Positive Displacement Pump - Definition, Types, Working

Positive displacement pump (PDP) is a type of pump in which a moving fluid is captured in a cavity and then discharges that fixed amount of fluid. The displacement of fluid takes place by some parts like plunger, piston, diaphragm etc. some of these pumps have expanding cavity at the suction side and a decreasing cavity at the discharge side. The liquid is sucked at the inlet side when the cavity expands and discharges it when the cavity decreases.

In order to understand it more clearly, let’s take a syringe which has a piston inside it. When the piston is drawn outward the cavity starts expanding and water starts to enter into the syringe cylinder. As the piston is pressed inward the cavity keeps on decreasing and the liquid inside the syringe experiences a force that makes the water to escape out of the syringe. So what is the conclusion of the illustration? We have seen in that the water is displaced from the syringe during suction and discharge stroke of the piston.


Types of Positive Displacement pump

By considering the mechanism used to move the fluid it is divided into three major types

1. Rotary Type Positive Displacement
2. Reciprocating Type Positive Displacement
3. Linear Type Positive Displacement

1. Rotary-Type Positive Displacement Pump

In this pump the fluid is moved by the use of a rotary part. It is the rotation which displaces the fluid from reservoir to the discharge pipe.
The common example of these types of pumps are: internal gear, screw pump, flexible vane or sliding vane, flexible impeller, circumferential pump, helical twisted roots etc.

The rotary type positive displacement pumps can be classified again into three main types

1. Gear pumps:  In this pump, the fluid is moved in between two rotating gears. The liquid is pushed between these two gears as it rotates.
2. Screw pumps: these pumps consist of two screw type rotor turning against each other. When the two screw rotates it sucks the water from the inlet and pump it to the outlet.
3. Rotary vane pumps: It is similar to scroll compressors. It consist of cylindrical rotor having vanes on it which is encased in a similar (i.e. cylindrical type) shaped housing. When it rotates the vanes on the rotor traps the fluid in between the rotor and casing and discharges it through outlet.

2. Reciprocating Types Positive Displacement Pump

In these pumps, there is a reciprocating part (which moves backward and forward) to pump the water. The reciprocating parts may be of plunger, piston or diaphragm type. It contains valves, inlet valves and outlet valves. The inlet valves open and outlet valves remain closed during suction of liquid. And inlet valves remain closed and outlet valves gets open during discharge of the liquid.

Reciprocating pump

As shown in the diagram above, as the piston moves to the right, the cavity expands and the water is sucked into it. And when the plunger moves to the left, it pushes the liquid which makes the discharger valve opens and water starts discharging through the cavity.
  • Some reciprocating pump has an expanding cavity at inlet side and a decreasing cavity at the outlet side. The Liquid is sucked into the cavity as it expands and discharges when the cavity starts decreasing.
  • The reciprocating pump's category ranges from simple (with one cylinder) to Quad (four) or even more. Most of their types have duplex (two) or triplex (three) cylinder.
  • It can powered by manually, by steam or air, or through a belt driven by an engine.
  • It is most commonly used in 19th century as boiler feed water pump. Now days it is used to pump highly viscous fluids like heavy oils and concrete, and also used in special applications where fluid is needed at low flow rates against high resistance.
They can be either single acting type or double acting type.

1. Single Acting Reciprocating pump: In this, suction takes place in one direction motion of the piston and discharge in other direction.
2. Double Acting Reciprocating pump: Suction and discharge takes place in both directions.

Typically reciprocating pumps can be classified as

1. Plunger pumps: A plunger is used for pumping water.
2. Piston: It has piston for pumping fluid.
3. Diaphragm: It works same as plunger pump But it has diaphragm for suction and discharge of liquid.

Linear Type Positive Displacement Pump

In this, the fluid displacement takes place linearly (i.e. in straight line). Rope pumps and chain pumps are the examples of these types.

For Better Explanation About Types Watch the Video Given Below:

The List of pumps working on the principle of positive displacement are:
  1. Rotary lobe pump
  2. Progressive cavity pumps
  3. Rotary gear pumps
  4. Piston pumps
  5. Diaphragm pumps
  6. Screw pumps
  7. Gear pumps
  8. Hydraulic pumps
  9. Rotary vane pumps
  10. Peristaltic pumps
  11. Rope pumps
  12. Flexible impeller pump
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For more about Pumps Visit: https://en.wikipedia.org/wiki/Pump

What is CVT - Continuously Variable Transmission and How it Works?

