BENIER’S HOT AIR ENGINE.

The hot air engine, although theoretically recognized for some time past as the most economical means of converting heat into motive power, has up to the present met with little success.  This is due to the fact that the arrangement of the motors of this class that have hitherto been constructed has been such as to render them but slightly practical.  In the Benier hot air engine (illustrated herewith), however, obstacles that were once considered insurmountable have been overcome, and the motor presents many advantages over all the types that have preceded it.  Among such advantages we shall cite the possibility of utilizing air at a high temperature (1,200 or 1,500 degrees), while the rubbing surfaces remain at a moderate temperature (60 or 80 degrees).  The fire grate is placed in the interior of the cylinder, and is traversed by the cold air forced by a pump.  The expanded hot gases fill the cylinder and act against the piston directly above the grate.

The type herewith illustrated is of 6 horse power.  The motive cylinder, cc’, is bolted to the extremity of the frame, A. Upon this latter is fixed a column, B, which carries a working beam, E. This latter transmits the motion of the piston, P, to the shaft, D. A pump, G, placed within the frame, forces a certain quantity of cold air at every revolution into the driving cylinder.  The piston of this pump is actuated by the connecting rod, G’, jointed to the lever, F’, which receives its motion from the rod, F. A slide valve, b’, actuated by a cam, regulates the entrance of the cold air into the pump during suction, as well as its introduction into the cylinder.  There is a thrust upon the piston during its upward travel, and an escape of hot gas through the eduction valve, h, during the downward travel.

The cylinder is in two parts, C and C’.  The piston, which is very long, rubs at its upper end against the sides of the cylinder, C. The lower end is of smaller diameter, and leaves an annular space between it and the cylinder.  The grate is at the bottom of the cylinder, C’.  The sides of the cylinder at the level of the fire box are protected with a lining of plumbago.  When the piston is at the bottom of its travel, the eduction valve closes.  The slide valve, b’, establishes a communication between the pump chamber and the cylinder.  The air contained in the pump is already compressed in the latter to a pressure of nearly a kilogramme at the moment of the communication.  This air enters the cylinder, and the communication between the latter and the pump continues until all the air is forced into the driving cylinder, the piston of the pump being at the bottom of its travel, and that of the cylinder about midway.

[Illustration:  Benier’s hot air engine.]