Random thoughts thread

[Dimman]

Originally Posted by old greg

Where's the deception? The Inlet Volumetric Flow Rate already includes the volumetric efficiency.

Misunderstanding on my part?

How I'm interpreting it is that is the flow into the SC, not the engine. Sizing an SC or turbo I could care less about what goes in that side. I want to know what's coming out of it. Centris offer mass flow out of then on their maps plus efficiency and pressure ratio.

Roots is volume flow in. So if the R1900 is sucking in 1.9l per rev it is only spitting out 1.65l per rev (at 10k rpm or whatever the speed for the 87% VE). So for my calculations on sizing the x on the graph of an Eaton map is not the same as the x on an old turbo map that uses CFM, for example.

Wrong?

[ichitaka05]

Originally Posted by Snoopyalien24

Pretty clever, and wow, that guy.. sucks like a lot

So it'l look like this right?

Yup pretty much... I'm currently on debate to keep the RS spoiler or go w different spoiler (STi spoiler or small duckbill spoiler).

[Snoopyalien24]

Originally Posted by ichitaka05

Yup pretty much... I'm currently on debate to keep the RS spoiler or go w different spoiler (STi spoiler or small duckbill spoiler).

Hmm what wing is this?

[ichitaka05]

Originally Posted by Snoopyalien24

Hmm what wing is this?

STi

[Asterisked Accolade]

"What you have to remember is that i'm not a God, and i never was. I was a very powerful result of dark-medical experimentation. I was a regrettable and horrific result of a test of human limitation. I had it in me to follow The Obelisk's murderous whispers, as well as to fight against them. In the beginning, fighting was not simple nor was it easy. But i had changed, i had grown and i was a fine-tuned weapon. Forged from the same evils in the same laboratories. I failed to save the world, and my guilt was ever more powerful than Saera's lust for death and reign. The following battle would prove that." William B. Hendriks, White Rook III: Exodus (Final Chapter: Revelations)


"I was immortal-- i had died and i had been reborn from nothing other than the limitless engine of the universe. It could be said that nothing in the living realm could then be difficult. But you'd be wrong. Felix Miles, or as i had always addressed him, Wade-- was my best friend and he was constricted to a bed in a laboratory. The Obelisk had collapsed his mind and left him brain dead. I was given the paralyzing choice of whether or not to pull the plug. There was no compelling beauty, no metaphorical silver lining. There was only hurt and sadness. If this were France, doctors with no relation would have pulled the plug despite my wishes. I couldn't decide which situation was worse. All i knew was that despite my 'immortality' and expanded sense of life, experience, and justice-- i could not make a moral decision." -William B. Hendriks, White Rook III: Exodus

"The world is never an absolute, William. That's what makes it bearable; even though it may be hell in one part, you can always find happiness in another." -Wade (Felix Miles), White Rook II: Dawn of the Accolade

[Snoopyalien24]

Originally Posted by ichitaka05

STi

Nice, in my opinion I like this one. But I also like your RS one.

So it's up to you Fugu

Choose wisely padawan

[Asterisked Accolade]

"I was dying. Wade would not be coming to my rescue. Marcum wouldn't either, I was on my own. Saera stood over me, observing my broken body with a bone-chilling smile. The sky beyond her silhouette was orange from the fires of the burning continents. Everything was covered by hot, orange sand. The trees and grass had been charred away. She reared her leg back and kicked me in the neck, sending me skidding through the hot sand and breaking most of the bones above my rib cage. It was excruciating and paralyzing. I tried to command the particles around me into a force-field, but the pain interrupted my focus. I had no choice but to lie on the ground, writhing in pain. When i opened my eyes for a moment, the sun was blocked by Saera's flowing black hair in the smokey winds as she stood over me once more. 'I admit, human. . .it is much more gratifying to crush you with my bare hands than to simply turn you to atomic mist.' She raised her foot above my face and focused her strength into it. 'At long last. . .this world is mine.' She lowered her foot with a force so enormous, that my head-- my skull was compressed into particles as small as the sand on which i died. The force quaked the entire Earth and knocked it nearly nine inches off of it's axis. At the very least, i went out with a bang.'' - William Bernard Hendriks, White Rook III: Exodus

[ichitaka05]

Originally Posted by Snoopyalien24

Nice, in my opinion I like this one. But I also like your RS one.

So it's up to you Fugu

Choose wisely padawan

Yeah, buying STi or duckbill spoiler, either way, I need to go paints hop to get my hood, trunk & spoiler painted

[old greg]

Originally Posted by Dimman

Misunderstanding on my part?

How I'm interpreting it is that is the flow into the SC, not the engine. Sizing an SC or turbo I could care less about what goes in that side. I want to know what's coming out of it. Centris offer mass flow out of then on their maps plus efficiency and pressure ratio.

Roots is volume flow in. So if the R1900 is sucking in 1.9l per rev it is only spitting out 1.65l per rev (at 10k rpm or whatever the speed for the 87% VE). So for my calculations on sizing the x on the graph of an Eaton map is not the same as the x on an old turbo map that uses CFM, for example.

