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Journal articles on the topic 'Theory of engines'
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1
Wang, Meng-Hui, and Pi-Chu Wu. "Fault Diagnosis of Car Engine by Using a Novel GA-Based Extension Recognition Method." Mathematical Problems in Engineering 2014 (2014): 1–7. http://dx.doi.org/10.1155/2014/735485.
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Due to the passenger’s security, the recognized hidden faults in car engines are the most important work for a maintenance engineer, so they can regulate the engines to be safe and improve the reliability of automobile systems. In this paper, we will present a novel fault recognition method based on the genetic algorithm (GA) and the extension theory and also apply this method to the fault recognition of a practical car engine. The proposed recognition method has been tested on the Nissan Cefiro 2.0 engine and has also been compared to other traditional classification methods. Experimental results are of great effect regarding the hidden fault recognition of car engines, and the proposed method can also be applied to other industrial apparatus.
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Li, Xi Qin, Su Yan Cai, Bing Liu, and Xue Qun He. "Study on Emission Control of CNG Engine Based on D-S Evidence Theory." Applied Mechanics and Materials 109 (October 2011): 281–84. http://dx.doi.org/10.4028/www.scientific.net/amm.109.281.
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To reduce emissions, CNG engines are commonly equipped with three-way catalytic converters. However when the engines run at transient conditions, the air fuel ratio can not be precisely controlled at theoretical value by traditional means, so the catalytic converters can not achieve their desired effect. This paper presents a new method for CNG engines to control air fuel ratio at transient conditions. The moments which intake and exhaust valves open are used as the trigger signals for ECU to collect the test data simultaneously. The dynamic information of CNG engine is detected by multiple sensors; the nonlinear coupling relationship between air fuel ratio of CNG engine and the operating conditions are established through information fusion and neural network control. The requirement of real time control for air fuel ratio is achieved, so the emissions of CNG engines are reduced further.
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Nambiar, K. K. "Theory of search engines." Computers & Mathematics with Applications 42, no. 12 (December 2001): 1523–26. http://dx.doi.org/10.1016/s0898-1221(01)00259-0.
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Anisimov, Victor, and Vasyl Muzychuk. "DETERMINATION OF RESIDUAL FUEL RESOURCE AUTOTRACTOR DIESEL EQUIPMENT BY MATHEMATICAL MODELING WITH METHOD APPLICATION SMALL DEVELOPMENTS." ENGINEERING, ENERGY, TRANSPORT AIC, no. 3(110) (October 30, 2020): 4–15. http://dx.doi.org/10.37128/2520-6168-2020-3-1.
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The reliability of automotive internal combustion engines is a function of the reliability of their mechanisms and systems. For many years, domestic and foreign engineers have tested many auto-tractor internal combustion engines and it has been proven that if mathematical models reliably describe physical phenomena, cycles or processes that take place in engines, then the theory of small deviations for theoretical research is much better than any experiment on control characteristics and many second parameters The theory of small deviations for fuel equipment of autotractor diesel engines is considered in the article. The method of transition from the ordinary differential equations describing the quality of diesel fuel spraying to the equations in small deviations. Equation of kinematics and hydrodynamics of precision pairs of fuel equipment in small deviations. Consumption characteristics of fuel in the process of injection in small deviations. Methods of similarity, dimension theory, mathematical statistics, and probability theory, which are used in determining the resource and predicting the operation of tractor engines. It is shown that the most practically accepted method for determining the residual life of autotractor engines is the method of mathematical statistics and probability theory. The role of mathematical modeling in determining the residual life of fuel equipment of autotractor diesel engines is established. It is also noted that it is advisable to use the small deviation method to accurately describe the processes in the fuel equipment of autotractor diesel engines. The mathematical model is based on the known physical laws that describe the interdependencies of the two groups of parameters, control and operational, both within and between groups. The transition of the classical differential equations describing the processes of fuel supply and injection, taking into account fuel leaks in precision pairs, into equations with small deviations of parameters, is shown. The relationship between injection, fuel supply and fuel leakage is analyzed and the most influential parameters found. Impact coefficients are found and their dependencies are plotted on their corresponding parameters. Using the obtained dependencies, the influence of the technical condition of precision pairs on the effective performance of the engine is characterized. Dependences of change of injection characteristics on small deviations of parameters characterizing the technical condition of precision pairs of fuel equipment are also established.
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Smith, Zackary, Priyo S. Pal, and Sebastian Deffner. "Endoreversible Otto Engines at Maximal Power." Journal of Non-Equilibrium Thermodynamics 45, no. 3 (July 26, 2020): 305–10. http://dx.doi.org/10.1515/jnet-2020-0039.
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AbstractDespite its idealizations, thermodynamics has proven its power as a predictive theory for practical applications. In particular, the Curzon–Ahlborn efficiency provides a benchmark for any real engine operating at maximal power. Here we further develop the analysis of endoreversible Otto engines. For a generic class of working mediums, whose internal energy is proportional to some power of the temperature, we find that no engine can achieve the Carnot efficiency at finite power. However, we also find that for the specific example of photonic engines the efficiency at maximal power is higher than the Curzon–Ahlborn efficiency.
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Cur, Krzysztof, Mirosław Kowalski, Paweł Stężycki, and Dariusz Ćwik. "Checking Aircraft Engines Adjustment." Journal of KONBiN 51, no. 2 (June 1, 2021): 153–62. http://dx.doi.org/10.2478/jok-2021-0029.
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Abstract The paper presents a new approach to the process of regulating the basic parameters of a turbine jet engine. It presents a system for monitoring these parameters developed and put into operation and the creation of the so-called phase mapping of the engine speed increment. Its modular structure is described, which allows it to be adapted quite quickly to other types of aircraft engine units. Individual modules are based on mathematical descriptions from the theory of aircraft engines. The phase mapping of the engine speed indicates a dynamic change of this parameter. On this basis, the characteristic ranges and individual points of engine operation are presented. The following are examples of characteristics and their interpretation.
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Bilousov, E. V., and P. Billier. "FRENCH ENGINEER SABATHE LOUIS GASTON AND HIS ROLE IN CREATION OF DUAL COMBUSTION CYCLE." Internal Combustion Engines, no. 1 (July 26, 2021): 92–98. http://dx.doi.org/10.20998/0419-8719.2021.1.12.
