Development of a combined mean value–zero dimensional model and application for a large marine four-stroke Diesel engine simulation

Abstract

h i g h l i g h t sDevelopment of a combined mean value-zero dimensional engine model. Application for simulating a large marine Diesel four-stroke engine. Results comparable to the respective ones of the mean value model. Enhancement of mean value models predictive ability with adequate accuracy. Appropriate where the mean value approach exceeds its limitations. a b s t r a c tIn this article, a combined mean value-zero dimensional model is developed using a modular approach in the computational environment of Matlab/Simulink. According to that, only the closed cycle of one engine cylinder is modelled by following the zero-dimensional approach, whereas the cylinder open cycle as well as the other engine components are modelled according to the mean value concept. The proposed model combines the advantages of the mean value and zero-dimensional models allowing for the calculation of engine performance parameters including the in-cylinder ones in relatively short execution time and therefore, it can be used in cases where the mean value model exceeds its limitations. A large marine four-stroke Diesel engine steady state operation at constant speed was simulated and the results were validated against the engine shop trials data. The model provided results comparable to the respective ones obtained by using a mean value model. Then, a number of simulation runs were performed, so that the mapping of the brake specific fuel consumption for the whole operating envelope was derived. In addition, runs with varying turbocharger turbine geometric area were carried out and the influence of variable turbine geometry on the engine performance was evaluated. Finally, the developed model was used to investigated the propulsion system behaviour of a handymax size product carrier for constant and variable engine speed operation. The results are presented and discussed enlightening the most efficient strategies for the ship operation and quantifying the expected fuel savings.

Dynamic energy modelling for ship life-cycle performance assessment

“…In this respect, a modular mean value model, which was previously developed (Theotokatos, 2010) and extensively validated (Guan et al, 2014;Theotokatos and Tzelepis, 2015;Baldi et al, 2015), is used. Each part of the engine is modelled using a separate block, which exchanges variables with the adjacent blocks of the model through the appropriate connections.…”

“…For the two-stroke engines, the incoming air mass flow rate is calculated considering the equivalent of two consecutive orifices, each one representing the cylinders scavenging ports and exhaust valve (Meier, 1981). For the four-stroke engines, the pumping flow rate, which is a function of engine speed and volumetric efficiency, is additionally taken into consideration (Baldi et al, 2015). The mass flow rate of the exhaust gas, exiting the engine cylinders, is found by adding the mass flow rates of the air entering the engine cylinders and the injected fuel.…”

A Two-Zone Combustion Model for Knocking Prediction of Marine Natural Gas SI Engines

“…Since the third equilibrium reaction in Equation (11) contributes less to NO formation and slows down the calculation speed of the overall model, only the first two reactions are used to calculate NO concentration, i.e., the basic Zeldovich mechanism. According to Equation (12), NO concentration can be calculated with temperature assuming that main in-cylinder species reach equilibrium in a negligible time:…”

“…On the other hand, simulation models enable engineers to explore the details comprehensively during the design period in order to determine the best case, saving research time and development cost. In general, numerical simulation of the natural gas engine working process is classified as follows: the mean value model, zero-dimensional model, quasi-dimensional model and multi-dimensional model [12]. The mean value model is not primarily intended for engine development, but it is efficient for integrated system research, thus it is usually based on a large amount of engine test data and has scarcely no ability to predict [13,14].…”

Adaptive feedforward control of exhaust recirculation in large diesel engines

“…IMO's stepwise introduction of NO x emission limits led to research into the use of variable geometry turbines as in (Stefanopoulou and Smith, 2000). A more recent development and investigation of a large twostroke engine model without EGR was recently published in (Theotokatos, 2010;Baldi et al, 2015;Guan et al, 2014Guan et al, , 2015Theotokatos and Tzelepis, 2015).…”