scholarly journals Numerical Simulation of Two-Stage Variable Geometry Turbine

Energies ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 5349
Author(s):  
Dariusz Kozak ◽  
Paweł Mazuro ◽  
Andrzej Teodorczyk
Keyword(s):  
Combustion Engine ◽  
Three Dimensional ◽  
High Load ◽  
Operating Conditions ◽  
Two Stage ◽  
Variable Turbine Geometry ◽  
Low Load ◽  
Variable Geometry Turbine ◽  
Stage System ◽  
Maintenance Requirements

The modern internal combustion engine (ICE) has to meet several requirements. It has to be reliable with the reduced emission of pollutant gasses and low maintenance requirements. What is more, it has to be efficient both at low-load and high-load operating conditions. For this purpose, a variable turbine geometry (VTG) turbocharger is used to provide proper engine acceleration of exhaust gases at low-load operating conditions. Such a solution is also efficient at high-load engine operating conditions. In this paper, the result of an unsteady, three-dimensional (3D) simulation of the variable two-stage turbine system is discussed. Three different VTG positions were considered for those simulations, along with three different turbine speeds. The turbine inlet was modeled as six equally placed exhaust pipes for each cylinder to eliminate the interference of pressure waves. The flow field at the outlet of the 1st stage nozzle vane and 2nd stage rotor was investigated. The simulations showed that the variable technologies significantly improve the efficiency of the two-stage turbine system. The highest overall efficiency of the two-stage system was achieved at 60,000 rpm and 11o VTG position.

Application of an Improved Streamline Curvature Approach to a Modern, Two-Stage Transonic Fan: Comparison With Data and CFD

2002 ◽  
Author(s):  
Keith M. Boyer ◽  
Walter F. O’Brien
Keyword(s):  
Three Dimensional ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Model Parameters ◽  
Two Stage ◽  
Streamline Curvature ◽  
Wide Range ◽  
Improved Model ◽  
Transonic Fan ◽  
Streamline Curvature Method

A streamline curvature method with improvements to key loss models is applied to a two-stage, low aspect ratio, transonic fan with design tip relative Mach number of approximately 1.65. Central to the improvements is the incorporation of a physics-based shock model. The attempt here is to capture the effects of key flow phenomena relative to the off-design performance of the fan. A quantitative analysis regarding solution sensitivities to model parameters that influence the key phenomena over a wide range of operating conditions is presented. Predictions are compared to performance determined from overall and interstage measurements, as well as from a three-dimensional, steady, Reynolds-averaged Navier-Stokes method applied across the first rotor. Overall and spanwise comparisons demonstrate that the improved model gives reasonable performance trending and generally accurate results. The method can be used to provide boundary conditions to higher-order solvers, or implemented within novel approaches using the streamline curvature method to explore complex engine-inlet integration issues, such as time-variant distortion.

scholarly journals Experimental Research of Fibrous Materials for Two-Stage Filtration of the Intake Air of Internal Combustion Engines

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7166
Author(s):  
Tadeusz Dziubak ◽  
Leszek Bąkała ◽  
Sebastian Dominik Dziubak ◽  
Kamil Sybilski ◽  
Michał Tomaszewski
Keyword(s):  
Pressure Drop ◽  
Absorption Coefficient ◽  
Internal Combustion Engines ◽  
Filter Material ◽  
Internal Combustion ◽  
Operating Conditions ◽  
Combustion Engines ◽  
Two Stage ◽  
Stage System ◽  
Dust Absorption

