AS 201 and 202 - The Internal Combustion Engine

AUTO SHOP PRACTICE

Title: The Internal Combustion Engine

Code: AS 201 and 202

Objectives: See your laboratory Manual

General Theoretical Knowledge:

          The internal combustion engine is an engine in which the burning of a fuel occurs in a confined space called a combustion chamber. This exothermic reaction of a fuel with an oxidizer creates gases of high temperature and pressure, which are permitted to expand. The defining feature of an internal combustion engine is that useful work is performed by the expanding hot gases acting directly to cause movement, for example by acting on pistons, rotors, or even by pressing on and moving the entire engine itself.
          This contrasts with external combustion engines, such as steam engines, which use the combustion process to heat a separate working fluid, typically water or steam, which then in turn does work, for example by pressing on a steam actuated piston.
          The term Internal Combustion Engine (ICE) is almost always used to refer specifically to reciprocating engines, Wankel engines and similar designs in which combustion is intermittent. However, continuous combustion engines, such as Jet engines, most rockets and many gas turbines are also internal combustion engines.
Internal combustion engines are seen mostly in transportation. Several other uses are for any portable situation where you need an non-electric motor. The largest application in this situation would be an Internal combustion engine driving an electric generator. That way, you can use standard electric tools driven by an internal combustion engine.

Applications

          Internal combustion engines are most commonly used for mobile propulsion in automobiles, equipment, and other portable machinery. In mobile scenarios internal combustion is advantageous, since it can provide high power to weight ratios together with excellent fuel energy-density. These engines have appeared in almost all automobiles, motorcycles, boats, and in a wide variety of aircraft and locomotives. Where very high power is required, such as jet aircraft, helicopters, and large ships, they appear mostly in the form of turbines. They are also used for electric generators and by industry.

Operation

          All internal combustion engines depend on the exothermic chemical process of combustion: The reaction of a fuel, typically with air, although other oxidizers such as nitrous oxide may be employed.

The most common fuel in use today are made up of hydrocarbons and are derived from mostly petroleum. These include the fuels known as diesel fuel, gasoline, and petroleum gas, and rare use of propane gas. Most internal combustion engines designed for gasoline can run on natural gas or liquified petroleum gases without major modifications except for the fuel delivery components. Liquid and gaseous biofuels, such as Ethanol and biodiesel, a form of diesel fuel that is produced from crops that yield triglycerides such as soy bean oil, can also be used. Some can also run on Hydrogen gas.

All internal combustion engines must have a method for achieving ignition in their cylinders to create combustion. Engines use either a electrical method or a compression ignition system.

Gasoline ignition Process

          Electrical/Gasoline-type ignition systems (that can also run on other fuels as previously mentioned) generally rely on a combination of a lead-acid battery and an induction coil to provide a high voltage electrical spark to ignite the air-fuel mix in the engine's cylinders. This battery can be recharged during operation using an electricity-generating device, such as an alternator or generator driven by the engine. Gasoline engines take in a mixture of air and gasoline and compress to less than 170 psi and use a spark plug to ignite the mixture when it is compressed by the piston head in each cylinder.

Diesel engine ignition process

          Compression ignition systems, such as the diesel engine and HCCI (Homogeneous Charge Compression Ignition) engines, rely solely on heat and pressure created by the engine in its compression process for ignition. Compression that occurs is usually more than three times higher than a gasoline engine. Diesel engines will take in air only, and shortly before peak compression, a small quantity of diesel fuel is sprayed into the cylinder via a fuel injector that allows the fuel to instantly ignite. HCCI type engines will take in both air and fuel but will continue to rely on an unaided auto-combustion process due to higher pressures and heat. This is also why diesel and HCCI engines are also more susceptible to cold starting issues though they will run just as well in cold weather once started. Most diesels also have battery and charging systems however this system is secondary and is added by manufacturers as luxury for ease of starting, turning fuel on and off which can also be done via a switch or mechanical apparatus, and for running auxiliary electrical components and accessories. Most modern diesels, however, rely on electrical systems that also control the combustion process to increase efficiency and reduce emissions.

