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Homework Assignment 3 on Fluid-Power Systems

4600:460 Concepts of Design Fall 2015

Prepared for all sections of 460 by Shao Wang, Associate Professor

Page numbers, if any, refer to the textbook Engineering Design by Dieter & Schmidt, 5th ed. Homework must be neatly written and readable, must be on 8.5-by-11-inch paper sheets of good quality (no sheet torn from a notebook with ripped edge, etc.) and must be stapled. Homework must be from individual efforts (not by a group) and is to be turned in at the beginning of the class on the due date. Copying homework from one another or from a Solutions Manual will result in a reduced grade. Please write your full name and the lecture section number: 460-001 (8:50 a.m.), 460-002 (9:55 a.m.), etc.

Date due: Sections 001 and 002: Tuesday, November 24, 2015 in the classroom before the lecture starts.

(Maximum possible score: 50 points.)

1. A hydraulic pump having a displacement (swept volume) of 1.7 cm3 per revolution is driven by an electric motor at 1500 rev/min. The pump has a volumetric efficiency of 87% and an overall efficiency of 76%.

1(a) Draw the part of a hydraulic circuit including all the devices mentioned above in this problem statement. 1(b) Calculate the pump delivery in liters per minute. 1(c) Calculate the power required to drive the pump when it is operating against a pressure of 150 bar.

2. A hydraulic circuit using 25 liters of fluid per minute is supplied by a pump having a fixed displacement of 12.5 cm3/rev driven at 2880 rev/min. The pump has a volumetric efficiency of 0.85 and an overall efficiency of 0.75. The system pressure is set at 180 bar by a relief valve.

2(a) Draw the part of a hydraulic circuit including all the devices mentioned above in this problem statement. 2(b) Calculate the quantity of fluid delivered by the pump (lit/min). 2(c) Calculate the power required to drive the pump. 2(d) Calculate the heat generation rate owing to the excess flow passing over the relief valve.

3. A hydraulic motor with a displacement of 475 cm3/rev is used to drive directly a conveyor drum having a diameter of 0.7 m. The pressure drop over the motor is 140 bar and the actual flow into the motor is 48 liters/min. The overall and torque efficiencies of the motor are 0.9 and 0.94, respectively.

3(a) Draw the part of a hydraulic circuit including both the hydraulic motor and a simple symbolic representation of the load. 3(b) Determine the torque at the conveyor drum. 3(c) Determine the power in kilowatts supplied to the conveyor drum. 3(d) Determine the linear speed of the conveyor belt.