[Footnote 2: Abstract of paper read before the Institution of Mechanical
Engineers.]
By Mr. THOMAS URQUHART.
Comparing naphtha refuse and anthracite, the former has a theoretical
evaporative power of 16.2 lb. of water per lb. of fuel, and the latter of
12.2 lb., at a pressure of 8 atm. or 120 lb. per square inch; hence
petroleum has, weight for weight, 33 per cent. higher evaporative value
than anthracite. Now in locomotive practice a mean evaporation of from 7
lb. to 7½ lb. of water per lb. of anthracite is about what is generally
obtained, thus giving about 60 per cent. efficiency, while 40 per cent. of
the heating power is unavoidably lost. But with petroleum an evaporation
of 12.25 lb. is practically obtained, giving 12.25/16.2 = 75 per cent.
efficiency. Thus in the first place petroleum is theoretically 33 per
cent. superior to anthracite in evaporative power; and secondly, its
useful effect is 25 per cent. greater, being 75 percent. instead of 60
percent.; while, thirdly, weight for weight, the practical evaporative
value of petroleum must be reckoned as at least from (12.25 - 7.50)/7.50 =
63 per cent. to (12.25 - 7.00)/7.00 = 75 per cent. higher than that of
anthracite.
_Spray injector._--Steam not superheated, being the most convenient for
injecting the spray of liquid fuel into the furnace, it remains to be
proved how far superheated steam or compressed air is really superior to
ordinary saturated steam, taken from the highest point inside the boiler
by a special internal pipe. In using several systems of spray injectors
for locomotives, the author invariably noticed the impossibility of
preventing leakage of tubes, accumulation of soot, and inequality of
heating of the fire box. The work of a locomotive boiler is very different
from that of a marine or stationary boiler, owing to the frequent changes
of gradient on the line, and the frequent stoppages at stations. These
conditions render firing with petroleum very difficult; and were it not
for the part played by properly arranged brickwork inside the fire box,
the spray jet alone would be quite inadequate. Hitherto the efforts of
engineers have been mainly directed toward arriving at the best kind of
"spray injector," for so minutely subdividing a jet of petroleum into a
fine spray, by the aid of steam or compressed air, as to render it
inflammable and of easy ignition. For this object nearly all the known
spray injectors have very long and narrow orifices for petroleum as well
as for steam; the width of the orifices does not exceed from ½ mm. to 2
mm. or 0.02 in. to 0.08 in., and in many instances is capable of
adjustment. With such narrow orifices it is clear that any small solid
particles which may find their way into the spray injector along with the
petroleum will foul the nozzle and check the fire. Hence in many of the
steamboats on the Caspian Sea, although a single spray injector suffices
for one furnace, two are used, in order that when one gets fouled the
other may still work; but, of course, the fouled orifices require
incessant cleaning out.
_Locomotives._--In arranging a locomotive for burning petroleum, several
details are required to be added in order to render the application
convenient. In the first place, for getting up steam to begin with, a gas
pipe of 1 inch internal diameter is fixed along the outside of the boiler,
and at about the middle of its length it is fitted with a three-way cock
having a screw nipple and cap. The front end of the longitudinal pipe is
connected to the blower in the chimney, and the back end is attached to
the spray injector. Then by connecting to the nipple a pipe from a
shunting locomotive under steam, the spray jet is immediately started by
the borrowed steam, by which at the same time a draught is also maintained
in the chimney. In a fully equipped engine shed the borrowed steam would
be obtained from a fixed boiler conveniently placed and specially arranged
for the purpose of raising steam. In practice steam can be raised from
cold water to 3 atm. pressure--45 lb. per square inch--in twenty minutes.
The use of auxiliary steam is then dispensed with, and the spray jet is
worked by steam from its own boiler; a pressure of 8 atm.--120 lb.--is
thus obtained in fifty to fifty-five minutes from the time the spray jet
was first started. In daily practice, when it is only necessary to raise
steam in boilers already full of hot water, the full pressure of 7 to 8
atm. is obtained in from twenty to twenty-five minutes. While
experimenting with liquid fuel for locomotives, a separate tank was placed
on the tender for carrying the petroleum, having a capacity of about 3
tons. But to have a separate tank on the tender, even though fixed in
place, would be a source of danger from the possibility of its moving
forward in case of collision. It was therefore decided, as soon as
petroleum firing was permanently introduced, to place the tank for fuel in
the tender between the two side compartments of the water tank, utilizing
the original coal space. For a six-wheeled locomotive the capacity of the
tank is 3-1/2 tons of oil--a quantity sufficient for 250 miles, with a
train of 480 tons gross exclusive of engine and tender. In charging the
tender tank with petroleum, it is of great importance to have strainers of
wire cloth in the manhole of two different meshes, the outer one having
openings, say, of 1/4 in., the inner, say 1/8 in.; these strainers are
occasionally taken out and cleaned. If care be taken to prevent any solid
particles from entering with the petroleum, no fouling of the spray
injector is likely to occur; and even if an obstruction should arise, the
obstacle being of small size can easily be blown through by screwing back
the steam cone in the spray injector far enough to let the solid particles
pass and be blown out into the fire-box by the steam. This expedient is
easily resorted to even when running; and no more inconvenience arises
than an extra puff of dense smoke for a moment, in consequence of the
sudden admission of too much fuel. Besides the two strainers in the
manhole of the petroleum tank on the tender, there should be another
strainer at the outlet valve inside the tank, having a mesh of 1/3 in.
