whether the NOx value and the SOOT value in the exhaust pipe meet the requirements.

[0030] Preferably, step S400 is specifically judging whether the NOx value and the SOOT value in the exhaust pipe meet the requirements. X Preferably, step S400 is specifically judging whether the NOx value and the SOOT value in the exhaust pipe meet the requirements.

[0031] Preferably, step S400 is specifically judging whether the NOx value and the SOOT value in the exhaust pipe meet the requirements. X Preferably, step S400 is specifically judging whether the NOx value and the SOOT value in the exhaust pipe meet the requirements. 3 Preferably, step S400 is specifically judging whether the NOx value and the SOOT value in the exhaust pipe meet the requirements. 3

[0032] Advantages:

[0033] The engine gas supply system provided by the application can ensure that the exhaust gas pressure supplied into the engine cylinder is stable and does not fluctuate. In addition, the EGR control valve arranged on each EGR branch pipe can control the opening and closing of the corresponding EGR branch pipe to adjust the exhaust gas intake time of each cylinder, thereby ensuring the uniformity of the EGR rate of each cylinder.

[0034] The EGR rate determination method provided by the application applies the above-mentioned engine gas supply system, obtains the duration t0 during which the pressure P1 in the gas tank is greater than the pressure P2 in the cylinder of the engine, compares t0 with the opening time t of the EGR control valve, adjusts the pressure P1 in the gas tank and / or the injection hole cross-sectional area A of the fuel injector according to the comparison result, and iterates the EGR rate in the subsequent performance index evaluation process, so as to determine the value of the optimal EGR rate and realize the controllability of the EGR exhaust gas mass entering each cylinder, thereby improving the uniformity of the EGR rate of each cylinder. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 is a structural schematic diagram of the engine gas supply system provided by the application;

[0036] Figure 2 is a flow schematic diagram of the EGR rate determination method provided by the application. ​

[0037] Fig.:

[0038] 1, engine; 11, cylinder;

[0039] 21, intake pipe; 22, exhaust pipe; 23, intercooler; 24, EGR cooler;

[0040] 31, gas reservoir; 32, main control valve; 33, EGR main pipe; 34, EGR branch pipe; 35, EGR control valve;

[0041] 41, turbine; 42, compressor. DETAILED DESCRIPTION

[0042] The application will be further described below in conjunction with the drawings and embodiments. It should be understood that the specific embodiments described herein are intended to be merely illustrative of the application and not in limitation thereof. It should also be understood that, for the purpose of clarity, only those structures of the application that are relevant to the present application have been shown in the drawings.

[0043] In the description of the present application, unless otherwise explicitly specified and limited, the terms "connected", "connected", "fixed" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0044] In the present application, unless otherwise explicitly specified and limited, the first feature "on" or "under" the second feature can include that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, the first feature "on", "above" and "above" the second feature includes that the first feature is directly above and obliquely above the second feature, or only indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature "below", "below" and "below" the second feature includes that the first feature is directly below and obliquely below the second feature, or only indicates that the horizontal height of the first feature is less than that of the second feature.

[0045] In the description of the present embodiment, the terms "up", "down", "right", and other orientation or position relationships are based on the orientation or position relationship shown in the drawings, and are only for the purpose of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second" are only used to distinguish in the description, and have no special meaning.

[0046] The embodiment provides an engine air supply system. Referring to Figure 1 As shown in the figure, the engine air supply system comprises an engine 1, an air inlet pipe 21, an exhaust pipe 22 and an EGR assembly, wherein the engine 1 has a plurality of cylinders 11, the air inlet pipe 21 is communicated with air inlet ends of the plurality of cylinders 11, the exhaust pipe 22 is communicated with exhaust ends of the plurality of cylinders 11, the EGR assembly comprises a gas storage tank 31, a master valve 32, an EGR main pipe 33 and a plurality of EGR branch pipes 34, a first end of the EGR main pipe 33 is communicated with the exhaust pipe 22 through the master valve 32, a second end of the EGR main pipe 33 is communicated with the gas storage tank 31, the gas storage tank 31 is communicated with the air inlet ends of the plurality of cylinders 11 through the plurality of EGR branch pipes 34, and each of the EGR branch pipes 34 is provided with an EGR control valve 35.

