ASA CODES PowerPlant Flashcards
What factors establish the maximum compression ratio limit in engines?
- Design limitations of the engine, the degree of supercharging, and spark plug rating.
- Detonation characteristics of the fuel and installation of the engine.
- Detonation characteristics of the fuel and specifications of the engine, and the degree of supercharging.
What is the importance of design limitations in engines?
Engines not designed strong enough to withstand high cylinder pressures cannot have a high compression ratio.
What is the effect of supercharging on compression ratios?
The greater pressures are a function of both the initial pressure in the cylinder and the pressure caused by the supercharger.
What is the principal advantage of using reduction gears in propellers?
- To enable the propeller RPM to be increased without an accompanying increase in engine RPM.
- To enable the engine RPM to be increased without an accompanying increase in power, allowing the propeller to remain at a lower, more efficient RPM.
- To enable the engine RPM to be increased with an accompanying increase in propeller pitch.
What determines the horsepower produced by a reciprocating engine?
The horsepower produced by a reciprocating engine is determined by its RPM. The higher the RPM, the greater the horsepower.
What will decrease volumetric efficiency in a reciprocating engine?
- Fuel that operates poorly.
- High carburetor air temperatures.
- Cylinder head temperatures, improper valve timing, and sharp bends in the induction system.
How is piston displacement calculated in a reciprocating engine?
The piston displacement of a reciprocating engine is the total volume swept by the piston in one revolution of the crankshaft, calculated by multiplying the area of the piston in square inches by the stroke in inches.
What is the formula for total piston displacement?
Total piston displacement = volume of one cylinder (in cubic inches) multiplied by the number of cylinders.
What is the total piston displacement of a one-cylinder engine with a bore of 3.5 inches and a stroke of 5 inches?
740 cubic inches.
What are the four strokes in a four-stroke engine?
Intake, compression, power, and exhaust.
What occurs during the compression stroke?
The piston moves upward, compressing the air-fuel mixture.
What happens during the power stroke?
The air-fuel mixture burns, forcing the piston downward.
What is the role of the exhaust stroke?
The piston pushes upward, forcing exhaust gases out of the cylinder.
What is valve overlap?
Valve overlap occurs at the end of the exhaust stroke and the beginning of the intake stroke.
What can cause no clearance in a valve operating mechanism?
Carbon and sludge becoming trapped in the system.
When does the intake valve open in a four-stroke cycle?
The intake valve opens when the piston is moving upward at the end of the exhaust stroke.
When is the actual ignition in a conventional reciprocating engine?
Shortly before the piston reaches the top of the compression stroke.
What happens if the intake valve opens too early?
Exhaust gases could flow into the intake manifold, causing a backfire.
When does the exhaust valve open during the exhaust stroke?
The exhaust valve opens shortly after the piston reaches the bottom of the stroke.
What is the typical timing for the intake valve in a four-stroke aircraft engine?
The intake valve closes on the compression stroke.
What is the typical timing for the exhaust valve in a four-stroke aircraft engine?
The exhaust valve opens on the exhaust stroke.
