The influence of back pressure on the flow discharge coefficients of plain orifice nozzle

Yu, Byeong-Hun; Fu, Pengfei; Zhang, T.; Zhou, H-C.

doi:10.1016/j.ijheatfluidflow.2013.08.005

Cited by 33 publications

(22 citation statements)

References 16 publications

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“…When the Reynolds number is not less than 5000, the calculation equation proposed by Hall GW is adopted [17]:…”

Section: Discharge Coefficient Theoretical Calculationmentioning

confidence: 99%

Discharge coefficient calculation method of landing gear shock absorber and its influence on drop dynamics

Ding¹,

Wei²,

Nie³

et al. 2018

J. vibroeng.

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Oleo-damping performance is a key factor affecting the landing gear buffer performance, while the flow discharge coefficient determines buffer damping force. For improving the calculation precision of discharge coefficient estimation method in aircraft design manual, a model for discharge coefficient is established based on pipeline fluid mechanics and damping orifice structure, and a numerical calculation is performed. Computational fluid dynamics (CFD) analysis is also conducted for damping orifice structure using the commercial software FLUNET. The simulation result of damping orifice discharge coefficient correlates well with the theoretical result. On this basis, landing gear drop dynamic response are calculated with the numerical analysis method using obtained discharge coefficient and compared with experimental results. Furthermore, the influences of current discharge coefficient estimation method and simulation method are analyzed and compared on the hydraulic force and the ground reaction force. The study demonstrates that the poor precision of discharge coefficient estimation method in aircraft design manual leads to more than 30 % differences between the drop dynamic estimation results and the experimental results. The method of CFD simulation or theoretical analysis can improve the calculation precision of discharge coefficient by about 17 %.Yong-Ping Li received the B.S. degree in aircraft design from Nanchang Hangkong University, Nanchang, China, in 2015. Now he is studying for a Master degree with aircraft design,

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“…When the Reynolds number is not less than 5000, the calculation equation proposed by Hall GW is adopted [17]:…”

Section: Discharge Coefficient Theoretical Calculationmentioning

confidence: 99%

Discharge coefficient calculation method of landing gear shock absorber and its influence on drop dynamics

Ding¹,

Wei²,

Nie³

et al. 2018

J. vibroeng.

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“…Geometric factor, indicated with nondimensionalized gap length / ld in which l is the gap length and d is the hydraulic diameter of the leakage gap; 2. gas motion parameter, indicated with nondimensionalized velocity ratio ld / uu ; 3. gas state parameters including Reynolds number and Mach number, for the latter using pressure ratio ld / pp instead for convenience. For every major effect on the discharge coefficient, abundant analytical and empirical models have been proposed by researchers [29,31,32]. However, for wave rotor leakage flows, the discharge coefficient is influenced by various effects and the above models failed to be applied directly.…”

Section: Modelling Of the Discharge Coefficient With Empirical Correlmentioning

confidence: 99%

Nonsteady Shock Wave Attenuation Due to Leakage

Liu

2018

Energies

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Leakage flow between the rotor and the stator can cause serious performance degradation of wave rotors which utilize nonsteady shock waves to directly transfer energy from burned gases to precompressed air. To solve this problem, primary flow features relevant to leakage are extracted and it was found that the leakage-attributed performance degradation could be abstracted to a special initial-boundary value problem of one-dimensional Euler equations. Then, a general loss assessment method is proposed to solve the problem of nonsteady flow loss prediction. Using the above method, a reasonable physical hypothesis of the initial-boundary value problem depicting the nonsteady leakage flow process is proposed and further, a closed-form leakage loss analytical model combined with an empirical correction method for the discharge coefficient is established. Finally, with the experimentally verified CFD method, comprehensive numerical verification is conducted for the loss prediction model; it is proved that the physical hypothesis of the proposed model in this paper is reasonable and the model is capable of predicting nonsteady shock wave attenuation due to leakage exactly within the range of parameter variations of wave rotors.

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“…Hydraulic flip takes place at the second inflection point along this curve [71] (symbol contoured with a solid circle for p 2 ≤ 1.1 MPa). As can be inferred, Re cr depends on p 2 , and increases as p 2 grows, because the tendency to cavitation is counteracted by any augmentation in p 2 ; Re cr has also been shown to depend on the type of liquid (water, oil, etc.)…”

Section: (B) Liquid Flow and Dependence Of C D On Rementioning

confidence: 99%

“…As already mentioned, a choked flow rate can be observed in figure 5, when p 1/2 = (p 1 − p 2 ) 1/2 increases beyond a certain threshold. Although the order of magnitude of this threshold can vary to a great extent for different cases [24,62], the quantity value (CN cr ) 1/2 is usually in the 1.1-1.7 range for different fluids and nozzle geometries [71,120]. that connects two water reservoirs: CN cr = 1.30 and the plotted data correspond to a flow choking condition (CN ≈ 1.29).…”

Section: Physics Of Cavitation and Comparison With Supersonic Flowsmentioning

confidence: 99%

Fluid dynamics of acoustic and hydrodynamic cavitation in hydraulic power systems

Ferrari¹

2017

Proc. R. Soc. A.

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Cavitation is the transition from a liquid to a vapour phase, due to a drop in pressure to the level of the vapour tension of the fluid. Two kinds of cavitation have been reviewed here: acoustic cavitation and hydrodynamic cavitation. As acoustic cavitation in engineering systems is related to the propagation of waves through a region subjected to liquid vaporization, the available expressions of the sound speed are discussed. One of the main effects of hydrodynamic cavitation in the nozzles and orifices of hydraulic power systems is a reduction in flow permeability. Different discharge coefficient formulae are analysed in this paper: the Reynolds number and the cavitation number result to be the key fluid dynamical parameters for liquid and cavitating flows, respectively. The latest advances in the characterization of different cavitation regimes in a nozzle, as the cavitation number reduces, are presented. The physical cause of choked flows is explained, and an analogy between cavitation and supersonic aerodynamic flows is proposed. The main approaches to cavitation modelling in hydraulic power systems are also reviewed: these are divided into homogeneous-mixture and twophase models. The homogeneous-mixture models are further subdivided into barotropic and baroclinic models. The advantages and disadvantages of an implementation of the complete Rayleigh-Plesset equation are examined.

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The influence of back pressure on the flow discharge coefficients of plain orifice nozzle

Cited by 33 publications

References 16 publications

Discharge coefficient calculation method of landing gear shock absorber and its influence on drop dynamics

Discharge coefficient calculation method of landing gear shock absorber and its influence on drop dynamics

Nonsteady Shock Wave Attenuation Due to Leakage

Fluid dynamics of acoustic and hydrodynamic cavitation in hydraulic power systems

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