This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1913 Excerpt: ...under control. The mixture should be almost completely burned before the piston has moved an appreciable distance on the expansion stroke and the spark must be made to pass at such a time as will bring about this result. Experience has shown that the charges used in internal-combustion engines do not burn ...
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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1913 Excerpt: ...under control. The mixture should be almost completely burned before the piston has moved an appreciable distance on the expansion stroke and the spark must be made to pass at such a time as will bring about this result. Experience has shown that the charges used in internal-combustion engines do not burn instantaneously but that it takes a very definite length of time for the flame to spread throughout the mixture from the point at which the spark starts it. For this reason the spark is practically always made to pass slightly before the end of the compression stroke so that by the time the piston reverses its direction of rotation the mixture will be well inflamed and a large part of it will be entirely burned. As it will always take practically the same length of time to burn a given mixture in a given clearance with a given compression pressure it is easy to see that ignition must be made to occur earlier in the compression stroke the higher the speed of the engine because the time during which the piston is at the end of its stroke is proportionally reduced. For best operation the time of ignition should also be varied as the quality of the mixture changes, as the condition of the atmosphere varies, as the load on the engine is altered and so forth. The effects of proper and improper timing of ignition are easily studied by means of indicator diagrams. For the sake of simplicity the lower loops may be omitted from these diagrams as they have little, if any, effect upon the phenomena under discussion. The upper loop of a diagram which would represent very good performance is shown in Fig. 60. It will be observed that the line representing rise of pressure due to combustion is not quite vertical as originally drawn in Fig. 11, but tips slightly to the ri...
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