DE102015215560A1 - Reducing agent supply unit for a selective catalytic reduction with optimized fluid heating in the vehicle area - Google Patents

Abstract

A reductant delivery unit reduces nitrogen oxide (NOx) emissions from a vehicle. The supply unit comprises a spool-driven fluid injector having a fluid inlet and a fluid outlet. The inlet receives an amount of the reductant and the outlet communicates with an exhaust flow path of the vehicle such that the fluid injector controls injection of the reductant into the exhaust flow path. The fluid injector has an inlet tube for diverting the reductant between the inlet and the outlet. A coil heater is integrally formed with the fluid injector and is constructed and arranged to inductively heat the inlet tube and thus at least a portion of the reductant, such that an unheated volume of the reductant in the inlet tube, which adjacent to the fluid outlet is less than about 100 cubic millimeters.

Description

area

The invention relates to a reductant delivery unit (RDU) which supplies a reducing agent to an engine exhaust system, and more particularly to an RDU which directly heats substantially a total volume of the reductant just prior to injection.

background

The advent of a new stringent exhaust emissions legislation in Europe and North America is driving the adoption of new exhaust after-treatment systems, particularly for lean-burn engine technologies such as diesels (diesel) engines and stratified charge spark-ignition engines (usually with direct injection) operating under lean and ultra-rich engines. working lean combustion conditions. Lean engines have high levels of nitrogen oxide (NOx) emissions, which are difficult to handle in lean-burn exhaust gas atmospheres that are characteristic of lean-burn combustion. Currently, exhaust aftertreatment technologies are being developed which treat NOx under these conditions. One of these technologies includes a catalyst that enables the reactions of ammonia (NH ₃ ) with the exhaust oxides of nitrogen (NOx) to produce nitrogen (N ₂ ) and water (H ₂ O). This technology is referred to as Selective Catalytic Reduction (SCR).

Ammonia in its pure form is difficult to handle in the vehicle environment. Therefore, it is common in these systems to use a liquid aqueous urea solution, typically in a 32% concentration of the urea solution (CO (NH ₂ ) ₂ ). The solution is referred to as AUS-32 and is also known by its commercial name AdBlue. The urea solution is fed to the hot exhaust stream and, after undergoing thermolysis, is converted to ammonia in the exhaust gas, or converted into ammonia and isocyanic acid (HNCO) after undergoing thermal decomposition. The isocyanic acid then undergoes hydrolysis with the water present in the exhaust gas and is converted into ammonia and carbon dioxide (CO2). The ammonia resulting from the thermolysis and the hydrolysis then undergoes a catalytic reaction with the nitrogen oxides, as previously described.

In today's manufacturing systems, the RDU is typically mounted under the vehicle body at a downstream location on the exhaust line. This results in relatively low temperatures on the SCR catalyst, longer light-off times (of the catalyst), and low conversion efficiency for the NOx. The lower exhaust gas temperatures (ie, lower enthalpy) also prevent the thermal decomposition of the urea thermolysis reaction, or, in the case of the thermolysis HNCO by-product, the low temperatures also prevent the hydrolysis reaction. The result is the presence of excess urea and / or HNCO in the SCR catalyst and an insufficient amount of ammonia for participation in the NOx reduction reactions. A good example of this situation can be found in SAE 2007-01-1582: "Laboratory and engine study of urea-related deposits in urea-SCR aftertreatment systems" (Laboratory and Engine Study on Urea-Related Deposits in Diesel-Urea SCR Aftertreatment Systems) , Engine test bench data from this study shows that at exhaust gas temperatures below 300 ° C, a measurable proportion of the injected urea remains unconverted in either HNCO or NH3.

The industry is also investigating the potential of alternative reducing agents. Some of these agents (for example, guanidinium formate) have higher decomposition temperatures than urea. For these alternatives to be useful, they require preheating, typically in a dedicated reformer located in a bypass flow section away from the main exhaust line. A description of such a procedure can be found in SAE 2012-01-1078, "Development of a third generation SCR NH3-direct dosing system for highly efficient DeNOx" (development of a 3G SCR NH3 direct dosing system for a highly efficient DeNOx) , During the startup phase, these reformer concepts typically rely on electrically heating the bypass gas flow and using hydrolysis reaction catalysts to ensure the appropriate conditions for conversion of the carriers to ammonia.