Energy

          Once successfully ignited and burnt, the combustion products, hot gases, have more available energy than the original compressed fuel/air mixture (which had higher chemical energy). The available energy is manifested as high temperature and pressure which can be translated into work by the engine. In a reciprocating engine, the high pressure product gases inside the cylinders drive the engine's pistons.

Once the available energy has been removed, the remaining hot gases are vented (often by opening a valve or exposing the exhaust outlet) and this allows the piston to return to its previous position (Top Dead Center—TDC). The piston can then proceed to the next phase of its cycle, which varies between engines. Any heat not translated into work is normally considered a waste product, and is removed from the engine either by an air or liquid cooling system.

Parts

          The parts of an engine vary depending on the engine's type. For a four-stroke engine, key parts of the engine include the crankshaft (purple), one or more camshafts (red and blue) and valves. For a two-stroke engine, there may simply be an exhaust outlet and fuel inlet instead of a valve system. In both types of engines, there are one or more cylinders (gray and green) and for each cylinder there is a spark plug (darker-gray), a piston (yellow) and a crank (purple). A single sweep of the cylinder by the piston in an upward or downward motion is known as a stroke and the downward stroke that occurs directly after the air-fuel mix in the cylinder is ignited is known as a power stroke.

A Wankel engine has a triangular rotor that orbits in an epitrochoidal (figure 8 shape) chamber around an eccentric shaft. The four phases of operation (intake, compression, power, exhaust) take place in separate locations, instead of one single location as in a reciprocating engine.

A Bourke Engine uses a pair of pistons integrated to a Scotch Yoke that transmits reciprocating force through a specially designed bearing assembly to turn a crank mechanism. Intake, compression, power, and exhaust all occur in each stroke of this yoke.

Classification

          There is a wide range of internal combustion engines corresponding to their many varied applications. Likewise there is a wide range of ways to classify internal-combustion engines, some of which are listed below.

Although the terms sometimes cause confusion, there is no real difference between an "engine" and a "motor." At one time, the word "engine" (from Latin, via Old French, ingenium, "ability") meant any piece of machinery. A "motor" (from Latin motor, "mover") is any machine that produces mechanical power. Traditionally, electric motors are not referred to as "engines," but combustion engines are often referred to as "motors." (An electric engine refers to locomotive operated by electricity.)

With that said, one must understand that common usage does often dictate definitions. Many individuals consider engines as those things which generate their power from within, and motors as requiring an outside source of energy to perform their work. Evidently, the roots of the words seem to actually indicate a real difference. Further, as in many definitions, the root word only explains the beginnings of the word, rather than the current usage. It can certainly be argued that such is the case with the words motor and engine.

By Engine cycle

     Two-stroke

Engines based on the two-stroke cycle use two strokes (one up, one down) for every power stroke. Since there are no dedicated intake or exhaust strokes, alternative methods must be used to scavenge the cylinders. The most common method in spark-ignition two-strokes is to use the downward motion of the piston to pressurize fresh charge in the crankcase, which is then blown through the cylinder through ports in the cylinder walls. Spark-ignition two-strokes are small and light (for their power output), and mechanically very simple. Common applications include snowmobiles, lawnmowers, weed-whackers, chain saws, jet skis, mopeds, outboard motors, and some motorcycles. Unfortunately, they are also generally louder, less efficient, and far more polluting than their four-stroke counterparts, and they do not scale well to larger sizes. Interestingly, the largest compression-ignition engines are two-strokes, and are used in some locomotives and large ships. These engines use forced induction to scavenge the cylinders. two stroke engines are less fuel efficient than other types of engines because unspent fuel being sprayed into the combustion chamber can some times escape out of the exhaust duct with the previously spent fuel. Without special exhaust processing, this will also produce very high pollution levels, requiring many small engine applications such as lawnmowers to employ four stroke engines, and smaller two-strokes to be outfitted with catalytic converters in some jurisdictions.

      Four-stroke

Almost all cars currently use what is called a four-stroke combustion cycle to convert gasoline into motion. The four-stroke approach is also known as the Otto cycle, in honor of Nikolaus Otto, who invented it in 1867. The four strokes are illustrated in Figure 1. They are:

• Intake stroke
• Compression stroke
• Combustion stroke
• Exhaust stroke

Engines based on the four-stroke cycle or Otto cycle have one power stroke for every four strokes (up-down-up-down) and are used in cars, larger boats and many light aircraft. They are generally quieter, more efficient and larger than their two-stroke counterparts. There are a number of variations of these cycles, most notably the Atkinson and Miller cycles. Most truck and automotive Diesel engines use a four-stroke cycle, but with a compression heating ignition system. This variation is called the diesel cycle.

