Cooling System for Actively Cooling an Exhaust Gas System

Abstract

A cooling system for actively cooling an exhaust gas system, comprises an exhaust pipe which conducts an exhaust gas flow of an internal combustion engine and an air-conducting element. The air-conducting element surrounds the exhaust pipe and forms an air-conducting channel. The exhaust pipe is cooled by an air flow which flows through the air-conducting channel.

Description

FIELD

The present disclosure relates to a cooling system for actively cooling an exhaust gas system.

BACKGROUND

Due to current exhaust emission legislation, exhaust gas post-treatment systems for reducing pollutant emissions are being used in internal combustion systems, including Diesel engine systems. In certain operating situations, the exhaust gases of such engines can reach high temperatures. The exhaust gas post-treatment systems may contain a diesel particulate filter (DPF) for filtering out soot particles. The soot particles are deposited in the porous filter wall of the DPF, so that the exhaust gas backpressure increases with increasing clogging level of the DPF. In order to regenerate the DPF and reduce clogging levels, the deposited soot particles are burned off at regular intervals. For this purpose, the temperature of the exhaust gas stream is temporarily increased by appropriate measures to temperatures ordinarily above 600° C. This may cause correspondingly high surface temperatures of the exhaust pipe. If the exhaust pipe is a part of an exhaust system for an agricultural machine for example, the hot exhaust pipe may cause a burn injury to an operator of the machine. Such a hot exhaust pipe may also cause a fire in the immediate surroundings, for example when the machine is parked in a barn. Finally, material deposited on the hot exhaust pipe can self-ignite.

A jacketed exhaust pipe is known from DE 1 027 084. While driving and depending on the speed, air led past the exhaust pipe removes heat by convection between the exhaust pipe and the jacket and dissipates it into the open air. Such a passive cooling system may not function properly for agricultural vehicles such as tractors, which generally travel at a slow speed or operate in stationary mode when providing power via the power takeoff shaft (PTO), because of insufficient air flow. It is desired to have a cooling system for an exhaust gas system that is largely independent of the travel speed.

SUMMARY

According to an aspect of the present disclosure, a cooling system for actively cooling an exhaust gas system includes an exhaust pipe for conducting a flow of exhaust gas from an internal combustion engine and an air-conducting element, which is arranged relative to the exhaust pipe such as to form an air-conducting channel which cools the exhaust pipe by introducing an air flow into the air-conducting channel. The cooling system also includes a fan which pushes an air flow into the air-conducting channel.

This system ensures that the cooling power of the active cooling system for the exhaust gas pipe is at least largely independent of a vehicle speed and is dependent only on the cooling power of the fan. In this way an active cooling is assured by an air flow that is produced by the fan into the air-conducting channel even during field work under load with an agricultural machine having typical speeds of less than 10 km/h or in stationary operation for outputting power via the power takeoff.

The fan preferably compresses the air flow to an elevated pressure level relative to an ambient pressure. This guarantees, even at low travel speed, a pressure gradient which creates an air flow into the air-conducting channel. The ambient pressure is the atmospheric air pressure.

In a preferred embodiment, the fan supplies cooling air flow for the internal combustion engine and to the air-conducting channel. Preferably, the air flow entering the air-conducting channel is previously filtered by a filtering system of the cooling system.

In a further preferred embodiment, the air-conducting element has an air inlet opening into the air-conducting channel, and the air-conducting channel is connected via the air inlet opening to an engine compartment for the internal combustion engine in order to supply the cooling air flow. The engine compartment guarantees that an elevated pressure level can be adjusted, which then causes the cooling exhaust stream to pass through the air inlet opening into the air-conducting channel. The engine compartment encloses the internal combustion engine, and includes a hood, one or more panel parts, and also the bulkhead of a driver's cab. Apart from an air supply opening to the fan unit and an air outlet opening corresponding to the air inlet opening of the air-conducting channel, the engine compartment is largely an air-tight enclosure.

The fan is preferably a fan unit of a coolant system for the internal combustion engine. Because such a cooling system ordinarily has a fan unit, the increased pressure level towards the exhaust gas system can be advantageously generated by the existing engine cooling fan.

