Fichas
General Aviation, Week 2: Engines
Fichas del conjunto (62)
- 1what are some characteristics of a horizontally opposed engine?- 2 banks of cylinders opposite each other with the crank shaft in the center
-Most popular type used on smaller aircraft
- high power-to-wight ratio
- has low vibration
-reduction in drag - 2what are some characteristics of a v-type engine?- 2 in-line banks set 60degrees
- most engines have 12 cylinders
- were used a lot in WWII and are limited to older aircraft - 3what are some characteristics of an inline engine?- even number of cylinders
- Can be liquid or air cooled
- 1 crankshaft either above or below the cylinders
- confined to low- and medium-horsepower engines used in very old light aircraft. - 4what are some characteristics of a radial engine?- a row, or rows of cylinders arranged radially about a central crankcase
- has a favourable power-to-weight ratio - 5what are the major components of a reciprocating engine?crankcase, cylinders, pistons, connecting rods, valves, valve-operating mechanism, and crankshaft
- 6what's a crankcase and what does it provide?- the foundation of the engine/ supports external and internal mechanisms of the engine
- contains bearing support in which the crankshaft revolves
- provides tight enclosure for lubricating oils - 7what is the purpose of the crankshaft?main purpose is to transform the reciprocating motion of the piston and connecting rod into rotary motion for rotation of the propeller.
- 8what does the connecting rod do?- its the link that transmits forces between the piston and the crankshaft.
- 9what are the 4 types of connecting rods?1. Plain
2. Fork and blade
3. Master and articulated
4. Split-type - 10what are the 4 movements of a piston in a 4 stroke engine (AKA otto cycle)?1. piston move down, drawing in the fuel/air mixture
2. moves up, compressing the charge and ignition/combustion occurs
3. expanding gases, force the piston down
4. piston moves up and forces the exhaust out - 11what are the two types of pistons?1. slipper type (not used in modern high powered engines)
2. trunk type - 12why do some styles of pistons have recessed heads?to prevent interference with the valves
- 13what are the two types of rings on a piston?- compression rings
- oil rings - 14what is the purpose of the piston pin?The piston pin joins the piston to the connecting rod.
- 15what is the purpose of the piston ring?The piston rings prevent leakage of gas pressure from the combustion chamber and reduce to a minimum the seepage of oil into the combustion chamber
- 16whats the purpose of the compression ring?The purpose of the compression rings is to prevent the escape of combustion gases past the piston during engine operation.
- 17whats the purpose of the oil control ring in a piston?Oil control rings regulate the thickness of the oil lm on the cylinder wall.
- 18what' the purpose of the oil scrapper ring?In the reverse position, the scraper ring retains the surplus oil above the ring on the upward piston stroke, and this oil is returned to the crankcase by the oil control rings on the downward stroke.
- 19what are the 4 major factors that need to be considered in the design of cylinders?1. Be strong enough to withstand the internal pressures developed during engine operation.
2. Be constructed of a lightweight metal
3. Have good heat-conducting properties for efficient cooling.
4. Be comparatively easy and inexpensive to manufacture, inspect, and maintain. - 20what does the cylinder provide?- provides a combustion chamber where the burning and expansion of gases take place, - houses the piston and the connecting rod.
- 21what are the 4 possible engine types?- reciprocating engine
- turboprop
- turbojet
- turbofan - 22what are the 4 types of piston engines?1. inline
2. opposed
3. v-type
4. radial - 23what are the two major parts of a cylinder?- cylinder head (provides a place for the combustion of fuel/air mixture)
- cylinder barrel (where the piston operates) - 24what is the purpose of the piston?- A cylindrical member that moves linearly
- Acts as a moving wall within the combustion chamber - 25what is the purpose of a camshaft?- The camshaft is connected to the crankshaft and it operates the opening and closing of the inlet and exhaust valves via the pushrod and the rocker arms
- It rotates at 1⁄2 the crankshaft speed - 26whats the purpose of the push rod?• Transmits the lifting force to the rocker arm
- 27what does the inlet valve do?The inlet/intake valve lets the fuel-air mixture into the cylinder
- 28what does the exhaust valve do?The exhaust valve lets exhaust gases out of the cylinder after the combustion process
- 29in detail, what does the intake step in the four stroke cycle involve?- The piston travels downward, causing a drop in pressure within the cylinder
- This allows a fuel/air mixture to pass through the intake pipes and intake valves into the cylinder
- The throttle setting determines the quantity or weight of the fuel/air mixture - 30in detail, what does the compression step in the four stroke cycle involve?The piston moves upward, compressing the fuel/air mixture to obtain the desired burning and expansion characteristics
- 31in detail, what does the combustion/power stroke step in the four stroke cycle involve?The piston is forced to travel downward due to the combustion and the rapid expansion of the burning gases
- 32in detail, what does the exhaust step in the four stroke cycle involve?- The piston travels upward, pushing the burnt exhaust gases out through the exhaust valve
- The speed of the exhaust gases leaving the cylinder creates a low pressure within the cylinder - 33what is the modified otto cycle about and what are the four steps of the modification?Adjustments on the ignition timing and the valve timing were needed to achieve a higher and more reliable power output
• Spark advance
• Valve lead
• Valve lag
• Valve overlap - 34what is involved in the spark advance of the modified otto cycle?- The fuel/air mixture to be fired by means of an electric spark as the piston approaches TDC
- Typically 20°~35° before TDC - 35what is involved in the valve lead of the modified otto cycle?The intake valve opens before the piston reaches TDC on the exhaust stroke.
