Numerical Study of SI Engine Part Load Operating Conditions Using Different VVA Strategies

2011 ◽  
Author(s):  
Michele Battistoni ◽  
Carlo N. Grimaldi ◽  
Francesco Mariani
Keyword(s):  
Numerical Study ◽  
Control Strategies ◽  
Fluid Dynamic ◽  
Operating Conditions ◽  
Load Control ◽  
Valve Closure ◽  
Intake Valve ◽  
Flamelet Model ◽  
Part Load ◽  
Engine Model

In SI engines, VVA (Variable Valve Actuation) technology is mainly used for the reduction of pumping losses at part load. This paper presents the results of fluid dynamic analyses on a 4V engine about the effects of different VVA strategies, by comparing and discussing the results in terms of organized charge motions, turbulence levels, flame developments, NO and CO emissions. CFD simulations cover five load control cases: comparison is among conventional throttling, EIVC (Early Intake Valve Closure) with symmetric and asymmetric intake lifts, LIVC (Late Intake Valve Closure) and symmetrical Multi-Lift strategies. 3D U-RANS simulations are performed, adopting the Extended Coherent Flamelet Model (ECFM) for the description of premixed SI combustion. The 3D model is also coupled to a 1D engine model which provides inlet/outlet boundary conditions. Simulation results highlight the potential of asymmetric Early Intake Valve Closure (EIVC) strategy which allows reducing pumping losses and, at the same time, achieving good turbulence intensity and combustion speed, if compared to other load control strategies. Multi-Lift strategy resulted excellent in terms of burn duration, but pumping losses are practically the same as in the throttled engine.

Simulation of Extended Expansion Lean Burn Spark Ignition Engine

2004 ◽  
Author(s):  
A. Manivannan ◽  
R. Ramprabhu ◽  
P. Tamilporai ◽  
S. Chandrasekaran
Keyword(s):  
Heat Transfer ◽  
Compression Ratio ◽  
Thermal Efficiency ◽  
Numerical Study ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Valve Closure ◽  
Intake Valve ◽  
Lean Burn ◽  
Atkinson Cycle

This paper deals with Numerical Study of 4-stoke, Single cylinder, Spark Ignition, Extended Expansion Lean Burn Engine. Engine processes are simulated using thermodynamic and global modeling techniques. In the simulation study following process are considered compression, combustion, and expansion. Sub-models are used to include effect due to gas exchange process, heat transfer and friction. Wiebe heat release formula was used to predict the cylinder pressure, which was used to find out the indicated work done. The heat transfer from the cylinder, friction and pumping losses also were taken into account to predict the brake mean effective pressure, brake thermal efficiency and brake specific fuel consumption. Extended Expansion Engine operates on Otto-Atkinson cycle. Late Intake Valve Closure (LIVC) technique is used to control the load. The Atkinson cycle has lager expansion ratio than compression ratio. This is achieved by increasing the geometric compression ratio and employing LIVC. Simulation result shows that there is an increase in thermal efficiency up to a certain limit of intake valve closure timing. Optimum performance is attained at 90 deg intake valve closure (IVC) timing further delaying the intake valve closure reduces the engine performance.

THE STUDY OF THE EFFECT OF INTAKE VALVE TIMING ON ENGINE USING CYLINDER DEACTIVATION TECHNIQUE VIA SIMULATION

2015 ◽  
Vol 77 (8) ◽  
Author(s):  
S. F. Zainal Abidin ◽  
M. F. Muhamad Said ◽  
Z. Abdul Latiff ◽  
I. Zahari ◽  
M. Said
Keyword(s):  
Fuel Consumption ◽  
Internal Combustion Engines ◽  
Gasoline Engine ◽  
Engine Performance ◽  
Intake Valve ◽  
Cylinder Deactivation ◽  
Part Load ◽  
Engine Model ◽  
Engine Efficiency ◽  
Load Conditions