Have you ever imagined that gear ratio can be possible without gears? Interestingly right, what if system creates countless gear ratios? To create infinite gear ratio is an extraordinary thinking but is it possible? Yes everything is possible when it is a matter of automobiles. Manual gearbox or traditional transmission system has fixed number of gears and gear ratios. Metamorphosis of automotive technology is unpredictable and developed two pulley system of power transmission from engine to the wheel. The vehicle with continuously variable transmission (CVT) more popular in recent years and Japanese automobile companies are good at using this technology in their vehicles. CVT is a simple and amazing mechanism which offers infinite gear ratios.

Small History:

The Formula One (F1) sport is a most prestigious form of racing in the world. In 1993 The Williams FW15C for testing purpose they fitted with the completely different mechanism for transmission of power from an engine to the wheels. This test model of CVT technology was banned by F1 before hitting on the race track. Because this technology used as driver aid which reduces the driver efforts from shifting gear without any action by driver and racing is not much challenging for completion. Another big reason behind the ban was CVT powered car is quicker than manual gearbox and at the same time, it produces more noise. Japanese automobile manufacturing companies adopted this technology and implemented CVT in a very effective way and successfully presented joyful and effortless driving experience to customers.

Also Read: Torque Converter Working, Principle, Main Parts and Application.
Also Read: Fluid Coupling - Main Parts, Principle , Working and Application

Main Parts:

The basic CVT consist of (1) Primary pulley (2) Secondary pulley and (3) Belt

Pulley and Sheave:

Gearbox is an only way of connecting the engine to wheel. The vehicle does not require always same power or constant power output, sometimes high torque-low speed and low torque-high speed gear ratio done their work. In CVT system conical pulleys replaces gears arrangement that’s why it is also referred as pulley transmission. Drive pulley or primary pulley is directly connected to the crankshaft of the engine. Whereas driven pulley or secondary pulley is connected to drive shaft (Means Output shaft –Differential-Wheel).Both pulleys have static and moveable sheave, the combination of both static and moveable sheave called pulley. Both pulleys have its own axle shaft and parallel to each other. Infinite gear ratios can be achieved by both pulleys driven by belt while pulleys diameter varies according to the movement of sheaves. The direction of contraction and expansion of pulleys at both ends are different. If drive pulley expand then driven pulley contract at the same time and vice versa; let’s see how it works

At low speed:

What is CVT - Continuously Variable Transmission and How it Works?

At an initial stage vehicle required more torque (Doesn’t required speed) to move further, that’s why bigger gear used as a first gear in the manual transmission. In CVT system, belt pushes the pulleys and as soon as the crankshaft rotates the primary or driving pulley’s movable sheave moves away from the static sheave which makes the smaller diameter of the driving pulley. Due to the same movement of sheaves at the same time secondary or driven pulley become larger in diameter which leads to creating greater torque at vehicle’s starting position.

At high speed:

What is CVT - Continuously Variable Transmission and How it Works?

While accelerating, vehicle required high speed (Doesn’t required torque) for that driven pulley or secondary pulley diameter become smaller (smaller diameter more revolutions) as the moveable sheave moves away from the static sheave. Due to the same movement of sheaves at the same time, primary or driving pulley become bigger in diameter which creates gear ratio between them. One revolution at driving pulley is equal to four revolutions at the driven pulley.

How sheave movement takes place?

Inside the conical sheave, it has cylindrical rollers. These rollers are subjected to undergo centrifugal force. Sheave pocket placed upon the rollers which take the movement of inside and outside as per roller gets centrifugal force. Whenever rpm increases or decreases these rollers pushes the pocket inside or outside.

2. Push Belt:

Push belt transfer the torque from driving pulley to the driven pulley. Two types of belts are used in continuously variable transmission. V-Shape Kevlar rubber belt is used in the scooter which has more flexibility than the normal rubber belts. V-shape rubber can easily travel and pushes in-between the two pulleys. Steel belts are widely used in CVT; the construction of this belt is very unique, stronger and flexible than the V-shape belt. The complex steel belt has thin individual steel rings (Circular steel ring) and the whole bunch of small toothed steel elements which can easily travel and pushes the pulleys at any rpm range.

Working of Continuously Variable Transmission (CVT)

The manual and automatic transmission systems have complex working which depends upon gear shifting. There, two gears can achieve gear ratio, but in CVT two pulleys mechanism provides not only single gear ratio but countless or infinite gear ratio. Both are connected by a push belt, one pulley (Primary) is connected with the engine and another (Secondary) pulley with a drive shaft. Each pulley attached with moveable sheave which causes expansion and contraction of the pulleys at both ends. As the engine turns the primary pulley and secondary pulley diameter size gets changed due to moving sheaves of both pulleys. If one pulley’s size is decreased, at the same time second pulley’s size is increased and vice versa. The size variation of pulleys means diameters also varies which creates the continuous gear ratios. In manual gearbox input and output gear teeth decides the ratios, but here variation in diameter decides the ratios.

