BS EN 62097:2009 pdf download

BS EN 62097:2009 pdf download.Hydraulic machines, radial and axial – Performance conversion method from model to prototype.
NOTE 2 In case of aged prototype machWxes with heavily rusted surfaces with Ra values larger than 50 pm, It is recommended to consider the followings In evaluating the surface roughness.
Firat Is the ditliculty in the measurement ot roughness. On aged machines. the roughness values are otlen beyond any existing portable roughness tester range. In these situations, it is recommended to take molds at mQt represenlative locations using appropriate plastic material arid measure the roughness at these molds by using a coordinate measuring machine’ to hnd an equivalent Ra value. Other methods can also be uaed (like depth indicators, or roughness comparison coupons. arc) it a mutual agreement is reached among h. concerned panics In such a situation, however, the equivalent Ra roughness should be determined caielully, as II is allected by the roughness profile and the density of dispersed voids,
Secondly, a consideration should be taken in choosing the mearwngful roughness values from the measurements. Based on ih• actual slat. ot knowledge. it is believed that areas having scattered deep voids do not create as much losses as their measured value would Indicate. Indeed, the stream lines over such areas pass over the voids without reaching the bottom and do not create signilicantly larger losses Thereore, in such case. it is r.commended to ignor, areas with deep voids when measuring roughness deep voids are considered as being depressions deeper than approxImately 1.3 mm).
Once the above considerations nave been taken Into account, the relationship between k and Ba as espress.ed by Equation B 2 (or Equation 21 can be tentatively applied also to heavily rusted surfaces
Then, Equation B.1 is expressed as follows:
C.7 Determination of bulb turbines
The scalable loss of runner blades of bulb turbines is considered to be the same as of Kaplan turbines, Then, ãERUr 0.030.
Regarding the scalable loss in stationary part, no data Is available at present to determine the friction loss en the stationary part of bulb turbines. However, ills considered that the friction loss In the upstream part including the annular passage around the bulb Is smaller than that of the spiral case of Kaplan turbines. On the other hand, the friction loss in the guide vane area is considered to be slightly larger than that of Kaplan turbines because of narrower passages. Al present, the exact amount of these subtraction or addition of friction loss against that of Kaplan turbines is not known.
In any case, it is estimated that the friction loss in the stationary part of both Kaplan and bulb turbines Is somewhere around 1,0 — 2,0%. Therefore, if we adopt the assumption that the above subtraction and addition could cancel with each other, the error of OESTr& caused by this assumption would not exceed 0,5 %. Then the probable error of the step-up amount calculated from this ÔESTIeI would be in the range of 0,05 — 0,1 %. Hence, it is thought that this assumption is acceptable.
Based on the above considerations, it is prescribed in this standard that 8ECOret and 5ErOt for bulb turbines shall be the same as of Kaplan turbines.
C.8 Derivation of scalable hydraulic energy loss index, dEt.,
C.8.1 Scalable loss Index for runner blades
Regardless of the specific speed of the machine or the number of runner blades, the values of KdRu and KURU defined at the blade tip are approximately given as follows:
Outside of these ranges, their values may not be correct. Therefore, if the step-up equations
in this standard are applied to the evaluation of the contractual model test results beyond the
above specific speed range, prior agreement shall be made among the concerned parties.
C.10 Direct step-up for a whole turbine
Similar to the direct step-up method for radial flow machines, the direct step-up method for
axial flow machines is shown hereafter.
To represent the whole machine, the reference flow velocity index Ku0 and the representative
roughness of the machine Rao need to be defined.