Richard,

I have similar problems with another message board, it is too the point where I type what I want to post in a word doc, then cut and paste into the board message area before it loses my password again.

The next time I go to an airport or see a plane fly over I'll be sure to ask them if their engines are successfully working.

Why isn't the rotary engine's design used everywhere by people?

BTW: The first jet engines were based off of centrifugal turbochargers. Then slowly they refined them and made them into the more efficient monsters that we have today. There isn't a single commercially made engine today that isn't an axial turbine. There are actually only a couple of turbocharger companies out there. Everyone just uses them with their own labels stamped on them. It is far easier to use what already exists and you are familiar with then to take the time and money to do it another way. Let's use the piston engine as an example to that. People fear change which is why they typically fight it.

im a licensed aircraft engineer. Yes, i am a mechanic, not university educated, but as i have a licence i am seen as a professional, unlike in america where one person does one job, i can actually multi task!
ROtary god i thin u will find that the first engine to fly was in fact german and this was an axial flow type, the reason whittles engine was more successful was due to the fact that he used a centrifugal compressor, and this did not need to be stripped down every 6 hours for overhaul. And also if u look up garret u will find that the TPE 331 is in actual fact has 2 centrifugal compressors! The PT6 uses avial and a centrifugal compressor.
THe only down point of the rotary is the fuel consumption. Apart from that its an excellent invention, why the hell do u think i bought one.
Napier bought out an engine called the nomad, was 12 cylinder horizontally opposed diesel, the intersting part about the engine was the fact that it was supercharged with axial flow stages and also a supercharged with centrifugal fan, exhaust gases past through a turbine which was also linked to the crankshaft, and when real power was needed there was a combustion chamber which added extra heat to the exhaust which went through the turbine sextion, in fact there were 2 turbines ,with one having an actuator to let the exhaust gas onto the extra turbine. This was a great idea , SFC was about 0.34, and did it take off? No it didnt, probably due to the fact of gas turbines.
Rolls royce dart is another excellent engine, bit old but relied on 2 centrifugal compressors, and why did they choose it like this? Because it was simple and very effective!

AHH yes, the Nomad, I know very little of this engine. Yet I seem to know more then you. If you are going to use it as an example that is fine. Just tell the whole story. If you don't know it, I will tell you.

As you describe it That was the original concept. While they did get it to run it was belching fire, backfiring and almost never started. But that was 1950, by 1953 it did run. And how did they do that?? They scraped all of that bs stuff like the centrifugal compressor, reheat chamber and auxiliary turbine. The remaining turbine was linked to the gearbox by a variable-ratio Beier gear. It drove a single propeller from the crankshaft.

This was the engine that recorded sfc of .345. To be exact the first version was the E.125 The last and simplified version was the E.145. Still it never went anywhere.

*** MOD EDIT ***

Stop the flames, and let's stay on topic.

Surrey,

I recognize that you may not be here any more, however, I do want to comment on the comparison you've made between axial and centrifugal compressors. I will ignore the combativeness of the recent posts and try to focus on the facts as I see them. Just as a note: I've been involved in the gas turbine industry for the last 20+ years (both as a educator and a practitioner).

First, it is clear to me that you have some experience and knowledge in the aviation industry. I am not picking a fight with you. I am only trying to help people understand more clearly the differences/benefits of both axial and centrifugal compressor designs.

So... here I go.

1. It is true that centrifugal compressors have higher pressure ratios on a per stage basis than axial compressors. In general/realistic use, the maximum centrifugal compressor pressure ratio per stage max out about 8:1 and the axial stage max out about 1.6-1.8 per stage. Just as a note: Most high bypass ratio fans are single stage designs with design pressure ratios in the 1.4-1.7 range. This does not take into account any benefit of ram compression. Note: For automobile applications, we typically want boost pressures between 5-25 psig which translates to total pressure ratios of 1.35 to at most 3.0. Without pushing things too hard... this could be accomplished with a single stage centrifugal compressor or 3-4 stages of axial compressor

2. Both axial and centrifugal compressors have efficiency islands that show peak efficiency in the design operating range and those efficiencies drop off as the compressor operating point moves away from the design condition. There is some opportunity to influence these islands through the stage loading of each design. Neither of these compressors is going to maintain high efficiency from "automobile" idle to max rpm.

3. I do not have the direct manufacturing experience but... most centrifugal compressors are hogged out of a single block of metal with a 5-axis CNC machine. Where I work, we typically make 3-5 of these compressors at the same time with a 5 cutter machine to improve productivity. General machining time is on the order of 30 hours for 5 units or approx 6 hours per wheel. In most cases these are titanium or nickel based alloys which influences the machining time. Most aerospace axial compressors use forged or individually machined blades which are then inserted through broached slots in the compressor disks or circumferential slots in the case for stators. However, some more recent designs have used "integrally bladed disks" so called blisks. These designs use the same type of 5 axis CNC machines as centrifugal wheels. One of the issues here is whether you can flank mill or whether you are required to end mill the blades. Flank milling is faster but reduces the complexity of the blade shape and thus may compromise the aerodynamic performance somewhat. Note: Since metal moves while you are cutting it... you make course cuts first and clean cuts later. In either event you are limited in cutter speeds because of blade deflection. I would expect this is more a problem with axial blades than centrifugal. However, both designs have this problem.

