The Experts below are selected from a list of 225 Experts worldwide ranked by ideXlab platform

Stefan Jonsson - One of the best experts on this subject based on the ideXlab platform.

Madeleine Ekstrom - One of the best experts on this subject based on the ideXlab platform.

Gregory M. Shaver - One of the best experts on this subject based on the ideXlab platform.

  • Oxygen fraction estimation for diesel engines utilizing variable intake valve actuation
    2012 American Control Conference (ACC), 2012
    Co-Authors: Lyle E. Kocher, Karla Stricker, Ed. Koeberlein, D. G. Van Alstine, Gregory M. Shaver
    Abstract:

    Advanced diesel engine architectures employing flexible valve trains enable emissions reductions and fuel economy improvements through advanced combustion strategies. These combustion strategies, such as pre-mixed charge compression ignition (PCCI), homogenous charge compression ignition (HCCI) and low temperature combustion (LTC), are controlled and enabled through the use of flexible valve trains. The in-cylinder oxygen concentration serves as a critical input in controlling these strategies. Unfortunately, the in-cylinder oxygen concentration is extremely difficult to measure on production engines. However, the oxygen concentrations in the intake and Exhaust manifold can be utilized to calculate the in-cylinder oxygen concentration when the charge and residual in-cylinder mass are available. A model-based observer is developed to estimate the oxygen concentration in the intake and Exhaust Manifolds. The oxygen concentration estimates will be sensitive to errors in the mass flows of the manifold filling dynamics. To improve the EGR flow measurement, a high-gain observer is implemented to provide a more accurate EGR flow estimate. The observer estimates the oxygen concentrations to within 0.5% O2 and converges in less than 0.5 seconds.

A Benoit - One of the best experts on this subject based on the ideXlab platform.

  • cyclic behaviour of structures under thermomechanical loadings application to Exhaust Manifolds
    International Journal of Fatigue, 2012
    Co-Authors: A Benoit, M H Maitournam, L Remy, Frederic Oger
    Abstract:

    A structure subjected to thermomechanical cyclic loadings may exhibit various cyclic behaviours: perfect elasticity, elastic shakedown, plastic shakedown and ratchetting. The quantitative characterization of these different asymptotic states is addressed in this paper, in the context of the Generalized Standard Materials (GSM). Criteria are established to identify them and capture the trend line of their evolution, in the context of numerical simulation. The definitions are extended to the case of temperature dependent mechanical properties. Simple strain paths are first considered to illustrate the relevancy of the proposition. Finally, as an application, the example of an Exhaust manifold subjected to a classical thermomechanical fatigue test is analyzed.

  • asymptotic behaviour of structures subjected to thermomechanical cyclic loadings application to Exhaust Manifolds
    2010
    Co-Authors: A Benoit, L Remy, Habibou Maitournam, Frederic Oger
    Abstract:

    Under cyclic loadings, structures can show different types of asymptotic behaviour: elastic shakedown when the asymptotic answer is purely elastic, cyclic plasticity when plastic deformations become periodic and ratchetting, plastic deformations will then accumulate and lead to the ruin of the structure. For industrial components, elastic shakedown is related to high cycle fatigue, while cyclic plasticity and ratchetting mean low cycle fatigue, but ratchetting must be prevented since it could drastically limits the lifetime of the structure. In the automotive industry, cold parts like suspension systems often present elastic shakedown whereas hot parts like Exhaust systems and cylinder heads are subjected to thermomechanical loadings and often exhibit cyclic plasticity. To evaluate the lifetime of components, one can follow the evolution of a damage variable or use a fatigue criterion that assesses the lifetime of a structure from macroscopic thermomechanical quantities evaluated on the stabilized cycle. Ambrico and Begley suggested a method to identify the different types of asymptotic behaviour in the case of fretting. In this study, we propose slightly different definitions of the cyclic part and of the ratchetting part of the deformation. The ratchetting part of the deformation er(t) is built for all instants t, taking account of the whole evolution of the plastic deformation during the cycle. Then a new definition of the amplitude of the cyclic plastic deformation during cycle k, Dec(k) is given. This definition takes into account multiaxial loadings and corresponds to the difference between two deformation states really reached during the cycle. This method is adapted to thermo-mechanical loadings with a material which mechanical characteristics depend on temperature. Finally, an application example is given on an Exhaust manifold subjected to a classical thermomechanical fatigue test

Karla Stricker - One of the best experts on this subject based on the ideXlab platform.

