ENGINES, AIR. The air-engine described below, built by the Ticonderoga Machine Co., at Ticonderoga, N. Y., is based on the well-known Stirling principle, in which the working-air is confined to the machine, and originally compressed to a high press ure. Fig. 1 is a perspective view, and Fig. 2 is a sectional elevation. For the purpose of making its operation easily understood, Fig. 3 is intro duced, which is a sketch of the simplest form of single acting engines on the same principle.
A is the furnace, of simple and common form, with door, ash-pit, fine, and grate, on which a fire is built to heat the lower end of the reverser, which stands above the fur mice. The bottom of the re verser-cylinder B, called the "heater," is made of special form, shown in Fig. 2. and of a special metal, and is ar ranged to be separately re newed. The top of the re verser is a common cylinder head. The reverser consists of two cylinders, one within the other, and having the same vertical axis. The inner cylinder is fitted with a valveless piston having a piston-rod. This piston is moved by the engine, and does no work on its crank-arm. The inside cylinder of the reverser does not extend to the top or bottom of the outside cylinder, and has no heads, so that there is free communication from below the piston to the top at all times, no valves at any time intervening. It will be seen that by the upward stroke of the piston the air is forced by way of the annular space between the two cylinders to the bottom of the cylinder, and the downward stroke of the reverser-piston produces the reverse motion of the air to the top of the cylinder via the same annular space. The upper portion of this annular space is partitioned horizontally, and made into a water-jacketed condenser or cooler F. having verti cal copper tubes surrounded by flowing water, the tubes allowing the air to pass freely through. as forced by the piston, without coming in contact with the water. The annular space E E below the cooler extending down into the heater, or lower end of the reverser-cyl inder, is occupied by a regenerator of wire-screen cloth. When the air is moving upward, having just come from the hot surface B. on account of the air being warmer than the wire, the wire receives a portion of the heat of the air, and the air as it goes upward becomes cooled, first by the wire, then by the water-cooled pipes. The heat which the running water takes up
is lost, but the heat in the regenerator is utilized in reheating the air on its return to the bot tom of the regenerator. These operations go on at each stroke of the piston. If the piston of the reverser is forced downward, the air in the reverser is cooled ; if it is forced upward, the air is heated. It is found that it does not matter how quickly this stroke is made, or what the pressure of the air inside the reverser. When a fire is made and the heater properly heated. and the water running through the cooler, the air when at the lower end of the reverser is at 600 F.; and as the pressure is the same on the top and bottom of the re verser-piston at any instant, all the power re quired to move the piston is that necessary to overcome the friction of the air in the re generator and cooler. Some of these engines have tam 200 turns per min., so that the air is 200 times heated and 200 times cooled per min. The engine is designed upon the well known principle that if a volume of air at any pressure is confined, and its volume not al lowed to increase, while its temperature is in creased 480'. the tiressure will be doubled. On the temperature being decreased 480' again, the pressure decreases to the original pressure. It is found that but little more coal is required to keep up heat when using four atmospheres than in carrying, one atmosphere-pressure in the reverser. The advantage of using the higher pressure is very great. notably in effi ciency of engine, less hulk, weight, and cost of manufacture, and operation As shown in Fig. 1. the reverser is connected by a pipe with a cylinder containing a working-piston, and the two pistons are connected by mechan ism in such a way that the reverser-piston is 00' ahead of the working-piston, and makes a stroke for each stroke of the working-piston. This arrangement produces pressure in the working-eylinder varying between the pressure due to 120' F. temperature and that due to 600' F. in the reverser. When the engine is started it is run on common air until a small pump which it carries compresses enough air into the en gine, say 45 lbs. above atmosphere: from that time on this air-pump is only called on to supply whatever the may be. An air-tank is connected with the engine, to store a small quantity of air for starting the engine when under load.