SSCBD Posted March 15, 2017 Share Posted March 15, 2017 1 Link to comment Share on other sites More sharing options...
M61A1 Posted March 15, 2017 Share Posted March 15, 2017 If you don't like the price of a rotax, you won't like the price of an Allison c250. 1 Link to comment Share on other sites More sharing options...
scre80 Posted March 15, 2017 Share Posted March 15, 2017 You can see it in action here. Link to comment Share on other sites More sharing options...
Nico13 Posted March 15, 2017 Share Posted March 15, 2017 Many years back I used to fit those to the Nomad N22 and N24 at GAF Avalon, brought back a few memories. The series we were fitting back then in the late 70's was 250 B17B, the chopper engine turned upside down. Link to comment Share on other sites More sharing options...
Geoff_H Posted March 15, 2017 Share Posted March 15, 2017 Gas turbines are great. Providing that the compressor gives a high pressure and the cooling of the blades allows a high inlet temperature. Otherwise the weight of the turbine is low but the fuel load for any travel distance is huge.The Cri Cri has had several models built with model jet engines ( a Turbine with fewer turbine blades, well almost) had elementary low pressure compressors, and are extremely inefficient, limiting flights to not much more than flight minimum reserves. Link to comment Share on other sites More sharing options...
facthunter Posted March 15, 2017 Share Posted March 15, 2017 To get maximum advantage you need height for cruise and that means pressurization. Nev Link to comment Share on other sites More sharing options...
Geoff_H Posted March 15, 2017 Share Posted March 15, 2017 The gas turbine and the piston Engines have a lot in common. The compression ratio, one from displacement the GT from how good the compressor is. A high efficiency GT will generate 250psi at the combustion chamber. The high efficiency GT has a compression ratio of around 15 to 1. As with a piston Engine the GT be less effective at altitude by the same ratio as a piston Engine. So a high efficiency GT will use a lot less fuel at altitude. Link to comment Share on other sites More sharing options...
flyvulcan Posted March 15, 2017 Share Posted March 15, 2017 Perhaps a realistic alternative will be the engine that I have been developing and am in the process of launching. It is still at least 2 years away for first deliveries but we are making steady headway to that target. The engine shown in the above video is our Proof of Concept engine. It uses a gas generator designed by us but for cost reasons, off the shelf components were used for the interstage, power and gearbox sections. These OTS components are by no means optimized. Indeed, our computer analysis determined that the power turbine section would be offering significantly lower efficiency than needed which proved to be true - the good news is that the design optimization program will result in a power turbine that will deliver the required performance to meet the target specifications. The POC engine is shown on its dyno in the video and the video is of an early test run that validated the theoretical analysis that had been completed on the POC engine design. The engine is only being run to around 70% gas generator capability in the video. The entire engine is undergoing a full redesign, based on the results of our testing/analysis and also to incorporate some technical innovations that will significantly enhance fuel efficiency and reliability/TBO to achieve our target specifications. The anticipated specs for the commercial engine are T/O power 120hp, optimum cruise power (best SFC) 100-110hp, installed weight <120lbs/54kgs, fuel burn at 100hp around 8gph. The prop will be a constant speed unit and engine/prop will be controlled by a single lever (very simple). The engine's ECU/FADEC will automatically ensure no engine limits are exceeded and will also offer full data acquisition to facilitate engine health monitoring. Cost is expected to be around the same price as a Rotax 914, give or take a bit. 3 2 Link to comment Share on other sites More sharing options...
ben87r Posted March 15, 2017 Share Posted March 15, 2017 If you can make those figures that will be a winner. It my maths are right that's about 20% less fuel than a PT6? Link to comment Share on other sites More sharing options...
SSCBD Posted March 15, 2017 Author Share Posted March 15, 2017 Just in general terms - What is the expected TBO, and maintenance times and costs expected. Link to comment Share on other sites More sharing options...
M61A1 Posted March 16, 2017 Share Posted March 16, 2017 Link to comment Share on other sites More sharing options...
