The compressors are explained along with types, different components, basic working principles, etc.
Let’s get into the article!
The compressor is pretty much an important component in most industrial machines and even for some household applications. From internal combustion engines to refrigerators the compressors are used and have a very important role in the operations.
They have a wide range of applications. Let’s know more about them in detail.
The compressors and pumps are kind of similar but no worries. We will differentiate between these two in this article itself.
So, the compressors are mostly used in the stages. The later stage is smaller than the first one. To increase the discharge pressure the stages are used. The more stages more will be compression.
Let’s know about the wide range of compressor types.
The compressors are divided into two types. One is the positive displacement compressor that is mostly used and the other one is the dynamic compressor.
We will see the types and later each of them in detail.
The positive displacement compressor is the compressor, that compresses the air by the displacement of a mechanical linkage reducing the volume.
In simple words, this compressor draws a discrete amount of volume of gas inside and forces them to exit the outlet of the compressor.
It is classified as follows,
2. Rotary compressors
The dynamic compressors work at a constant pressure. Though the performance of the dynamic compressors is affected by the external conditions.
In these compressors, the air is drawn between the blades with the help of rapidly rotating impellers. Later the gas is discharged via a diffuser.
These compressors are only having two types, depending on the main direction of the gas flow.
Before going into the details of each compressor, let’s know about the general parts or components used in the compressor.
The compressor parts are follows,
The pistons are the integral part of the reciprocating compressors.
The connecting rods attached to the piston and used to move piston up and down. They take the heavy workload and thus they are made by keeping durability in considerations.
The actuators are responsible for creating rotary and linear movements.
The bushings are used to create a space between the moving parts.
These are protection devices for the compressors. The air in the compressor should not be leaked and they should tight and sealed completely to avoid any accidents or breakdowns.
These are provided to various parts of the compressor where leak protection should be implemented, Like,
The rotors are the parts of the rotor compressors.
The vales are the controlling equipment’s for the operation of compressors.
The motor is used to run the operation of compressed air. However, there may be other drivers that can be used, like –
The intercoolers are used to increase the overall performance of the compressors. It can be used to set the stages in the compressor.
They prevent the leaking from the high-pressure systems.
Now its time to go into some brief details of each of the compressor types. Starting from the positive displacement compressor.
Reciprocating compressors as the names suggests they are reciprocating nature with piston inclusion.
Reciprocating compressors are further classified based on the number of discharge strokes per crankshaft revolution.
In case of air compressions, the double-acting multi-stage reciprocating compressors are best suited. But they are costlier than the rotary compressors.
The reciprocating compressors are able to compress a wide range of gases, refrigerants. This characteristic of the reciprocating compressors enables them to be used in various applications by varying size, number of cylinders, etc.
Diaphragm compressors are the variant of reciprocating compressors. They have a flexible membrane that moves back and forth with the help of rod and crankshaft mechanisms. They are suited for pumping toxic and explosive gases.
It has the two helical screws meshed with each other. The helical screws push the gas to move into smaller space and hence get compressed.
They are generally used for larger industrial applications for the supply of compressed air. Mostly used where the demand for continuous air is required.
Rotary vane compressors are equipped with the blades that are inserted in the radial slots available on the rotor. The rotor is mounted in kind of offset with the larger housing. When the rotors turns blades will slide in and out of the slots.
The rolling piston as the name suggests it has the piston included which makes a partition. The partition is made between the vane and rotor.
The scroll compressors are also known as the spiral compressors because of its shape and structure. They are used in the air conditioning, as an automobile supercharger and as a vacuum pump.
These are the sub-type of the dynamic compressors and are also known as radial compressors. They achieve the compression with the help kinetic energy addition to the flow of fluid with the aid of rotor or impeller.
Later the kinetic energy is converted to the potential energy by slowing the flow via a diffuser.
They are used in wide range of applications like diesel engine turbochargers and superchargers. In the pipelines of natural gases to move the gas from production site to consumers of the gas.
In Air conditioning and refrigeration centrifugal compressors supply the compression in cycle of water chillers.
The second type of dynamic compressor is the axial compressors. These are the gas compressors that can continuously pressurize the gases. Axial compressor uses the arrays of fan-like air foils to compress the fluid.
Axial compressors has the high efficiencies but they are expensive and require high quality materials. They are mostly used in the large gas turbines, natural gas pumping stations and chemical plants.
Now we have seen both dynamic as well as positive displacement compressors.
Now let’s know the key differences between dynamic and positive displacement compressors.
Compressor capacity is calculated in terms of FAD, that is Free Air Delivery and it is stated at actual conditions.
It is expressed, as Q
Q = (P2-P1)/P0 x V/T Nm3/Min
P0 = Atm pressure, kg/cm2
P1 = Innitial Pressure, kg/cm2
P2 = Final Pressure, kg/cm2
V = Storage Volume, m3
T = Time taken to build pressure.
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A typical compressor specification shall consists the followings,
There are a few differences between positive displacement and dynamic compressor.
|Sr No||Positive displacement compressor||Dynamic compressor|
|1)||The positive displacement compressors compress the air with the help of mechanical linkages, it physically reduces the volume and increases pressure.||In the dynamic ones, the fluid is provided with velocity by the impeller, and then with the help of a diffuser pressure is increased.|
|2)||It compresses the fixed packets of the fluid.||It will compress the fluid in a continuous manner.|
|3)||The velocity of fluid doesn’t require to be high.||Velocity of fluid must be high.|
|4)||PDP will give constant flow rate against variable output pressure.||Dynamic will give a variable flow rate against variable output pressures.|
|5)||The fluid will directly give the pressure energy.||First fluid have the kinetic energy and then converted to pressure energy.|
One more thing is to differentiate between the pump and compressor. Because of their similarities of work they often gets confused so to ease out your doubt here is the difference between the compressor and the pump.
There are a few differences between compressor and pump.
|1)||Compressor increases the potential energy by pressuring in smaller volumes.||The pump increases the kinetic energy of fluid which will further increase the pressure energy.|
|2)||Fluid used can be only gas.||Any type of fluid can be used.|
|3)||The volume change is occurred.||There is no volume change from inlet to outlet.|
|4)||Compressors are more expensive.||They are cheaper than compressors.|
|5)||Compressors are available with the storage facility.||Pumps don’t have any storage facility.|
|6)||Compressible fluids are used.||Normally incompressible fluids are used.|
|7)||It doesn’t associate with the cavitation problem.||It may associate with the cavitation problems.|
There are few standards used to design compressors, as follows,
So, these are the differences you should know about the compressors and the pump. There are lots of new advancements being made in compressor for increasing efficiencies and performances.
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