Large Engineering Research Articles

Combustion chamber development features for converted small gas turbine

Conversion and modernization of a gas turbine engine involves solving a number of tasks, one of which is the development of a combustion chamber for operation on various gaseous fuels. The complexity of solving this problem is associated with a variety of interrelated processes occurring in the CC, which are complex and insufficiently studied. The work on the small-size gas turbine engine CC is even more complicated by the lack of a generally accepted and well-developed finishing technique typical of large gas turbine engines, which is emphasized both in domestic and foreign works. The report considers the main approaches to classifying the dimensions of combustion chambers of gas turbine engines [1] according to various criteria, namely: to the power type size (according to CIAM)Classification based on the reduced air flow through the compressor. The criteria included in the classification are analysed, in relation to the implemented designs, the most objective classification is selected for further consideration of the design of the combustion chamber of a small-sized gas turbine engine when converting it to gaseous fuel. The features and technical limitations of converting the combustion chamber from liquid to gaseous fuel are considered, which is an urgent task against the background of gasification programs of the fuel and energy complex in the Russian Federation. Attention is paid to the factors that have the greatest impact on the environmental characteristics of the converted combustion chambers.

Estimation of Damping for a Double-Layer Grid Using Input-Output and Output-Only Modal Identification Techniques

In large civil engineering structures, the output-only modal identification is the most applicable technique for estimating the modal parameters such as damping. However, due to no measurement and control of excitation force, the identified parameters obtained by output-only technique have more uncertainty than those derived from the input-output technique. Given the different nature and uncertainties of the two modal identification techniques, in the present study, the damping related to the first 12 modes of a double-layer grid developed from the ball joint system were identified via the two techniques and compared with each other. For this purpose, a double-layer grid was constructed by pipes and balls with free-free boundary conditions provided for both input-output and output-only experiments. Exciting the grid, its acceleration response was measured at appropriate degrees of freedom. Then, by using these data and performing modal analysis, involving four different methods of input-output and five different methods of output-only, the natural frequencies and damping ratios of the desired modes were extracted. The results indicated that despite the good agreement between the modal damping of the grid, as identified by different methods of input-output together and by different methods of output-only together, the results of input-output and output-only methods were different with each other. The damping values through the input-output modal identification methods were on average 65% higher than the corresponding values of the output-only modal identification methods.

A Novel Posture Positioning Method for Multi-Joint Manipulators

Safety and automatic control are extremely important when operating manipulators. For large engineering manipulators, the main challenge is to accurately recognize the posture of all arm segments. In classical sensing methods, the accuracy of an inclinometer is easily affected by the elastic deformation in the manipulator's arms. This results in big error accumulations when sensing the angle of joints between arms one by one. In addition, the sensing method based on machine vision is not suitable for such kind of outdoor working situation yet. In this paper, we propose a novel posture positioning method for multi-joint manipulators based on wireless sensor network localization. The posture sensing problem is formulated as a Nearest-Euclidean-Distance-Matrix (NEDM) model. The resulting approach is referred to as EDM-based posture positioning approach (EPP) and it satisfies the following guiding principles: (i) The posture of each arm segment on a multi-joint manipulator must be estimated as accurately as possible; (ii) The approach must be computationally fast; (iii) The designed approach should not be susceptible to obstructions. To further improve accuracy, we explore the inherent structure of manipulators, i.e., fixed-arm length. This is naturally presented as linear constraints in the NEDM model. For concrete pumps, a typical multi-joint manipulator, the mechanical property that all arm segments always lie in a 2D plane is used for dimension-reduction operation. Simulation and experimental results show that the proposed method provides efficient solutions for posture sensing problem and can obtain preferable localization performance with faster speed than applying the existing localization methods.

