Question

A marine engineer uses hydraulic machine. The hydraulic system of the machine consisting two ​cylinders connected with a flexible pipe. The cylinders and pipe is filled by incompressible liquid ​and both cylinders are fitted with moveable pistons. The area of small piston is 0.058 m2 and the ​area of large piston is 0.24 m2. ​​​​​​​[10 marks]

​(a) ​Draw a complete arrangement of hydraulic system.​​​​

​(b)​If the pressure exerted 3000 KPa the calculate the force applied at smaller piston.

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​(c)​Calculate the force exerted by the liquid at larger piston.​​​

​(d)​Discuss the advantage of using incompressible liquid rather than air in system (1 mark)

Answer 1

Given the area of the small piston A1 = 0.058m2 and the area of the larger piston A2 = 0.24m2.

(a) The complete arrangement of the hydraulic system is shown below.

(b) The pressure exerted is P = 3000 kPa= 3000 x 103 Pa. We know that if F is the force and A is the area, then pressure P is given by

So the force F1 applied at the smaller piston is,

The force applied at the smaller piston is 174000 kN.

(c) The force exerted by the liquid at larger piston is,

So the force exerted by the liquid at larger piston is 720 kN.

(d) The air is compressible but incompressible liquids are not. So bubrication is better in liquids and gives smoother motion compared to air. Also the pressure or force loss is less in liquids compared to air. Thus efficiency is greater for liquids.