Experimental Research on Explosion in the Diesel Engine Starting Air Manifold

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概要

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• In recent years, almost all large marine diesel engines were built for starting by compressed air. Any critical damage to starting air system will make engine start impossible and, consequently, put the ship at risk of grounding or colliding. The damages to starting air systems that we have experienced so far were nearly all due to explosions in starting air manifolds. Accordingly, such accidents also pose potential risk of resulting in injuries or even death of crew because of their nature of explosion, and there were, actually, some examples. Such explosions tend to occur at the moment of starting astern after a long voyage, such as during ahead-astern trials for preparing to enter port, or when engaging crash astern in order to avoid colliding. The average frequency of serious explosions was estimated to be about 10 per year among the fleet classed with major classification societies. Until quite recently the cause of such explosions was said to be the backfire from cylinders due to malfunction of starting valves. Some preventive measures based on this view were required to take in 1972 by International Association of Classification Societies (IACS). However, the authors recently realised that, based on the fact that several latest explosions occurred before fuel injection, something rather than backfire could be the real cause. The real cause was determined to be the high temperature in the end of starting air manifold, resulting from rapid compression by piston-like action of compressing air. Air originally inside manifold will be swept to the end of the manifold by high pressure air from the air tank when the main starting valve is opened and is rapidly compressed, quickly reaching a temperature as high as around 400℃, especially during astern starting process. Such a high temperature could ignite the oily sludge deposited on the inner surface of the manifold and, in some conditions, cause a powerful explosion.

• 財団法人日本海事協会の論文

著者

• Sasaki Senichi

  Research Institute

• Song Yuzhong

  Research Institute

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