Soviet Interpretation of the Ideas Of Fordism as a Basis for Transformation of the Soviet Tank Industry During the Great Patriotic War

Introduction. Fordism, as a specific concept of production management, radically changed the face of the world industry. The system, proposed by the famous engineer and entrepreneur H. Ford, was based on the principle of large-scaled flow-conveyor production founded on the most specialized, standardized and automated industrial equipment. It made possible to produce goods cheaply under the conditions of the domination of low-skilled personnel. The American experience turned out to be widely in demand in the USSR during the industrialization period, since the country needed to create a modern and competitive mechanical engineering in the shortest possible time, primarily with the aim of strengthening its defense capability. Materials and Methods. The basis of the methodology of the work is the problem-chronological approach, which ensures the identification of tendencies and contradictions in the implementation of plans for the construction of the tank industry of the USSR in the 1930–1940s, allows them to be interpreted in a historical sequence. The principle of objectivity is based on the recognition of cause-and-effect patterns in the development of phenomena and events. In addition, the following methods are used: analysis of documents, scientific literature and state regulatory acts. Results and Discussion. The formation of the tank industry of the USSR in the pre-war period proceeded according to the principle of convergence of the technological characteristics of specialized military factories, traditionally engaged in the manufacture of tanks, and large civil engineering enterprises appeared during the years of industrialization, relying on Fordist, auto-tractor technology. In the pre-war period, low qualified personnel of the Soviet automobile and tractor plants, never been able to master the mass production of armored vehicles developed by engineers of specialized factories. The outbreak of the Great Patriotic War led to the evacuation of the capacities of most specialized military factories involved in the production of tanks in the USSR to the sites of civil engineering plants created during the period of industrialization. At the same time, the main forces of the country’s tank industry were moved to the Volga region, at the Urals and Siberia. In order to start producing tanks in a new place, in the extreme conditions of war, with the loss of qualified personnel and valuable industrial equipment, the industry leadership turned to radically transformation of the whole technology of tank production towards at Fordist principles. Key elements of the Fordism concept, as applied to the socialist command economy of the USSR during the war, were used by the party-state leadership to achieve the maximum concentration of limited resources. Conclusion. The system of organization and management of tank production, built during the war years in the tank industry of the USSR and the Urals in accordance with the basic principles of Fordism, can be assessed as “inflexible mass production”. This meant that it was impossible to quickly change the characteristics of products manufactured on a flow-conveyor basis, since this required stopping the conveyor and changing equipment. The system made it possible to mass produce and even improve the designs of the T-34 and “KV” (then “IS”) – tanks developed in the pre-war period, creating the prerequisites for their gradual transformation into an acceptable instrument of “total war”.

Using shock control bumps to improve engine intake performance and operability

AbstractShock control bumps can be used to control and weaken the shock waves that form on engine intakes at high angles of attack. In this paper, it is demonstrated how shock control bumps applied to an engine intake can reduce or eliminate shock-induced separation at high incidence, and also increase the incidence at which critical separation occurs. Three-dimensional Reynolds-average Navier–Stokes (RANS) simulations are used to model the flow through a large civil aircraft engine intake at high incidence. The variation in shock strength and separation with incidence is first studied, along with the flow distribution around the nacelle. An optimisation process is then employed to design shock control bumps that reduce shock strength and separation at a fixed high incidence condition. The bump geometry is allowed to vary in shape, size, streamwise position and circumferential direction around the nacelle. This is shown to be key to the success of the shock control geometry. A further step is then taken, using the optimisation methodology to design bumps that can increase the incidence at which critical separation occurs. It is shown that, by using this approach, the operating range of the engine intake can be increased by at least three degrees.

A Novel Method for Simultaneous Removal of NO and SO2 from Marine Exhaust Gas via In-Site Combination of Ozone Oxidation and Wet Scrubbing Absorption

The stringent international regulations on marine emission abatement have exerted a huge push on the development of marine desulfurization and denitrification technologies. However, for the traditional vessels driven by large two-stroke diesel engines, simultaneous removal of NOx and SO2 is still a big challenge at present. Here, a one-stage ozone oxidation combined with in-situ wet scrubbing for simultaneous removal of NO and SO2 is proposed. A series of experiments were performed based on a bench-scale reaction system. The results showed that in-situ wet scrubbing could effectively decrease flue gas temperature, and then suppress the thermal decomposition of ozone, which was beneficial for improve oxidant utilization. Meanwhile, the in-situ combination of ozone injection and wet scrubbing was in favor of improving the selectivity oxidation of NO over SO2 by ozone, which was possibly due to the high aqueous solubility of SO2 in water. Aiming to reduce the electric power consumption by an ozone generating system, O3/NO molar ratio was kept as low as possible. A complete removal of SO2 and a high NOx removal efficiency could be achieved through the introduction of other oxidative additives in scrubbing solution. This integrated system designed for marine application was of great significance.

