Turbofan engines operate by compressing the ambient air and feeding it to the combustion section. The air is compressed via an axial turbopump. The turbopump is driven by a gas turbine directly connected to the same shaft. There is another type of turbopump that can compress the air, the centrifugal turbopump.
My proposition is to separate the combustion area and the compressing stage for a turbofan engine. The resulting engine would inhale air from vertically above and exhaust the burned gasses horizontally behind. The idea is to reduce the air drag induced by the high cross section of a turbofan engine. The centrifugal turbopump embedded on top of a fuselage of a plane would induce no extra drag. Moreover, air intake above the plane would result in a low-pressure zone at the top which contributes positive to the lift of the plane.
Unlike a traditional turbofan which powers its turbopump via the output of itself, my proposed design powers the centrifugal turbopump separately. Long tubular frame of the plane allows more turbopumps to be added in succession to increase the amount of air compressed without adding no additional air drag.
The compressed air would then be used to combust the fuel and generate high velocity exhaust gas. The lack of gas turbine after the combustion zone would yield higher efficiencies. The fuel pump would be driven by the exhaust gasses generated by powering the turbopumps.
Typical jet fighters utilize very low bypass ratio (Pratt & Whitney F135 => 0.57:1) compared to passenger jet engines (CFM International LEAP-1A => 11:1). This results in much less fuel efficiency. My proposal increases the bypass ratio by adding more turbopumps one after the other which improves the fuel efficiency without inducing additional air drag.
One final advantage of my design is the reduction of overall complexity of a typical turbofan engine. Breaking the design into smaller and manageable sections decreases design and manufacturing times.
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