BACKGROUND
Small scale turbojets are used for various applications amongst the military and commercial industry. Given their diverse capability, these engines need to perform at an optimal level to maintain success in their missions. The purpose of the presented design is to improve the thrust-to-weight ratio of a small turbojet engine by only modifying the nozzle. For demonstration purposes, a JetCat P100-RX turbojet engine will be used for analysis and testing. The primary challenge is to increase thrust with minimal increase in weight. Several solutions were constructed such as nozzle geometry optimization, exit guide vane addition, and material improvement to maximize the thrust-to-weight ratio. The final design included an optimized nozzle geometry configured with seven exit guide vanes with leading edges oriented 10-degrees into the exhaust flow. This new nozzle was additively manufactured in titanium to reduce weight and mitigate deformation from high exhaust gas temperatures. The improved nozzle resulted in a thrust increase of 20.2% and coupled with a design that utilized a much lighter material, led to an overall thrust-to-weight improvement of 22.7%. The approach taken to increase the thrust-to-weight ratio by solely modifying the nozzle on the JetCat P100-RX was proven to be effective and could easily be replicated across other small turbojet engine platforms.
SUMMARY OF TECHNOLOGY
The purpose of the invention is to improve the thrust-to-weight ratio of a small turbojet engine by replacing the original stock exhaust nozzle with a lightweight nozzle optimized for increased thrust. For demonstration purposes, a JetCat P100-RX turbojet engine was used for the prototype. Typically, small turbojet engines suffer from poor thrust specific fuel consumption inherent to low pressure rise in the compressor resulting in reduced thermal and overall efficiencies. The challenge addressed with this technology is increased engine thrust with minimal increase in weight and without effecting fuel consumption rate. The invention includes three key design elements to construct an exhaust nozzle with optimal flow path geometry, integrated exit guide vanes, and material selection to maximize the thrust-to-weight ratio. The prototype includes an improved nozzle design with an optimized geometry and seven exit guide vanes having leading edges oriented 10-degrees into the exhaust flow. The new nozzle was additively manufactured with titanium to reduce weight and prevent deformation from high temperature exhaust gases. The nozzle includes a flange with bolt holes aligned with the existing engine exhaust mounting holes for easy replacement of the stock nozzle. The design also incorporates a shoulder to prevent flange deformation at high temperatures that could lead to exhaust gas leakage. The improved nozzle prototype was independently validated by the Air Force to result in a thrust increase of 20.2% and an overall thrust-to-weight improvement of 22.7% when installed on the JetCat P100-RX. The approach taken to increase thrust-to-weight ratio by solely replacing the nozzle of a Jetcat P100-RX with an improved nozzle is easily replicated across other small turbojet engines.
POTENTIAL AREAS OF APPLICATION
MAIN ADVANTAGES
STAGE OF DEVELOPMENT