Reduced (Mean Value) Engine Models

Models can be classified according to the spatial and time resolution adopted for the problem representation and usually two groups can be identified: emptying and filing (E&FMs) and mean-value models (MVEMs). E&FMs are used for computer-aided engineering applications and often lead to design decisions. MVEMs are used for model-based controller design and simulations. Within MVEM, simpler models are used for engine control in real-time, in the form of transfer functions and state space equations.

A MVEM typically consists of several sub-models that represent the engine sub-systems, i.e. inlet fixed fluid, compressor, scavenge receiver, engine cylinders, exhaust receiver, turbine, exhaust fixed fluid, crankshaft and turbocharger shaft. It is capable of simulating engine performance both in steady state and transient loadings and is based on physical principles and empirical relationships between relevant engine parameters, expressed as a series of coupled algebraic and ordinary differential equations. As MVEMs capture load changes adequately, they can be further simplified to the form of transfer function for controller design purposes.

Controller design for a hybrid powetrain (Simulation results using a diesel engine reduced model)

Simulation results of a zig-zag maneuver of a VLCC (Engine MVEM in conjuction with hull and propeller model)