The research of diesel injection pumps performance on biofuel with different viscosity rate

Abstract

The main purpose of this research work is to determine the influence of fuel viscosity on the performance of diesel injection pumps of different design in order to clear up some of the changes in fuel feeding when running them in accordance with governor characteristics on the biofuel derived from vegetable oil.

The given fuel temperature/viscosity relationships and dependencies of fuel feeding on its viscosity applying biofi1el on different injection pumps can be practically useful for adjusting them for the work on bio-diesel. According to the analysis of the got results the in-line diesel injection pumps are more suitable for their adaptation for the work on bio-diesel. In this case only small adjustments of biofuel feeding rate are needed.

First Published Online: 19 Dec 2011

Full text

!59
ISSN
1648-4142
TRANSPORT
http:/www. vtu.lt/english/editions
TRANSPORT- 2002.
Vol
XVII.
No
4,
159-162
THE
RESEARCH
OF
DIESEL
INJECTION
PUMPS
PERFORMANCE
ON
BIOFUEL
WITH
DIFFERENT
VISCOSITY RATE
Gvidonas
Labeckas,
Stasys Slavinskas
Transport
and
Power Machinery Department, Lithuanian University
of
Agriculture
Studentt(
g.l5,
Akademija, LT-4324 Kaunas region, Lithuania, Te/.(37) 397-811, E-mail: gvidonas@info.lzua.lt
Received 2002 05 20; accepted 2002 05 17
Abstract. The main purpose
of
this research work
is
to determine the influence
of
fuel viscosity on the performance
of
diesel injection pumps
of
different design
in
order to clear up some
of
the changes
in
fuel feeding when running them
in
accordance with governor characteristics on the biofuel derived from vegetable oil.
The given fuel temperature/viscosity relationships and dependencies
of
fuel feeding on its viscosity applying
biofi1el
on different injection pumps can be practicalJy useful for adjusting them for the work on bio-diesel. According
to
the
analysis
of
the got results the in-line diesel injection pumps are more suitable for their adaptation for the work on bio-diesel.
In
this case only small adjustments ofbiofuel feeding rate are needed.
Keywords: diesel engine, injection pump, biofuel, density, viscosity, delivery rate.
1.
Introduction
The resources
of
crude oil
in
the earth deposits are
limited. This
is
one
of
the main reasons why humanity
is
imposed to think about the advantages which the usage
in internal combustion engines
of
renewable fuel sources
derived from vegetable oil gives. The next reason why
population must use biofuel
is
related to the ecological
situation -biofuel at least partly will assist solving the
actual problems
of
reduction carbon dioxide
in
atmosphere
and global warming [1]. Without mentioned reasons
biofuel promotion initiative creates new
job
places and
agricultural production sector tends to technical crops
growing
and processing.
So
biofuel has undeniable
advantages, but nevertheless it has also certain specific
properties which differ from diesel fuel.
The analysis
of
bench testing results shows that
applying Rape Oil Methyl Ester (RME) on diesel engines,
fuel consumption in mass units increases 12-15% [1-4]. It
depends finally on the engine load and frequency
of
crankshaft revolutions. Bearing
in
mind that density
of
RME
is
roughly about 7% higher
in
comparison with diesel
fuel, it is possible to assume that volumetric biofuel
consumption rate increases
5-8%.
It means that a fuel
injection pump without additional adjustments delivers
correspondingly enhanced volumetric portions
of
fuel.
2.
Purpose
ofthe
Research
Changeable kinematic viscosity
of
fuel not adequately
int1uences the quantity
of
injected per stroke fuel because
of
its different impact on high-pressure chamber charging
efficiency
of
the sections and
leakages
through the
clearance in a plunger-barrel unit.
The
t1ow
of
fuel through high pressure lines can be
described by the equations
of
movement continuity and
t1ow
[5,
6]:
(1)
where p -fuel pressure in the pipe; c - fuel flow speed
inside high pressure pipe;
pd-
fuel density;
a-
velocity
of
pressure wave propagation in compressed fuel; k -
coefficient which appreciates hydraulic resistance
of
the
fuel delivery system:
(2)
where Re =
cd._y_
-Reinold's number; d -internal diameter
v
of
high
pressu~e
fuel delivery pipe;
v-
kinematic viscosity
of
the fuel.
As we can notice from the analysis
of
equations
(I,
2) fuel injection characteristics are significantly influenced
by the physical properties
of
the fuel
-especially
by its
density and kinematic viscosity. The difference between
RME and diesel fuel actualises itself exactly on the basis
of
higher density and viscosity [2]. These two factors
may have int1uence on the hydraulic wastes
of
the injection

