tailieunhanh - Bearing Design in Machinery Episode 2 Part 3

Tham khảo tài liệu 'bearing design in machinery episode 2 part 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Fig. 10-4 Slideway supported by constant-flow-rate pads. Copyright 2003 by Marcel Dekker Inc. All Rights Reserved. In a multipad support one of the following two methods for feeding the oil into each recess is used. 1. Constant-flow-rate system where each recess is fed by a constant flow rate Q. 2. Constant pressure supply where each recess is fed by a constant pressure supply ps. The oil flows into each recess through a flow restrictor such as a capillary tube . The flow restrictor causes a pressure drop and the recess pressure is reduced to a lower level pr ps. The flow restrictor makes the bearing stiff to displacement due to variable load. In the case of the constant-flow-rate system the fluid is fed from a pump to a flow divider that divides the flow rate between the various recesses. The flow divider is essential for the operation because it ensures that the flow will be evenly distributed to each recess and not fed only into the recesses having the least resistance. High stiffness is obtained whenever each pad is fed by a constant flow rate Q. The explanation for the high stiffness lies in the relation between the clearance and recess pressure. For a bearing with given geometry the constant flow rate Q is proportional to h0 Q a n pr m 10-22 A vertical displacement Dh of the slide will increase and decrease the clearance h0 at the lands of the opposing hydrostatic pads. For constant flow rate Q and viscosity Eq. 10-22 indicates that increase and decrease in the clearance h0 would result in decrease and increase respectively of the recess pressure the recess pressure is inversely proportional to h03 . High stiffness means that only a very small vertical displacement of the slide is sufficient to generate a large difference of pressure between opposing recesses. The force resulting from these pressure differences acts in the direction opposite to any occasional additional load on the thrust bearing. Theoretically the bearing stiffness can be very high for a .