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Almost immediately after Rudolph Diesel created his "rational" engine, attempts were made to improve it. Since at the end of the nineteenth and the beginning of the twentieth century, the theory of internal combustion engines had not yet been formed as a unified scientific system, there were no unified approaches to assessing the innovations proposed by individual engineers and scientists either. In this regard, disputes and litigations periodically arose related to the recognition of priority for a specific design or the proposed principle of work for a specific author. First of all, this was due to the possibility of obtaining material benefits from the introduction of a patented innovation into production. It should be noted that profit-related litigation and information campaigns were not always objective, and the development of progress at the turn of the century were so rapid that the same ideas entered the heads of several independent inventors at once, but the same discoveries were made in different parts of the world by different scientists. By the beginning of the twentieth century, the accumulated experience, as well as theoretical and experimental studies have shown that it was possible to significantly improve the nature of the flow of the working process of piston engines by replacing the isochoric or isobaric heat supply in the process of fuel combustion with a combined one with heat supply, first at a constant volume (by isochore), and then at constant pressure (isobar). Three scientists - Gustav Trinkler, Myron Zaliger and Louis Gaston Sabathe claimed priority in the development of such a cycle. Each of them came to this decision in different ways, and each made his own contribution both to the formation of the theory of working processes of piston engines, and to the formation of engine building in general. It is to this contribution made by the French engineer Louis Gaston Sabathe that this article is devoted.
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Bi, Shu Sheng, Shi Xing Fang, and Shi Hao Wang. "Electromagnetic Propulsion Aero-Engine Design Based on Ampere Theorem." Applied Mechanics and Materials 411-414 (September 2013): 1773–78. http://dx.doi.org/10.4028/www.scientific.net/amm.411-414.1773.
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This paper means to provide an innovative design of aero-engine after investigating existing aero-engines. It is a late model power plant design which is based on the watercraft electromagnetic propulsion technology and the theory that in electromagnetic field magnetic field generates Ampere force to current flow and in combination with specific structures of aero-engines. The design principle of this engine is that when the air working medium with high conductivity goes through an arc generator, it will ionize and produce plasma, which actions in the magnetic field that produced by built-in superconducting magnetic and generates forward push. This design will provide a theoretical reserve for future development of aero-engines and has potential market prospects.
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Girtler, Jerzy. "A Model of Fuel Combustion Process in The Marine Reciprocating Engine Work Space Taking Into Account Load and Wear of Crankshaft-Piston Assembly and The Theory of Semi-Markov Processes." Polish Maritime Research 23, no. 3 (September 1, 2016): 50–57. http://dx.doi.org/10.1515/pomr-2016-0031.
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Abstract The article analyses the operation of reciprocal internal combustion engines, with marine engines used as an example. The analysis takes into account types of energy conversion in the work spaces (cylinders) of these engines, loads of their crankshaft-piston assemblies, and types of fuel combustion which can take place in these spaces during engine operation. It is highlighted that the analysed time-dependent loads of marine internal combustion engine crankshaft-piston assemblies are random processes. It is also indicated that the wear of elements of those assemblies resulting from their load should also be considered a random process. A hypothesis is formulated which explains random nature of load and the absence of the theoretically expected detonation combustion in engines supplied with such fuels as Diesel Oil, Marine Diesel Oil, and Heavy Fuel Oil. A model is proposed for fuel combustion in an arbitrary work space of a marine Diesel engine, which has the form of a stochastic four-state process, discrete in states and continuous in time. The model is based on the theory of semi-Markov processes.
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Chen, Lu Hua. "Study on Analysis of Vehicle Engine Failure Risk Based on ANP_FE." Advanced Materials Research 588-589 (November 2012): 198–202. http://dx.doi.org/10.4028/www.scientific.net/amr.588-589.198.
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The study focuses on the problem of risk analysis of vehicle engines’ failure. Based on investigation and analysis of vehicle engine, an index system which is suitable for analyzing vehicle engines’ failure is established. And a much perfect technique ANP_FE is introduced into the risk analyzing of vehicle engines’ failure. It has been found that this index system and analyzing technique has a good adaptability, the result could be used as a theoretical proof for the production and improvement. The theory, system, thinking and method could be used as a reference to the similar product.
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Yeh, Chung Wei, and Kee Rong Wu. "An Integrated Multimedia Learning System for Reciprocating Internal Combustion Engines: RICEM." Applied Mechanics and Materials 39 (November 2010): 91–96. http://dx.doi.org/10.4028/www.scientific.net/amm.39.91.
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A cost-effective multimedia learning system, RICEM, for reciprocating internal combustion engines was proposed in this study. This system contained the graphical introduction of engine components, engine structure animation, thermal theory, feedback and assessment based on Mayer’s multimedia learning cognitive theory. Reciprocating internal combustion engines are used all over the world to drive compressors, pumps, electric generators, motor ships and other equipments. We used multimedia software to construct the learning system. An experiment comprising of two groups of 30 participants separately was conduct to test the effectiveness and showed that there was a significant difference between the pre-test and post-test score in the RICEM group, as compared with the control group. This study suggested that a collaborative application appeared to be promising in supporting effective learning of modern technology, by combining the integration of learning theory and multimedia design.
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Andoga, Rudolf, Ladislav Főző, Radovan Kovács, Károly Beneda, Tomáš Moravec, and Michal Schreiner. "Robust Control of Small Turbojet Engines." Machines 7, no. 1 (January 4, 2019): 3. http://dx.doi.org/10.3390/machines7010003.
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Modern turbojet engines mainly use computerized digital engine control systems. This opens the way for application of advanced algorithms aimed at increasing their operational efficiency and safety. The theory of robust control is a set of methods known for good results in complex control tasks, making them ideal candidates for application in the current turbojet engine control units. Different methodologies in the design of robust controllers, utilizing a small turbojet engine with variable exhaust nozzle designated as iSTC-21v, were therefore investigated in the article. The resulting controllers were evaluated for efficiency in laboratory conditions. The aim was to find a suitable approach and design method for robust controllers, taking into account the limitations and specifics of a real turbojet engine and its hardware, contrary to most studies which have used only simulated environments. The article shows the most effective approach in the design of robust controllers and the resulting speed controllers for a class of small turbojet engines, which can be applied in a discrete digital control environment.
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Anisimov, Victor, and Vasyl Muzychuk. "ANALYSIS AND CHOICE OF RESEARCH METHODS RELIABILITY OF AUTOTRACTOR ENGINES." ENGINEERING, ENERGY, TRANSPORT AIC, no. 3(106) (November 29, 2019): 35–45. http://dx.doi.org/10.37128/2520-6168-2019-3-5.
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The study of the reliability of the engine as a whole can be represented as a study of the probabilistic characteristics of its reliability according to the given probabilistic characteristics of the reliability of individual engine elements, that is, systems and mechanisms. The article substantiates that the method of similarity and dimensional theory allows us to establish patterns of change in the wear rate tgα depending on the adjustment of the engine parameters, and numerous experiments are required, which makes it little practical in determining the resource and predicting the operation of tractor engines. A more practically acceptable method for determining the residual life of automotive engines is the method of mathematical statistics and probability theory, and, in particular, the law of normal distribution. However, to determine the resource of engines, using this law, it is also necessary to conduct a large amount of testing. Thus, at the current stage of scientific and technological progress in automotive engineering, it is necessary to find other methods that are most practically acceptable and contribute in a short time, without a large amount of testing, to determine the resource of machines with maximum durability, which will be developed in subsequent works of the authors of the article.
