WO2015115973A1

WO2015115973A1 - Thermal protection arrangement

Info

Publication number: WO2015115973A1
Application number: PCT/SE2015/050077
Authority: WO
Inventors: Udo JAHN; Mokhlos Almaliki
Original assignee: Scania Cv Ab
Priority date: 2014-01-28
Filing date: 2015-01-27
Publication date: 2015-08-06
Also published as: SE1450079A1

Abstract

A thermal protection arrangement (2) for at least one heat-sensitive component (4), comprising an elongate radiation screen (6) configured to at least partly enclose said component (4) and to protect the component from radiant heat, comprising a delineating wall (8) which defines a space (10) for said component and is configured to be at a distance from said component (4). The radiation screen (8) has an inflow end portion (12) defining a cross-sectional area A1, and an outflow end portion (14), for the respective inflow and outflow of a cooling airflow (16), the thermal protection arrangement (2) comprises an airflow means (18) configured to supply said cooling airflow (16) to said inflow end portion (12), and the cross-section of the cooling airflow (16) defines an area A2, the ratio A1/A2 being within the range 0.5 to 2.

Description

THERMAL PROTECTION ARRANGEMENT

Field of the invention

The present invention relates to a thermal protection arrangement according to the preamble of the independent claim.

In particular, the invention relates to an arrangement intended to reduce the temperature around a temperature-sensitive component, e.g. a temperature measurement sensor situated close to the exhaust system of a vehicle.

Background to the invention

In vehicles there are now a plurality of components which are sensitive to too high temperatures. Many such components, e.g. various types of sensors such as temperature sensors, are essential for the regulation of the vehicle's engine.

One example is in applications on a gas engine of Otto type which has higher exhaust temperatures than other combustion engines and consequently higher engine compartment temperatures, more particularly close to/around the turbine. The location of a sensor intended to measure the exhaust temperature will be such that it is exposed to high temperatures, with consequent risk of ceasing to function, e.g. because parts of the sensor become carbonised. This results in impairment of the engine's performance as a result of less effective regulation, since no temperature values for the exhaust gases will be available.

More specifically, the location of the sensor means that radiant heat reaching the engine block in this region will be converted to warm air. The region where the sensor is situated becomes a heat trap which warm air cannot make its way out of and cool air from the engine's cooling fan cannot reach.

The specifications described below refer to some of the various existing solutions for cooling the engine compartment of a vehicle.

RECORD COPY TRANSLATION

(Rule 12.4) US-2010/0186395 refers to a device for cooling of overheated gas in the engine compartment of a vehicle. The device comprises a pipe, a radiator fan and a diffuser. The radiator fan generates an air flow which is mixed with overheated gas and guided into a pipe which passes through the casing of the engine compartment.

US-2012/010371 1 refers to a machine and a system for cooling of exhaust systems by means of cooling fans.

The object of the present invention is to improve the thermal protection of heat- sensitive components situated in, for example, a vehicle. More specifically, the object is to prevent the risk that the temperature close to the component or components, e.g. temperature sensors, might exceed a level at which their function would be jeopardised, with potential effects on the regulation of other functions of the vehicle.

Summary of the invention

The above objects are achieved with the thermal protection arrangement defined by the independent claim.

Preferred embodiments are defined by the dependent claims.

The thermal radiation from various heat-generating systems which are situated in the vicinity of, and have an interface with, a heat-sensitive component is prevented from reaching the component by the provision of a radiation screen close to the component. In addition, an airflow means is provided to convey cooling air to the region near to the component. The region around the component will thus be cooled so that the temperature does not exceed a level at which the component's function might be jeopardised. The cross-sectional area A1 of the radiation screen's inflow end portion and the cross-sectional area A2 of the cooling airflow being of the same order of magnitude provides assurance that a substantial part of the cooling airflow will enter and cool the space defined by the radiation screen.

The thermal protection arrangement according to the invention protects the heat- sensitive component from direct radiant heat. In addition, cooling air is supplied via the airflow means [PAGE 3 LINE 3 READING "luftflodesmedlet" WITHOUT THE FIRST "luft"] which cools the component. It is preferable to use cooling air from the engine's cooling fan, which entails no extra cost, since other components also need cooling.

