Purpose of an engine • Converts the heat of burning fuel into useful energy Let's take a look at how the engine was invented.
Nikolaus August Otto: Inventor of the Internal Combustion engine Story of Nickolaus August Otto, inventor of the four-stroke internal combustion engine, the device used to power automobiles, motorboats and motorcycles.
Nikolaus August Otto was born on June 14, 1832 in Holzhausen, Germany. At the age of sixteen, Otto dropped out of high school and worked in a grocery store. He also worked as a clerk in Frankfurt and as a traveling salesman. He sold sugar, kitchenware and tea to grocery stores on the German side of the Belgian and French border. It was when he was a traveling salesman that he learned about the gas engine that was invented by Etienne Lenoir. This was the first workable internal combustion engine. According to the University of Nottingham publication, “The Otto and Langen Free Piston Atmospheric Engine,"
“Unhappily, the Lenoir engine failed to come up to initial expectations and fell suddenly from popularity. This was due, partly to the troublesome electrical ignition system, but mainly to the high consumption of, what was then expensive gas. In practice almost 100 cubic feet of gas were burnt per horsepower per hour. Also, the quantity of cooling water required was considerable and the heat generated was so great, that unless the bearings were copiously oiled, the engine seized.”
Otto felt that the Lenoir engine would have more uses if it could run on liquid fuel. Otto devised a carburetor for this engine and worked to improve it in other ways. In 1861, Otto patented a two-stroke engine that ran on gasoline. Otto and his partner, German industrialist Eugen Langen, built a factory and worked on improving the engine. Their two-stroke engine won a gold medal at the 1867 World’s Fair in Paris.
The company was named N.A. Otto & Cie., which was the first company to manufacture internal combustion engines. The company exists today as Klockner-Humbolt-Deutz AG, the oldest company manufacturing internal combustion engines and the world’s largest manufacturer of air-cooled diesel engines.
In May 1876, Otto built the first four-stroke piston cycle internal combustion engine. This was the first practical alternative to the steam engine. In the next ten years, over 30,000 of the engine were sold. This engine was the prototype of the combustion engines that have since been built. The engine was named the “Otto cycle” in his honor.
The engine’s design consists of four stokes of a piston which draws in and compresses a gas-air mixture within a cylinder. This process results in an internal explosion. SUCK SQUEEZEBANG BLOW
Otto’s gas-motor engine had patent no. 365,701. In 1862, Aphonse Beau de Rochas, a French engineer, patented the four-stroke cycle. Even though Otto was the first to build a four-stroke cycle engine, in 1886, his patent was revoked, when Rochas’s patent was revealed.
Daimler - Benz Gottlieb Daimler constructed a very light engine, using Otto’s model and attached one of them to a bicycle. This became the world’s first motorcycle. Karl Benz built his first three-wheel automobile employing Otto’s engine. Daimler also constructed an automobile, using Otto’s engine. The firms of Daimler and Benz merged and manufactured the famous Mercedes-Benz vehicles.
Otto’s practical internal combustion engine is used to power automobiles, motorcycles and motorboats. Also, the Diesel engine is a form of internal combustion engine, which employs a four-stroke cycle that is similar to Otto’s. Nikolaus August Otto died on January 26, 1891.
To understand engine performanceyou must understand charging and starting systems.
REVIEW STARTING AND CHARGING CFE WATCH MOVIE
What Makes an Engine Run? • FUEL • COMPRESSION • IGNITION (FIRE)
COMPRESSIONThe mechanical side What is an engine? An engine is a group of related parts assembled in a specific order. In operation, it is designed to convert the energy given off by burning fuel into useful form.
There are many parts in the modern engine, each essential to the engines operation. For right now, let's think of an engine as a device that lets us pour fuel into one end and get power from the other
Internal Combustion Engine Terms Internal Combustion Burning within Engine Device in which fuel is burned Fuel Indicated what is being burned.
What to use for fuel If you are going to convert fuel into useful energy you will need a fuel that will: • Ignite (burn) easily • Burn clean • Reasonably inexpensive (yea right) • Produce sufficient power • Available in quantity • Safe to use and easy to transport
How about gasoline? Gasoline is a product obtained by refining crude oil (petroleum) obtained from wells drilled into the earth. The crude oil is treated in various ways to produce gasoline Since gasoline is a mixture of carbon and hydrogen atoms, it is termed a hydrocarbon
Octane rating: The octane rating indicates how well the gasoline will resist detonation (burning too rapidly) in the cylinders. The lower the octane rating the faster the fuel burn Slower burning fuel provides more even combustion throughout the power stroke of the piston.
Unleaded gasoline All gasoline sold today is unleaded. Unleaded gasoline contains no tetraethyl lead. Tetraethyl lead quickly destroys catalytic converters.
Preparing the fuel As you know, gasoline burns readily. However to get the most power from this fuel, and in fact, to get it to power an engine, special treatment is required.
