GB2358433A

GB2358433A - Connecting an i.c. engine breather pipe to the exhaust system

Info

Publication number: GB2358433A
Application number: GB0001314A
Authority: GB
Inventors: Andrew Darley
Original assignee: Perkins Engines Co Ltd
Current assignee: Perkins Engines Co Ltd
Priority date: 2000-01-20
Filing date: 2000-01-20
Publication date: 2001-07-25
Anticipated expiration: 2020-01-20
Also published as: GB2358433B; US20010015067A1; US6418712B2; GB0001314D0

Abstract

Breather pipe 3 is connected, eg by hose clip 26, to a nozzle 23 which is secured inside a larger diameter adapter 21 welded to the wall of the exhaust tailpipe 5 close to the muffler. The outlet end of the nozzle 23 is set back from the junction 22 of the adapter 21 and the exhaust pipe 5. This arrangement leads to a substantial temperature difference between the exhaust gas steam and the nozzle 23 such that oil droplets in or around the nozzle 23 do not carbonise. In a modification, a thermally insulating insert (37, fig.3) is placed in a recess in the adaptor (31) ceramic insulating material. The invention may obviate the need for the conventional breather gas/oil separator but one can be provided.

Description

2358433 Engine Breather Apparatus The present invention relates to an

internal combustion engine breather apparatus and in particular an improved apparatus for introducing internal combustion engine breather gases into the exhaust gas stream of an internal combustion engine.

In an internal combustion engine such as a diesel engine, the pressure differential above and below the piston causes a small amount of gas leakage from the combustion chamber past the piston and into the crankcase. The pressure rise thus brought about in the crankcase can lead to oil being forced past the crankcase oil seals and to other similarly undesirable effects.

It is known to maintain a relatively constant and low level of crankcase pressure by connecting the crankcase to the environment via an open breather through which gas may pass. However, there are disadvantages to open breathers in that oil droplets may coalesce and drip from the breather, thus contravening environmental regulations or expectations in respect of fluid leakage from machines. Further, gas pressure pulsation may cause dust from the local environment to be drawn into the engine.

2 To overcome the above-mentioned problems, it is knowi provide closed circuit breather systems in which breather gas is fed into the intake air of the engine subsequent combustion. However, some of the oil Car, with the breather gas will carbonise upon contact i hot engine components such as turbocharger comprest and intake air intercoolers and thus impede air flow. reduce this problem, gas/oil separators are 01 employed but these add cost to the engine and do totally remove the oil content of the breather particularly where this is in the form of a fine aer rather than sizeable droplets.

A further problem with closed circuit breathers conne to the engine air intake system concerns the risk of carryover into the air intake system in such quan't that the engine may become fuelled by the oil and eng run-away (uncontrolled engine acceleration) may he occur.

In an effort to overcome various or all of the abcy mentioned problems, it has been proposed in the prior (for example, patents GB 1531080 and DE 3312818) to f the breather gas into the exhaust system of the engi A disadvantage of feeding the breather gas into exhaust before the muffler, or silencer, is that a dev.l. such as a venturi will be needed to reduce the pressu in the exhaust pipe at the point of entry of the breathE 3 gas, such that the resultant pressure in the crankcase remains at a relatively constant and low level.

The prior art generally either discloses passing the 5 breather gas into the exhaust at a point relatively close to the engine or is silent regarding the point in the exhaust at which the breather gas enters. An exception is Japanese unexamined patent application 8-61037 which proposes that the breather gas be introduced into the exhaust system at a point downstream of the muffler. However, the apparatus disclosed within JP 8-61037 has severe disadvantages as are described forthwith.

In JP 8-61037, the breather pipe outlet passes through 15 the wall of the muffler tailpipe and is contained largely within the tailpipe in the flow of the exhaust gas stream. The mass flow of exhaust gas will be far higher than the mass flow of breather gas, hence the breather pipe outlet will be at, or very close to, the exhaust gas temperature which can range up to 560 OC in the tailpipe of a turbocharged diesel engine exhaust system. Lubricating oil carbonises at around 180-200 OC, therefore a significant proportion of the oil carried within the breather gas during its passage through the breather pipe outlet will carbonise and this will very quickly block the outlet and cause an unacceptably high crankcase 4 pressure. Frequent and possibly diff-i,li decarbonisation will thus be needed. 1 Further, an apparatus constructed in accordance wit) 8-61037, with the breather pipe outlet normal to the i 1 of the tailpipe but formed with a bend, will not (i severely exacerbate the carbonisation and subseqt decarbonising problems but will prove relatii( expensive to manufacture and install. 10 Considering the foregoing matters, it is an object of present invention to provide an engine breather appar,, with a view to obviating or mitigating the drawbacks the existing or previously proposed arrangements. 15 It is an object of the present invention to provide improved apparatus for introducing engine breather into the engine exhaust gas in particular downstream o muf f ler. 20 It is a further object to provide an apparatus which -W avoid significant carbonising of the oil content of breather gas and which apparatus is relatively easy economical to install and clean or otherwise service. 25 It is a further object to provide an apparatus which 4 passively regulate engine crankcase gas pressures wit: an acceptable pressure range.