You can see in the figure that a device called a piston replaces the potato in the potato cannon. The piston is connected to the crankshaft by a connecting rod. As the crankshaft revolves, it has the effect of "resetting the cannon." Here's what happens as the engine goes through its cycle:

1. The piston starts at the top, the intake valve opens, and the piston moves down to let the engine take in a cylinder-full of air and gasoline. This is the intake stroke. Only the tiniest drop of gasoline needs to be mixed into the air for this to work. (Part 1 of the figure)
2. Then the piston moves back up to compress this fuel/air mixture. Compression makes the explosion more powerful. (Part 2 of the figure)
3. When the piston reaches the top of its stroke, the spark plug emits a spark to ignite the gasoline. The gasoline charge in the cylinder explodes, driving the piston down. (Part 3 of the figure)
4. Once the piston hits the bottom of its stroke, the exhaust valve opens and the exhaust leaves the cylinder to go out the tailpipe. (Part 4 of the figure)

Now the engine is ready for the next cycle, so it intakes another charge of air and gas.

Notice that the motion that comes out of an internal combustion engine is rotational, while the motion produced by a potato cannon is linear (straight line). In an engine the linear motion of the pistons is converted into rotational motion by the crankshaft. The rotational motion is nice because we plan to turn (rotate) the car's wheels with it anyway.

Engine configuration

Internal combustion engines can be classified by their configuration which affects their physical size and smoothness (with smoother engines producing less vibration). Common configurations include the straight or inline configuration, the more compact V configuration and the wider but smoother flat or boxer configuration. Aircraft engines can also adopt a radial configuration which allows more effective cooling. More unusual configurations, such as "H," "U," "X," or "W" have also been used.
Multiple-crankshaft configurations do not necessarily need a cylinder head at all, but can instead have a piston at each end of the cylinder, called an opposed piston design. This design was used in the Junkers Jumo 205 diesel aircraft engine, using two crankshafts, one at either end of a single bank of cylinders, and most remarkably in the Napier Deltic diesel engines, which used three crankshafts to serve three banks of double-ended cylinders arranged in an equilateral triangle with the crankshafts at the corners. It was also used in single-bank locomotive engines, and continues to be used for marine engines, both for propulsion and for auxiliary generators. The Gnome Rotary engine, used in several early aircraft, had a stationary crankshaft and a bank of radially arranged cylinders rotating around it.

Assignments:

1.

·         2. Rags: Keep a clean, lint-free rag in your vehicle to wipe your oil or transmission dipstick or to clean the inside of your windshield if it clouds up.

·         Spare parts: If you replace your spark plugs, save the old ones if they’re not too worn. Carry them in your trunk-compartment toolbox for quick replacements if necessary. The same goes for old air filters and other minor gizmos. A couple of extra nuts, bolts, and screws also are useful to have on hand.

·         Emergency parts: Carry a spare set of windshield wiper blades, an extra radiator cap, and extra fuses. If you plan to travel in hot weather in remote regions, top and bottom radiator hoses are a good idea. Although they’re more costly, it’s good to carry extra accessory belts.

·         Spare tire: Check your spare tire often. It’s humiliating to find that your spare is flat, just when you need it.

·         Lug wrench: A lug wrench is sometimes provided, along with a jack, on new vehicles. If you buy a lug wrench, get the cross-shaft kind, which gives you more leverage.

·         A can of inflator/sealant: This item saves you the trouble of changing a flat on the road. It attaches easily to the valve stem on your flat tire and inflates the tire with goop that temporarily seals the puncture.

·         Jumper cables: One of the most common automotive malfunctions is the loss of power to start the engine, either from an old or faulty battery or from leaving the headlights on by mistake.

·         Snow and ice equipment: If you live in a cold area, carry tire chains or a bag of sand. A small shovel is useful for digging your tires out, and a scraper allows you to clear your windshield of snow and/or ice. A can of de-icer is useful in icy weather.

