400 GASEOUS FUEL 



of smoke were formed. Further trouble arose because steam had to be supplied, and as 

 on a Service vessel this would mean extra boilers this was a great drawback. 



Of the burners which sprayed the oil under pressure without the use of either steam or 

 air, the Korting and Swensson had already proved successful in many cases, but a great 

 improvement was introduced by I. I. Kermode, who designed a burner in which the oil 

 under pressure issued from the nozzle in a swirling cone of mist, the particles not being 

 driven straight forward as in other types by the spraying, and the rate at which it traverses 

 the combustion space is thus reduced. Air injection for the oil, although on theoretical 

 grounds it might be expected to be the most advantageous, has never found much favour 

 for marine work, as auxiliary power has to be provided to drive the pumps for the air com- 

 pression, but where an intense temperature is required it has been used largely, and especially 

 in furnace work on land has proved very successful. One of the most successful forms of 

 burner for this purpose has also been designed by Kermode and may be used with either 

 steam or air. 



At the present time the use of liquid fuel direct in the internal combustion engine has 

 occupied a large amount of attention, and the Diesel engine has already shown itself well 

 adapted for marine use where the power required has not been very high. The successful 

 installations in the tank steamer "Vulcanus" and in the "Selandia" have demonstrated 

 its great possibilities, whilst the fact that one B.H.P. can be obtained with a consumption of 

 something like 0.45 of a pound of liquid fuel of much the same character as that used for 

 burning under a boiler gives very high economy in its employment. 



The first British destroyer fitted with Diesel engines for propulsion was the "Hardy," 

 launched in October 1912, in which, for full speed, turbines fed with steam from boilers 

 fired with oil fuel are used, whilst the Diesel engines are employed for cruising speeds, 

 at which the turbine shows a marked falling off in efficiency. 



In Germany, where there is a heavy import tax upon oil, the use of tar and tar oils in the 

 Diesel engine has attracted considerable attention, and for the last ten years tar and creosote 

 oils have been satisfactorily used. The troubles that at first arose with tar oils were that 

 the pipes and nozzles of the burners were found to become choked with muddy deposits of 

 solid hydrocarbons, consisting mainly of napthalene, which formed a crust also at the 

 mouths of the burners. These deposits made the working of the feed pumps difficult, and 

 the solid hydrocarbons increased the temperature of ignition. The crude tar oils varied in 

 composition and quality with differences in the temperature of carbonisation, even when 

 the same coal had been used, which necessitated constant alteration in the feed and air 

 adjustments of the engine. Of recent years, however, improved methods of fractionation 

 and refining the tar oil, together with careful selection of the material, have ensured a 

 supply of fuel of constant and regular quality, without the drawbacks incidental to the 

 use of crude tar oils. 



3. Gaseous Fuel. 



The most important development in the use of gas as fuel that has taken place since 

 the invention by Bunsen of the atmospheric burner promises to arise from the so-called 

 principle of "surface combustion." Although a mixture of hydrogen and oxygen in the 

 proportions in which they combine to form water has an ignition point of about 550 C. 

 at ordinary atmospheric pressure, yet the two gases will combine in contact with certain 

 metals at lower temperatures, but the rate of combination is so slowed down that the 

 ignition point may never be reached. This power of inducing combination between 

 gases at comparatively low temperatures has been known to be possessed by metals of 

 the platinum group, since Sir Humphry Davy first established the fact in 1816, whilst 

 Dulong and Thenard afterwards proved that all solid bodies possess in varying degrees 

 the power of accelerating combustion below the ignition point. It is only within recent 

 years that the study of this phenomenon has been revived by the researches of Professor 

 W. A. Bone, and the phenomenon of surface combustion is now receiving a considerable 

 amount of attention, and promises to lead to most important commercial developments. 



If a mixture of coal gas and air in the explosive ratio of i to 6 be directed on to the 

 surface of red hot nickel gauze or incandescent fireclay and asbestos, it is found that the 

 acceleration of the 'combustion is not confined to low temperatures only, but flameless 

 combustion ensues on the incandescent refractory surface, producing there a more in- 

 tense combustion, with the result that the material is raised to a high degree of incan- 

 descence, and a much greater proportion of the heat energy of the gaseous mixture is 

 converted into radiant heat. 



There are two possible conditions under which gaseous combustion may take place 

 the first, homogeneous combustion, in which the velocity of the chemical change is 



