CN112211756A - Low-pressure EGR system and gas flow control method - Google Patents
Low-pressure EGR system and gas flow control method Download PDFInfo
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- CN112211756A CN112211756A CN202011027029.0A CN202011027029A CN112211756A CN 112211756 A CN112211756 A CN 112211756A CN 202011027029 A CN202011027029 A CN 202011027029A CN 112211756 A CN112211756 A CN 112211756A
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
- F02M26/02—EGR systems specially adapted for supercharged engines
- F02M26/04—EGR systems specially adapted for supercharged engines with a single turbocharger
- F02M26/06—Low pressure loops, i.e. wherein recirculated exhaust gas is taken out from the exhaust downstream of the turbocharger turbine and reintroduced into the intake system upstream of the compressor
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/0025—Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
- F02D41/0047—Controlling exhaust gas recirculation [EGR]
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
- F02M26/12—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems characterised by means for attaching parts of an EGR system to each other or to engine parts
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
- F02M26/13—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories
- F02M26/17—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories in relation to the intake system
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
- F02M26/13—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories
- F02M26/22—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories with coolers in the recirculation passage
- F02M26/23—Layout, e.g. schematics
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
- F02M26/13—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories
- F02M26/35—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories with means for cleaning or treating the recirculated gases, e.g. catalysts, condensate traps, particle filters or heaters
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
- F02M26/45—Sensors specially adapted for EGR systems
- F02M26/46—Sensors specially adapted for EGR systems for determining the characteristics of gases, e.g. composition
- F02M26/47—Sensors specially adapted for EGR systems for determining the characteristics of gases, e.g. composition the characteristics being temperatures, pressures or flow rates
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D29/00—Details, component parts, or accessories
- F04D29/02—Selection of particular materials
- F04D29/023—Selection of particular materials especially adapted for elastic fluid pumps
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D29/00—Details, component parts, or accessories
- F04D29/26—Rotors specially for elastic fluids
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/40—Engine management systems
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- Physics & Mathematics (AREA)
- Fluid Mechanics (AREA)
- Analytical Chemistry (AREA)
- Exhaust-Gas Circulating Devices (AREA)
Abstract
The invention relates to a low-pressure EGR system and a gas flow control method, which comprise an EGR gas inlet pipe arranged at the downstream of a post-processing system, wherein the EGR gas inlet pipe is communicated with an EGR gas outlet pipe through an EGR module assembly; the EGR cooler water return pipe is connected with the EGR cooler water outlet; the EGR valve is arranged at one end of the EGR cooler, the temperature sensor is arranged on the EGR cooler and is close to an air inlet of the EGR valve, the air taking positions of two differential pressure pipe joints are respectively positioned at the front end and the rear end of the EGR valve, one end of a first differential pressure sensor connecting pipe and one end of a second differential pressure sensor connecting pipe are respectively connected with the two differential pressure pipe joints, the other end of the first differential pressure sensor connecting pipe and the other end of the second differential pressure sensor connecting pipe are connected with the two joints of the differential pressure sensor, and the engine ECU acquires information of the differential pressure sensor; the invention can accurately control the flow of EGR gas.
Description
Technical Field
The invention relates to the field of engines, in particular to a low-pressure EGR system and a gas flow control method.
Background
With the increasing pressure of the earth energy and the environment, the requirements on the emission and the oil consumption of an engine are strict; in order to meet the increasingly strict requirements of oil consumption regulations, the engine is developed in the direction of low oil consumption, low emission and high heat efficiency; therefore, the use of low-pressure EGR systems (which can improve the thermal efficiency of the engine and optimize fuel consumption and emissions) in engines is increasing.
When the low-pressure EGR system is used, the EGR gas is condensed by the cooler to generate more condensed water, and meanwhile, the EGR gas contains pollutants such as sulfide, fine carbon particles and the like generated after gasoline is combusted; when the EGR gas carries pollutants and fine condensed water and is pressed into an engine cylinder through a supercharger, the pollutants and fine condensed water drops pass through a compressor impeller of the turbocharger rotating at high speed and can cause great damage to the impeller; meanwhile, when the air temperature is below zero, condensed water generated by the low-pressure EGR system is accumulated in a large volume and freezes, so that a pipeline air port is blocked, and the work of an engine is influenced; at the present stage, the EGR gas cannot directly detect the flow through a related sensor, meanwhile, the gas pressure difference between the EGR gas inlet end and the EGR gas outlet end is too small under the low-load working condition of the low-pressure EGR in the engine, and when a conventional engine uses a low-pressure EGR system, the flow of the EGR exhaust gas cannot be accurately controlled to be matched with various operating conditions of the engine.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides a low-pressure EGR system and a gas flow control method.