·         Flashlights and reflectors: A flashlight in your glove compartment can help your kids locate dropped toys on the floor of the car, enable you to see under the hood if your vehicle breaks down, and serve as an emergency light for oncoming traffic if you have to stop on the road for repairs.

·         First-aid kit: Keep a first-aid kit in your vehicle. Choose one that’s equipped with a variety of bandages, tweezers, surgical tape, antibiotic ointment, something soothing for burns, and a good antiseptic.

·         Hand cleaner: Most hand cleaners are basically grease solvents.

·         Gloves: Keep a pair of gloves in the vehicle for emergencies. Industrial rubber gloves, available at swimming pool supply stores, aren’t affected by gasoline, solvent, or battery acid.

• Screwdrivers: The difference between a standard screwdriver and a Phillips screwdriver is the shape of the head, as shown here.

Standard (a) and Phillips (b) drivers and their screws.

Offset screwdrivers are handy because they make it easy to get to screws that have little clearance over the head. Offset screwdrivers come in both standard and Phillips styles and some have one of each type of head at either end.

An offset screwdriver.

• Screwholders: Instead of holding a screw in place with the fingers of one hand while wielding the screwdriver with your other hand, you fit the screw into the screwholder and use it to insert and tighten the screw.

A screwholder helps you get into hard-to-reach places.

• Wrenches: Wrenches are probably the most basic tools for auto repair. Most wrenches are available in both standard — also known as SAE (Society of Automotive Engineers) — and metric measurements. Today, most American vehicles have a mix of SAE and metric nuts and bolts. Foreign vehicles or foreign components used on American vehicles (a practice that’s becoming quite common) use metric nuts and bolts — even the inch-based British.

A socket wrench set.

• Socket wrenches: Socket wrenches come in sets for a wide variety of prices, depending on quality and how many wrenches are in the set.

You need at least one ratchet handle; most sets have two or three handles with at least one adapter.

Socket extenders are indispensable items to help you reach those almost-unreachable nuts and bolts.

A spark-plug socket (a), a ratchet handle (b), and an extension bar (c).

• Combination wrenches: Combination wrenches have one open end and one boxed end. These wrenches come in sets of several sizes, and each wrench is made to fit a nut of a specific size, whichever end you use.
• Torque wrenches: These wrenches are designed to tighten a nut, bolt, or screw to an exact degree to avoid under-tightening or over-tightening.

A dial torque wrench (a) and a deflecting beam torque wrench (b).

• Adjustable wrenches: You probably already have a crescent wrench in the house, and you can adjust the jaws to fit a variety of nuts and bolts simply by turning the wheel.
• Pliers: If you have to buy pliers, the very best kind to get are combination slip-joint pliers. You can adjust this general-purpose tool to several widths with a sliding pin.

Needle-nosed pliers (a) and combination slip-joint pliers (b).

• Gauges: Several tools are available to help you determine when enough oil, fluid, air, pressure, or whatever is enough. The gauges here are the most useful:

Wire feeler gauges.

• Tire pressure gauges: If you never check anything else on your vehicle, make a habit of regularly checking the tire pressure; it’s critical both for safety and good fuel economy.
• Wire and taper feeler gauges: You use wire and taper feeler gauges for “gapping” spark plugs.
• Compression gauges: You use compression gauges to check the pressure that builds up in each cylinder as your engine runs.

Question 3:

1. Look under your car to find the drain plug.

The drain plug is a large nut or plug located under the oil pan at the bottom of the engine. If you can’t reach your oil drain plug easily, you’ll have to either crawl under your car to reach it or jack up the car.

1. Push a container under the oil drain plug.

You want this container to catch the oil, so make sure it’s big enough.

2. Unscrew the oil drain plug.

Protect your hand with a rag or some paper towels, and be ready to move your hand out of the way. The oil now drains out of your engine into the container.

3. Remove the cap from the oil filler hole at the top of your engine and unscrew the oil filter, using a wrench if you can’t do it by hand.

To unscrew the filter, twist it counterclockwise. The filter will have oil in it, so be careful not to spill it when you remove it. If any remnants of the filter’s rubber seal remain on your engine, remove them.

