Question

A 50 mm diameter pressure fed journal bearing is operating at 50 rev/s under a load of 5 kN giving a projected unit load of 2 MPa. Half journal length is l' = 25 mm, and radial clearance is c = 25 microns. Oil inlet temperature is maintained at 30 °C and average temperature is to be kept at 70°C. Viscosity of the oil used is then 12 mPa.s. What is the minimum required supply pressure [kPa] that maintains this operating condition? (note 1/d=1/2)

Answer 1

H. Pressure fed Journal bearing Given, diameter of Journal of 50mm. Ns = 50 revls; Load (W)=5KN% Pressure (P) = 2Mpa ; d = (2582) = 50mm; Radial clearance (e) = 25*100m j. oil inlet temperature (T) = 30°c ; Average temperature (Tav) = 70°C Viscosity of oll (2) = 12 x 103 pars ;. we know, Tax = TT (AT). where, AT = temperature rise of oid => 70 = 30 + (CI) So, AT =,80°C. we know, INs *r* l) 2 AT = 804 1018 C C Here, &- radius of Journal Lo Ps = supply pressure (Mpa) Ki = Eccentricity Correction factor = 1 K₂ = (1 + (2 e

calculating Sommerfeld Number (s). 50/2 x 1032 1. PL (12 x 103 +50. 2x106 25x10-6 - 0.3 From the table of full Journal bearing. at Hd = 1 and s= 0.3 we get The ) = 0.62 Minimum filin thickness. So, ho = (0.62 x 25 x 100 m. R = 0.0155 mon we know ho = ca e . so e = 60.0155+ 25x103) = 0.0095min SKET > On09 = 1:031

1018 3)2) * (12810-3) So from equation x = 80*72 x (1.081) + (50*50/4507 (1271 ((25 x 10-3 27 So, Ps = 9.7858 18-6 Mpa Ps = 9.785 x 103 kpa (Ang). This is the minimum supply pressure required for operating Condition.

Answer is boxed and calculation is shown clearly. Thank You and have a great day.