PPT13: Turbocharger and Supercharger

Supercharged Induction Systems

A system that compresses the fuel/air mixture, restoring or boosting air pressure at higher altitudes.

Non-supercharged

No compressor used.

Supercharged

- Internally Driven
- Externally Driven (Turbocharged)

Ground-boosted Engines (true supercharged engine)

Boosts manifold pressure above ambient, e.g., 30+ inches Hg.

Internally Driven Superchargers

- Compress the fuel/air mixture after it leaves the carburetor.
- Driven through a mechanical connection e.g. by means of a belt, gear, shaft, or chain etc.
- Used in high horsepower radial engines.

Externally Driven Superchargers (Turbosuperchargers)

- Compress the air before it is mixed with the metered fuel from the carburetor.
- Deliver compressed air to the inlet of the carburetor or fuel/air control unit of an engine.
- Derive their power from engine exhaust gases directed against a turbine that drives an impeller that compresses the incoming air.

Turbocharger

- Exhaust-driven air compressor used to increase the power of a reciprocating engine.
- Uses a small radial inflow turbine in the exhaust system to drive a centrifugal-type air compressor on the turbine shaft.
- Compressed air is directed into the engine cylinders to increase power.
- Turbochargers were originally known as turbosuperchargers when all forced induction devices were classified as superchargers.

Impeller

Picks up the air entering through the compressor casing using blades to accelerate the air, giving it high velocity.

Diffuser

- Positioned after the impeller, it has vanes that direct the high-velocity air.
- It also converts the air's velocity into pressure, increasing the air pressure before it enters the engine.

Casing

Encloses the impeller and diffuser, directing the air through the system.

3 Main Parts of Turbosuperchargers

1. Compressor Assembly:
2. Turbine Wheel Assembly: Driven by exhaust gases.
3. Floating Shaft Bearing Assembly.

Normalizer Turbocharger Systems

- Compensates for power lost due to the pressure drop resulting from increased altitude.
- On many small aircraft engines, the turbocharger (normalizing) system is designed to be operated only above a certain altitude, 5,000 feet for example, since maximum power without normalizing is available below that altitude.

Ground-Boosted Turbosupercharger Systems (sea level-boosted engines)

- By controlling how much exhaust passes through the turbine, the system manages the compressor speed and intake boost.
- Increases power from sea level to the critical altitude.
- Can develop more power at sea level than an engine without turbosupercharging.
- An engine must be boosted above 30 "Hg to truly be supercharged.
- This type of turbocharger accomplishes this by increasing the manifold pressure above 30 "Hg to around 40 "Hg.
- Uses a filtered ram-air intake located on the nacelle side.
- Has an alternate air door that permits compressor suction automatically to admit alternate air (heated engine compartment air) if the induction air filter becomes clogged.

Pressurized engine oil

is used to control the boost level (extra manifold pressure).

waste-gate actuator and controllers

are powered by engine oil for their power supply. They control the turbocharger.

Waste gate actuator

Connected to the waste gate via a mechanical linkage. Controls the position of the waste gate butterfly valve.

Waste gate

Bypasses the engine exhaust gases around the turbocharger turbine inlet.

True

To be a true supercharger, it must boost the manifold pressure above 30 "Hg.