Regarding 1 becomes a conventional RDU 10 shown, which generally with reference numerals 10 is characterized and a fluid injection nozzle 12 having. The injector 12 is used to supply fluid, such as urea solution, and uses an induction coil heater 13 with the goal of heat (or heat) from the coil heater 13 to an inlet pipe 14 the injector 10 and transfer to the fluid. Regarding 2 extends the coil heater 13 however, due to limitations imposed by the installation of a fuel injector port in a cylinder head or intake manifold, it is not fully down to the tip or outlet 16 the injector 12 , The result is a through arrows A in 2 characterized magnetic flux path, which in its extent is limited and which induces a heating range which is six to eight millimeters above the metering point or outlet 16 the injector 12 ends. The result is a non-heated volume V of the fluid of 213 mm ³ which is not from a direct heating path to the inductive heating source (coil 13 ) profits. This volume V must be evacuated before heated fluid can be expelled - that is, at a flow rate of 5.2 mg / s (a typical flow rate during a vehicle cold-start for emission test cycles), theoretically, a minimum of 45 seconds would be required to complete this non-exhaustion. remove heated fluid. For urea injection applications where cold start activity is required, this delay reduces the efficiency of the system to start reducing NOx emissions emitted by the engine.

Thus, there is a need to directly heat a reductant in an injector closer to the metering point to ensure more efficient heat transfer and to produce the desired reductant temperature so as to reduce the time required to remove the unheated reductant.

Summary

It is an object of the invention to meet the above-identified requirements. In accordance with the principles of the present invention, this object is achieved by providing a reductant delivery unit for reducing nitrogen oxide (NOx) emissions from a vehicle. The reductant delivery unit includes a coil driven fluid injector having a fluid inlet and a fluid outlet. The fluid inlet is configured and arranged to receive an amount of reductant, wherein the fluid outlet is configured and arranged to communicate with an exhaust flow path of the vehicle such that the fluid injector injects reductant into the exhaust flow path controls. The fluid injector has an inlet tube for diverting the reductant between the fluid inlet and the fluid outlet. A coil heater is integrally formed with the fluid injector and is constructed and arranged to heat the inlet tube upon energization to thereby heat the reductant within the inlet tube. A coil heater housing surrounds a portion of the coil heater. A potting structure covers the coil heater housing in potting. An injector housing covers at least a portion of the potting structure and is configured and arranged to form a sealing connection with the potting structure due to the absence of an O-ring such that an end of the coil heater is disposed generally adjacent the fluid outlet of the injector ,

In accordance with another aspect of a disclosed embodiment, a method supplies a reductant to reduce nitrogen oxide (NOx) emissions from a vehicle. The method assigns a coil-operated fluid injector to the exhaust flow path. The fluid injector has a fluid inlet and a fluid outlet. The fluid inlet receives an amount of a reducing agent. The fluid outlet communicates with the exhaust gas flow path. The fluid injector has an inlet tube for diverting the reductant between the fluid inlet and the fluid outlet. At least a portion of the reductant is heated while in the inlet tube such that an unheated volume of reductant in the inlet tube adjacent the fluid outlet is less than about 100 mm ³ . The fluid injection nozzle is operated to inject the reducing agent into the exhaust gas flow path.

Further objects, features and characteristics of the present invention as well as the methods of operation and the functions of the respective structural elements, the combination of parts and the economy of manufacture will become more apparent upon a consideration of the following detailed description and the appended claims, with reference to the accompanying drawings , which all form part of this specification.

Brief description of the drawings

The invention will be better understood from the following detailed description of the preferred embodiments thereof, taken in conjunction with the accompanying drawings, wherein like numerals denote like parts, and wherein:

1 Fig. 12 is a cross-sectional view of a conventional RDU including a fluid injector;

2 a view of a lower portion of the injection nozzle of the conventional RDU 1 is;

3 Figure 3 is a cross-sectional view of an RDU including a fluid injector provided in accordance with an embodiment;

4 a view of a lower portion of the injection nozzle of the RDU 3 is;

5 Fig. 12 is a view of the lower portion of an RDU in accordance with another embodiment; and

6 a view of the lower portion of the RDU 3 is.