According to a first aspect of the present invention there is provided a breather gas outlet means comprising an adaptor comprising a hollow member having a first end lying downstream in use and adapted to engage at an aperture in a wall of an exhaust system of an engine to provide a breather gas communication thereinto; and a nozzle comprising a second hollow member to serve as a breather gas passage, positioned inside the adaptor, having a mounting portion sealingly engaging with an inside surface of the adaptor towards a second end thereof, and a nozzle portion extending laterally downstream towards but ending short of the said first end thereof, the nozzle portion having an outer dimension less than the inner dimension of the adaptor so as to form a space therebetween.

Setting back the nozzle away from the aperture in the wall of the exhaust reduces the flow of exhaust gases around the nozzle, thus reducing heating of the nozzle by the exhaust gases. Carbonising of the oil content of the breather gases is thereby significantly reduced, reducing maintenance / cleaning / service requirements.

Preferably, the end of the nozzle is set back a distance between 40% and 150% of the bore diameter, and more preferably between 60% and 100% of the bore diameter.

6 The effect is enhanced by ensuring that, towards downstream end of the outlet means where the adap engages over an aperture in the exhaust, the nozzle dimensioned such that the nozzle wall is spaced al) 5 from the adaptor wall.

Even where this is merely an air gap, the feature some insulating effect. This is enhanced in alternative embodiment of the invention, wherein 1,, insulating material, such as a ceramic, is provided the space between the inner surface of the adaptor the outer surface of the nozzle.

The inclusion of a heat insulator between the adaptor the nozzle further increases the temperature different between the exhaust gas / wall and the breather ga:

nozzle both by limiting the flow of any exhaust, around the outer wall of the nozzle and by limit:L transfer of heat from the adaptor to the nozzle. 1 carbonisation of any oil present in the breather gas: thus further reduced.

Preferably, one or both of the adaptor and nozzle is body of rotation. The nozzle portion of the nozzle i the corresponding surrounding forward portion of adaptor may be substantially cylindrical andmay concentric. Alternatively, other profiles may preferred. For example, the nozzle portion may 7 tapered.

Preferably, the adaptor is adapted to engage the wall of the exhaust system such as to extend perpendicular to the 5 wall of the exhaust system when so engaged.

The invention further comprises an exhaust system comprising the above breather gas outlet means engaged upon a side wall of an exhaust to effect breather gas communication into the exhaust.

It will be appreciated by the man skilled in the art that it will frequently be convenient for the breather gas outlet means to be positioned to engage the exhaust downstream of its muffler, for example at a sidewall of a tailpipe of the exhaust, given the pressure differential considerations discussed above. However, it will be understood that the invention is not restricted to such a position and that standard modifications known to the skilled man could be made to the apparatus of the invention to enable it to be positioned upstream of the muffler. For example, means, such as a venturi, may be provided.

Part of the breather gas outlet means, such as the adaptor, may be integral with the exhaust.

The invention also comprises a breather system comprising 8 the above breather gas outlet means or the above exh i system and further comprising a breather gas condi such as a flexible pipe or hose, adapted for connect:1 to a crankcase of an engine, and an engine witt, breather system so fitted. A gas/oil separator may provided in the breather gas stream to reduce the C content in the gas stream.

According to a further aspect of the present inventio there is provided a method of fitting a breather g outlet to an engine exhaust, comprising the steps providing a hollow nozzle member at a downstream end o breather gas conduit; mounting the nozzle inside a hol, adaptor member, by sealingly engaging a mounting portL of the nozzle with an inside surface of the adaptor, sU that a nozzle portion of the nozzle extends lateral towards but ends short of a downstream end of 1-1 adaptor, the nozzle portion having an outer dimensT less than the inner dimension of the adaptor so as form a space therebetween; and engaging the downstrz end of the adaptor at an aperture in a wall of an exhaiE system of an engine to provide a breather w communication thereinto.

The man skilled in the art will be aware of oth( preferred or alternative features of the method of t] invention by analogy with those features of the inventi above described.

9 By way of example, the invention will be described with reference to the accompanying drawings, of which:- Figure 1 is a schematic drawing of the apparatus of the present invention fluidly connected to the exhaust and.breather systems of an engine; Figure 2 is a detailed drawing of the apparatus in accordance with a first embodiment of the invention; Figure 3 is a detailed drawing of an apparatus in accordance with a second embodiment of the invention; Figure 4 shows the variation of temperature differential brought about by the apparatus of figure 2; and Figure 5 shows the variation of temperature differential brought about by the apparatus of figure 3.

