AME T109 Reciprocating Engine Theory (Part Two) Flashcards by B DEWITT

On a Two-Stroke Engine, which of the five events occur on the upstroke and which occur on the downstroke?

Five Events:

1) Intake
2) Compression
3) Ignition
4) Power
5) Exhaust

Upstroke:
Intake and Compression

At top of Stroke:
Ignition

Downstroke:
Power and Exhaust

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On a Two-Stroke engine, where does the fuel and air enter through?

What third ingredient else is mixed in and why would it be present?

Fuel and Air enters through the crankcase.

Oil is present as well for lubrication purposes.

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What are some advantages to the two-stroke engine?

Disadvantages?

Advantages:
Light Weight 
Has no Valve Mechanism 
No Lubrication System 
Excellent Power to Weight Ratio 
Position of Piston has no effect on Operation

Disadvantages:
Lower Dependability
Operator needs to manually mix the Fuel and Oil
BSFC Rating is Less Efficient

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On Diesel Engines, what is injected into the cylinder before TDC?

What is generated as a result causing Ignition?

Fuel.

Heat is generated which causes Ignition.

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In regards to the Diesel Engine…
(Fill in the Blank & may want to write down.)

a) It is a high ______ engine.

b) This engine utilizes a ______ stroke.
(A ______ power level is used as a result).

c) The compression ratio is ______ to ______
d) The mixture ratio is ______ to ______ while the engine is ______.
e) At idle the ratio could be up to ______.

(In regards to Detonation)

f) Kerosene (Jet Fuel) is less ______ than gas.
g) This fuel does not combust, it ______
h) Less ______ occurs as a result.

Word Bank Below:

1) Wear
2) Longer
3) Burns
4) Lower
5) Volatile
6) 16:1, 22:1
7) 80:1
8) 30:1, 35:1
9) Running
10) Compression

a) Compression
b) Longer, Lower
c) 16:1, 22:1
d) 30:1, 35:1
e) 80:1
f) Volatile
g) Burns
h) Wear

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Why was diesel abandoned for aircraft applications?

Far more advancements in gasoline based technologies took place.

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What must a Crankcase be strong enough to support?

Horizontally Opposed Engine Cases

A Crankcase must be strong enough to support the loads stemming from the Crankshaft.

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Horizontally Opposed Engine Cases:

Passageways are cast into the case for what purpose?

They are cast so that oil may lubricate various parts of the engine.

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Horizontally Opposed Engine Cases:

What is it made from?

Cast Aluminum.

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Horizontally Opposed Engine Cases:

What method is used to seal the two halves together?

Silk Thread is run along the perimeter of the Crankcase for the purpose of sealing them together.

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Radial Engine Crankcases:

What is this Case made of?

Forged Steel Alloy.

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Radial Engine Crankcases:

What does this Case support?

The loads produced by the Power Stroke.

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Radial Engines:

What is the purpose of the Crankshaft?

To transmit the reciprocating motion to a linear motion.

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What threee things does the crankshaft consist of?

Radial Engines

1) Main Journals
2) Crank Cheeks
3) Crank Pins

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Radial Engines:

What might be built into the Crank Pins and why?

Crank pins may have sludge tubes built into them to collect any oil impurities.

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What does a Radial Engine Crankshaft possess only one of per bank?

A single throw per bank.

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The Radial Engine is connected to the Crankshaft and Piston via what?

A Master Link.

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Horizontally Opposed Engines:

What two crankshaft types may be used?

180 Degree Crankshaft

60 Degree Crankshaft

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What do Dynamic Vibration Dampeners consist of?

Dynamic Balane weights attached to Mounting Blades on the Crankshaft.

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Which kind of Crankshaft (in regards to Horizontally Opposed Engines) use Dynamic Vibration Dampeners?

180 Degree Crankshaft Design.

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How do Dynamic Vibration Dampeners work?

A force acts in one direction and the balance counters it in the opposing direction.

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Horizontally Opposed Engines:

Between the Master and Articulating Rods, which is the most important to the aircraft?

The Master Rod.

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Horizontally Opposed Engines:

What kind of connecting is used?

Plain Connecting Rods.

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What is the bottom of the Piston called?

The Piston Skirt.

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What is the Piston Pin made from?

A Steel Alloy

The Piston Pin is place within what?

The Piston Boss.

What is the purpose of the Piston Pin?

To assist in protecting the Cylinder Walls from scoring.

What are the three possible Propeller Shaft (Crankshaft) designs?

Tapered Splined Flanged Type.

What is unique about the Tapered Crankshaft Design?

Has a slot for a woodruff key.

Why does the Tapered Propeller Shaft design limit the propeller to 100 Hp?

The Woodruff Key Slot is a point of weakness.

