Exhaust gas

“ Some makers of high speed engines open the inlet slightly before the exhaust closes as it is claimed that the inertia of the exhaust gas passing through the exhaust pipe creates a slight vacuum that is an aid in filling the cylinder with a fresh charge. It should be borne in mind that this condition only exists when the piston has come to rest and exerts no pressure on the exhaust gas. The vacuum is due to the velocity inertia of the gas after it has been reduced to atmospheric pressure. ”

“ The overrunning of the exhaust ports at once causes the pressure in the cylinder to fall to atmosphere, and then the pressure in the displacer overcomes the pressure in the motor cylinder and opens the lift valve, when the charge flows in to the motor cylinder through the conical compression space and displaces the exhaust gases through the ports E, while it fills up the cylinder A with the inflammable charge. ”

“ At high engine speeds there is great risk of the hot exhaust gases in the working cylinder setting fire to the incoming charge in the inlet ports, thus causing backfiring into the crankchamber. To avoid all possibility of backfire, some form of air scavenging must be adopted, but the general arrangement of this form of two-stroke engine does not lend itself to such an addition—it would merely reduce still further the quantity of gas reaching the cylinder. ”

“ At very high speeds the charge is diluted by a considerable quantity of burnt gas which has not had time to escape through the port causing a further loss of power. With the throttle nearly closed on a light load, the impact of the incoming mixture is so slight that the percentage of exhaust gas left in the cylinder is very high. This dilution is so great that with moderately low speeds (easily within the capacity of the four stroke cycle engine) it is either impossible to ignite the charge or it is impossible to ignite two in succession. ”

“ Fuel lines to gasoline and oil engines frequently pass over the exhaust pipe. When the machine is at rest, you can stab a small hole in the fuel line and plug the hole with wax. As the engine runs and the exhaust tube becomes hot, the wax will be melted; fuel will drip onto the exhaust and a blaze will start.
(7) If you have access to a room where gasoline is stored, remember that gas vapor accumulating in a closed room will explode after a time if you leave a candle burning in the room. A good deal of evaporation, however, must occur from the gasoline tins into the air of the room. ”

“ The same conditions will prevail if there is an insufficient supply of air for a given quantity of gasoline vapor, and consequently a rich mixture may be obtained by reducing the air flow as well as by adding to the amount of gas admitted to the mixing chamber.
A rich mixture will cause irregular explosions in the cylinders, and will often emit a black, pungent smoke at the exhaust. The motor will probably overheat easily, due to the slow-burning properties of the mixture and the resulting fact that a large portion of the cylinder walls uncovered by the pistons will be exposed to the flame. ”

“ It is evident that if a charge of the mixture has not been normally exploded, either because its constituents have not been mingled in the proper proportion, or because the ignition apparatus has missed fire, this charge at the moment of exhausting will pass out of the cylinder without any acquired speed, and will flow back in part at the end of the exhaust stroke past the prematurely opened admission-valve, thereby lodging in the air suction apparatus. ”

“ The chief danger with an apparatus of this sort is its liability to accident by the careless use of the gas, and, as a mixture of hydrogen and air is very explosive, great care must be taken to exhaust all the air in the generator and tubes before attempting to light the gas at the blow pipe. The only way to make sure that the air is exhausted is to test the gas, as described under the head of “The Flame and Its Management.” ”

“ The exhaust-chest should be placed as near as possible to the engine; it should never be buried; for the joints of the inlet and outlet pipes of the exhaust-chest should be easily accessible, so that they may be renewed when necessary. The 84 author recommends the placing of the exhaust-chest in a masonry pit, which can be closed with a sheet-metal cover. For engines of 20 horse-power and upward, these joints should be entirely of asbestos. Pipes screwed directly into the casting are liable to rust. Exposed as they are to the steam or water of the exhaust, they cannot be detached. ”

“ Again we make large exhaust valves and provide a free escape through the silencer for the exhaust gases, so that when we have snatched our useful one-third of the heat supply we may throw the remainder away into the atmosphere as rapidly as possible.—this part is of no use to us, we cannot turn it into work, then why let it stay here and heat our cylinder walls and piston still further? ”

“ Engines using low grade fuels such as kerosene, usually experience much trouble in obtaining a proper mixture when the fuel is vaporized in an external carbureter even when the carbureter is specially designed for the heavy oil. This leads to fuel waste, starting troubles and cylinder carbonization, to say nothing of the objections of an odorous, dirty exhaust. ”

“ The vaporizer is heated by a special petroleum lamp. Ignition takes place when the explosive mixture comes into contact with the heated walls of the vaporizer, their temperature being always high enough to ensure ignition taking place. The consumption of fuel is regulated by a governor acting on the oil-pump, preventing it from supplying more oil than is absolutely necessary to keep up the speed. The governor regulates the exhaust valve as well, so that the speed, which is pretty high, is kept quite constant. ”

“ 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 exhaust from the cylinders is used in two ways, first to create a draft for the fire, and second to heat the feed water pumped into the boiler. The draft is increased by exhausting a portion of the steam into a nozzle placed directly under the stack. The friction of the steam on the surrounding air, draws the air with it, forming a partial vacuum over the grate at each puff, and in this way it causes additional air to rush through the fuel and increases the temperature of the combustion. ”