In order to solve the technical problems, the invention is realized by the following technical scheme:
a low-pressure EGR system comprises an EGR gas inlet pipe arranged at the downstream of an aftertreatment system, wherein the EGR gas inlet pipe is communicated with an EGR gas outlet pipe through an EGR module assembly, and an EGR cooler water inlet pipe is connected with an EGR cooler water inlet; the EGR cooler water return pipe is connected with the EGR cooler water outlet; the EGR module assembly comprises an EGR cooler, an EGR valve is arranged at one end of the EGR cooler, a temperature sensor is arranged on the EGR cooler and is close to an air inlet of the EGR valve, the temperature of the air inlet of the EGR valve is measured, the air taking positions of two differential pressure pipe interfaces are respectively arranged at the front end and the rear end of the EGR valve, one end of a first differential pressure sensor connecting pipe and one end of a second differential pressure sensor connecting pipe are respectively connected with the two differential pressure pipe interfaces, the other end of the first differential pressure sensor connecting pipe and the other end of the second differential pressure sensor connecting pipe are connected with the two interfaces of the differential pressure sensor, an engine ECU acquires the information of the differential pressure sensor and the temperature sensor, the real-time EGR mass flow in the working process of the engine.
Further, the calculation process is specifically performed according to the following formula:
wherein, Se: effective sectional area of the EGR valve;
and Qm: EGR mass flow;
ρ: the density of the gas;
Δ P: the pressure difference is obtained through a pressure difference sensor, the pressure difference sensor can respectively measure the pressure at two ends of the EGR valve, and the pressure difference is obtained through calculation;
the gas density ρ in the above formula is obtained by experiments in combination with the equation for the ideal gas state:
r is a constant, the value is 283, rho is density, P is the pressure of gas at the air inlet end of the EGR valve (obtained by a differential pressure sensor which can respectively measure the pressure at two ends of the EGR valve and then calculate the pressure difference), and T is the gas temperature (obtained by measuring by a temperature sensor).
Further, the system also comprises an air temperature flow sensor, a mixing valve and a mixing valve connecting pipe, wherein the air temperature flow sensor is arranged close to the outlet end of the air filter, one end of the air filter is connected with the mixing valve, the mixing valve is connected with a turbocharger through the mixing valve connecting pipe, and the turbocharger is connected with the aftertreatment system.
Furthermore, the post-treatment system comprises a three-way catalytic purifier and a particle catcher arranged below the three-way catalytic purifier, an air inlet of an EGR air inlet pipe is provided with an upward inclined angle, the air inlet is arranged in the whole post-treatment system, the EGR module assembly is arranged with an upward inclined angle when the whole machine is arranged, the turbocharger is connected with the three-way catalytic purifier, and an EGR air outlet pipe is also connected with a mixing valve connecting pipe; the whole pipeline section of the first differential pressure sensor connecting pipe and the whole pipeline section of the second differential pressure sensor connecting pipe are provided with upward inclination angles.
Further, the compressor end impeller of the turbocharger is provided with a Ni-P special coating.
Further, the mixing valve connecting pipe comprises a connecting pipe body, an EGR connecting pipe connected with the connecting pipe body, a carbon tank connecting pipe and a respirator connecting pipe, and the EGR outlet pipe is connected with the EGR connecting pipe.
Further, a water inlet on the EGR cooler is close to a gas inlet of the cooler, and a water outlet is close to a gas outlet of the EGR cooler, so that the gas flow direction is the same as the water flow direction.
The invention relates to a gas flow control method of a low-pressure EGR system, which is carried out as follows: the engine ECU collects the EGR gas temperature measured by the exhaust gas temperature sensor, collects the pressure values at two ends of the EGR valve measured by the EGR pressure difference sensor, calculates the pressure difference at two ends, calculates the real-time EGR mass flow in the working process of the engine, and performs the following steps:
in the formula, Se: effective sectional area of the EGR valve;
and Qm: EGR mass flow;
ρ: the density of the gas;
Δ P: a pressure difference;
the gas density ρ in the above formula is obtained by experiments in combination with the equation for the ideal gas state:
r is a constant, the numerical value is 283, rho is the density, P is the pressure of gas at the air inlet end of the EGR valve (obtained by a differential pressure sensor which can respectively measure the pressure at two ends of the EGR valve and then calculate the pressure difference), and T is the gas temperature (obtained by measuring by a temperature sensor); the engine ECU obtains EGR mass flow according to the value of the effective sectional area of the EGR valve; the engine ECU acquires an air flow value of an air temperature flow sensor at the outlet end of an air filter to obtain the ratio of EGR mass flow to fresh air flow under the real-time work of the engine, and adjusts the opening degree of an EGR valve according to the work requirement of the engine to adjust the ratio of proper EGR mass flow to fresh air flow to meet the work requirement of the engine.