- 36what is involved in the valve lag of the modified otto cycle?The closing of the exhaust valve is delayed after the piston passes TDC during the intake stroke.
- 37what is involved in the valve overlap of the modified otto cycle?- Valve lead + valve lag
- Increased amount of fuel/air mixture into the cylinder
- Better cooling
- Better scavenging - 38what are the two type of abnormal combustion?1. detonation
2. pre-ignition - 39what is carburation?The process of vapourising liquid fuel and mixing with air in
specific proportions - 40what is the purpose of carburation?- To control the amount of air being drawn into the engine
- To dispense the correct quantity of fuel required
- To mix this fuel with the incoming air to ensure complete vaporisation - 41what are the two systems in carburation?1. carburettor system
2. fuel injection system - 42what is the chemically correct mixture (CCM) ratio?1:15
- 43what is the mixture ratio for best economy?1:16
- 44what is the mixture ratio for best power?1:12
- 45when should the mixture be set for FULL RICH?take-off, climb and landing
- 46what is something important to remember with mixture control?As altitude increases, the air becomes less dense and thus the amount of fuel needs to be reduced to maintain optimum fuel/air mixture ratio
- 47whats a common mistake made during descent involving mixture settings?The fuel/air mixture becomes lean if a mixture control is not changed during a descent
- 48explain the carburettor systemThe filtered air flows into the carburettor and through a venturi that creates a low pressure area, causing the fuel to flow through a main fuel jet
- 49what are 3 disadvantages of the float type carburettor system?- Adversely affected by abrupt manoeuvres
- Not suited to certain types of supercharged system
- Susceptibility to carburettor icing - 50what are the 3 types of carburettor icing?1. impact ice
2. fuel evaporation ice
3. throttle ice - 51what is impact icing?-Occurs when supercooled water droplets are in contact with the intake filter and/or the metal surfaces of the inlet air scoop and ducting
- Occurs when the outside air temperature is near or below 0°C and visible moisture (e.g., cloud, rain etc) is present - 52what is fuel evaporation icing?- Occurs when the temperature of the fuel/air mixture is lowered substantially during fuel vaporisation
- Fuel ice forms when the temperature of the fuel/air mixture drops to between 0°C and -8°C
- Fuel ice can occur in ambient air temperatures well above freezing - 53what throttle ice?- Ice forming on the throttle valve
- Greater chance at low throttle settings due to the smaller opening
- Can occur at any time when the outside air temperature is within the approx. range of -10°C ~ +20°C with high relative humidity - 54explain the fuel injection system- A venturi system coupled to a Fuel Control Unit (FCU), from which metered fuel is piped to the fuel distributor
- Then, a separate fuel line to the discharge nozzle in each cylinder head (Direct system) or into the inlet port near the inlet valve (Indirect / Continuous flow system) - 55what are the advantages of the fuel injection system??- Significant reduction in fuel icing
- More uniform delivery of the fuel/air mixture
- Improved control of fuel/air ratio
- Better response
- Increased engine efficiency - 56what are the disadvantages of the fuel injection system?- Difficulty in starting a hot engine
- Greater susceptibility to any fuel contamination
- Fuel imbalance - 57whats a hot tip for refuelling?never use a fuel grade lower than recommended
- 58what is the function of the fuel system?to store fuel and continuously deliver it to the carburettor (or fuel-injection system) in adequate quantities at the proper pressure
- 59what are the two types of fuel systems?1. gravity fed fuel system
2. pump/pressure-fed fuel system - 60what does the pressure fed fuel system have that the gravity fed system doesn't?- auxiliary fuel pump (electric boost pump)
- mechanical fuel pump (with by-pass) - 61what are some of the main components in the fuel system?- Fuel tank
- Fuel filler cap
- Fuel expansion space
- Fuel vent
- Sump and drain
- Fuel strainers and filters
- Fuel selector valves
- Fuel quantity detectors/indicators
- Fuel pumps - 62what are the ways you can manage fuel?- always know current fuel quantity & endurance
- fuel starvation
- fuel exhaustion
Información
- Descripción
- Engine types, their characteristics and how they operate
- Creado por
- Amelia Murphy
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