Newly developed method for measuring jacket pressure coefficient of controlled-clearance piston-cylinders

Pressure dependence of the effective area A_e of controlled-clearance piston-cylinder (CCPC) has been evaluated based on the Heydemann-Welch model. Among deformational characteristics to be evaluated, the jacket pressure coefficient d, which denotes the relative change in A_e due to applied jacket pressure p_j, is focused in this paper. A new method is proposed for precisely estimating d at pressures up to 1 GPa. The method uses precise pressure transducers as monitoring devices. Both p_j and weights loaded on CCPC are changed so that the pressure generated by CCPC remains constant, which is monitored by the transducers. The change in A_e due to p_j is estimated by the change of the weights loaded on the CCPC. Using this method, d for a 1 MPa/kg CCPC is measured at pressures up to 1 GPa. The new method is advantageous over the conventional method in terms of efficiency and operability especially at higher pressures.