In a further preferred embodiment, the air-conducting element has at least two outlet openings for the air conducting channel, the first outlet opening being arranged in the vicinity of a discharge opening of the exhaust pipe and the second outlet opening being arranged upstream of the discharge opening. An excessively high backpressure in the air-conducting channel is advantageously avoided by the second outlet opening.

The exhaust pipe preferably has a Venturi nozzle arrangement surrounding the exhaust pipe in order to draw in air, and the air-conducting element forms an annular gap downstream of the Venturi nozzle arrangement. This ensures in an advantageous manner that cooling air is supplied to the exhaust gas via the Venturi nozzles, whereby the high exhaust temperatures during regeneration of the DPF are lowered in order to counteract the creation of undesired nitrogen oxides in the exhaust pipe due to the high temperatures.

The annular gap is preferably arranged between two outlet openings of the air-conducting element. This guarantees that any existing overpressure is dissipated to a certain extent via the second outlet opening, so that no cooling air is blown off by the annular gap, but instead additional cooling air is drawn in from the exterior via the chimney effect that results downstream of the annular gap.

The annular gap is preferably constructed as a Venturi nozzle arrangement, for drawing ambient air into the air-conducting channel. Thereby the Venturi nozzle arrangement in combination with the chimney effect that results downstream in the exhaust pipe can be used to draw in ambient air for supporting the cooling.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective overall view of a cooling system according to the invention for active cooling of an exhaust gas system; and

FIG. 2 is a cross section through the cooling system of FIG. 1.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an agricultural vehicle 48 or tractor with a cab 50, a frame 52. A hood or engine cover 70 covers an internal combustion engine (not shown). An exhaust gas system 12 discharges an exhaust gas flow 22. The internal combustion engine is arranged inside an engine compartment 34 in a conventional manner. The exhaust gas system 12 includes a soot particulate filter (not shown), an exhaust pipe 14 and an air-conducting element 18 that surrounds the exhaust pipe 14, forming an air-conducting channel 20. The exhaust gas system 12 can comprise additional components (not shown), such as one or more catalytic converters.

The internal combustion engine has a conventional liquid cooling circuit (not shown), with a high temperature heat exchanger (not shown) to which cooling air drawn in from the surroundings via a radiator grille, downstream filter inserts and a fan unit 28. The cooling air directed into the engine compartment 34 is largely free of contaminants due to the filter inserts. The compression of the cooling air produced by the fan unit 28 leads to an elevated pressure level of the cooling air in the engine compartment 34 relative to the ambient atmospheric pressure. The cooling air directed through the high temperature heat exchanger and the engine compartment 34 is introduced as a cooling air flow 26 for actively cooling the exhaust gas system 12 in the air-conducting channel 20, which is formed by the air-conducting element 18 which surrounds the exhaust pipe 14.

In order to cool the exhaust gas flow 22 downstream of the soot particulate filter 52, the exhaust pipe 14 has a Venturi nozzle arrangement 42, as best seen in FIG. 2. The Venturi nozzle arrangement 42 is formed by constructing the exhaust pipe 14 in two parts, and constructing the upstream exhaust pipe element 54 so as to form a discharge area 56, which extends in a nozzle shape into the open end 58 of the downstream exhaust pipe element 60 of the exhaust pipe 14. The Venturi nozzle arrangement 42 has a substantially circular cross-section. The Venturi produces a negative pressure which draws air out of the air-conducting channel 20 into the exhaust pipe 14 in order to cool the exhaust gas flow 22.

The air-conducting element 18 is formed in two parts in the illustrated embodiment, consisting of an engine-side protective cover 62, a horizontal protective cover 66 comprising two cover shells 64, 64′, and a vertical protective cover 68. The number of parts from which the air-conducting element is formed can vary in other embodiments of the invention.

The air-conducting element 18 surrounds the exhaust pipe 14 and thus forms an air-conducting channel 20 together with the exhaust pipe 14. The air-conducting channel 20 is connected to the engine compartment 34 via an air inlet opening 32. The air inlet opening 32 is formed by constructing an air gap 72 between the exhaust pipe 14 and the lateral engine cover 70. The air gap 72 is covered with respect to the surroundings by the vertical protective cover 66, which is formed in a half shell shape. In the assembled state, the two cover shells 64, 64′ of the horizontal protective cover 66 form the second outlet opening 38, which is directed downwards towards the ground and is arranged on the downstream end of the protective cover 66. Due to the fact that the second outlet opening 38 is directed downwards, both the sound and the hot cooling air is discharged downwards in the direction of the ground.

