No abstract
The sandstones and coquinas of the upper 20 m of the Sundance Formation are interpreted as a tidal inlet, back‐barrier shoal and sandy tidal‐flat sequence deposited at the close of marine Jurassic sedimentation in north‐central Wyoming. The barrier strandline maintained a generally E‐W trend as it prograded to the north. The lateral migration of inter‐barrier tidal inlets along the regressive shoreline of the late Sundance sea caused the coquinas and sandstones of the uppermost Sundance Formation to be deposited as tabular, laterally‐extensive units. Tidal bundles, sigmoidal reactivation surfaces, herringbone cross‐lamination and abundant mud drapes within the sandstones are evidence of considerable tidal influence during the deposition of the uppermost Sundance Formation. Earlier models, which attach an offshore environment of deposition to the sequence, do not explain the tabular geometries of the sandstone and coquina units and their conformable stratigraphic relationship with the overlying non‐marine sediments of the Morrison Formation.
As part of a study involving methods of control of an axial piston pump, it is required to obtain linear or linearized equations of motion of the system’s states. The torque imposed on the plate by the pumping action of the pistons is the most important term in the equation of motion of the swashplate. The torque is a result of a nonlinear and partly discontinuous relationship; this relationship being a function of the geometrical features of the pump and the system operating conditions. Mathematical equations describing swashplate torque are derived from general hydraulic and mechanical considerations given in this paper. This mathematical model can be linearized so that linear parameters for the equation of motion of the swashplate can be obtained. In addition, results of predictions made by the model are presented and compared with some experimental data provided by Sundstrand. An indication is also given as to changes in torque resulting from variation in swashplate angular velocity and timing position of the valve plate.
A mathematical model of an axial piston pump is described which consists of a second-order differential equation of the swashplate motion and two first-order equations describing the flow continuity into the pump discharge chamber and into the swashplate control actuator. The equation of the swashplate angle contains torque components due to operating states. A method is presented by which the average torque can be computed for a pump of given geometry and at any given set of operating conditions. From the calculated average torque, the coefficients of the basic equation can be evaluated; agreement to within 10 per cent of experimental values for torque has been achieved. A state variables analysis of the dynamic behaviour has shown that there are two dominant poles at low frequency and that the damping ratio associated with these poles reduces by approximately one half when the downstream control volume increases by a factor of three, and varies from 0.84 to 0.48 as the pump rotational speed increases from 126 to 209 rad/s. It has been concluded that the assumption of linear variation with the basic parameters, which is a necessary prerequisite for the use of states variables analysis, is justified. The work outlined in this paper represents a step in the design process associated with the optimal control of an axial piston pump.
The equations of motion have been solved for a journal bearing for L/D = 1/8, 1/2, 1.0, and 12.0. Trajectories have been obtained for motion of the bearing center in both uncavitated and cavitated conditions and the effect of out of balance and of friction in specific cases has been examined. From the trajectories calculated, whirl stability boundaries have been produced. The boundaries are in general accord with work by other authors. It is found that when out-of-balance load is added it sometimes makes the bearing more stable and sometimes less stable. When friction is included it always improves stability. Experimental work with no out-of-balance shows approximate agreement with theory.
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