Level Crossing Probabilities for Cyclostationary Processes with Two Frequencies in Marine Diesel Engine Shafting Systems

1995 ◽  
Author(s):  
Dimitrios V. Lyridis ◽  
Anastassios N. Perakis ◽  
Michael G. Parsons
Keyword(s):  
Diesel Engine ◽  
Marine Diesel Engine ◽  
Level Crossing ◽  
Marine Diesel ◽  
Crossing Probabilities

Probabilistic Torsional Vibration Analysis of a Marine Diesel Engine Shafting System: The Level Crossing Problem

1989 ◽  
Vol 56 (4) ◽  
pp. 953-959 ◽  
Author(s):  
Efstratios Nikolaidis ◽  
Anastassios N. Perakis ◽  
Michael G. Parsons
Keyword(s):  
Diesel Engine ◽  
Torsional Vibration ◽  
Probabilistic Approach ◽  
Series Representation ◽  
Harmonic Series ◽  
Complex Conjugate ◽  
Time Interval ◽  
Marine Diesel Engine ◽  
Level Crossing ◽  
Marine Diesel

A probabilistic approach to the torsional vibration problem of a marine diesel engine shafting system has been developed. In this analysis, the shafting shear stress is found to be a Gaussian, harmonizable cyclostationary process with a harmonic series representation consisting of two complex conjugate components. In this paper, the level crossing problem for this stress process is studied. Two methods for estimating the probability that the stress exceeds a specified threshold at least once over a given time interval are presented. In the first method, a local maximum of the process is approximated by the value of the corresponding envelope at the time of occurrence of this maximum. A Markov-type condition is assumed to hold for the local maxima. The second method assumes that the maximum of the process over a reasonable number of cycles is approximately equal to that of the envelope process. The envelope crossings are assumed to constitute a Poisson process. The two methods are applied to estimate the upcrossing probability in various cases. The results of both approaches are found to be in good agreement with those from Monte Carlo simulation.

Structural Reliability Analysis of Marine Diesel Engine Shafting Systems: An Equivalent Stationary Process Approach to the Level Crossing Problem

1994 ◽  
Vol 38 (03) ◽  
pp. 253-258
Author(s):  
Dimitrios V. Lyridis ◽  
Anastassios N. Perakis ◽  
Michael G. Parsons
Keyword(s):  
Diesel Engine ◽  
Random Process ◽  
Failure Probability ◽  
Structural Reliability ◽  
Stationary Process ◽  
Process Approach ◽  
Marine Diesel Engine ◽  
Level Crossing ◽  
Cyclostationary Process ◽  
Marine Diesel

This paper is concerned with the level crossing problem of a stress above some limit. The problem arises when the structural reliability of a diesel engine shafting system is examined. The first excursion failure probability is derived for the case that the stress on the shaft is a one-frequency cyclostationary random process. A new method is introduced where the cyclostationary random process is replaced with an equivalent stationary one, defined to have an envelope process with the same upcrossing rate as the envelope of the original cyclostationary process. Both processes are assumed to have the same probability of upcrossing a specific threshold. The agreement between this approach, which results in an analytical expression, and the "exact," computationally time-consuming "Markov approach" presented in earlier work is excellent.

Selection of a Waste Heat Recovery System for a Marine Diesel Engine Based on Exergy Analysis

2016 ◽  
Vol 25 ◽  
pp. 36-51
Author(s):  
Salman Abdu ◽  
Song Zhou ◽  
Malachy Orji
Keyword(s):  
Diesel Engine ◽  
Heat Recovery ◽  
Waste Heat Recovery ◽  
Waste Heat ◽  
Marine Diesel Engine ◽  
Exergetic Efficiency ◽  
Waste Heat Recovery System ◽  
Recovery System ◽  
Heat Recovery System ◽  
Marine Diesel

Highly increased fuel prices and the need for greenhouse emissions reduction from diesel engines used in marine engines in compliance with International Maritime Organization (IMO) on the strict regulations and guidelines for the Energy Efficiency Design Index (EEDI) make diesel engine exhaust gas heat recovery technologies attractive. The recovery and utilization of waste heat not only conserves fuel, but also reduces the amount of waste heat and greenhouse gases dumped to the environment .The present paper deals with the use of exergy as an efficient tool to measure the quantity and quality of energy extracted from waste heat exhaust gases in a marine diesel engine. This analysis is utilized to identify the sources of losses in useful energy within the components of the system for three different configurations of waste heat recovery system considered. The second law efficiency and the exergy destroyed of the components are investigated to show the performance of the system in order to select the most efficient waste heat recovery system. The effects of ambient temperature are also investigated in order to see how the system performance changes with the change of ambient temperature. The results of the analysis show that in all of the three different cases the boiler is the main source of exergy destruction and the site of dominant irreversibility in the whole system it accounts alone for (31-52%) of losses in the system followed by steam turbine and gas turbine each accounting for 13.5-27.5% and 5.5-15% respectively. Case 1 waste heat recovery system has the highest exergetic efficiency and case 3 has the least exergetic efficiency.

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