共查询到20条相似文献，搜索用时 69 毫秒
1.
| 1. |
An intake structure with a closed flow having a vertical axis of rotation contributes to the development of a favorable kinematic structure in the channel, which makes it possible to minimize scouring beyond the structure.
| | 2. |
Excedence of the near-bottom average and maximum velocities above the average velocities in the channel comes about atl3.3hc downstream from the axis of the intake.
| | 3. |
The magnitude of the ratio of the maximum 1st-percentile and average 50th-percentile flow velocities (v1%/v50%), which characterizes the velocity pulsation, attains values for the undisturbed flow in the near-bottom region at a distancel4.1hc.
| | 4. |
Complete equalization of the plan diagram of velocities is noted at a distance (4.9–7.8)hc from the axis of the intake structure.
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Translated from Gidrotechnicheskoe Stroitel'stvo, No. 4, pp. 17–19, April, 1991. 相似文献
2.
| 1. |
The installation of a conical transitional segment between a tower (shaft)-type water intake-outlet and penstock affects a significant reduction in head loss in the pump mode, but has virtually no effect on the magnitude of the latter in the pump mode.
| | 2. |
The existence of a conical transitional element in the pump mode appreciably lowers the discharge velocities of the flow and increases the effective height of the water-passing openings by 1.5–1.7 times when the height of the intake openings h0.5dp.
| | 3. |
The head losses in the intake-outlet decrease in the pump mode of operation with increasing degree of expansion of the transitional diffusor segment.
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Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 11, pp. 21–23, November, 1992. 相似文献
3.
| 1. |
An increase in the oil temperature in baths of bearings with EMP segments from 30–35 to 60°C leads to a decrease of friction losses by 20–30% due to a decrease of the oil viscosity in the oil film, and also produces an additional effect from a reduction of the consumption of water for cooling.
| | 2. |
A decrease of the operating reliability of the bearings with EMP segments does not occur when the oil temperature in the bath is increased to 60°C. Therefore there is no need to introduce restrictions in the operating regimes of the units.
| | 3. |
The existing systems of sealing the oil baths of the bearings do not prevent the escape of oil vapors from the oil baths at an oil temperature of 55–60°C. Therefore reconstruction of the seals is necessary before changing to an oil temperature increased to 60°C.
| | 4. |
On operating units of hydrostations it is expedient to increase the oil temperature in the baths of the bearings from 30–35° to 45–50°C by reducing the flow rate of the cooling water or disconnecting a part of the coolers, which leads to a decrease of friction losses by 12–15% and does not noticeably increase the escape of oil vapors from the bearing baths.
| | 5. |
On newly designed bearings with EMP segments it is expedient to specify a smaller number of oil coolers, and it is possible to do away with them entirely by increasing the cooling capacity of the walls of the oil baths, for example, by means of fins on them.
| | 6. |
To reduce losses in the bearings, the use of other, less viscous oils or other low-viscosity liquids is possible.
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Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 11, pp. 20–24, November, 1990. 相似文献
4.
| 1. |
Oscillations due to low-frequency sources of excitation beneath the impeller in the draft tube develop in long pipelines of water-storage power plants.
| | 2. |
For the Zagorsk water-storage power plant with a long (790 m) and flexible pipeline, the natural frequency of the first type of the system's oscillation is many times lower than the predominant frequency of the lowest-frequency component of the spectrum of pressure fluctuations beneath the impeller (0.24–0.25)fre. For a shorter and stiffer pipeline, the system would approach resonance.
| | 3. |
The dynamic properties of the system depend on the opening of the guide apparatus: for small openings, the natural frequency approaches f1=(C/4)L; with large openings, it approaches f2=(C/2)L.
| | 4. |
When the unit is operating in the stationary mode, the hydrodynamic loads on the pipe lining do not exceed 0.05 MPa; this corresponds to an additional stress of 0.07 MPa in the lining and vibrational displacements of 0.183 mm (when C=780 m/sec), i.e., not more than 0.06 of the radius of the pipeline; when C=965 m/sec, the vibrational displacements do not exceed 0.08 mm.
| | 5. |
The loads on the pipeline supports do not exceed 0.36 tons on any one pile.
