Discharge Coefficients of a Heavy Suspension Nozzle

Carlos Rio-Cano,Angel Comas,Navid M Tousi,Josep M Bergada

doi:10.3390/app11062619

Carlos Rio-Cano, Angel Comas + Show 2 more

Open Access

https://doi.org/10.3390/app11062619

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Journal: Applied sciences	Publication Date: Mar 15, 2021
Citations: 2	License type: CC BY 4.0

Affiliation: Universitat Politècnica de Catalunya

Abstract

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.

Highlights

Hydro-pneumatic suspensions consist on two or more oil chambers and a couple of gas ones
The discharge coefficient is defined as cd = ṁṁt, where ṁ characterizes the real mass flow flowing through the nozzle, while ṁt is the mass flow obtained using a theoretical equation
Initially the measured temporal pressure evolution inside the reservoirs is compared with the ones obtained from the Computational Fluid Dynamic (CFD) simulations

Summary

Introduction

Hydro-pneumatic suspensions consist on two or more oil chambers and a couple of gas ones. Some of the recent papers simulating compressible flow conditions at high Mach numbers inside nozzles are Reference [22,23,24,25] From all these studies, it is relevant to highlight the work done by Farzaneh-Gord et al [15], where they numerically evaluated the exit flow of natural gas through a purging valve, during its opening time. They used the RANS method with a Realizable k − e turbulent model and they investigated the effect of injection pressure on the fuel flow under fuel compressibility conditions They concluded that the nozzle discharge coefficient for compressible flow was larger than when fluid was considered as incompressible. The discharge coefficients as a function of the Reynolds number, and for both flow directions, are presented and discussed, and the paper ends with the conclusions

Experimental Test Rig

Dynamic Computational Fluid Dynamic Simulations

Results and Discussion

Conclusions