Three-dimensional phase-field modeling of mode I + II/III failure in solids

One major merit of phase-field models for fracture is that cracks nucleation, propagation, branching, merging, coalescence and even fragmentation, etc., can be accounted for seamlessly within a standalone regularized variational framework. This fascinating feature overcomes the cumbersomeness in the characterization of non-smooth crack surfaces and the tracking of complex crack paths. However, the numerical algorithms frequently adopted in solving the coupled governing equations are not robust or efficient enough, together with the high computational cost in resolving the fracture process zone, largely hindering application of these models to general 3D problems. In this work, several 3D benchmark problems involving mode I, I+II or I+III failure in brittle and quasi-brittle solids is addressed based on our recent theoretical and numerical progresses on the unified phase-field theory for damage and fracture (Wu, 2017). Complex 3D fracture problems with over 2 million elements and more than 6 million degrees of freedom (dofs) can be tackled using normal computation facilities within acceptable computational time. Moreover, we are able to not only reproduce qualitatively evolution of the complex fracture pattern, but also compare quantitatively the global responses against experimental results. With the need neither to characterize the non-smooth crack surface nor to track the twisting crack path, the 3D computer implementation is almost the same as the 2D counterpart, paving the way to the phase-field modeling of large scale engineering problems.

Nonlinear dynamic responses of beamlike truss based on the equivalent nonlinear beam model

The main goal of this paper is to develop an equivalent nonlinear beam model (ENBM) for forced vibration analysis of the nonlinear beamlike truss (NBT) and its numerical implementation for describing the nonlinear behaviors of the periodic NBT. For the equivalent dynamic modeling method based on the energy equivalence principle of the truss structures, most of the existing approaches focus on studying the linear characteristic which cannot satisfy the nonlinear dynamic analytical requirement. Here, we extend the equivalent dynamic modeling to nonlinear forced vibration responses of the large NBT civil engineering structure with two pinned ends. We introduce the geometric nonlinearity into the equivalent dynamic model using the von Karman nonlinear strain-displacement relationship to imitate the nonlinear behaviors of the beamlike truss. On the basis of the Hamilton principle, the fourth-order governing partial differential equations of motion of the ENBM are obtained and solved utilizing the Galerkin method. It is shown that the ENBM accurately captures the nonlinear dynamic response of the beamlike truss subjected to external load by using the first four order modes. In order to showcase the efficiency and accuracy of the ENBM, time histories, phase maps and fast Fourier transform frequency spectra are investigated for the NBT and the ENBM under different external excitation magnitudes and frequencies. Comparisons between results of the ENBM and those obtained from the finite element simulations of the NBT show good agreements and identify the periodic motions of them. Furthermore, the effect of the external loading and damping parameters on the frequency-response and force-response curves is discussed. In addition, computing time of the proposed ENBM are compared with that of the full-scale finite element model in ANSYS so as to highlight the significant less computational cost of the equivalent nonlinear dynamic modeling. Particularly, the proposed ENBM can achieve the nonlinear mechanism of the NBT in analytical method and design the low-order control law conveniently.

Simulation of a Defect in a Concrete Dam Structure Using Steady-State Infrared Thermography

A roller compacted concrete (RCC) dam is a large civil engineering structure that is subject to a permanent load of water hydrostatic thrust, and the construction of such a structure requires enormous human, material and financial resources. It gives rise to a reserve of water upstream in billions of m3; therefore, a problem in its stability will generate a catastrophe at its end. Among the means of controlling the dam body is the detection of abnormalities by infrared thermography. In this communication, we will simulate a structure of a dam containing a defect, and the discontinuity of the concrete gives rise to a contrast in the thermo-gram of the downstream surface. Thus several parameters will be studied in this dam, namely the positioning of the defect with respect to the downstream surface, the thickness of this defect and finally the orientation. The thermal images of the downstream surface are recovered in order to interpret the contrast and to draw explanations of what is inside this dam.

