共查询到20条相似文献,搜索用时 31 毫秒
1.
K. Park 《Journal of Mechanical Science and Technology》1996,10(3):351-361
In modern small compact combustion chambers of diesel engines with high speed injection spray, the wall impaction of spray is encountered. A number of combustion systems have been developed which deliberately employ wall impaction as a means of breaking up the fuel spray and/or directing it in a desired direction. As a link of this, in a further type of geometry, which has been presented by Park et al. cut-off pips were provided for a number of sprays directed not only straight down into combustion chamber centre but also across and down into the bowl in the normal radial direction. The sizes of the pips and their positions were tested for axisymmetrical shape, and their results were analyzed. The further type was simulated in here by using 3D non-orthogonal spray engine code. The simulation results show that the further type is much better than general conventional shapes, i.e. well mixing of fuel vapour and spray high qualified droplet atomization, etc. Thus the improvement of the engine performance is expected by the shaped engine. 相似文献
2.
Won-Tae Kim Sam-Goo Lee Byung-Joon Rho Shin-Jae Kang 《Journal of Mechanical Science and Technology》1998,12(5):907-916
The quality of spray atomization ejected from an injector has a definitive influence upon the engine’s performance. Furthermore,
considerable attention to the Earth’s environmental pollution is increasing now more than ever before. This experimental investigation
has been carried out to clarify the characteristics of the intermittent spray using a pintle type gasoline fuel injector.
Both the image processing system and the Phase Doppler Anemometer are utilized for the visualization of a spray behavior and
the simultaneous measurements of dropsizes and their velocities, which have been conducted at the axial downstream from the
injector exit plane. The fuel injection duration was fixed at 3ms and the injection pressure was varied from 250 kPa to 350
kPa. For a high injection pressure of 350 kPa, the spray tip arrival time was fluctuated at the vigorously disintegrated regions.
It evidently shows a linear correlation between the axial velocity and the fuel drop size farther downstream. 相似文献
3.
Sam-Goo Lee 《Journal of Mechanical Science and Technology》2008,22(6):1237-1243
To assess the significant physics associated with the increase of ALR and configuration ratio of the nozzle tip in pneumatic
swirling flows, comprehensive observations using a 3-D PDPA system were experimentally carried out. Profiles of mean velocities,
turbulence intensities, SMD variations, and correlations between droplet size and turbulence components were quantitatively
acquired. As discussed in a previous literature, axisymmetric swirl angle of 30° is selected for this investigation because
of its strong turbulence levels in the flowfield and finer droplet disintegrations. Various ALRs (Air-to-Liquid Mass Ratio)
as well as the length-to-diameter ratios of nozzle tip as parameters were chosen. Due to the complex interactions in swirling
flows under these variables, this experimental observation will be of fundamental importance to the understanding of turbulence
structures. From the observations, it indicated that increasing the ALR causes the spray development to be positively fluctuated
on the atomization in both axial and tangential RMS velocities. Also, it can be concluded that the SMD decreases continuously
with increase of ALR, substantiating the fact that the fluctuations are inversely proportional to the SMD variation. Meanwhile,
the spray behavior is characteristic with a reduction of length-to-diameter ratio; smaller the configuration ratio, the higher
the turbulence intensities and smaller SMD variations in the flowfield. 相似文献
4.
Seung-hwan Choi Chunghwan Jeon Young June Chang 《Journal of Mechanical Science and Technology》2002,16(7):986-998
Flow and spray characteristics are critical factors that affect the performance and exhaust emissions of a direct injection
diesel engine. It is well known that the swirl control system is one of the useful ways to improve the fuel consumption and
emission reduction rate in a diesel engine. However, until now there have only been a few studies on the effect of flow on
spray. Because of this, the relationship between the flow pattern in the cylinder and its influence on the behavior of the
spray is in need of investigation. First, in-cylinder flow distributions for 4-valve cylinder head of Dl (Direct Injection)
Diesel engine were investigated under steady-state conditions for different SCV (Swirl Control Valve) opening angles using
a steady flow rig and 2-D LDV (Laser Doppler Velocimetry). It was found that swirl flow was more dominant than that of tumble
in the experimented engine. In addition, the in-cylinder flow was quantified in terms of swirl/tumble ratio and mean flow
coefficient. As the SCV opening angle was increased, high swirl ratios more than 3.0 were obtained in the case of SCV -70ΰ
and 90ΰ. Second, spray characteristics of the intermittent injection were investigated by a PDA (Phase Doppler Anemometer)
system. A Time Dividing Method (TDM) was used to analyze the microscopic spray characteristics. It was found that the atomization
characteristics such as velocity and SMD (Sauter Mean Diameter) of the spray were affected by the in-cylinder swirl ratio.
