Voith Turbo-Transmissions
Turbo transmission are hydrodynamic multiple-circuit drive for rail vehicles propelled by internal combustion engines. The first turbo- transmission was developed in 1932 by Voith in Heidenheim an der Brenz. Since then, the turbo transmission and adapted to the ever growing demands of the diesel traction and take today by the dominant electric power transmission, the world's most important position.
In Turbo transmissions, the implementation of engine power wheel power occurs hydrodynamically via the torque converter and fluid coupling by means of kinetic or dynamic energy of a fluid mass. This blade is deflected in channels with high flow rates and low pressures. They are therefore different from the hydrostatic transmissions in which the energy conversion takes place is also a liquid, but at a high static pressure and low flow rates according to the displacement.
Principle
Turbo transmission are hydrodynamic multiple-circuit drive, in which the power is transmitted hydrodynamically throughout the operating range after Föttingerprinzip. Torque converter, turbo couplings and, optionally, hydrodynamic brakes are combined into multiple-circuit transmissions. All have in common is their use in railway vehicles with drive diesel engines.
History
The first turbo transmission from 1932 was very simple. It contained a torque converter for the starting range and a fluid coupling for the operating range, which were arranged on a common rotor shaft. The most important feature of the new turbo transmission was the principle of filling and emptying of the hydrodynamic circuits acquired from the Föttinger marine transmissions. It offered wear-free starting, wear-free gear changes without interruption of traction, freewheeling effect by draining the circuits and high efficiency through the fluid coupling in the operating range.
In contrast to Föttinger used Voith turbo transmissions at the beginning of low-viscosity mineral oil as a working fluid instead of water. In the thirties, many improvements have been made on the turbo transmission: Installation of high gear, compact design and adaptability to various motors, automatic gear shift and heat dissipation via heat exchangers.
Beginning of the sixties came the hydrodynamic brake added as the third cycle type to converter and clutch. All made over the decades constructive improvements had to threaten the goal with the same construction effort to increase the allowable transmission power without the high reliability of transmission.
Transmission with two circuits for railcars
For the lower power range of diesel railcars of 200 to 300 hp a small turbo transmission T r 211 was developed as an alternative to the hydromechanical Busgetrieben 1969. Like the first turbo transmission it has the rotor combination converter clutch, but with high response and significantly improved efficiency in the conversion range. It still contains also the turning part and can be equipped if necessary with a hydrodynamic brake. The circuit diameters are only slightly greater for the 346 mm and 305 mm for the converter clutch. The rotor speed is 4170 min-1 with significantly higher by the high gear. Which reserves in the hydrodynamic part of the T 211 r stuck, show the gains and improvements made since that time. This relates solely to the mechanical part ( gears, storage and waves) and the transmission control. In contrast, the profile diameter of converter, clutch and brake remained unchanged. The peripheral speeds of the circuits increased according to the increase of the allowable transmission power input of 205 kW to 350 kW. The rotor speed is reached at 350 kW almost 5000 min -1, the peripheral speed at the maximum speed of the vehicle ( emptied converter! ) Of the freely rotating converter turbine at the outlet of 74 m / s To ensure adequate heat removal from the converter even at 350 kW, the filling pump has been strengthened. Encouraging at this 3.5 l / s oil through the heat exchanger in traction operation, 9 l / s are in the short-circuited circuit when the brake is operating. The brake rotor then acts simultaneously as a circulation pump. Externally visible changes compared to the previous type T 211 re.3 with 320 kW maximum input power is the transmission directly attached electronic control unit and the enlarged vent filter.
Transmission with three cycles for railcars
For the new fast rail trains with tilting technology VT 611/612 of the Deutsche Bahn an entirely new concept in transmission of the type converter clutch coupling with integrated hydrodynamic brake T 312 bre for 650 kW power is developed in 1995. In order to achieve a short overall length, two runners are driven via a high gear trio similar to the turbo reversing transmissions. The electronic transmission control is mounted on the transmission. The two reversing cylinders are hydraulically actuated, thus eliminating the need to provide the control air pressure to the transmission. Following the same approach followed five years later, the T 212 bre for 460 kW, which can be in contrast to the larger gear mounted directly on the engine. This allows a short- slung engine-transmission unit for underground installation in high-speed railcars up to 200 km / h. From T 211 r it took over the size of circuits. The T 212 br offers the advantage that over 50 % of the maximum can be driven in low coupling efficiency areas. This is a great advantage that leads under the same operating performance at lower fuel consumption especially used in the fast regional traffic DMUs.
