VALUES OF COALLocation of MinePROXIMATE ANALYSISCalorific Value in B.T.U. per Lb. of CoalMoistureVolatile MatterFixed CarbonAshSulphurANTHRACITENorthern Pa.3.394.4183.308.17.7313,200Eastern Pa.3.703.0786.426.18.6313,440Western Pa.3.123.7681.6010.61.5312,875SEMI-ANTHRACITE1.258.1583.306.271.6313,900SEMI-BITUMINOUSPennsylvania.8015.6077.405.35.8514,900Pennsylvania1.5516.4571.508.631.8714,200Pocahontas Va.1.0021.0024.403.02.5815,100West Virginia.9017.8377.703.30.2715,230BITUMINOUSYoughiogheny Pa.1.0036.5059.002.59.8614,400Sample No. 21.2030.1859.008.84.7814,400Hocking Valley6.535.0648.808.051.5912,100Kentucky4.0034.0054.707.00.0312,800Indiana8.0030.2054.207.6012,500Illinois10.5036.1537.0012.903.4510,500Colorado6.0038.0147.908.0912,200LIGNITE9.0042.2644.303.271.1811,000
TheCALORIFIC VALUEof a fuel may be calculated from its analysis, or may be determined by means of theCALORIMETERfrom a sample of the coal; the latter method is the most reliable. Table gives approximately the calorific values, and the proximate analysis of several representative coals from various sections of the country. The values given in the table are not exact, as the coal from each locality varies considerably in quality, but the figures will indicate what may be expected from each type of coal.
Connellsville, Pa., Coke has a calorific value of approximately 13,000 B.T.U.’s per pound, contains no volatile matter, and has an approximate content of 10% ash. Coke is a valuable fuel for the gas producer, but is rather expensive. It is clean and the absence of volatile matter reduces the “scrubbing” problem to a minimum.
Small coal such as buckwheat and pea contain a much higher percentage of moisture than given in the table, running from 5% to 10% higher than the given values.
Bituminous coal is high in hydrocarbons or volatiles which condense easily and form tar. If the tar is not removed or converted into a permanent gas, it will clog the passages of the producer and the engine and cause trouble.
The removal of the tar and ash from a gas is calledSCRUBBING, and is performed by a device much resembling a filter. Anthracite coal and coke are low in volatiles or hydrocarbons, and therefore do not cause trouble with tar deposits.
A high percentage of volatile matter also causes trouble by the tar cementing the particles of fuel together. This interferes with the proper action of the producer.
Fuels having a high percentage of ash call for perfect filtering or “scrubbing” as such fuels will fill the gas passages with dust. Dust should be kept out of the engine at all costs, for the dust even in a quantity will cause wear in the cylinder.
Depending on the quality of the fuel, bituminous coal will produce about 4½ pounds of ammonia and 12 gallons of tar with about 5% of sulphur.
Anthracite coal will produce approximately six pounds of tar, and two pounds of ammonia with traces of sulphur.
Loose Anthracite coal requires approximately 40 cubic feet of storage space per ton of 2240 pounds and weighs about 56 pounds per cubic foot (market sizes).
Loose Bituminous coal requires approximately 45 cubic feet of storage space per ton of 2240 pounds, and weighs about 52 pounds per cubic foot in market sizes.
Dry coke requires approximately 85 cubic feet of storagespace per ton of 2240 pounds, and weighs about 26 pounds per cubic foot.
Crude oil, a natural product, is the base of the fuels most commonly used in internal combustion engines, especially in the smaller sizes. From this compound the following derivatives are obtained by the process of distillation, a separation possible because of the different boiling points of the various oils. As each derivative orDISTILLATEhas a different boiling point, the temperature of the crude oil is maintained at the boiling point of that product that is desired, and the resulting vapor is condensed. The following list is not anywhere near complete for there are several hundred distinctly different distillates, but it contains those that are of the most interest to the engine man.
The specific gravity of the crude oil as obtained in the field will range from 12° to 56° Beaumé scale. The crude from Pennsylvania will average 40° Beaumé while that from Texas will average 20°. The accompanying table will give the calorific values and general properties of the principle liquid fuels. It should be noted that the weight or density of the liquids is given in terms of specific gravity or Beaumé scale, in which theSPECIFIC GRAVITYof the fuel is the ratio of its weight per unit volume to the weight of an equivalent volume of water. The specific gravity of a liquid is generally determined by an instrument known as aHYDROMETERwhich consists of a glass tube sealed at both ends carrying a graduated scale on the upper portion of the stem, and a ballast weight of shot or mercury at the bottom.
