Parallel Multi-Cycle LES of an Optical Pent-Roof DISI Engine Under Motored Operating Conditions

2017 ◽  
Author(s):  
Noah Van Dam ◽  
Wei Zeng ◽  
Magnus Sjöberg ◽  
Sibendu Som
Keyword(s):  
Experimental Data ◽  
Direct Injection ◽  
Operating Conditions ◽  
New Strategy ◽  
Long Time ◽  
Order Of Magnitude ◽  
Structure Index ◽  
Number Of Cycles ◽  
The Many ◽  
Direct Injection Spark Ignition

The use of Large-eddy Simulations (LES) has increased due to their ability to resolve the turbulent fluctuations of engine flows and capture the resulting cycle-to-cycle variability. One drawback of LES, however, is the requirement to run multiple engine cycles to obtain the necessary cycle statistics for full validation. The standard method to obtain the cycles by running a single simulation through many engine cycles sequentially can take a long time to complete. Recently, a new strategy has been proposed by our research group to reduce the amount of time necessary to simulate the many engine cycles by running individual engine cycle simulations in parallel. With modern large computing systems this has the potential to reduce the amount of time necessary for a full set of simulated engine cycles to finish by up to an order of magnitude. In this paper, the Parallel Perturbation Methodology (PPM) is used to simulate up to 35 engine cycles of an optically accessible, pent-roof Direct-injection Spark-ignition (DISI) engine at two different motored engine operating conditions, one throttled and one un-throttled. Comparisons are made against corresponding sequential-cycle simulations to verify the similarity of results using either methodology. Mean results from the PPM approach are very similar to sequential-cycle results with less than 0.5% difference in pressure and a magnitude structure index (MSI) of 0.95. Differences in cycle-to-cycle variability (CCV) predictions are larger, but close to the statistical uncertainty in the measurement for the number of cycles simulated. PPM LES results were also compared against experimental data. Mean quantities such as pressure or mean velocities were typically matched to within 5–10%. Pressure CCVs were under-predicted, mostly due to the lack of any perturbations in the pressure boundary conditions between cycles. Velocity CCVs for the simulations had the same average magnitude as experiments, but the experimental data showed greater spatial variation in the root-mean-square (RMS). Conversely, circular standard deviation results showed greater repeatability of the flow directionality and swirl vortex positioning than the simulations.

Commutation Loss in Hydrostatic Pumps and Motors

2021 ◽  
Author(s):  
Robin Mommers ◽  
Peter Achten ◽  
Jasper Achten ◽  
Jeroen Potma
Keyword(s):  
Experimental Data ◽  
Energy Loss ◽  
Simulation Model ◽  
Operating Conditions ◽  
Chamber Pressure ◽  
Working Mechanism ◽  
Working Chamber ◽  
Lumped Parameter ◽  
Long Time ◽  
Pressure Changes

Abstract In mobile hydraulic applications, more efficient machinery generally translates to smaller batteries or less diesel consumption, and smaller cooling solutions. A key part of such systems are hydrostatic pumps and motors. While these devices have been around for a long time, some of the causes of energy loss in pump and motors are still not properly defined. This paper focuses on one of the causes of energy loss in pumps and motors, by identifying the energy loss as a result of the process of commutation. By nature, all hydrostatic pumps and motors have some form of commutation: the transition from the supply port to the discharge port of the machine (and vice versa). During commutation, the connection between the working chamber and the ports is temporarily closed. The chamber pressure changes by compression or decompression that is the result of the rotation of the working mechanism. Ideally, the connection to one of the ports is opened once the chamber pressure equals the port pressure. When the connection is opened too early or too late, energy is lost. This paper describes a method to predict the commutation loss using a lumped parameter simulation model. To verify these predictions, experimental data of a floating cup pump was compared to the calculated values, which show a decent match. Furthermore, the results show that, depending on the operating conditions, up to 50% of all losses in this pump are caused by improper commutation.

Assessment of CFD Approaches for Next-Generation Combustor Design

2014 ◽  
Author(s):  
Kumud Ajmani ◽  
Hukam C. Mongia ◽  
Phil Lee
Keyword(s):  
Experimental Data ◽  
Direct Injection ◽  
Operating Conditions ◽  
Reacting Flow ◽  
Cfd Analysis ◽  
Next Generation ◽  
Lean Direct Injection ◽  
Liquid Spray ◽  
Exit Temperature ◽  
Computational Predictions

An effort was undertaken to perform CFD analysis of fluid flow in Lean-Direct Injection (LDI) combustors with axial swirl-venturi elements for next-generation LDI-2 design. The National Combustion Code (NCC) developed at NASA Glenn Research Center was used to perform reacting flow computations on an LDI-2 combustor configuration with thirteen injector elements arranged in four fuel stages. Reacting computations were performed with a consistent approach for mesh-optimization, liquid spray modeling and kinetics modeling. Computational predictions of Emissions Index (EINOx) and combustor exit temperature were compared with two sets of experimental data at medium and high-power operating conditions, for two different pressure-drop conditions in the combustor. The NCC simulations predicted the combustor exit temperature to within 1–2% of experimental data. The accuracy of the EINOx predictions from the NCC simulations was within 10% to 30% of experimental data.

