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Powerplants > Test 1 > Flashcards

Test 1 Flashcards

1
Q

When/who was the first practical gas engine made?

A

Made in 1860 by Jean Joseph Etienne Lenoir. It used coal not gas.

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2
Q

Engines need to be:

A

High power-to-weight ratio, efficiency, lower cost, environmentally friendly, reliable, fuel-efficient, ease of maintenance, and low sound levels

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3
Q

When was the first four-stroke engine made?

A

It was made by August Otto and Eugen Langen in 1876

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4
Q

Who made the first truly successful gasoline engine?

A

Gottlieb Daimler in 1885.

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5
Q

First aircraft engine

A

The wright brothers om 1903.

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6
Q

Gas turbine engines

A

Turbo jet
Turbo fan
Turbo prop
Turbo shaft

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7
Q

Types of reciprocating engines

A

Rotary type Radial
In-line
V-type
Radial
Multi-row radial
Oppose

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8
Q

Rotary Type Radial

A
  • Crankshaft is held stationary to the engine mount.
  • Cylinders rotate around the crankshaft
  • Propeller is attached to the engine case

Disadvantages
- Torque and gyro effect of the engine’s large rotating mass made the aircraft difficult to control
- Castor oil was used as engine lube. The oil fumes were often nauseating and could act as a laxative

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9
Q

In-line engines

A
  • Cylinders are arranged in a parallel row to the crankshaft
  • Cylinders can be above or below (inverted) the crankshaft
  • Cylinders were often limited to 6 to aid in cooling and weight
    (Was air cooled and so the back cylinders wouldn’t cool all the way cause the air would get hot by the time it got to the back)
  • Even number of cylinders for balance
  • Used for low/medium power
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10
Q

V-Type engines

A
  • Cylinders are arranged into two rows which are put into a “v” shape
  • Even # of cylinders
  • Liquid-cooled
  • Frontal area is only slightly larger than in-line
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11
Q

Single Row Radial

A
  • Odd # of cylinders (5-9)
  • All pistons are connected to a single throw 360 crankshaft
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12
Q

Double Row Radial

A
  • Looks like a single row on one crankshaft
  • Cylinders range from 14-18
  • Cylinders are staggered for cooling purposes
  • Lowest weight-to-horsepower ratio of all reciprocating engines

Disadvantages
- Large frontal area creates drag
- Cooling problems

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13
Q

Multi-Row Radial

A
  • Largest and most powerful radial engine
  • Was replaced by gas-turbine engines because the gas turbine engines were more powerful and lightweight, they had less moving parts, and the time between overhaul (TBO) greatly increased
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14
Q

Opposed and Flat (Boxer engine)

A
  • Most popular for light conventional aircraft/heli
  • Most efficient and economical for light aircraft
  • Mounted with the cylinders and crankshaft horizontal
  • Flat shape is easy to streamline
  • Reasonably free from vibration
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15
Q

Different Cylinder Arrangements

A

In-line upright/inverted
V-Type upright/inverted
Double V/Fan
X type
Opposed or flat
Radial Single/Double/Multi row

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16
Q

Engine Designations

A

Letters indicate characteristics
Numbers indicate displacement (to the nearest 5 in^3)

L = Left-hand rotation
T = Turbocharged
I = Fuel Injected
G = Geared
S = Supercharged
O = Opposed
R = Radial

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17
Q

Air Cooled

A
  • Heat generated by engines is removed using convection (movement of air)
  • Thin metal fins (cooling fins) project from the cylinder

Advantages of Air Cooling
- Less weight cause there is no liquid
- Less vulnerable to cold weather or gunfire

Disadvantages
- Requires forward movement for ram air to sufficiently cool the engine
(Engine can overheat if it is just sitting on the runway waiting to take off)

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18
Q

Baffles

A

Are used to direct airflow around the engine and maximize cooling

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19
Q

Liquid Cooling

A
  • Slowly moving into aviation
  • Liquid passes around certain spots on the engine
  • Radiator cools the liquid as it passes back through it
  • Has connecting pipes/hoses and relief valve to relieve pressure
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20
Q

Crankcase

A
  • Foundation of the engine (must support itself)
  • Uses bearing to turn the crankshaft
  • Provides mounting for cylinders and mounting to the aircraft
  • Mostly made of aluminum alloys