Compared with the prior art, the invention has the following advantages:
all air passage pipelines of the invention are arranged with upward inclination angles, which can effectively prevent the accumulation of condensed water when the engine works and the phenomena of air passage blockage caused by icing in cold temperature environment;
the surface of the compressor impeller of the turbocharger in the system adopts the Ni-P special chemical coating, so that the strength (resistance to particulate matter impact) can be improved, and meanwhile, the corrosion of pollutants can be prevented;
the system of the invention adopts an EGR differential pressure sensor and an exhaust gas temperature sensor, the two sensors can calculate the EGR gas flow in the working process of the engine through a model under the cooperative work, and the ratio of the EGR flow and the fresh air flow under the real-time work of the engine can be calculated by combining a MAF sensor (air temperature flow sensor) (the function is to measure the fresh air flow of the engine); the flow of the EGR gas can be accurately controlled through the linkage control of the electrically controlled EGR valve and the air inlet mixing valve, particularly the flow of the EGR gas under medium and low loads.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a schematic diagram of the system of the present invention;
FIG. 2 is a first side view of the system of the present invention;
FIG. 3 is a second side view of the system of the present invention;
FIG. 4 is a schematic diagram of an EGR module;
FIG. 5 is a top view of FIG. 4;
FIG. 6 is a schematic structural diagram of a mixing valve nozzle;
FIG. 7 is a side view of the mixing valve nipple;
labeled in FIGS. 1-7 are: 1. EGR intake pipe, 2, EGR module assembly, 2.1, EGR cooler, 2.2, EGR valve, 2.3, temperature sensor, 2.4, differential pressure pipe interface, 3, EGR outlet pipe, 4, EGR cooler inlet pipe, 5, EGR cooler return pipe, 6, differential pressure sensor connecting pipe A, 7, differential pressure sensor connecting pipe B, 8, differential pressure sensor, 9, MAF sensor (air temperature flow sensor), 10, air inlet mixing valve, 11, mixing valve connecting pipe, 11.1, mixing valve connecting pipe body, 11.2, EGR connecting pipe, 11.3, carbon tank, 11.4, respirator connecting pipe, 12, turbocharger, 13, air filter connecting pipe.
Detailed Description
The technical solutions in the embodiments will be described clearly and completely with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the examples without making any creative effort, shall fall within the protection scope of the present invention.
Unless otherwise defined, technical or scientific terms used in the embodiments of the present application should have the ordinary meaning as understood by those having ordinary skill in the art. The use of "first," "second," and similar terms in the present embodiments does not denote any order, quantity, or importance, but rather the terms are used to distinguish one element from another. The word "comprising" or "comprises", and the like, means that the element or item listed before the word covers the element or item listed after the word and its equivalents, but does not exclude other elements or items. "mounted," "connected," and "coupled" are to be construed broadly and may, for example, be fixedly coupled, detachably coupled, or integrally coupled; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. "Upper," "lower," "left," "right," "lateral," "vertical," and the like are used solely in relation to the orientation of the components in the figures, and these directional terms are relative terms that are used for descriptive and clarity purposes and that can vary accordingly depending on the orientation in which the components in the figures are placed.
As shown in fig. 1-3, the low pressure EGR system of the present embodiment includes an EGR inlet pipe 1, an EGR module assembly 2, an EGR outlet pipe 3, an EGR cooler inlet pipe 4, an EGR cooler return pipe 5, a first differential pressure sensor connection pipe 6, a second differential pressure sensor connection pipe 7, a differential pressure sensor 8, a MAF sensor (air temperature and flow sensor) 9, an inlet mixing valve 10, a mixing valve connection pipe 11, a turbocharger 12, and an air cleaner 13; the mixing valve adapter 11 is connected with the intake mixing valve 10, the turbocharger 12 and the EGR outlet pipe 3.
