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  (In/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.4475
Key Words:Atomization  Characteristics,  Intermittent Diesel  Spray,  SMD  (Sauter  Mean  Di-
ameter),  PDPA  (Phase  Doppler  Particle  Analyzer)
1.  Introduction
Recently, multi-hole nozzles are widely used  in
direct  injection  (D.  I.)  diesel engines, owing to  its
potentiality in  the  reduction of exhaust emissions.
However,  the  spray  characteristics  of  the  multi-
* Corresponding Author,
E-mail :  j klee  @  mec.hiroshima-u.ac.jp
TEL: +81-824  24  7566;  FAX : +81-824-22-7034
Department  of  Mechanical System Engineering, Uni-
versity  of  Hiroshima, Hi&ashi-Hiroshima  739-8527,
Japan.  (Manuscript Received July  3,  2001;Revised
September 30, 2002)
hole  nozzle  are  not  clear  until  now  due  to  the
sophisticated  geometry  and  the  flow  structure
inside  the  nozzle  tip,  contrary  to  the  cases  of
single-hole  nozzles.  Moreover,  many  experimen-
tal  studies  on  the  spray  characteristics  deal  with 柴油喷嘴雾化英文文献和翻译:http://www.youerw.com/fanyi/lunwen_1165.html