SethU

Let's simplify it. The engine is being run on an engine dyno. WOT at peak hp rpm for 10 minutes, air to water intercooler, infinate supply of 40ºF water. And let's just say there's a 1psi pressure differential across the intercooler.

Now add a second intercooler and a second infinite supply of 40ºF water and run it again.

Is the post intercooler charge temperature the same or cooler?
Is the post intercooler charge pressure higher or lower?

kingtal0n

iTrader: (1)

You are still not providing enough information. To answer the question I need to know what air temperature is inside the tube before, during, and after the first intercooler (the differential). Allow me to provide you with the necessary knowledge with a picture from a physics textbook.



According to the physics book, when a thermal equilibrium is established, heat is neither gained nor lost by the system to it's surroundings. So what is the air temperature differential along the path, and at what point does it, if ever, achieve a thermal equilibrium? Is the answer to your question. Am I allowed to ask you a question now?

SethU

For simplicity, let's say there's zero humidity.
Ambient temperature is 70ºF and we're at sea level
We're pushing 20 psig and the compressor efficiency is 60%.

Using the delta of the resultant pre-intercooler charge temp and the 40ºF intercooler water to calculate the single intercooler efficiency, results in 85% efficiency.

Need anything else?

SethU

Sure. Fire away.

kingtal0n

iTrader: (1)

You are leaving out a lot of information, and providing useless information. Ambient temp is useless because you claim there is an infinite supply of 40* water and never mentioned a flow rate or engine size. Thermal equilibrium is established between the walls of the intercooler and the 40* water, therefore, the intercooler is 40*, which means the air traveling through the intercooler is also going to be in contact with 40* "ambient air temp" while it is inside. The size of the intercooler (volume) and flow rate of the compressor will determine how long each air molecule spends in the intercooler, which determines whether or not the air inside it will reach a thermal equilibrium.

I will fabricate some data that you have not provided.

If the size of the engine is 5.7L, the RPM is 6000, volumetric efficiency is 100%, adiabatic efficiency is 100%, then the flow rate at 20psi is 616CFM*2.37 = 1459CFM
Now we know that there is a turbocharger which flows approx 120lb/min installed, given the engine size is 5.7L which you never mentioned, it could have been a 2.0L engine or 1.0L engine or 15L engine for all I know, which affects flow rate, and thus intercooler capacity.

Now knowing that we are dealing with ~100lb/min or approx 1500CFM of airflow, we look at the intercooler size which you also failed to mention the volume. If the volume of such an intercooler were, say, .00005L, then it would do nothing to cool the air. If the volume were 9999999999L (approaching infinity) then it would gobble all the air up and nothing would ever come out the other side to feed the engine. So let us assume an intercooler volume of X, this will be our variable. If I assume we have 20psi prior to the intercooler, and 19PSI after the intercooler,The 20psi figure you quoted must be measured at the compressor outlet, which you also fail to mention where it was being measured from.

All of this missing data is making me fabricate/assume quite a bit.

Here is an equation for finding the air temp coming off the compressor

http://www.gnttype.org/techarea/turbo/turboflow.html

The data closely resembles our situation, the outlet temp is around 250*F.

So now we can extrapolate the starting and ending temperature of the air as it passes through an intercooler with a volume of X,

Air temperature before and after an intercooler volume of X, with a reservoir temperature of 40*F and infinite heat capacity (it never goes up to 41*F no matter how much thermal energy it absorbs)

Inlet air temperature is 250*F, using an exponential or logarithmic scale for our single constant to condense the information here (as when the number "5" is approaching infinity, and X+1 is a "perfect size intercooler") for X is negative 5 to positive 4:
Outlet temperature when volume is X-5 = 250*F
Outlet temperature when volume is X-4 = 240*F
Outlet temperature when volume is X-3 = 220*F
Outlet temperature when volume is X-2 = 180*F
Outlet temperature when volume is X-1 = 120*F
Outlet temperature when volume is X-0 = 80*F
Outlet temperature when volume is X+1 = 40*F
Outlet temperature when volume is X+2 = 40*F
Outlet temperature when volume is X+3 = 40*F
Outlet temperature when volume is X+4 = 40*F

