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Research Papers: Internal Combustion Engines

Hydraulic Performance Comparison Between the Newly Designed Common Feeding and Standard Common Rail Injection Systems for Diesel Engines

[+] Author and Article Information
A. Ferrari, F. Paolicelli, P. Pizzo

Department of Energy,
Politecnico di Torino,
Turin 10129, Italy

Contributed by the IC Engine Division of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 28, 2015; final manuscript received December 14, 2015; published online March 22, 2016. Assoc. Editor: Timothy J. Jacobs.

J. Eng. Gas Turbines Power 138(9), 092801 (Mar 22, 2016) (13 pages) Paper No: GTP-15-1378; doi: 10.1115/1.4032644 History: Received July 28, 2015; Revised December 14, 2015

A new-generation common feeding (CF) fuel injection system without rail has been compared with the standard common rail (CR) apparatus for diesel engine passenger cars. The high-pressure pump in the CF apparatus is connected directly to the injectors, and a volume of about 2.5 cm3 is integrated at the pump delivery. Experimental tests on solenoid injectors have been carried out for the CF and CR apparatus at a hydraulic test rig. The dependence of the injected volumes and total injector leakages on the energizing time (ET) of the two systems has been investigated for different rail pressure levels. Furthermore, the measured injected flow-rates of the CF and CR systems have been compared for single and pilot–main injection events. In general, the injection performance of the two systems is very similar, even though the differences occur in the high-pressure transients. The dynamics of the pressure waves changes because the high-pressure hydraulic layouts of the two systems are different, and the propagation and reflection of the rarefaction waves, triggered by the injection events, occur in different ways. A previously developed one-dimensional (1D) code for the CF high-pressure layout has been further validated by means of a comparison with the experimental data. The effects of either a calibrated orifice installed at the pump delivery or an injector-integrated Minirail on the CF performance have been investigated by means of the model. Numerical parametrical tests have also been conducted on the pump-to-injector pipe length. The additional orifices that can be installed in the high-pressure circuit of the CF are effective, provided their diameter is smaller than the diameter of any other orifice inserted in the injector. Furthermore, the presence of a Minirail within the injector has an impact on the injected flow-rates of small injections, such as pilot, pre, after, and post, and also induces a reduction in the energy stored in the pressure waves. Another relevant active damping strategy of the pressure waves for the CF involves shortening the pump-to-injector pipe as much as possible. Finally, the fluid dynamical transients within the solenoid injector have been discussed for the CF and CR systems. The numerical time distributions of the main variables within the injector are shown to be independent of the presence of the rail in the layout.

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References

Figures

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Fig. 1

Standard (a) and innovative (b) pilot-valves schemes

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Fig. 2

CF and CR injection system layouts

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Fig. 3

Comparison of the injected flow-rate and pinj data between the CF and CR systems (pnom = 400 bar and ET = 800 μs)

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Fig. 4

Comparison of the injected flow-rate and pinj data between the CF and CR systems (pnom = 1600 bar and ET = 800 μs)

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Fig. 5

Comparison of the injected flow-rate and pinj data between the CF and CR systems (pnom = 800 bar and DT = 600 μs)

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Fig. 6

Comparison of the EMI injector characteristics (injected volume versus ET) between the CF and CR systems

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Fig. 7

Comparison pf the KMM curves (total injector leakages versus ET) between the CF and CR systems

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Fig. 8

Hydraulic model of the CF system

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Fig. 9

Electrical driving signals of the injector (ET = 800 μs)

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Fig. 20

Pressure at the inlet of the injector for different dor values (pnom = 400 bar and ET = 400 μs)

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Fig. 19

Predicted flow-rates through Z and A holes (pnom = 1000 bar, DTPil–Pre = 1000 μs, and DTPre–Main = 600 μs)

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Fig. 18

Predicted pilot-valve and needle lifts (pnom = 1000 bar, DTPil–Pre = 1000 μs, and DTPre–Main = 600 μs)

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Fig. 17

Injected flow-rate: comparison between the experimental and numerical GI (pnom = 1000 bar, DTPil–Pre = 1000 μs, and DTPre–Main = 600 μs)

