Two stroke engine cycle pdf




















The scavenging characteristics are quantified by evaluating three global parameters, namely the delivery ratio, the trapping efficiency and the charging efficiency [5]. The use of air as a scavenging fluid is a common choice.

Unfortunately, a certain amount of air flows away through the exhaust valves and this increases the work for pumping due to the amount of air which is lost. For this reason, the inlet mass flow rate is generally higher than the amount of air theoretically required to scavenge the cylinder.

Indeed, the delivery ratio is commonly in a range between 1. Energies , 14, 10 of 19 Figure Contour plot of the Burned Gas mass fraction at several instants on the plane XY. Figure Contour plot of the Burned Gas mass fraction at several instants on the plane XZ. Energies , 14, 11 of 19 The scavenging process under theoretical conditions can be described by two simpli- fied models [13]. On one side, the perfect displacement model considers that the burned gases are pushed out by the fresh air without any mixing between them.

On the other hand, the perfect mixing assumes that the incoming fresh air mixes instantaneously and uni- formly with the gas mixture already in the cylinder. As a matter of fact, the real scavenging process will be in between such models and will differ from both.

For the baseline case, the delivery ratio is equal to 1. These efficiencies are close to those corresponding to a perfect mixing condition. Influence of Inlet Mass Flow Rate Several simulations have been performed by varying the inlet mass-flow rate, G, from 0. Figure 12a shows the mass flow rate of Fresh Air through the intake ports as a function of time for the different cases. The flow rate is assumed to be negative for fresh air entering into the cylinder, otherwise it is assumed to be positive.

As expected, by increasing G, the flow rate of fresh air entering into the cylinder increases as well. In Figure 12b, the Burned Gas BG mass fraction profiles are given based on the relationship between the BG mass fraction in the cylinder, along the x-axis, and the BG mass fraction in the exhaust ducts, along the y-axis.

The figure shows the short-circuiting phenomenon for different inlet mass flow rates. Indeed, it can be observed that, with the lower mass flow rates, the Fresh Air enters into the exhaust pipes faster, thus diverging from the perfect displacement condition.

The lowest appearance of the short-circuiting phenomenon is observed with 0. Nevertheless, the higher the intake mass flow rate, the lower the percentage of Burned Gas in the cylinder at the end of the scavenging process.

In Figure 12c,d, the trapping and the charging efficiency, respectively, are plotted as a function of the delivery ratio. Each square symbol corresponds to a given inlet mass flow rate. The figure shows that the delivery ratio increases with the inlet mass flow rate. As expected, the trapping efficiency decreases with increasing delivery ratio, whereas the charging efficiency increases with the delivery ratio. Figure 12e depicts the projection of the velocity field vectors on the XZ middle-height plane of the cylinder.

The figure clearly shows the swirl motion that develops into the cylinder as a consequence of the inlet ports angle. As the inlet mass flow rate increases, higher velocities are obtained, corresponding to a higher swirl ratio in the cylinder.

The values of the swirl ratio are given in Table 3. The table shows that, for the baseline mass flow rate Gb , the swirl ratio is about 2, which corresponds to a typical value for this type of engine.

Table 3. Swirl ratio as a function of the inlet flow rate. Scavenging performance for Cylinder 3. Influence of Cylinder Number and Outlet Boundary Conditions A computational analysis has also been performed for Cylinder 1 and Cylinder 5, and the scavenging performances of all the three cylinders are finally compared. The measured pressure profiles at the outlet sections differ for the three cylinders, as given in Figure The remaining initial and boundary conditions are the same as for the baseline case, as well as the computational mesh.

Energies , 14, 13 of 19 Figure Experimental pressure profiles at the exhaust sections for the three cylinders as a function of CAD. The mass of Fresh Air trapped into the three cylinders has been computed along with the cylinder total mass, i. At the start of the simulation, as the exhaust valves open, the amount of mass in the cylinder decreases, whereas the Fresh Air is still zero, up to the point that the intake ports open and both the total and the Fresh Air mass in the cylinders increase.

Due to the back-flow through intake ports, the increase of fluid mass in the cylinder is slower for Cylinder 1 with respect to the other two cylinders. Nevertheless, at the end of the scavenging process, the three profiles are very similar to each other. Moreover, some differences are observed in the Burned Gas mass fraction profiles of Figure 14c.

Indeed, Cylinder 1 shows a faster appearance of the short-circuiting phenomenon but, at the end of the scavenging process, the BG mass fraction in the exhaust pipes is noticeably higher with respect to the other two cylinders, due to the different profiles of Fresh Air mass flow rate through the intake ports, as reported in Figure 14a. Cylinder 3 and Cylinder 5 have a similar behavior. The results are given in Figure 14d, thus showing that, at the start of the scavenging process, all the air delivered through the intake ports is trapped within the cylinder, then the trapping efficiency decreases during the scavenging.

