Wikipedia:Reference desk/Archives/Science/2021 September 28

= September 28 =

How can a petrol burn slowly in vehicle engine?
If I burn petrol, then it fire quickly. But in engine, how does petrol burn slowly? Is it Piston ring behind this? Rizosome (talk) 06:56, 28 September 2021 (UTC)
 * It doesn't burn slowly. It ignites within a sealed combustion chamber. Internal combustion engines are designed so that only measured quantities of fuel are injected into and ignited within each combustion cycle, thus preventing rapid combustion of the entire fuel stored in the tank. PaleCloudedWhite (talk) 07:31, 28 September 2021 (UTC)
 * There is no answer to 'how' it burns slowly because it does not burn slowly. It rather explodes. And a pressure caused by the explosion pushes the piston, which makes a useful force. For more explanation see Internal combustion engine (and then possibly External combustion engine, too.) For even more details, see Spark-ignition engine with Ignition system and Diesel engine. --CiaPan (talk) 11:07, 28 September 2021 (UTC)
 * It does not explode. There is a distinct difference between an explosion and combustion. 41.165.67.114 (talk) 11:55, 28 September 2021 (UTC)
 * "Combustion is produced by the reaction of oxygen and some sort of fuel at high temperatures" and "Detonation is a process of intramolecular breakdown." See https://cs.stanford.edu/people/eroberts/courses/ww2/projects/firebombing/detonation-and-combustion.htm 41.165.67.114 (talk) 11:59, 28 September 2021 (UTC)
 * I've heard combustion described as a "controlled explosion". ←Baseball Bugs What's up, Doc? carrots→ 15:33, 28 September 2021 (UTC)
 * In a combustion chamber, the difference is one of degree, not of principle. --Lambiam 18:02, 28 September 2021 (UTC)
 * Here's one example of the term. ←Baseball Bugs What's up, Doc? carrots→ 00:58, 29 September 2021 (UTC)
 * The rate of fuel consumption in a combustion engine depends on the fuel injection, which is regulated by a throttle. In a car, the driver can control with the accelerator pedal. If the pedal is pushed in, more fuel is consumed. --Lambiam 18:02, 28 September 2021 (UTC)
 * If petrol explodes in the combustion chamber you get detonation, which is a bad thing if sustained. Normally it burns, with a flame speed of around 17 m/s, but that number depends on many things - slightly rich mixtures burn faster than lean mixtures which is why you need to advance the ignition on lean mixtures. Greglocock (talk) 22:41, 28 September 2021 (UTC)
 * See: engine knocking. Fgf10 (talk) 07:38, 29 September 2021 (UTC)