0
Internal Combustion Engines

Diesel Injector Coking: Optical-Chemical Analysis of Deposits and Influence on Injected Flow-Rate, Fuel Spray and Engine Performance

[+] Author and Article Information
S. d’Ambrosio

 Dipartimento di Energetica, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129, Torino, Italy

A. Ferrari1

 Dipartimento di Energetica, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129, Torino, Italyalessandro.ferrari@polito.it

A process that rounds off the inlet radius of the holes and improves hole wall roughness. The hydro grinding level (He) is defined as the ratio of the difference between injected mass flow-rates after and before the process to the value of the injected flow-rate before hydro grinding.

1

Corresponding author.

J. Eng. Gas Turbines Power 134(6), 062801 (Apr 12, 2012) (14 pages) doi:10.1115/1.4005991 History: Received June 15, 2011; Revised December 07, 2011; Published April 09, 2012; Online April 12, 2012

The physical origin of injector coking in diesel engines has been clarified and the most critical design parameters and operating variables pertaining to the occurrence of the phenomenon have been identified. Fouling has been shown to be affected by many factors, such as injector temperature, nozzle configuration, hole diameter and conicity as well as fuel composition. Optical and scanning electron microscope (SEM) analyses have been conducted both inside and outside injectors of different type and four locations have been identified as the main deposition sites. Furthermore, different coking typologies, i.e., dry and wet coking, have been assessed and discussed. Energy Dispersive X-ray (EDX) spectroscopy images of the deposits on the spray hole walls have revealed that minute quantities of Zn catalyze the coking reactions to a great extent. Significant quantities of Zn have also been found in the injector deposits. An extensive experimental test campaign has been carried out at the engine test bench with different nozzle setups in order to evaluate performance deterioration after different ageing procedures. The effects of both the Zn concentration in the fuel and running time have been assessed separately on the fouling rate. Injection rate time histories have been acquired at the hydraulic test rig, under different working conditions, for both new and aged injectors. The experimental changes in the EVI profiles subsequent to fouling have been analyzed and related to the corresponding variations in engine power measured at the engine test bench. A previously developed combustion multi-zone diagnostic model has also been applied to gain a further insight into the cause and effect relationships between the experimental in-cylinder pressure time histories and engine-out emissions.

Copyright © 2012 by American Society of Mechanical Engineers
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Figure 6

Coking deposits on type 1 injectors: (a) ‘dry’ sample and (b) ‘wet’ sample

Grahic Jump Location
Figure 7

Mass spectrography of the deposits on the nozzle tip with zinc doped diesel fuel ([Zn] = 1 ppm)

Grahic Jump Location
Figure 8

Effect of [Zn] on the percentage mass composition of deposits on the nozzle tip

Grahic Jump Location
Figure 9

Full load performance for Engine 1 with type 1 and type 2 injectors (the quantities are normalized with respect to the “After injector run-in” values)

Grahic Jump Location
Figure 10

Fuel consumption at full load for type 1 injectors (fc is normalized with respect to the “After injector run-in” value)

Grahic Jump Location
Figure 11

Type 1 injectors: soot-NOx trade off (a) and NOx versus λ (b) at n = 2000 rpm and bmep = 5 bar

Grahic Jump Location
Figure 25

MIES images of the spray at prail  = 800 bar, ET = 690 μs (new nozzle on the left, aged nozzle on the right)

Grahic Jump Location
Figure 26

Spray penetration versus t (prail  = 1600 bar, ET = 840 μs)

Grahic Jump Location
Figure 27

Spray angle versus t (prail  = 1600 bar, ET = 840 μs)

Grahic Jump Location
Figure 18

Engine 2, type 3 injectors at n = 2500 rpm and bmep = 8 bar: heat release rate (a), soot (b), CO (c), and charge thermodynamic evolution in the φ-T diagram (d)

Grahic Jump Location
Figure 19

Type 1 injectors: (a) prail  = 800 bar, ET = 690 μs and (b) prail  = 1600 bar, ET = 840 μs

Grahic Jump Location
Figure 20

EMI characteristics of the Type 1 injectors at different rail pressures after ageing

Grahic Jump Location
Figure 21

CD at prail  = 500 bar as a function of the vehicle covered distance (type 2 injectors)

Grahic Jump Location
Figure 22

CD at prail  = 500 bar after Bosch ageing cycles (type 2 injectors)

Grahic Jump Location
Figure 23

Type 3 injector in cylinder 3 (inner cylinder), prail  = 1000 bar: (a) ET = 200 μs and (b): ET = 1000 μs.

Grahic Jump Location
Figure 24

MIES images of the spray at prail  = 1600 bar, ET = 840 μs (new nozzle on the left, aged nozzle on the right)

Grahic Jump Location
Figure 1

The spray visualization test equipment

Grahic Jump Location
Figure 2

Bosch ageing base load profile

Grahic Jump Location
Figure 3

Deposits on the needle of a type 1 injector

Grahic Jump Location
Figure 4

Deposits on the nozzle tip: (a) optical analysis (type 3) and (b) SEM analysis (type 1)

Grahic Jump Location
Figure 5

Coking deposits for type 1 injector: (a) at the injection hole outlet and (b) on the inner hole surface

Grahic Jump Location
Figure 12

Type 2 injectors: soot-NOx trade off (a) and NOx versus λ (b) at n = 2000 rpm and bmep = 5 bar

Grahic Jump Location
Figure 13

Effect of K-factor on bsfc after run-in (n = 2000 rpm and bmep = 5 bar)

Grahic Jump Location
Figure 14

Type 1 versus type 2 injectors: (a) soot-NOx trade off and (b) NOx versus λ at n = 2500 rpm and bmep = 8 bar

Grahic Jump Location
Figure 15

Type 3 injectors: (a) soot-NOx trade-off and (b) bsfc versus λ at n = 2000 rpm and bmep = 5 bar

Grahic Jump Location
Figure 16

Type 3 injectors: (a) soot-NOx trade-off and (b) bsfc versus λ at n = 2750 rpm and bmep = 12 bar

Grahic Jump Location
Figure 17

{Soot} - {NOx } trade-off for type 3 injectors: (a) n = 2000 rpm, bmep = 5 bar and (b) n = 2750 rpm, bmep = 12 bar

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