The sun. [volume] (New York [N.Y.]) 1916-1920, 1919-08-31

under the conditions made possible by
the best designs of Diesel motors. 1t
is said that in the most economical!
OF these motors 1t is feasibleS to OBJ
tain a thermal efficiency of from 20 to
26 per cent.-the remainder of the heat
generated being lost through radia-
ton or in the exhausted gases. How
ever, II Is authoritatiyoly declared that
this measure OF efficiency can be real
lied only when the engines are new;
before long they begin to drop below
this mark. In the case OF the most
carefully designed steam turbines II Is
practicable to utilize 1873 per cent. OF
the potential energy of the heat units
stored in the coal burned. This shows
how far steam propulsion, under the
most favorable conditions, falls short
of the Diesel performance. Keep these
figures in mind in order to appre-
ciate what is promised in the stu
motor, which cuts down the heat losses
to a notable degree.
Details regarding this engine were
revealed some weeks ago at meeting
of the Royal Society of Arts in Lon
don, when Il paper was read by Capt.
f. Z. d. Acland. (The developmental
work on the Still engine was kept
secret during the war; AS Capt
Acland has disclosed, the fundamental
idea of the Still engine is to combine
in a single motor the greater thermal
efficiency of the internal combustion
engine and the much lower thermal
cycle Of n steam driven machine by
utilizing n very considerable percent
age of the heat which now goes to
waste.
To this end the heat that normally
passes into the circulating water by
| radiation through the cylinder walls,
or is discharged with the exhaust
| gases is used to generate steam, and
the steam moves the piston ono way,
while the oil in the combustion cham
| Der alternately drives it the other
way. Normally, an internal combus-
| ton engine receives its power impulse
only on one side of the piston, and
! the reverse stroke is the result OF mo
mentum. BY his arrangement, Mr..
Still puts his motor in the double act
ing class of the reciprocating engine,
where steam for propulsive purposes
Is alternately admitted on each side OF
the cylinder, and every stroke is a
power stroke.
What stiH strove For.
According to Capt Acland's paper
Il contradictory as 1t may seem, Mr.
Stills primary purpose is not really to
/ raise steam by arresting the escape OF
what would otherwise be waste heat
\ q. O., energy), but instead 10 improve
the operative conditions OF the pri-
mary combustion cylinder in which
! LIQUID fuel Is burned. He insures the
oil being consumed at n higher degree
I OF efficiency by reducing the amount
of heat lost in that stage OF the cycle
4 Clearly, the cooler the Sefrigeratlne
medium circulating outside of the
T combustion cylinder the greater woulc
be the radiation from the infamec
} gases within the cylinder, and by just
so much would the expansion OF these
gases be arrested and their push OF
the piston reduced,
} How, then, does Mr.. Still obviat,
} this Objectionable feature, which |!
, common to all oil engines where thu
) refriserant Is circulating water at I
Il, relatively low temperature7 He does !
= by moving through the enVelopinl
5 Jacket a flow of water which communi
. Gates with a steam boiler or steam
] generator; the latter is an integra
4 part of the circulating system. Tha
/ is 10 say. this water is at tempera