Optimization of automatic control of the speed of rotation of a marine diesel engine

Annotation – The well-established method of tuning the speed governors (SG) of diesel engines during their operation under conditions of step disturbances, which are characteristic of diesel-generators, cannot be used for the main marine engines, the dynamic modes of which are associated, first of all, with heavy seas, because disturbances cannot change stepwise both along the channel for setting the rotational speed and along the load channel. In this regard, the practical need for the development of a method for tuning the SG of the main engines, which takes into account the peculiarities of their operation in heavy seas, has been determined. The study simulates the automatic speed control system (ASC) of the main marine engine HYUNDAI – MAN B&W 6G70ME-C9.2 of the large crude carrier "GOLDWAY" with the AutoChief 600 electronic SG. The minimum of instability of the controlled parameter was used as an optimality criterion, i.e. the amplitude of the oscillations of the rotational speed of the diesel engine shaft, with the most probable values of the amplitude and period of oscillations (rolling) of the disturbing effect. The study has established that changing the tuning parameters of the governor may lead to local extrema of the optimality criterion when using an electronic governor in the ACS in the factor space of disturbances on a diesel engine, which are typical for heavy seas. It means that the task, requiring finding local extrema using specialized methods, can be set when using an electronic governor in the ACS. However, a significant decrease in the instability of the rotational speed was achieved by carrying out a simple enumeration of the tuning parameters of the SG. It was also found that with a "heavy" propeller, the rotational speed stability can be increased by decreasing the proportional gain, as well as increasing the integrator time.

Determining the causes, prevention and elimination of unstable modes of gas turbochargers of marine diesels

Annotation – With commissioning of the “Socofl Star” ship’s series, negative occurrences relative to surging of the Main Engine (ME) «Hanshin Diesel» 6LF46 turbochargers (TC) VTR 401-2. To elimination of a surging, it was necessary reduce loading of ME to the safe level. This action caused the ship’s speed to fall from 11 – 10 to 4 knots which resulted in worsening of the ship’s maneuverability characteristics and lead to the failure to provide the ship’s service speed stipulated in the contractual arrangements. Existence of this problem instigated the shipowner to charge us as experts with the mission of carrying out appropriate investigations and working out recommendations as to how to prevent and eliminate surging of TC. This task was solved on the m/v “Socofl Star”. Based on results the ME shop test and trial test of the vessel and also the saved-up data of work of ME in various conditions of swimming, the analysis of the causes of a surge of the TC was made. It is established that small values of safety factor of stability of the compressor of TC on a surging – KCT which are not allowing to ensure effective functioning of TC on the main modes of loading of ME are its reason. For increase in area of steady work of TC it is necessary to reduce the hydraulic resistance of components of the Air-Gas Path (AGP) of the ME which can be realized by changes in a design of units of air supply and gas exchange or reduction of productivity and extent of increase in pressure of air in the compressor of TC. Under operating conditions vessels an optimal solution an objective is removal of a part of blowing-off air after compressor of the TC. The air can be discharged into the flue gas header after the waste heat recovery boiler or directly into the atmosphere. This allowed the shipowner not to make constructive changes to the components of the AGP of ME and TC. The description of the operated unloading device controlled remotely on removal of air which ensures effective functioning of TC and ME that is confirmed by results of natural tests and the subsequent operating experience of vessels of the “Socofl Star” series is provided.

Improving the management of fuel combustion in ship boilers

Annotation – The article discusses the issues of increasing the efficiency of the combustion of liquid fuel in the furnaces of ship steam boilers using the proposed neural network system for automatic correction of the excess air coefficient. It is indicated that modern systems for automatic flame detection have a number of disadvantages, in particular, low sensitivity to extraneous illumination, etc. hot air or flue gases on the walls of the boiler furnace. Such pulsations reduce the reliability of the combustion monitoring and control system. Therefore, the task of developing and introducing on ships new, economically inexpensive and effective methods of effective control and management of the fuel combustion process in ship boilers using modern means of intelligent control is urgent. On the basis of the experiments carried out on a Mitsubishi MV 50 marine steam boiler and the collected experimental data, the values for training the neural network system of the air flow correction process, taking into account the color of the burner flame and the color of the flue gases, were obtained. The use of a trained neural network in the control system, taking into account the fuzzy expert system for monitoring the color of the flame and smoke, makes it possible to achieve the best excess air ratio depending on the steam load of the SEP units. Simulation modeling of the proposed neural system was carried out in a specialized program Matlab (Neural Networks Toolbox). The simulation results showed that the use of a neural network control system for the combustion of liquid fuel, using the example of a marine boiler, allows maintaining a given thermal regime over the entire range of steam load of the power plant units, and also allows timely correction of the excess air ratio, i.e. avoid excessive consumption of fuel.