[0047] In the embodiment, the engine air supply system is provided with the gas storage tank 31 in the EGR assembly, and part of exhaust gas discharged from the exhaust pipe 22 can enter the gas storage tank 31 through the master valve 32 and the EGR main pipe 33 during the exhaust process of the exhaust pipe 22, the part of exhaust gas can be temporarily stored in the gas storage tank 31, the pressure of the part of exhaust gas is stabilized, and then the part of exhaust gas is supplied into each cylinder 11 through the plurality of EGR branch pipes 34, so that the exhaust gas pressure supplied into the cylinders 11 of the engine 1 is stabilized, and fluctuation is avoided. In addition, the EGR control valve 35 is arranged on each of the EGR branch pipes 34, the corresponding EGR branch pipe 34 can be opened and closed to adjust the exhaust gas inlet time of each cylinder 11, and the uniformity of the EGR rate of each cylinder 11 is ensured.

[0048] In the embodiment, the EGR control valve 35 is configured to unidirectionally guide the EGR branch pipe 34 from the gas storage tank 31 to the cylinder 11. In this way, the function of unidirectionally guiding the exhaust gas is achieved, backflow of the exhaust gas is avoided, and the stable and reliable operation of each cylinder 11 of the engine 1 is further ensured, and pressure fluctuation caused by backflow is avoided.

[0049] Optionally, the master valve 32 is an electromagnetic valve.

[0050] Optionally, the EGR control valve 35 is an electromagnetic valve.

[0051] Specifically, the air inlet pipe 21 comprises an air inlet main pipe and a plurality of air inlet branch pipes, the plurality of air inlet branch pipes are connected to the air inlet main pipe, and the plurality of air inlet branch pipes are connected to the plurality of cylinders 11 in one-to-one correspondence.

[0052] Specifically, the air inlet pipe 21 is provided with a intercooler 23, and the exhaust pipe 22 is provided with an EGR cooler 24 between the gas storage tank 31 and the master valve 32. Specifically, the intercooler 23 is arranged on the air inlet main pipe, and the arrangement of the intercooler 23 can cool fresh air in the air inlet pipe 21. The arrangement of the EGR cooler 24 can cool exhaust gas in the EGR main pipe 33.

[0053] Specifically, the engine air supply system further comprises a turbine 41 and a compressor 42, the turbine 41 is connected to the compressor 42, the turbine 41 is arranged on the exhaust pipe 22, and the compressor 42 is arranged on the air inlet pipe 21. Specifically, the exhaust gas in the exhaust pipe 22 is discharged to drive the turbine 41 to rotate and work, and the turbine 41 drives the compressor 42 to work in turn, so that the fresh air is pressurized and sent into the air inlet pipe 21.

[0054] With reference to the above description, the embodiment further provides an EGR rate determination method, which applies the engine air supply system. Figures 1 to 2 The EGR rate determination method mainly comprises the following steps:

[0055] S100, an EGR rate is proposed, and a calculation value α of the EGR rate is given;

[0056] S200, according to α, the duration t0 that the pressure P1 in the gas tank 31 is greater than the pressure P2 in the cylinder 11 of the engine 1 is obtained;

[0057] S300, the opening time t of the EGR control valve 35 to be determined is obtained, and it is judged whether t < t0 is satisfied;

[0058] If yes, step S400 is performed;

[0059] If no, the pressure P1 in the gas tank 31 and / or the injection hole cross-sectional area A of the fuel injector are adjusted, and then the step S200 is returned;

[0060] S400, performance index evaluation is performed, and it is judged whether the evaluation requirement is satisfied;

[0061] If yes, the EGR rate determination is completed;

[0062] If no, a new EGR rate is proposed and given to α, and then the step S200 is returned.