For Better Explanation About Continuously Variable Transmission (CVT) Watch the Video Given Below:


  • Lightweight, compact, and easy to handle.
  • Smooth shifting and it offers a smooth ride, No up and down shifting problem, and jerking can be eliminated.
  • Reduces the fuel consumption (up to 6-10 percentage) and no power loss due to no gear arrangement.
  • Better fuel economy and efficiency.
  • Quick and better acceleration.


  • Very expensive and if any damage occurs it needed costly repair.
  • Cannot transmit more torque and cannot withstand high horsepower because it is a belt driven system.
  • Not long lasting.
  • Noise from CVT system is more during acceleration as compared to usual transmission


CVT is used in automotive vehicles as the advanced transmission system
  • Examples: Scooters and Cars, Honda Activa.
  • Best CVT Cars available in India are Honda Amaze VX , Honda Civic, Honda City SV, Maruti Suzuki Baleno, Nissan Micra XL , Toyota Corolla Altis.

How DTSi Engine Works - Explained?

In DTSI engine, Dtsi stands for Digital Twin Spark Ignition. Before understanding DTSi technology, let’s understand why this technology is developed. Especially in internal combustion, which stroke is a main and effective stroke of an engine? Obviously, everyone is wondering about all the four strokes and started jumbling to find the better answer. Let’s come to one point if the burning of the air-fuel mixer would happen well then more power will be produced in the combustion chamber. So, in which stroke combustion of fuel takes place? It is at the end of compression stroke that means it is a power stroke or expansion stroke which is started via spark plug and it is effective among the other three strokes available. By improving the power stroke may change the entire scenario of an engine performance. Bajaj Auto Ltd has done some R&D on the power stroke and invented a new technology named as DTSI ( Digital Twin Spark Ignition). In this technology, it uses two spark plug for the combustion of fuel within the engine cylinder. The use of two spark plug increase the burning efficiency of the fuel and produces more power with less amount of fuel.

Working Principle:
How DTSi Engine Works - Explained?

It works on the principle of twin spark produced by the two spark plugs. As compared with the single spark fired engines, in twin spark engines the combustion of the air-fuel mixture takes place at optimal level and it produces more power. Because of the use of twin spark plug, the spark produced is more which burns the fuel more efficiently and rapidly. It results in  increase of mileage, power and less emission of exhaust gases. The Dtsi engine produces 26% more power as compared with conventional single spark engines of same capacity.

They are Digitally controlled by Electronic Control Unit (ECU)

Also Read: How Battery Ignition System Works?
Also Read: Magneto Ignition System - Parts, Working Principle, Advantages and Disadvantages with Application

Main part:

1. ECU:

It is a heart of the DTS-I. ECU consist microprocessor chip with preprogrammed data of Ignition Timings for various engine rpm and engine loads. It controls the firing of spark plugs as per the requirement.

2. Spark plug:

It is a small device placed upon the cylinder head.In dtsi engine two spark plugs are used for the combustion of fuel. It is an initiator of the power stroke. The electrical energy (High Voltage) transmitted through it and creates a spark in the combustion chamber. Spark plug usually requires a voltage of 12,000-25,000 volt to produce spark.

Working of DTSi Engine

First of all, it is a technology in which two spark plugs are used. DTS-I stands for Digital Twin spark ignition. Basically, it has two spark plugs at the opposite end of engine cylinder head in 90 degrees; instead of one spark plug which is common in a conventional engine. Two spark plugs produces the spark during the power stroke according to input requirement.

According to engine load, RPM and at low-high speed the ECU sends the low and high- frequency pulses to spark plug to perform as per situations. Spark timing of these two spark plugs is controlled digitally. DTS-I engines are known for efficient burning of air-fuel mixer at right time.

Internal Process:

The conventional engine equipped with only one spark plug. After suction of air-fuel mixer piston can move BDC to TDC, it is called compression. At the end of compression stroke piston will be at TDC and before starting of power stroke compressed air-fuel mixer get spark via spark plug and burnt. Burnt fuel produces the energy which pushes the piston down side. With single spark plug produced flame diameter is less which take more time to reach other portion, it means the rate of combustion is slow (from top to bottom in the combustion chamber). But, dual spark plug can overcome this issue and create larger diameter flame which can burn the complete air-fuel mixer uniformly and quickly in very less time. Due to this reason force upon the piston would be great which leads to better work output.