Hybrid Heat Transfer Search and Passing Vehicle Search optimizer for multi-objective structural optimization

A novel hybrid optimizer called Multi-Objective Hybrid Heat Transfer Search and Passing Vehicle Search optimizer (MOHHTS–PVS) is proposed while its performance is investigated for the structural design. The HHTS–PVS optimizer combines the merits of Heat Transfer Search (HTS) and Passing Vehicle Search (PVS). The design problem is posed for weight minimization and maximization of nodal deflection subject to multiple constraints of trusses. In the proposed optimizer, HTS acts as the main engine and PVS is added as an auxiliary stage into it to overcome its limitations and enhance the performance while simultaneously creating harmony between global diversification and local intensification of the search. Five challenging structure optimization benchmarks are optimized having discrete design variables. For performance validation, four state-of-the-art optimizers are compared with the proposed optimizer. Pareto Front Hypervolume and Spacing-to-Extent test are performance indicators for all the test examples. HHTS–PVS achieved the best non-dominated Pareto fronts with continuous and well diverse solutions set. The statistical analysis is done by performing Friedman’s rank test and allocating respective ranks to the optimizers. As per the outcomes, it is concluded that HHTS–PVS outperforms other optimizers and simultaneously shows its competency in solving large engineering design problems.

Influence of recessing nozzle extent on a process of heat exchange in the combustion chamber of a solid fuel rocket engine

This paper considers issues of numerical simulation of the spatial gas dynamics and heat transfer in the pre-nozzle volume of the combustion chamber of a large solid-fuel rocket engine. It is investigated the effect of the degree of recessing of the nozzle specifying the ratio of flow rates of a gas through the channel and the supra-nozzle gap of the processes in the pre-nozzle volume. An analysis of a topology of the flow structure and thermophysical processes near inlet surface of the recessing nozzle was performed. The distribution of the heat transfer coefficient equation on the inlet surface of the recessed nozzle and a criterial for the estimation of heat transfer depending on topological features on the surface of the recessed nozzle are obtained.

On the Adoption of Global/Local Approaches for the Thermomechanical Analysis and Design of Liquid Rocket Engines

Large Liquid Rocket Engines for Aerospace applications usually need to be cooled regeneratively since they are characterized by high pressure levels and heat flux with the presence, in the inner structure, of very high thermal gradients—thus necessitating the adoption of elastic-plastic nonlinear material models to study the thermomechanical behavior of the chamber and its service life. Tackling such nonlinearity makes the finite element analyses computationally intensive, particularly so when dealing with three-dimensional models. In these instances, it is highly recommended to adopt optimized numerical approaches that can save computation time while maintaining high levels of accuracy. The aim of the present paper is to implement an iterative coupling technique between two finite element models, a Global linear model and a Local nonlinear one, in the framework of a Global/Local procedure, to improve the accuracy of the numerical simulations. Both conformal and non-conformal meshes at the interface between the Global and the Local models have been considered. The results show that, even with a very few iterations, significant accuracy improvements are achieved.

Experimental Framework to Simulate Rescue Operations after a Natural Disaster

Computational simulation is a powerful tool for performance evaluation of computational systems. It is useful to make capacity planning of data center clusters, to obtain profiling reports of software applications and to detect bottlenecks. It has been used in different research areas like large scale Web search engines, natural disaster evacuations, computational biology, human behavior and tendency, among many others. However, properly tuning the parameters of the simulators, defining the scenarios to be simulated and collecting the data traces is not an easy task. It is an incremental process which requires constantly comparing the estimated metrics and the flow of simulated actions against real data. In this work, we present an experimental framework designed for the development of large scale simulations of two applications used upon the occurrence of a natural disaster strikes. The first one is a social application aimed to register volunteers and manage emergency campaigns and tasks. The second one is a benchmark application a data repository named MongoDB. The applications are deployed in a distributed platform which combines different technologies like a Proxy, a Containers Orchestrator, Containers and a NoSQL Database. We simulate both applications and the architecture platform. We validate our simulators using real traces collected during simulacrums of emergency situations.

