Features Of An Efficient Engine - Article Example

Mohammed Al-Sahreef Research-Design-Proposal Sara MacDougall March 28, Features Of An Efficient Engine For economic and environmental reasons, having an efficient engine design has emerged to be greatest the concern to many modern mechanical engineers. There is a great need to have a car that does not use environmentally hazardous fuels as well as having a powerful engine with a low fuel intake. Initially, internal combustion engines (ICE) were made of four cylinder engines that produced twenty horsepower. However, modern ICEs are designed to produce about 250 horsepower while on the same time being environmentally friendly. One of the advances that have created efficient engines is the direct injection system. This system allows fuel to mix with air inside the cylinder hence resulting to efficient fuel use. However, cylinder deactivation is the most efficient feature in ICEs. Cylinder deactivation makes it possible to control the intake of fuel according to engine demand. Engine efficiency can further be developed from the concept behind turbo chargers. Turbo chargers have the ability to compress air under higher pressure inside the cylinder resulting to complete combustion hence generating more power. The exhaust air is diverted into driving a turbine that makes a pump to suck air and compress it into the cylinder. Turbo chargers works best when the engine is running very fast enough to produce a lot of exhaust gases so as to drive the turbine. However, turbo engines are not economical in themselves because they are big. Downsizing the size of the engine can result to a higher efficiency. Varying valve timing is a very critical aspect when it comes to designing an efficient engine. Valve timing allows higher RPM range of the engine to achieve maximum power while to the contrary allowing low range to be economical. Theoretically, a lot of power up to 30% is lost in moving various parts of the engine. Since fuel is burned inside the ICEs, undertaking some improvements on the amount of air that enters the cylinder can significantly improve the engine’s efficiency. Allowing larger volumes of air into the engine transfers more energy to the pistons making the crankshaft to move rapidly. Lobes found in the camshaft controls the valves of the engine in every cycle hence maintaining the valve lift constant. Under simple engines, a single camshaft controls the intake and the exhaust valves in one cylinder. Improving these engines such that a specific camshaft only controls the intake shaft while another one controls the exhaust valve will greatly increase the volumetric efficiency of such engines. This way, one cylinder can have more than one intake and exhaust valves making it easier for air to flow into the engine as well as moving out. This maximizes the volume of air that goes into the engine. An engine should be designed to perform excellently under various conditions i.e. when the engine is idle, partial load or when it is at full throttle. An engine in full throttle needs to produce much power. This requires a lot air. Therefore the engine should be designed to have open valves in most parts of the cycle. An open valve before the start of the intake stroke fills the cylinder with air. The air does not disappear as the partial vacuum pulls in the air since a new stroke has just begun. There is a period of overlap in the engine when the intake valve and the exhaust valves are open. A higher overlap translates to a high engine performance. The timing for the intake and exhaust valves is different among various engine speeds and loads. The solution to improving the efficiency of the engine can be achieved through the timing of the valves. A typical example on the application of this principle is the way Honda VTEC is designed. However, most engine designers and manufacturers use various approaches in coming up with the variable engine valve timing system. Variable valve timing is very effective in engines with two camshafts. An engine with one camshaft is designed in way such that it has two lobes controlling the valves. One lobe is then made to run at low speed while the other lobe does the task of opening and closing of the valve. The engine shifts from one lobe to another depending on the speed. Optimizing engine’s variable timing system for only two conditions is not efficient. Designing an engine that is optimized to recognize the time to alter the opening and closing of the valves due to some other variables like speed and the temperatures of the oil is ideal. BMW has implemented this. It changes its intake valve lift depending on the pressure applied on the accelerator. When the valve lift is controlled by the accelerator, it opens widely paving way for a lot of air to get into the cylinder and hence increasing the engines efficiency by some percentage. Rather than using a throttle to control the air into the engine, intake valves are also used in some designs of engines. The crankshaft turns one camshaft just like other engine. However, hydraulic dampers are fitted between the camshaft and` the intake valves. These dampers are accurately