Unformatted text preview: ecent larger than exhaust port for better cylinder
(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
= 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
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
π dp· h cos α = (d p ) or h =
4 cos α
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
The valve seats usually have the same angle as the
valve seating surface. But it is preferable to make the...
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This note was uploaded on 09/30/2012 for the course MECHANICAL 403 taught by Professor A.thirumoorthy during the Spring '11 term at Anna University Chennai - Regional Office, Coimbatore.
- Spring '11