A Dynamic Model of a Locomotive Diesel Engine and Electrohydraulic Governor

Abstract

As part of a comprehensive simulation of a prototype locomotive propulsion system, a detailed model has been developed that predicts the dynamic response of an experimental two-stroke, turbocharged and intercooled diesel engine. Engine fueling and brake torque are computed from regression equations derived from an extensive data base. Corrections are applied to the calculated steady-state torque to account for dynamic deviations of in-cylinder trapped air-fuel ratio from the steady-state value. The engine simulation accurately represents the operation of the turbocharger, which is gear-driven at low turbocharger speeds, and freewheels through an overrunning clutch when exhaust energy accelerates the turbocharger beyond its geared speed. Engine fueling level, i.e., rack, is determined from a dynamic simulation of an electrohydraulic governor, which responds to the difference between the desired and the actual engine speeds. The governor representation includes: (1) finite rate of change of engine set speed; (2) load regulator feedback for control of applied engine loads; and (3) fuel limiting under conditions of excessively high load demand. The fundamentals of the engine/governor model are given in the paper along with examples that emphasize the dynamic operation of these particular components.