Machine Parts

1.       The latest possible inlet valve should be accumulated. 2.       The length of flame travel should be as short as possible. 3.       There should not be hot surface at the end of region –region of gas. 4.       The exhaust valve should be kept small. 5.       The highest flame front velocity should be created by creating correct amount of turbulence. 6.       The largest mass of charge small burn as soon as possible after ignition. 7.       The heat flow should be minimum in the zone around spark plug. 8.       In the end gas region surface to volume ratio should be large so that there is good cooling in detonation zone. 9.       The spark plug should be positioned that it will be scored by any exhaust residual ...

  Test have that under continued full-load conditions, exhaust valves may reach a temperature of 1475 F a cherry red. Valves of large diameter run hotter than smaller ones and the valve temperature increases with engine speed. An increase in the compression ratio as a rule lowers the valve temperature but if the compression is carried too high and detonation sets in, the effects is reversed. It is usually assumed that exhaust valve temperature are highest with retarded ignition and weak mixtures, probably because the exhaust pipe hottest under these conditions, but a larger of number of tests carried out on a particular engine showed that the reverse holds true, the exhaust valve temperature being lower with a weak mixture and retarded ignition. The explanation is that the temperature of the valve depends not only on that of the exhaust gases, but also on the temperature of combustion, which latter is lowered by weaking the mixture and retarding the spark. ...