Carburetion 2

Question 1

Mixture limits, CCM, max power, best economy

Answer 1

1:9-1:18
1:15
1:12
1:16

Question 2

Fuel air emulsion

Answer 2

Fuel metered by weight
Air bleed emulsifies fuel into a lighter more frothy mixture
Less viscous
Less inertia
Fuel responds faster

Question 3

Diffusion

Answer 3

Mixing air with liquid

Question 4

Atomisation

Answer 4

Breaking down liquid into gaseous molecules

Question 5

Accelerating system

Answer 5

A pump and check valve that provide fuel straight to the Venturi when necessary due to inertia of other fuel and lack of fast response ie rapid throttle increases

Question 6

Idling system

Answer 6

Seperate pathway with idle air bleed provides fuel past the butterfly when pressure differential is insufficient

Kicks in at approx 1000 rpm

Question 7

Power enrichment system

Answer 7

Second metering jet to supply more fuel to Venturi and prevent detonation and overheating
Operates when throttle is near fully open
Can be mechanically operated or by high manifold pressure

Question 8

Back suction

Answer 8

Varies air pressure in float chamber through line to Venturi changing amount of fuel delivered at given throttle setting
Mixture valve vents float chamber to atmosphere
Pilot controls mixture using mixture control lever

Question 9

Incorrect mixture

Answer 9

Over rich
Loss of power
Rough running
Plug fowling
Lead deposits

Over lean
High temperatures and detonation

Question 10

Carb ice

Answer 10

Impact ice
Throttle ice
Refrigeration ice
Fuel evaporation ice

Question 11

Disadvantages carb

Answer 11

Negative g and other manoeuvres disturb fuel flow
Susceptibility to ice
Float can become waterlogged leading to over rich
Fuel contamination can block jets leading to starvation
Nozzle breaks off and Jams butterfly valve

Question 12

Pressure injection

Answer 12

Float chamber replaced with pressure regulator unit
Still uses Venturi and throttle valve

Question 13

Basic fuel injection

Answer 13

Fuel delivery pump
Fuel distribution
Fuel injectors

Question 14

Pressure injection advantages

Answer 14

Less ice
Gravity and inertia have little effect
More accurate fuel metering
Better atomisation/mixing
Protection against vapour lock in fuel lines

Question 15

Requirements for pressure injection

Answer 15

Fuel pump and fuel distribution system
Mixture control/idle cut off
Accelerator pump
Power enrichment system
Idling system

Question 16

Pressure injection parts

Answer 16

Poppet valve opens based on pressure differences open s due to a and b closes due to c and d
Intake chamber a : high pressure (dynamic from impact tube)
Outtake chamber b: low pressure (connected to Venturi)
C: metered fuel after metering jet (lower pressure than d)
D: unmetered fuel high pressure (filled due to pressure difference betweeen a and b )
Nozzle diaphragm gathers sufficient pressure and fuel before releasing it towards discharge nozzle(after throttle butterfly)