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Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 8, pp. 27–30, August, 1992. 相似文献
5.
| 1. |
The construction ana operation of the upstream wing wall of the Tashkumyr hydroelectric station confirmed the possibility and expediency of using lean rollcrete and simple designs for dams. After 3 years' operation the wall is in a completely satisfactory state.
| | 2. |
The use of rollcrete with a cement content of 80–120 kg/m3 during concreting by the technology proposed and perfected during construction of the wall provided the obtainment of concrete grades M100180–M200180 (classes V7.5–V15). When designing rollcrete it is necessary to take into account its increased nonuniformity — the coefficient of variation of the strength values of the concrete of the wall was 0.20–0.25.
| | 3. |
A uniform temperature regime with low values of the maximum temperatures is characteristic for rollcrete masonry. The measured temperature of the wall masonry corresponded to those calculated. The possibility of predicting the temperature regime of the rollcrete mass during its construction is thereby confirmed.
| | 4. |
When designing hydraulic structures it is necessary to take into account the anisotropy of the density of rollcrete masonry. Horizontal joints have a high permeability, which requires either a special technology of forming them or structural protection of such masonry with the outer zones made of vibrated concrete.
It is expedient to protect the rollcrete masonry with a gunite layer mainly for temporary dams. 相似文献
6.
| 1. |
The hydraulic characteristics of cohesive mudflows in the case of a hydraulic jump, other conditions being equal, differ considerably from those for a pure water flow.
| | 2. |
The scheme of calculating a hydraulic jump of a cohesive mudflow requires taking into account, along with the hydrostatic pressure, also the pressure caused by cohesive forces and angle of internal friction of the mudflow mixture.
| | 3. |
The change in the ratio of the depth H2/H1 before and after the jump completely depends on the kinetics parameter of the mudflow, values of cohesion and angle of internal friction.
| | 4. |
Several subcritical depths, determined by the concentration of the mudflow mixture and physical and mechanical properties of the medium, correspond to the jump function of a cohesive mudflow.
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Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 12, pp. 45–47, December, 1991. 相似文献
7.
| 1. |
The arch dam of the Khudoni hydrostation can be constructed by the continuous conveyor technology as enlarged blocks.
| | 2. |
The rate of concreting the dam for the proposed dimensions of the blocks and times of covering them can reach 200–250 m3/h.
| | 3. |
To attain the indicated rate of concreting, it is necessary to construct near the dam site a new concrete plant with facilities for cooling or heating the concrete mix.
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Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 8, pp. 13–14, August, 1990. 相似文献
8.
| 1. |
A comparison of laboratory and on-site data on a determination of the maximum range of oscillations at the end of a direct hydraulic jump when waves enter it from a chute with the results of calculations by theoretical formulas (1), (2), and (3) confirms the applicability of one of these formulas (2) for superrapid flow and flow transitional from superrapid to rapid.
| | 2. |
The stilling basin generates secondary waves, reaching half of the depth of the basin d with respect to its height. With submergence of the basin from the lower pool, the range of variations of the level increases additionally by 2.0–2.5 times.
| | 3. |
On the apron behind the stilling basin, the drop of waves is insignificant, since the wave transformation coefficient at distance (40–90)hn, where hn is the natural depth, remains equal to
.
| | 4. |
The periods and lengths of the waves transformed in the stilling basin decrease with increase of discharge and Froude number Fr0 and approach in value the wave periods.
| | 5. |
Formulas (6) and (10) were obtained for calculating the maximum amplitude of oscillations of the free surface and maximum depth at the crest of oblique waves on the narrowing sections of the wave chutes and they were checked experimentally, which proved the applicability of these formulas for calculating a nonstationary oblique hydraulic jump.
| | 6. |
The proposed empirical formulas (12)–(17) can be recommended for an approximate evaluation of the parameters of the largest first waves on the narrowing stretch.
| | 7. |
Under these conditions, the use of a stilling basin as an energy dissipator of a superrapid flow is not rational, since not dissipation but generation of secondary waves is observed in it.
When designing narrowing sections of chutes, it is necessary to take into account an increase of depth of the oblique jump with passage of roll waves. 相似文献
9.
| 1. |
Modified wood is an effective substitute of the laminated wood lining of bearing bushings for vertical pump units.
| | 2. |
An investigation of modified wood showed that this material in some indices (friction coefficient and wear resistance) is better than laminated wood.
| | 3. |
Since there is no mass manufacture and centralized supply of modified wood, it is possible to create a technological department for its production.
| | 4. |
Organization of the department does not require capital expenditures and special accommodations.
| | 5. |
Machining of the wood is performed on ordinary metal-cutting machines with the use of the tools used when machining laminated woods.
