The modeling of unsteady friction loss in gas pipeline has been studied to improve their accuracy and efficiency because of its importance such as in gas transmission lines and pneumatic control systems. The computation of unsteady friction loss in liquid pipeline is most efficiently and most easily by using the instantaneous acceleration-based (IAB) model. However, IAB model has been derived only in case of liquid pipeline. This paper presents a new equation of the unsteady laminar friction loss in gas pipeline developed by expanding the concept of IAB model to gas pipeline. In general, the unsteady friction loss in gas pipelines is greater than that in liquid pipelines due to the damping effect of the energy equation. The author therefore showed how to take into account the energy equation in the present IAB model. A characteristic solution for unsteady pipe flow is described in which the present IAB model is used to predict unsteady friction loss. Comparisons of numerical test results with measured data from the laboratory experiments and analytical solution by using the high speed and accurate computing method showed excellent agreement. The empirical constants in which the present model includes could be determined by using the approximate curves described in this paper. It was also demonstrated that the developed method requires less computation time and computation memory compared with the high speed and accurate computing method.

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A test rig of slippers of swashplate type axial piston motors and pumps was manufactured, in which the clearance shapes between the slipper and the rotating disk and temperature distributions of the slipper pad were measured simultaneously. The sliding surface diameter of the test slipper was 32mm; the test oil was hydraulic oil with VG46. The six contact-type displacement sensors were set to determine the clearance shape and the four thermo-couples were embedded to assess the pad temperature. The test conditions were: the supply pressure up to 35 MPa (load of 17 kN), the rotational speed up to 26.7 s^-1 (sliding speed of 9.2 m/s), and the oil temperature at 30 to 50℃ (kinematic viscosity of 66.7 to 35.9 mm²/s). In conclusions, i) At higher pressure and lower speed conditions, the clearance became small, while the pad inclination and azimuth less changed; ii) The temperature of the slipper pad was high at the outer circumference-side edge, but it was low at the leading edge; iii) Under the conditions of higher oil temperature, higher pressure, and higher speed, the location of the high temperature part moved to the trailing edge, and iv) As the supply pressure and rotational speed increased, the temperature of the slipper pad increased.

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