On the Influence of the Position of the Hydrodynamic Coupling Rotation Axis on Its Characteristics

A. V. Murin

(Presented by the scientific seminar of the Department of Applied Mechanics)

As far as we know, the literature has not covered the question of the influence of the position of the axis of rotation of a hydrodynamic coupling in space on its characteristics, although in some cases—for example, in drives of suspended conveyors—the need arises to use the coupling with its axis in a vertical position. It is natural to suppose that, with a change in the position of the rotation axis of a hydrodynamic coupling, the parameters of the hydraulic flow will also change to some extent, owing to a change in the relative direction of the forces of its own weight, and, as a result, its characteristics will change.

For the purpose of comparing the characteristics of a hydrodynamic coupling (Fig. 1) when operating with a horizontal and a vertical arrangement of its axis of rotation, the author built a special test stand, the platform of which, together with the hydrodynamic coupling under test and the braking device, could be installed both in a horizontal and in a vertical position.

Fig. 1. Diagram of the hydrodynamic coupling.

As a result of tests of the hydrodynamic coupling, characteristics were obtained (Fig. 2) at one and the same filling, but with different positions of the coupling. Characteristics 1 and 2 were obtained in the horizontal position, and 3 and 4 in the vertical position (the pump wheel was located below). Curves 1 and 3 were obtained during gradual braking of the turbine wheel; curves 2 and 4 during release of the brake. As can be seen from Fig. 2, the characteristics of the hydrodynamic coupling obtained, with all other conditions equal, in the horizontal and vertical positions are practically identical at large slips (from 60 to 100%) and differ only slightly at slips from 0 to 60% (curves 1 and 3). The difference consists primarily...

The point is that, in the vertical position, the coupling has a somewhat increased slip at identical transmitted torques. When transmitting the nominal torque \(M_{\mathrm{nom}}\), the coupling has a slip of \(6.5\%\) in the horizontal position and \(7.5\%\) in the vertical position; and at torques close to the maximum torque (in the region of relatively small slips), \(M_{\max}\), the corresponding values are \(12.5\) and \(16\%\).

Fig. 2. Characteristics of the hydrodynamic coupling in horizontal (curves 1 and 2) and vertical (curves 3 and 4) positions at 65% filling and pump-wheel speed \(n_1 = 1500\) rpm.

In addition, the ratio

\[ \frac{M_{\max}}{M_{\mathrm{nom}}}, \]

as well as the ratios

\[ \frac{M_{\min}}{M_{\mathrm{nom}}} \quad \text{and} \quad \frac{M'_{\min}}{M_{\mathrm{nom}}} \]

(Fig. 2), in the case of the vertical position, are somewhat smaller (by 4, 9, and 14%, respectively) than the same ratios in the horizontal position.

Thus, as a result of the investigations carried out, the influence of the position of the axis of rotation of the hydrodynamic coupling on its characteristics has been experimentally confirmed. When the coupling operates in the vertical position, its characteristic becomes “softer” (i.e., the increment of torque per unit slip in its working range is smaller) than when operating in the horizontal position, and the minimum torque during disengagement is also noticeably reduced, i.e., its starting properties deteriorate.

These changes in the characteristics must be taken into account when using hydrodynamic couplings in the vertical position, if their bench tests were carried out in the horizontal position.