BURAL ENGINEERING. 189 



relating to ease of starting, steady and efficient operation at all loads, complete 

 combustion, simplicity in regulation, and low first cost. 



The fuel economy of heavy oil engines is briefly summarized as follows: 

 Approximately 0.4 lb. of oil is consumed per horsepower hour, whereas for a 

 steam engine of the best triple expansion tyi^e from 1.1 to 1.8 lbs. of fuel are 

 necessary, thus giving an economy ratio of approximately 1 : 3 in favor of the 

 oil engine. 



Fuels that may be successfully used in heavy oil engines are enumerated as 

 follows: Petroleum products, "Steinkohle" oil products, bituminous oils, lignite 

 products, turf oils, shale oils, vegetable oils, animal oils, alcohols, and wood 

 oils. 



Specifications for fuels and lubricants for heavy oil engines are summarized 

 'as follows: The oil should be mobile at 0° C. Sluggish oils should be heated 

 before being introduced into the engine, and oil should contain not more than 

 0.4 per cent of material insoluble in xjieue. The residue on coking should not 

 be greater than 3 per cent and there should not be more than a trace of free 

 carbon in the oil. At least 80 per cent of the oil should distill over at 350° 

 and heavy oils and residues should properly be distilled before using. The 

 flash point should be between 60 and 100°. A heavy oil containing no material 

 having a low flash point should be enlivened by the addition of about 2 per 

 cent of a " gas oil," the flash point being 60 to 100° or less. The specific gravity 

 should not be greater than 0.920. The heating value should be not less than 

 9,000 calories, the hydrogen content not less than 10 i^er cent, and the sulphur 

 content not more than 0.75 per cent. The oil should contain no free ammonia, 

 alkali, or mineral acids, not more than 0.05 per cent of noncombustible mineral 

 matter, and not more than 1 per cent of water. The resin content should be 

 low, the parafiin content not more than 15 per cent, the creosote content not 

 more than 12 per cent, and the asphaltum content sufficiently low to allow 

 the fluid to flow. Fine atomization is essential. 



The viscosity of lubricants should be between 9 and 10° Engler at 50°. The 

 lubricants should be liquid at — 5° and should not freeze solid above — 10°. 

 The flash point should, be between 220 to 240° in a Pensky-Martens closed 

 tester. The lubricant should lose not more than 10 per cent by carbonization 

 when agitated with concentrated sulphuric acid, should dissolve completely 

 and clearly in benzene, and should be free from acids and alkali. Animal and 

 vegetable oils should not be used. 



It is stated in conclusion that the heavy oil engine can not yet be considered 

 as fully developed, but the fact that petroleum containing as high as 20 per 

 cent asphaltum as well as oils from tars have been successfully used is most 

 encouraging for its future. 



Naphthalin for gas engines (Gas Engine, 15 (1913), No. 8, pp. 455, 456). — 

 Attention is called to the use of naphthalin in internal-combustion engines. It 

 is stated that this material consists of approximately 94 per cent carbon and 

 6 per cent hydrogen, melts at 174° F., boils at 424°, and has a speciflc gravity 

 of 1.15. 



Carbureters adapted to the use of naphthalin are (1) those which melt and 

 vaporize the naphthalin itself, and (2) those which vaporize a solution of the 

 substance in some volatile liquid. Ether is the best solvent, but its cost is 

 prohibitive. Benzine dissolves from 30 to 40 per cent at atmospheric tempera- 

 ture, and alcohol may be also used, although in every case a heated carbureter is 

 necessary. 



The advantages claimed for naphthalin are as follows: It is not readily in- 

 flammable ; for a given amount of work it occupies smaller space than gasoline ; 



