A Novel Method to Determine the Discharge Coefficient of Constant Section Nozzles Under Compressible Dynamic Flow Conditions

Comas, Á; Rio-Cano, C.; Bergadà, Josep M.

doi:10.1115/1.4042374

Cited by 2 publications

(11 citation statements)

References 13 publications

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“…Numerical simulations clarified where the sonic conditions are to be expected. Discharge coefficients were dependent on the flow direction and the Reynolds number, and they agree well with the ones obtained by Comas et al [13] and Nagao et al [9], specially when considering the different nozzle length to diameter ratio. In the CFD simulations, the fluid was considered as ideal, and similar CFD simulations were performed by Lakzian et al [18] and Mazzelli et al [17], where the fluid was considered as ideal, as well, and studied under similar pressure differentials and the same turbulence model.…”

Section: Resultssupporting

confidence: 89%

“…In the CFD simulations, the fluid was considered as ideal, and similar CFD simulations were performed by Lakzian et al [18] and Mazzelli et al [17], where the fluid was considered as ideal, as well, and studied under similar pressure differentials and the same turbulence model. From the comparison of the present study with Reference [9,13,17,18], it can be concluded that the error generated by the CFD simulations is small and acceptable under the engineering applications point of view.…”

Section: Resultsmentioning

confidence: 63%

“…The only problem associated with this methodology was that the fluid temperature had to be estimated. As previously defined by Kagawa et al [2] and Comas et al [13], if the reservoirs were large enough, the fluid temperature was likely to remain constant. Yet, which were the required dimensions to fulfill this condition, for each particular case, was not clearly stated.…”

Section: Mathematical Equations and Analytical Process Followed To Determine The Physical Variablesmentioning

confidence: 92%

“…The measured temperature was almost constant in both reservoirs, and it was used to instantaneously estimate the heat transferred through the walls. Therefore, providing that the only trustworthy dynamic information in both reservoirs was the temporal pressure evolution, the methodology employed to determine the mass flow between reservoirs was based on the following equations, developed by the authors in a former paper [13]. Equation (1) was obtained from the application of the energy equation in the upstream reservoir, it characterizes the temporal mass variation in the upstream reservoir, dm u dt , as a function of the tank's temperature T u , the heat transferred to the fluid dQ u dt , the upstream pressure temporal variation…”

Section: Mathematical Equations and Analytical Process Followed To Determine The Physical Variablesmentioning

confidence: 99%

“…In most of the research undertaken previously, the theoretical work was not supported by an experimental method, which could allow working directly with the experimental data. These aspects were covered in Reference [13], where, for constant section short nozzles, an expression defining the discharge coefficient was developed using an experimental method and a gas flow model based on the Lee-Kesler equation of state [14]. Experimental results were compared with the ones obtained from the new developed equation, observing that, for tests performed using nitrogen up to 7.6 MPa pressure differential, a good correlation was obtained.…”

Section: Introductionmentioning

confidence: 99%

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Discharge Coefficients of a Heavy Suspension Nozzle

et al. 2021

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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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Section: Resultssupporting

confidence: 89%

Section: Resultsmentioning

confidence: 63%

Section: Mathematical Equations and Analytical Process Followed To Determine The Physical Variablesmentioning

confidence: 92%

Section: Mathematical Equations and Analytical Process Followed To Determine The Physical Variablesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Discharge Coefficients of a Heavy Suspension Nozzle

et al. 2021

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Estudio del coeficiente de rigidez y de amortiguación de una suspensión neumática multicámara

Río Cano

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Heavy vehicles are generally equipped with Shock Absorber Suspension Cylinders, which, in addition to integrating in the same element, the damping and suspension mechanism, allow obtaining greater suspension travels, maintaining the rest extension in the event of possible variations of load. They are normally made up of two or more oil chambers and a pair of Nitrogen chambers. During reciprocating suspension movements, oil and gas flow up and down between two consecutive chambers often separated by one or more nozzles or valves. The main objective of this Doctoral Thesis is to make a model that predicts the performance of an asymmetric shock absorber of known geometry, under dynamic conditions of use. Addressing such a complex issue in an agile and simple way has motivated the author to study the cylinder by subdividing it into different sub-models, initially evaluating the mass transfer between the gas chambers, Cd, later studying the evolution of pressures, only contemplating the gas chambers interconnected with the study nozzle and concluding with a general model that studies the entire Damped Suspension Cylinder and which is the object of study in this Thesis. The simulation of the dynamic characteristics of mechanical components of this nature makes it possible to predict the performance of said cylinders based on the design parameters and the initial operating conditions, saving design time and development means, while also avoiding the generation of significant errors in said designs. This contribution allows the possibility of optimizing and applying significant improvements without the need to invest resources in experimental studies. All this translates into financial savings, always sought after by developers. Thanks to the large volume of experiments carried out and analysed, in the different test benches, designed and built for this purpose, a model capable of predicting the behaviour of the CSA in the face of external disturbances has been validated, obtaining a good correlation between the experimental data and the theoretical data, the maximum error obtained being less than 7%, for the working conditions proposed in the study. Los vehículos pesados generalmente están dotados de Cilindros de Suspensión Amortiguada (CSA), los cuales además de integrar en un mismo elemento, el mecanismo de amortiguación y de suspensión, permiten obtener mayores recorridos de la suspensión, manteniendo la extensión de reposo ante posibles variaciones de la carga. Normalmente están formados por dos o más cámaras de aceite y por un par de cámaras de Nitrógeno. Durante los desplazamientos alternativos de la suspensión, el aceite y el gas fluyen hacia arriba y hacia abajo entre dos cámaras consecutivas a menudo separadas por una o varias boquillas o válvulas. El objetivo principal de esta Tesis Doctoral, es realizar un modelo que prediga las prestaciones de un amortiguador asimétrico de geometría conocida, en condiciones dinámicas de utilización. Abordar una temática tan compleja de una forma ágil y sencilla ha motivado al autor a estudiar el cilindro subdividiéndolo en diferentes submodelos, evaluando inicialmente la trasferencia de masa que hay entre las cámaras de gas, Cd, estudiando posteriormente la evolución de las presiones, únicamente contemplando las cámaras de gas interconectadas con la tobera de estudio y concluyendo con un modelo generalista que estudie el Cilindro de Suspensión Amortiguada al completo y que es el objeto de estudio en esta Tesis. La simulación de las características dinámicas de componentes mecánicos de esta índole permite predecir las prestaciones de dichos cilindros en función de los parámetros de diseño y de las condiciones iniciales de operación, ahorrando tiempos de diseño y medios de desarrollo evitando también la generación de errores importantes en dichos diseños. Esta contribución permite la posibilidad de optimizar y aplicar mejoras significativas sin la necesidad de invertir recursos en estudios experimentales. Todo esto se traduce en un ahorro económico, siempre perseguido por los desarrolladores. Gracias al gran volumen de experimentos realizados y analizados, en los diferentes bancos de ensayos, diseñados y construidos para tal fin, se ha validado un modelo capaz de predecir el comportamiento del CSA ante perturbaciones externas, obteniendo una buena correlación entre los datos experimentales y los datos teóricos, siendo el error máximo obtenido inferior al 7 %, para las condiciones de trabajo propuestas en el estudio

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A Novel Method to Determine the Discharge Coefficient of Constant Section Nozzles Under Compressible Dynamic Flow Conditions

Cited by 2 publications

References 13 publications

Discharge Coefficients of a Heavy Suspension Nozzle

Discharge Coefficients of a Heavy Suspension Nozzle

Estudio del coeficiente de rigidez y de amortiguación de una suspensión neumática multicámara

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