CN113931721A

CN113931721A - Engine exhaust hydrocarbon injection system and control strategy thereof

Info

Publication number: CN113931721A
Application number: CN202011152626.6A
Authority: CN
Inventors: 杨延相; 徐露明; 乐起奖
Original assignee: Zhejiang Fai Electronics Co Ltd
Current assignee: Zhejiang Fai Electronics Co Ltd
Priority date: 2020-06-29
Filing date: 2020-10-26
Publication date: 2022-01-14

Abstract

The utility model provides an engine exhaust hydrocarbon injection system, includes engine exhaust pipe, air feed subassembly, fuel feeding unit, mixing chamber, injection pipe, HC nozzle and the control unit, the air feed subassembly with the fuel feeding unit is connected respectively the mixing chamber, the HC nozzle be located mixing chamber low reaches and with the mixing chamber intercommunication, the air feed subassembly includes compressed air source, air valve, the fuel feeding unit includes low-pressure oil source, fuel cut-off valve and measuring pump, the measuring pump is a solenoid pulsed measurement injection unit for the accurate measurement gets into the fuel volume of mixing chamber. The invention aims to provide the hydrocarbon injection system which is high in injection precision, good in atomization effect, high in system reliability and low in cost.

Description

Engine exhaust hydrocarbon injection system and control strategy thereof

Technical Field

The invention belongs to the field of engine emission control, and particularly relates to an engine exhaust hydrocarbon injection system, in particular to a hydrocarbon injection system for a thermal management and particulate matter trapping filter (DPF) regeneration system of exhaust aftertreatment.

Background

In recent years, along with the increasing strictness of emission regulations, a requirement for modification of exhaust gas aftertreatment technology of vehicles is also provided, a Particulate Filter (DPF) technology of a Diesel engine system is considered to be the most effective aftertreatment means for reducing soot particles in exhaust gas at present, the PM capture efficiency can reach more than 90%, and when the exhaust gas passes through a Filter, the DPF filters the PM in the exhaust gas, and when the exhaust gas is accumulated to a certain degree, the soot particles in the exhaust gas must be burned through high-temperature exhaust gas containing oxygen to realize regeneration of the DPF, so that the DPF is prevented from being blocked and burnt and damaged due to excessive carbon deposition. On the other hand, in an exhaust aftertreatment system with an SCR (selective catalytic reduction NOx reduction device), in order to ensure efficient operation of the SCR, it is also necessary to raise the exhaust temperature, i.e., perform exhaust heat management, under a condition where the engine exhaust temperature is low. No matter exhaust heat management or DPF regeneration, the system is reliable and effective, does not affect power oil consumption of an engine, and does not affect power oil consumption of the engine.

The existing DPF regeneration hydrocarbon injection device comprises a system which adopts a cam pump to form pressurized fuel, measures the flow of the fuel by the opening time of an electromagnetic control valve and directly injects the fuel into an exhaust pipe through a self-opening HC nozzle. However, in this solution, the nozzle working environment is extremely harsh, and strong water cooling is required to ensure the operational reliability of the nozzle, and on the other hand, because the pressure of the pressurized fuel oil is generally the fuel supply pressure, which is less than 10bar, the pressure of the pure liquid is poor in fuel oil atomization, and relatively large fluctuation of the pressure also causes large metering error. The nozzle usually adopts a multi-pore scheme, and due to poor fuel atomization effect and incapability of removing fuel at the nozzle end, carbon deposition or high-temperature damage of the nozzle is easily caused, and the reliability of the system is still difficult to ensure.

For the improvement technology of the system, the gas-liquid mixed injection scheme is adopted at present, namely, a gas auxiliary device is added, fuel oil and air are mixed at the front end of an HC nozzle and then are sprayed out from the HC nozzle, and the HC nozzle is a normally open nozzle with a fixed structure and does not have a moving part, so that liquid cooling is not needed. The known fuel metering method also adopts a solenoid valve opening time metering method. The scheme improves the reliability and the atomization effect of the system, increases the oxygen content in the exhaust gas, and is more beneficial to hydrocarbon combustion to improve the exhaust temperature.

