Mean-Line Modelling of a Variable Geometry Turbocharger (VGT) and Prediction of the Engine-Turbocharger Coupled Performance

2017 ◽  
Author(s):  
Anand Mammen Thomas ◽  
Jensen Samuel ◽  
A. Ramesh
Keyword(s):  
Pressure Ratio ◽  
Operating Conditions ◽  
Relaxation Techniques ◽  
Variable Geometry ◽  
Test Bed ◽  
Variable Geometry Turbocharger ◽  
Initial Assumption ◽  
Blockage Factor ◽  
Pressure Boundary Condition ◽  
Variable Geometry Turbine

Mean-line modelling approach which has generally been applied to fixed geometry turbocharger turbines has been extended to predict the performance of the variable geometry turbine for different inlet blade angles. The model uses an initial assumption of turbine inlet pressure which was iteratively corrected based on outlet pressure boundary condition. The model was implemented in MATLAB and stable and convergent solutions were obtained using relaxation techniques for different operating conditions. Experiments were done on a state of the art transient diesel engine test bed using the same VGT turbine in the turbocharger at different engine torques and speeds. Using experimental data the model was calibrated for the aerodynamic blockage in the fixed nozzle and rotor blade passages. Results revealed that turbine overall pressure ratio can be predicted accurately if a blockage factor varying with nozzle blade orientation is used in the model.

Investigation of a Variable Geometry Turbine Nozzle for Diesel Engine Turbochargers

2019 ◽  
Author(s):  
Anuj Srivastava ◽  
Kuldeep Kumar ◽  
Ganesh Banda
Keyword(s):  
Pressure Ratio ◽  
Boost Pressure ◽  
Variable Geometry ◽  
Efficient Design ◽  
Performance Variation ◽  
High Efficient ◽  
Emission Regulations ◽  
Variable Geometry Turbine ◽  
Potential Benefits ◽  
Wide Operating

Abstract High power demand, emission regulations, high efficient design are the prime requirement for the design of turbochargers. VGT (variable geometry turbocharging) is most widely used and explored compared to other available options to deal with today’s market. VGT turbochargers offers several potential benefits when compared to fixed geometry turbochargers, like increased transient response, wide operating range, improved torque characteristics, boost pressure recovery and better fuel economy. In this paper performance variation of compressor and turbine viz, — Pressure ratio, mass flow, and efficiency, and throat area are optimized to reach to the operating point of the engine. Different vane angles (0, +4°, +7°, +10° & +15°) are studied to understand the variation of transient turbine response. Authors also discussed the mechanical conceptualization of the VANT (Variable area nozzle) in thought of having great impact on the performance.

Lean and Straight Nozzle Vanes in a Variable Geometry Turbine: A Steady and Pulsating Flow Investigation

2008 ◽  
Author(s):  
Srithar Rajoo ◽  
R. F. Martinez-Botas
Keyword(s):  
Pressure Ratio ◽  
Velocity Ratio ◽  
Pulsating Flow ◽  
Maximum Pressure ◽  
Variable Geometry ◽  
Flow Investigation ◽  
Variable Geometry Turbine ◽  
The Difference ◽  
Vane Angle ◽  
Ratio Range

Variable Geometry Turbines (VGT) are widely used to improve engine-turbocharger matching and currently common in diesel engines. VGT has proven to provide air boost for wide engine speed range as well as reduce turbo-lag. This paper presents the design and experimental evaluation of a variable geometry mixed flow turbocharger turbine. The tests have been carried out with a permanent magnet eddy current dynamometer within a velocity ratio range of 0.47 to 1.09. The peak efficiency of the variable geometry turbine corresponds to vane angle settings between 60° and 65°, for both the lean and straight vanes in the region of 80%. The variable geometry turbine was tested under pulsating flow with straight and lean nozzle vanes for different vane angle settings, 40Hz and 60Hz flow. In general, the range of mass flow parameter is higher in the straight nozzle vanes with an average of 66.4% and 69.7% for 40Hz and 60Hz flow respectively. The straight nozzle vanes also shows increasing pressure ratio range compared to the lean nozzle vanes, which is more apparent in the maximum pressure ratio experienced by the turbine in an unsteady cycle. In overall, the cycle averaged efficiency in the straight vane configuration is marginally higher than the lean vane. Furthermore, the difference to the equivalent quasi-steady is better in the straight vane configuration compared to the lean vane.

