She's real fine my 4-0-9
She's real fine, my 4-0-9
My 4-0-9
Nothing can catch her, nothing can stop my 4-0-9, 4-0-9
Giddy-up giddy-up giddy-up 409!

 

("409," by the Beach Boys, 1962)

 

COMMON HARDWARE FOUND IN INTERNAL COMBUSTION ENGINES

Every Reciprocating Internal Combustion Engine will have the below hardware:

A Cylinder ... the upside-down can-shaped container in which the hydrocarbon fuel is ignited.

A Piston that moves up and down within each Cylinder.

The Piston has critical job duties:

• The downward movement of the Piston sucks in combustion air.
• The Piston is also the tool used to compress the not-yet-combusted hydrocarbon fuel.

• And it is also the Piston that is impacted by the expanding force of the Working Fluid which plunges the Piston downward creating The Power Stroke...aka mechanical/motive Power.

 

A Connecting Rod/Crankshaft linkage which changes the straight-line, up-and-down motion of the Piston into a rotary motion that goes around and around. This rotary motion can drive a Load (like a Pump or a Compressor) or turn an electricity generator or spin a propeller, etc.

The Crankcase surrounds the Connecting Rod/Crankshaft.

 

 

Additional common Engine hardware includes Valves andPorts which control the flow of fuel and combustion air into the Cylinder and expel (aka "Exhaust") the combustion products from the Cylinder.

There will also be hardware dedicated to controlling the amount of fuel that enters the Cylinder and some means to ignite the fuel.

As stated in PTOA Segment #200, the most popular use of the Internal Combustion Engine as a Prime Mover/Driver in the process industries is the critically important function of back up electricity generation.

 

The power needed for such an important service ... as well as to drive the road-worthy common motor vehicle … cannot be provided by a single Piston and Cylinder.

Powerful Internal Combustion Engines have multiple Cylinders that work in timed coordination within a Cylinder Block and a Cylinder Head.

Okay!

The form of the hardware found in a Reciprocating Internal Combustion Engine has been introduced!

And now it is time to understand the function of that hardware!

 

THE COMBUSTION CYCLE OF INTERNAL COMBUSTION ENGINES

All hydrocarbon burning Engines operate in the same general way regardless of whether the generated motive force slides back and forth "reciprocating" or circles around and around in "rotary" motion.

The back and forth reciprocating motion that is converted into a mechanical force in a Reciprocating Internal Combustion Engine was shown in the gif that appeared in the previous section.

The cycling around and around motion of a Rotary Internal Combustion Engine is shown in the nearby gif.

Both the Reciprocating and Rotary Internal Combustion Engines create their motive/mechanical forces by following the steps of The Combustion Cycle.

The Combustion Cycle for Internal Combustion Engines is most easily illustrated with a   Four-Stroke Internal Combustion Engine example.

 

Step 1: "Intake" of Hydrocarbon Fuel into the Cylinder.

This step begins with the Piston at the top of the Cylinder where the Intake Valve and Inlet Port are positioned.

This position is called "Top of Dead Center" (aka TDC) and the fill-volume of the Cylinder is at the minimum.

During this step the Intake Valve opens which allows a specific amount of  vaporized fuel and air (gasoline engine) or just air (diesel engine) to be sucked into the Cylinder through the Intake Port.

The vaporized fuel and air sucked into the Cylinder during Intake is shown as light blue in the nearby nifty gif of a Four-Stroke Internal Combustion Engine.

Throughout the Intake Step, the Piston moves so that it is fully extended and at the bottom of the Cylinder, a position described as "Bottom of Dead Center" (aka  BDC).

The fill-volume of the Cylinder is maximum at the end of the Intake Step.

As illustrated by the nearby gif, at the conclusion of the Intake Step, the Cylinder is full of light blue vaporized fuel and air (for a gasoline Engine) or just air (for a diesel Engine).

 

Step 2: Compression:

Intake Valves are closed so that no material can enter or leave the Cylinder.

The Piston moves from BDC upward, continuously decreasing the volume in the Cylinder  thus compressing the trapped vaporized fuel and air (gasoline Engine) or just air (diesel Engine).

In the animated gif of the Four-Stroke Internal Combustion Engine, the fuel and air in the Cylinder turns darker blue while being compressed into a much smaller volume.

The change from light blue to dark blue visually illustrates that the Temperature as well as the Pressure of the vaporized fuel/air mixture (gasoline Engine) or just air (diesel Engine) increases throughout the Compression Step.