For Better Explanation Watch the Video Given Below:

Also Read: Anti-lock Braking System (ABS) - Working Principle, Main Components with Advantages and Disadvantages
Also Read: Manual Vs Automatic Transmission


  1. Detonation can be reduced: DTSI engine cannot frequently undergo detonation because complete combustion of air-fuel will not create any disturbance between piston and wall. 
  2. Better fuel efficiency
  3. Less emission of exhaust gases.
  4. Less vibrations and noise due to smooth function.
  5. Engine breathing performance is easy even at high rpm.
  6. No overheating issue.
  7. Complete combustion, No unburnt issue.
  8. Fast engine response even in winter and cold condition (Two spark plug).


  1. Expensive
  2. Replacement of both spark plug even one is damage (Reason is series in connection , But parallel connection could not be achieved high voltage).
  3. Complex in design.


The application of this technology is widely used in BAJAJ engines Example; Discover 150, pulsar 150, 200, 220.

Different Types of Pumps Used in the World

Pump is a mechanical device which moves the fluids from one place to another by mechanical action. It may be driven by manual operation, electricity, engines or wind power. They come in various sizes starting from microscopic to large industrial pumps.

They mostly operate on the mechanism of reciprocating and rotary. It consumes energy in order to do mechanical work for moving fluid. They are almost used everywhere such as pumping water from the wells, pond filtering, fuel injection, for operating cooling towers etc.

Types of Pumps

Types of pumps

Basically pumps are divided into two main types and these are
1. Positive displacement pumps
2. Centrifugal pumps

But it can be classified on the basis of different factors

On basis of number of impellers 

1. Single stage pump: A pump with one impeller rotating in its casing is called as single stage pump.

2. Double stage pump: A pump with two impellers rotating in its casing is called as double stage pump.

3. Multi-stage pump: When a pump has more than two impellers in its casing than it is called as multi stage pump.

Also Read: Reciprocating Pump - Main Parts, Types, Working, Advantages, Disadvantages with Application
Also Read: Types of Turbine

On the basis of methods of displacement of fluid they are classified as
1. Positive displacement pumps
2. Impulse pumps
3. Velocity pumps
4. Gravity pumps
5. Valveless pumps

1. Positive Displacement Pumps:

It is a pump in which fluid is moved by sucking a fixed amount of fluid in a cavity and then forcing this fluid from the cavity to the discharge pipe. Some positive displacement has an expanding cavity at suction side and decreasing cavity at the discharge side. As the cavity expands the fluid enters in the cavity and when the cavity decreases, the fluid forces to the discharge pipe.
Examples of these types of pumps are: internal gear pump, piston pumps, diaphragm pumps, rope pumps etc.

They are also classified as

(i) Rotary Type Positive Displacement: screw pump, internal gear, shuttle block, flexible vane or sliding vane, circumferential piston, flexible impeller, helical twisted roots or liquid ring pumps.

(ii) Reciprocating Type Positive Displacement: plunger pumps, piston pumps and diaphragm pumps.

(iii) Linear Type Positive Displacement: Rope pumps and chain pumps

2. Impulse Pumps

Impulse pump is operated by the pressure created by the gas (usually air ). In some of these pumps what happen, the gas is trapped in the liquid (mostly in water), is released and accumulated somewhere in the pump, this creates pressure that pushes part of liquid upwards. For example: hydraulic ram pumps, pulser pumps and airlift pumps.

Also Read: Pelton Turbine Working, Main Parts, Application with Diagram

3. Velocity Pumps: 

In velocity pumps, the kinetic energy is added to the fluid by increasing the flow velocity. This gain in kinetic energy is converted into potential energy (pressure) by decreasing the velocity as the flow exits the pump into the discharge pipe. For example: rotodynamics pumps such as centrifugal pump.

4. Gravity Pumps:

The pump in which the flow of fluid takes place with the help of gravity is called gravity pumps. For example – syphon and heron’s fountain.

5. Valveless Pumps: 

It is a pump in which the valves are not present and the flow of water takes place in the absence of valves. For example – impedance pump.

On the basis of types of flow

1. Axial Flow Pumps: It is a pump in which the flow of water takes place axially (i.e. parallel to the axis of rotation)
2. Radial Flow Pumps: In these types of pumps the flow of fluid takes place in radial direction i.e. at right angles to the axis of rotation.
3. Mixed Flow Pumps: In these pumps, the fluid enters axially and comes out radially or vice versa. It is a combination of axial and radial flow pumps.


Comparison Between Roots, Twin Screw and Centrifugal Supercharger

Increasing the engine horsepower is not a simple work, yes there are several ways and one of them is forced induction. In automobile world, there is a device called supercharger which is specially developed and it can fulfill the requirement of extra horsepower from the engine. Superchargers are used for the increase in air pressure or density at inlet valve before sending it to combustion chamber. Adding the extra air into the cylinder means more oxygen and it can burn more fuel which produces more horsepower. All the superchargers powered by belt or chain drive from the engine’s crankshaft. We have already seen the types of it and how they work. Now we will discuss here the comparison between them.