Investigations Into the Performance of a Turbogenerated Biogas Engine During Speed Transients

2011 ◽  
Author(s):  
Ian Thompson ◽  
Stephen Spence ◽  
Charles McCartan ◽  
David Thornhill ◽  
Jonathan Talbot-Weiss
Keyword(s):  
Engine Speed ◽  
Combustion Engine ◽  
Pressure Ratio ◽  
Exhaust Gas ◽  
Variable Geometry ◽  
System Efficiency ◽  
Variable Geometry Turbine ◽  
Exhaust Stream ◽  
Full Power ◽  
System Operating

Turbogenerating is a form of turbocompounding whereby a Turbogenerator is placed in the exhaust stream of an internal combustion engine. The Turbogenerator converts a portion of the expelled energy in the exhaust gas into electricity which can then be used to supplement the crankshaft power. Previous investigations have shown how the addition of a Turbogenerator can increase the system efficiency by up to 9%. However, these investigations pertain to the engine system operating at one fixed engine speed. The purpose of this paper is to investigate how the system and in particular the Turbogenerator operate during engine speed transients. On turbocharged engines, turbocharger lag is an issue. With the addition of a Turbogenerator, these issues can be somewhat alleviated. This is done by altering the speed at which the Turbogenerator operates during the engine’s speed transient. During the transients, the Turbogenerator can be thought to act in a similar manner to a variable geometry turbine where its speed can cause a change in the turbocharger turbine’s pressure ratio. This paper shows that by adding a Turbogenerator to a turbocharged engine the transient performance can be enhanced. This enhancement is shown by comparing the turbogenerated engine to a similar turbocharged engine. When comparing the two engines, it can be seen that the addition of a Turbogenerator can reduce the time taken to reach full power by up to 7% whilst at the same time, improve overall efficiency by 7.1% during the engine speed transient.

Exhaust Pressure Estimation Using a Diesel Particulate Filter Mass Flow Model in a Light-Duty Diesel Engine Operated With Dual-Loop Exhaust Gas Recirculation and Variable Geometry Turbocharger Systems

2014 ◽  
Vol 136 (11) ◽  
Author(s):  
Hyunjun Lee ◽  
Manbae Han ◽  
Jeongwon Sohn ◽  
Myoungho Sunwoo
Keyword(s):  
Mass Flow ◽  
Flow Model ◽  
Operating Conditions ◽  
Particulate Filter ◽  
Exhaust Gas ◽  
Variable Geometry ◽  
Diesel Particulate ◽  
Variable Geometry Turbocharger ◽  
Light Duty ◽  
Gas Recirculation

This paper presents a novel method to estimate an exhaust pressure at 357 different steady-state engine operating conditions using a diesel particulate filter (DPF) mass flow model to precisely control the air quantity for a light-duty diesel engine operated with dual-loop exhaust gas recirculation (EGR) and variable geometry turbocharger (VGT) systems. This model was implemented on a 32 bit real-time embedded system and evaluated through a processor-in-the-loop-simulation (PILS) at two transient engine operating conditions. And the proposed model was validated in a vehicle. By applying Darcy's law, the DPF mass flow model was developed and shows a root mean square error (RMSE) of 3.7 g/s in the wide range of the DPF mass flow and above 99% linear correlation with actual values. With such reasonable uncertainties of the DPF mass flow model, the exhaust pressure was estimated via the application of a nonlinear coordinate transformation to the VGT model. The DPF mass flow based exhaust pressure estimation exhibits below 6% error of the exhaust pressure under steady-state conditions. The method was also validated through the PILS and the vehicle test under transient conditions. The results show a reasonable accuracy within 10% error of the exhaust pressure.

Nonlinear Compensators of Exhaust Gas Recirculation and Variable Geometry Turbocharger Systems using Air Path Models for a CRDI Diesel Engine

2013 ◽  
Vol 136 (4) ◽  
Author(s):  
Yeongseop Park ◽  
Inseok Park ◽  
Joowon Lee ◽  
Kyunghan Min ◽  
Myoungho Sunwoo
Keyword(s):  
Diesel Engine ◽  
Exhaust Gas Recirculation ◽  
Operating Conditions ◽  
Exhaust Gas ◽  
Variable Geometry ◽  
Variable Geometry Turbocharger ◽  
Model Based ◽  
Path Models ◽  
Gas Recirculation ◽  
Feedforward Compensators

This paper investigates the design of model-based feedforward compensators for exhaust gas recirculation (EGR) and variable geometry turbocharger (VGT) systems using air path models for a common-rail direct injection (CRDI) diesel engine to cope with the nonlinear control problem. The model-based feedforward compensators generate set-positions of the EGR valve and the VGT vane to track the desired mass air flow (MAF) and manifold absolute pressure (MAP) with consideration of the current engine operating conditions. In the best case, the rising time to reach 90% of the MAF set-point was reduced by 69.8% compared with the look-up table based feedforward compensators.

