A new comprehensive tribo-dynamic analysis for lubricated translational joints in low-speed two-stroke marine engines

2019 ◽  
Vol 21 (8) ◽  
pp. 1336-1361 ◽  
Author(s):  
Rui Li ◽  
Xianghui Meng ◽  
Wenda Li ◽  
Jingjin Dong
Keyword(s):  
Transverse Velocity ◽  
Early Model ◽  
Stiff Differential Equations ◽  
Connecting Rod ◽  
Low Speed ◽  
Piston Skirt ◽  
Crank Angle ◽  
Marine Engines ◽  
Simulation Results ◽  
Lubricant Viscosity

In low-speed two-stroke marine engines, the effect of connecting rod inertia is important for the tribo-dynamics of crosshead slipper-guide and piston skirt-liner. However, this has not been considered in previous research. Therefore, a new tribo-dynamic model that considers the connecting rod inertia is presented for the two lubricated translational joints, and the lubricant viscosity–temperature properties are accurately incorporated into the model. The modified extended backward differentiation formulate method is used to solve the nonlinear stiff differential equations effectively. The simulation results show that the effect of connecting rod inertia on the dynamic characteristics of two translational joints is mainly observed during the latter half of the upward stroke. For the crosshead slipper, the amplitude of the transverse velocity is increased by 30% at a crank angle of approximately 300° compared to the early model that ignored the connecting rod inertia. With the increase of the connecting rod mass, the secondary motions of both the crosshead slipper and the piston skirt are increased. Furthermore, a decrease of the connecting rod mass can reduce the friction losses of the engine.

Deep and Shallow Water Low-Speed Maneuvering Tests: Comparison Between Experimental and Simulation Results

2016 ◽  
Author(s):  
Felipe Ribolla Masetti ◽  
Pedro Cardozo de Mello ◽  
Guilherme F. Rosetti ◽  
Eduardo A. Tannuri
Keyword(s):  
Mathematical Model ◽  
Small Scale ◽  
Shallow Waters ◽  
Hydrodynamic Coefficients ◽  
Low Speed ◽  
Tunnel Model ◽  
Oceanographic Research ◽  
Simulation Results ◽  
The University ◽  
The Mathematical Model

This paper presents small-scale low-speed maneuvering tests with an oceanographic research vessel and the comparison with mathematical model using the real time maneuvering simulator developed by the University of São Paulo (USP). The tests are intended to verify the behavior of the vessel and the mathematical model under transient and low speed tests. The small-scale tests were conducted in deep and shallow waters, with a depth-draft ratio equal to 1.28, in order to verify the simulator ability to represent the vessel maneuverability on both depth conditions. The hydrodynamic coefficients used in the simulator model were obtained by CFD calculations and wind tunnel model tests carried out for this vessel. Standard turning circle and accelerating turn maneuvers were used to compare the experimental and numerical results. A fair agreement was achieved for shallow and deep water. Some differences were observed mainly in the initial phase of the accelerating turn test.

scholarly journals Experimental Research on Controllability and Emissions of Jet-Controlled Compression Ignition Engine

Energies ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2936 ◽  
Author(s):  
Hua Tian ◽  
Jingchen Cui ◽  
Tianhao Yang ◽  
Yao Fu ◽  
Jiangping Tian ◽  
...  
Keyword(s):  
Thermal Efficiency ◽  
High Speed ◽  
Compression Ignition ◽  
Compression Ignition Engine ◽  
Engine Emissions ◽  
Spark Timing ◽  
Crank Angle ◽  
Marine Engines ◽  
Si Engines ◽  
Ci Engines

Low-temperature combustions (LTCs), such as homogeneous charge compression ignition (HCCI), could achieve high thermal efficiency and low engine emissions by combining the advantages of spark-ignited (SI) engines and compression-ignited (CI) engines. Robust control of the ignition timing, however, still remains a hurdle to practical use. A novel technology of jet-controlled compression ignition (JCCI) was proposed to solve the issue. JCCI combustion phasing was controlled by hot jet formed from pre-chamber spark-ignited combustion. Experiments were done on a modified high-speed marine engine for JCCI characteristics research. The JCCI principle was verified by operating the engine individually in the mode of JCCI and in the mode of no pre-chamber jet under low- and medium-load working conditions. Effects of pre-chamber spark timing and intake charge temperature on JCCI process were tested. It was proven that the combustion phasing of the JCCI engine was closely related to the pre-chamber spark timing. A 20 °C temperature change of intake charge only caused a 2° crank angle change of the start of combustion. Extremely low nitrogen oxides (NOx) emission was achieved by JCCI combustion while keeping high thermal efficiency. The JCCI could be a promising technology for dual-fuel marine engines.

