4 fs 2d s 1 3 2 dp t example 326 the conical valve of

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Unformatted text preview: ecent larger than exhaust port for better cylinder charging. (b) Thickness of the valve disc The thickness of the valve disc (t), as shown in Fig. 32.22, may be determined empirically from the following relation, i.e. p σb = Constant = 0.42 for steel and 0.54 for cast iron, = Diameter of the port in mm, = Maximum gas pressure in N/mm2, and = Permissible bending stress in MPa or N/mm2 = 50 to 60 MPa for carbon steel and 100 to 120 MPa for alloy steel. t = k.dp where k dp p σb (c) Maximum lift of the valve h = Lift of the valve. The lift of the valve may be obtained by equating the area across the valve seat to the area of the port. For a conical valve, as shown in Fig. 32.22, we have dp π 2 π dp· h cos α = (d p ) or h = 4 cos α 4 where α = Angle at which the valve seat is tapered = 30° to 45°. 1192 n A Textbook of Machine Design In case of flat headed valve, the lift of valve is given by dp h= 4 The valve seats usually have the same angle as the valve seating surface. But it is preferable to make the...
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