The hydrometer is floated in the liquid to be tested, and the lower the specific gravity, the lower the hydrometer sinks, and vice versa. The specific gravity of the liquid is read directly from the graduation on the stem that are on a level with the surface of the liquid under test. As in the case of thermometers, hydrometers are all graduated in two different scales, the specific gravity scale and the Beaumé scale. The specificgravity scale reads at 1.00 when floated on distilled water, and the Beaumé at 10.00 when floated on the same liquid.
A difference in temperature affects the density of a liquid, hence all hydrometers are graduated for a standard temperature of 60°F unless otherwise specified. For a difference of 10°F there is a variation of one degree gravity in the Beaumé scale, and for a difference of 20°F in temperature there is a change of one degree on the specific gravity scale. If the temperature differs from 60°F, the corresponding correction should be made in the reading.
To convert the Beaumé reading (B) to terms of the specific gravity scale (S) use the following formula:
It will be noted that the petroleum products contain an enormous amount of heat energy, nearly 25% more than that of the same weight of pure carbon. It will also be noted that the lighter products such as gasoline, kerosene, etc., have more heat per pound but less per gallon than the heavier oils. This is rather confusing at first, but as will be seen after deliberation that the heavier fuel is the most economical since the least is used per horse-power, and is bought by the gallon. The calorific values given in the table are obtained by a calorimeter, and are burnt in the open air, and consequently have a different heating value when under compression in the cylinder of the engine.
In all cases the liquids are vaporized before being introduced in the cylinder, the more volatile liquids such as gasoline being converted into vapor at atmospheric temperature, and the heavier non-volatiles by being sprayed into a heated vessel or preheated air. The percentage of liquid fuel contained in a cubic foot of air vapor mixture depends on the temperature, the boiling point of the liquid and upon the pressure and humidity.
Gasoline consists principally of compounds of the methane series, the one representative of gasoline being Hexane (C6H14). It requires 15.5 pounds of air for combustion theoretically and about 10 per cent. more in practice. The formation of gasoline vapor produces a drop in temperature of 50°F, and should be heated 100°F above the atmosphere for the best results. The volume of air required for the combustion is about 192 cubic feet. With alcohol at 20 cents per gallon and gasoline at 12½ cents the number of B.T.U.’s for one cent in the case of alcohol is 3594 and 9265 in the case of gasoline. In the engine the difference is not so great owing to the difference in compression pressures.
Because of the increasing interest in the Diesel type engine and the low grade fuels that it has made possible, we quote the specifications laid down by Dr. Rudolph Diesel, the inventor, before the English Institution of Engineers.
(1.) Tar-oils should not contain more than a trace of constituents insoluble in xylol. The test on this is performed as follows:—25 grammes (0.88 oz. av.) of oil are mixed with 25 cm.3(1.525 cub. in.) of xylol, shaken and filtered. The filter-paper before being used is dried and weighed, and after filtration has taken place it is thoroughly washed with hot xylol. After re-drying the weight should not be increased by more than 0.1 gr.
(2.) The water contents should not exceed 1 per cent. The testing of the water contents is made by the well-known xylol method.
(3.) The residue of the coke should not exceed 3 per cent.
(4.) When performing the boiling analysis, at least 60 per cent. by volume of the oil should be distilled on heating up to 300° C. The boiling and analysis should be carried out according to the rules laid down by the Trust. (German Tar Production Trust on Essen-Ruhr.)
(5.) The minimum calorific power must not be less than8,800 cal. per kg. For oils of less calorific power the purchaser has the right of deducting 2 per cent of the net price of the delivered oil, for each 100 cal. below this minimum.
(6.) The flash-point, as determined in an open crucible by Von Holde’s method for lubricating oils, must not be below 65° C.
(7.) The oil must be quite fluid at 15° C. The purchaser has not the right to reject oils on the ground that emulsions appear after five minutes’ stirring when the oil is cooled to 8°.
Purchasers should be urged to fit their oil-storing tanks and oil-pipes with warming arrangements to redissolve emulsions by the temperature falling below 15° C.
(8.) If emulsions have been caused by the cooling of the oils in the tank during transport, the purchaser must redissolve them by means of this apparatus.
Insoluble residues may be deducted from the weight of oil supplied.
Coal tar oil is the distillate of the tar obtained from gas works, from which all valuable commercial materials such as aniline have been removed. Coal oil tar is also known as creosote oil and anthracene oil, the heat value of which is not quite 16,000 B.T.U. per pound.
