Numerical and experimental analysis of coupled transverse and longitudinal vibration of a marine propulsion shaft

An appropriate assessment of the dynamic behavior of marine propulsion shaft in ships is essential to enable optional delivery of power to the propeller and to minimize unnecessary vibration. Various vibrations coupling with each other can significantly influence the dynamical behavior of the shaft and threaten the reliability of ships. This paper presents a finite element analysis model with multiple constraint conditions to analyze the coupled transverse and longitudinal vibrations of a marine propulsion shaft. Based on this model, in addition to the coupled natural frequencies of each direction, the maximum acceleration are also determined. Furthermore, the simulation of an idling and loading vibration analysis is discussed and validated against experimental results, over a range of rotational speeds. The output of numerical simulation is found to agree with the corresponding results from experimental tests. Finally, an accurate and applicative FEA model for coupled transverse-longitudinal vibration of shaft has been obtained.     

Effects of a turbocharger cut out system on vibration characteristics of a propulsion shafting system and a large low speed marine diesel engine

To cope with the long term recession in the shipping industry due to oversupply of ships and high oil prices and due to reinforcement of environmental regulations to reduce greenhouse gas emission from ships, large container vessels built recently have ultra-long stroke engines with high propulsion efficiency. For these, de-rated engine and tuning technologies are used to reduce fuel oil consumption. However, previously built vessels were optimized for high ship speed. In these case, lowering ship speed to reduce ship operating cost does not provide similar benefits. Therefore, engine manufacturers have developed a turbocharger cut-out system to reduce fuel oil consumption at low speed. This has the advantage of reducing fuel consumption at low speeds, but also has the characteristic of producing higher torsional exciting force than is typical in existing engines for low load ranges. In this paper, the performance and dynamic characteristics of a marine diesel engine were reviewed after applying a turbocharger cut-out system. Then the effects on the engine body vibration and the torsional vibration were examined for a corresponding propulsion shafting system in a Panamax container-vessel equipped with a turbocharger cut-out system optimized for slow steaming. As a result, the torsional vibratory stress in shafts was increased. This had a larger effect on the X-mode shape of the engine body vibration and on the upper structure vibration, when one of three turbochargers was cut out.     

Modeling of a hydraulic engine mount for active pneumatic engine vibration control using the extended Kalman filter

The attenuation of engine vibration transmitted to a chassis has been a major focus in the automotive community for the increase of comfort for the driver and passengers. A hydro-mount system is designed to reduce the transmission of engine vibration to the chassis. It is also used for supporting the static load by an engine weight. In this paper, we present a modeling and parameter estimation of hydro-mount systems. Nonlinear model aspects are developed and used with experimental data to validate the model response characteristics. These parameters will be modeled as a variable vector and its value is estimated via linearized and extended Kalman filter. This approach can help engineers reduce design time by providing insight into the effects of various parameters within the hydro-mount. Based on the estimated parameters, the simulation result confirmed that the derived passive model describes the dynamic behavior of the hydro-mount system accurately. This paper was recommended for publication in revised form by Associate Editor Shuzhi Sam Ge Arjon Turnip received his B.S. and M.S. degrees in Engineering Physics from the Institute of Technology Bandung, Indonesia, in 1998 and 2003, respectively. He is currently a Ph.D. program student in the School of Mechanical Engineering, Pusan National University, Korea. His research areas are integrated vehicle control, adaptive control, and estimation theory. Keum-Shik Hong received the B.S. degree in mechanical design and production engineering from Seoul National University in 1979, the M.S. degree in ME from Columbia University in 1987, and both the M.S. degree in applied mathematics and the Ph.D. degree in ME from the University of Illinois at Urbana-Champaign in 1991. He served as an Associate Editor for Automatica (2000–2006) and as an Editor for the International Journal of Control, Automation, and Systems (2003–2005). Dr. Hong received Fumio Harashima Mechatronics Award in 2003 and the Korean Government Presidential Award in 2007. Dr. Hong’s research interests include nonlinear systems theory, adaptive control, distributed parameter system control, robotics, and vehicle controls. Seonghun Park received his B.S. and M.S. degrees in mechanical engineering from KAIST in 1994 and 1996, respectively, and his Ph.D. degree from Columbia University in 2005. Dr. Park is currently a professor of mechanical engineering at Pusan National University, Korea. His research interests are in the areas of control, tribology, and biomechanics.     

