Probabilistic Main Bearing Performance for an Internal Combustion Engine

2004 ◽  
Author(s):  
Zissimos P. Mourelatos ◽  
Nickolas Vlahopoulos ◽  
Omidreza Ebrat ◽  
Jinghong Liang ◽  
Jin Wang
Keyword(s):  
Performance Measures ◽  
Probabilistic Analysis ◽  
Combustion Engine ◽  
Random Variables ◽  
Simulation Models ◽  
Threshold Value ◽  
Oil Viscosity ◽  
Main Bearing ◽  
Structural Dynamic ◽  
Engine System

A probabilistic analysis is presented for studying the variation effects on the main bearing performance of an I.C. engine system, under structural dynamic conditions. For computational efficiency, the probabilistic analysis is based on surrogate models (metamodels), which are developed using the kriging method. An Optimum Symmetric Latin Hypercube (OSLH) algorithm is used for efficient “space-filling” sampling of the design space. The metamodels provide an efficient and accurate substitute to the actual engine bearing simulation models. The bearing performance is based on a comprehensive engine system dynamic analysis which couples the flexible crankshaft and block dynamics with a detailed main bearing elastohydrodynamic analysis. The clearance of all main bearings and the oil viscosity comprise the random variables in the probabilistic analysis. The maximum oil pressure and the percentage of time within each cycle that a bearing operates with oil film thickness below a threshold value of 0.27 μm at each main bearing constitute the system performance measures. Probabilistic analyses are first performed to calculate the mean, standard deviation and probability density function of the bearing performance measures. Subsequently, a probabilistic sensitivity analysis is described for identifying the important random variables. Finally, a Reliability-Based Design Optimization (RBDO) study is conducted for optimizing the main bearing performance under uncertainty. Results from a V6 engine are presented.

Probabilistic Analyses for the Performance Characteristics of the Main Bearings in an Operating Engine Due to Variability in Bearing Properties

2003 ◽  
Author(s):  
Jin Wang ◽  
Nickolas Vlahopoulos ◽  
Zissimos P. Mourelatos ◽  
Omidreza Ebrat ◽  
Kumar Vaidyanathan
Keyword(s):  
Design Space ◽  
Combustion Engine ◽  
Hydrodynamic Lubrication ◽  
Simulation Models ◽  
Threshold Value ◽  
Integrated System ◽  
Probabilistic Methods ◽  
System Level ◽  
Oil Viscosity ◽  
Main Bearing

This paper presents the development of surrogate models (metamodels) for evaluating the bearing performance in an internal combustion engine. The metamodels are employed for performing probabilistic analyses for the engine bearings. The metamodels are developed based on results from a simulation solver computed at a limited number of sample points, which sample the design space. An integrated system-level engine simulation model, consisting of a flexible crankshaft dynamics model and a flexible engine block model connected by a detailed hydrodynamic lubrication model, is employed in this paper for generating information necessary to construct the metamodels. An optimal symmetric Latin hypercube algorithm is utilized for identifying the sampling points based on the number and the range of the variables that are considered to vary in the design space. The development of the metamodels is validated by comparing results from the metamodels with results from the actual simulation models over a large number of evaluation points. Once the metamodels are established they are employed for performing probabilistic analyses. The initial clearance between the crankshaft and the bearing at each main bearing and the oil viscosity comprise the random variables in the probabilistic analyses. The maximum oil pressure and the percentage of time (the time ratio) within each cycle that a bearing operates with oil film thickness less than a user defined threshold value at each main bearing constitute the performance variables of the system. The availability of the metamodels allows comparing the performance of several probabilistic methods in terms of accuracy and computational efficiency. A useful insight is gained by the probabilistic analysis on how variability in the bearing characteristics affects its performance.

scholarly journals Reliability-Based Safety Evaluation of the BISTOON Historic Masonry Arch Bridge

2020 ◽  
Vol 30 (1) ◽  
pp. 87-110 ◽  
Author(s):  
Majid Pouraminian ◽  
Somayyeh Pourbakhshian ◽  
Ehsan Noroozinejad Farsangi ◽  
Sevil Berenji ◽  
Salman Keyani Borujeni ◽  
...  
Keyword(s):  
Probabilistic Analysis ◽  
Safety Evaluation ◽  
Random Variables ◽  
Load Resistance ◽  
Maximum Tensile Stress ◽  
Safety Index ◽  
Limit States ◽  
Masonry Arch ◽  
Arch Bridge ◽  
Historic Masonry

AbstractThis research examines the probabilistic safety assessment of the historic BISTOON arch bridge. Probabilistic analysis based on the Load-Resistance model was performed. The evaluation of implicit functions of load and resistance was performed by the finite element method, and the Monte-Carlo approach was used for experiment simulation. The sampling method used was Latin Hypercube. Four random variables were considered including modulus of elasticity of brick and infilled materials and the specific mass of brick and infilled materials. The normal distribution was used to express the statistical properties of the random variables. The coefficient of variation was defined as 10%. Linear behavior was assumed for the bridge materials. Three output parameters of maximum bridge displacement, maximum tensile stress, and minimum compressive stress were assigned as structural limit states. A sensitivity analysis for probabilistic analysis was performed using the Spearman ranking method. The results showed that the sensitivity of output parameters to infilled density changes is high. The results also indicated that the system probability of failure is equal to p fsystem =1.55 × 10−3. The bridge safety index value obtained is βt = 2.96, which is lower than the recommended target safety index. The required safety parameters for the bridge have not been met and the bridge is at the risk of failure.

