. Applied thermodynamics for engineers. cu. tests gave for the Lenoir and Hugon engines 90 cu. ft.; for the Brayton,50; and for the modified Otto, 21. The possibility of a great increase in economyby the use of an engine of a form somewhat similar to that of the Brayton will bediscussed later. 305. Complete Pressure Cycle. The cycle of Art. 303 merits detailed exami-nation. In Fig. 129, the heat absorbed is l(Tf; — Tc) ; that rejected is the efficiency is 4 Tr-To Tg-TnT^-Tc~^Te-Tc The entropy diagram may be drawn as ebmnd, Fig. 124, showing this cycle to bemore efficient than the equ
. Applied thermodynamics for engineers. cu. tests gave for the Lenoir and Hugon engines 90 cu. ft.; for the Brayton,50; and for the modified Otto, 21. The possibility of a great increase in economyby the use of an engine of a form somewhat similar to that of the Brayton will bediscussed later. 305. Complete Pressure Cycle. The cycle of Art. 303 merits detailed exami-nation. In Fig. 129, the heat absorbed is l(Tf; — Tc) ; that rejected is the efficiency is 4 Tr-To Tg-TnT^-Tc~^Te-Tc The entropy diagram may be drawn as ebmnd, Fig. 124, showing this cycle to bemore efficient than the equal-length-stroke Otto cycle, but less efficient than theAtkinson. With complete expansion down to the lower pressure limit, the cyclebecomes BCEFH, Fig. 129, or elod, Fig. 124; the strokes are still of unequallength, and the efficiency is (Fig. 129) Tn-Tn, y 184 APPLIED THERMODYNAMICS If the strokes be made of equal length, with incomplete expansion, Tq-cycle becomes the ordinary Otto, and the efficiency is Ti. -Ta_Tc-Tn Tn, the 1 Tc. Fig. 130. Arts. 306, 307. —DieselCycle. 306. Oil Engines: The Diesel Cycle. Oil engines may operate in eitherthe two-stroke or the four-stroke cycle, usually the latter; and combus-tion may occur at constant volume (Otto), constant pressure (Brayton), orconstant temperature (Diesel). Diesel, in 1893 (15), first proposed whathas proved to be from a thermal standpoint the most economical heatengine. It is a four-cycle engine, approaching more closely than theOtto to the Carnot cycle, and theoretically applicable to solid, liquid, or gaseous fuels, although actually used onlywith oil. The first engine, tested by Schroterin 1897, gave indicated thermal efficienciesranging from to (16). The ideal-ized cycle is shown in Pig. 130. The opera-tions are adiabatic compression, isothermalexpansion, adiabatic expansion, and dis-charge at constant volume. Pure air is com-pressed to a high pressure and temperature,and a spray of oil is then gradual
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