Liquid Penetration Length Research Articles

Analysis of Micro-Explosion Phenomenon in a Constant Volume Chamber by Butanol-Biodiesel-Diesel Blend Fuel

Different blend ratio of ternary component fuel was tested inside a constant volume chamber to investigate fuel injection and combustion under similar real engine working conditions. Because liquid spray light scattering is the different reflective rate from the liquid droplets and its surrounding background, butanol-biodiesel-diesel liquid jet penetration length can be highlighted in the images taken by high speed camera. Various ambient temperatures from 800K to 1200K and fuel composition were investigated. Measured results showed that sudden but repeatable drop of liquid jet penetration length at constant ambient temperature conditions of 800K and 900K. With ambient temperature increasing, this phenomenon became weak and disappeared. So more works focus on non-combusting experiments in order to delete combustion reflect. With butanol and biodiesel content increasing, micro explosion becomes prone excited and more violent because of the enlarged differences in volatilities and boiling point among the components. It is concluded that micro explosion which will distinctly enhances premixed combustion process and heat release rate but it present under certain initial ambient temperature conditions only and the light fuel content shouldn’t be lower than 10%.

DEVELOPMENT AND APPLICATION OF IMAGING SYSTEM TO EVALUATE LIQUID AND VAPOR ENVELOPES OF MULTI-HOLE GASOLINE FUEL INJECTOR SPRAYS UNDER ENGINE-LIKE CONDITIONS

A novel high-speed imaging system capable of acquiring schlieren and elastic scattering images in a near-simultaneous fashion along the same line of sight has been developed. Liquid and vapor envelopes of sprays from a multi-hole gasoline fuel injector operating under engine-like conditions were systematically investigated. For the conditions evaluated, the maximum liquid penetration length was found to be inversely proportional to injection pressure. Penetration lengths derived from the elastic scattering envelops and schlieren envelopes were found to be quite similar up until the occurrence of the peak liquid penetration, implying that little vapor exists ahead of the penetrating liquid.

Modeling and simulation of severe slugging with mass transfer effects

A mathematical model and numerical simulations are presented to investigate the dynamics of gas, oil and water flow in a pipeline-riser system. The pipeline is modeled as a lumped parameter system and considers two switchable states: one in which the gas is able to penetrate into the riser and another in which there is a liquid accumulation front, preventing the gas from penetrating the riser. The riser model considers a distributed parameter system, in which movable nodes are used to evaluate local conditions along the subsystem. Mass transfer effects are modeled by using a black oil approximation. The model predicts the liquid penetration length in the pipeline and the liquid level in the riser, so it is possible to determine which type of severe slugging occurs in the system. The method of characteristics is used to simplify the differentiation of the resulting hyperbolic system of equations. The equations are discretized and integrated using an implicit method with a predictor–corrector scheme for the treatment of the nonlinearities. Simulations corresponding to severe slugging conditions are presented and compared to results obtained with OLGA computer code, showing a very good agreement. A description of the types of severe slugging for the three-phase flow of gas, oil and water in a pipeline-riser system with mass transfer effects are presented, as well as a stability map.

Visual Spray and Evaporization Character of Biodiesel Blend Fuels in a Combustion Chamber

Different from traditional engine test, an optical constant volume chamber simulated HTHP ambient condition was employed by using biodiesel-diesel-butanol blends. With high-speed camera and synchronized copper vapor laser, recorded fuel spray and combustion process, measured liquid jet penetration length and heat release rate under variable ambient temperature and fuel composition conditions. With ambient temperature increasing, burn process converted from premixed combustion to diffusion combustion, and the micro-explosion became weak and disappeared. It was concluded that micro-explosion could occur under particular initial ambient temperature and specific blend ratio conditions for the biodiesel-diesel-butanol fuel, that will distinctly enhance fuel evaporation and premixed combustion process.

Liquid-Phase Penetration under Unsteady In-Cylinder Conditions: Soy- and Cuphea-Derived Biodiesel Fuels Versus Conventional Diesel