scholarly journals Turbocharger surge behavior for sudden valve closing downstream the compressor and effect of actuating variable nozzle turbine

2022 ◽  
Vol 960 (1) ◽  
pp. 012013
Author(s):  
A Danlos ◽  
P Podevin ◽  
M Deligant ◽  
A Clenci ◽  
P Punov ◽  
...  
Keyword(s):  
Flow Rate ◽  
Rotation Speed ◽  
Operating Point ◽  
Variable Geometry ◽  
Variable Geometry Turbocharger ◽  
Engine Torque ◽  
Surge Margin ◽  
Stable Operating ◽  
Servo Actuator ◽  
Variable Geometry Turbine

Abstract Surge is an unstable phenomenon appearing when a valve closing reduces the compressor flow rate. This phenomenon is avoided for automotive turbochargers by defining a surge margin during powertrain system design. This surge margin established with measurements in steady state testing regime limits the maximal engine torque at low levels of output. An active control of the compressor could reduce the surge margin and facilitate a transient compressor operation for a short time in surge zone. In this paper, an experimental study of the transient operation of a turbocharger compressor entering the surge zone is performed. Control of the turbocharger speed is sought to avoid unsteady operation using the variable geometry turbine (VGT) nozzle actuator. From a given stable operating point, surge is induced by reducing the opening of a valve located downstream of the compressor air circuit. The effect of reducing the speed of rotation by controlling the VGT valve is investigated, as this should lead to more stable compressor operation. The rotation speed of the turbocharger is controlled to avoid an unstable operating point using servo-actuator of variable geometry turbine. From a stable operating point, the surge appearance is caused by closing a butterfly valve downstream the air circuit of the compressor. The effect on the compressor rotation speed when the opening of variable geometry turbocharger valve is modified is studied. Measurements have been conducted for different control profiles of the VGT valve placed downstream the compressor. This article presents the means used to carry out these tests as well as the results of the measurements of the instantaneous signals of pressure, temperature, flow rate and rotation speed, allowing the analysis of the surge phenomenon.

Control of a variable-geometry turbocharged and wastegated diesel engine

2005 ◽  
Vol 219 (11) ◽  
pp. 1361-1368 ◽  
Author(s):  
R Rajamani
Keyword(s):  
Diesel Engine ◽  
Time Estimation ◽  
Lyapunov Theory ◽  
Operating Conditions ◽  
Intake Manifold ◽  
Control Synthesis ◽  
Variable Geometry ◽  
Variable Geometry Turbocharger ◽  
Non Linear ◽  
Diagnostic Applications

This paper addresses the problem of controlling a turbocharged diesel engine so as to minimize NOx and smoke emissions while ensuring that the driver's torque demands are met. A diesel engine equipped with a variable-geometry turbocharger (VGT) and an exhaust gas recirculation (EGR) valve is considered. The technical challenges in the control design task include the multivariable non-linear dynamics of the system and the unavailability of key states for feedback. A control strategy based on non-linear control synthesis is developed and shown accurately to control the air-fuel ratio (AFR) and the burned gas fraction in the intake manifold, F1, to desired values in the presence of changing operating conditions. The variables F1 and AFR are shown to be crucial for feedback. Since neither of these variables can be measured, an observer based on flow and pressure sensor measurements is developed for their real-time estimation. Lyapunov theory is used to show that the developed observer is asymptotically stable. Simulation results confirm the performance of the observer and the observer-based feedback controller. The importance of the developed observer extends beyond the application discussed in this paper. It could be useful for a wide variety of different control and diagnostic applications in diesel engines.

Simplified Decoupler-Based Multivariable Controller With a Gain Scheduling Strategy for the Exhaust Gas Recirculation and Variable Geometry Turbocharger Systems in Diesel Engines

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Seungwoo Hong ◽  
Inseok Park ◽  
Jaewook Shin ◽  
Myoungho Sunwoo
Keyword(s):  
Diesel Engines ◽  
Exhaust Gas Recirculation ◽  
Gain Scheduling ◽  
Operating Conditions ◽  
Feedback Controller ◽  
Exhaust Gas ◽  
Variable Geometry ◽  
Variable Geometry Turbocharger ◽  
Scheduling Strategy ◽  
Gas Recirculation