4105柴油机曲轴扭转振动与减振器匹配研究

利用软件EXCITE-designer对柴油机4105曲轴进行数学建模,建立了基于集中质量-弹簧-阻尼的系统模型,获得了曲轴扭转振动的自由振动频率和振型,计算了曲轴的强迫振动;分析了减振器的惯性块惯量对谐次波的影响,匹配了减振器。结果表明,柴油机在2 560,2 735和3 125 r/min附近转速下发生了较大的扭转共振;随着减振器惯性块惯量ID的增大,各谐次波的临界转速逐渐减小,匹配减振器后大幅降低了曲轴的扭转振幅,表明所设计减振器有较好效果。     

柴油机活塞的热机耦合计算研究

应用ANSYS分析软件,对某柴油机活塞的换热边界条件进行研究分析,以活塞表面的整个循环过程中的燃气温度和燃气传热系数以及缸套冷却水的温度和传热系数为第三类边界条件进行设置,计算得到活塞的三维稳态温度场分布规律.结果表明,该活塞顶部最高温度是519.9K,位于燃烧室偏置一侧的喉口上沿处,热负荷不高.以此为基础,计算了在标定工况下,该活塞在机械负荷和热负荷的热机耦合共同作用的应力和应变,最大耦合等效应力184MPa出现在活塞销座与销接触面上的上方销座内侧.     

Dynamic modeling and analysis of axial vibration of a coupled propeller and shaft system

The dynamic and acoustic characteristics of a coupled propeller and shaft system which is modeled by the transfer matrix method are studied. The elasticity of the propeller is taken into consideration by employing the equivalent reduced modeling method. Thus the influence of the elastic propeller on the vibro-acoustic responses of the coupled system is investigated. To reduce the axial vibration of the coupled propeller-shaft system, the influence and location of the vibration isolator on the structural and acoustic responses is presented. Simulation results demonstrate that utilizing the relationship between the natural frequency of the propeller and the resonance frequency range of the shaft can control the vibration of the coupled system without other vibration control method. Utilizing a vibration isolator is another effective way to control vibration. The optimal position for the isolator installed between the shaft and the thrust bearing is investigated.     

Analysis of torsional crankshaft oscillations in a diesel engine on the basis of cylinder-block vibration

Torsional crankshaft oscillations in the diesel engine of an automobile are studied experimentally. Their relation to the cylinder-block vibration is considered. It is established that the vibrations appearing not only at the resonant harmonic but at higher frequencies are due to torsional crankshaft oscillations, which produce impacts in the crankshaft’s slip bearings.     

Free vibration analysis of a resilient impact damper

The free vibration of a vibratory system equipped with a resilient impact damper is studied. A simple model of impact damper is constructed using spring, mass and viscous damper. The important feature to be carried out in the analysis of this model is that the deformation of an impact damper during the collision with and the main mass can be formulated; therefore, the contact time is taken into consideration. This feature is important for a resilient rather than a rigid impact damper when the noise issue is concerned. The investigation showed that the effective reduction of the vibration response depends not on the number of impacts but primarily on the type of collision that the impact mass collides with the main mass face-to-face. Results also show that the clearance of an effective impact damper should be smaller than twice of the initial displacement of the main mass of the vibration system if the system is stimulated by an initial displacement only. Finally, an example of application of an impact damper on a cantilever beam is demonstrated.     

某大功率柴油机结构振动辐射噪声源探究

某公司研发的大功率柴油机装车后,用户反映怠速时发动机后端噪声大,并伴有“格拉拉”的异响。为确定发动机的噪声源,本文分别在台架和整车上对发动机做了振动噪声试验,试验结果显示发动机的噪声主要来自齿轮室、高压油泵和空压机以及缸盖罩壳,发动机“格拉拉”的异响是齿轮室的齿轮撞击声,造成齿轮撞击的主要原因是齿轮啮合间隙过大。对此本文提出了两种降噪方案：第一在齿轮室、高压油泵和空压机等处加装遮蔽罩;第二改进齿轮和缸盖罩壳设计,减小齿轮啮合间隙和缸盖罩壳耦合振动,降低噪声。     

船用柴油机曲轴转子-轴承系统动力学试验台的研制

根据大功率低速船用柴油机曲轴转子-轴承系统的动力学特性,研究了动力学试验台的设计原则、各个组成部分的功能、动力学试验台应具有的性能等问题,最后,成功研制出一台动力学试验台.该试验台可用于研究系统的时间响应、频率响应、轴心轨迹,检测气缸内的压力变化规律,控制曲轴的转速和气缸内的压力等.     