The protection arrangement according to the invention is particularly suitable in the context of Otto engines and temperature sensors close to such engines, since this type of engine has higher exhaust temperatures than conventional

combustion engines.

The protection arrangement according to the invention protects the component and provides assurance that the engine can operate normally. The protection arrangement thus comprises a radiation screen configured to protect the component (e.g. the temperature sensor) from radiant heat, and an airflow means for supplying cooling air to the sensor.

In one embodiment the component thus takes the form of a temperature sensor for measuring the temperature of exhaust gases from a combustion engine. The sensor has a heat-sensitive seal at the transition from the monitoring portion to connecting lines. This seal may well become carbonised at too high

temperatures, e.g. over 200°C, and thereby short-circuit the connecting lines. The radiation screen protects the component from radiant heat from neighbouring heat-generating items, e.g. the catalyst, the exhaust pipe, etc. In one application the radiation screen may lower the temperature of the component from about 300° to about 200°C.

To further lower the temperature, an airflow means is provided which is configured to supply a cooling airflow to the space which is defined by the radiation screen and in which the component is situated.

Brief description of drawings

Figure 1 depicts a schematic side view of a thermal protection arrangement according to an embodiment of the present invention.

Figure 2 depicts a schematic perspective view of a thermal protection

arrangement according to the embodiment depicted in Figure 1 .

Figure 3 depicts a schematic side view of a thermal protection arrangement according to another embodiment of the present invention.

Figure 4 depicts a schematic perspective view of the radiation screen according to an embodiment of the present invention.

Figure 5 depicts a schematic perspective view of the radiation screen according to another embodiment of the present invention. Detailed description of preferred embodiments of the invention

The thermal protection arrangement will now be described with reference to the attached drawings, in which the same reference notations are used throughout for the same or similar parts. The thermal protection arrangement is particularly suitable for vehicles, e.g.

buses, trucks, work vehicles and cars, but may also be used on watercraft and in industries where heat-sensitive components are in environments with high temperatures. The thermal protection arrangement will now be described with reference initially to Figures 1 and 2. The thermal protection arrangement 2 is intended to protect at least one heat- sensitive component 4 from too much heat.

The heat-sensitive component 4 may for example be a temperature sensor configured to measure the temperature of an exhaust flow in an exhaust pipe 5, e.g. in a bus or a truck.

The thermal protection arrangement comprises an elongate radiation screen 6 configured to at least partly enclose the component 4 and protect the component from radiant heat.

The radiation screen comprises a delineating wall 8 which defines a space 10 for the component 4 and which is configured to be at a distance from the component. The space 10 defined by the radiation screen is such that the heat-sensitive component will be at least about 3 cm from the inside surface of the delineating wall.

The radiation screen 8 comprises an inflow end portion 12 defining a cross- sectional area A1 (see Figure 2), and an outflow end portion 14, for the respective inflow and outflow of a cooling airflow 16.

The thermal protection arrangement 2 comprises an airflow means 18 configured to supply the cooling airflow 16 to the inflow end portion 12. The cross-section of the cooling airflow 16 defines an area A2 (see Figure 2) and the ratio A1/A2 is within the range 0.5 to 2.

In another embodiment depicted in Figure 3 the airflow means 18 takes the form of one or more airflow guiding means 17, 19, e.g. one or more flanges or deflecting plates, so arranged that the cooling airflow 16 is guided in such a way that the airflow entering the inflow end portion has a cross-sectional area A2 which conforms to the ratio indicated above relative to the cross-sectional area A1 . For a description of the other parts in Figure 3, please refer to the above description pertaining to Figures 1 and 2. The configuration of the radiation screen 6 is such that it protects the component from direct radiant heat. The configuration will be appropriate to the space in which the component is fitted and may therefore take many different forms. What is common to all of its forms is that they have an inflow end portion 12 and an outflow end portion 14 such that the cooling airflow can pass through the radiation screen and carry away warm air which has accumulated in the space 10.

Figures 4 and 5 depict two examples of general configurations of the radiation screen.

