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To attain high-performance ejector configurations, an ejection characteristic testing system was established initially to validate the reliability of the Realizable k-εturbulent model. Subsequently, optimization investigations were conducted on lobed nozzle ejectors with various structural parameters. The effects of four key structural parameters, including lobed nozzle expansion angle α, lobed nozzle width d, number of lobes in the nozzle n, and height of the square-to-circle section h, were systematically studied. Furthermore, the CRITIC method was employed for multi objective evaluation to identify the optimal design configuration for the casing ejector. The research findings revealed that among the structural parameters, the lobed nozzle expansion angle α exerted the greatest influence on the ejection coefficient and pressure loss coefficient. The weights of the evaluation criteria were determined by the CRITIC method as follows: ejection coefficient (49.38%) < pressure loss coefficient (50.62%). The optimal design configuration determined by the CRITIC method included α = 45°, d = 150 mm, n = 14, and h = 600 mm. The resulting enclosure design ensures smooth airflow within the system, preventing the backflow of high temperature mainstream fluid and heating the enclosure. It also maintains a temperature distribution in the typical cross-section that meets specified requirements. Additionally, it facilitates improved mixing of mainstream and secondary fluid and reduces exhaust gas temperature. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering for Thermal Energy & Power / Reneng Dongli Gongcheng is the property of Journal of Engineering for Thermal Energy & Power and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Recent developments in ceramic-matrix composites and their successful use in combustor liners and shrouds have generated interest among researchers to adopt these materials in rotating gas turbine blades, especially in the first stages of high-pressure turbines where gas temperatures are highest. CMC blades have the potential of being retrofitted to replace superalloy turbine blades in operating gas turbines. In this paper, a comparative study on the thermodynamic performance of a marine gas turbine engine, LM 2500, featuring directionally solidified nickel superalloy blades versus novel CMC blades in the high-pressure turbine sections has been reported. Mathematical modeling of the gas turbine cycle components has been developed and then coded in C ++ language. The effects of turbine inlet temperature on thermodynamic efficiencies, coolant mass flow rates, and work ratios on the two systems have been analyzed. Finally, the exergy analysis of the systems' components has been done to identify the benefits of adopting CMC blades in the LM 2500 system. It has been observed that when compared to the directionally solidified bladed turbine system, the projected first law efficiency of CMC bladed LM 2500 gas turbines can be enhanced over 7% (from 34.17% to 41.21%). The projected work ratio can be improved by over 16% (from 0.49 to 0.57) at the turbine inlet temperature of 1725 K. [ABSTRACT FROM AUTHOR]

The high-temperature exhaust gases and the hot surfaces of the ejector device in marine gas turbines generate significant levels of infrared radiation. An appropriate nozzle structure can effectively lower the exhaust gas temperature and reduce the high-temperature radiation surface area, thereby minimizing external infrared radiation. In this study, a numerical simulation of the nozzle structure in the ejector device was conducted using computational fluid dynamics (CFD) methods. By investigating the orthogonal combinations of nozzle inclination angles and the number of nozzles, the temperature distribution and flow characteristics under different operating conditions were analysed. The results showed that as the nozzle inclination angle increased, the entrainment coefficient (Ce) and the temperature ratio at the inlet and outlet (Rt) initially improved but then worsened. Simultaneously, the pressure loss coefficient (Cpl) increased with the inclination angle. The CRITIC weight method was employed to objectively allocate weights to Rt, Ce, and Cpl, determining the optimal solution. The results indicated that Rt and Cpl had significant and similar weights. The optimal solution was found in Case 10 (α = 5°, x = 4), with corresponding evaluation indices of Ce=2.38, Cpl=11.45, and =0.68. This study's findings are of great importance for enhancing the performance of marine gas turbines and reducing external infrared radiation. [ABSTRACT FROM AUTHOR]

ObjectivesThe marine gas turbine is an important piece of marine power equipment, and its development is characterized by great difficulty, long cycle and high cost. Thus, the cost-effectiveness is a significant evaluation indicator. As such, it is significant to estimate the major life cycle cost of marine gas turbines based on their dominant technical indicators and parameters, as well as to further evaluate their full life-cycle economy during the early proposal stage.MethodsThe technical indicators, physical parameters and cost data of typical marine power equipment are collected to build a development cost model and purchase price estimation model which are validated against existing data. At the same time, combined with the cost characteristics of the operation and maintenance stages, a main life cycle cost analysis framework and estimation model are established.ResultsThe development cost and purchase price models achieve high accuracy with an error less than 5%, while the estimation method for operation and maintenance is plausible and easy to apply to real work.ConclusionsValidation against the available data shows that these analytical framework and estimation models are applicable and feasible. This paper proposes effective approaches to support economic analysis in the marine gas turbine proposal stage.

