Let off the throttle slowly.......

Eric

 

Yeah, thought this was covered, but maybe not.

Turbo bark specifically is caused by the sudden loss of turbine Hp at high boost.

The turbine and the compressor are always in perfect balance Hp wise. This is because they are connected by a solid shaft. At a steady state condition the compressor consumes 100% of the Hp generated by the turbine. A condition of steady state can be thought of when ever the RPM of the turbo is constant. The amount of Hp the turbine can generate is directly proportional to the pressure, temperature and flow rate of exhaust gas it is recieving from the engine. If the turbine is generating more Hp that the compressor is consuming then the RPM increases until the Hp being consumed (loading) of the compressor matches it. Of course in the process, the compressor builds more pressure and the process is only transitional. The opposite is what produces a bark.

So now to barking....

Condsider the engine running at 2700 RPM under acceleration. Boost is 35 psi and then the throttle is rapidly let off. Consider now that the exhaust gas flow from the engine diminishes rapidly. This in turn causes a rapid decrease of turbine Hp because that is the motive force for the turbine. Now the compressor has also just lost a major portion of its motive force and RPM of the turbo drops off rapidly. This drop in RPM of the compressor means that it can no longer sustain the pressure increase across it. So now there is higher pressure in the manifold than the compressor can hold back at its lower RPM. The pressure wins and air back flows through the compressor to the air filter. The time period for this to occur is really short, like less than 1/2 a second, and is very massive. Thats what produces the barking noise.

Sorry to be long winded again. Follow Eric's advice and barking is greatly diminished. I have found that tuning my waste gate helped a ton.

Jim

 

Yep, NOSEEUM has it perfectly correct.


qmcdt, you TRAITOR !!! how could you go from a nice big steamer to a little ole gas turbine cogen !!! lol just kidding with ya.

But I am more than slightly biased to big coal-fired steamers !!!

Burning up NGV's are ya......Sounds like to need to have the OEM look at adding more/larger perforations to your combustor ....... Drop the flame front velocity and pull that flame in tight and get the burn over with sooner to drop your first stage temps.... Alas, but then thats a NOx-creatin monster ... ARggghhh.. Does'nt it just drive you nuts how combustion based NOx control flys in the face of traditional good combustion techniques..... I'm sure thats whats causing your high 1st stage temps, is a late/slow burn, low-NOx combustor....You're still burning going through the NGV and entering the 1st stage..........You could just add an SCR to it to control NOx and then covert it back to a standard combustor....


Kp

 

600megawatts. We haven't burnt up anything here. We have dry low NOX on the unit and it just won't fire as hard at +20 as it will at -20. We could spray intercool it but we are pretty much a dry plant. No cooling towers, no nothin. Just the coffe maker, the toilets and a shower. Coal was dirty, nasty and hard on my lungs. When we run out of natural gas, syn gas, oil and asphalt I'll be back to burnin it, don't you worry. Back to the main point though, I have thought of a way to end turbo bark with out having to back out of the throttle nice and gentle. Sometimes you have to go from one peddle to the other in a big hurry, hech mine coughs if it don't feather out of it going from 3rd to 4th while towing. It's really noticable with the cold air intake. If you know a good machinest we should build a prototype and then sell it to someone like ATS or NADP.