As a result, it was concluded that the swirl ratio improves atomization characteristics uniformly. 相似文献
5.
With increasing requirements for the less harmful exhaust emissions and the better fuel economy, the conventional injectors
in gasoline engines can be replaced by the air shrouded injector in order to provide improved combustion in engine operations.
To find out the optimal shape of air shrouded atomizer attached to the conventional injector nozzle, the critical design parameters
such as droplet size, fuel and air inlet angles, and injection angles were investigated based on experimental analyses. To
explain the characteristics of fuel atomization, these experimental approaches were carried out using a Phase Doppler Particle
Analyzer (PDPA) system. The droplet sizes of injected air fuel mixture were obtained by using the beam diffraction phenomenon.
In order to improve the atomization effect, the various atomizers were investigated. The Sauter Mean Diameter (SMD) measured
at the predetermined locations outside the atomizer represented the performance of fuel atomization. The experimental results
show that the design factors and atomization mechanism needed for developing air shrouded injectors. The suggested design
parameters in this paper can be a useful reference in the early design stage. 相似文献
6.
Soot has a great effect on the formation of PM (Paniculate Matter) in D.I. (Direct Injection) Diesel engines. Soot in diesel
flame is formed by incomplete combustion when the fuel atomization and mixture formation were poor. Therefore, the understanding
of soot formation in a D.I. diesel engine is mandatory to reduce PM in exhaust gas. To investigate soot formation in diesel
combustion, various measurements have been performed with laser diagnostics. In this study, the relative soot diameter and
the relative number density in a D.I. engine was measured by using LIS (Laser Induced Scattering) and LII (Laser Induced Incandescence)
methods simultaneously which are planar imaging techniques. And a visualization D.I. diesel engine was used to introduce a
laser beam into the combustion chamber and investigate the diffusion flame characteristics. To find the optimal condition
that reduces soot formation in diesel combustion, various injection timing and the swirl flow in the cylinder using the SCV
(Swirl Control Valve) were applied. From this experiment, the effects of injection timing and swirl on soot formation were
established. Effective reduction of soot formation is possible through the control of these two factors. 相似文献
7.
Nae Hyun Lee Jong Ho Park Kyu Hoon Choi 《Journal of Mechanical Science and Technology》1999,13(3):286-293
One of the important research for developing a spark-ignited direct injection engine is optimization of the fuel spray distribution
and air flow field in the cylinder. Therefore, spray pattern and mean fuel droplet size of swirl injector were investigated
using Laser Light Sheet Photography and PDPA' respectively. And, for the formation of stratified mixture with adequate strength
near a spark plug at injection mode in compression stroke, spray distribution after impingement on flat piston or bowl piston
in a transparent motoring engine was visualized for the three different injector positions.
KIA Motors Corp. 相似文献
8.
In this paper, the spray atomization characteristics of a gasoline direct-injection injector were investigated experimentally
and numerically. To visualize the developing spray process, a laser sheet method with a Nd :YAG laser was utilized. The microscopic
atomization characteristics such as the droplet size and velocity distribution were also obtained by using a phase Doppler
particle analyzer system at the 5 MPa of injection pressure. With the experiments, the calculations of spray atomization were
conducted by using the KIVA code with the LISA-DDB breakup model. Based on the agreement with the experimental results, the
prediction accuracy of LISA-DDB breakup model was investigated in terms of the spray shapes, spray tip penetration, SMD distribution,
and axial mean velocity. The results of this study provides the macroscopic and microscopic characteristics of the spray atomization,
and prediction accuracy of the LISA-DDB model. 相似文献
9.
The effects of change in injection pressure on spray structure in high temperature and pressure field have been investigated.