Accelerated dilution of engine lubrication oil with unburned fuel is a significant potential issue when utilizing fuels that contain biodiesel. Biodiesel produced from some feedstocks is less volatile than conventional diesel, which makes wall impingement of liquid fuel more likely and reduces the ability of the fuel to evaporate out of engine oil once dilution has occurred. These are growing concerns, particularly with the emergence of strategies that involve injection of fuel into relatively cool, low-density, in-cylinder gases. Examples of these strategies include early direct-injection and late-cycle post-injection, which facilitate partially premixed low-temperature combustion and aftertreatment system regeneration, respectively. A quantitative understanding of liquid-phase penetration for biodiesel fuels is needed to help mitigate these potential issues. This work reports liquid penetration lengths measured in an optical engine under time-varying in-cylinder conditions for soy- and cuphea-derived biodiesel fuels (soy methyl esters = SME and cuphea methyl esters = CuME, respectively) and a commercial ultralow-sulfur diesel (ULSD). Experiments included laser light scattering for measurement of the liquid length and cylinder-pressure data acquisition for heat-release analysis. Data were acquired for multiple injection pressures, intake-manifold pressures, and injection timings for each fuel. SME and CuME both were found to have ∼20−30% longer liquid lengths than ULSD, despite a large concentration of higher-volatility components in CuME. Compared to ULSD and SME, however, CuME liquid lengths were more dependent on injection timing. Results suggest that early direct-injection and late-cycle post-injection strategies may benefit from the use of CuME vs SME.

A unified spray model for engine spray simulation using dynamic mesh refinement

This study is based on dynamic mesh refinement and uses spray breakup models to simulate engine spray dynamics. It is known that the Lagrangian discrete particle technique for spray modeling is sensitive to gird resolution. An adequate spatial resolution in the spray region is necessary to account for the momentum and energy coupling between the gas and liquid phases. This study uses a dynamic mesh refinement algorithm that is adaptive to spray particles to increase the accuracy of spray modeling. On the other hand, the accurate prediction of the spray structure and drop vaporization requires accurate physical models to simulate fuel injection and spray breakup. The present primary jet breakup model predicts the initial breakup of the liquid jet due to the surface instability to generate droplets. A secondary breakup model is then responsible for further breakup of these droplets. The secondary breakup model considers the growth of the unstable waves that are formed on the droplet surface due to the aerodynamic force. The simulation results are compared with experimental data in gasoline spray structure and liquid penetration length. Validations are also performed by comparing the liquid length of a vaporizing diesel spray and its variations with different parameters including the orifice diameter, injection pressure, and ambient gas temperature and density. The model is also applied to simulate a direct-injection gasoline engine with a realistic geometry. The present spray model with dynamic mesh refinement algorithm is shown to predict the spray structure and liquid penetration accurately with reasonable computational cost.

Liquid penetration length of heptamethylnonane and trimethylpentane under unsteady in-cylinder conditions

While strategies employing early or late direct-injection of fuel can improve emissions, they also can lead to impingement of liquid-phase fuel on the piston and/or cylinder wall due to low in-cylinder temperatures and densities during the injection event. Previous work has shown that liquid-phase fuel films formed in this way can lead to pronounced degradations in efficiency and emissions. To avoid these problems, a quantitative understanding of fuel-property effects on the liquid penetration length is needed, and this understanding must include conditions where in-cylinder thermodynamic conditions and the injection rate vary with time. This work reports liquid penetration lengths measured in an optical engine under such time-varying conditions. Diagnostics included laser light scattering for measurement of the liquid length and conventional pressure-data acquisition for heat-release analysis. Unsteady liquid penetration was characterized for different injection timings, injection pressures, intake-manifold pressures, and fuel volatilities to gain an understanding of the relative importance of these factors. Fuel volatility was studied by using two fuels, 2,2,4,4,6,8,8-heptamethylnonane (HMN) and 2,2,4-trimethylpentane (TMP), which have very different volatility characteristics. Measured liquid lengths changed as in-cylinder conditions changed, with increasing temperature and density during the compression stroke causing a decrease in liquid length, and decreasing temperature and density during the expansion stroke causing an increase in liquid length. Intake-manifold pressure and fuel volatility were found to be primary factors governing liquid length. Heat loss from the charge gas to the engine and local charge cooling due to fuel vaporization were found to have a secondary influence on liquid length. Injection pressure was found to have little effect.

G0700-3-3 移流スキームがディーゼル噴霧のLES解析に与える影響(エンジンシステム部門一般講演(3))

Large Eddy Simulation (LES) directly solves vortexes larger than a computational grid size. Therefore, LES is expected to make better predictions of unsteady turbulent reacting flow. This study was focused on refine predictions of diesel spray simulation, using KIVALES. Thus, we incorporated central difference method and forth-order Runge-Kutta method for the convection term of momentum equations and calculated evaporating diesel spray and diesel spray flame. The results showed that unsteady behavior in the near nozzle locations was predicted as compared with the conventional simulation results using CIP method. Additionally, good agreement of liquid and vapor penetration length and the heat release rate was obtained between the computational result and the experiments result.

