A switched inertance hydraulic system uses a fast switching valve to control flow or pressure and is potentially very efficient as it does not rely on dissipation of power by throttling. This article studies its performance using an analytical method which efficiently describes the system in the time domain and frequency domain. A lumped parameter model and a distributed parameter model have been used for investigation using different parameters and conditions. The analytical models have been validated in experiments and the results on a prototype device show a very promising performance. The proposed analytical models are effective for understanding, analysing and optimizing the characteristics and performance of a switched inertance hydraulic system.

The transmission line method is a very efficient method for dynamic modelling of flow in pipelines and uses delay elements to represent wave propagation. In this article, an existing transmission line method model is investigated and shown to have some deficiencies. An alternative technique is introduced to enhance the transient and steady-state accuracy. Extremely good agreement is obtained between this new transmission line method and an analytical model. The model has been implemented in simulation of a number of highly dynamic systems and has been found to be robust and reliable.

This paper reports on theoretical and experimental investigations of a switched inertance device, which is designed to control the flow and pressure of a hydraulic supply. The device basically consists of a switching element, an inductance and a capacitance. It is able to boost the pressure or flow with a corresponding drop in flow or pressure respectively, analogous to a hydraulic transformer. In this paper, an enhanced analytical distributed parameter model in the frequency domain, which includes the effect of switching transition, non-linearity and leakage of the valve, is proposed and validated by simulation and experiments. A flow booster test rig is studied as a typical system. Simulated and experimental results show good performance, and accurate estimation of system pressure and dynamic flowrate can be obtained by using the enhanced analytical model. The model is very effective for understanding, analysing and optimising the characteristics and performance of a switched inertance device. It also can be used to aid in the design of a switched inertance hydraulic system.

A novel method for estimation of unsteady flow rate using pressure at two or three points along a pipeline is described in this paper. The pressure data are processed using a wave propagation model to determine the unsteady flow. The comparison and analysis of two-transducer and three-transducer techniques are investigated through simulation. The proposed method is shown to be effective for unsteady flow rate measurement over a high bandwidth. However, if the pressure values from two transducers are used, inaccuracies exist at certain frequencies when the transducer spacing coincides with multiples of half a wavelength. The accuracy can be improved by adding a third transducer with unequal spacing. The three-transducer method has been implemented in experiments and has been found to be robust and reliable.

No abstract