Search

Ventilation cooling design is one of the key technologies during the design of large hydrogenerator. With the increase of hydrogenerator capacity, the overheating problem of rotor region become more and more serious. In this paper, a 250 MW hydrogenerator is analyzed. The transient electromagnetic field of the hydrogenerator is calculated. The losses (heat sources) of rotor components in the rotor region of the hydrogenerator are determined. Three-dimensional fluid and thermal coupled mathematic model of the hydrogenerator rotor region is established. The rotor rotation of the hydrogenerator is considered. The distribution of complex fluid velocity in the rotor region is calculated using the finite volume method. The influence of fluid velocity in the different directions on the temperature of the rotor excitation winding is studied under the different flow rates in the rotor region. The surface heat-transfer coefficient distribution of the rotor components is determined. The temperature distribution of the rotor excitation winding, rotor pole body, rotor press plate, rotor damping bar, and rotor end ring is obtained. The calculated temperature results match well with test values. These provide an important reference for the rotor structural design and optimization of larger hydrogenerator.

C23H23Br4CuN3O3, P 1‾ $\overline{1}$ (no. 2), a = 10.4769(4) Å, b = 10.7829(5) Å, c = 12.9824(5) Å, α = 98.153(2)°, β = 111.484(2)°, γ = 105.035(2)°, V = 1271.43(9) Å3, Z = 2, R gt(F) = 0.0338, wR ref(F 2) = 0.1158, T = 273.15 K.

Thermal management is often considered a bottleneck in the pursuit of the next generation hydrogenerator in the electric power system. Overheating of the complex rotor parts has become one of the main problems affecting safe and stable hydrogenerator operation. In this paper, a 250 MW hydrogenerator is analyzed. The transient electromagnetic field of the hydrogenerator is calculated and the losses of the rotor parts are obtained. The rotation of the hydrogenerator rotor is considered. Three-dimensional fluid and thermal mathematic and physical models of the hydrogenerator are established. The loss values from electromagnetic field calculations are applied to the rotor parts as heat sources in the temperature field. After solving the fluid and thermal equations of fluid-solid conjugated heat transfer, influence of the structures of rotor support plate, rotor pole body insulation, and rotor excitation winding on the fluid flow and temperature distribution in the rotor region of hydrogenerator is studied using the finite volume method. The calculated temperature result of rotor excitation winding is compared with the measured value. The calculated temperature result agrees well with the measured value. It provides an important reference for optimizing the rotor structure of the larger hydrogenerator.

C13H8BrClN2O, (M = 323.57 g/mol), monoclinic, P21/c (no. 14), a = 11.7584(5) Å, b = 7.4336(3) Å, c = 14.1134(6) Å, β = 104.861(2)°, V = 1192.35(9) Å3, Z = 4, Rgt(F) = 0.0301, wRref(F2) = 0.0794, T = 150.0 K.

C16H14Cl2N2O2, monoclinic, P21/n (no. 14), a = 6.8492(14) Å, b = 11.515(2) Å, c = 10.018(2) Å, β = 107.11(3)°, V = 755.2(3) Å3, Z = 2, Rgt(F) = 0.0592, wRref(F2) = 0.1369, T = 293(2) K.

OBJECTIVE: To define the prevalences and manifestations of reproductive tract infections (RTIs) in rural Peruvian women. METHODS: During 1997-98, we visited 18 rural districts in coastal, highlands, and jungle regions of Peru. We administered standardized questionnaires and pelvic examinations to members of women's community-based organizations; and collected vaginal fluid for pH, amine odour, Gram stain, microscopy, and culture for Trichomonas vaginalis; cervical specimens for Chlamydia trachomatis, Neisseria gonorrhoeae; human papilloma virus (HPV) by polymerase chain reaction (PCR) assays, and blood for syphilis serology. FINDINGS: The 754 participants averaged 36.9 years of age and 1.7 sex partners ever; 77% reported symptoms indicative of RTIs; 51% and 26% reported their symptoms spontaneously or only with specific questioning, respectively. Symptoms reported spontaneously included abnormal vaginal discharge (29.3% and 22.9%, respectively). One or more RTIs, found in 70.4% of participants, included bacterial vaginosis (43.7%), trichomoniasis (16.5%), vulvovaginal candidiasis (4.5%), chlamydial infection (6.8%), gonorrhoea (1.2%), syphilis seropositivity (1.7%), cervical HPV infection (4.9%), and genital warts or ulcers (2.8%). Of 715 adequate Pap smears, 7 revealed cancer, 4 high-grade squamous intra-epithelial lesions (SIL) and 15 low-grade SIL. Clinical algorithms had very low sensitivity and predictive values for cervical infection, but over half the women with symptoms of malodorous vaginal discharge, signs of abnormal vaginal discharge, or both, had bacterial vaginosis or trichomoniasis. CONCLUSION: Overall, 77% of women had symptoms indicative of RTIs, and 70% had objective evidence of one or more RTIs. Women with selected symptoms and signs of vaginal infection could benefit from standard metronidazole therapy.