  • Oxygen fraction estimation for diesel engines utilizing variable intake valve actuation
    2012 American Control Conference (ACC), 2012
    Co-Authors: Lyle E. Kocher, Karla Stricker, Ed. Koeberlein, D. G. Van Alstine, Gregory M. Shaver
    Abstract:

    Advanced diesel engine architectures employing flexible valve trains enable emissions reductions and fuel economy improvements through advanced combustion strategies. These combustion strategies, such as pre-mixed charge compression ignition (PCCI), homogenous charge compression ignition (HCCI) and low temperature combustion (LTC), are controlled and enabled through the use of flexible valve trains. The in-cylinder oxygen concentration serves as a critical input in controlling these strategies. Unfortunately, the in-cylinder oxygen concentration is extremely difficult to measure on production engines. However, the oxygen concentrations in the intake and Exhaust manifold can be utilized to calculate the in-cylinder oxygen concentration when the charge and residual in-cylinder mass are available. A model-based observer is developed to estimate the oxygen concentration in the intake and Exhaust Manifolds. The oxygen concentration estimates will be sensitive to errors in the mass flows of the manifold filling dynamics. To improve the EGR flow measurement, a high-gain observer is implemented to provide a more accurate EGR flow estimate. The observer estimates the oxygen concentrations to within 0.5% O2 and converges in less than 0.5 seconds.

  • Physically based volumetric efficiency model for diesel engines utilizing variable intake valve actuation
    International Journal of Engine Research, 2012
    Co-Authors: Lyle Kocher, Karla Stricker, Ed. Koeberlein, D. G. Van Alstine, Gregory Shaver
    Abstract:

    Advanced diesel engine architectures employing flexible valve trains enable emissions reductions and fuel economy improvements. Flexibility in the valve train allows engine designers to optimize the gas exchange process in a manner similar to how common rail fuel injection systems enable optimization of the fuel injection process. Modulating valve timings directly impacts the volumetric efficiency of the engine since it directly controls how much mass is trapped in the cylinders. In fact, it will be shown that the control authority of valve timing modulation over volumetric efficiency, that is, the range of volumetric efficiencies achievable due to modulation of the valve timing, is three times larger than the range achievable by modulation of other engine actuators such as the Exhaust gas recirculation valve or the variable geometry turbocharger. Traditional empirical or regression-based models for volumetric efficiency, while suitable for conventional valve trains, are therefore challenged by flexible valve trains. The added complexity and additional empirical data needed for wide valve timing ranges limit the usefulness of these methods. A simple physically based volumetric efficiency model was developed to address these challenges. The model captures the major physical processes occurring over the intake stroke, and is applicable to both conventional and flexible intake valve trains. The model inputs include temperature and pressure in both the intake and Exhaust Manifolds, intake and Exhaust valve event timings, engine cylinder bore, stroke, connecting rod lengths, engine speed, and effective compression ratio. The model is physically based, requires no regression tuning parameters, is generalizable to other engine platforms, and has been experimentally validated using an advanced multi-cylinder diesel engine equipped with a fully flexible variable intake valve actuation system. Experimental data were collected over a wide range of the operating space of the engine and augmented with air handling actuator and intake valve timing sweeps to maximize the range of conditions used to thoroughly experimentally validate the model for a total of 286 operating conditions. The physically based volumetric efficiency model will be shown to predict the experimentally calculated volumetric efficiency to within 5 per cent for all cases with a root mean square error of less than 2.5 per cent for the entire dataset. The physical model developed differs from previous physical modelling work through the novel application of effective compression ratio, incorporation of no tuning parameters, and extensive validation on a unique engine test bed with fully flexible intake valve actuation.