 

Yo! Fred! Your Mentor sees you stressing out!

Don't you dare give Your Mentor that "HUH?" look!

There is not one dedicated PTOA Reader or Student who is surprised that a trapped gas in a rigid container (like a Cylinder) would experience an increase in the Temperature upon being compressed (by a Piston) into a smaller volume. All those mysterious yet common sense "laws" that predict gas behavior were featured in PTOA Segments #152 and #153 and #154.

 

The Temperature increase of compressed air in a diesel Engine can reach 1000 °F!

Plenty hot for ignition to take place!

 

Step 3a: Ignition:

In a gasoline Engine, the vaporized fuel/air mixture is ignited by a Spark Plug.

The Spark Plug in the nearby gif of a Two-Stroke Internal Combustion Engine is on the top left side angling downward, very close to where vaporized hydrocarbon fuel (light green) is squirted into combustion air (blue).

A Spark Plug is a dinky electrical generator that creates periodic high voltage pulses.

The technological name for a Spark Plug is a "magneto." ***

Diesel Engines do not use Spark Plugs for ignition.

The very hot, compressed air and drops of aspirated diesel fuel self-ignite because of the high Temperature that results from the Compression Step.

*** PTOA Reader Eric M offers the following clarification to other PTOA Readers who may be similarly irritated with the above statement which equates a Spark Plug to a "magneto."

Step 3b: Working Fluid Creation and Expansion … aka THE POWER STROKE!

The burning fuel rapidly morphs into a hot gas composed of carbon dioxide, water vapor and not-completely burned combustion products.

These gases .. aka The Working Fluid … rapidly expand and the force of expansion pushes the Piston downward, creating the almighty Power Stroke of the Engine.

The nearby gif shows Ignition and Expansion creating  The Power Stroke.

The dark blue compressed fuel and air are ignited and turn red.

Immediately following Ignition, the Piston is blasted downward, filling the Cylinder with red combustion products.

Voila!

The Power Stroke is THE motive power that turns the Crankshaft!

Unfortunately … many illustrations of The Internal Combustion Engine Combustion Cycle don't really show The Power Stroke!

The typical illustration shows the end of Compression Step and then the beginning of the last step Exhaust.

So just be aware!

The Power Stroke is why all the complex technology went into building the Engine in the first place!

 

Step 4: Exhaust of The Working Fluid (aka Combustion Products).

The Exhaust Valve opens.

The Piston moves upward, pushing The Working Fluid of red combustion products out of the Cylinder through the Exhaust Port.

The Connecting Rod/Crankshaft convert the Exhausted red combustion products into motive/mechanical power (however, this action is not shown in the gif).

The Exhaust Port closes at the end of the Exhaust Step. Then the Intake Valve opens and the Internal Combustion Engine Combustion Cycle repeats.

 

 

THE COMPRESSION RATIO OF AN ENGINE

The Ford built Model T featured in the first movies …

like the no-talkies featuring Charlie Chan ...

bumped along because of "Pre-ignition."

The "Pre-ignition" of the vaporized gas and air during the Compression Step is the main reason that the first automobiles had that chug-chug-chugging motion which rattled the bones of the drivers and passengers.

"Pre-ignition" happens when the vaporized fuel/air mixture gets so hot while being compressed that the mixture self-ignites before the end of the Compression Step ...which in a gasoline engine  is supposed to progress to a planned ignition via a Spark Plug.

 

"Pre-ignition" causes loss of motive power and wears down Pistons and other Internal Combustion hardware.

To limit the occurrence of Pre-ignition, Engine manufacturers developed an Engine design parameter called The Compression Ratio.

The Compression Ratio limits the PV Pressure exerted on the Cylinder walls during the Compression Step.

Limiting the increased PV Pressure during the Compression Step limits the increase in Temperature that the Cylinder contents will experience, hence limiting Pre-ignition.

 

The Compression Ratio can be estimated by dividing the filled volume of the Cylinder at the very end of the Intake Step (before the Compression Step begins) by the much smaller filled volume of the Cylinder at the conclusion of the Compression Step … prior to Ignition.

In the nearby gif The Compression Ratio could be estimated by dividing the volume of the light blue fuel/air mixture at the end of Intake by the much smaller dark blue volume of the fuel/air mixture at the very end of Compression (just prior to turning red due to Ignition).

 

Generally speaking …

 

The greater The Compression Ratio ... the greater the maximum PV Pressure exerted on the walls of the Cylinder after Combustion.

