Spray Characteristics and Wall Impingement of Diesel-CNG Dual Fuel Jet Using Schlieren Imaging Technique

Abstract—Natural gas for direct-injection (DI) compression ignition (CI) engines is considered to be the best optimized method due to its high volumetric efficiency, high thermal efficiency and low emissions. However, CNG has the penalty of high auto-ignition temperature and lower cetane number. An effective way to use CNG in CI engines is to inject the CNG with a pilot of diesel fuel for ignition purposes. This research is an experimental investigation of the direct injection of CNG jet, diesel spray and combination of fuels (i.e. natural gas with pilot of diesel fuel) in a constant volume chamber using an optical method. The jets were created using two parallel injectors. A low pressure CNG injector (electronic) was used at different injection pressures ranging from 14 bar to 18 bar, while a diesel sprayed injector was used for a high pressure common rail injector ranging from 500 to 700 bar. The Schlieren technique was used for flow visualization and a high speed video camera was used for image acquisition. Series of images of a jet at different time intervals from the beginning of the injection were taken to determine the macroscopic characteristics such as jet penetration rate, jet cone angle and jet tip velocity. The jet radial and height travel along the wall under different injection pressures and temperatures were also measured. Image processing software was developed and used for the analysis.

Index Terms—CNG, Diesel-CNG dual fuel, spray wall impingement, schlieren, image processing.

Mhadi A. Ismael is with the Bahri University, Malaysia (e-mail: xmhadosx@yahoo.com).
M. R. Heikal is with the Universiti Teknologi Petronas, He is now with the Department of Mechanical, Bandar Seri Iskandar, 31750 Tronoh, Malaysia (e-mail: morgan.heikal@petronas.com.my).
M. B. Bahroom is with the Mechnical Engineering Department, University Teknologi Petronas, Boulder, Bandar Seri Iskandar, 31750 Tronoh, Malaysia (e-mail: masrib@petronas.com.my).

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Cite: Mhadi A. Ismael, M. R. Heikal, and M. B. Bahroom, "Spray Characteristics and Wall Impingement of Diesel-CNG Dual Fuel Jet Using Schlieren Imaging Technique," International Journal of Materials, Mechanics and Manufacturing vol. 3, no. 3, pp. 145-151, 2015.