[0063] Specifically, in order to ensure that the EGR rate in the cylinder 11 can be obtained as large as possible, and the mixture is uniform, the opening time of the EGR control valve 35 is in the process of opening the intake valve of each cylinder 11. When the pressure in the gas tank 31 is greater than the pressure in the cylinder 11, the EGR control valve 35 is opened to allow exhaust gas to enter the corresponding cylinder 11, and in the subsequent intake compression process, the exhaust gas and fresh air are mixed by the flow movement in the cylinder 11. The method applies the above-mentioned engine air supply system, by obtaining the duration t0 that the pressure P1 in the gas tank 31 is greater than the pressure P2 in the cylinder 11 of the engine 1, and comparing t0 with the opening time t of the EGR control valve 35, adjusting the pressure P1 in the gas tank 31 and / or the injection hole area A of the fuel injector according to the comparison result, and continuously iterating the EGR rate in the subsequent performance index evaluation process, so as to determine the value of the optimal EGR rate, and realize the controllability of the EGR exhaust gas mass entering each cylinder 11, and improve the uniformity of the EGR rate of each cylinder 11.

[0064] Specifically, first, an initial EGR rate is proposed, the pressure P1 in the gas tank 31 and the pressure P2 in the cylinder 11 of the engine 1 are obtained, and the duration t0 that the pressure P1 in the gas tank 31 is greater than the pressure P2 in the cylinder 11 is obtained by calculation using the GT-POWER software. Specifically, the pressure P1 in the gas tank 31 and the pressure P2 in the cylinder 11 are obtained by a pressure sensor.

[0065] Subsequently, the opening time t of the EGR control valve 35 is obtained using the previously proposed initial EGR rate. Specifically:

[0066] The mass m of the EGR gas of the cylinder 11 is obtained e And the mass flow q m Then Wherein,

[0067] m1 is the fresh air intake mass of the cylinder 11, m is the fresh air intake mass flow of the cylinder 11, and n is the speed of the engine 1;

[0068] P is the gas density in the gas tank 31; T1 is the gas temperature in the gas tank 31; R is the gas constant.

[0069] According to the above parameters, the initial EGR rate a is brought in, that is, the following formula is obtained

[0070] In order to ensure that the exhaust gas can enter the cylinder 11 sufficiently, the EGR control valve 35 time should be less than or equal to the duration that P1 is greater than P2.

[0071] Determine whether t satisfies: t < t0.

[0072] If the determination is yes, then proceed with the subsequent performance evaluation;

[0073] If the determination is negative, adjust the pressure P1 inside the air tank 31 and / or the nozzle cross-sectional area A of the injector, then return to step S200 to continue calculating the new t0. This continues until the requirement of t < t0 is finally met.

[0074] In this embodiment, the pressure P1 inside the gas storage tank 31 is adjusted by adjusting the model of the compressor 42.

[0075] Furthermore, performance evaluation mainly includes experimental simulation evaluation based on simulation software and experimental evaluation based on real conditions, which need to be evaluated through both simulation and experiment.

[0076] Specifically, the performance index evaluation to determine whether the evaluation requirements are met involves: determining the NO content in the exhaust gas from exhaust pipe 22. X And whether the smoke opacity values ​​all meet the requirements.

[0077] Understandably, different emission regulations have different reference thresholds. Taking the non-road Stage IV regulation as an example: the NO4 of a certain 260 horsepower model in the NRSC emission cycle... X The required content is 1.398 g / (kW·h). Correspondingly, the NO content in the exhaust gas from exhaust pipe 22 is... X The specific requirements for smoke opacity are as follows: Determine if the following condition is met: 1g / (kW·h) < NO X The content is <2g / (kW·h) and 5mg / m³ 3 Smoke content <10mg / m³ 3 If the determination is yes, it indicates that the EGR rate has been determined; if the determination is no, a new EGR rate needs to be proposed and assigned to α before returning to step S200, and the above steps are repeated, that is, the EGR rate is iterated until the optimal EGR rate value is determined, so as to achieve controllable EGR exhaust gas quality entering each cylinder and improve the uniformity of EGR rate of each cylinder.

[0078] In some other alternative implementations, performance evaluation can also refer to other indicators. Taking marine diesel engine emission regulations as an example: the regulations stipulate that for Category I marine engines (single-cylinder displacement less than 5L) with an equivalent displacement of 1.2L to 5L, the limit for HC+NOx is 5.8g and the limit for PM is 0.3g / kWh.

