Generation of Power from Ocean Tidal Vibrations - Coursework Example

Research Paper—Engineering -Vibrations As vibrations can be good or bad depending on their characteristics, this paper discusses broadly the application and result of mechanical vibrations. The analysis of different types of vibrations and the natural frequency of the vibration as determined by experiments like tuning fork method precedes the section detailing advantages and disadvantages of vibration. Generation of power from ocean tidal vibrations is detailed briefly. The paper then discusses about the use of shock absorbers and dampers for absorbing the excessive vibration in a moving machine. The causes of industrial problems occurring due to vibration in factories come next, followed by examples of unwanted vibration in moving automobiles, with possible remedial measures. Introduction Vibration is a condition of movement, which can occur in every rotating device, as oscillations in a dynamic mechanical system. As the characteristic of vibrations are good and bad, depending upon the type, some vibrations are dangerous. For example, earth quick vibrations cause disasters, which are well known to human kind. However, vibration can be defined as the characteristics of every machine or device, which produces the work output through rotating or reciprocating action. It is essential to control the vibration, which is possible by measuring it. The measurement can be done by adopting the following units. Velocity of the rotating or reciprocating machine, measured in m/sec. Acceleration in the speed, measured in mm/second square Displacement caused by vibration, measured in inches or millimeters. Types of vibration Various types of induced vibrations caused by the mechanical action are briefly detailed below. Free vibrations This type does not require any artificial or external power to induce vibration in the system. Such vibrations occur forever and cannot be stopped. For example, the movement of neutrons, in any electronic application, is natural and cannot be stopped or induced. Electrons always keep moving causing some kind of vibrations. Forced vibrations When machinery is subject to some kind of force that causes vibration for a certain period, such type of vibration is called forced vibration. For example when a lathe machine stats working on any tool, the vibration is induced into the system, which remains until the lathe stops rotating. During an accident, an automobile experiences vibration induced by the crushing forces, which last only for a few milliseconds. On the other hand, a moving crankshaft, in any IC engine of a car develops torques of varying degree, over a certain period, due to the induced vibrations. Linear and non-linear vibrations When there is a relationship between the excitation force magnitude and the response in a linear system, the vibrations caused by such action are called linear vibrations. On the other hand, non-linear systems produce non-linear vibrations. Examples of non-linear vibrations include chatter in the machine tools or airfoils flutter. Random and deterministic vibrations Deterministic vibrations occur when a rotating part of any machine is in unbalanced condition. The mechanical system running in an unbalanced condition experiences a net dynamic force. However, the time variation and amplitude of this excitation force is always known, as running speed of the system would match the unbalance excitation. Hence, the system can be said to experience deterministic vibrations, when varying time and amplitude of the external disturbances are precisely known. However, when the period of excitation duration cannot be accurately known, the vibrations experienced in the system are called random vibrations. For example, a moving car can experience changing excitation force due to road roughness. The duration of this force is unknown, as road condition for next few seconds of driving remains unknown to the driver. (Overview) Natural Frequency Vibration has close relation with harmonic motion and resonance. For example, when a mass is connected to a flexible cantilever beam, it will resonate with the spring action caused by application of an external force like periodic vibration or a single time impulse. Accordingly, the frequency of resonance in the system will be its “natural frequency”. The following images depict the frequency characteristic, when resonance is applied to a lower and higher mass. (source: http://www.newport.com/Fundamentals-of-Vibration/140234/1033/content.aspx) While natural frequency will increase in case of lower mass, it will decrease for the higher mass. Similarly, if the beam is stiff, it will result in higher natural frequency and softer beam will produce lower frequency. The tuning fork is a perfect example of natural frequency phenomenon, as can be understood by the following figure: (source: http://www.newport.com/Fundamentals-of-Vibration/140234/1033/content.aspx) Here the length and mass of tines can determine the natural frequency of the tuning fork. However, damping causes great difference in the vibrations within a system, as it attenuates quick vibrations caused by dissipation of mechanical energy within the system. For example, the action of immersing tuning fork tips into the water will result in instantly attenuated vibrations.(Fundamentals) Advantages of vibrations Vibrations are not always problematic, as they do find some useful application in factories and human life. For example, vibrating tumblers and oscillating sanders require vibration for surface finishing and shuffling of materials. In civil constructions, vibrators are used to remove the honeycombs while laying the RCC. Road rollers use vibratory energy to compress the asphalt during any road laying or maintenance operation. Industrial vibratory belts make it convenient in factories to move material from one shed to another in an economical manner.(An introduction) As repeated oscillation produces vibration in any mechanical system, there are many causes of setting up a vibratory motion in a system. These include winds, external forces, and unbalanced forces responsible for centrifugal action. External excitation and any friction between two rubbing surfaces can also cause vibration or frequent oscillation. Vibrations are helpful in stimulating earthquake conditions for the purpose of geological investigation. The geo-technical well drilling gets help from mechanical vibration to complete the job efficiently. In addition, there are varied advantages of vibration, as experienced in daily human lives. For example, the trees shed their fruit with the help of mechanical vibrations, during the harvest season. The body trimming machines use mechanical vibrations to produce the desired results. Similarly, most of exercising equipment utilizes vibration for best performance. Vibrations find use in the trimming and slimming equipment that promise reduction of body fat though vibratory belts and other devices. However, results from such equipment need further investigation. Disadvantages of vibration Often vibration is considered as hazardous, since it produces undue wear and tear in the mechanical system. However, the measuring and controlling