40 SURFACE MACHINERY AND METHODS FOR OIL-WELL PUMPING.
almost constant fuel economy over a fairly wide range in load. Thus at
three-fourths load the increase in fuel consumption per brake horsepower-hour
is only 2 to 5 per cent, and at one-half load 10 to 15 per cent greater than
at full load in high-grade engines, which is in marked contrast with fuel
increases in other prime movers. The ability to create higher initial tem-
peratures, aside from increased thermal efficiency, enables the Diesel engine
to burn a greater variety of fuels. In addition to the fuel being thoroughly
atomized by highly compressed air, the heated oxygen has an augmented
power of combining with the carbon and hydrogen in the fuel, so that the
velocity of the chemical reaction at the high temperature in a Diesel engine
is greatly increased. As a result the range of fuels suitable for the Diesel
engine comprises such heavy liquid fuels as petroleum residues, coal-tar oils,
and coal tars.
A serious fuel loss in explosion engines is frequently caused by the decom-
position of the fuel oil sprayed into the hot ball. Various hydrocarbons are
formed with a separation of carbon and oil soot; part of this coats the hot
ball and the cylinder, and a larger part is expelled with the gaseous products
of combustion. From time to time accumulated soot in the exhaust piping
catches fire and burns, necessitating precautions against fire from this source.
Comparative economies of Diesel and of explosion oil engines are shown in
Table 2 following. On a basis of oil costing $1 a barrel, the minimum yearly
fuel cost in dollars corresponds to a number of barrels of oil consumed yearly.
Oil usually costs more than $1 a barrel, especially gas oils, which are the
only oils suitable for use in explosion oil engines. On the other hand, residues
and heavy fuel oils can be burned in the Diesel engine. Lubricating expense
is also materially higher in explosion than in Diesel engines. With a fairly
good load factor it will not take long to make up the difference in first cost
by greater economy, particularly when the fuel cost is increased by long hauls.
TABLE 2.-Coi)paratif Cconomlies of Diesel and of explosion oil engines
(Cost of fuel oil taken as at $1 a barrel of 320 pounds; cost of lubricating oil taken as at 35 cents a gallon.)
Diesel engine, American make.' Explosion oil engine, American make.'
cost per Per cost per
Item. Fuel Per Bar- horse- Fuel ce Bar- horse-
per cent rels power- per fuel rels power-
Load. horse- fuel per year Load. horse- year
power- per year. (8,760 power- per per (8,760
hour. horse- horse- hour. ose year. horse-
power power power
F 4/4 0. 48 100 986 $13.15 4/4 0. 75 100 1, 540 $20. 53
cost at different loas. 2/4 . 58 120. 8 610 16. 27 2/4 .95 12. 7 975 26. 00
Oil consumed for lubri- 360 to 550..----------------------- 1,100 to 1,460.
cation, gallons per year.
Cost of lubrication --..... $128 to $193 per year, or $1.70 to $2.60 $380 to $510 per year or $5.10 to $6.80
installation in- per horsepower year. per horsepower year.
Cost of installation in- $90 per horsepower_..---------------- $60 per horsepower.
1 75-horsepower, one-cylinder, single-acting engine having a four-stroke cycle.
2 75-horsepower, two-cylinder, single-acting engine having a two-stroke cycle.
The engineers of the Bureau of Mines believe that the oil engine
has proved its usefulness as a prime mover in oil fields whose gas
George, H. C. Surface Machinery and Methods for Oil-Well Pumping. Washington D.C.. UNT Digital Library. http://digital.library.unt.edu/ark:/67531/metadc12407/. Accessed August 30, 2015.