Geoff_H Posted March 16, 2017 Share Posted March 16, 2017 A 25% efficiency is what the numbers suggest. Low for a modern gas turbine. Having been involved in the design of gas turbines for Siemens in Florida I can see that a low efficiency GT is possible with basic tools. The TIT for such efficiency is quite low, what are you expecting and what materials and cooling are you using for your Turbine Inlet blades? The blades and combusted are the expensive bits. I hope that you can get the price so low, but that is not my experience but am hoping that you can! Link to comment Share on other sites More sharing options...
flyvulcan Posted March 16, 2017 Share Posted March 16, 2017 Answering in no particular order, unrecuperated, the best SFC that we would likely get for this small scale turbine engine is around .60 lbs/hp/hr. If recuperated, we could be close to .55 lbs/hp/hr (so 100hp optimized cruise power setting = 55 lbs/hr @ an sg of 6.76 lbs/gal for JetA = 8.1 gal/hr). We plan to recuperate to get the SFC down. So its not sipping fuel at 100hp but at the same time, the Rotax 912iS etc. cannot run continuously at 100hp but the 914 at 100hp isn't burning that much less fuel. The Rotaxes only start to sip fuel at their lower power settings. Ultimately, we'd like to get the TBO out to 3000+ hours. Given the simplicity of the design and the lower acquisition/manufacturing costs for exotic and conventional materials these days, we anticipate an overhaul cost of around US$5-6000, so probably less than the cost to overhaul the Rotax at 2000 hours. Routine maintenance is expected to be significantly less than for a piston engine. The actual materials to be used, the cooling requirements and the need for ceramic coatings on the hot section components is being investigated by our engineers as part of the optimization program for the design. Ceramic coatings may not be required but if it is, a number of recently developed cost effective solutions are available. The addition of a recuperator to our base design will result in the usual re-analysis of all components and that exercise is about to be commenced. Material requirements will be identified as part of that process. Current power turbine/NGV assembly cooling on the POC engine is from bleed air tapped from the compressor. We did a low-key introduction of our engine to the experimental/LSA airframe manufacturers at Oshkosh last year. It was an interesting experience observing their attitude change from our initial introduction where we advised them that we were developing a small turboprop engine (skepticism/disbelief) to when we showed them the video and explained where we were at in our development program. The excitement that was evident from the manufacturers was validation to us that there is a strong desire for such a product and the offers of support from those manufacturers in the form of test airframes to flight test the engine in as well as offers to provide airframes as demonstrators for the engine was very pleasing for us. A number of leading manufacturers expressed their desire to work with us through the development program such that when the engine was ready, they would have designed a totally new airframe to take advantage of the distinctive features of the engine, i.e. low weight, small size, low frontal area etc. 1 Link to comment Share on other sites More sharing options...
flyvulcan Posted March 16, 2017 Share Posted March 16, 2017 BTW, you can probably guess what powerplant I hope to put into the Lightning Bug... Link to comment Share on other sites More sharing options...
bexrbetter Posted March 16, 2017 Share Posted March 16, 2017 That's great news Flyvulcan, I suggest you start a thread from scratch because not everyone will find this buried in another thread, I for one didn't initially go past the first thread as I wasn't really interested. 1 Link to comment Share on other sites More sharing options...
flyvulcan Posted March 16, 2017 Share Posted March 16, 2017 Thanks Bex. Done 1 Link to comment Share on other sites More sharing options...
Geoff_H Posted March 16, 2017 Share Posted March 16, 2017 Any reply on blade material and cooling method? This is what affects the efficiency the most. When at Siemens we paid for the blade technologies to Pratt and Whitney, it involved exotic materials and very fine cooling holed that delivered uncompusted air to the leading edge of the blades so that the sir formed a blanket between the cooled combusted air. OK we were after 45% efficiency, but lower quality blades can only take a lower temperature and it is this temperature that controls blade life and efficiency. I am truly interested and would like you to succeed. Link to comment Share on other sites More sharing options...
spacesailor Posted March 16, 2017 Share Posted March 16, 2017 I think if you can get enough horses you can almost "take-off" before moving! notice the torque twisting the chassis . ( home built motor, from a billet block of aluminum). Pic thanks to "Sainty racing" Link to comment Share on other sites More sharing options...
spacesailor Posted March 17, 2017 Share Posted March 17, 2017 You guy's don't want "sound" on this one, do you. Fantastic sound quality when at full bore. spacesailor Link to comment Share on other sites More sharing options...
Raytol Posted March 21, 2017 Share Posted March 21, 2017 Hi flyvulcan, I have three projects that could use your turbine. I'm not that fussed about saving fuel. Are you going to be able to supply the gas generator without the gearbox as well? Ray Link to comment Share on other sites More sharing options...
flyvulcan Posted March 21, 2017 Share Posted March 21, 2017 Hi Ray, You may remember me from around 1985. We fired up my pressure jet engine next to your hangar at Camden, making a lot of noise! At that time, we were considering putting 2 of them on your ultralight. Those engines never did work properly... We aren't really keen to offer the engine as a pure jet. We intend to have a turbofan derivative. I haven't got time to type now as I have a very early morning flight tomorrow. I'll contact you when I get back from my trip in around week. Cheers, Dave Link to comment Share on other sites More sharing options...
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