We've all seen them before, the mysterious chunks of metal under the hoods of our cars. They start when we turn the key and take us where we want to go. But how does an engine work? Internal combustion engines are a very important part of everyday life. We use them in our cars, trucks, airplanes. boats, snowmachines, 4 wheelers, and heavy machinery. These pages will help familiarize you with the basic concepts of how an engine works, an understanding of engine output, and some information on how forced induction or "boost" increases power output.
Engine Basics
A very common variant of the internal combustion engine is the four stroke engine. These engines have four "strokes" for each combustion cycle. These engines are
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The chemical equation is as follows.
2 C8H18 (gas) + 25 O2 = 16 CO2 + 18H2O
This equation is representative of a stoichiometric air fuel ratio (14.7:1). However under normal driving conditions an engine will encounter lean conditions when cruising on the highway (better milage) and rich conditions when accelerating (better power). The lean condition results in oxide and harmful nitrogen compound production. Rich conditions result in carbon monoxide production. For this reason a catalytic converter is used on most larger engines.
The catalyst material in a cat is in a wire mesh or honeycomb. This allows a high surface area to be exposed to the passing exhaust gasses. The catalyst (typically platinum) converts the harmfull nitrogen oxides and carbon monoxide into nitrogen, carbon dioxide, and oxygen. Catalytic converters work best when warm (as the reaction rate increases with temperature) so some car manufacturers are putting "pre cats" in the exhaust manifold to convert the gasses while the exhaust system is still warming up.
That covers the basic function of an engine fron intake to exhaust. Next we will explore the relationship of Horsepower vs Torque.
Engine output is measured in two ways. The first is a direct measurement of engine output: Torque. Torque is defined as the amount of mass that can be lifted a certain distance from the center of
The main issue with the internal combustion engine was its energy transfer efficiency. A large portion of the engines energy was lost through heat and kinetic energy through the exhaust, Alfred Büchi was obsessed with the idea it could be changed. A naturally aspirated engine, also known as N/A, is the engine most cars on the market today have. It relies on the intake stroke of the engine to pull the necessary air into the cylinders and use it for the combustion. The turbo charger is in simpler words a compressor, which uses exhaust fume energy to drive a shaft supplying power to the compressor. The
These two engines impact the world in a tremendous way in the transportation industry from driving your cars to work and hauling freight across the
A turbine is placed in the path of the exhaust gases which are exiting the engine. These gases are caught in the turbine causing it to spin. This spins a shaft along with another pinwheel called the compressor, which is placed in the intake air’s path. This compresses the air on its way into the engine. Normal aspirated engines work to draw in their intake air. As the intake valve opens, the piston’s downward movement creates a vacuum which “sucks” in some air through the intake system. After the work performed by the expansion of the gas in a small space, where the high pressure creates a push against the piston, most of the heat or energy is dumped into the exhaust. This heated air is not in the cylinder long enough to convert all the heat into mechanical energy.
They design high-performance exhaust headers to increase engine efficiency. This is accomplished by allowing the free flowing exit of exhaust gases after combustion is complete. In
The invention and use of the internal combustion engine was a pivotal point in the history of the automobile. The first attempt at an internal combustion engine was in 1673 by Christian Huygens, using gunpowder as the fuel source, though it was basically worthless as you had to open the engine up and put new gunpowder in it after every single stroke ("The Fuel & Engine"). This lack of a fuel for internal combustion engines sidelined its development for a couple hundred years. In 1860 Jean Joseph Etienne Lenoir built the first effective internal combustion engine using natural gas (Bottorff). The ignition of the gas would create a vacuum and the resulting pressure difference between the vacuum and the atmosphere would drive the power stroke (Bottorff). This gas-atmospheric engine, as it is known, was an effective system capable generating 20hp, still it was imperfect. It was further improved with the development
In the first chapter of this book, the authors take some time to shortly talk about Horsepower and Torque. To begin, Torque and Horsepower are directly related to each other. In this section of the book, it explains how Horsepower is not a measurable force, but is a calculated measurement of Torque. Torque on the other hand is an actual force and can be measure through a variety of ways. It can be measured through engine, chassis, or even hand held dynamometers. Likewise, Torque is a twisting force, and is expressed in Pounds feet of Torque or Newton Meters for the metric system. Furthermore, the authors explain when the term Horsepower was first used. Moreover, James Watt, an entrepreneur and engineer who lived in the early 1700’s came up
The energy input (Qin) required to power the internal combustion engines is contained in its fuel. In such engines, the chemical energy of the fuel is mainly converted to shaft energy (BP), energy transferred to the cooling water (Qw), energy transferred to the exhaust gases (Qe) and uncounted losses (Qu) due to radiation, friction, heat transfer to the surrounding, etc.
Society is driven by the thought of improving every existing invention to make it bigger, smaller, more cost effective, or simply better. The internal combustion engine has been used in transportation for everyone who lives in a civilized area; whether it is a motorcycle, car, bus, airplane, etc. The most important advances in technology for these engines involve efficiency. Gas mileage, performance, and displacement are key concerns for all engineers of internal combustion engines. With the invention of the turbocharger all of these factors can be improved. The inventor, progression, impact, and current adaptation of the turbocharger are very important in understanding this engineering innovation.
The piston is now at the bottom of the cylinder, which is filled with exhaust gases left over from the chemical reaction in the combustion cycle, the rotating crankshaft now pushes upward on the piston, as the piston moves upwards exhaust valves open, allowing the pistons movement to push the gas out of the cylinder so that the engine can start the 4 stroke cycle
Complete Cat Back Exhaust: Get more power and better fuel economy with aftermarket exhaust upgrade
To start off you need to know how a rocket engine works. The conventional rocket engine creates thrust by burning a fuel and an oxidizer, such as Liquid hydrogen and Liquid Oxygen. When burnt together in the combustion chamber, the gases created expand and shoot out the nozzle producing thrust which is
Conventional cars use internal combustion engines to generate power to put the car into motion. All conventional cars use what is called a “four-stroke combustion cycle” which are “intake stroke, compression stroke combustion stroke, and exhaust stroke” to
The spark plugs are run by a set of coils, the number of them depends on the amount of cylinders the engine has. The coils receive an electrical current from the engine, and it is run through the distributor which has wires that go to each spark plug. The electricity transfers through the spark plug into the combustion chamber of the cylinder head and ignites the fuel. The cylinder head is where the valves are located. In most internal combustion engines, there are two valves per cylinder. One for the intake of air, and the other to release the gases which are a product of the explosion inside of the cylinder. The valves open and close in synchronization with the pistons in order for the engine to work correctly. There is another part which opens and closes the valves. This part is called the camshaft. The camshaft is much smaller than the crankshaft, and it has lobes which are in offset positions to open and close the intake and exhaust valves at the correct times. The Valves are opened and closed by a set of pushrods for each cylinder. The pushrods are located on top of a part called the lifter. The lifter is what catches the lobes
Table 3 provides a summary of the mean piston speed, BMEP and specific power for three different engines. Due to resistance to flow or inertial stresses of moving parts, mean piston speed is limited within 8-15 m/s. Automobile engines usually operate at the higher end of this range, whereas marine engines typically have lower piston speeds (as evident below). In addition, as expected, the BMEP for the 2-Stroke SI marine engine was less than that of the two 4-stroke engines. This is because of
Air subsystem is a key factor in determining torque output and, engine performance. More the cylinder charged with clean air, the higher the maximum possible engine power output. Figure 1 shows the main components of an air subsystem: