Research Papers: Internal Combustion Engines

Understanding the Acoustic Oscillations Observed in the Injection Rate of a Common-Rail Direct Injection Diesel Injector

[+] Author and Article Information
Julien Manin

Sandia National Laboratories,
Combustion Research Facility,
7011 East Avenue,
Livermore, CA 94551
e-mail: jmanin@sandia.gov

Alan Kastengren

Argonne National Laboratory,
Center for Transportation Research,
9700 South Cass Avenue,
Building 362,
Argonne, IL 60439

Raul Payri

CMT–Motores Térmicos,
Universitat Politecnica de Valencia,
Camino de Vera s/n,
46022 Valencia, Spain

1Corresponding author.

Contributed by the IC Engine Division of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 9, 2012; final manuscript received July 13, 2012; published online October 11, 2012. Editor: Dilip R. Ballal.

This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States. Approved for public release; distribution is unlimited.

J. Eng. Gas Turbines Power 134(12), 122801 (Oct 11, 2012) (10 pages) doi:10.1115/1.4007276 History: Received July 09, 2012; Revised July 13, 2012

Measuring the rate of injection of a common-rail injector is one of the first steps for diesel engine development. The injected quantity as a function of time is of prime interest for engine research and modeling activities, as it drives spray development and mixing, which, in current diesel engines, control combustion. On the other hand, the widely used long-tube method provides results that are neither straightforward nor fully understood. This study, performed on a 0.09-mm axially drilled single-hole nozzle, is part of the Engine Combustion Network (ECN) and aims at analyzing the acoustic oscillations observed in the rate of injection signal and measuring their impact on the real injection process and on the results recorded by the experimental devices. Several tests have been carried out for this study, including rate of injection and momentum, X-ray phase-contrast of the injector, and needle motion or injector displacement. The acoustic analysis revealed that these fluctuations found their origin in the sac of the injector and that they were the results of an interaction between the fluid in the chamber (generally gases) or in the nozzle sac and the liquid fuel to be injected. It has been observed that the relatively high oscillations recorded by the long-tube method were mainly caused by a displacement of the injector itself while injecting. In addition, the results showed that these acoustic features are also present in the spray, which means that the oscillations make it out of the injector, and that this temporal variation must be reflected in the actual rate of injection.

Copyright © 2012 by ASME
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Fig. 1

Equivalent hole diameter along the orifice of the injector

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Fig. 2

Mass flow and momentum flux as a function of time for the “Spray A” injection case

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Fig. 3

Discharge coefficient as a function of Reynolds number for two discharge pressures

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Fig. 4

Area coefficient as a function of Reynolds number for two discharge pressures

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Fig. 5

Sketch of the experimental arrangement to record injector acceleration

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Fig. 6

Phase-contrast imaging experimental arrangement to record needle motion

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Fig. 7

Measured injection pressure (MPa), acceleration (m/s2 ), mass flow rate (g/s), and momentum flux (N) for two injection durations. The difference in time between control volume closure and EOI is also indicated. pinj = 150 MPa; pb = 20 bar.

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Fig. 8

Normalized spectral density of ROI, momentum, acceleration, and line pressure at “Spray A”

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Fig. 9

X-ray beam absorption to show injector oscillations during “Spray A” injection

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Fig. 10

Needle position and speed in the axial direction as a function of time for the “Spray A” case

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Fig. 11

Normalized spectral density of the acceleration, injector oscillations, and needle speed for “Spray A”

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Fig. 12

Schematic of the injector showing the internal fuel tubing and the mechanism to action the needle

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Fig. 13

Normalized spectral density of the ROI, momentum, and acceleration for the large oscillations period during a 4-ms-long injection

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Fig. 14

Projected fuel density in the spray (0.1 mm from exit) as a function of time for “Spray A” injection. The dashed lines represent a period of the main oscillations.




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