tailieunhanh - Internal Combustion Engines Fundamentals Episode 2 part 1

Tham khảo tài liệu 'internal combustion engines fundamentals episode 2 part 1', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 452 INTERNAL COMBUSTION ENGINE FUNDAMENTALS Otherwise normal combustion events the phenomena is called spark-knock. Repeatedly here means occurring more than occasionally the knock phenomenon varies substantially cycle-by-cycle and between the cylinders of a multicylinder engine and does not necessarily occur every cycle see below . Spark-knock is controllable by the spark advance advancing the spark increases the knock severity or intensity and retarding the spark decreases the knock. Since surface ignition usually causes a more rapid rise in end-gas pressure and temperature than occurs with normal spark ignition because the flame either starts propagating sooner or propagates from more than one source knock is a likely outcome following the occurrence of surface ignition. To identify whether or not surface ignition causes knock the terms knocking surface ignition and nonknocking surface ignition are used. Knocking surface ignition usually originates from preignition caused by glowing combustion chamber deposits the severity of knock generally increases the earlier that preignition occurs. Knocking surface ignition cannot normally be controlled by retarding the spark timing since the spark-ignited flame is not the cause of knock. Nonknocking surface ignition is usually associated with surface ignition that occurs late in the operating cycle. The other abnormal combustion phenomena in Fig. 9-58 while less common have the following identifying names. Wild ping is a variation of knocking surface ignition which produces sharp cracking sounds in bursts. It is thought to result from early ignition of the fuel-air mixture in the combustion chamber by glowing loose deposit particles. It disappears when the particles are exhausted and reappears when fresh particles break loose from the chamber surfaces. Rumble is a relatively stable low-frequency noise 600 to 1200 Hz phenomenon associated with deposit-caused surface ignition in high-compression-ratio engines. This type of