The research activity illustrated in this work has been conceived with the strong intention to introduce a new strategy to identify in the early stages of an engine project the best design concept for a high feature Diesel Cylinder Head capable to satisfy tight quality requirements. The approach follows a precise algorithm based on a Sensitivity Analysis on the reliability and durability of the Cylinder Head to different engine parameters. The proposed analysis should be included into the next generation Analysis Development and Validation plan. The new tool would lead engineers to release a design concept robust enough before to start the standard Virtual Validation loop typically required for the product details definition. Nowadays leaders of the global automotive industry are placing a big effort in order to develop new high confidence math-based simulation tools to reduce engineering costs. ‘Road to Lab to Math (RLM)’ would describes the effort to reduce the amount of on-road testing and replace them with laboratory testing of components and subsystems, and, when possible, by using mathematical models that make evaluation more precise and more representative of in-use conditions. The new strategy here proposed would take a deep step forward in the Road to Lab to Math (RLM) initiative. The Sensitivity Analysis would support engineers to understand the effect on the Cylinder Head structure of varying critical engine parameters in order to recognize the most appropriate design feature. The interaction between causes and effects is obviously not easy to reach especially due to the complexity of the system and the high number of different loads that effect dynamically the structure. Anyway the intention is always to find out a simple relation between the load and the induced stress for unbelievably complicated scheme like the engine structure. If there is no possibility to control the load cycling, the engineers need to design a structure strong enough to guarantee the expected product reliability. To figure out the best architecture and the detailed feature characteristics able to satisfy the expected lifetime without a clear vision on the effective load scheme can be really hard. The Sensitivity Analysis produces a simple estimation between the load and the induced stress for an engine subsystem. The workflow process has been split in three different main objects: Variation Plan as input phase; Virtual Validation for the processing stage; Sensitivity Analysis as output of the algorithm. The processing is performed on math base modeling by using a series of multidisciplinary simulations. The result of each simulation is the input to the others. For the Virtual Validation phase of the Sensitivity Analysis, the standard base engine fatigue analysis has been selected, including the Thermal analysis (Heat release analysis, Coolant flow field, Heat transfer solution) and the Fatigue analysis (High cycle fatigue). The processing task consists meanly in a multiple run of simulations by using the same design configuration but varying interesting engine parameters. The parallel runs generate multiple overlapped maps of wished results (Mean Stress σm, Alternating Stress σa, Safety Factors SF, Temperature Field, at al.). Each map is the outcome of conventional base engine fatigue simulation using a set up of engine parameters. Those are varied within a selected range of interest to create numbers of configurations, each one used as calculation set up for the sequential multidisciplinary fatigue simulation run. This is the core of the method: the Variation plan for the processing input definition. Generally fractional factorial designs like Orthogonal arrays are used for the trial run planning. As engine parameters of interest to be varied all the ones that by experience are able to influence the lifetime of the Cylinder Head are typically selected . Those can be design parameters and therefore values typically determined during the development phase, anyway imposed at least for what concern the nominal target expected. The analysis can take in consideration the sensitivity to the geometry variation as well. The workflow has been applied step by step to a specific high feature Diesel Cylinder Head. Specifics responses to selected engine parameters are evaluated to recognize proper strategies for the design development before to start the standard Virtual Validation loop. The algorithm releases a Sensitivity Map which is defined as a collection of response graphs mapped on the interested location of the Cylinder Head. Moreover based on the established model, it is possible to estimate, through a typical interpolation function f, the response to each parameter set up without performing an additional simulation trial run. The decision of using math-based simulation model is not considered a limit of the analysis rather the highest power and time effective solution to provide a precise and accurate status of in-use conditions. The usage of mathematical models for a so complex problem is a magnifying glass to inspect behaviors and estimate performances where on-road and lab testing fall down. A robust assessment on the correlation between the results from in-laboratory durability testing and the ones achieved by the response graphs required generally a big effort (months of intensive testing). The correlation feedback on a statistical base will provide the possibility to estimate the capability of the chosen Variation Plan. As the number of factors and levels increases, the number of limitations and assumptions is reduced but the number of runs required for the execution of the planned Design of Experiment rapidly outgrows the resources availability. Last but not least, the Sensitivity Analysis to different engine parameters can be used to develop an investigation on specific set up for any durability test procedures. In particular the engine parameters that will affect more the durability of the Cylinder Head can be used as specific acceleration parameter for a dedicated accelerated test. The Sensitivity Analysis provides as well estimated parameters levels set up to get the desired test acceleration The proposed employment of a math based algorithm for the definition of new lab testing activity is an additional deep step forward in the Road to Lab to Math initiative absolutely required by the next generation Product Development Process.

Sensitivity analysis on the reliability and durability of the cylinder head to different engine parameters / Maccarrone, Domenico. - (2012).

