Dynamic analysis of shuttle technique performance applied on hydraulic transformer

• 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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