Under the Vickers system of mechanical fuel injection, there is, of course, no introduction of very highly compressed air, and, consequently, first ignition is rendered easier. From this, it will at once be seen that an oil possessing a high flash point can be more easily burned in the Vickers engine than in the ordinary Diesel, with the necessary adjunct of an air compressor. Provision is also made (should the type of fuel used require it) for a higher temperature of compression, and such oils are, therefore, much more easily dealt with than in the ordinary Diesel engine.
From what I have already said, it will be evident to the reader that it is only a question of time for air spraying, with its attendant use of the compressor, to become a thing of the past.
The mechanism involved by the adoption of the new system of fuel injection developed by Messrs. Vickers is exceptionally simple. It consists of a small fuel pump, such as is ordinarily used for pumping fuel, a reservoir or accumulator of novel form to retain the charge, and a valve with a special nozzle to admit the fuel in the form of a fine spray into the cylinder. The accumulator, I may here mention, is merely a tube, flattened slightly on the sides, and of sufficient length, when the oil is forced into it, to enable it to yield and store up a charge of fuel at the required high pressure, as explained in the next paragraph.
The principal feature of the system (and the secret of its great success) is the very high pressure at which the oil is injected into the cylinder. This pressure is kept up at about 4,000 lb. the square inch, so that the oil fuel, when it enters the cylinder and encounters the hot compressed air therein, is in the form of a very finely atomized mist, a conjunction of circumstances most favourable for ignition. As in all great inventions, the simplicity of the arrangement is not the least of its merits.
This somewhat rough, yet brief, outline will suffice to explain the astonishing success of the Vickers heavy oil engine, but, if the whole history of these (and other) noteworthy experiments could be written, a highly interesting story would be produced, showing indomitable perseverance in the face of discouragement, difficulty, and very heavy expense.
I have avoided touching upon the ordinary kerosene engines, for I imagine they are too well known to need more than passing reference here; nor have I gone into the details concerning the advent of the ordinary Diesel engine, which was a German invention.
I have preferred rather to deal with a British invention which is already revolutionizing oil engine construction generally, and which, obviously, has limitless fields open to it.
CHAPTER IX
PETROLEUM IN ENGLAND
There will be no chapter in this little treatise which will be more carefully perused than the present one, for the subject is of direct interest to every reader, whether actually associated with the search for oil or not. To-day, as I have already mentioned in another chapter, this country is dependent for practically the whole of its petroleum requirements upon foreign oil-producing countries, and though ample evidence is forthcoming to suggest that there are possibilities of obtaining liquid oil in England—in fact, many years ago this was actually obtained in not inconsiderable quantities—it is very strange that only recently have serious efforts been made in the direction of systematic search for the valuable liquid.
That large quantities of petroleum can be produced in this country is agreed by all who have given the subject more than passing thought; the question is, by what means shall this production be brought about. While it is problematical as to the amount of commercial success which will attend the present search for liquid oil, though those who are most competent to judge believe that large stores of liquid oil will be found, it is already certain that there are vast possibilities in England for the production of petroleum from the treatment of the bituminous shales which freely abound in many parts.