Replacing the last-stage stator and the outlet guide vane of the low-pressure compressor of the marine gas turbine with a large turning blade can reduce the number of compressor blades and reduce the size and weight of marine gas turbines. At present, there are few studies on similar profiles, and it is necessary to verify the feasibility of this type of compressor profile with a large turning angle. The performance of this profile is investigated by combining experimental measurement with numerical simulation calculation. The analysis of the experimental and numerical results reveals that this profile has a large flow turning angle, a wide operating range, and low overall total pressure losses. The loss of the profile only suddenly increases at some large positive angles of attack due to the large separation of the suction surface. The results show that this profile can compress air and increase the turning ability at a low loss, and can play the role of both the original last-stage stator and the outlet guide vane. This research provides a reference for the design and analysis of marine gas turbines and guidance for the application of the blade to gas turbines in other fields. [ABSTRACT FROM AUTHOR]

The propulsion demands of high-speed naval vessels often rely on gas turbines, producing significant amount of power achieving thus high performance requirements. Gas turbines can be used either to provide purely mechanical propulsion, or alternatively to generate electricity, which is subsequently used by electric drives to propel the ship. However, the thermal efficiencies of gas turbines are lower than those of Diesel engines of similar power. In the context of improving the performance of existing marine gas turbines, it is proposed to enhance engine's performance by integrating a pressure wave supercharger (or wave rotor), while keeping the basic components of the baseline engine unchanged. This article is an application of a method developed by the author for marine gas turbines with and without recuperator, [Fatsis 2019]. It is found that important benefits are obtained for the topped engines in comparison to the self-standing baseline engines. The wave rotor integration is more appropriate for engines with low compression ratios and high turbine inlet temperatures. Application of wave rotor technology to recuperated marine gas turbines shows efficiency gain exceeding 19% for all the compression ratio and turbine inlet temperatures examined. Abbreviations: COGAS, Combined gas turbine and steam turbine; COGES, Combined gas turbine electric and steam; GTE, Gas turbine engines [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering for Thermal Energy & Power / Reneng Dongli Gongcheng is the property of Journal of Engineering for Thermal Energy & Power and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The article presents a continuation of research carried out concerning identification of energy consequences of mechanical fatigue within a propeller shaft in a rotating mechanical system, while working under conditions of the loss of the required alignment of shaft lines. Experimental research was carried out on a physical model reflecting a full-sized real object: i.e., the propulsion system of the ship. It is proven, by means of an active experiment, that changes in propeller shaft deflection are reflected in the amount of dissipated kinetic energy of masses in rotational motion and the accumulated internal energy in its construction material. Adoption of a high-cycle fatigue syndrome, consisting of diagnostic symptoms determined from the action of the propeller shaft associated with the transformation of mechanical energy into work and heat, as well as with the generation of mechanical vibrations and elastic waves of acoustic emission, is proposed. To assess the diagnostic information quantity brought about by the defined features of propeller shaft fatigue, an experimental research program was developed and implemented, in which two statistical hypotheses are verified: the significance of the impact of the values enforcing the fatigue process, presented in the first part of the article, and the adequacy of the regression equation describing the fatigue durability of the propeller shaft in the energy aspect, constituting the second part of the article. This finally gives us the opportunity, after the appropriate translation of the model test results into full-sized real objects, to develop a methodology to diagnose marine propeller shaft fatigue in operating conditions. The third part of the article is devoted to this issue

Replacing the last-stage stator and the outlet guide vane of the low-pressure compressor of the marine gas turbine with a large turning blade can reduce the number of compressor blades and reduce the size and weight of marine gas turbines. At present, there are few studies on similar profiles, and it is necessary to verify the feasibility of this type of compressor profile with a large turning angle. The performance of this profile is investigated by combining experimental measurement with numerical simulation calculation. The analysis of the experimental and numerical results reveals that this profile has a large flow turning angle, a wide operating range, and low overall total pressure losses. The loss of the profile only suddenly increases at some large positive angles of attack due to the large separation of the suction surface. The results show that this profile can compress air and increase the turning ability at a low loss, and can play the role of both the original last-stage stator and the outlet guide vane. This research provides a reference for the design and analysis of marine gas turbines and guidance for the application of the blade to gas turbines in other fields.

