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- Johansson, Andreas, et al.
(författare)
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Dynamic analysis of shuttle technique performance applied on hydraulic transformer
- 2002
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Ingår i: Proc. of the 3rd International Fluid Power Conference (IFK'3). - 9783826599002 ; , s. 249-261
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Konferensbidrag (refereegranskat)abstract
- As an alternative to traditional valve coutrol, hydraulic transformation has proved to be an attactive approach from an efficiency point of view. According to the Innas1 concept, hydraulic transformation is achicved using a modified displacement machine design. In order to realise the transformation using only one displacement machine, it is necessary to use a valve plate containing three kidney slots for the three supply lines: supply, load and tank. By displacing the valve plate, pressure/flow ratio can be transformed, ideally with preserved efficiency. When using three kidney slots together with a traditional displacement machine with two dead centres, the commutation between two subsequent kidneys will occur while the piston is moving. This will result in pre-compression or decompression of the cylinder fiuid, with severe pressure peaks as a consequence. Besides noise and vibration, these pressure peaks will decrease the total efficiency considerably. Also driving shaft torque variations will appear, which will affect the rotational movement by speed fluctuations. In order to minimise the pressure peaks during valving land passages. small pistons between pairs of cylinders in the barrel are introduced. This is referred to as shuttle technique. Using these shuttles, excess of cylinder fluid during commutation can be transferred to adjacent cylinders, and thus prevent cylinder pressure peaks from appearing.It is very difficult to measure the internal states of the shuttle in an operating transformer. By using computer simulation techniques, detailed analyses of the internal workings of the shuttle can be performed. In this work, a detailed description of the dynamic behaviour of the shuttle is given. Advantages and disadvantages of the technique are discussed.1 Innas BV, Netherlands
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| 4. |
- Werndin, Ronnie, 1972-
(författare)
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Hydraulic transformers for energy efficient systems
- 2002
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- THE FOCUS OF this thesis is to evaluate and analyse secondary controlled hydraulic systems with linear loads. The main objective has been the hydraulic transformer, with special respect to Innas Hydraulic Transformer, IHT1. One advantage of secondary controlled systems is that energy consumption can be kept low as energy can be regained when potential or kinetic energy is reclaimed, resulting in energy-efficient systems. The main obstacle to wider usage of secondary controlled systems is the difficulty of implementing linear loads, i.e. hydraulic cylinders, in an efficient way. The hydraulic transformer is the most interesting solution.The principle of the IHT design is studied in detail. As the displacement control of the IHT design differs from conventional variable axial piston machines, port commutation will occur at other locations than the piston dead centres. At these positions the pistons will have considerable velocities, introducing pressure peaks and cavitation. Further, the design will cause driving torque variations, which in combination with torque losses of a stick-slip nature have a negative influence on low-speed controllability.The presented study shows promising results concerning both efficiency and controllability of the IHT concept. The mechanism behind the torque variations is analysed and methods like shuttle technique and different port configurations are studied in order to minimise pressure peaks and torque variations. Problems and difficulties concerning low-speed controllability are also pointed out and different control strategies are studied.
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