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Rudolf Diesel
(18 Mar 1858 - 29 Sep 1913)
German engineer who invented a more energy-efficient internal combustion engine that needed no spark to ignite the fuel-air mixture in the cylinders, but instead produced ignition by high compression.
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The Diesel Engine
by Dr. Rudolf Diesel
From The Library of Original Sources (1915)
[p.226] The Diesel engine has been characterized as the most revolutionary and important development in the field of motive power since the invention of the steam engine by Watt. Its vital importance lies not so much in the fact that it is capable of producing approximately twice as much energy as the steam engine can from the same amount of fuel, but more in the fact that it can be operated with tar and tar oils, derived from coal by coking, and produce more energy than if the coal had been burned under the boiler of a steam engine. In short, after the coal has been coked and the gas, coke, and finer by-products have been removed, the tar and tar oils remaining, when used in a Diesel engine, will produce more energy than could have been secured from the coal itself if used in a steam engine. The Diesel engine, briefly, is an internal combustion engine which uses highly heated, compressed air for ignition, instead of the electric spark, as in the ordinary gasoline engine. The piston, on the down stroke, draws in the ordinary air and on the up stroke compresses this air, against the cylinder head, under a pressure of 500 pounds to the square inch. Air under such pressure acquires a temperature of over 1,000 degrees Fahrenheit and when the air is hottest a jet of finely atomized oil is forced into the cylinder. The oil is ignited and the explosion forces the piston back and the operation is repeated.
By Dr. Rudolf Diesel
Since its first appearance about fourteen years ago, many thousands of Diesel engines have been installed in all kinds of factories in all industrial countries, and also in the remotest corners of the world; proof has thus been obtained that the motor, when properly installed, [p.227] is a reliable machine, whose operation is as satisfactory as the best of other types of engine, and, in general, simpler, owing to the absence of all auxiliary plant and because the fuel can be employed directly in the cylinder of the motor in its original natural condition, without any previous transformatory process.
In 1897, when after four years of difficult experimental work I completed the construction of the first commercially successful motor in the Augsburg Works, it was proclaimed by the numerous engineering and scientific committees and deputations from various countries, who tested the machine, that a higher heat efficiency was attained by it than with any other known heat engine. As a result of subsequent experience in practice, and the gradual improvement in the manufacture, still better results have been obtained, and at the present time the thermal efficiency the motor attains is up to about 48 per cent and the effective efficiency in some cases up to nearly 35 per cent.
Technical knowledge and science are always progressing, and in later days these figures will be even further improved, but in the present state of our knowledge a higher efficiency cannot be reached by any process for changing heat into work; a further advance seems only possible by a new process of conversion, with an essentially novel method of operation which we today cannot conceive.
Therefore the Diesel motor is the engine which develops power from the fuel directly in the cylinder without any previous transformatory process, and in as efficient a manner as, according to the present state of science, seems possible; it is therefore the simplest and at the same time the most economical power machine.
These two conditions explain its success, which lies in the novel principle of its method of operation and not in constructional improvements or alterations to earlier engine types. Naturally the questions of construction, and the careful design of the details, are of considerable moment in a Diesel motor as in every engine; but they are not the cause of the great importance of this motor in the world’s industry.
A further reason for this importance lies in the fact that the Diesel engine has destroyed the monopoly of coal, and has in the most general way solved the problem of the employment of liquid fuel for motive purposes. The Diesel motor has thus become, in relation to liquid fuel, what the steam and gas engine are to coal, but in a simpler and more economical manner; it has by this means doubled the resources of man in the sphere of power development, and found employment for a product of nature which previously lay idle.
[p.228] In consequence thereof the Diesel motor has had a far-reaching effect in the liquid fuel industry, which is now progressing in a way that could not previously be anticipated. I cannot here enlarge on this point, but it may in general be said that owing to the interest which the petroleum producers have taken in this important matter new wells are being constantly opened out, and fresh developments inaugurated, and that from the latest geological researches it has been shown that there is probably as much, and perhaps more, liquid fuel than coal in the earth and, moreover, in much more favorable and more widely distributed geographical positions.
That the undertakings dependent on the petroleum industry have been equally strongly influenced is shown by the marked development which in quite recent times has occurred in the oil transport trade, especially the great development in the number of tank vessels which themselves use the Diesel motor for propulsion.
