what is difference between rapid combustion and turbulent combustion
Neither phrase has a really tight and rigorous definition. Where the difference matters, "rapid" combustion generally refers to the rate at the flame front propagates through the medium, "turbulent" combustion refers to how much the flame front is spread by the motion of the burning medium. Turbulence generally makes for more rapid combustion, and often when more rapid combustion is desired it's easier to design the combustion chamber to produce more turbulence than it is to switch to a faster-burning fuel.
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