The Physics Behind the Power of an Engine :: Physics Engine Essays

The Physics Behind the Power of an Engine Insert the key, turn, and vroom. And down the road you go. Most people take for granted the strange conglomeration of metal and plastic under that sheet of metal either in front or back of their vehicle. The engine as you may have guessed, is modern marvel- so to speak. They’re found in cars, trucks, boats, airplanes†¦All with various power outputs. To discuss the power output, first the cycles of the engine itself needs to be mentioned. 1.Intake: The intake valve opens allowing fresh oxygen rich air mixed with fuel to enter the cylinder. 2.Compression: The piston is pushed upward by the flywheel's momentum compressing the air/fuel mix. 3.Combustion: As the piston reaches the top of its stroke or TDC, the spark plug fires, igniting the mixture. Due to the high compression of this mixture it is very volatile and it explodes when the spark is introduced. This pushes the piston downward and produces power. 4.Exhaust: After the Air/Fuel mix has been burnt the remaining chemicals in the cylinder (water and CO2 for the most part) must be removed so that fresh air can be brought in. As the piston goes back up after combustion the exhaust valve opens allowing the exhaust gasses to be released. Ideally an engine takes in Air (Oxygen and Nitrogen) and fuel (hydrocarbons) and produces CO2, H2O, and the N2 just passes through. However under normal driving conditions an engine will encounter lean conditions when cruising on the highway (better mileage) and rich conditions when accelerating (better power). The lean condition results in oxide and harmful nitrogen production. Rich conditions result in carbon monoxide production. For this reason catalytic converters are used on an engine’s exhaust. 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 converts the harmful nitrogen oxides and carbon monoxide into nitrogen, carbon dioxide, and oxygen. Catalytic converters work best when warm, so some car manufacturers are putting "pre cats" in the exhaust manifold to convert the gasses while the exhaust system is still warming up. 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 rotation. Torque is what accelerates a car.