GB2377730A

GB2377730A - Air supply for pneumatically powered aircraft flight instruments taken from the supercharged induction system of a reciprocating-piston engine

Info

Publication number: GB2377730A
Application number: GB0117549A
Authority: GB
Inventors: Mark Conrad Wilksch
Original assignee: Seneca Tech Ltd
Current assignee: Seneca Tech Ltd
Priority date: 2001-07-19
Filing date: 2001-07-19
Publication date: 2003-01-22
Also published as: GB0117549D0

Abstract

A two-stroke or four-stroke reciprocating-piston engine, especially a compression-ignition light aircraft engine, has a supercharger 20 and/or a turbocharger 40. A connection 50 is made to bleed a small quantity of pressurised air which is passed via bleed line 55 to the instruments 110, eg of the gyroscopic type, via a receiver/filter 100 and a pressure regulator 105. The system obviates the need for venturis or vacuum pumps in light aircraft and allows the instruments to operate over a range of engine power settings. The engine may be inverted as shown, or may have vertical in-line, horizontally-opposed, Vee or radial cylinders.

Description

REGULATED AIR SUPPLY FOR PNEUMATIC AIRCRAFT FLIGHT INSTRUMENTS This invention relates to a system for powering aircraft flight instruments.

Pneumatically powered flight instruments are well known in aircraft, usually being powered by a vacuum supply derived from a venturi mounted in the external airstream or by an engine driven vacuum pump. Ventury, however, cause drag and are sometimes not aesthetically acceptable. Vacuum pumps add to the capital cost and also require maintenance.

Alternatively, such instruments have been powered by suitably regulated air bled from the compressor of a gas turbine engine, such engines always having available a large quantity of air at high pressure compared to the instrument's needs. While the use of"bleed air"from a gas turbine engine to power aircraft ancillaries such as de-icing equipment, air conditioning systems and instruments is relatively straightforward and well established such a system has not been used on piston engines where"Bleed air"powered flight instruments have hitherto not found practical application in the known art. Commercial piston

engines used on aircraft have not had a sufficiently high constant air pressure and so there was no regular supply of bleed air available.

According to the present invention, bleed air is tapped from the induction system of a piston engine of the compression ignition type which is boosted by turbocharging or supercharging or both.

A suitable engine is the subject of the applicant's patent GB2349180. According to the present invention, the engine is configured so that enough boost pressure is available to power flight instruments over a usable engine power range from near idle conditions to full power conditions. Further, a pressure regulator is provided so that the aircraft flight instruments are supplied with a substantially constant pressure air source. To extend the range of the system to near idle power settings the regulator can be designed so that it presents minimal resistance to flow at conditions where no pressure control is required of it. The invention is expected to be most suitable to induction boosted compression ignition aircraft piston engines either two-stroke or four-stroke. This suitability is due to the diesel engine's higher air flow at part load conditions compared with a gasoline engine of equivalent power output. Flight instruments require an uninterrupted source of air over a range of part and full load conditions. The invention could nevertheless also be applied to boosted spark ignition engines, albeit with

substantial effort in re-mapping of fuel, ignition and boost controls and compromises in operational performance.

Specific embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which :- Figure 1 shows an aircraft engine that is both turbocharged and supercharged and is a two-stroke compression ignition engine.

Figure 2 shows an engine that is turbocharged and is a four-stroke engine compression ignition engine.

While Figures 1 and 2 show engines arranged with"inverted" cylinders the invention could equally be applied to other well

know cylinder arrangements for example "vertical in-line", "horizontally opposed","V-form"and"radial". Referring to Figure 1 an engine arrangement uses boosted or forced induction using a turbocharger 40 and supercharger 20 to force air into the air chest 15 and thence into the cylinders of the reciprocating engine 30. A connection 50 is provided to bleed a relatively small quantity of air from the engine postsupercharger 20. A compression ignition engine such as the one shown at Figure 1 will be configured to use relatively high boost allowing sufficient pressure to be available for aircraft

instruments, even at low and near-idle power settings, since such a two stroke engine must always have a positive pressure induction system to achieve scavenging of the working volume.