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KOWALAK, Przemysław, Stefan ŻMUDZKI, and Tadeusz BORKOWSKI. "Marine diesel engine – a novel approach of indicated power determination and related uncertainty level." Combustion Engines 168, no. 1 (February 1, 2017): 15–20. http://dx.doi.org/10.19206/ce-2017-102.
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A proposal of a new method for marine engine indicated power determination, based on direct piston position, instead of crankshaft angular position measurement, was presented. With the aid of bond graph theory, it was proved, that the new method is equivalent to conventional method. To verify hypothesis, that the new method has potential of determined indicated power uncertainty reduction, simulated calculations were carried out. Results of calculations for two marine diesel engines: medium-speed, four stroke and slowspeed two stroke type, at assumption of engine crankshaft constant speed, were compared with results obtained by a conventional method. Data, collected by means of a typical portable, industrial, digital indicator on engines in service, were used for simulation. The uncertainties of engines indicated power determined by means of two methods were analysed. The indicated power uncertainty, achieved for conventional method, was nearly twice higher than for new proposed method. Finally, uncertainty structure was analysed and evaluated for both: new and conventional method of engine indicated power determination.
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Daren, Y., C. Tao, and B. Wen. "An idea of distributed parameter control for scramjet engines." Aeronautical Journal 111, no. 1126 (December 2007): 787–96. http://dx.doi.org/10.1017/s0001924000001901.
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AbstractScramjet engines are used under extreme temperatures and with wide range of Mach numbers from 3 to 8 or higher and have shown different control properties from other airbreathing engines. New control problems involving distributed parameter control have been found concerning investigations of the control of scramjet engines whose physical states are spatially interacted and whose governing equations are partial differential equations. The work of this paper is based on the application of distributed parameter control conception to study the control problems of scramjet engines with the aim of achieving the desirable design properties and increasing control reliability. A new control idea based on shape control theory is put forward to realise the distributed parameter control of scramjet engines with the preconditions of proper space dimension and frequency-domain simplification. Simulation results and theoretic analysis for an axisymmetric, wall-injection scramjet engine show the feasibility and validity of the control idea.
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Yeh, Chung Wei. "An Integrated Multimedia Learning System for Reciprocating Internal Combustion Engines: RICEM." Advanced Materials Research 213 (February 2011): 211–15. http://dx.doi.org/10.4028/www.scientific.net/amr.213.211.
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A cost-effective multimedia learning system, RICEM, for reciprocating internal combustion engines was proposed in this study. This system contained the graphical introduction of engine components, engine structure animation, feedback and assessment based on Mayer’s multimedia learning cognitive theory. Reciprocating internal combustion engines are used all over the world to drive compressors, pumps, electric generators, motor ships and other equipments. We used multimedia software to construct the learning system. An experiment comprising of two groups of 30 participants separately was conduct to test the effectiveness and showed that there was a significant difference between the pre-test and post-test score in the RICEM group, as compared with the control group. This study suggested that a collaborative application appeared to be promising in supporting effective learning of modern technology, by combining the integration of learning theory and multimedia design.
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Neider, Daniel, P. Madhusudan, Shambwaditya Saha, Pranav Garg, and Daejun Park. "A Learning-Based Approach to Synthesizing Invariants for Incomplete Verification Engines." Journal of Automated Reasoning 64, no. 7 (July 13, 2020): 1523–52. http://dx.doi.org/10.1007/s10817-020-09570-z.
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Abstract We propose a framework for synthesizing inductive invariants for incomplete verification engines, which soundly reduce logical problems in undecidable theories to decidable theories. Our framework is based on the counterexample guided inductive synthesis principle and allows verification engines to communicate non-provability information to guide invariant synthesis. We show precisely how the verification engine can compute such non-provability information and how to build effective learning algorithms when invariants are expressed as Boolean combinations of a fixed set of predicates. Moreover, we evaluate our framework in two verification settings, one in which verification engines need to handle quantified formulas and one in which verification engines have to reason about heap properties expressed in an expressive but undecidable separation logic. Our experiments show that our invariant synthesis framework based on non-provability information can both effectively synthesize inductive invariants and adequately strengthen contracts across a large suite of programs. This work is an extended version of a conference paper titled “Invariant Synthesis for Incomplete Verification Engines”.
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GIRTLER, Jerzy. "Possibility of estimating the reliability of diesel engines by applying the theory of semi-Markov processes and making operational decisions by considering reliability of diagnosis on technical state of this sort of combustion engines." Combustion Engines 163, no. 4 (November 1, 2015): 57–66. http://dx.doi.org/10.19206/ce-116857.
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The paper presents semi-Markov models of technical state transitions for diesel engines, useful for determining the reliability of engines. A possibility of application of a three-state model with a simplified matrix function, or even a two-state model, to determine reliability of the engines, has been described herein on examples of known from literature semi-Markov models, for the case when appropriate diagnosing systems (SDG) are used to identify the technical condition of the engines considered as diagnosed systems (SDN). A risk function and a renewal (restitution) function have been proposed for developing a two-state model of engine state transitions. An opportunity for considering the reliability of diagnosis for making operational decisions by applying the statistical decision theory, has also been presented. Conditional probability P(si/Ki) is recognized as a measure of reliability of diagnosis
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Garcia-Atance Fatjo, Gonzalo, Edward H. Smith, and Ian Sherrington. "Piston-ring film thickness: Theory and experiment compared." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 232, no. 5 (July 31, 2017): 550–67. http://dx.doi.org/10.1177/1350650117722257.
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A review of the published literature has demonstrated a large variability and discrepancies in the measured and predicted values of piston-ring lubricating film thickness in internal combustion engines. Only two papers have been found that compare experiments in firing engines directly with outputs from sophisticated ring-pack lubrication models. The agreement between theory and experiment in these comparisons was limited, possibly because of inadequacies in the models and/ or inaccuracies of measurement. This paper seeks to contribute to the literature by comparing accurately calibrated experimental measurements of piston-ring film thickness in a firing engine with predictions from an advanced, commercial software package alongside details of the systematic analysis of the measurement errors in this process. Suggestions on how measurement accuracy could be further improved are also given. Measurements of oil-film thickness with an error (standard deviation) of ±15% have been achieved. It is shown that this error can be reduced further, by changes in the design and installation of the sensors. Detailed experimental measurements of film thickness under the top compression ring in a firing petrol engine have been made and compared with the predictions from a commercial, state-of-the art modelling package. The agreement between theory and experiment is excellent throughout the stroke in most cases, but some significant differences are observed at the lower load conditions. These differences are as yet unexplained, but may be due to the sensor topography influencing the hydrodynamic lubrication, lubricant availability, out-of-roundness in the cylinder or squeeze effects. This is a topic that requires further study.