Propeller Shafts with a woodruff key slot have what limit?

The propeller is limited to 100 Hp.

Describe the Splined Propeller Shaft Design.

It has multiple straight indentations around the circumference.

What is a master Spline in regards to a Splined Propeller Shaft?

It is a indentation that is twice the width or depth of the other straight indentations making up the Propeller Shaft.

What are the four types of Piston Head Designs? Which is the most common? Which is utilized in low compression applications? Which is used for high compression applications?

1) Flat - Most Common 2) Recessed 3) Cup (Concave) - Low Compression Applications 4) Dome (Convex) - High Compression Applications

What differentiates a Cam Ground Piston from just a Piston?

Cam Ground Pistons are ten thousandths of an inch oblong until it reaches operating temperature. Heat causes expansion which makes the Piston Round.

What is the main purpose of Piston Rings? What is their secondary purpose? Their third purpose?

To seal the combustion chamber. Prevent oil from entering the combustion chamber. Aids in the dissipation of heat.

What are some of the materials that Piston Rings may be made of?

Cast Iron | Chrome Plated Steel

Chrome Plated Steel may ONLY be used on what kind of Cylinder?

Steel Cylinders.

What are the three kinds of Piston RIng Joint designs?

Butt Joint Step Joint Angle Joint

What is the Blow-By Phenomenon? What causes it? What alleviates this phenomenon?

Pressure from the ombustion chamber works its way down and into the crankcase. Occurs due to the improper sealing of the Piston Rings. A hole exists at the top of the crankcase to allow this pressure to escape.

What are the three types of Piston Rings?

Compression Rings Oil Control Rings Oil Scraper Rings

What is the purpose of the Compression Piston Ring?

To seal the combustion chamber.

What is the purpose of the Oil Control Piston Ring?

Controls the amount of oil sprayed onto the cylinder walls.

If a Piston or Cylinder needs to be replace what component(s) should be replaced also?

The Piston Rings.

Explain what the Cylinder Choke is. | Why does this exist?

This is the diameter at the top of the Cylinder that is ever so slightly smaller than the diameter at the bottom of it. It accounts for the expansion of the metal. The cylinder is oblong before this expansion occurs.

You notice orange is painted onto the aircraft piston(s), what does this indicate? What about Blue? If no paint is present?

Orange: The Piston(s) are made of Chrome Plated Mild Steel. Blue: The Cylinder is nitrided. No Colour: It is standard Steel.

Why is Checal Chrome used to make some pistons?

It keeps oil on the Cylinder Walls.

Number of Cylinders is done from what view-point?

From behind. | From the Pilot's Position

Horizontally Opposed Engine Cylinders are numbered how?

Odd numbered cylinders are located on the right while even numbered cylinders are located on the left.

Why are Horizontally Opposed Engine Cylinders numbered with odd numbers on the right and even numbers on the left? (Two Reasons)

For Identification Purposes and for Firing Order.

Radial Engine Cylinder Identification: On single row Engines, where is Cylinder #1 located? Cylinder #2?

``` #1: Located at twelve o'clock. #2: Located directly to the right of #1. ```

Radial Engine Cylinder Identification: On double row Engines, where is Cylinder #1 located? Cylinder #2?

``` #1: Located at twelve o'clock. #2: Located directly to the right and aft of #1. ```

What is the Intake Valve made of? | Two possibilities

Nickel Chrome | Tungsten

Which Valve has a larger diameter - Intake or Exhaust?

Intake is always larger.

What is the Exhaust Valve made of? | Three Possibilities

Inconel Silicone Chromium Cobalt

What may be added to the Exhaust Valve to aid in Heat Dissipation?

Metallic Sodium.

Metallic Sodium may be added to which Valve and for what purpose?

May be added to the Exhaust Valve to aid in Heat Dissipation.

When the Exhaust Valve has Metallic Sodium added, what are the two ends known as?

A Stellite Face and Tip.

What component may have a Stellite Face and Tip and why what does this mean?

An Exhaust Valve may have a Stellite Face and Tip meaning that it has Metallic Sodium added to its construction to aid in Head Dissipation.

What are the four possible Valve Head Profiles?

Flat Head Tulip Head Semi-Tulip Head Mushroom Head

In regards to Valves, what is the purpose of a Split Key?

IT prevents the valve from falling into the chamber.

What is a Split Key in regards to Valves?

Two Springs of Different sizes are used on the Valve.

Why would two Springs be used on a Valve instead of one?

Two are used so that they have different Resonating Frequencies. Ensures the Valve will work at all RPM Speeds.

What is the purpose of Valve Guides?

To keep the Valve in its Optimum Position.

Horizontally Opposed Valve Train: | What is the purpose of the Rocker Arm?

To open the Valves.

