Fuel efficiency

“ Diesel Oil Engine. The Diesel engine marks the greatest progress in the internal combustion field made in the last few years. It marks a distinct advance in both thermal efficiency, and in the character of the fuel that it has made a commercial possibility. By the use of cheap fuel heretofore unavailable for any type of prime mover, such as the asphaltum residual oils, coal tar, etc., it has lowered the cost of power production to a point where it is unapproached by any type of heat engine. ”

“ Perhaps the most challenging task contemplated for the fuel cell is to bring about the consumption of raw or slightly processed coal, gas, and oil fuels with atmospheric oxygen. If fuel cells can be made to use these abundant fuels, then the high natural conversion efficiency of the fuel cells will make them economically superior to the lower efficiency steam-electric plants now in commercial service. ”

“ It may be started at once, with no delay as in getting up a fire under a boiler; when the fuel-supply is cut off, the motor stops and needs no attention: these are important in automobile practice. Gas engines are gainfully united to systems of gas storage so that a producer may be run at high efficiency when convenient, and its gas held in holders till needed: this is helpful when a plant is worked overtime, or is liable to stresses of extreme demand at certain hours of the day. ”

“ The Vehicle Fuel Economy Mandate specifies a national mandatory fuel economy standard of 35 miles per gallon by 2020, which will save billions of gallons of fuel and increase efficiency by 40 percent. ”

“ The fuel is fed from underneath, either continuously by a screw, or intermittently by plungers. The principle upon which these stokers base their claims for efficiency and smokelessness is that the green fuel is fed under the coked and burning coal, the volatile gases from this fresh fuel being heated and ignited in their passage through the hottest portion of the fire on the top. ”

“ The remarkable efficiency of the Diesel engine is due principally to the extremely high compression pressure, which was from 500 to 600 pounds per square inch. When this is compared to the 60 to 70 pounds compression pressure used with automobile engines it is easy to see where the Diesel gains its efficiency. It is evident that as much depends on the manner in which the fuel is used in the engine as on the calorific value of the fuel. ”

“ As the semi-Diesel type engine will operate successfully on the lowest grades of crude oils, with an efficiency that compares favorably with the true Diesel type, the operating expenses are very much lower than with the gas or gasoline engine. With the same fuels, the semi-Diesel will show greater net saving than the Diesel with a low load factor, as the fuel saving is not eaten up by the high first cost, and overhead charges of the true Diesel. ”

“ Fourth, radiation, the dissipation of heat, and condensation, are always at work, and thus detract from the efficiency of the engine.
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The gasoline motor, the next prime motor of importance, is still less efficient in point of fuel economy, since less than one-third of the fuel is actually represented in the mechanism which it turns.
The production of energy, in both cases, involves the construction of a multiplicity of devices and accessories, many of them difficult to make and hard to understand.
To produce power for commercial purposes, at least two things are absolutely essential. ”

“ The efficiency of the gas or gasoline engines is sometimes as high as 25 per cent. This engine is free from smoke and is also compact and quickly started. While the fuel, gas or gasoline, is somewhat expensive it is light and easily [Pg 225] carried. Suppose a gas engine produces 1 horse-power and uses 20 cu. ft. of gas an hour, what is its efficiency? 1 horse-power-hour = 550 × 60 × 60 = 1,980,000 ft.-lbs. 20 cu. ft. of gas = 20 × 600 × 778 = 9,336,000 ft.-lbs.
Efficiency = work out/work in = 1,980,000/9,336,000 = 21.2 per cent.
Fig. 167.—The principle of the steam turbine. ”

“ Efficiency of Gas Engines.—One may test the efficiency of a gas engine by determining the amount of power developed and comparing it with the mechanical equivalent of the fuel burned. Illuminating gas is sometimes employed to drive gas engines. One cubic foot of illuminating gas should produce 600 B.T.U. when burned. ”