Figure 4 depicts a configuration of the radiation screen 6 with a cross-section in the form of a substantially open rectangle formed by three wall elements 1 1 , 13, 15 which constitute a cover or hood under which the component is situated. The cover or hood has an open underside whereby the cooling airflow can naturally also leave the space 10. The length of the radiation screen is for example 15 cm, the height 10 cm and the width 10 cm.

Figure 5 depicts a configuration of the radiation screen 6 with a cross-section which is substantially a semicircle. This configuration may likewise be regarded as constituting a cover or hood under which the component is situated, likewise with an open underside. In this configuration with a semicircular cross-section the radiation screen has a radius of about 10 cm and a length of about 15 cm. The radiation screen's delineating wall 8 takes preferably the form of a plate of uniform thickness within the range 1 to 3 mm. The delineating wall is also made of material which withstands heat up to 350°C. In one embodiment the material is a metal, e.g. stainless steel or aluminium. In addition, the outside needs to be such that it reflects thermal radiation.

The radiation screen is fastened, e.g. to the engine block, by one or more weld seams, one or more threaded connections or some other fastening means. The airflow means 18 takes preferably the form of at least one cooling air pipe (see Figure 2) which has one end connected to a deflecting cover of a fan (not depicted). The other end of the pipe leads to close to the inflow end portion 12 of the radiation screen in order to supply the cooling airflow to the space in which the component is situated. A cooling airflow at a temperature of about 20-50°C will lower the temperature in the space to about 150°C.

The airflow means is so configured that the cooling airflow is guided into the inflow end portion of the radiation screen 6.

In the embodiment in which the airflow medium is a pipe, this guidance is achieved by the mouth of the pipe being situated close to the inflow end portion in such a way that the airflow is directed towards the inflow end portion.

The magnitude of the cooling airflow 16 depends on where the thermal protection arrangement is fitted. Where it is fitted in a vehicle, the airflow will be of the order of 10-50 litres per minute.

The present invention is not restricted to the preferred embodiments described above. Sundry alternatives, modifications and equivalents may be used. The above embodiments are therefore not to be regarded as limiting the invention's scope which is defined by the attached claims.

Claims

1 . A thermal protection arrangement (2) for at least one heat-sensitive component (4) situated close to an exhaust system in a vehicle, comprising an elongate radiation screen (6) configured to at least partly enclose said component (4) and to protect the component from radiant heat, comprising a delineating wall (8) which defines a space (10) for said component and is configured to be at a distance from said component (4),

c h a r a c t e r i s e d in that said radiation screen (8) has an inflow end portion (12) defining a cross-sectional area A1 , and an outflow end portion (14), for the respective inflow and outflow of a cooling airflow (16) from an engine's cooling fan, that the thermal protection arrangement (2) comprises an airflow means (18) configured to supply said cooling airflow (16) to said inflow end portion (12), and that the cross-section of the cooling airflow (16) defines an area A2, the ratio A1/A2 being within the range 0.5 to 2.

2. The thermal protection arrangement (2) according to claim 1 , in which said radiation screen (6) has a cross-section which is a substantially open rectangle formed by three wall elements.

3. The thermal protection arrangement (2) according to claim 1 , in which said radiation screen (6) has a cross-section which is substantially a semicircle.

4. The thermal protection arrangement (2) according to any one of claims 1 -3, in which said delineating wall (8) takes the form of a plate of uniform thickness within the range 1 to 3 mm.

5. The thermal protection arrangement (2) according to any one of claims 1 -4, in which said delineating wall (8) is composed of material which withstands heat up to 350°C.

6. The thermal protection arrangement (2) according to any one of claims 1 -5, in which said delineating wall (8) is made of metal.

7. The thermal protection arrangement (2) according to any one of claims 1 -6, in which said delineating wall (8) is made of stainless steel.

8. The thermal protection arrangement (2) according to any one of claims 1 -7, in which said airflow means (18) comprises at least one cooling air pipe.

9. The thermal protection arrangement (2) according to any one of claims 1 -7, in which said airflow means (18) comprises one or more airflow guiding means.