Wrong?

Kind of. What goes in must come out.

The VE on a roots blower is the ratio of what it pulls in vs. what it theoretically could pull in, ie. Inlet Volumetric Flow Rate / (Blower Displacement * Blower RPM). The R1900 in your example would have an Inlet Volumetric Flow Rate of 1.65L. The volume exiting the blower would be dependent on the pressure ratio and the adiabatic efficiency, and doesn't figure in to the volumetric efficiency.

But anyway, say you've gone through the usual calculations and found that to make ~400 bhp @ 6000rpm you would need to have 44lbm/min (~1000 m^3/hr @ 70F) of air @ a pressure ratio of 2.0:1. You would look at the compressor map and draw your "x" as usual to get your adiabatic efficiency, and then interpolate to find what RPM the blower would need to run at to move that much air at that pressure. In the case of the R1900 that would mean ~10,000 RPM, so you'd need a 3:5 pulley ratio.

Don't forget, though, that you need to account for the parasitic loss. So use the adiabatic efficiency and the flow rate to calculate the work done by the blower, then divide by a mechanical efficiency of, say, ~0.85 to find the parasitic power loss. Or, if you can convince someone at Eaton to give you the full technical data on the blower, just look it up. Anyway, take that number and use it to recalculate your airflow requirements, rinse and repeat until you start to converge on a solution.

[Dimman]

Originally Posted by old greg

Kind of. What goes in must come out.

The VE on a roots blower is the ratio of what it pulls in vs. what it theoretically could pull in, ie. Inlet Volumetric Flow Rate / (Blower Displacement * Blower RPM). The R1900 in your example would have an Inlet Volumetric Flow Rate of 1.65L. The volume exiting the blower would be dependent on the pressure ratio and the adiabatic efficiency, and doesn't figure in to the volumetric efficiency.

But anyway, say you've gone through the usual calculations and found that to make ~400 bhp @ 6000rpm you would need to have 44lbm/min (~1000 m^3/hr @ 70F) of air @ a pressure ratio of 2.0:1. You would look at the compressor map and draw your "x" as usual to get your adiabatic efficiency, and then interpolate to find what RPM the blower would need to run at to move that much air at that pressure. In the case of the R1900 that would mean ~10,000 RPM, so you'd need a 3:5 pulley ratio.

Don't forget, though, that you need to account for the parasitic loss. So use the adiabatic efficiency and the flow rate to calculate the work done by the blower, then divide by a mechanical efficiency of, say, ~0.85 to find the parasitic power loss. Or, if you can convince someone at Eaton to give you the full technical data on the blower, just look it up. Anyway, take that number and use it to recalculate your airflow requirements, rinse and repeat until you start to converge on a solution.

Isn't sealing the issue with Roots-types though? So it sucks in whatever on the X but the efficiency losses also come from leakage past the vanes, so it is pushing out less than it sucks in?

I thought I would have to adjust my X by the blower's VE as well. Not the case?

Lysholm maps look much more complete, having VE and power requirements all on it as well.

[old greg]

Originally Posted by Dimman

Isn't sealing the issue with Roots-types though? So it sucks in whatever on the X but the efficiency losses also come from leakage past the vanes, so it is pushing out less than it sucks in?

I thought I would have to adjust my X by the blower's VE as well. Not the case?

Lysholm maps look much more complete, having VE and power requirements all on it as well.

No need to adjust, it's already accounted for in the map. It's why the RPM lines aren't vertical; they curve off to the left with increasing pressure ratios because of the drop in volumetric efficiency due to leakage. But inlet flow rate is the net flow rate after leaks and any other horrible stuff that might happen.

Lysholm maps are more complete. Eaton has all that info and more, they just choose not to share it on their website. I'm not sure how willing they would be to hand it out to the general public, even if you asked nicely, but it wouldn't hurt to try (especially if you've got some credentials).

[Zaku]

LOL I'm nervous because I'm live streaming art work for the first time. // dies

[serialk11r]

Originally Posted by old greg

Don't forget, though, that you need to account for the parasitic loss. So use the adiabatic efficiency and the flow rate to calculate the work done by the blower, then divide by a mechanical efficiency of, say, ~0.85 to find the parasitic power loss. Or, if you can convince someone at Eaton to give you the full technical data on the blower, just look it up. Anyway, take that number and use it to recalculate your airflow requirements, rinse and repeat until you start to converge on a solution.

Wait uh, isn't the mechanical efficiency already accounted for in those maps? You'd just be left with whatever losses the pulley has right?

[old greg]

Originally Posted by serialk11r

Wait uh, isn't the mechanical efficiency already accounted for in those maps? You'd just be left with whatever losses the pulley has right?

Not exactly sure what you're saying... Mech. efficiency in this case would be work into the pulley / work into the air. If your compressor map already has power consumption info (Lysholm, or proprietary Eaton data) then yeah, it's already accounted for. If you need to work back from Adiabatic Efficiency and Flow rate, then no.