At the end of the process, the final delivery ratio is higher for Cylinder 5, meaning that a higher amount of air is flowed through the intake ports with respect to Cylinder 3 and, even more, to Cylinder 1.

However, the trapping efficiency is higher for Cylinder 1 with respect to Cylinder 3 and, even more, to Cylinder 5, thus showing that the scavenging process is more efficient for Cylinder 1.

The trapping and charging efficiencies are given as a function of delivery ratio in Figure 14e,f, respectively. The figures show that the efficiency of Cylinder 5 is lower than that of the other two cases. Besides, the percentage of Fresh Air trapped with respect to the in-cylinder total mass, given in Table 4 for the baseline inlet mass flow rate, is lower for Cylinder 5 and higher for Cylinder 3. The results are given in Figure 15a,b. Slight differences are now obtained for the three cylinders.

Cylinder 3, which is in the mid-located, is the most favorable to reach higher efficiencies for all cases, whereas the Cylinder 5 location is the worst one with higher delivery ratios.

It can be concluded that the exhaust pressure profile plays a major role in the scaveng- ing outcome of the three cylinders, in agreement with the scientific literature [10], whereas the cylinders position has a minor effect on the scavenging efficiencies.

Negligible differences are expected by comparing the results obtained with the left and right banks, since the bank geometries are very similar.

In order to confirm this issue, the scavenging performances of Cylinder 3, belonging to the right bank, and of Cylinder 4, being the corresponding mid-way cylinder of the left bank, have been compared. The simulation of Cylinder 4 has been performed by using the same initial and boundary conditions of the baseline case, in order to investigate only the role of the different locations.

The results are given in Figure 16 in terms of trapping and charging efficiencies versus delivery ratio. Negligible differences between Cylinder 3 and Cylinder 4 performances are obtained.

Table 4. Cylinder 1 Cylinder 3 Cylinder 5 Scavenging performances of the GF56 right bank. Energies , 14, 15 of 19 Figure Influence of cylinders location in the bank on scavenging performances. Scavenging performances of right and left banks of GF Influence of the Intake Ports Geometry In order to increase the tangential velocity of Fresh Air flow through the intake ports, a geometry modification of such ports is proposed.

This choice enables to increase the swirl ratio, in agreement with the scientific literature [9], but keeping nearly constant the delivery ratio with respect to the previous geometry. The contour plot of the Burned Gas mass fraction is shown in Figure 18 at different time instants. By comparing these results with those obtained with the initial configuration, given in Figure 10, a partially unscanveged zone can be observed close to the cylinder axis, whereas burned gas is not found near the liner throughout the whole scavenging process.

This is the result of the increase of the swirl motion, which helps to scavenge the regions near the cylinder walls at the expense of the central region of the chamber. It is worth noting that the volume enclosed in the near-axis zone of a cylinder is much smaller than the volume enclosed in the near-liner region of the same cylinder.

Trapping and charging efficiencies as a function of the delivery ratio are given in Figure 19b,c, respectively. The results show that the delivery ratio only slightly decreases with the new configuration with respect to the previous one.

Both the trapping and the charging efficiencies improve with the new geometry and with delivery ratios higher than 1. Schematic of the new geometry for the intake ports.

Contour plot of the Burned Gas mass fraction at different time instants for the new geometry. Energies , 14, 17 of 19 Figure New geometry scavenging performance.

This is due to the different velocity field obtained with the new intake ports geometry, as shown in Figure 19d. With the new configuration, the in-cylinder tangential velocity noticeably increases, leading to a substantial increase of the swirl ratio, equal to about 3. Conclusions A detailed 3D CFD investigation of the scavenging process of a uniflow, two-stroke, multi-cylinder engine, named GF56, has been carried out. GF56 is a diesel common- rail direct injection engine for the general aviation market, with six cylinders in a boxer configuration and a total volume displacement of cc.

The right bank has been analyzed by considering the plenum, the intake manifold, all cylinders and the exhaust pipes. The results are analyzed in terms of trapping and charging efficiencies to show that the cylinders are characterized by similar scavenging performances, with Cylinder 5 slightly under-performing. The scavenging process is strongly influenced by the pressure at the outlet section. Indeed, with the same exhaust pressure for all of the three cylinders, the differences are negligible and the scavenging profiles are almost on top of each other, with a somewhat lower efficiency, at high delivery ratios, for Cylinder 5, which is in the less favored position.