Heck!

That general observation just makes common sense!

Brilliant PTOA Readers and Students already know that the PV Pressure is simply a Force bearing down over an Area because they learned so way back in PTOA Segment #142 .

So The Power Stroke that follows the Compression Step can be visualized as a Force spread over the Area of a Cylinder bottom.

Ergo … the greater The Compression Ratio of an Engine, the more powerful The Power Stroke blasts the Piston downward.

So no PTOA Reader or Student would be surprised to conclude that …

The greater The Compression Ratio and hence Power Stroke …the more efficient the Engine is with respect to consuming fuel to generate motive power.

 

Does that mean there are no limits to The Compression Ratio in Engine design?

Heck no!

The composition of readily available hydrocarbon fuels limits the designed Compression Ratio of Internal Combustion Engines.

For example:

To prevent Pre-ignition, automobile gasoline is blended to a minimum octane and diesel fuels are blended to a minimum cetane.

Fun Fact! The "66" in the "Phillips 66" brand of gasoline was a marketing ploy for the Phillips Company to brag about their ability to produce a gasoline with a whopping 66 octane … a great achievement back in the day.

Todays modern automobiles driven in non-mountainous USA states require a much higher averaged octane of 87 to prevent Pre-Ignition.

 

Natural gas burning Engines are designed for a Compression Ratio of 5:1.

So that means the filled volume of the Cylinder before the Compression Step is five times greater than the filled volume of the Cylinder after the Compression Step has ended (and just prior to the Ignition Step).

This limitation on The Compression Ratio of natural gas Engines results in approximately 120 psig pressure being exerted on the walls of the Cylinder right before Ignition takes place.

 

Diesel Engines are much more efficient than gasoline Engines because the Compression Step is not heating up a hydrocarbon/air mixture but rather just air!

The atomized diesel that is injected at the end of the Compression Step does not need to be heated up because the compressed air is already very hot. This design allows the pressure exerted on the Cylinder walls to be quite high, in the 450 to even 600+ psig range.

The resulting Power Stroke …

which drives the Crankshaft and ultimately the Load of a diesel vehicle's drivetrain …

yields an inherently efficient conversion of diesel fuel into motive power.

Otherwise stated, the diesel Engine yields many more miles per gallon than the gasoline Engine.

 

BASIC ENGINE TYPES

By now PTOA Readers and Students should be picking up the gist that the various designs of Internal Combustion Engines differ in how they handle:

• What type of fuel is used.
• How the fuel is injected.
• How air is introduced into the Cylinder.
• When and where the vaporized or atomized fuel is mixed with oxygen from air..
• How the hydrocarbon is ignited.
• The Compression Ratio.

 

There are dozens of Internal Combustion Engine design improvements that surpass the PTOA's immediate goal of introducing the basic form and function of Internal Combustion Engines used as Prime Movers/Drivers in the industrial processing industries.

Only the most common Internal Combustion Engines and design improvements are mentioned below.

 

Two-Stroke versus Four-Stroke Engines

Both the Two-Stroke Engine and Four-Stroke Engine cycle through all the steps of the Internal Combustion Engine Combustion Cycle that were featured above.

A Two-Stroke Engine is shown working in the nearby gif.

The difference is that …

The Two-Stroke Engine yields a Power Stroke for each and every full revolution of the Crankshaft.

The Crankshaft in the Four-Stroke Engine rotates two times for each single Power Stroke.

Notice in the nearby Two-Stroke Engine gif that red combustion products (aka The Working Fluid) are Exhausted ...

and are hence converted into motive/mechanical power...

each time the Piston moves upward.

Compare the Two-Stroke Engine gif to the nearby Four-Stroke Engine gif.

Light brown Exhausted combustion products (aka The Working Fluid) leave the left side of the Cylinder ...

and are hence converted into motive/mechanical power ...

every-other time the Piston moves upward.

Thus the Crankshaft of the Four-Stroke Engine rotates two complete times to yield one Power Stroke from the Engine.

 

The benefits of the Two-Stroke Engine versus the Four-Stroke Engine are:

The Two-Stroke Engine generates more motive/mechanical power than the Four-Stroke Engine.

 

The Two-Stroke Engine is physically less complex and smaller than the Four-Stroke Engine.

 

However ..

The Two-Stroke Engine is less efficient than the Four-Stroke Engine because it uses more fuel to produce a unit of horsepower than the Four-Stroke Engine does.

