Turbojet Engine w/ Afterburner
Designed and fabricated a self-sustaining turbojet engine with an afterburner using a car turbo.
Timeline
Jan 2026 - Sept 2026
Tools & Software
ANSYS Fluent, Onshape, Matlab
Engineering Focus
Propulsion & Thermal-Fluid Systems
01 - Project Overview & Objectives
The objective of this project was to design and fabricate a self-sustaining turbojet engine, meaning that it can run on its own power without external factors. The idea was to take an automotive turbocharger and build all the necessary jet engine components around it.
The engine was build around a t3/t4 turbocharger (durable/cheap), and I built a custom flame tube and combustion housing, connections from cold and hot side of turbo to combustor, an afterburner, fuel/throttle system, oil system (to cool and lubricate the turbo), ignition system, and structural supports.
My goal for building this project was to apply theory learned in class, such as thermodynamics, fluid mechanics, and mechanical design, and applying it to a real hands-on project, as I wanted to see the "math" in action. Moreover, I've always loved getting my hands dirty, and recently started to develop an interest in propulsion systems, so what better way to strengthen machine shop skills, theoretical mechanical knowledge, and introduce propulsion than building a turbojet engine.
02 - Research and Preliminary Design
Going into this project, I had absolutely zero knowledge how jet engines worked, except knowing they sound cool. So granted, the first step was conducting research not only on how jet engines worked, but also on how to build such a system surrounding a car turbo instead having all the components inside a cylindrical housing.
Because the funding for this project was mostly coming from my own pockets, I had to account for cost of the parts and the feasibility of manufacturability. Therefore my "philosophy" for this project was to get the cheapest parts that will do the job right. From my findings, I deciding to use 304 stainless steel for most of my components. Materials such as Inconel and even 321 stainless would be preferred due to higher melting temperatures and better resistance to oxidation, however I would go off budget using them. On the other hand, cheaper alloys such as mild/galvanized steel wouldn't survive the extreme heat (I recorded 1150C, which is far above mild steel's useful structural temperature range).
My engine uses a T3/T4 turbo, having a compressor A/R of 0.5, turbine A/R of 0.63, and compressor inducer of 52.7mm, which provided the starting point for combustion chamber requirements and the dimensions of the parts.
The engine I've built works exactly the same to a proper turbojet with regards to the thermodynamic process. Both follow the Brayton cycle and have the same flow:
air enters the combustor -> gets compressed -> fuel burns in combustor -> hot gas expands through turbine -> gas exits through nozzle to create thrust
For my design (see image below):
I had a powerful leaf blower spool the compressor wheel, which in turn compressed the air, exiting the turbo and entering the combustor
In the combustion chamber, I would ignite the spark plug, spray in the fuel (propane), and combustion would happen uniformly throughout the flame tube.
The exhaust gasses would then travel back into the hot section of the turbo, spooling the turbine wheel inside the turbo.
The gasses (and leftover oxygen from dilution zone in flame tube) would then exit through the afterburner, where more fuel and spark are introduced right after the v-gutters. Combustion happens again and the gasses exit through the nozzle with greater velocity and thrust.
As simple as the above process sounds, I also had to build 3 subsystems:
Fuel System: I used a combination of propane hoses, 304ss pipes, and compression fittings to supply fuel to the main chamber and afterburner:
Propane tank->regulator(set to 30PSI)->t-fitting↓->ball valve->afterburner
ball valve->main chamber
Oil System: The turbo wheels are spinning at roughly 100K RPM, and running it dry would destroy the turbo fast. Therefore, I've built a pressurized oil system, which included an oil reservoir, oil pump, regulator, gauge, and braided lines.
Ignition System: I used spark plugs for the igniters for both the main combustion chamber and the afterburner. To supply the necessary 40,000 volts to the spark plug, I used a high voltage generator, and used buck converters to supply 3V to the generators from a 12V battery.
03 - CAD Modeling and Simulation Analysis
Following the preliminary design phase, I modeled the design in Onshape, and experimented with different designs of the oil reservoir, mounting structure, and placements of the remaining parts.
The combustion chamber consisted of the outer shell/housing, and an interior flame tube. The main purpose of the flame tube was to hold and stabilize combustion, and the size of the primary, secondary, and dilution holes was estimated from the compressor inducer area (following the golden rule of 30/20/50% of the inducer area respectively).
I then ran this engine through a CFD simulation (using ANSYS Fluent). I ran a cold-flow simulation to get an idea of the airflow in the combustion chamber and afterburner. My boundary conditions:
Inlet: mass flow rate (0.25kg/s, calculated from m=pAV), turbulence intensity (5%), and turbulent viscosity ratio (10)
Outlet: Gauge pressure (0 Pa)
The result gave me insight on how my geometry influenced airflow, and the image below (showing velocity) gave me insight to reduce the v-gutters in the afterburner as they were too restrictive and undermined the total thrust output.
MATLAB was also used to estimate the theoretical performance.
