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EGK Engines > Piston Engine Fuel Systems > Flashcards

Piston Engine Fuel Systems Flashcards

1
Q

Pressure Balance Duct

A

Venturi Effect
Ensure correct mixture ratio at high speed/low speed flights

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2
Q

EGT

A

Exhaust Gases Temp
Used for adjusting mixture ratio

Cooler when excess lean
Cool when excessive mixture due to excess fuel

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3
Q

Grades of AVGAS

A

AVGAS 100ll (Blue) - Low lead

AVGAS 100 (Green) - High Lead

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4
Q

AVGAS density

A

15 degrees about 0.72kg

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5
Q

Vapour Lock

A

Vaporise in fuel lines restricting fuel flow

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6
Q

Detonation definition and symptoms

A

Rapid combustion after burning has begun

  • knocking sound
  • reduce power output
  • CT temp rises
  • Rough running
  • Damage cylinder
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7
Q

Causes of detonation

A

Fuel with poor anti knock qualities
Incorrect mixture ratio
Raising temp or pressure of mixture before burning (low rpm)
High engine temp

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8
Q

Definition of pre-ignition symptoms/causes

A

Ignition of mixture before spark plug has fired

  • tendency for engine to run after shut down
  • worsens with increased rpm
  • weak mixture
  • hot cylinder
  • contaminated with carbon deposits
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9
Q

Octane Rating

A

Resistance to detonation

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10
Q

Power ratio/economic ratio/ideal ratio

A

Ideal - 15:1 (Very high combustion temp so not used)
8:1 (rich) to 20:1 (lean)

Ideal Cruise - 12:1
Economy - 17:1

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11
Q

EGT vs Mixture

A

Combustion cooler at richer mixture due to cooling effect
Cooler when mixture is very lean (Excess air in mixture)

Power Cruise - leaning mixture to achieve peak EGT then enriching more until EGT DROPS

Economy cruise - leaning mixture until peak EGT then leaning again until slight drop

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12
Q

Petrol vs Diesel (Carbon monoxide)

A

Petrol produced more carbon monoxide but less soot than diesel

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13
Q

Engine driven pump role

A

Ensure a positive supply of fuel under pressure to the carb under all engine conditions.

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14
Q

Float valve role

A

Control level of fuel in chamber

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15
Q

Throttle butterfly valve

A

Controls the amount of air passing through the throat

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16
Q

Pressure balance duct

A

Ensure that correct mixture ratio is maintained across a range of airspeeds and flight conditions

Increase in pressure in throat causes drop in fuel flow
Weak mixture

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17
Q

Diffuser

A

Ensure correct mixture ratio across whole speed range of the engine

Large addition of fuel leading excess rich mixture at high airflows

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18
Q

Slow Running Jet

A

Additional jet to cater for low power conditions
- places near butterfly to take advantage of strong pressure drop

Provide rich mixture at idle

19
Q

Power Enrichment

A

Provide rich mixture needed to cool cylinder at high power settings

20
Q

Accelerator Pump

A

Injects fuel directly into Venturi

21
Q

Carb Icing most likely + symptoms

A

Dependent on humidity/ambient temp and throttle position

18/25 degrees + 30% humidity likely icing conditions

Cruise/descent power

Loss of RPM
Reduce Performance
Reduced inlet manifold pressure
Decreased exhaust gas temp
Rough running
Jammed throttle

22
Q

Carb Heat advantages

A

Provides alternative source of air in event primary air intake becomes blocked

Prevents and removes ice in throat of carburettor

23
Q

Carb heat disadvantages

A

Reduces engine power
Further reduce power when breaking down ice
Cause detonation at high power setting
Enrich mixture (hot air less dense)

24
Q

Purpose of induction systems

A

Introduce the mixture into each cylinder

25
Q

Induction Icing

A

Occur in airframe icing conditions

26
Q

Fuel injection systems

A

Provide fuel delivery better icing protection and quicker throttle response than carburettor

27
Q

Engine Driven Pump - Fuel injection

A

Supplies fuel at pressure to injector assembly

28
Q

Manifold valve - injections

A

Distributes fuel from injector to fuel nozzle

29
Q

Injector Assembly - Injection

A

Adjusts fuel flow according to throttle position and mixture setting

30
Q

Specific fuel consumption is…

A

Mass of fuel required to produce unit power for unit time

31
Q

Engine Driven Pump - Carburettor

A

Pumps filtered fuel into carburettor
Ensure positive supply of fuel under pressure in all engine conditions

32
Q

Fuel Injection 5 components

A

Engine drive pump - supplies fuel at pressure to injector assembly
Electrically driven pump - also supplies fuel to injector assembly
Injector assembly - adjust fuel flow according to throttle/mixture
Manifold valve - distributes fuel from injector to fuel nozzle
Fuel nozzle - spray fuel into inlets

33
Q

Mixture control valve

A

Only means of adjusting fuel to air ratio on fuel injector

34
Q

Manifold valve - injection

A

Divides metered fuel between all cylinders
Provide positive means of stopping all fuel flow when mixture control set to idle cut off

35
Q

CHT

A

Cylinder head temperature
Sensors fitted on all or the hottest cylinder
Measured by thermocouple no electrical supply

Affected by:
- power
- speed
- temp of cooling air
- ratio of mixture

36
Q

Weak Mixture leads to

A

Lower RPM/Lower EGT/Higher CHT

37
Q

Rich mixture leads to

A

Higher RPM/Higher EGT/Lower CHT

38
Q

Fuel tanks vent purpose and location large a.c

A

Air intakes on the underside of the wing provide ram air for pressurisation

Tanks are vented at the wing tips

Allow air into the fuel tank to replace volume of fuel consumed by engine - equalisation of pressure
Helps reduce evaporation and fuel transfer

39
Q

Fuel tanks vents purpose and location on light a.c

A

Single pipe on top of fuel tanks

40
Q

Fuel booster pump failure will limit…

A

Max operating altitude

Vapor lock is fuel boiling. Ambient pressure drops at higher alt thus fuel changes to vapour more easily.

41
Q

Spark Park Fouling causes

A

Prolonged idle power
Execessive priming
Use of high octane fuels
Continuous climb with a mixture setting fully rich

42
Q

Safest method of priming a piston engine for start is

A

Injection of fuel in the cylinder intake port

43
Q

Mixture Ratio

A

The ratio between the mass of fuel and mass of air

EGK Engines (22 decks)

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