However, the following disadvantages still exist for such a system: since the pressure fluctuations are still large, for sufficient metering accuracy, one or even more than 2 pressure sensors must be used, which increases the system cost more; on the other hand, the electromagnetic valve with larger size is adopted, the working frequency is lower, the dynamic regulation range of the oil supply flow is limited by the PWM duty ratio, and the regulation precision is still lower.

Disclosure of Invention

The present application is directed to the above-mentioned problem, and its aim at provides an engine exhaust hydrocarbon injection system that injection precision is high, and atomizing effect is good, and system reliability is high and with low costs.

In order to achieve the purpose, the invention adopts the following technical scheme: the utility model provides an engine exhaust hydrocarbon injection system, includes engine exhaust pipe, air feed subassembly, fuel feeding subassembly, mixing chamber, injection pipe, HC nozzle and the control unit, the air feed subassembly with the fuel feeding subassembly is connected respectively the mixing chamber, the HC nozzle is located mixing chamber low reaches and communicates with the mixing chamber.

The air supply assembly includes a compressed air source and an air valve. The compressed air source is connected to the mixing chamber through an air valve to form an air path. Be provided with a check valve on the gas circuit, the check valve sets up between air valve and mixing chamber, is a check valve, prevents that liquid from flowing to the gas source end in the mixing chamber.

The oil supply assembly comprises a low-pressure oil source, an oil cut-off valve and a metering pump, wherein the low-pressure oil source is from a low-pressure oil path of the engine, low-pressure fuel oil is conveyed to the metering pump through the oil cut-off valve, and the low-pressure fuel oil is pressurized by the metering pump and then is pumped to the mixing chamber to form an oil path. The metering pump is a solenoid pulse type metering injection unit, is controlled by the control unit and is driven to work through electromagnetic force, each pulse of the metering pump conveys fuel oil with fixed volume from an inlet of the metering pump to the mixing chamber, and the flow rate of the fuel oil is adjusted by adjusting working frequency. The single pulse flow precision of the metering pump can be controlled to be about 1 percent, and the fuel quantity entering the mixing chamber can be accurately metered.

The fuel pressure of a low-pressure oil source of the engine exhaust hydrocarbon injection system is 2-10 bar, and the air pressure of a compressed air source is 4-8 bar.

Furthermore, the metering pump comprises an oil inlet cavity and an inner part, the inner inlet end of the metering pump is communicated with the oil inlet cavity at the bottom, the volume of the oil inlet cavity is more than 10 times of the single conveying volume of the metering pump, and when the oil inlet cavity is filled with pressurized gas, the metering pump acts to convey the gas in the oil inlet cavity to the mixing chamber, so that the pressure in the oil inlet cavity can be kept to be basically balanced with the pressure in the mixing chamber.

The lowest boundary of the oil inlet cavity is more than 40mm above the upper part of the internal inlet of the metering pump, when the fuel oil with pressure is opened by the fuel cut-off valve, the residual gas in the oil inlet cavity can compress the gas in the oil inlet cavity to be positioned at the upper part of the oil inlet cavity, the liquid fuel oil is positioned at the lower part of the oil inlet cavity, so that the internal inlet of the metering pump is covered, and the action of the metering pump can only convey the liquid fuel oil to the mixing chamber.

The HC nozzle is installed at the upstream of the engine exhaust system and is a swirl nozzle. The HC nozzle input end comprises a quick-connection connector, and the injection pipe enables the HC nozzle to be communicated with the mixing cavity in a quick-connection mode. The injection end of the HC nozzle comprises a rotational flow sheet structure, the mixture of gas and liquid fuel flowing into the mixing chamber flows into the HC nozzle through the injection pipe, and the liquid fuel is atomized and sprayed into an exhaust pipe of the engine under the rotational flow effect of the high-speed airflow.

In addition, the engine exhaust gas hydrocarbon injection system further includes an air filter disposed at a front end of the air valve and a fuel filter disposed at a front end of the fuel cut-off valve. The air filter is used for filtering compressed air entering the air path, and the fuel oil filter is used for filtering fuel oil entering the oil path, so that the dirt is prevented from blocking the pipeline or the nozzle, and the stability of the system is prevented from being influenced. The air valve and the fuel cut-off valve are on-off electromagnetic valves for switching on and off the supply of air and liquid, are always in a closed state in a power-off state or a driving current-free state, and can be opened to supply air and fuel only under the driving of the control unit.