As you might have guessed, once a certain volume of intercooler is installed, the air temp can go no lower than its reservoirs thermal equivalent, as the physics book example I posted above, heat will no longer leave or enter the system once a thermal equilibrium is established. You can install as many intercoolers as you like after X+1 and it will make no difference to the temperature. Pressure, on the other hand, will continue to drop, as long as you are adding plumbing volume, it doesn't matter if the plumbing is an intercooler or a straight pipe; the volume itself is responsible for carrying the additional weight of air molecules which require additional effort on behalf of the engine or compressor, thus lowering pressure.


My question is a beginners calculus 2 question involving infinite series, since you are having trouble grasping at infinity I thought it appropriate to show how we can work with an infinity symbol to find a solution.

Question:
If we take a half of a square, and cut it in half, and then again, and again, an infinite number of times, each time placing the half that we cut next to the previous half, what is our final area in terms of the original square? Assume the original square has an area of 1 square unit.

SethU

Slow down for a moment. You said you needed the temperature before, during, and after the intercooler. I gave you what you asked for, you'll just have to calculate it out. But, you wont be able to without ambient temp.

The engine size, intercooler/piping volume, and mass flow is arbitrary given the constants you have to work with.

SethU

Hahaha... I grasp the concept just fine. However, when I use my IMAGINATION for imagining an infinately long pipe, I picture a pipe... and start walking along side of it. Where does it end? Let's see. I keep walking and walking and walking. I go past a dairy farm. A school bus honks and the driver gives me a friendly wave as it passes by.

No end yet and my feet are getting sore. So I get in my car and follow this infinately long pipe, looking for the end. I follow this pipe through all the contiguous states, stopping to take in the sites to be seen. Mt. Rushmore was cool. Then on up into Canada. Then down to Mexico. This damn never-ending-pipe, never ends.

I then get to a point that it turns straight up into the sky and disappears in the clouds. There must be an end to the never ending pipe up there. So, I get in a helicopter and check it out. Man, I'll tell ya. You can see a lot of stuff from way up here. It's a pretty damn amazing sight to see. However, that damn pipe! Still no end to it. I went as high as that chopper would go and the pipe still disappeared in the distance above me, right into space.

I've gone this far, why stop now? Off to NASA. I'm in space now and following that damn pipe. Wouldn't you know it... it passed by all the planets and shot straight through the sun. That was pretty amazing. Good thing my ship has solar powered A/C.

I keep following the pipe. I increase the speed of my space ship to the Speed of light and everything but the pipe I'm following becomes a blur.

I keep going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going and going.

And there's still no end to this infinite length of pipe. WTF man? There's gotta be an end to this infinately long pipe. I'm half way there because I know there's one end. That's where I started.

That's about the time I lose interest in imagining an infinite length of pipe.

And there in lies the distinction between Imagine and Hypothesize.


I don't know.

ddnspider

iTrader: (26)

Fixed it for you. Man please let this thread die....

SethU

LOL

You're crazy. I'm enjoying the hell outta this.

I'm wondering how many more posts about how he doesn't have enough information to do a full thermodynamic assessment of the situation it will take before he forms an opinion and presents a supporting argument given the information available?

Maybe we should start a dedicated "Ask the King" thread.

MY_2K_Z

iTrader: (1)

I hate when a thread turns into 2 guys writing novels back and forth. Nobody wants to read that ****.

kingtal0n

iTrader: (1)

so then dont read it. You are not obligated to come into this thread and read anything. We are not forcing you to come and read the words on these pages. Am I forcing you somehow? I didn't realize you had lost your own will to do as you please, and were now at the beck and call of the internet. Has it enveloped you completely and you are now lost in the sea?

I have seen it before. The solution I suggest is to turn off the computer (or destroy it) and go outside, find a pool or basketball court and swim or play a game of ball, lift some weights until you are sore and tired, eat a huge meal with anything you want, make sure you get desert, then get a good nights sleep. repeat as necessary until the haunting thoughts of being forced to read the internet forums dissipates completely.

