
MVM 2022  Volume 48  Number 3
 THE INDICATOR DIAGRAMS IN PV COORDINATES CALCULATED AND MEASURED ON THE ENGINE STAND
Authors: Vasile Blaga, Mihai Blaga
DOI: 10.24874/mvm.2022.48.03.01
Abstract
This paper presents the numerical results of a simulation of the thermodynamic cycle for in spark ignition engine (SI) in normal external conditions (T0=293 K; p0=105 Pa) and revolution n=5500 rpm, at full charge. The simulation took in account the constraint for =1, for air pollution reduction whit combustible gases. The indicator diagram was calculated in pV coordinates, and in pα coordinates. Equations for thermal processes that take place in the engine were determined and then entered into a computer program. Using these equations, the state parameters were calculated at the characteristic points of the engine cycle. The research was conducted in order to obtain information that could be used improving the characteristics of an engine SI. The operating mode of the engine is defined by the speed of rotation and load, but it involves knowledge, in addition to these, of the thermal regime (parts temperature, cooling fluid temperature, intake air temperature, exhaust temperature, altitude corrections and etc.). The logic diagram of the calculation program is presented. The calculation program for determining the indicator diagram is done in Mathcad, both for the low pressure area and for the high pressure. The engine stand and the pressure transducer with their characteristics are presented. The diagrams are shown in pV and pφ coordinates. The pV indicator diagrams are calculated by the presented program based on data measured on the engine stand.
Keywords: thermodynamic cycle, indicator diagram, engine stand, characteristic points, the engine speed, low pressure, high pressure