A control strategy for an engine exhaust hydrocarbon injection system includes the following steps.

And S01, balancing air pressure, namely before starting hydrocarbon injection, operating the metering pump at a fixed frequency to balance the upstream and downstream pressures of the pump, discharging redundant air in the pipe, closing the oil cut-off valve and closing the air valve.

S02: and in the step of oil supply and filling, the metering pump stops working, the oil cut-off valve is opened, the metering pump is filled with pressure liquid generated by a low-pressure oil source, and the air valve is kept opened at the moment.

S03: and a step of pre-mixing and filling, wherein the metering pump works at a fixed pulse width, the fuel cut-off valve and the air valve are still in an open state, and fuel and air are pre-mixed in the mixing cavity and reach the HC nozzle through the injection pipe.

S04: and metering and injecting fuel oil by the metering pump according to the requirement, wherein the fuel oil is mixed with the air reaching the mixing cavity, flows to the HC nozzle and is atomized and injected into the exhaust pipeline by the HC nozzle.

S05: and in the residual injection step, at the tail end of the exhaust treatment process, the fuel cut-off valve is closed, and the metering pump continuously works at a given pulse width to consume residual fuel in the oil inlet cavity and the pipeline.

Further, the control strategy of the engine exhaust gas hydrocarbon injection system also comprises a step of cleaning and cooling and a step of HC nozzle maintenance which are carried out regularly when no hydrocarbon injection is needed.

And the step of cleaning and cooling is that after regeneration is finished, the air valve is continuously opened, and air passes through the HC nozzle so as to be cooled, so that the nozzle is protected from being damaged by high temperature of regenerative combustion.

The maintenance step of the HC nozzle is carried out during the period that the regeneration treatment is not needed, namely, in the time period that no regeneration is needed, according to the set maintenance period, the air valve is opened intermittently, so that the HC nozzle is cooled and the nozzle is prevented from being accumulated carbon.

The working states of the metering pump, the air valve and the oil cut-off valve are controlled by the control unit, and the time sequence of each state execution element is determined according to requirements. The control unit obtains a demand instruction of hydrocarbon injection through communication with an engine controller EECU, and controls the engine exhaust hydrocarbon injection system to inject fuel into an engine exhaust pipe.

The following technical solutions further define or optimize the present application.

Drawings

FIG. 1 is a schematic diagram of an embodiment of a system for engine exhaust gas hydrocarbon injection according to the present invention.

FIG. 2 is a schematic diagram of an HC nozzle of the engine exhaust gas hydrocarbon injection system according to the present invention.

FIG. 3 illustrates a system operating mode of the engine exhaust hydrocarbon injection system provided by the present invention.

FIG. 4 is a timing diagram illustrating control of various modes of the engine exhaust hydrocarbon injection system provided by the present invention.

Detailed Description

The invention is further described below with reference to the figures and examples.

The schematic structural diagram of the system embodiment of the engine exhaust hydrocarbon injection system provided by the invention, as shown in fig. 1, includes an engine exhaust pipe 110, an air supply assembly 120, an oil supply assembly 121, a mixing chamber 112, an injection pipe 108, an HC nozzle 109 and a control unit 114. The mixing chamber 112 comprises a mixing chamber 112b and a three-way port 112a, the port 112a is respectively connected with the air supply assembly 120, the oil supply assembly 121 and the injection pipe 108, and the compressed air and the fuel oil are mixed in the mixing chamber 112b and then are pumped to the injection pipe 108 and are output by the HC nozzle 109 at the tail end of the injection pipe 108.

The air supply assembly 120 includes a compressed air source 100, an air filter 101, an air valve 102, and a check valve 107. The air filter 101 is disposed between the compressed air source 100 and the air valve 102 for filtering air entering the hydrocarbon injection system. The air valve 102 is an on-off type solenoid valve for controlling the supply of compressed air, and is always in a closed state in a power-off or no-driving-current state, and is opened only by the driving of the control unit 114. The check valve 107 is disposed between the air valve 102 and the mixing chamber 112 and is a one-way valve that prevents liquid in the mixing chamber 112 from flowing to the air side.

The compressed air source 100 of the air supply assembly 120 has an air pressure of 4-8 bar, and when the air valve 102 is opened, the compressed air is filtered by the air filter 101, passes through the air valve 102 and the check valve 107, and reaches the mixing chamber 112, and the pipes between the elements are connected in sequence to form an air path.

