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Average net weight of coke fed into cupola during each

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63.125

hour in lbs. Total volume of gas produced during trial, in cubic feet 31,150 Average volume of gas produced per hour, in cubic feet Volume of gas produced per lb. of coke supplied, in cubic feet

5,191.6

82.24

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41.44

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40.7

130.73

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Total revolutions of engine in fifteen minutes
Average revolutions of engine per minute (n)
Mean effective radius of brake lever, in feet (r)
Average net load due to spring balances, in lbs. (l)
2 r n l
33,000

Brake horse-power

Number of indicator cards taken

Scale of indicator spring

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Average mean pressure, neglecting pumping stroke, in lbs. per square inch

Net mean effective pressure, after allowing for work done in pumping stroke, in lbs. per square inch Average maximum initial pressure above atmosphere, in lbs. per square inch

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Maximum possible explosions in fifteen minutes
Maximum possible explosions per minute

Total actual explosions in fifteen minutes, shown by
explosion recorder .

Average number of actual explosions per minute

Average indicated horse-power

Indicated horse-power capacity of producer, as deduced

from gas-production test

Gas used by engine per hour, in cubic feet

Estimated volume of gas required to drive fan, in cubic

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Gas used per I.H.P. per hour, in cubic feet (including
fan)
Coke required per I.H.P. per hour (neglecting fan), in lbs.
Coke required per 1.H.P. per hour to drive fan (estimated)
Total coke required per I.H.P. per hour (including fan)

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Comparison of Fuel Consumption per I.H.P. per hour, between high-class Steam Engines and Boilers, and your Gasproducer Plant with a good Gas Engine

'In basing the comparison between the fuel consumption per indicated horse-power per hour, as given in diagram V., and that obtaining in modern high-class boilers and steam engines, perhaps the most reliable figures that can be taken to represent boilers and engines, as working in actual practice, are those given by the Research Committee of the Institution of Mechanical Engineers, in connection with the propelling machinery in the six steamers named as follows: "Meteor," "Colchester," "Tartar," "Fusi-yama," "Iona," and "Ville de Douvres." These figures refer to marine engines of fairly large power, and generally designed with a view to the promotion of economy of fuel. They may, therefore, be accepted as having a higher range of working economy than even the higher class of stationary steam engines of a power corresponding to that shown in the accompanying tables, which is in every case under 30 I.H.P. But in order to do full justice to the steam engine in this comparison, I will take the Research Committee's results as representing its economy.

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To form a fair comparison, it is well to at first consider the relative calorific values of the fuels used in each case. The mean equivalent carbon value of the various steam coals used by the Research Committee was 0.952. In the absence of calorimetric tests of the fuels used in your gas producers, I will assume the following equivalent carbon values, which, judging from former experiments, will be a fair approximation :

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The Research Committee's results show that the fuel required in the six vessels above named was 2:06 lbs. per I.H.P.

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per hour, as expressed in carbon value. If we take this weight as expressing the unit of economical efficiency for steam engines, the comparative efficiency of your plant is shown in the following table:

COMPARATIVE EFFICIENCY AS REGARDS FUEL CONSUMPTION PER I.H.P. PER HOUR

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'In connection with the above figures, it may be stated that they are strictly net, as regards your plant, for full allowance has been made in the way of fuel-equivalent for the steam and fan blast, and in computing the indicated horse-power from the indicator diagrams.

'I have purposely confined myself in the foregoing comparison to the relative weight of fuel alone.'

CHAPTER XXXVI

GAS ENGINE TESTS

THE author was pleased to receive an invitation from Professor Capper, to be present on January 10 and 11, 1895, when a 7 H.P. NOM. engine by Messrs. Crossley Bros. was tested in his laboratory at King's College, London, for purely scientific purposes.

I have Professor Capper's permission to publish the following report :

In gas engine trials it has hitherto been usual to assume that the temperature of the explosive mixture during constant volume ignition varies directly as the pressure. As this treatment does not seem altogether justifiable, I have recently carried out a number of trials in my laboratory in which complete

gas and exhaust analyses have been made for me by Mr. G. N. Huntley, A.R.C.S., F.I.C.S., and the temperatures and heat additions have been calculated from the constants so obtained.

The following full-power trial will illustrate the method. This trial was carried out on January 10, Mr. W. Norris, M.I.Mech.E., being present.

The engine was run in working condition, the last time it was disconnected for cleaning being some eight months before the trial.

Engine. The engine is a 7 NOM. H.P. Crossley engine with tube ignition and loaded ball governor. It was built in 1892, and has been in constant use driving the workshops and running experimental trials ever since. Its cylinder is 8.5 inches diameter x 18 inches stroke. The clearance volume is 2467 cubic feet.

Trial. The trial on January 10 lasted forty minutes, indicator diagrams and all other observations being taken every five minutes.

Indicator Diagrams.-A Wayne indicator, calibrated under steam upon my mercury column, was used. For the power diagrams a spring and for the pumping stroke a spring was employed. From the indicator diagrams (see fig.

Card taken at 3.04 pm.
Mean pressure 60·0

Atmospheric Line

INDICATOR CARD FULL SIZE

PRESSURE, 120 lbs. to the In

FIG. 200

200) which approached nearest to the average of the whole number taken, a mean diagram has been drawn on an enlarged scale, shown in fig. 201. A pumping diagram is shown, actual size, in fig. 202.

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