There are many technologies that being developed to increase the efficiency of internal combustion engines as well as reducing their fuel consumption.  In this paper, the main area of focus is on cylinder deactivation (CDA) technology. CDA is mostly being applied on multi cylinders engines. CDA has the advantage to improve fuel consumption by reducing pumping losses at part load engine conditions. Here, the application of CDA on 1.6L four cylinders gasoline engine is studied. One-dimensional (1D) engine modeling work is performed to investigate the effect of intake valve strategy on engine performance with CDA. 1D engine model is constructed based on the 1.6L actual engine geometries. The model is simulated at various engine speeds at full load conditions. The simulated results show that the constructed model is well correlated to measured data. This correlated model is then used to investigate the CDA application at part load conditions. Also, the effects on the in-cylinder combustion as well as pumping losses are presented. The study shows that the effect of intake valve strategy is very significant on engine performance. Pumping losses is found to be reduced, thus improve fuel consumption and engine efficiency.

The Role of Simulation in the Development of a Fast-Actuation Solenoid C.R. Injection System

2004 ◽  
Author(s):  
Gian Marco Bianchi ◽  
Piero Pelloni ◽  
Giovanni Osbat ◽  
Marco Parotto ◽  
Rita Di Gioia ◽  
...  
Keyword(s):  
Dynamic Response ◽  
Control Strategies ◽  
Fluid Dynamic ◽  
Numerical Approach ◽  
Linear Analysis ◽  
Operating Conditions ◽  
System Model ◽  
Injection System ◽  
Multiple Injection ◽  
Pressure Regulator

Upcoming Euro 4 and Euro 5 emission standards are increasing efforts on injection system developments in order to improve mixture quality and combustion efficiency. The target features of advanced injection system are related to their capability of operating multiple injection with a precise control of amount of fuel injected, low cycle-by-cycle variability and life drift, within flexible strategies. In order to accomplish this task, performance must be optimised since injection system concept development by acting on. The extensive use of numerical approach has been identified as a necessary integration to experiments in order to put on the market high quality injection system accomplishing strict engine control strategies. The modelling approach allows focusing the experimental campaign only on critical issues saving time and costs, furthermore it is possible to deeply understand inner phenomena that cannot be measured. The lump/ID model of the whole system built into the AMESim® code was presented in previous works: particular attention was devoted in the simulation of the electromagnetic circuits, actual fluid-dynamic forces acting on needle surfaces and discharge coefficients, evaluated by means 3D-CFD simulations. In order to assess new injection system dynamic response under multiple injection strategies reproducing actual engine operating conditions it is necessary to find to proper model settings. In this work the integration between the injector and the system model, which comprehends the pump, the pressure regulator, the rail and the connecting-pipes, will be presented. For reproducing the dynamic response of he whole system will be followed a step-by-step approach in order to prevent modelling inaccuracies. Firstly will be presented the linear analysis results performed in order to find injection system own natural frequencies. Secondly based on linear analysis results will be found proper injection system model settings for predicting dynamic response to external excitations, such as pump perturbations, pressure regulator dynamics and injection pulses. Thirdly experimental results in terms of instantaneous flow rate and integrated injected volume for different operating conditions will be presented in order to highlight the capability of the modelling methodology in addressing the new injection system design.

Analysis on the Performance Characteristics of SOFC/GT Hybrid Systems Based on a Commercially Available MW-Class Gas Turbine

2005 ◽  
Author(s):  
Tae Won Song ◽  
Jeong L. Sohn ◽  
Tong Seop Kim ◽  
Sung Tack Ro
Keyword(s):  
Gas Turbine ◽  
Hybrid System ◽  
Guide Vane ◽  
Control Strategies ◽  
Operating Conditions ◽  
Performance Characteristics ◽  
Inlet Guide Vane ◽  
Part Load ◽  
Optimal Power ◽  
Selection Of

To investigate the possible applications of the SOFC/MGT hybrid system to large electric power generations, a study for the kW-class hybrid power system conducted in our group is extended to the MW-class hybrid system in this study. Because of the matured technology of the gas turbine and commercial availability in the market, it is reasonable to construct a hybrid system with the selection of a gas turbine as an off-the-shelf item. For this purpose, the performance analysis is conducted to find out the optimal power size of the hybrid system based on a commercially available gas turbine. The optimal power size has to be selected by considering specifications of a selected gas turbine which limit the performance of the hybrid system. Also, the cell temperature of the SOFC is another limiting parameter to be considered in the selection of the optimal power size. Because of different system configuration of the hybrid system, the control strategies for the part-load operation of the MW-class hybrid system are quite different from the kW-class case. Also, it is necessary to consider that the control of supplied air to the MW-class gas turbine is typically done by the variable inlet guide vane located in front of the compressor inlet, instead of the control of variable rotational speed of the kW-class micro gas turbine. Performance characteristics at part-load operating conditions with different kinds of control strategies of supplied fuel and air to the hybrid system are investigated in this study.