of such vibrations can restrict its disadvantages. Vibrations can cause stress that is not required or desired in a mechanical system. This can result into faster deterioration of the system, particularly the machine parts. Bearings and gears of a mechanical system or any machine can quickly wear out due to unwanted vibration. Due to friction involved, these parts wear out in the normal course of their function. However, any undesired vibration in them can cause faster wear-out of these parts. During the course of an earthquake, the vibrations can cause collapse of building structures, which can be dangerous for human lives. Accordingly, the vibratory waves produced during earthquakes are the most disadvantageous vibrations, experienced by human kind so far. Trimming belts and other vibratory devices that are used for reducing the excess fat and body weight can causes damage to the body, due to excessive vibrations. Generation of power from ocean waves vibration The tidal waves have tremendous potential, as the vibration from these waves can be a renewable energy source for kinetic energy. When such energy is converted into electric power, it can provide multiple utilities in varied marine environments. Combination of this power with solar energy would result in round the clock energy supplies to various marine equipment and ships. The harvesting of such energy requires utilization of long oscillation periods, generated from sea tidal waves into an excitation source that can be part of an extendable harvesting chain for vibration energy. Joining series of dynamic cells through required interfaces, the inertial mass of every cell is used to produce the induced dynamics against the background of negative stiffness. The system is connected to a coil, which gets current from the oscillation mass, which is magnetic in nature and has certain inertial mass. The energy conversion takes place when this coil is connected to a circuitry meant for harvesting the induced energy. The formation of a chain that links the individual cells results in the transmission of impulses though the system, thus creating vibration cascades, which are converted into energy. This way the energy conversion is increased manifold from every impulse event. Experimental research studies reveal that cells when connected though a chain produce higher conversion of energy results, when compared to individual chains, without any connection. The impulse generated by the multi-stable chains, thus developed, can be used to harvest the ocean tidal vibration energy in an efficient manner.(Harne, Shoemaker & Wang) Shock absorbers/dampers Undesirable vibrations in a mechanical system can cause deterioration of the machine parts and reduce their life span, while interfering with the running of various movable parts in the system. Hence, vibration shock absorbers or dampers are utilized, which convert the kinetic energy produced by moving parts into the thermal energy. This process, in turn, reduces heavy oscillation amplitudes, to decrease the undesirable impact of vibration. The hydraulic oil based shock absorbers or dampers result in the force distribution in the compression and tension directions in a symmetrical way. This results in the damping effect to remain evenly distributed, even when the system experiences reversal of movement. During the reversal of loads, the damping action can start instantaneously by connecting the vibration dampers directly to result in positive force transmission.(Vibration dampers) Problems that occur due to vibrations in factories In factories, vibrations are part of the total operational sequence, as they are unavoidable in most cases. For example, compressors and reciprocating pumps cannot avoid vibrating while running. Similarly, gear drives and internal combustion engines cannot avoid vibrations while in operation. Well-maintained equipment, based on good design, will never pose any problem due to the inherent vibrations. However, smooth operation by rotary pumps, blowers, fans, compressors and motors require minimum vibration during operation to avoid undue wear and tear. Therefore, they are a cause of concern in most of the factories. Following are some of the examples that cause problems in factories due to vibrations. Imbalance Vibrations result due to unbalanced load on the axis of a machine, as the rotating weight creates a centrifugal force. The reasons for this include faulty design, poor maintenance, machining or casting errors. With increase in the speed of such machine, the unbalanced weight can drastically reduce the life of bearings due to heavy vibrations. Normal wear and tear As rotating parts like gears and bearings wear out, they cause excessive vibrations. This can result in machine breakdown, if the timely remedial action is not taken to rectify the error. Loose parts Common cases of damage due to vibrations in factories include the operation of rotary machines that have loose components, like roller or ball bearings, mounting pads. Such excessive vibrations can cause damage to the equipment, when left unattended. Shaft misalignment Some machines that have misaligned shafts can cause heavy vibrations. The causes for this can be non-parallel axis alignment of the rotating equipment like rotary pumps and a motor. The misalignment problem needs immediate investigation, to avoid heavy damage to the running equipment. Avoiding unwanted vibration in cars There are various reasons that cause unwanted vibrations in running machines like cars. The Engine mounts with cracked rubber can cause excessive engine vibration particularly when the car starts or stops. Therefore, regular checks of engine mountings always help in avoiding this problem. As car body vibrations result in more noise and wear/tear, it is essential to check the body frame fitting and assembly of vehicle frame for detecting any looseness in the fittings. In addition, regular maintenance of car body, which may experience heavy rattles due to rough road conditions, always helps.(Parker) Conclusion While vibrations may not be cause of concern in many cases, they pose heavy threat to the machinery and equipment if not properly monitored and controlled. Some vibrations like those experienced during an earthquake can prove fatal, while normal vibrations need checking if they go beyond the desired limits. There are many applications of vibrations being put to good use, which include conveyor belts, vibrating shufflers and compact vibrators used in civil construction projects. However, mechanical vibrations in factories can pose threat to men and machinery, if the problems are not identified and rectified in time. Work-cited “An Introduction to Machinery Vibration”, Fluke corpn., relablepalnt.com nd, web, 7 April 2015: “Fundamentals of vibration”, Newport.com, nd, web, 7 April 2015: Harne. L, Shoemaker. M, Wang.W , “Multistable Chain for Ocean Wave Vibration Energy Harvesting”, SPIE. Digital Library, 2014, web, 7 April 2015: “Overview of Mechanical Vibrations”, nptl.ac.in nd, web, 7 April 2015: Parker.A, , “5 Innovations that Reduce Engine Vibrations”, auto.howstufworks.com, , nd, web, 7 April 2015 “Vibration Dumpers”, stbilus.com, nd, web, 7 April 2015 Read More