Compressed Air Work And Diving 1909

TWO-STA GE COMPRESSION. 107 compression cannot be truly isothermal, and it will there- fore be somewhere between adiabatic and isothermal and generally more nearly approaching the adiabatic line. When 11 is reachecl the air will be discharged into the receiver at 75 Ibs. pressure. The piston then travels to 1, the small space 1-0 representing the clearance. As the piston returns the small amount of highly compressecl air left in the clearance expands till j is reached, when poub/e Stige C°mP D,ou ble By fermission of Messrs Fraser Chalmers, Lid. Fig. 16. AIR CARDS For single and double stage compression. Clearance in L.P. CYL. =3 per cent. AV”oän^i“?n±:T}33 Ibs. per square inch. Average pressure in double-stage 1 compression____________f 2900 ,, Work done in coinpressing single stage 1 1 cubic foot of free air to 90 Ibs. absolute -5552 fcel Ibs. pressure_________________________I ' Work done in compressing double stage | 1 cubic foot of free air to 90 Ibs. absolute [-4500 ,, pressure _________________________ Saving of double-stage compression against single stage atmospheric air begins to be taken in. The work done during single-stage compression up to 75 Ibs. pressure is represented by the cycle B, ii, i, j, and the free air capacity by j, b. But in the case of a single-action cliving pump the work done woulcl be representeel by b, ii, i, a, since, neglecting friction, the work representeel by a, i, j is lost in the return stroke.