Background technique
Diesel engine is owing to having petrol engine incomparable advantage, particularly CO aspect power character, Economy and the reliability
2Discharge amount is low especially, so its purposes is promoted greatly, the occupancy of diesel-powered car on market is greatly improved.NOx and PM (particulate matter) are that two kinds of diesel engine mainly discharge pollutants, and the generation relation of mutual contradiction is arranged between the two.Only rely at present the optimization of combustion system can't satisfy the emission request of increasingly stringent.Realize that Europe IV to NOx and the lower requirement of PM, roughly has two machine after-purification technology paths at present: the one, earlier by optimized combustion, re-use selective catalytic reduction SCR (selective catalytic reduction) and reduce the NOx discharging that produces because of burning optimization; The 2nd, EGR (exhaust gas recirculation)+DPF (grain catcher) route promptly earlier by the composition of the NOx in the EGR reduction discharging, captures the particulate matter that slightly increases because of use EGR with DPF again, thereby reaches the effect that reduces NOx and PM simultaneously.The SCR Technology Need installs " adding indigo plant " equipment onboard additional, but the SCR technology is insensitive to the sulphur in the fuel oil, and deduction also can make fuel economy improve 5%~7% after adding blue expense.Though the EGR+DPF technology does not need to add and do not add blue infrastructure device, need to use Low Sulfur Fuel Oil and fuel economy relatively poor, and it is less to make engine emission reach the possibility of Europe V and above standard.
SCR system basic functional principle: urea is mixed with proper proportion with water, spray in the waste gas of diesel engine discharge, make the NOx in the waste gas be reduced into harmless N
2(nitrogen) and H
2O (water vapour), its chemical equation is:
CO(NH
2)
2+H
2O→2NH
3+CO
2
4NH
3+2NO
2+O
2→3N
2+6H
2O↑
4NH
3+4NO
2+O
2→4N
2+6H
2O↑
Urea just can be hydrolyzed into ammonia and carbon dioxide at normal temperatures, in being higher than 300 ℃ environment, and NH
3(ammonia) and NOx reaction rapidly under the effect of catalyzer generate N
2(ammonia) and H
2O (water vapour).The delivery temperature of diesel engine generally in 300 ℃~500 ℃ scopes, has satisfied the required temperature conditions of NOx reduction.
The aqueous solution of urea of common commercial usefulness (mass fraction is 32.5%) becomes and adds indigo plant, it is nontoxic, clean, odorlessness, be difficult for catching fire, no explosion risk, the density under the normal temperature (20 ℃) is 1.09kg/m3, be alkalescence, its pH value is 8.8.Although the aqueous solution of urea of higher concentration can reduce the weight of vehicle, but the aqueous solution of urea of 32.5% mass fraction can provide minimum solidification point (11 ℃) in addition when the solution part is freezing, solution concentration does not change, so the aqueous solution of urea of selecting 32.5% mass fraction usually is as reactant.Must be kept under the temperature environment that is lower than 50 ℃ but add indigo plant, be decomposed avoiding.
Though SCR has many advantages, some problems still appear when promoting.Use the weight that not only will increase SCR device itself behind the general SCR to be about 150~300kg, also will increase by one and add blue case and add blue solution.Can consume the 5L liquid area aqueous solution when generally speaking, consuming the 100L fuel oil.Automobile runs 6000km and calculates, and the useful load of a car loss is about 350kg.The straying quatity of urea must be complementary with the concentration of NOx in addition, when guaranteeing to reduce NOx, can not guarantee to surpass certain metering.The straying quatity of urea is very few, does not reach due processing horizontal; Spray into too much, then can make unnecessary ammonia enter atmosphere, cause new pollution.So the calculating of the discharge capacity of NOx is most important.
In a word, the SCR system wants the problems such as the determining of discharge capacity, insulation, jet atomization of reasonable treatment S CR system equipment quality, motor NOx.