The transitional area from the horizontal protective cover 66 to the vertical protective cover 68 forms an annular gap 44. In the present embodiment, the annular gap 44 is constructed as a Venturi nozzle arrangement 46. The horizontal protective cover 66 has a discharge area 74 tapering down in the downstream direction, which protrudes in a nozzle shape into the open end 76 of the vertical protective cover 68. In this way, an intake region is formed between the discharge region 74 and the open end 76, in which intake region a negative pressure relative to the surroundings is produced according to the Venturi principle upon passage of a cooling airflow through the air-conducting channel 20, so that ambient air is drawn into the air-conducting channel 20. The cooling air flow enters the surroundings via the outlet opening 36 in the area of the discharge opening 40 for the exhaust pipe 14.

In addition, a filter element or perforated grid (not shown), can be provided in the region of the annular gap 44 or in the intake region of the Venturi nozzle arrangement 46, to prevent coarse contaminants from clogging the air-conducting channel 20.

The air-conducting element 18 is thus a shield which prevents contact with the hot exhaust pipe 14 by completely surrounding the latter, and also an air-conducting channel 20 around the exhaust pipe 14, via which an actively introduced airflow guarantees cooling.

LIST OF REFERENCE NUMBERS

10 Cooling system12 Exhaust gas system14 Exhaust pipe16 Internal combustion engine18 Air-conducting element20 Air-conducting channel22 Exhaust gas flow24 Air flow26 Cooling air flow28 Fan unit30 Cooling circuit32 Air inlet opening34 Engine compartment36 Outlet opening38 Outlet opening40 Discharge opening42 Venturi nozzle arrangement

44 Annular gap

46 Venturi nozzle arrangement48 Agricultural vehicle

50 Cab

52 Soot particulate filter54 Exhaust pipe element56 Discharge region

58 Open end

60 Exhaust pipe element62 Protective cover64, 64′ Cover shell66 Protective cover68 Protective cover70 Engine cover

72 Air gap

74 Discharge region

76 Open end

While the disclosure has been illustrated and described in detail in the drawings and foregoing description, such illustration and description is to be considered as exemplary and not restrictive in character, it being understood that illustrative embodiments have been shown and described and that all changes and modifications that come within the spirit of the disclosure are desired to be protected. It will be noted that alternative embodiments of the present disclosure may not include all of the features described yet still benefit from at least some of the advantages of such features. Those of ordinary skill in the art may readily devise their own implementations that incorporate one or more of the features of the present disclosure and fall within the spirit and scope of the present invention as defined by the appended claims.

Claims

1-9. (canceled)

10. A cooling system for actively cooling an exhaust gas system, having an exhaust pipe for discharging an exhaust gas flow from an internal combustion engine, and an air-conducting element which forms an air-conducting channel which cools the exhaust, characterized by: a fan which moves a flow of air into the air-conducting channel.

11. The cooling system according of claim 10, wherein: the fan compresses the air flow to an elevated pressure level relative to an ambient pressure.

12. The cooling system of claim 10, wherein: the fan supplies a cooling air flow for the internal combustion engine as the air flow to the air conducting channel.

13. The cooling system of claim 12, wherein: the air-conducting element forms an air inlet opening which communicates with the air-conducting channel, wherein the air-conducting channel is connected via the air inlet opening to an engine compartment for the internal combustion engine in order to supply the cooling air flow.

14. The cooling system of claim 10, wherein: the air-conducting element has at least two openings for the air-conducting channel, both of the openings being arranged upstream of a discharge end of the exhaust pipe.

15. The cooling system of claim 10, wherein: the exhaust pipe has a Venturi nozzle arrangement, and the air-conducting element forms an annular gap downstream of the Venturi nozzle arrangement.

16. The cooling system of claim 15, wherein: the air-conducting element has at least two outlet openings for the air-conducting channel, and the annular gap is arranged between the two outlet openings.

17. The cooling system of claim 16, wherein: the annular gap comprises a Venturi nozzle which draws ambient air into the air-conducting channel.