rcman50166
Member
Building 400HP Turboshaft
Joined: November 2016
Posts: 34 
|
Post by rcman50166 on Dec 6, 2016 13:48:54 GMT -5
This is some very interesting talk I'm reading. I was unaware turbocharger based engines were capable of such power output. My original post starts off with commercial engines because I assumed the power levels I wanted were unattainable with anything home made. I am completely open to the idea of building an engine to meet the specification. I would need to use a few turbochargers to reach the power output goal. But assuming I can financially get out ahead of a commercial option in the long run, I'd prefer it. I think 500hp at 75-90% power will allow me to keep enough designed safety margin from having to nanny the engines.
I need clarification though. Anders is saying I would need a massive amount of space to make an engine large enough to output 500-1000hp (ie school bus). However the information John is giving me suggests I would need 2-4 units. Who is exaggerating here? Would having all the units feed to/from a single combustor help/be feasible for space constraints?
|
|
|
|
Post by Johansson on Dec 6, 2016 14:30:18 GMT -5
I am probably the one who stretched the truth a bit regarding the space needed, at least if you use new top-of-the-line turbochargers and not old salvaged lorry turbos.  A friend and I have built a twin turbo engine with two Borg Warner S500 turbos, no beasts with their moderate 80mm inducers but if we used a freepower section instead of the large single can afterburner we could probably extract 200hp out of it. No matter how you do the finished 500hp DIY engine will be much more space consuming than a commercial engine, especially if you consider the need for an external large capacity oil system for the turbochargers. It will be insanely cool though and the amount of credit you will get for building your own engine instead of "just" use a commercial one will be huge! I vote for a DIY engine! Cheers! /Anders |
|
|
|
Post by racket on Dec 6, 2016 16:53:26 GMT -5
Hi
I wouldn't be thinking of anything bigger than 500 HP as it would require at least 3 turbos whereas sub 500 HP could be made with just a pair.
Big turbos don't come cheap , if new they'll be ~$US 4,000 each, almost impossible to source second hand in the size you need, even harder for a matched pair , so with ancillaries etc etc , you'd be looking at >$10,000 minimum just for the gas producers, add on your freepower stage bits which would require probably Garrett TPE331 aero parts and you can add on some more $,000s , a commercial engine starts to look attractive once into that sorta cost range, if you want >500 HP then the costs will escalate even further.
It might pay to reconsider what sort of vehicle you wish to play with , small lightweight and nimble with a single large turbo based engine in the ~200 HP range at "reasonable??" cost , or go for a larger heavier and much more costly arrangement with either a commercial engine or multiple turbos.
It is possible to feed a matched pair of turbos to a single combustor and has been done in the UK with a couple of large turbos.
The other alternative is using either a single or pair of large RC micro turbine engines feeding a freepower , but you'd be up for probably $US 20,000 just for the engine/s .
Playing with turbines can become expensive if we want new components/engines and is the reason why guys either make their own large engines or use older/obsolete commercial engines, there's not many choices :-(
Cheers
John
|
|
rcman50166
Member
Building 400HP Turboshaft
Joined: November 2016
Posts: 34
|
Post by rcman50166 on Dec 6, 2016 18:15:49 GMT -5
Hi John,
It is certainly possible to scale back the scope of what I want to do. A dual or single turbo setup would put the scope of the vehicle into the FSAE or Formula Ford class. Obviously non-compliant, but they are very good rule books for designing a safe vehicle with production parts readily available, keeping cost low. Sustaining the operation the car is a very high priority of mine. But don't confuse this with practicality. If I wanted to go that route I'd just buy a Miata. Hi initial cost is okay, high maintenance costs is not okay.
So, based on what I've learned so far, a dual turbo set up seems most plausible. I want to stay away from single turbo just for the sake of breaking away from the convention which is sort of the whole point.
Now I'm sort of wondering what my next move should be. I've never built one before, but I'm guessing a lot of that is just calculation, tuning and fabrication. I have no issues with that. I want to broaden my gaze a little to focus on the milestones of the project. Should I build a proof of concept? Is there anything to learn that this community doesn't already know?