Comparison Between Roots, Twin Screw and Centrifugal Supercharger in Tabular Form:

Powered by a belt driven from the engine crankshaft.
It is also powered by a belt driven from the engine crankshaft.
Centrifugal supercharger also gets power via belt or chain drive from engine crankshaft.
Working principle: Positive displacement type.
Positive displacement type.
Centrifugal type.
Fixed amount of air per rotation.
Fixed amount of air per rotation.
Not fixed amount of air per rotation.
Working: When two lobes turn in opposite direction, the air suction starts at fill side and pushes the same quantity of air at discharge side.
Two same spiral rotors turn in opposite direction and both sides of gear pocket mesh together. Air flow at the inlet in auxiliary motion transported at discharge port compress as radially.
Created force rotates the impeller at very high speed and it can suck the low-pressure air at the inlet and delivers the high-pressure air at the discharge port.
It makes much power in low rpm range.
It also makes much power in low rpm range.
Unlike root and screw supercharger it is good for high rpm range.
Least efficient.
More efficient than the roots supercharger.
Very much efficient. Almost same as turbocharger.
Less horsepower, Torque, and boost can be achieved.
More horsepower, Torque and boost than the root but less than the centrifugal.
Great horsepower, high torque, and more boost can be achieved.
Parasitic load: The device absorbs the crankshaft power to run themselves is more.
Less parasitic load compared to roots type.
Very less parasitic load is required.
Creates lot of noise.
Less noisy than the roots type.
Creates very less noise.
Creates lot of heat.
Creates less heat compared to roots type.
No Heating issue.
The construction is bulky and placed upon the top of the engine.
 Construction and design same as the roots type. This is also bulky.
Small and compact. Placed in front of the engine.
Installation is difficult and some modification required in the inlet manifold.
Installation is difficult but does not require extra modification.
Easy installation.
Maintenance is required.
Less maintenance compared to roots type.
 Less maintenance required.

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Centrifugal Supercharger - Working Principle, Main Parts, Advantages, Disadvantages with Application

Who wouldn’t want some little extra power? But adding the power into an internal combustion is not an easy task. Can small device change engine output? Yes, Horsepower can be added up to 40-80%. There is the magic device which is placed upon or beside the engine. You feel big wow! When engine sounds like crazily vroom-vroom at that same time boost can move your vehicle faster from zero to triple digit speed. All the respect to this little device called Centrifugal Supercharger. It provides the more air density for each intake cycle of the engine. More air means more oxygen to burn more fuel in combustion chamber. This is a much valuable to automobile vehicles for boost and that extra horsepower which is needed for racing. Centrifugal supercharger is looked same as a turbocharger, but this is run by the belt drive or chain drive via engine's crankshaft whereas turbocharger gets its power from exhaust gases. This is widely used compared to positive displacement superchargers.

Centrifugal Supercharger

Working Principle:

As soon as impeller get rotational motion via driving pulley which is connected by chain drive or belt drive via a crankshaft. This impeller rotates at very high speed can start sucking the less pressurized and high-velocity air and drawn directly at diffuser. The diffuser is placed inside the housing and fixed with an impeller and which converts this centrifugal force into the high pressure and less velocity having the hot air density transported through an outlet of the housing to the intercooler. The intercooler can decrease the air temperature and cool air having the more air molecules and more oxygen sends into the inlet valve of the engine during the suction stroke. More air can burn more fuel to produce huge horsepower from an internal combustion engine.

Also Read: Types of Supercharger in Automobile

Main Parts:

Centrifugal Supercharger Main Parts

1. Impeller:

It is a rotating wheel which must be spin at high rpm. It can be removable by scrolling the nut at end of the impeller shaft. Impeller made of steel and composite alloys and machined on CNC milling machine. The impeller speeds can reach up to 100,000 rpm.

2. Diffuser:

It is a stationary wheel having the larger vane compare to an impeller. The impeller sucks the air at high-speed and less pressure. A diffuser converts it to low speed and high-pressure air. This air goes throughout the housing outlet.

3. Driven Pulley:

Drive pulley is getting the rotational moment from engine crankshaft which has connected via belt or chain with drive pulley of an engine.

4. Bearings:

Ball bearings actually support the rotating shaft which absorbs the drive loads. After a long usage of device, bearing may be worn out and causes noise problem

5. Gears:

Gearing section is large in the centrifugal supercharger. The sun gear is smaller which is surrounded by the mid-size three gears are closed with a ring gear.