160
G.
Labeckas,
S.
Slavinskas I
TRANSPORT-
2002,
Vol
XVII, No
4.
I 59-162
system and fuel charging efficiency to high-pressure
chamber above plunger, on quantity
of
the fuel that leaks
out through a clearance in plunger-barrel assembly and
fuel injection pressures. The formation
of
fuel spouts and
their spreading across the combustion chamber dynamic
as well as the preparation quality
of
combustible fuel-air
mixture largely depend on the level
of
injection pressure
and fuel viscosity rate. In accordance with the acoustic
laws velocity and time
of
pressure wave propagation
in
the injection line (velocity
of
sound) that is the actual
start
of
fuel injection process also depends on fuel physical
properties.
The quantity
of
the fuel that leaks out through the
clearance between the plunger and the barrel assembly
is
evaluated by the equation [6]:
rtdp
(C5
P +
Bpsf
1
~
1
P.;
Inc
Z I = - - - - - - -
-)-
- - '
12/pJ.l.d(cPs
-1
(3)
where l
p-
length
of
sealing surface
of
plunger;
dp
-
diameter
of
plunger;
()P-
radial clearance in plunger and
barrel assembly; B -coefficient that evaluates cons-
truction and materials
of
plunger-barrel unit; p5 -fuel
pressure in the chamber above plunger; P
1 -coefficient
that evaluates deviation
of
plunger geometrical measu-
rements from ideal cylinder form;
J.l.d
-kinematic
viscosity
of
the fuel.
The quantity
of
the fuel that leaks out through the
clearance between the nozzle needle and the injector body
is
estimated as follows [6]:
(4)
where
la
-length
of
the sealing surface
of
the nozzle
needle;
d"
-diameter
of
the nozzle needle; (ja
-radial
clearance between the nozzle needle and the injector body;
p
-fuel
pressure that acts the nozzle needle sealing cone;
p
~
2
-coefficient that evaluates deviations
of
geometrical
nozzle needle measurements from ideal cylinder form;
The purpose
of
this research work
is
to investigate
the influence
of
the fuel viscosity on the performance
of
diesel injection pumps
of
different types and design in
order to clear up some
of
fuel delivery changes in governor
characteristics applying the biofuel with various viscosity
rates.
3. Research Objects and Methods
The research work has been done with four sorts
of
fuel with different viscosity
index-
diesel fuel, RME, pure
rape oil (RO) and RO mixture with diesel
fuel
(25% RO +
75
% D). One
of
the critical factors to be considered in this
work is fuel temperature and its kinematic viscosity
relationship which
is
presented
in
logarithmic (lg) scale in
Fig 1 for the tested sorts
of
fuel.
1000
"'
;:;-
--&--Diesel
fuel
E
--+--
25%R0t-75%D
E
100
.c
·;;;
0
u
.~
;>
u
-~
E
QJ
c::
~
0
15
30
45
60
75
90
Temperature
ac
Fig
1.
Fuel
kinematic
viscosity
and
temperature relationship
The fuel kinematic viscosity was measured by capil-
lary viscometers [7]. The analysis
of
graphics shows that
when temperature rises up kinematic viscosity
of
the
biofuel drops down faster than in the case
of
diesel fuel.
However in spite
of
this the viscosity
of
warmed RME and
especially pure RO remains higher than that
of
diesel fuel.
In order to get a sort
of
the biofuel with kinematic viscosity
lower than RME but at the same time, higher than diesel
fuel, we decided to choose the mixture compiled
of
25%
R0+75%D.
The basic technical data
of
the fuel injection pumps
Trade-mark of UTN-5 ND-21/4 VE
4/9
injection pump
Type of pump In-Line Distributor Distributor
Governor type
m,
v1)
m,
v1) m, m2)
Plunger diameter,
8,5
9 9
mm
Plunger stroke,
mm
8 8
2,2
Rated speed,
min-
1
850
900
2400
I)
mechanical variable-speed;
2)
mechanical minimum-maximum-
speed
The research work
wa<>
performed with three different
types
of
the fuel injection pumps: in-line type pump UTN-
5 produced
in
fuel equipment manufacture in Noginsk
(Russia), distributor type pump ND-21/4 manufactured
byfuel equipment company
in
Vilnius (Lithuania) and
Bosch firm distributor type fuel pump VE 4/9. All
of
them
were equipped with mechanical governors (Table). The
tested injection pumps are designed for the agriculture
purpose tractors D-50, D-144 and for light personal cars
VW
diesel engines correspondingly.
The
research work has been done on the diesel
injection pumps checking and adjusting stand Motorpal
NC
108-
1291. During the tests fuel pressures developed
by a supply pump and quantities
of
fuel which were
delivered per chosen number
of
injection strokes through
every
of
four injection units were measured. As a result