Further since for a compression ignition engine the fuel is usually injected directly into the engine cylinders, the connection 50 provides bleed air with no fuel content.

Referring to Figure 2 a four-stroke compression ignition aircraft engine arrangement uses a turbocharger 40 to force air into the cylinders of the reciprocating engine 30. Optionally, the turbocharger 40, may be fitted with a dump valve or"wastegate" or other control to achieve regulation of the engine induction boost. A connection 50 is provided to bleed a relatively small quantity of air from the engine induction manifold 70. A compression ignition engine, when fitted with a boost control can be configured to run with significant induction pressure, even at low and near-idle power settings, allowing a useful bleed air supply over a wide operating range. Further since the fuel is usually injected directly into the engine cylinders, the connection bleed air with no fuel content.

Referring to Figures 1 and 2, the air having been bled from the engine boost system is passed via bleed air line 55 to a receiver/filter 100 then to a pressure regulator 105. From the regulator the controlled pressure supply is connected to a

network or manifold 115 that supplies at least one flight instrument 110 typically of the gyroscopic type. The supply may advantageously also be connected to a pressure gauge to allow the instrument supply pressure to be monitored.

Typically the regulated pressure is set to between 0. 1 and 0.2 Bar for conventional flight instruments used in light aircraft, however the system could be configured to operate at somewhat higher or lower pressures depending on the engine and instrument's characteristics.

The present invention may be retrofitted to existing forcedinduction engines, though some reconfiguration of the engine's induction system may be required.

COMPONENT LIST 5 Propeller Drive Flange 10 Crank Case 15 Air Chest 20 Supercharger 30 Reciprocating Engine 40 Turbocharger 50 Bleed Air Connection Point 55 Bleed Air Line 60 Engine air Inlet 65 Air Transfer Pipe 70 Induction Manifold 100 Air Filter/Dryer 105 Air pressure regulator 110 Flight Instruments 115 Distribution rail

Claims

CLAIMS 1. A reciprocating internal combustion engine having a forced- induction system for supplying air at an elevated pressure to the engine cylinder (s), wherein air bleed means are arranged to bleed air from between forced-induction system and said engine cylinder (s), the air bleed means being arranged to supply air to one or more pneumatically powered instruments.

2. The engine according to claim 1, wherein a regulator is fitted between the air bleed means and instruments arranged to regulate the air supply to suit the requirements of the instruments.

3. The engine according to claim 2, wherein the regulator is designed so that it presents minimal resistance to flow at low engine boost conditions.

4. The engine according to claims 1 to 3, wherein a dryer and/or filter is fitted in the air bleed means upstream of the instruments.

5. The engine according to any one of claims 1 to 4, wherein the engine is boosted by a supercharger, turbo-supercharger or both.

6.-The engine according to any one of claims 1 to 5, wherein

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the engine is a compression ignition engine.

7.-The engine according to any one of claims 1 to 6, wherein the engine uses the 2-stroke cycle.

3. An aircraft including an engine according to any one of claims 1 to 7.

9. A method of supplying air to pneumatically powered instruments, comprising : a ; providinq air bleed means fr m me elevated pressure

flow of a reciprocating internal combustion engine Le nav. inc' a forced induction system ; and : v : tVlnc ; -3 rOl : Cb.. 1 In'~IU : : Ton sys. em ; ana instr'uments to said air bleed means.

10. The method of claim 9, wherein t.'hc engine is according to aj-r art s. is- -ie 3 4 rr, S engi.. ne as ] !.. R. reciprocating interna" : combustion engine as hereinbefore described with reference to, and as illustrated by, the accompanying drawings.

12. A :', alrcraft as hereinbefore described with reference ic, and. as illustrated by rhe accomoanying arawings.

1 3. ? \ method of s upp, y i n g air t p n e uma t i c a 11 y p o w e e e .

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I i-I instruments as hereinbefore described with reference to,. and as illustrated by, the accompanying drawings.