What Are the Components of an Aircraft Turbocharger System?
A turbocharger system consists of a turbine and a compressor connected by a shared axis. The turbine inlet receives exhaust gasses from the engine exhaust manifold, causing the turbine wheel to rotate. This rotation drives the compressor, allowing it to compress ambient air and deliver it to the air intake of the engine. To better understand turbocharger systems, this blog will provide a brief overview of their function and importance.
The main purpose of a turbocharger is to improve the size-to-output efficiency of an engine by making up for one of its principle limitations. An engine supplied with air exclusively uses the downward stroke of a piston to produce an area of low pressure in order to draw air into the cylinder. The number of air and fuel molecules determines the potential energy available to force the piston down on the combustion stroke.
Due to the relatively constant pressure of the atmosphere, there is a limit to the amount of air and fuel filling the combustion chamber. The ability of the turbocharger to fill the cylinder with air is defined as its volumetric efficiency. It is important to note that the turbocharger increases pressure until air enters the cylinder, and the quantity of air drawn into the cylinder is highly dependent on time and pressure. As such, more air is drawn in as the pressure increases.
Turbochargers have four main components, those of which include the turbine, impeller wheels, center hub rotating assembly (CHRA), and bearing system. The turbine and impeller wheels are positioned within their own cone-shaped housing on opposite sides of the CHRA. Meanwhile, the housing collects and directs gas flow through the wheels as they rotate. The CHRA houses the shaft that links the impeller and turbine, and it contains a bearing system to suspend the shaft, enabling it to spin at a very high speed with minimal friction.
There are other important terms to become familiar with when talking about a turbocharger system. To begin, turbo boost refers to the increase in the manifold pressure produced by the turbocharger in the intake path. Boost pressure is limited by the operating range controlling the waste gate, which shunts the exhaust gasses away from the exhaust side of the turbine.
Next, the waste gate assembly is the next element to familiarize yourself with. By spinning at a high speed, the compressor draws in a large volume of air and forces it into the engine. As the turbocharger’s output flow volume surpasses the engine’s volumetric flow, air pressure builds up in the intake system which is often referred to as a turbo boost. Since a turbo can spin at RPMs beyond what is required, the speed must be controlled.
The waste gate itself is controlled by a pneumatic or hydraulic control system. At take-off, the waste gate is kept open while at sea level it is only kept partially open. As the aircraft ascends, the waste gate is gradually closed, keeping the manifold pressure at or above sea level. Keep in mind that the main function of the waste gate is to permit a portion of the exhaust to bypass the turbine when the set intake pressure is obtained.
Lastly, a pressure relief valve prevents the engine manifold pressure from exceeding the engine’s design limitations. Installed in the intake system downstream of the turbocharger compressor, the valves open to stop the engine from over boosting. If you are repairing a turbocharger system or its related components and require parts fast, rely on Hardware Orbit.
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