Abstract
There are a surprising number of cases where oil, gas or steam engines will show better economy than purchased power and electric motors, and this may be emphasized where the exhaust from steam engines is valuable for heating or process work. Any development which will improve the efficiency of reciprocating engines, and at the same time simplify their construction should be of interest.
Up to now, reciprocating engines have suffered from losses due to incomplete expansion. There has been a compromise between such losses and mechanical ones connected with the use of very large cylinders. Oil engines, multiple-expansion and uniflow steam engines are coming to use high ratios of expansion, and these are doing much to reduce exhaust losses. Many advantages may be gained, however, if the energy remaining in the exhaust at release can be converted into kinetic energy, and from that into partial vacuum in the cylinder. In double-acting uniflow steam engines, for instance, pistons and cylinders may be made smaller and shorter for a given load, the number of exhaust ports reduced, and a greater range of back pressures may be negotiated without extra clearance or exhaust valves. By attention to design of exhaust pipes and nozzles the performance and efficiency of such engines may be a good deal improved.
The theoretical problems are presented in this paper for discussion, and practical applications to either single-cylinder or multi-cylinder engines are suggested and illustrated.
