An analytical method to quantify the damping force of a twin tube shock absorber is proposed. Fluid and chambers compressibility effects and fluid cavitation are included. A comparison of a calculated damping force against the ideal damping force (assuming that non-cavitation occurs) is presented.
An analytical method to quantify the damping force of a generic twin-tube shock absorber for an automobile is proposed. Previous models by the present authors have accounted for fluid compressibility, chamber deformation, and fluid cavitation. This paper extends the work to thermal effects which have now been included. The variation in the force due to thermal effects caused by the energy dissipated within the damper is determined and the shock absorber temperature field is calculated. The results from the model are compared with those from simpler models (which do not include thermal effects) and are validated against the results from a real shock absorber. In terms of damping force, a good correlation is obtained, while acceptable results are obtained for the temperature field calculation.
The present paper introduces a novel transient experimental method employed to determine the discharge coefficient of constant section nozzles of small diameters of 1–3 mm and with a length/diameter ratio of around one. Flow is considered to be real and compressible; the discharge process was analyzed at relatively high pressures, the fluid used was N2. Based on the experimental data, a generalized expression characterizing the discharge coefficient for nozzles of different diameters, lengths, and fluid conditions was developed. In order to check the precision of the analytical equation presented, experimental upstream reservoir pressure decay was compared with the temporal pressure decay obtained using the new analytical equation. Good correlation was achieved for pressure differentials up to 7.6 MPa. Despite the fact that the procedure established can be extended to other gases and nozzle configurations, so far the equation presented to estimate the discharge coefficient, can only be applied to orifices with length to diameter ratios of around one.
The suspensions used in heavy vehicles often consist of several oil and two gas chambers. In order to perform an analytical study of the mass flow transferred between two gas chambers separated by a nozzle, and when considering the gas as compressible and real, it is usually needed to determine the discharge coefficient of the nozzle. The nozzle configuration analyzed in the present study consists of a T shape, and it is used to separate two nitrogen chambers employed in heavy vehicle suspensions. In the present study, under compressible dynamic real flow conditions and at operating pressures, discharge coefficients were determined based on experimental data. A test rig was constructed for this purpose, and air was used as working fluid. The study clarifies that discharge coefficients for the T shape nozzle studied not only depend on the pressure gradient between chambers but also on the flow direction. Computational Fluid Dynamic (CFD) simulations, using air as working fluid and when flowing in both nozzle directions, were undertaken, as well, and the fluid was considered as compressible and ideal. The CFD results deeply helped in understanding why the dynamic discharge coefficients were dependent on both the pressure ratio and flow direction, clarifying at which nozzle location, and for how long, chocked flow was to be expected. Experimentally-based results were compared with the CFD ones, validating both the experimental procedure and numerical methodologies presented. The information gathered in the present study is aimed to be used to mathematically characterize the dynamic performance of a real suspension.
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