3o8 



SCIENTIFIC NEWS. 



[Sept. 21, 1 1 



been running continuously for over a year, and Messrs. 

 Crossley estimate that this saves about 20 tons of coal 

 per annum. It is also worthy of note that at these 

 large works, owing to the use of gas, there is no chimney 

 except for the blacksmiths' shop. The returns sent me by 

 eleven users of Otto engines working regularly in dif- 

 ferent places, and averaging each 35 h.p., also show an 

 average fuel consumption of about 1-3 lb. per indicated 

 h.p. per hour. Messrs. Ibotson, of the Colnbrook Paper 

 Mills were supplied with a single cylinder Otto 

 engine to indicate about 45 h.p. with this gas, on the 

 guaranteed condition that the engine and gas plant could 

 be worked continuously day and night, and that the fuel 

 consumption should not exceed \\ lb. per indicated 

 h.p.perhour. A trial was made extending over two weeks, 

 the engine being indicated day and night at frequent 

 intervals, and the result showed that the guarantee was 

 in all respects fulfilled. The Otto engine makers in 

 Germany have made exhaustive trials with this gas in 

 connection with several of their engines, and have fully 

 confirmed the results obtained by Messrs. Crossley in 

 this country. Professor K. Teichmann, of the Royal 

 Technical School of Stuttgart, and Mr. F. Becking, Chief 

 Engineer of the Rhenish Society for examining steam 

 boilers, made a joint test of a twin-cylinder Otto engine 

 worked with this gas. The engine developed a brake 

 power of about 52 h.p., and the total fuel consumption 

 including that used for the super-heating boiler was 1 6 

 lb. per brake, or barely 1*3 lb. per indicated h.p. per 

 hour. Professor Witz, of Lille, a well-known scientific 

 authority on the gas engine, has tested two Delamare- 

 Debouteville engines worked with this gas — one of 9 

 h.p., and the other of 25 h.p effective. The first trial, 

 of which full details were published in Engineering, gave 

 a consumption of 89 c. ft. of gas, equal to 133 lbs. of 

 coal per brake h.p. per hour. I have not exact particulars 

 of the second trial, but I understand from the maker of 

 the engine, Mr. Thomas Powell, of Rouen, that the result 

 was even more favourable. Seeing that all these results 

 have been obtained under practical working conditions, the 

 record is certainly satisfactory, and I am pleased to add 

 that I have also many letters testifying to the ease with 

 which the gas-plant can be managed. This is an impor- 

 tant point, for if the saving of fuel could only be effected 

 in a complicated way, the apparatus could not be 

 generally adopted. The total number of engines already 

 made to work with this gas is 71, and the aggregate 

 horse power is 2,390, or an average of nearly 34 horse 

 power each. 



I consider myself justified in saying that gas power is 

 now fairly launched in competition with steam power, 

 and to my mind there are reasonable grounds for sup- 

 posing that eventually the former will to a great extent 

 supersede the latter. In this view I am confirmed by 

 the late Professor Fleeming Jenkin, who, in his lecture at 

 the Institution of Civil Engineers, on " Gas and Caloric 

 Engines," remarked — 



" Since theory shows that it is possible to increase the 

 efficiency of the actual gas engine, two — or even three — 

 fold, then the conclusion seems irresistible that gas 

 engines will ultimately supplant the steam engine. The 

 steam engine has been improved nearly as far as possible, 

 but the internal combustion gas engine can undoubtedly 

 be greatly improved and must command a brilliant 

 future." 



It has been proved that the absolute efficiency of the gas 

 engine — i.e., the ratio between the indicated h.p. and the 



total quantity of heat generated by the fuel per minute 

 — is already about double that of the best steam engine. 

 As regards the mechanical efficiency — i.e , the difference 

 between the gross indicated power developed in the 

 cylinder, and the effective power given off on the brake — 

 in the condensing steam-engine it is taken at about 80 per 

 cent., and in the non-condensing engine at about 85 per 

 cent. In the gas engine I showed, in my Inst.C.E. paper 

 before referred to, that the average of several examples 

 given was about 84 per cent. The Otto and other com- 

 pression engines are of comparatively recent invention, 

 and it is fair to assume that further improvements will 

 yet be made, as the principles on which they should be 

 based are now well understood. An important modifica- 

 tion, for instance, has only recently been made in the 

 Otto engine, the slide valves being entirely dispensed 

 with. 



We have seen that the results already obtained with 

 this generator gas are good, but I cannot help feeling that 

 still better results can and will be obtained, when the 

 engine is really designed to give the best effect with a 

 gas of this kind. It is well known that in the Otto 

 engines each new charge of gas is diluted with a portion 

 of the products of combustion from the previous charge, 

 and, for reasons I need not now discuss, this answers very 

 well with ordinary lighting gas. But as generator gas 

 such as mine has only about one-fourth the explosive 

 power of the other gas, it is a disadvantage to dilute it 

 with products of combustion. Sooner or later this point 

 will no doubt receive due attention, especially as the 

 economical use of gas engines of high power must depend 

 on their being worked with cheap gas. Looking to the 

 probable extension cf gas power, it is, in fact, most 

 important that the best possible engine should be made 

 for the fuel gas. 



For gas engines, as now made, it is important that 

 the generator gas should be as clean and free from 

 sulphur compounds and ammonia as ordinary lighting 

 gas. With this in view the best fuel to use is anthra- 

 cite, as it does not yield tar or other condensable 

 products which foul the pipes and valves. It is also 

 suitable because it does not cake, and because it makes 

 a dense fire, free from holes. Good qualities of anthra- 

 cite yield but a small percentage of clinker and of 

 sulphur compounds, and no ammonia. With some 

 special precautions ordinary gas-coke can also be used. 

 The quality of gas-coke varies, however, very much in 

 different localities, and this is doubtless due in some 

 measure to the different kinds of coal from which the 

 coke is made, but also to the varying heats to 

 which it is subjected in the retorts of different gas 

 woiks. Some coke yields very large quantities of 

 clinker, and is quite unfit for use in such an ap- 

 paratus as mine. Other samples yield less clinker, 

 but owing to the comparatively low temperature to which 

 they have been subjected in the retorts, they retain 

 hydro-carbonaceous bodies which vaporise in the gene- 

 rator, and are afterwards troublesome to remove from the 

 gas. As before mentioned, these difficulties are not met 

 with when the hot generator gas can be taken direct to a 

 furnace ; but when it is necessary to cool and clean the 

 gas, as for engine work, special precautions must be taken. 

 N Several trials have shown that when the gas apparatus 

 is worked with anthracite the actual fuel consumption is 

 about 13 lb. per 1,000 eft., including that used for pro- 

 ducing the steam required, but to cover all sources of 

 waste, as well as inferiority of quality, I usually allow 