6. Transmission:

Planetary gears help to an impeller for achieving greater speed and necessary to produce the desired boost. Sun gear is directly attached to impeller shaft and the ring gear is connected via belt or chain with engine's crankshaft.

7. Aeration Pump:

Aeration pump placed at below the transmission. It provides self-contained oiling with good bearing lubrication.

8. Housing:

The outer body of the device is called housing. It is made up of aluminum and material has high in strength, weigh less, also corrosion resistance. Housing is manufactured by the casting process and machined such a way that should match the impeller design and size.

Also Read: Difference Between Turbocharger and Supercharger

Working of Centrifugal Supercharger

  1. As the engine starts, the supercharger connected to the crankshaft through the belt also starts rotating.
  2. the impeller of the centrifugal supercharger starts rotating and sucks the high speed and low pressure air from the atmosphere axially. It compresses the air, reduces the speed of the air and gives high density air at its outlet. The pressure increases and velocity decreases as the air moves from impeller blades to the diffuser blade and then finally from the casing.
  3. The high density and high pressure compressed air is passed to the inlet manifold of the engine.
  4. This high dense air burnt the fuel in the engine cylinder more efficiently and increases the power of the internal combustion engine to a greater extent.
  5. The impeller rotates at a speed of upto 100,000 rpm.
For Better Explanation Watch the Video Given Below:


  • Boost level is high compared to other superchargers (up to 40 psi).
  • Less heat generation.
  • Small and compact.
  • Parasitic load: power required to turn centrifugal supercharger is very less.


  • Not great for low rpm boost.
  • Engine oil required.


Centrifugal superchargers are used in: Automotive, Truck, marine, aircraft and Utility vehicles

If you find anything missing in that, than suggest or makes us correct through your valuable comments. And if this article has enhanced your knowledge than don't forget to share it.

Twin Screw Supercharger - Main Parts, Working, Advantages, Disadvantages with Application

Twin Screw Supercharger also works same as other supercharger, and driven from the engine's crankshaft via a belt or gear drive. Twin screw name has given because, it uses a pair of spiral rotor which is identical and both are in the shape of screw. It comes under the positive displacement device and more efficient than the roots type. It is used for increasing air quantity in the engine cylinder for more combustion which actually leads to more horsepower and torque from the engine. Air suction and compression process is done in a very unique way where as in other devices, just air get sucked at inlet side and pushed at discharge side. It looks similar to roots supercharger

Twin Screw Supercharger

Main Parts:

1. Bypass Actuator:

This is can controls the bypass valve opening and closing action for intake manifold to provide required boost level. It is control by ECU and it has boost control shaft and boost control solenoid. At low speed no boost is required, at that time by pass valve stay opened and there is no pressure in intake manifold. But when high speed high boost is required, the by-pass valve get closed, which causes the increase of pressure in the intake manifold

Also Read: Types of Supercharger in Automobile

2. Housing:

It is an outer body of device in which spiral rotors are being placed and assembly of the twin screw supercharger. It is made up of high thermal resistant material made up of cast aluminum. But carbon fibres as a recent material used in housing for less weight and more strength.

3. Front Cover:

Front portion where input shaft is placed Inside of it and driven pulley fixed at outside. It is in conical shape

4. Drive Pulley:

From drive pulley, this device gets the rotational power from engine belt. As pulley rotate two rotors can try to move in different direction as per mechanism. It can initiate further process for the twin screw supercharger.

5. Bearings:

Anti-friction ball bearings actually support the backside of both rollers which absorbs the drive loads. After a long usage of device, bearing may be wear out and causes noise problem.

6. Time Gears:

It has the helical gears and must be of high quality with good tolerance to maintain gap between the rotors. A small inaccuracy in gear profile makes contact in rotors and also causes the noise.

7. Rotors:

Rotors are spiral in shape and designed in such a way that they never touch each other or housing. Each rotor will get rotational motion in opposite direction. Both rotors are slightly differing in edges, one looks like conical taper and another looks like worm gear.

Also Read: How Turbocharger Works - Explained?

Working Of Twin Screw Supercharger

Twin Screw Supercharger Working

This device starts its function from driving pulley and power transmitted to input shaft that makes the rotors to move in opposite direction. One of its rotors has taper teeth section and second rotor has warm gear teeth section. When both side of rotor pocket meshes together, air gets squeezed between them. When air get start to compress by both side of rotor’s pockets the air flow in auxiliary motion at inlet and transported horizontally all the way to discharge side in radial motion. From the discharge side the compressed air goes to intercooler, here it decreases the high temperature to a desired low temperature and pressurized air goes into the inlet manifold of engine. At less temperature of air the density of air will be greater so, more air molecules means more oxygen to burn more fuel to achieve more power and torque from the engine

For Better Explanation Watch the Video Given Below: 


  1. More horsepower and boost can be achieved as compared to root type supercharger.
  2. During the each rotation, a specific fixed amount of air is trapped and moved to discharge side where it is compressed
  3. Produces more horsepower  throughout entire rpm range. 
  4. Less noisy.