How does a Rocker Arm cause wear? | Horizontally Opposed Valve Trains

A side load is put onto the tip of the Valve... | This causes wear over time.

In regards to Rocker Arms: | What indicates that wear has occurred at the contact points?

A space grows at the contact points which causes a Hammering Noise to emit.

What do Hydraulic Lifters (or Tappets) eliminate the need for?

The Two Springs within the Valve Train.

Why are Springs not ideal when incorporated into a Valve Train?

They resist compression which allows to little movement.

What kind of phenomenon is usually bad news for a Valve Train but with the use of Hydraulic Lifter is an asset to the system?

Hydraulic Lock.

What other name is the Hydraulic Lifter known as?

Zero Lash Lifters.

What is unique about a Solid Type Valve Lifter?

These have an adjsutable Rocker Arm.

What is a downfall to the Solid Type Valve Lifter?

They must be calibrated on a regular basis.

How is oil moved through the Valve Train?

Oil is pumped down the Pushrod to the Rockers Cup (The Back) and then to the Rocker Bearing.

What component turns Rotary Motion into Linear Motion?

The Camshaft.

Radial Engines Valve Train: | What is used in place of a Camshaft?

A Cam Ring.

Within Radial Engine Valve Trains, what controls the pushrod?

A Cam Roller runs along a Cam Ring.

What are the five key components to a typical Valve Train?

``` Camshaft Lifter Pushrod Rocker Arm A Valve ```

Propeller Reduction Gearing: | What does Spur Gear Reduction consist of?

A large and smaller gear.

Propeller Reduction Gearing: | Why is Spur Gear Reduction used?

This setup is used to allow higher Propeller RPM.

Propeller Reduction Gearing: | What is an issue that inherently comes with the Spur Gear Reduction method?

It is sensitive to power changes. | The more power changes occur, the faster this system will wear.

Propeller Reduction Gearing: | What does the Planetary Gear Reduction method consist of?

A center Sun Gear is surrounded by Planetary Gears. | All of the aforementioned gears are found within an outer Ring Gear.

Propeller Reduction Gearing: | Why would one use Planetary Gear Reduction?

Allows the engine t orun at a higher RPM at the propeller.

Horizontally Opposed Engines: Why is a specific firing order utilized? (Three Reasons)

To provide smooth operation. Maintains dynamic balance. aids in the reduction of vibration.

In square engines, why are the piston and stroke diameter the same?

Is thought to be a characteristic of an efficient engine.

What does it mean if an engine is "under square?"

The Piston Diameter is smaller than the Stroke Length.

What are some major disadvantages to Under Square Engines? | Name Three

1) Typically have mechanically inefficient crank angles. 2) The Power Band (RPM) is lower. 3) Higher Friction Losses. (More Heat is produced).

What does it mean is an engine is "over square?"

The Piston Diameter is greater than the Stroke Length.

What are some advantages to Over Square Engines? | Name Three

1) Has more efficient Crank Angles. 2) In general, these engines are under less crank stress. 3) Has a lower Peak Piston Speed relative to Engine Speed.

What is the purpose of Cylinder Fins?

Increase surface area for improved heat reduction.

Which Valve will have more Cylinder Fins? - Intake - Exhaust

Always Exhaust.

What is the purpose of Engine Baffles?

To force air to circulate throughout the engine.

How do Cowl Flaps increase airflow throughout an engine?

By creating a low pressure zone which draws air in.

Aside from ciculating Oil, what is the purpose of the Oil System?

To remove heat from the engine. | Bearings especially.

How does the Oil System reduce heat throughout the engine?

Through the use of Heat Exchangers.

Put simply, what does it mean if an engine is Liquid Cooled?

The Cylinders are Water Jacketed.

Overall on Liquid Cooled Engines, | what aspect of the engine increases and what other aspect decreases?

Increases Engine Performance. | Decreases Reliability.

Constant Speed Engines: | Explain their general concept.

Engine RPM remains constant at all times.

Constant Speed Engines: | What two components make these kinds of engines possible?

A Variable Piston Propeller and a Governor.

Constant Speed Engines: | What does Oil Pressure control?

Propeller Blade Angle.

Constant Speed Engines: | What controls Oil Pressure?

The Propeller Governor.

Constant Speed Engines: | What controls Propeller Blade Angle?

Oil Pressure.

Power Curve Charts are used to claculate what?

Fuel Burn.

What is necessary to read a Power Curve Chart?

An Engine RPM.

There are four steps to reading a Power Curve Chart, | what are they?

1) Use RPM to find lbs / Hp / Hr 2) FInd Brake Hp 3) Multiply the above two numbers. 4) Multiply the products with the number of hours in which the aircraft is being operated.

What is the formula for Cylinder Displacement?

Area of Piston multiplied by the Length of Stroke.