GB2366836A

GB2366836A - Longlife lightweight exhaust silencer with composite casing

Info

Publication number: GB2366836A
Application number: GB0022491A
Authority: GB
Inventors: Peter Warwick Wright
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-09-14
Filing date: 2000-09-14
Publication date: 2002-03-20
Also published as: GB0022491D0

Abstract

The silencer has an inner perforated pipe 2, overwrapped with sound absorption material 3, eg mineral fibre or glass wool, in a corrosion and impact resistant composite casing 1. The pipe has a flange 4 towards one end, to which the casing is attached eg by screws or rivets. The casing is demountable for ease of assembly and to facilitate repacking and renewal of the sound absorption material as required. The casing may include carbon fibre, glass fibre, aramid fibre or silica fibre layers with a fire-resistant phenolic inner matrix material in combination with a tougher epoxide, vinyl ester or polyester outer matrix resin. A sliding joint, with an optional clamp 5 for adjustment, may be provided at the downstream end to avoid axial thermal stresses. A version for use in light aircraft, fig.2, has a low-drag aerodynamic shape. A return flow version is also described, fig.3.

Description

<Desc/Clms Page number 1> LONG LIFE LIGHTWEIGHT COMPOSITE SILENCER TECHNICAL FIELD Silencers for vehicles and light aircraft are currently made from mild steel, are heavy and suffer high corrosion rates,particularly in cooler sections, where exhaust products condense out to produce corrosive acids.As a long life alternative.stainless steel replacements have been developed mainly for classic and sports vehicles but these are heavy and costly to tool up and have limited "high tech" appeal.

In the motorcycle and competition car area,carbon fibre replacement silencers have been developed where light weight and a high technology image is the perceived benefit by enthusiasts. The present state of the art in composite silencers comprises simple cylindrical casings which are restricted by the conventional designs, materials and moulding meth;ds used.The few attempts so far to use composites, tend to be too flimsy to withstand general use and the rivets normally used to secure end fittings do not survive long under the heat and vibration experienced in service.

TECHNICAL INNOVATION According to the present invention,there is provided a robust lightweight demountable fibre composite outer casing moulded in one piece and attached to a light gauge metal internal perforated pipe by means of a metal or moulded composite flange.The pipe is wrapped with wire wool and sound absorption material such as mineral or glass fibre wool.Novel features include; * The use of two or more carbon fibre,glass. fibre,aramid fibre or silica fibre layers, with fire resistant phenolic inner matrix material in combination with a tougher epoxide,vinyl ester or polyester outer matrix resin.

*The provision of a free sliding joint,at the downstream end, to avoid axial thermal stresses which would arise from differential temperatures and thermal expansion coefficients betweem the inner pipe and outer casing.

* the optional provision of simple clamp to adjust the rear sliding joint clearance.

*The reduction in the number of joints to a single demountable connection to allow repacking, reduce manufacturing cost and increases reliability.This will be particularly critical for aircraft silencers where reliability is a key safety issue.

* The construction of the inner pipe in lightweight modular form using a heavier gauge entry pipe,lightweight perforated section and outlet pipe.

EXAMPLES The examples in the accompanying drawings show three applications of the novel features which have been tested.

FIG 1 shows a lightweight silencer for motorcycles, single seat and sports racing and rally cars,used in competition,wbere lightweight and efficient noise reduction with low power loss are critical.

FIG 2 shows a silencer for light aircraft,microlights and powered gliders,where lightweight,clean aerodynamic shape and reliability are critical and where improved noise abatement is curently an important issue.

The Composite outer casing (1) is typically a single piece moulding with a fire resistant inner layer and tough outer layer. The Heavy gauge entry pipe section (2A) connects to a Light gauge perforated pipe section (2B) which in turn connects to a Light gauge outlet pipe section (2C).

The Wire wool first layer pipe wrap (3A) protects the sound absorption Mineral wool or glass fibre packing (3B) The Light gauge attachment flange (4) is fixed to the inner pipe and provides the demountable attachment for the outer casing either by screws or rivets.

The Clearance adjustment clamp (5) for example a Jubilee clip is optional.

An Optional seal (6) for example graphite shaft packing can be used in some critical applications.

The Low drag aerodynamic shape (7) is particularly useful for high speed applications where the silencer is exposed to the external airflow. FIG 3 shows a return flow version which offers a more compact package and higher noise attenuation efficiency.

Claims

CLAIMS 1.A long life, lightweight composite silencer comprising a central perforated tubular pipe wrapped with sound absorption packing and surrounded by a fibre composite outer casing moulded in one piece from fire resistant materials such as carbon fibre fabric and phenolic matrix resin, the said casing being demountable for ease of assembly and to facilitate repacking if required. 2 A long life lightweight composite silencer as in claim 1 with an additional outer fibre composite layer of carbon fibre.glass fibre or Aramid fibre fabric or braid, with an epoxide,vinyl ester or polyester matrix resin, to provide enhanced structural integrety and toughness. 3.A long life lightweight composite silencer as claimed in Claim 1 and Claim 2, in which the casing is provided with a sliding joint to avoid axial thermal stresses which would arise from the differential temperatures and thermal expansion coeficients between inner pipe and outer casing. 4.A long life lightweight composite silencer as in Claim 3 in which a clamp is provided to adjust the clearance of the sliding joint. 5 A long life lightweight composite silencer as in Claim 3 and Claim 4 in which a seperate seal is provided at the sliding joint. 6 A lightweight composite silencer as in Claim 1 in which the inner pipe is constructed with a flange near one end and made from different gauge materials,using lighter gauge materials for the flange, perforated section and outlet sections. 7 A long life lightweight composite silencer substantially as described herein with references to Figs 1 - 3 of the accompanying drawings.