Volumetric efficiency (VE) in internal combustion engine engineering is defined as the ratio of the mass density of the air-fuel mixture drawn into the cylinder to the mass density of the same volume of air at atmospheric pressure (during the intake stroke). goes. intake manifold. The term is also used in other engineering contexts, such as hydraulic pumps and electronic components.
Internal combustion engines
Volumetric efficiency in an internal combustion engine design refers to the efficiency with which the engine can move fuel and air charges into and out of the cylinders . It also refers to the ratio of the volume of air drawn into the cylinder to the swept volume of the cylinder. [1]More specifically, volumetric efficiency is the ratio (or percentage) of the mass of air and fuel trapped by the cylinder divided by the mass that would occupy the displaced volume if the air density in the cylinder equal to the ambient air density. Flow restriction in the intake system creates a pressure drop in the inlet flow which reduces condensation (unless a turbo or supercharger or cam tuning technology such as Boost is used). Volumetric efficiency can be improved in a number of ways, most effectively by compressing the induction charge ( forced induction ) or by aggressive cam phasing in naturally aspirated engines as seen in racing applications. . Volumetric efficiency can exceed 100% in the case of forced induction.
There are many ways to improve volumetric efficiency, but a system-wide approach is used to realize its full potential.
Many high -performance cars use carefully arranged air intake and tuned exhaust systems that use pressure waves to push air in and out of the cylinders using the system’s resonance . Two-stroke engines are very sensitive to this concept and may use expansion chambers that return the escaping air-fuel mixture back into the cylinders. A more modern technology for four-stroke engines , variable valve timing, attempts to address the change in volumetric efficiency with change in engine speed: at higher speeds the valves are required to be open for a greater percentage of the cycle time to transfer charge to the engine. in and out of the engine.
Volumetric efficiencies above 100% can be reached using forced induction, such as supercharging or turbocharging . With proper tuning, more than 100% volumetric capacity can also be reached by naturally aspirated engines . The naturally aspirated engine has a range of about 130%; [2] These engines are usually of a DOHC layout with four valves per cylinder . This process is called inertial supercharging .It is called and uses the resonance of the intake manifold and the mass of air to achieve a pressure higher than atmospheric at the intake valve. With proper tuning (and dependent on the need for sound level control), VE of up to 130% has been reported in various experimental studies. [3]
More “radical” solutions include the sleeve valve design, in which the valves are replaced outright with a rotating sleeve around the piston, or alternatively a rotating sleeve under the cylinder head. In this system the port can be as large as necessary to the entire cylinder wall. However, due to the strength of the sleeve having a practical upper limit, at large sizes the pressure inside the cylinder can “pop” the sleeve if the port is too large.
Hydraulic pump
Volumetric efficiency in a hydraulic pump refers to the percentage of actual fluid flow from the pump compared to the flow of the pump without leakage. In other words, if the flow from a 100cc pump is 92cc (per revolution), the volumetric efficiency is 92%. Volumetric efficiency will change with the pressure and speed at which the pump operates, so when comparing volumetric capacity, information on pressure and speed should be available. When a number is given for volumetric efficiency, it will typically be at rated pressure and speed.
Electronics
In electronics, volumetric efficiency measures the performance of some electronic function per unit volume, usually in as small a space as possible. This is desirable because advanced designs require increased functionality in smaller packages, for example, maximizing the energy stored in the battery powering cellphones. In addition to storing energy in batteries, the concept of volumetric efficiency appears in the design and application of capacitors , where the “CV product” is a figure of merit calculated by multiplying the capacitance (C) by the maximum voltage rating (V) , known as Quantity is divided. The concept of volumetric efficiency can be applied to any measurable electronic characteristic, including resistance , capacitance ,, inductance , voltage , current , energy storage , etc.