The oil supply assembly 121 comprises a low-pressure oil source 103, a fuel oil filter 104, an oil cut-off valve 105 and a metering pump 113, wherein the low-pressure oil source 103 is from a low-pressure oil circuit of the engine, and the fuel oil pressure is 2-10 bar. The fuel filter 104 is arranged between the low-pressure fuel source 103 and the fuel cut-off valve 105, the fuel of the low-pressure fuel source 103 is filtered by the fuel filter 104, then is conveyed to the metering pump 113 after passing through the fuel cut-off valve 105, the low-pressure fuel is pressurized by the metering pump 113 and then is pressurized and conveyed to the mixing chamber 112, and pipelines among all elements are sequentially connected in the process to form an oil path. The fuel cut-off valve 105 is an on-off type electromagnetic valve for controlling the supply of low-pressure fuel, and is always in a closed state in a power-off state or a non-driving current state, and only when a signal is given from the control unit 114, the fuel cut-off valve 105 is opened and the pressure fuel is delivered to the metering pump 113.

The metering pump 113 is a solenoid pulse type metering injection unit, and is controlled by the control unit 114 to operate by electromagnetic force, and the metering pump 113 delivers a fixed volume of fuel per pulse from the inlet of the metering pump 113 to the mixing chamber 112, and adjusts the flow rate of the fuel by adjusting the operating frequency. The single pulse flow precision of the metering pump 113 can be controlled to be about 1%, and the fuel quantity entering the mixing chamber 112 can be accurately metered.

The metering pump 113 includes an oil inlet chamber 106 with an oil inlet 106a, an internal inlet 113a, and an injection port 113 b. The oil cut-off valve 105 is connected with an oil inlet 106a of the oil inlet cavity, an inner inlet 113a end of the metering pump 113 is communicated with the oil inlet cavity 106 at the bottom, and an injection end 113b of the metering pump 113 is communicated with the mixing chamber 112. The volume of the oil inlet cavity 106 is more than 10 times of the single conveying volume of the metering pump 113, when the oil inlet cavity 106 is filled with gas with pressure, the metering pump 113 acts to convey the gas in the oil inlet cavity 106 to the mixing chamber 112, and therefore the pressure in the oil inlet cavity 106 can be kept basically balanced with the pressure in the mixing chamber 112.

The lowest boundary of the oil inlet chamber 106 is above 40mm above the upper portion of the internal inlet 113a of the metering pump 113, when the fuel cut-off valve 105 opens pressurized fuel, the residual gas in the oil inlet chamber 106 will compress the gas in the oil inlet chamber 106 at the upper portion thereof, while the liquid fuel is at the lower portion thereof, thereby covering the internal inlet 113a of the metering pump 113, and the metering pump 113 will only deliver the liquid fuel to the mixing chamber 112.

The HC nozzle 109 of the hydrocarbon injection system is installed upstream of the engine exhaust system, and is a swirl nozzle, which is shown in fig. 2 and includes an injection flow passage 200, a quick connector 201, a swirl body 205, and a mounting seat 202.

The quick-connection plug 201 is positioned at the input end of the HC nozzle, and the injection pipe 108 enables the HC nozzle 109 to be communicated with the mixing cavity 112b in a quick-connection mode. The swirling body 205 comprises a swirling sheet 203 with a swirling channel 203a and a nozzle 204, the swirling body 205 is located at the injection end 113b of the HC nozzle 109, the mixture of gas and liquid fuel flowing into the mixing chamber 112 flows into the injection channel 200 of the HC nozzle 109 through the injection pipe 108, and the liquid fuel is atomized and sprayed from the nozzle 204 to the exhaust pipe 110 of the engine under the swirling action of the high-speed airflow.

The mount 202 is fixed to the HC nozzle 109 and includes a mounting surface 202a and a mounting hole 202 b. The HC nozzle 109 is fastened to the engine exhaust pipe 110 by a mounting seat 202, and the mounting plane 202a and the mounting hole 202b may be arranged according to the structure of the exhaust pipe 110.

