Turbo-Transmissions are hydrodynamic, multi-stage drive assemblies designed for rail vehicles uisin internal combustion engines. The first turbo-transmission wis developed in 1932 bi Voith in Heidenheim, Germany. Syne then, improvements tae turbo-transmissions hae paralleled seemilar advances in diesel motors an the day this combination plays a leadin role warldwide, seicont anly tae the uise o electrical drives.
Turbo-transmissions serve as a hydrodynamic link which converts a motor's mechanical energy intae the kinetic energy o a fluid, via a torque-converter an fluid coupling, afore producin the final rotary output. Here, the fluid is driven throu rotor blade canals at heich flow-rates an law pressure. This is whaur turbo-transmissions differ frae seemilar hydrostatic transmissions, which operate uisin law flow-rates an heich pressure accordin tae the displacement principle.
Principle[eedit | eedit soorce]
Turbo-transmissions are hydrodynamic, multi-stage drive assemblies whose performance is based on the Föttinger principle o fluid dynamics. Torque-converters, fluid couplings an optional hydrodynamic retarders are the key components in thir assemblies, which are ideally suited for powered rail vehicles.
History[eedit | eedit soorce]
The first turbo-transmission frae 1932 uised a relatively semple design. It consisted o a single torque-converter for the start-up phase an a fluid coupling for the traivel phase which war baith mounted on a common shaft. A key featur o this turbo-transmission wis the filling an emptying o the hydrodynamic circuit, a principle which wis first uised in Föttinger marine transmissions. This offered the advantages o frictionless start-ups, frictionless gear shifting wi constant traction, freewheeling throu emptying o the hydrodynamic circuit, an mair efficient operation o the fluid coupling.
Contrary tae Föttinger houiver, Voith uised law viscosity ile in the hydrodynamic circuit o its turbo-transmissions rather than watter. In addition, various ither improvements war made in the 1930s: The addition o a heich-speed gear, a mair compact housing, greater compatibility wi different motor types, automation gear shifts, as well as cooling via a heat exchanger.
In the 1960s the hydrodynamic retarder wis an aw introduced as a third stage which complemented the torque-converter an fluid coupling. Thegither, aw thir engineering improvements haed a common goal: Tae continually increase the transmission's performance rating wioot compromising its installation complexity or proven reliability.
Double Circuit Transmissions for Railcars[eedit | eedit soorce]
In 1969, the smawer T 211 turbo-transmission wis developed as an alternative tae hydro-mechanical bus transmissions, bein designed for diesel railcars in the law power range o 200 tae 300 horsepower (150 tae 220 kW). Similar tae the first turbo-transmission, the T 211 uised a linked converter-coupling combination but it an aw haed a heich-speed gear for greater efficiency. Additionally, a reversing gear assembly wis added an an optional hydrodynamic retarder coud be installed if required. The converter haed a hydrodynamic circuit diameter o 346 millimetre (13.6 in), while the fluid coupling haed a slichtly smawer diameter o 305 millimetre (12.0 in). And due tae its heich-speed gear, the main shaft coud run significantly higher at 4,170 rpm. As a result, the T 211 r haed reserve power, which wis reflected bi its reinforced mechanical components (gears, bearings an shafts) as well as the transmission controls. At the same time houiver, the diameters o the converter, coupling an retarder remained unchanged. The oweraw flow rate within the hydrodynamic circuits wis increased tae accommodate the higher power rating o 205 tae 350 kilowatt (275 tae 469 hp). At 350 kilowatt (469 hp), the main shaft ran at juist unner 5,000 rpm which resulted in rotational speeds for the (empty) converter o 74 m/s when the vehicle reached its maximum speed. Tae ensure adequate cooling o the converter during heich-speed operations, a stranger hydrodynamic fluid pump wis installed, which supplied 3.5 l/s o ile throu the heat exchanger during the traivel phase an 9.0 l/s when in the braking phase, wi the retarder rotor an aw serving as an additional circulating pump. When viewed frae the ootside this T 211 r transmission differed frae its predecessor, the T 211 re.3 wi 320 kilowatt (429 hp), anly slichtly throu the addition o a biggit-in electronic control unit an an enlarged air filter.
