ASE Question Of the Month 
Sponsored By
 
Federated Auto Parts
 
Which is correct?

You’re correct if you answered D!

HCCI stands for “Homogenous Charge Compression Ignition”. Homogenous Charge (HC) refers to the charge state prior to ignition. A substance is homogeneous if its composition is identical wherever you sample it. This means that the charge mixture (fuel and air) has a uniform composition throughout the cylinder. Compression Ignition (CI) refers to the method that is used to drive the fuel past its autoignition point. When air is compressed rapidly, the molecules are accelerated off of the moving piston where they hit one another. The kinetic energy from the piston is turned into vibrational energy of the atoms causing a heating effect. This process is called Adiabatic Compression. The Adiabatic processes are characterized by zero heat transfer with the surroundings. In the case of rapid compression, the process occurs too fast for any heat transfer to occur. Heat transfer is a slow process. This rapid compression of the air creates a rapid heat increase that is used to drive the fuel well past its autoignition point.   

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