Experimental and Numerical Study of Stall Flutter in a Transonic Low-Aspect Ratio Fan Blisk

2003 ◽  
Author(s):  
A. J. Sanders ◽  
K. K. Hassan ◽  
D. C. Rabe
Keyword(s):  
Aspect Ratio ◽  
Numerical Study ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Strain Gages ◽  
Pressure Transducers ◽  
Low Aspect Ratio ◽  
Benchmark Data

Experiments are performed on a modern design transonic shroudless low-aspect ratio fan blisk that experienced both subsonic/transonic and supersonic stall-side flutter. High-response flush mounted miniature pressure transducers are utilized to measure the unsteady aerodynamic loading distribution in the tip region of the fan for both flutter regimes, with strain gages utilized to measure the vibratory response at incipient and deep flutter operating conditions. Numerical simulations are performed and compared with the benchmark data using an unsteady three-dimensional nonlinear viscous computational fluid dynamic (CFD) analysis, with the effects of tip clearance, vibration amplitude, and the number of time steps-per-cycle investigated. The benchmark data are used to guide the validation of the code and establish best practices that ensure accurate flutter predictions.

A numerical procedure for the calibration of a turbocharged spark-ignition variable valve actuation engine at part load

2016 ◽  
Vol 18 (8) ◽  
pp. 810-823 ◽  
Author(s):  
Fabio Bozza ◽  
Vincenzo De Bellis ◽  
Luigi Teodosio
Keyword(s):  
Fuel Consumption ◽  
Spark Ignition ◽  
Specific Fuel Consumption ◽  
Brake Specific Fuel Consumption ◽  
Valve Closure ◽  
Intake Valve ◽  
Part Load ◽  
Variable Valve Actuation ◽  
Variable Valve ◽  
Valve Actuation

Referring to spark-ignition engines, the downsizing, coupled to turbocharging and variable valve actuation systems are very common solutions to reduce the brake-specific fuel consumption at low-medium brake mean effective pressure. However, the adoption of such solutions increases the complexity of engine control and management because of the additional degrees of freedom, and hence results in a longer calibration time and higher experimental efforts. In this work, a twin-cylinder turbocharged variable valve actuation spark-ignition engine is numerically investigated by a one-dimensional model (GT-Power™). The considered engine is equipped with a fully flexible variable valve actuation system, realizing both a common full-lift strategy and a more advanced early intake valve closure strategy. Refined sub-models are used to describe turbulence and combustion processes. In the first stage, one-dimensional engine model is validated against the experimental data at full and part load. The validated model is then integrated in a multipurpose commercial optimizer (modeFRONTIER™) with the aim to identify the engine calibration that minimizes brake-specific fuel consumption at part load. In particular, the decision parameters of the optimization process are the early intake valve closure angle, the throttle valve opening, the turbocharger setting and the spark timing. Proper constraints are posed for intake pressure in order to limit the gas-dynamic noise radiated at the intake mouth. The adopted optimization approach shows the capability to reproduce with good accuracy the experimentally identified calibration. The latter corresponds to the numerically derived Pareto frontier in brake mean effective pressure–brake specific fuel consumption plane. The optimization also underlines the advantages of an engine calibration based on a combination of early intake valve closure strategy and intake throttling rather than a purely throttle-based calibration. The developed automatic procedure allows for a ‘virtual’ calibration of the considered engine on completely theoretical basis and proves to be very helpful in reducing the experimental costs and the engine time-to-market.

