Tuning intake / outlet pipes on recips

[swn1]

Not my field, forgive me if this is dumb, but I did search first and didn't find anything with "tuned" or "tuning".

On automotive engines, tuning intake and exhaust plumbing makes a measurable MPG difference. I would assume that for new reciprocating compressor designs modern tuning is being applied. Anybody here know anything about tuning the headers for old, medium-to-large reciprocating compressors?

Any experience to support or contradict the idea that it would improve efficiency?

How do you measure the extent to which the existing tubing is mis-tuned?

XLEs delivering plant air are my immediate focus.

Thanks!

 

[Montemayor]

swn1:

I don't have the vaguest idea of what you mean to do with the suction and discharge of a reciprocating compressor by "tuning" it. Are you refering to pressure drop? Are you refering to torsional analysis? Are you refering to vibrational analysis? Those I've done or had done on recips. "Tuning" is something I've never heard of with regards to recips. I've never seen or read it anywhere.

Perhaps if you define what you mean by "tuning", "headers", "medium-to-large", "tubing", I could learn something after 46 years. The terms you use are related to internal combustion engines and not reciprocating compressors. Maybe you are refering to an engine driver for a reciprocating compressor and I'm missing the point. Also, which efficiency are you refering to?

 

[sms]

What you are talking about in recip compressors is called pulsation control. Typically a recip compressor will have a pulsation damper on both the suction and discharge flange. This is either a large acoustic volume, or a hemholz filter. Pipe lengths after the pulsation damper are typically not tuned (lengths adjusted to give a certain acoustic response). However if a pipe length is found to be strongly resonant then the designer will either adjust lengths, add orifices, or change pipe diameters.

Strong pulsation in a recip compressor can have significant effect both on efficiency as well as compressor valve life.

There are a number of digital simulation programs for doing this kind of analysis on a new machine. In addition it is not unusual on an existing installation to use dynamic pressure transducers to measure the cylinder PV curve and compare it with predicted to determine if pulsation effects are causing a compressor efficiency loss.


-The future's so bright I gotta wear shades!

 

[sms]

Oh, by the way, search on reciprocating compressor pulsation control and you find articles. Also search on Southwest Research Institute or Engineering Dynamics. These two outfits have lots of papers and provide consulting services in the area of pulsation control.

-The future's so bright I gotta wear shades!

 

[swn1]

Thank you, gentlemen.

Again, I'm not a mechanical engineer so this is a cartoon level appreciation, but it is my understanding that in reciprocating internal combustion engines they actually design the "pulsation control" to provide a standing acoustic wave with pressure peaks synchronized with intake valve opening and conversely with the negative pressure peaks at the exhaust valves.

Energy balance works because you are using waste acoustic energy to replace some of the suction to drive air through the intake valve.

Montemayor, my question was based on reasoning by analogy between IC engines and recip compressors. Apparently the considerations are not as similar as I had naively expected.

Perhaps the IC engine efficiencies are more sensitive to effective intake air density than compressors are? Total air delivery might be improved slightly but not energy efficiency for the compressor case?

 

[sms]

Well, it can work very much like an IC engine. When I used to do this kind of design work, the first priority was reducing pulsation energy out in the pipe work, to prevent vibration and failures. The second priority was optimizing efficiencies. The gas passage geometry in a recip cylinder is fixed in the cylinder casting, unlike an IC engine where you have the headers external, and therefore the lengths for each discharge valve are tunable. There is only so much you can do to adjust the standing wave such that the compressor performance is optimized, since all the valves take suction from or discharge to a commone volume. Having said that, an orifice at the compressor flange, or optimizing the length of pipe between the compressor flange and the pulsation bottle can achieve the same effect that you are talking about with IC engines.

-The future's so bright I gotta wear shades!

 

[gurmeet2003]

swn1,

Tuning as defined by you is not done on reciprocating compressors. One of the reasons is that recip. compressors work with vairable compression ratios as opposed to engines which have a fixed compression ratio. Though theoretically it may be possible to charge the compressor to a higher suction pressure and thus improve the through-put nobody does it in practice because of above reason.

Another reason is the type of valves used in recip compressors. These valves are not timed and are pressure actuated. They have a much more complicated dynamics compared to engine valves which are camshaft driven.

Gurmeet

 

[NickE]

There are however texts on tuning recip intake and outlet passages for sound.

See: Perdue university, I forget the rest and as the whole office is being moved I dont have any references handy.

(I know you can find this through their website however.)

 

[crjones]

You may want to go back to the manufacturer of you compressor. They sometimes have recommendations in this regard.

 

[PulseMaster]

I make a living "tuning" compressor piping. It is something that should be done during an API-618 DA3 study. It has been done since the 50's. I believe Southwest Research started the technology with their Analog computer.

"Tuning" simply means adjusting the lengths of piping such that they are placed off resonance. For machines that run at a fixed speed, this is easy. For high speed/variable speed machines, it becomes difficult/impossible, and pressure drop (i.e., orifice plates) must be used for pulsation control.

In the case of a car engine, there is lots of hype regarding tuning, and from what I can tell, it is just hype.

 

[sms]

I worked in the SwRI analog lab for a while. It was a fun place to be....

-The future's so bright I gotta wear shades!