356 



SCIENCE. 



[Vol. XIII. No. 327 



compound engine, size for size, as well. In explanation of this, it 

 is said that it is a high-speed compound engine, the high rotative 

 speed tending to economy of steam by using it quick and using it 

 hot, and to that extent reducing condensation. 



Again, the relative position of the two smgle-acting cylinders, 

 with the cranks opposite instead of at right angles, gets rid at once 

 of an intermediate receiver, and the consequent loss by free expan- 

 sion due to exhausting from the high- pressure cylinder into the 

 partially emptied receiver at each stroke, which is inseparable from 

 other forms of construction. 



But more important than any other factor of economy is the al- 

 most theoretical perfection of the steam-distnbution. This is the 

 more interesting from the fact that the first step in the design of 



Both practice and theory have demonstrated as a necessity to 

 secure the maximum economy of steam, not only that exhaust 

 compression shall exist, but that it shall be raised exactly to the 

 initial pressure of the incoming steam at the commencement of the 

 stroke. We say exactly, since over-compression is equivalent to 

 non-productive load in any other form; and, still more serious, un- 

 der-coinpression fails to restore heat to the cylinder surfaces, be- 

 sides leaving the clearance volume to be filled at the expense of 

 live steam. This is true in general of any type of engine. It is 

 therefore necessary not only that mechanism should be provided 

 for effecting the full initial compression above indicated, but also 

 that this mechanism, while still maintaining compression exactly to 

 the initial, should at the same time possess the capacity of varying 



WESTINGHOUSE COMPOUND ENGINE, REAR VIEW. 



the compound engine was the laying-out and perfecting of a theo- 

 retical diagram on the lines of maximum efficiency, upon which 

 -diagram the relative volumes and the valve functions were schemed. 

 This is the reverse of the usual process ; but the results, it is 

 ■claimed, were most conspicuous in their success. 

 ^The governing idea in the design is a compound engine in which 

 •thej functions of admission, cut-off, exhaust, and compression on 

 both the high and low pressure cylinders shall be effected by a 

 single valve, in which intermediate reduction of pressure without 

 •corresponding production of useful work shall be obviated, and in 

 which substantially uniform compression to the full initial pressure 

 shall be effected in the high-pressure cylinder, under all variations 

 'of load and boiler-pressure, and for all points of cut-off. Such a 

 ■distribution of steam is theoretically perfect, and has been consid- 

 ered impos sible in practice. 



its effort, in order to meet each and every variation of load and 

 pressure under which the engine may from moment to moment be 

 operated. Such a capacity, or the attainment of such a result, 

 constitutes the peculiar feature of the single-acting compound en- 

 gine on which the Westinghouse Company rests its claims of supe- 

 rior economy. 



In general form, the compound engine more nearly resembles 

 their Junior engine. The mechanical characteristics of the single- 

 actuig engine are retained in every particular. One cylinder is en- 

 larged to practically three and a half times the area of the other. 

 The valve-chest is across the top of the cylinders, being the con- 

 struction which admits of the least possible clearance in the low- 

 pressure cylinder. The valve-chest is in one piece, the various steam- 

 passages being chambered in it. The valve-seat is in the form of a 

 bush, in which the ports are cut, not cast, to an exact register. This 



