共查询到8条相似文献,搜索用时 0 毫秒
1.
Jeekuen Lee Shinjae Kang Byungjoon Rho 《Journal of Mechanical Science and Technology》2002,16(12):1693-1701
The intermittent spray characteristics of a multi-hole and a single-hole diesel nozzle were experimentally investigated. The
hole number of the multi-hole nozzle was 5, and the hole diameter of the 5-hole and the single-hole nozzle was the same as
dn=0.32 mm with the constant hole length to diameter ratio (ln/dn=2.81). The droplet diameters of the spray, including the time-resolved droplet diameter, SMD (Sauter mean diameter) and AMD
(arithmetic mean diameter), injected intermittently from the two nozzles into the still ambient were measured by using a 2-D
PDPA (phase Doppler particle analyzer). Through the time-resolved evolutions of the droplet diameter, it was found that the
structure of the multi-hole and the single-hole nozzle spray consisted of the three main parts : (a) the leading edge affected
by surrounding air and composed of small droplets ; (b) the central part surrounded by the leading edge and mixing flow region
and scarcely affected by the resistance of air ; (c) the trailing edge formed by the passage of the central part. The SMD
decreases gradually with the increase in the radial distance, and the constant value is obtained at the outer region of the
radial distance (normalized by hole diameter) of 7-8 and 6 for the 5-hole and single-hole nozzle, respectively. The SMD along
the centerline of the spray decrease shapely with the increase in the axial distance after showing the maximum value near
the nozzle tip. The SMD remains the constant value near the axial distance (normalized by hole diameter) of 150 and 180 for
the 5-hole and the single-hole nozzle, respectively. 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.
Swirl effect on the spray characteristics of a twin-fluid jet 总被引:1,自引:0,他引:1
Byung-Joon Rho Shin-Jae Kang Je-Ha Oh Sam-Goo Lee 《Journal of Mechanical Science and Technology》1998,12(5):899-906
In the liquid fuel combustion chamber, employed fuel must be atomized before being injected into the combustion zone. Therefore,
the complete fuel atomization is the most important condition for the combustion efficiency. The atomization quality strongly
affects the combustion performance, exhaust pollutant emissions, and flame stability. Therefore, the whole process of spray
atomization is of fundamental significance. During past decades many experimental and theoretical studies in this field have
been carried out and some improved results have been obtained. Two-phase atomizers, having a variety of advantages such as
spray uniformity, appreciable atomization, and smaller SMD with an increase of ambient gas, are considered to be applied in
various industrial processes. The purpose of present study is to investigate the mean velocity, turbulence shear stress, turbulence
intensity, mean drop size distribution, and droplet data rate in a two-phase swirling jet using PDPA systems. 相似文献
4.
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
5.
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
6.
The intermittent spray characteristics of a multi-hole diesel nozzle with a 2-spring nozzle holder were investigated experimentally.
Without changing the total orifice exit area, the hole number of the multi-hole nozzle varied from 3 (dn=0.42 mm) to 5 (dn=0.32mm). The time-resolved droplet diameters of the spray including the SMD (Sauter mean diameter) and the AMD (arithmetic
mean diameter), injected intermittently from the multi-hole nozzles into still ambient air, were measured by using a 2-D PDPA
(phase Doppler particle analyzer). The 5-hole nozzle spray shows the smaller spray cone angle, the decreased SMD distributions
and the small difference between the SMD and the AMD, compared with that of the 3-hole nozzle spray. From the SMD distributions
with the radial distance, the spray structure can be classified into the three regions : (a) the inner region showing the
high SMD distribution; (b) the mixing flow region where the shear flow structure would be constructed; and (c) the outer region
formed through the disintegration processes of the spray inner region and composed of fine droplets. Through the SMD distributions
along the spray centerline, it reveals that the SMD decreases rapidly after showing the maximum value in the vicinity of the
nozzle tip. The SMD remains the constant value near the Z/dn=166 and 156.3 for the 3-hole and 5-hole nozzles, which illustrate that the disintegration processes of the 5-hole nozzle
spray proceed more rapidly than that of the 3-hole nozzle spray. 相似文献
7.
Numerical and experimental study on hollow-cone fuel spray of highpressure swirl injector under high ambient pressure condition 总被引:4,自引:0,他引:4
Young-Sam Shim Gyung-Min Choi Duck-Jool Kim 《Journal of Mechanical Science and Technology》2008,22(2):320-329
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 x
2 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. 相似文献
8.
Sam-Goo Lee 《Journal of Mechanical Science and Technology》2008,22(8):1633-1639
In an effort to obtain the significant features associated with the ALR and length/diameter ratio of the final discharge orifice
in swirling flows, experimental observations using a 3-D PDPA system were carried out. Profiles of SMD distributions depending
on l
o
/d
o
, correlation between SMD and turbulence intensities in terms of l
o
/d
o
and correlations between droplet size and turbulence components were quantitatively analyzed. As discussed in a previous
literature, an axisymmetric swirl angle of 30° was selected for this investigation because of its strong turbulence levels
in the flow-field and finer droplet disintegrations. Three ALRs of 0.093, 0.106, and 0.122 as well as the length/diameter
ratio of 0.15, 0.45, and 0.60 were chosen as parameters. Due to the complex interactions in swirling flows under these variables,
this experimental observation will be of fundamental importance to the understanding of geometrical effects on spray trajectory.
From the observations, it is indicated that increasing the ALR causes the spray development to be more dependent on number
density and volume flux. The results indicated that the SMD decreases discernibly with smaller l
o
/d
o
, substantiating the fact that turbulence intensities are inversely proportional to the SMD. But, l
o
/d
o
is quite proportional to the SMD. 相似文献