This paper presents a simplified decoupler-based multivariable controller with a gain scheduling strategy in order to deal with strong nonlinearities and cross-coupled characteristics for exhaust gas recirculation (EGR) and variable geometry turbocharger (VGT) systems in diesel engines. A feedback controller is designed with the gain scheduling strategy, which updates control gains according to engine operating conditions. The gain scheduling strategy is implemented by using a proposed scheduling variable derived from indirect measurements of the EGR mass flow, such as the pressure ratio of the intake, exhaust manifolds, and the exhaust air-to-fuel ratio. The scheduling variable is utilized to estimate static gains of the EGR and VGT systems; it has a large dispersion in various engine operating conditions. Based on the estimated static gains of the plant, the Skogestad internal model control (SIMC) method determines appropriate control gains. The dynamic decoupler is designed to deal with the cross-coupled effects of the EGR and VGT systems by applying a simplified decoupler design method. The simplified decoupler is beneficial for compensating for the dynamics difference between two control loops of the EGR and VGT systems, for example, slow VGT dynamics and fast EGR dynamics. The proposed control algorithm is evaluated through engine experiments. Step test results of set points reveal that root-mean-square (RMS) error of the gain-scheduled feedback controller is reduced by 47% as compared to those of the fixed gain controller. Furthermore, the designed simplified decoupler decreased the tracking error under transients by 14–66% in various engine operating conditions.

Numerical Investigation on Aerodynamic Characteristics of Variable Geometry Turbine Vane Cascade for Marine Gas Turbines

2020 ◽  
Author(s):  
Jie Gao ◽  
Dongchen Huo
Keyword(s):  
Energy Loss ◽  
Gas Turbines ◽  
Aerodynamic Characteristics ◽  
Loss Coefficient ◽  
Operating Conditions ◽  
Numerical Calculations ◽  
Variable Geometry ◽  
Turning Angle ◽  
Tip Leakage ◽  
Variable Geometry Turbine

Abstract Variable geometry turbines for marine gas turbines typically use variable vane technology to regulate turbine performance under variable operating conditions, but the variable geometry turbine produces additional losses as compared to the fixed geometry turbine. The method of combining experiment and numerical calculations was adopted to investigating the variable vane tip leakage loss at different vane turning angles, and its influence on the vane aerodynamic characteristics. The numerical calculations were performed using the ANSYS CFX 18.0 numerical prediction code, adopting the SST k-ω turbulence model to investigate the aerodynamic parameter distribution downstream of the variable vane under five different vane turning angles (−6°, −3°, 0°, +5° and +10°) and three different Mach Numbers (0.3, 0.5 and 0.6). The results showed that the tip leakage is the main source of aerodynamic loss of variable vanes. The tip leakage vortex and passage vortex show strong mixing characteristics in the downstream of variable vanes, especially at the 0.3Mach condition. The change of the vane turning angle alters not only the incidence angle to the vane itself, but also the outflow angle downstream of the vane. There is a linear relationship between the downstream outflow angle and the turning angle of the vane. The total pressure loss coefficient and energy loss coefficient decrease as the Mach number increases, and the changes of energy loss coefficient value from 0.3Mach to 0.5Mach are most obvious. Results from this investigation are well presented and discussed in this paper.

scholarly journals Investigation of Unsteady Aerodynamic Excitation on Rotor Blade of Variable Geometry Turbine

2019 ◽  
Vol 2019 ◽  
pp. 1-13
Author(s):  
Jian Liu ◽  
Wei-Yang Qiao ◽  
Wen-Hua Duan
Keyword(s):  
Pressure Fluctuation ◽  
Rotor Blade ◽  
Pressure Fluctuations ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Variable Geometry ◽  
Blade Surface ◽  
Variable Geometry Turbine ◽  
Mach Numbers ◽  
Fluctuation Energy

To investigate the aerodynamic excitations in variable geometry turbines, the full three-dimensional viscous unsteady numerical simulations were performed by solving N-S equations based on SAS SST method. The aerodynamic excitations at varied expansion ratios with six different vane stagger angles that cause the unsteady pressure fluctuation on the rotor blade surface are phenomenologically identified and quantitatively analyzed. The blade pressure fluctuation levels for turbines with different vane stagger angles in the time and frequency domain are analyzed. As the results suggest, the blade excitation mechanisms are directly dependent on the operating conditions of the stage in terms of vane exit Mach numbers for all test cases. At subsonic vane exit Mach numbers the blade pressure fluctuations are simply related to the potential filed and wake propagation; at transonic conditions, the vane trailing edge shock causes additional disturbance and is the dominating excitation source on the rotor blade, and the pressure fluctuation level is three times of the subsonic conditions. The pressure fluctuation energy at subsonic condition concentrates on the first vane passing period; pressure fluctuation energy at higher harmonics is more prominent at transonic conditions. The variation of the aerodynamic excitations on the rotor blade at different vane stagger angles is caused by the varied expansion with stator and rotor passage. The aerodynamic excitation behaviors on the rotor blade surface for the VGT are significantly different at varied vane stagger angle. Spanwise variation of the pressure fluctuation patterns on is also observed, and the mechanism of the excitations at different spans is not uniform.

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