Part 4 (2/2)

[Illustration: One of the low-pressure turbines of the _Car Its size will be inferred fro]

THE EXPANSIVE ACTION OF STEAM IN A TURBINE

On reaching the end of D1 it enters the second, or interreater diaer and set soe to the now partly expanded steaained velocity

The process of ain in D3, the low-pressure dru by this time expanded very many times; and it is found advisable, for reasons explained in connection with coines, to have a separate turbine in an independent casing for the extrees of expansion

The vanes are e Cunard liner, 1,115,000 vanes are used The largest diameter of the druhs 350 tons

BALANCING OF THRUST

The push exerted by the steam on the blades not only turns the drum, but presses it in the direction in which the steam flows This end thrust is counterbalanced by means of the ”dummy” pistons, P1, P2, P3

Each dus projecting fro so sh-pressure compartment the steam pushes P1 to the left with the saht After coe C, which communicates with the second piston, P2, and the pressure on that piston negatives the thrust on D2

Sie E causes the steam to press equally on P3 and the vanes of D3 So that the bearings in which the shaft revolves have but little thrust to take This form of compensation is necessary in marine as well as in stationary turbines In the former the duiven by them and the screw co vanes

[Illustration: One of the turbine drums of the _Car tested for perfect balance on two absolutely level supports]

ADVANTAGES OF THE MARINE TURBINE

(1) Absence of vibration Reciprocating engines, however well balanced, cause a shaking of the whole shi+p which is very unpleasant to passengers The turbine, on the other hand, being alhest speeds that, if the hand be laid on the covering, it is sometimes almost impossible to tell whether the machinery is inthere is little noise in the engine-roo engines (2) Turbines occupy less room

(3) They are more easily tended (4) They require fewer repairs, since the rubbing surfaces are very sines (5) They are h speeds It h speeds

If run slowly, the steato its construction, a turbine cannot be reversed like a cylinder engine It therefore becomes necessary to fit special astern turbines to one or more of the screw shafts, for use when the shi+p has to be stopped or moved astern Under ordinary conditions these turbines revolve idly in their cases

The highest speed ever attained on the sea was the forty-two miles per hour of the unfortunate _Viper_, a turbine destroyer which developed 11,500 horse power, though displacing only 370 tons This velocity would coood many expresses on certain railways that we could name In the future thirty miles an hour will certainly be attained by turbine-driven liners

[7] Even at this speed the wheel has a circumferential velocity of two-thirds that of a bullet shot frorains (about 1/2 oz) exerts under these conditions a centrifugal pull of 15 cwt on the wheel!

Chapter IV

THE INTERNAL-COMBUSTION ENGINE

The ine--The ine--The carburetter--Ignition of the charge--Advancing the spark--Governing the engine--The clutch--The gear-box--The coear--The silencer--The brakes--Speed of cars

THE MEANING OF THE TERM ”INTERNAL-COMBUSTION ENGINE”

In the case of a steay of coht vessel The fuel does not actually touch the ”working fluid” In the gas or oil engine the fuel is brought into contact andfluid, which is air It coy is developed so rapidly that the act is called an explosion Coal gas, en and carbon If air, which contributes oxygen, be added to any of these in due proportion, theapplied, oxygen and carbon unite, also hydrogen and oxygen, and violent heat is generated, causing a violentthe mixture Now, if the mixture be _compressed_ it beconites spontaneously Early gas-engines did not conition Alphonse Beau de Rochas, a Frenchine squeeze the nition; and from the year 1862, when he proposed this innovation, the success of the internal-coine may be said to date