Sliding mode control of a shear-mode type ER engine mount

This paper presents feedback control characteristics of a shear-mode type electro-rheological (ER) engine mount. The field-dependent yield stress of an arabic gum-based ER fluid is obtained using a couette type electroviscometer, and it is incorporated into the governing equation of motion of the ER engine mount, which is derived from a bond graph model. A sliding mode controller which directly represents the field-dependent damping force is formulated by taking into account the stiffness and damping properties of the systems as parameter uncertainties. The controller is then experimentally realized by imposing a semi-active actuating condition. The effectiveness of the proposed ER engine mount is demonstrated showing capabilities of isolating the vibrations due to sinusoidal and random excitations.     

Simulation of combustion in a porous-medium diesel engine

The future internal-combustion (IC) engines should have minimum emissions level under lowest feasible fuel consumption. This aim can be achievable with a homogeneous combustion process in diesel engines. We used a porous medium (PM) to homogenize the combustion process. This research studies simulation of a direct-injection diesel engine, equipped with a chemically inert hemispherical PM. Methane is injected into a hot PM, assuming mounted up the cylinder in head. Combustion with lean mixture occurs inside PM. A numerical model of PM engine was carried out using a modified version of the KIVA-3V code. PM results were evaluated with experimental data of unsteady combustion-wave of methane in a porous tube. The results show the mass fraction of methane, CO, NO and temperature in solid and gas phases of the PM and in-cylinder fluid. Also presented are the effects of injection timing and compression ratio on combustion.

     

Precise instrumentation of a diesel single-cylinder research engine

The accuracy of any empirical result is a direct consequence of the quality of experimental setup and the strict control over testing conditions. For internal combustion engines, a large number of parameters that also exhibit complex interdependence may significantly affect the engine performance. Therefore, this work describes the essentials required to establish a high-quality diesel engine research laboratory. A single-cylinder diesel engine is taken as the fundamental building block and the requirements for all essential sub-systems including fuel, intake, exhaust, coolant and exhaust gas recirculation (EGR) are laid out. The measurement and analysis of cylinder pressure, and exhaust gas sampling/conditioning requirements for emission measurement are discussed in detail. The independent control of EGR and intake boost is also highlighted. The measurement and analysis techniques are supported with empirical data from a single-cylinder diesel engine setup. The emphasis is on providing the necessary guidelines for setting up a fully-instrumented diesel engine test laboratory.     

胶层厚度对三点支撑反射镜面形的影响

以45nm浸没式光刻物镜中采用的三点支撑反射镜为研究对象,建立了胶层连接的三点边缘支撑结构模型,用以确定胶层厚度对三点支撑反射镜面形变化的影响。分析了重力作用下三点支撑反射镜的面形变化情况,通过解析表达式描述了胶层厚度对反射镜受力变形的影响。建立了"支撑块-胶层-反射镜"的有限元计算模型,针对不同胶层厚度对反射镜的面形变化进行了仿真分析。仿真结果表明:随着胶层厚度的增大,反射镜的面形变化(均方根值RMS)呈现先减小后增大的趋势;当胶层厚度为280μm时,反射镜面形变化的RMS值最小,约为1.25nm。最后,通过实验测量了柔性双脚架三点边缘支撑导致的反射镜面形变化。结果显示:当胶层厚度为200,280,400μm时,反射镜面形的变化结果均与仿真结果一致,验证了本文仿真结果的正确性。     

Multidimensional engine modeling: NO and soot emissions in a diesel engine with Exhaust Gas Recirculation

The effects of EGR (Exhaust Gas Recirculation) on heavy-duty diesel engine performance, NO and soot emissions were numerically investigated using the modified KIVA-3V code. For the fuel spray, the atomization model based on the linear stability analysis and spray wall impingement model were developed for the KIVA-3V code. The Zeldovich mechanism for the formation of nitric oxide and the soot model suggested by Hiroyasu et al. were used to predict the diesel emissions. In this paper, the computational results of fuel spray, cylinder pressure, and emissions were compared with experimental data, and the optimum EGR rates were sought from the NO and soot emissions trade-off. The results showed that the EGR is effective in suppressing NO but the soot emission was increased considerably by EGR. Using cooled EGR, soot emission could be enhanced without worsening of NO.     

柴油机冷却系统的数值模拟

对某柴油机的冷却系统进行数值模拟,包括了机体和气缸盖的水套.运用CFD(Computational Fluid Dynamics)分析软件SC/Tetra计算温度场及流场.通过计算发现水套存在诸多不足,如机体水套冷却不均匀,机体进气侧与非进气侧冷却液流速相差大,鼻梁区流量偏小等缺陷.然后对其结构进行改进,取得了比较好的效果.     