Detailed Description of the Exemplary Embodiments

Regarding 3 an RDU is shown, which generally has reference numerals 10 ' in accordance with an embodiment. The RDU 10 ' can be used in a system of the type disclosed in US Patent Application Publication No. 2008/0236147 A1, the contents of which are hereby incorporated by reference in this specification.

The RDU 10 ' includes a coil-driven fluid injector 12 ' , which provides a metering function for the fluid and the injection preparation of the fluid in the exhaust gas flow path 15 of a vehicle by means of a dosing application for reducing nitrogen oxide (NOx) emissions from a vehicle. Thus, the fluid injector is 12 ' formed and arranged to the exhaust gas flow path 15 upstream of an SCR catalytic converter in a conventional manner. The fluid injector 12 ' is preferably an electrically operated coil fuel (gasoline) injector, such as of the type as shown in FIG U.S. Patent Number 6,685,112 is disclosed, the contents of which are hereby incorporated by reference in this specification. Thus operates a first electromagnetic coil 20 the fluid injector 12 ' when energizing in the conventional way.

The fluid injector 12 ' is inside an internal vehicle 22 arranged. An inlet cap structure, generally with reference numerals 24 includes an inlet cap 26 and an inlet connector 28 which is integral with the inlet cap 26 trained or coupled with this. The inlet connector 28 defines the fluid inlet 30 the injector 12 ' , The inlet connector 28 is typically in communication with a quantity (or source) of the fluid reductant 32 , such as urea solution, which the injection nozzle 12 ' over the inlet pipe 14 is supplied to the metering point 16 or the fluid outlet of the injector 12 starting to be injected. Thus, the inlet pipe passes 14 Urea solution between the fluid inlet 30 and the fluid outlet 16 , The inlet pipe 14 can also be considered as a valve body.

An injector shield 34 is with the injector carrier 22 coupled so that the shielding 34 with respect to the injector 12 ' is fixed. The shield 34 surrounds at least a portion of the injection nozzle 12 ' and isolates them from environmental factors, such as whirled up pieces (eg, pebbles, gravel, etc.), high pressure water jets, splashes, etc. The shield 34 poses for the RDU 10 ' It also provides structural support. Openings 36 are through the shield 34 through for air cooling of the fluid injector 12 ' provided.

The urea solution 32 is through the inlet 30 is fed to the coil-operated fluid injection nozzle 12 ' forwarded under pressure. The urea solution is dosed and exits the injection nozzle 12 ' at the dosing point 16 in a conventional manner, due to the displacement of the solenoid-operated valve 38 with reference to the seat 40 , The RDU 10 ' is with a flange 18 at the exhaust system 41 fastened, preferably with a V-clamp (not shown). Of course, other attachment methods may be used, such as using bolts or other mechanical bonding techniques.

To heat the urea solution when needed and before injection is an induction coil heater 13 ' in the coil-driven injection nozzle 12 ' provided. The induction coil heating 13 ' becomes electric with the help of the injector 10 ' Power supplied, the coil heating 13 ' energetization an electromagnetic field (see arrows A 'in 4 ) provides to the injector inlet pipe 14 to heat inductively, and thus also to heat the urea solution located therein adjacent to the heating zone Z '. Regarding 2 and 4 is the coil heater 13 ' compared to the conventional coil heater 13 out 2 closer to the dosing point 16 been repositioned. Thus, the primary active heating zone Z 'of the inlet pipe became 14 also to the dosing point 16 um-positioned. This leads to a reduction of the "unheated" fluid volume V 'by more than 50%, wherein the volume V' less than about 100 mm ³ is. Since more volume of urea solution is heated just before injection, earlier start of injection is possible after engine start, which further reduces NOx emissions.