holes.
_Driving locomotives._--In lighting up, certain precise rules have to be
followed, in order to prevent explosion of any gas that may have
accumulated in the fire box. Such explosions do often take place through
negligence; but they amount simply to a puff of gas, driving smoke out
through the ash-pan dampers, without any disagreeably loud report. This is
all prevented by adhering to the following simple rules: First clear the
spray nozzle of water by letting a small quantity of steam blow through,
with the ash-pan doors open; at the same time start the blower in the
chimney for a few seconds, and the gas, if any, will be immediately drawn
up the chimney. Next place on the bottom of the combustion chamber a piece
of cotton waste, or a handful of shavings saturated with petroleum and
burning with a flame. Then by opening first the steam valve of the spray
injector, and next the petroleum valve gently, the very first spray of oil
coming on the flaming waste immediately ignites without any explosion
whatever; after which the quantity of fuel can be increased at pleasure.
By looking at the top of the chimney, the supply of petroleum can be
regulated by observing the smoke. The general rule is to allow a
transparent light smoke to escape, thus showing that neither too much air
is being admitted nor too little. The combustion is quite under the
control of the driver, and the regulation can be so effected as to prevent
smoke altogether. While running, it is indispensable that the driver and
fireman should act together, the latter having at his side of the engine
the four handles for regulating the fire, namely, the steam wheel and the
petroleum wheel for the spray injector, and the two ash-pan door handles
in which there are notches for regulating the air admission. Each
alteration in the position of the reversing lever or screw, as well as in
the degree of opening of the steam regulator or the blast pipe, requires a
corresponding alteration of the fire. Generally the driver generally
passes the word when he intends shutting off steam, so that the alteration
in the firing can be effected before the steam is actually shut off; and
in this way the regulation of the fire and that of the steam are virtually
done together. All this care is necessary to prevent smoke, which is
nothing less than a waste of fuel. When, for instance, the train arrives
at the top of a bank, which it has to go down with the brakes on, exactly
at the moment of the driver shutting off the steam and shifting the
reversing lever into full forward gear, the petroleum and steam are shut
off from the spray injector, the ash-pan doors are closed, and if the
incline be a long one, the revolving iron damper over the chimney top is
moved into position, closing the chimney, though not hermetically. The
accumulated heat is thereby retained in the fire-box; and the steam even
rises in pressure, from the action of the accumulated heat alone. As soon
as the train reaches the bottom of the incline and steam is again
required, the first thing done is to uncover the chimney top; then the
steam is turned on to the spray injector, and next a small quantity of
petroleum is admitted, but without opening the ash-pan doors, a small fire
being rendered possible by the entrance of air around the spray injector,
as well as by possible leakage past the ash-pan doors. The spray
immediately coming in contact with the hot chamber ignites without any
audible explosion; and the ash-pan doors are finally opened, when
considerable power is required, or when the air otherwise admitted is not
sufficient to support complete combustion. By looking at the fire through
the sight hole it can always be seen at night whether the fire is white or
dusky; in fact, with altogether inexperienced men it was found that after
a few trips they could become quite expert in firing with petroleum. The
better men contrive to burn less fuel than others, simply by greater care
in attending to all the points essential to success. At present
seventy-two locomotives are running with petroleum firing; ten of them are
passenger engines, seventeen are eight-wheel coupled goods engines, and
forty-five are six-wheel coupled. As might be expected, several points
have arisen which must be dealt with in order to insure success. For
instance, the distance ring between the plates around the firing door is
apt to leak, in consequence of the intense heat driven against it, and the
absence of water circulation; it is therefore either protected by having
the brick arch built up against it, or, better still, it is taken out
altogether when the engines are in for repairs, and a flange joint is
substituted, similar to what is now used in the engines of the London and
Northwestern Railway. This arrangement gives better results, and occasions
no trouble whatever.
