Homebuilt Turbo-Turbine Engine with a Twist  
 

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11/17/05- The basic structure of the XCombustor has been essentially completed and the final touches are going on to prepare it for initial testing. In the meantime, I have begun production of the hot side elements that will duct the hot gases produced in the XCombustor into the power turbine assembly first, and then into the turbocharger assembly. I decided to use stainless steel to build the hot side ductwork, for its temperature resistance and low thermal conductivity. So far, I have a few pieces of stainless sheet of varying thicknesses, some pre-made parts which I will have to weld to stainless flanges, and a rolled and seam welded tapered duct that will act as the main component of the nozzle box assembly.

The pictures on the top right and bottom left show the main nozzle box duct and the existing JFS-100 power turbine nozzle.The duct will feed high energy gas from the XCombustor into the nozzle assembly and power turbine. The duct was cut from .060 stainless sheet, rolled, and seam welded. Later, stainless flanges I am having made will be Mig welded to both ends of the duct to provide the necessary mating surfaces. The bottom center picture shows the seamless tapered stainless pipe segments and stainless turbo inlet flange that I received from a fabricator. I will stack and mig weld these segments together and onto the flange to bolt onto the turbocharger. On the large end, I will weld a specially made stainless flange which I will clamp into the large exhaust outlet on the JFS-100 power turbine assembly, as shown in the picture on the bottom right. This completed pipe will be the interstage turbine ducting. Gas that has been expanded through the power turbine will then make its way through this pipe into the turbo turbine, to drive the compressor before it is exhausted to the atmosphere. There are a few more parts I must fabricate to form the nozzle box assembly, but I must wait until I receive the flanges.

 

8/30/05- As progress on production of the XCombustor continues, I am continuing to work on the design and production of the turbomachinery portion of the project.

Based on calculations of the XCombustor airflow capacity, I determined what the airflow and pressure ratio requirements of the compressor will be. From this I selected an appropriate turbocharger assembly for the project, and have gone out and bought one.

The Garrett T3/T40E Hybrid Turbocharger

The nature of the XCombustor, according to our calculations is that it will require far less airflow for a given power output than a typical gas turbine engine, so although the Garrett T3/T04E hybrid turbocharger may seem a tad on the small side for the power requirements, it should work very well.

Since the compressor is rather small, we are quite sure that the power requirements to drive the compressor turbine will be much less than that of typical gas turbine engine for the same power output. As a result, we decided that it would make more sense to place the power turbine upstream of the compressor turbine, something that it is very uncommon in gas turbine engines. (though not completely unheard of) As a result, I have altered the basic architecture of the engine with regard to gas flow, as shown by the following sketch.

 

For this project I will be using the power turbine assembly from my first JFS-100, whose gas producer went into creating the JFS-100 Turbojet which is in the original Turbokart. This JFS was also the first gas turbine engine that I owned. The picture on the far right shows the turbocharger assembly next to the power turbine assembly. With all of the turbomachinery in my hands, all I need to build now is the necessary ductwork to connect everything up, and the frame in which I will mount the engine and all of its accessories. next entry

 

 

7/08/05- Production of the first prototype XCombustor unit has now begun, and is in the very early machining and fabrication stages. We expect to have a working prototype of the combustor in the next few months for initial testing. We are already beginning to align ourselves with working collaborators who are willing to donate materials and help to the project to become part of this potentially revolutionary concept.

On my end, I have begun designing the basic turbomachinery and drive components as represented in the sketches below. (Forgive the poor drawing skills, I'm a lunatic, not an artist, damn it!!!)

The sketch on the left shows the basic layout of the turbomachinery. This will consist of a reasonably large automotive turbocharger assembly whose turbine must eventually feed into a second turbine, the free power turbine assembly. Since we expect to derive around 100 shaft horsepower from this engine, I saw fit to use the power turbine assembly from a JFS-100/13A, a small gas turbine engine that I am most familiar with, same as the engine in my Formula Turbokart project. In order to smoothly integrate gas flow from the compressor (turbo) turbine to the free power turbine, I will have to fabricate a nozzle box assembly. Superficially, the nozzle box assembly will resemble a jet pipe in reverse. Flanges will join the two structures together, a cone will smoothly guide gas flow to the power turbine, and the power turbine nozzle assembly from the JFS-100 will be integrated into the assembly to accelerate the gas flow so that it may impinge upon the turbine with the greatest force possible. Notice how I will use a large A/R ratio on the turbo turbine to allow a good portion of the gas energy to make it to the power turbine, and to also minimize backpressure on the system. The sketch in the middle shows the basic layout of the nozzle box assembly. On the right, I show how I will extract shaft horsepower from the power turbine assembly. This will be a very similar arrangement to the drive on my Formula Turbokart shaft driven go kart, with a few minor improvements. I will use a broached shaft supported by a bearing in a machined aluminum carrier to which a typical high performance dirtbike chain sprocket will be mounted. I can then take drive off of the sprocket to drive the external load. The whole thing will be supported in a welded steel box section tube frame which I will fabricate.

As I continue designing, I will start looking to procure the parts that I need. The first thing will be a turbocharger assembly. I have calculated the flow and pressure ratio that I will need from the compressor at this point and will begin my search for a suitable turbo. Stay tuned for more developments. next entry

6/26/05- I am embarking on a brand new project here at Turbokart.com which is somewhat of a special project for numerous reasons. Because of the special nature of this project, I have decided to call this Project X. (Not the most original name, but work with me here.)

Project X is basically, at this point, a Do It Yourself, homebuilt gas turbine engine that is being designed and built by a team of individuals including myself. In case some of you are not aware, there is a whole network of people out there, possibly numbering in the hundreds, who have built home made gas turbine jet engines by using an automotive or truck turbocharger assembly connected to a fabricated combustor. Some run on gaseous fuel, some run on liquid fuel, and I have seen some very impressive units with afterburners that make upwards of 100 lbs. of thrust.

There are two elements that differentiate Project X from a typical DIY gas turbine project: The first distinction is that the engine will be a free shaft turbine, with two turbines; one to drive the compressor and one to drive an output load. Some have attempted this and have been successful, but for this project, we are looking for a power ouput on the order of 100 shaft horsepower, which, I believe, would make it one of the most powerful, if not the most powerful, turbo derived DIYGT engine around.

The second distinction which really makes this project special is that the engine is being built with a top secret, experimental combustor unit which, together with the turbomachinery, will become the basis for the development of a novel type of gas turbine engine. The completed engine will serve as the first developmental prototype in the design of this new engine concept, with targets such as greatly reduced fuel consumption across the complete operational range, more rapid response, cleaner emissions, lower production costs, and a wider range of applications than current gas turbine engines.

Due to patent considerations, very little information about the combustor unit can be disclosed at this point. However, since building of the prototype is a gas turbine project, I will be documenting progress on the project on this webpage. Currently, the experimental combustor unit is in the design and engineering phase, with production of a prototypical unit which I will refer to as the XCombustor slated to begin very soon.

Once it is determined that the XCombustor will be operational according to our pre-set parameters, I will begin fabrication work for the turbomachinery portion of the project, which is the portion of the project that I am in charge of, due to my experience in the area of small gas turbines.

In the meantime, I am working on designing the turbomachinery. I will post some pictures and sketches in the near future. next entry

 

 

 
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