High-pressure Swirl Injector Research Articles

Numerical Simulation of Pressure-Swirl Spray Dispersion by Using Eulerian-Lagrangian Method

To gain a general understanding of atomization and sheet breakup processes, the interaction of pressure-swirl hollow-cone sprays and a quiescent medium was investigated computationally. The spray characteristics of Iso-octane (n-C8H18) with high pressure-swirl injector in the ambient conditions are modeled. The Linearized Instability Sheet Atomization (LISA) model has been used to describe the primary breakup processes of the spray. Sauter Mean Diameter, sheet thickness and exit velocity were computed as the results of primary breakup. Disintegration of large drops is simulated using Taylor analogy breakup (TAB) model in which the Rosin-Rammler distribution is used. Evaporation and collision models are deactivated in this study. The model considers the transient behavior of the pre-spray and steady-state behavior of the main spray for three various injection pressures and liquid mass flow rates. Qualitative and quantitative comparisons between the simulated and experimentally measured results were made. The numerical simulations can successfully demonstrate the spray characteristics, such as spray tip penetration, drop sizes and overall spray structure.

Liquid film thickness inside the high pressure swirl injectors: Real scale measurement and evaluation of analytical equations

Liquid film thickness inside two swirl injectors for direct injection (DI) gasoline engines was measured at different injection pressure conditions ranging from 2.0 to 7.0 MPa and then previous analytical and empirical equations were examined from the experimental results. Based on the evaluation, a new equation for the liquid film thickness inside the swirl injectors was introduced. A direct photography using two real scale transparent nozzles and a pulsed light source was employed to measure the liquid film thickness inside the swirl injectors. The error in the liquid film thickness measurement, generated from different refractive indices among transparent nozzle, fuel and air, was estimated and corrected based on the geometric optics. Two injectors which have different nozzle diameter and nozzle length were applied to introduce a more general empirical equation for the liquid film thickness inside the pressure swirl injectors. The results showed that the liquid film thickness remains constant at the injection pressures for direct injection gasoline engines while the ratio of nozzle length to nozzle diameter (L/D) shows significant effect on the liquid film thickness. The previously introduced analytical and empirical equations for relatively low injection pressure swirl injectors overestimated the effect of injection pressure at the operating range of high pressure swirl injectors and, in addition, the effect of L/D ratio and swirler geometry was rarely considered. A new empirical equation was suggested based on the experimental results by taking into account the effects of fuel properties, nozzle diameter, nozzle length and swirler geometry.

Simulation of the Internal Flow of the High-Pressure Swirl Injector

The simulation of the internal flow of a kind of high-pressure swirl injector was carried out with multiphase and cavitation models basing on the movement mesh. The spray was also simulated with the result of the internal flow simulation. The result of spray simulation was compared with experimental results. In addition, the effect on the internal flow which comes from the swirl flutes, the parts for generating the swirl flow, was investigated. It is shown that the amount and configuration of swirl flutes have crucial influence on the swirl velocity and cavitation of the internal flow.

Numerical modeling of hollow-cone fuel atomization, vaporization and wall impingement processes under high ambient temperatures

In the following paper, a numerical study of the atomization, vaporization and wall impingement processes of hollow-cone fuel spray from high-pressure swirl injectors under various ambient temperature conditions was carried out. Also, the availability of applied models and the effect of ambient temperature on spray characteristics is discussed. The Linearized Instability Sheet Atomization (LISA) model combined with the Aerodynamically Progressed Taylor Analogy Breakup (APTAB) model, the improved Abramzon model and the Gosman model are used to calculate the atomization, vaporization and wall impingement processes of hollow-cone fuel spray, respectively. Spray models are implemented with the modified KIVA code. The calculation results of the spray characteristics under two ambient temperatures, including spray tip penetration, spray structure and radial distance after spray-wall impingement are compared to the experimental results obtained by the Laser Induced Exciplex Fluorescence (LIEF) technique. The droplet size distribution, ambient gas velocity field, vapor phase distribution and fuel film mass generated by spray-wall impingement, measurements which are generally difficult to obtain by experimental methods, are also calculated and discussed. Quantitative discussions on the effect of the ambient temperature on the spray development process are conducted. It is shown that the applied models are applicable even in the high ambient temperature condition.

