BACK VIEW OF ENGINE
Already a very large number of their engines have been constructed, the approximate brake horse-power produced by same being upwards of 337,600. These engines are of various sizes, ranging from 200 to 2,000 horse-power. The cylinders vary in diameter from 10 to 29 inches, and are arranged to work in groups to suit the power required, and may be either two-stroke or four-stroke cycle. The high temperatures set up in starting the engine are sufficient to ignite the fuel, the introduction of which in a finely-divided condition has been the object of so many experiments at Barrow; and so successful in this direction have Messrs. Vickers been that they are now able to deal satisfactorily, by careful adjustments of the engine to suit the various fuels, with the most troublesome oils.
As already referred to, the elimination of the air compressor constitutes the chief improvement embodied in the Vickers type of engine, seeing that the greatest worry which the Diesel engineer has had to encounter has been this very compressor. Needless to remark, therefore, this feature alone strongly recommends the new system to the experienced man. Further, the power required to drive the compressor above-mentioned is considerable, so that economy is not one of the least results due to its absence.
The principal advantages that can be claimed for the Vickers engine may be summarized as under—
1. Safety in working. (Many accidents have been due to the use of the air compressor.)
2. Weight is saved.
3. Space is saved.
4. Lower air compression in the cylinders for ignition, and economy in air for starting the engine.
5. Reduction in first costs; and
6. Reduction in upkeep expenses.
900 B.H.P. HIGH DUTY REVERSING ENGINE FOR LIGHT CRAFT
1,250 B.H.P. LOW DUTY VICKERS MARINE ENGINE FOR OIL TANK VESSEL
With regard to (4), the low compression claimed is rather interesting, as Messrs. Vickers have successfully demonstrated that, although a high compression temperature is necessary in the ordinary Diesel engine with the usual air spraying compressor, a much lower degree suffices for their mechanical injection system, whilst there is a greater certainty of ignition of the fuel on its first introduction, even with the existence of lower compression in the cylinder. The reason of this is that the spraying air used in the ordinary Diesel is usually compressed to about 60 atmospheres (900 lb. per square inch). What happens when air spraying is practised is this. When the cold air carrying the very high pressure above mentioned enters the cylinder, it necessarily expands, owing to the lower temperature already existent there, and such expansion chills the whole mixture, frequently preventing ignition on the first introduction of the fuel.