THE OPTIMIZATION OF THE STEAM PLANT BY MEANS OF AN ENGINE ROOM SIMULATOR

U radu je prikazano optimiranje parnoturbinskog pogonskog postrojenja na brodu za prijevoz ukapljenog prirodnog plina. Izvršena je analiza pogonskih radnih parametara te su na simulatoru brodske strojarnice simulirane situacije koje utječu na iskoristivost postrojenja. Izvršene simulacije na simulatoru LNG broda omogućile su praćenje promjene radnih parametara pri pojavi neželjenih i neočekivanih stanja za koje postoji vjerojatnost pojavljivanja unutar funkcionalnog realnog sustava. Na taj način je moguće bolje dijagnosticirati greške unutar realnog sustava te odrediti optimalno ponašanje pojedinih elemenata sustava. Kod generatora pare analiziran je utjecaj pojave čađe na cijevima zagrijača vode i pregrijača pare na potrošnju goriva, te utjecaj izgaranja različitih goriva na emisiju NOx. Kod parne turbine analiziran je utjecaj istrošenosti odrivnog ležaja turbine i istrošenosti lopatica niskotlačne turbine na snagu, aksijalni pomak i na pojavu vibracija turbine. Dobiveni rezultati pokazuju da primjena simulatora može poslužiti brodarskim kompanijama i pomorskim edukacijskim ustanovama za uvježbavanje pomoraca i studenata za rad u različitim okolnostima te za brzo i učinkovito reagiranje u kritičnim situacijama.The optimization of the steam propulsion plant on LNG tankers is dealt with in this paper. The operational parameter analysis was performed and the situations influencing the plant efficiency were simulated on the engine room simulator. The performed simulations on the LNG simulator module enabled monitoring of the operational parameters change in undesirable and unexpected conditions for which there is a probability to occur within the operational system. In such a way an enhanced diagnostics of failures within a real system and the determination of the optimal performance of individual components are possible. The boiler analysis has concentrated not only on the influence of soot deposit on the economizer and superheater piping to the fuel consumption but also on the influence of burning different fuels to NOx emission. Another analysis has been carried out in the main turbine in which the influence of worn out thrust bearing and low-pressure turbine blades to the turbine output, axial displacement and vibrations was analysed. The results have shown that the simulator can serve the shipping companies and maritime educational institutions to train the students and seafarers for working in various situations and to prepare them to respond to emergencies promptly and efficiently

Antibacterial Mechanism of Action of Arylamide Foldamers ▿ †

Small arylamide foldamers designed to mimic the amphiphilic nature of antimicrobial peptides (AMPs) have shown potent bactericidal activity against both Gram-negative and Gram-positive strains without many of the drawbacks of natural AMPs. These foldamers were shown to cause large changes in the permeability of the outer membrane of Escherichia coli. They cause more limited permeabilization of the inner membrane which reaches critical levels corresponding with the time required to bring about bacterial cell death. Transcriptional profiling of E. coli treated with sublethal concentrations of the arylamides showed induction of genes related to membrane and oxidative stresses, with some overlap with the effects observed for polymyxin B. Protein secretion into the periplasm and the outer membrane is also compromised, possibly contributing to the lethality of the arylamide compounds. The induction of membrane stress response regulons such as rcs coupled with morphological changes at the membrane observed by electron microscopy suggests that the activity of the arylamides at the membrane represents a significant contribution to their mechanism of action