These results show that the position of the cylinders in the bank plays a minor role and that the same pressure profile at the exhaust is able to provide a similar scavenging performance for all the cylinders. Moreover, a comparison between left and right banks of the engine is provided with very similar performances for both banks as a consequence of their quasi-specularity.

Finally, the influence of the intake ports geometry has been analyzed. Specifically, a modification of such a geometry of the ports is proposed to increase the swirl ratio of the in-cylinder flow field by keeping the delivery ratio nearly constant.

This new geometry configuration leads to a considerable increase of the swirl ratio and provides better scavenging performance with delivery ratios generally employed during engine running conditions. Author Contributions: Conceptualization, A. M; software, M. M; validation, M. All authors have read and agreed to the published version of the manuscript. Conflicts of Interest: The authors declare no conflict of interest.

References 1. Sigurdsson, E. Numerical analysis of the scavenge flow and convective heat transfer in large two-stroke marine diesel engines.

Energy , , 37— Raptotasios, S. Application of a multi-zone combustion model to investigate the NOx reduction potential of two-stroke marine diesel engines using EGR. Energy , , — Benajes, J. Analysis of the combustion process, pollutant emissions and efficiency of an innovative 2-stroke HSDI engine designed for automotive applications.

Rinaldini, C. CFD analyses on 2-stroke high speed diesel engines. SAE Int. Engines , 4, — Heywood, J. Pulkrabek, W. Sturm, S. Wang, X. Analysis of scavenge port designs and exhaust valve profiles on the in-cylinder flow and scavenging performance in a two-stroke boosted uniflow scavenged direct injection gasoline engine. Engine Res.

A high-efficiency two-stroke engine concept: The boosted uniflow scavenged direct-injection gasoline busdig engine with air hybrid operation.

Engineering , 5, —, doi: Nora, M. Effects of valve timing, valve lift and exhaust backpressure on performance and gas exchanging of a two-stroke GDI engine with overhead valves. Energy Convers. Liu, Y. Study on the synthetic scavenging model validation method of opposed- piston two-stroke diesel engine.

Jia, B. Design and simulation of a two- or four-stroke free-piston engine generator for range extender applications. Ma, F. Energies , 10, , doi: Andersen, F. CFD analysis of the scavenging process in marine two-stroke diesel engines, Vol.

Wu, Y. Three-dimensional CFD computational fluid dynamics analysis of scavenging process in a two-stroke free-piston engine. Energy , 68, —, doi: A parameterization process that deals with the low measurement data availability, compared to the available data on automotive engines, is also investigated and described. As a result, the proposed model is parameterized to two different two-stroke engines showing a good agreement with the measurements in both stationary and dynamic conditions.

Several engine components have been developed. One of these is a new analytic in-cylinder pressure model that captures the influence of the injection and exhaust valve timings without increasing the simulation time. A new compressor model that can extrapolate to low speeds and pressure ratios in a physically sound way is also described. This compressor model is a requirement to be able to simulate low engine loads. Moreover, a novel parameterization algorithm is shown to handle well the model nonlinearities and to obtain a good model agreement with a large number of tested compressor maps.

Furthermore, the engine model is complemented with dynamic models for ship and propeller to be able to simulate transient sailing scenarios, where good EGR controller performance is crucial. The model is used to identify the low load area as the most challenging for the controller performance, due to the slower engine air path dynamics. Further low load simulations indicate that sensor bias can be problematic and lead to an undesired black smoke formation, while errors in the parameters of the controller flow estimators are not as critical.

This result is valuable because for a newly built engine a proper sensor setup is more straightforward to verify than to get the right parameters for the flow estimators. The mistake which had crept in have been elinimated. Book Summary: A Textbook of Automobile Engineering is a comprehensive treatise which provides clear explanation of vehicle components and basic working principles of systems with simple, unique and easy-to-understand illustrations. The textbook also describes the latest and upcoming technologies and developments in automobiles.

This edition has been completely updated covering the complete syllabi of most Indian Universities with the aim to be useful for both the students and faculty members. The textbook will also be a valuable source of information and reference for vocational courses, competitive exams, interviews and working professionals. This new edition introduces new engine models that will be most commonly installed in ships over the next decade, as well as the latest legislation and pollutant emissions procedures.

Since publication of the last edition in , a number of emission control areas ECAs have been established by the International Maritime Organization IMO in which exhaust emissions are subject to even more stringent controls.

In addition, there are now rules that affect new ships and their emission of CO2 measured as a product of cargo carried. Provides the latest emission control technologies, such as SCR and water scrubbers Contains complete updates of legislation and pollutant emission procedures Includes the latest emission control technologies and expands upon remote monitoring and control of engines.