Enhancement of the Accuracy of the Modified (P–ω) Method Through the Implementation of a Nonlinear Robust Observer

2005 ◽  
Author(s):  
G. A. Kfoury ◽  
N. G. Chalhoub ◽  
N. A. Henein ◽  
W. Bryzik
Keyword(s):  
Internal Combustion Engines ◽  
Sliding Mode ◽  
Angular Displacement ◽  
Digital Simulation ◽  
Friction Torque ◽  
Original Version ◽  
State Variables ◽  
Connecting Rod ◽  
Simulation Results ◽  
Elastic Modes

The original version of the (P–ω) method is a model-based approach developed for determining the instantaneous friction torque in internal combustion engines. This scheme requires measurements of the cylinder gas pressure, the engine load torque, the crankshaft angular displacement and its time derivatives. The effects of the higher order dynamics of the crank-slider mechanism on the measured angular motion of the crankshaft have caused the (P–ω) method to yield erroneous results, especially, at high engine speeds. To alleviate this problem, a nonlinear sliding mode observer has been developed herein to accurately estimate the rigid and flexible motions of the piston-assembly/connecting-rod/crankshaft mechanism of a single cylinder engine. The observer has been designed to yield a robust performance in the presence of disturbances and modeling imprecision. The digital simulation results, generated under transient conditions that represent a decrease in the engine speed, have illustrated the rapid convergence of the estimated state variables to the actual ones in the presence of both structured and unstructured uncertainties. Moreover, this study has proven that the use of the estimated rather than the measured angular displacement of the crankshaft and its time derivatives can significantly improve the accuracy of the (P–ω) method in determining the instantaneous engine friction torque. However, the effects of structural deformations of the crank-slider mechanism have rendered the original version of the (P–ω) method to be inapplicable at high engine speeds. This problem has been addressed herein by modifying the formulation of the (P–ω) method in order to account for the first two elastic modes of the crankshaft torsional vibration. The simulation results confirm the good performance of the modified (P–ω) method in determining the instantaneous friction torque at high engine speeds.

scholarly journals Comparison of the Performance of Different Mechanisms on Soot Generation of Low-Speed Two-Stroke Marine Engines

2019 ◽  
Vol 158 ◽  
pp. 4572-4578
Author(s):  
Xingyu Liang ◽  
Xinyi Cao ◽  
Fei Zhang ◽  
Enxing Zhang ◽  
Peijian Yang ◽  
...  
Keyword(s):  
Low Speed ◽  
Marine Engines

Effect of Inertia Variation Due to Reciprocating Parts and Connecting Rod on Coupled Free Vibration of Crankshaft

1997 ◽  
Vol 119 (1) ◽  
pp. 257-263 ◽  
Author(s):  
S. Rajendran ◽  
M. V. Narasimhan
Keyword(s):  
Free Vibration ◽  
Natural Frequencies ◽  
Free Vibrations ◽  
Connecting Rod ◽  
Single Cylinder ◽  
Considerable Error ◽  
Inertial Coupling ◽  
Single Cylinder Engine ◽  
Crank Angle ◽  
Engine Crankshaft

The inertia due to reciprocating parts and connecting rods, as felt by the crankshaft, varies with the crank angle. The effect of inertia variation on torsional free vibration of crankshafts has been studied extensively. In this paper, the effect on combined torsional and bending free vibrations is examined. Single-cylinder engine crankshaft geometry is considered for the study. The results indicate that the inertial coupling, introduced by the reciprocating parts and connecting rod, significantly influences the free vibration characteristics, particularly when the natural frequencies of the crankskahft are closely spaced. The results suggest that, under such conditions, modeling the crankshaft as a pure torsional system would involve considerable error.

scholarly journals The Analysis of Secondary Motion and Lubrication Performance of Piston considering the Piston Skirt Profile

2018 ◽  
Vol 2018 ◽  
pp. 1-27 ◽  
Author(s):  
Yanjun Lu ◽  
Sha Li ◽  
Peng Wang ◽  
Cheng Liu ◽  
Yongfang Zhang ◽  
...  
Keyword(s):  
Thermal Deformation ◽  
Work Performance ◽  
Cylinder Liner ◽  
Connecting Rod ◽  
Piston Skirt ◽  
Piston Cylinder ◽  
Lubrication Performance ◽  
Rod System ◽  
Liner System ◽  
Secondary Motion

