The Prediction of Gas Pressures within the Ring Packs of Large Bore Diesel Engines

The established orifice and volume method for predicting the gas pressures between piston rings in reciprocating machines is extended to take account of the energy loss due to wall friction in the circumferential gas flow between the piston and cylinder liner.

The results show that such energy losses are significant when gas flow rates exceed 10^-2 kg/s and that this is most likely to occur in engines of over 0·5 m bore with worn piston rings. Under these conditions the angular displacement of the ring gaps significantly affects ring pack gas flow. In particular, it is shown that the maximum resistance to the flow of gas through the ring pack occurs when adjacent ring gaps are separated by more than 90 degrees.

In the analysis of piston ring lubrication in ring packs it is necessary to ascertain the inter-ring pressures and the present paper enables such pressures to be determined with greater accuracy and for a wider range of engines.