Physics-based turbine power models for a Variable Geometry Turbocharger (original) (raw)
Related papers
Implementing Turbomachinery Physics into Data Map-Based Turbocharger Models
SAE International journal of engines, 2009
A convenient way of modelling turbochargers is based on data maps. These models are easy to put into place, require low CPU charge and are control-oriented. Data relative to compressor and turbine are read from tables: pressure ratio and efficiency are determined as functions of mass flow rate and rotary speed on two distinct data maps. Nevertheless, this type of model has drawbacks: • Usually, only higher turbocharger speed data are mapped (> 90000 rpm) although the low rpm zone is the most useful zone for normalized driving cycles simulations. Moreover, maps are poorly discretized, leading to the use of specific extra-interpolation methods (many are identified in [5]). • These methods are purely mathematical, which gives inaccurate results in extrapolation zones. Relation between pressure ratio and efficiency is then broken (i.e., if one implements a pumping model for the compressor, the pressure ratio will be affected, but not the efficiency). The present paper develops a new extra/interpolation model incorporating physical laws. An analysis of turbomachinery equations is performed. A new approach for extra-interpolating performance maps, which satisfies the physical laws stated in turbomachinery equations, is derived from this work. Results from this new model are compared with standard methods. The major conclusions drawn from this study are: 1-The new model improves the simulation accuracy while keeping the same easiness of use and robustness. 2-Extrapolation in the low rpm zone is derived from physical equations. 3-This method is applicable to both compressor and turbine. 4-The pressure ratio and efficiency maps are now linked.
Control-oriented turbine power model for a variable-geometry turbocharger
Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, 2017
A control-oriented model for the variable-geometry turbocharger is critical for model-based variable-geometry turbocharger control design. Typically, the variable-geometry turbocharger turbine power is modeled with a fixed mechanical efficiency of the turbocharger on the assumption of an isentropic process. The fixed-efficiency approach is an oversimplification and may lead to modeling errors because of an overpredicted or underpredicted compressor power. This leads to the use of lookup-table-based approaches for defining the mechanical efficiency of the turbocharger. Unfortunately, since the vane position of a variable-geometry turbocharger introduces a third dimension into these maps, real-time implementation requires three-dimensional interpolations with increased complexity. Map-based approaches offer greater fidelity in comparison with the fixed-efficiency approach but may introduce additional errors due to interpolation between the maps and extrapolation to extend the operatio...
Assessment of Cycle Averaged Turbocharger Maps Through One Dimensional and Mean-Line Coupled Codes
Volume 6C: Turbomachinery, 2013
Downsizing the internal combustion engine has been shown to be an effective strategy towards CO 2 emissions reduction, and downsized engines look set to dominate automotive powertrains for years to come. Turbocharging has been one of the key elements in the success of downsized internal combustion engine systems. The process of engine-turbocharger matching during the development stage plays a significant role towards achieving the best possible system performance, in terms of minimizing fuel consumption and pollutant emissions. In current industry practice, engine modeling in most cases does not consider the full unsteady analysis of the turbocharger turbine. Thus, turbocharged engine performance prediction is less comprehensive, particularly under transient load conditions. Commercial one-dimensional engine codes are capable of satisfactory engine performance predictions, but these typically assume the turbocharger turbine to be quasi-steady, hence the inability to fully resolve the pulsating flow performance. On the other hand, a one-dimensional gas dynamic turbine model is capable of simulating the pressure wave propagation in the model domain, thus serving as a powerful tool to analyze the unsteady performance. In addition, a mean-line model is able to compute the turbine power and efficiency through the conservation method and Euler's Turbomachinery Equation. However, none of these mod- * Address all correspondence to this author. eling methods have been widely implemented into commercial one-dimensional engine codes thus far. The objective of this paper is to assess the possibility of numerically producing the steady equivalent cycle averaged turbocharger turbine maps, which could be used in commercial engine codes for performance prediction. The cycle-averaged maps are obtained using a comprehensive turbocharged engine model including accurate pulsating exhaust flow performance prediction. The model is validated against experimental results and effects of flow frequency on the maps are discussed in detail.
Turbocharger matching methodology for improved exhaust energy recovery
10th International Conference on Turbochargers and Turbocharging, 2012
Current engine simulation codes rely on user-input turbine maps to predict the performance of turbocharged engines. These experimentally obtained maps are limited in range as they are typically obtained through the use of an aerodynamically limited turbine loading device, the compressor. In order to extend the range of the map for simulation, several fitting techniques are utilized in order to obtain the values of efficiency and mass flow over the entire range of pressure ratio for all speeds. This investigation compares predicted turbine maps, obtained from narrow ranges of pressure ratio with more reliable, wider maps obtained experimentally for the same turbines by replacing the compressor with a dynamometer. The outcome of this investigation can be used to improve the fitting of efficiency and mass flow rate curves in engine simulation software.
A Scalable Modeling Approach for the Simulation and Design Optimization of Automotive Turbochargers
SAE International Journal of Engines, 2015
Engine downsizing and super/turbocharging is currently the most followed trend in order to reduce CO 2 emissions and increase the powertrain efficiency. A key challenge for achieving the desired fuel economy benefits lies in optimizing the design and control of the engine boosting system, which requires the ability to rapidly sort different design options and technologies in simulation, evaluating their impact on engine performance and fuel consumption.
