Marine Internal Combustion Engines Research Articles

Laivų vidaus degimo variklių tepimo alyvos keitimo intervalų optimizavimas: algoritmo tyrimas ir sudarymas

This study investigates an algorithm for optimal oil change intervals in the marine engine fleet, which reduces the costs due to the recommendations of ship engine manufacturers, which may have a large margin of error. At the same time, the algorithm provides measures to avoid exceeding the limits of sustainable operation of the installation. The main objective of the algorithm is to reasonably extend the service life of the lubricating oil in accordance with the recommendations of the engine manufacturers and while maintaining a reminiscent operating condition of the machinery. The variation of lubricating oil quality parameters during engine operation is a very important factor which, if ignored, can lead to high costs associated with ship idling. The obtained theoretical algorithm can be applied in the optimization process, but it is necessary to check and compare it with the results of the laboratory experiments and, if necessary, make corrections to the algorithm. These published results of the algorithm research and design are the first phase of the optimization of the lubrication oil change intervals for marine internal combustion engines, which must be verified by the results of applied research, mathematical analysis and, if necessary, adjusted as needed. Keywords: lubricating oil, marine engines, fleet exploitation.

A Distributed Cyber-Physical Framework for Sensor Fault Diagnosis of Marine Internal Combustion Engines

A Distributed Cyber-Physical Framework for Sensor Fault Diagnosis of Marine Internal Combustion Engines

Digital Twin Test-Bench Performance for Marine Diesel Engine Applications

Abstract The application of Digital Twins is a promising solution for enhancing the efficiency of marine power plant operation, particularly their important components – marine internal combustion engines (ICE). This work presents the concept of applying a Performance Digital Twin for monitoring the technical condition and diagnosing malfunctions of marine ICE, along with its implementation on an experimental test-bench, based on a marine diesel-generator. The main principles of implementing this concept involve data transmission technologies, from the sensors installed on the engine to a server. The Digital Twin, also operating on the server, is used to automatically process the acquired experimental data, accumulate statistics, determine the current technical state of the engine, identify possible malfunctions, and make decisions regarding changes in operating programs. The core element of the Digital Twin is a mathematical model of the marine diesel engine’s operating cycle. In its development, significant attention was devoted to refining the fuel combustion model, as the combustion processes significantly impact both the engine’s fuel efficiency and the level of toxic emissions of exhaust gases. The enhanced model differs from the base model, by considering the variable value of the average droplets’ diameter during fuel injection. This influence on fuel vapourisation, combustion, and the formation of toxic components is substantial, as shown. Using the example of calibrating the model to the test results of a diesel engine under 27 operating modes, it is demonstrated that the application of the improved combustion model allows better adjustment of the Digital Twin to experimental data, thus achieving a more accurate correspondence to a real engine.

Quantumness in Diagnostics of Marine Internal Combustion Engines and Other Ship Power Plant Machines

Abstract The article provides proof that the diagnostics of marine internal combustion engines and other ship power plant machines should take into account the randomness and unpredictability of certain events, such as wear, damage, the variations of mechanical and thermal loads, etc., which take place during machine operation. In the article, the energy E, like the other forms (methods) that it can be converted into (heat and work), is considered the random variable Et; at time t, this variable has the mean value E ¯ t {\bar E_t} , which is the observed value of the statistic E ¯ s t {\bar E_{st}} with an asymptotically normal distribution N ( E ( E t ) , σ t n ) N\left( {E\left( {{E_t}} \right),{{{\sigma _t}} \over {\sqrt n }}} \right) , irrespective of the functional form of the random variable Et. A proof is given that shows that the expected value estimated in the above way, considering the time t of the performance of task Z by a marine internal combustion engine or other ship power plant machine, can be used to determine the machine’s possible action (DM). When compared to the required action (DW) needed for task Z to be performed, this possible action makes it possible to formulate an operating diagnosis concerning whether the engine or machine of concern is able to perform task Z. It is assumed that an energy device of this type is able to perform a given task when the inequality DM≥DW holds. Otherwise, when DM < DW, the device cannot perform the task for which it was adopted in the design and manufacturing phase, which means that it is in the incapability state, although it still can be started and convert energy into the form of heat or work..