How should I construct the power turbine? I looked at the TPE331 and it seems like it might be difficult to come across or maintain. I could attempt to build one using a modified turbocharger/s. I could make a axial single stage turbine as well. I know the suppliers who make the metals used in the commercial/military jet game. It would not be difficult to get the correct metallurgy. That solution would get expensive but it would have very high efficiency and I could package it how I want to conserve space. What are the more common ways to solve the free turbine issue? I have difficulty finding any details on how hobbyists do it.
|
|
|
|
Post by racket on Dec 6, 2016 19:06:06 GMT -5
Hi Heres the twin turbo unit www.youtube.com/watch?v=hLWckcSAJW-Do a Google search for Turbonator twin jet engine pics . Nick Haddock made this engine years ago and there was a lot of input from the DIY Turbine community, its probably the way to construct things , though now that its in a vehicle and operational , there'll be some additional info/advice available , also there are newer turbos with better performance now available , if I remember correctly Nicks engine flowed ~4 lbs/sec , this is more than an Allison 250 C20 heli engine of 400 HP............so >250 HP output would be very easy to obtain . TPE331 turbine wheels come up on Ebay from time to time , you'd be needing the third stage wheel .......................a "helpful" overhaul facility might provide a time expired one for free if they are happy with what you intend using it for, they may need to render it "destructed" , but still usable outside of an aero engine . I wouldn't worry about building a proof of concept ...................LOL, the guys here have already been down that road and should be able to steer you in the right direction . Making a DIY type engine using turbochargers is relatively "simple" and straightforward , all you need is the combustor which replaces the IC engine for burning fuel , and a bespoke lube system/pipe. The combustor/flametube is easily calculated and if the engine is equipped with a single fuel spray nozzle , either high pressure simplex of lower pressure dump type , fueling is very simple . If you could get hold of a couple of BIG remanufactured/second hand turbos from a huge CAT or Cummins engine, they often have multiples on their several thousand horsepower engines , you'd be able to easily make the engine at a reasonable cost , its just a case of making sure the turb wheel is Inconel 713C not the inferior GMR235 , you need turbos with comp wheel inducers of ~ 98 - 106 mm and the turbine scroll with the right A/R to "match" the comp flow for when the turbo is turned into a GT , generally speaking , diesel turbos have fairly well matched components . Cheers John |
|
rcman50166
Member
Building 400HP Turboshaft
Joined: November 2016
Posts: 34
|
Post by rcman50166 on Dec 6, 2016 21:33:57 GMT -5
So who can route me to the design theory of these engines? I found JetSpecs and an oddly detailed instructables on how to build them. There are a lot of assumptions made. Where are these numbers coming from? |
|
|
|
Post by racket on Dec 6, 2016 22:50:04 GMT -5
|
|
rcman50166
Member
Building 400HP Turboshaft
Joined: November 2016
Posts: 34
|
Post by rcman50166 on Dec 7, 2016 11:17:25 GMT -5
Great! I'll take a look in the next few days at that. My computer has been down for the past week so I can't do any major analytical or design work. In the meantime I'm going to look at turbochargers from various companies to see what's out there. Most of you guys seem to use Garrets. Good company, no doubt, but I want to see if there others that make larger options or might be more compliant to sending me better dimensions than what is publicly available. So far this is who I'll look at/contact:
ABB Turbocharging
Borg Warner
Bosch Mahle TurboSystems
D. Napier & Son
Garrett AiResearch
Holset Engineering
Honeywell Turbo Technologies
HS Turbochargers
IHI Tubochargers
KBB
MAN Diesel & Turbo
Mitsubishi Heavy Industries
Napier Turbocharges
Precision Turbo & Engine
Rotomaster
Turbocam
Turbonetics
Turbonique
Turbotechnics
|
|
|
|
Post by Johansson on Dec 7, 2016 12:18:11 GMT -5
Great! I'll take a look in the next few days at that. My computer has been down for the past week so I can't do any major analytical or design work. In the meantime I'm going to look at turbochargers from various companies to see what's out there. Most of you guys seem to use Garrets. Good company, no doubt, but I want to see if there others that make larger options or might be more compliant to sending me better dimensions than what is publicly available. So far this is who I'll look at/contact: ABB Turbocharging Borg Warner Bosch Mahle TurboSystems D. Napier & Son Garrett AiResearch Holset Engineering Honeywell Turbo Technologies HS Turbochargers IHI Tubochargers KBB MAN Diesel & Turbo Mitsubishi Heavy Industries Napier Turbocharges Precision Turbo & Engine Rotomaster Turbocam Turbonetics Turbonique Turbotechnics That is quite a list. Remember that the turbochargers mustn´t only have a large compressor inlet, both the compressor and turbine stage must be correctly sized both in themselves and in relation to each other in order to be suitable for gas turbine construction. Just asking if they keep large turbochargers in stock isn´t going to produce any useful answers, you need to know exactly what you want first. The Garrett GT6041 is proven to work and is one of the largest modern turbochargers out there that still is fairly lightweight. A train/boat turbo have huge compressors/exhaust turbines but the weight is terrible since it isn´t of a concern in those applications. |
|
|
|
Post by racket on Dec 7, 2016 14:59:49 GMT -5
Hi
Yep , quite a list .