Residual oil is the residue left after the lighter oils have been distilled from the petroleum, which before the advent of the Diesel engine were useless. Residual oil which was hardly fluid at ordinary temperatures has been successfully used in the Diesel and semi-Diesel types of engines, by preheating it before admission to the inlet valves. The enormously increased demand for gasoline has resulted in a great increase of the formerly useless residual oil so that it is possible that the demand for gasoline will make the production of the residual great enough so that it can be seriously considered as a fuel.
Gasoline is by the far the most widely used fuel for internal combustion engines because of its great volatility and the ease with which it forms inflammable mixtures with the air at ordinary temperatures. Another point in its favor is the fact that it burns with a minimum of sooty or tarry deposits, without a disagreeable smell with moderate compression pressures and without preheating through a wide range of air ratios. Gasolineis a product of crude oil from which it is obtained by a process of distillation, and as it forms but a small percentage of the crude oil it is rapidly becoming more and more expensive as the demand increases. Some Pennsylvania crude oils will yield as much as 20 per cent of their weight in gasoline, while the low grade Texas and California crudes very seldom contain more than 3 per cent.
When considered as a term applying to some specific product, the word “Gasoline” is a very flexible expression as it covers a wide range of specific gravities, boiling points, and compositions, the latter items depending on the demand for the fuel and the taste of the manufacturer. Since the specific gravity of gasoline is a factor that determines its suitability for the engine, at least in regard to its evaporating power or volatility, it is graded according to its density in Beaumé degrees as determined by the hydrometer. According to this scale gasoline will range from 85° to 60° Beaumé, and even lower, although 60° is supposed to mark the lowest limit and to form the dividing line between gasoline and naphtha.
The density of the gasoline in Beaumé degrees is an index to the volatility, for the higher the degree as indicated on the hydrometer, the higher is the volatility at a given temperature, consequently a high degree gasoline will give a better mixture at a low temperature than one of a low degree. In cold weather all gasoline should be tested with a hydrometer when purchased to insure a grade that will be volatile enough for easy starting when the engine is cold. In cold weather the gasoline should not be lower than 68°, and for the best results should be above 72°, at least for starting the engine. Good gasoline should evaporate rapidly and should produce quite a degree of cold when a small amount is spread on the palm of the hand, and it should leave neither a greasy feeling nor a disagreeable odor after its evaporation.
The high gravity gasoline is of course the most expensive, as there is less of it in a gallon of the crude oil from which it is made; gasoline of 76° Beaumé being approximately 15c. per gallon in carload lots, while naphtha of 58° Beaumé brings 8½c. per gallon.
The calorific value of gasoline increases as the gravity Beaumé decreases per gallon; 85° gasoline having approximately 113,000 B.T.U. per gallon while 58° naphtha has an approximate value of 122,000 B.T.U. per gallon. The calorific value remains nearly constant per pound for all gravities.
It should be remembered that heat is absorbed in evaporating gasoline as well as in evaporating water, and that effects of cold weather are greatly increased by the amount of heat absorbed, (or cold produced) by the vaporization of the fuel. While the heat absorbed by evaporating a given quantity of gasoline is only .45 per cent of that absorbed by an equal amount of water, it is a fact that this heat must be supplied from some source to prevent a reduction in the vapor density. In starting the engine, the heat of evaporation is supplied by the atmosphere, and should the temperature of the air be below that required for a given vapor density, the engine will refuse to start.
By the use of two tanks and a three way valve, it is possible to use two grades of fuel: one tank containing high gravity gasoline, and the other low gravity; the high gravity being used for starting the engine in cold weather, and the cheaper, low gravity, being used for continuous running after the engine is warmed up—the change of fuels being made by throwing over the three way valve.
TheVAPOR DENSITYof gasoline vapor is the ratio of the weight of the vapor compared with the weight of an equal volume of dry air at the same temperature. If the weight of a cubic foot of gasoline vapor is divided by the weight of a cubic foot of air atthe same temperature the result will be the vapor density of the gasoline vapor. Compared to air, the gasoline vapor is quite heavy so that if a small quantity of gasoline is poured on the top of a table, the vapor will flow over the edge of the table and drop to the floor where it will remain until it has united with the air by the process of diffusion. Experiments have shown that pure, dry gasoline vapor has a density of about 3.28, or in other words weighs 3.28 times as much as an equal volume of dry air. This weight of course is the weight of pure vapor which is considerably heavier than the mixture of vapor and air that is used in the cylinder of the engine.