Referring to the drawings, figure 1 shows an internal combustion engine 1 having a breather gas outlet 2 to which is connected a flexible breather pipe 3 having, in this example, an inside diameter of 20 mm. The pipe is terminated by a gas outlet means 7 in accordance with the first aspect of the invention, providing fluid communication with an exhaust system 4 which terminates in a tailpipe 5 of a muf f ler 6, the tailpipe 5 in this example having a bore of 60 mm- Figure 2 shows a ferrous adaptor 21 of 80 mm in le) with a through bore of 21,3 mm diameter and a counter at a first end of 28,3 mm diameter and 60 mm length. adaptor 21 is welded to a wall of the tailpipe 5 with counterbore in fluid communication with a port 22 thr(,. the wall of the tailpipe 5. The adaptor 21 may positioned at any location along the tailpipe 5 but preferably positioned relatively close to the mufj end.

A breather nozzle 23 of length 148 mm, outside diamf 21,3 mm and inside diameter 16 mm is introduced into bore and counterbore of the adaptor 21 until a first is spaced 12 mm inwardly from the first end of adaptor 21 and is retained to the adaptor 21 in t position by a pipe-nut 24 acting on a swage 25. breather pipe 3 is retained to a second end of the no4 23 by means of a hose clip 26.

During engine operation, breather gases generated wit. the engine 1 are conveyed via the breather pipe 3 to nozzle 23 and issue from the first end of the nozzl(,, into an exhaust gas stream passing through the exhz tailpipe 5. The reduced internal diameter of the no,, 23 in relation to the breather pipe 3 will cause breather gas to increase in velocity before issuing j 11 the nozzle 23 to the extent that a substantial proportion of oil mist or droplets contained within the breather gas will be swept into the exhaust gas stream passing through the tailpipe 5 rather than coalescing within or around the nozzle 23 or dripping from it to foul the vicinity.

A benefit identified in tests with an apparatus constructed as described above, with a radial clearance between the nozzle 23 and the adaptor 21 of 3, 5 mm in combination with the first end of the nozzle 23 being set back from the first end of the adaptor 21 by 12 mm, was a surprisingly substantial difference in temperature between the exhaust gas stream and the nozzle 23.

In the example apparatus, as adapted to a turbocharged diesel engine, the temperature differences between the exhaust gas in the tailpipe 5 and the breather nozzle 23 ranged to over 400 OC under high speed, full load, conditions. Thus, with a typically maximum exhaust tailpipe gas temperature of 560 OC under these conditions, the breather nozzle 23 had a temperature in the region of 0C, comfortably below the oil carbonisation temperature of 180-200 OC. The result of this is that any oil mist or droplets collecting in or around the nozzle 23 will not carbonise and the apparatus will therefore not require frequent decarbonising maintenance.

12 It should be noted that the dimensions given for t example apparatus were those found to provide the E mode for this particular example only and will vary apparatus to apparatus depending upon at least lt exhaust and breather gas flow rates, the exhaust temperature and the exhaust tailpipe diameter. The gJ,.

dimensions may be used as a starting point for ot installations of the apparatus but the optimum dimensi will need to be found by experimentation.

In a further embodiment of the present invention w, reference to figure 3, the adaptor 31 terminates at second end in a drilled and tapped face and include, recess into which is placed an insert 37 manufactui from a thermally insulating material, for example ceramic material.

The nozzle 33 includes a flange 38 spaced apart from tl f irst end by an amount equal to the length of the inse:

37 and of slightly smaller diameter than the maxi i diameter of the insert 37. The f irst end of the noz2. 33 is introduced into the insert 37 until the flange engages with the insert 37 and hence the first end of t nozzle 33 is approximately level with a first end of t insert 37.

A thermally insulating washer 39 and a clamping plate are placed over the second end of the nozzle 33 and t 13 clamping plate 40 is held to the tapped face of the adaptor 31 by threaded fasteners 41, thus clamping the washer 39, nozzle flange 38 and insert 37 to the adaptor 31. The flexible breather pipe 3 is then retained to the second end of the nozzle 33 with the hose clip 36. Thus the breather pipe 3 and nozzle 33 are thermally insulated from the exhaust system.

In tests on the apparatus of figure 3, in comparison with tests on the apparatus of figure 2, small improvements were found in the temperature difference between the exhaust gas and the breather nozzle, probably a result of the inability for exhaust gas to gain entry between the adaptor and the nozzle.

The improvements in temperature differentials that will be brought about with the apparatus of the first embodiment of the present invention compared with the apparatus disclosed in the prior art are considerable.

However, there may be instances where the further small improvements brought about by the apparatus of the second embodiment can be usefully employed. The test performance of the example apparatus of each embodiment of the present invention will be apparent with reference to figures 4 and 5.

