Experimental and numerical analysis on the surge instability characteristics of the vortex flow produced large vapor cavity in u-shape notch spool valve

Lu, Lerong; Xie, Shuaihu; Yin, Yajun; Ryu, Shohei

doi:10.1016/j.ijheatmasstransfer.2019.118882

Cited by 30 publications

(10 citation statements)

References 38 publications

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“…en, the fixed cavitation bubbles break into smaller travelling cavitation bubble and flowing downstream as shown in Figure 4(b). at is to say, the re-entrant jet is the main reason for cavitation breakup [22]. From the moment t 0 + 0.15 ms t 0 + 0.30 ms, the recirculation flow becomes long and narrow; the break-off phenomenon is more evident.…”

Section: Resultsmentioning

confidence: 95%

Study on Unsteady Cavitation Flow and Pressure Pulsation Characteristics in the Regulating Valve

Liu

et al. 2021

Shock and Vibration

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A combined numerical-experiment investigation on the unsteady cavitation flow and pressure fluctuation characteristics in the regulating valves is conducted in this paper. The cavitation flow in the regulating valve is an unsteady and periodic flow which could be divided into fixed and travelling cavitation bubbles. The fixed cavitation bubbles are formed in the gap in the initial stage and then fell off and formed the travelling cavitation bubbles because of the re-entrant jet. The travelling cavitation bubbles move downstream, oscillate, and break up into several smaller bubbles. Changes in the length/radius ratio (L/R0) of the valve spool is an important factor affecting unsteady cavitation flow and pressure pulsation characteristics in the regulating valve. The length of travelling cavitation bubbles increases firstly and then decreases with increasing time. With the increase of the length/radius ratio (L/R0), the oscillation period of cavitation bubbles also increases. In the initial stage of cavitation bubbles, the velocity distribution inside the regulating valve is relatively stable, and no re-entrant jet could be found although L/R0 is different. In the collapse stage of cavitation bubbles, the velocity distribution becomes extremely unstable because the collapsing cavitation bubbles affect the pressure drop and velocity field in the flow channel. Furthermore, the amplitude of pressure pulsation increases gradually, and the peak time of the pressure pulsation is gradually delayed while increasing the length/diameter ratio.

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Section: Resultsmentioning

confidence: 95%

Study on Unsteady Cavitation Flow and Pressure Pulsation Characteristics in the Regulating Valve

Liu

et al. 2021

Shock and Vibration

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“…However, the flow status through each orifice must be known in order to determine the subsonic flow equation or the supersonic flow equation in Equation (3) [20]. The finite element method by ANSYS is the most effective tool to do numerical analysis on flow and pressure characteristics of microchannels [21,22]. In this work, ANSYS is also applied to simulate the pressure distribution of the single XMFCD.…”

Section: Modelling and Simulationsmentioning

confidence: 99%

Design, Simulation, and Experiment of an LTCC-Based Xenon Micro Flow Control Device for an Electric Propulsion System

Guan¹,

Shen²,

Yao³

et al. 2019

Processes

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A xenon micro flow control device (XMFCD) is the key component of a xenon feeding system, which controls the required micro flow xenon (µg/s–mg/s) to electric thrusters. Traditional XMFCDs usually have large volume and weight in order to achieve ultra-high fluid resistance and have a long producing cycle and high processing cost. This paper proposes a miniaturized, easy-processing, and inexpensive XMFCD, which is fabricated by low-temperature co-fired ceramic (LTCC) technology. The design of the proposed XMFCD based on complex three-dimensional (3D) microfluidic channels is described, and its fabrication process based on LTCC is illustrated. The microfluidic channels of the fabricated single (9 mm diameter and 1.4 mm thickness) and dual (9 mm diameter and 2.4 mm thickness) XMFCDs were both checked by X-ray, which proved the LTCC method’s feasibility. A mathematical model of flow characteristics is established with the help of finite element analysis, and the model is validated by the experimental results of the single and dual XMFCDs. Based on the mathematical model, the influence of the structure parameters (diameter of orifice and width of the groove) on flow characteristics is investigated, which can guide the optimized design of the proposed XMFCD.

