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Centrifugal pump oil seal structure improvement and application (2)
Helical seal helix angle α at 5 ° 6 'when the minimum power, and 15 ° 39' take the same length when the maximum sealing pressure, combined with some information to give practical experience, taking into account the sealing pressure, power consumption and structure length, and leave some safety (1), helix angle α For the 100Y pump, the shaft end diameter d = 65mm, the length of the outer shaft can be spiral seal L0 = 56.5 mm, the shaft end associated with the coupling, leaving 7mm interval, so take the seal length L = 39.5mm. Since the length and diameter are small, the seal pressure formula (see below) [1], the sealing pressure is small, so the larger the helix angle selected as α = 5 ° 49 '. Then the tangent of α t = tan α = 0.1019 (this value is calculated later). (2), the relative groove width u generally take u = 0.5 ~ 1.0, where u = a / (a ​​+ b) = 0.75. (3), the relative groove depth υ generally take υ = 2 ~ 10, taken as υ = (c + h) / c = 5. (4), the sealing clearance c recommended c = (0.6 ~ 2.6) / 10000m take c = 0.26mm, due to the centrifugal seal before the spiral seal to ensure sealing performance, take a big gap in order to prevent errors due to processing and installation error, and Shaft friction. (5), the groove depth h, h is calculated by the formula h = c * (υ-1): h = 0.26 * (5-1) = 1.04, h = 1.0mm. (6), the number of heads i, the number of heads i The principle of selection by the number of heads discussed above: high speed (n> 5000 r / min), menu head; low speed Take s = πd * tanα, α = 5 ° 49 '(8), the width of the spiral groove a, tooth width b by the formula a = πu * d * tan α / i = 3.00 mm b = π * 1-u * d * tan α / i = 1.0 mm Calculating the angular velocity ω of the shaft and the helical circumferential velocity v: ω = 2πn / 60 = 308.9 rad / sv = πn /60=7.6m/s (10), the length of spiral structure is L = 39.5mm (11), screw seal pressure Δp ', Δp' = rωwdLCp / c2 [1] tu (1-u) ) (υ3-1) where: Cp = (1 + t2) υ3 + t2u (1-u) (υ3-1) 2 Replace u = 0.75, t = 0.1019, υ = = 0.178, the viscosity of thin oil lubrication taking the small μ = 0.00223 × 9.8Pa / s, ω = 308.9rad / s, d = 0.065m, L = 0.0395m, c = 2.6 × 10-4m substituted, calculated Δp `= 35800Pa.