Investigation on the Emission Characteristics with a Wet-Type Exhaust Gas Cleaning System for Marine Diesel Engine Application

Global air pollution regulations are becoming stricter for large diesel engines powering automobiles and ships. In the automotive sector, Euro 4 regulations came into force in January 2013 in accordance with European Union (EU) emission standards for heavy-duty diesel engines and are based on steady-state testing. In the marine sector, the International Maritime Organization(IMO) Maritime Environment Protection Committee(MEPC) is a group of experts who discuss all problems related to the prevention and control of marine pollution from ships, such as efforts to reduce ozone-depleting substances and greenhouse gas emissions. To reduce the harmful emissions from marine diesel engines, a wet-type exhaust gas cleaning system was developed in this study. As a test, seawater, electrolyzed water, and sodium hydroxide were sequentially injected into the exhaust gas. SO2 was reduced by 98.7–99.6% with seawater injection, NOx by 43.2–48.9% with electrolyzed water injection, and CO2 by 28.0–33.3% with sodium hydroxide injection.

Googling for Ticks and Borreliosis in Germany: Nationwide Google Search Analysis From 2015 to 2018.

BackgroundBorreliosis is the most frequently transmitted tick-borne disease in Europe. It is difficult to estimate the incidence of tick bites and associated diseases in the German population due to the lack of an obligation to register across all 16 federal states of Germany.ObjectiveThe aim of this study is to show that Google data can be used to generate general trends of infectious diseases on the basis of borreliosis and tick bites. In addition, the possibility of using Google AdWord data to estimate incidences of infectious diseases, where there is inconsistency in the obligation to notify authorities, is investigated with the perspective to facilitate public health studies.MethodsGoogle AdWords Keyword Planner was used to identify search terms related to ticks and borreliosis in Germany from January 2015 to December 2018. The search volume data from the identified search terms was assessed using Excel version 15.23. In addition, SPSS version 24.0 was used to calculate the correlation between search volumes, registered cases, and temperature.ResultsA total of 1999 tick-related and 542 borreliosis-related search terms were identified, with a total of 209,679,640 Google searches in all 16 German federal states in the period under review. The analysis showed a high correlation between temperature and borreliosis (r=0.88), and temperature and tick bite (r=0.83), and a very high correlation between borreliosis and tick bite (r=0.94). Furthermore, a high to very high correlation between Google searches and registered cases in each federal state was observed (Brandenburg r=0.80, Mecklenburg-West Pomerania r= 0.77, Saxony r= 0.74, and Saxony-Anhalt r=0.90; all P<.001).ConclusionsOur study provides insight into annual trends concerning interest in ticks and borreliosis that are relevant to the German population exemplary in the data of a large internet search engine. Public health studies collecting incidence data may benefit from the results indicating a significant correlation between internet search data and incidences of infectious diseases.

Novel Approach to Thermal Processing Development for Precision Sand Casting Process (PSCP) of Aluminum Engine Blocks

The latest generation of high-performance engine blocks are produced with the precision sand casting process (PSCP). Their enhanced mechanical properties are provided by an integrated cast iron chill in the bulkhead section and thus result in large variations in secondary dendrite arm spacing (λ2) throughout the whole casting, providing unique challenges in both heat treat (T7 temper) development and compliance to the CQI-9 protocol. This research examines the influence of chemistry, controlled solution/quench, residence time between quench and the start of artificial age and artificial age temperature, on the mechanical properties and cryogenic testing observations on PSCP engine blocks. The results are obtained from large population engine block castings (n = 204), heat treated within an industrial plant environment with strict control over furnace temperature gradients. The results indicated that age temperature differences of as little as 4 °C (within CQI-9 for furnace temperature specification of ± 5 °C) can alter yield strength and elongation significantly, which in turn changes crack susceptibility (warranty issues). In addition to the above analysis, it was found that extending the time between the solution/quench operation and the start of artificial age results in a continual drop in yield strength due to the influence of natural aging.

