Abstract
Natural gas, a fuel abundant in nature, cannot be used by itself in conventional diesel engines because of its low cetane number. However, it can be used as the primary fuel with ignition by a pilot diesel spray. This is called dual-fuelling. The gas may be introduced either into the inlet manifold or, preferably, directly into the cylinder where it is injected as a short duration, intermittent, sonic jet. For accurate delivery in the latter case, a constant flow-rate from the injector is required into the constantly varying pressure in the cylinder. Thus, a sonic (choked) jet is required which is generally highly under-expanded. Immediately at the nozzle exit, a shock structure develops which can provide essential information about the downstream flow. This shock structure, generally referred to as a “barrel” shock, provides a key to understanding the full injection process. It is examined both experimentally and numerically in this paper.
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Abbreviations
- A :
-
Area (m2)
- CFD:
-
Computational fluid dynamics
- CI:
-
Compression-ignition
- D :
-
Diameter (m)
- DF:
-
Dual-fuel
- HPCR:
-
High-pressure common-rail
- M :
-
Mach number
- NG:
-
Natural gas
- SI:
-
Spark-ignition
- SOI:
-
Start of injection
- UHC:
-
Unburned hydrocarbons
- V :
-
Volume (m3)
- x :
-
Distance from the nozzle (m)
- ρ :
-
Density (kg/m3)
- γ :
-
Ratio of specific heats
References
Abd Alla, G.H., Soliman, H.A., Badr, O.A., Abd Rabbo, M.F.: Effect of pilot fuel quantity on the performance of a dual fuel engine. SAE Paper 1999-01-3597 (1999)
Ashkenaz H., Sherman F.S.: Rarefied Gas Dynamics, vol. 1. Academic Press, New York (1966)
Clement, S., Rathakrishnan, E.: Characteristics of sonic jets with tabs. Shock Waves 15(3–4) (2006)
Hodgins, K.B., Hill, P.G., Ouellette, P., Hung, P.: Directly injected natural gas fuelling of diesel engines. SAE Paper 961671 (1996)
Johansson, L., Lundqvist, V.: CFD Simulation of Laminar Methane-Air Diffusion Flame. School of Mechanical and Manufacturing Engineering, UNSW (2002)
Karim G.A., Jones, W., Raine, R.R.: An examination of the ignition delay period in dual fuel engines. SAE Paper 892140 (1989)
Lacerda, N.L.: On the Start up of Supersonic Underexpanded Jets. Ph.D. Thesis, Graduate Aeronautical Laboratories, California Institute of Technology (1987)
Li, G., Ouellette, P., Dumitrescu, S., Hill, P.G.: Optimization study of pilot-ignited natural gas direct-injection in diesel engines. SAE Paper 1999-01-3556 (1999)
Miao, H.: Fundamental Studies of combustion phenomena in dual fuel engines. Ph.D. Thesis, School of Mechanical and Manufacturing Engineering, UNSW (2001)
Naboko I.M., Bazhenova T.V., Opara A.I., Belavin V.A.: Formation of a Jet of Shock-heated Gas Outflowing into evacuated space. Astronaut. Acta 17, 653–658 (1972)
Radulescu M.I., Law C.K.: The transient start-up of supersonic jets. J. Fluid Mech. 578, 331–369 (2007)
Rubas, P.J., Paul, M.A., Martin, G.C., Coverdill, R.E., Lucht, R.P., Peters, J.E., del Vecchio, K.A.: Methane jet penetration in a direct-injection natural gas engine. SAE Paper 980143 (1998)
Zakrzewski, S.: A numerical and experimental investigation of high-speed liquid jets—their characteristics and dynamics. Ph.D. Thesis, School of Mechanical and Manufacturing Engineering, UNSW (2001)
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Communicated by B.W. Skews.
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White, T.R., Milton, B.E. Shock wave calibration of under-expanded natural gas fuel jets. Shock Waves 18, 353–364 (2008). https://doi.org/10.1007/s00193-008-0158-6
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DOI: https://doi.org/10.1007/s00193-008-0158-6