Book Summary: Engineering Thermodynamics is a comprehensive text which presents the broad spectrum of the principles of thermodynamics while encapsulating the theoretical and practical aspects of the field. The book provides clear explanation of basic principles for better understanding of the subject. Additionally, the book includes numerous laws, theorems, formulae, tables, charts and equations for learning apart from extensive references for more-in-depth information.

The revised edition of the book has been completely updated covering the complete syllabi of most universities and is aimed to be useful to both the students and faculty. Book Summary: Automobile or Automotive Engineering has gained recognition and importance ever since motor vehicles capable for transporting passengers has been in vogue.

Now due to the rapid growth of auto component manufacturers and automobile industries, there is a great demand for Automobile Engineers. Automobile Engineering alias Automotive Engineering or Vehicle Engineering is one of the most challenging careers in the field of engineering with a wide scope.

For the perfect blend of manufacturing and designing automobiles, Automobile Engineering uses the features of different elements of Engineering such as mechanical, electrical, electronic, software and safety engineering. To become a proficient automobile engineer, specialized training is essential and it is a profession, which requires a lot of hard work, dedication, determination and commitment.

The major task of an Automobile Engineer is the designing, developing, manufacturing and testing of vehicles from the concept stage to the production stage The automotive industry is one of the largest and most important industries in the world. Cars, buses, and other engine-based vehicles abound in every country on the planet, and it is continually evolving, with electric cars, hybrids, self-driving vehicles, and so on.

Technologies that were once thought to be decades away are now on our roads right now. Engineers, technicians, and managers are constantly needed in the industry, and, often, they come from other areas of engineering, such as electrical engineering, process engineering, or chemical engineering.

Introductory books like this one are very useful for engineers who are new to the industry and need a tutorial. Also valuable as a textbook for students, this introductory volume not only covers the basics of automotive engineering, but also the latest trends, such as self-driving vehicles, hybrids, and electric cars.

Not only useful as an introduction to the science or a textbook, it can also serve as a valuable reference for technicians and engineers alike. The volume also goes into other subjects, such as maintenance and performance. Data has always been used in every company irrespective of its domain to improve the operational efficiency and performance of engines. This work deals with details of various automotive systems with focus on designing various components of these system to suit the working conditions on roads.

Whether a textbook for the student, an introduction to the industry for the newly hired engineer, or a reference for the technician or veteran engineer, this volume is the perfect introduction to the science of automotive engineering. Book Summary: Basic Mechanical Engineering curriculum focuses on what mechanical engineering is all about: design, analysis, materials and manufacture of systems.

To that extent, all mathematics, science, and engineering courses relate their contents to analysis, design, development and manufacturing. Mechanical Engineering explains about the knowledge and understanding of the concepts in the mechanical engineering discipline.

This book focuses on basic engineering concepts which will help student to perform well in the engineering field. Book Summary: This machine is destined to completely revolutionize cylinder diesel engine up through large low speed t- engine engineering and replace everything that exists. This handbook documents the last twenty years in particular. In light of limited oil current state of diesel engine engineering and technol- reserves and the discussion of predicted climate ogy.

Once the patent as further increasing diesel engine power density and was filed in and work on his engine commenced enhancing operating performance. Book Summary: A workshop guide to the strip-down, rebuild, maintenance and repair of two-stroke motorcycle engines. Author Dave Boothroyd covers the principles and practice of two-stroke engine work, examining a wide range of marques and road, racing and trail motorcycles.

With over colour photographs, this new book covers: the chronological development of two-stroke engines and workshop procedures for each era; the examination of each major engine component in turn, including cylinder head, piston, piston rings, crankcase, flywheel, bearings, inlet manifold, clutch, gearbox and primary drive, and, finally, racing motorcycles and tuning engines for best performance; diagnosing problems and workshop safety.

This practical reference guide is for the two-stroke motorcycle owner or restorer and is illustrated throughout with over colour photographs.

The author addresses a myriad of topics, covering both traditional and innovative approaches. Additionally, the book includes numerous tables. The element of design is what principally distinguishes engineering from science.

The engineer is a creator. He brings together knowledge and experience from a variety of sources to serve his ends, producing goods of value to the individual and to the community. An important source of information on which the engineer draws is the work of the scientist or the scientifically minded engineer. The pure scientist is concerned with knowledge for its own sake and receives his greatest satisfaction if his experimental observations fit into an aesthetically satisfying theory.

The applied scientist or engineer is also concerned with theory, but as a means to an end. He tries to devise a theory which will encompass the known experimental facts, both because an all embracing theory somehow serves as an extra validation of the facts and because the theory provides us with new leads to further fruitful experimental investigation.

