The Otto Cycle and the Development of the Internal Combustion Engine

The Otto Cycle and the Development of the Internal Combustion Engine

Daniel

University of ______, 2017

Contents

• History of the Otto Cycle                                                                                   2
• General Process of the Otto Cycle                                                                  3
• Specific Process of the Otto Cycle                                                                  5
• References                                                                                                  7

Table of Figures

• Figure 1                                                                                                   2
• Figure 2                                                                                                  3
• Figure 3                                                                                                  5

History of the Otto Cycle

The internal combustion engine (ICE) is a relatively new invention, created by Nikolaus Otto in 1876. It is now the primary means of producing power in automobiles, tanks, ships, buses, and even planes. Modern internal combustion engines use a process called the Otto cycle, illustrated in Figure 1, to produce relatively efficient levels of power compared to steam- and coal-powered engines. This four-part cycle, which consists of the intake, compression, power, and exhaust strokes, is utilized in almost every single internal combustion engine today.[pic 1][pic 2]

        Since the beginning of humanity, ancient leaders and researchers wanted to be able to haul cargo and people over long distances easily. First humans utilized horses, which did not really solve either problem. The horses could not carry that much on their backs and if they were carrying too much they would tire out quickly. Horse-drawn carriages and wagons solved the cargo problem, but being fully loaded with cargo meant that there was no space for people. In addition to the space and occupancy capacity issues, the horses would tire quickly if they were overburdened. Then, Karl Benz created the first car with the internal combustion engine, called the Benz Patent-Motorwagen. It would no longer require a horse to pull it and it could accommodate a few people without ever tiring.

However, there have been some issues surrounding the internal combustion engine. The foremost concern scientists, politicians, and consumers have is efficiency; how do we get maximum power output for minimal fuel consumption and residuals? Since their inception in 1876, scientists have constantly and tirelessly developed new technologies to increase the efficiency of internal combustion engines. For example, “in many countries researchers have investigated the performance and emission characteristics of diesel engines fuelled with ethanol-biodiesel-diesel blends...” [1] and from these tests, they’ve determined that engines running on ethanol-mixed fuels are significantly more efficient than traditional gasoline-powered engines. But the engines and the Otto cycle themselves are, by nature, very inefficient. According to “a recent study to determine the source and magnitude of frictional losses in automobiles… with current technology, the authors concluded that only 21.5 percent of the fuel's energy output in a combustion engine is actually used to move the car” [2]. Because most of the energy lost in an internal combustion engine is lost due to friction, and therefore heat, new technologies, such as advanced lubricators, lower viscosity oil, and low friction tires, are constantly increasing the internal combustion engine’s efficiency.

General Process of the Otto Cycle[pic 3]

As aforementioned, the Otto cycle can be broken up into four steps: intake, compression, ignition (power), and exhaust. Figure 2 illustrates the steps of the Otto cycle. Before delving into the dissection of the figure, steps 3 and 4 are theoretically the same; they were just separated to help the reader what happens between ignition and the opening of the exhaust valve. The first step is intake. In the figure, you can see that the piston, the grey T-shaped object that goes into the engine’s cylinder, is all the way down and the intake valve, which allows the air-fuel mixture to enter and fill the cylinder, is open. Step 2 is the compression step; the piston starts to move upwards and apply pressure to the air-fuel mixture and this creates a significant amount of potential energy that adds to the already-great amount of potential energy stored within the fuel. Step 3 illustrates the ignition step, also known as the power step, where the piston-pressurized air-fuel mixture is exposed to an electrical spark from the spark plug, a device that simply produces a spark, igniting the air-fuel mixture. This ignition causes the air-fuel mixture to rapidly expand, putting enough pressure on the top of the piston to drive it downwards, which is shown in “step 4”. After the ignition occurs, there is an excess gaseous mixture of air and fuel, which is let out by the exhaust valve, as shown in step 5. In real life internal combustion engines, steps 1 and 5 happen simultaneously. The intake and exhaust valves are open at almost the same time so that the gaseous mixture left over from the previous cycle is forced out of the cylinder by the incoming fluid gas-air mixture. [pic 4]