[0079] The EGR rate determination method provided by this invention utilizes the aforementioned engine air supply system. It obtains the duration t0 during which the pressure P1 inside the air tank 31 is greater than the pressure P2 inside the cylinder 11 of the engine 1, and compares t0 with the opening time t of the EGR control valve 35. Based on the comparison result, it adjusts the pressure P1 inside the air tank 31 and / or the nozzle cross-sectional area A of the fuel injector. In the subsequent performance evaluation process, it iterates the EGR rate to determine the optimal EGR rate value, thereby achieving controllable EGR exhaust gas quality entering each cylinder 11 and improving the uniformity of the EGR rate of each cylinder 11.

[0080] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art will be able to make various obvious changes, readjustments, and substitutions without departing from the scope of protection of the present invention. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for determining EGR rate, applied to an engine air supply system, characterized in that, The engine air supply system includes: Engine (1) has multiple cylinders (11); An intake pipe (21) is connected to the intake end of one or more of the cylinders (11); An exhaust pipe (22) is connected to the exhaust end of one or more of the cylinders (11); The EGR assembly includes an air tank (31), a main control valve (32), an EGR main pipe (33), and multiple EGR branch pipes (34). The first end of the EGR main pipe (33) is connected to the exhaust pipe (22) through the main control valve (32), and the second end of the EGR main pipe (33) is connected to the air tank (31). The air tank (31) is connected to the intake end of multiple cylinders (11) through multiple EGR branch pipes (34). Each EGR branch pipe (34) is equipped with an EGR control valve (35). The method for determining the EGR rate includes the following steps: S100, Determine an EGR rate and assign it to the calculated EGR rate value α; S200, According to α, the duration t0 of the pressure P1 in the gas storage tank (31) being greater than the pressure P2 in the cylinder (11) of the engine (1) is obtained; S300, obtain the opening time t of the EGR control valve (35) to be determined, and determine whether it satisfies: t < t0; If so, proceed to step S400; If not, adjust the pressure P1 in the gas tank (31) and / or the nozzle cross-sectional area A of the injector before returning to step S200; S400: Conduct performance evaluation to determine whether the evaluation requirements are met; If so, the EGR rate determination is complete; If not, a new EGR rate is proposed and assigned to α, then return to step S200.

2. The EGR rate determination method according to claim 1, characterized in that, The EGR control valve (35) is configured to unidirectionally guide the EGR branch pipe (34) from the gas storage tank (31) to the cylinder (11).

3. The EGR rate determination method according to claim 1, characterized in that, An intercooler (23) is provided on the intake pipe (21), and an EGR cooler (24) is provided on the exhaust pipe (22) between the gas storage tank (31) and the main control valve (32).

4. The EGR rate determination method according to claim 1, characterized in that, It also includes a turbine (41) and a compressor (42), the turbine (41) being connected to the compressor (42), the turbine (41) being located on the exhaust pipe (22), and the compressor (42) being located on the intake pipe (21).

5. The EGR rate determination method according to claim 1, characterized in that, In step S200, the duration t0 during which the pressure P1 inside the gas storage tank (31) is greater than the pressure P2 inside the cylinder (11) is calculated using GT-POWER software.

6. The EGR rate determination method according to claim 1, characterized in that, The pressure P1 inside the gas storage tank (31) and the pressure P2 inside the cylinder (11) are obtained by pressure sensors.

7. The EGR rate determination method according to claim 1, characterized in that, In step S300, the opening time t of the EGR control valve (35) is specifically obtained as follows: The mass m of the EGR gas in the cylinder (11) is obtained. e and mass flow rate q m ,but ;in, ; m1 is the fresh air intake mass of the cylinder (11), m is the fresh air intake mass flow rate of the cylinder (11), and n is the rotational speed of the engine (1). ; ρ is the gas density inside the gas storage tank (31); T1 is the gas temperature inside the gas storage tank (31); R is the gas constant.

8. The EGR rate determination method according to claim 1, characterized in that, Step S400 specifically involves: determining the NO content in the exhaust gas from the exhaust pipe (22). X And whether the smoke opacity values ​​all meet the requirements.

9. The EGR rate determination method according to claim 8, characterized in that, Determine the NO content in the exhaust gas from the exhaust pipe (22). X And whether the smoke opacity values ​​all meet the requirements, specifically: Determine if the following condition is met: 1g / (kW·h) < NO X The content is <2g / (kW·h) and 5mg / m³ 3 Smoke content <10mg / m³ 3 .

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