Friction model of a marine diesel engine piston assembly

In modern marine diesel engines, power output and in-cylinder firing pressures are constantly increasing, leading to higher friction in engine components and especially in the piston assembly. A good understanding of the friction contributions of the various engine components is needed, if mechanical efficiency is to be improved. A friction model for the engine piston assembly has been developed and is presented in this paper. The model, based on lubrication theory, considers the detailed engine geometry and the complete lubricant action, and thus can be applied to a wide range of engines. In detail, the analysis takes into account the friction components of compression rings, oil control rings, piston skirt and gudgeon pin of the engine piston assembly. The model was applied to a four-stroke (medium speed) marine diesel engine and the effect of engine speed and load on friction was examined and compared with results from other semi-empirical models. The engine friction was predicted at constant rotational speed (generator operation) and variable rotational speed (propulsion operation).     

Source separation of diesel engine vibration based on the empirical mode decomposition and independent component analysis

Vibration signals from diesel engine contain many different components mainly caused by combustion and mechanism operations,several blind source separation techniques are available for decomposing the signal into its components in the case of multichannel measurements,such as independent component analysis(ICA).However,the source separation of vibration signal from single-channel is impossible.In order to study the source separation from single-channel signal for the purpose of source extraction,the combination method of empirical mode decomposition(EMD) and ICA is proposed in diesel engine signal processing.The performance of the described methods of EMD-wavelet and EMD-ICA in vibration signal application is compared,and the results show that EMD-ICA method outperforms the other,and overcomes the drawback of ICA in the case of single-channel measurement.The independent source signal components can be separated and identified effectively from one-channel measurement by EMD-ICA.Hence,EMD-ICA improves the extraction and identification abilities of source signals from diesel engine vibration measurements.     

Combustion characteristics of a swirl chamber type diesel engine

A numerical model that utilizes Computational Fluid Dynamics (CFD) techniques is simulated for the analysis of a swirl chamber type diesel engine. This research also reveals the effects of swirl chamber passage hole geometry on the combustion characteristics of a swirl chamber type diesel engine depending on the shape, angle, and area of the jet passage. Turbulence kinetic energy is generated by compound effects of the pressure, heat release, NOx concentrations, and soot concentrations. Results show that combustion characteristics are affected by the passage hole areas and the passage hole inclination angles.     

Investigation of emission characteristics affected by new cooling system in a diesel engine

In a typical cooling system of automotive engine, a mechanical water pump is used to control the flow rate of coolant. However, this traditional cooling system is not suitable for a high efficiency performance in terms of fuel economy and exhaust emission. Therefore, it is necessary to develop a new technology for engine cooling systems. These days, the electronic water pump is spotlighted as the new cooling system of an engine. The new cooling system can provide more flexible control of the coolant flow rate and the engine temperature, which used to be strongly relied on the engine driving conditions such as load and speed. In this study, an engine experiment was carried out on a New European Drive Cycle (NEDC) with a 2.7L diesel engine. The electric water pump operated by BLDC motor and the electronic valve were installed in the cooling system to control the coolant flow rate and temperature. This paper explains that the exhaust emissions were reduced with an increase in the engine temperature and a decrease in the coolant flow. From this experiment, we found that increasing coolant temperature had a significant effect on reducing the emissions (e.g. THC and CO). Decreasing coolant flow also affected the reduction of emissions. In contrast, NOx emission was observed to increase in these conditions. This paper was presented at the 7th JSME-KSME Thermal and Fluids Engineering Conference, Sapporo, Japan, October 2008. Kyung-Wook Choi received his B.S. degree in Mechanical Engineering from Hanyang University, Korea, in 2006. He is now working on a doctoral degree in Hanyang University. Kyung-Wook’s research interests include Hybrid Electric Vehicle, Internal Engine Combustion, and Engine Cooling System. Ki-bum Kim was awarded a bachelor’s degree in naval architecture and ocean engineering from Chung-Nam National University in the Republic of Korea. In August 2001, he began graduate study at the University of Florida. Kibum graduated with a Master of Science degree in mechanical engineering from the University of Florida in August 2003. He went on to earn his Ph.D. in mechanical engineering, also at the University of Florida, in August 2006. He is working as a research professor at Hanyang University. Ki-Hyung Lee is a Professor at the department of mechanical engineering in Hanyang University. He received his B.S and M.S degree in Hanyang University in 1983 and 1986. Then he graduated with a Ph.D. degree in mechanical Engineering at Kobe University, Japan in 1989. He worked as a research engineer at Nissan motor’s central technical center for 4 years.