7th may 2024
i have always wanted to build a micro gas turbine engine. with zero knowledge, i started with the theory. after getting the basic fundamentals ready, i felt the need to get some experience on the practical side of things. after all,
i get these numbers from calculations. however, i had not a single idea on what these numbers meant in real life, what is safe, what can be built at home, these were questions i wish i knew the answer for during my initial days. i started with the goal of building a 30 KN low bypass turbofan (might feel stupid to pursue the goal that time), did cycle analysis, and even reached on designing the tract of the axial compressor. thats when it struck that this is too big and its time to downsize. picked up to design an 80kg engine, i wanted to keep it small, 17 cm was the outer diameter limitation i kept. even though this was a stupid idea, i got familiar with the numbers a lot. a turbofan did not make much sense with the size. at lower bypass ratios, all my fan thrust would be eaten up by boundary layers because the Δr between the fan and compressors was really small. at higher bypass ratios, i do not have enough mass flow to the engine core. so i then decided to stick with a fully turbojet engine. i choose to have an axial compressor for the sole purpose of learning to make one. even though this too was a stupid idea, i learnt the art of making the tract, balancing the need to get higher blade speeds while maintaining decent blade height. spinning such a thing at 30000 rpm terrified me, balancing is a different story. time to downsize even more.
i decided to go with off the shelf centrifugal compressor wheels (HX35), calculations showed that i need them to be spun at 120k rpm to get a pressure ratio of 4, giving some space for all the losses. that was really scary. i did not know how to proceed. thats when i discovered the JATO community. it is a community of hobby gas turbine builders active since the 90s. John suggested me to try building a turbocharger based engine to get some experience as they come in really good containers.
Hi Soorkie,
It might be beneficial for you to build a turbocharger based engine first to gain experience before
attempting the much more complex task of building an axial engine , the turbocharge has containment
built in , so much safer
Cheers
John
the hobby gas turbine community in the west is pretty matured. i could not find any traces of such a community in India. there are are a handfull of folks, but they have already commited themselves to building their enterprise. i believe that a state achieves mastery in a technology when: for all tech colleges, with high probability, there exist a student who has mastered the technology.
i will be posting details about my turbocharger based engine in my next log.
live long and prosper,
soorkie