Experimental study on the effect of vortex cavitation in scaled-up diesel injector nozzles and spray characteristics

Cao, Tianyi; He, Zhixia; Zhou, Han; Guan, Wei; Zhang, Liang; Wang, Qian

doi:10.1016/j.expthermflusci.2019.110016

Cited by 32 publications

(18 citation statements)

References 42 publications

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“…24 Karathanassis et al 31 characterized the periodic breakup and lifetime of string cavitation behavior in a replica of an enlarged diesel injector nozzle through X-ray Phase Contrast Imaging (XPCI). An interesting insight was brought up that the conclusions of string cavitation dynamics captured in large-scale transparent nozzles were reported to be closely linked to those in real metal nozzles from the research of Moon et al 32 In the work of Cao et al, 33 a plate with a slit was used to intercept the plane of a three-dimensional conical spray injected from the enlarged optical nozzle hole, and the experiment image validated the presence of the hollow-cone spray structure under the influence of intense string cavitation.…”

Section: Introductionmentioning

confidence: 96%

Optical investigations of nozzle geometrical and dynamic factors on formation and development characteristics of string cavitation with large-scale diesel tapered-hole nozzles

Guan

Duan

et al. 2020

International Journal of Engine Research

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Cavitation is known to be an essential physical phenomenon to induce the fuel primary breakup process, which further influences subsequent secondary atomization and combustion in diesel engines. Different from normal geometry-induced cavitation, the special vortex-induced cavitation, which may influence strongly spray characteristics, is seldom investigated comparatively. In this paper, formations and developments of string cavitation are captured in scaled-up transparent replicas of diesel tapered-hole nozzles by high-speed imaging technology. The ensemble average images were post-processed by MATLAB code for characterizing the string cavitation at fixed needle lifts. The results indicate that string cavitation tends to occur initially in the middle of the nozzle holes. Besides, shedding bubbles from geometry-induced cavitation may stimulate the string cavitation inception as an inducing factor. The morphology and duration of both two types of string cavitation are largely influenced by needle lifts and cavitation number. Moreover, it is concluded that string cavitation hardly occurs in nozzles with low hole entrance location, and the hole entrance rounding structure changes the distribution characteristics of string cavitation. Finally, it is ascertained that the variation of magnification ratio changes little or nothing about development and distribution characteristics of string cavitation.

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Section: Introductionmentioning

confidence: 96%

Optical investigations of nozzle geometrical and dynamic factors on formation and development characteristics of string cavitation with large-scale diesel tapered-hole nozzles

Guan

Duan

et al. 2020

International Journal of Engine Research

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“…The results revealed that the evolution of cavitation had a significant effect on the liquid film thickness and the velocity at the nozzle outlet, which in turn caused significant changes in the spray angle and the droplet mean diameter. Cao et al 12 conducted an experimental study on the optical visualization of a nozzle and found that the vortex and cavitation were important factors influencing pressure fluctuations in the injection system. Lešnik et al 13 used a combination of numerical simulations and experiments to investigate the influence of the flow field, cavitation, and fuel characteristics inside a nozzle on the spray development and initial combustion processes.…”

Section: Introductionmentioning

confidence: 99%

Study of the influence laws of the flow and cavitation characteristics in an injector control valve

Ren

Tie-xiong

et al. 2022

Energy Science & Engineering

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Fuel cavitation can cause damage to the structure of an injector control valve, which can further affect the service life of the injector. Therefore, it is of great importance to carry out research on the mechanism of cavitation in injector control valves. In this study, the dynamic evolution of the cavitation and fuel flow characteristics during the opening of a ball valve in a high‐pressure common rail injector control valve were studied. First, a transient CFD simulation of the cavitation during the opening of the control valve was performed using dynamic mesh technology to analyze the evolution and formation mechanism of the cavitation. The cavitation was influenced by the fuel flow velocity, which was affected by the sealing cone angle and the ball valve movement. Additionally, the fuel reflux could effectively inhibit the development of cavitation. By comparing with the pressure, velocity, and mass flow rate of the fuel under conditions without cavitation, it was found that the cavitation had a remarkable effect on reducing the hydraulic shock to the ball valve and sealing cone as well as stabilizing the fluctuation of the fuel velocity in the control chamber. In addition, the cavitation noticeably decreased the fuel mass flow rate (by up to 32% at 0.015 ms) and increased the average pressure in the chamber (by up to 29.1% at 0.01 ms), ultimately leading to a slower response of the control valve. The analysis of different inlet pressures of the control valve indicated that the increase in the inlet pressure caused the cavitation to extend upward along the sealing cone, and that the cavitation ring area and the cavitation strength increased.

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“…1,8 The possible locations of this type of cavitation are in the sac and the nozzle region. 1,9 The cavitation in the sac region is termed as needle-originated cavitation 10 while needle-string cavitation 2 occurs at high injection pressures. The vortex-based cavitation forming in the nozzle region is referred to as hole-to-hole cavitation that influences the injection mass flow rates at low injection pressures and leads to smaller spray cone angles while the needle-originated cavitation occurs at high-pressure injection resulting in wider cone angles.…”

Section: Introductionmentioning

confidence: 99%

Three-component multi-fluid modeling of pseudo-cavitation phenomenon in diesel injector nozzles

Mishra

Jiwani

Jarrahbashi

2021

International Journal of Engine Research

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Cavitation in fuel injectors occurs in the nozzle region where local pressure drops below the fuel saturation pressure. The pressure drop might simultaneously induce the formation of gas bubbles such as nitrogen dissolved in the fuel, also known as pseudo-cavitation. A new cavitation model has been developed that accounts for the nitrogen bubbles separation from the fuel stream by accounting for the solubility changes of nitrogen with the pressure drop. A multi-fluid model integrated with the volume-of-fluid interface tracking approach has been developed to capture the interface between the liquid fuel, fuel vapor and the de-gassed nitrogen. Differentiating between cavitation and pseudo-cavitation is a very challenging task experimentally. The new model allows distinguishing between the volume fraction occupied by fuel vapor and de-gassed nitrogen. Comparing the predicted void fraction along the nozzle with available experimental data demonstrates that this model significantly improves the predictions of size/location of the cavitation compared with single-fluid mixture models and the existing multi-fluid simulation results. For the standard fuel case, the bulk of bubble formation is correlated with the de-gassing and these bubbles are observed along the nozzle with higher concentration downstream of the flow. However, for the de-gassed fuel case, vapor cavitation bubbles are focused near the walls with higher concentrations near the entrance. The transient behavior of void formation shows that the local pressure at the nozzle entrance near the walls drops to below the saturation pressure initially and forms the vapor bubbles. As the pressure stabilizes at a pressure higher than the saturation pressure, the de-gassing phenomenon takes over vapor cavitation, leading to void formation throughout the nozzle attributed to the non-condensable gases. The sensitivity of the void fraction predictions to model parameters indicates that controlling the ratio of evaporation to condensation rate is essential for accurate prediction of steady state void fraction.

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Experimental study on the effect of vortex cavitation in scaled-up diesel injector nozzles and spray characteristics

Cited by 32 publications

References 42 publications

Optical investigations of nozzle geometrical and dynamic factors on formation and development characteristics of string cavitation with large-scale diesel tapered-hole nozzles

Optical investigations of nozzle geometrical and dynamic factors on formation and development characteristics of string cavitation with large-scale diesel tapered-hole nozzles

Study of the influence laws of the flow and cavitation characteristics in an injector control valve

Three-component multi-fluid modeling of pseudo-cavitation phenomenon in diesel injector nozzles

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