Improving Combustion Engine Efficiency

On a global scale, motor vehicles are responsible for emitting nearly a billion tons of carbon dioxide annually, leading to a greenhouse effect and negatively impacting our environment. In addition, with the price of gas nearing $3.60 in the United States, the demand for increasingly efficient cars is continually growing. Since most cars only covert about 40% (or less) of energy input into forward momentum, there is plenty of room for improvement. Some ways for increasing engine efficiency would be to reduce friction of the pistons and other moving parts, dynamically changing the amount and volume of the valves, and treat the gas and oxygen components before they are used in the combustion area of the engine.

As the engine converts chemical energy in the form of fuel into kinetic energy, one source of energy loss is friction. Decreasing the friction of the pistons and other parts in a combustion engine will reduce this source of loss. In order to reduce friction, the pistons and all other moving parts could be coated in a space-age polymer with an exceptionally low coefficient of friction. While expensive, there would be a sizeable reduction in wasted energy and wear of the parts, resulting in improved efficiency. Better lubricants would help as well, yet must be fire-resistant because engines can get very hot and the lubricant cannot serve its purpose if it is on fire.

Some energy is also lost in the engine due to wasted fuel. This can be minimized using at least two different techniques. The first of these methods would be to introduce a method of varying the timing with which the valves in the engine open and close, more specifically the valves which allow the air/fuel mixture into the engine and which allow the exhaust to exit the engine. In most engines, the valves open and close for a constant amount of time and that amount of time never varies, regardless of how hard the engine is working. If the duration of the opening and closing of the valves was changed such that the engine receives just enough air and fuel for how hard it is working, then the amount of wasted energy could be reduced. The second of these methods to reduce wasted fuel would be to introduce a system to activate and deactivate cylinders based on how hard the engine had to work to move the car at a given velocity. Although this method would not be as effective for a 4-cylinder engine as it would be for, say, an 8 cylinder engine, it could still reduce wasted fuel. For example, in most engines, all of the cylinders are always active regardless of whether or not they are needed and as long as they are active, they are consuming fuel. If the cylinders that are not needed could be deactivated and then reactivated when they are needed again then the amount of fuel needed to produce a given amount of rotational energy could be reduced.

The arguably largest increase in engine efficiency can be realized by optimizing the fuel combustion process to ensure that all fuel is consumed in the reaction. If fuel is heated, vaporized, and then pressurized there will be a large increase in efficiency. This would assure the maximum fuel surface area and optimal combustion conditions. The octane level in fuel also determines how much the gas can be compressed before it spontaneously ignites. If the gas is compressed to a greater degree before it is ignited, then the engine will require less fuel to produce the same amount of rotational energy, thereby increasing efficiency. Following that same line of thought, if fuel is heated and pressurized before it is injected into the combustion chamber, then the fuel can even be ignited without a spark. This modification will makes the fuel burn more cleanly and completely, thereby increasing the efficiency of the engine. A higher octane fuel would have to be used because if the fuel ignites prematurely, a wasteful result known as “knocking” is produced. Knocking is an undesirable effect that wastes energy and therefore should be avoided. One way of combating knocking would be to cool the air before injecting it into the engine. This would also have the benefit of increasing the amount of air in the engine, which would increase efficiency. Another way of combating the tendency for gasoline to ignite prematurely when compressed to a certain degree is to spray the inside of the compression and combustion chambers with a fluid to reduce temperatures in those areas of the engine. Less fuel can also be used to attain the same amount of rotational energy if a turbocharger is added to the engine, as a turbocharger increases compression. However, instead of compressing the gasoline in the engine, it compresses the air. Therefore, it could in theory be used with a type of direct fuel injection system to achieve maximal gas/air compression. However, as with the previous methods, a high octane gas would also have to be used with this method to avoid knocking. In conclusion, there are a myriad of methods that have the potential to increase the efficiency of a 4-cylinder combustion engine, such as friction reducing compounds, selectively disabling cylinders, and treating the air / gas mixture in various ways to maximize combustion. However, it is important to keep in mind that perhaps the more important factor in engine efficiency is the mindset of the person driving the car.

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