Efficiency of limiting nitrogen oxides emissions by exhaust gas recirculation systems of marine internal combustion engines

The subject of this study is systems for ensuring environmental safety of marine internal combustion engines, in particular, technologies for limiting emissions of nitrogen oxides (NOx). The regulatory requirements for reducing emissions are presented in the paper. The main theoretical aspects of the problem of nitrogen oxides formation during combustion in a diesel engine are considered. On the basis of these theoretical aspects the effectiveness of using various methods to achieve the requirements for the permissible level of NOx concentration in the exhaust gases is assessed. Exhaust gas recirculation (EGR) systems and selective catalytic reduction (SCR) systems are considered as the main technologies; they allow achieving the highest indicators of nitrogen oxide emissions control in accordance with the requirements of the Tier 3 standard. Taking into account the peculiarities of the requirements for the design and layout of systems as part of a ship power plant, as well as operational and investment costs, the main attention in the work is paid to systems of indirect influence on the engine in-cylinder processes, which include exhaust gas recirculation systems. Based on the comparison of high and low pressure EGR, the advantages and disadvantages of the designs are determined. It is noted that high-pressure exhaust gas recirculation systems have a number of advantages, which primarily include the compactness and high speed of the system response to changes in operational conditions. On the example of the leading manufacturers developments, the potential capabilities of the high-pressure EGR system and the engine characteristics confirming the effectiveness of its use are demonstrated. Based on the results of the work, a conclusion about the high efficiency and expediency of using exhaust gas recirculation systems to meet the requirements of the current environmental safety standards of ship power plants is made.

PROCESSING OF INDICATOR DIAGRAM IN THE TASKS OF CONSTRUCTING DIGITAL PROFILES OF THE WORKING PROCESS OF SHIP ENGINES

During the operation of marine internal combustion engines, the procedure for indicating the working process in certain operating modes is widely used, followed by an analysis of indicator diagrams and a comparison of the results obtained with the reference ones obtained during engine factory tests. However, the general trend in the world fleet towards a decrease in the commercial speeds of ships, on the one hand, and the use of tight traffic schedules, on the other hand, have led to the fact that in most cases it is impossible to carry out indexing according to the procedures prescribed in the rules for the technical operation of engines. Thus, the ability of maintenance personnel to objectively assess the current technical condition of the engine is lost, and to determine the necessary list of preventive measures for maintenance and repair, which, of course, affects the efficiency of engines and the safety of navigation in general. One of the effective ways to solve this problem is the use of digital profiles of engine work processes, which characterize their work in the entire range of operating modes. With the help of a digital profile, it is possible to obtain a calculated reference indicator diagram, which can be used for comparison with the one obtained during the planned indication of the engine in any mode of its operation. As a basis for building digital profiles, it is appropriate to use the results of acceptance test bench tests of the engine by the manufacturer. However, taking into account the rather long service life of marine engines, test reports usually exist only in a raster format, which greatly complicates the processing of the indication results given in them, which, most often, was performed using mechanical indicators. To use this information to build digital profiles, the authors proposed a method for processing such indicator diagrams, described in previous articles. However, the efficiency of generating digital profiles significantly depends on the quality of the basic diagrams on which these profiles are built. This article is devoted to the processing of such diagrams.

Diagnosing Cracks in the Injector Nozzles of Marine Internal Combustion Engines during Operation Using Vibration Symptoms

In the operation of internal combustion engines, despite technical state monitoring, some cracks that develop in metal components go undetected, leading to secondary, critical, or degradation damage. The diagnostic systems used in floating objects mainly use quasi-static thermodynamic signals, which alert operators too late about emerging damage. Although various methods have been developed to detect cracks in internal combustion engine components, the effectiveness and implementation of the proposed methods are not satisfactory. Therefore, this article presents the use of selected vibration and in-cylinder pressure signals to diagnose the development of damage in some components of marine diesel engines. The investigations were conducted under the natural conditions of the operation of sea-going vessels during port-handling operations. During these investigations, it was possible to observe clear changes in the values of diagnostic symptoms, which corresponded to the development of damage. The developing damage detected in the study involved cracks in injector nozzles manufactured from alloy steel. Despite advances in design, materials, and manufacturing technology, injector nozzle cracks still occur. The diagnostic symptoms used to detect damage development were the amplitude and spectral and wavelet measurements of vibration acceleration signals. This work aimed to search for crack-oriented methods of signal analysis, for example, computer visualization and the recording of diagnostic parameters in various domains. Decimation, windowed, time, amplitude, and time-frequency domain analyses; wavelet statistics; color analysis; and machine learning were used for classification using artificial neural networks. Experimental investigations showed the possibility of diagnosing the development processes of damage to marine diesel engines. The advanced signal processing methods used made it possible to obtain many signal measurements, from which the most useful diagnostic symptoms were selected. The new symptoms found with decimation, time-domain windowed analysis, and Haar wavelet statistics were more useful than the existing ones.