Summary of the invention
In order to address the above problem, the present invention proposes the SCR system that a kind of fixed quantity accurately sprays, and comprises the pressurized air performance element, adds blue jar, antifreeze electric heating wire, heater switch, adds blue temperature transducer, adds blue controller, temperature transducer A, temperature transducer B, catalyst converter, engine electronic control unit, air ejector, adds blue sparger.
The described indigo plant jar that adds is built-in with antifreeze electric heating wire, and the electric heating wire two ends are parallel with heater switch.Heater switch with add blue controller and link to each other.Add blue jar respectively by adding blue liquid level sensor and adding blue temperature transducer and add blue controller and link to each other.Described add blue sparger by delivery line with add blue jar and add blue controller and link to each other.Add blue controller and link to each other with engine electronic control unit by pipeline, engine electronic control unit links to each other with the pressurized air performance element, and the pressurized air performance element links to each other with air ejector by outlet pipe.Catalyst converter is installed on the engine exhaust pipe, and the inlet of catalyst converter and outlet port are separately installed with catalyst temperature sensor A and catalyst temperature sensor B, and temperature transducer A and temperature transducer B are installed on the engine exhaust pipe.
On the outlet pipe between engine electronic control unit and air ejector, also the NOx sensor can be installed, the NOx sensor with add blue controller and link to each other.Because the NOx sensor can accurately collect the NOx amount in the exhaust, therefore compare more accurate by engine electronic control unit control, and treatment effect is better for the control of the emitted dose of adding blue solution.
The invention has the advantages that:
1, the mechanism and the structure of adding the injection of blue sparger employing fixed quantity that adopt among the present invention, the relative conventional spray method of control strategy is simpler;
2, add the effect that blue sparger has compression pump simultaneously among the present invention, make system architecture compact more thereby in this ejecting system, saved traditional blue pump that adds;
3, adding among the present invention only sucks the quantitative blue solution that adds in the blue sparger working procedure, do not need to add blue solution return line and voltage-regulating system, makes SCR ejecting system pipeline structure obtain simplifying.
Embodiment
The present invention is described in further detail below in conjunction with accompanying drawing.
As shown in Figure 1, the SCR system that a kind of fixed quantity of the present invention accurately sprays comprises pressurized air performance element 1, adds blue jar 2, antifreeze electric heating wire 3, heater switch 4, adds blue temperature transducer 5, adds blue liquid level sensor 6, adds blue controller 7, temperature transducer A8, temperature transducer B9, catalyst converter 10, engine electronic control unit (ECU) 11, air ejector 12, adds blue sparger 13.
Described add to be used for holding for blue jar 2 add blue solution, add blue jar 2 and be built-in with antifreeze electric heating wire 3, be used for for add blue solution heating, make add blue solution can be owing to extraneous cold not solidifying, make the system of the present invention also can proper functioning under cold climate thus.The electric heating wire two ends are parallel with heater switch 4, control the opening and closing of electric heating wire by heater switch 4.Heater switch 4 with add blue controller 7 and link to each other.
Add blue jar 2 respectively by adding blue liquid level sensor 6 and adding blue temperature transducer 5 and add blue controller 7 and link to each other, add blue controller 7 and add blue liquid level sensor 6 and add liquid level signal and the temperature signal that blue temperature transducer 5 sends, detect and store to add in blue jar 2 and add blue solution level height and temperature by collection.Detect to add and add blue temperature in blue jar 2 when being lower than setting temperature when adding blue controller 7, add blue controller 7 control heater switch 4 and open, heat for adding blue solution thereby open antifreeze electric heating wire 3.Detect to add and add blue liquid level in blue jar 2 when being lower than setting height when adding blue controller 7, add blue controller 7 and will send relevant information to the user, drive the tutorial light alarm of analog amount simultaneously, remind the driver that indigo plant is added in filling by the CAN bus.
Described add blue sparger 13 by delivery line with add blue jar 2 and add blue controller 7 and link to each other, adding blue solution will add blue solution by delivery line and be conveyed into and add in the blue sparger 13, control the unlatching and closure of adding blue sparger 13 by adding blue controller 7, thereby the injection of blue solution is added in control.
