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ATKINSON CYCLE AND ITS PROCESS

 Atkinson Cycle is an Ideal Cycle for an Otto Engine exhausting to a gas turbine. In this cycle, the   isentropic expansion (3-4) of an Otto Cycle is allowed to further expand to lowest cycle pressure (3-5) so   as to increase the work output. 




 For 1kg gas, 

Q1 = Cv (T3 - T2)

Q2 = Cp(T5 - T1)

Ncycle = 1- ((Cp(T5-T1)) / (Cv(T3-T2))

            = 1- (Y(T5 - T2) / (T3 - T2)

Let rk, compression ratio = v1 / v2,

      re , expansion ratio = v5 /v3 ,

       T2 / T1 =  v1 / v2    ie, T2 = T1 rk^(y-1)

       T3 / T2 = p3 /p2 = (p3 / p5) * (p5 / p2) = (p3 / p5) * (p1 / p2) 

       p3 / p5 = (v5 / v3)^y = re ^ y

       p1 / p2 = (v2 / v1) ^ y = 1 / rk^y 

       T3 = T2 * re^y * 1 / rk^y  

             = T1 (re^y / rk) 

       T5 / T3 = (v3 / v5)^ (y-1) = 1 / re^(y-1)

        T5 = T3 (1 / re^(y-1)) = T1 (re / rk)

 Substituting T2, T3 and T5, 

  N atkinson = 1- Y((re-rk) / ( (re^y) - (rk^y)))

 

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