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Brian Kim Stefans. "Terrible Engines:." Comparative Literature Studies 51, no. 1 (2014): 159. http://dx.doi.org/10.5325/complitstudies.51.1.0159.
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Forest, Florent, Quentin Cochard, Cecile Noyer, Marc Joncour, Jérôme Lacaille, Mustapha Lebbah, and Hanene Azzag. "Large-scale Vibration Monitoring of Aircraft Engines from Operational Data using Self-organized Models." Annual Conference of the PHM Society 12, no. 1 (November 3, 2020): 11. http://dx.doi.org/10.36001/phmconf.2020.v12i1.1131.
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Vibration analysis is an important component of industrial equipment health monitoring. Aircraft engines in particular are complex rotating machines where vibrations, mainly caused by unbalance, misalignment, or damaged bearings, put engine parts under dynamic structural stress. Thus, monitoring the vibratory behavior of engines is essential to detect anomalies and trends, avoid faults and improve availability. Intrinsic properties of parts can be described by the evolution of vibration as function of rotation speed, called a vibration signature. This work presents a methodology for large-scale vibration monitoring on operating civil aircraft engines, based on unsupervised learning algorithms and a flight recorder database. Firstly, we present a pipeline for massive extraction of vibration signatures from raw flight data, consisting in time-domain medium-frequency sensor measurements. Then, signatures are classified and visualized using interpretable self-organized clustering algorithms, yielding a visual cartography of vibration profiles. Domain experts can then extract various insights from resulting models. An abnormal temporal evolution of a signature gives early warning before failure of an engine. In a post-finding situation after an event has occurred, similar at-risk engines are detectable. The approach is global, end-to-end and scalable, which is yet uncommon in our industry, and has been tested on real flight data.
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Dariusz Stanisław Sobolewski, Michał Amadeusz Sobolewski, Marek Juliusz Sobolewski, Joanna Paulina Sobolewska, and Natalia Julia Sobolewska. "New Generations of Rocket Engines." JOURNAL OF ADVANCES IN PHYSICS 17 (May 22, 2020): 322–46. http://dx.doi.org/10.24297/jap.v17i.8747.
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The article, based on mathematical model of the space and particles revealed in "Theory of Space" (Sobolewski D. S., Theory of Space, 2016) (Sobolewski D. S., Theory of Space, 2017) and the description of the propagation of photons stated in publication entitled “Geometry of the Dark Matter and Preliminary Analysis of Alpha and Beta Photons’ Properties Based on Theory of Space” (Sobolewski, Sobolewski i Sobolewski, 2017), describes transverse waves propagating in space, including gravitational, fluctuating and matter waves. In particular, it focuses on waves of matter in which orientation of the spatial channels, connecting four-dimensional boundary hypersurfaces and , had been stabilised. For this type of the wave of matter the minimum energy value for deformation of boundary hypersurfaces of the matter waves has been appointed, which is smaller by several orders of magnitude than energy needed to change the orientation of vertical disturbances of space which connect four-dimensional boundary hypersurfaces and, The obtained results were used to introduce a new classification of rocket engines and to provide examples of their implementation. Furthermore, the article demonstrates first attempts to construct a rocket engine of the new type, including description of the principle of operation of the engine, which is subject of patent application entitled "HTS Photonic Rocket Engine" (Poland Patent nr P.421517, 2017), as well as presents an example of spacecraft shell implementation, which enables stabilization of orientation of its spatial channels. The Article thus reveals new perspectives for interplanetary travel through significant increase in spacecraft velocities, while simultaneously reducing the energy required to achieve them. In addition, the article describes interaction of photons with the boundary hypersurface , while determining the change in photon frequency depending on its curvature .
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Reyes-Menendez, Ana, Jose Saura, Pedro Palos-Sanchez, and Jose Alvarez-Garcia. "Understanding User Behavioral Intention to Adopt a Search Engine that Promotes Sustainable Water Management." Symmetry 10, no. 11 (November 2, 2018): 584. http://dx.doi.org/10.3390/sym10110584.
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An increase in users’ online searches, the social concern for an efficient management of resources such as water, and the appearance of more and more digital platforms for sustainable purposes to conduct online searches lead us to reflect more on the users’ behavioral intention with respect to search engines that support sustainable projects like water management projects. Another issue to consider is the factors that determine the adoption of such search engines. In the present study, we aim to identify the factors that determine the intention to adopt a search engine, such as Lilo, that favors sustainable water management. To this end, a model based on the Theory of Planned Behavior (TPB) is proposed. The methodology used is the Structural Equation Modeling (SEM) analysis with the Analysis of Moment Structures (AMOS). The results demonstrate that individuals who intend to use a search engine are influenced by hedonic motivations, which drive their feeling of contentment with the search. Similarly, the success of search engines is found to be closely related to the ability a search engine grants to its users to generate a social or environmental impact, rather than users’ trust in what they do or in their results. However, according to our results, habit is also an important factor that has both a direct and an indirect impact on users’ behavioral intention to adopt different search engines.
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Duc Luu, Do, and Nguyen Quang Vinh. "Affections of Turbine Nozzle Cross-Sectional Area to the Marine Diesel Engine Working." Naše more 68, no. 2 (March 2021): 65–73. http://dx.doi.org/10.17818/nm/2021/2.1.
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After a long period of use, some important technical parameters of the main marine diesel engines (MDE) gradually become worse, such as the turbine speed, intake pressure, exhaust temperature, engine power, and specific fuel oil consumption (SFOC). This paper studies the affections of the turbine nozzle cross-sectional area (AT) to MDE and presents a method of AT adjustment to improve the performances of MDE. A mathematical model of an engine was built based on the existent engine construction and the theory of the diesel engine working cycle and the simulation was programmed by Matlab/Simulink. This simulation model accuracy was evaluated through the comparison of simulation results and experimental data of the MDE. The accuracy testing results were acceptable (within 5%). The influences of AT on the engine working parameters and the finding optimization point were conducted by using the simulation program to study. The predicted optimization point of the nozzle was used to improve the engine’s performances on board. The integration of the simulation and experiment studies showed its effectiveness in the practical application of the marine diesel engine field.
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Ilyushchanka, A. Ph, A. K. Kryvanos, A. D. Chorny, and Y. Ya Piatsiushyk. "Methods of determination of the gas-dynamic characteristics of a jet nozzle of an aerodynamic object." Proceedings of the National Academy of Sciences of Belarus, Physical-Technical Series 66, no. 3 (October 12, 2021): 320–28. http://dx.doi.org/10.29235/1561-8358-2021-66-3-320-328.