The makers of large, limited number, industrial turbos like ABB, Napier etc , can be discounted as the cost of just a comp wheel will be more than a complete turbo from one of the popular manufacturers , also most of those very large turbos are just that, LARGE , and their turb wheels are generally a "low temp" variety as their exhaust temps are low in an attempt to achieve high SFC .
I must have spent hundreds of hours surfing the net for info on turbos ...........there ain't much..... Garrett is about the only one that provides both comp and turb flow maps , Holset is getting better , but theres so much proprietary information withheld due to the relationships between the turbo manufacturer and the engine companies .
Your only options for relatively lightweight compact high flow turbos at reasonable cost are the Holset HX82 , the Garrett GT6041 , Turbonetics Thumpers , the tractor pulling turbo suppliers like Columbus Diesel , Precision Turbo etc, but as Anders has said , the turbo needs to have matched components , unfortunately that generally isn't the case as with that Garrett GT5533R I mentioned in an earlier email , fantastic compressor stage but it has an undersized turb stage , so useless as a candidate for making a GT from .
The turb stage is often the limiting factor , it has to be big enough and constructed of Inco 713C so that we can run the required temps for good results , low temps mean low power outputs.
The largest readily available turbine wheel is ~129 mm inducer , with exducers up to ~112mm , the GT6041 is a tad larger , so this limits the actual mass flow that it can swallow , and yes , it has to voluntarily swallow the flow , we can't force it through as an IC engine can by the pistons supplying exhaust gases at a higher pressure than the comp discharge pressure , our turb inlet pressure is always lower.
Cheers
John
|
|
|
|
Post by racket on Dec 9, 2016 19:26:42 GMT -5
|
|
|
|
Post by Johansson on Dec 10, 2016 14:43:57 GMT -5
It says "Hydrodynamic 360° thrust bearing system" so I assume brass bearings. A twin turbo turbine with those would be truly awesome! If only Olov and I had 4 grand to spend on turbos for the next jet kick we would definitely consider a pair of Precision PT106 turbos! |
|
|
|
Post by racket on Dec 10, 2016 16:24:13 GMT -5
Hi Anders
Yeh , the thrust bearing sorta indicates "brass" , I guess being a "high performance" turbo supplier they don't like to advertise the fact they've only got "brass" bearings like common old diesel truck turbos, the funny part is , companies like ABB use "brass" in their huge ship turbos that are running continuously 24/7 at boost pressures Precision can only dream of .
LOL, 5.5 lbs/sec would certainly be "interesting" ;-)
Cheers
John
|
|
rcman50166
Member
Building 400HP Turboshaft
Joined: November 2016
Posts: 34
|
Post by rcman50166 on Dec 10, 2016 16:58:57 GMT -5
Oh wow, those do look good. Way less than what I was planning to spend as well. I might have to give them a call. $2300 is the MSRP. I'll bet I could find those for a few hundred under that. A new Garrett is something like $3500. A significant amount of development time is going to be solid modelling the system after doing the maths. I wonder if they can supply a .step I can use. I've already contacted them and I guiess I'll find out. Otherwise I might be able to make some sort of stand in that has the important dimensions in the right place.
Edit: Where'd you find the 5.5lb/s figure? I'd love a compressor map.
|
|
|
|
Post by racket on Dec 10, 2016 20:02:15 GMT -5
|
|
