. Graphical and mechanical computation. exhibit the choice of moduli and the equations of thescales. Reaction TurbineModulus Equation wi = X = iV, W2 = y = N nis = Scale Limits N, 10 to 100 N up to 2000 1000 H 200 W4 = Wi = z = = H^ Length 109 10 Scale H Limits2 to 6up to 2000 1000 Tangential Water Wheel 2000 W4 = Modulus wi = W2 = W3 = Equation X = Nsy = Nz = Wi Length = / = H^ 10 Fig. 38a shows the position of the scales. The x- and z-axes coincideSO that the iV,-
. Graphical and mechanical computation. exhibit the choice of moduli and the equations of thescales. Reaction TurbineModulus Equation wi = X = iV, W2 = y = N nis = Scale Limits N, 10 to 100 N up to 2000 1000 H 200 W4 = Wi = z = = H^ Length 109 10 Scale H Limits2 to 6up to 2000 1000 Tangential Water Wheel 2000 W4 = Modulus wi = W2 = W3 = Equation X = Nsy = Nz = Wi Length = / = H^ 10 Fig. 38a shows the position of the scales. The x- and z-axes coincideSO that the iV,- and are constructed on opposite sides of the Art. 38 SPECIFIC SPEED OF TURBINE AND WATER WHEEL 75 common axis; similarly for the iV- and i7-scales. The charts for the re-action turbine and the tangential water wheel have been combined asshown in the diagram, , the axes for the former have been placed per-pendicular to the axes of the latter, and both charts use the same trans- 5PECIF/C SPEED (Ns) OF REACT/ON SPEED IN) IN REV. PER MIN. (R. SPECIFIC SPEED OP TURBINE AND WATER WHEEL. N VTTp. Ns = Hh Fig. 386. versal on which the index lines intersect, one index line joining iV, and iVand the other joining and H. Fig. 386 gives the completed chart; for the reaction turbine, the indexlines show that when N = 1000 , // = 70 ft., and = 201,then Ns = 70; for the tangential water wheel, the index lines show thatwhen N = 1000 , // = 700, and = 275, then N, = 76 NOMOGRAPHIC OR ALIGNMENT CHARTS Chap. IV (V). EQUATION OF FORM /,(u) = Mv) -Utv) - Ut) ....TWO OR MORE INTERSECTING INDEX LINES. 39. Charts for equation (V). — A large number of equations involv-ing three or more variables can be written in the form (V), which issimilar to the second form of equation (II), but in Art. 28 we used log-arithmic scales, whereas here we shall use natural scales. Equation (IV)is a special case of equation (V) when there are four variabl
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