Adding blue controller 7 links to each other with engine electronic control unit 11 by pipeline, be used for providing the working condition of adding blue sparger 13 to engine electronic control unit 11, thereby calculate by engine electronic control unit 11 and to add blue emitted dose accordingly, and will add blue emitted dose signal and send to adding blue controller 7, and then carry out feedback control and adjusting to adding blue sparger 13.Engine electronic control unit 11 links to each other with pressurized air performance element 1, and pressurized air performance element 1 links to each other with air ejector 12 by outlet pipe.Control pressurized air performance element 1 discharges certain pressure and volume in outlet pipe air by engine electronic control unit 11, and spray pressurized air to adding blue sparger 13 places by air ejector 12, can guarantee thus to add blue atomizing effect and bulk range, also can reduce the temperature of adding blue sparger 13 nozzle places.Do not need to spray when adding blue operating mode when engine electronic control unit 11 operates in, engine electronic control unit 11 also may command pressurized air performance element 1 continues to spray pressurized air and reduce the temperature of adding blue sparger 13 nozzle places to adding blue sparger 13 places.
The described blue sparger 13 that adds is n, and n is a natural number, and n 〉=1, a plurality ofly adds blue sparger 13 and can reduce the single number of times of operation that adds blue sparger 13 when adopting, and adding blue sparger 13 so in use need be with very fast speed operation.And if be used for specifically adding blue solution and spray, adopt a plurality of volumes different add blue sparger 13, can make each add blue sparger 13 and carry different urea amounts, for example, one is added blue sparger 13 each impulse jet amount is 1mm
3Zong so each emitted dose is exactly 1mm
3Multiple, i.e. 1mm
3, 2mm
3, 3mm
3, 4mm
3On above-mentioned one basis of adding blue sparger 13 an individual pulse emitted dose being installed again is 0.5mm
3Add blue sparger 13, then each total emitted dose just can be 1mm
3, 1.5mm
3, 2mm
3, 2.5mm
3, 3mm
3This shows, add more accurate that blue controller 7 can be to the control of the urea amount carried in each work cycle.
Catalyst converter 10 is installed on engine exhaust pipe 14, and catalyst converter 10 is used for the gas (NOx) of engine exhaust pipe 14 dischargings is reduced.Inlet and outlet port at catalyst converter 10 are separately installed with catalyst converter 10 temperature transducer A8 and catalyst converter 10 temperature transducer B9, temperature transducer A8 and temperature transducer B9 are installed on the engine exhaust pipe 14, are used for gathering the temperature of the gas of discharging in the engine exhaust pipe 14.By temperature transducer A8 and temperature transducer B9 with add blue controller 7 and be connected, thereby by adding that blue controller 7 is gathered in real time and the temperature of control catalyst converter 10 inlets and the gas of outlet port discharging.
As shown in Figure 2, in said structure, described air ejector 12 with add blue sparger 13 and be installed on the engine exhaust pipe 14, and air ejector 12 and add blue sparger 13 successively between the temperature transducer A8 of engine exhaust pipe 14 and catalyst converter 10 ingress.As shown in Figure 3, adding blue sparger 13 also can be installed on the injection prolongation pipeline 15 with air ejector 12, spraying prolongation pipeline 15 links to each other with engine exhaust pipe 14, spray an end connecting end that prolongs pipeline 15, the other end is a free end, and the connecting end that spray to prolong pipeline 15 is connected on the engine exhaust pipe 14 between the temperature transducer A8 of engine electronic control unit 11 and catalyst converter 10 ingress; Described air ejector 12 is installed in and sprays the free end that prolongs pipeline 15, adds blue sparger 13 and is connected between free end and the connecting end.The air that ejects by air ejector 12 can directly impact and add the indigo plant of adding that blue sparger 13 ejects thus, for adding blue sparger 13 coolings and improving and add blue atomizing effect.And be arranged in independent pipeline owing to add blue sparger 13, make it avoid directly contacting, thereby improve the working environment that adds blue sparger 13 with high-temp waste gas.
