=Paper=
{{Paper
|id=Vol-452/paper-24
|storemode=property
|title=A cluster nozzle concept with high injection pressures for DI Diesel engine
|pdfUrl=https://ceur-ws.org/Vol-452/poster4.pdf
|volume=Vol-452
}}
==A cluster nozzle concept with high injection pressures for DI Diesel engine==
https://ceur-ws.org/Vol-452/poster4.pdf
A Cluster Nozzle Concept with high injection pressures for DI Diesel Engine
1 1*
N. Peters , H. Won
1
Institute of Combustion Technology,
RWTH Aachen University
A combination of high pressure injection and small orifices will be one of strategies to achieve the lean combustion.
But the small orifice tends to increase soot under high load conditions because of short spray tip penetration. For this
reason, a cluster concept was proposed in this study. The difference of the cluster nozzle is that the cluster has sev-
eral groups of orifices; each group consists of two small orifices which are very close to each other and have in-
cluded-angle. The cluster nozzle was investigated with different injection pressure under part load conditions and
high load conditions in a single cylinder Diesel engine and it was compared with a reference nozzle. Among the expe-
rimental results, the clusters tend to make higher smoke than the reference nozzle under conventional injection timing
because the spray from the cluster with a shorter spray tip penetration loses momentum near the piston bowl. But the
clusters have improved smoke emissions with higher injection pressures. With the increase of injection pressure, the
clusters have a potential to reduce, to some extent, the adverse effects on spatial distribution of spray due to better
fuel atomization and evaporation.
Introduction
One possibility to realize the desired decrease
in orifice diameter and increase in orifice number is
to abandon the equispaced design and to cluster
the orifices. Nishida et al. [1] and Gao et al. [2]
study group-hole nozzles, as they call them, con-
sisting of two sprays with an included angle of -10
to 10°. For converging sprays (negative included
angle), spray penetration behavior was found to be
similar to the corresponding conventional nozzle. Fig. 1: The cluster nozzle configuration
For the diverging nozzles (positive included angle),
a reduction in the penetration of the spray tip is Experimental setup
found. Zhang et al. [3, 4] investigated the spray- The engine experiments are performed on a 0.8
wall interaction of sprays from group-hole nozzles. liter single-cylinder engine (16:1 compression ratio)
They found better atomization characteristics and with a swirl ratio of 1.5 based on a V-8 Duramax-
asymmetries in the impinging spray on the wall engine from General Motors. Piezo injectors (CRI
when comparing the group-hole nozzles to con- 3.3) were used for the experiments.
ventional ones. Different studies have suggested
advantages of cluster nozzles in engines under Test point TP1 TP2
part-load conditions with convergent configurations Speed [rpm] 1400 1400
being more advantageous than the divergent ones
[5, 6]. Gao et al. [7] have shown advantage of di- Rail Pressure
500 - 900 1200 & 1500
vergent cluster nozzles over conventional ones in [bar]
terms of soot formation through soot luminosity IMEP [bar] 4.5 10.5
measurements in an optical engine. As no such Start of Pulse -30 ~ -3 -10 ~ 4
advantage in terms of soot emissions in engines [aTDC] (step 3deg) (step 2deg)
has been observed in other studies, it seems that Boost Pres-
the sprays from cluster nozzles have deficits in 1.15 1.57
sure [bar]
terms of soot oxidation. Boost Temp.
The cluster with included angle of 10° having 55 57
[°C]
orifices in a plane perpendicular to the injector axis Temp. Oil &
was designed with the same spray-cone angle as 90 90
Coolant [°C]
the reference injector (158°) for better targeting. EI Nox(EGR)
The Cluster in Fig. 1 was named according to their 4 4.5
[g/kg of fuel]
geometry. The first part denotes total number of
orifices (14). The two numbers separated by a Table 1: The engine operating conditions
slash denote te sprayh cone angle formed by the
orifices in different orifice circles (158/158). The The cluster 14x158/158 and the reference noz-
two orifices of a cluster were separated by 0.6mm. zle were separately tested under low-load and
high-load condition at 1400 rpm. Injection duration
was varied to maintain the IMEP, while NO x was
* Hyun Woo Won: h.won@itv.rwth-aachen.de
Towards Clean Diesel Engines, TCDE2009
maintained at constant levels for different sets of condition, hydrocarbon (HC) and carbon monoxide
experiments by varying EGR (Exhaust Gas Recir- (CO) emissions are of major concern, because HC
culation). Injection rate measurements were car- and CO emissions are usually higher when the
ried out for all the nozzles to determine the actual combustion temperature is low. The cluster shows
injected mass for the test points. The table 1 an improvement for HC, because the reference
shows the engine operating conditions. nozzle with long spray tip penetration causes more
fuel in proximity of the cylinder liner and combus-
Result and discussion tion chamber walls, where flame quenching occurs.
