Maximum Penetration Length Research Articles

CFD ANALYSIS OF SECTOR COMBUSTION SIMULATION IN FOUR STROKE DIRECT INJECTION DIESEL ENGINE

In this article an attempt has been made in cylinder sector combustion CFD simulation of four stroke petrol engines using ANSYS fluent 2019 to obtain very useful results using a modelled engine. In order to improve engine quality, understanding on sector combustion properties in engine cylinder is of major importance because combustion condition significantly influences engine efficiency, Capabilities in providing optimum combustion conditions which include high optimum swirl ratio, and optimum tumble ratio in respective engine can result in enhancement of engine power and comfort, along with reduction of fuel consumption, exhaust emission and noise. The simulation is applied for a geometry with crank radius (55mm), connecting rod length (165mm), Engine speed (1800rpm), which is developed to study the effect combustion inside the cylinder. Piston starts from bottom dead center about 541degrees and the maximum pressure reaches at 716 degrees. The pressure increases from 542 crank angle degree to 716 crank angle degree and reaches its maximum value at 716 crank angle degrees. The Maximum pressure at the end of compression is 63.69Kpa and temperature is 1200K. The maximum penetration length of injection is occurred at crank angle 722 degree is 0.014mm.

Comparison of apical sealing ability between bioceramic and zinc oxide eugenol-based sealer during root canal treatment, in vitro

Obturation with a sealer material that provides an adequate apical sealing ability is required to prevent endodontic treatment failure due to microleakage. However, there are no sealers that meet all the physical and chemical properties to be able to hermetically seal the root canal system to date. Various sealer materials have been developed in recent years including the use of bioceramic materials which are claimed to have excellent biocompatibility to tissues. This study aimed to compare the apical sealing ability of bioceramic-based and zinc oxide eugenol (ZOE)-based sealer in root canal treatment. A total of 27 extracted mandibular premolars were decoronated to the standard root length of 14 mm. The root canals were prepared with a crown-down technique using manual instrument to file F3 (30/.09). The samples were then divided into three groups: obturation with bioceramic-based sealer (n=9); ZOE-based sealer (n=9); and control group (n=9). Microleakage was measured using a dye penetration method with 1% methylene blue and observed under stereomicroscope at x20 magnification. The mean of the maximum penetration length from the lowest to the highest was found in the bioceramic-based sealer group (0.825 mm), the ZOE-based sealer group (3.850 mm), and the control group (4.444 mm). One-way ANOVA test showed a significant difference in the maximum penetration length between the three groups (p<0.05). The post hoc LSD test showed a significant difference in the maximum penetration length between the bioceramic-based and ZOE-based sealer groups (p<0.001). Obturation with bioceramic-based sealer provides a better apical sealing ability than that with ZOE-based sealer.

Radial penetration of cementitious grout – Laboratory verification of grout spread in a fracture model

During the past two decades of research and development in the field of grouting in hard jointed rock, the design process has taken a number of significant leaps forward. A grouting design in hard rock can now be based on the penetration length of grout in individual rock fractures. For cementitious grouts, the most common rheological model used is the one for a Bingham fluid. The model is a conceptualisation of grout spread where two rheological properties of the grout – viscosity and yield stress – govern the penetration length along with the fracture aperture and applied grouting overpressure.This paper focuses on verification of radial Bingham flow of cementitious grout using a fracture model constructed from acrylic glass. Each test conducted using the fracture model was filmed, allowing the grout spread to be analysed as penetration length over time. The measured penetration lengths were then compared with analytical solutions derived for Bingham grout in a plane parallel fracture.The results indicate that the penetration of cementitious grout in fracture apertures of 125 μm and 200 μm is verified for up to 40% of the maximum possible penetration length. This can be compared to normal grouting, where the penetration lengths achieved are around 20% of the maximum penetration length.

Interaction of vortex ring with a stratified finite thickness interface

This work experimentally investigates the dynamics of interaction between a propagating vortex ring and density stratified interface of finite thickness. The flow evolution has been quantified using a high speed shadowgraph technique and particle image velocimetry. The spatial and temporal behaviours of the vortex in the near and far field of the interface and the plume structure formed due to buoyancy are investigated systematically by varying the vortex strength (Reynolds number, Re) and the degree of stratification (Atwood number, At). Maximum penetration length (Lpmax) of the vortex ring through the interface is measured over a range of Reynolds (1350 ≤ Re ≤ 4600) and Richardson (0.1 ≤ Ri ≤ 4) numbers. It is found that for low Froude number values, the maximum penetration length varies linearly with the Froude number as in the study of Orlandi et al. [“Vortex rings descending in a stratified fluid,” Phys. Fluids 10, 2819–2827 (1998)]. However, for high Reynolds and Richardson numbers (Ri), anomalous behaviour in maximum penetration is observed. The Lpmax value is used to characterize the vortex-interface interactions into non-penetrative, partially-penetrative, and extensively penetrative regimes. Flow visualization revealed the occurrence of short-wavelength instability of a plume structure, particularly in a partially penetrative regime. Fluid motion exhibits chaotic behaviour in an extensively penetrative regime. Detailed analyses of plume structure propagation are performed by measuring the plume length and plume rise. Appropriate scaling for the plume length and plume rise is derived, which allows universal collapse of the data for different flow conditions. Some information concerning the instability of the plume structure and decay of the vortex ring is obtained using proper orthogonal decomposition.