Numerical study of injection strategies for marine methanol/diesel direct dual fuel stratification engine

To explore the application potential of renewable methanol and direct dual fuel stratification (DDFS) technology in marine internal combustion engines, this study conducted a fuel injection strategy research based on performance optimization for a marine methanol/diesel DDFS engine under high methanol substitution rate (95%). The results show that the fuel mixing process plays a crucial role in methanol/diesel DDFS engine combustion state switching. Premature methanol injection under methanol single-stage injection strategy causes ringing intensity (RI) to exceed the engine limit. Additionally, when start of diesel injection (SOID) occurs earlier than start of methanol injection (SOIM), the shorter methanol/diesel injection interval (MDI) leads to the deterioration of diesel premixed combustion for reason of methanol spray interference. Therefore, adopting an injection strategy with SOID earlier than SOIM under methanol single-stage strategy combined with an appropriately extended MDI achieves better comprehensive engine performance. Further optimization of methanol/diesel DDFS engine using a methanol two-stage injection strategy shows that the methanol two-stage injection strategy provides better fuel economy while maintaining acceptable RI. By increasing the methanol pre-injection ratio (MR1) and optimizing the methanol two-stage injection interval (MMI), the engine economy was further enhanced. Compared with the methanol single-stage injection strategy, the optimized methanol two-stage injection strategy reduced equivalent indicated specific fuel consumption (EISFC) by 3.95%. However, it should be noted that the combustion completeness under the methanol two-stage injection strategy decreased, leading to higher emissions of HC, CO and soot. On the other hand, this strategy resulted in lower NOX emissions due to more sufficient premixed combustion.

Efficiency of fuel gas supply on LNG-fueled vessels

The widespread use of LNG as a fuel for marine internal combustion engines makes to pay attention to the quality of gas fuel supply systems and its specifics. The objective of this paper is to review modern gas fuel supply systems and analyze their efficiency. The goal is to determine the most important parameters of gas fuel that affect the stability of the working process of marine dual-fuel engines and ways to maintain them within the specified limits. Evaluation of the gas fuel preparation efficiency is carried out on the basis of operational data obtained on the gas carrier vessel board. Data collection is carried out under non-standard operating conditions, which makes it possible to evaluate the quality of the resulting gas fuel with a time-varying composition of the initial natural gas. To analyze the obtained data, modern software, which is used by leading developers of marine diesel engines, is used (Wartsila Methane Number Calculator, AVL BoostTM and Python 3 statistic libraries). The analysis results are approximated for gas fuel supply systems for gas-fueled vessels, but not being gas carriers. This approximation is made taking into account the design features of gas fuel supply systems, since the specificity of the design imposes certain restrictions on the applicability of the conclusions obtained as a result of the previous analysis. Also, attention is paid to the accumulation of residual heavy hydrocarbons in bunker tanks, the excess of which can adversely affect the quality of gas fuel. Since there is no universal way to solve this problem, only general assumptions about possible ways to dispose of them have been made.

РАСЧЕТ БАРИЧЕСКИХ КОЭФФИЦИЕНТОВ ТЕПЛОПРОВОДНОСТИ СМЕШАННЫХ РАСТВОРОВ ЭЛЕКТРОЛИТОВ

In the paper presents the calculated optimal values of the baric thermal conductivity coefficients corresponding
 to the minimum of the quadratic functional in comparison with the baric dependences of aqueous solutions of
 ethylene glycol and electrolytes in the cooling systems of marine internal combustion engines. For the pressure
 dependences of electrolyte solutions, an equation was obtained that makes it possible to calculate the thermal
 conductivity of mixed solutions at any pressure with an average error of 1.2%. Scientific interest lies in the
 study of the nature of the dependence of the baric coefficients of thermal conductivity of mixed electrolyte
 solutions on temperature when using the latter along with ethylene glycol coolants

