Istraživanje i razvoj metode za analizu radnog procesa motora na osnovu merenja trenutne ugaone brzine kolenastog vratila

Abstract

Proces sagorevanja kod motora SUS najčešće se simulira Vibeovim parametarskim modelom. Parametri modela zavise od geometrijskih karakteristika komore i termo- i gaso-dinamičkih pojava u cilindru, zbog čega se korišćenjem empirijskih relacija njihove vrednosti ne mogu odrediti lako i sa dovoljnom tačnošću. Osim determinističkih metoda koje ne omogućuju sistemski pristup, za odreĎivanje parametara modela oslobaĎanja toplote koriste se i indirektni postupci zasnovani na minimizaciji greške izmeĎu vrednosti modeliranog i izmerenog pritiska u cilindru. U ovom radu prkazan je postupak identifikacije parametara modela oslobaĎanja toplote na primeru višecilindarskog benzinskog motora primenom optimizacione metode Levenberg-Markvart sa fiksnim ograničenjima za minimizaciju sume kvadrata razlika izmerene i modelirane trenutne ugaone brzine kolensatog vratila. Pritisak u cilindru i moment gasne sile u ugaonom domenu simuliran je pomoću nelinearnog dvozonskog, nultodimenzionalnog modela radnog procesa. Moment mehaničkih gubitaka u ugaonom domenu simuliran je pomoću detaljnog, višekomponentnog analitičkog modela trenja u tribološkim sistemima motora. Razvijeni modeli iskorišćeni su za analizu uticaja parametara dinamičkog modela motora na tok trenutne ugaone brzine kolenastog vratila i istraživanje odstupanja u merenjima radi definisanja ograničenja u procesu identifikacije parametara modela

Most frequently used approach to describe combustion process in IC engines is based on Wiebe function. Its parameters are strongly influenced by geometric and in-cylinder gas- and thermodynamic processes and can’t be predicted easily and with sufficient accuracy using available empirical relations. Along with deterministic methods lacking in systematic approach, indirect analysis methods based on minimization of error between simulated and measured in-cylinder pressure have been successfully demonstrated. In this paper the same concept is introduced to identify combustion model parameters of a multi-cylinder SI engine based on box constrained Levenberg-Marquardt minimization of nonlinear Least Squares (LSQ) given for measured and simulated instantaneous crankshaft angular speed determined from the solution of the engine dynamics torque balance equation. For predictions of gas pressure and engine torque, a nonlinear, detailed, angle resolved two-zone, zero-dimensional multi-cylinder SI engine combustion model has been developed as well as a detailed analytical component model of engine friction and mechanical losses. The models are used to analyze the influences of engine combustion and dynamics model parameters on instantaneous crankshaft speed and to investigate biases in measurement in order to recognize and establish the constraints in process of combustion model parameters identification