Method to Determine the Indicated Power in a Combustion Engine

This study investigates a method for determining the indicated power of a combustion engine. To accomplish this, it was necessary to obtain the combustion pressure curve for each cylinder as a function of the crankshaft’s angular position, along with the geometric data of the connecting rod and crank mechanism. The combustion pressure was used to calculate the work transferred from the gas to the engine piston. Pressure measurements were obtained using a piezoelectric pressure transducer, which operates on the piezoelectric effect: a quartz crystal subjected to pressure generates an electrical signal. This signal is then converted into a proportional and linear signal that can be analyzed by a data acquisition system. Once acquired, the data were evaluated using a log P–log V diagram to verify quality and ensure the measurements accurately represented the physical phenomenon. The pressure versus volume (P–V) diagrams were generated, and the area under these curves during the compression and expansion phases—corresponding to the indicated work—was calculated via numerical integration. The indicated mean effective pressure (IMEP) obtained by this method was compared to values measured by an AVL Indiset 620 pressure indicator, showing good agreement. All other results were analyzed and compared with data from the literature, demonstrating good consistency. The technologies available for measuring combustion pressure and evaluating engine performance are essential for studying the combustion process and for the development of engines with higher power output, lower fuel consumption, and reduced toxic emissions.