Dampness, or the presence of water vapor in the air reduces the quantity of gasoline vapor taken up by the air, but only by a small amount, the maximum difference being only about 2 per cent. Since it is very likely that the water vapor is broken up into its original elements, oxygen and hydrogen, by the heat of the combustion it is likely that there is no heat loss due to the vapor passing out through the exhaust. The principal trouble due to dampness is the mixture of water and liquid gasoline caused by the condensation of the water vapor.
All gasolines and oils contain water to a more or less degree,hence provision should be made for the draining of the water which collects in the bottom of the tank. Water in liquid fuels is the cause of much trouble.
Water in gasoline may be detected by dropping scrapings from an indelible pencil into a sample of the suspected fluid. If water is present in any quantity the gasoline will assume a violet color.
In filling a supply tank with gasoline, a chamois filter or chamois lined funnel should always be used, as the chamois skin allows the gasoline to pass but retains the water and impurities contained therein. There are many funnels of this type now on the market.
The rate at which gasoline burns depends on the amount of surface presented to the air by the fluid, for a given quantity of gasoline burns faster in a wide shallow vessel than in a deep jar. Since a spray of minute particles presents an enormously greater surface than the liquid its burning speed is correspondingly greater, and as a true vapor has an almost limitless area, its speed is much greater than that of the spray, the combustion under the latter condition being almost instantaneous. Besides the question of subdivision of the liquid, the rate of combustion also depends on the intimacy of contact of the vapor with the air and on the pressure applied to the vapor as previously explained under the head of “COMPRESSION” in another chapter.
CARBURETING AIR, or producing an explosive mixture of gasoline vapor and air is accomplished by two different methods, first by passing the air over the surface of the liquid, or by passing it through the liquid in bubbles; second by spraying the liquid into the air. The latter is the method most generally in use at the present time, the spray being formed by the suction of the intake air upon the open end of the spray nozzle. The vapor density of the mixture thus formed depends on the suction of the air and upon the nozzle opening, either of which may be varied in the modern carburetor to vary the richness of the mixture.
As a suggestion to the users of gasoline we append the following remarks.
Gasoline vapor will readily combine with air to form explosive mixtures, at ordinary temperature. This property at once makes it the most suitable fuel and the most dangerous to handle.
Never fill tanks or expose gasoline to the air in the presence of an open flame, or do not attempt to determine the amountof gasoline in a tank with the aid of a match. There are a number of people who have successfully accomplished this feat, and a very great number who have not.
Be very sparing in the use of matches around a gasoline engine; there are such things asleaks.
Always carefully replace the stopper or filler cap in a gasoline tank after filling. Never use the same funnel for water and gasoline, and avoid any possibility of water finding its way into the tank.
If you do succeed in igniting a quantity of free gasoline, do not attempt to extinguish the fire with water. Pouring water on burning gasoline spreads the fire. Extinguish it with earth or sand, or by the use of one of the dry powder extinguishers now on the market.
Water may be removed from gasoline by placing a few lumps of desiccated calcium chloride in the tank, the amount depending on the quantity of water.
Calcium chloride, has a great capacity for absorbing water, and in a short space of time will absorb all of the moisture contained in the tank.
The best way to introduce the chloride is to wrap the lumps in a sheet of wire gauze and lower into tank with a wire, the wire allowing it to be easily removed when saturated with water.
Benzol has been used to some extent in Europe as a fuel, its use being due to the rapidly increasing cost of gasoline.
Benzol is a distillate of coal tar, and is a by-product of the coke industry. In England benzol brings approximately the same price as gasoline (called petrol), but benzol proves economical for the reason that it develops more power per gallon.
Benzol is not as volatile as gasoline, but is sufficiently volatile to allow of easy motor starting.
Benzol is also used for denaturing alcohol.
Alcohol is of vegetable origin, being the result of the destructive distillation of various kinds of starchy plants or vegetables. Starch is the base of alcohol.
As a fuel, alcohol has much in its favor, as it causes no carbon deposit, has smokeless and odorless exhaust, can stand high compression, and requires less cooling water than gasoline, asthe heat loss is less through the cylinder walls, and for this reason it is more efficient fuel than gasoline.
At the present time the price of alcohol prohibits its general use. In order that alcohol equal gasoline in price per horse-power hour, it should sell for 10c. per gallon, the price of gasoline being 15c. per gallon.
Alcohol can be used in any ordinary gasoline engine with readjustment of carburetor and the compression.
