CHAPTER V

Defining the Liquid Fuels Commonly Used and Methods of Vaporizing to Obtain Explosive Gas-Methods of Carrying Fuel in Automobiles-Development of Modern Carburetor from Early Vaporizer Forms-Elements of Carburetor Design Outlined-Typical Gasoline Vaporizers Described in Detail-How Kerosene May be Utilized-Discussing Fuel Supply by Direct Injection-Inlet and Exhaust Manifold Design-Muffler Forms in Common

Use.

THERE is no appliance that has more material value upon the efficiency of the internal combustion motor than the carburetor or vaporizer which supplies the explosive gas to the cylinders. It is only in recent years that engineers have realized the importance of using carburetors that are efficient and that are so strongly made that there will be little liability of derangement. As the power obtained from the gas engine depends upon the combustion of fuel in the cylinders, it is evident that if the gas supplied does not have the proper proportions of elements to insure rapid combustion the efficiency of the engine will be low. When a gas engine is used as a stationary installation it is possible to use ordinary illuminating or natural gas for fuel, but when this prime mover is applied to automobile or marine service it is evident that considerable difficulty would be experienced in carrying enough compressed coal gas to supply the engine for even a very short trip. Fortunately, the development of the internal combustion motor was not delayed by the lack of suitable fuel.

Engineers were familiar with the properties of certain liquids which gave off vapors that could be mixed with air to form an explosive gas which burned very well in the engine cylinders. A very small quantity of such liquids would suffice for a very satisfactory period of operation. The problem to be solved before these liquids could be applied in a practical manner was to evolve suitable apparatus for vaporizing them without waste. Among the liquids that can be combined with air and burned, gasoline is the most common and is the

fuel utilized by the majority of internal combustion engines employed in self-propelled conveyances.

The widely increasing scope of usefulness of the internal combustion motor has made it imperative that other fuels be applied in some instances because the supply of gasoline may in time become inadequate to supply the demand. In fact, abroad this fuel sells for fifty to two hundred per cent more than it does in America because most of the gasoline used must be imported from this country or Russia. Because of this foreign engineers have experimented widely with other substances, such as alcohol, benzol, and kerosene. The properties of these fuels, their derivation and use should be considered fully before describing the types of apparatus utilized for vaporizing them.

Distillates of Crude Petroleum.-Crude petroleum is found in small quantities in almost all parts of the world, but a large portion of that. produced commercially is derived from American wells. The petroleum obtained in this country yields more of the volatile products, than those of foreign production, and for that reason the demand for it is greater. The oil fields of this country are found in Pennsylvania, Indiana, and Ohio, and the crude petroleum is usually in association with natural gas. This mineral oil is an agent from which many compounds and products are derived, and the products will vary from heavy sludges, such as asphalt, to the lighter and more volatile components, some of which will evaporate very easily at ordinary temperatures.

The compounds derived from crude petroleum are composed principally of hydrogen and carbon and are termed "Hydro-Carbons." In the crude product one finds many impurities, such as free carbon, sulphur, and various earthy elements. Before the oil can be utilized it must be subjected to a process of purifying which is known as refining, and it is during this process, which is one of destructive distillation, that the various liquids are separated. The oil is broken up into three main groups of products as follows: Highly volatile, naphtha, benzine, gasoline, eight to ten per cent. Light oils, such as kerosene and light lubricating oils, seventy to eighty per cent. Heavy oils or residuum, five to nine per cent. From the foregoing it will be seen that the available supply of gasoline is determined largely by the de

mand existing for the light oils forming the larger part of the products derived from crude petroleum.

As a very small portion of the distillates can be used with ordinary. vaporizing devices any improvements to make possible the use of less liquid or utilize the cheaper fuels, such as kerosene, will be of great value in increasing the usefulness of internal combustion motors. Considerable attention is being given to mixing devices which will permit the use of kerosene, and many authorities have agreed that this material or alcohol will be the fuel of the future. To show the enormous consumption of gasoline in this country, it has been said that if all of the engines in use which depended on this fuel were to be operated continuously together for a ten-hour day that over five million gallons of liquid would be consumed. When one considers that the number of explosive engines is constantly augmenting it will not be difficult to perceive the reason why the development of devices to use fuels other than gasoline should be encouraged.