Fig. 2 shows the pressure curves, heat releases Lower soot emissions for the lower oxygen con-
and cumulative heat releases of reference nozzle centration conditions, which have substantially
and Cluster 14x158/158 for -12° CA aTDC SOI lower flame temperatures, suggest that NOx and
with 900bar rail pressure for TP1. Ignition delay in soot can potentially be simultaneously reduced
the case of the cluster nozzle is generally shorter with small orifices and exhaust gas recirculation.
than that in the case of the reference nozzle. The The BSFC, HC and smoke levels stay pretty much
rate of heat release is also higher for the cluster the same with different NOx levels. It seems that a
nozzle. The combustion period is shortened. It change in NOx, which is achieved by a change in
seems that the cluster has better fuel atomization, EGR, has no effect on BSFC, HC and smoke,
fuel evaporation, and air entrainment with smaller which is different from what is seen with conven-
orifices. tional injection timings. There are two strong ef-
fects with the increase of already high EGR for
early injection strategy. The first effect is dilution of
oxygen with high EGR, which has a negative effect
for BSFC, HC and smoke emissions and the sec-
ond one is a longer ignition delay with higher EGR
(ignition closer to TDC), which has a positive effect
for them. Because of these effects the tradeoffs of
BSFC, HC and smoke with NOx were reduced for
early injection timings under part load conditions.
Fig. 2: Pressure curves and heat release for TP1:
1400rpm, 900bar rail pressure, -12° CA aTDC SOI,
4.5bar IMEP, 4g/kg_fuel NOx.
In Premixed charge compression ignition
(PCCI), fuel is injected very early to produce a
premixed fuel-air charge before ignition. It requires
a large amount of cooled EGR to delay the ignition
timing, which lowers the combustion temperature.
The results are discussed for an early injection
timing of -27°CA aTDC with 600bar rail pressure
for different EGR rates under TP1. The results for Fig. 3: BSFC, HC and Smoke with different EGR for
smoke, HC and fuel consumption are shown in TP1: 1400rpm, 600bar rail pressure, -27° CA aTDC SOI.
Fig.3. The cluster having small orifices is regarded Cluster 14x158/158_10° was also used to in-
as a promising approach to lower fuel consumption vestigate effects of rail pressure and was com-
because the sprays from clusters have a greater pared with the reference nozzle. The results for rail
mass of entrained ambient gas and more mass of pressure variation under TP1 are shown in Fig.4.
fuel vapor compared to the reference nozzle. The The graph on the top shows smoke emission for
BSFC (brake specific fuel consumption) of the different rail pressures at an SOI of -5° CA aTDC.
cluster is lower than the reference nozzle. In PCCI The graphs at the center and bottom show smoke
for different SOI with 600bar and 900bar rail pres-
sure respectively. All the results are for TP1 with
NOx emission index of 4. The cluster shows higher
smoke than the reference nozzle under conven-
tional injection timing for TP1 because the spray
from a cluster with a shorter spray tip penetration
loses momentum near the piston bowl. But the
cluster shows improved smoke emission with high-
er injection pressures. With the increase of injec-
tion pressure, the cluster shows a potential to re-
duce, to some extent, the adverse effects on spa-
tial distribution of spray due to better fuel atomiza-
tion and evaporation. A combination of high pres-
sure injection and clusters with small orifices could
be one of the alternative hardware to achieve lean
combustion. Clusters with high pressure injection
have improved fuel consumption and emissions as
better fuel atomization and evaporation are
achieved, while holding momentum near piston Fig. 5: Smoke with different rail pressures for TP2:
1400rpm, 10.5bar IMEP, 4.5g/kg_fuel NOx
bowl and maintaining the penetration of the spray.
The results for rail pressure variation under TP2 Conclusion
are also shown in Fig.5. The graph shows smoke A combination of high pressure injection and
of different SOI with 1200bar and 1500bar rail multi-hole nozzle with small orifices could be one
pressure respectively. The cluster shows higher of the alternative hardware configurations to
smoke than the reference nozzle with 1200bar rail achieve lean combustion. Ignition delay of the clus-
pressure but the cluster with the increase of injec- ter nozzles is shorter and the initial rate of heat
tion pressure show similar smoke to the reference release and the maximum rate of heat release of
nozzle. diffusion combustion are higher than the conven-
tional nozzle. The cluster has low smoke level with
high injection pressures, despite the experiments
being performed with a wide piston bowl without
optimized swirl level.
Acknowledgments
This work was financially supported by General
Motors R&D. The authors would like to thank the
working group of the GM Collaborative Research
Lab at the RWTH Aachen University for their sup-
port and contribution.
References
[1] Nishida, K., Nomura, S. and Yuhei, M., 10th Interna-
tional Congress on Liquid Atomization and Spray
Systems, Kyoto, Japan, August 2006. Paper ID
ICLASS06-171.
[2] Gao, J., Matsumoto, Y. and Nishida, K, SAE Tech-
nical Paper 2007-01-1889, (2007).
[3] Zhang, Y., Nishida, K., Nomura, S. and Ito, T., SAE
Technical Paper 2003-01-3115, (2003).
[4] Zhang, Y., Nishida, K., Nomura, S. and Ito, T., Ato-
mization and Sprays, 16:35-49(2006).
[5] Adomeit, P., Rohs, H., Korfer, T. & Busch, H., Spray
Interaction and Mixture Formation in Diesel Engines
with Grouped Hole Nozzles, THIESEL Conference
on Thermo- and Fluid Dynamic Processes in Diesel
Fig. 4: Smoke with different rail pressures for TP1: Engines, Valencia, Spain, 2006.
1400rpm, 4.5bar IMEP, 4g/kg_fuel NOx. Top: Rail pres- [6] Dohle, U.; Kruger, M.; Naber, D.; Stein, J.O. & Gau-
sure variation for -5° CA aTDC SOI, Center and Bottom: thier, Y., Results of Combustion Optimization by Use
SOI variation for 600bar and 900bar rail pressure of Multihole Nozzles in Modern Passenger Car Di-
esel Engines, 27. Internationales Wiener Motoren-
symposium, Vienna, Austria, 2006.
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