Principle of a Gas Turbine Engine
Gas Turbine Engines, GTE
In WW-II and shortly thereafter, piston powered aircraft peaked in power, performance and complexity wise. Power went up to over 4000 bhp for large multi-row radial engines. Only to be defeated by the jet, which was developed by (among others) Germany's Dr. Hans von Ohain and separately in the UK by Sir Frank Whittle. Its principles are based on the "Aeolipile" of the ancient Greek scientist Hero and other great thinkers like Leonardo da Vinci and the laws of Isaac Newton.
Compared to a piston, the gas turbine has less parts and the moving parts rotate in only one direction without stopping and accelerating as the pistons normally do in a engine. Thus, a running gas turbine is basically free of the vibrations normally found in piston models, which translates in much longer service life (TBO) and higher reliability.
A short list of GTE manufacturers is below to give you an impression of what is available on the market today.
Pratt & Whitney
Pratt & Whitney PT6 series engine
A widely known turboprop from Pratt & Whitney Canada is the PT6A series engines. It is a multi fuel, reverse flow, free turbine and has proven to be a very reliable engine with millions of flight hours and is installed on a multitude of aircraft like the Cessna Caravan (675 hp), Quest Kodiak (750 hp, PT6A-34) and Pacific Aerospace 750 XL (750 hp, PT6A-34AG).
To learn more about this remarkable gas turbine read these PT6A technical specifications.
Rolls Royce RR500
Mooney Aircraft is also bringing out a new model aircraft with a turbine engine, the new Rolls Royce RR-500. This engine could also be used by experimental aircraft builders in their designs. Click the following link if you want to read about the RR500 technical specifications.
Quote from Mooney: "The benefits of developing the RR500 to power a four place aircraft include improved global fuel availability in emerging markets where 100LL is scarce to nonexistent".
I think that this hits the nail exactly, as time goes by AVgas will become more a thing of the past. Especially when aviation diesel engines will finally lift off.
This commonly known turboprop (from the Czech Republic) is used in numerous aircraft commercial and experimental, for example, the Turbine Legend uses the Walter M601-D. Power output is 675 bhp. Lately the Honeywell Garrett TPE331-10 is installed for extra climb performance and speed at altitude, this engine delivers about 1070 bhp.
The Walter M601 is a dual shaft, reverse flow, free turbine turboprop made by Walter Engines a.s.. The gas generator section consists of two axial and
one centrifugal compressor stages, an annular combustion chamber, and a single stage axial compressor turbine. The power section consists of a single stage axial power turbine, exhaust system, and a two stage planetary reduction gearbox (15:1) with torque meter.
You will see this engine in a number of aircraft like the Lancair IV-P, CompAir turbine models, Murphy T-Moose and many more.
The GE H75, 80 and 85 model series engine is a continued development from the original Walter with new materials, better aerodynamics with 3D aero airfoils turbine blades, centrifugal fuel slinger eliminating hot spots and contamination resulting in no hot section inspections or fuel nozzle maintenance. Additionally the engine features push button start technology monitoring RPM and temperatures until it idles. Recently GE announced an EEC for the engine and electronic propeller governor resulting in single lever power control for the pilot. Basic TBO is 3600 to 4000 hours.
Contrary to the Walter M601 and the PT6A, the Garrett is not built as a free turbine engine. The core shaft is direct connected to the propeller through a gearbox. When shutdown you can see that easily as the propeller blades are in flat (fine pitch) position, the free turbine engine has the blades in full coarse pitch when it is shutdown.
Sources claim that an aircraft with the Garrett turbine runs with less fuel than one with a Walter or Pratt & Whitney PT-6 turboprop and this is with the same speed/power setting. Noise level seems to be higher on the ground but much lower when flying.
CompAir uses a 1650 hp version in their turboprop aircraft and a popular conversion by Texas Turbine Conversions for the Cessna Caravan uses the TPE331-12JR with a four blade 110" Hartzell propeller to increase power to 900 bhp with increased thrust and reduced fuel consumption.
Kestrel Aircraft switched from a PT6A engine to a Garrett TPE331-14GR for their aircraft in 2011.
From the site: PBS Velká Bíteš is a precision engineering company, the manufacturer of high-speed turbine machines for the aerospace, power and transport industries. Our business covers a wide range of engineering areas, including the manufacture of precision castings, hi-tech machining of metals, electroplating and subsequent assembly of finished products.
The TP 100 turboprop is based on the proven TJ 100 turbojet engine. TJ 100 is used as a gas generator that generates combustion gases for powering the free turbine and, via a gearbox the propeller. The system is designed for use in both push and tractor configuration depending on its mounting position on the aircraft. Thanks to its low weight and 180 kW output the engine is an ideal solution for powering ultralight manned and unmanned aerial vehicles (UAV). More details in the TP-100 engine specifications
This engine is in the USA also known under the name of Diemech Turbine Solutions TP-100 and a RV-10 has been equipped with it.
Has been under development from 1997 to 2009, the Innodyn turboprop engine had a direct spooled and a centrifugal compressor and radial inflow turbine. The fuel system is FADEC controlled and accepts diesel, JET, biodiesel and kerosene. They were never really open about the fuel consumption, but I expected it to be fairly high (13-15 USG/h).
Installed weight is 188 lbs and maintenance was supposed to be really easy: change gear oil every 500 hours, the spark plugs biannually and inspect the turbine for damage. Propeller was an electric controlled type. The engines have a power range between 165 bhp and 255 bhp.