The increase of thermal efficiency of the dryer together with increased speed of the machine to 800 m/min is characterized by the decrease of two basic indices: the ratio of the weight of metal of the dryer to the weight of the evaporated water, and the ratio of the weight of steam expended on drying to the weight of evaporated water by 34 and 42%, respectively, in comparison with analogous indices in the investigated period. LITERATURE CITED i. 2.

3. 4. 5.

6.

V. N. Samoilo and M. D. Lotvinov, Optimization of Thermal Expenditures on Wide Paper Machines [in Russian], TslNTlkhimneftemash, Moscow (1984). G. P. Builov and E. V. Khardikov, Automatic Inspection and Control of the Processes of Drying Paper, Board, and Pulp on Paper, Cardboard, and Drying Machines [in N~ssian], VNIPIEllesprom, Moscow (1986). V. N. Samoilo, Steam and Condensate Systems and Their Role in the Optimization of Drying Regimes [in Russian], TslNTlkhimneftemash, Moscow (1980). OST 26-08-2005-82. Method of Computerized Heat Engineering Calculation of the Dryers of Paper, Cardboard, and Drying Machines. V. N. Samoilo and M. D. Lotvinov, Methods of improving the thermal efficiency and intensity of contact drying, in: Express Information, Series K~M-3, No. 3, TslNTlkhimneftemash, Moscow (1984), pp. 1-20. RD 50-374--82. Methodological Instructions for the Composition and Content of Norms of Fuel and Power Expenditure per Unit Output (Labor) Introduced into Standards and Technical Conditions.

RELATIVE EXTRUSION RESISTANCE OF RUBBER SEALING RINGS A. V. Samoilenko, A. F. Kon'kova, P. N. Velikanov, and I. D. Voronin

Rubber sealing pressures (up to 70 tween the parts and costly, and require

UDC [678.4.06:62-762.444]:620.178

rings are subjected to the action of high temperatures (up to 200~ and MPa) during use. This causes the ring to be extruded into the gap beultimately leads to failure. The existing field tests are laborious, too much time.

The All-Union Research, Design, and Technological Institute for the Rubber Industry (VNIKTIRPom)~ has developed the "Methodology for testing rubber rings." The rig shown in Fig. i is used for evaluating the relative extrusion resistance of rubber rings at different gaps, temperatures, and pressures. The test temperature can be varied from 20 to 200~ with the help of the thermostat. The gap to be sealed can be varied in the range of 0.i; 0.2; 0.3; 0.4; and 0.5 mm by means of interchangeable rods having different outer diameters. Moreover, additional grooves are provided on the rod to enable testing of rubber rings along with guard rings made of F4S15 fluoroplastic. The rubber rings are placed in the grooves and the pump is used to develop the required pressure (35 or 70 MPa). Tests are then conducted at a specified temperature and gap for a duration of 30 min. The readings of the pressure gauge during tests indicate whether there is any leakage. After pressure is released, the rings are taken out and inspected visually. If leakage is absent and the ring does not show any cracks or cuts, then the ring can be considered resistant to extrusion. Tests have been conducted with rings (size 012-016-25 as per GOST 9833-73) made of the following types of rubber: Gidrin i00 (hardness 70 and 80 on the Shore A scale); SKN-40M (hardness 70 and 90); and SKF-26 (hardness 70, 80, and 90). Tests were also conducted with guard rings made of modified fluoroplastic. The test temperatures were 20, I00, 150, and 200~ the test pressures were 35 and 70 P~a. Based on the tests it was found that the extrusion resistance of rubber rings decreases when the working temperature and pressure increase, while the resistance increases when the rubber hardness is increased or when guard rings made of modified fluoroplastic are used. Translated from Khimicheskoe i Neftyanoe Mashinostroenie, No. 7, pp. 15-16, July, 1988.

0009-2355/88/0708-0349512.50

9 1989 Plenum Publishing Corporation

349

J\

Fig. i. Diagram of rig for evaluating the relative extrusion resistance of rubber sealing rings: i) pump; 2) pressure gauge; 3) pipe; 4) thermostat; 5) rod; 6) coupling; 7) rubber ring; 8) guard ring. Under similar test conditions and hardness (70 • 5 on Shore A scale) the rings made of epichlorgidrin rubber (Gidrin i00) had lower extrusion resistance compared to the SKN-40Mand SKF-26 types. The rings made of SKN-40M and SKF-26 rubbers with hardness 90 • 5 on Shore A scale were found to be extrusion-resistant at a pressure of 35 MPa and temperatures up to 200~ as well as at a pressure of 70 MPa and temperatures up to 100~ The use of guard rings made of F4S15 modified fluoroplastic along with the rubber rings of 80-90 hardness (on Shore A scale) helps to increase the operating temperature from 150 to 200~ at a pressure of 35 MPa, and from i00 to 150~ at a pressure of 70 MPa. These results can be used when designing seals and selecting the conditions for tests on laboratory rigs.

RATIONAL CONTOURS FOR THE DYNAMIC-TRANSPORT*

SURFACES OF THE FLOW

CHANNELS IN HYDRAULIC MACHINES V. F. Shtofov, I, A. Kovalev, E. I. Zelenskii, and S~ P. Overchik

UDC 621.671.514.7

The main parameters of centrifugal and torque flow pumps, like efficiency and service life, which determine their competitiveness, depend to a large extent on the geometrical shape of the inlet and outlet pipes and on the design of the guide elements -- the flow channels in the machinery. Usually, the transition zones of these parts are designed as composites of various surface sections, arcs of curves and straight lines (cylinders, cones, toruses), or of logarithmic and Archimedes' spirals. Analysis of the effect of the geometrical shape on performance [i, 2] is not carried out. In most cases, the transition zones between adjacent geometrical surfaces are designed to ensure first-order smoothness (concidence of tangents), without considering the nature of change of the differential-geometric properties of the resultant contour. The main evaluation criteria are the invariant components of the curves and surfaces: curvature, twist, direction of the tangents and normals, monotony of curvature change, coincidence of the Darboux vectors of the mating arcs of the spatial trajectories, etc. Theoretical and practical information about hydraulic, gaseous, aerodynamic and particulate streams indicates that there are considerable variations in normal acceleration when the change in curvature of the trajectories is not strictly monotonic. The adverse effect of this phenomenon is increased pressure of the transported fluid on the walls, formation of local zones with increased turbulence, and cavitation. All these effects lead to significant energy losses and premature wear of the transport surface. There are known methods of designing composite surfaces with second-order smoothness (common tangents and equal curvatures at the junctions, as well as strict monotonic change in curvature along the trajectory). The mathematical techniques of designing the contours of dynamic surfaces can be used in many cases to avoid the adverse hydrodynamic effects mentioned earlier [3]. *These aye composite surfaces through which the hydraulic, gaseous, aerodynamic, or particulate streams flow. In geometry such sufaces are termed transport or dynamic-transport surface contours. Translated from Khimicheskoe i Neftyanoe Mashinostroenie, 350

0009-2355/88/0708-0350512.50

No. 7, pp. 16-17, July, 1988o

9 1989 Plenum Publishing Corporation