. Locomotive engineering : a practical journal of railway motive power and rolling stock . -ders. The diagrams shown on pages 417and 418 are taken from an engine equippedwith this valve, and themselves. For the purpose of illustrating the dif-ference between the double-ported, the.■Mien and the plain valve. Fig. 2 has beenprepared to show their respective behav-iors when cutting off at stroke. The LO<OMOTI VE ENOINKKKI N( 1 full line No. I represents an indicator dia-gram from a double-ported valve, the dot-ted line No. 2 that of a plain valve, andthe broken line. No. 3, that
. Locomotive engineering : a practical journal of railway motive power and rolling stock . -ders. The diagrams shown on pages 417and 418 are taken from an engine equippedwith this valve, and themselves. For the purpose of illustrating the dif-ference between the double-ported, the.■Mien and the plain valve. Fig. 2 has beenprepared to show their respective behav-iors when cutting off at stroke. The LO<OMOTI VE ENOINKKKI N( 1 full line No. I represents an indicator dia-gram from a double-ported valve, the dot-ted line No. 2 that of a plain valve, andthe broken line. No. 3, that of Allen valve—all conditions being equal, with the ex-ception of the auxiliary port. The diagram is laid down with the as-sumption that the steam has the same ve- 415 still considerably in excess of the portopening. The resulting lower final pres-sure effects a lower back-pressure duringthe return stroke. The admission, and consequently theexpansion line, of the plain valve fall be-low that of the other valves; the releaseis proportionately lower, and as the area Central Position. locity at corresponding points of the dif-ferent diagrams. The admission and expansioti linesfrom the Allen and double-ported valves,of course, coincide, but the exhaust andback-pressure lines indicate a decided ad-vantage in favor of the latter. From the release point, C to E, the ef-fect of the auxiliary port shows plainly,while the area of the exhaust nozzle is Locomotive Engintcring of the exhaust opening is the same as inthe Allen, the exhaust line will be beneathit all the way. while the exhaust line ofthe double-ported valve crosses that ofthe plain valve at an early portion of period. Another advantage of the double-portedvalve is illustrated by Fig. 3. representingcards taken while drifting. The entrainedair is compressed to the point A when the 4i6 LOCOMOTIVE ENGINEERING September, 1895. auxiliary port relieves the pressure be-fore the piston arrives at the end of itsstroke
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectrailroa, bookyear1892