Three-dimensional simulation of liquid injection, film formation and transport, in fluidized beds

Liquid injection, and film formation and transport in dense-phase gas–solids fluidized beds are numerically simulated in three dimensions using a collisional exchange model that is based on the mechanism that collisions cause transfer of liquid mass, momentum, and energy between particles. In the model, each of the particles is represented by a solid core and a liquid film surrounding the core. The model is incorporated in the framework of the commercial code Barracuda ® developed by CPFD Software. The commercial software is an advanced CFD-based computational tool where the particles are treated as discrete entities, calculated by the MP-PIC method, and tracked using the Lagrangian method. Details of the collisional liquid transfer model have been previously presented in O’Rourke, Zhao, and Snider (2009); this paper presents new capabilities and proof-testing of the collision model and a new method to better quantify the penetration length. Example calculations of a fluidized bed without liquid injection show the expected effect of collisions on the reduction of granular temperature (fluctuational kinetic energy) of the bed. When applied to liquid injection into a dense-phase fluidized bed under different conditions, the model predicts liquid penetration lengths comparable to the experiments. In addition, the simulation reveals for the first time the dynamic mixing of the liquid droplets with the bed particles and the transient distribution of the droplets inside the bed.

Numerical investigation of a multiple injection strategy on the development of high-pressure diesel sprays

Computational fluid dynamics results are presented providing information on the influence of multiple injection strategy on fuel vaporization characteristics under conditions typical of direct injection, turbocharged, high-speed automotive diesel engines. The fuel is assumed to be injected from a high-pressure common rail injector nozzle. Focus is given on the number of multiple injections and dwell-time on the evaporating spray plume development. Comparison between the different cases is performed in terms of liquid and vapour penetration curves, the spatial distribution of the air—fuel equivalence ratio and the fuel vapour spatial distribution difference between the cases considered. The results confirm that, under the operating conditions investigated, the liquid penetration length, known to freeze at a distance from the nozzle exit, is not significantly affected by the injection strategy, while vapour penetration follows the time-shift of the dwell-time. Longer dwell-times retard the diffusion of the vapour in the carrier gas. Although injection of small fuel quantities prior to the main pulse does not affect the liquid penetration, it contributes up to 5 per cent more stoichiometric fuel vapour present in the area of observed auto-ignition sites. Post injection and splitting of the main injection in two pulses modify the vapour distribution by creating two spatially separated fuel-rich zones.

Simulation of Molten Metal Penetration and Freezing Behavior in a Seven-Pin Bundle Experiment

Analysis of a hypothetical core disruptive accident is important in the safe design of the future generation of reactors such as liquid-metal-cooled reactors. This study determines the fundamental mechanisms underlying the penetration and freezing behavior of molten metal flowing through a sevenpin channel. We conducted a series of simulant experiments that focused on the fuel-pin-bundle geometry under various thermal conditions of the molten metal and pins, and produced data for the fundamental verification of the safety analysis code SIMMER-III. The liquid penetration length and the solidified frozen metal in the flow channel were investigated in the experiments. Visual information was obtained using a digital video camera. A numerical simulation using the SIMMER-III code was carried out to validate its model and method in terms of the bulk freezing behavior of molten metal. The simulation showed that the code reasonably represents the melt penetration and freezing behavior observed in the experiments.

Influence of Diesel Injection Parameters on End-of-Injection Liquid Length Recession

Diesel injection parameters effect on liquid-phase diesel spray penetration after the end-of-injection (EOI) is investigated in a constant-volume chamber over a range of ambient and injector conditions typical of a diesel engine. Our past work showed that the maximum liquid penetration length of a diesel spray may recede towards the injector after EOI at some conditions. Analysis employing a transient jet entrainment model showed that increased fuel-ambient mixing occurs during the fuel-injection-rate ramp-down as increased ambient-entrainment rates progress downstream (i.e. the entrainment wave), permitting complete fuel vaporization at distances closer to the injector than the quasi-steady liquid length. To clarify the liquid-length recession process, in this study we report Mie-scatter imaging results near EOI over a range of injection pressure, nozzle size, fuel type, and rate-of-injection shape. We then use a transient jet entrainment model for detailed analysis. Results show that an increased injection pressure correlates well with increasing liquid length recession due to an increased entrainment wave speed. Likewise, an increased nozzle size, with higher jet momentum and faster entrainment wave, enhances the liquid length recession. A low-density, high-volatility fuel does not decrease the strength of the entrainment wave; however, it decreases the steady liquid length causing the entrainmentmore » wave to reach the liquid spray tip earlier, which ultimately results in faster liquid length recession. A slow ramp down in injection rate causes a weaker entrainment wave so that the liquid length recession occurs even prior to injector close.« less

