Зображення сторінки
PDF
ePub

of ample volume is quite effectual and creates little

back pressure.

The well-known Yankee mufflers are constructed with a combination of these two systems. Sectional views are shown in Figs. 110 and III. The gases entering at A

Fig. 108.-Muffler with Perforated Pipes

partly pass through the perforations at B and are partly deflected by the partition C and the interior of the pipe D, and then expand in the chamber E. From this chamber they pass through the opening in the plate at F and hence through perforations in the outlet pipe at G and

Fig. 109.—Baffle-plate Muffler

into the air through the tail piece H. In the Ejector muffler a very different system is used. This is illustrated in Fig. 112. It consists of three expansion chambers, A, B, C, which are separated by conical plates, D, E, F, perforated at top and bottom and arranged in two sets.

The central tube G, leading through the muffler, is of varying diameter and a portion of the gases from the exhaust passes directly into the central chamber B and hence through the second set of cones D, E, F (2), before the gas which enters the first chamber A has

.

Fig. 110. "Yankee" Auto Muffler

passed through the first series of cones D, E, F (1). A small portion of the gas is also led straight through the central pipe G to the outlet at a very high velocity. This creates a partial vacuum in the third chamber C,

WATER

WATER

Fig. III.-"Yankee " Marine Muffler

and the gas moves rapidly from the second chamber B to fill the partial vacuum in the chamber C. The forward movement of the gas through the first and second chambers A, B, to the third C, causes a sudden expansion which removes the heat from the gases and reduces the

pressure in the muffler to below that of the atmosphere, thus allowing the gases to escape with no appreciable noise and no back pressure. These mufflers work

B

[ocr errors]

D-E - F(2)

D-E - F (1)

Fig. 112.-"Ejector" Muffler

side of this tube pass

excellently both in vehicle, stationary, and marine use; and in the latter case still better results are obtained by running a portion of the circulation water into the exhaust before it enters the muffler.

In

the Hydrex silencer, which is intended for marine use, and which is shown in Fig. 113, deflecting plates with small openings, an expansion chamber,and a watercooling system are combined. The gases from the motor enter the silencer at A and are deflected upward and given a whirling motion by the internal cone. Water from the jacket enters at B, through an annular opening which forms a circular sheet of water, into the tube or inverted cone V. The gases deflected upward by the outthrough this sheet of water

and are again deflected down through the inner tube

by the lips C, into the chamber E. The hot gases striking the water instantly lose their heat and pressure and noise, so that the cooled gases then issue quietly from the chamber by the outlet G. Any excess of water is provided for by a drain cock B at bottom of silencer, which leads directly to the bot

[graphic]

G

Fig. 113.-" Hydrex" Silencer

tom of the boat. The Thermex silencer works in a similar manner and is illustrated in Fig. 114. Various other forms of excellent mufflers are in use, and new ones are constantly being designed and put on the market. Mufflers in which the gases are given a rotary or whirling motion are quite satisfactory; and silencers have been used in which the gases were led into a casing surrounding the fly-wheel which, being provided with fans or blades, acted as a blower. Whatever style of muffler, silencer, or expansion chamber is used, care should be taken to have the same of ample size to accommodate the exhaust gases without back pressure. A volume of 32 times the square of the piston diameter times the stroke will usually be large enough, but even under the best conditions the perforations or other openings in a muffler will frequently become clogged with soot or rust and the silencing device and exhaust pipes should be frequently examined and cleaned, especially if an excess of oil is used.

Whenever a motor is used under conditions of varying load or work, some method must be used to prevent the engine from racing or speeding up when running free and at the same time allow it to operate at its maximum speed and power when working. Such devices are known as governors, and are used principally on Water

Exhaust Inlet

Exhaust Outler

Drain

Fig. 114. "Thermex" Silencer

stationary motors. Many large marine motors as well as numerous vehicle motors also use governors, and their use adds much to the life and efficiency of any motor of considerable size and power. There are various methods of governing, the principal kinds being Hit-or-miss, Throttling, and Varying Ignition. In the hit-or-miss the action of the governor is to shut off the fuel supply, open or close the exhaust valve, shut off ignition, or disengage the valve mechanism. In the throttling method the fuel supply is reduced or the explosive gas throttled. In the varying-ignition system the governing is accom

« НазадПродовжити »