Numerical and experimental study on hollow-cone fuel spray of highpressure swirl injector under high ambient pressure condition

A hybrid breakup model was proposed as a trustworthy prediction of hollow-cone fuel spray in the present study and the atomization process of the hollow-cone fuel spray of a high-pressure swirl injector in a Gasoline Direct Injection (GDI) engine under high ambient pressure conditions was studied by a new hybrid breakup model. The proposed hybrid breakup model is composed of the Linearized Instability Sheet Atomization (LISA) model as a primary breakup process. The Aerodynamically Progressed Taylor Analogy Breakup (APTAB) model, instead of the Taylor Analogy Breakup (TAB) model, was used as a secondary breakup process. The effects of the droplet deformation on a droplet aerodynamic external force are considered in the APTAB model. In addition, we replaced the x2 distribution function used in previous the APTAB model by the Rosin-Rammler distribution function to improve the prediction precision. The Laser Induced Exciplex Fluorescence (LIEF) technique and the Phase Doppler Anemometry (PDA) system were used to produce a set of experimental data for the model validation. The estimation of the prediction ability of the LISA+APTAB model was carried out, and spray characteristics, which are difficult to obtain by experimental method, were calculated and discussed. The suggested hybrid breakup model showed better prediction capability compared with the previous model (LISA+TAB model). From the calculated results, the effect of the ambient pressure on the SMD (Sauter Mean Diameter) and droplet velocity could be discussed quantitatively.

벽면 캐비티 각에 따른 GDI 분무의 벽 충돌 과정에 대한 수치적 연구

A spray-wall impingement process of a hollow-cone fuel spray from the high-pressure swirl injector in the Gasoline Direct Injection (GDI) engine were experimented and calculated at various wall geometries. The Linearized Instability Sheet Atomization (LISA) & the Aerodynamically Progressed Taylor Analogy Breakup (APTAB) model and the Gosman model were applied to model the breakup and the wall impingement process of the hollow-cone fuel spray. The numerical modelings were implemented in the modified KIVA code. The calculation results of spray characteristics, such as a spray development process and a radial distance after wall impingement, compared with the experimental results by the Laser Induced Exciplex Fluorescence (LIEF) technique. The droplet size distribution and the ambient gas velocity field, which are generally difficult to obtain by the experimental methods, were also calculated and discussed. It was found that the radial distance after wall impingement and Sauter Mean Diameter (SMD) decreased with increasing a cavity angle.

Spray characteristics of high-pressure swirl injector fueled with alcohol

The spray characteristics of methanol and ethanol with high-pressure swirl injector were explored experimentally and numerically. experimental results show that the spray characteristics of methanol and ethanol had displayed the same trends as that of gasoline. Under the low back-pressure ambient conditions, the spray behavior exhibited a hollow cone with wide spray angle and initial spray slug at the tip, while the spray presented a solid cone in the case of high back-pressure. Vortexes in the opposite direction existed in the rear part of the spray under low back-pressure ambient conditions while the vortexes formed in the middle part under high back-pressure ambient conditions. Experiments also showed that methanol had the largest cone angle, while ethanol and gasoline presented almost the same cone angle. Simulation results indicated that methanol and ethanol had a slightly larger Sauter mean diameter (SMD) than that of gasoline with swirl injector. The SMD profile of methanol coincided well with that of ethanol under low back-pressure ambient conditions, but displayed a slightly larger value under high back-pressure due to fuel evaporation Numerical simulation could successfully demonstrate the spray characteristics of high-pressure swirl injector for methanol and ethanol fuels.

Spray Characteristics of High-Pressure Swirl Injector Fueled with Methanol and Ethanol

The spray characteristics of methanol and ethanol with high-pressure swirl injector are explored experimentally and numerically. Experimental results showed that the spray characteristics of methanol and ethanol gave the same trend as that of gasoline. Under the low back-pressure ambient conditions, the spray behavior exhibits a hollow cone with wide spray angle and initial spray slug at the tip, while the spray presents a solid cone in the case of high back pressure. Vortexes in the opposite direction exist in the rear part of the spray under low back-pressure ambient conditions while the vortexes form in the middle part under high back-pressure ambient conditions. Experiments also showed that methanol gave the largest cone angle, while ethanol and gasoline present almost the same cone angle. Simulation results indicated that methanol and ethanol have a slightly larger SMD than that of gasoline with swirl injector. The SMD profile of methanol coincides well with that of ethanol under low back-pressure am...

