The Ericsson Respirator

We have already announced the signal success of the new motive power discovered by Mr. Ericsson, and applied by him to the beautiful vessel bearing his name, and we proceed to-day, in compliance with our promise, to offer such an explanation of its principle as we hope may prove intelligible, if not satisfactory, to our readers.

We will say, then, as preliminary to this explanation, that all the power used in Captain Ericsson’s engines is obtained from the expansion of the atmosphere by heat. He uses no water and makes no steam, but employs the atmosphere very much as the steamers employ water; with this difference, that instead of throwing away the heat after it has been used as the steam engine does by condensation, he separates it from the escaping air, and used it over again in heating each new charge of air which is supplied to his cylinders. This economy of the heat of course results in a corresponding economy of fuel, furnace room, and firing equipage, equal, it is supposed, to a difference, in point of expense, of five parts in every six.

We will now give, as near as we can, the process by which this important economy is effected. We desire our figures and facts to be understood as applying to the vessel which we visited yesterday.

The Ericsson, by Carpenter’s measure, rates as a 2,200 ton vessel. She is supplied with two pairs of engines, and each pair is supplied with two “working cylinders,” as they are termed, and two “supply cylinders” inverted over them. The supply cylinders are smaller titan the working cylinders, and are filled with cold air from a reservoir over them, at every descent of the piston, which creates a vacuum for its admission. The working cylinders, which are immediately below the supply cylinders, and over the furnaces, are filled by heated or rarified air, and are as much larger than the supply cylinders as is necessary to realize the difference in force between air at its natural temperature and in •a rarified state.

When the air in the working cylinder is heated, the piston ascends and drives the cold air out of the supply cylinder into a reservoir, where it remains until the rarified air has exhausted its force and is expelled by the des cent of the piston in the working cylinder; then, upon the ascent of the piston again, this cold air rushes into the working cylinder, where it is again rarified, and repeats the motion we have described, and multiplies the force which propels the vessel.

Before proceeding to describe the novelty of the machinery, the process by which the heat is separated from the waste air, and held in deposit for future use, we will give a few of the more important statistics of the dimensions and capacities of the machinery we have already described.

The diameter of each of the working cylinders is 168 inches and its: area 22,800 square inches, about three times the area of any of the cylinders of the Collins steamers; and yet they weigh only ten tons, while those of the Collins steamers weigh fifteen tons. The pressure on these cylinders is ten pounds to the square inch, which gives an aggregate pressure of 223,000 pounds for each cylinder.
Some of our readers may better appreciate the extent of this power if we add, what is an ascertained fact, that a single pound of pressure upon the piston will raise eleven tons.

The “supply cylinder” is 137 inches in diameter, and its area 14,400 square inches. The two pistons, the supply and the working, are connected by eight massive wrought iron rods, which ensure a perfectly simultaneous and sympathetic, motion. The power from the piston is communicated to the crank of the paddle shaft by connecting rods placed at an angle of forty-five degrees, and working in such a way as to entirely dispense with the centre shaft in use in steamboats, and obviating all inconvenience from what is technically known among mechanics as the “dead centre.”

This appliance is also an invention of Mr. Ericsson, and scarcely less important in its results than that which it is our principal purpose to-day to describe; but we do not feel at liberty to explain its principle in detail at present, as Mr. Ericsson is desirous of securing his patent right for it in foreign countries before exposing it to the public. We may say of this invention, however, that it is one which is quite sure of being as universally adopted as his motive power.

We will now attempt to describe the powers by which the heat is economized.

By the side of each working cylinder is a vessel or box filled with a collection of wire discs, like sieves, six feet by four, placed vertically in the box. There are two hundred of these discs in each box. The hot air on leaving the working cylinder, after performing its function by driving the piston up, is expelled through the box of wire, which Mr. Ericsson terms a “regenerator;” but which may be more properly termed a “respirator,” as our readers will perceive when they come to appreciate its office.

In passing through the disc, the expelled air gives off all, or nearly all, of its heat—all but about 30°—to the wire, where it is held on deposite, as it were, until the process of expulsion is complete, and the valves open for the admission of the cold atmospheric air, which is waiting to undergo the process of ratification. When the valves open the cola air rushes through the respirator, in which the heat is deposited, takes it up, and thus enters the working cylinder almost as hot as the air which a moment before deposited the same heat in the reservoir, thus leaving the furnace the moderate duty of supplying a trifling difference of only about 30° of temperature to the air in the working cylinder.

The capacity of these wire meshes to absorb and retain the caloric will not be questioned by practical men when we state that the four “respirators” in the “Ericsson” present a surface of over 15,000 superficial feet, while there are more than 100,000,000 of cells between the meshes. The wire in this boat is about 1/16th of an inch in diameter, but that may be varied of course according to circumstances, as may the number of discs, both depending upon the amount of heat which is sought to be deposited. The surface of wire employed in absorbing the heat in the “Ericsson” is equal to the entire fire surface of four of the very largest size marine steam-boilers.

By a most elaborate series of experiments, the details of which, though exceedingly curious and instructive, we have no time to-day to narrate, Capt. Ericsson ascertained that each particle of air occupies just 1-30th of a second in passing quite through the disc, and in that time undergoes a change of temperature of 400°; that is, the expelled hot air is four hundred degrees cooler when it leaves the respirator than when it enters it, and the cold becomes four hundred degrees warmer when it enters the working cylinder, or heating chamber, than it was when it entered the respirator.
It deserves, in this connexion, to be borne in mind that Capt. Ericsson’s patent never contemplates a greater heat in the working cylinder than 500°. Yesterday the heat was only about 450°.

In passing through the respirator, it is ascertained that the hot air deposites all but about 30° of its heat; that is, the waste or escape air is only about 30° warmer than when it entered the reservoir cold, and consequently the waste heat is only about 10 per cent. on every 300° employed, and it is this waste only which it is the function of the furnaces to repair. A greater saving might be obtained by employing a greater number of wire discs, and some other obvious cautions, but no practical advantage would be derived from carrying the process of abstraction any further.