A phenomenological mixture homogenization model for spark-ignition direct-injection engines

2017 ◽  
Vol 19 (2) ◽  
pp. 168-178 ◽  
Author(s):  
Stefan Frommater ◽  
Jens Neumann ◽  
Christian Hasse
Keyword(s):  
Equivalence Ratio ◽  
Direct Injection ◽  
Three Dimensional ◽  
Control Unit ◽  
Spark Ignition ◽  
Engine Control Unit ◽  
Operating Conditions ◽  
Spark Ignition Engines ◽  
Ratio Distribution ◽  
Direct Injection Spark Ignition

In modern turbocharged direct-injection, spark-ignition engines, proper calibration of the engine control unit is essential to handle the increasing variability of actuators. The physically based simulation of engine processes such as mixture homogenization enables a model-based calibration of the engine control unit to identify an ideal set of actuator settings, for example, for efficient combustion with reduced exhaust emissions. In this work, a zero-dimensional phenomenological model for direct-injection, spark-ignition engines is presented that allows the equivalence ratio distribution function in the combustion chamber to be calculated and its development is tracked over time. The model considers the engine geometry, mixing time, charge motion and spray–charge interaction. Accompanying three-dimensional computational fluid dynamics, simulations are performed to obtain information on homogeneity at different operating conditions and to calibrate the model. The calibrated model matches the three-dimensional computational fluid dynamics reference both for the temporal homogeneity development and for the equivalence ratio distribution at the ignition time, respectively. When the model is validated outside the calibrated operating conditions, this shows satisfying results in terms of mixture homogeneity at the time of ignition. Additionally, only a slight modification of the calibration is shown to be required when transferring the model to a comparable engine. While the model is primarily aimed at target applications such as a direct-injection, spark-ignition soot emission model, its application to other issues, such as gaseous exhaust emissions, engine knock or cyclic fluctuations, is conceivable due to its general structure. The fast calculation enables mixture inhomogeneities to be estimated during driving cycle simulations.

scholarly journals A New Strategy for Accurately PredictingI-VElectrical Characteristics of PV Modules Using a Nonlinear Five-Point Model

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Sakaros Bogning Dongue ◽  
Donatien Njomo ◽  
Lessly Ebengai
Keyword(s):  
Experimental Data ◽  
Nonlinear Effect ◽  
Solar Irradiance ◽  
Great Accuracy ◽  
Operating Conditions ◽  
Point Model ◽  
Photovoltaic Modules ◽  
Pv Modules ◽  
Good Comparison ◽  
New Strategy

This paper presents the modelling of electricalI-Vresponse of illuminated photovoltaic crystalline modules. As an alternative method to the linear five-parameter model, our strategy uses advantages of a nonlinear analytical five-point model to take into account the effects of nonlinear variations of current with respect to solar irradiance and of voltage with respect to cells temperature. We succeeded in this work to predict with great accuracy theI-Vcharacteristics of monocrystalline shell SP75 and polycrystalline GESOLAR GE-P70 photovoltaic modules. The good comparison of our calculated results to experimental data provided by the modules manufacturers makes it possible to appreciate the contribution of taking into account the nonlinear effect of operating conditions data onI-Vcharacteristics of photovoltaic modules.

scholarly journals Numerical Investigation of Spray Collapse in GDI with OpenFOAM

Fluids ◽  
2021 ◽  
Vol 6 (3) ◽  
pp. 104
Author(s):  
Jan Wilhelm Gärtner ◽  
Ye Feng ◽  
Andreas Kronenburg ◽  
Oliver T. Stein
Keyword(s):  
Experimental Data ◽  
Direct Injection ◽  
Operating Conditions ◽  
Test Case ◽  
Direct Injection Engines ◽  
Shock Interactions ◽  
Single Hole ◽  
First Case ◽  
Collapse Behavior

During certain operating conditions in spark-ignited direct injection engines (GDI), the injected fuel will be superheated and begin to rapidly vaporize. Fast vaporization can be beneficial for fuel–oxidizer mixing and subsequent combustion, but it poses the risk of spray collapse. In this work, spray collapse is numerically investigated for a single hole and the spray G eight-hole injector of an engine combustion network (ECN). Results from a new OpenFOAM solver are first compared against results of the commercial CONVERGE software for single-hole injectors and validated. The results corroborate the perception that the superheat ratio Rp, which is typically used for the classification of flashing regimes, cannot describe spray collapse behavior. Three cases using the eight-hole spray G injector geometry are compared with experimental data. The first case is the standard G2 test case, with iso-octane as an injected fluid, which is only slightly superheated, whereas the two other cases use propane and show spray collapse behavior in the experiment. The numerical results support the assumption that the interaction of shocks due to the underexpanded vapor jet causes spray collapse. Further, the spray structures match well with experimental data, and shock interactions that provide an explanation for the observed phenomenon are discussed.

