WorksheetsQuiz on Positive Displacement Machines
Total questions: 29
Worksheet time: 10mins
What is the main function of a positive displacement pump?
To deliver a variable volume of liquid
To mix fluids
To deliver a constant volume of liquid
To create a vacuum
In a reciprocating pump, what component moves to create the pumping action?
Crankshaft
Piston
Valve
Gear
What happens to the fluid when the piston moves out in a reciprocating pump?
Fluid is forced out
Fluid is sucked into the cylinder
Fluid is compressed
Fluid remains stationary
What is the purpose of inlet valve in the reciprocating pump diagram?
To prevent back-flow
To increase pressure
To decrease flow rate
To allow fluid to exit
What type of flow does a reciprocating pump produce?
Steady flow
Pulsating flow
Laminar flow
Continuous flow
What is the formula for the theoretical discharge of a single acting pump?
Q = πD²LN/60
Q = 2πD²LN/120
Q = πD²LN/240
Q = 2πD²LN/240
What does %SLIP represent in pump theory?
Efficiency of the pump
Difference between stroke volume and displacement volume
Total volume of fluid pumped
Speed of the pump
What is the effect of leakage on actual discharge in a pump?
Increases efficiency
Has no effect
Decreases actual discharge
Increases actual discharge
What is the purpose of a flywheel in a double acting pump?
To increase speed
To smooth out discharge
To reduce weight
To increase pressure
What does the Darcy formula help to calculate in a pumping system?
Head loss due to friction
Power required
Flow rate
Pump efficiency
What is the maximum speed of a pump to avoid separation if the suction pressure is 2.4 m?
Must be calculated based on head
Must be less than 40 rpm
Depends on the pump type
Is always constant
What happens when the absolute pressure in the cylinder drops below 2.4 m head?
Flow rate increases
Cavitation occurs
Pressure remains stable
Pump efficiency increases
What is the role of air vessels in a reciprocating pump system?
To decrease flow rate
To smooth out flow
To reduce friction
To increase pressure
What is the effect of installing air vessels on the velocity of flow in pipes?
Velocity decreases
Velocity increases
Velocity becomes constant
Velocity becomes variable
What is the formula for calculating the average power required to drive a pump?
P = ρgQH_f,mean
P = ρgQH
P = ρgQH_total
P = ρgQH_f
What is the significance of the crank radius in a double acting pump?
Determines the speed
Determines the stroke length
Affects the pressure
Affects the discharge
What is the theoretical discharge for a double acting pump?
Q = πD²LN/120
Q = πD²LN/240
Q = 2πD²LN/60
Q = 2πD²LN/120
What does the term 'volumetric efficiency' refer to in pump theory?
Ratio of actual to theoretical discharge
Total volume of fluid pumped
Pressure in the cylinder
Speed of the pump
What is the effect of friction on the suction stroke of a pump?
Decreases suction pressure
Increases flow rate
Increases suction pressure
Has no effect
What is the formula for calculating the pressure head in the cylinder during discharge?
H = H_atm - H_s - H_as - H_fs
H = H_atm + H_d + H_ad + H_fd
H = H_atm + H_s + H_fd
H = H_d + H_s + H_as
What is the maximum force on the piston of a pump determined by?
Pressure difference across the piston
Length of the stroke
Speed of the pump
Diameter of the piston only
What is the purpose of the pressure gauge in a reciprocating pump system?
To measure temperature
To measure speed
To measure flow rate
To measure pressure
What happens to the discharge flow when the piston moves towards the bottom dead centre?
Fluid is sucked in
Flow increases
Fluid is forced out
Flow stops
What is the relationship between stroke volume and displacement volume?
Stroke volume is always greater
They can differ due to slip
Displacement volume is always greater
They are equal
What is the effect of a long and flat discharge pipe on pump operation?
Increases efficiency
Decreases efficiency
May cause back-flow
May allow flow after stroke
What is the significance of the crankshaft in a reciprocating pump?
Converts rotary motion to linear motion
Controls the speed
Increases pressure
Decreases flow rate
What is the primary advantage of using a centrifugal pump over a positive displacement pump?
Lower maintenance requirements
Constant flow rate regardless of pressure
Ability to handle viscous fluids
Higher efficiency at low flow rates
What is the role of the discharge valve in a reciprocating pump?
To allow fluid to enter the pump
To prevent backflow during discharge
To regulate the flow rate
To increase pressure in the cylinder
What is the effect of increasing the stroke length in a reciprocating pump?
Decreases the flow rate
Increases the pressure only
Increases the flow rate
Has no effect on flow rate