 

The Rotary Internal Combustion Engine Design … The Wankel Engine

The Rotary Internal Combustion Engine design figured out that rotary motion …

going around and around instead of reciprocating back and forth...

can result in a smaller, more compact Engine which can generate more "power per rotation" than the up and down movement of a Piston moving within a Cylinder.

Unfortunately the Wankel design also exhausts more emissions into the atmosphere.

Once again it is time to "You Tube and Chill."

Many thanks to Engineering Explained for creating the below You-Tube which explains "How Rotary Engines Work".

As always, be certain to LIKE this great video to show appreciation for the creator's effort to clue you in.

If the below direct access to the Engineering Explained You Tube on "How Rotary Engines Work" doesn't work then access the You Tube by clicking HERE.

The beginning of the video clearly shows how the rotary hardware functions though the same steps of the Internal Combustion Engine Combustion Cycle. The hardware just looks a lot different than Pistons and Cylinders!

Hang on to the end of the video and learn the benefits of the Rotary Internal Combustion Engine when compared to the Reciprocating Internal Combustion Engine.

 

 

"Supercharging" and "Turbocharging" an Engine

The goal of "Supercharging an Engine" is to cram more air into the Cylinder for the purpose of burning more fuel which will increase the Engine's power output.

Supercharging is achieved by supplying intake air with a greater density than mere atmospheric air pressure (14.7 psia). This "dense" air must be maintained within the Cylinder at the beginning of the Compression Step.

A blower is typically used to supply the air.

But hey ... the blower is a Load ... so what drives it?

The blower must be powered by the Engine or a separate, electrically driven Motor.

Sometimes the Engine's exhaust is used to drive a Turbine that supplies the "dense" air. Engines with this design feature are described as "Turbocharged."

 

Wow!

That was a lot of information to learn about the Prime Movers/Drivers known as Internal Combustion Engines considering that Process Operators are typically just responsible for making certain the emergency backup power genset is ready when needed.

In a large, complex processing plants Process Operators are much more likely to interface with the variable speed Prime Mover/Driver known as a Steam Turbine … which is featured in the next PTOA Segment!

 

TAKE HOME MESSAGES: Reciprocating Internal Combustion Engines have Pistons and Cylinders which combust the hydrocarbon fuel and Connecting Rods/Crankshafts which  convert the back and forth reciprocating motion of the Piston into the rotary mechanical motion that drives a Load.

Rotary Internal Combustion Engines do not need Connecting Rods and Crankshafts to covert combusted fuel into rotary motion.

Common hardware in both Reciprocating and Rotary Internal Combustion Engines include:

• Intake Valves, Intake Ports, Exhaust Ports, and Exhaust Ports
• Means to control the amount of fuel and air.
• Hardware dedicated to the Ignition Step.

 

Reciprocating Internal Combustion gasoline Engines have:

• Spark Plugs, magnetos that initiate combustion.
• Crankcases
• Cylinder Blocks
• Cylinder Heads

 

Both Reciprocating and Rotary Internal Combustion Engines work via the Internal Combustion Engine Combustion Cycle:

(1) Intake, (2)Compression,(3) Ignition & Expansion = The Power Stroke (4)Exhaust of The Working Fluid which is made of combustion products.

The Compression Ratio is a design parameter for Reciprocating Internal Combustion Engines which was developed to limit the occurrence of Pre-ignition.

The Compression Ratio determines how much Pressure will be exerted on the Cylinder after Combustion, hence how much Power will be generated by the Engine.

The diesel engine is more efficient than the gasoline engine for reasons explained in this PTOA Segment.

The Two-Stroke Engine yields a Power Stroke per each revolution of the Crankshaft but the Four-Stroke Engine takes two rotations to yield one Power Stroke.

The Two-Stroke Engine is more powerful and lighter than a Four-Stroke Engine but is also less fuel-efficient.

Rotary Engines (aka Wankel Engines) yield more power for their compact size yet also yield more emissions.

Many Thanks to Engineering Explained for the great You Tube that illustrates how the Wankel Rotary Engine navigates The Combustion Cycle.

The primary interface of Process Operators with Engines in the processing facility will be monitoring the condition and performance of the Internal Combustion Engine that has been installed to drive an emergency electrical power generator. The diesel engine in a genset works as detailed in this PTOA Segment. 

©2018 PTOA Segment 0192

PTOA Process Variable Pressure Focus Study Area
PTOA PV Pressure Rotating Equipment Focus Study
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