Effect factors of part-load performance for various Organic Rankine cycles using in engine waste heat recovery

The Organic Rankine Cycle (ORC) is regarded as one of the most promising waste heat recovery technologies for electricity generation engines. Since the engine usually operates under different working conditions, it is important to research the part-load performance of the ORC. In order to reveal the effect factors of part-load performance, four different forms of ORCs are compared in the study with dynamic math models established in SIMULINK. They are the ORC applying low temperature working fluid R245fa with a medium heat transfer cycle, the ORCs with high temperature working fluid toluene heated directly by exhaust condensing at low pressure and high pressure, and the double-stage ORC. It is regarded that the more slowly the system output power decreases, the better part-load performance it has. Based on a comparison among the four systems, the effects of evaporating pressure, condensing condition, working fluid, and system structure on part-load performance are revealed in the work. Further, it is found that the system which best matches with the heat source not only performs well under the design conditions, but also has excellent part-load performance

PRIMJENA NAPREDNIH RAČUNALNIH TEHNOLOGIJA U MODELIRANJU I UPRAVLJANJU POMORSKIH SUSTAVA

The paper deals with some application possibilities of advanced computing technologies in marine systems modelling and control. New computing technologies and techniques like fuzzy logic (FL), expert systems (ES), artificial neural networks (ANN), genetic algorithms (GA), object oriented programming (OOP) offer new, extended possibilities to identification, modelling and control of dynamic systems. This paper presents some possibilities of practical use of advanced computing technologies applied to the modelling and control of marine diesel engines. The emphasis is put on two well recognised techniques, fuzzy logic and expert systems. Some application examples are illustrated in the paper to show effectivness of using such methods and techniques in marine diesel engine modelling and control.U radu se daju neke mogućnosti primjena novih računalnih tehnologija u modeliranju i upravljanju sustava u pomorstvu. Nove računalne tehnologije i tehnike kao: neizrazita logika (FL), ekspertni sustavi (ES), umjetne neuronske mreže (ANN), genetički algoritmi (GA), objektno orjentirano programiranje (OOP) pružaju nove proširene mogućnosti za identifikaciju, modeliranje i upravljanje dinamičkih sustava. U ovom radu prezentiraju se neke od mogućnosti praktičnog iskorištenja naprednih računalnih tehnologija s primjenom u svrhe modeliranja i upravljanja drodskih dizelskih strojeva. Naglasak se u radu daje na dvije priznate i dobro prihvaćene tehnike, neizrazite logike i ekspertnih sustava. U radu se daje nekoliko primjera primjene ovih tehnika i metoda, te pokazuje njihova učinkovitost

Towards marine dual fuel engines digital twins - integrated modelling of thermodynamic processes and control system functions

This study aims at developing an integrated model that combines detailed engine thermodynamic modelling and the control system functional modelling paving the way towards the development of fidel digital twins. To sufficiently represent the combustion process, a multi-Wiebe function approach was employed along with a database for storing the Wiebe functions parameters and the use of quadratic interpolation. The developed model was employed for the systematic investigation of a marine four-stroke dual fuel engine response during demanding transient operation with modes switching and load changes. The derived results are analysed for identifying the engine critical components and their effect on the engine operational limitations. The results demonstrate that the developed model can sufficiently represent the engine and its subsystems/components behaviour and effectively capture the engine control systems functionality. The appropriate turbocharger matching along with the sufficient design of the exhaust gas waste gate valve and fuels control systems are crucial for ensuring the smooth engine operation of dual fuel engines

A comparison of advanced heat recovery power cycles in a combined cycle for large ships

Strong motivation exists within the marine sector to reduce fuel expenses and to comply with ever stricter emission regulations. Heat recovery can address both of these issues. The ORC (organic Rankine cycle), the Kalina cycle and the steam Rankine cycle have received the majority of the focus in the literature. In the present work we compare these cycles in a combined cycle application with a large marine two-stroke diesel engine. We present an evaluation of the efficiency and the environmental impact, safety concerns and practical aspects of each of the cycles. A previously validated numerical engine model is combined with a turbocharger model and bottoming cycle models written in Matlab. Genetic algorithm optimisation results suggest that the Kalina cycle possess no significant advantages compared to the ORC or the steam cycle. While contributing to very high efficiencies, the organic working fluids possess high global warming potentials and hazard levels. It is concluded that the ORC has the greatest potential for increasing the fuel efficiency, and the combined cycle offers very high thermal efficiency. While being less efficient, the steam cycle has the advantages of being well proven, harmless to the environment as well as being less hazardous in comparison