Modelling thermal effects in cavitating high-pressure diesel sprays using an improved compressible multiphase approach

“…It is reported that elliptical orifice with a horizontally oriented axis generates more cavitated flow with a higher discharge coefficient. Yu et al [13] considered the involvement of thermal effects on cavitation of diesel spray, so a multiphase energy equation is used that takes into account the enthalpy of phase change. The results revealed that vapor production depends on the start of hydraulic flip restricting the inbound ambient air.…”

Section: Introductionmentioning

confidence: 99%

Numerical characterization of transient two-phase flow of nozzle under the impact of diesel fuel temperature and injector backpressure

Taghavifar

2020

J Braz. Soc. Mech. Sci. Eng.

View full text Add to dashboard Cite

The inner fluid flow within the micro-sac injector is investigated numerically via AVL-Fire CFD code particularly in a microscale dimension of nozzle hole is carried out in the present work. The structural parameters of the injector are left unchanged, while the physical properties of the fluid such as pressure gradient and fluid temperature are taken into account to survey their influence on vapor volume fraction evolution, vapor mass flow rate, cavitation inception, and discharge coefficient. The reliability of modeling results is confirmed by comparing obtained data with experimental one and numerical results of Payri et al. and a close match served as an indication for the accuracy of the methodology. The multiphase modality is activated for the two-fluid model application in the nozzle segment, while the interfacial source term accounts for the momentum exchange of phases in the cavitation drag model. According to results, increasing the fuel temperature is a factor for increasing turbulent kinetic energy; meanwhile, vapor volume fraction at different times shows a different trend. Concerning the discharge coefficient, it seems that increasing the fluid temperature reduces this parameter. In contrast, increasing the pressure gradient leads to a considerable increase in the discharge coefficient.

show abstract

“…14 They are difficult to understand and control because the nozzles are extremely small, the flows move at a high speed with the Reynolds number on the order of 50,000, and transient with injection duration on the order of milliseconds. Various types of geometric cavitation in diesel injectors have been studied experimentally 15–17 and theoretically 18–20 in recent decades, which indicates that cavitating flows inside diesel nozzles were influenced by many factors, such as the nozzle geometry, 21–23 fuel thermodynamic properties, 24–26 injection or backpressure conditions 27–29 and needle motion. 5,30,31 However, few studies have been done on string cavitation.…”

Section: Introductionmentioning

confidence: 99%

Visual experimental investigations of string cavitation and residual bubbles in the diesel nozzle and effects on initial spray structures

Guo

Zhang

et al. 2018

International Journal of Engine Research

View full text Add to dashboard Cite

In this article, optical experiments on string cavitation and residual bubbles inside the real-size transparent tapered diesel nozzle and near-nozzle spray structures were performed based on a high-pressure common rail fuel injection system with a high-speed camera. The tapered nozzle which has high flow efficiency with weak or even no geometric cavitation has been widely used in commercial injectors, while there still exists string cavitation which may also influence the in-nozzle flow and subsequent spray. This article put focus on the tapered nozzle and the result indicated that the in-nozzle string cavitation provided a reasonable explanation for the two bumps of spray cone angles during the opening and closing stages of needle of real diesel engine injection processes. The suction and compression of air bubbles at the start and end stages of injection processes, and the various shot-to-shot near-nozzle spray patterns were captured and analyzed. These different near-nozzle spray patterns were attributed to the distribution of residual bubbles inside the nozzle orifice. The residual bubbles were survived from the last injection or sucked into the nozzle during needle opening stages. Stagnant bubbles were compressed and then accelerated the residual fuel which was close to the injector tip, leading to the formation of mushrooms. This study confirmed that the initial mushroom and the tail were generated by the interactions between the residual/sucked bubbles and the residual/initial fuel, and the leading mushroom was incurred by the combination of the transverse expansion of the jet and the laminar layer theory. This work pointed out and analyzed the new sources of the cycle-to-cycle variation of air/fuel mixture and spray.

show abstract

Modelling thermal effects in cavitating high-pressure diesel sprays using an improved compressible multiphase approach

Cited by 26 publications

References 39 publications

On the thermodynamic behaviors and interactions between bubble pairs: A numerical approach

On the thermodynamic behaviors and interactions between bubble pairs: A numerical approach

Numerical characterization of transient two-phase flow of nozzle under the impact of diesel fuel temperature and injector backpressure

Visual experimental investigations of string cavitation and residual bubbles in the diesel nozzle and effects on initial spray structures

Contact Info

Product

Resources

About