Восстановление деформированных судовых валов правкой

The article focuses on studying the crankshaft as an essential part of the marine internal combustion engine. Typical defects of crankshafts of marine diesel engines are considered. The loads causing the curvature of a crankshaft axis under operating conditions are indicated. The causes and nature of violation of the shaft axis geometry are determined. The statistical assessment in the cases of axle warping during diesel operation is found necessary. The recommendations of the Russian Maritime Register of Shipping on eliminating the curvature of the shaft axis are considered. A long-term practical experience of straightening crankshafts at the ship repair plants is taken into account. Methods for eliminating shaft deflections under repair conditions are described. Methods of mechanical straightening without heating are considered. The advantages and disadvantages of mechanical methods of shaft straightening are clarified. The conditions and necessary requirements for thermomechanical shafts straightening are described. The conditions for applying the thermal method of straightening ship shafts are substantiated. High labor intensity and instability of a shaft shape after straightening are pointed out. There has been proposed method of straightening crankshafts of marine internal combustion engines by stress relaxation based on the creep of the shaft material. Theoretical foundations of the processes of creep and stress relaxation in the shaft material are considered. There has been inferred a necessity of further research of operational reliability of crankshafts of marine internal combustion engines after their restoration by the stress relaxation method.

Моделирование влияния нагрузки судовых дизелей на работу системы охлаждения

The article provides analysis of the load effect of the marine internal combustion engines (ICE) on the tem-perature parameters of the water cooling system of ICEs equipped with L32-40 Vis diesel engines. In ICE cooling systems the drive motors of the pumps supplying the cooling water operate at a constant speed and provide a constant water supply. The thermal state of a marine diesel ICE is regulated by valves according to deviation of the actual temperature values of cooling water from the preset values. By closing or opening the water lines the valves change the proportion of cooling water flows of the external and internal circuits fed to the heat exchangers. There is implemented the principle of regulating the deviation of the main coordinate - the temperature of the cooling water. The influence of other factors on the operation of the system is taken into account with a delay. Modeling the operation of the high-temperature circuit of the cooling system of the main ship engine of the ferry was carried out using the simulator 
 of the engine room TRANSAS TechSim 5000. There have been obtained graphical results of changing the cooling circuit water temperature with increased and decreased loads on diesel engines by changing the set speed with different initial and final values at a constant water temperature in the external cooling circuit. The graphs helped obtain numerical and qualitative indicators of transient processes (duration, oscillation, overshoot, final temperature values, etc.) for the different initial conditions - ranges of diesel load changes. The resulting graphical dependences are analyzed, conclusions about the modes of working out the disturbing influences by the cooling system, the parameters 
 of transient processes and the features of the operation of the standard control system and the cooling system circuit 
 of the main marine diesel engine in terms of ensuring optimal performance of the system are drawn. It has been inferred that the standard control system under some initial conditions does not provide the optimal parameters of transient processes.

The Effect of Hydrogen Addition on the Pollutant Emissions of a Marine Internal Combustion Engine Genset

Hydrogen, as a maritime fuel, is one of the solutions that will assist the shipping sector in addressing the challenges regarding decarbonization, taking into consideration the targets set for 2030 and 2050. The extensive utilization of hydrogen requires massive production of green hydrogen and the development of proper infrastructure to support a sustainable supply chain. An alternative solution is based on the on-board production of hydrogen, where production units are installed on-board the vessel. Along these lines, the HYMAR project aims to test the utilization of a hydrogen production unit for on-board use. The article deals with the use of hydrogen as a fuel for internal combustion engines, taking into consideration reports from literature and the preliminary results of the HYMAR project, focusing on the environmental impact and the reduction in emissions. Experimental investigation on a marine auxiliary engine for power generation, under the HYMAR project, leads to promising results regarding the environmental footprint of the internal combustion engine when hydrogen is added in the fuel mix with increasing percentages.

Development of a phenomenological model for the description of RCCI combustion in a dual-fuel marine internal combustion engine

Increasingly stringent pollutant and CO2 emission standards require engine manufacturers to investigate innovative solutions. Among these techniques, low-temperature combustion (LTC) concepts have a large potential to simultaneously reduce NOx emissions and fuel consumption. A promising manner to realize LTC consists of adopting ultra-lean mixtures, where the combustion evolution is controlled by a proper spatial distribution of fuels with different chemical reactivities. In this context, depending on the proportion and stratification of the fuels, the heat release can primarily depend on chemistry progression, leading to a Reactivity Controlled Compression Ignition (RCCI) mode, or on flame propagation, locally initiated by a high reactivity fuel.In this work, the combustion characteristics of a large-bore research engine are experimentally investigated. Natural gas is supplied into the intake port, while light fuel oil (LFO) is directly injected in the cylinder. An experimental campaign is carried out including sweeps of engine load, air/fuel proportion, LFO amount, valve timing, and intake air temperature. Global engine operating parameters as well as cylinder pressure traces are recorded and analyzed.Based on the available experimental data, a phenomenological model handling both chemistries of fuels with different reactivities and flame propagation is developed and validated. The model is based on a multi-zone approach, where auto-ignition chemistry is solved by a tabulated method to preserve the computational effort. The proposed numerical approach shows the ability to simulate the experimental data with good accuracy, using a fixed tuning constant set. A dedicated correlation is built to reproduce the expected in-cylinder distribution of the directly injected liquid fuel. Global performance and combustion parameters are predicted with an average error below 5%. The model demonstrates to correctly describe the behavior of the tested engine under different operating conditions and to capture the physics behind such advanced combustion concepts.