The work performance of piston-cylinder liner system is affected by the lubrication condition and the secondary motion of the piston. Therefore, more and more attention has been paid to the secondary motion and lubrication of the piston. In this paper, the Jakobson-Floberg-Olsson (JFO) boundary condition is employed to describe the rupture and reformation of oil film. The average Reynolds equation of skirt lubrication is solved by the finite difference method (FDM). The secondary motion of piston-connecting rod system is modeled; the trajectory of the piston is calculated by the Runge-Kutta method. By considering the inertia of the connecting rod, the influence of the longitudinal and horizontal profiles of piston skirt, the offset of the piston pin, and the thermal deformation on the secondary motion and lubrication performance is investigated. The parabolic longitudinal profile, the smaller top radial reduction and ellipticities of the middle-convex piston, and the bigger bottom radial reduction and ellipticities can effectively reduce the secondary displacement and velocity, the skirt thrust, friction, and the friction power loss. The results show that the connecting rod inertia, piston skirt profile, and thermal deformation have important influence on secondary motion and lubrication performance of the piston.

Crank-Angle Resolved In-Cylinder Friction Measurements With the Instantaneous IMEP Method

2005 ◽  
Author(s):  
M. E. Leustek ◽  
C. Sethu ◽  
S. Bohac ◽  
Z. Filipi ◽  
D. Assanis
Keyword(s):  
Engine Speed ◽  
Operating Conditions ◽  
Spark Ignition Engine ◽  
Design Parameters ◽  
Connecting Rod ◽  
Pressure Transducers ◽  
Crank Angle ◽  
Friction Measurements ◽  
Force Calibration ◽  
Speed Fluctuations

The instantaneous IMEP method is used to measure crank-angle resolved in-cylinder friction force in a series production spark ignition engine as a function of design parameters and operating conditions. An improved telemetry system, which continues to provide data after 50+ hours of operation at speeds as high as 2000 rpm, is presented. Primary sources of error associated with the technique will be presented. These include intra-cycle engine speed fluctuations, the effect of thermal shock on pressure transducers, the effect of connecting rod force calibration and measurement error. The instantaneous IMEP method is used to measure crank-angle resolved in-cylinder engine friction as functions of engine speed and coolant (oil-film) temperature. Both crank-angle resolved and cycle-integrated results are compared.

scholarly journals Study of the Piston Secondary Movement on the Tribological Performance of a Single Cylinder Low-Displacement Diesel Engine

Lubricants ◽  
2020 ◽  
Vol 8 (11) ◽  
pp. 97
Author(s):  
Jorge Duarte Forero ◽  
Guillermo Valencia Ochoa ◽  
Wlamyr Palacios Alvarado
Keyword(s):  
Mathematical Model ◽  
Diesel Engine ◽  
Hydrodynamic Lubrication ◽  
Lateral Displacement ◽  
Cylinder Liner ◽  
Deformation Model ◽  
Analysis Tool ◽  
Connecting Rod ◽  
Single Cylinder ◽  
Piston Skirt

The present study aims to analyze the secondary movement of the piston considering the deformations present in the piston skirt, the hydrodynamic lubrication, and the effects of the clearances in the connecting rod bearings. The analysis of the piston movement is performed by developing a mathematical model, which was used to evaluate the dynamic characteristics of the piston movement, the slap force on the piston skirt, the effect of the secondary piston movement on the connecting rod, and the influence of clearances in the connecting rod bearings and in the piston. For the study, the geometric of the crankshaft-connecting rod–piston system of a single-cylinder diesel engine is taken as a reference. The deformation model of the piston was carried out by means of a symmetric finite element model (FEM), which was integrated into the mathematical model of the piston. MATLAB® software (The MathWorks Inc., Natick, MA, USA) is used for the development of model simulations. The obtained results show that during the combustion cycle, there are six changes of direction in the secondary movement of the piston with lateral and angular velocities that can reach a magnitude of 0.13 m/s and 4 rad/s. The lateral and angular movement of the piston during its travel causes the appearance of impacts on the piston skirt with the cylinder liner, which produces an increase of approximately 500 N in the hydrodynamic forces in the connecting rod bearings. The force analysis shows that the range of the maximum magnitudes of these forces is between 1900 N and 3480 N. The increase in clearance between the cylinder liner and the piston skirt (Cpc) causes a greater lateral displacement and an increase in the angle of inclination of the piston. Analysis of the change in connecting rod bearing clearance shows that there are critical values in relation to clearance Cpc. The model presented allows us to analyze the different characteristics of the secondary movement of the piston, which involve the interaction between the piston skirt and the cylinder liner. Additionally, the influence of this movement on the connecting rod bearings is considered. The foregoing can be used as an analysis tool for the study of designs and/or modifications in the engine in such a way that greater durability of the components, reductions in acoustic emissions, and reduction in friction losses are achieved.

