What is the maximum flow rate of a liquid (hydraulic oil) in a pipe. I have been given to understand that there is limit as to how much oil will pass through a pipe irrespective of the pump pressure, is this true and if so, how do i work it out. Trying to develope hydraulic drive system, according to my calculations the system would need to move just 17cc per engine revolution through the system ( engine revs rising up to 6000rpm)
2006-10-21 11:35:34 · 2 answers · asked by Old Cynic 3 in Science & Mathematics ➔ Physics
it's not an easy one. You need to get your hands on the Moody diagram (probably available online). Assume you have a hydraulically smooth pipe for simplicity. You'll need the density and viscosity of your oil and the diameter of your pipe. Then work out the velocity of the oil in the pipe. You then calculate the Reynolds number, and from that read off the pressure drop per unit length (it's encoded in the friction factor). That tells you how hard your pump has to pump.
There's a lot of nasty algebra in this but your hydraulic drive depends on you getting your head round this.
Beware: the American version of friction factor is different to the British one, by a factor of 4. Make sure you know which one you're calculating.
2006-10-21 11:42:48 · answer #1 · answered by wild_eep 6 · 2⤊ 0⤋
cant solve the calculations sorry, my uni Friend was the computational fluid dynamisist but you have been informed correctly the most certainly is a limit to the amount of fluid that can pass through a given aperture irrespective of pressure. The reasons he tells me are to do with the compressibility index of the fluid ( theres only so far it will compress) the inter-wall Resistance (the "friction" between the molecules and the pipe) he used to use a "super computer" to work this stuff out. From my more engineering background why not give it a go and see what happens. You can spend forever in calculations but a little trial and error can solve the problem in moments. The pressures and flow rates you think you need are minimal but still test it behind a ballistic screen.
Update just looked a little more closely at the math. you are looking at moving 102000 cc per minute, what on earth are you trying to do? definitely use a ballistic screen, (might be just me i deal with small bore stuff) also check out the pressure ratings of the pipes. it can be done of course but more detail is needed
2006-10-21 11:48:39 · answer #2 · answered by pete m 4 · 1⤊ 0⤋