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  • 1.
    Hellström, Fredirk
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Renberg, Ulrica
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Westin, Fredrik
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO (closed 20101231).
    Fuchs, Laszlo
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Industrial Engineering and Management (ITM), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO (closed 20101231).
    Predictions of the Performance of a Radial Turbine with Different Modeling Approaches: Comparison of the Results from 1-D and 3-D CFD2010In: SAE technical paper series, ISSN 0148-7191, no 01-1223Article in journal (Refereed)
    Abstract [en]

    In this paper, the performance of a radial turbine working under pulsatile flow conditions is computed with two different modeling approaches, time resolved 1-dimensional (1-D) and 3-dimensional (3-D) CFD. The 1-D modeling approach is based on measured turbine maps which are used to compute the mass flow rate and work output from the turbine for a given expansion ratio and temperature at the inlet. The map is measured under non-pulsatile flow conditions, and in the 1-D method the turbine is treated as being a quasi-stationary flow device. In the 3-D CFD approach, a Large Eddy Simulation (LES) turbulence approach is used. The objective of LES is to explicitly compute the large scales of the turbulence while modeling the effects of the unresolved scales.

    Three different cases are considered, where the simplest case only consist of the turbine and the most complex case consist of an exhaust manifold and the turbine. Both time resolved data, such as pressure ratio, temperature and shaft torque and time mean data from the two different modeling approaches are compared. The results show that the computed time mean shaft power differs between the two different modeling approaches with as much as 100%. Since the considered operation point for the engine in this study is 1500 rpm with wide open throttle, the turbine operates in an area where the turbine map is extrapolated. Only by using a few operation points from CFD to extend the map, an improvement is achieved for the 1-D results, but still the deviation is large. Also, the pressure ratio and temperature drop over the turbine differs for the used modeling approaches. The causes for the deviations are assessed and discussed to get a better understanding of eventually limitations of the 1-D modeling approach.

  • 2.
    Renberg, Ulrica
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Westin, Fredrik
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.). KTH, School of Industrial Engineering and Management (ITM), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO (closed 20101231).
    Ångström, Hans-Erik
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Fuchs, Laszlo
    KTH, School of Engineering Sciences (SCI), Mechanics, Fluid Mechanics of Industrial Processes.
    Study of Junctions in 1-D & 3-D Simulation for Steady and Unsteady Flow2010In: SAE technical paper series, ISSN 0148-7191, no 01-1050Article in journal (Refereed)
    Abstract [en]

    In this work a comparative study between 1-D and 3-D calculations has been performed on different junctions. The geometries are a 90° T-junction with an area ratio of unity and a 45° junction with an area ratio of 1.78 between the main pipe and the side branch. The latter case had an offset between the centerlines of the main and the branched pipe. The 3-D modeling framework uses the Reynolds Averaged Navier-Stokes (RANS) equations with the k-ε model both for the steady and the unsteady flow cases. The comparison is made both under steady and pulsating flow conditions. The aim has been to assess the 1-D/3-D differences in terms of measures for flow losses.

    There are large discrepancies between the 1-D and 3-D computed losses in junctions. The relative differences between 1-D and 3-D computed losses in isentropic power are 63 % and 175 % for the 90° and the 45 ° junctions without including the losses in downstream pipe legs. These figures are reduced to 12 % and 114 % respectively when including a straight pipe segment of one diameter downstream of the junction outlets.

    For the 90° junction at pulsating flow, the discrepancy in 1-D and 3-D computed loss is lower compared to the steady flow case if comparing only the losses in the junction, but similar to the steady discrepancy if including the downstream pipe losses. For the 45° junction, the discrepancies are much larger. The 1-D loss is near six times that of the corresponding 3-D value if comparing the losses in the junction alone, and 3 times the 3-D value if including the losses in 10 diameter of the outlet pipe.

  • 3. Vuorinen, Ville Anton
    et al.
    Hillamo, Harri
    Kaario, Ossi
    Nuutinen, Mika
    Larmi, Martti
    Fuchs, Laszlo
    KTH, School of Industrial Engineering and Management (ITM), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO (closed 20101231).
    Effect of Droplet Size and Atomization on Spray Formation: A Priori Study Using Large-Eddy Simulation2011In: Flow Turbulence and Combustion, ISSN 1386-6184, E-ISSN 1573-1987, Vol. 86, no 3-4, p. 533-561Article in journal (Refereed)
    Abstract [en]