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The efficiency of aerodynamic objects with jet engines is the result of many factors, among which nozzle parameters are of great importance in relation to the general engine design and the energy source, that determines the composition and properties of the engine working medium. In this respect, an urgent need was to calculate nozzle gas-dynamic characteristics and geometric parameters at various designing and testing stages of jet engines. Relatively simple calculations involving a large number of assumptions and detailed modeling with regard to the maximum possible number of factors are the basis of the existing modeling approaches. In the present work, the problem was to assess an agreement between such modeling methods of a specific ‘high-energy material – working medium – nozzle’ system and the experimental ones. The calculations using one-dimensional nozzle theory and the gas dynamics modeling method revealed a 6 % difference in the results of various parameters. At the same time, a closer agreement was noted between the experimental data and the results predicted by the gas dynamics modeling method. Moreover, in comparison to one-dimensional theory, the gas dynamics modeling method of an engine jet nozzle is more labor-intensive and expensive for calculations. Therefore, from the practical viewpoint, it is advisable to give preference to one-dimensional theory to calculate the engine construction and to verify calculations with the use of the modeling methods.
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Molyakov, V. D., and B. A. Kunikeev. "Using the Similarity Theory in the Design of Gas Turbine Engines." Proceedings of Higher Educational Institutions. Маchine Building, no. 6 (735) (June 2021): 48–57. http://dx.doi.org/10.18698/0536-1044-2021-6-48-57.
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At present, in the promising development of gas turbine engines compared to at least the fourth generation products, there have been significant changes in the approaches to the design of engine. First of all, it is an increase in maximum values of temperature, gas pressure and circumferential flow speeds, an increase in power of the turbine stage, as well as improvement of the turbine manufacturing technology. All these factors lead to the fact that when designing the flow parts of the gas turbine, it is necessary at the fixed design flow rate of the working medium in the engine, i.e. at the fixed diameters, lengths of the nozzle and rotor blades forming the outline of the inter-blade channels, to increase the blade chords with the corresponding reduction of the number of blades in the row. The increase in turbine stage power associated with the increase in temperature, pressure (density), and circumferential velocity increases the bending stresses leading to the need to increase chords at a fixed blade length. Significant reduction of number of blades in stages, simplifies technology of blades manufacturing. A substantial increase in the maximum gas temperature, in the perspective of more than 2000 K, also leads to the need to increase the blade chords, due to the need to place cooling cavities in the blades. As a result, contradictions arise with the use of similarity theory in the design of stages of turbines of different purpose, as some of the main requirements of similarity are violated — geometric similarity of blade channels of the flow part and then the use of the generally accepted number Re by the chord of blades loses meaning. Therefore, it is necessary to carry out detailed investigations of all flow parameters in four stages of turbines with detection of influence of change of rotor blade chords at equal length of blades. And justify the effect of change of rotor blade chords on physical processes in flow parts of turbines in engines of various purpose.
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Weinberg, Jonathan M. "Attentional Engines: A Perceptual Theory of the Arts." Journal of Aesthetics and Art Criticism 80, no. 1 (November 24, 2021): 121–24. http://dx.doi.org/10.1093/jaac/kpab069.
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Ahmed, Heersh, and Boris Osipov. "MULTI-MODE IDENTIFICATION OF OBTAINING THE ADEQUATE MODEL OF TURBOJET ENGINE TJ-100A-Z FOR DIAGNOSTICS BY THERMALGASDYNAMIC PARAMETERS." Perm National Research Polytechnic University Aerospace Engineering Bulletin, no. 60 (2020): 5–14. http://dx.doi.org/10.15593/2224-9982/2020.60.01.
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When monitoring and diagnosing the state of gas turbine engines by thermodynamic parameters, adequate mathematical models of these engines are used. This name means diagnostic methods based on special processing and analysis of the values of thermogasdynamic and other parameters measured on a working turbojet engine [1] using its mathematical model. The most important in the system of technical diagnostics is the mathematical model of the engine. Its creation is a problem since, as a rule, the specifications of engine components are not given in the technical documentation. In this regard, obtaining complete mathematical models of engines for diagnostic purposes is an urgent task. There are various approaches to obtaining the characteristics of nodes and one of them is the use of generalized characteristics, for example, developed at the N.E. Zhukovsky Air Force Engineering Academy at the Department 201 "Theory of Air-Jet Engines" under the direction of Professor Nechayev Yu.N. Experience using such characteristics has shown that such characteristics can be used, but in a fairly narrow range of throttle modes. As a rule, this range was limited to no more than 40 % of the calculated (nominal) mode, which significantly limits the capabilities of the mathematical model of turbojet engines when implementing diagnostics using thermodynamic and dynamic parameters. This article proposes an algorithm developed by the authors a lot of mode identification, implemented as a computer program. As an object of study used turbojet engine TJ-100A-Z manufactured in the Czech Republic. For this, the turbojet engine obtained the characteristics of the main components (compressor, combustion chamber, turbine and nozzle) using the throttle characteristics given in the technical conditions. The calculation results are presented in the form of tables and graphs with error analysis in the calculation before and after identification. The comparison of the errors of the parameters of the throttle characteristics with the errors of the sensors for measuring these parameters is given.
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Alicki, Robert, David Gelbwaser-Klimovsky, and Alejandro Jenkins. "The Problem of Engines in Statistical Physics." Entropy 23, no. 8 (August 22, 2021): 1095. http://dx.doi.org/10.3390/e23081095.
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Engines are open systems that can generate work cyclically at the expense of an external disequilibrium. They are ubiquitous in nature and technology, but the course of mathematical physics over the last 300 years has tended to make their dynamics in time a theoretical blind spot. This has hampered the usefulness of statistical mechanics applied to active systems, including living matter. We argue that recent advances in the theory of open quantum systems, coupled with renewed interest in understanding how active forces result from positive feedback between different macroscopic degrees of freedom in the presence of dissipation, point to a more realistic description of autonomous engines. We propose a general conceptualization of an engine that helps clarify the distinction between its heat and work outputs. Based on this, we show how the external loading force and the thermal noise may be incorporated into the relevant equations of motion. This modifies the usual Fokker–Planck and Langevin equations, offering a thermodynamically complete formulation of the irreversible dynamics of simple oscillating and rotating engines.
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Sevryugina, N. S., and A. S. Apatenko. "Research of influence of thermal loadings on reliability of gas-diesel engines of transport and technological machines." Power and Autonomous equipment 2, no. 3 (October 30, 2019): 121–28. http://dx.doi.org/10.32464/2618-8716-2019-2-3-121-128.
