0
Research Papers: Internal Combustion Engines

Numerical-Experimental Study and Solutions to Reduce the Dwell-Time Threshold for Fusion-Free Consecutive Injections in a Multijet Solenoid-Type CR System

[+] Author and Article Information
Andrea E. Catania, Alessandro Ferrari, Ezio Spessa

 IC Engines Advanced Laboratory, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy

J. Eng. Gas Turbines Power 131(2), 022804 (Dec 22, 2008) (14 pages) doi:10.1115/1.2938394 History: Received April 14, 2007; Revised April 10, 2008; Published December 22, 2008

In “multijet” common rail (CR) diesel injection systems, when two consecutive injection current pulses approach each other, a merging of the two injections into a single one can occur. Such an “injection fusion” causes an undesired excessive amount of injected fuel, worsening both fuel consumption and particulate emissions. In order to avoid this phenomenon, lower limits to the dwell-time values are introduced in the control unit maps by a conservatively overestimated threshold, which reduces the flexibility of multiple-injection management. The injection fusion occurrence is mainly related to the time delay between the electrical signal to the solenoid and the nozzle opening and closure. The dwell-time fusion threshold was found to strongly decrease particularly with the nozzle closure delay. A functional dependence of the nozzle opening and closure delays on the solenoid energizing time and nominal rail pressure was experimentally assessed, and the injection temporal duration was correlated to the energizing time and rail pressure. A multijet CR injection-system mathematical model that was previously developed, including thermodynamics of liquids, fluid dynamics, mechanics of subsystems, and electromagnetism equations, was applied to better understand the cause and effect relationships for nozzle opening and closure delays. In particular, numerical results on the time histories of delivery- and control-chamber pressures, pilot- and needle-valve lifts, and mass flow rates through Z and A holes were obtained and analyzed to highlight the dependence of nozzle opening and closure delays on injector geometric features, physical variables, and valve dynamics. The nozzle closure delay was shown to strongly depend on the needle dynamics. Parametric numerical tests were carried out to identify configurations useful for minimizing the nozzle closure delay. Based on the results of these tests, a modified version of a commercial electroinjector was built, so as to achieve effectively lower nozzle closure delays and very close sequential injections without any fusion between them.

Copyright © 2009 by American Society of Mechanical Engineers
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Figure 2

Total injected-volume fluctuations

Grahic Jump Location
Figure 3

pinj,in, pdc, and Qinj for a high SOPI pdc level

Grahic Jump Location
Figure 4

pinj,in, pdc, and Qinj for a low SOPI pdc level

Grahic Jump Location
Figure 5

pinj,in, Qinj, and EC at a main-post injection fusion

Grahic Jump Location
Figure 6

Single-injection pinj,in, Qinj, EC, and characteristic time intervals

Grahic Jump Location
Figure 7

Predicted lifts (lpv, ln) and pressures (pcc, pdc)

Grahic Jump Location
Figure 8

Predicted needle velocity

Grahic Jump Location
Figure 9

Predicted flow rates through A and Z holes

Grahic Jump Location
Figure 10

Numerical versus experimental pinj,in and Qinj

Grahic Jump Location
Figure 11

Predicted lifts (lpv, ln) and pressures (pcc, pdc)

Grahic Jump Location
Figure 12

Predicted flow rates through A and Z holes

Grahic Jump Location
Figure 13

Numerical versus experimental pinj,in and Qinj

Grahic Jump Location
Figure 14

Predicted lifts (lpv, ln) and pressures (pcc, pdc)

Grahic Jump Location
Figure 15

Predicted flow rates through A and Z holes

Grahic Jump Location
Figure 16

NOD dependence on ET and prail

Grahic Jump Location
Figure 17

NCD dependence on ET and prail

Grahic Jump Location
Figure 18

Numerical versus experimental pinj,in and Qinj

Grahic Jump Location
Figure 19

Predicted lifts (lpv, ln) and pressures (pcc, pdc)

Grahic Jump Location
Figure 20

Predicted flow rates through A and Z holes

Grahic Jump Location
Figure 21

Numerical versus experimental pinj,in and Qinj

Grahic Jump Location
Figure 22

Predicted lifts (lpv, ln) and pressures (pcc, pdc)

Grahic Jump Location
Figure 23

Predicted flow rates through A and Z holes

Grahic Jump Location
Figure 24

Experimental ITL dependence on ET and prail

Grahic Jump Location
Figure 25

IFT predictive correlations versus experimental data

Grahic Jump Location
Figure 26

Predicted ln, pcc, and pdc time histories for a double injection with flow-rate fusion: prail=1000bar, ETmain=1000μs, ETpost=400μs, DT=665μs

Grahic Jump Location
Figure 27

IFT dependence on ET and prail

Grahic Jump Location
Figure 28

Reference conditions for IFT reduction study: ETmain=1000μs, ETpost=400μs

Grahic Jump Location
Figure 29

Needle and control-piston mass effect on IFT

Grahic Jump Location
Figure 30

Needle-spring stiffness effect on IFT

Grahic Jump Location
Figure 31

Needle-spring preload effect on IFT

Grahic Jump Location
Figure 32

Needle mechanical stroke-end effect on IFT

Grahic Jump Location
Figure 33

Numerical versus experimental flow-rate time patterns for the modified injector: prail=1250bar, ETmain=1000μs, ETpost=400μs, DT=750μs

Grahic Jump Location
Figure 34

IFT versus ETmain at prail=1250bar for two needle mechanical stroke-end limited maximum lifts

Grahic Jump Location
Figure 35

Control chamber

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In