The actuators of the engine exhaust hydrocarbon injection system comprise a metering pump 113, an air valve 102 and a fuel cut-off valve 105, the operating states of the actuators are controlled by a control unit 114, and the control unit 114 obtains a demand instruction of hydrocarbon injection by communicating with an engine controller EECU to control the engine exhaust hydrocarbon injection system to inject fuel into an engine exhaust pipe 110.

Referring to fig. 3 and 4, the system operation mode and the control sequence of each mode of the engine exhaust gas hydrocarbon injection system provided by the invention comprise the following steps.

And S01, balancing the air pressure, wherein in a TH1 period, the metering pump 113 works in a pressurizing mode, the oil cut-off valve 105 is closed, and the air valve 102 is closed. Before the hydrocarbon injection is started, in this mode, the metering pump 113 is operated at a fixed frequency, so that the pressure upstream and downstream of the pump is equalized, and excess air in the pipe is discharged, at which time the fuel cut-off valve 105 is closed and the air valve 102 is closed.

S02: in the oil supply filling step, during a period TH2, the metering pump 113 stops operating, the oil cut-off valve 105 opens, and the air valve 102 opens. The pressure liquid generated by the low-pressure oil source 103 fills the oil inlet chamber 106 and the metering pump 113, and the residual gas in the oil inlet chamber 106 is compressed to be in the upper space of the chamber, and at this time, the air valve 102 is opened.

S03: in the premix filling step, during a period TH3, the fuel cut valve 105 is opened, the metering pump 113 is pressurized, and the air valve 102 is opened. In this mode, the metering pump 113 is operated at a fixed pulse width, and fuel and air are premixed in the mixing chamber 112b and reach the HC nozzle 109 through the injection pipe 108.

S04: in the step of metering injection, the fuel cut-off valve 105 is opened, the metering pump 113 is pressurized, and the air valve 102 is opened during a period TH 4. In the process, the metering pump 113 receives a pulse signal and injects fuel as required, and the fuel is mixed with air reaching the mixing chamber 112b and flows to the HC nozzle 109, and is atomized and injected into the exhaust pipe by the HC nozzle 109 for exhaust treatment.

S05: in the residual injection step, in the period TH5, the fuel cut-off valve 105 is closed, the metering pump 113 keeps pressurized, and the air valve 102 keeps open. At the end of the exhaust treatment process, the metering pump 113 is continuously operated at a given pulse width, and the air valve 102 is opened to continuously supply compressed air to consume residual fuel in the fuel inlet chamber 106 and the pipeline.

Further, the engine exhaust gas hydrocarbon injection system, in the case of no hydrocarbon injection requirement, further includes a step of purge cooling and a step of maintenance of the HC nozzle 109, which are performed at regular time, and the operation mode is as follows.

S06: the step of cool purge, at TH6, when the exhaust treatment process has ended, the fuel cut-off valve 105 is closed, the metering pump 113 stops operating, and the air valve 102 continues to open for a period of time, and compressed air passes through the HC nozzle 109 to cool, protecting the nozzle from high temperatures of regenerative combustion.

S07: the HC nozzle 109 maintenance procedure, during the TH7 period, during which there is no regeneration demand, intermittently opens the air valve 102 by the system according to a set maintenance cycle so that the HC nozzle 109 is cooled and nozzle fouling is prevented.

The above examples are only for illustrating the essence of the present invention, but not for limiting the present invention. Any modifications, simplifications, or other alternatives made without departing from the principles of the invention are intended to be included within the scope of the invention.

The present invention is not concerned with parts which are the same as or can be implemented using prior art techniques.

Claims

1. An engine exhaust hydrocarbon injection system comprises an engine exhaust pipe, an air supply assembly, an oil supply assembly, a mixing chamber, an injection pipe, an HC nozzle and a control unit, wherein the air supply assembly and the oil supply assembly are respectively connected with the mixing chamber, the HC nozzle is positioned at the downstream of the mixing chamber and communicated with the mixing chamber,

the fuel supply assembly comprises a low-pressure fuel source, a fuel cut-off valve and a metering pump, wherein the metering pump is a solenoid pulse type metering injection unit and is used for accurately metering the fuel quantity entering the mixing chamber.

2. The engine exhaust gas hydrocarbon injection system of claim 1, wherein said HC nozzle is mounted upstream of the engine exhaust system, proximate an exhaust inlet of the exhaust system, as a swirl nozzle, and wherein the mixture of gaseous and liquid fuel flowing into said mixing chamber flows through said injection tube into said HC nozzle, and wherein liquid fuel is atomized into the engine exhaust pipe by the swirling action of the high velocity gas stream.

