Engineering Abstracts 1950

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Engineering Abstracts from 1950

Explosion of Empty Diesel-oil Fuel Tank

The vapours of petrol, when mixed with the proper proportion of air, are highly explosive, a fact which is known to most men whose work requires them to handle this fuel. In some quarters, however, there seems to be an impression that the vapours of Diesel oil are not dangerous. This is a fallacy which , in one recent casualty , caused the death of a workman who was attempting to weld a leak in a Diesel-oil tank . As regards the explosiv equalities of Diesel-oil vapours, these are of approximately the same order as those of petrol.

The reason that Diesel oil is safer to handle than petrol is that it is not as volatile. Consequently the liquid does not evaporate ai readily, and , therefore, at any given temperature, petrol will evolve a greater quantity of fumes than Diesel oil.

When, however, due to heat or other circumstances, Diesel oil has evaporated, its vapours are as dangerous as those of petrol and have only to be mixed with the correct proportion of air to form a combination merely a waiting a source of ignition to explode. In the case referred to, an un inspected fishing vessel, powered with Dieselmotors, developed a leak in one of its fuel tanks.

A welder was sent for to repair the leak. As preparation for his operations, the tank was emptied of all fuel, but no attempt was made to gas-free it. The welder, who was equiped with a petrol torch for welding the tank, seated him self on a stool at the end of the tank and prepared to weld the defective seam.

Shortly after the work was begun an explosion occurred which knocked a nearby crew member down without injuring him to any extent and threw the welder against a column in the vessel, fracturing his skull.

A fire ensured and due to the heat, gas, and smoke, the compartment containing the tanks could not be entered until the arrival of the town fire department approximately 10 or 15 minutes later, at which time firemen with gas masks extricated the welder from the tank room, placed him in an ambulance, and rushed him to the local hospital where he died approximately 10 hours later. The lesson from this casualty is obvious— no tank which has contained oil fuel, even Bunker C , should be worked on with a welding torch until it has been gas-freed .

— Marine Engineering and Shipping Review, Vol. 55, September 1950, p. 80.

Diesel Engine Research

This paper reviews Diesel engine research carried out at the Diesel Research Laboratory of Caterpillar Tractor Co. under the sponsorship of the author as Director of Research. For many years intensive effort has been made to understand the combustion process in this type of engine by a better knowledge of the fundamentals of ignition and the mechanism of the combustion process, and this study has been developed in the laboratory on a competitive basis. Originally six combustion systems were put to trial and a modified precombustion-chamber engine won the palm of victory on the basis o f its ability to maintain uniformity over extended periods of operation.

Briefly, the character of the comparative combustion studies followed two general classifications: (1) visual comb ustion studies; (2) study of combustion-chamber deposits. In order to make extended studies of the combustion phenomena by visual means, a quartz window was designed to achieve maximum cleanliness without the distraction of soot condensation on the cold windows.

The author describes the precombustion-chamber process, and deals with the composition of combustion gases, flame duration , temperature distribution, the mechanism of ignition, and comb ustion-chamber deposits. He also discusses the development of fuel-injection equipment, pretiming, precalibrating , and the evolution of the fuel pump; he describes the characteristics of several types of check valve and fuel valve, and the fuel-pump control of engine torque characteristics. Spray characteristics and the flow through the fuel-valve orifice are also examined.

Comments are made upon materials for cylinder liners and piston rings, and the effect of fuel in clusionson cylinder wear; lubrication is also considered. It is believed that excellent performance has been achieved in the precombustion-chamber engine with aminimum of complication in the fuel-injection equipment, and that the development of this principle of combustion has not yet reached its limit of progress.

— James Clayton Lecture by C. G. A. Rosen, read at a meeting of The Institution of Mechanical Engineers, 14th November 1950.