In the embodiment, an EGR gas inlet pipe 1 is arranged at the downstream of the post-treatment system, the EGR gas inlet pipe 1 and an EGR gas outlet pipe 3 are communicated with an EGR module assembly 2, and an EGR cooler water inlet pipe 4 is connected with an EGR cooler water inlet; the EGR cooler water return pipe 5 is connected with the water outlet of the EGR cooler; the EGR module assembly 2 comprises an EGR cooler 2.1, an EGR valve 2.2 is arranged at one end of the EGR cooler 2.1, a temperature sensor 2.3 is arranged on the EGR cooler 2.1 and is close to an EGR valve air inlet to measure the temperature of an EGR valve air inlet, the air taking positions of two differential pressure pipe interfaces 2.4 are respectively positioned at the front end and the rear end of the EGR valve 2.2, one end of a first differential pressure sensor connecting pipe 6 and one end of a second differential pressure sensor connecting pipe 7 are respectively connected with the two differential pressure pipe interfaces 2.4, the other end of the first differential pressure sensor connecting pipe and the other end of the second differential pressure sensor connecting pipe are connected with two interfaces of a differential pressure sensor 8, an engine ECU (electronic control Unit) collects information of the differential pressure sensor 8 and the temperature sensor 2.3 to calculate the real-time EGR mass flow in the working process of the engine.
The mixing valve nozzle 11 comprises a nozzle body 11.1, an EGR nozzle 11.2, a canister nozzle 11.3, and a respirator nozzle 11.4, as shown in fig. 4-5.
The air temperature and flow sensor 9 is arranged close to the outlet end of an air filter 13, one end of the air filter 13 is connected with a mixing valve 10, the mixing valve 10 is connected with a turbocharger 12 through a mixing valve connecting pipe 11, and the turbocharger 12 is connected with an aftertreatment system.
The post-treatment system comprises a three-way catalytic purifier and a particle catcher arranged below the three-way catalytic purifier, an air inlet of an EGR air inlet pipe is provided with an upward inclination angle, the air inlet is arranged in the whole post-treatment system, the EGR module assembly 2 is arranged with an upward inclination angle when the whole machine is arranged, a turbocharger 12 is connected with the three-way catalytic purifier, and an EGR air outlet pipe 3 is also connected with a mixing valve connecting pipe 11; the whole pipeline sections of the first differential pressure sensor connecting pipe 6 and the second differential pressure sensor connecting pipe 7 are inclined upwards.
The mixing valve connecting pipe 11 comprises a connecting pipe body 11.1, an EGR connecting pipe 11.2 connected with the connecting pipe body 11.1, a carbon tank connecting pipe 11.3 and a respirator connecting pipe 11.4, and the EGR outlet pipe 3 is connected with the EGR connecting pipe 11.2.
The water inlet pipe 4 of the EGR cooler is connected with the water inlet of the EGR cooler; the EGR cooler water return pipe 5 is connected with the water outlet of the EGR cooler; one end of the first differential pressure sensor connecting pipe 6 and one end of the second differential pressure sensor connecting pipe 7 are connected with a differential pressure pipe interface 2.4 on the EGR module assembly, and the other end of the first differential pressure sensor connecting pipe and the second differential pressure sensor connecting pipe are connected with two interfaces of a differential pressure sensor 8.
As shown in FIGS. 6-7, the EGR adapter 11.2, the carbon canister adapter 11.3 and the respirator adapter 11.4 are all mounted on the adapter body 11.1, and the pipelines are communicated with each other.
In the present embodiment, the EGR gas intake pipe 1, the pipe air intake, is disposed downstream of the entire aftertreatment system including a three-way catalytic converter (TWC) and a particle trap (GPF) disposed below the three-way catalytic converter.
The EGR gas obtained according to the technical scheme is filtered by the post-treatment system and purified, so that adverse effects on carbon deposition, corrosion and the like of a compressor impeller in the turbocharger 12 can be reduced; the pipe body is made of high-temperature-resistant stainless steel corrugated pipe, so that the high-temperature-resistant corrosion-resistant pipe is high in high-temperature resistance and reliability; when the air inlet of the EGR air inlet pipe is designed and arranged, the upward inclined angle is formed, and the adverse effect that the air passage is blocked by the accumulation of condensed water in the working process can be prevented.
In this embodiment, the EGR module assembly 2, the first differential pressure sensor connection pipe 6, and the second differential pressure sensor connection pipe 7 are arranged with an upward inclination angle when the whole machine is arranged, so that adverse effects of blocking an air passage due to accumulation of condensed water in the working process can be prevented.