But the influence of the Diesel engine on the world’s industry does not end here. Already in the year 1899 I employed in my motor the by-products from the distillation of coal, and the manufacture of coke —tar or creosote oil—with the same success as with natural liquid fuel. The quality of these oils was, however, generally unsatisfactory for use in Diesel motors and subject to continual variations. Only recently the interested chemical industries have succeeded in getting the necessary quality, and today this product enters definitely into the sphere of influence of the Diesel motor.
It follows, therefore, that this engine has an important influence on the two further industries—gas and coke manufacture—from which the by-products have now become so important that a great movement is beginning in connection with this question. It is impossible to further discuss this matter here, but one fact arises distinctly from this movement, namely, that the coal which appeared to be threatened by the competition of liquid fuels will, on the contrary, enter into a new and better era of utilization through the Diesel motor. Since tar oil can be employed three to five times more efficiently in the Diesel motor than coal in the steam engine, it follows that coal can be much more economically utilized when it is not burnt barbarously under boilers, or grates, but converted into coke and tar by distillation. The coke is then employed in metallurgical work and for all heating purposes; the valuable products from the tar must be extracted and used in the chemical industries, while the tar oil, and its combustible derivatives, [p.229] and under certain circumstances the tar itself, can be put to exceptionally favorable use in Diesel motors.
It is, therefore, of the greatest interest to employ the largest possible amount of coal in this refined and more economical manner, and thus both coal mining and the related chemical industry come within the influence of the Diesel motor, which is not inimical, but most helpful, to the development of the coal industry. The proper evolution of the fuel question which has already begun and is now progressing rapidly is as follows: On the one side use liquid fuel in Diesel motors, on the other side, gas fuel, also in the form of coke, in gas motors; solid fuel should not be employed at all for power production, but only in the refined form of coke for all other uses of heat in metallurgy and heating. The liquid fuels already mentioned by no means exhaust the list of fuel which may be used for Diesel motors.
It is well known that lignite, whose production is about 10 per cent of that of coal, leaves tar on dry distillation, which, when worked for pure paraffin, leaves as a by-product the so-called paraffin oil. Not all kinds of lignite are suitable for this purpose; nevertheless, so much of this oil is produced that up to now it has supplied, for instance in Germany, a very large proportion of the demand for liquid fuel for Diesel motors. Further, there are to be considered other products available in smaller but noteworthy quantities, such as shale oil, etc.; certain countries, as for instance France and Scotland, have large quantities of them and they are in use in many Diesel engine installations.
But it is not generally known that it is possible to use animal and vegetable oils direct in Diesel motors. In 1900 a small Diesel engine was exhibited at the Paris exhibition by the Otto Company, which, on the suggestion of the French Government, was run on Arachide oil, and operated so well that very few people were aware of the fact. The motor was built for ordinary oils, and without any modification was run on vegetable oil. I have recently repeated these experiments on a large scale with full success and entire confirmation of the results formerly obtained. The French Government had in mind the utilization of the large quantities of arachide, or ground nuts, available in the African colonies and easy to cultivate, for, by this means, the colonies can be provided with power and industries without the necessity of importing coal or liquid fuel.
Similar experiments have also been made in St. Petersburg with [p.230] castor oil with equal success. Even animal oils, such as fish oil, have been tried with perfect success.
If at present the applicability of vegetable and animal oils to Diesel motors seems insignificant, it may develop in the course of time to reach an importance equal to that of natural liquid fuels and tar oil. Twelve years ago we were no more advanced with the tar oils than today is the case with the vegetable oils; and how important have they now become!
We cannot predict at present the role which these oils will have to play in the colonies in days to come. However, they give the certainty that motive power can be produced by the agricultural transformation of the heat of the sun, even when our total natural store of solid and liquid fuel will be exhausted.
Finally, a few words on the manufacturing: The Diesel motor must be constructed with extreme care, and the best materials employed in order that it may properly fulfill all its capabilities; only the best and most completely equipped works can build it. Fourteen years ago there were very few factories which were able to undertake its construction, and it may be said that through the Diesel engine the manufacture of large machines has been raised to a higher level, in the same way as the manufacture of small machines has been brought on new lines by the automobile engine.
The Diesel motor is therefore not a cheap engine, and I would add a warning that the attempt should never be made to try to build it cheaply, by unfinished workmanship, particularly for export.
These fundamental conditions regarding the construction of the Diesel engine are no disadvantage, as has been frequently proved; on the contrary, they are precisely the reason of its strong position and form a guarantee of its worth.
Diesel.
Munich, December 1911