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Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 7, pp. 33–35, July, 1991. 相似文献
10.
| 1. |
For a porosity of about 5% the quality indices of APC are at the level of the requirements of the existing specifications P20-85:K
F0.85,R
20>3 MPa,R
50>1.2 MPa,K
th>2.5–3.
| | 2. |
The experiments on the impermeability of APC showed that material with a porosity of 4–5% withstands a water pressure of 0.2–0.3 MPa without its infiltration through the specimens.
| | 3. |
The results obtained give grounds to revise the traditional requirements imposed on the residual porosity — not more than 3% — of APC-base structural members. Compaction of asphaltic and asphaltic polymer-impregnated concrete mixes to a residual porosity of 4–5% will make it possible to reduce expenditures on compaction. In this case, variants of compacting mixes to various residual porosities are possible in combination with surface treatment of the material with sealing compositions (for example, with a bitumen-polymer binder) which must be substantiated by technical and economic calculations for the particular conditions of conducting works on constructing watertight facings of hydraulic structures.
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Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 11, pp. 28–30, November, 1988. 相似文献
11.
| 1. |
Deformation of the slopes of earth canals and the eolian process related to wind phenomena disturb the regime of the bed load. Consequently, when designing and operating large irrigation canals the effect of wind on the flow should be regarded as one of the main factors requiring engineering consideration when predicting the bed-load discharge and other design parameters.
| | 2. |
When evaluating the eroding or transporting ability of a flow with wind waves in canals it is necessary to proceed from the fact that the maximum bottom shear stresses are created in the case of an opposing wind in the trough section of the wave. Consequently, it should also be taken as the design value, for determination of which relation (6) can be used as a first approximation.
| | 3. |
Relation (4) includes the main wind-wave parameters, with respect to which the mechanism of movement of the bed load under wind conditions is also determined. Therefore, for a first approximation it can be recommended as a correction factor of the bed-load discharge under natural conditions.
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Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 9, pp. 34–36, September, 1988. 相似文献
12.
| 1. |
Absorbing formwork has a substantial effect on concrete quality for concretes with W/C0.365.
| | 2. |
The concrete surface quality depends on the quality of the absorbing formwork materials used.
| | 3. |
The possible amount of water removed from the concrete by means of the absorbing (vacuum) formwork was 2.4–3.57 kg/m2.
| | 4. |
Before the start of hardening of the concrete, its water content decreases by 20–30% at a depth to 15 cm from the absorbing formwork. During hardening of concrete, its water content equalizes over the entire length of the specimen (thickness of the block), and under these conditions the W/C ratio of the concrete near the formwork is not more than 1% below the initial.
| | 5. |
According to the results of testing the concrete for cavitation resistance, the best indices were noted for formwork containing ensonite. In this case, the cavitation resistance of the concrete was increased up to 1.4 times. The latter circumstance permits recommending for use as formwork absorbing material fine-porous paperboard of the ensonite type (with pore sizes 20–100 Å), which freely passes water molecules but retains cement particles.
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Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 11, pp. 39–41, November, 1989. 相似文献
13.
| 1. |
In certain cases of constructing dams salt-containing soils serve as their foundation.
| | 2. |
Under these conditions reliable operation of the structures can be provided only by developing special engineering measures to control dissolution.
| | 3. |
All existing methods of protecting saliferous foundation soils of hydraulic structures from dissolution can be divided into passive, active, and combined.
| | 4. |
The combined methods should be considered the most effective for preventing removal of salts from foundation soils by the seepage flow.
| | 5. |
Large-scale field investigations of the work of the combined method of protecting saliferous foundation soils of the planned Lower Kafirnigan hydro development showed its high effectiveness even in the case of complex engineering-geological conditions at the construction site.
| | 6. |
Individual elements of the set of dissolution protective measures investigated under field conditions can be used in hydrotechnical and hydropower construction practice.
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Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 10, pp. 10–14, October, 1994. 相似文献
14.
| 1. |
A microprocessor-based device was developed for checking (measuring) the level of the insulation resistance of the stator winding of a unit in the range 0.5–500 M and absorption coefficient in the range 1–10 with output of the measurement results to a digital indicator.
| | 2. |
All measurements are taken on a stopped or operating unit in a semiautomatic regime after pushing a button on the face panel of the device. It is possible to use the device as part of a process control system or in a diagnostic system with automatic control from a computer.
| | 3. |
The device underwent a check on the units of the Skhodnya and Chirkey hydrostations, where it showed good results. It is suggested that it be introduced.
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Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 9, pp. 43–45, September, 1989. 相似文献
15.
| 1. |
The relative method of measuring the flow rates of water through a turbine is realized by simple means and provides a sufficient accuracy for the needs of hydrostation operation.
| | 2. |
Further works of design organizations, operating services, and manufacturing plants is necessary for increasing the reliability of the entire flow-rate measuring system.
| | 3. |
The operating staffs of hydrostations need to be materially encouraged to use the discharge efficiently for producing electricity.