4. Empty the oil from the filter into a drain pan.

After the filter is empty, wrap it in newspaper and set it aside to take to a recycling center with your old oil.

5. Open a new bottle of oil and dip a finger into it.

Use the oil to moisten the gasket on the top of the new oil filter.

6. Screw the new filter into the engine where the old one was.

Follow directions on the filter, or turn it gently by hand until it “seats” and then give it another three-quarter turn.

7. Wipe around the place where the oil drain plug goes.

Do this step only after all the oil has drained out.

8. Replace the oil drain plug and use an adjustable wrench to tighten it.

If your vehicle uses an oil drain plug gasket, make sure the old one has been removed and lay a new gasket on the pan before you replace the plug.

9. Use a funnel to pour all but 1 quart of the fresh oil into the oil filler hole.

Pour slowly to allow the oil time to run down.

10. Replace the oil filler cap and run the engine for 30 to 60 seconds.

Check for leaks from the oil drain plug and around the filter.

11. Shut off the engine and wait 5 to 10 minutes for the oil to settle into the oil pan, and then check the oil level again.

Remove the oil dipstick, wipe it with a clean, lint-free rag, and shove it back in. Pull it out again and check it.

12. 13Keep adding oil a little at a time.

Check the stick after each addition until you reach the “Full” line on the dipstick.

13. Remove the drain pan from under the vehicle and give the car a test drive.

Go around the block a couple of times.

14. Let the oil settle down again for 5 to 10 minutes, then recheck the dipstick.

If it’s still at “Full,” you’re good to go!

Dispose of the old oil by taking it to an auto parts store or other oil-recycling center.

Question 4: You will be asked to write an assignment on this. Therefore, you must have done it before writhing this report.

Question 5: It is adviced to change oil after traveling 5,000 miles with your car on optimum operating conditions.

Question 6:

Problem: Spark plug problem.

Advice: If spark plug is not giving any spark, then the only thing left to do is to clean up the spark plug with a dry piece of cotton cloth. Because in rainy days, sometimes due to presence of water inside plug, spark plugs doesn't spark. If still car is not starting, then call a car ignition specialist for detailed check up. And remember, DO NOT left your car parked outside when it's raining. Spark Plug Problems

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Problem: Ignition switch & steering column heat up.

Advice: Check out ignition switch for corrosion, because when ignition switch comes in contact of corrosion, it cause resistance. Replacing your ignition switch will definitely solve your problem.

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Problem: Engine over heat.

Advice: When we start a car, there is a controlled explosion occur inside the engine which emit large amount of heat. This high temperature is controlled by coolant. Sometimes no repairing from long time will cause improper working of this cooling system. Check coolant level and system time to time to avoid over heating problem.

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Problem: Ignition switch heat up when you start the engine.

Advice: Problem is in your ignition switch. It may be because of loose connection or broken ignition switch wire. Changing the ignition switch can solve your problem.

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Problem : Car start easily but when you turn the car off, it doesn't.

Advice : This ignition problem arises because of fault in the link of ignition lock and the switch. To solve this problem just replace the ignition switch and key tumbler assembly.

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Problem : Engine won't start

Advice 1 : If your engine is not starting then check out your battery, it has to be charged sufficient to run the engine. There may be a problem of defective ignition wire which obstruct battery to supply the sufficient current to the engine. Repairing the car ignition switch or it's wiring will definitely help you.

Advice 2 : If your engine is ok, your battery is in working situation but your car still not starting then verify your key chain. Is you carrying weighted key chain? Too many keys in your key chain? Just remove all your keys form your key chain except the ignition key. It happens because parts inside ignition switch made up of plastic and when you carry heavy key chain it moves constantly back and forward which cause continuous damage in the ignition switch. After some time the ignition switch become malfunctioned and will need a replacement. So if your car is not starting then first check your key chain.

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Problem : Battery is OK but car won't start

Advice : If your battery is ok but car making trouble in starting then there may be an ignition problem. Let's check out, turn the key on, but not to start, if the red warning light on dash light up then it means switch is ok if it doesn't then it means your ignition switch need a replacement.