Analysis of the M x/G/1 queue by N-policy and multiple vacations

1994 ◽  
Vol 31 (02) ◽  
pp. 476-496
Author(s):  
Ho Woo Lee ◽  
Soon Seok Lee ◽  
Jeong Ok Park ◽  
K. C. Chae
Keyword(s):  
Performance Measures ◽  
Queue Length ◽  
Time Distribution ◽  
Queueing System ◽  
Random Variables ◽  
System Size ◽  
The Other ◽  
Waiting Time Distribution ◽  
Multiple Vacations ◽  
Linear Cost

We consider an Mx /G/1 queueing system with N-policy and multiple vacations. As soon as the system empties, the server leaves for a vacation of random length V. When he returns, if the queue length is greater than or equal to a predetermined value N(threshold), the server immediately begins to serve the customers. If he finds less than N customers, he leaves for another vacation and so on until he finally finds at least N customers. We obtain the system size distribution and show that the system size decomposes into three random variables one of which is the system size of ordinary Mx /G/1 queue. The interpretation of the other random variables will be provided. We also derive the queue waiting time distribution and other performance measures. Finally we derive a condition under which the optimal stationary operating policy is achieved under a linear cost structure.

scholarly journals A Design of the Compression Chamber and Optimization of the Sealing of a Novel Rotary Internal Combustion Engine Using CFD

Energies ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2362
Author(s):  
Savvas Savvakis ◽  
Dimitrios Mertzis ◽  
Elias Nassiopoulos ◽  
Zissis Samaras
Keyword(s):  
Internal Combustion Engine ◽  
Cfd Simulation ◽  
Combustion Engine ◽  
Numerical Study ◽  
Simulation Models ◽  
Internal Combustion ◽  
Intake Port ◽  
Significant Difference ◽  
Port Design ◽  
Compression Chamber

The current paper investigates two particular features of a novel rotary split engine. This internal combustion engine incorporates a number of positive advantages in comparison to conventional reciprocating piston engines. As a split engine, it is characterized by a significant difference between the expansion and compression ratios, the former being higher. The processes are decoupled and take place simultaneously, in different chambers and on the different sides of the rotating pistons. Initially, a brief description of the engine’s structure and operating principle is provided. Next, the configuration of the compression chamber and the sealing system are examined. The numerical study is conducted using CFD simulation models, with the relevant assumptions and boundary conditions. Two parameters of the compression chamber were studied, the intake port design (initial and optimized) and the sealing system size (short and long). The best option was found to be the combination of the optimized intake port design with the short seal, in order to keep the compression chamber as close as possible to the engine shaft. A more detailed study of the sealing system included different labyrinth geometries. It was found that the stepped labyrinth achieves the highest sealing efficiency.

Comparison of VISSIM and CORSIM Traffic Simulation Models on a Congested Network

2000 ◽  
Vol 1727 (1) ◽  
pp. 52-60 ◽  
Author(s):  
Loren Bloomberg ◽  
Jim Dale
Keyword(s):  
Sensitivity Analysis ◽  
Performance Measures ◽  
Traffic Simulation ◽  
Simulation Models ◽  
Design Decision ◽  
Simulation Tools ◽  
Critical Design ◽  
Complex Program ◽  
Comparative Information ◽  
Model Approach

Traffic simulation packages like CORSIM and VISSIM are frequently used as tools for the analysis of traffic since they are effective approaches for quantification of the benefits and limitations of different alternatives. The concern of those who are cautious or skeptical about the application of a complex program to making a critical design decision is often appropriate, as many models are unproven or little information about their accuracy is available. As these simulation models become easier to use, it may be practical to use more than one model in some studies. The two-model approach was applied as a means of making the analysis more reliable and the results more defensible. The results proved the consistency and reasonableness of the simulation tools and provided everyone involved with confidence about the analysis. The study also illustrated the value of using a range of performance measures and a sensitivity analysis. More generally, it proved the value of providing as much comparative information as possible before making a design decision. The results were generally consistent, and the end product was a set of clear, defensible, and well-supported conclusions. Although the experience gained through the application of CORSIM and VISSIM was in some ways unique to the study area, this experience can provide insight to other transportation professionals charged with selecting and applying these simulation models to similar networks. To that end, some of the characteristics of both models are contrasted.

Computational Methods Applied to Modelica Simulation Models in a Web Based Framework

2005 ◽  
Author(s):  
Bjo¨rn Johansson
Keyword(s):  
Design Optimization ◽  
Computational Methods ◽  
Probabilistic Analysis ◽  
Service Oriented Architecture ◽  
Simulation Models ◽  
Computational Design ◽  
Design Data ◽  
Web Based ◽  
Actuation System ◽  
Service Oriented

In this paper, it is illustrated how computational design methods such as design optimization and probabilistic analysis is applied to system simulation models in a web based framework. Special emphasis is given models defined in the Modelica modeling language. An XML-based information system for representation and management of design data for use together with Modelica models as well as other types of models is proposed. This approach introduces a separation between the model of the system and data related to the design of the product. This is important in order to facilitate the use of computational methods in a generic way. A web based framework for integration of simulation models and computational methods is further illustrated. The framework is based on open standards for distributed computing and enables so-called service oriented architecture. Finally, an example is presented, where design optimization and probabilistic analysis is carried out on a Modelica model of an aircraft actuation system using the proposed and implemented tools and methods.

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