Estimation of exhaust gas aerodynamic force on the variable geometry turbocharger actuator: 1D flow model approach (original) (raw)
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Acta Mechanica Slovaca, 2011
In the present work, a numerical study of a turbulent flow through a turbocharger turbine in a static state is presented. Solutions of the time averaged Navier-Stokes in conjunction with the standard k-f turbulence model were developed using a control volume discretization method. The resolution was found by the commercial code Fluent 5.6. Geometry and the meshing were built by the software Gambit 6.1. This study is expected to provide a finer knowledge of structures of the flow such as velocity, pressure, turbulent kinetic energy, dissipation rate of the turbulent kinetic energy and viscosity. The proposed model has been tested on a turbocharger turbine of type Garrett TA03 automotive engines. The numerical results have been compared with ones found by other experimental results.
Simulation of the Performance of a Variable Geometry Turbocharger for Diesel Engine Road Propulsion
Advanced research work has lead to the development of a new simulation program and the thermodynamic parameters at engine inlet and exhaust of an engine-mounted variable-geometry turbine can thus be evaluated. The machine is divided into characteristic sub-blocks and resolution of thermomechanical flow equations is carried out using the necessary geometrical parameters. A detailed study of losses is conducted experimentally and numerically into the scroll, the vaned nozzle and the rotor in relation to nozzle opening angles. Simulation results made on the variable geometry turbine are analyzed in relation to main flow entry parameters and are compared systematically with experimental data gathered on turbocharger test equipment, and on a Diesel engine used for industrial applications.
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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...
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SAE Technical Paper Series
The modern automotive industry is under strict regulations to reduce emissions to comply with the Kyoto Protocol, a universally acknowledged treaty aiming at reducing exhaust gas emissions. In order to achieve the required future emission reduction targets, further developments on gasoline engines are required. One of the main methods to achieve this goal is the application of engine downsizing. Turbocharging is a cost-effective method of downsizing an engine whilst reducing exhaust gas emissions, reducing fuel consumption and maintaining prior performance outputs. For these reasons, the turbocharging is becoming the most widely adopted technology in the automotive markets. In 2012, 32% of passenger and commercial vehicles sold had a turbocharger installed, and is predicted to be 40% of 2017 [1]. Even if the engine turbocharging is a widespread technology, there are still drawbacks present in current turbocharging systems. The main problem is overcoming the issue of turbo-lag, which is the poor initial response of the turbocharger to the driver commands due to its inertia. Indeed, the system turbine plus compressor is characterized by an own rotational inertia, therefore, the turbocharger will take a certain time to accelerate and produce the desired boost when a higher amount of exhaust gas is sent to the system. In this work, an innovative solution to the turbo-lag phenomenon will be analyzed: a vaneless stator-axial flow turbine. The proposed turbine configuration would improve the transient response of the system since the axial turbine has intrinsically a lower inertia than the radial turbine as stated by the research works of Ford first [2] and Honeywell after [3]. The whole design process is presented in this paper and particular relevance has been given to the thermo-fluid-dynamic aspect of the machine. Several CFD investigations have been carried out in order to deeply understand the new turbine behavior and, thanks to a 1D model of the target engine, it has been possible to validate the new design simulating the performance of the system engine + turbocharger.
Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 2020
In our previous paper, the steady-state test results of a mixed flow turbine with variable nozzle vanes for a turbocharger are reported. In this paper, the transient response of the same mixed flow turbine along with that of a similarly sized radial flow turbine is presented. The turbine size is suitable for handling the flow capacity of the diesel engines with swept volume up to 1.5 L. The previous experimental test set up is modified by adding a quick-release valve – actuation system before the turbine inlet to obtain a transient response. The radial and mixed flow turbines are tested for different turbine inlet pressures and for various opening positions of the nozzle vanes while matching the turbine mass flow parameters between radial and mixed flow turbines. Typically at nozzle vane openings corresponding to 50% mass flow parameter and 1.5 bar (abs) pressure at the inlet to the turbine, the transient response time for the turbine with mixed flow variable nozzle vanes configurat...
Variable Geometry Mixed Flow Turbine for Turbochargers: An Experimental Study
International Journal of Fluid Machinery and Systems, 2008
This paper investigates a variable geometry (VG) mixed flow turbine with a novel, purposely designed pivoting nozzle vane ring. The nozzle vane ring was matched to the 3-dimensional aspect of the mixed flow rotor leading edge with lean stacking. It was found that for a nozzle vane ring in a volute, the vane surface pressure is highly affected by the flow in the volute rather than the adjacent vane surface interactions, especially at closer nozzle positions. The performance of the VG mixed flow turbine has been evaluated experimentally in steady and unsteady flow conditions. The VG mixed flow turbine shows higher peak efficiency and swallowing capacity at various vane angle settings compared to an equivalent nozzleless turbine. Comparison with an equivalent straight vane arrangement shows a higher swallowing capacity but similar efficiencies. The VG turbine unsteady performance was found to deviate substantially from the quasi-steady assumption compared to a nozzleless turbine. This is more evident in the higher vane angle settings (smaller nozzle passage), where there are high possibility of choking during a pulse cycle. The presented steady and unsteady results are expected to be beneficial in the design of variable geometry turbochargers, especially the ones with a mixed flow turbine.
Mechanics & Industry
The turbine, a key component of a turbocharger, is usually characterized by steady flow solutions. This method seems to be physically unrealistic as the fluid flow within a turbine is strongly unsteady due to the pulsating nature of the flow in the exhaust manifold of a reciprocating engine. This paper presents a new 1D gas dynamic code, written in the FORTRAN language, to characterize a radial turbine of one turbocharger embedded to a small gasoline engine. This code presents the novelty of meanline-1D coupling and the feature of numerical schemes choice. In this study, the turbocharger turbine is simulated with six different finite difference schemes. The computed distribution of the downstream mass flow rate, from the different cases, is compared to test data in order to choose the most suitable scheme. Test data are gathered from a developed test facility. Based on the computed results, unsteady performance of the turbine has been computed and discussed for the different schemes...
Determination of Flow Field in the Stator of the Variable Turbocharger
To increase the efficiency of the turbochargers at low engine speeds, the turbines with a directing movable blades are being set up on the branch of the internal combustion engine exhaust system. Blades have the task of directing stream of the exhaust gases to turbine's rotor wings to use in the best way available stream exhaust pressure and improve pre-ramming in the compressor and at lower speeds. In order to eliminate some negative characteristics in the work, some manufacturers in the construction of turbines built in a special part of stator which directs stream of the exhaust gases towards the rotor's wings. To get a clearer picture about the phenomenon of flow between directing blades, and the influence of the directing part of the stator on streaming of the exhaust gases in the stator part of the turbine, it is necessary to make a detailed CFD analysis.