_Storage of petroleum._--The length of line now worked with petroleum is
from Tsaritsin to Burnack, 291 miles. There is a main iron reservoir for
petroleum at each of the four engine sheds, namely at Tsaritsin, Archeda,
Filonoff, and Borisoglebsk. Each reservoir is 66 ft. internal diameter and
24 ft. high, and when full holds about 2,050 tons. The method of charging
the reservoir, which stands a good way from the line, and is situated at a
convenient distance from all dwelling houses and buildings, is as follows:
On a siding specially prepared for the purpose are placed ten cistern cars
full of oil, the capacity of each being about ten tons. From each of these
cars a connection is made by a flexible India rubber pipe to one of ten
stand pipes which project 1 ft. above the ground line. Parallel with the
rails is laid a main pipe, with which the ten stand pipes are all
connected, thus forming one general suction main. About the middle of the
length of the main, which is laid underground and covered with sawdust or
other non-conducting material, is fixed a Blake steam pump. As soon as all
the ten connections are made with the cistern cars, the pump is set to
work, and in about one hour the whole of the cars are discharged into the
main reservoir, the time depending of course upon the capacity of the
pump. All the pipes used are of malleable iron, lap-welded, and of 5 in.
internal diameter, having screwed coupling muffs for making the
connections. At each engine shed, in addition to the main storage
reservoir, there is a smaller distributing tank, which is erected at a
sufficient height to supply the tenders, and very much resembles the
ordinary water tanks. These distributing tanks are circular, about 8½ ft.
diameter and 6 ft. high, and of ¼ in. plates; their inside mean area is
calculated exactly, and a scale graduated in inches stands in the middle
of the tank; a glass with scale is used outside in summer time. Each inch
in height on the scale is converted into cubic feet, and then by means of
a table is converted into Russian poods, according to the specific gravity
at various temperatures. As it would be superfluous to graduate the table
for each separate degree of temperature, the columns in the table show the
weights for every 8 degrees Reaumur, which is quite sufficient: namely,
from 24 deg. to 17 deg., from 16 deg. to 9 deg., and so on, down to -24
deg.; the equivalent Fahrenheit range being from 86 deg. down to -22 deg.
Suppose the filling of a tender tank draws off a height of 27 in. from the
distributing tank, at a temperature of say -20 deg. R., these figures are
shown by the table to correspond with 200.61 poods = 7,245 lb., or 3.23
tons, of petroleum. This arrangement does very well in practice; both the
quantity and the temperature are entered on the driver's fuel bill at the
time of his taking in his supply.
_Engines._--The engines used in the trials were built by Borsig, of
Berlin, Schneider, of Creusot, and the Russian Mechanical and Mining
Company, of St. Petersburg. Their main dimensions and weights were about
the same, as follows, all of them having six wheels coupled, and 36 tons
adhesive weight; as originally constructed they had ordinary fire boxes
for burning anthracite or wood; cylinders 18-1/8 in. diameter and 24 in.
stroke; slide valves, outside lap 1-1/16 in., inside lap 3/32 in., maximum
travel, 4-9/16 in.; Stephenson link motion; boiler pressure, 120 lb. per
square inch; six wheels, all coupled, 4 ft. 3 in. in diameter; distance
between centers of leading and middle wheels, 6 ft. 2-3/4 in.; between
middle and trailing, 4 ft. 9-1/4 in.; total length of wheel base, 11 ft.;
weight empty, on leading wheels, 12.041 tons; middle, 10.782 tons;
trailing, 10.685 tons; total weight, 33.508 tons empty; weight in running
order, on leading wheels, 12.563 tons; middle, 11.885 tons; trailing
12.790 tons; total weight, 37.238 tons in running order. Tubes number 151;
outside diameter, 2-1/8 in.; length between tube plates, 13 ft. 10-1/8
in.; outside heating surface, 1,166 square feet; fire box heating surface,
82 square feet; total heating surface, 1,248 square feet; fire grate area,
17 square feet; tractive power =
65 per cent. of boiler pressure × (cyl. diam.)² × stroke / diameter of wheels
= 0.65 × 120 × (18.125)² × 24 / 51 = 5.383 tons. Ratio of tractive power
to adhesion weight = 5.383 / 37.238 = 1 / 6.9.
_Tender._--Contents: water, 310 cubic feet, or 1,933 gallons, or 8½
tons; anthracite, 600 poods, or 10 tons; or wood, 1½ cubic sajene, or
514 cubic feet; weight empty, 13.477 tons; weight in running order, 28.665
tons; six wheels.
