Surrogate model that enables replication of essential variables from a master cylinder to the remaining cylinders with appropriate phasing.1-dimensional engine mechanics model that uses less computational resources than multibody option.SCR: Selective Catalytic Reduction, map based.DPF: Diesel Particulate Filter, map based.DOC: Diesel Oxidation Catalyst, map based.Three-way catalytic converter: map based, or chemical kinetic based.A Dymola engine and/or controller model can be compiled to an FMU that can be run in other simulation environments, such as Simulink or DSpace. Turbocharger: Stodola and Ellipse law and map based, or equation based.Heat release model: it consists of a Wiebe heat release model and a predictive combustion model.Reaction model: table based that predicts combustion species.Knock detection: empirical correlation based that classifies knocks to no knock, trace knock, medium knock and strong knock.BMEP: calculates IMEP, PEMP, FMEP, BMEP, BSFC, brake torque and brake power.The following lists all the components in Figure 8. Introduction of the model structures and their functionalities can be found inįigure 8. Figure 8: A collection of some of the VeSyMA-Engines components Figure 7: A three cylinder naturally aspirated engine modelĪn engine model consists of an intake, an exhaust, a timing, a camshaft, a cylinder block, a crankshaft, a friction model, a starter motor, a cooling circuit and a lubrication circuit. Figure 6: Engine-on-dyno experimentsĪn engine-on-dyno experiment includes the engine model, ECU, rig controller, dynamometer, cooling system and lubrication system, see Figure 6. The VeSyMA-Engines library contains two types of engine model: crank angle resolved and mean value. That will need to be analysed separately. For higher load points, the valve timing effects may not apply consistently across the higher load points. Advancing the intake valve opening also improves BSFC. Advancing the exhaust valve opening will always result a higher BSFC and is not beneficial. larger effective expansion to compression ratio. Retarding intake opening will also benefit BSFC due to improved effective compression ratio, i.e. This is because the delayed exhaust opening allows for a slightly increased expansion work. In summary, in the part load condition analysed in this blog post, retarding the exhaust valve opening will always yield an improved BSFC. In the top centre of figure 1, retarding exhaust opening will improve BSFC by 1.62%. However retarding the intake valve opening, without retarding the exhaust valve opening will improve BSFC, see middle right in figure 1. In the middle left in figure 1, advancing the intake valve opening, without retarding the exhaust valve opening does not increase or decrease fuel consumption. It is seen that advancing the exhaust valve opening is not beneficial for improving fuel consumption. A more detailed introduction of the VeSyMA-Engines can be found in Figure 8 in the appendix.įor the two cases at the bottom left and the bottom centre in Figure 1, early exhaust valve opening reduces the expansion work, which shortens the time for the exhaust gas to expel which results in a higher mass of exhaust gas remaining in the cylinder as IEGR, figure 4. The specific heat release model used in this work is predictive combustion model based which is a kinetic energy based semi-dimensional model that models thermodynamics, turbulence, ignition delay and flame entrainment, as it is used in the engine model shown in Figure 6 and Figure 7 in appendix. This blog post uses VeSyMA-Engines for the simulation work, which is one of the products of Claytex Ltd. Figure 1 shows the BSFC improvement against intake valve opening (IVO) and exhaust valve closing (EVC). Throttle angle and spark timing are controlled to keep the specified load and MFB50 condition for each set of intake valve and exhaust valve timing. Mass fraction burned at 50% (MFB50) is maintained at 8 degrees after TDC (aTDC). All experiments are run at stochiometric AFR. This blog post carries out an investigation at part load condition (3000 RPM, 3 Bar BMEP) for a three-cylinder 1 Litre SI engine with VVT to analyse the benefit of VVT on fuel consumption. The effects of continuously variable valve timing (VVT) are relatively well known.
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