IFAC Proceedings Volumes
Faults in the intake and exhaust path of turbocharged common rail Diesel engines can lead to an increase of emissions and performance losses. Application of turbocharger models can help to detect and diagnose more faults as standard fault detection methods. The modeling of the turbocharger for onboard fault diagnosis can be obtained by different models. The differences between an approach based on the isentropic efficiencies and an approach based on Euler's turbo-machinery equation are investigated in this paper. The two models for a GT1749MV turbocharger are parameterized with data from the engine testbed. The comparison is applied by issues of measured model inputs, number of intern parameters, parameterization effort and model accuracy. Both models are compared regarding the application for onboard diagnosis.
Review of Turbocharger Mapping and 1D Modelling Inaccuracies with Specific Focus on Two-Stag Systems
SAE Technical Paper Series, 2015
The adoption of two stage serial turbochargers in combination with internal combustion engines can improve the overall efficiency of powertrain systems. In conjunction with the increase of engine volumetric efficiency, two stage boosting technologies are capable of improving torque and pedal response of small displacement engines. In two stage sequential systems, high pressure (HP) and low pressure (LP) turbochargers are packaged in a way that the exhaust gases access the LP turbine after exiting the HP turbine. On the induction side, fresh air is compressed sequentially by LP and HP compressors. The former is able to deliver elevated pressure ratios, but it is not able to highly compressor low flow rates of air. The latter turbo-machine can increase charge pressure at lower mass air flow and be bypassed at high rates of air flow. In fact, bypass valves and waste-gated turbines are often included in two stage boosting systems in order to regulate operations and divert flow away from the turbocharger when necessary. Bypass valves are often external to the turbocharger and wastegates valves are incorporated in the turbine housing. One-dimensional modelling approaches are considered fundamental to investigate interaction between boosting systems and internal combustion engines. In this scenario, turbomachinery performances are imposed into the model through compressor and turbine maps which are previously measured in gas stands as single stages. This procedure could not capture all the effects that occur in a system layout due to combination of heat transfer and motion of internal flow. This has a significant importance for defining HP compressor and LP turbine performances which could be influenced by swirling flows induced by the previous turbo-component in the series. Additionally, bends between the two compressors/turbines can reduce uniformity of flow and cause pressure drops at the same time. As in single turbochargers, heat transfer influences the boundary conditions which would influence performance predictions of the machine in the sequence. In this paper, a review of the available literature containing approaches and study to quantify the effects of heat transfer on turbocharger efficiency and flow non-uniformities on two stage serial turbochargers performance predictions is explored. Furthermore, an appropriate mapping strategy has been proposed which could minimize the cause of inaccuracies in predicting turbochargers performance in two-stage systems. Conclusively, a methodology for map integration into 1D models has been proposed.
Turbine adapted maps for turbocharger engine matching
Experimental Thermal and Fluid Science, 2011
This paper presents a new representation of the turbine performance maps oriented for turbocharger characterization. The aim of this plot is to provide a more compact and suited form to implement in engine simulation models and to interpolate data from turbocharger test bench.
Physical Modeling of Automotive Turbocharger Compressor: Analytical Approach and Validation
SAE Technical Paper Series, 2011
Global warming is a climate phenomenon with worldwide ecological, economic and social impact which calls for strong measures in reducing automotive fuel consumption and thus CO 2 emissions. In this regard, turbocharging and the associated designing of the air path of the engine are key technologies in elaborating more efficient and downsized engines. Engine performance simulation or development, parameterization and testing of model-based air path control strategies require adequate performance maps characterizing the working behavior of turbochargers. The working behavior is typically identified on test rig which is expensive in terms of costs and time required. Hence, the objective of the research project "virtual Exhaust Gas Turbocharger" (vEGTC) is an alternative approach which considers a physical modeled vEGTC to allow a founded prediction of efficiency, pressure rise as well as pressure losses of an arbitrary turbocharger with known geometry. The model is conceived to use smallest possible number of geometry as well as material parameters. Thus, conventional expensive and time-consuming application processes can be countered and test rig as well as in vehicle measurements can be reduced. Furthermore, the vEGTC model enables the prediction of different turbocharger behavior caused by geometry variations. Within this paper it is shown in which way the radial compressor as a representative modeling component can be described by zero-dimensional equations: in order to simulate the working behavior of the compressor the geometry, the thermodynamic state of the inlet-air and the turbocharger speed are assumed to be known. The loss mechanisms are devised using analytical and semi-empirical loss correlations. In order to validate the compressor efficiency the heat transfer from the turbine to the compressor is considered. Finally, the simulation output is compared to manufacturer maps of three different turbochargers pointing out the reliability of the model. Thus, a comprehensive validation of the vEGTC model is yielded. The object-oriented language Modelica is used for modeling and the simulations are provided by the Dymola solver.
2015
The increasing complexity of modern engines has rendered the prototyping phase long and expensive. This is where engine modelling has become, in the recent years, extremely useful and can be used as an indispensable tool when developing new engine concepts. The purpose of this work was to provide a flexible thermodynamic model based on the filling-and-emptying approach for the performance prediction of a four-stroke turbocharged compression ignition engine and to present in the qualitatively point of review the effect of a number of parameters considered affecting the performance of turbocharged diesel engines. To validate the model, comparisons were made between results from a computer program developed using FORTRAN language and the commercial GT-Power software operating under different conditions. The comparisons showed that there was a good concurrence between the developed program and the commercial GT-Power software. The range of variation of the rotational speed of the diesel...