Jerzy Girtler

The semi-Markov model of the process of appearance of sea-going ship propupsion system ability and inability states in application to determining the reliablity of these systems

ABSTRACT The article presents possible application of the theory of semi-Markov processes in creating the eight-state model of the process of appearance of the propulsion systems ability and inability states on sea-going vessels performing transportation tasks in a relatively long operating time t (t → ∞). The model has been proved to be able to be successfully used for determining the reliability of the abovementioned systems. The probability of faultless operation in time t was assumed the measure of system reliability. Operating situations of sea-going vessels were characterised, with special attention being paid to the fact that the loads of propulsion system components of these vessels are of random nature. These loads lead to damages which for this reason were also considered random events. It was also assumed that the damages provoke the appearance of states of inability of particular ship propulsion system components which means that these states are random events as well. The states of ability of a given ship propulsion system have been assumed to exist when all components of this system are in the state of ability. In case when at least one component is in the state of inability, the entire system is in the state of inability. Conditions were formulated for the reliability model of an arbitrary system to be able to be worked out in the form of the semi-Markov process. The need for the use of technical diagnostics in reliability examination of sea-going ship propulsion systems was indicated. In conclusions, certain qualities of the article were highlighted which are, in author’s opinion, of highest importance in reliability examination of sea-going ship propulsion systems.

The semi-Markov model of energy state changes of the main marine internal combustion engine and method for evaluating its operation during ship voyage

The semi-Markov model of energy state changes of the main marine internal combustion engine and method for evaluating its operation during ship voyage The article presents a method for evaluating the operation of internal combustion engines used as the main engines in the propulsion systems of sea-going ships in various operating conditions. This method enables calculating the engine operation value based on the theory of semi-Markov processes and mathematical statistics. What is noteworthy, the operation of the examined internal combustion engines is compared to a physical quantity which is expressed in the form of a number with the measure unit called joule-second. a model having the form of a semi-Markov process is proposed to describe the energy state changes taking place in the main engines during their operation. Also proposed is the use of the point and interval estimation at a given confidence level β for determining the value of the energy converted in the engine during its operation for the known and unknown standard energy deviation treated as the random variable. The semi-Markov model of changes of the energy converted in the engine during its operation is presented in a general form. The above model was used for determining the ships main engine operation, which is in the examined case a function of the energy converted in particular energy states, the expected value of the time of duration of these states and the probability of their existence. These probabilities compose the limiting distribution of the semi-Markov process, the values of which are the specified main engine energy states.

A probabilistic concept of load assessment of self-ignition engines

A probabilistic concept of load assessment of self-ignition engines A proposal of probabilistic interpretation of loading process of self-ignition combustion engines, was presented. Probabilistic description of loading the engines was proposed with taking into account known parameters (indices) of their operation. It was demonstrated that instantaneous load of such engines can be considered a random variable. Attention was paid to the fact that the load can be taken as a multi-dimensional random variable. Engine load changes during its operation were considered as the loading process and presented in the form of a multi-dimensional stochastic process whose states are loads considered to be random variables. It was demonstrated that the loading process can be taken as the stochastic one of asymptotically independent incements, stationary and ergodic. Justification of the above mentioned features of the loading process is contained in the presented hypotheses. It was also demonstrated that in testing the load process of self-ignition engines stochastic relation between thermal and mechanical loading should be taken into account.

Application of theory of semi-Markov processes to determining distribution of probabilistic process of marine accidents resulting from collision of ships

ABSTRACT In this paper is presented possible application of the theory of semi-Markov processes to elaborating an eight-state model of the process of occurrence of serviceability state and unserviceability states of sea-going ships making critical manoeuvres during their entering and leaving the ports. In the analysis it was taken into account that sea-going ships are in service for a very long time t (t → ∞). The model was elaborated to determine the probability (P0) of correct execution of critical manoeuvres during ship’s entering and leaving the port as well as the probabilities Pj(j = 1, 2, 3, …, 7) of incorrect execution of critical manoeuvres by a ship, that leads to marine accidents. It was assumed that such accidents result from: ship’s grounding on port approaching fairway, collision with a ship on port approching fairway, collision with a pierhead during passing through port entrance, collision with a hydrotechnical structure during ship’s passing through port channels, collision with a port quay during coming alongside it and collision with a ship already moored to the quay. The probability (P0) was assumed a measure of safe execution of a critical manoeuvre. The probability characterizes possibility of avoiding any collision during ship’s entering and leaving the port. The probability Pa = 1 - P0 was assumed a measure of occurrence of a collsion and - consequently - marine accident. The probability Pa was interpreted as a sum of the probabilities Pj(j = 1, 2, 3, …, 7) of occurrence of all the selected events. In summing up the paper, attention was drawn to its merits which - in opinion of this author - are crucial for research on real process of accidents during entering the port and leaving it by sea-going ship in difficult navigation conditions.