Liquid penetration length in direct diesel fuel injection

We have conducted experimental measurements to estimate the liquid penetration length of a diesel fuel jet injected into an inert environment. We analyzed the effects of the characteristic parameters, i.e., the nozzle diameter, discharge coefficient, injection pressure, and working fluid density. The transient fuel injection process was recorded using optical access, and the liquid penetration length before the second break-up regime was measured using the ombroscopy technique. The experimental data were subsequently fitted to a correlation that accurately predicts liquid penetration length at conditions typical of modern Heavy Duty common rail diesel engines operating with direct fuel injection. A statistical analysis of our experimental measurements suggests a power function correlation to model the liquid penetration length. The proposed model is in good agreement with experimental data and yields a correlation coefficient R 2 = 93.3%. It is expected that this correlation can be of assistance in the successful designing of combustion chambers required by modern heavy duty diesel engines.

분사각 변화에 따른 횡단류에 분사되는 액체제트의 분무특성에 대한 수치적 연구

The spray characteristics of liquid jet in cross flow with variation of injection angle are numerically studied. Numerical analysis was carried out using KIVA code, which was modified to be suitable for simulating liquid jet ejected into cross flow. Wave model and Kelvin- Helmholtz(KH)/Rayleigh-Taylor(RT) hybrid model were used for the purpose of analyzing liquid column, ligament, and the breakup of droplet. Numerical results were compared with experimental data in order to verify the reliability of the physical model. Liquid jet penetration length, volume flux, droplet velocity profile and SMD were obtained. Penetration length increases as flow velocity decreases and injection velocity increases. From the bottom wall, the SMD increases as vertical distance increases. Also the SMD decreases as injection angle increases.

An investigation of ignition behavior in diesel sprays

Ignition behavior in diesel sprays is explored by comparing computed and measured ignition characteristics in diesel sprays injected into a constant-volume chamber. The ignition parameter that are explored include ignition delay times and the location of ignition in the spray. The effect of changes in chamber density and temperature on these parameters is studied. The computations are carried out with a multi-dimensional model for diesel sprays. Heplane is used to represent the fuel employed in the measurements. The chemical kinetics of heptane is incorporated through an interactive flamelet model. The model is able to reproduce the trends in measured ignition delay times qualitatively. Improved quantitative agreement is achieved in cases where the ignition delay period is relatively longer. The quantitative disagreement is believed to be less important from the point of view of predicted overall heat release rates when the ignition delays are shorter. Ignition is prediced to occur closer to the orifice as chamber density is increased and also as chamber temperature is increased. Consistent with the measurement results, ignition in the spray is shown to be a two-stage process. Ignition is predicted to occur in the rich mixture downstream of the maximum liquid penetration length where the equivalence ratio is about 3.0. As the chamber density and temperature increase, the location of ignition moves upstream in the spray and the corresponding equivalence ratio decreases.

THEORETICAL STUDY OF NONUNIFORM DROPLETS CONCENTRATION DISTRIBUTION ON VENTURI SCRUBBER PERFORMANCE

ABSTRACT A new three-dimensional dispersion model has been developed and was used to study particulate removal operations in a venturi type scrubber. The model takes into account the effect of nonuniform droplets concentration distribution on the particulate removal efficiency of the scrubber of Brink and Contant (1958). Experimental data was used to test the results of the mathematical model. The results from the model are in good agreement with the experimental data. After validating the model, it was used to predict the effect of parameters such as liquid to gas flow rate ratio, gas throat velocity, and angle of the divergent section and nozzle diameter on the extent of nonuniformity of drops. Removal efficiency will increase with increasing uniformity of droplets concentration distribution. Thus, any factor that increases removal efficiency increases uniformity and vice versa. The factors affecting uniformity are: droplet diameter, liquid jet penetration length and size of scrubber.

Freezing-Controlled Penetration of a Saturated Liquid Into a Cold Tube

The penetration of a saturated liquid (a liquid at its freezing temperature) into a tube that is initially empty and maintained at a temperature below the freezing temperature of the liquid is treated theoretically and experimentally. A convenient approximate method is introduced which involves postulating a reasonable functional form for the instantaneous shape of the frozen layer along the tube wall. Graphical velocity-time and penetration distance-time curves are presented displaying the principal effects of a single dimensionless parameter. In the limit of negligible liquid inertia, shown to be relevant to high Prandtl number materials, a closed-form expression for the liquid penetration length is obtained. The expression compares well with the experimental results.