3. The engine exhaust hydrocarbon injection system of claim 1, wherein said air supply assembly further includes a check valve disposed between the air valve and the mixing chamber and being a one-way valve preventing liquid in the mixing chamber from flowing toward the air source end.

4. The engine exhaust hydrocarbon injection system of claim 1, wherein said air valve and said fuel cut-off valve are normally closed on-off valves that are always closed in the off or no drive current condition, and that open the supply of air and fuel only upon actuation of said control unit.

5. An engine exhaust gas hydrocarbon injection system according to claim 1, wherein said metering pump delivers a fixed volume of fuel per pulse from the metering pump inlet to said mixing chamber, and the operating frequency of the metering pump is used to adjust the flow rate of the fuel.

6. The engine exhaust hydrocarbon injection system according to claim 5, wherein the internal inlet end of the metering pump is communicated with an oil inlet chamber at the bottom, the volume of the oil inlet chamber is more than 10 times larger than the single delivery volume of the metering pump, and when the oil inlet chamber is filled with gas with pressure, the action of the metering pump can deliver the gas in the oil inlet chamber to the mixing chamber, so that the pressure in the oil inlet chamber can be kept basically balanced with the pressure in the mixing chamber.

7. An engine exhaust hydrocarbon injection system according to claim 6, wherein the lowermost extent of said oil intake chamber is greater than 40mm above the upper portion of the internal inlet of said metering pump, and wherein residual gas within said oil intake chamber, when a fuel cut-off valve opens pressurized fuel, will compress the gas within said oil intake chamber above it and liquid fuel below it, thereby covering the internal inlet of said metering pump, and metering pump action will deliver only liquid fuel to said mixing chamber.

8. The engine exhaust gas hydrocarbon injection system of any one of claims 1 to 7, wherein the fuel pressure of said low pressure source is 2 to 10bar and the air pressure of said compressed air source is 4 to 8 bar.

9. A control strategy for an engine exhaust gas hydrocarbon injection system as set forth in claim 8 including the steps of:

s01, balancing air pressure, namely, before starting hydrocarbon injection, working a metering pump to balance the upstream and downstream pressures of the pump and discharge air in the pipe;

s02: a step of oil supply and filling, in which pressure liquid generated by a low-pressure oil source fills a metering pump;

s03: the step of premixing and filling, namely, the metering pump works, the air valve is opened, and fuel oil and air enter the mixing cavity to be premixed and reach the HC nozzle through the injection pipe;

s04: metering and injecting, namely supplying fuel oil by the metering pump according to the requirement, continuously opening the air valve, mixing the fuel oil with air in the mixing cavity, flowing to the HC nozzle, atomizing and injecting the fuel oil into an exhaust pipeline by the HC nozzle,

s05: and (4) residual injection, namely closing the fuel cut-off valve and continuously operating the metering pump at the tail end of the exhaust treatment process to consume residual fuel in the oil inlet cavity and the pipeline.

10. The engine exhaust hydrocarbon injection system control strategy of claim 9, further comprising the steps of timing purge cooling and HC nozzle maintenance when there is no hydrocarbon injection demand.

11. The engine exhaust gas hydrocarbon injection system control strategy of claim 10, wherein the purge cooling step is cooling by continuing to open the air valve and passing air through the HC nozzle after regeneration is complete.

12. The engine exhaust gas hydrocarbon injection system control strategy according to claim 11, wherein the HC nozzle maintenance step is performed during a period when no regeneration process is required, and the air valve is intermittently opened according to a set maintenance cycle during a period when no regeneration is required, so that the HC nozzle is cooled and nozzle fouling is prevented.

13. The control strategy for an engine exhaust gas hydrocarbon injection system according to one of claims 9-12, characterized in that the operating states of the metering pump, the air valve, the fuel cut-off valve are controlled by a control unit.

14. The engine exhaust hydrocarbon injection system control strategy of claim 13, wherein the control unit obtains a hydrocarbon injection demand command by communicating with an engine controller EECU to control the engine exhaust hydrocarbon injection system to inject fuel into an engine exhaust pipe.