The repositioning of the coil heater is as a result of the function evaluation of the lower O-ring 42 the conventional injector 10 ( 2 ) possible. In a fuel injection system with a port for which the injectors 10 are provided, the lower O-ring 42 for providing an intake air seal of the intake manifold or the cylinder head to the Injector installation point required. In the RDU application, this sealing function is no longer needed so that the O-ring 42 at the injector 10 ' the embodiment can be omitted. With reference to the circled area 44 in 3 To prevent the ingress of water and dirt, a minimum seal is required. This sealing can be achieved by the proposed change to the potting structure 46 be achieved, which the coil heater housing 48 covered in potting, which is a section of the coil heating 13 ' surrounds. An injector housing 50 covers a portion of the potting structure 46 and interacts with the potting structure 46 to form a seal. It may be preferred, if a more robust seal is required, to have a small cross-section O-ring in a groove in the potting structure 46 which continues to reposition the coil heater 13 ' would allow.

An advantage of the embodiment 4 is that the geometry of the inner molded coil heater housing 50 with respect to the conventional injector 10 out 2 unchanged. It is clear that still further embodiments are possible, which leads to an even further optimization of the reduction in respect of the unheated volume, if the geometry of this housing 50 is modified. Such a modification of the housing 50 ' is in 5 shown, in comparison with the conventional housing 50 the in 6 represented RDU 10 ' , Thus, the housing includes 50 ' instead of the tapered section 52 to show how the case 50 out 6 the case is a section 52 ' , which with respect to the longitudinal axis B of the injection nozzle 10 ' extends transversely and adjacent to one end 54 the coil heater 13 ' which is generally connected to the fluid outlet 16 borders. This allows the end 54 the coil heater 13 ' continue to the dosing point 16 is shifted, as compared to the end 54 ' the heating coil 13 ' out 6 , whereby the volume of fluid in the inlet tube 16 even more heated.

It is anticipated that the implementation of these embodiments will reduce the time to injection of the hot fluid into the exhaust, with a consequent reduction in cold start NOx emissions.

Although urea solution as the reducing agent 32 It is preferred that further reducing agents be used, such as guanidinium formate, since the agent is now heated upon injection.

Although the RDU 10 ' is disclosed for use in an SCR system, the RDU 10 ' also be used in a lean burn NOx trap (LNT) system where the reducing agent is diesel fuel (ie, a hydrocarbon based fuel).

The foregoing preferred embodiments have been shown and described for the purposes of illustrating the structural and functional principles of the present invention, as well as illustrating the methods of practicing the preferred embodiments, and are alterable without departing from such principles. Therefore, this invention includes all modifications which are included within the spirit of the following claims.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 6685112 [0019]

Cited non-patent literature

• SAE 2007-01-1582: "Laboratory and engine study of urea-related deposits in diesel urea SCR aftertreatment systems" (Laboratory and Engine Study on Urea-Related Deposits in Diesel-Urea SCR Aftertreatment Systems) [0004]
• SAE 2012-01-1078, "Development of a third generation SCR NH3-direct dosing system for highly efficient DeNOx" (Development of a 3G SCR NH3 Direct Dosing System for a Highly Efficient DeNOx) [0005]

Claims (19)