“ The fuel that is used will depend upon the type of furnace and the relative prices prevailing for different kinds. Recent developments in oil heating bring this fuel in close competition from the standpoint of economy with coal or coke. Oil is particularly adaptable as a source of fuel in homes in the country since tank trucks can readily deliver oil to the home owner. Improvements in securing the maximum efficiency from all types of fuel are being developed continually ”

“ During the last thirty-five years gas engines have been perfected, and more recently oil engines, and in point of efficiency both convert a somewhat larger percentage of the heat energy of the fuel into mechanical energy than the best steam engines. All successful oil and gas engines are at present internal-combustion engines, the fuel being burned in a gaseous form inside the working cylinder. ”

“ It is not essential for the plant manager to be a fuel expert, but he should be familiar with the instruments that give a check on the daily operations. It is a mistake not to provide proper instruments, for they guide the firemen and show the management what has taken place daily. Instruments provided for the boiler room manifest the interest taken by the management toward conserving fuel. It indicates cooperation and encourages the firemen to work harder to increase the efficiency.
A second factor effecting fuel economy is the selection of fuel for the particular plant. ”

“ The efficiency of this turbine compressor was found to be about 65 per cent. The total efficiency of the combined turbine and compressor was low, as the fuel consumption amounted to nearly 3.9 lb. of gasoline per B. H. P. hour. An ordinary gasoline engine with a moderate compression can 83readily give its power at the rate of 0.5 lb. ”

“ As the calorific effect of petroleum is almost double that of coal, the engine is nearly as efficient as a steam-engine of large size, and much more so than one of the same power, while, on account of the cheapness of petroleum, the expense for fuel is no greater. The oil used can be obtained in comparatively small quantities at from six to seven cents a gallon, and at the latter price the cost of a horse-power per hour would be a little less than one and a quarter; cent, an expense considerably below the best results obtained in any of the engines using gas. ”

“ A wide range of fuels may be used in an internal-combustion engine. They may be either gaseous, liquid, or even solid. In stationary engines hydrogen, coal gas, natural gas, blast-furnace gas, and [156] producer gas are employed to advantage. Volatile fuels, such as alcohol, bensol, gasoline, and kerosene, are turned into a mist or vapor and then burned as a gas. In engines of the Diesel type any liquid fuel ranging down to thick crude oils may be employed, and in one type of engine, which, however, has not proved commercially practicable, coal dust is burned in the cylinder. ”

“ Where petroleum oil can be cheaply obtained, say for twopence per gallon, one of the Otto Cycle Oil Engines, for powers up to 20 indicated horse-power, can be advantageously employed.
These engines have the advantage of being a self-contained power, requiring neither chimney nor steam boiler, and may be said to be a waterless power. The objection is the necessity to rely upon oil as fuel, and the dangers attending the storage of oil. A good oil engine should not require to use more than a pint of refined petroleum per indicated horse-power working for one hour. ”

“ Further, a very decided saving of fuel may be effected by this combination of oil-gas producer with the internal-combustion engine, in place of the boiler and steam-engine, in many places where suitable oil is cheap or plentiful, or where intermittent work is required. On the other hand, more heat may be produced by the direct combustion of liquid fuel with dry steam and air than by converting the oil into gas before using it as a fuel. Oil-gas is a safe, rich, permanent gas made from petroleum oil, and burned with excellent results in the gas-engine cylinder. ”

“ As petroleum is being used as a substitute for coal—and inasmuch as the whole problem of fuel supply is one—we are ultimately compelled to an investigation of the ability of our petroleum supply to meet its present drain and to meet the expansion in its use, which is the most surprising development of our day in the study of power creation. ”

“ The great increase in the consumption of petroleum is ascribable partly to the more extensive use of it as a fuel, in substitution for coal, but mainly to the greater use of gasoline which is directly attributable to the automobile. ”

“ And after three decades of inaction, we raised fuel economy standards so that by the middle of the next decade, our cars will average nearly 55 miles per gallon. That’s nearly double what they get today. ”

