STRIKING INVENTION

Sun (Auckland), Volume III, Issue 788, 8 October 1929, Page 6

STRIKING INVENTION

COMPOUND CAR ENGINE Many attempts have been made in the past to apply the principle of compounding to internal-combustion engines, so that the publication of a patent granted to Mr. H. R. Ricardo on this subject is an event of no little importance, says “The Motor.” Compounding is, of course, widely * employed for steam engines, the principle being that the steam does work

first of all in a high-pressure cylinder and is then passed on to a low-pressure cylinder in which it gives up a further supply of energy. In the case of the ordinary petrol engine the exhaust gases are released at a pressure of at least 401 b a square inch and are at a high temperature, so that if they could economically be passed on into another cylinder, or into a turbine, a considerable amount of useful energy could be extracted from them which is at present wasted. One of the difficulties hitherto encountered has been to make the transfer valves employed between the highpressure and low-pressure cylinders stand up to their work, and this has proved almost insuperable in the case of poppet valves. Another difficulty is to make the engine sufficiently com-

pact, so as to use short and direct passages between the cylinders. These problems have all been tackled by Mr. Ricardo, and his ingenious solution is to employ three cylinders in line, two being high-pressure units, while the third is a large, low-pressure cylinder receiving the exhaust gases from the other pair. By employing cranks placed at 180 degrees, as shown in the illustration, very good mechanical balance is obtained and a compact engine design results. To obviate all difficulty with valves, Mr. Ricardo uses the oscillating (Burt M’Collum) sleeve type for the highpressure cylinders, a single sleeve having a combination of reciprocating and rotary movements being employed to control ports for the admission and release of the gases. Explosions take place alternate in the high-pressure cylinders, as these work on the ordinary Otto four-stroke cycle. During each exhaust stroke hot gases at considerable pressure pass directly through the ports to the low-pressure cylinder, performing useful work on the large central piston. On the up stroke of this piston these gases are finally expelled through an exhaust valve which may be of the poppet type.