Industrial and Large Engines

Industrial and Large Engines

Advantages of Closed Crankcase Ventilation for Large Engines

Advantages of Closed Crankcase Ventilation for Large Engines

Microscale testing and modelling for damage tolerant composite materials and structures

There is a need for damage tolerant composite material for very large engineering structures such as wind turbine rotor blades. The development of improved composite materials with higher damage tolerance will be most efficiently guided by models of the relevant damage modes. Two damage modes are considered in the present paper: Fatigue damage due to in-plane tensile stresses in the fibre direction and cyclic delamination crack growth from a ply drop. For both failure modes the damage evolution is considered at macro- and microscale. Micromechanical models are used to illustrate how changes in the mechanical properties of fibre, matrix and the fibre/matrix interface can lead to an increased damage tolerance material. Also, micromechanical testing methods for characterizing the relevant micromechanical parameters are discussed.

Scientific Drilling ‐ to Construct the Telescopes that Inserting to the Earth Interior

AbstractMankind live in the earth for countless years, but until now; people do not really understand the connotation of the Earth. We know that the earth composition including the lithosphere, the asthenosphere, mantle and core. Of course, the lithosphere supports all the life on Earth. For a long time, geoscientists trying to use all kind of methods such as geological, geophysical and geochemical methods to detect and study the earth, but the knowledge about earth are mostly indirect. Through the direct observation to the lithosphere, people can understand and recognize the plate movement of ocean and the mainland, crustal stress, earthquakes, volcanic processes, deep resources, the origins of life, global climate change and biodiversity. They are all the basis of a series of geosciences problems (Su and Yang, 2010).Geological specimens, especially the true samples from deep of the Earth, are the most directly study subjects for geologists. But the only way to access the true samples from deep of the earth is drilling. The most directly relevant evidence always originated from the deep of the earth, such as core, cuttings, fluid samples and other physical samples.Continental scientific drilling has been demonstrated which is an efficient technique for directly obtaining information from the Earth's surface to the deep crust, and is acknowledged as “to build a telescope inserting to the interior of the Earth”, as well as “a key for opening the door of the Earth”. Over the last four decades, continental scientific drilling has achieved great success in enhancing our knowledge of the Earth, and in providing information on mineral resources, large engineering projects and global change. SinoProbe‐05 is a new scientific drilling venture, which builds on the success of the Chinese Continental Scientific Drilling Project (CCSD), and is similar to the current major scientific drilling project on the Wenchuan earthquake fault. SinoProbe‐05 will focus on 6 critical tectonic and mineral resource regions, including the Jinchuan Cu‐Ni sulphide deposits in Gansu, the Luobusa chromite deposits in Tibet, the Tengchong volcano‐thermal tectonic zone in Yunnan, the Yudu‐Ganxian polymetallic deposits in South China, the Tongling polymetallic deposit and the Luzong volcanic basin and mineral deposit district in Anhui. As of the end of 2013, all of these pilot holes have been completed, all of them have achieved the desired scientific objectives.The construction of another ICDP project, Songke No.2 well, has come to an end. Current well depth is 5929m. Drilling throughout the Cretaceous strata is just around the corner (The design well depth is 6400m.). This will be the first complete Cretaceous stratigraphic profile in the world.The deep exploration project which will be stared soon will build a large number of different depths of scientific drilling holes. The deepest hole depth will reach to 13000m. We believe that the construction of these scientific coring drilling holes will provide geologists with a lot of real core samples. These cores can meet the needs for different geoscience research areas. No doubt, the research results based on these cores will promote China's geological science research to a new height, of course; will also contribute to the progress of the world's earth science. This is also a good opportunity to promote China's drilling technology.So, we know that no advanced drilling technology, no enough high quality samples from the deep of the Earth, the in‐depth studies for geosciences will be restricted of course (Zhang et al., 2013).