The compressor can be centrifugal or a Roots-type for positive displacement compression. Superchargers use various different types of compressors but are all powered directly by the rotation of the engine, usually through a belt drive. A turbocharger is a centripetal compressor driven by the flow of exhaust gases. Two commonly used forced-induction compressors are turbochargers and superchargers. High combustion temperatures lead to higher NOx emissions, thus forced induction can give higher NOx fractions. High compression causes high combustion temperatures. This level is government regulated for emissions as commonly seen at inspection stations. One of the primary concerns in internal combustion emissions is a factor called the NOx fraction, or the amount of nitrogen/oxygen compounds the engine produces. However, a forced induction engine can have a higher total compression without detonation because the air charge can be cooled after the first stage of compression, using an intercooler. High compression on a naturally aspirated engine can reach the detonation threshold fairly easily. This is called preignition, detonation, or knock and can cause severe engine damage. The reason all engines are not higher compression is because for any given octane, the fuel will prematurely detonate with a higher than normal compression ratio. Therefore, the thermal efficiency of the engine is increased in accordance with the vapour power cycle analysis of the second law of thermodynamics. Higher compression engines have the benefit of maximizing the amount of useful energy evolved per unit of fuel. This particularly helps aviation engines, as they need to operate at higher altitudes with lower air densities. A compressor feeding pressure into another greatly increases the total compression ratio of the entire system. An additional compressor feeding into the intake of the engine causes forced induction of air. The compression stroke of the engine is the main compression that every engine has. A forced induction engine is essentially two compressors in series. An engine without forced induction is considered a naturally aspirated engine.įorced induction is used in the automotive and aviation industry to increase engine power and efficiency. A forced induction engine uses a gas compressor to increase the pressure, temperature and density of the air. Forced induction is the process of delivering compressed air to the intake of an internal combustion engine.
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