Operational problems of large power diesel engines combusting biofuels, considered together with assessment of their operation

Operational problems of large power diesel engines combusting biofuels, considered together with assessment of their operation In this paper the problem is discussed of supplying high power diesel engines with biofuels in the aspect of consequences which occurr during their operation. Attention was paid to advantages and difficulties associated with application of biofuels to self-ignition engines. A relevant research problem was characterized and research targets were proposed to make it possible to most favourably shape energy merits of the engines. Special attention was given to wear process of such engines and their failures resulting from application of biofuels. The following problems were also considered: calcium carbonate sedimentation, closing graphite platelets in structure of cylider bearing surface and surface defects of piston rings made of aluminium bronze. It was demonstrated that to assess operation of the engines is possible under the assumption that in a valuating approach their operation can be compared to a physical quantity represented numerically and measured with the use of the joule*sec unit. Conclusions resulting from the domestic and foreign investigations on power and reliability of such engines were also presented.

A method for evaluating theoretical and real operation of diesel engines in energy conversion formulation taking into account their operating indices

A method for evaluating theoretical and real operation of diesel engines in energy conversion formulation taking into account their operating indices The article proposes valuating the operation of an arbitrary diesel engine, based on the sample case of a ships main engine in which energy conversion processes take place in a given time. The above operation is understood as the energy transfer to the screw propeller in the given time in which the energy conversion into work and/or heat and its further transmission take place. The here proposed method for evaluating the operation of the main engines installed in marine power plants consists in comparing the operation of these engines to a physical quantity the measuring unit of which is the joule-second (joule x second). A new term is introduced which bears the name of the theoretical engine operation and is the standard (ideal) operation which can be compared to the operation of real engines revealing different levels of wear. It was shown that the calculations of the theoretical operation defined in the above way cannot make direct use of commonly known theoretical Diesel and Sabathe cycles. Instead they should use the cycles modified by heat abstraction taking place in accordance with the isobaric, or isothermal process. Other new terms introduced in the article are: the degree of excellence of energy conversion to work, considered as the measure of excellence of engine operation, and the degree of engine operation dissipation, being the measure of its real operation. It is shown that if in time t of engine operation the case takes place that: Li = idem and Le = idem, then the engine operation dissipation is equal to its mechanical efficiency.

Features of Load and Wear of Main Propulsion Devices on Sea-Going Ships with Piston Combustion Engines and Their Impact on Changes in Technical States of the Systems

Abstract The paper presents the specificity of operation of propulsion systems of seagoing ships which causes the need to control the load on them, especially on their engines called main engines. The characteristics of the load on the propulsion systems, especially on the main engines as well as on the shaft lines and propellers driven by the engines, along with the process of wear in tribological joints (sliding tribological systems) of the machines have been described herein. Using examples of typical types of wear (both linear and volumetric) for the tribological systems of this sort, interpretation of states of their wear has been provided with regards to the wear levels defined as acceptable, unacceptable and catastrophic. The following hypotheses have been formulated: 1) hypothesis explaining necessity to consider the loads on the systems under operation as stochastic processes; 2) hypothesis explaining a possibility of considering the processes as stationary; and 3) hypothesis explaining why it can be assumed that a given technical state of any tribological system can be considered as dependent only on the directly preceding state and stochastically independent of the states that existed earlier. Accepting the hypotheses as true, a four-state continuous-time semi-Markov process has been proposed in the form of a model of changes in condition of a propulsion system (PS) of any ship. The model includes the most significant states affecting safety of a ship at sea, such as: s0 - PS ability state, s1 - PS disability state due to damage to the main engine (ME), s2 - PS disability state due to damage to the shaft line (SL) and s3 - PS disability state due to damage to the propeller (P). Probability of occurrence (changes) of the states has also been demonstrated.