Copyright of Journal of Engineering for Thermal Energy & Power / Reneng Dongli Gongcheng is the property of Journal of Engineering for Thermal Energy & Power and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Weather data is nowadays used in a variety of navigational and ocean engineering research problems: from the obvious ones like voyage planning and routing of sea-going vessels, through the analysis of stability-related phenomena, to detailed modelling of ships’ manoeuvrability for collision avoidance purposes. Apart from that, weather forecasts are essential for passenger cruises and fishing vessels that want to avoid the risk associated with severe hydro-meteorological conditions. Currently, there is a wide array of services that offer weather predictions. These services include the original sources – services that make use of their own infrastructure and research models – as well as those that further postprocess the data obtained from the original sources. The existing services also differ in their update frequency, area coverage, geographical resolution, natural phenomena taken into account and finally – output file formats. In the course of the ROUTING project, primarily addressing ship weather routing accounting for changeable weather conditions, the necessity arose to prepare a report on the state-of-the-art in numerical weather prediction (NWP) modelling. Based on the report, this paper offers a thorough review of the existing weather services and detailed information on how to access the data offered by these services. While this review has been done with transoceanic ship routing in mind, hopefully it will also be useful for a number of other applications, including the already mentioned collision avoidance solutions.

The paper presents a research stand being a diagnostic model of radial lip seals used, among others, on crankshafts of piston combustion engines in order to identify the correctness of their operation. The possibility of determining the technical condition of lip seals on the basis of the proposed coefficient of correctness of operation has been described. The basic features of seals influencing their correctness of operation were also described, along with examples of determining the durability limits of lip seals. A modified version of the friction node of the T-02 four-ball apparatus is presented. It allows to check the correctness of sealing lips operation as well as to test the compatibility between the steel shaft, sealing lip and sealed lubricating oil. It was shown that the test results con-firmed the usefulness of the hypothesis that the quality of oil affects the durability of sealing lips and their coefficient of correctness. Additionally, attention was paid to the possibility of analyzing the pumping effect affecting the transition of the seal-shaft system from the state of partial suitability S2 to the state of full suitability S1 or to the state of unfitness S3, and because the change in the state of such a system is random, it requires a probabilistic analysis.

The dependency of marine gas turbine on the ambient temperature leads to a decrease of the gas turbine power output in arid areas. Very often gas turbine power output demand is high and the power margins originally designed into the driver, has been exhausted. In such circumstances the inlet air fogging is an effective compensation of gas turbine power. In this paper an analysis of inlet air fogging applicability to marine gas turbine has been conducted. Different areas of ship’s voyage have been taken into account. The use of inlet air fogging in marine gas turbine must be evaluated on the basis of turbine characteristics, climate profile of ship’s voyage, and expectations of gas turbine power augmentation. The authors expect that the considerations provide useful guidance for users of marine gas turbines to decide the feasibility of installing an inlet air fogging system.

Due to the influence of the marine environment, marine gas turbine lubricants are required to have good thermal conductivity. However, the current research on marine gas turbine lubricants mainly focuses on its corrosion resistance. Therefore, a real-time numerical simulation of thermal conductivity of marine gas turbine lubricating oil under complex sea conditions is proposed. In this paper, the turbulent kinetic energy equation and the loss transport equation are obtained by introducing the turbulent column and the k-ε model. The Nusselt number in the k-ε model can be regarded as the ratio of convective heat transfer between fluid and solid wall and internal heat transfer of fluid. According to the equations, the transient heat transfer model of vertical moving contact parts is established, and the heat transfer relationship between lubricating oil and plug group is obtained. The experimental results show that the area of low temperature in this scheme is larger than that in the traditional scheme, which means that the efficiency of impingement cooling is improved after the introduction of the pin structure in the impingement cooling design. The heat transfer process on the suction surface is stronger than that on the pressure surface, and the heat transfer coefficient of the blade increases continuously, reaching the local maximum value at about X/L = 0.65. [ABSTRACT FROM AUTHOR]

Machine learning is an effective way to realise the condition monitoring of marine machinery. However, it is challenging to realise this purpose based on supervised learning in practice due to the lack of labelled data. To overcome this problem, we propose to use isolation forest to realise the decay detection of a marine gas turbine with normal data. Besides, we consider the impact of data contamination for the first time compared with previous literatures. We also experiment with the same datasets with support vector data description (SVDD) as a comparison. The results show that the isolation forest is very suitable for the decay detection of the marine gas turbine, and it shows a significant advantage over support vector data description in the tolerance to contaminated data. The dataset we experiment with is from a real-data validated numerical simulator developed for a Frigate's propulsion plant. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering for Thermal Energy & Power / Reneng Dongli Gongcheng is the property of Journal of Engineering for Thermal Energy & Power and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Gas turbine is a widely-used propulsion device for power convection in marine dynamical system. Conventional coolants such as impingement cooling and thermal protection material have lower convective heat transfer efficiency on the target surface which can hinder the development of marine gas turbine combustor. In this paper, impact cooling simplification models are established, which have simulated the function of the transition segment of marine gas turbine combustor to be protected from high temperature. Being enlightened by the butterfly scale, four types of bionic ribs are designed on the simplification models. During the analysis, conservation equations for mass, momentum and energy are solved by using finite volume method with Realizable k−ε turbulence model. By comparing the four types bionic ribs models, the surface with Type 3 rib structure has the best cooling efficiency. The results show that the sharp corner and unequal length fins of bionic rib could affect the cooling efficiency. The inspire application of the bionic structures will provide a reference for new cooling structure design in marine gas turbine combustor.

