Investigation of the Influence of Injection Rate Shaping on the Spray Characteristics in a Diesel Common Rail System Equipped with a Piston Amplifier

[+] Author and Article Information
J. Benajes, S. Molina, V. Soare

CMT-Motores Térmicos,  Universidad Politécnica de Valencia, Valencia, Spain

R. Payri1

CMT-Motores Térmicos,  Universidad Politécnica de Valencia, Valencia, Spainrpayri@mot.upv.es


Corresponding author.

J. Fluids Eng 127(6), 1102-1110 (Jul 27, 2005) (9 pages) doi:10.1115/1.2062767 History: Received July 21, 2004; Revised July 27, 2005

The quality of the mixing process of fuel and air in a direct injection diesel engine relies heavily on the way the spray develops when injected into the combustion chamber. Among other factors, the spray development depends on the injection rate of the fuel delivered by the injector. The paper presents a study, at both a macroscopic and microscopic level, of a Diesel spray generated by a common-rail injection system featuring a piston pressure amplifier. By modifying the timing and the duration of the injector and amplifier piston actuation, it is possible to obtain high injection pressures up to 180MPa, and different shapes for the injection rate, which would not be achievable with a regular common rail injection system. The spray evolution produced by three different injection rate shapes (square, ramp, and boot) has been investigated in an injection test rig, by means of visualization and PDPA techniques, at different injection conditions. The main conclusions are the important effect on spray penetration of the initial injection rate evolution and the small influence of the maximum injection pressure attained at the end of the injection event. Smaller or even negligible effects have been found on the spray cone angle and on the droplet Sauter mean diameter.

Copyright © 2005 by American Society of Mechanical Engineers
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Figure 1

Common rail injection system with piston amplifier

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Figure 2

“Square,” “ramp,” and “boot” type ideal injection rates

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Figure 3

Pressure evolution at the injector and piston energizing signal

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Figure 4

Actual injection rate shapes

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Figure 5

The rig’s testing section; there can also be noticed the laser beams for PDPA measurement, the device collecting the second spray, and a dimension for scaling

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Figure 6

PDPA measurement positions

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Figure 7

Shadography image example for “square,” “ramp,” and “boot” (in this order, starting from above), corresponding to 1ms after start of injection, and the test conditions from Fig. 9

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Figure 8

Injection rate, spray cone angle, and tip penetration comparison: Prail=35.5MPa, Pinj=100MPa, ET=1.6ms

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Figure 9

Effect of different rate shapes and energizing times; Prail=35.5MPa, Pinj=100MPa

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Figure 10

Effect of different injection pressures, boot mode

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Figure 11

On-axis PDPA results, 20 and 50mm from injector orifice

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Figure 12

Off-axis PDPA results, 20mm from injector orifice, 1.5 and 3mm radial distance

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Figure 13

Effect of injection pressure on droplet size



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