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Introduction: the factors determining the development trends of the machine-building industry on the example of modernization of the internal combustion engine are considered. The evaluation of the effectiveness of cooperation between manufacturers and the scientific potential of leading scientists in the development of designs of gas-diesel engines. The requirement of time of increase of ecology of internal combustion engines is proved, the reasons braking mass introduction of gas-diesel engines for transport and technological cars are revealed. The parameter of influence on the thermal load of the piston group in gaseous fuel is allocated. The estimation of constructive perfection of development of system of cooling of the piston of the engine is given. The effects of increased temperature on individual parts of the piston in the form of scrapes, chips, causing failure of the internal combustion engine as a whole are shown. The influence of engine oil quality on the engine operation is revealed. It is proposed to Supplement the design of the internal combustion engine with an oil level control device, developed an algorite and a software product for calculating the residual life of the engine oil on key parameters, with the establishment of the term of their replacement.Methods: the study is based on the analysis of the works of leading domestic and foreign scientists in the field of improving the design of power equipment. The theoretical and methodological basis of the study was the system approach, methods of mathematical analysis, reliability theory, analytical and statistical processing of results.Results and discussion: the theoretical justification for the increased thermal load of piston in a gas-diesel engine, justifies the addition of the construction device control engine oil level and consideration of the resource and replacement intervals for the parameters of the actual physical and chemical condition, using the database presented in the software product.Conclusion: operation of gas-diesel engines requires from the operator more strict control over the temperature regime of the engine, the condition of the engine oil and the efficiency of the engine oil, the proposed solutions will allow to assess the quality of the engine oil in real time and to carry out its replacement according to the actual condition, which will ensure.
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Shao, Ying Li. "A Study on Exhaust Muffler Using Counter-Phase Counteract." Advanced Materials Research 986-987 (July 2014): 810–13. http://dx.doi.org/10.4028/www.scientific.net/amr.986-987.810.
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The exhaust noise, which falls into low-frequency noise, is the dominant noise source of a diesel engines and tractors. The traditional exhaust silencers, which are normally constructed by combination of expansion chamber, and perforated pipe or perforated board, are with high exhaust resistance, but poor noise reduction especially for the low-frequency band noise. For this reason, a new theory of exhaust muffler of diesel engine based on counter-phase counteracts has been proposed. The mathematical model and the corresponding experimental validation for the new exhaust muffler based on this theory were performed.
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Shao, Ying Li. "A Study on the Acoustic Characteristics of the Counter-Phase Muffler." Applied Mechanics and Materials 130-134 (October 2011): 41–44. http://dx.doi.org/10.4028/www.scientific.net/amm.130-134.41.
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The exhaust noise, which falls into low-frequency noise, is the dominant noise source of a diesel engines and tractors. The traditional exhaust silencers, which are normally constructed by combination of expansion chamber, and perforated pipe or perforated board, are with high exhaust resistance, but poor noise reduction especially for the low-frequency band noise. For this reason, a new theory of exhaust muffler of diesel engine based on counter-phase counteracts has been proposed. The mathematical model and the corresponding experimental validation for the new exhaust muffler based on this theory were performed.
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Yang, Wenping. "BASED ON FRATCAL THEORY FOR STEYR DIESEL ENGINES DIAGNOSE." Chinese Journal of Mechanical Engineering 38, no. 02 (2002): 49. http://dx.doi.org/10.3901/jme.2002.02.049.
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CHIKAHISA, Takemi, and Tadashi MURAYAMA. "Theory on combustion similarity for different size diesel engines." Transactions of the Japan Society of Mechanical Engineers Series B 54, no. 508 (1988): 3579–84. http://dx.doi.org/10.1299/kikaib.54.3579.
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Choi, Sei-Bum, and J. K. Hedrick. "Robust Throttle Control of Automotive Engines: Theory and Experiment." Journal of Dynamic Systems, Measurement, and Control 118, no. 1 (March 1, 1996): 92–98. http://dx.doi.org/10.1115/1.2801156.
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An adaptive, sliding control algorithm is developed for automated throttle control of an I.C. engine to be used in drive-by-wire applications such as coordinated engine/transmission gear shiftings, traction control and autonomous vehicle control (IVHS). The paper presents a new sliding control formulation that includes combustion transport delays and a simplified adapation law to account for slowly varying engine parameters. The new technique is evaluated by computer simulation and laboratory dynamometer tests.
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CHIKAHISA, Takemi, and Tadashi MURAYAMA. "Theory on Combustion Similarity for Different-Sized Diesel Engines." JSME international journal. Ser. 2, Fluids engineering, heat transfer, power, combustion, thermophysical properties 33, no. 2 (1990): 395–400. http://dx.doi.org/10.1299/jsmeb1988.33.2_395.
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Punsly, Brian. "Spectral Diagnostics of Blazar Central Engines. II. Hydromagnetic Theory." Astrophysical Journal 473, no. 1 (December 10, 1996): 178–203. http://dx.doi.org/10.1086/178135.
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Knaub, Ludmila. "Improvement of mixing processes in diesel engines." Technology audit and production reserves 3, no. 1(59) (June 30, 2021): 16–18. http://dx.doi.org/10.15587/2706-5448.2021.232050.
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The object of research is gas-dynamic vortex processes in heterogeneous polydisperse flows. One of the most problematic issues in engine building is the completeness of combustion and the rate of fuel burnout in the given coordinates on the allotted hourly interval in the combustion chamber. These indicators, in turn, determine stringent requirements for used fuels in terms of thermophysical parameters that affect sawing, evaporation and mixing with an oxidizer. In the course of the study, methods of mathematical modeling were used based on the theory of similarity. Methods have been developed for preparing a combustible mixture for detonation-free combustion of a cheap alternative fuel. A method for assessing the quality of spraying low cetane fuel is proposed. A mathematical model is obtained for calculating the change in the parameters of the quality of atomization and the differential characteristics of fuel injection. This is necessary for theoretical studies of gas-dynamic processes in additional power systems for diesel engines in an unsteady three-dimensional flow with variable parameters of a polydisperse flow of a combustible mixture. It has been proven that with a decrease in the camshaft rotational speed, the injection speed will be insufficient to achieve the required spray quality due to a decrease in the speed. This made it possible to redesign the additional system using a separate dual fuel supply. Research samples of an additional power supply system for the ЯМЗ–24 ОН diesel engine (Yaroslavl Motor Plant, Russia) have been developed. Comparative tests of the engine operation on stable gas condensate with the main fuel equipment and an additional system have been carried out. Oscillograms of the tests were obtained and analyzed. The research results provided the basis for the use of low cetane cheap gas condensate in diesel engines. This will improve the economic, power and environmental performance of the engines. Compared to standard cetane fuels, the price of fuel will decrease by 40 %, engine power will increase by 20 %, and the environmental performance of exhaust gases will decrease by 10–30 %.
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Dixon, H. E., M. L. Ginsberg, E. M. Luks, and A. J. Parkes. "Generalizing Boolean Satisfiability II: Theory." Journal of Artificial Intelligence Research 22 (December 1, 2004): 481–534. http://dx.doi.org/10.1613/jair.1555.