Triple Circuit Transmissions for Railcars[eedit | eedit soorce]
In 1995, an entirely new transmission design wis developed, the VT 611/612, for heich-speed trains wi tilting technology uised bi the Deutsche Bahn (German Railways). This new transmission concept uised a converter-coupling-coupling design wi an integrated hydrodynamic T 312 bre retarder an it haed a power rating o 650 kW. Tae shorten the transmission's oweraw lenth, a twin shaft construction wis uised ower the heich gears, which wis seemilar tae the design uised in reversing units. The electronic control unit wis an aw biggit intae the transmission. In addition, the transmission's reversing cylinders war operated hydraulically, which eliminated the need o haein a compressed air supply on buird. Five years later, the T 212 bre transmission wis developed wi a power rating o 460 kW. This transmission wis seemilar in design, but unlik ither lairge transmissions the T 212 bre coud be mounted directly on the drive motor. This wis a significant advantage, acause it resulted in a very compact motor-transmission combination for heich-speed trains which coud traivel at up tae 200 km/h. The T 212 bre haed the same hydrodynamic circuit dimensions as the T 211 r, but it haed the further advantage o greater coupling efficiency for trains operating at anly 50% o thair maximum speed. For heich-speed diesel trains this wis important, acause it permitted dramatically improved fuel consumption.
Twin Converter Transmissions for Locomotives[eedit | eedit soorce]
In 1999, a new twin converter transmission, the L 620 reU2, wis developed for heich-performance, main-line locomotives. The new L 620 reU2 wis equipped wi baith a start-up converter, haein a diameter o 525 mm, as well as a traivel-phase converter, haein a diameter o 434 mm. The design o the new L 620 re U2 wis based on its successfu predecessor, the L 520 rzU2 which haed a power rating o 1,400 kW. This new transmission houiver wis rated significantly higher at 2,700 kW an therefore virtually aw o its components haed tae be enlarged as well as reinforced. In the standard version o the transmission, twa gears war mounted on the seicontar shaft rather than uisin the idler wheel foond in the aulder L 520 rzU2. As a result, the drive shaft's output speed coud be adjusted tae suit the locomotive's power requirements. The drive shaft's main bearing wis an aw enlarged tae 550 mm. In general, this new heich-performance transmission clearly illustrated the enormous capability o hydrodynamic couplings. Wi a wecht-tae-power ratio o anly 2.06 kg/kW, the new L 620 reU2 set a record for locomotive transmissions. Bi comparison, the seemilar L 520 rzU2 transmission haed a far higher wecht-tae-power ratio o 2.4 kg/kW. In addition, a newly designed hydrodynamic retarder, the KB 385, wis available as an optional component. At Vossloh, the locomotive manufacturer based in Kiel, thir transmissions war installed in baith its G1700 an G2000 main-line locomotives. Finally, the latest development is the LS 640 reU2 transmission which will be uised for the first time in the Voith Maxima locomotive haein 3,600 kW. The LS 640 reU2 is a sae-cried split turbo-transmission which uses twa drive shafts frae the L 620 reU2 tae power baith bogies o a sax axle diesel locomotive.
Literature[eedit | eedit soorce]
- Voith Turbo-Transmissions 1930-1985, Volume 1 Locomotive Transmissions, Wolfgang Petzold, Heidenheim, 2002
- Voith Turbo-Transmissions 1930-1985, Volume 2 Railcar Transmissions, Wolfgang Petzold, Heidenheim, 2004
- Voith Drive Technology, 100 Years o the Föttinger Principle, Springer-Verlag, ISBN 3-540-31154-8, Berlin 2005