Assessment of Relationship Between Grouted Values and Calculated Values in the Bazoft Dam Site

Seepage through foundation and abutments of a dam can potentially result in a waste of the water stored in dam reservoir, erosion of foundation materials, and development of uplift pressure in dam foundation which, consequently, threatens the long-term stability of the dam. In this study, the grout volume is estimated based on parameters such as joint aperture, the maximum penetration length of the grout, and calculated grout take in Bazoft dam site. Bazoft Dam is a hydroelectric supply and double-curvature arch dam with a height of 211 m located in Chaharmahal and Bakhtiari Province of Iran. The bedrock of Bazoft dam site consists of Asemari Formation (limy marl and marly lime), in the middle and upper parts of left abutment, and Jahrom Formation (limestone and dolomite) in the right abutment, river bed, and lower part of left abutment. The joint apertures were calculated based on the permeability and the joint spacing. Next, the maximum penetration length of the grout and grout volume were calculated. Using a statistical analysis, the relationship of the joint aperture, maximum penetration length, and the calculated grout volume with real grout take was also investigated. The results show that the grout take can be predicted with appropriate accuracy based on the calculated grout volume.

Inclined Injection of Supersonic Steam into Subcooled Water: A CFD Analysis

The phenomenon of direct-contact condensation gains attention because of various industrial applications; nuclear reactor emergency core cooling systems,steam driven jet injectors, direct-contact heat exchangers etc..The phenomenon was investigated computationally by injecting an inclined steam jet using a supersonic nozzle submerged in subcooled water. The condensation mechanism is based on two resistance model, which involves consideration of the heat transfer process on both sides of the interface along with use of a variable steam bubble diameter. For computations, ANSYS Fluent based Euler-Euler multiphase model is used. The angle of inclination varies from 5o to 45o at constant inlet pressure of 7 bars with water temperature of 30°C. The maximum penetration length is achieved using a right angled vertical injection.

커먼레일 연료시스템에서의 DME 분무 특성에 대한 실험과 해석적 연구

Abstract : Spray visualization and computer simulation of a DME injector have been conducted to investigate the enlarged injection hole diameter effect. To increase reliability of the computational result, simulation results have been compared with the visualization results, and the behavior of DME spray under transient engine condition has been predicted. It is 3.57% discrepancy that exists between experimental and computational penetration length on conditions of injection pressure 35MPa and ambient pressure 5MPa. In the case of engine simulation condition, maximum penetration length of fully developed DME spray is 42mm on condition that temperature to pressure ratio is 300K/MPa. DME spray behavior is dominantly affected by the ambient pressure under the condition that the ratio is less than 300K/MPa, and by the ambient temperature under the condition that the ratio is more than 300K/MPa. Corresponding Author, sjjeong@katech.re.krⒸ 0000 The Korean Society of Mechanical Engineers - 기호설명 -We : 웨버수[-]c : stripping 분열 계수Re : 레이놀즈수[-]

Holographic jets in an expanding plasma

We use the holographic principle to study quark jets using trailing strings in an expanding plasma with asymptotic Bjorken hydrodynamics. We make use of the fact that the trailing string is the locus of the light delay in bulk to obtain the explicit form for quark jets in the expanding plasma. From the trailing string solution we calculate the drag coefficient of a heavy quark in the strongly coupled expanding plasma. The energy scaling of the maximum penetration length of an ultrarelativistic light quark jet using light rays in bulk is estimated.

