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For those familiar with liquid engines in other types of vehicles, you’ll know that many mix the propellants before combusting them in order to optimize the combustion. In many general aviation aircraft engines and older car engines, you’ll find this premixer is the carburetor. In contrast, premixing in liquid rocket engines is usually not advisable because of the volatility of the propellants, and so ensuring optimal mixing inside the combustion chamber is also a task for the injector. However, do note that in some advanced rocket engines (like SpaceX’s Raptor!), premixing before entering the combustion chamber is a thing that can be done.
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Injector Performance
Before we get into the more specific aspects of injector design, it would be good to first understand what principles and metrics we’re trying to satisfy with the injector. Also, throughout the design process, you’ll often want to assess how ‘good’ your injector actually is at doing its job. But how do we evaluate this?
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