Three broad types
- Opposed engine crankcase
- Radial engine crankcase
- In-line and V-type crankcase

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21
Q

Opposed Engine Crankcase

A
  • Consists of two matching, reinforced aluminum alloy castings
  • Castings are divided vertically at the centerline
  • Fastened together w/ studs and nuts
    -Oil passages are drilled to supply lube to
    -Crankshaft Bearings
    -Camshaft bearings
    -Other parts that need lube
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22
Q

Radial Engine Crankcase

A

Has multiple sections (3-7)
~Front Section (Nose)
-Bell-shaped aluminum alloy housing
-Supports prop thrust bearing and other prop components
-High-power engines will have magnetos on the nose for better
cooling
~Main power section
-Has 1-3 pieces of high-strength alloy/steel
-Oil seals are located between the front section and the main
power section
~Fuel induction and distribution
-Blower (when air and oil mix)/supercharger impeller and
diffuser vanes are in this section
~Accessory section
-Provides mounting pads for the fuel pump, vacuum pump,
lubrication oil pump, starters, magnetos

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23
Q

In-Line and V-Type Crankcase

A

~Front Section
-May be part of the power section or may be a separate part
-Houses the prop shaft, prop thrust bearing, etc.
~Power Section
-May be 1 or 2 parts and supports crankshaft bearings
-Cylinders are mounted here
-Provides attachment points to the engine mount
~Fuel Induction/Distribution System
-Houses different diffuser vanes
Supports internal blower impeller
~Accessory
-Can be a separate unit onto the Fuel Induction/Distribution
system or form a part of the section
-Has mounting pads for the fuel pump, coolant pump, vacuum
pump, magnetos, and any other devices

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24
Q

Aircraft Bearings

A
  • Produces minimum friction
  • Maximum wear resistance
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25
Q

Characteristics of a good bearing

A
  • Made strong enough to withstand the pressure on it
  • Permit the other surface to move w/ minimum friction or wear
  • Provide quiet and efficient operation w/o loss of movement
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26
Q

Thrust Bearings

A

When they take thrust loads, radial loads, and a combo of both

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27
Q

Plain Bearings

A
  • Low-power engines
  • Designed to take radial loads
  • Can be used as a thrust bearing when flanges are added
  • Used for connecting rods, crankshaft, and camshaft

Common materials
- Silver
- Bronze
- Lead
- Combo of the others

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28
Q

Roller Bearings

A
  • High-power applications, made in a variety of shapes and sizes
  • Tapered rollers can withstand both radial and thrust loads
  • Straight rollers are used for radial loads
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29
Q

Bearing Race

A
  • Channel where rollers travel
  • Hardened Steel
  • Rollers are situated between inner/outer race
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30
Q

Ball Bearings

A

~Provides less friction than others
~Components of ball bearings
-Inner/Outer race
-Polished steel balls
-Ball retainer
~Some ball bearings have two rows of balls and two sets of races
~Very good with radial loads

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31
Q

Crankshaft

A
  • Transforms the reciprocating motion of the piston to rotary motion of the propeller
  • Throws are located at definite positions
    -Throws are offsets formed into the shaft before its machined
  • Backbone of the engine
  • Usually forged from steel alloy
  • May be constructed from one or more pieces
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32
Q

Main Journal

A
  • Absolute center/centerline of the crankshaft
  • Where the crankcase supports the crankshaft
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33
Q

Crankpin

A
  • One crankpin per cylinder on an engine
    -It is the offset part of the crankshaft
  • Are hollow to allow oil to lubricate the bearings, but also to collect any sludge or unwanted substances
    -Are hollow to save weight
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34
Q

Crank cheek

A

Connects the crankpins to the crankshaft

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35
Q

Counterweights or Dampeners

A
  • Extension of the crank cheek
  • Helps dampen vibrations
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36
Q

OEM

A

Original Equipment Manufacturer

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37
Q

Single Throw Crankshafts

A

counterweight must balance

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38
Q

Dynamic Dampeners

A

Relieves the whip and vibration from rotation

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39
Q

Throw

A

Also known as crankpins

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40
Q

Tapered Propeller shaft

A
  • Tapered end has a milled slot for a key
  • Prop is positioned in the correct orientation and location by key
  • The threaded forward end of the shaft receives the prop retaining nut
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41
Q