Figure 4 represents the test results for an engine and exhaust system fitted with an apparatus in accordance 14 with the first embodiment (figure 2) of the preIE invention. The temperature differential readings E taken over a range of engine speeds with the enc- j running at full load. 5 Note that the dip in the temperature differential at.. engine speed of 2000 rpm may be due to turbule instability in the exhaust / breather gas flows at t h speed.

Figure 5 represents the test results for an engine exhaust system fitted with an apparatus including ceramic or similar nozzle insulating means in accord, with the second embodiment. As with figure 4, temperature differential readings were taken over a ra. of engine speeds with the engine running at full load.

Each embodiment of the apparatus was found to provid crankcase pressure well within the range acceptable an engine f itted with a closed circuit breathi specifically +20 / --50 MM H20 This was facilitated the approximately proportional relationship between m. exhaust gas and mass breather gas flow levels over majority of the engine speed and load range. Hence additional apparatus was required to dampen pressi pulses or control crankcase pressure levels within engine.

The apparatus of the present invention will normally preclude the need for a breather gas/oil separator. However, if the particular characteristics of the engine require a separator, this can be included in a conventional manner.

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Claims

1. A breather gas outlet means comprising an ada comprising a hollow member having a first end adapte(" engage at an aperture in a wall of an exhaust system an engine to provide a breather gas communica-z thereinto; and a nozzle comprising a second hollow meq to serve as a breather gas passage, positioned inside adaptor, having a mounting portion sealingly engaS with an inside surface of the adaptor towards a sec end thereof, and a nozzle portion extending laterE towards but ending short of the said first end therE the nozzle portion having an outer dimension less t: the inner dimension of the adaptor so as to form a sp. therebetween.

2. A breather gas outlet means as claimed in claim wherein heat insulating material is provided in the sp' between the inner surface of the adaptor and the out( surface of the nozzle.

3. A breather gas outlet means as claimed in preceding claim, wherein at least one of the adaptor a nozzle is substantially a body of rotation.

4. A breather gas outlet means as claimed in 0 preceding claim, wherein the adaptor is adapted to enga the wall of the exhaust system such as to extreo substantially perpendicular to the wall of the exhaust system when so engaged.

5. A breather gas outlet means as claimed in any preceding claim, wherein the adaptor sealingly engages the nozzle by means of a circumferential projection on the inner surface of the adaptor adapted to engage a swage on the mounting portion of the nozzle, and means are provided for urging the projection on the adaptor and the swage together.

6. A breather gas outlet means as claimed in claim 5, wherein the urging means comprises a pipe nut acting on the swage.

7. A breather gas outlet means as claimed in any one of claims 1 to 4, wherein the nozzle is provided with a flange, a first side of the flange limiting the extent to which the nozzle is inserted into the adaptor, the other side thereof being in contact with an insulating washer, held in position by means of a cover plate releasably secured to the adaptor so as to sealingly engage the adaptor and nozzle.

8. An exhaust system comprising a breather gas outlet means as claimed in any one of claims 1 to 7, wherein the outlet means is engaged upon a side wall of an exhaust to effect breather gas communication into the exhaust.

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9. An exhaust system as claimed in claim 8, wherein t breather gas outlet means is engaged to the exh.L downstream of its muffler.

10. An exhaust system as claimed in claim 9, wherein t breather gas outlet means is engaged to a side wall.f tailpipe of the exhaust.

11. An exhaust system as claimed in any one of claim3 to 10, wherein the part of the breather gas outlet mea is formed integrally with the exhaust.

12. A breather system comprising the breather gas out means as claimed in any one of claims 1 to 7 or exhaust system of any one of claims 8 to 11 and urt. comprising a breather gas conduit adapted for connect.. to a crankcase of an engine.

13. A breather system as claimed in claim 12, wher: the breather gas conduit comprises a flexible pipe.

14. A breather system as claimed in claim 12 or cl 13, wherein a gas/oil separator is provided in breather gas stream.

15. A method of fitting a breather gas outlet to engine exhaust, comprising the steps of:

19 (a) providing a hollow nozzle member at a downstream end of a breather gas conduit; (b) mounting the nozzle inside a hollow adaptor member, by sealingly engaging a mounting portion of the nozzle with an inside surface of the adaptor, such that a nozzle portion of the nozzle extends laterally towards but ends short of a downstream end of the adaptor, the nozzle portion having an outer dimension less than the inner dimension of the adaptor so as to form a space therebetween; and (c) engaging the downstream end of the adaptor at an aperture in a wall of an exhaust system of an engine to provide a breather gas communication thereinto.

16. A breather gas outlet means substantially as hereinbefore described with reference to Figures 1 and 2 of the drawings.

17. A breather gas outlet means substantially as hereinbefore described with reference to Figures 1 and 3 of the drawings.