Full-scale strength tests of the blades were carried out on a Francis turbine having the following parameters: runner diameter 6 m, design head 34 m, rated power 85 MW, rotational speed 88.25 rpm, number of guide vanes 24, number of runner blades 15. The runner was of a weld--cast design.The blades were made of steel 20 GSL and faces on the rear side with stainless steel.The tests were performed with the use of the strain-gauge method and had the purpose: to determine the dependence of the static and dynamic stresses on the operating regime of the turbine; to compare the actual stresses with the theoretical values obtained by calculation by the finite-element method; to develop a method of protecting the transducers from the entry of water in connection with setting up analogous experimental investigations of high-head turbines (H = 150 m).Works on installing the transducers on the blades and laying the measuring cables were performed without dismantling the unit. Compensation strain gauges cemented on individual plates were installed next to the working strain gauges.The transducers were protected from the entry of water by a special paste (mixture of wax, petrolatum, etc.) on which two layers of epoxy-impregnated fiberglass fabric were then applied.To pick up the signal from the rotating parts of the turbine it was first amplified and only after this did it go to the slip ring and was recorded on a light-beam oscillograph. For this purpose 16 amplifiers were installed on the turbine shaft, which made it possible to simultaneously record 16 transducers without stopping the unit.A schematic diagram of laying the cables and arrangement of the measuring apparatus is shown in Fig. i. The accuracy of measuring the stresses is estimated to be 5 MPa.In addition to measuring the stresses, the pressure fluctuations in the flow passage and rotational speed of the unit were recorded.The first cycle of strength tests was carried out on unit No. 2 on two oppositely located blades (8 and 13).To determine the character of the stress--strain state, the strain gauges were installed in the same places on the front and rear sides (Fig. 2).Experiments at head H = 39.65 m showed that the maximum level of stresses is observed in the zones of the trailing edge and hub.The stresses near the lower rim and in the region of the leading edge and middle of the blade are extremely negligible and do not exceed 20 MPa (Table i). But even these negligible values were recorded only by the transducers installed in a longitudinal direction of the blade, whereas in a transverse direction (blade 8, strain gauges ii, 13, 15, etc.) the stresses did not exceed i0 MPa. With consideration of the low level of stresses recorded by the majority of transducers, further investigations were conducted mainly with strain gauges located in the region of the trailing edge and hub.The data of additional tests at a lower head H = 33 m are given for these same strain gauges also in Table i. The following conclusions can be made from the test results.The stresses from...

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Для количественной оценки надежности гидротурбин предложен физически обоснованный коэффициент оперативной готовности. расчеты показали, что в зависимости изменения во времени коэффициентов готовности можно выделить три характерных участка: начальный период эксплуатации с пониженными значениями показателей надежности оборудования, период эксплуатации с максимальными значениями этих коэффициентов и период постепен-ного снижения показателей надежности оборудования. Предложена методика, позволяющая оценить целесообразность реконструкции гидротурбины по условию надежности.

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