Q Could you explain the form and purpose
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of a pulse-converter? I understand that an experiment with such a system has been conducted by the Sulzer company on fourstroke diesels. Apparently it either utilizes or removes the pulsations in the inlet or exhaust manifold.
AA pulse generator system has been
applied to a Foden four-cylinder twostroke engine and to a Ruston AO engine of the same type and is known to have considerably improved the output of the units. Little is known of this system but a fairly detailed account of an apparently similar system (described as an exhaust injector type) is given in the German periodical MTZ of September 1968.
A summary of the article, "A new exhaustgas system for improving the breathing of naturally-aspirated four-stroke engines and decontaminating petrol-engine exhaust," by H. Kern, is given in the Motor Industry Research Association's Monthly Survey of World Literature, October 1968 issue. We quote from this summary.
The author deals with the advantage of an exhaust injector system as a means of maintaining the performance of a petrol engine that has been modified by changes in mixture distribution or the filling of a catalytic afterburner to reduce the carbon monoxide content of the exhaust gases. The system was originally developed to improve breathing or scavenging. It has provided an increase in engine output in some cases.
The system consists of two jet orifices, an annular secondary-air duct, a mixing chamber and a diffuser installed between the end of the exhaust manifold branches and the exhaust collector. Consecutive cylinders to fire are connected to alternate manifold branches. The exhaust-gas pressure wave in one branch then induces a suction wave in the other branch. As a result of the pulsating depression in the mixing chamber, secondary air is drawn from the atmosphere through the annular duct in a volume proportional to the instantaneous exhaust-gas volume and intensively mixed therewith.
Oscillograms show the breathing of a highspeed four-stroke engine equipped with this system and a tuned intake manifold for valve overlaps of 46 deg and 118 deg crank angle respectively. Although the air consumption— without secondary air—has increased by about 10 per cent in the latter case, pressures in the exhaust system have scarcely changed, indicating that, given suitable valve timings, the system described is capable of sufficiently increasing the through-put of air in the engine by intensive scavenging of the combustion chamber.