Titolo: | Sensitivity analysis on the reliability and durability of the cylinder head to different engine parameters | |

Autori: | ||

Data di pubblicazione: | 2012 | |

Abstract: | The research activity illustrated in this work has been conceived with the strong intention to in...troduce a new strategy to identify in the early stages of an engine project the best design concept for a high feature Diesel Cylinder Head capable to satisfy tight quality requirements. The approach follows a precise algorithm based on a Sensitivity Analysis on the reliability and durability of the Cylinder Head to different engine parameters. The proposed analysis should be included into the next generation Analysis Development and Validation plan. The new tool would lead engineers to release a design concept robust enough before to start the standard Virtual Validation loop typically required for the product details definition. Nowadays leaders of the global automotive industry are placing a big effort in order to develop new high confidence math-based simulation tools to reduce engineering costs. ‘Road to Lab to Math (RLM)’ would describes the effort to reduce the amount of on-road testing and replace them with laboratory testing of components and subsystems, and, when possible, by using mathematical models that make evaluation more precise and more representative of in-use conditions. The new strategy here proposed would take a deep step forward in the Road to Lab to Math (RLM) initiative. The Sensitivity Analysis would support engineers to understand the effect on the Cylinder Head structure of varying critical engine parameters in order to recognize the most appropriate design feature. The interaction between causes and effects is obviously not easy to reach especially due to the complexity of the system and the high number of different loads that effect dynamically the structure. Anyway the intention is always to find out a simple relation between the load and the induced stress for unbelievably complicated scheme like the engine structure. If there is no possibility to control the load cycling, the engineers need to design a structure strong enough to guarantee the expected product reliability. To figure out the best architecture and the detailed feature characteristics able to satisfy the expected lifetime without a clear vision on the effective load scheme can be really hard. The Sensitivity Analysis produces a simple estimation between the load and the induced stress for an engine subsystem. The workflow process has been split in three different main objects: Variation Plan as input phase; Virtual Validation for the processing stage; Sensitivity Analysis as output of the algorithm. The processing is performed on math base modeling by using a series of multidisciplinary simulations. The result of each simulation is the input to the others. For the Virtual Validation phase of the Sensitivity Analysis, the standard base engine fatigue analysis has been selected, including the Thermal analysis (Heat release analysis, Coolant flow field, Heat transfer solution) and the Fatigue analysis (High cycle fatigue). The processing task consists meanly in a multiple run of simulations by using the same design configuration but varying interesting engine parameters. The parallel runs generate multiple overlapped maps of wished results (Mean Stress σm, Alternating Stress σa, Safety Factors SF, Temperature Field, at al.). Each map is the outcome of conventional base engine fatigue simulation using a set up of engine parameters. Those are varied within a selected range of interest to create numbers of configurations, each one used as calculation set up for the sequential multidisciplinary fatigue simulation run. This is the core of the method: the Variation plan for the processing input definition. Generally fractional factorial designs like Orthogonal arrays are used for the trial run planning. As engine parameters of interest to be varied all the ones that by experience are able to influence the lifetime of the Cylinder Head are typically selected . Those can be design parameters and therefore values typically determined during the development phase, anyway imposed at least for what concern the nominal target expected. The analysis can take in consideration the sensitivity to the geometry variation as well. The workflow has been applied step by step to a specific high feature Diesel Cylinder Head. Specifics responses to selected engine parameters are evaluated to recognize proper strategies for the design development before to start the standard Virtual Validation loop. The algorithm releases a Sensitivity Map which is defined as a collection of response graphs mapped on the interested location of the Cylinder Head. Moreover based on the established model, it is possible to estimate, through a typical interpolation function f, the response to each parameter set up without performing an additional simulation trial run. The decision of using math-based simulation model is not considered a limit of the analysis rather the highest power and time effective solution to provide a precise and accurate status of in-use conditions. The usage of mathematical models for a so complex problem is a magnifying glass to inspect behaviors and estimate performances where on-road and lab testing fall down. A robust assessment on the correlation between the results from in-laboratory durability testing and the ones achieved by the response graphs required generally a big effort (months of intensive testing). The correlation feedback on a statistical base will provide the possibility to estimate the capability of the chosen Variation Plan. As the number of factors and levels increases, the number of limitations and assumptions is reduced but the number of runs required for the execution of the planned Design of Experiment rapidly outgrows the resources availability. Last but not least, the Sensitivity Analysis to different engine parameters can be used to develop an investigation on specific set up for any durability test procedures. In particular the engine parameters that will affect more the durability of the Cylinder Head can be used as specific acceleration parameter for a dedicated accelerated test. The Sensitivity Analysis provides as well estimated parameters levels set up to get the desired test acceleration The proposed employment of a math based algorithm for the definition of new lab testing activity is an additional deep step forward in the Road to Lab to Math initiative absolutely required by the next generation Product Development Process. | |

Appare nelle tipologie: | 8.1 Doctoral thesis Polito |

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`http://hdl.handle.net/11583/2497232`