Pollutant properties in intake air to internal combustion engines were analyzed. Mineral dust particles’ influence on accelerated engine components’ wear was discussed. Dust concentration values in the air under various operating conditions in trucks and special vehicles were presented. The idea and necessity for using two-stage filters, operating in a “multi-cyclone–porous partition” system for vehicles operated in dusty air conditions, are presented. Information from the literature information has been presented, showing that impurities in small grain sizes reduce fiber bed absorbency. It has been shown that such a phenomenon occurs during filter material operation, located directly behind the inertial filter (multi-cyclone), which off-road vehicles are equipped with. It results in a greater pressure drop intensity increase and a shorter proper filter operation period. It has been shown that filter material selection for the motor vehicle air filter requires knowledge of the mass of stopped dust per filtration unit area (dust absorption coefficient km) determined for a given permissible resistance value Δpfdop. It has been shown that there is no information on absorption coefficient values for filter materials operating in a two-stage “multi-cyclone–porous partition” separation system. Original methodology and conditions for determining dust absorption coefficient (km) of a separation partition, operating under the conditions of two-stage filtration, were presented. The following characteristics were tested: separation efficiency, filtration performance, and pressure drop characteristics of three different filtration partitions. These were A (cellulose), B (cellulose and polyester), and C (cellulose, polyester, and nanofibers layer), working individually and in a two-stage system—behind the cyclone. Granulometric dust composition dosed into the cyclone and cyclone downstream was determined. During tests, conditions corresponding to air filter’s actual operating conditions, including separation speed and dust concentration in the air, were maintained. For the pressure drop values, the dust absorption coefficient (km) values of three different filtration partitions (A, B, and C), working individually and in a two-stage system—behind the cyclone—were determined experimentally.

Steady Modeling of a Turbocharger Turbine for Automotive Engines

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Fabio Bozza ◽  
Vincenzo De Bellis
Keyword(s):  
Combustion Engine ◽  
Numerical Procedure ◽  
Engine Performance ◽  
Operating Conditions ◽  
Flow Equations ◽  
Automotive Engine ◽  
1D Modeling ◽  
Variable Geometry Turbine ◽  
Geometrical Data ◽  
Actual Operation

Nowadays the turbocharging technique is playing a fundamental role in improving automotive engine performance and reducing fuel consumption and the exhaust emissions, in spark-ignition and compression ignition engines, as well. To this end, one-dimensional (1D) modeling is usually employed to compute the engine-turbocharger matching, to select the boost level in different operating conditions, and to estimate the low-end torque level and the transient response. However, 1D modeling of a turbocharged engine requires the availability of the turbine and compressor characteristic maps. This leads to some typical drawbacks: (1)Performance maps of the turbocharger device are usually limited to a reduced number of rotational speeds, pressure ratios, and mass flow rates because of turbine/compressor matching limits; (2) as a consequence of previous issue, unphysical extrapolation of maps' data is commonly required; and (3) heat transfer conditions may strongly differ between test bench measurements and actual operation, where turbocharger is coupled to an internal combustion engine. To overcome the above problems, in the present paper a numerical procedure is introduced: It solves 1D steady flow equations inside the turbine components with the aim of accurately reproducing the experimentally derived characteristic maps. The steady procedure describes the main phenomena and losses arising within the stationary and rotating channels constituting the turbine. It is utilized to directly compute the related steady maps, starting from the specification of a reduced set of geometrical data. An optimization process is employed to identify a number of tuning constants included in the various loss correlations. The procedure is applied to the simulation of five different turbines: three waste-gated turbines, a twin-entry turbine, and a variable geometry turbine. The numerical results show good agreement with the experimentally derived maps for all the tested devices. The model is, hence, used to evaluate the turbine performance in the whole operating domain.

Numerical Analysis of Flow at Water Jacket of an Internal Combustion Engine

2011 ◽  
Vol 282-283 ◽  
pp. 702-705 ◽  
Author(s):  
De Zhi Zhang ◽  
Ying Ai Jin ◽  
De Yuan Su ◽  
Qing Gao
Keyword(s):  
Two Phase Flow ◽  
Cooling System ◽  
Combustion Engine ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Phase Flow ◽  
Three Dimensional Model ◽  
Two Phase ◽  
Water Jacket ◽  
Model And Simulation

With the increasing degree of the enhancement of engine, engine cooling system design is considered particularly important. This paper used an established three-dimensional model of an engine water jacket to study, and used UDF function in the two-phase flow of the CFD, describe the mathematical model and simulation the engine at different operating conditions, and get the water jacket flow rate transfer thermal process. Finally, the results of the relationship between the engine water jacket of boiling heat transfer and flow velocity have been studied, and the importance of using two-phase flow model has been summarized.

