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Research Papers: Internal Combustion Engines

Experimental Investigation of Dynamics Effects on Multiple-Injection Common Rail System Performance

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

 IC Engines Advanced Laboratory, Dipartimento di Energetica, Politecnico di Torino, C.so Duca degli Abruzzi, 24 10129–Torino, Italy

J. Eng. Gas Turbines Power 130(3), 032806 (Mar 28, 2008) (13 pages) doi:10.1115/1.2835353 History: Received April 13, 2007; Revised November 09, 2007; Published March 28, 2008

Fundamental aspects of Common Rail (CR) fuel-injection-system dynamics were investigated, paying specific attention to the wave propagation induced pressure oscillations and to their relationships with the system control parameters and multiple-injection performance. A detailed experimental analysis of the pressure-wave propagation phenomena in a last-generation CR Multijet equipment of the solenoid type was carried out on a high performance new test-bench Moehwald-Bosch MEP2000-CA4000 under real engine simulated conditions. The experimental results include pressure time histories in the rail and at the injector inlet, as well as flow-rate patterns, for both single and multiple injection events. The measured volume of fuel injected at each injection pulse is also reported. The analysis of the system oscillating behavior was carried out with the support of a simple lumped parameter model. Such a model was shown to be capable of predicting the main frequencies of the hydraulic circuit and their dependence on the geometrical parameters. The good agreement between the outcome of this simple model and the experimental data also substantiated the reliable authors’ interpretation of the primary cause and effect relations underlying the complex flow phenomena occurring in the system. A refined computational model was developed and validated in a parallel work, providing a hydrodynamic analysis tool that is complementary to experimentation and also a means of hydraulic-system layout design and optimization. Finally, the mutual fluid-dynamic interactions taking place between consecutive injection events by distinct injectors of the same system are investigated in addition to the difference in dynamics of valve covered orifice and Minisac-nozzle injectors. Cycle-to-cycle variations in system performance were also investigated.

Copyright © 2008 by American Society of Mechanical Engineers
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Figures

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Figure 2

Test-bench layout and instrumentation

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Figure 3

CR injection-system layout and measuring instruments

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Figure 5

EMI2 operation scheme

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Figure 6

EVI operation scheme

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Figure 7

Pressure wave in the EVI measuring tube

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Figure 8

Reference frame integral with the compression wave in the EVI measuring tube

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Figure 9

Pressure, flow rate, and current time histories for ET=1400μs

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Figure 10

Pressure waves (a) at the start and (b) at the end of injection

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Figure 11

System response for ET=700μs

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Figure 12

System response for ET=400μs

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Figure 13

Injected volumes for pilot and main injections at prail=1000bars

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Figure 14

System response at prail=1000bars, ET=400∕600μs, and DT=1825μs

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Figure 15

System response at prail=1000bars, ET=400∕600μs, and DT=2300μs

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Figure 16

Comparison between injected flow rates for different DT and same ET

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Figure 17

Injected volumes of pilot and main injections at prail=1250bars

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Figure 18

System response at prail=1250bars, ET=400∕900μs, and DT=1755μs

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Figure 19

System response at prail=1250bars, ET=400∕900μs, and DT=2230μs

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Figure 20

Comparison between main injected flow rates at prail=1250bars

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Figure 21

Rail-pipe-injector LC model

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Figure 22

Pressure distributions at Injector 1 inlet and in the rail: (a) main injection only and (b) pilot and main injections

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Figure 23

Main-injection volume deviations for different rail pressures

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Figure 24

Main-injection volume deviations for different engine speeds

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Figure 25

(a) VCO- and (b) Minisac-nozzle geometries

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Figure 26

VCO versus Minisac nozzle: (a) injected flow rate and (b) inlet pressure

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Figure 27

Cycle-to-cycle variations: Minisac nozzle, prail=1000bars, and n=2000rpm

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Figure 28

Cycle-to-cycle variations: Minisac nozzle, prail=500bars, and n=1500rpm

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Figure 29

Cycle-to-cycle variations: Minisac nozzle, prail=1000bars, ET=400∕600μs, and n=1500rpm

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Figure 30

Cycle-to-cycle variations: VCO nozzle, prail=500bars, and n=1500rpm

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