. Steam engines, a thorough and practical presentation of modern steam engine practice . engine, viz, one high, one intermediate, andtwo low. This arrangement gives better balance and is often usedin marine work. For triple engines there must be a. receiver between each twocylinders. Fig. 22 shows the essential features of a triple expansionengine. Quadruple Engmes. Quadruple engines expand their steam infour stages instead of three. Multiple expansion engines are nearlyalways condensing. STEAM ENGINES 29 Cylinder Ratios. There are several considerations to be remem-bered when proportioning th
. Steam engines, a thorough and practical presentation of modern steam engine practice . engine, viz, one high, one intermediate, andtwo low. This arrangement gives better balance and is often usedin marine work. For triple engines there must be a. receiver between each twocylinders. Fig. 22 shows the essential features of a triple expansionengine. Quadruple Engmes. Quadruple engines expand their steam infour stages instead of three. Multiple expansion engines are nearlyalways condensing. STEAM ENGINES 29 Cylinder Ratios. There are several considerations to be remem-bered when proportioning the cyUnders of the multiple expansionengines. The ratio of the cylinders should be such that each devel-ops nearly the same power, and the drop in pressure between thecylinders and receivers should be as small as possible. There are many formulas in use, some simple, others more com-plex involving mathematical calculation. A common rule for com-pound engines is to make the ratio of the cylinders equal to the squareroot of the total ratio of expansion. Thus, if the steam has an expan-. Fig, 22. Section of Essential Features of Triple Expansion Engine sion ratio of 9, the ratio of the cylinder volmnes will be l/ 9j or 3; thatis, the low pressure cylinder will have a volume three times as greatas the high pressure cylinder. If the cylinder ratio is 3 and thelength of the stroke is the same for both, the diameter of the lowpressure cylinder will be times that, of the high pressure cylinder. Another rule is to make the cylinder ratio equal to the totalratio of expansion multiplied by the fractional part of the stroke com-pleted when cut-off occurs in the high pressure cylinder. Suppose the ratio of expansion is 9, as above, and that cut-offoccurs at one-third of the stroke in the high pressure cylinder, theratio of cylinder volumes will be 9Xi, or 3. If cut-ofF occurs atone-half of the stroke, the ratio will be 9X5, or 30 STEAM ENGINES For triple expansion engines the low p
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