“ When air is applied in too great quantity, and especially if some of the tubes convey oxygen gas, then a violent combustion and flame is excited, which will, in all probability, consume or burn out the furnace or grate, or if it do not, it will burn out the fuel, and thus exhaust itself. ”

“ The air drawn in combines with the carbon during its downward journey, and then passes through a cooling tower surrounded by a water jacket which acts as a boiler. The heat extracted from the gas is therefore used to produce steam, which drives an engine working the pump which aspirates the air. The exhaust steam from this engine passes into the incandescent fuel and is decomposed, forming hydrogen and carbon monoxide. The valves which govern the supplies of air and steam are so arranged that producer gas or water gas, or both at once, may be generated at will. ”

“ 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. ”

“ By the time that the exhaust gases have passed through the pipes and have expanded in the muffler, some of the blue smoke may have disappeared, and consequently the fact that a car does not give a trace of vapor at its exhaust should not necessarily be taken as an indication that the motor is not well lubricated. ”

“ At the end of the working stroke the exhaust valve must liberate the gases and remain open to the end of the scavenging stroke to eliminate the residual gas while the closed inlet valve prevents the burnt gases from being forced through the inlet pipe and carburetor. ”

“ That which comes from the exhaust is no longer inflammable. It has served its purpose in the combustion chamber by burning with rapid expansion, furnishing power. It has undergone chemical changes, has been split up, the hydro-carbon uniting for the most part with the oxygen of the air in the mixture and forming carbon monoxide and carbon dioxide. The latter is carbonic acid gas, in which no living thing can live. The carbon monoxide is no less deadly, and besides there is the nitrogen from the air, which225 will suffocate as well, unless it mingles with the air freely. ”

“ Notwithstanding much which has been said as to varying mixture, there is only one mixture of air and petrol which gives the best results—that in which there is some excess of oxygen, more than sufficient to burn all the hydrogen and carbon present. It is necessary to secure this mixture under all conditions, not only to obtain economy in running but also to maintain purity of exhaust gases. ”

“ When the maximum power is required, the exhaust valve is not interfered with, and opens to its fullest compass. When less power is required, the exhaust valve is prevented from opening to that extent. Consequently the exhaust gases are not fully expelled, and as they partly occupy the space in the combustion chamber, a full charge of mixture cannot be admitted through the induction valve, and the explosion is weakened. ”

“ The waste of energy is clearly evident in the exhaust pipe of an internal combustion engine. The gases after doing their work on the piston rush out [165] with such velocity as to produce a sharp explosive sound. The noise of the exhaust is highly objectionable in automobiles and must be overcome, but instead of utilizing the boisterous energy of the escaping gases and getting a little more useful work out of them, means are provided for hushing their noise. ”

“ 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. ”

“ In some apparatus an air inlet is provided immediately adjacent to the ash-pit. This arrangement is faulty for the reason that it gives rise to gaseous emanations which take place by reaction after each suction stroke of the engine. Furthermore, it is advisable that the air supplied below the ash-pit be as hot as possible. For this reason the employment of preheaters is desirable. The dry air forced in by the fan stimulates combustion, and the hot gas produced and mixed with smoke escapes through a separate flue, generally arranged beyond the vaporizer and serving as a chimney. ”

“ The petrol-engine, as now used, emits the products of combustion at a high pressure. If unchecked, they expand violently, and cause a partial vacuum in the exhaust pipe, into which the air rushes back with such violence as to cause a loud noise. ”

“ Even the best of mufflers will use up nearly 5 per cent of the engine power. The energy that escapes at the exhaust is not the only loss. All the heat that radiates from the engine represents just so much wasted energy. In our water and air-cooled systems we deliberately abstract heat from the burning gases and throw it away. If we had materials that would stand the intense heat of burning gases and enable us to conserve all the heat developed in the cylinder we could use our fuels much more economically. ”

“ First the mechanism compresses air alone to 500 pounds per square inch, then and then only the oil for combustion is injected, to take fire instantly from the heat of the compressed air. A governor regulates the period of burning; this is usually during one tenth part of the stroke, the expansion of the burned products completing the stroke. Because 500 pounds is a pressure out of the question for the compression of the mixed charge of air and combustible gas in an ordinary gas cylinder, the Diesel engine excels in economy any gas engine thus far built. ”

“ There is one thing, however, which will actually put out a gasoline fire, and it is such a safeguard that no owner can afford to be without it. That is the carbon tetra-chloride compound, which is the basis of all liquid extinguishers on the market. This, discharged close to the seat of the flames, forms a dense smoke-like gas which has no oxygen to feed the fire, which therefore goes out for lack of fuel. ”

“ There are two causes why all the heat which fuel may furnish is not obtained. First, that the inflammable gases 329evolved by the heat are not all consumed from want of a sufficient supply of oxygen, the air drawn through the fire being only sufficient to decompose more fuel than when decomposed it could burn, or supply with oxygen. The thick smoke that escapes from a chimney when fresh fuel is thrown on a hot fire, is unconsumed gas; decomposed from the fuel, but without oxygen enough to burn—although there may have been a sufficient supply of heat. ”