scholarly journals Output of the dependence of the torque on theangleof rotation of the half couplings of the rope hyperbolic coupling «MAMSAR»

2020 ◽  
pp. 140-145
Author(s):  
М.А. Минасян ◽  
А.М. Минасян ◽  
Л.Х. Ха
Keyword(s):  
Experimental Data ◽  
Operating Temperature ◽  
Operating Conditions ◽  
Correction Coefficient ◽  
Labor Costs ◽  
Temperature Conditions ◽  
Hard Radiation ◽  
Long Time ◽  
Temperature Ranges

Виброизолирующие муфты приводов с упругими канатными элементами являются относительно новым направлением и в литературных источниках малоизвестны [1-14]. Они имеют несколько неоспоримых преимуществ перед другими типами муфт. Их характеристики практически не зависят от температурных режимов эксплуатации (температурные диапазоны эксплуатации – от –200 и вплоть до +370 С); они пожаробезопасны, инертны к агрессивным средам; это практически единственный тип муфт, способный долго работать в зонах повышенной и жесткой радиации. Такая нечувствительность к агрессивным средам и условиям эксплуатации позволяет до минимума сократить трудозатраты на их техническое обслуживание. Статья является логическим продолжением работ авторов о возможности использования канатных опор «MAMSAR» [1-4] в качестве отдельных или сборных муфт приводов. В данной работе в качестве объекта исследования рассматривается муфта с гиперболическим канатным элементом [1]. Целью настоящей статьи является вывод зависимости крутящего момента от смещения для муфт приводов с упругими канатными элементами в виде гиперболы «MAMSAR» [1]. Поставленная цель достигается реализацией следующих задач: 1.Получить формулу зависимости крутящего момента от смещения для гиперболической канатной муфты. 2. Экспериментально определить зависимость крутящего момента от смещения для гиперболической канатной муфты 3. Уточнить формулу – зависимость крутящего момента от смещения для гиперболической канатной муфты с использованием коэффициента поправки на основе экспериментальных данных. Vibration-isolating drive couplings with elastic rope elements are a relatively new direction and are little known in the literature [1-14]. They have several undeniable advantages over other types of couplings. Their characteristics practically do not depend on operating temperature conditions (operating temperature ranges – from -200 and up to +370 C); they are fire-safe, inert to aggressive environments; this is almost the only type of couplings that can work for a long time in areas of high and hard radiation. This insensitivity to aggressive environments and operating conditions allows you to minimize the labor costs for their maintenance. The article is a logical continuation of the authors work on the possibility of using "MAMSAR" rope supports [1-4] as separate or combined drive couplings. In this paper, a coupling with a hyperbolic rope element is considered as an object of research [1]. The purpose of this article is to derive the dependence of torque on displacement for drive couplings with elastic rope elements in the form of a "MAMSAR" hyperbola [1]. This goal is achieved by implementing the following tasks: 1. Get the formula for the dependence of torque on displacement for a hyperbolic cable coupling. 2. Experimentally determine the dependence of torque on displacement for a hyperbolic cable coupling 3. Refine the formula-the dependence of torque on displacement for a hyperbolic cable coupling using the correction coefficient based on experimental data.

Numerical and experimental study on knocking combustion in turbocharged direct-injection engines for a wide range of operating conditions

2021 ◽  
pp. 146808742110601
Author(s):  
Magnus Kircher ◽  
Emmeram Meindl ◽  
Christian Hasse
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Numerical Study ◽  
Direct Injection ◽  
Operating Conditions ◽  
Auto Ignition ◽  
Spark Timing ◽  
Crank Angle ◽  
Wide Range ◽  
The Mean

A combined experimental and numerical study is conducted on knocking combustion in turbocharged direct-injection spark-ignition engines. The experimental study is based on parameter variations in the intake-manifold temperature and pressure, as well as the air-fuel equivalence ratio. The transition between knocking and non-knocking operating conditions is studied by conducting a spark timing sweep for each operating parameter. By correlating combustion and global knock quantities, the global knock trends of the mean cycles are identified. Further insight is gained by a detailed analysis based on single cycles. The extensive experimental data is then used as an input to support numerical investigations. Based on 0D knock modeling, the global knock trends are investigated for all operation points. Taking into consideration the influence of nitric oxide on auto-ignition significantly improves the knock model prediction. Additionally, the origin of the observed cyclic variability of knock is investigated. The crank angle at knock onset in 1000 consecutive single cycles is determined using a multi-cycle 0D knock simulation based on detailed single-cycle experimental data. The overall trend is captured well by the simulation, while fluctuations are underpredicted. As one potential reason for the remaining differences of the 0D model predictions local phenomena are investigated. Therefore, 3D CFD simulations of selected operating points are performed to explore local inhomogeneities in the mixture fraction and temperature. The previously developed generalized Knock Integral Method (gKIM), which considers the detailed kinetics and turbulence-chemistry interaction of an ignition progress variable, is improved and applied. The determined influence of spark timing on the mean crank angle at knock onset agrees well with experimental data. In addition, spatially resolved information on the expected position of auto-ignition is analyzed to investigate causes of knocking combustion.

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