The analysis of liquid and vapor phases of injected fuel is important for emissions control of diesel engines. Therefore,
this work examines the evaporating spray structure using a constant volume vessel. The injection pressure is selected as the
experimental parameter, is changed from 22 MPa to 112 MPa using a high pressure injection system (ECD-U2). Also, we conducted
simulation study by modified KIVA-II code. The results of simulation study are compared with experimental results. The images
of liquid and vapor phase for free spray were simultaneously taken by exciplex fluorescence method. As experimental results,
the vapor concentration of injected fuel is leaner due to the increase of atomization in the case of the high injection pressure
than in that of the low injection pressure. The calculated results obtained by modified KIVA-II code show good agreements
with experimental results. 相似文献
10.
This paper presents the effect of injection pressure on the atomization characteristics of high-pressure injector in a direct
injection gasoline engine both experimentally and numerically. The atomization characteristics such as mean droplet size,
mean velocity, and velocity distribution were measured by phase Doppler particle analyzer. The spray development, spray penetration,
and global spray structure were visualized using a laser sheet method. In order to investigate the atomization process in
more detail, the calculations with the LISA-DDB hybrid model were performed. The results provide the effect of injection pressure
on the macroscopic and microscopic behaviors such as spray development, spray penetration, mean droplet size, and mean velocity
distribution. It is revealed that the accuracy of prediction is promoted by using the LISA-DDB hybrid breakup model, comparing
to the original LISA model or TAB model alone. And the characteristics of the primary and secondary breakups have been investigated
by numerical approach. 相似文献
11.
The effects of change in injection pressure on spray structure in high temperature and pressure field have been investigated.
The analysis of liquid and vapor phases of injected fuel is important for emissions control of diesel engines. Therefore,
this work examines the evaporating spray structure using a constant volume vessel. The injection pressure is selected as the
experimental parameter, is changed from 400 bar to 800 bar by using a common rail injection system. Also, we conducted simulation
study by modified KIVA-II code. The results of simulation study are compared with experimental results. The images of liquid
and vapor phase for free spray were simultaneously taken by exciplex fluorescence method. As experimental results, the vapor
concentration of injected fuel is leaner due to the increase of atomization in the case of the high injection pressure than
in that of the low injection pressure. The calculated results obtained by modified KIVA-II code show good agreements with
experimental results. 相似文献
12.
Sam-Goo Lee 《Journal of Mechanical Science and Technology》2008,22(12):2509-2515
The experimental objective was to compare disintegration characteristics from the internal mixing pneumatic nozzles under
the different operating conditions in terms of swirl angles. For this investigation, supplied air pressures and nozzle configuration
ratios were fixed. This experimental comparison is of fundamental importance to the understanding and modeling of turbulent
atomization because the axisymmetric swirling flows involve relatively complex interactions. For the measurement, four internal
swirl mixing nozzles with axisymmetric holes at swirl angles of 15°, 30°, 45°, and 60° to the central axis were employed,
which is responsible for the enhancement of mixing in pneumatic jets. To illustrate the swirl phenomena quantitatively, the
distributions of mean velocities, turbulence intensities, and SMD (Sauter mean diameter, or D32) variations with different configuration ratio were comparatively analyzed. It indicated that the atomization characteristics
are performed well in the case of 30° of swirl angle, and that turbulence intensities are gradually degenerated with the increase
of radial distances, showing a slight increment of SMD at downstream region. In particular, measurements showed that nozzle
configuration is one of the significant geometrical parameters affecting the spray trajectories.
This paper was recommended for publication in revised form by Associate Editor Jun Sang Park 相似文献
13.
In this study, numerical and experimental analysis on the spray atomization characteristics of a GDI injector is performed.
For numerical approach, four hybrid models that are composed of primary and secondary breakup model are considered. Concerning
the primary breakup, a conical sheet disintegration model and LISA model are used. The secondary breakup models are made based
on the DDB model and RT model. The global spray behavior is also visualized by the shadowgraph technique and local Sauter
mean diameter and axial mean velocity are measured by using phase Doppler particle analyzer. Based on the comparison of numerical
and experimental results, it is shown that good agreement is obtained in terms of spray developing process and spray tip penetration
at the all hybrid models. However, the hybrid breakup models show different prediction of accuracy in the cases of local SMD
and the spatial distribution of breakup. 相似文献
14.
Chan Tat Leung 《机械工程学报(英文版)》1996,(3)
MODELINGOFASOLIDCONEPRESSURE-SWIRLATOMIZERMODELINGOFASOLIDCONEPRESSURE-SWIRLATOMIZERChanTatLeung(TheHongKongPolytechnicUniver... 相似文献
15.
