Smart questions
Smart answers
Smart people
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Member Login




Remember Me
Forgot Password?
Join Us!

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips now!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

Join Eng-Tips
*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Donate Today!

Do you enjoy these
technical forums?
Donate Today! Click Here

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.
Jobs from Indeed

Link To This Forum!

Partner Button
Add Stickiness To Your Site By Linking To This Professionally Managed Technical Forum.
Just copy and paste the
code below into your site.

Venezueladq (Petroleum) (OP)
16 Feb 13 18:10
hola a todos,


me gustaría saber, si alguien sabrá por que cuando hago las corridas en el programa de simulación ARIEL, en las gráficas me muestra que a medida que voy incrementando la presión de succión la carga sobre la barra por compresión aumenta en los cilindros compresores de simple acción, a que se debe este fenómeno?



yo pienso que en este caso, la fuerza ejercida del lado del cabezal del cilindro en este tipo de cilindros de simple acción la da, el volumen de gas muerto que se encuentra en este extremo y debido a que no se da un incremento en la presión la fuerza ejercida sobre el pistón es pequeña, generando entonces esfuerzos mínimos sobre la barra del pistón por efecto de compresión.


De antemano gracias por su ayuda...
y si alguien puede ayudarme a traducir a ingles lo anteriormente escrito, se lo agradeceré
feliz día..!!



DRWeig (Electrical)
17 Feb 13 12:01
Hola, Venezueladq,

Bienvenidos a eng-tips.

Mi español no es el mejor. Por favor, espere a que otro miembro de verificar esta respuesta. Este foro (ayuda a la traducción) es nuevo. Por favor, tenga paciencia.

¿Se puede escribir "el volumen de gas muerto que se encuentra en este extremo" con otras palabras? No entiendo lo que esto significa. Tal vez otro traductor ayudará.


English here:

[I also parphrased for clarity as best I can. Terms I do not know are translated literally and highlighted, and I have asked for clarification above.]

Hello everyone,

In the simulation program ARIEL, the graphs show that as I increase the suction pressure, the compression load on the piston rod increaases. The cylinders are single-acting. Can anyone tell me why?

I think that in this case, the force exerted on the cylinder head is given by the dead volume of gas that is at this end. Since there is no increase in pressure, the force exerted on the piston is small, so it will generate minimal compression force on the piston rod.

Thanks in advance for your help... and if anyone can help me translate the above written English, I will be greatful.

Have a great day!!

Best to you,

Goober Dave

Haven't see the forum policies? Do so now: Forum Policies

DRWeig (Electrical)
17 Feb 13 12:25
Venezueladq,

Después de que me digas otra manera de escribir "el volumen de gas muerto que se encuentra en extremo este," Yo le ayudará a obtener una respuesta de los otros.

Gracias!

Best to you,

Goober Dave

Haven't see the forum policies? Do so now: Forum Policies

zdas04 (Mechanical)
17 Feb 13 12:39
DRWeige,
"Dead volume of gas" is a good way to indicate what we normally call "Clearance". The phrase you translated as "at this end" would probably be either "head end" or "crank end", can you make either of those phrases out of the original?.

Your translation makes good sense to me (who has no Spanish) and I could answer that question.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

DRWeig (Electrical)
17 Feb 13 12:55
Thanks David,

That makes sense too.

For the dead gas volume, I bet you are correct. I just didn't really know if one would call the volume "dead" at the top of stroke or bottom of stroke. If so, the "this end" probably refers to the end of the stroke at which dead volume (clearance) exists.

A much-condensed paraphrase might be:

"In a single-acting cylinder, why would ARIEL tell me that the compression force on the piston rod increases when the cylinder suction pressure increases?"

I live in the Atlanta area, so I often get to practice my Spanish speaking skills. This will be resurrecting my writing and tech-term skills. To be honest, I hope a truly bilingual engineer shows up do displace me. For now, it's fun and I'll do my best.

Best to you,

Goober Dave

Haven't see the forum policies? Do so now: Forum Policies

Venezueladq (Petroleum) (OP)
17 Feb 13 15:14
DRWeig

thank DRWeig , when I write "el volumen de gas muerto que se encuentra en este extremo" is the "clearance" in "head end".
thank you very much for the translation of the question,

I'm learning English but understood your translation, is excellent learn more for here,


zdas04

thanks zdas04 the "clearance" is in "head end".


thank you very much, I await your prompt answer.
Artisi (Mechanical)
17 Feb 13 23:22
Ok, now this brings up the next question, should this now be reposted by "ourselves" to the appropriate forum, do we ask the OP to repost the translation in the appropriate forum or do we hope that someone will pick it up and reply with a technical answer?.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

zdas04 (Mechanical)
17 Feb 13 23:39
Good question, and I was expecting the OP to do it since he/she has the most to gain.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

patprimmer (Publican)
18 Feb 13 0:30
I think it would be good to repost the translated forms into the appropriate technical area.

I agre that is the OPs responsibility.

Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules

Artisi (Mechanical)
18 Feb 13 0:42
I can go along with that, the OP should repost, however - it would be a good idea to remind / direct the OP to repost in the appropriate forum.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

abeltio (Mechanical)
18 Feb 13 3:21
Hola, pienso que es solamente una cuestión de superposición de efectos.

Si la presión de succión es Ps y la presión suministrada por el émbolo es ^p (delta p) la presión final o de descarga (Pd) es:

Pd = Ps + ^p

Al ser de simple acción, no existe contrapresión que balancee la carga sobre el émbolo. De ahí que la carga aumente con la presión de succión.

saludos.
a.

DRWeig (Electrical)
18 Feb 13 4:56
Venezueladq,

Para continuar con la discusión, por favor haga una copia de las traducciones e insertarlos en el foro original. He combinado las dos traducciones aquí para hacer más fácil para usted. Comienza con la palabra "Translations."