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Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 9, pp. 28–31, September, 1989. 相似文献
16.
| 1. |
The data base for existing ACS PP at hydroelectric plants can be successfully employed as points for monitoring the conservation of an environment of local significance.
| | 2. |
It is expedient to discuss this problem with organizations, including local control groups interested in the development of territorial-basin systems for ecological monitoring.
| | 3. |
The initiative in creating local territorial-basin support points for monitoring should emanate from guidelines for hydroelectric plants with ACS PP.
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Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 12, pp. 1–4, December, 1992. 相似文献
17.
| 1. |
A study of the strength and deformation properties of asphaltic concrete is necessary for analyzing the stress-strain state of dams with asphaltic concrete diaphragms. The properties of asphaltic concrete substantially depend not only on composition but also on temperature. The results obtained make possible an evaluation of the main deformation and strength properties of asphaltic concrete, diaphragms, and facings of dams in relation to composition and temperature at early design stages.
| | 2. |
To obtain generalized indices of properties in relation to composition and temperature of asphaltic concrete, all experiments were conducted on the basis of the mathematical theory of design of experiments. Each experiment had threefold replication.
| | 3. |
The experiments showed that the angle of internal friction for 7% bitumen in excess of 100% of the mineral part is practically independent of temperature. The strength of the material increases due to cohesion, which with a drop of temperature from 200 to 10 increases about fivefold.
| | 4. |
Investigation of the deformation properties of asphaltic concrete showed that the modulus of volume changeE
0 for=0.1 MPa varies by 4–7 times depending on the temperature.
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Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 5, pp. 26–30, May, 1989. 相似文献
18.
| 1. |
A method was developed for calculating structures for static and dynamic actions with consideration of deterministic and probabilistic approaches to the solution of the problems.
| | 2. |
The strength and reliability of structures of the machine hall of the powerhouse during discharge of floodwaters were estimated with the use of methods of statistical dynamics.
| | 3. |
Elements of reliability theory of engineering systems were used in estimating the reliability of the structures.
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Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 4, pp. 25–31, April, 1994. 相似文献
19.
| 1. |
An analysis of the causes of failures of PUs from the standpoint of reliability theory enbles design and operating organization to increase the probability of no-failure operation by revealing and reconstructing limiting elements.
| | 2. |
An evaluation of the intensity of the thermal effect of solar radiation on the concrete of water-supply structures of PSs with consideration of seasonal and daily maxima of the effect of insolation showed that in July–August consideration of insolation adds to the daily mean ambient temperatures up to 10–15°C. This value must be taken into account when predicting cavitation phenomena in pumps.
| | 3. |
Daily variations of the intensity of insolation affect the stress-strain state of the structures, increasing during the growing season the compressive stresses on surfaces exposed to the sun, which also must be taken into account when designing and operating hydraulic structures of PSs. The absolute maxima of the temperature of the pumped water and cavitation phenomena occur in the evening. The simplest measure reducing the variation of the intensity of insolation is to paint white the exposed surfaces of the intake of the PS, thereby reducing Ks in formula (4).
| | 4. |
The new layouts of the structures and devices improve the hydraulic conditions of the supply of water to the PUs, facilitate the removal of sediments and driftwood, and reduce the production costs of the water being pumped.
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Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 9, pp. 32–35, September, 1989. 相似文献
20.
| 1. |
Provision for stability of slopes is one of the main problems in designing plains PSHS.
| | 2. |
The reasons for occurrence and a chain reaction of development of landslide phenomena on the south slope of the area of basic structures of the Zagorsk PSHS were peculiarities of its engineering-geological structure that were not properly taken into account in designing and carrying out construction work.
| | 3. |
For the purpose of stabilizing the landslide slope, a system of engineering measures was developed and implemented, including a change in the configuration and structure of the right-bank abutment of the upper-basin levee to the water intake, construction of a banquette, filling of a counterbanquette, draining of moraine loams, grading of the slope, surface water diversion, and monitoring of the state of the slope and elements of the antilandslide protection.
| | 4. |
Data from full-scale observatins indicate the effectiveness of the antilandslide measures that were performed and a state of the slope corresponding to criteria for the hydro development's safe operation.
| | 5. |
Innovative elements of the system of measures to stabilize the south landslide slope of the Zagorsk PSHS are:
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| – |
the complex nature of measures, providing for the optimum set of criteria with respect to reliability, technological efficiency, construction time, and cost of adjusted expenditures;
| | – |
minimization of one-time and total excavation for the banquette, providing for the least disruption of the slope in the process of construction;
| | – |
draining of moraine loams, which has no known analog;
| | – |
the use of an ejector unwatering system, which provides for minimum adjusted expenditures on construction and operation of the drainage system.
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Deceased. 相似文献
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