Theoretical Study on Two-Stage Anaerobic-Aerobic Biological Treatment of a CTMP Effluent

1996 ◽  
Vol 31 (1) ◽  
pp. 1-20 ◽  
Author(s):  
H.W. Liu ◽  
S.N. Lo ◽  
H.C. Lavallée
Keyword(s):  
Retention Time ◽  
Hydraulic Retention Time ◽  
Operating Conditions ◽  
Time Range ◽  
Two Stage ◽  
Cell Age ◽  
Initial Substrate ◽  
Stage System ◽  
Basic Equations ◽  
Monod Kinetic

Abstract Basic equations based upon the Monod kinetic model are presented for a two-stage, sequential anaerobic-aerobic treatment system. The effects of operating conditions, such as hydraulic retention time, mean cell age, concentration of microorganisms and initial substrate concentration, on the behaviour of the two-stage system for the treatment of a CTMP effluent were studied theoretically. This was done in terms of removal of BOD5 and RFA, and sensitivity to changes in operating conditions. The study revealed that unstable operation of the anaerobic process could be due to the treatment being carried out in a time range in which the operation was very sensitive to the variation in either hydraulic retention time or mean cell age.

Application of a Supercharger in a Two-Stage Boosting System for a Gasoline HCCI Engine: A Simulation Study

2011 ◽  
Author(s):  
Prasad Shingne ◽  
Dennis Assanis ◽  
Aristotelis Babajimopoulos ◽  
Alan Mond ◽  
Hakan Yilmaz
Keyword(s):  
High Load ◽  
Two Stage ◽  
Engine Simulation ◽  
Engine Model ◽  
Load Limit ◽  
High Pressure Stage ◽  
Stage System ◽  
Intake Pressure ◽  
Better Than ◽  
Fresh Charge

Recently, a number of studies have demonstrated that boosting can extend the high load limit of HCCI. This paper compares two two-stage boosting systems for a 4-cylinder, 2.0 liter engine, within the framework of a 1D engine simulation. A series two-stage boosting system wherein both high and low pressure stages are turbochargers (TCTC) is compared with another series two-stage system, where the high pressure stage from TCTC is replaced with a small supercharger (TCSC). The engine model in these configurations is operated in steady state at high load boosted HCCI points (∼ 6.5 bar BMEP) over a range of engine speeds. The comparison has been carried out by two methods: in Method I the intake pressure to the engine has been matched for both TCTC and TCSC; and in Method II, the amount of fresh charge into the engine has been matched for both systems. A detailed energy balance shows that the performance in terms of BSFC for the TCSC system is worse for Method I. However, this changes for Method II, and the TCSC system is comparable or even better than the TCTC system. This is achieved by greatly reducing the pumping losses associated with the TCTC system, while the parasitic losses of the supercharger are minimized by having to boost to lower intake pressures due to lowered back pressures in the TCSC system.

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.

The anaerobic treatment of a ligno-cellulosic substrate offering little natural pH buffering capacity

1998 ◽  
Vol 38 (4-5) ◽  
pp. 29-35 ◽  
Author(s):  
C. J. Banks ◽  
P. N. Humphreys
Keyword(s):  
Ph Control ◽  
Anaerobic Treatment ◽  
Buffering Capacity ◽  
Single Stage ◽  
Stable Operation ◽  
Reactor Performance ◽  
Two Stage ◽  
Ph Buffering ◽  
Stage System ◽  
The Stability

The stability and operational performance of single stage digestion with and without liquor recycle and two stage digestion were assessed using a mixture of paper and wood as the digestion substrate. Attempts to maintain stable digestion in both single stage reactors were unsuccessful due to the inherently low natural buffering capacity exhibited; this resulted in a rapid souring of the reactor due to unbuffered volatile fatty acid (VFA) accumulation. The use of lime to control pH was unsatisfactory due to interference with the carbonate/bicarbonate equilibrium resulting in wide oscillations in the control parameter. The two stage system overcame the pH stability problems allowing stable operation for a period of 200 days without any requirement for pH control; this was attributed to the rapid flushing of VFA from the first stage reactor into the second stage, where efficient conversion to methane was established. Reactor performance was judged to be satisfactory with the breakdown of 53% of influent volatile solids. It was concluded that the reactor configuration of the two stage system offers the potential for the treatment of cellulosic wastes with a sub-optimal carbon to nitrogen ratio for conventional digestion.

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