  1. Installation is complex.
  2. Continuously  compression and discharge irrespective of  boost  requirement at low or high speed.
  3. It also exhibits heating issue but less as compared with root type.


Twin screw supercharger used in automobiles to boost engine power. For example it mostly used in racing cars.

Reciprocating Pump - Main Parts, Types, Working, Advantages, Disadvantages with Application

What is Reciprocating Pump?

Reciprocating pump is a hydraulic machine which converts the mechanical energy into hydraulic energy. It does this work by sucking liquid into a cylinder containing a reciprocating piston which exerts a thrust force on the liquid and increases its hydraulic energy ( pressure energy of liquid).  It is a type of positive displacement pump which consists of piston or plunger. Piston is present in a cylinder in which it does reciprocating motion. It is used at a place where relatively small amount of water is to be delivered at higher pressure.

Main Parts

The main parts of a reciprocating pump is as follows:
  1. A cylinder with piston, piston rod, connecting rod and a crank.
  2. Suction pipe,
  3. Delivery pipe,
  4. Suction valve,
  5. Delivery valve and
  6. Air vessel.
 main parts of a reciprocating pump

Let's discuss all these parts in detail

1. A cylinder with piston, piston rod, connecting rod and a crank.

Cylinder is used to suck water and delivers it to the desired location. The piston executes reciprocating motion (back and forth motion) within the cylinder. Piston is connected to the crankshaft through connecting rod. An external power source is used to drive the piston within the cylinder. As the piston moves backward it sucks the liquid in the cylinder and when it moves forward it delivers the water from the cylinder to the required location.

2. Suction Pipe

As its name indicates, it is used to suck the water from the water reservoir to the cylinder. It connects the inlet of the pump with water tank.

3. Delivery Pipe

It is a pipe which is used to deliver the water from the cylinder to the desired location. It connects the outlet of the pump to the tank where the water is to be delivered.

4. Suction Valve

It is a valve which is present at the suction side of the pump. It opens during suction of water from the tank to the cylinder and remains closed during compression of the liquid. 

5. Delivery Valve

It is a valve which is present at delivery side and opens during compression of the liquid and remains closed when the water is sucked from the water tank.

6. Air Vessels

Air vessels in the reciprocating pump is used to get uniform discharge rate. It is provided on both suction and delivery side and connected to suction and delivery pipe.

Also Read: Centrifugal Pump - Working Principle, Main Parts with Application

Types of Reciprocating Pump

It is divided on the basis of source of work and the mechanism of operation.

On the basis of source of work it is divided as

1. Simple hand operated: Bicycle pump for the tyre inflation.
2. Power operated: Deep well pump

On the basis of mechanism

1. Single Acting Reciprocating Pump: In this, only one side of the piston engages to displace the liquid. Eg : piston syringe.

2. Double Acting Reciprocating Pump: In this, both sides of the piston engages to displace the fluid. In each stroke of the piston, two process i.e. suction and discharge carried at the same time. It consists of two inflow and two outflow pipes


Single Acting Reciprocating pump

Single Acting Reciprocating pump

During suction stroke, the piston moves backward and this opens the suction valve making the water enter into the cylinder. During suction the delivery valve remains closed and no water is discharged through it.

After suction stroke, the piston moves forward, delivery valve gets open and suction valve come into close position. As the piston moves forward it exerts thrust force on the liquid and it starts escaping out of the cylinder through delivery pipe. The water from the delivery pipes reaches to its required destination.

Also Read: All Types of Turbine That You Must Know

Double Acting Reciprocating Pump

Double Acting Reciprocating Pump

As the piston moves to the right hand side as shown in the fig above. The following process takes place at left and right side.

At left side: The suction valve opens and delivery valve gets closed. The water from the water reservoir is sucked into the cylinder.
At right side: The suction valve is gets closed and delivery valve gets open. the water sucked in the previous stroke is discharges out of the cylinder.

In the same way as the piston moves to left hand side, the discharge of the liquid takes place at left side and suction takes at the right side. And in each stroke of the piston, both suction and discharge of liquid takes place at the same time. If suction is taking place at right side than discharge takes place at left and vice-versa.