    The paper is mainly focused to the vast number of researchers who work within direct injection (DI) engine fuel spray simulations. The most common simulation framework today within the community is the Reynolds Averaged Navier Stokes (RANS) approach together with the Lagrangian Particle Tracking (LPT) method. In fact, this study is one of the first studies where high resolution LES/LPT diesel spray modeling is considered. The potential of LES to deepen the present day multidimensional LPT fuel spray simulations is discussed. Spray evolution is studied far from an injector by modeling a spray as a particle laden jet (PLJ). The effect of d on mixing in non-atomizing and atomizing sprays is thoroughly investigated at jet inlet Reynolds number Re = 10(4) and Mach number Ma = 0.3. Based on and justified by rather recent and also quite old ideas, novel and compact views on droplet breakup in turbulent flows are pointed out from the literature. We use LES/LPT to illustrate that even in a low Weber number flow (We < 13) the droplet breakup modeling may need considerable attention in contrast to what is typically assumed in the present-day breakup models. LES and LPT techniques are first applied to essentially confirm certain expected droplet size effects on spray shape in non-atomizing monodisperse sprays. In the simulations LES e.g. produces an expected turbulent dispersion pattern that depends on droplet diameter (d) without a droplet dispersion model in contrast to RANS. A new compact droplet breakup model is formulated and tested for droplets that break with a natural resonance time rate according to the Poisson process. As a result of the study: 1) the analysis gives a rigorous and enriching proof of currently existing views on droplet size effects on mixing, and 2) the presented a priori analysis points out the importance of modeling the resonance breakup even at a low We.

  • 4.
    Westlund, Anders
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO.
    Winkler, Niklas
    KTH, School of Industrial Engineering and Management (ITM), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO.
    Diotallevi, Fabrizio
    KTH, School of Industrial Engineering and Management (ITM), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO.
    Ångström, Hans-Erik
    KTH, School of Industrial Engineering and Management (ITM), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO.
    Predictions and Measurements of Transient NO Emissions for a Two-stage Turbocharged HD Diesel Engine with EGR2008In: Proceedings THIESEL 2008 Conference on Thermo-and Fluid Dynamic Processes in Diesel Engines, 2008Conference paper (Refereed)
  • 5.
    Westlund, Anders
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO.
    Ångström, Hans-Erik
    KTH, School of Industrial Engineering and Management (ITM), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO.
    Evaluation of Techniques for Transient PM-Measurements2008In: SAE Papers 2008-01-1680, SAE International , 2008Conference paper (Refereed)
    Abstract [en]

    PM-emissions during a load transient have been measured regarding particle mass, exhaust transparency and particle number concentrations in different size ranges. The load transient was from low to medium load at constant speed and was performed with a single cylinder research engine. Mass measurements were conducted with a Tapered Element Oscillating Microbalance . Exhaust transparency was measured with an Opacimeter. Particle Number Concentrations were measured with two different Condensation Particle Counters , CPCs, where one of them was equipped with a Particle Size Selector , PSS, in order to distinguish accumulation mode particles from nucleation mode. An Engine Exhaust Particle Sizer , EEPS, was also used in parallel with the CPCs and provided a full size distribution. For dilution, a rotating disc diluter and a two stage ejector diluter was used. In total two stages of hot dilution and one unheated. It was found that all instruments, except the TEOM, had acceptable time resolution for dynamic measurements with the dilution and acquisition setup used in this experiment. In most aspects, the measurements from the different instruments were consistent and the discrepancies could be explained by their measuring principles. In some cases, simultaneous use of different instruments could provide a more detailed description of the emitted PM. It was also concluded that the rotating disc diluter, with some reservations, could be used for transient measurements.

  • 6.
    Westlund, Anders
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO.
    Ångström, Hans-Erik
    KTH, School of Industrial Engineering and Management (ITM), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO.
    Fast Physical Emission Predictions for Off-line Calibration of Transient Control Strategies2009In: SAE Papers 2009-01-1778, SAE International , 2009Conference paper (Refereed)
    Abstract [en]

    A clear trend in engine development is that the engines are becoming more and more complex both regarding components and component-systems as well as controlling them. These complex engines have great potential to minimize emissions but they also have a great number of combinations of setting. Systematic testing to find these optimum settings is getting more and more challenging. A possible remedy is to roughly optimize these settings offline with predictive models and then only perform the fine tuning in the engine test bed. To be able to do so, two things are needed; firstly a engine model that will predict how the different setting affect engine performance and secondly how the engine performance affects the emissions.

  • 7.
    Westlund, Anders
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO.
    Ångström, Hans-Erik
    KTH, School of Industrial Engineering and Management (ITM), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO.
    Fast Physical Prediction of NO and Soot in Diesel Engines2009In: SAE Papers 2009-01-1121, SAE International , 2009Conference paper (Refereed)
    Abstract [en]

    A clear trend in engine development is that the engines are becoming more and more complex both regarding components and component-systems as well as controlling them. These complex engines have great potential to minimize emissions but they also have a great number of combinations of setting. Systematic testing to find these optimum settings is getting more and more challenging. A possible remedy is to roughly optimize these settings offline with predictive models and then only perform the fine tuning in the engine test bed. To be able to do so, two things are needed; firstly a engine model that will predict how the different setting affect engine performance and secondly how the engine performance affects the emissions.

1 - 7 of 7
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