Two converter transmission for locomotives
For powerful locomotives a new two Wandlergetriebe L 1999 620 reU2 constructed with a starting converter of 525 mm and a march converter of 434 mm section diameter, 520 rzU2 for 1 inspired 400 kW of power in the concept of the proven L. According to the higher input power of 2700 kW all parts of the gear must be enlarged and strengthened. In the range gear two gears on the countershaft arranged instead of the intermediate wheel at L 520 rzU2. The output speed level can be adjusted via the output gear pair to the respective requirements of the locomotive. The output shaft receives a large support base of 550 mm. Overall, the new large transmission, the enormous concentration of power provides the hydrodynamic power transmission. With a power to weight ratio of 2.06 kg / kW, the new L 620 reU2 has not yet reached a value at Lokomotiv gears. The comparable L 520 rzU2 has a power to weight ratio of 2.4 kg / kW. The optional attachable hydrodynamic brake KB 385 is redeveloped for this transmission. The Kiel locomotive manufacturers, Vossloh builds these transmissions into his big B'B' - line locomotives G1700 and G2000. The TurboSplit gear LS 640 reU2 has two runners of the L 620 reU2 for the separate drive of the two bogies of a six-axle diesel locomotive and the first to be installed in the locomotive Voith Maxima with 3600 kW engine power.
Power design choice the turbo transmission
The to-install engine performance and choosing the appropriate transmission are determined by the operating program of the rail vehicle. These are the conditions with trailer loads of diesel locomotives and seating capacity for diesel railcars, the topography of the routes to be used and especially in non-European operations, the climatic conditions. These criteria are included in the technical tender conditions and determine the points:
Speed , vehicle mass, acceleration and uphill stretches determine to be installed motor power. Added to this is the power requirement for the auxiliary system, ie air conditioning, cooling system, brake compressor and locomotives possibly a central power supply for the air conditioning and heating of passenger cars. Thus, the diesel engine can be selected, locomotives large V - engines, lying in railcars 6-cylinder underfloor engines or originating from the commercial vehicle sector, compactly built 12 - cylinder V- engines. Underground transmission combined with the engine as a power pack with low installation height are the preferred solution for modern diesel railcars.
The development of the hydrodynamic torque converter
The turbo transmissions, the torque converter is the heart, which was adapted to the demands of traction diesel locomotives over the decades. The objective of the development work is not only a good efficiency as possible, but high speed conversion without sacrificing solidity at the Anfahrwandlern and as constant as possible power consumption at the march converters. Of the many converter designs, the single-stage converter had done with centrifugal through-flow turbine as the most suitable. He 's just very well suited in building and by the high hoop strength of its radial turbine for high speeds. He became the standard converter Voith turbo transmissions.
Early seventies enabled the development of the required pulling force transducer characteristics - up to the amount of starting tractive effort - with a two- converter transmission instead of the previous three Wandlergetriebe achieve. Even today, the transducer development is not completed, even though it has reached a high level. Numerical flow simulations (Computational Fluid Dynamics - CFD) provide an insight into the entire flow field also to be measured technically difficult to access the rotating paddle wheels. The oil-filled flow chamber is modeled to the computer as a fine computational grid. For each grid node then the flow parameters velocity, pressure, etc. are calculated. In a subsequent analysis, the circulation flow - for example, by a three-dimensional streamline display - made visible. Efficiency -reducing mechanisms such as vortex flow separation at surfaces and Fehlanströmungen the blade rings can be localized so accurately. In addition to the visualization of these effects is also a recognition of the associated power loss is possible.
Thus, a relationship between changes in the flow field and a change in efficiency can be derived from the improvement. The calculated parameters agree over a wide operating range very well with the measured values match, deviations arise from time -saving simplifications in the simulation. Improvements to existing units as well as the development of new types of transducers can be done on the computer so purely virtual. The prototyping and verification of the results in the experiment at the end of the development process.