Spline Propeller Shaft

A
  • Rectangular grooves are machined in the shaft
  • Grooves mate w/ grooves inside the prop hub
  • One groove is blocked by a screw to ensure prop position
    -Blocked groove is called a “blind” groove
42
Q

Flange Shaft

A
  • A short stub forward of the flange supports and centers the prob hub
  • Six high-strength bolts or studs secure the prop to the flange
    -Bolts/studs need to be tightened in sequence (star pattern)
43
Q

Connecting Rod

A
  • Attaches the crankshaft to the piston
    -Large end that connects to the crankshaft is called the crankpin end
    -Short end that connects to the piston is known as the piston end
  • Transfers motion from the piston to the crankshaft
44
Q

3 Types of Connecting Rods

A

1) Plain Connecting Rod
-Commonly used for in-line and opposed engines
- Small end has a bearing

2) Fork and Blade Connecting Rod
- Used for V-Type engines

3) Master and Articulated Rod
- Used for radial engines
- Master rod provides attachment points from articulated rods
- Articulated rods are attached using a steel knuckle pins
- Master rods aren’t made anymore and are very expensive

45
Q

Piston Head Types

A

Flat
Recessed (Has two inverted triangles on the surface)
Concave (Cup)
Convex (Dome)
Truncated Cone (Ends are cut at an angle)

46
Q

Piston Ring

A
  • Rings are split so they can be slipped into ring grooves
  • The “split” can have 3 different types of joints
    -Butt
    -Step
    -Angle
  • They are used to keep the combustion in the piston
    _ The rings should be staggered or else the fuel-air mixture will get out
47
Q

Blowby

A

The flow of gases from the combustion chamber into the crankcase

48
Q

Compression Rings

A

Can find rectangular, tapered, or wedge piston rings

49
Q

Oil Rings

A
  • Controls thickness of oil film on the cylinder walls
  • Prevents oil from passing into the combustion chamber
  • Two Types
    -Oil Control Rings
    -Oil Wiper Rings (Scrapper Rings)
  • Placed below compressions rings
    -Usually the third ring
  • Lets new oil get to piston while scraping old oil away
50
Q

Piston Pins (Wrist Pins)

A
  • Used to attach piston to the connecting rod
  • Stationary Piston Pin
    -Not free to move in any direction
    • Set in place by a screw
      -Semi-Floating
    • Held by a clamp screw
  • Full Floating
    • Free to run/slide in the connecting rod and the piston
51
Q

Piston Pin Retainers

A
  • AKA piston pin plugs
  • Non ferrous metal plugs
  • Inserted in the open ends of the piston pin
  • Soft material allows for contact w/ cylinder wall w/o damage
    Aluminum alloy w/ copper, brass, or bronze
52
Q

Cylinder Assembly requirements

A
  • Need to be strong to withstand internal pressure
  • Light weight
  • Needs to be able to cool efficiently
  • Cheap manufacturing, inspection, and maintenance
53
Q

Cylinder Barrel

A
  • High strength steel alloy
  • Surface roughness is carefully controlled
    • Too smooth, it won’t hold oil sufficiently
    • Too rough, causes excessive wear to piston rings and cylinder walls
    • They intentionally scratch the inside of the surface (honing) so the oil can stick
  • Cooling fins are put on the outside
54
Q

Cylinder Head

A
  • Encloses the combustion chamber
  • Contains intake and exhaust values and valve guides/seats
  • Supports the rocker shafts
  • Combined to cylinder barrel using heating/cooling
    - Barrel = liquid nitrogen cooled so it shrinks
    - Head = heated so it expands
55
Q

** Exhaust vs Intake **

A

Intake does not have cooling fins. EXHAUST HAS COOLING FINS

56
Q

Valves

A
  • Regulates amount of direction of flow
  • Main purpose is to open/close two parts
    • Intake Port = allow fuel-air charge to enter cylinder
    • Exhaust Port = allow burned gases to expel from cylinder
  • Each cylinder has at least one intake and one exhaust
57
Q

