Between the compression-cylinder and the power-cylinder is situated the regenerator I), which is so placed between the cylinders as to be trav ersed by the air in its passage backward and forward. 0 is a check-valve which supplies any leakage of air that may occur. It is placed at the back of the engine, but it is necessarily shown in the sectional cut on the side. The other portions of the engine are readily understood by inspection of the Figure.
The operation of the engine is, briefly, as follows: The compression piston 4 first compresses the cold air in the lower part of the compression cylinder II, when, by the advancing or upward motion of the power-piston C and the completion of the down stroke of the compression-piston A, the air is transferred from the compression-cylinder II through the regenerator D into the heater E without appreciable change of volume. The result is a great increase of pressure, corresponding to the increase of tempera ture, and this impels the power-piston up to the end of its stroke. The pressure still remaining in the power-cylinder and reacting on the com pression-piston Al forces the piston A upward till it reaches the top of its stroke, when, by the cooling of the charge of .air, the pressure falls to its minimum, the power-piston descends, and the compression again begins. In the mean time, the heated air, in passing through the regenerator, has left the greater portion of its heat in the regenerator plates, to be picked up and utilized on the return of the air toward the heater.
name "sun-motor" is employed to designate an apparatus by which the heat of sun-rays is concentrated upon a generator (steam-boiler or other) which furnishes steam or other motive vapor to an engine. It differs from an ordinary "self-contained" motor merely by the addition of a reflector which concentrates the rays upon a spot or strip on the blackened surface of the generator, and which has a clockwork to make it " follow the sun." For many centuries the idea of utilizing the sun's heat in pumping water or in driving machinery has been a favorite one with inventors. Euclid, Archimedes, Hero of Alexandria, Solomon de Caus, Buffon, De Saussure, Ducarla, Pouillet, Fanchot, Ericsson, Mou chot, and others experimented in that direction. In 186r, Mouchot pro duced a " heliopompe " or "sun-pump," followed in 1865 by several others; and Ericsson experimented for twenty years prior to 1883, when he produced what may be said to be his first working engine. His experi ments were continued up to his death in 1889, and it is to be hoped that some other able experimenter may push them to a desirable conclusion.
Mouchot's Sun-engine, exhibited in Figure 3 107), consists of a masonry pedestal (A); of a stirrup-shaped cast-iron support (B) turning on a shaft by which, in order to face the sun squarely and get the full effect of its rays, the apparatus is given an elevation relative to the latitude of the spot on which it is erected; of a sector (not seen in the Figure) fitted on a shaft (b), by which the apparatus is made to follow the diurnal move ment of the sun in order that the effect may be continuous and the mirror (z) not left partly in its own shadow; of a framework (E) to which the boiler and the skeleton of the reflector are attached; of a plate-iron tubu lar boiler (F), which is surrounded with a glass jacket (G) to aid in con centrating the heat, and which is provided with a steam-dome (H), a safety-valve (I), and a steam-gauge (J); of a sector (if) worked by a screw (m) for giving the latitudinal inclination; of a train of geared wheels actuated by a handle (11) for the diurnal movement sector; and of a sector (S) fitted on a shaft (r), and worked by a screw (o) to alter the position of the boiler and the reflector according to the different sol stitial angles in summer and winter. The extreme diameter of the reflector
was about 16.4 feet; the area of the opening, therefore, was about 65 feet. The boiler—nominally, three horse-power (?)—weighed, with its accesso ries, four hundred and forty pounds. It had an extreme length of 8.2o feet and a capacity of forty-four gallons or 3.53 cubic feet, 1.059 cubic feet of which was steam space, and the remainder, or 2.471 cubic feet, water. The usual time required to get up steam varied with the intensity of the sun's rays, the state of the atmosphere, etc., and was generally one and a quarter hours for the first and eight minutes for every succeeding fif teen pounds pressure; and adopting the data of September 22 as the result of mean autumnal influence and as a fair criterion, we find that on that day a steam-pump connected with the apparatus was lifting between 200o and 3000 litres, or 4600 gallons, per hour for a short time with a steam pressure of three atmospheres. The pressure at times rose as high as seven and eight atmospheres; but it was quite apparent that, owing to the late ness of the season or to the imperfections of the boiler, which by allowing the steam to collect on the inner surface of the glass jacket prevented the passage of the rays, or to the leaky state of the pump and consequent loss of power, or to whatever fortuitous circumstances it may be ascribed— although the initial pressure at starting was six and a half atmospheres it sank so rapidly—namely, at the rate of one atmosphere in every three minutes—that no reliance could be placed on the experiment as illus trating the practicability of the principle.