MECHANICAL SUPERCHARGING of DIESEL ENGINES

THE most serious problem arising from higher degrees of supercharging is the increase in exhaust temperatures and the amount of additional heat to be handled. This conclusion is expressed foHowing a theoretical exploration into the possibilities of supercharging and the ultimate limit to which it is possible to go. Efficiencies which may be expected with increasing degrees of supercharging, with and without compressor intercooling, are predicted. Some of the present-day superchargers are discussed, including the Roots, vane, centrifugal, and exhaust turbo-type blowers, and the advantages and disadvantages of each are given. Before closing his paper, Mr. Knudsen emphasizes the need for more compact and efficient accessories. No attempt has been made, he says, to improve the specific capacity of these units, with the result that, "as we go down in engine size and up in horsepower, the auxiliaries become larger, heavier and bulkier than ever-so much so that, at the present time, we are almost to the point where the engine proper is completely hidden behind an assorted number of clumsy and unwieldy accessories."