Describedly add that blue sparger 13 comprises case of sprayer 12a, adds blue inlet passage 12b, one-way valve A12c, one-way valve B12d, add blue outer pipe 12f, piston 12g, biasing spring 12h, solenoid 12i, volute spring 12j.
Case of sprayer 12a inner and upper has adds blue chamber 12e, adds in the housing of blue chamber 12e below to have control chamber 12k.Be provided with dunnage 12l in the control chamber bottom, the upper surface of dunnage 12l is equipped with piston 12g.Add the axial outside that is positioned at piston 12g among the blue chamber 12e and be disposed with biasing spring 12h and solenoid 12i, solenoid 12i is connected to engine electronic control unit 11 by circuit.Make the upper-lower position relative fixed of piston 12g in control chamber by biasing spring 12h.The top of described piston 12g is inserted into adds among the blue chamber 12e.
On the sidewall of housing, be equipped with and add blue inlet passage 12b, add blue inlet passage 12b and add blue chamber 12e and communicate.Assigned one-way valve A12c in adding blue inlet passage 12b, the end of one-way valve A12c extend into and adds among the blue chamber 12e, the other end and add between blue inlet passage 12b helical spring 12m is installed.
Be equipped with on the top of housing and add blue outer pipe 12f, the bottom of outer pipe communicates with adding blue chamber 12e by through hole 12n, is provided with one-way valve B12d in the outer pipe bottom, and one-way valve B12d top is provided with volute spring 12j.
Add blue solution and enter into and add blue chamber 12e, prevent to add the backflow of blue solution by one-way valve A12c by adding blue inlet passage 12b.
Piston 12g is by biasing spring 12h and solenoid 12i acting in conjunction, piston 12g is pumped in control chamber, before basket is added in injection, the biased spring 12h of piston 12g is depressed into minimum point (promptly adding the point of blue chamber 12e volume maximum), solenoid 12i energising then, thus pulling dunnage 121 contacts with solenoid 12i or approximate contact.Power by piston 12g opposing biasing spring 12h, thereby piston 12g is moved upward make and add the 12e internal volume minimizing of blue chamber, pressure raises, and adds the one-way valve B12d that the volute spring 12j among the blue outer pipe 12f is loaded until pushing open, finally makes to add blue solution and spray from add blue outer pipe 12f.
In case solenoid 12i outage, biasing spring 12h just promotes piston 12g downwards, and promotes dunnage away from solenoid 12i.Add the 12e volume increase of blue chamber owing to moving downward of piston 12g can make, thereby one-way valve B12d closes, one-way valve A12c opens.The piston 12g of motion will add blue solution and be evacuated to and add blue chamber 12e from adding blue inlet, finish and add the filling of adding blue solution among the blue chamber 12e.
The blue sparger 13 that adds of said structure makes piston 12g can set the distance of its motion in each operation, thereby the emitted dose that has guaranteed to add blue solution is constant in each operation, and no longer need reflux valve to control unnecessary blue backflow of adding, also do not need to add simultaneously blue pump and control supply and add blue solution.
On the engine exhaust pipe 14 of 12 of engine electronic control unit 11 and air ejectors, also NOx sensor 16 can be installed, NOx sensor 16 with add blue controller 7 and link to each other.Add blue controller 7 and receive the NOx discharge amount information that NOx sensors 16 send, thereby carry out the calculating of the reduction dosage that injected before catalyst converter 10 injecting catalysts, and send pulse signal to adding blue sparger 13, the number of times of operation of blue sparger 13 is added in control.Because NOx sensor 16 can accurately collect the NOx amount in the exhaust, therefore compare more accurate by engine electronic control unit 11 controls, and treatment effect is better for the control of the emitted dose of adding blue solution.