. The railroad and engineering journal . e exhaust. 35g. What governs the period of compression? Answer. As compression begins when release ends, or whenthe port Is closed to the exhaust, it is controlled by exactly thesame causes, and as the two events occur simultaneously, ofcourse whatever shortens the period of release lengthens thatof compression. Question 360. What effect do the clearance spaces and steam-ways have upon the compression of the confined steam ,< .Answer. By referring to the motion-curves in fig. 227, it willbe seen that the steam-port is closed by the exhaust-
. The railroad and engineering journal . e exhaust. 35g. What governs the period of compression? Answer. As compression begins when release ends, or whenthe port Is closed to the exhaust, it is controlled by exactly thesame causes, and as the two events occur simultaneously, ofcourse whatever shortens the period of release lengthens thatof compression. Question 360. What effect do the clearance spaces and steam-ways have upon the compression of the confined steam ,< .Answer. By referring to the motion-curves in fig. 227, it willbe seen that the steam-port is closed by the exhaust-edge of thevalve, or compression begins some time before the pistonreaches the end of the stroke. The result is that the remainingportion of the cylinder, through which the piston must moveafter the port is closed to the exhaust, is filled with steam ofatmospheric pressure, or possibly a little above that this is confined in the cylinder, it is compressed by the ad-vance of the piston. If there was no room between it and the. Fig 233. cylinder at the end of the stroke, then either the cylinder wouldbe burst or the valve would lift so as to allow the compressedsteam to flow hack into the steam chest. The clearance andthe steam-passages, however, afford considerable room, intowhich the confined steam can be compressed without danger ofbursting the cylinder or of raising the slide-valve when there issteam in the steam-chest. As the clearance spaces and steam-ways must be filled with high-pressure steam at the beginningof each stroke, it must be obtained either by taking a supply of/;V<r * steam from the steam-chest, or by compressing intothe clearance spaces the low-pressure steam that still remainedin the cylmder when the port was closed to the Bythe latter process, a certain quantity of steam is saved at theexpense of increased back pressure. It should be borne inmind also that the total heat of the compressed steam increaseswith its pressure, and as its
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