GB2536976A

GB2536976A - De-rotators with added sound attenuation

Info

Publication number: GB2536976A
Application number: GB1505886.0A
Authority: GB
Inventors: John Bayram Peter
Original assignee: Individual
Current assignee: Individual
Priority date: 2015-04-04
Filing date: 2015-04-04
Publication date: 2016-10-05
Also published as: GB201505886D0

Abstract

A de-rotating volute with acoustic insulation provided by sound absorbing materials positioned on an internal wall of the volute. The insulation may be contained in an acoustically transparent material and arranged against the wall of the volute. It may also extend towards the volutes flow inlet, or beyond, into the connecting conduit. This extended insulation may be capped with an acoustic sound-reflective facing that may be either flat or a flattened dome.

Description

Intellectual Property Office Application No. GII1505886.0 RTM Date:21 October 2015 The following terms are registered trade marks and should be read as such wherever they occur in this document: Kevlar Intellectual Property Office is an operating name of the Patent Office www.gov.uk /ipo DE-ROTATORS WITH ADDED SOUND ATTENUATION.

1 This invention relates to adding to the inherent sound attenu-ating effect that de-rotating volutes produce upon the sound power content of spirally rotating fluids entering them. As such, this invention principally relates to attenuating the noise of internal combustion (i.c.) engine exhausts.

When i.c.engines, such as twin scroll turbo'ed engines and jet engines with both pre-rotating and de-rotating volutes, operate they will be less noisy than more conventional piston and jet i.c.engines. As would also be the case with any diesels having in their exhaust systems such inherently sound baffling devices as: a) centrifugal separators; b) centrifugal separator de-rotating volutes; c) turbo turbines, and d) turbo turbine de-rotating volutes.

However, such engine's exhausts are so fundamentally noisy that even with the inherent sound attenuation of their volutes, exhauSt turbo turbines, and separators, they will still be noisy -such that their exhaust systems would have silencer boxes, or longitudinal annular sound attennuators that involve cost and space requirements. To overcome these problems, or minimise them, the present invention proposes that de-rotating volutes' * .. flat internal faces, opposite their lateral flow connections, * * * be acoustically insulated faces, to, thereby, significantly in-e5 crease their sound attenuation by adding sound absorption to * thei inherent 'end-reflection' sound insertion loss, whilst only adding minimal frictional flow resistance -since flow velocities across said particular faces are relatively low (be-***.

ing zero at their centre) -and minimal extra depth to them *;*30 (doubling the depth of acoustic insulation less than doubles its attenuation). With such added attenuation (particularly in *the case of turbo diesels having de-rotated particulates sepa-* * * rators there would be, at least, two (2) sound attenuated de- * rotators, a sound baffling centrifugal separator and a sound * .35 attenuating turbo's exhaust turbine) silencer boxes might poss-ibly be omitted, or, at least be less baffled (reducing exhaust back-pressure) such as 'turbo' silencers are (turbos don't like back-pressure). To further increase sound attenuation other interior surfaces of such sound attenuating de-rotators could also be acoustically insulated faces, but would increase fric-tional flow resistance disproportionately since flow velocities across such surfaces would be somewhat higher. Attenuation can also be increased by excrescently extending the acoustically insulated face oposite the volutes flow inlet into the volute's void, and which could be part concave curved, or cylindrical, or combinations thereof, that could extend into, or beyond the said inlet, and have ends, or centres, that are acoustically non-transparent to tend-reflect sound) -preferably, and flat, or are bevelled thereof, or 'bull-nosed' to reduce flow resist-ance without unduly reducing acoustic end-reflection -since such excrescences are in the 'eye' of rotating flow/s their surface flow velocities are inherently relatively low such that their (additional) frictional flow resistances would be similarly low. IIt should be noted that sound does not spirally ro-tate, it simply radiates, bounces around and. in the process of radiating into molecules and bouncing off surfaces (both of which absorb some sound power), decays.] The invention will now be described solely by way of example and with reference to the accompanying artistic-Licence drawings in which: Figure 1 shows a cross section through a de-rotating volute having a recess on one (1) side containing acoustic sound-absorbing insulation material.

Figure 2 similarly shows an alternative sound attenuated de-rotating volute having a concave curved and 'bull-nosed' pod extending beyond its flow inlet.

In figure 1, de-rotating volute 1 has a recess 2 containing mineral wool acoustic insulation 3 faced with a heat resistant Kevlar membrane contained by perforated stainless steel facing 2C) 4 and spot welded to volute l's stainless steel casing. For non-high temperature applications the recess could simply be lined with rigid glass fibre faced with a material such as Revertex bonded to it (cut from slabs of such bonded together acoustic insulation) and affixed to the volute's casing (which could be galvanised steel) by epoxy glued-on duct pins having * sr* barbs to retain metal insulation retainers (where other non-* * **** * flat surfaces might also be desired to be acoustically insula- * ted, non-rigid insulation, retained by a second skin of perfor- * * ated steel, rather than duct pins, may be necessary -particu-larly for high velocity/high pressure applications).

In figure 2, de-rotating volute 5 has a recess 6 and contains a *** * concave curved excrescence 7 whose outer surfaces 8, apart from * its 'bull-nosed' (**) pod end 9, are acoustically semi-trans- * 035 parent (comprising a Kevlar membrane and perforated stainless * * * steel) containing mineral wool acoustic insulation 10. EA pod * with a streamlined, or pointed end would acoustically reflect * * significantly less sound than one with a 'bull-nose', such that total sound attenuation would be that much less than when 'bull-nosed', or, alternatively, flat and peripherally bevell-ed. (**) Semi-domed with a flat centre. SD O* *

Claims

CLAIMS: 1 1) A sound attenuated de-rotating volute in which it accommo-dates means for acoustically insulating one (1), or more, of its interior faces with one (1), or more, sound absorbing materials with, or without, facings.
2) A sound attenuated de-notating volute according to claim 1, in which at least some, or all of the accommodated acoustic insulation is restrained within an acoustically semi-transparent, or perforated, or permeable facing, or within a com-bination of them.
3) A sound attenuated de-rotating volute according to claim 1, or claim 2, in which the accommodated acoustic insulation extends, at least partly, into the volute's flow inlet, or beyond it -into its connected device, or conduit.
4) A sound attenuated de-rotating volute according to claim 3, in which the extended acoustic insulation is terminated with an acoustic sound-reflecting facing.* * 5) A sound attenuated de-rotating volute according to claim 4, in which the said termination is flat, or flat and peripherally bevelled, or 'bull-nosed' (i.e. semi-domed with a flat centre). * * * O0 * * * * **** * *** ** um * * * 0 0 * * * * * *