G.
Labecka.1·,
S.
Slavinskas
/TRANSPORT-
2002,
Vol
XVI!,
No
4,
I 59-162
161
governor characteristics
of
injection pumps were obtained
while running them on biofuel with different viscosity
rate. The camshaft rotation frequency
of
the injection
pumps was changed from the point which corresponds to
diesel engine starting revolutions
(I
00
min- 1) up to its
highest speed which occurs at the absolute fuel delivery
shutting-off point.
The
fuel temperature during testing
procedures was kept at permanent 20 °C level.
4. The Obtained Results
Governor characteristics
of
the fuel injection pumps
are presented on the graphics
of
Figs
2,
3 and 4. They
reflect the dependencies
of
average fuel quantity being
injected per stroke at different camshaft revolutions on
kinematic viscosity
of
the fuel. As we can notice on the
graphics, as far as kinematic viscosity
of
the biofuel
increases up to a certain level, the average quantity
of
the
fuel being injected per stroke with all tested pumps also
increases.
As far as kinematic viscosity
of
the fuel increases
from 3,6
mm
2/s (diesel fuel) to 15,8 mm2/s (RME) fuel
delivery rate
per
stroke for an in-line type injection
pump
UTN-5 (Fig 2) increases
from2.30%
(nc = 600 min- 1) to
2,96%
(n,.
= 400 min- 1
).
It means that fuel delivery rate
increases
from 0, I 15 to
0,400
mm
3
/cycle
for
every
additional kinematic viscosity unit
(mm
2/s).
The
main
reason
of
the increased fuel delivery while running on
RME
can be related with higher viscosity and pressure
that develops
in
a plunger-type fuel supply pump, better
high-pressure
chamber
above
the
plunger
charging
conditions and smaller leakages through a plunger-barrel
clearance.
However while applying pure RO, a in-line injection
pump UTN-5 which kinematic viscosity at
20
°C reaches
78,5
mm
2/s (Fig I), the fuel delivery
per
stroke across the
whole governor characteristic alternation zone decreases
!00
300 500 700 900 II
00
Fig
2.
Governor characteristics
of
an
in-line type
fuel
injection
pump
UTN-5
4,7-
11,7 %. The biggest decrease
of
fuel delivery while
running
on pure
RO
was
received
on rated
camshaft
revolutions frequency (nc = 850 min- 1
).
The influence
of
the fuel viscosity reveals itself even more when a camshaft
of
the injection
pump
rotates at the
speed
which cor-
responds to the engine full-load point at torque curve
maximum (nc = 700 min- 1
).
At this critical point the fuel
viscosity influence is noticeable even when the injection
pump
runs on less viscous RME. the fuel delivery per
stroke
decreases
3, 19%.
This
can be related with the
marginal fuel viscosity level and worse plunger-barrel
sections charging conditions. The viscosity influence is
especially noticeable at the boosted pump speed and full-
load fuel delivery zone because charging pressure
of
the
supply system remains at a low level
(0,3-
0,6 bar).
90 6
80 -5,5
-+----
2,5
200 400 600 800 1000
Fig
3.
Governor characteristics
of
a distributor
type
fuel
injection
pump
ND-21/4
Analysing the performance peculiarities
of
a fuel
injection pump
of
a distributor type ND-2114 while running
it on the biofuel with various viscosity rate, one must bear
in mind four times higher recurrence
of
the process
in
comparison with an in-line type pump, correspondingly
shorter
high-pressure
chamber
charging
duration and
about ten times higher boosted fuel charging pressure
from the supply system (Fig 3). As in the case with an in-
line pump UTN-5, when camshaft revolution frequency
decreases below engine rated speed and torque-control
unit boosts the quantity
of
the fuel to be injected, biofuel
viscosity influence becomes even more evident. In the
case
of
a distributor type injection
pump
ND-21/4
the
replacement
of
diesel fuel by
RME
leads to the increase
of
biofuel delivery rate in the torque-control zone from 2,25%
(n,.
= 800 min- 1) to 9,02%
(nc
= 500 min- 1
).
It means that the
increase
of
the fuel kinematic viscosity results in rising
of
its delivery rate 0,123 and 0.510
mm
3/stroke per every
(1
mm
2/s) unit
of
viscosity correspondingly. Because
of
the shorter
chamber
above
plunger
charging
duration
(0,0
16-0,026
s) and significant intluence on the charging
process
of
enlarged kinematic viscosity
of
pure RO, fuel
delivery rate decreases
in
comparison with an in-line pump

