MW54

Specifications

Diameter:  87mm
Length:  150mm
Thrust:  75 Newtons (16.8 lbs)
Max revs:  160,000 rpm
Temp:  575 deg C
Weight:  700 -800 grams depending on builder
Fuel consumption:  105 grams/min (1 litre per 9.8mins @ 6lbs thrust)

Historic information

The MW54 prototype first ran in -------------. It set a precident in small physical engine size which made it possible to convert smaller airframes to turbine power. It was shortly followed by a gas-generator version which formed the basis of the first practical home-build turboprop.
Designed by Mike Murphy, it has undergone continual development.

Design

This entirely new engine has been designed by Mike Murphy and developed as a joint project with John Wright. The engine design has been based around a smaller compressor with the aim of reducing power output and weight so it can be flown on smaller airframes than the KJ size of engine. Power levels though are still high and more than adequate for 50" wingspan deltas . The engines light weight of 650 grams makes it ideal for twin installations.

This engine was developed both as a thrust engine and as a gas generator for a turbo prop attachment. The Turboprop drawings are now available. In order for the engine to work the turbo prop it is necessary to run at very low temperatures. With the cone off and with a gas generator wheel fitted the 2 prototypes are running at temperatures 350-380 deg C.

The comprehensive plans come with a detailed written set of instructions and the design makes a welcome addition to the list of home built designs. The engine is based on the 54mm dia Garrett compressor wheel and a new design 55 mm diameter cast turbine wheel.


Materials

The front of the engine has a plastic plug-in insert and an aluminium outer cover. The case is made from wrapping stainless sheet into a tube and spot welding the seam. The compressor wheel is available either trimmed to the size or using the cheaper alternative and the vanes are trimmed to size. The combustion chamber is stainless steel (UK 316 or 310 spec) the NGV assembly at the rear and can be made from Inconel if longer life is required. The cast Inconel 713 turbine wheel used is a special wheel available from Wren Turbines.. The shaft is made from EN24T.

Compressor

The engine is specified with the Garrett T25 46633500 - 9 compressor wheel.

Turbine wheel

An engine like this needs a well made properly profiled turbine wheel to make the most of its potential. Part of the secret of its very high performance/efficiency is the design. The wheels are available either in cast form. The balancing is achieved by grinding the small raised rings cast into the face of the wheel.

Bearings

The engine uses a new ISO 688 full complement cageless ball race from GRW and the same bearing is used at both ends of the engine. The bearing tube is aluminium.

MW54

This is an engine that builds off well understood principles but a new much smaller combustion chamber has been developed by Mike and John. All the combustion occurs inside the chamber that measures only 47mmlong . The sticks have bends in them to increase the surface available for vaporisation. Angled in from the side are special air jets that supply oxygen to the seat of the flame. The main cooling holes have been moved to the rear of the chamber. The result is a chamber that will burn efficiently and with exceptionally cool EGT.

Plans

Plans are available from Wren Turbines  
wrenturbines.co.uk