Thread: Remote Turbo's?

Originally Posted by stirlsilver

At the end of the day, there is more energy going in the exhaust system at one end (from the engine) than what is going out (into the turbo) because there is energy losses in the pipe. Without going through the thermal dynamic equations to show this, the energy content in the exhaust gas reduces as it goes along a pipe because you have heat being radiated/convected out into the atmosphere. This energy that is lost is now no longer in the gas and as a result, less energy is being delivered to the turbo for it to produce shaft power for the compressor.

Correct, but only if you are talking about a positive displacement pump.
with a turbine and more so with a centrifugal turbine ( key word centrifugal) Mass is the motivator, energy is Mass X velocity.

Add heat and you get much more velocity but less Mass per volume.

Have a look at Jet engines and why they have moved away from centrifugal to Coaxial.

Originally Posted by stirlsilver

Perhaps having some length between the engine and the turbo is beneficial, since the exhaust gas is delivered in pulses rather than a continuous flow, but i'm really not sure here. But from a thermal dynamics stand point, less pipe the better.

You could even use the sonic pulses to speed up the Velocity, or to smooth out the gas pulses or us the gas pulses to scavenge, not of which is an option with close mounting a turbo. Infact a close mounted turbo instantly will decrease the efficiency of a IC but the benefits of boost exceed this loss.

Originally Posted by stirlsilver

I would be interested to see this chart actually. And you are probably right, depending on what temperatures hot or cold are, the cold gas at 7psi could be denser than the hot gas at 14psi.

I haven’t seen one for years, now days I work with water mainly. Had a quick Google with no luck.
if I remember correctly the most efficient expansion for energy used was only about 380 deg C to double the expansion you needed to go to 1200 deg C i think?

Originally Posted by stirlsilver

By the way, I'm not intending to take stabs at you here or anything, I just enjoy these sorts of discussions

Same here, I understand completely what you are saying, i just have a different understanding of the application. Having said all that if i was to mount a turbo on the rear bar of the county i suspect i would be quite disappointed. The R&D is massive

Temperature
- t -
(oC) Density
- ρ -
(kg/m3) Specific heat capacity
- cp -
(kJ/kg K) Thermal conductivity
- l -
(W/m K) Kinematic viscosity
- ν -
(m2/s) x 10-6 Expansion coefficient
- b -
(1/K) x 10-3 Prandtl's number
- Pr -
-150 2.793 1.026 0.0116 3.08 8.21 0.76
-100 1.980 1.009 0.0160 5.95 5.82 0.74
-50 1.534 1.005 0.0204 9.55 4.51 0.725
0 1.293 1.005 0.0243 13.30 3.67 0.715
20 1.205 1.005 0.0257 15.11 3.43 0.713
40 1.127 1.005 0.0271 16.97 3.20 0.711
60 1.067 1.009 0.0285 18.90 3.00 0.709
80 1.000 1.009 0.0299 20.94 2.83 0.708
100 0.946 1.009 0.0314 23.06 2.68 0.703
120 0.898 1.013 0.0328 25.23 2.55 0.70
140 0.854 1.013 0.0343 27.55 2.43 0.695
160 0.815 1.017 0.0358 29.85 2.32 0.69
180 0.779 1.022 0.0372 32.29 2.21 0.69
200 0.746 1.026 0.0386 34.63 2.11 0.685
250 0.675 1.034 0.0421 41.17 1.91 0.68
300 0.616 1.047 0.0454 47.85 1.75 0.68
350 0.566 1.055 0.0485 55.05 1.61 0.68
400 0.524 1.068 0.0515 62.53 1.49 0.68

Were do you mount the airbox and how do you run 16' of 1 1/2 pipe underneath a defender?.How much lag will you have after dumping 18' of exhaust gas then getting back on the throttle?. Pat

Originally Posted by clean32

Correct, but only if you are talking about a positive displacement pump.
with a turbine and more so with a centrifugal turbine ( key word centrifugal) Mass is the motivator, energy is Mass X velocity.

Add heat and you get much more velocity but less Mass per volume.

Have a look at Jet engines and why they have moved away from centrifugal to Coaxial.