I answered your question twice already from multiple points of view and even included a variable for temperature. Its up to you figure it out.
If you wish for the solution to the question I posted the answer is in the shape of the square surface area, simply imagine an infinite number of half sections getting smaller and smaller until you are down to splitting a single atom, what then do you wind up with? I would not ask you to split that atom; instead consider the ultimate consequence of being left with a single atom on the edge of infinity, in the shape provided for you as a single square unit.

kingtal0n

iTrader: (1)

I think the issue with this is that you are far too concerned with the pipe itself, and not concerned at all with what is inside of the pipe. Think about the air molecules in that pipe. Imagine first that instead of infinity length, you have 0.0001" length pipe. Then a 0.001" pipe. Then a 0.1" pipe. Then a 1.0" pipe. Then a 10' pipe. Then a 100' pipe. Start small and work your way to infinity. For each example try to imagine the pipe as a straw, and you are the engine sucking or blowing into the straw. You can be in outer space where there is no gravity; imagine a 1" long straw , and 1' long straw, and a 500' long straw in space (you are in a space shuttle with artificial pressure of course), try to drink from each one, imagine the mass of the air molecules in the straw responding to the force provided by the vacuum or pressure of your mouth and lungs. Is it as easy to drink from the 500' long straw in space where there is no gravity, as it is to drink from the 1" long straw?

Neglecting gravity is important because a vertical straw here on earth of 500' long would be much harder to drink from than a horizontal straw of the same length, so by placing you in a space station or space craft without interference from gravity we are essentially free from determining the orientation of the straw, and can focus solely on the effort required based on the length of it. Also when I say drink, you can imagine drinking air molecules instead of liquid. Liquid has special considerations in space, depend more on surface tension I am told, so feel free to assume the straw is full of air and you are drinking only normal breathable air for this experiment (drinking sounded better than "sucking or blowing air" I did this out of consideration for the terminology, as males tend to differ from being told to suck or blow anything).

SethU

Touche.

I'm not gonna do that.

kingtal0n

iTrader: (1)

lets talks a bit about why boost falls off on the big end. Or why power falls off. Since this is the thread topic.

First the easy part: If the compressor is tapped, then either boost or power falling off is due to the compressor being out of flow rate. All compressors have some maximum flow rate, beyond which any additional flow is going to reduce the number of moles (molecules) of air even if pressure increases at a fixed volume, due to temperature also increasing. Compressors also have a maximum safe RPM they will typically not wish to exceed; a mechanical limitation like any other engine part that moves must be observed.

How do you know if the compressor is tapped? The easy way is to look at the compressor map. Usually they are in volume/time but can be converted to mass/time, either way is useful. You can calculate the flow rate of the engine at a specific boost pressure, to get a general idea of what the flow rate of the engine would be at that pressure, and compare it to the flow rate of the compressor in question at that compressor RPM. This is usually called charting a compressor map, as you may wish to plot multiple engine RPM points along the compressor map and connect the dots for a preview of what it looks like to run that compressor on the engine. You can search online for hundreds of websites which help you do that sort of thing.

here is the one charted for the compressor on my 5.3L engine I will be running


The red dots are the plotted points my engine is guesstimated to run through as the RPM increases from 1k to 6k, as noted by the red dots. The 1.8 on the left that the red dots seem to trace along is the pressure ratio, it means 1.8 times the atmospheric pressure, or 14.5psi*1.8 = 26.1psi total, or 26.1 - 14.5 = ~11.6psi of boost pressure. Remember that atmospheric pressure counts as some 14.5psi of pressure at sea level, it is like a 100% adiabatic efficient turbocharger ever present in our atmosphere (since the air is always compressed, or already compressed, depending how you look at it) we are only adding pressure on to that in any increment we choose, except that a compressor is not 100% adiabatic efficient and does add some temperature to the boost pressure. The islands on the compressor map show us the adiabatic effiiency; note that my red dots run straight through the center island, and they end up nearly running right off the map at max engine RPM; this is no accident. By taking a full advantage of the compressor map at the desired boost pressure we are using the smallest compressor possible to get the job done, which means the wheel will be the smallest and lightest possible, and "lag" effects will be minimized. By running the compressor through its most efficient islands the air temperature will be kept as low as possible, minimizing the workload of the intercooler and keeping necessary water/methanol injection to a minimum.