“ In some cases the work done in a steam-engine by 2 tons of coal has been performed by 1 ton of oil fuel, but in others the proportions have been as 3 to 2, and these latter can be safely relied on in practice as a minimum. This saving, combined with the savings of labour and transit already explained, will in the near future make the use of liquid fuel compulsory, except in places so near to coal-fields that the cost of coal becomes sufficiently low to counterbalance the savings in weight of fuel consumed and in labour in handling it. ”

“ Gas.—Gas engines are now occupying considerable attention and receiving general favour; the attention needed in working these motors is comparatively nil, and they admit of such exact regulation that there is practically no loss of power and fuel, for in reducing speed or work the supply of fuel (gas) must first be reduced. A noticeable feature is the extreme cleanliness, as there is no furnace and stoking, no boiler safety-valve nor pressure gauge, &c. ”

“ When but moderate temperatures are desired, as in warming a house, exhaust steam serves admirably, and so might the exhausts from gas engines. Indeed we here strike the key-note of modern fuel economy which is that wherever possible fuel should first deliver all the motive power that can be squeezed out of it, when and only when the remainder of its heat, much the larger part of the whole, should be used for warming. ”

“ For illuminating purposes it is the cheapest form of artificial light; as a fuel it is supplanting coal, where the latter is dear or its cost of carriage high, as on ocean steamers. Finally, the construction of light and convenient gasoline motors has given it great importance as a source of motive power. Natural gas is closely related to petroleum, but the supply has been so reduced by rapid and reckless use that it has but a limited economic outlook and is of local significance only. ”

“ This brings about the necessity for injecting the fuel in a well-atomized condition at the time that combustion is desired and the quantities of fuel injected at this time control the amount of heat generated; that is, an infinitesimally small quantity of fuel will be burned just as efficiently in the Diesel engine as a full charge of fuel, whereas in the gasoline engine the mixture ratio must be kept reasonably constant and, if the supply of fuel is to be cut down for throttling purposes, the supply of air must be correspondingly reduced. ”

“ Total consumption of motor fuel experienced an equally rapid growth, rising from the depression low in 1933 of approximately 141⁄4 billion gallons to nearly 24 billion gallons in 1941, an increase of 68 percent in the 8 years. ”

“ We have not yet taken full advantage of the laws of combustion, or adapted our apparatus to the peculiarities of the best and cheapest fuel. Nature manages more wisely in her machinery. Combustion, the union of fuel with oxygen, ceases for want of air as well as for want of fuel. In the case of fuels compounded of carbon and hydrogen, if the air be withheld when the mass is in rapid combustion, the heat will cause a portion of the fuel to pass off by distillation, unconsumed, and this portion will be lost. ”

“ Exposition, 1904, three Diesel engines, using oil costing three cents per gallon, delivered for seven months, during eleven hours each day, at half-load, an average of 250 kilowatts at an expense for fuel of but three tenths of one cent per kilowatt hour on the switchboard, including all generator and line losses. Engineers of the first rank are convinced that the Diesel principle may be successfully embodied in gas engines. That done, with a success approaching the effectiveness of Diesel’s oil motor, we may expect steam engines and turbines to be largely dismissed from service. ”

“ Correspondingly well-designed alcohol and gasoline engines when running under the most advantageous conditions for each, will consume equal volumes of the fuel for which they are designed. This statement is based on the results of many tests made under the most favorable practical conditions that could be obtained for the size and type of engines and fuel used. An average of the minimum fuel consumption values thus obtained, gives a like figure of eight-tenths (.8) of a pint per hour per brake horsepower for gasoline and alcohol. ”

“ It should not be forgotten that, in large engines fed with producer-gas, economy of consumption is a secondary consideration, because of the low quantity of fuel required. The cost, moreover, may well be sacrificed to that steadiness of operation which is of such great importance in large engines furnishing the power of factories; for in such engines sudden stops seriously affect the work to be performed. For this reason engine builders have been led to the construction of motors provided with very effective cooling apparatus. ”