tically identical, the lighter oils being most powerful because they contain the highest percentage of hydrogen, but the difference is immaterial. The evaporative efficiency of the small boilers of cars and canoes, is less than that of large boilers simply because it is not desirable to load up a car with too great a weight of heating surface. In fig. 60 is shown the starting device employed on automobile cars, a pad fed with a drop feed of oil being ignited by a match and giving preliminary heat to the burner.

IN

Chapter XXIV

COMPARISON OF AIR AND STEAM ATOMIZATION

The Ellis and Eaves System.

N this system the atomizing is done by steam, and heated air is supplied to the furnaces, the draught being fan induced. The air is heated in tubular heaters having two-thirds of the boiler heating surface, and placed over the boiler in the

Fig. 61. ELLIS AND EAVES SYSTEM, MARINE BOILER ARRANGEMENT, FOR HEATING AIR

course of the gases to the fan, as shown in fig. 61; the admission of air to the furnaces being, as in fig. 62, round the outside of the atomizer.

Tests were also made with air as the atomizing agent. The air pressure was 20 pounds per square inch, and the results are given below. A subsequent test with air at 35 pounds pressure showed 11,108 pounds of water per hour from and

FAN DISCHARGE

at 212°F. and 15-49 pounds per pound of oil. This is somewhat less than air at the more moderate pressure of 20 pounds. The atomizing air was not heated, and had a temperature of 80°F. only, or it might have given better results.

The difference between steam and air atomizing seems to be practically nil.

Fig. 62. ELLIS AND EAVES SYSTEM, FURNACE DOOR ARRANGEMENT

It remains simply to compare the amount of steam used direct with that used in compressing the air.

The analysis of the flue gases showed a mean result of 11-2 per cent. of CO, and 10 per cent. of oxygen in the left hand furnace and 14.1 per cent. of CO, and 8.4 of oxygen in the right hand furnace, the mean of both being CO2 =12-6, 0=9-6, CO=0.

2

The tests made with this system of induced draught and oil fuel burning of six hours duration, were a success, but the question was raised whether the system could be worked for a lengthened period without giving trouble through deposits of soot and unconsumed oil becoming ignited in the air heater and casings.

A continuous test of 120 hours was made, careful observations being taken of the temperatures, evaporation, etc., during that time.

Particulars of boiler, which were the same as in the previous tests

12 ft. mean diameter by 11 ft. mean length, fitted with two Purves furnaces of

3 ft. 9 in. inside diameter.

148 Servé tubes, 3 in. outside diameter by 7 ft. 9 in. long and retarders. Heating surface, 1,200 sq. ft. Grate surface (for coal burning) 43 sq. feet. Ratio of H.S. to G.S. 28 to 1.