Exhaust Valve

A
  • Exhaust valve is filled w/ sodium metal because sodium is a good heat conductor
58
Q

Valve Stem

A

Hardened to reduce wear

59
Q

Valve Tip

A
  • Hardened to reduce wear
  • Has a groove for split-ring stem keys
60
Q

Intake Valves

A
  • Are not hollow
  • Low-power engines = flat head
  • High-power engines = tulip head
61
Q

Valve Guides

A
  • Supports and guides the stems of the head and it goes on the valve head
62
Q

Valve Seats

A

Used to close the cylinder

63
Q

Valve Springs

A
  • Closes the valves
  • Installed over the stem of the valve
  • Held in place by valve spring retainers
64
Q

Valve Operating Mechanism Components

A
  • Cam
    • Actuates the valve lifting mechanism
      Valve lifter or Tappet
    • Transmits the force of the cam to the valve pushrod
      Pushrod
    • Rod/tube between the valve lifter and the rocker arm.
    • Transmits the motion of the valve lifter
      Rocker Arm
    • For opening and closing the valves
    • One end of the arm presses on the stem of the valve while the other
      end receives the motion from the pushrod
65
Q

Heat Engines

A
  • Utilizes heat energy to produce power for propulsion
  • Source of Energy = Fuel
  • Work = heat expands gases creating pressure against a piston in a cylinder
66
Q

Boyle’s Law

A

Volume of any dry gas varies inversely w/ the absolute pressure sustained by it, the temp remains constant

V1/V2 = P2/P1

67
Q

Charles’ Law

A

The pressure of a confined gas is directly proportional to its absolute temp

V1/V2 = T1/T2

68
Q

Stroke

A
  • Distance the piston travels
    • Top of stroke is called Top Dead Center (TDC)
    • Bottom of stroke is called Bottom Dead Center (BDC)
  • A stroke is the distance between TDC and BDC
69
Q

Bore

A

Width of the cylinder

70
Q

Compression Ratio

A

Ratio of the volume of space in the cylinder when the piston is at BDC to the volume when the piston is at TDC

71
Q

Intake Stoke (Suck)

A
  • Piston starts at TDC
  • Intake is open; exhaust is closed
  • Fuel air mixture is sucked into the cylinder
  • Piston moves downward
72
Q

Compression Stroke (Squeeze)

A
  • Intake valve closes
  • Fuel air mixture is compressed
  • Before TDC, fuel air is ignited by a spark
73
Q

Combustion Stroke (Bang)

A
  • Heat and pressure from ignited fuel mixture forces the piston downward
74
Q

Exhaust Stroke (Blow)

A
  • Before piston reaches BDC, the exhaust valve opens
  • Gases are forced out as the cylinder moves back up
75
Q

Valve Overlap

A
  • Intake valve opens before TDC; Exhaust closes after TDC
  • Intake closes past BDC; Exhaust opens before BDC
76
Q

Two Stoke Engine

A
  • Mechanically more simple
  • Less efficient
  • More difficult to lubricate
  • Doesn’t have valve. Has ports on the side.
  • Oil is mixed with the fuel
  • Two stroke engines are air cooled
  • There are still five events, but they happen almost simultaneously

Disadvantages
- Loss of efficiency when air fuel mixes with exhaust gases (when both ports are open at the same time)

77
Q

Four Stroke vs Two Stroke

A

Four Stroke
- More mechanically complex
- More efficient
- Less difficult to lubricate
- Has valves
- Oil and fuel are separate until it is in the cylinder

Two Stoke
- Mechanically more simple
- Less efficient
- More difficult to lubricate
- Doesn’t have valve. Has ports on the side.
- Oil is mixed with the fuel

78
Q

Wankel Cycle

A
  • Invented by Felix Wankel in 1957
  • Used as low horsepower engines
  • Problems w/ internal seals
  • Four events happen 3 times per revolution (Triangle in oval cylinder)
  • Has two sparkplugs (Leading and trailing)
  • Has seals to help prevent the corners from digging into the sides
79
Q