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This is the second of three planned papers describing ZAP, a satisfiability engine that substantially generalizes existing tools while retaining the performance characteristics of modern high performance solvers. The fundamental idea underlying ZAP is that many problems passed to such engines contain rich internal structure that is obscured by the Boolean representation used; our goal is to define a representation in which this structure is apparent and can easily be exploited to improve computational performance. This paper presents the theoretical basis for the ideas underlying ZAP, arguing that existing ideas in this area exploit a single, recurring structure in that multiple database axioms can be obtained by operating on a single axiom using a subgroup of the group of permutations on the literals in the problem. We argue that the group structure precisely captures the general structure at which earlier approaches hinted, and give numerous examples of its use. We go on to extend the Davis-Putnam-Logemann-Loveland inference procedure to this broader setting, and show that earlier computational improvements are either subsumed or left intact by the new method. The third paper in this series discusses ZAP's implementation and presents experimental performance results.
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Aydin, Alhun, Altug Sisman, and Ronnie Kosloff. "Landauer’s Principle in a Quantum Szilard Engine without Maxwell’s Demon." Entropy 22, no. 3 (March 3, 2020): 294. http://dx.doi.org/10.3390/e22030294.
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Quantum Szilard engine constitutes an adequate interplay of thermodynamics, information theory and quantum mechanics. Szilard engines are in general operated by a Maxwell’s Demon where Landauer’s principle resolves the apparent paradoxes. Here we propose a Szilard engine setup without featuring an explicit Maxwell’s demon. In a demonless Szilard engine, the acquisition of which-side information is not required, but the erasure and related heat dissipation still take place implicitly. We explore a quantum Szilard engine considering quantum size effects. We see that insertion of the partition does not localize the particle to one side, instead creating a superposition state of the particle being in both sides. To be able to extract work from the system, particle has to be localized at one side. The localization occurs as a result of quantum measurement on the particle, which shows the importance of the measurement process regardless of whether one uses the acquired information or not. In accordance with Landauer’s principle, localization by quantum measurement corresponds to a logically irreversible operation and for this reason it must be accompanied by the corresponding heat dissipation. This shows the validity of Landauer’s principle even in quantum Szilard engines without Maxwell’s demon.
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Yue, Zongyu, and Rolf D. Reitz. "An equilibrium phase spray model for high-pressure fuel injection and engine combustion simulations." International Journal of Engine Research 20, no. 2 (December 6, 2017): 203–15. http://dx.doi.org/10.1177/1468087417744144.
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High-pressure fuel injection impacts mixture preparation, ignition and combustion in engines and other applications. Experimental studies have revealed the mixing-controlled and local phase equilibrium characteristics of liquid vaporization in high injection pressure diesel engine sprays. However, most computational fluid dynamics models for engine simulations spend much effort in solving for non-equilibrium spray processes. In this study, an equilibrium phase spray model is explored. The model is developed based on jet theory and a phase equilibrium assumption, without modeling drop breakup, collision and finite-rate interfacial vaporization processes. The proposed equilibrium phase spray model is validated extensively against experimental data in simulations of the engine combustion network Spray A and in an optical diesel engine. Predictions of liquid/vapor penetration, fuel mass fraction distribution, heat release rate and emission formation are all in good agreement with experimental data. In addition, good computational efficiency and grid-independency are also seen with the present equilibrium phase model. The examined operating conditions cover wide ranges that are relevant to internal combustion engines, which include ambient temperatures from 700 to 1400 K, ambient densities from 7.6 to 22.8 kg/m3 and injection pressures from 1200 to 1500 bar for diesel sprays.
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Goward, G. W., and L. W. Cannon. "Pack Cementation Coatings for Superalloys: A Review of History, Theory, and Practice." Journal of Engineering for Gas Turbines and Power 110, no. 1 (January 1, 1988): 150–54. http://dx.doi.org/10.1115/1.3240078.
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Nickel and cobalt-base superalloy blades and vanes in the hot sections of all gas turbines are coated to enhance resistance to hot corrosion. Pack cementation aluminizing, invented in 1911, is the most widely used coating process. Corrosion resistance of aluminide coatings can be increased by modification with chromium, platinum, or silicon. Chromium diffusion coatings can be used at lower temperatures. Formation and degradation mechanisms are reasonably well understood and large-scale manufacturing processes for these coatings are gradually being automated. Pack cementation and related diffusion coatings serve well for most aircraft engine applications. The trend for industrial and marine engines is more toward the use of overlay coatings because of the greater ease of designing these to meet a wide variety of corrosion conditions.
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Gierens, Klaus. "Theory of Contrail Formation for Fuel Cells." Aerospace 8, no. 6 (June 10, 2021): 164. http://dx.doi.org/10.3390/aerospace8060164.
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The theory of contrail formation for fuel cells is derived. It is a variant of the well-known Schmidt-Appleman theory. The contrail factor or G-factor for fuel cells is much larger than for jet engines, such that condensation of the exhaust water vapour can happen even at the Earth’s surface in sufficiently cold (a few degrees above zero) weather. Contrail formation from fuel cells will occur frequently in the lower troposphere and is unavoidable below moderate temperature limits, in the upper troposphere and in the stratosphere. Despite the high frequency of contrail formation from fuel cells, their climate impact is lower than that of contrails from jet engines. Most fuel cell contrails will be short and those persistent ones will be optically thinner and have on average a shorter lifetime than traditional persistent contrails. From a climate point of view, the introduction of fuel cells into aviation can be recommended.
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Kotake, Kei, Tomoya Takiwaki, Yudai Suwa, Wakana Iwakami Nakano, Shio Kawagoe, Youhei Masada, and Shin-ichiro Fujimoto. "Multimessengers from Core-Collapse Supernovae: Multidimensionality as a Key to Bridge Theory and Observation." Advances in Astronomy 2012 (2012): 1–46. http://dx.doi.org/10.1155/2012/428757.
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Core-collapse supernovae are dramatic explosions marking the catastrophic end of massive stars. The only means to get direct information about the supernova engine is from observations of neutrinos emitted by the forming neutron star, and through gravitational waves which are produced when the hydrodynamic flow or the neutrino flux is not perfectly spherically symmetric. The multidimensionality of the supernova engine, which breaks the sphericity of the central core such as convection, rotation, magnetic fields, and hydrodynamic instabilities of the supernova shock, is attracting great attention as the most important ingredient to understand the long-veiled explosion mechanism. Based on our recent work, we summarize properties of gravitational waves, neutrinos, and explosive nucleosynthesis obtained in a series of our multidimensional hydrodynamic simulations and discuss how the mystery of the central engines can be unraveled by deciphering these multimessengers produced under the thick veils of massive stars.
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Liang, Jinhui, Dongdong Zhang, and Shuwen Wang. "Vibration characteristic analysis of single-cylinder two-stroke engine and mounting system optimization design." Science Progress 103, no. 3 (July 2020): 003685042093063. http://dx.doi.org/10.1177/0036850420930631.