Characteristics of Nonevaporating Free Sprays of a High-Pressure Swirl Injector under Various Ambient and Injection Pressures

The characteristics of a nonevaporating free spray of a high-pressure swirl injector in a gasoline direct injection (GDI) engine under various ambient and injection conditions are investigated. The fuel spray with a hollow-cone structure, widespreading and large spray angle is observed under injection conditions simulating the GDI engine operation at full load. The study shows that a vortex structure can be clearly demonstrated in the spray tip region. Meanwhile, an initial spray slug also appeared at the tip of the main spray. Under the injection conditions of GDI engine at partial load, the structure of the fuel spray changes into a more compact and solid-cone shape spray with decreased width. Moreover, the influence of the injection pressures and ambient pressures on the spray characteristics is investigated. Furthermore, an empirical correlation for the tip penetration of the main spray is obtained, expressed as L = 0.027(ΔP/ρa)0.25t0.5. Good agreement in spray penetration between calculated and measu...

Gasoline direct injection spray simulation

In this paper the problems related to mixture formation in a GDI engine are analyzed. The atomization of a hollow cone fuel spray generated by a high pressure swirl injector is studied by means of a numerical technique. The model distinguishes between primary atomization and secondary breakup. The latter was modeled, as done in a previous work on Diesel atomization, using different mechanisms as the droplet Weber number changes. At first the spray atomization in a quiescent chamber, at ambient pressure and temperature, was considered. The validation of the model was made comparing the numerical penetration and spray morphology with experimental results. Combustion simulations were also performed comparing numerical results with experimental data of a GDI (Gasoline Direct Injection), 4 stroke, 4 cylinder, 4 valves per cylinder engine. Such simulations were made to analyze and understand the mixture formation mechanism in both stoichiometric and stratified operation mode. The results show how, the interaction between the air motion and the fuel spray, leading factor in spray atomization, is fundamental to realize an efficient mixture formation and combustion locally very lean, typical of stratified charge combustion.

Characterization of an evaporating direct-injected gasoline spray using laser-induced exciplex fluorescence and particle image velocimetry techniques

The purpose of this study is to characterize an evaporating direct-injected (DI) gasoline spray from a high-pressure swirl injector using the laser-induced exciplex fluorescence (LIEF) technique and particle image velocimetry (PIV). A fluorobenzene/diethylmethylamine (DEMA) system was used as the exciplex-forming dopants. The behaviour of the liquid and vapour phases was analysed by image processing. For the analysis of vorticity inside the spray, droplet velocity data obtained by PIV were used. The experiments were performed at two ambient temperatures (293 and 473 K) and three different ambient pressures (0.1, 0.5 and 1.0 MPa). It was found that ambient temperature had a significant effect on the axial and radial growth of the liquid phase of the evaporating spray at atmospheric pressure while it had little effect under elevated pressures. Radial growth of the vapour phase of the evaporating spray was more dominant than axial growth under high temperature and pressure conditions. As the ambient pressure was elevated, the liquid phase of the spray transformed from a hollow cone to a solid cone of bell shape, while the vapour phase varied from a widespread distribution to a compact shape with a locally richer mixture. The evaporating spray could be divided into two spray regions from the analysis of vorticity and the distributions of liquid and vapour phases. The cone region (penetrations of 0.3-0.5) was mainly liquid phase and disappeared rapidly at the end of injection. The mixing region contained the active interaction between entrained air and fuel vapour.

Liquid Sheet Break-up of High-Pressure Swirl Injector for DISI Engine(Spray Technologies, Atomization)