4. In general axial flow compressor designs have lower inertia than centrifugal designs. This is because the majority of the metal in an axial design is kept near the inner radius. The centrifugal wheel gets a fair amount of its compression from radius change and the diffusion that goes with it... this requires metal to move out in radius and results in increased inertia. Since I do performance modeling of both axial and centrifugal designs at a gas turbine company... I am very comfortable with this comment. You can tell me I'm wrong but that will not change the facts.

5. Guys, there are good reasons for using axial compressors and good reasons for using centrifugal compressors. In general, as the compressor pressure ratio gets higher and higher.... the air density increases.... and the flow area gets smaller. Think about what happens in an axial compressor as you move from front to the back. The blades get smaller and smaller. While the blade heights are being reduced... the tip clearances are not changing (tip clearances do not scale).... so the ability of the compressor to compress air efficiently is compromised. Because of this issue, there is a logical point where you would like to move to a centrifugal design. In general we would use corrected or referred flow calculations to decide the transition point between axial and centrifugal designs. With that said, all of the large aircraft engine companies use axial flow compressor designs because they make sense for large engines with high corrected/referred flows. Most small gas turbine manufacturers use a combination of axi-centrifs or centrifugal designs because it makes sense for the lower corrected/referred flow they are designing for.

6. In general, centrifugal compressors have wider operating range than axial flow designs. When centrifs are pushed into the stall region.. often times they become less efficient but they continue to pump air. This is influenced significantly by the backsweep angle of the blading in centrifs. Improved materials and analysis techniques have allowed centrif designers to provide centrifugal wheels that have very progressive stall behavior and still survive the stresses caused by the curved radial blades. Additionally, splittered entrance blades have served to improve airflow handling in the eye of the impeller.

7. So, if centrifs are cheaper and have wider operating range... why would you ever consider using an axial design. Well, I can think of a couple of reasons. First, centrifugal compressors typically have a higher lapse rate of airflow against speed than axial flow designs. Because of this, it may be possible to match the airflow versus speed behavior of the Renesis engine better with an axial compressor than with a centrif. Second, packaging, the axial flow design is smaller in diameter and generally tube shaped so it may be easier to find a place for it in the engine bay. Third, novelty, there aren't many axial flow designs out there and there is something to be said for being different.

Bottomline: I don't know yet which design makes the most sense for the Renesis. In fact, different people have different interests and desires. I'm here to learn what I can, to try and filter the information from the misinformation and to decide for myself what makes the most sense for me. While I do that, I'm trying not to inflame or placate too many people. I will encourage anyone who is willing to invest their own time and money to try and make performance improvements on our automobile. At the end of the day, I will chose which one, I think, has done the best job in that regard. Peace :)



"Centrifugal flow compressors are shorter than the axial flow compressors and becasue of their spoke like design they can accelerate air faster and immediatley diffuse it into the direction of flow.
Advantages are of centrifugal comps. are :-
1) High px. rise per stage, compression ratios upto 15:1 possible.
2) Good effiency over a wide rotational speed range, this is from idle to full rpm.
3)Simplicity of manafacture, relatively low cost.
4)Low weight
5)Low inertia loads aids spool up.
Disadvantages are:-
1) Large frontal area for a give airflow. 2) More than 2 stages impractical

Axial flow flow compressors require a large amount of stages to gain a high pressure rise, unlike the centrifugal compressor which has very high compression ratio's the axial flow can only manage a pressure rise of about 1.25 per stage. To gain a large compression u will havbe to add more stages, hence why most turbines have up to 13 stages of compression.
Some advantages are:-
1) High peak efficiencies from RAM AIR, created by its straight through design (N/A to RX8)
2) High peak pressures attainable by addition of extra stages.
3) Small frontal area
Disadvantages
1) Difficulty in manafacture and costs.
2) Relative high weight
3)Low pressure rise per stage 1.25:1
4) High inertia.
5) Poor effiencies at low speeds"

Great post Turbine_pwr! I hope I speak for most here on the board -- we really appreciate intelligent and useful information without all the BS and "I'm smarter than you are" attitude.

They keep scrubbing my milititant posts!! I do have alot of experince with turbines, on the maintenance side of things! Basically what u have said is pretty much what i said and i agree with u! Though! Im not sure axial flow comps are any good in this installation but at the end of the day as u say there are advantages and disadvantages to it and novolty factor.