Adjustment of drilling slurry density during transportation by Platform Supply Vessels

Annotation – The issues of maintaining the drilling fluid density during its transportation from shore to the oil drilling platform by the Platform Supply Vessels were considered. The research was carried out on the vessel of 5650 deadweight tons, which made 2 ... 2.5 day voyages from port to drilling platform with possible waiting for direct approach to the platform for 1 ... 1.5 days. The drilling fluid was transported in four tanks of equal-size, arranged in pairs on each side of the vessel. It was found that during this period of time there is a latent stratification of drilling fluid along the depth of cargo tank, causing stratification of its density. The density of the drilling fluid was measured at depths corresponding to 10, 50 and 90 % of the total tank depth. The drilling fluid density stratification is defined as the relative density change in the upper (at 10 % depth) and lower (at 90 % depth) parts of the cargo tank. The hydrometer was used to measure density, allowing measurements in the range of 650 ... 1630 kg/m3 with an accuracy of 1 kg/m3 while controlling the temperature. Density measurements were taken at 6-hour intervals. It has been experimentally proved that during the 48-hour transportation of the drilling fluid with the density of 1295 kg/m3, the density value at the indicated depths is 1163 and 1524 kg/m3 respectively, while the density stratification reaches 31 %. It is offered to prevent the density stratification by creating a forced X-shaped circulation of the drilling fluid between cargo tanks which stand side by side. It is offered to regulate and maintain automatically the drilling fluid density in the range of 2 ... 7 % by using programmable controllers. When the density stratification reaches 7 %, the controller switches on the circulation pumps and circulates the drilling fluid between tanks which stand side by side. This increases the drilling fluid uniformity and helps to reduce the density stratification along the depth of the cargo tank. The process of additional circulation of the drilling fluid is rationally ensured until the density stratification reaches a value of 2 %. Fulfilment of the above-mentioned conditions will ensure that the drilling fluid maintains its operational properties and the energy consumption associated with the additional operation of the circulation pumps is minimised.

Dynamics of marine diesels when using motor oils with different structural characteristics

Annotation – The influence of the structural characteristics of engine lube oil on the dynamics of a marine diesel engine is considered. It is indicated that micron layers of marine engine lube oils separating the contact surfaces of marine diesel engines acquire the properties of liquid crystals and are characterized by an ordered molecular structure. The qualitative indicator of this structure is the degree of ordering of the molecules, and the quantitative indicator is the thickness of the ordered (boundary) lubricating layer. It is proposed to determine the structural characteristics of marine engine lube oils (the degree of ordering of the molecules of the boundary layer and its thickness) using the optical method of absorption dichroism. A diagram of an experimental setup is presented that allows such studies to be carried out. It has been experimentally established that for Shell Rimula X15 and Castrol TPL 123 engine lube oils (used in the oil system of the Caterpillar CatC18 marine diesel engine), the thickness of the ordered (boundary) lubricating layer is 14.3 ... 14.7 microns and 16.4 ... 16.6 microns, respectively. The degree of ordering of molecules in the boundary layer for Shell Rimula X15 engine lube oil is in the range of 0.56 ... 0.58, for Castrol TPL 123 engine lube oil – in the range of 0.63 ... 0.64. The results of studies of the dynamics of the CatC18 marine diesel engine by Caterpillar, carried out in the starting mode, as well as at various increases and decreases in load, are presented. As indicators, which were used to assess the dynamics of the diesel engine, the overshoot of the rotational speed and the time to reach a new steady state mode were taken. Experiments have confirmed that Castrol TPL 123 engine lube oil, which has a higher molecular structure in the boundary layer compared to Shell Rimula X15 lube oil, ensures the transient processes of the Caterpillar CatC18 marine diesel engine with less overspeed and less time to reach a new state work. The proposed technology for determining the structural characteristics of engine lube oils can be used for any type and grade of oil (mineral or synthetic, high and low viscosity, used both in circulating and cylinder lubrication systems). The proposed method for assessing the dynamic characteristics of marine diesel engines (by overshoot of the speed and the time to reach a steady state of operation in the event of a change in load) can be used for any types of internal combustion engines (low-, medium- and high-speed; as well as performing the functions of both main and auxiliary engines).