Horizontal gas and gas/solid jet penetration in a gas–solid fluidized bed

In this paper, the real time, dynamic phenomena of the three-dimensional horizontal gas and gas/solid mixture jetting in a 0.3 m (12 in) bubbling gas–solid fluidized bed are reported. The instantaneous properties of the shape of the jets and volumetric solids holdup are qualified and quantified using the three-dimensional electrical capacitance volume tomography (ECVT) recently developed in the authors’ group. It is found that the horizontal gas jet is almost symmetric along the horizontal axis during its penetration. As the jet width expands, the total volume of the gas jet increases. A mechanistic model is also developed to account for the experimental results obtained in this study. Comparison of jet penetration length and width between the model prediction and ECVT experiment shows that both the maximum penetration length and the maximum width of the horizontal gas jet increase with the superficial gas velocity. When the horizontal gas jet coalesces with a bubble rising from the bottom distributor, it loses its symmetric shape and can easily penetrate into the bed. For the horizontal gas/solid mixture jet penetration in the bed, the tail of the jet at the nozzle shrinks and the jet loses its jet shape immediately when the jet reaches its maximum penetration length, which are different from the characteristics exhibited by the gas jet. The solids holdup in the core region of the gas/solid mixture jet is higher than that in the gas jet. The penetration length of the horizontal gas/solid mixture jet is also larger than that of the gas jet.

REAL GAS EFFECTS IN MIXING-LIMITED DIESEL SPRAY VAPORIZATION MODELS

The maximum penetration length of the liquid phase in diesel sprays is of paramount importance in reducing diesel engine emissions. Quasi-steady liquid length values have been successfully correlated in the literature, assuming that mixing of fuel and air is the limiting step in the evaporation process. Since fuel injection in engines takes place at high pressure, non-ideal gas effects may significantly affect the phase equilibrium. In this work, real gas effects are implemented into the mixing-limitedspray vaporization models of Siebers and of Versaevel et al., taking into account enhancement of the fuel saturated vapor pressure by the high pressure ambientgas. Results show that this effect is significant at ambient densities relevant for diesel combustion. The effect of gas pressure on mixture enthalpy (and therebyon liquid length) is also considered, but found to be negligible for relevant diesel conditions. Since both models discussed are based on almost the same premises,but give different results, their intrinsic differences are evaluated by deriving a new closed-form expression for the Versaevel model. It is shown that the models can be equalized by adding a correction factor to the Siebers model, making it physically more consistent. However, for the (limited) data set considered in this paper, this does not improve its predictive capability. It is argued that the remaining error in model predictions is most probably due to the cross-sectional averaging approach.

Study on Thermal Stratification by Cavity Flow in a Branch Pipe with a Closed End (Concept of L1 Evaluation Method).

In a branch pipe with a closed end, the cavity flow penetrates into the branch pipe from the main loop and the thermal boundary layer occurs because the cavity flow is a hot fluid, but the heat removal causes the colder fluid in the branch pipe. It is possible for the thermal stratification to affect the structural integrity. Therefore, it is necessary to establish the pipe design standard to suppress thermal fatigue. The pipe design standard consists of the maximum penetration length (L1) and the minimum penetration length (L2). First of all, in order to establish the evaluation method for Li, the visualization tests and the high temperature and pressure test were carried out. The method reproduces the penetration length by cavity flow in several types of the vertical branch pipes within 10% accuracy.

F215 滞留部の熱成層化による高サイクル熱疲労に関する研究 : L_1 評価手法の概要

There are a lot of types of branch pipes with a closed end in a nuclear power plant. At a branch pipe connected to a main such as a main coolant pipe, there is temperature gradient in the layer between the cavity flow and the colder fluid by heat removal. It is necessary to evaluate the structural integrity of a pipe in the front of the cavity flow and to establish the piping design standard. In the piping design standard, there are the maximum penetration length (L_1) and the minimum one (L_2) in order to avoid the elbow between L_2 and L_1. The L_1 evaluation method is shown in the present report. The method is based on the momentum balance model by defining the boundary layer coefficient. The method reproduced the penetration length by cavity flow in several types of the vertical pipes within 10% accuracy. The piping design standard is going to be established by using the method.

Optimization of Overfire Air Systems of Cylindrical Combustion Chambers

ABSTRACT The optimization of overfire air injection in cylindrical combustion systems with respect to the combustion performance is studied. Relevant integral performance parameters regarding residence time and overall mixing are discussed. Finally, different design concepts are screened and the influence of some geometrical parameters is investigated. The results are translated in terms of a maximum penetration length. The findings show good agreement with experiments carried out before. Key words: Air system design; computational fluid dynamics; mixing; residence time distribution; jets in crossflow

The effect of tube length on wave phenomena in an H-S tube.

The unsteady, one-dimensional flow in an H-S tube was calculated using the Random-Choice Method, in which the wall friction and the heat transfer wre taken into account. In particular, the effect of the length of the tube was examined, and the following conclusions were drawn: 1. The amplitude of the pressure oscillation decreases with an increase in the tube length. 2. for a tube of L=10m, the initial penetration length of the contact surface is 60% of the tube length measured from the open end, and after the interference of the contact surface with the shock wave, it becomes stationary without flow oscillation. 3. The maximum penetration length of the contact surface for a tube of L=1m is 37% of the tube length.