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Compared with four-stroke engines, single-cylinder two-stroke engines have the characteristics of small inertia, high rotational speed, and wide excitation frequency range. However, the structural vibration and noise generated by the two-stroke engine are very violent. Hence, it is necessary to reduce the vibration and noise of the single-cylinder two-stroke engine. Based on the design theory of the engine mounting system, the excitation frequency, direction, and magnitude of a single-cylinder two-stroke engine are analyzed. The rubber isolator is selected as the new mount element, and the dynamic model of the engine powertrain mounting system is established based on ADAMS software. Based on the sensitivity analysis of the design variables of the mounting system, the natural frequency of the mounting system is used as an objective, and the three-directional stiffness of the mounting system is taken as design variables for the optimization problem. The optimization model is solved by the sequential quadratic programming method. The results show that the maximum frequency of the mounting system after optimization is less than 1/[Formula: see text] of the excitation frequency, and the isolation effect is achieved. The dynamic model and the optimization method presented in this article would provide a useful tool for the design and optimization of mounting system for the single-cylinder two-stroke engine to reduce vibration from the engine to the engine support.
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Plaza, Beatriz, Pilar González-Casimiro, Paz Moral-Zuazo, and Courtney Waldron. "Culture-led city brands as economic engines: theory and empirics." Annals of Regional Science 54, no. 1 (December 25, 2014): 179–96. http://dx.doi.org/10.1007/s00168-014-0650-0.
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Čerňan, Jozef, Karol Semrád, Katarína Draganová, and Miroslava Cúttová. "Fatigue stress analysis of the DV-2 engine turbine disk." Aircraft Engineering and Aerospace Technology 91, no. 4 (April 1, 2019): 708–16. http://dx.doi.org/10.1108/aeat-03-2018-0096.
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Purpose The purpose of this study is to improve life prediction of certain components. Fatigue of the high-stressed structural elements is an essential parameter that affects the lifetime of such components. In particular, aviation engines are devices whose failure due to fatigue failure of one of the important components can lead to fatal consequences. Design/methodology/approach In this study, two analyses in the turbine disk of the jet engine during the simulated operating load were performed: The first one was the analysis of the heat-induced stresses using the finite element method. The goal of the second analysis was to determine the residual fatigue strength of a loaded disk by the software tool using the Palmgren - Miner Linear Damage Theory. Findings The results showed a high degree of similarity with the real tests performed on the aircraft engine and revealed the weak points in the design of the jet engine. Research limitations/implications It should be mentioned that without appropriate experiments, results of this analysis could not be verified. Practical implications These results are helpful in the re-designing of the jet engines to increase their technical feasibility. Originality/value Such analysis has been realized in the DV-2 jet engine research and development program for the first time in the history of jet engine manufacturing process in Slovakia and countries of Eastern Europe region.
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Pasricha, M. S. Pasricha, and F. M. Hashim. "Effect of the reciprocating mass of slider-crank mechanism on torsional vibrations of diesel engine systems." ASEAN Journal on Science and Technology for Development 23, no. 1&2 (October 30, 2017): 71. http://dx.doi.org/10.29037/ajstd.94.
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The torsional vibration phenomenon in the running gear of reciprocating engine systems isusually dealt with by considering a series of constant inertias connected by sections of massless shafting. However in reality, a slider crank mechanism is a vibrating system with varying inertia because the effective inertia of the total oscillating mass of each crank assembly varies twice per revolution of the crankshaft. Large variations in inertia torques can give rise to the phenomenonof secondary resonance in torsional vibration of modern marine diesel engines which can not be explained by conventional theory incorporating only the mean values of the varying inertias. In the past associated secondary resonances and regions of instability tended to be dismissed by most engineers as interesting but of no importance. The situation changed in recent years since there is evidence of the existence of thesecondary resonance effects which could have contributed to a number of otherwise inexplicable crankshaft failures in large slow speed marine engines. The cyclic variation of the polar moment of inertia of the reciprocating parts during each revolution causes a periodic variation of frequency and corres ponding amplitude of vibration of reciprocating engine systems. It also causes an increase in the speed range over which resonance effects are experienced and only a partial explanation of the behaviour of the systems has been worked out. It is impossible to avoid these instabilities by changes in thedesign , unless of course the variations in mass and spring constant can be made zero. In the present paper a critical appraisal of the regions of instability as determined from the equation of motion which takes into account variation of inertia is given. The motion in the form of complex waveforms is studied at different speeds of engine rotation. A comparison of theoretical results with Goldsbrough’s experimental resultsand Gregory’s analysis is included.
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Dixon, H. E., M. L. Ginsberg, D. Hofer, E. M. Luks, and A. J. Parkes. "Generalizing Boolean Satisfiability III: Implementation." Journal of Artificial Intelligence Research 23 (April 1, 2005): 441–531. http://dx.doi.org/10.1613/jair.1656.
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This is the third of three papers describing ZAP, a satisfiability engine that substantially generalizes existing tools while retaining the performance characteristics of modern high-performance solvers. The fundamental idea underlying ZAP is that many problems passed to such engines contain rich internal structure that is obscured by the Boolean representation used; our goal has been to define a representation in which this structure is apparent and can be exploited to improve computational performance. The first paper surveyed existing work that (knowingly or not) exploited problem structure to improve the performance of satisfiability engines, and the second paper showed that this structure could be understood in terms of groups of permutations acting on individual clauses in any particular Boolean theory. We conclude the series by discussing the techniques needed to implement our ideas, and by reporting on their performance on a variety of problem instances.
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Bradley, Derek. "Autoignitions and detonations in engines and ducts." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 370, no. 1960 (February 13, 2012): 689–714. http://dx.doi.org/10.1098/rsta.2011.0367.
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The origins of autoignition at hot spots are analysed and the pressure pulses that arise from them are related to knock in gasoline engines and to developing detonations in ducts. In controlled autoignition engines, autoignition is benign with little knock. There are several modes of autoignition and the existence of an operational peninsula, within which detonations can develop at a hot spot, helps to explain the performance of various engines. Earlier studies by Urtiew and Oppenheim of the development of autoignitions and detonations ahead of a deflagration in ducts are interpreted further, using a simple one-dimensional theory of the generation of shock waves ahead of a turbulent flame. The theory is able to indicate entry into the domain of autoignition in an ‘explosion in the explosion’. Importantly, it shows the influence of the turbulent burning velocity, and particularly its maximum attainable value, upon autoignition. This value is governed by localized flame extinctions for both turbulent and laminar flames. The theory cannot show any details of the transition to a detonation, but regimes of eventually stable or unstable detonations can be identified on the operational peninsula. Both regimes exhibit transverse waves, triple points and a cellular structure. In the case of unstable detonations, transverse waves are essential to the continuing propagation. For hazard assessment, more needs to be known about the survival, or otherwise, of detonations that emerge from a duct into the same mixture at atmospheric pressure.