I have laboured these perhaps rather obvious points because they are well exemplified in this present book. The first internal combustion engines, produced just over one hundred years ago, were very simple, the design being based on very limited experimental information.

The current engines are extremely complex and, while the basic design of cylinder, piston, connecting rod and crankshaft has changed but little, the overall performance in respect of specific power, fuel economy, pollution, noise and cost has been absolutely transformed. Book Summary: Optimization of combustion processes in automotive engines is a key factor in reducing fuel consumption.

This book, written by eminent university and industry researchers, investigates and describes flow and combustion processes in diesel and gasoline engines. The subject matter has been explained clearly and precisely in the simplest way. Salient features are Solved ExamplesA number of exercises at the end of every chapter Multi-Choice. Book Summary: The third edition of this book exposes the reader to a wide array of engineering principles and their application to agriculture.

It presents an array of more or less independent topics to facilitate daily assessments or quizzes, and aims to enhance the students' problem solving ability. Each chapter contains objectives, worked examples and sample problems are included at the end of each chapter. This book was first published in the late 60's by AVI. It remains relevant for post secondary classes in Agricultural Engineering Technology and Agricultural Mechanics, and secondary agriculture teachers.

Book Summary: This handbook is an important and valuable source for engineers and researchers in the area of internal combustion engines pollution control. It provides an excellent updated review of available knowledge in this field and furnishes essential and useful information on air pollution constituents, mechanisms of formation, control technologies, effects of engine design, effects of operation conditions, and effects of fuel formulation and additives.

The text is rich in explanatory diagrams, figures and tables, and includes a considerable number of references. An important resource for engineers and researchers in the area of internal combustion engines and pollution control Presents and excellent updated review of the available knowledge in this area Written by 23 experts Provides over references and more than explanatory diagrams, figures and tables.

Book Summary: Technology is constantly changing, but the basic principles stay the same. This publication provides a detailed look into the operation of fire apparatus and equipment. The text covers the various engine systems, chassis and component parts, pump operations, aerial operations and driving procedures.

A study guide is also available. Despite the considerable advantages, its operational range is rather limited and controlling the combustion timing of ignition and rate of energy release is still an area of on-going research.

Commercial applications are, however, close to reality. HCCI and CAI engines for the automotive industry presents the state-of-the-art in research and development on an international basis, as a one-stop reference work. Book Summary: This new volume covers the important issues related to environmental emissions from SI and CI engines as well as their formation and various pollution mitigation techniques.

The book addresses aspects of improvements in engine modification, such as design modifications for enhanced performance, both with conventional fuels as well as with new and alternative fuels. It also explores some new combustion concepts that will help to pave the way for complying with new emission concepts. Alternative fuels are addressed in this volume to help mitigate harmful emissions, and alternative power sources for automobiles are also discussed briefly to cover the switch over from fueled engines to electrics, including battery-powered electric vehicles and fuel cells.

The authors explain the different technologies available to date to overcome the limitations of conventional prime movers fueled by both fossil fuels and alternative fuels. Book Summary: Light and Heavy Vehicle Technology, Second Edition deals with the theory and practice of vehicle maintenance, procedure, and diagnosis of vehicle trouble, including technological advances such as four-wheel drive, four-wheel steering, and anti-lock brakes.

The book reviews the reciprocating piston petrol engine, the diesel engine, the combustion chambers, and the different means of combustion processes.

To counter friction, heat and wear, lubrication to the different moving parts is important. To counter excessive heat which can cause breakdown of lubricating oil films and materials such as gaskets, O-rings, the engine is designed with a cooling system that uses air, water, or engine coolants. Petrol engines use the carburation or injection type of fuel delivery; diesel engines use a high pressure system of fuel injection owing to the higher pressures existing in the diesel combustion chamber.

The text explains the operation of the other parts of the vehicle including the ignition and starter system, emission controls, layshaft gearboxes, drive lines, and suspension systems.

Heavy vehicles need highly efficient air brakes to stop them compared to the hydraulic brake systems used in smaller and lighter vehicles. The book is suitable for mechanical engineers, engine designers, students, and instructors in mechanical and automotive engineering. Author : Prof. Pune—52 Ex. Pathak Sr. Kulkarni Associate Professor Zeal E.

Now the book is quite up-to-date. This edition of the book is entirely new and different from its previous editions. We hope, the book will prove more useful and will serve its purpose better. This book will be useful for various branches, competitive examinations, engineering services and ICS Examinations. Number of problems have been solved in detail. Subject matter is supported by very good diagrams.



0コメント

  • 1000 / 1000