En caso de que no lo sé, "OP" puede referirse al autor original de la pregunta, o "OP" también puede referirse a la pregunta original.


Translations:

1) OP (by Venezueladq):

In the simulation program ARIEL, the graphs show that as I increase the suction pressure, the compression load on the piston rod increaases. The cylinders are single-acting. Can anyone tell me why?

I think that in this case, the force exerted on the cylinder head is given by the clearance volume at the head end. Since there is no increase in discharge pressure, the force exerted on the piston is smaller, so it will generate less compression force on the piston rod.

2) Reply (from forum member abeltio):

Hello, I think it's only a matter of overlapping effects.

If the suction pressure is Ps and the pressure on the piston is provided by the ^p (delta p), the discharge pressure (Pd) is:

Pd = Ps + ^p

Being single action, the backpressure balances the load on the piston. Hence, the load increases with the suction pressure.

Best to you,

Goober Dave

Haven't see the forum policies? Do so now: Forum Policies

abeltio (Mechanical)
18 Feb 13 19:20
Goober,
My post states that: because it is simple action, the back pressure that balances out the load on the piston does not exist

saludos.
a.

DRWeig (Electrical)
19 Feb 13 5:05
You are correct, abeltio, I read your Spanish post too late at night.

Sorry! blush

Best to you,

Goober Dave

Haven't see the forum policies? Do so now: Forum Policies

Venezueladq (Petroleum) (OP)
19 Feb 13 7:38
DRWeig,

Gracias por la colaboración, lo copiaré en el foró original.
Venezueladq (Petroleum) (OP)
19 Feb 13 8:02
abeltio,

cuando usted dice presión final o de descarga, ¿está referido a la presión de descarga del cilndro?

Si es afirmativa su respuesta, ¿como existirá presión de descarga sí no se llega a comprimir el gas en el lado del cabezal del cilindro?

si es negativa, ¿a que está referida esta presión final o de descarga?
DRWeig (Electrical)
19 Feb 13 11:40

Quote (Venezueladq)

abeltio,

cuando usted dice presión final o de descarga, ¿está referido a la presión de descarga del cilndro?

Si es afirmativa su respuesta, ¿como existirá presión de descarga sí no se llega a comprimir el gas en el lado del cabezal del cilindro?

si es negativa, ¿a que está referida esta presión final o de descarga?

English (abeltio or others, feel free to help):

When you say final pressure, are you referring to the cylinder discharge pressure?

If yes, how can a discharge pressure exist if there is no compressed gas in the cylinder at the cylinder head?

If no, to what location does "final pressure" refer?

Best to you,

Goober Dave

Haven't see the forum policies? Do so now: Forum Policies

DRWeig (Electrical)
19 Feb 13 17:18
Latest from the original thread:

Post from zdas04:

Abeltio didn't get it quite right. It is more a function of the way the program works than a physical phenomena.

Work done by a compressor (and therefore rod load) at constant rpm is a function of: (1) gas composition (which did not change); (2) compression ratios (which went down); and (3) mass flow rate (which went up if you didn't lower the rpm in the simulation). At the end of the calculation the mass flow rate has the largest contribution to work. If you look at the report from Ariel Performance instead of the graph, you'll see that the volume flow rate at standard conditions is quite different on each of your runs and neither one matches your input flow rate.

I really like Ariel Performance, but you have to watch carefully to make sure that a "small" change in operating conditions didn't put you way outside the flow rate range that you are interested in. The program always honors your input rpm, suction pressure, and discharge pressure so that only leaves flow rate for it to adjust and it does. My approach is to make a change, run the report and look at the flow rate, then go back to the compressor picture and change the rpm up or down to get my target flow rate and THEN look at the rest of the report. If you do that, then you'll find that for the same flow rate the rod load goes down when you raise suction pressure at a constant mass flow rate just like your intuition expected.

En español:

Abeltio es casi correcto, pero no del todo. Es más una función de la forma en que el programa trabaja con un fenómeno físico.

El trabajo realizado por un compresor (y por lo tanto, la carga ejercida sobre el vástago de pistón) con velocidad de rotación constante es una función de:

(1) la composición del gas (que no cambia);

(2) relaciones de compresión (disminuyen); y,

(3) la tasa de flujo másico (que aumenta solo si la velocidad de rotación no disminuye en la simulación).

La tasa de flujo de masa hace que la mayor contribución a trabajar. Si nos fijamos en el informe de rendimiento de Ariel en lugar del gráfico, verá que la velocidad de flujo de volumen en condiciones normales es muy diferente en cada uno de sus resultados y ninguno coincide con su caudal de entrada.

Me gusta mucho el rendimiento Ariel, pero hay que mirar con cuidado para asegurarse de que un "pequeño" cambio en las condiciones de operación no aumenta o disminuye el flujo más allá del rango de caudal que en la que está interesado.

El programa siempre honra la entrada la velocidad de rotación, la presión de succión y la presión de descarga. Lo único que queda para que el programa es cambiar la velocidad de flujo. El programa cambia la velocidad de flujo.

Mi enfoque es hacer un cambio, ejecutar el informe y ver la velocidad de flujo. En ese momento, voy a cambiar la velocidad de rotación hacia arriba o hacia abajo para obtener mi caudal objetivo. Después de eso, me fijo en el resto del informe. Si usted hace eso, usted encontrará que para el mismo flujo másico, la carga ejercida sobre el vástago de pistón disminuye cuando aumenta la presión de succión.

Esto es lo que tu intuición te lo dije

Best to you,

Goober Dave

Haven't see the forum policies? Do so now: Forum Policies

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close