The nozzle in the carburetor has to be of larger bore for alcohol than for gasoline, and the compression for alcoholin the neighborhood of 180 pounds per square inch.
The inlet air should be heated to about 280°F for alcohol fuel; approximately 6% of the heat of the alcohol is required for its vaporization. Alcohol is much safer to handle than gasoline owing to its low volatility.
90% alcohol has a calorific value of 10,100 B.T.U. per pound, its specific gravity being .815.
WOOD, orMETHYLalcohol is made by distilling the starch contained in the fibres of some species of wood (Poisonous).
GRAIN, orETHYLalcohol is the result of the distillation of the starch contained in grains, potatoes, molasses, etc.ETHYL, orGRAINalcohol rendered unfit for drinking by the addition of certain substances, is calledDENATURED ALCOHOL. The process of denaturing does not affect the calorific value of alcohol to any extent.
Kerosene is a fractional distillate of crude oil which has a considerably higher vaporizing temperature than gasoline. It does not form an inflammable mixture with the air at ordinary temperatures, but is vaporized in practice by spraying it into a chamber heated to above 200°F. Kerosene forms a greater percentage of crude oil than gasoline and as there has been less demand for it up to the present time it is much cheaper. Pennsylvania crude oil produces only 20 per cent of gasoline while the kerosene contents will average nearly 42 per cent according to figures at hand.
Kerosene has a very high calorific value per gallon, 8.5 gallons of kerosene having the same heating effect as 10 gallons of gasoline. Because of its high calorific value and its low cost per gallon, many types of engines have been developed for its use during the last few years, several of which have been very successful. Before the advent of the modern kerosene enginemuch difficulty was experienced with the fuel because of its high vaporizing temperature and its tendency to carbonize in the cylinder, but as the price of gasoline continued to rise, the inventive genius of the gas engine builder overcame these troubles so that the kerosene engine is now as reliable as any form of prime mover.
Kerosene Vaporizer on Fairbanks-Morse Engine. The Engine is Started on Gasoline and When Hot, the Kerosene Feed is Turned on.
Kerosene Vaporizer on Fairbanks-Morse Engine. The Engine is Started on Gasoline and When Hot, the Kerosene Feed is Turned on.
Kerosene Vaporizer on Fairbanks-Morse Engine. The Engine is Started on Gasoline and When Hot, the Kerosene Feed is Turned on.
Any gasoline engine will run on kerosene, after a manner, if the engine is thoroughly heated to insure the vaporization of the kerosene, and if the fuel isheated in the carburetor. Such an arrangement is make-shift, however, and is not productive of good results in continuous service. If kerosene is to be used as a regular fuel, a kerosene engine should be used to avoid vaporizing and carbonizing difficulties as well as the sooty, offensive exhaust, and the loss of fuel represented by the soot.
Many kerosene engines are arranged to start on gasoline, and, after becoming heated, have the running feed of kerosene admitted through a three way valve. The gasoline feed is then stopped.
The above arrangement admits of easy starting in all weathers and temperatures.
In the Diesel engine there is no evaporating of fuel, and no deposits of carbon because of the high temperature of the combustion chamber. With engines that draw the mixture of vapor and air into the cylinder there are several methods of applying heat to the liquid, and the combustion of the vapor thus formed is perfected by the injection of water into the combustion chamber. It has been found by experiment that a small amount of water vapor introduced into the cylinder of a kerosene engine makes the engine run more smoothly and prevents a smoky exhaust and carbon deposits in the cylinder. The water is introduced into the cylinder through an atomizer in the form of a mist or fog, the particles of water being in a very finely subdivided state.
Kerosene Vaporizer on Fairbanks-Morse Vertical Engine. Started on Kerosene Directly by Heating Vaporizer with Torch.
Kerosene Vaporizer on Fairbanks-Morse Vertical Engine. Started on Kerosene Directly by Heating Vaporizer with Torch.
Kerosene Vaporizer on Fairbanks-Morse Vertical Engine. Started on Kerosene Directly by Heating Vaporizer with Torch.
The deposits of free carbon (soot) caused by the “cracking” or decomposition of the kerosene vapor before ignition, due to the high temperature of the cylinder, are burnt to carbon dioxide by the oxygen of the water which is also set free by the heat of the cylinder. This produces an odorless gas (CO2) which indicates complete combustion. Besides the increase of fuel efficiency due to the water vapor, the cylinder is more thoroughly cooled and is more efficiently lubricated because of the reduction in temperature.