DEVELOPMENT OF METHODS FOR EVALUATION OF TECHNICAL CONDITION OF ENGINES ACCORDING TO THE RESULTS OF INDICATION OF WORKING PROCESS ON MODES DIFFERENT FROM NOMINAL

Technical condition assessment of marine internal combustion engines by the parameters and nature of the workflow is a common practice in their operation. Taking and analysis of indicator diagrams is a mandatory procedure provided by the rules of technical operation for the main range of large and medium-sized marine engines. There is a whole arsenal of indication means for such evaluation: from classical mechanical systems to electronic means of periodic or continuous action. The rapid development of electronic control systems and changes in approaches to logistics operations in maritime transport have imposed a number of limitations, somewhat narrowing the possibilities of using these methods. Most of the vessels that form the basis of the world merchant fleet were built 10...15 years ago. Information about the results of the indication of the engines of such vessels during bench tests is presented in the form of raster images. This complicates the process of using them as the reference needed to compare them with the actual diagrams obtained in operation by means of electronic control systems, which have replaced mechanical indicators over the past few years. In addition, tendencies to reduce the speed of vessels complicate, and often make it impossible to indicate the engines in the specified operating modes. As a result, the efficiency of using indicator diagrams to assess the current technical condition is sharply reduced. In this regard, there is an objective need to compare different methods of obtaining and storing information about the results of indication and in a unified method of presenting this information, convenient for processing and analysis. In addition, there is a need to develop methods for obtaining reference diagrams for nonspecific modes on the basis of processing the results of acceptance and commissioning bench tests of a particular engine to assess its technical condition by the results of indication on the partial load modes. This study is devoted to the comparison of different methods of presenting information and obtaining reference indicator diagrams for non-specific operating modes of engines.

Design of a Thermoelectric Device for Power Generation through Waste Heat Recovery from Marine Internal Combustion Engines

Modern ships discharge large amounts of energy into the environment. More specifically, internal combustion engines (ICE) of commercial and passenger ships waste significant amounts of thermal energy at high temperature through their exhaust gases that are discharged to the atmosphere. A practical approach of recovering some amount of this energy is by using thermoelectric generator systems, which can convert thermal into electrical energy, given that there is a significant temperature difference. It is the aim of this work to propose a thermoelectric generator to recover energy from the exhaust gases of marine ICEs. The proposed thermoelectric generator uses the outside surface of the ICE manifold as the hot side of the thermoelectric module, while the cold side is maintained at a low temperature through a heat sink and induced water flow. The goal of this work is to design this thermoelectric generator and identify the configuration that produces the maximum electric power. The analysis and design are performed with the use of modeling and simulation, while commercial software is employed to study the 3-dimensional coupled fluid flow and heat transfer at a steady state. A sensitivity analysis is carried out to identify the parameters with the highest influence on power production. In addition to a full factorial sensitivity analysis, the more efficient Latin hypercube sampling is used. The analysis shows that significant energy of the exhaust gases can be converted into electric power with the use of an optimized heatsink, which creates the highest temperature difference between the two sides of the thermoelectric module.

Работоспособность механических демпферов крутильных колебаний судовых двигателей внутреннего сгорания

The article considers the danger of torsional vibrations in ship power plants, which is recognized by leading specialists of the shipbuilding, engine-building and ship repair industries and supervisory authorities – the Russian Maritime Register of Shipping (RMRS), the Russian River Register (RRR), as well as foreign classification societies. There are a number of factors that can lead to serious accidents due to torsional vibrations, therefore, dampers (liquid or mechanical) are installed on the crankshafts of marine engines to reduce the oscillation amplitudes and tangential twisting stresses in the shafts and flexible elements of the coupling couplings of the engine-propulsion complex. Since the warranty period of the dampers is 30,000 hours, the shipowners need to make periodic measurements (on average, after 15,000 hours) using a torsiography method, upon the results of which an approximate residual life of the dampers is established until the next check. A special feature in the operation of mechanical dampers in marine diesel engines is the lack of methods approved by the supervisory authorities – RMRS and RRR for the non-selective assessment of the residual life of mechanical dampers, due to the fact that previously mechanical dampers were not used so widely in marine diesels. There have been analyzed the factors and criteria that affect the performance of mechanical torsional vibration dampers and can be used in the development of a method for non-selective diagnostics and assignment of the residual life of mechanical torsional vibration dampers of marine internal combustion engines.