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Fig. 16

Injected flow-rate: comparison between the experimental and numerical data (pnom = 400 bar and DT = 150 μs)

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Fig. 15

Injector internal dynamics during a double injection event (pnom = 400 bar and DT 150 μs)

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Fig. 14

Injected flow-rate: comparison between the experimental and numerical data (pnom = 1000 bar and ET = 600 μs)

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Fig. 13

Injector internal dynamics during a single injection event (pnom = 1000 bar and ET = 600 μs)

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Fig. 12

Comparison between the experimental and numerical pinj and GI for the pilot–pre–main injections (pnom = 1000 bar, DTPil–Pre = 500 μs, and DTPre–Main = 600 μs)

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Fig. 11

Comparison between the experimental and numerical pinj and GI for the main–after injections (pnom = 1600 bar and DT = 900 μs)

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Fig. 10

Comparison between the experimental and numerical pinj and GI for the pilot–main injections (pnom = 1600 bar and DT = 300 μs)

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Fig. 21

Pressure at the inlet of the injector for different dor values (pnom = 1600 bar and ET = 800 μs)

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Fig. 22

Pressure in the delivery chamber for different Vdc values (pnom = 400 bar and ET = 400 μs)

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Fig. 23

Pressure in the delivery chamber for different Vdc values (pnom = 1000 bar and ET = 800 μs)

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Fig. 24

Needle valve lift for different Vdc values (pnom = 400 bar and ET = 400 μs)

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Fig. 25

Injected flow-rate for different Vdc values (pnom = 400 bar and ET = 400 μs)

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Fig. 26

Injected flow-rate for different Vdc values (pnom = 1000 bar and ET = 800 μs)

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Fig. 35

CR system: comparison between the numerical and experimental data (pnom = 1600 bar and ET = 800 μs)

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Fig. 36

CF system: comparison between the numerical and experimental data (pnom = 1600 bar and ET = 800 μs)

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Fig. 27

Pressure at the inlet of the injector for different l values (pnom = 1000 bar and ET = 600 μs)

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Fig. 28

Injected flow-rate for different l values (pnom = 1000 bar and ET = 600 μs)

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Fig. 29

Delivery chamber pressure for different l values and with SOIaft in the neighborhood of a local minimum of pDC(t) (pnom = 1600 bar, ETmain = 430 μs, and ETaft = 240 μs)

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Fig. 30

Injected flow-rate for different l values and with SOIaft in the neighborhood of a local minimum of pDC(t) (pnom = 1600 bar, ETmain = 430 μs, and ETaft = 240 μs)

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Fig. 31

Needle lift for different l values and with SOIaft in the neighborhood of a local minimum of pDC(t) (pnom = 1600 bar, ETmain = 430 μs, and ETaft = 240 μs)

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Fig. 32

Delivery chamber pressure for different l values and with SOIaft in the neighborhood of a local maximum of pDC(t) (pnom = 1600 bar, ETmain = 430 μs, and ETaft = 240 μs)

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Fig. 33

Injected flow-rate for different l values and with SOIaft in the neighborhood of a local maximum of pDC(t) (pnom = 1600 bar, ETmain = 430 μs, and ETaft = 240 μs)

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Fig. 34

Needle lift for different l values and with SOIaft in the neighborhood of a local maximum of pDC(t) (pnom = 1600 bar, ETmain = 430 μs, and ETaft = 240 μs)

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Fig. 41

CR versus CF systems: injector internal mechanical variables (pnom = 400 bar and ET = 250 μs)

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Fig. 42

CR versus CF system: flow-rates through holes A and Z (pnom = 400 bar and ET = 250 μs)

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Fig. 37

CR versus CF systems: injector internal mechanical variables (pnom = 1600 bar and ET = 800 μs)

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Fig. 38

CR versus CF system: flow-rates through holes A and Z (pnom = 1600 bar and ET = 800 μs)

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Fig. 39

CR system: comparison between the numerical and experimental data (pnom = 400 bar and ET = 250 μs)

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Fig. 40

CF system: comparison between the numerical and experimental data (pnom = 400 bar and ET = 250 μs)

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