Hydraulic vs

Questions and Answers

What did Pascal observe about confined fluids?

They transmit pressure unevenly

They transmit pressure in one direction only

They transmit pressure in all directions equally (correct)

They do not transmit pressure

How is the principle of conservation of energy illustrated in the hydraulic circuit?

It increases pressure in one direction

It acts like a force multiplier (correct)

It reduces pressure in one direction

It has no effect on pressure

What does the conservation of energy principle require in the hydraulic circuit?

No effect on fluid volume

Increase in fluid volume

Conservation of fluid volume (correct)

Decrease in fluid volume

What does the hydraulic circuit act like in terms of energy conservation?

A gear reducer Signup and view all the answers

What principle is used in hydraulic circuits between any two cross-section points?

Conservation of mass Signup and view all the answers

What is assumed about the mass of the fluid in the volume between two points in hydraulic circuits?

It does not change Signup and view all the answers

What is the function of a pressure intensifier in a hydraulic circuit?

Increases pressure and reduces flow rate Signup and view all the answers

What is the main control component in hydraulic circuits for metering fluid flow?

Valves Signup and view all the answers

What is the function of a pressure control valve in a hydraulic system?

Maintains a desired pressure Signup and view all the answers

What are the three major considerations for sizing a valve?

Flow rating, pressure rating, speed of response Signup and view all the answers

What is a key difference in solenoid design between proportional valves and ON/OFF valves?

Proportional valves have a fairly constant current–force relationship Signup and view all the answers

What is a characteristic of proportional valve spools compared to ON/OFF valve spools?

Proportional valve spools are carefully designed with desired orifice profiles Signup and view all the answers

What does Bernoulli's equation consider?

Energy added or removed, and energy losses due to friction Signup and view all the answers

What does viscosity measure?

Fluid's resistance to flow Signup and view all the answers

How is kinematic viscosity defined?

Relative to dynamic viscosity and measured as the time for a standard volume of fluid to flow through a standard orifice Signup and view all the answers

What do heat exchangers do?

Transfer heat between separate fluids and can function as coolers or heaters Signup and view all the answers

What does bulk modulus represent?

The compressibility of fluid volume and is a function of pressure and temperature Signup and view all the answers

How can entrapped air affect a hydraulic line?

It can reduce the bulk modulus of a hydraulic line, affecting system motion Signup and view all the answers

What type of piston pumps are designed to reduce cyclic flow rate and pressure pulsation?

Radial piston pumps Signup and view all the answers

What is used to change displacement in axial piston pumps?

Swash plate angle control Signup and view all the answers

Which type of axial piston pumps is most widely used in mobile hydraulic applications?

Bent-axis piston pumps Signup and view all the answers

What do the number, diameter, and stroke of pistons determine in a pump?

Pump displacement Signup and view all the answers

What do variable displacement pumps have in terms of energy-saving potential?

Energy-saving potential Signup and view all the answers

What is used to change output shaft speed in an over-center motor?

Swash plate movement Signup and view all the answers

What are the main components of electrical circuits?

Voltage, current, resistors, capacitors, inductors, and diodes Signup and view all the answers

What determines the pump output pressure in a hydraulic system?

Load pressure and pressure drop on the valve Signup and view all the answers

What is the function of a line relief valve in a hydraulic system?

Limits the maximum allowed line pressure and returns the flow back to the tank if the line pressure exceeds a set limit Signup and view all the answers

What is the difference between fixed displacement pumps and variable displacement pumps?

Fixed displacement pumps have a fixed flow volume pumped per stroke, while variable displacement pumps allow control of the flow rate by adjusting the displacement per stroke Signup and view all the answers

What is the principle of operation for vane pumps?

Oil is taken in on the side with increasing volume and pushed into the part of the pump with decreasing volume, increasing the pressure before reaching the outlet port Signup and view all the answers

What recent development has led to piston pumps dominating the market for mobile hydraulics?

Made quieter and cheaper Signup and view all the answers

Study Notes

Hydraulic and Electrical Circuits Comparison and Positive Displacement Pumps

Electrical circuits consist of voltage, current, resistors, capacitors, inductors, and diodes, while hydraulic circuits involve pressure, flow, orifice restriction, accumulators, and check valves.
Three main differences between hydraulic and electrical circuits: flow-pressure relationship is nonlinear, medium of power transmission is compressible in hydraulics, and voltage is relative while pressure has an absolute zero.
The flow-pressure relationship involves the displacement of the valve spool, orifice area, pressure differential, and electrical resistance, while hydraulic resistance is a function of orifice area opening and its geometry.
The functional block diagram and operating principle of a pump are shown, highlighting the conversion of mechanical power to hydraulic power by a positive displacement pump.
In a hydraulic system, the pump output pressure is determined by the load pressure and the pressure drop on the valve, with check valves controlling the flow direction.
The line relief valve limits the maximum allowed line pressure and returns the flow back to the tank if the line pressure exceeds a set limit.
The volume expansion during the in-stroke and contraction during the out-stroke provide the suction and pumping action for the pump, with the volume spanned by the piston per stroke being called the "pump displacement per stroke."
Fixed displacement pumps have a fixed flow volume pumped per stroke, while variable displacement pumps allow control of the flow rate by adjusting the displacement per stroke.
Gear pumps operate by carrying fluid between the tooth spaces of two meshed gears, are always unbalanced by design, and are popular due to their simplicity, low cost, and robustness.
Vane pumps operate more quietly than gear pumps, and a variable displacement vane pump works on the principle of oil being taken in on the side with increasing volume and pushed into the part of the pump with decreasing volume, increasing the pressure before reaching the outlet port.
Recent developments have made piston pumps quieter and cheaper, leading them to dominate the market for mobile hydraulics.
Changing the position of the cam ring in relation to the rotor changes the displacement of the pump in a vane pump.

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Description

Explore the differences between hydraulic and electrical circuits, and delve into the workings of positive displacement pumps with this quiz. Learn about the unique characteristics of hydraulic and electrical systems, and gain insights into the functionality and operation of positive displacement pumps, including fixed and variable displacement pumps, gear pumps, vane pumps, and piston pumps.