« НазадПродовжити »
hydrocarbons because the elements hydrogen and carbon are the chemical constituents o. most liquids suitable for burning.
Q. Name the principal liquid fuels.
A. The principal liquid fuels mentioned in order of their importance are gasoline, naphtha, benzol, kerosene, and alcohol.
Q. Which is the best suited to modern engines?
A. The internal combustion engines used for vehicle propulsion have been designed with a view of using hem with readily evaporated liquids, such as gasoline.
Q. What is gasoline?
A. Gasoline is a highly volatile liquid that not many years ago was a by-product of but little value. It was used to a limited extent for removing oil stains from cloth or for cleansing delicate fabrics. It could be bought for four or five cents a gallon, and there was little market for it at that price until the gasoline stove was introduced. Engineers soon discovered that this substance evaporated very easily and mixed with air at ordinary temperatures to form a highly inflammable explosive gas.
Q. From what is gasoline derived ?
A. Gasoline is one of the first products obtained by the distillation of crude petroleum. Petroleum is a dark, evil smelling liquid that comes from subterranean deposits and is obtained in large quantit es in several states, notably, Pennsylvania, Texas, Indiana, and Ohio. Crude petroleum is usually in association with natural gas. It is found in almost all parts of the world, but the largest proportion of that produced commercially is obtained from American wells. The petroleum found in this country yields more of the volatile products than those of foreign production. Many products and compounds are derived from crude oil, but before the crude product can be used it must be freed of the impurities such as free carbon, sulphur and various earthy elements which are in suspension in the liquid.
Q. What is the process of obtaining gasoline?
A. The process of purifying crude oil is one of destructive distillation and during this refining the various liquids of which the crude oil is composed are separated from each other and their common base. The oil is heated in large stills and the gases given off are condensed in a cooling coil and again turned to liquid. The oil is broken up into three main groups of products as follows: Highly volatile, which include naphtha, benzine, and gasoline; light oils, such as kerosene and light lubricating oils, and heavy oils or residuum.
Q. What proportion of the crude oil is gasoline?
A. The proportion of volatile products, such as gasoline, obtained from a given amount of crude oil varies from 6 to 10 % of the total. About 60% of the refined products is kerosene, 20% is light lubricating oil, while the remainder are various heavy oils and greases, such as vaseline, petroleum jelly and compounds of that nature.
Q. What are the properties of gasoline making it suitable as a fuel?
A. Gasoline evaporates readily at ordinary temperatures and can be mixed with air to form a satisfactory fuel gas by simple methods.
Q. Is gasoline dangerous?
A. Gasoline in itself is not dangerous unless enough of the vapor becomes mixed with air to form an inflammable gas. Owing to the volatile nature of this fluid, vapors are constantly given off whenever it is exposed to the action of the air, and because of this, the use of a naked flame or spark should always be avoided where gasoline is present in any quantity.
Q. What is kerosene?
A. Kerosene forms one of the most importart of the distillates of crude petroleum and is the substance that is given off during the refining process following the evaporation of the more volatile gases that are condensed into the various grades of gasoline.
Q. Can it be used in engines of present design?
A. The chief difficulty which prevents the use of kerosene is that it will not vaporize readily at ordinary temperatures, and before it will evaporate sufficiently to form a gas, it must be heated. This calls for specially constructed vaporizing devices and water jacketed manifolds. Owing to the low rate of evaporation, kerosene cannot be used successfully on high speed motors where is it desired to have flexible control and where the engine must be accelerated from a minimum to the highest speed in a short time.
Q. What are the advantages of kerosene?
A. At the present time kerosene is much more plentiful than gasoline, and when vaporized properly, it actually has more heat units and is capable of giving more power than does gasoline in equal quantities.
Q. Is kerosene dangerous ?
A. Kerosene is not considered dangerous by the insurance companies, and large quantities of it can be stored without introducing the same element of fire risk that is present with gasoline. It is not constantly giving off vapors at ordinary temperatures, and will not burn unless it is spread in a thin film over some object where a large quantity will be exposed to the air. A burning match can be thrust into kerosene and the flame will be put out. The very condition that makes kerosene safer than gasoline, makes it less suitable as a fuel for present day orms of engines.
Q. Why is kerosene better for stationary power plants than for automobile engines?
A. Owing to the slow rate of vaporization, kerosene is more suitable for slow and moderate speed motors such as sed for stationary and marine service than it is on high speed power plants.
Q. What is the relative value of kerosene and gasoline as fuels?
A. Kerosene actually contains more heat units per pound than gasoline does.
Q. What precautions are necessary to use kerosene?
A. When kerosene is to be used, it is necessary to provide some form of preheating coil through which the fuel is passed before it reaches the carburetor, to thoroughly heat the vaporizing chamber and induction manifold, and to proportion the mixture passages so the velocity of the entering gas will be high. It is necessary to provide an auxiliary device so the engine may be run on gasoline until it becomes warm enough to use the kerosene vapor. As kerosene contains more carbon in its composition than gasoline, and as the
combustion of kerosene vapor is not apt to be as complete as gasoline gas, with some forms of carburetor, a minute stream of water is sprayed into the mixture before it reaches the combustion chamber. The water is decomposed by the heat and liberates oxygen which facilitates combustion and which tends to minimize carbon deposit.
Fig. 58A.–Showing Method of Carrying Fuel Tank at Rear of Chassis
on Lozier Cars. Q. What is benzol?
A. Benzol is a by-product incidental to the manufacture of illuminating gas and coke. The crude product is a foul smelling liquid which has about the same color as ale, but when subjected to a refining process, the liquid is changed to one of about the same color of gasoline. Coke was formerly produced by a process of destructive distillation and the gases evolved were permitted to escape. At the present time these gases are retained and passed through a condensing coil to form benzol. About three gallons of benzol are obtained for each ton of coal converted into coke or gas.
Q. How is it used?
A. Benzol is not as volatile as gasoline but much more so than kerosene. A motor supplied with a carburetor of ordinary water or exhaust gas jacketed construction may be started without difficulty with this fuel. It has received considerable application in England.