Analysis of a 6 Cylinder Turbocharged HCCI Engine Using a Detailed Kinetic Mechanism

2002 ◽  
Author(s):  
Giuseppe Cantore ◽  
Luca Montorsi ◽  
Fabian Mauss ◽  
Per Amne´us ◽  
Olof Erlandsson ◽  
...  
Keyword(s):  
Combustion Engine ◽  
Control Strategies ◽  
Fluid Dynamic ◽  
Combustion Process ◽  
Operating Conditions ◽  
Engine Control ◽  
Gas Composition ◽  
Time Step ◽  
Hcci Engine ◽  
Power Code

When analyzing HCCI combustion engine behavior, the integration of experimental tests and numerical simulations is crucial. Investigations of possible engine control strategies as a function of the different operating conditions have to take the behavior of the whole HCCI engine into account, including the effects both of the combustion process and of complex devices. Therefore the numerical simulation code must be able both to model accurately the gas-dynamic of the system and to evaluate the combustion chemical kinetics. This paper focuses on the coupling between the commercial one-dimensional fluid-dynamic GT-Power Code and our in-house detailed chemical kinetic Ignition Code. An interface has been developed in order to exchange information between the two codes: the Ignition Code considers as boundary conditions the GT-Power Code values provided for the gas composition at IVC and the pressure and temperature at every time step and passes back to GT-Power the burnt fuel fraction and stores in an external file the in cylinder gas composition. Thus the whole engine cycle can be accurately simulated, estimating the interactions between the gas-dynamics phenomena along the intake and exhaust pipes and through the valves, and the chemical processes occurring during the closed valves period. This tool makes it possible to analyze the engine behavior under duty cycle operating conditions, and therefore it represents a useful support to the experimental measurements, reducing the number of tests required to assess the proper engine control strategies.

Numerical Study of Cage Dynamics Focused on Hydrodynamic Effects of Guidance Land Clearances for Different Ball-Pocket Clearances in Cryogenic Environments

2017 ◽  
Author(s):  
Bok Seong Choe ◽  
Jeon Kook Lee ◽  
Doyoung Jeon ◽  
Yongbok Lee
Keyword(s):  
Ball Bearing ◽  
Rotation Speed ◽  
Numerical Study ◽  
Fluid Dynamic ◽  
Operating Conditions ◽  
Cfd Analysis ◽  
Dynamic Motion ◽  
Light Load ◽  
Dynamic Forces ◽  
Inner Race

This study presents the dynamic motion of a ball bearing cage submerged in a cryogenic fluid under high-speed conditions. The dynamic motion of the cage has been studied as a function of the race land–cage and ball–cage pocket clearances for different inner race rotation speeds under light load conditions. In addition, this study conducted computational fluid dynamics (CFD) analysis using commercial software to analyze the fluid dynamic forces on the cage. The hydraulic force obtained from the CFD analysis was coded in commercial ball bearing analysis software as a function of the eccentricity ratio and rotation speed of the cage. Finally, the dynamic motion of the ball bearing cage considering the effects of fluid dynamic forces has been studied. The results include the cage whirling amplitude, fluctuation of cage whirling speed, and cage wear for various cage clearances and rotation speeds. The cage outer guidance clearances studied were 1.14, 1.04, 0.94, 0.84, and 0.74 mm and the ball–pocket clearances were 0.62, 0.92, 1.22, 1.52, and 1.82 mm. The rotation speeds of the inner race were 5,000, 8,000, and 11,000 rpm. The cage whirling amplitude decreases as the outer guidance clearance decreases, and it decreases as the rotation speed increases up to 11,000 rpm because of the increasing hydrodynamic force of the liquid nitrogen (LN2). However, the probability density function (PDF) curves indicate that an increase in the rotor speed increases the standard deviation in the cage whirling frequency. The wear loss of the cage was greatest for the largest race land–cage and the smallest ball–cage pocket clearances, owing to the increased number of intermittent collisions between the cage and the ball bearings (ball–race). Consequently, the analysis results for various operating conditions (inner race rotation speeds, cage clearances, traction coefficients, etc.) are in good agreement with the reference results.