scholarly journals Numerical Study on the Explosive Separation of Pyrotechnic Cutter

2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
Shihui Xiong ◽  
Yaokun Ye ◽  
Yanhua Li ◽  
Yuquan Wen
Keyword(s):  
Finite Element ◽  
Numerical Study ◽  
Cutting Speed ◽  
Simulation Software ◽  
Cutting Process ◽  
Connecting Rod ◽  
Optimal Distance ◽  
Maximal Speed ◽  
Cutting Effect ◽  
Simulation Results

Pyrotechnic cutters are widely used in the wrapping-band connecting structures of carrier rockets. In this article, a three-dimensional (3D) finite element model of a pyrotechnic cutter is proposed to determine the influence of the explosive dynamic fracture process and the cutter blade acceleration distance on the cutting effect, using AUTODYN finite element simulation software. Numerical simulations of the cutting process reveal that the initial shear speed, the maximal speed, and the speed at which the cutter connects the rod increase linearly with increasing distance between the cutter blade and the cutting board. As the distance increases, the difference between the initial cutting speed and the maximal speed of the cutter gradually decreases and effectively disappears for a distance of 8.5 mm. At this time, the acceleration effect of the gunpowder gas on the cutter is nearly maximal. When the distance between the cutter and the connecting rod is less than 7.5 mm, the cutting time decreases significantly with increasing spacing. For distances between 7.5 mm and 8.5 mm, the distance has little effect on the cutting time as it increases. There is a small increase in the cutting time, and it can be seen that there is an optimal distance between the cutter and the cutting board during the cutting process. The cutting effect is the strongest for this distance. For the cutter studied in this article, the optimal distance was 7.5 mm. In addition, numerical studies were also performed by varying the maximal cutting diameter of the connecting rod of the pyrotechnic cutter. The discrepancy between the simulation results and actual test data was under 10%, and the simulation result for the cut state of the connecting rod was also consistent with the test result. The simulation results in this article can deepen the understanding of the action mechanism and process of the pyrotechnic cutter and reveal the maximal cutting diameter of the connecting rod of the pyrotechnic cutter under different charging conditions. This provides a reference for future cutter design optimization.

A Study on the Fatigue Strength of a Low-Speed Diesel Engine Connecting Rod Made of 42CrMoA

2020 ◽  
Vol 49 ◽  
pp. 139-151
Author(s):  
Wasim M.K. Helal ◽  
Wen Ping Zhang ◽  
Xiao Bo Li ◽  
Gui Xin Wang
Keyword(s):  
Diesel Engine ◽  
Fatigue Limit ◽  
Safety Factor ◽  
Great Influence ◽  
Connecting Rod ◽  
Low Speed ◽  
Factor Evaluation ◽  
Long Stroke ◽  
Minimum Safety Factor ◽  
Moving Parts

In recent years, diesel engine is developing rapidly in the direction of high power and super long stroke, which requires higher strength of its key moving parts. Connecting rod is one of the key moving parts of diesel engine which is subjected to complex alternating load during the working process. This loading condition has a great influence on its structural strength and reliability. In the proposed study, the strength and fatigue of a low-speed diesel engine con-rod made of 42CrMoA are analyzed. The 3-D model of the con-rod assembly built in the proposed study. The stress distribution and deformation of the con-rod assembly under the maximum explosive pressure are presented and studied. In the present paper, fatigue safety factor of all parts of con-rod assembly under the maximum explosive pressure condition is checked. According to the results carried out from the proposed work, the corresponding alternating stress is 340MPa, while the fatigue limit of 42CrMo material is above 430-540MPa, which means that the con-rod parts work under the alternating stress far below the fatigue limit. The kirasushvili method is adopted in the present paper as the standard of safety factor evaluation of con-rod. According to the allowable safety factor table of kirasushvili method, the minimum safety factor of the big and small ends of the con-rod and rod body can meet the requirements without fatigue damage.

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