Overall, CAD models, CFD simulations, and MATLAB calculations gave this project a solid foundation, connecting the theoretical design concept to something real.
04 - Fabrication & Assembly
The fun part! In summary, the fabrication mostly consisted of welding (mostly TIG), angle grinding, cutting, using the drill press, and some plasma cutting. Most of the fabrication was completed in the Foothill Engineering Club's machine shop, and MakerNexus (public makerspace).
I started off with the flame tube; I bought a car exhaust (4in OD), used a miter saw to cut the needed length, and used the drill press to drill the necessary diameter holes. The tube was then welded to a circular flat mount (with clearance holes), which allowed me to screw in the flame tube assembly into the housing (allowing me to take out the flame tube and modify it later on). The next step was connecting the circular combustion chamber into a square turbo hot side inlet. In order to do that, I used the remainder of my car exhaust, cut triangular slits on one side, flatted out the slits, and with the power of heat bended the 4 slits together to form a rectangular exit, which aligned with the turbo hot side inlet. I then welded this connection to the chamber.
For the cold-side piping, I used a miter saw to cut 4 pieces (2in OD) with 22.5 angle (therefore 90 deg total), and weld them together to create a custom elbow pipe. To mount this pipe to the chamber housing (5.5in OD), I used a carbide hole saw (2in), and drilled an inlet hole at an angle to the housing to allow for compressed air to enter at an angle for the swirling pattern. In the end, I had one end of the pipe welded to the combustion chamber, and the other mounted to the turbo via a silicone pipe.
For the main fuel injector, I used a 8mm OD 304ss pipe, clamped/welded one end shut, and drilled 4 holes (1mm) radially outward. The fuel injector protruded in the combustion area by about 30mm (just were the primary holes of the flame tube started).
For many flat brackets and mounts, I used send-cut-send to plasma cut the parts for me (as I wasn't licensed to use the plasma cuter at my makerspace).
For the afterburner, I bought multiple cone pipes with varying diameters, welded them together (for extended nozzle and diffuser cones), and welded them to the main housing pipe (4in OD). Inside the afterburner, I had the fuel injection be in a form of a circular ring that was also a support for the v-gutters. I used a pipe bender to bend a 8mm OD tube into a ring (2in OD), and drill 1mm holes radially throughout the ring (8 holes total, 4 spraying radially out, 4 radially in). I then had the fuel pipe welded to the ring that protruded out of the housing and connected to the fuel assembly. The v-gutters and fuel ring were then welded together, and the whole assembly was welded inside the afterburner housing (6in from the front).
To mount the spark plugs, I would weld a nut to the other side of the main chamber/afterburner, making them screw in and easily replaceable if they burn out.
For the main structure, I used 19mm diameter square pipes, cut them into necessary pieces, and welded them all together. I added the triangles on the base for greater stability.
For the oil system, I fabricated my custom oil tank by welding 6 rectangular flat sheets together to form a rectangular tank (about 1.5L capacity).
The turbo itself was screwed to the main structure, in the event if the turbo needed replacement. Aligning all the brackets and clearance holes together was proven more difficult than I anticipated as I didn't account for pieces to warp and expand due to the heat when welding the structure/brackets.
05 - Testing & Results
Finally, after 7 months of researching, designing, simulating, and fabricating the engine, I got the chance to test my project!
In order for the engine to have a smooth first start, I first tested the oil system and its capability of sustaining the required pressure, as well as tested for any leaks in the system. I also tested the ignition system before mounting it to the final project.
After checking all the sub-systems, and priming the new turbo, I proceeded with my startup procedure;
I attached my leaf blower to the inlet
Ran my oil pump before spooling the turbo
Started up the leaf blower and waited for the chamber to gain sufficient boost
Once sufficient boost is reached, I triggered the main chamber spark plug, and opened the throttle valve.
If the combustion starts successfully, I would stop the spark plug, and I'd slowly increase the throttle until it has sufficient power for me to turn off the leaf blower.
I first tested this engine without the afterburner, which was a success! It even had the sound of a proper jet engine, which I personally got the most excited about. I then welded the afterburner to the bracket which connects to the turbo, and ran the full assembly test.
The engine with the afterburner started up as well! I decided to run the engine for about 40 seconds or so every test run, as the afterburner area got extremely hot. The highest temperature I recorded inside the afterburner (using a temp sensor) was 1150 degrees Celsius (2102 F), which was already past stainless steel strength capacity. Surprisingly, after testing the engine for about 10 test runs or so, all the components, including the turbo internals, were all in good condition despite me pushing the engine past its limits.
The afterburner didn't fully work as intended, and I had trouble properly igniting the propane (I had only a couple successful-ish runs with the afterburner active).
When it came to thrust output, the engine produced minimal thrust. However, end goal was to have it run self-sustaining, which was proven to be a success. Improving the engine for a greater thrust output is definitely a future project I'd consider.
All in all, this project was proven successful, and the main goal was reached!
