Assessing diagnostic applicability of heat release characteristics determined based on ship engine indicator diagrams

In order to determine indicator diagrams-based heat release characteristics, a single-zone model of net heat release was used for perfect gas. It was proved that when a constant value for isentropic exponent is assumed, the error in determining the characteristics can be limited to 1% at the nominal load. The effect of errors in determining the position of piston TDC, as well as that of gas passages and indicator valves on the calculated characteristics was evaluated. It was shown that for low-speed engines the effect of gas passages in negligible, while for medium-speed engines the characteristics reveal some deformations (waves), which are repeatable for an individual cylinder in the examined engine construction. The results of the performed investigations and analyses suggest possibility and advisability of the use of heat release characteristics in diagnosing ship engines, in particular low-speed machines.