1. High pressure is obtained at the outlet.
2. Priming process is not needed in this pump.
3. It provides high suction lift.
4. It is also used for air.


1. It requires high maintenance because of more wear and tear of the parts.
2. Low flow rate i.e. it discharges low amount of water.
3. They are heavy and bulky in size.
4. High initial cost.


  • It is used at a place where low discharge rate is required with high pressure. It is mostly used to deliver water at large heights such as in deep well.
  • It is used for inflation of tyres of bicycles.

How Roots Supercharger Works - Easily Explained?

Roots supercharger is the oldest among the other superchargers, roots name comes after the roots type blower the American inventors and brothers Philander and Francis Marion Roots, founders of the Roots Blower Company of Connersville, Indiana USA, who actually patented the basic design and idea for this. All the superchargers mean to produce more power in internal combustion engine. Engine works by drawing a mixture of air and fuel into its cylinders, compressing that mixture, and then burning it. If is used for pressurizes the air at intake or increase the air density which supplied to internal combustion, more air means more oxygen allowing it to burn more fuel and to get more power by increase in air during the combustion in an engine. The more air that can be used to create the large amount of explosion to produce the more power and torque the engine produces. For that Roots supercharger is a one of its kind of the supercharger like other centrifugal and twin-screw supercharger.

Main Parts 

Main Parts of Roots Supercharger

The roots supercharger is constructed almost entirely of cast iron, with the exceptions of shafts, bearings and gears. A rotor is a combination of lobes and shafts. There are two different designs available for this type of supercharger, one is straight and another is twisted lobes. The lobes are supported on anti-friction bearings by the end plates or head plates which are fixed at front and back side of the device and surround the lobes.

Also Read: How Turbocharger Works - Explained?

Let’s see each part in detail:

1. Drive pulley:

From the drive pulley this device gets the rotational power from engine belt. As pulley rotate two rotors and lobes can try to move in different direction as per mechanism. It can initiate further process for the root supercharger.

2. Lobes:

The most important part of the root supercharger is the lobe also known as impeller. Lobes normally are cast grey iron with cast ductile iron for greater strength. It required corrosion or erosion resistance because of continuous air flow from outside can make humidity and temperature differ as per environment.

3. Bearings:

Which support the lobes and anti-friction type; it may be ball or roller. After a long use of device bearing may be wear out and causes noise problem

4. Gears:

It has the helical types of gears. And it must be of high quality with good tolerance to maintain clearance between two lobes of the rotor. A small inaccuracy in gear profile makes contact in rotating lobes and also causes the noise.

5. Shafts:

Both shafts are support the lobes. It has restricted design and diameter in order to support rotor and lobe. Shaft is usually made up of ductile iron. It has the unique characteristic that can be replaceable without changing the other components when damage cause.

6. Casing:

The casing is outer body of root supercharger, it looks like the box, In that all parts lobes, rotors, inlet and discharge ports are fixed and casing made up of cast grey iron. Another consideration is noise level, if thicker the casing the lower the noise.

Working Principle of Roots Supercharger

It can be powered mechanically by engine belt. The roots supercharger is a positive displacement supercharger, works on a very simple principle. As the drive shaft is rotated by engine belt, the lobes turn in opposite directions with very tiny clearances between each other and between the rotors and the casing. As each lobe passes air at the inlet fill side, a measured quantity of air is trapped between the lobes and the casing. As the shafts continue to rotate, this amount of air is transported around the casing to the discharge port side and created high pressure air directly send to inlet manifold through inter cooler and then cylinder of an engine. With this more quantity of air is used to burn more fuel and produce more power and torque in result.

Roots supercharger

Lets discuss its working step by step.
  1. The air from the air filter enters into the casing of the supercharger. The left lobe rotates anti-clockwise and right lobe rotates clockwise. 
  2. As the lobes rotates it traps the air in the space between the lobes and casing and compresses it.
  3. The compressed air is then discharged to the inlet manifold of the internal combustion engine through intercooler. the intercooler reduces the temperature of the air and brings it to the desired value suitable for combustion.
  4. Both the lobes works in the same manner but the direction their rotation is different.

For Better Explanation Watch the Video Given Below:


  • It creates the instant boost at low engine rpm.
  • Simple in construction and easier installation.
  • Do not use engine oil.


  • Create lot of heat.
  • Bulky in size.
  • Only delivers fixed amount of air per revolution.


  1. It is widely used in automobiles, especially in muscle and drag racing cars and hot rods 
  2. Used in Truck, tractors and pickup trucks.
In this article we have learnt about how roots supercharger works, it main parts, working principle, advantages and disadvantages with application. If you find anything missing or modification, please give your valuable comment. And if you get some information from this article than don't forget to like and share it.