Calculation of contact pressure and contact zone in slip pairs of marine diesels

Annotation – The durability of marine diesels significantly depends on the operation of friction pairs, such as: piston rings - cylinder liner; crankshaft - bearing shell, plunger - sleeve, and others. This is primarily due to the constant contact interaction of the elements of the friction pairs at different temperatures and load. Therefore, the research of normal pressure and the definition of contact areas in the friction pairs, the studying of the influence of the quality of lubricants on these characteristics are important tasks for predicting the longevity of marine diesels. The solution of these problems is based on the application of mathematical models of processes (numerical simulations) that occur in friction pairs. This considers two main processes that occur during the operation of the friction pairs: the research of contact and tangential stresses that occur in friction pairs in the framework of elastic or elastic-plastic contact models; study of hydrodynamic processes in a thin layer of oil between the elements of the friction pairs. The combination of these processes allows to sufficiently assess the influence of the elastic-mechanical properties of the sliding vapor elements and the viscosity and hydrodynamic characteristics of the oils on the durability of the marine diesel unit. The first process is researched in this work. In particular, for the analysis of contact stresses and contact zones in friction pairs, the method of numerical modeling is used, which is based on the differential equations of the theory of elasticity. With the help of fundamental solutions (influence functions), the problem is reduced to an integra-differential equation with the Gilbert’s kernel. The solution of which is constructed using the method of orthogonal polynomials as well as easy-to-use approximation formulas. Numerical simulations were performed, as a result, the maximum pressure and contact zone parameters for some combinations of friction pairs materials of marine diesel engines were determined. In particular, the influence of the radial gap on the pressure distribution and the size of the contact zone between the elements of the friction pairs of marine diesels is established.

Operation of marine diesel on biodiesel

Annotation – The influence of biodiesel fuel on the economic and ecological performance of the marine diesel engine is considered. The reasons limiting use of alternative fuels (including fuels based on biological origin) on vessels are indicated. The results are performed on a specialized vessel with a deadweight of 10,820 tons, which carried out short-term (within 4 ... 6 days) transitions between ports, were it was possible to replenish alternative fuel stocks. Studies performed on 5DC-17A Tier II Daihatsu Diesel marine diesels in the range of their operational loads 55 ... 85 %, from a fuel mixture consisting of 80 ... 95% of DMB diesel fuel and 5 ... 20% of B99.9 FAME biofuel, next conclusion have been done: in all range of loads and for all content of biofuels in the fuel mixture there is an increase in the specific efficient fuel consumption; on the operating modes in range 55 ... 65% of nominal loading and 5 ... 10 % of the maintenance of biofuel in mix this increase makes 1.92 ... 2.96 %, on the modes 75 ... 85 % of loading and at use mixtures with a content of 15 ... 20 % biofuels increase in fuel consumption reaches 4.04 ... 6.67 %; most of all, the efficiency of the diesel engine detected during its operation at loads of 55 ... 65 % and 15 ... 20 % of the biofuel content in the mixture, in this conditions, the increase in specific fuel efficiency reaches 7.39 ... 8.17 %; during the operation of the diesel engine in the load range of 55 ... 85 %, the emission of nitrogen oxides is observed, with best efficacies (up to 23.8 ... 24.3 %) corresponding to 10 ... 15 % of the biofuel content in mixtures; with an increase in the content of biofuels in the mixture up to 20 % reduction in emissions of nitrogen oxides is in the range of 10.1 ... 15.2 %; the use of biofuels helps to reduce the volume concentration of carbon monoxide in the exhaust gases; the greatest efficiency is corresponding at load 75 ... 85 % and use of the fuel mix containing 20 % of biofuel, under such conditions decrease in concentration of carbon monoxide reaches 25.4%; which further enhances the energy efficiency of ships. The optimal composition of the fuel mixture containing biofuel has been proposed, taking into account its environmental (before the emission of nitrogen oxides and the volume concentration of carbon monoxide in the exhaust gases), as well as economic performance of marine diesel.