Sure, Mass x velocity is the rate at which work is being done (watts, hp, kW etc). But as far as I understand it, mass is just a means of transporting energy from one point to the other. You say that mass flow rate is that does the work in turning the turbine, sure I agree with that. But, you don't have any mass flow without a pressure differential to move it in the pipe.

I suppose you are taking the view that the engine has to do some work move exhaust gas out into the exhaust system and through the turbo, and regardless of the temperature of the gas that mass needs to go past the turbo, but what moves this mass is the fact that gas wants to go from a high pressure zone to a low pressure zone and these pressures change depending on temperature.

Say you had two balloons hooked to a small turbine which you could extract some energy from and measure, If both balloons were inflated with the same amount of mass (x kilograms of air) at the same temperature. And you then heated one balloon and cooled the other. You would phycially see the cold balloon reduce in size and the hot balloon increase in size, if you then vented these balloons through the turbine and measured the amount of work done I would expect to see that more work is done by the hot balloon than the cold one despite the fact that they both have the same mass of air stored within them.

Also with the centrifugal and coaxial in jet engines, i'm assuming you are talking about a compressor here and not a turbine? I can't think of any gas turbine engines that use a centrifugal turbine?... and I did aeronautical engineering so this is rather suprising. I know that centrifugal compressors are good at achieving high compression in a single stage, but they aren't very efficient which is why they have gone to multistage coaxial compressors... but no idea as a turbine.

Originally Posted by clean32

i suspect i would be quite disappointed. The R&D is massive

Originally Posted by PAT303

Were do you mount the airbox and how do you run 16' of 1 1/2 pipe underneath a defender?.How much lag will you have after dumping 18' of exhaust gas then getting back on the throttle?. Pat

Mate must be getting late

Originally Posted by stirlsilver

Sure, Mass x velocity is the rate at which work is being done (watts, hp, kW etc). But as far as I understand it, mass is just a means of transporting energy from one point to the other. You say that mass flow rate is that does the work in turning the turbine, sure I agree with that. But, you don't have any mass flow without a pressure differential to move it in the pipe..

Correct,, turn it the othere way around energy moves mass.

Originally Posted by stirlsilver

I suppose you are taking the view that the engine has to do some work move exhaust gas out into the exhaust system and through the turbo, and regardless of the temperature of the gas that mass needs to go past the turbo, but what moves this mass is the fact that gas wants to go from a high pressure zone to a low pressure zone and these pressures change depending on temperature..

correct, regardless of temperature

Originally Posted by stirlsilver

Say you had two balloons hooked to a small turbine which you could extract some energy from and measure, If both balloons were inflated with the same amount of mass (x kilograms of air) at the same temperature. And you then heated one balloon and cooled the other. You would phycially see the cold balloon reduce in size and the hot balloon increase in size, if you then vented these balloons through the turbine and measured the amount of work done I would expect to see that more work is done by the hot balloon than the cold one despite the fact that they both have the same mass of air stored within them.

along as you didn’t cool the balloon down to where the internal pressure was = or less than ambient. AND each turbine was designed for each different application, the energy measured would be the same.

Amazing aye

Originally Posted by clean32

along as you didn’t cool the balloon down to where the internal pressure was = or less than ambient. AND each turbine was designed for each different application, the energy measured would be the same.

Amazing aye

you are going to have to explain that one to me. Bit of a thread hijack... but it is still sorta relevant.

Also, see above, I made a comment on the centrifugal turbines which you may have missed as I edited my post afterwards.

Originally Posted by stirlsilver

Also with the centrifugal and coaxial in jet engines, i'm assuming you are talking about a compressor here and not a turbine? I can't think of any gas turbine engines that use a centrifugal turbine?... and I did aeronautical engineering so this is rather suprising. I know that centrifugal compressors are good at achieving high compression in a single stage, but they aren't very efficient which is why they have gone to multistage coaxial compressors... but no idea as a turbine.

Centrifugal compressors are not good at achieving high compression, that’s why they went to muilty stage centrifugal compressors, and then on to mulity stage coaxial, and to believe that they have compression ratios of over 35:1 and a bypass of 45:1 what would Whittle be thinking now ( probably Dam Germans he was on the wrong track)

A centrifugal turbine was dropped really early on, about the same time as muilty cans got joined together.