Inside the intake of the engine there is a flapper valve that allows start air which also acts as cool down air during shutdown, this prevents pressurized air from escaping out the intake. It was debated to pull all induction air through an oversized blower, but the flapper valve was devised to prevent unnecessary work on the compressor. The valve was constructed out of a piece of sheet metal that rests against a short section of cut PVC pipe in the induction tee. No springs or actuators , it works purely off of differential pressure and provides the engine with a simple automated method for start and cool down air.
Turbocharge Based Gas Turbine
At this point the engine was able to run for a very short amount of time before oil temperatures were too high. The blower you see attached was plumbed into the intake and provided cool down air during shutdown as well as start air. Impingement air through the hardline running into the compressor housing provides the start spool in conjunction with the cool down blower. A automated method for bypassing air to the intake had to be devised to prevent all the airflow from being pulled through the blower. The solution was a flapper valve in the tee which has the intake screen attached.
Getting close , this was a mock up of all the main components, the only component missing was the exciter box. Everything fit fairly well with the exception of the oil drain tube , originally it was planned to be a stainless hardline but that soon turned into a rubber one due to bad planning.
One of the ideas I had floating around when I was removing the wastegate from the turbocharger was a simple fuel governor/over speed limiter that utilized the actuator. The actuator was set at the turbochargers operating parameters so using it to limit fuel at that given point was desirable. A small bracket was made and a 1/4" ball valve was set to be closed when the actuator was given a preset P3 pressure. Later with the initial testing of the engine , the engine was given excessive fuel while it was just above self sustaining speed and during rapid acceleration , the engine suddenly stopped and maintained its speed when the actuator engaged.
The main components for the fuel and oil system seen above. The oil reservoir was made out of 2 1/2" stainless with supply and return bungs welded. I did some searching around for premade reservoirs and tanks that could function as the same purpose, but most were very expensive. In the end the custom build one was certainly the better choice due to less adaptors and fittings utilized. Other oil components seen are the Tilton transmission oil cooler pump, oil cooler and oil filter adapter. The Tilton transmission oil pump has been a solid choice for the oil requirements of these engines. The pump comes preset at 60 psi with the ability to be adjusted between 20 to 120 psi and can handle the high temperatures associated. Fuel system components seen are the Start solenoid, Run solenoid and P3 governor.
An airbox was built to cover the intake screen and direct all induction air through the oil cooler.
The fuel system is a basic one consisting of two solenoids and two needle valves which are then fed through the governor. This system provides two metered amounts of fuel that allowed the engine to be started with two toggle switched ( Run and Start) rather than slowly metering fuel via a valve upon startup. A future component would be a accumulator that would smooth the transition between the Run and Start.
The intention of this project was to build a small gas producer unit that was to be used for a separate power turbine module. Self contained and easy to start was the main goal in conjunction with keeping it as compacted as possible. The ideas of a pull through oil cooler and utilizing the oil reservoir as the frame had been floating around my head for this project as well. The basis of this engine was a Garrett T3 series turbocharger that was pulled from a piece of unknown diesel farm equipment. The turbo was a "new take off" unit that found its way on eBay for 150$ . It's certainly not a common model seeing the oil feed and drain were a mystery thread pitch.