Experimental investigations of fuel breakup very close to nozzle of practical high-pressure swirl injector, which is used in direct injection spark ignition (DISI) engine, were carried out. In DISI engines, fuel is directly injected into cylinder therefore the spray characteristics and mixture formation are of primary importance. Many experimental investigations using several measurement techniques like laser sheet method with high-speed camera, LIF or PDA have been carried out for better understandings of spray and combustion characteristics. However, experimental investigations of atomization process were restricted due to very high-speed and very small region phenomena. Although scale-up models have been used to study the primary spray structure, it is impossible to match Reynolds, Weber, and cavitation numbers and time scales in practical high-pressure swirl injector. Microscopic investigation of primary spray structure of practical swirl injector is needed. On the other hand, numerical simulations have been conducted for better understanding of spray formation process. These researches indicated qualitatively good agreement, but the initial conditions, such as liquid sheet thickness and break-up length, were not accurately since break-up process of the liquid sheet from swirl injector has not been examined. In numerical simulation of spray behavior, a sub-model for atomization phenomena is very important. Therefore the primary atomization process and the break-up process of liquid sheet play an important role. In this research, visualizations of primary spray formation process were demonstrated using a high-speed video camera (maximum speed: Imfps) with a long-distance microscope. Initial state and development of the spray were discussed under the different ambient (back) pressure condition. During the injection period, the length and thickness of the liquid sheet, which is produced from the nozzle exit, were measured using Ar-ion laser sheet and high-speed camera. Moreover, fluctuations of the length and thickness of liquid sheet were discussed. Three main conclusions were drawn from this study. (1) It has been shown that the liquid fuel column without swirl motion was injected as a compact jet at the beginning of the injection. During the injection period, the spray indicates the quasi-steady state mode. (2) Liquid film sheet has a ligament structure. Using Ar-ion laser sheet and high-speed camera, length and thickness of the liquid sheet can be measured. (3) Surface waves of liquid sheet can be recognized. Higher ambient (back) pressure makes shorter wavelength of surface waves of liquid sheet of swirl injector.

CHARACTERIZATION OF INITIAL SPRAY FROM A D.I. GASOLINE INJECTOR BY HOLOGRAPHY AND LASER DIFFRACTION METHOD;

In the injection of a high-pressure swirl injector for direct-injection (D.I.) gasoline engine use, an initial spray (also called a leading spray or a preswirl spray [1]) is generated from the fuel downstream of the swirl grooves in the initial stage of the injection. This initial spray is almost unaffected by tangential forces, it has feeble swirl velocity, and it atomizes poorly. The initial spray has different characteristics and behavior than the main spray, such as larger droplet size, farther penetration distance, and irregular shape. Therefore, the air—fuel mixing process of the initial spray is quite different from that of the main spray. In this study, the structure of the initial spray by a high-pressure swirl injector for D.I. gasoline engine use is analyzed from observation of the reconstructed images of a hologram. The origins of the initial spray are clarified by observing the spray structures with and without cleaning the injection hole, and by comparing the volume of the initial spray with those of the injector interior, such as the annular volume and tangential grooves. The droplet size distributions in the initial spray at different imaging times are investigated. The spatial distribution of the droplet size in the initial spray is clarified, as are the effects of ambient pressure on the characteristics of the initial spray. Finally, the temporal variations of droplet size of the whole spray at fixed position is studied by a laser diffraction-based method, and the results are compared to the holographic results.

혼합모델에 의한 GDI 분무예측의 비교

The purpose of this study is to obtain the information about the development process of GDI spray. To acquire the characteristics of GDI spray, the computational study of hollow cone spray for high-pressure swirl injectors was performed. Several hybrid models using the modified KIVA code have been introduced and compared. WB model and LISA model were used for the primary breakup, and DDB and APTAB models were used for secondary breakup. To compare with the calculated results, the experimental results such as cross-sectional images and SMD distribution were acquired by laser Mie scattering technique and Phase Doppler Analyzer respectively. The results show that LISA+APTAB hybrid model has the best prediction for spray formation process.

A111 ガソリンインジェクタのノズル近傍における噴霧形成過程の可視化

Experimental investigations of primary spray structure very close to nozzle of practical high-pressure swirl injector, which is used in gasoline direct injection (GDI) engine, were carried out. Visualizations of primary spray structure were demonstrated using a high-speed video camera with a long-distance microscope. Evaluation of system performance was investigated. Three kinds of light source, such as metal-halido lump, laser beam and laser sheet of Ar-ion laser were applied. Strong intensity of the light source is needed to obtain the image with very high camera speed. Moreover, initial state and development of the spray of the swirl injector were discussed. It has been shown that the liquid fuel column without swirl motion was injected as a compact jet at the beginning of the injection. During the injection period, the spray indicates the quasi-steady state mode. Liquid sheet from the nozzle exit has a ligament structure. Using Ar-ion laser sheet and high-speed camera, length and thickness of the liquid sheet can be measured.

