What Is Volumetric Efficiency In Manufacturing & Why Is It Important?

Volumetric Efficiency of Compressors | KB Delta

There are many sorts of compressors. Compressors are used to compress air, fuel, coolant, and other gaseous substances in order to create potential energy, which powers many kinds of machines used every day. In common use, there are reciprocating, rotary, screw, centrifugal, and scroll compressors, each with its own design and common uses. Regardless of the mechanics involved, all compressors need volumetric efficiency.

In a compressor, the main factors that influence efficiency are how much gas can be taken into the cylinder, how well the gas is compressed, and how much of the original gas correctly passes through the compressor to be used.

Compressors are designed to increase the pressure of a gaseous substance by reducing its volume.

It is essential to have high volumetric efficiency so that the maximum gas enters the cylinder and remains in the system to be used.


What Is Volumetric Efficiency?

Volumetric efficiency is defined as a ratio of a gaseous substance entering a cylinder to the volumetric displacement of a piston.

Inside a compressor, there are cylinders into which fuel, air, coolant, or another gaseous substance is injected.

A piston forces this gas into a smaller volume. This creates pressure, which is also potential energy.

If the gas enters the chamber, completely fills it, is correctly compressed, and is all transferred to the next part of the system, the compressor is said to have high volumetric efficiency.

If not much of the gas that enters is able to be used in the system, the efficiency is low.

It simply measures how efficiently a given gas passes through a compressor.


Measuring The Efficiency

Volumetric efficiency is measured by comparing the amount of a gas that enters the cylinder versus the gas that exits.

Since the exiting gas has been compressed, it will have a different volume. However, it can be measured based on how much gas has escaped.

In a given cylinder, there is a theoretical maximum volume. For example, by simple measuring, it can be discovered that a cylinder holds one liter.

This is a theoretical maximum, however, because there are many reasons a cylinder will not hold that full liter of a gaseous substance during compression, and therefore cannot be as efficient.

If the entering gas were to completely fill the cylinder and if all of the gas that enters the cylinder were to subsequently exit into the system where it can be used, the compressor would be 100% efficient.

If, however, 30% of the gas does not correctly pass through the compressor, the efficiency would be 70%.

Compressors are never 100% efficient but can get close with the proper construction and maintenance.



Why Is Efficiency Important?

Compressors are used in a variety of engines. This is because it is one of the more effective ways of generating potential energy.

In vehicles, fuel is injected into cylinders and compressed, which causes it to combust and powers the engine.Complete Proper Compressor Valve | KB Delta

Within air compressors, simple air is forced into the cylinder and compressed to store up the air so that it can be used to fill tires and for other uses.

In cooling systems, coolant is compressed in the cylinder which causes a rapid heat loss.

This is seen inĀ household refrigerators and commercial coolant systems.

This quickly condenses water vapor into liquid form, which is used to pull heat from the target areas.

If the efficiency in any of these compressors is low, not as much compression is happening. Therefore, the compressor is not accomplishing much.

Reducing problems with the compressor, valves, and pistons can help increase the efficiency.

This allows higher speeds in engines and quicker compression of air in air compressors.

It also provides more rapid cooling in refrigerators and air conditioners.


Common Reasons for Poor Volumetric Efficiency

Preventing poor volumetric efficiency will cause the compressor to be more useful.

Some common reasons for the maximum gas being unable to enter the cylinder or exit into the system where it can be used include the following:


  • Small valves which do not allow enough gas to pass through
  • A single valve with low intake versus multiple valves that allow plenty of intake
  • Unevenness or excessive angles that prevent gas from advancing directly to the cylinder
  • Uneven heating along the intake valves which can cause gas to expand prior to compression
  • Poorly designed or old cracked seals
  • Ineffective valves that don’t open and close smoothly or are unable to withstand the substances that pass through them


The most efficient compressors are created with large, even, insulated valves. These allow the correct amount gas to pass directly into the cylinder without undue friction or expansion.

If a compressor lacks the proper valves, if the incoming gas is inhibited by friction or uneven heating, or if parts of the intake have become old and frayed, the efficiency will decrease.


Volumetric Efficiency in Compressors

If you want the engines in your machinery to work as well as possible, it is essential to find and maintain effective compressors.

Some compressors are poorly designed or incorrectly manufactured and will never achieve high volumetric efficiency.

However, with correct compressor maintenance and the proper parts, they can be made more efficient.

For example, by smoothing the intake valves and consistently replacing seals before they become wimpy and old, the compressor will still have reasonable efficiency for its kind.

Keep in mind that no matter how well designed it is, a compressor has not yet been invented that is 100% efficient.

While there are methods of turbocharging fuel or pre-compressing air to maximize the potential energy, it remains impossible to perfectly capture every molecule of a given substance in a compressor with current technology.



In every engine with a compressor, it is possible to measure the volumetric efficiency.

Since compressors are commonly used in everyday mechanical devices including commercial equipment and household appliances.

It makes sense to find ways to make the compressors as efficient as possible.

By maximizing this efficiency, these engines become more energy-efficient and faster at doing what they were designed to do.

With a bit of simple maintenance, even poorly designed compressors can be made more efficient.

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