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Problem : Car start but only run a few seconds

Advice : If you are facing this problem then it means there is a problem in either in spark, compression or fuel. Check whether fuel tank is filled with fuel or not, compression is ok and spark is working properly. If any one of three is not ok then check for professional ignition services in your area and call them

Question 7:

When a car dies and stalls or loses power while under power, it has to be related to the absence of fuel or spark.

Solution: Check Fuel level and refill fuel. If the car does not start, check the fuel injector if it is supplying fuel. If it is no supplying fuel, change the injector.

Question 8:

1. Application

• Automobile Engine
• Aircraft Engine
• Locomotive Engine
• Marine Engine
• Stationary Engine

2. Basic Engine design

• Reciprocating: Single cylinder, Multi-cylinder In-line, V, radial, opposed cylinder, Opposed Piston.
• Rotatory: Single motor, Multi motor

3. Operating cycle

• Atkinson (For complete expansion SI Engine)
• Diesel (For the Ideal Diesel Engine)
• Dual (For the Actual Diesel Engine)
• Miller (For Early/Late Inlet valve closing type SI Engine)
• Otto (For the Convectional SI Engine)

4. Working cycle

• Four stroke cycle
• Two stroke cycle
• Scavenging ; direct/crankcase/cross flow; back flow/loop; Uni flow
• Naturally Aspirated or Turbocharged

5. Valve/port Design and location

• Design of valve/port
• Poppet valve
• Rotatory valve
• Location of valve/port
• T-head
• L-head
• F-head
• L-head

6.Fuel

• Convectional
• Crude oil derivatives; Petrol, diesel
• Other sources; coal, Bio-mass, Tar stands, shale
• Alternative
• Petroleum derived: CNG, LPG
• Bio-mass Derived: alcohols, Vegetable oils, producer gas,   Biogas and Hydrogen
• Blending
• Bi-fuel and Dual fuel

7. Mixture preparation

• Carburetion
• Fuel injection

8. Ignition

• Spark ignition
• Compression Ignition

Question 9:

1.      Wrenches

2.      Ratchets

3.      Sockets

4.      Screw drivers

5.      Pliers

6.      Hammer

7.      Breaker bars

8.      Pry bar

9.      LED Flashlight

10.  Multimeter

11.  Bolt Extensions

12.  Swivels

13.  Jack

14.  Jack Stand

Question 10:

            Spark Ignition engine: is an internal combustion engine where the combustion process of the air-fuel mixture is ignited by a spark from a spark plug.

            Compression ignition engine: is an internal combustion engine in which ignition of the fuel that has been injected into the combustion chamber is initiated by the high temperature which a gas achieves when greatly compressed.

            Stroke: It is the distance travelled by the Piston from one of its dead centre position to the other dead centre position.

Top Dead Centre: the top most position of the Piston towards the cover end side of the cylinder is known as Top Dead Centre.

            Bottom Dead Centre: the lower position of the Piston towards the Crank end side of the cylinder is known as Bottom Dead Centre.

            Combustion Chamber: It is also known as a burner, combustion chamber or flame holder. In a gas turbine engine, the combustor or combustion chamber is fed high pressure air by the compression system. The combustor then heats this air at constant pressure.

            Ignition temperature: the autoignition temperature or kindling point of a substance is the lowest temperature at which it will spontaneously ignite in normal atmosphere without an external source of ignition, such as a flame or spark.

            Two-stroke-cycle engine: a two-stroke, or two-cycle, engine is a type of internal combustion engine which completes a power cycle with two strokes (up and down movements) of the piston during only one crankshaft revolution.

            Four-Stroke-cycle engine: a four-stroke cycle engine is an internal combustion engine that utilizes four distinct piston strokes (intake, compression, power, and exhaust) to complete one operating cycle. The piston make two complete passes in the cylinder to complete one operating cycle.

            Engine Capacity: Engine Capacity is also known as ‘Engine Displacement’, which means the displacement of the piston inside the cylinder from Top Dead Centre (TDC) to the Bottom Dead Centre (BDC) in engine’s one complete cycle. The Engine Capacity is also measured in Liters corresponding to Cubic Centimeters.

            Priming: an explosive used to ignite a charge.

           

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About Stephen Djes

Stephen Djes is a passionate Graduate of Engineering from the University of Benin, and he is geared towards helping fellow engineering students in the great institution of UNIBEN to do better at academics.