Analysis of mechanical energy losses in marine diesels

The object of research is marine diesel engine oils, which provide lubrication, cooling and separation of friction surfaces. The subject of the research is the process of ensuring minimum mechanical losses in marine diesel engines. A problematic point in ensuring the lubrication of the cylinder-piston group and motion bearings is the lack of analytical and experimental studies that establish the relationship between the structural characteristics of engine oils and mechanical losses arising in marine internal combustion engines. The degree of orientational ordering of molecules and the thickness of the boundary lubricating layer are considered as the structural characteristics of engine oils. The determination of these values was carried out using the optical method based on the anisotropy of the light absorption coefficient by the boundary lubricant layer and the isotropic volume of the liquid (engine oil). The assessment of the level of mechanical losses arising in marine diesel engines was carried out according to an indirect indicator – the overshoot of the rotational speed and the time to reach the steady state of operation in the event of a change in load. It has been experimentally established that for engine oils used in marine internal combustion engines, the thickness of the boundary layer can be 15–17.5 µm. Motor oils, which are characterized by a higher ordering of molecules and a thickness of the boundary lubricant layer, ensure the flow of transient dynamic processes with less overshoot and a shorter transient time. This ensures the level of minimal mechanical losses occurring in marine diesel engines. The technology for determining the structural characteristics of engine oils can be used for any type and grade of oil (mineral or synthetic; high or low viscosity; used in both circulating and cylinder lubrication systems). The method of indirect assessment of mechanical losses of marine diesel engines can be used for any types of internal combustion engines of ships of sea and river transport (low-, medium- and high-speed; as well as performing the functions of both main and auxiliary engines).

ENSURING EFFICIENCY AND ENVIRONMENTAL OF MARINE DIESEL ENGINES WHICH USING EXHAUST GAS BYPASS SYSTEM

The mechanism of formation toxic components in exhaust gases during oxidation and combustion of fuel in marine internal combustion engines is considered. The system of ship engine by-pass exhaust gases 6L20 Wartsila has been observed. Upon experimental results it has been stated that the by-pass exhaust gases usage favor the ecological parameters of ships engine operation modes – by this at the range of exploitation load 0.55 … 0.85 % from nominal power the nitrogen oxide concentration in exhaust gases is decreased on 1.32 ... 12.97 %, but the specific effective fuel oil consumption is increasing to 4.13 %.

Влияние коэффициента избытка воздуха при горении на показатели напряженности двухтактного дизеля в широком диапазоне режимов

The article describes the specific features of the forced diesel engines operating on a helical characteristic. One of them is a decreasing coefficient of excessive air during combustion with a decreasing power. Reducing the air charge of the cylinder and its available work require a greater cyclic supply of fuel to provide a given power, which affects the engine efficiency. It is possible to increase the boost pressure and the mass of the air charge of the cylinder by acting on the adjustable nozzle apparatus of a turbo-charging unit. In this case, gas parameters significantly change over the diesel cycle, which leads to changes in the indicators of thermal and mechanical tension. There have been presented the results of theoretical studies of indicators and criteria of thermal and mechanical tension of a marine two-stroke internal combustion engine operating in a wide range of modes with a constant coefficient of excessive air during combustion. Direct control of air flow at shared load modes was performed by turning the blades of an adjustable nozzle apparatus of a turbo-charging unit. The study of a diesel engine was carried out theoretically for two options: the original version (without adjustable nozzle unit) and under direct control of the air flow using an adjustable nozzle unit; the results were processed depending on the relative power of the diesel fractional load modes. There have been illustrated the graphs of dependence of the blade rotation angle of the nozzle apparatus of a turbocharging unit, relative change of the gas temperature behind the cylinder, cycle average temperature of the working fluid, average heat flux, relative change in the heat stress criterion of the piston, heat stress criterion for the cylinder, change in the pressure cycle of the working fluid, degree of increase working fluid during combustion, maximum rate of pressure rise depending on the load of the diesel engine.