* * * * *
_Petroleum Refuse--Comparative Trials with Petroleum, Anthracite,
Bituminous Coal, and Wood, between Archeda and Tsaritsin on Grazi and
Tsaritsin Railway, in Winter Time._
-----+---+-----+------+---+-----+------+-----------+-------------+------+------------
| L | | | | | | | |
| o | | Train | | | | Consumption | |
| c | | alone. | | | | Including | |
Date.| o | | | | | | Lighting up.| |
1883.| m | |----+-----| | | | | Cost |
| o |Train|Num-| | Dis-| Car | | | of |Atmospheric
| t | |ber |Gross|tance|miles.| Fuel. |-------+-----| fuel |temperature
| i | | of |load.| run.| | | | Per | per | and
| v | |Loa-| | | | | Total |train| train| weather.
| e | |ded | | | | | |mile.| mile.|
| . | |cars| | | | | | | |
-----+---+-----+----+-----+-----+------+-----------+-------+-----+------+------------
| | | No.| Tons|Miles| | | | |Pence.|
-----+---+-----+----+-----+-----+------+-----------+-------+-----+------+------------
| 8|32-23| 25 | 400 | 388 | 9,700|Anthracite.| 31799 |81.90|11.957|-17° to -18°
| |32-23| | | | | | lb. | lb. | | Reau.,
Feb.| | | | | | | | | | | equiv. to
8 | |24-21| | | | | | | | |-6° to -8½°
| 14|24-21| 25 | 400 | 388 | 9,700|Bituminous |37557.5|96.53|14.093| Fah.
| | | | | | | Coal. | lb. | lb. | |
| 7|26-29| 25 | 400 | 194 | 4,830|Petroleum | 9462 |48.77| 5.487| Strong
| | | | | | refuse. | lb. | lb. | | side wind.
-----+---+-----+----+-----+-----+------+-----------+-------+-----+------+------------
| 24|32-23| 25 | 400 | 194 | 4,850|Anthracite.|12639.5|65.15| 9.512|-5° to -9°
March| | | | | | | | lb. | lb. | | Reau.,
6 | 21|24-21| 25 | 400 | 194 | 4,850|Wood, in | 1071.8| 5.52| 8.5 | equiv. to
| | | | | | | billets. | c. ft.|c. ft| | 21° to 12°
| | | | | | | | | Fah.
| 23|26-27| 25 | 400 | 194 | 4,850|Petroleum | 7228 |37.28| 4.188| Light
| | | | | | refuse. | lb. | lb. | | side wind.
-----+---+-----+----+-----+-----+------+-----------+-------+-----+------+------------
Prices of fuel:
Petroleum refuse, 21s. per ton; Anthracite and bituminous coal, 27s. 3d. per ton;
Wood, in billets, 42s. per cubic sajene = 343 cubic feet;
equivalent to 1.47d. per cubic foot.
Dimensions of locomotives:
Cylinders, 18 1/8 in. diam. and 24 in. stroke; Wheels, 4 feet 3 in. diam.;
Total heating surface, 1,248 sq. feet: Total adhesion weight, 36 tons;
Boiler pressure, 8 to 9 atm.
The preceding table shows the results of comparative trials made in winter
with different sorts of fuel, under exactly similar conditions as to type
of engine, profile of line, and load of train. Two sets of comparative
trials were made, both of them in winter. The three engines used were some
of those built by Schneider. In comparison with anthracite, the economy in
favor of petroleum refuse was 41 per cent. in weight, and 55 per cent. in
cost. With bituminous coal there was a difference of 49 per cent. in favor
of petroleum as to weight and 61 per cent. as to cost. As compared with
wood petroleum was 50 per cent. cheaper. At a speed of fourteen miles an
hour up an incline of 1 in 125 the steam pressure was easily kept up at 9
to 9½ atm. with a No. 9 injector feeding the boiler all the time.
Up to the present time the author has altered seventy-two locomotives to
burn petroleum; and from his own personal observations made on the foot
plate with considerable frost he is satisfied that no other fuel can
compare with petroleum either for locomotives or for other purposes. In
illustration of its safety in case of accident, a photograph was exhibited
of an accident that occurred on the author's line on 30th December, 1883,
when a locomotive fired with petroleum ran down the side of an embankment,
taking the train after it; no explosion or conflagration of any kind took
place under such trying circumstances, thus affording some proof of the
safety of the petroleum refuse in this mode of firing. Although it is
scarcely possible that petroleum firing will ever be of use for
locomotives on the ordinary railways of coal-bearing England, yet the
author is convinced chat, even in such a country, its employment would be
an enormous boon on underground lines.
* * * * *