Development of a mathematical model and analysis of the impact of fuel system malfunctions on the dynamics of the diesel engine

Abstract

Conventional diagnosis of mechanically governed diesel fuel systems requires removal and bench testing of pumps and injectors, whereas existing non-intrusive methods rarely relate crankshaft-speed features to specific physical faults. This study develops an integrated model of the MMZ D-243 four-cylinder diesel engine to quantify how wear and malfunctions in its fuel system distort crankshaft rotation. A single-zone first-law cylinder model with Wiebe heat release is coupled to slider-crank dynamics and parametric sub-models of the in-line UTNM pump, hydromechanical injectors, and air path. Seven fault families are simulated in MATLAB from idle to rated speed and from 30% to full load. Faults that unbalance cyclic fuel delivery dominate the coefficient of rotational unevenness: single-section plunger wear increases it by 19.6%, pump-section maladjustment by 13.6%, and delivery-valve leakage by 9.3%. Uniform air or fuel starvation reduces the coefficient slightly but decreases power by up to 32%. Wall-heat-transfer, operating-point, sensitivity, and Monte Carlo analyses preserve the fault ranking. A cylinder-resolved peak-acceleration ratio separates the faulty and healthy cases by approximately eight standard deviations, whereas the global coefficient provides only about two. A diagnostic threshold of 0.94 is therefore proposed for cylinder-by-cylinder screening.