"They" is ME, and it's not just your posts. There is no reason to turn this thread into a flame fest. Check your PMs.

Some weasel looking git keeps doing it

You don't respond to my PM, then you attempt to insult me. Bad idea. Bye bye.

i'll second that.

Some 1 ban surrey puma Admin please BAN HIM FOR BEING A TROLL

Thnx to Omicron my posting is fixed. It was my new security firewall.
Now I forgot what I needed to answer. I think the plumbing?
I intend to keep as much stock as possable. There is no reason to remove something that worked.

The engine doesnt just wake up someday and know it has a blower added. The engine thinks in terms of absolute pressure. It thinks you just drove below sea level. It doesnt know where the line is that we call zero. If you think of absolute gauges like in aircraft the 0 we use is 29.92 hg. so there is no line and you do not speak of vacuume as negative from zero. Car gauges have vacuume marked in terms of less from 0 like "I have 10 inches of vacuume."

Meaning you have 20 inches of pressure. still less then standaed at sea level but mesured as positive from absolut negative. Example: At 4000 ft elevation you have 25.84 inches hg. at 6000 you have 23.98 in hg abs. if you were reading an automotive gauge at those elevations it would still read 0. that's called gauge pressure. If you see PSIG. that iswhat it means. Pressure absolute and it would read the prior numbers.


So then why do we instantly think that when we go over this number that we must change everything. There will come a point due to the delta pressures that a gain can be had by tuning to the new operating pressure but I don't think you reach that point with street pressures. So we will try to keep all the advantage built into the stock system at great expense to Mazda.


13 If that is your picture next to your name then you're the best looking and most loyal member on the forum.


What am I doing with the blower you ask??
Well nothing for a few more days, the shop is apart while we make room for a new CNC lathe. Due this week. I'm also upgrading the test equipment. There are both 4 and 5 stage blowers ready to test. It takes awhile to get the test things working and in between we have to support the shop.

If I forgot anyones question remind me.

Richard

:cool:
Actually, that's me. Bureau13 is the guy who is my pet. He's OK, but he thinks I don't know about computers, so let's keep that part between you and me.

Skye

Actually, I was wondering where you're planning on installing it... maybe replacing the accordian hose? If so, it may be pretty easy to deinstall before we take our cars in for warranty service at Mazda, and that would definitely be an advantage...

What, you're worried about him giving the " *Puma " a bad name? LOL. He's gone, anyway - see the posts above yours. Although I wouldn't call him a troll per se, more someone who can't hold his temper.

Let's get back to thread guys...

I have a couple of questions... :p

I understand that the Mazda supercharged version of the RX8 that is under development was confirmed to be an electrically assisted one. Apparently, on this version at low RPM an electric motor assists the supercharger to produce boost (and torque), and at higher RPM the supercharger works in a normal way.

Can somebody please confirm this?

AND

What are the Pro's, and Con's of each of these systems (the electrically assisted Mazda supercharger, and this one?),

Which one would be more suitable for road use?,

What rwhp figures should we expect from each of these???...

Thanks.

I believe that was an electrically assisted turbo...wouldn't make much sense otherwise. Also, I'm not sure "confirmed" is as accurate as "rumored to be." I have no trouble believing they are doing some R&D on that, but I'm not ready to bet the farm we ever see it on an RX-8.

jds

RP and Guys,
Yes, thanks Omni for your sterilization. That cat was getting on my nerves.
I think Mazda knows it has too much car here to leave it alone for long. In some form the HP will increase. Look at the competition. Mazda will have to respond or eat crow.
RP I think yours is the best looking unit that I have seen and I also think(i think a lot) that its "matches" if you will, the ambience of this car. It's differant just like this car is differant from anything on the road. Most people I know would be VERY staisfied with 300hp or so at the wheel and dependability. There are a lot of good ,honest,hard working, smart people out there trying to get a FI unit on this car. My money is on Richard. The ecu is going to be the problem.
With the obious engine bay heat increase I wonder if there is anyway we can make the side vents actually functional? That would be cool. Anyone thinking we may be heading for some type of cowl induction?
olddragger

The side vents are FAKE!!!!!
And they are in a great low pressure area too.
IS there a way???
I think with all the heat everyone talks about someone would have looked at this.
Were they always just for looks or did Mazda put them there for their own option.

On another topic, wasn't it a hydraulic blower drive Mazda was looking at??

Omicron, did you ever find my pictures?? I can have ajax repost them.
Then I"ll tell you where the blower goes. You will probably be disapointed thogh. I doubt it will be a snap it in and out.

The side vents are real

Your pics are there, they just aren't displaying. Still looking into what's wrong.

it would be great to use those vents to exhaust all the heat. lets see them in stainless steel or poloshed in some way.

check to see if they're displaying now. The server I host from was apparently down.