In the embodiment, an EGR differential pressure sensor 8 and an exhaust gas temperature sensor 16 are adopted, the two sensors measure the EGR gas temperature and the pressure difference between two ends of an EGR valve under the cooperative work, then the real-time EGR mass flow in the working process of the engine can be calculated through a pore plate flow model, and the ratio of the EGR flow and the fresh air quantity under the real-time working of the engine can be calculated by combining with an MAF sensor (namely an air temperature flow sensor) 9 for measuring the fresh air flow of the engine; the flow of the EGR gas can be accurately controlled by controlling the opening of the EGR gas flow passage and the linkage control of the intake mixing valve 10 and the electrically controlled EGR valve 2.2, especially the flow of the EGR gas under low load in the engine.
The intake mixing valve 10 controls the opening of a fresh air flow passage from the air filter to a mixing valve connecting pipe, and adjusts the negative pressure in the mixing valve connecting pipe, thereby being beneficial to the mixing of EGR gas and fresh air.
The method is specifically carried out according to the following formula:
in the formula: se: effective sectional area of the EGR valve;
and Qm: EGR mass flow;
ρ: the density of the gas;
Δ P: pressure difference (obtained by a pressure difference sensor which can respectively measure the pressure at two ends of the EGR valve and then calculate to obtain the pressure difference);
ρ (gas density) in the above formula is obtained by experiments with the equation for the ideal gas state:
r is a constant, the value is 283, rho is density, P is the pressure of gas at the air inlet end of the EGR valve (obtained by a differential pressure sensor which can respectively measure the pressure at two ends of the EGR valve and then calculate the pressure difference), and T is the gas temperature (obtained by measuring by a temperature sensor).
The EGR differential pressure sensor 8 and the exhaust gas temperature sensor 16 respectively collect pressure difference and gas temperature, and the engine ECU obtains EGR mass flow according to the value of the effective sectional area of the EGR valve.
In this embodiment, the water inlet of the EGR cooler 14 in the EGR module assembly 2 is close to the air inlet of the cooler, and the water outlet is close to the air outlet of the EGR cooler, i.e. the gas flow direction is the same as the water flow direction; the arrangement design enables flowing low-temperature cooling water to cool high-temperature EGR gas in time, and is beneficial to inhibiting local boiling generated when the cooling liquid meets the high-temperature EGR gas.
The compressor-end impeller of the turbocharger 12 must be Ni-P coated to improve strength (resistance to particulate impact) and prevent corrosion of contaminants; the EGR gas contains water vapor, and the water vapor is condensed to separate out water drops when meeting fresh air with lower temperature and then collides with a pressure end impeller of a supercharger rotating at high speed to cause impact corrosion; after the pressure end impeller is strengthened by the coating, the impact resistance strength can be improved.
The mixing valve connecting pipe 11 body is made of aluminum alloy, and an O-shaped ring is arranged on the mounting end face; one end of the mixing valve connecting pipe is connected with an inlet of the turbocharger through a bolt, and the other end of the mixing valve connecting pipe is connected with an outlet of the mixing valve through a bolt.
The MAF sensor (air temperature and flow sensor) 9 is arranged close to the outlet end of the air filter 13, so that the MAF sensor (air temperature and flow sensor) can accurately measure the flow and the temperature of fresh air, and the interference effect of other gases is weakened. The ratio of the EGR flow and the fresh air amount at the engine real-time operation can be calculated by combining the MAF sensor 9.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (8)
1. A low pressure EGR system characterized by: the device comprises an EGR gas inlet pipe (1) arranged at the downstream of an aftertreatment system, wherein the EGR gas inlet pipe (1) is communicated with an EGR gas outlet pipe (3) through an EGR module assembly (2), and an EGR cooler water inlet pipe (4) is connected with an EGR cooler water inlet; the EGR cooler water return pipe (5) is connected with the water outlet of the EGR cooler; the EGR module assembly (2) comprises an EGR cooler (2.1), an EGR valve (2.2) is arranged at one end of the EGR cooler (2.1), a temperature sensor (2.3) is arranged on the EGR cooler (2.1) and is close to an air inlet of the EGR valve to measure the temperature of an air inlet of the EGR valve, air taking positions of two differential pressure pipe interfaces (2.4) are respectively positioned at the front end and the rear end of the EGR valve (2.2), one ends of a first differential pressure sensor connecting pipe (6) and a second differential pressure sensor connecting pipe (7) are respectively connected with the two differential pressure pipe interfaces (2.4), the other ends of the first differential pressure sensor connecting pipe and the second differential pressure sensor connecting pipe are connected with two interfaces of a differential pressure sensor (8), and the engine ECU acquires information of the differential pressure sensor (8) and the temperature sensor (2.3) to calculate real-time EGR mass flow in the working process of the engine and controls the EGR gas mass flow in real time by controlling the opening.