In this paper, the homotopy method is used for stress analysis of rotating disk subjected to thermal load in marine gas turbine engine. Apply the thermal loading on the disk with exponential thickness distribution by using the homotopy method and Considering the physical and mechanical properties variations with temperature, are the most important aspects of innovation in this paper. Disc thickness variations are considered exponential and the inner and outer rims of disk are considered constant thickness. Due to the use of homotopy analysis method, important and effective parameters in this method are selected and presented. Furthermore, results are compared and validated with finite element code and good agreement of results with this method is showed. Finally, stress distribution in disks with constant, exponential and hyperbolic thickness distribution are considered and compared. The results showed the efficiency and acceptable accuracy of the method for analysis of rotating disk subjected to thermal and mechanical loading in gas turbine engine.

The use of inlet air fogging installation to boost the power for gas turbine engines is widely applied in the power generation sector. The application of fogging to mechanical drive is rarely considered in literature [1]. This paper will cover some considerations relating to its application for gas turbines in ship drive.

Strong restrictions on emissions from marine power plants (particularly SOx, NOx) will probably be adopted in the near future. In this paper, a combined solid oxide fuel cell (SOFC) and gas turbine fuelled by natural gas is proposed as an attractive option to limit the environmental impact of the marine sector. It includes a study of a heat-recovery system for 18 MW SOFC fuelled by natural gas, to provide the electric power demand onboard commercial vessels. Feasible heat-recovery systems are investigated, taking into account different operating conditions of the combined system. Two types of SOFC are considered, tubular and planar SOFCs, operated with either natural gas or hydrogen fuels. This paper includes a detailed thermodynamic analysis for the combined system. Mass and energy balances are performed, not only for the whole plant but also for each individual component, in order to evaluate the thermal efficiency of the combined cycle. In addition, the effect of using natural gas as a fuel on the fuel cell voltage and performance is investigated. It is found that a high overall efficiency approaching 70% may be achieved with an optimum configuration using SOFC system under pressure. The hybrid system would also reduce emissions, fuel consumption, and improve the total system efficiency.

This paper discusses the suitability of using natural gas as a fuel for marine gas turbine electric propulsion (DFGE), utilizing natural boil-off gas and forced boil-off gas, as well as investigating its economical and environmental benefits over other propulsion options. The benchmark ship chosen for this study has a capacity of 150,000 m3 and is powered by conventional steam propulsion. For this purpose a spreadsheet model was developed to determine the liquefied natural gas carrier operating costs for different propulsion options. This is in addition to a sensitivity analysis to study the effect of varying range, heavy fuel oil (HFO) and natural gas prices on ship operating cost. Recently, about 40% of the new orders shifted to slow speed diesel engines with re-liquefaction plant and dual fuel diesel electric propulsion. To date, marine gas turbines are not used in liquefied natural gas carriers.It was found that using natural gas as a fuel with the proposed marine gas turbine cycle at current HFO and natural gas prices provides the highest cost saving for a distance less than 4000 nautical miles (NM). With the expected changes in fuel prices, the proposed cycle achieves cost saving of 3% per round trip, and this saving is directly proportional to increasing fuel prices, compared to other options. [ABSTRACT FROM AUTHOR]

The marine fuel plays a key role in determining the performance of marine power plants onboard ships. Many studies have pointed to the possibility of using natural gas as an alternative fuel for marine power plants. The increase number of LNG carriers worldwide and the growing of its capacity in the last decades, this had given the opportunity to increase the possibility of using natural gas as a main fuel taking into account advantage of evaporation process which occurs during the voyage for energy generation. The current paper analyzes and discusses the change of the performance of marine gas turbine power plant when using natural gas as a main fuel. The study showed that the most significant parameters related to marine gas turbine performance had some (from -1.76% to +0.97%) of those achieved by diesel fuel. Concerning fuel consumption, the paper showed that the specific fuel consumption for natural gas is lower than that of diesel by about 13.5% at the same power output. This is an important factor to push this technology forward, particularly with growing environmental problems that are caused by the conventional marine fuel. [ABSTRACT FROM AUTHOR]

The structure and aerodynamics performance of gas turbine inlet system is an important part of technology of gas turbine installed on naval vessels. The design and numerical simulations of gas turbine inlet system are conducted and reliable foundation for design and manufacture of marine gas turbine inlet system of high performance is provided. Numerical simulations and experiments of two inlet system models of gas turbine are conducted with satisfactory results and are of significance to the actual application of the inlet system. [ABSTRACT FROM AUTHOR]