controlled by electronic means. They then control the force transmitted into the valves controlling the valve lift. This has been applied by fiat. The camshaft is efficiently optimized to perform excellently even at the maximum load. The hydraulic dampers transmit maximum force to the valves making them to open up fully. This allows more volumes of air to get into the engine. MultiAir is a very efficient feature in some engines. Under this system, every cylinder is independently controlled and it easily adapts to changing conditions. For instance the engine does not produce a lot of power when it is idling. This feature ensures that the fuel is not wasted. Therefore the intake valve can only be opened in the intake cycle. On the other hand, when the engine is subjected to partial load, intake valves respond and close early preventing the backflow of air from the cylinder. Another good way of achieving efficiency is by ensuring that the intake and the exhaust valves are kept closed completely while the engine is under a light load. This is the best alternative for small engines as opposed to turbo chargers which are ideal to big engines. Another efficient way of getting air into the cylinder can be through the use of forced induction. In most cases, for air to be sucked into the cylinder, most engines rely on the pressure difference between the atmospheric pressure and the low pressure inside the cylinder which is due to expansion. This process is usually referred to as normal aspiration. Though it is effective and can have a volumetric efficiency of up to 110%, engines that use forced induction have a volumetric efficiency of 150% and therefore considered to be an efficient alternative. There is another technological advancement in the gasoline engine as well. In recent development, instead of injecting gasoline into the combustion chamber directly, it is first of all heated and subjected to very high pressure. This does not require any sparks so as to combust fuel. The high heats as well as high temperatures that the gasoline is first subjected to are enough to cause combustion without sparks just like it is with diesel engines. This method is good because it presents a first and uniform combustion. This engine is efficient because there is no heat loss due to overheating of the combustion chambers as it is with other engines A supercharger can also be used to increase the efficiency of an engine. It ensures that more air goes into the engine by pressurizing air intake above the atmospheric pressure. As a result, more air combines with fuel producing a lot of energy. A supercharger rotates at a very fast rate, even faster than the engine itself hence forcing air into the combustion chamber. The result of this is more space created to accommodate extra fuel. This process produces a lot of energy up to 50% more than the normal engine capacity. Therefore attaching a supercharger to a car will make it work better and powerfully. Other methods of improving engine efficiency include electromagnetic braking. Since reducing the speed of a car through braking leads to loss of kinetic energy in form heat, it is good to apply regenerative braking as an alternative braking system. This way, small motors absorb energy and then charge a battery which stores this energy. Similarly, using two spark plugs will improve efficient fuel combustion in the engine. This is because some of the fuel usually undergoes partial combustion and is usually ejected before complete combustion is done in the combustion chamber. Sometimes the flame generated from the plug from one front fails to burn the fuel uniformly inside the engine. Having two spark plugs from opposite directions will ensure that the flame is uniformly distributed and hence resulting to complete combustion of fuel. The use of variable injection timing is highly efficient. The engine is already being used in marine vessels and it works in a way such that the effective pressure is maintained constant even at low speed giving room for low quality fuel to undergo complete combustion. In conclusion, having an efficient engine has been the subject of all the engineers working in the automobile industry. Several designs have been proposed and tested giving rise to new models of automobiles. However, this has not solved the grand problem of efficiency- having low fuelling consuming automobile that are environmental friendly. Honda and Toyota have produced 1.0 L gasoline engines which are currently considered among the most fuel efficient cars. These are just but few examples to illustrate how engine efficiency is being improved day by day. Works cited Campbell, Joe. Fuel Efficient Small Turbo Charged Engine. Canberra, A.C.T: Dept. of Resources and Energy, 1984. Print Guzzella,L, and Christopher H. Onder. Introduction to Modeling and Control of Internal Combustion Engine Systems. Berlin: Springer, 2010. Print. Hasegawa, Yōzō, and Tony Kimm. Clean Car Wars: How Honda and Toyota Are Winning the Battle of the Eco-Friendly Autos. Singapore: John Wiley & Sons (Asia, 2008. Print. Wharton, A J. Diesel Engines. Jordan Hill, Oxford: BH Newnes, 1991. Print. Read More