Main factors influencing the regulating parameters of gas-charged hydraulic accumulators are thermodynamic processes occurring during the gas compression and expansion. Method of experimental determination of the polytropic index of gas processes in the hydraulic accumulator is improved. An experimental setup was installed for the investigation of integral regulating parameters of the bladder-type hydraulic accumulator. The parameters of non-stationary expansion of the air in the accumulator's shell during its operation with a simple short pipeline are experimentally investigated and analyzed. Polytropic index was regularly decreasing in the cycles #1 to #4 from 2.07 to 1.95. Storage volume of hydraulic accumulator, at the same time, increased on 6.0 % while discharge time decreased on 3.6%. Obtained experimental trends are explained by the transient thermodynamic processes in the gas inside the hydraulic accumulator before the dynamic equilibrium with the external environment is established.

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