Figure 6.11: Relative suitability of the turboprop, turbofans, and ordinary turbojects for the flight at the 10 km attitude in various speeds. Adapted from Wikimedia Commons / CC-BY-SA-3.0.
Some of the most important types of jet engines will be now discussed. Specifically, turbojets, turbofans, turboprops, and after-burning turbojets. As a first touch, Figure 6.11 illustrate a sketch of the relative suitability of some of these types of jets. It can be observed that turboprop are more efficient in low subsonic regimes; turbofans are more efficient in high subsonic regimes; and turbojets (also after-burning turbojets) are more efficient for supersonic regimes. If one looks at higher mach numbers (\(M > 3-4\)), ramjet, scramjets or rockets will be needed. However these last types are beyond the scope of this course.