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“…Cavitation is the process of the formation, development and collapse of vapor or gas cavities in the liquid or at the liquid-solid interface when the local pressure in the liquid decreases [34,35]. In early studies, researchers aimed at developing a physical model, supported by experimental observations, described the formation and growth of microbubbles seen in patients with mitral mechanical heart valve [36].…”

Section: Introductionmentioning

confidence: 99%

Transient Study of Flow and Cavitation Inside a Bileaflet Mechanical Heart Valve

Gao

Jin

et al. 2020

Applied Sciences

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A mechanical heart valve (MHV) is an effective device to cure heart disease, which has the advantage of long life and high reliability. Due to the hemodynamic characteristics of blood, mechanical heart valves can lead to potential complications such as hemolysis, which have damage to the blood elements and thrombosis. In this paper, flowing features of the blood in the valve are analyzed and the cavitation mechanism in bileaflet mechanical heart valve (BMHV) is studied. Results show that the water hammer effect and the high-speed leakage flow effect are the primary causes of the cavitation in the valve. Compared with the high-speed leakage flow effect, the water hammer has a greater effect on the cavitation strength. The valve goes through four kinds of working condition within one heart beating period, including, fully opening stage, closing stage and fully closing stage. These four stages, respectively, make up 8.5%, 16.1%, 4.7% and 70.7% of the total period. The cavitation occurs on the fully closing stage. When the valve is in closing stage, the high pressure downstream of the valve lasts for about 20 ms and the high-speed leakage flow lasts for about 200 ms. This study systematically analyzes the causes of cavitation emerged in the process of periodic motion, which proposes the method for characterizing the intensity of the cavitation, and can be referred to for the cavitation suppression of the BHMV and similar valves.The main concerns of valve research have been the performance [3] and the internal flow properties [4]. In order to study the hydrodynamic characteristics of the mechanical heart valve, numerical simulation based on CFD is one powerful tool to study cardiovascular risk factors, especially those related to mechanical properties of artificial heart valve [5]. It is an effective way to improve the performance of the valve by structure optimization, which is applicable to many valves +(e.g., Tesla valve) [6,7], and the BMHV is no exception. Many works on the effect of geometric features of the BMHV on blood stream are performed by simulations in the past years. For example, it has been found that the maximum shear stress within the range of platelet activation can lead to thrombosis [8,9]. The strategy of self-adapting mesh is used to capture the motion of the leaflet realizing by user-defined functions (UDF) in the commercial software [10]. It is found that the valve leaflet and the valve pivot are continuously exposed to shear stress higher than 52.3 Pa, which can cause damage to the platelets. The problem of thrombosis can be solved by increasing the curvature of the leaflet of the bileaflet mechanical heart valve [11]. Results show that increasing the curvature of the leaflet can provide larger central circulation area and reduce the risk of thrombosis. Another way [12] is proposed by using BMHV with SH coating to reduce the interaction between blood and BMHV. Based on effect analysis of BMHV with SH coating on blood substances and hemodynamics, the performance index of BMHV with SH coating, w...

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Experimental and numerical analysis on the surge instability characteristics of the vortex flow produced large vapor cavity in u-shape notch spool valve

Cited by 30 publications

References 38 publications

Study on Unsteady Cavitation Flow and Pressure Pulsation Characteristics in the Regulating Valve

Study on Unsteady Cavitation Flow and Pressure Pulsation Characteristics in the Regulating Valve

Design, Simulation, and Experiment of an LTCC-Based Xenon Micro Flow Control Device for an Electric Propulsion System

Transient Study of Flow and Cavitation Inside a Bileaflet Mechanical Heart Valve

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