The use of model gas in the study of the gas engine of a power plant

Annotation – The analysis of scientific publications over the past ten years in the direction of creating gas ICEs in Ukraine, operating on natural gas, biogas or similar low-calorie fuels. The objectives of the work summarize the results of studies on the use of model gas in a gas internal combustion engine operating on a power plant drive. Developed recommendations on biogas additives to natural gas depending on the power plant load, and to develop a fuel control algorithm. The article provides recommendations on setting up the power system and automatic regulation of a gas engine running on a mixture of natural gas (methane) and biogas. To solve the tasks, a gas-electric installation with a rated power of 30 kW was tested. Initially, the installation was equipped with an 8-cylinder gasoline engine with spark ignition and an electric generator. The base ICE was converted to purely gas with a compression ratio of 8.5. In the physical modeling of biogas to natural gas additives in the model gas, the volume fraction of carbon dioxide increased to 30 % with a decrease in the load. By calculation, determined a similar ratio of compressed natural gas and biogas additives. For the calculation, it assumed that natural gas contains 90 ... 95 % methane, and biogas 60 % methane and 40 % carbon dioxide. The possibility of using biogas with 60 % methane as an additive to natural gas in piston ICEs with spark ignition has been confirmed. It was found that with a decrease in load, the biogas fraction increase and replace up to 85 % of natural gas. When working on biogas additives, the values of the concentrations of hydrocarbons and residual oxygen in the exhaust gases were determined to control the setting of the gas equipment of the internal combustion engine. Under operating conditions, three test modes selected for the power plant: idle, 50 % load, rated mode. The research results can serve as the basis for creating a control algorithm for the supply of biogas additives to natural gas, depending on load changes.

Prediction of dynamics and seaworthiness of amphibious hovercraft

Annotation – The creation of hovercraft projects is a very expensive procedure, and the emergence of new ships of this type and their evolution is proceeding at a very slow pace. Despite the fact that hovercraft have been used for decades and there is a large amount of literature that is related to the theory of such ships and the practice of their design, there are still a number of unresolved problems associated with these ships. There are various methods, theories and publications that allow to calculate and design various complexes and systems of hovercraft, and as a result, this allows to create vessels that are successful in operation and with good seaworthiness. But at the same time, until now, the main problem remains to achieve sufficient accuracy in predicting the operational characteristics of hovercraft under various modes. Therefore, it is not uncommon for a successful hovercraft project to be born after a series of unsuccessful trial and error. The presented work describes a methodology for creating simulations of hovercraft for various modes of their operation. Various types of simulations of such ships and the ways of their implementation into functioning software are considered. The main mathematical models that are involved in the implementation of such simulations are described and their structure is shown for various hovercraft. The described complex of mathematical models, embodied in the program, allows an in-depth analysis of the dynamics and operational characteristics of hovercraft before the completion of their design and before the start of construction. It is argued that the most difficult, but suitable for real practical problems of analyzing the dynamics of hovercraft is the simulation of this ship with 6 degrees of freedom. The study allows us to conclude that the described methodology for creating a complex of mathematical models makes it possible with high accuracy to predict the dynamics of hovercraft and simulate any hovercraft with 6 degrees of freedom, which will reduce the cost of designing and building a lead hovercraft with accurately predictable seaworthiness and operational characteristics.

Fiber optic flowmeter for ship information and measuring system

The main requirements for flow meters are high accuracy, reliability, durability, resistance to aggressive media, cost-effectiveness, and the ability to output a signal in digital form. Most flowmeters that allow measuring mass flow are characterized by a very complex mechanical design and create a large hydrodynamic resistance to the flow. Fiber-optic flow meters undoubtedly have indisputable advantages and benefits: the absence of electric currents and voltages in the sensitive area of ​​the device, immunity to external electromagnetic influences, absolute environmental and fire and explosion safety. At the same time, until recently, no successful circuitry solutions in the field of fiber-optic flowmeters for monitoring flammable liquids were known. Thus, the development and research of a new vortex fiber-optic flowmeter is an urgent scientific and technical problem. Analysis of the designs of known flow meters made it possible to specify the requirements for a new circuit design of the measuring device. The proposed design of the flow meter differs in that the main and control are essentially the same fiber made of sapphire glass, coaxially to which the sensitive fiber is located. And also a thermocompensating bimetallic plate is introduced into the meter circuit. The developed measuring device will provide: compensation of the influence of uncontrolled operational and climatological factors on the measuring and additional channel; lack of additional mechanical fiber tensioners; protection of sensitive elements of the device; constancy of the geometry of the optical channel under the influence of uncontrolled operational factors; identity of the location of the main and additional channels with respect to the flow of the controlled liquid; increased sensitivity and accuracy of the device.