1903 PIV によるスワールインジェクタのノズル近傍噴霧流動解析

1903 PIV によるスワールインジェクタのノズル近傍噴霧流動解析

Design and development of a new gasoline direct swirl injector

Numerical and experimental analyses were carried out to design and develop the optimum geometry of a gasoline direct swirl injector. In the numerical analysis, the needle cone angle, swirler inclined angle and needle lift were changed with mass flowrate as design parameters to determine the optimum sizes. The critical sizes of the needle cone angle, swirler inclined angle and needle lift are 140°, 120° and 100 μm respectively. Thus, the optimum sizes may be 130°, 110° and 80 °m respectively. Experiments were performed to observe spray phenomena and to measure the dynamic flowrate, penetration of the spray tip and mainstream, spray angle and the mean drop diameter using an image processing method. The formation of a counter-rotating vortex appears in the steady state as a feature of the high pressure swirl injector spray. The calculated needle cone and swirl inclined angles as well as the cone-type needle reduce the non-swirl and sac volumes of the non-swirl region such that the reduced volumes restrict the penetration of the spray tip. The sizes of the mean drop diameter range from 20μm to 23μm and the spray angles range from 64° to 66°, which satisfy the requirements of a gasoline direct injection engine.

Three phase cavitating flows in high-pressure swirl injectors

The internal combustion engine remains to be one of the most important sources of energy. The direct gasoline injection (DGI) is a new technology that promises considerable improvement of internal combustion engine efficiency. The key component in the DGI engine is its injection system. A three-phase flow simulation of the flow in the high-pressure swirl injector, typical for DGI engines, is presented here. The model is based on the multiphase extension of the two-fluid model. The most important characteristics of the flow were predicted. The results show the formation of a thin conical fuel sheet with an air core. Cavitation was also predicted in the pressure depression initiated in the air core. The presented approach seems to be very promising for the simulation of flows in DGI injectors.

Spray analysis of a gasoline direct injector by means of two-phase PIV

The hollow-cone spray of a high-pressure swirl injector for a direct-injection spark-ignition (DISI) engine was investigated inside a pressure vessel by means of particle image velocimetry (PIV). As the interaction between the spray droplets and the ambient air is of particular interest for the mixture preparation process, two-phase PIV techniques were applied. To allow phase discrimination, fluorescent seeding particles were used to trace the gas phase. Because of the periodicity of piston engine injection, a statistical evaluation of ensemble-averaged fields to reduce cycle-to-cycle variations and to provide more general information about the two-phase flow was performed. Besides the general spray/air interaction process the investigation of the spray collapse at elevated ambient pressures was the main focus of the study. Future investigations of transient interaction processes require simultaneous techniques in combination with a high-speed camera to resolve the transient interaction phenomena. Therefore, optical filters that attenuate Mie-scattered light and transmit fluorescent light were used to collect both phases on the same image. Consequently, phase separation techniques were employed for data analysis. A masking and a peak separation technique are described and a comparison between the results of an instantaneous two-phase flow field in the spray cone of a DISI injector is presented in the paper.

Investigation on the Drop Size Distribution of SpraysProduced by a High-Pressure Swirl Injector. Measurementsand Application of the Maximum Entropy Formalism

This paper reports an investigation on the volume-based drop size distribution of sprays produced by swirl atomizers dedicated to direct-injection spark-ignited engines. Because of the use of high injection pressures to reduce the atomization time, the spatial density of the spray is high and prevents from classical measurements of spray drop size distribution. This problem is overcome by combining an experimental approach to the application of the maximum entropy formalism (M.E.F.). Based on the determination of correction factor series to correct the measurements from multiple light scattering, the experimental procedure allows obtaining some distribution characteristic features. According to a previous study, two of these characteristics are used as information in a M.E.F. procedure to derive the spray volume-based drop size distribution. This characteristic is of paramount importance for evaluating the large drop population with accuracy. The overall procedure is presented in detail and discussed. It was applied to a series of four swirl atomizers in order to study the influence of the nozzle geometry and of the injection pressure on the injector performances. Conducted under both stationary and transient working conditions, this study allows a more precise understanding of the performances of GDI injectors as far as the spray drop size distributions are concerned.