Numerical Investigations on Extended Expansion Engine

2003 ◽  
Author(s):  
P. Tamilporai ◽  
S. Chandrasekaran ◽  
S. Subramaniyam ◽  
J. Jancirani ◽  
K. V. Lakshminarayanarao
Keyword(s):  
Power Output ◽  
Spark Ignition ◽  
Intake Manifold ◽  
Combustion Model ◽  
Emission Characteristics ◽  
Valve Closure ◽  
Intake Valve ◽  
Expansion Engine ◽  
Part Load ◽  
Performance And Emission

A great deal of research has been directed towards understanding the dependence of emissions and fuel economy on the operating and design characteristics of spark-ignition homogeneous-charge engine. Several recent investigations have been concerned with modifying the conventional spark-ignition such that the part load BSFC (brake specific fuel consumption) is decreased. Many of the proposed modifications convert the engine from fixed to variable displacement, i.e., the engine size is varied to suit the vehicle needs. Another possible modification to the conventional engine is to control the load of the engine by controlling the timing of the intake-valve closure rather than by variable-density throttling. This investigation examines the delaying intake valve closing as a method of controlling the engine load without incurring the usual part-load throttling losses. The extended expansion engine (EEE) is an engine with the power output regulated by controlling the crank angle at which the intake valve closes (IVC). As in case of a conventional engine the intake valve opens just prior to and remains open through out the intake stroke of the engine. However, the intake valve also remains open over a portion of the compression stroke while the piston pushes part of the cylinder charge back into the intake manifold and stored in a plenum. A one-way valve is provided to prevent the charge from re-entering the carburetor. After the intake valve closes, the actual compression starts and the expansion and exhaust strokes are similar to those of the conventional engine. The effective cylinder volume determines the trapped cylinder charge and therefore the power output, at the time of the intake valve closing. This paper mainly deals with the numerical studies on single cylinder, four stroke, spark ignition, Extended Expansion Engine extended expansion engine with intake valve closure delayed to produce an expansion ratio that is larger than the compression ratio. The Engine processes are simulated on a computer using thermodynamic and global modeling techniques. Further the concept of lean burn technology is applied to the simulated processes and the engine performance and emission characteristics are studied from the simulated results. Two-zone combustion model is adopted for the analysis of combustion. The model is also associated with sub models for calculating the combustion duration and equilibrium composition of five product species. From this investigations and comparison of results, it is concluded that the simulation work developed predicts the performance and emission characteristics of this engine reasonably well. Therefore it is evident that the developed code can be used with confidence for further parametric studies.

Control Strategies for Start-Up and Part-Load Operation of Solid Oxide Fuel Cell/Gas Turbine Hybrid System

2009 ◽  
Vol 7 (1) ◽  
Author(s):  
Wei Jiang ◽  
Ruixian Fang ◽  
Jamil Khan ◽  
Roger Dougal
Keyword(s):  
Fuel Cell ◽  
Gas Turbine ◽  
Hybrid System ◽  
Control Strategies ◽  
Operating Conditions ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Electrical Characteristics ◽  
Part Load ◽  
Start Up

Control strategy plays a significant role in ensuring system stability and performance as well as equipment protection for maximum service life. This work is aimed at investigating the control strategies for start-up and part-load operating conditions of the solid oxide fuel cell/gas turbine (SOFC/GT) hybrid system. First, a dynamic SOFC/GT hybrid cycle, based on the thermodynamic modeling of system components, has been successfully developed and simulated in the virtual test bed simulation environment. The one-dimensional tubular SOFC model is based on the electrochemical and thermal modeling, accounting for voltage losses and temperature dynamics. The single cell is discretized using a finite volume method where all the governing equations are solved for each finite volume. Two operating conditions, start-up and part load, are employed to investigate the control strategies of the SOFC/GT hybrid cycle. In particular, start-up control is adopted to ensure the initial rotation speed of a compressor and a turbine for a system-level operation. The control objective for the part-load operation regardless of load changes, as proposed, is to maintain constant fuel utilization and a fairly constant SOFC temperature within a small range by manipulating the fuel mass flow and air mass flow. To this end, the dynamic electrical characteristics such as cell voltage, current density, and temperature under the part load are simulated and analyzed. Several feedback control cycles are designed from the dynamic responses of electrical characteristics. Control cycles combined with control related variables are introduced and discussed.

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