Benzol and Its Properties.-In England, where gasoline sells for fifty cents a gallon or one hundred and fifty per cent more than the average price in this country, engineers have sought to use benzol, which is said to be adaptable to the present types of motors without change, and in cases where it has been used as much power is obtained as with gasoline. This material is a by-product incidental to the manufacture of illuminating gas and coke, and while it was formerly distilled from coal-tar and obtained only in small quantities, improved methods make it possible to produce about three gallons from every ton of coal changed into coke or gas. The former material was at one time produced by a process which permitted the gas to escape, but at the present time this is retained and condensed to form benzol. The crude product is a foul-smelling liquid which has about the same consistency and color as heavy ale. When subjected to a refining process the dirty liquid is converted to one that is about the same color as water.

Benzol is not so volatile as gasoline, but it is claimed that a motor may be started without difficulty with this fuel supplied to a carburetor of ordinary construction. Owing to the greater number of heat units it contains, it is said it will develop more power than gasoline, and as it will not evaporate so readily it does not become stale or

heavy by the vaporization of the lighter constituents. A disadvantage incidental to its use has been that owing to it being richer in carbon than gasoline it would deposit more of this substance on the piston head and interior of the combustion chamber. While this may be true of a poorly refined benzol and when mixture proportions are not correct, it applies equally well when low grades of gasoline are used and when the mixture of gasoline vapor and air supplied the cylinders is too rich.

Special Vaporizers Needed for Kerosene.-As kerosene forms one of the larger portions of the distillates of crude oil it is apparent that if this material could be used as fuel for internal combustion engines it might replace gasoline to a certain extent. If considered from a point of view of heat units contained or heating value kerosene would be a better fuel than gasoline, though considering it with its other disadvantages in mind it is not so suitable for use in existing types of motors. The chief difficulty which retards its use is that it will not vaporize readily at ordinary temperatures, and before it will evaporate sufficiently to form a gas with air it must be heated. This calls for specially constructed vaporizing devices and jacketed manifolds, which will be described in proper sequence. Owing to the low rate of evaporation it is contended that it cannot be used successfully on highspeed motors where flexibility of control is desired and where the engine must be accelerated from its minimum to the highest speed in a short time. On slow and moderate speed motors, such as used for stationary and marine service, kerosene has been employed with some degree of success. It contains more carbon in its composition, and as the combustion of kerosene vapor is not so apt to be as complete as gasoline gas, more carbon will be deposited in the interior of the combustion chamber than when gasoline is burned.

Advantages of Alcohol.-Considerable experimenting with alcohol has been done by French and German engineers, and there are many points to be considered in its favor when discussing its value as a fuel. Alcohol, instead of being derived from natural mineral deposits, which become more and more depleted as the demands increase, is derived from various plants and vegetables and is the one fuel that can be produced in quantities that could be augmented as the demand for it increased. The vegetable substances which are distilled to make alco

hol are reproduced each cycle of seasons, and in tropical countries there is no cessation to the growth of the vegetation. The raw materials from which alcohol may be manufactured are found in all parts of the earth. It is derived from any substance which contains either starch or sugar, and it can profitably be produced from fruits, grains, and vegetables. It may be made from beets, sugar-cane, rice, barley, rye, corn, wheat, or potatoes, and decaying fruit or other refuse, which could not be utilized otherwise, may be subjected to a process of distillation and alcohol derived therefrom.

Alcohol differs materially from gasoline, and as it is less volatile it requires more heat to vaporize it. Alcohol vapor can be compressed to a greater degree than the vapors of gasoline, and as the heat units liberated from a fuel vary with the degree of compression even though alcohol gives out less heat when burned under the same conditions, higher efficiency may be obtained by compressing the alcohol vapor to a higher degree. While this substance has been used for a decade or more abroad, in engines designed especially for its use, it has not been applied with any degree of economy in motors designed for use with gasoline.

A motor constructed for use with alcohol must use a higher degree of compression than a gasoline motor, and a form of carburetor which will heat the mixture before it is taken into the cylinder should be used. An engine designed for gasoline will use twice as much alcohol as it does gasoline to develop the same amount of energy, though in a special motor the same amount of power will be obtained as when equal quantities of gasoline are burned in the conventional engine. One of the disadvantages of alcohol that is shared in common with kerosene is that it is difficult to start an engine when cold, as alcohol is not very volatile unless heated.

The amount of air necessary for complete combustion is roughly estimated at one third that needed with gasoline. Twice the amount. of compression before ignition can be used with alcohol vapor. The range of explosive mixture proportions of alcohol and air is much greater than that possible with gasoline and air. Various authorities have stated that a compression of one hundred and fifty pounds per square inch is possible with alcohol, but it is doubtful if automobile. engines will ever be built using such high degrees of compression.