2. The low pressure EGR system of claim 1 wherein: calculating the real-time EGR mass flow in the working process of the engine according to the following formula:
in the formula, Se: effective sectional area of the EGR valve;
and Qm: EGR mass flow;
ρ: the density of the gas;
Δ P: the pressure difference is obtained through a pressure difference sensor, the pressure difference sensor can respectively measure the pressure at two ends of the EGR valve, and the pressure difference is obtained through calculation;
the gas density ρ in the above formula is obtained by testing the following equation in combination with the ideal gas state:
r is a constant, the value is 283, rho is density, P is the pressure of gas at the air inlet end of the EGR valve, the pressure is obtained through a differential pressure sensor, the differential pressure sensor can respectively measure the pressure at two ends of the EGR valve, and then the pressure difference is obtained through calculation; and T is the gas temperature measured by a temperature sensor.
3. The low pressure EGR system of claim 1 wherein: the system further comprises an air temperature flow sensor (9), a mixing valve (10) and a mixing valve connecting pipe (11), wherein the air temperature flow sensor (9) is arranged close to the outlet end of an air filter (13), one end of the air filter (13) is connected with the mixing valve (10), the mixing valve (10) is connected with a turbocharger (12) through the mixing valve connecting pipe (11), and the turbocharger (12) is connected with an aftertreatment system.
4. The low pressure EGR system of claim 3 wherein: the post-treatment system comprises a three-way catalytic purifier and a particle catcher arranged below the three-way catalytic purifier, an air inlet of an EGR (exhaust gas recirculation) air inlet pipe is provided with an upward inclination angle, the air inlet is arranged in the whole post-treatment system, an EGR module assembly (2) is arranged with an upward inclination angle when the whole machine is arranged, a turbocharger (12) is connected with the three-way catalytic purifier, and an EGR air outlet pipe (3) is also connected with a mixing valve connecting pipe (11); the whole pipeline sections of the first differential pressure sensor connecting pipe (6) and the second differential pressure sensor connecting pipe (7) are provided with upward inclination angles.
5. The low pressure EGR system of claim 4 wherein: the compressor end impeller of the turbocharger (12) is provided with a Ni-P special coating.
6. The low pressure EGR system of claim 3 wherein: the mixing valve connecting pipe (11) comprises a connecting pipe body (11.1), an EGR connecting pipe (11.2) connected with the connecting pipe body (11.1), a carbon tank connecting pipe (11.3) and a respirator connecting pipe (11.4), and an EGR outlet pipe (3) is connected with the EGR connecting pipe (11.2).
7. The low pressure EGR system of claim 1 wherein: the water inlet on the EGR cooler (2.1) is close to the air inlet of the cooler, and the water outlet is close to the air outlet of the EGR cooler, so that the gas flow direction is the same as the water flow direction.
8. A method of controlling gas flow in a low pressure EGR system, comprising: the method comprises the following steps: the engine ECU collects the EGR gas temperature measured by the exhaust gas temperature sensor (16), collects the pressure values at two ends of the EGR valve measured by the EGR pressure difference sensor (8) to calculate the pressure difference at two ends, then calculates the real-time EGR mass flow in the working process of the engine, and carries out the following steps:
in the formula, Se: effective sectional area of the EGR valve;
and Qm: EGR mass flow;
ρ: the density of the gas;
Δ P: a pressure difference;
the gas density ρ in the above formula is obtained by experiments in combination with the equation for the ideal gas state:
r is a constant, the value is 283, rho is density, P is the pressure of gas at the air inlet end of the EGR valve, the pressure is obtained through a differential pressure sensor, the differential pressure sensor can respectively measure the pressure at two ends of the EGR valve, and then the pressure difference is obtained through calculation; t is gas temperature measured by a temperature sensor; the engine ECU obtains EGR mass flow according to the value of the effective sectional area of the EGR valve; the engine ECU acquires an air flow value of an air temperature flow sensor (9) at the outlet end of an air filter (13) to obtain the proportion of EGR mass flow and fresh air flow under the real-time working of the engine, and adjusts the opening degree of an EGR valve according to the working requirement of the engine and adjusts the proportion of proper EGR mass flow and fresh air flow to meet the working requirement of the engine.
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