162
G.
Labeckas,
S.
S/avinskas I
TRANSPORT-
2002,
Vol
XVII, No
4,
159-162
even more rapidly (7, 1
-24,7
%).
In
the same manner as
with UTN-5 the fuel delivery per stroke decreases more
evidently when running the pump at boosted camshaft
speed
(nc
= 900 min- 1
).
In a distributor type fuel injection pump VE 4/9 the
integrated vane-type supply pump delivers fuel through a
pressure-control valve which ensures that the housing
pressure rises linearly from
1-2
to
8-9
bar
as
function
of
camshaft
rotating
speed
that alternates from 100 to
2500 min- 1 (Fig 4). In spite
of
higher fuel gauge pressure
and dissimilar design
of
rotary VE injection pump, viscosity
influence on the biofuel delivery rate
in
a wide range
of
governor characteristic remains almost unchangeable.
After the replacing
of
diesel fuel with RME, the biofuel
delivery rate per stroke
ofVE
pump increases from 1,3%
(nc=
2000
rnin-
1) to 9,3%
(nc=
500
min-
1)
or-from
0,031 to
0,166
mm3
/stroke
for
everyone
fuel
viscosity
unit
correspondingly. While applying pure RO,
in
VE 4/9 pump
the biofuel delivery per stroke decreases mostly
(7
-10%)
also at the camshaft rotation frequency which corresponds
engine torque-control (unit action) zone. Using the biofuel
(RME
or
RO) instead
of
diesel fuel, gauge pressure
developed by a vane-type supply pump increases well-
high 1 bar. This fuel gauge pressure directly controls the
timing device in the VE pump housing that advances the
start
of
the fuel delivery
as
the engine speed increases.
It
means that while running on the biofuel, the actual fuel
injection angle also slightly advances.
40
15
o Diesel fuel ;
35
13
11
·a
30
::;;;
~
9
25
E
E 7
cP
20
5
15
3
10
200 700 1200 1700 2200 2700
. Fig 4. Governor characteristics
of
a distributor type fuel
injection pump
VE
4/9
....
"'
.0
0:.
In spite
of
different design
of
the tested injection
pumps, the viscosity influence on the biofuel delivery rate
in a governor control zone goes towards minimum. It can
be related with a diminished quantity
of
the fuel to be
injected per stroke at the engine top no-load speed and
correspondingly that the chambers above the plungers
may be charged only partially.
S.
Conclusions
1.
In the case
of
an
in-line injection pump UTN-5 the
increase
of
the fuel kinematic viscosity from 3,6 (diesel
fuel) to 15,8 mm2/s (RME) leads to
an
average increase
of
fuel delivery per stroke 2,6%. The same biofuel viscosity
variation
in
distributor type pumps ND-21/4 and VE 4/9
results in 2 - 9% boosted delivery rate.
2.
However, if kinematic viscosity ofthe biofuel increases
up to 80 mm2/s (pure RO), biofuel delivery per stroke
decreases because
of
worse high-pressure chamber above
plunger charging conditions that greatly influence
in
the
case
of
a distributor type injection pump ND-21/4
(7,1-
24,7 %).
3.
After the camshaft revolution frequency reaches the
engine rated speed and exceeds it (governor action zone)
the influence offuel kinematic viscosity (except pure RO)
on the quantity
of
the fuel delivered per stroke becomes
less noticeable. In spite
of
different design it
is
a common
feature
of
all the tested fuel injection pumps
4.
It may be worth taking into account the given fuel
temperature/viscosity relationship and viscosity influence
on the injection rate adjusting different design
of
fuel
injection pumps for their performance on biofuel.
5.
The analysis
of
the given testing results shows that in-
line fuel injection
pumps
can be more suitable than
distributor ones for the performance on viscous biofuel.
In this case their adjusting procedures could be
mini~al.
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I.
Peterson
C.
L., Corada
M.
E., Sotley
L.
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J.
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6,
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Y.,
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