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SCIENCE PROGRESS 



shown in figs. 8, 9 and 10 are taken from the paper read by 

 Mr. Humphrey before the Institution of Mechanical Engineers 

 and show the relative efficiency as between the Humphrey 

 pump cycle and the ordinary Otto cycle calculated by means of the 

 usual formula and upon the assumptions stated on the diagrams. 



Compression pressure in lb. per sq. in. above atmosphere. 



so 40 m so ioo 120 



Formula /or pump-cycle diagram. 

 Efficiency = i — y 



T - p 



T = (for curve at i,ooo° C) = 273 + 1,000° C = 1,273° C Abs. 

 T = (for curve at i,6oo° C.) = 273 + 1,600° C = 1,873° C. Abs. 

 y = 1 '408. 



t = suction temperature = 17° C = 290° C Abs. 

 Adiabatic compression and expansion. 



Fig. 8. — Theoretical efficiency curves, pump cycle, air standard. 



These calculations are based on the assumption of the constant 

 specific heat ; but Prof. Dr. Eugen Meyer, of Charlottenburg, 

 has made the very laborious calculations involved when taking 

 the true specific heat of each constituent of the gas mixture and 

 allowing for the variations of the temperature involved at each 

 point on the curve. The absolute results are affected but the 