Analysis of catalitic reactors usefulness to reduce pollution generated by piston combustion engines with regard to ship main engines

Abstract The article presents results which indicate that the use of catalytic reactors to reduce emissions of harmful compunds contained in the exhaust gas is important in the operation of vehicle motors operation. Efforts of the shipbuilding industry to reduce the toxicity of exhaust gas emitted by the main engines have been indicated and pointed to the desirability of the use of these catalysts in maritime transport. It has been pointed out that studies of the harmful substances in exhaust gases performer at vehicle inspection stations have an impact on increasing the safety of drivers and other road users and contribute to preserving the natural environment by reducing the danger coming from cars operating on Polish roads. An opinion has been expressed that the most serious threats to the environment are emitted by car transport exhaust fumes, which are characterized by significant emission of toxic compounds excreted into the atmosphere from tailpipe emissions. It has been demonstrated that a fully functioning catalytic reactor, operating in a steady state at appropriate temperatures and the composition of the mixture close to stoichiometric ratio, can reduce emissions of carbon monoxide, hydrocarbons and nitrogen oxides by more than 90%. Also, an assessment has been presented reporting the efficiency of catalytic reactors of spark ignition engines operating in a test vehicle inspection station. The results of research in the evaluation of their performance were correlated with their operation waveforms. Such an approach is justified by the fact that during the operation of each vehicle the wear of its assemblies and components is different - including the catalytic reactor. The catalytic layer undergoes aging so that there are changes in the structure and chemical composition of the catalyst bed, while the overlapping of layers of different chemical compounds that block access to the active layer of the reactor. An opinion has also been expressed that it would be advisable to take steps to use research results presented in this article for research of catalytic reactors similar use in diagnostic systems of marine combustion engines, especially the main ones, which exhaust emissions are incomparably greater than in the case of car engines.

A model of fuel combustion process in the marine reciprocating engine work space taking into account load and wear of crankshaft-piston assembly and the theory of semi-Markov processes

Abstract The article analyses the operation of reciprocal internal combustion engines, with marine engines used as an example. The analysis takes into account types of energy conversion in the work spaces (cylinders) of these engines, loads of their crankshaft-piston assemblies, and types of fuel combustion which can take place in these spaces during engine operation. It is highlighted that the analysed time-dependent loads of marine internal combustion engine crankshaft-piston assemblies are random processes. It is also indicated that the wear of elements of those assemblies resulting from their load should also be considered a random process. A hypothesis is formulated which explains random nature of load and the absence of the theoretically expected detonation combustion in engines supplied with such fuels as Diesel Oil, Marine Diesel Oil, and Heavy Fuel Oil. A model is proposed for fuel combustion in an arbitrary work space of a marine Diesel engine, which has the form of a stochastic four-state process, discrete in states and continuous in time. The model is based on the theory of semi-Markov processes.

Operation evaluation method for marine turbine combustion engines in terms of energetics

Abstract An evaluation proposal (quantitative determination) of any combustion turbine engine operation has been presented, wherein the impact energy occurs at a given time due to Energy conversion. The fact has been taken into account that in this type of internal combustion engines the energy conversion occurs first in the combustion chambers and in the spaces between the blade of the turbine engine. It was assumed that in the combustion chambers occurs a conversion of chemical energy contained in the fuel-air mixture to the internal energy of the produced exhaust gases. This form of energy conversion has been called heat. It was also assumed that in the spaces between the blades of the rotor turbine, a replacement occurs of part of the internal energy of the exhaust gas, which is their thermal energy into kinetic energy conversion of its rotation. This form of energy conversion has been called the work. Operation of the combustion engine has been thus interpreted as a transmission of power receivers in a predetermined time when there the processing and transfer in the form (means) of work and heat occurs. Valuing the operation of this type of internal combustion engines, proposed by the authors of this article, is to determine their operation using physical size, which has a numerical value and a unit of measurement called joule-second [joule x second]. Operation of the combustion turbine engine resulting in the performance of the turbine rotor work has been presented, taking into account the fact that the impeller shaft is connected to the receiver, which may be a generator (in the case of one-shaft engine) or a propeller of the ship (in the case of two or three shaft engine).