Turbo normalizing

[Downunder]

To what degree does turbo normalizing assist? Is it able to be calculated?

Atmospheric pressure at 10 000 is about 2/3 that of sea level.

So turbo normalizing would boost me 1/3 more power than I would be getting normally aspirated.

I hit an aerodynamic wall at about 90 kts at sea level (I can get 100 kts with alot more fuel burn)so I'm guessing that barrier would be increased in thinner air higher up.

Currently, I'm still able to get about 90 kts at 9500 WOT with the lower power/rpm available, but I'm guessing it's a power level restriction rather than an aerodynamic restriction keeping my speed low.

It can't be as simple as my aerodynamic wall being 1/3 higher if atmospheric pressure is 1/3 less can it?

 

I'm wondering what speed gain I would get At 10 000 with a turbo normalized engine?

I also imagine going higher again (16 000) would yield far better performance gains if the turbo can keep up with the compression requirements?

 

 

[skippydiesel]

Turbo normalising is a technique almost exclusively use in aircraft.

 

Normally achieved using a turbo charger (exhaust powered turbine) to compress the air entering the engine, so as to maintain sea level (or slightly higher eg Rotax 914)) fuel burn efficiency at altitude.

 

To prevent over boosting  a "waist-gate" is employed to reduce the amount of exhaust gas flowing over the driven turbine. Waist-gate opening/closing is controlled automatically by the pressure changes in the inlet manifold or manually by the pilot with reference to an inlet manifold pressure gauge.

 

This system has no effect on propeller/wing (airfoil) performance at altitude.

 

I suspect the speed  "wall" you mention can only be changed by reducing drag on your airframe. Air density will be a factor in this. So I would expect that you would see significant improvements in air speed using an engine that will be relatively unaffected by altitudes into the mid to high teens however you may also need to have a propeller that can adjust to perform well in a  thinner atmosphere. 

 

You  will also need to take steps to mitigate the effects of reduced O2 and air density on yourself and

[spacesailor]

You need a Bigger turbo for top end revs in thin air,.

spacesailor

[M61A1]

A waist-gate.  🤣

[Thruster88]

A factor of about 1.17 applies to turbo normalized aircraft. 90kias @ 9500 = 108tas x 1.17 = 126knots true airspeed. 

[skippydiesel]

12 hours ago, spacesailor said:

You need a Bigger turbo for top end revs in thin air,.

spacesailor

Qualified agreement - The sizing of turbo chargers is very much on engine application.

 

In the high speed sports automotive world, where acceleration is the objective,  a single turbo is unable to spool up (accelerate) fast enough to supply the required "boost" from low engine rpm to high, so a staged system is used where a small (mainly refers to diameter of turbines) responsive turbo gives initial response,  with a larger turbo "taking over" at higher rpm.

 

Some aircraft applications use two equal sized turbos but I would speculate that this is for minimising space under the cowling in a boxer engine application, rather than further power enhancements.

 

In a near constant rpm application - aircraft/pumps/tractors/boats etc, single turbo's are sufficient and are usually sized to give the best response over the optimum (quite narrow) rpm range. Where a particularly constant rpm is projected, a waste gate may not be required.

 

I have no personal experience of sizing turbo's for aircraft (or anything else) but would speculate that the turbo would, as you say, need to be sized to give an acceptable level of boost at the projected maximum effective altitude. The waste gate is a vital component of any aircraft boost system as an over-boost would likely see an engine failure quite quickly.

 

Further - While all turbo charged engines will have improved altitude performance, it seems to me that an aircraft engine, of a given capacity, can also be designed to be turbo charged/enhanced as a way of increasing performance (volumetric efficiency) and therefor better power to weight ratio. Turbo Normalised engine do not have greatly improved performance BUT there advantage is to be able to maintain sea level performance to much higher altitude than a naturally aspirated equivalent.

 

 

 

[facthunter]

Turbo charged P & W 1830s operated above 30,000 ft. It's all going funny for pistons at that height. HT ignition leakage and oil freezing. the prop has less drag in the thin air and may need more blade area so it doesn't end up too coarse a pitch angle.. Nev

[skippydiesel]

1 hour ago, facthunter said:

Turbo charged P & W 1830s operated above 30,000 ft. It's all going funny for pistons at that height. HT ignition leakage and oil freezing. the prop has less drag in the thin air and may need more blade area so it doesn't end up too coarse a pitch angle.. Nev

To say nothing of the effects on the pilot/crew

[facthunter]

Two problems there. Hypoxia and the OAT which is around minus 40 C, frequently. Nev

[skippydiesel]

43 minutes ago, facthunter said:

Two problems there. Hypoxia and the OAT which is around minus 40 C, frequently. Nev

AND the negative effect of low atmospheric pressure on the body's ability to process gasses

[Downunder]

8 hours ago, Thruster88 said:

A factor of about 1.17 applies to turbo normalized aircraft. 90kias @ 9500 = 108tas x 1.17 = 126knots true airspeed. 

Thanks for that. I should have qualified the 90 kts as being TAS, not IAS at 9500.

I habitually just read off the TAS.....