FIRELESS ENGINE, a form of steam or vapor engine which is detached from the heating apparatus. Dr. Emile Lamm, of New Orleans, invented an engine in which the motive power was derived from the vapor of ammonia. The ammonia, as it escaped from the engine, was passed into a reservoir of water, in which it was absorbed; the water when heated to a temperature of about 135° F., gave up the ammonia as gas, which was returned to the engine to be used over again, and then again absorbed and returned as before. This engine was found efficient and economical for the movement of street cars. The use of ammonia was soon abandoned, steam taking its place. Water heated to 212° F. becomes vapor, if the pressure upon it be no more than the usual atmospheric 15 lbs. per sq. inch. If the pressure be greater, the water remains liquid until a higher temperature is reached, the temperature varying with the pressure according to well known laws. If steam at a high pressure be admitted to water of low temperature and pressure in a closed vessel, the steam will be condensed in the water, but the press ure in the vessel will be increased, while the volume of the water will be enlarged by the volume of that derived from the condensed steam. The water thus becomes charged with steam condensed under high pressure, and when the pressure is relieved, a portion of the steam reverts to its condition of vapor, and may be conducted in the usual way to a cylinder and piston, where it will do its customary work. The opening of the valves gives vent to the vapor, gradually reduces the pressure, and relieves the condensed steam; so that a tank, filled with water and stored with many times its volume of uncoudensed steam, will furnish motive power sufficient to move the engine and a considerable train of cars for a trip of several miles. On its return, the tank is
connected with a stationary boiler from which it receives a fresh supply of steam. It will not be forgotten that the real force of the steam is due to the heat which it contains, and that if the heat be lost, by radiation or otherwise, from the tank containing the con densed steam, its potential energy is so much reduced.
In applying these principles, the mechanism is that of an ordinary locomotive minus its fire-box, having a water-tank instead of a boiler; the appliances for stopping, start• ing, and backing, are as usual. The tank may be about 6 ft. long, and 3 ft. in diameter, covered thickly with felt and wood to retain its heat. Steam is taken until the gauge indicates 135 to 150 lbs., the temperature for 135 lbs. being 353°. With this accumula tion of power the machine will run 5 to 7 m. before the pressure is reduced to 60. lbs. The labor and care of firing is avoided on one of these engines, but in other respects they require the same skill needed in the common locomotive. The fireless engine has been used in several large cities, but does not seem to commend itself to practical men.