Recip Thrust Test 12/1

What is the basic formula for thrust?

Force = Mass x Acceleration (F = mA)

What happens to thrust when mass increases?

Thrust increases.

What happens to thrust when acceleration increases?

Thrust increases.

What is Static Thrust?

The amount of thrust developed by an engine when the aircraft is standing still on the ground, Gross thrust

What does Ve stand for?

Exhaust velocity or final velocity.

What is the formula for Net Thrust?

Fn = weight / 32.2 (Ve - Vi)

What is TSFC?

Thrust Specific Fuel Consumption; pounds of flow consumed to produce one lb of thrust for one hour of operation.

What is the impact of Ram Air Force on turbine engines?

Turbine engines are more effective when the aircraft flies fast due to ram air force.

What is a choked nozzle?

A nozzle that has reached the speed of sound, limiting the amount of air that can exit the engine.

What is Thrust Horsepower (THP)?

THP = Fn x MPH / 375; it relates net thrust to horsepower.

What is Equivalent Shaft Horsepower (ESHP)?

ESHP = SHP + thrust; it includes horsepower delivered to the shaft and thrust.

What is Propulsive Efficiency?

The efficiency of how fast the exhaust is leaving relative to the inlet velocity.

What are the ranges of thermal efficiency for recips and turbines?

Recip = 20-30%, Turbine = 30-45%.

What is thermal efficiency?

Hp output of the engine, how much provides forward thrust (output of engine over the hp in fuel)

What is the formula for Overall Efficiency?

Overall Efficiency = Propulsive Efficiency x Thermal Efficiency.

How does altitude affect thrust?

Less air pressure and cooling can lead to over-temperature of the engine.

What happens to pressure and velocity in the combustor?

Pressure slightly decreases while velocity stays steady.

What is the purpose of water injection in aviation engines?

To increase mass and enhance thrust.

Fg= w/ 32.2 (Ve)

Gross thrust formula

Fn= w/ 32.2 (Ve- Vi)

Net Thrust

Fn x mph/ 375

Thrust Horsepower (THP) formula

Fp= HP x 375/ mph

Turboprop (Propeller Thrust)

Peff= 2/ (1+ Ve/ Vi)

Propulsive Efficiency formula

TE= HP/ HP fuel

Thermal Efficiency formula

Pressure: gradually goes up

Velocity: vibrating up and down bc it’s slowing down the inlet velocity

Temperature: goes up slightly

Intake area

Pressure: peaks in pressure

Velocity: slows down

Temperature: steady

Diffuser area

Pressure: slight decrease so flame goes out the back, pressure turns into velocity

Velocity: steady, so it stays at 80 ft/sec

Temperature: steep rise

Combustor area

Pressure: goes down, zig zag down

Velocity: goes up

Temperature: starting to go down bc extracting energy

Turbine Area

# divide by 360 then times 5280

Change mph to ft/sec

What is ram Air Force?

Inlet divergent on subsonic increases pressure at inlet compressor,