UNIQUE MEASURING METHOD OF INDICATOR DIAGRAMS USING STRAIN HISTORY OF HEAD BOLTS (ENGINE IN-CYLINDER PRESSURE)

To obtain accurate indicator diagrams without the use of pressure transducers, the strain and displacement of various engine parts related to pressure variation in the cylinder were measured and analyzed mathematically. By measuring the strain of the cylinder head bolts, the horizontal displacement of the crankshaft end, and the vertical displacement of the intake valve stem, indicator diagrams could be easily obtained without a passage to the combustion chamber. Accurate indicator diagrams were estimated by applying the pressure-strain diagram obtained from the static pressure test in the cylinder to the strain variation in the cylinder head bolts. Better accuracy is possible by assuming that the cylinder head system is a one-degree-of-freedom vibration system. The strain measurement method can be applied to single-cylinder and multi-cylinder engines.