A reductant delivery unit for reducing nitrogen oxide (NOx) emissions from a vehicle, the reductant delivery unit comprising: a spool-driven fluid injector having a fluid inlet and a fluid outlet, wherein the fluid inlet is configured and arranged to receive an amount of a reductant, and wherein the fluid outlet is configured and arranged to communicate with communicating with an exhaust flow path of the vehicle such that the fluid injection nozzle controls injection of the reductant into the exhaust flow path, the fluid injector having an inlet tube to redirect the reductant between the fluid inlet and the fluid outlet; a coil heater which is integral with the fluid injection nozzle and, when energized, is configured and arranged to inductively heat the inlet tube so as to heat the reducing agent within the inlet tube, a coil heater housing surrounding a portion of the coil heater, a potting structure, which covers the coil heater housing in potting, and an injector housing covering at least a portion of the potting structure and being configured and arranged to form a sealing relationship with the potting structure in the absence of an O-ring so that one end of the coil heater is disposed generally adjacent the fluid outlet of the injector is. The supply unit of claim 1, further comprising a flange configured and arranged to secure the fluid injector to the exhaust gas flow path. The supply unit of claim 1, wherein the coil heater housing includes a portion which extends transversely with respect to a longitudinal axis of the fluid injector and is generally adjacent to the end of the coil heater adjacent the fluid outlet. Feeding unit according to claim 1, in combination with the amount of reducing agent, which is supplied to the fluid inlet. A feed unit according to claim 4, wherein the reducing agent is urea solution. A delivery unit according to claim 4, wherein the reducing agent is guanidinium formate. A feed unit according to claim 4, wherein the reducing agent is a hydrocarbon-based fuel. A reductant delivery unit for reducing nitrogen oxide (NOx) emissions from a vehicle, the reductant delivery unit comprising: a spool-driven fluid injector having a fluid inlet and a fluid outlet, wherein the fluid inlet is configured and arranged to receive an amount of reducing agent and wherein the fluid outlet is configured and arranged to communicate with a fluid inlet Exhaust flow path of the vehicle to communicate, so that the fluid injection nozzle controls an injection of the reducing agent in the exhaust gas flow path, wherein the fluid injection nozzle has an inlet tube for guiding the reducing agent between the fluid inlet and the fluid outlet, and a coil heater integral with the fluid injector and arranged and arranged to inductively heat the inlet tube upon energization, and thus at least a portion of the reducing agent therein, so that an unheated volume of the reducing agent in the inlet Tube adjacent to the fluid outlet is less than about 100 cubic millimeters. The feed unit of claim 8, wherein the injector further comprises: a coil heater housing surrounding a portion of the coil heater, a potting structure which covers the coil heater housing in potting, and an injector housing which covers at least a portion of the potting structure and is configured and arranged to form a sealing relationship with the potting structure in the absence of an O-ring so that one end of the coil heater is generally adjacent to the fluid outlet the injection nozzle is arranged. The supply unit of claim 8, further comprising a flange configured and arranged to secure the fluid injector to the exhaust gas flow path. The delivery unit of claim 8, wherein the coil heater housing includes a portion that extends transversely with respect to a longitudinal axis fluid injector and generally abuts the end of the coil heater adjacent the fluid outlet. A method of reducing nitrogen oxide (NOx) emissions from a vehicle, the method comprising the steps of: Assigning a coil-operated fluid injector to an exhaust flow path, the fluid injector having a fluid inlet and a fluid outlet, the fluid inlet receiving an amount of reductant, the fluid outlet communicating with the exhaust flow path the fluid injector has an inlet tube for directing the reductant between the fluid inlet and the fluid outlet, heating at least a portion of the reductant while in the inlet tube, such that a non-heated volume of the reductant in the inlet tube adjacent the fluid outlet is less than about 100 cubic millimeters; and operating the fluid injection nozzle to inject the reducing agent into the exhaust gas flow path. The method of claim 12, wherein the fluid injector includes a coil heater, and the step of heating the reductant comprises energizing the coil heater to inductively heat the inlet tube thereby isolating the reductant within the inlet tube except the unheated one To heat volume. The method of claim 13, wherein the fluid injector includes a coil heater housing surrounding a portion of the coil heater, a potting structure covering the coil heater housing, and an injector housing covering at least a portion of the potting structure further comprises: Sealing the injector housing with the potting structure due to a lack of an O-ring such that an end of the coil heater is disposed generally adjacent to the fluid outlet of the injector. The method of claim 14, wherein the coil heater housing comprises a portion that extends transversely with respect to a longitudinal axis of the fluid injector, and generally adjacent to the end of the coil heater, which is adjacent to the fluid outlet. The method of claim 12, wherein the assigning step comprises using a flange to attach the injector to the exhaust flow path. The method of claim 12, wherein the reducing agent is urea solution. The method of claim 12, wherein the reducing agent is guanidinium formate. The method of claim 14, wherein the reducing agent is a hydrocarbon-based fuel.

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