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Technical Paper

Engine Excitation Decomposition Methods and V Engine Results

2001-04-30
2001-01-1595
Engine excitation forces have been studied in the past using one of two methods; a lumped sum or a totally distributed approach. The lumped sum approach gives the well-understood engine inherent unbalance and the totally distributed approach is used in engine CAE models to determine the overall engine response. The approach that will be described in this paper identifies an intermediate level of sophistication. The methodology implemented considers single cylinder forces on the engine block, piston side thrust and main bearing forces, and decomposes them into their order content. The forces are then phased and geometrically distributed appropriately for each cylinder and then each order is analyzed relative to know distributions that are NVH concerns, V-block breathing, block side wall breathing, and block lateral and vertical bending.
Technical Paper

Concept Level Powertrain Radiated Noise Analysis

1999-05-17
1999-01-1746
Powertrain radiated noise is an important design factor that must be evaluated during the concept phase of the design process. Unfortunately, the tools currently available to evaluate radiated noise, empirically derived relationships, detailed CAE models, or experimental data, are not useful during this critical phase of the design when many of the fundamental design aspects are determined. Empirical models are too general to capture the impact of many typical design decisions, and detailed CAE models or hardware tests are not practical due to the level of design detail necessary, the cost involved, and the timing. This paper lays out a simplified approach for the prediction of powertrain radiated noise that is useful for both quantitative and qualitative evaluation of design alternatives.
Journal Article

Idle Combustion Stability Modeling

2011-05-17
2011-01-1501
Idle Combustion Stability has previously been difficult to predict prior to prototype engine development. This paper describes an empirical modeling approach to predicting upfront idle combustion stability. The model outputs are the combustion torque harmonic magnitudes and %LNV. The paper describes the modeling methodology and provides correlation results for different engine configurations.
Technical Paper

Eliminating Piston Slap through a Design for Robustness CAE Approach

2003-05-05
2003-01-1728
Piston slap is a problem that plagues many engines. One of the most difficult aspects of designing to eliminate piston slap is that slight differences in operating conditions and in part geometries from build to build can create large differences in the magnitude of piston slap. In this paper we will describe a design for robustness CAE approach to eliminating piston slap. This approach considers the variations of the significant control factors in the design, e.g. piston pin offset, piston skirt design, etc. as well as the variation in the noise factors the system is subjected to, e.g. assembly clearance, skirt collapse, peak cylinder pressure, cylinder pressure rise rate, and location of peak cylinder pressure. Using analytical knowledge about how these various factors impact the generation of piston slap, a piston design for low levels of piston slap can be determined that is robust to the various noise factors.
Technical Paper

Combustion Uniformity as a Measure for Engine Idle NVH

2003-05-05
2003-01-1429
Low levels of Engine Idle Shake are required to produce a vehicle that delivers to the customer the overall perception of quality. Some previous metrics used to measure idle shake, e.g. SDIMEP, LNV, etc. have not always been good discriminators of engines that produced low levels of idle shake and those that did not. This paper will propose a new metric, Combustion Uniformity, that does a better job of describing the phenomena that creates idle shake. This new metric will then be used to describe how different distributions of cylinder-to-cylinder variation create different levels of Combustion Uniformity and how those levels of Combustion Uniformity compare to previous metrics.
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