whenthesteady-statedesignfails!-資料下載頁
2024-10-17 21:48本頁面
【導(dǎo)讀】Statedesignfails!pipeline?Routinetransients. turbinegovernor?hunting?lawnsprinkler. ReinholdCompany.Graduallyvaried(“Lumped”)_________. Rapidlyvaried(“Distributed”)_________. K=____. Howlongwillittake?LfhhzzH21. Dg?g. f2VLHKgD?????????K=. _____44m/s. dVALHA???maF?mdVFdt=. HV?ALVHAt???K=. gtLHV?KD???NavierStokes?)(mVdtdF. abt. aVtanh?gHa?1f. aV?if. f?tanh!)(tanh1??f?s?fVt
【正文】 system? ?P1 = _____ ?P2 = _____ ?z2z1 = ___ High pressure pipe Stream Source pipe 0 0246810120 10 20 30 40t im e ( s )velocity (m/s)z3 z1 3zg?z z1 p zg?? ? ? ?31zz?ld V g p zhd t L g?????? ? ? ?????Reflections ?What is the initial head loss term if the pump stage begins after steady state flow has been reached? _____ ?What is ?_____ ?What is when V approaches zero? ______ ?Where is most efficient pumping? ___________ ?How do you pump the most water? ______ ld V g p zhd t L g?????? ? ? ?????z1 lp zhg?? ? ? ? z3 lp zhg?? ? ? ?31zz?Low V (low hl) Maintain high V Ram: Optimal Operation ?What is the theoretical maximum ratio of pumped water to wasted water? ?Rate of decrease in PE of wasted water equals rate of increase in PE of pumped water ? ?1 3 1w p u m p e dQ z Q z z??131pum pe dwQ zQ z z? ?High Q and Low loses? 0246810120 10 20 30 40t i m e ( s )velocity (m/s)ld V g p zhd t L g?????? ? ? ?????ld V g p zhd t L g?????? ? ? ?????? ?31dV gd zL zt ?? ?? ?1zdV gdt L? ??Acceleration Deceleration (pumping) Insignificant head loss Keep V high for max Q Cycle times ? ?1ac cac c gtdV tzdt L???? ?31de c e lde c e l gtdV t z zdt L???? ? ? ?1 3 1a c c d e c e lg t g tz z zLL ??131ac cde c e lt zt z z? ?Change in velocities must match de c e l ac cdV dVttdt dt??Summary (exercise) ? ? ? ? ? ? ? When designing systems, pay attention to startup/shutdown Design systems so that high pressure waves never occur High pressure waves are reflected at reservoirs or surge tanks Burst section of Penstock: Oigawa Power Station, Japan Chaudhry page 17 Collapsed section of Penstock: Oigawa Power Station, Japan Chaudhry page 18 Values for Wet Pit Analysis Flow rate before pump failure (m3/s) 2 plan view area of wet pit (m2) 24 pipeline length (m) 3170 inner diameter of pipe (m) elevation of outflow weir (m) 10 time interval to plot (s) 1000 pipe roughness (m) density (kg/m3) 1000 dynamic viscosity (Ns/m2) gravity (m/s2) Pressure wave velocity: Elastic Pipeline E = 200 GPa D = 1 m t = 1 cm tDEKKa??10? m /s 10201102001999???xxxa s to travel 500 m Hgp ??? ?m 520 /sm /s ) m /s ) ( 5 ( 10202???????gVaHp s i 740 = M P a 5 . 1 = m) ) ( 5 2 0m /s ) ( 9 . 8k g /m ( 1 0 0 0 23?? pRam Pump Water inlet Air Chamber Rapid valve Ram pump High pressure pipe Stream Ram Pump Source pipe H1 H2 Ram animation Ram Pump ??????????????????????DfLKLgHVVabtffV f2)(ta n ta n h1111Time to establish flow 0246810120 10 20 30 40t i m e ( s )velocity (m/s)2dV g Hdt L?dtdVALHA ?? ?Surge Tanks Real pressure traces At valve At midpoint
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