Gas Turbines
Perkins Mars/Solar T41
Scroll down for more pictures and sounds, also at the bottom of the page there is now a link to a video.
The following information is from Perkins Gas Turbine manuals and leaflets.
Perkins Gas Turbines Limited (a subsidiary of F. Perkins Limited, manufacturers of diesel engines) of Peterborough, England built these small gas turbine engines during the early 1960’s, under licence from Solar Aircraft Company of San Diego, California, USA. In the UK the engine is the Perkins Mars and in the USA the same engine is known as the Solar T41. They were used in a wide variety of applications i.e. portable pumps, electric generators, air producers, fog generators for smoke screens (from oil mist injected into the exhaust), de-icers, foam production for fire fighting, etc.
This particular engine is an ‘Instructional Set’ supplied to colleges and universities. It is fitted with a large air fan to act as a brake and an optical type torquemeter unit. A telescope with mirrors and an illuminated graduated scale is used to measure the relative twisting between an inner and outer shaft as the load is applied from the fan. This accurately measures the torque and therefore the shaft horsepower. It is continuously rated at 50 shp, the turbine runs at approximately 40,000 rpm and this is reduced through a gear unit, comprising a single spiral bevel gear and pinion, to an output shaft to approximately 4,400 rpm.
I understand that Solar was part of International Harvester, which is now owned by the Caterpillar Company. Perkins was sold by Lucas Varity in 1998 and is now coincidentally also owned by Caterpillar.
Technical data:
Rating 50 hp continuous. Engine speed 40,000 rpm approx., output speed 4,400 rpm approx. Starting hand or electrical. Fuels, diesel, paraffin (kerosene), petrol (gasolene). Weight including standard gearbox and engine accessories, 98 lb (44.5 kg). Dimensions, 24.5 x 17 x 22 inches (62.2 x 43.2 x 55.9 cm).
According to the Perkins Mars manual, how to start the engine:-
1. Commence vigorous hand cranking, 2 operators.
2. At IGNITE speed, tachometer indicating 450 to 550 rpm and fuel pressure gauge reading 550 lb/sq. in. minimum, open fuel control valve to on position.
3. Continue vigorous cranking to STOP CRANKING speed, 1200 to 1300 rpm indicated on tachometer, from which point the engine will accelerate normally to rated speed.
With engine stabilised at rated speed, oil pressure should be 20 lb/sq. in. minimum and exhaust temperature normal operating range is 600 to 950 deg. F, (315 - 510 deg. C).
Normal running speed is 4430 rpm, speed must not be allowed to fall below 3600 rpm and avoid running at speeds in excess of 4500 rpm.
Shut down sequence to stop engine, allow 2 to 3 minutes running at no load in order that engine may cool down, turn engine fuel control valve to off position.
Note that all tachometer speeds quoted are output shaft speeds, the turbine is actually turning at over 40,000 rpm. The spiral bevel gear in the gearbox is rotated at 9.1 to 1 by the bevel pinion mounted on the end of the turbine rotor shaft. A reversal of this speed reduction by hand cranking, together with the speed increase in the chain and sprocket linkage, allows the operator to crank the engine with an approx. 70 to 1 speed increase. The magneto operates continuously to fire the spark plug whilst cranking and stops when hand cranking is discontinued, the sprag clutch disconnects when the turbine speed exceeds the cranking speed.
Click below to download sound files of Perkins Mars gas turbine running, right click and select, save target as. These are not the best quality but give an idea of what it sounds like.
Engine Start (326 kb) wave file here after approximately 11 seconds sound of ignition can be heard.
Engine Accelerating to 40,000 rpm (649 kb) wave file here
Engine Shut Down (316 kb) wave file here
All of above (1,290 kb) as a wave file here
All of above (235 kb) as a mpeg file here
Click below for Technical Documents
Perkins Mars Engine Description and Performance Data
Perkins Mars Engine Applications
Click on the Thumbnails below for a larger image:
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Combustor, Turbine Scroll, Turbine Blades and Exhaust
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Video image of the gas turbine running as an avi file here to download right click and select, save target as.
The video is about 2 minutes long and approx. 3.3 Mb.
This is the day in March 2002 I went to view the engine and it was demonstrated to me prior to purchasing it, note the comments at end of the video. The engine is hand cranked, the fuel valve is opened then closed as engine fails to start and cranking continues. Insufficient speed can cause a 'hot start' with fuel burning outside the combustion chamber and flames coming out of the exhaust, this must be avoided as the exhaust gas temperature is excessive and can damage the turbine. When the fuel valve is opened for the second time a flash of flame can be seen from the exhaust, hand cranking continues until the engine becomes self sustaining and accelerates to normal running speed. The big red thing at the end of the engine bed is the air fan brake used to apply a load to the engine in order to measure engine torque and hence power on this 'instructional set'. In it's place on most engines would be an electrical generator or fire water pump.
These web pages and all pictures are the property of David Smith, please ask if you wish to reproduce anything on these pages elsewhere, it will normally be freely granted so long as an acknowledgement is made and the text or pictures are not passed off as somebody else’s work. Any queries or comments should be sent to:-
davidsmith@expeditus.freeuk.com