两相脉冲爆震发动机的燃油喷射、混合及其雾化研究 总被引:7,自引:1,他引:6
两相爆震燃烧近来得到了广泛的重视和关注,但在它走向应用之前仍有很多问题需要解决。燃油的喷射、混合和雾化对两相爆震燃烧的影响就是其中之一。本文利用激光喷雾测量仪分别就直射喷嘴与气动喷嘴研究了汽油的喷射雾化与混合雾化,得到了汽油的雾化粒度与供油量、供气量间的关系。利用CFD程序对混合室中油、气的混合特性进行了模拟,结果与试验结果非常吻合。结合脉冲爆震发动机模型机多循环爆震试验,发现汽油的粒度大小对脉冲爆震模型机的油气当量比、燃油填充比有显著的影响。 相似文献
16.
17.
Jeongkuk Yeom Jongsang Park Sungsik Chung 《Journal of Mechanical Science and Technology》2005,19(12):2281-2288
Because an injected spray development process consists of impinging and free spray in the diesel engine, it is needed to analyze
the impinging spray and free spray, simultaneously, in order to study the diesel spray behavior. To dominate combustion characteristics
in diesel engine is interaction between injected fuel and ambient gas, that is, process of mixture formation. Also it is very
important to analyze liquid and vapor phases of injected fuel on the investigation of mixing process, respectively and simultaneously.
Therefore, in this study, the behavior characteristics of the liquid phase and the vapor phase of diesel spray was studied
by using exciplex fluorescence method in high temperature and injection pressure field. Finally, it can be confirmed that
the distribution of vapor concentration is more uniform in the case of the high injection than in that of the low injection
pressure. 相似文献
18.
The world is faced with a problem of air pollution due to the exhaust emissions from automobile. Recently, lots of researchers
have been attracted to develope various alternative fuels and to use renewable fuels as a solution of these problems. There
are many alternative fuels studied in place of diesel fuel made from petroleum. Biodiesel fuel (BDF) is a domestically produced,
renewable fuel that can be manufactured from vegetable oils, used vegetable oils, or animal fats. In this study, the usability
of BDF, one of the oxygenated fuels as an alternative fuel for diesel engines was investigated in an IDI diesel engine. Emissions
were characterized with a neat BDF and with a blend of BDF and conventional diesel fuel. Since the BDF includes oxygen of
about 11%, it could influence the combustion process strongly. Therefore, the use of BDF resulted in lower emissions of carbon
monoxide and smoke emissions with some increase in emissions of oxides of nitrogen. It is concluded that BDF can be utilized
effectively as a renewable fuel for IDI diesel engines. 相似文献
19.
The objective of this study is to investigate the effects of fuel temperature on the spray characteristics of a dual-orifice
type swirl injector used in a gas turbine. The major parameters affecting spray characteristics are fuel temperature and injection
pressure entering into the injector. In this study, the spray characteristics of a dual-orifice type swirl injector are investigated
by varying fuel temperature from — 30°C to 120°C and injection pressure from 0.29 to 0.69 MPa. Two kinds of fuel having different
surface tension and viscosity are chosen as atomizing fluids. As a result, injection instability occurs in the low fuel temperature
range due to icing phenomenon and fuel property change with a decrease of fuel temperature. As the injection pressure increases,
the range of kinematic viscosity for stable atomization becomes wider. The properties controlling the SMD of spray is substantially
different according to the fuel temperature range. 相似文献
20.
When a column of droplets freely falling from an ultrasonic atomizer was ignited behind a reflected shock, no ignition occurred
at a temperature below 1100 K, even if the pressure was as high as IMPa. Although, a higher temperature condition ensured
ignition, no luminous flame was observable by high-speed photography, and even if a luminous flame lump appeared at an extremely
high temperature, it disappeared without spreading over the entire column of droplets in this case. It is known however that,
if a fuel is injected into a diesel cylinder or an electric furnace, ignition occurs even at a temperature as low as 650 K
with a luminous flame spreading over the entire spray. These differences could be caused by the effects of turbulent mixing
between fuel droplets and hot air, in fact, turbulence-generating rods were placed on the upstream side of the spray column.
Experimental results indicates that the ignition limit was lowered to 840 K, and the ignition delay period was decreased by
increasing the intensity of turbulence. Furthermore, the light emission of the flame was intensified, and normal spray combustion
was maintained in the low-temperature atmosphere after the shock tube ceased its operation. 相似文献