Back to the "boost falling off on the big end"
If you have determined that the compressor is not tapped out, and has plenty of flow left in it, there are a couple possible reasons for a boost to fall off "on the big end" or near maximum engine flow rate.

The first most likely culprit is a boost leak. Boost leaks force the compressor to flow more, it moves the compressor RPM up, creating additional exhaust get pressure, which reduces the flow rate of the engine. It also might move the compressor to the right of it's map (falling off the right of the compressor map) which raises intake air temperature rapidly and can cause detonation and engine failure quickly. Therefore, it is essential, absolutely every setup should be boost leak tested, no exceptions. The plumbing needs to be filled with 15psi~ (or whatever you intend to run) of air pressure to ensure there are no leaks. The pressure should stay in the plumbing for quite a while, more than just a second or two, sometimes as long as 15 to 30 seconds is seen, the longer the better.

The next possible culprit is the boost control method is insufficient. There are many reasons for this, such as poor wastegate position, poor solenoid operation, poor commanded attributes, etc... but the point remains this is the second most likely cause for "high end boost falling off". Often the spring in the wastegate is too small for the commanded boost pressure by the controller (if you are using a 5psi wastegate spring and trying to dial it up to 25psi of boost, that is not going to work out very well for you)

From there, you are on to considering the valvetrain and intake method, the flow rate of the head, the duration of the camshaft and associated parts. In other words, if engine volumetric efficiency is falling off, then that is why the torque is falling off, and that is why the power is falling off. This is why torque falls off "on the big end" of engines with stock style camshaft profiles. Increasing camshaft duration may fix the valve timing event profile, allowing VE to be maintained through the rising RPM, but it will not fix problems with the flow-rate of the head or intake design which may also incur VE losses. It is cheaper and easier to raise boost pressure through these regions than to try and fix the head/intake/camshaft profiles associated with VE losses, as long as the fuel quality in question is up the challenge.


Those are the big three, main reasons why power (torque) is dropping off as engine RPM increases to the "big end".

Game ova

I have visions of kingtalon at the track wearing a lab coat, standing in the staging lanes with a dial indicator, checking to make sure that the hot dog he just ordered is the perfect shape. Meanwhile his car runs 15.30s.

ddnspider

iTrader: (26)

There is something to be said for forum etiquette where you don't clog a thread with random crap and gibberish info from a textbook. Its funny, when you actually start building stuff and getting out in the real world, your reliance on textbook info lessens, but you know the saying.....Those who can, do; those who can't, teach.

SethU

Staging lanes? I don't know about that. In my vision he's still in the pits, standing on a milk crate, textbook open in one hand, and addressing people that are passing by like he's preaching the absolute truth of the world.

Hoping to put something in his mouth to shut him up a bit, a neighboring pit offers him a hot dog. A simple, yes please, or no thank you? No. A 15 minute speach about how hot dogs are made, why they are the shape and length they are, why they plump when you cook them, the chemical composition of the fillers used and other industrial applications that filler is used in.

Then the neighboring pit guy asks, "Is that a yes or no"?

I gave you my answer, but let's talk about...

kingtal0n

iTrader: (1)

I can use a dial indicator on my hot dogs? I have to try this.

Nice

So what is it I am not doing? If you think cars/vehicles are important, or that I care about my ET and post stats in my sig like a child, as if it were an important thing to be popular on an internet forum, well that is not the renegade style I abide. I'd rather people in my vicinity think me slow, dim witted and uneducated, it helps them underestimate the situation and the real danger they are in. Nobody knows what is really under my hood or what I "do", I do not boast talk or gab, it is useless.

Be more off topic than usual fiends, the internet has you in it's icy grasp and wont let go!

ddnspider

iTrader: (26)

now now, that whole " I'd rather be smarter than I look, than look smarter than I am" doesn't work cause you've already posted too much. I'd like to see you post more actual results and less kids textbook info since you decided to make the children comment.

SethU

Listening