If you were to place a small amount of gasoline in a jar and drop a match into it, it would burn. Such burning is fine to produce heat but it would not give us the explosive force needed to operate an engine.
OXYGEN,GOTTA HAVE IT In order to burn, gasoline must combine with oxygen in the air. For purposes of illustration imagine that a gasoline particle is square. It will burn on all sides. However it will still not burn quickly enough to for use in an engine
To make the gasoline burn more rapidly, we can break it up into smaller particles. Notice that as you divide it into smaller particles, you expose more surface area to the air.
The Basic Force of an Engine If you break up gasoline into very fine particles, burning is fierce. Rapid burning produces a tremendous amount of heat, which in turn causes rapid and powerful expansion. The burning gasoline gives off energy in the form of heat. You now have the basic force with which to do the work. Next you must harness this force .
Trapping the Explosion If you were to spray a mixture of gasoline and air into a container, place a lid on the container, and light the mixture, the resulting explosion would blow the lid off the container.
A Simple Engine If we were to use a rod to hook to the lid and attach the other end to a shaft shaped like the one shown. Support each end with a bearing and place a wheel at one end, When the lid is blown off the shaft will be given a sharp upward push, causing the wheel to spin.
Modern Crankshaft design Notice the reluctor wheel for Distributorless ignition systems
What was wrong with the simple engine? Lots of things. As the lid is forced down again it can land in any position. If the engine is to work, the lid must cover the container. Instead of covering the container, lets make the lid fit into the container.
If you were to bolt the container and the shaft bearing so the could not change position, you would have an engine that would spin the wheel every time you fire a fuel mixture.
Getting fuel into the engine You may have noticed that no provision was made to get the fuel into the upper cylinder area of this engine. A system must be developed to admit fuel and to exhaust the fuel after it is burned.
Valves The next logical step is to provide a device to open and close the ports. If the ports were left open the force of the explosion would not push the piston down. The port control device, or valve will have to be arranged so that it can open and close when desired.
When the valve sits on the valveseat, it seals the opening. The valves are held in position by a hole bored in the head called a valve guide. This hole is called a valve guide because it guides the valve stem up and down in a straight line. A spring, spring washer and keepers are also necessary to keep the valve in place
Four-Stroke Cycle At this point we have an intake valve to let fresh mixture into the cylinder and an exhaust valve to let burnt fuel out. The problem is how do you force the air/fuel mixture into the cylinder?
Vacuum is the key The air we live in presses on all things. This pressure is approximately 14.7 lb. per square in (103 kPa) at sea level. When we draw air out of a container, we form vacuum. A vacuum is unnatural, and the atmospheric pressure will do all it can to get into the low pressure area. If there is the slightest leak in the container, air will seep in until the pressure on the inside of the container is the same as the pressure on the outside.
INTAKE STROKE Fig 7: INTAKE STROKE The piston moves down the cylinder and the pressure will drop (negative pressure). The intake valve is opened. Because of the low pressure the air/fuel mixtures is sucked into the cylinder.
COMPRESSION STROKE COMPRESSION STROKE At Bottom Dead Center (BDC) the cylinder is at its maximum volume and the intake valve is closed. Now the piston moves backward the Top Dead Center (TDC) and compresses the air/fuel mixtures. The pressure is increased and the volume is decreased. The necessary work for the compression increases the internal energy of the mixtures - the temperature is increased. Because of the fast compression only a small part of the energy is transferred to the environment.
Fig 9: IGNITION Near the end of the compression stroke, the ignition starts the combustion and the mixture burns very rapidly. The expanding gas creates a high pressures against the top of the piston. The resulting force drives the piston downward in the cylinder.
POWER STROKE POWER STROKE: The force drives the piston downward to crank shaft (the valves are closed). The volume is increased and the pressure is decreased. No more energy is added and because of this the internal energy of the gas is decreased as so as the temperature.
EXHAUST STROKE • At BDC the exhaust valve is opened and the piston moves up the cylinder. The pressure drops near the pressure outside the cylinder because of the opened exhaust valve. Exhaust gas leaves the cylinder. The volume is decreased.
What opens and closes the valves Camshafts
Camshafts The shaft will have an egg shaped bump called a cam lobe. The cam lobe is machined as an integral part of the shaft. The distance the valve will be raises (lift) and the time the valve will stay open (duration) is machined into the cam lobe. The lobe in this illustration is located directly over the valve. Other camshaft placements will be discussed later
Valve Lifters The lifter is installed between the cam lobe and the valve stem. One end rides on the cam lobe and the other almost touches the end of the valve stem (usually .008 to .010 clearance). The lifter slides up and down in a hole adjacent to the camshaft and separates the valve stem from the camshaft.
The cam lobes are machined with a taper and the bottom of the lifter is crowned. This is done to rotate the lifter in the lifter bore to ensure even wear, lubrication, and prevent seizing.