Diesel Engine

A
  • Pure diesel does not require an electric ignition
  • Only pure air is drawn into the cylinder during the intake stage
  • On compression stroke, fuel is hot enough (due to compression) to ignite on its own
  • Fuel is injected into cylinder when piston approaches TDC
  • Glow plugs may be used to help start
  • Are considered compression ignition engines
  • Compression ratio is around 14:1
  • Can be two or four stroke
80
Q

Firing Order

A
  • Order in which cylinders fire
    • Different engines have different firing orders
    • Determined by position of throws on the crankshaft
    • Determined by lobes on camshaft
    • V-type and opposed engines aim to balance and eliminate vibrations
81
Q

Internal Combustion theory

A
  • Power = rate of doing work
  • Distance the force moves
  • Time required to do work
82
Q

Piston Displacement

A

Obtained by multiplying the area of a cross section of the cylinder bore by the total distance that the piston moves during one stroke

83
Q

Indicated Horsepower (ihp)

A

ihp = PLANK/# of ft lbs/min

P = Indicated mean effective pressure
L = Length of stroke
A = Area of piston
N = # of working strokes per cylinder per minute
K = # of cylinders

84
Q

Brake Horsepower (bhp)

A
  • Actual horsepower delivered by an engine to a propeller
  • Usually between 85-90% of ihp
85
Q

Friction Horsepower (fhp)

A
  • Horsepower needed to overcome friction of parts of the engine and accessories
86
Q

bhp = ihp - fhp

A

Some random ass equation

87
Q

Engine Lubricating Oils

A

Source = petroleum

88
Q

Crude Petroleum

A
  • Is separated into different products from gasoline to lubricating oils

Naphthenic
- Southern Texas and California
- About 60 million years old

Paraffinic
- Pennsylvania of Allegheny region
- About 100 million years old

89
Q

Lubricant

A
  • Natural or artificial substance that has an oily or greasy property
  • Used to reduce friction between moving parts
90
Q

Animal Lubrication

A
  • Highly stable at high temps
  • Lubricated firearms, sewing machines, and other machinery
  • Unsuitable for engines because fatty acids produced at high temps
91
Q

Vegetable Lubrication

A
  • Oxidizes when exposed to air
  • Lower coefficient of friction than mineral oils
  • Wears away steel rapidly
92
Q

Mineral Lubrication (3 Types)

A
  • Largely used in aircraft engines

Solid
- Does not dissipate heat enough for high-speed machines
- Provides a slippery film that reduces friction
- May be mixed w/ fluid lubricants to reduce wear

Semi-Solid
- Extremely heavy oils and greases
- Applied periodically to areas
- Not suitable for circulating or continuous operating lubrication
systems

Fluid
- Principle lubricant in aircraft engines
- Pump easily
- Spray easily
- Absorbs and dissipates heat quickly and provides a good cushioning
effect

93
Q

Synthetic Lubricants

A
  • Tolerates high temps
  • Mainly used for gas turbine engines
  • Does not evaporate and break down at high temps
  • Not made from natural crude oils
94
Q

Viscosity

A
  • Fluid friction of an oil
  • Heavy oil is high in viscosity and flows slowly
  • Lower the viscosity, the more freely the oil flows
95
Q

Viscosity

A

Piston engines oil is separated by viscosity

96
Q

Chemical and Physical Stability

A

Aircraft engine oil must have:
- Chemical Stability against oxidation, coking, and thermal cracking
- Physical Stability against pressure and temperature

97
Q

What lubrication should do

A

The oil should help reduce friction and adhere to the surface

98
Q

Friction (3 Types)

A

Sliding friction
- When one surface slides over another
- No matter how smooth the surface, there is friction

Rolling friction
- When a cylinder or sphere rolls over the surface of a plain object

Wiping friction
- Happens between gear teeth

99
Q

Characteristics of aircraft lubrication oil

A
  • Viscosity
  • High anti-friction characteristics
  • Max fluidity at low temps
  • Minimum change is viscosity when there is a change in temps
  • High anti-wear properties
  • Max cooling ability
  • Max resistance to oxidation
  • Noncorrosive
100
Q

Lubrication at different temps

A

When it is hot outside:
- Lubrication should have a higher viscosity so it can melt a little and
still be able to flow around the engine

When it is cold outside:
- Lubrication should have a low viscosity so it can move freely in cold
weather

Powerplants (3 decks)

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