A Transported Livengood-Wu Integral Model for Knock Prediction in CFD Simulation

2021 ◽  
Author(s):  
Zongyu Yue ◽  
Chao Xu ◽  
Sibendu Som ◽  
Charles Scott Sluder ◽  
K. Dean Edwards ◽  
...  
Keyword(s):  
Cfd Simulation ◽  
Operating Conditions ◽  
Spark Ignition Engine ◽  
Single Stage ◽  
Integral Model ◽  
Two Stage ◽  
Modeling Approach ◽  
Oscillation Analysis ◽  
Auto Ignition ◽  
Wide Range

Abstract This work describes the development of a transported Livengood-Wu (L-W) integral model for computational fluid dynamics (CFD) simulation to predict auto-ignition and engine knock tendency. The currently employed L-W integral model considers both single-stage and two-stage ignition processes, thus can be generally applied to paraffin, olefin, aromatics and alcohol. The model implementation is first validated in simulations of homogeneous charge compression ignition combustion for three different fuels, showing good accuracy in prediction of auto-ignition timing for fuels with either single-stage or two-stage ignition characteristics. Then, the L-W integral model is coupled with G-equation model to indicate end-gas auto-ignition and knock tendency in CFD simulations of a direct-injection spark-ignition engine. This modeling approach is about 10 times more efficient than the ones that based on detailed chemistry calculation and pressure oscillation analysis. Two fuels with same Research Octane Number but different octane sensitivity are studied, namely Co-Optima Alkylate and Co-Optima E30. The CFD model is validated against experimental data in terms of pressure traces and heat release rate for both fuels under a wide range of operating conditions. The knock tendency-indicated by fuel energy contained in the auto-ignited region-of the two fuels at different load conditions correlates well with the experimental results and the fuel octane sensitivity, implying the current knock modeling approach can capture the octane sensitivity effect and can be applied to further investigation on composition of octane sensitivity.

scholarly journals A Transported Livengood-Wu Integral Model for Knock Prediction in CFD Simulation

2020 ◽  
Author(s):  
Zongyu Yue ◽  
Chao Xu ◽  
Sibendu Som ◽  
C. Scott Sluder ◽  
K. Dean Edwards ◽  
...  
Keyword(s):  
Cfd Simulation ◽  
Operating Conditions ◽  
Spark Ignition Engine ◽  
Single Stage ◽  
Integral Model ◽  
Two Stage ◽  
Modeling Approach ◽  
Oscillation Analysis ◽  
Auto Ignition ◽  
Wide Range

Abstract This work describes the development of a transported Livengood-Wu (L-W) integral model for computational fluid dynamics (CFD) simulation to predict auto-ignition and engine knock tendency. The currently employed L-W integral model considers both single-stage and two-stage ignition processes, thus can be generally applied to different fuels such as paraffin, olefin, aromatics and alcohol. The model implementation is first validated in simulations of homogeneous charge compression ignition combustion for three different fuels, showing good accuracy in prediction of auto-ignition timing for fuels with either single-stage or two-stage ignition characteristics. Then, the L-W integral model is coupled with G-equation model to indicate end-gas auto-ignition and knock tendency in CFD simulations of a direct-injection spark-ignition engine. This modeling approach is about 10 times more efficient than the ones that based on detailed chemistry calculation and pressure oscillation analysis. Two fuels with same Research Octane Number (RON) but different octane sensitivity are studied, namely Co-Optima Alkylate and Co-Optima E30. Feed-forward neural network model in conjunction with multi-variable minimization technique is used to generate fuel surrogates with targets of matched RON, octane sensitivity and ethanol content. The CFD model is validated against experimental data in terms of pressure traces and heat release rate for both fuels under a wide range of operating conditions. The knock tendency — indicated by the fuel energy contained in the auto-ignited region — of the two fuels at different load conditions correlates well with the experimental results and the fuel octane sensitivity, implying the current knock modeling approach can capture the octane sensitivity effect and can be applied to further investigation on composition of octane sensitivity.

scholarly journals Pressure losses and oscillations in a compact valve of a steam turbine

2021 ◽  
Vol 345 ◽  
pp. 00027
Author(s):  
Václav Sláma ◽  
David Šimurda ◽  
Lukáš Mrózek ◽  
Ladislav Tajč ◽  
Jindřich Hála ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Pressure Oscillation ◽  
Operational Reliability ◽  
Operating Conditions ◽  
Steam Turbines ◽  
Valve Seat ◽  
Pressure Losses ◽  
Oscillation Analysis ◽  
Seat Angle ◽  
Wide Range

Characteristics of a new compact valve design for steam turbines are analysed by measuring pressure losses and oscillations on the valve model. It is the model of an intercept valve of the intermediate-pressure turbine part. This valve is relatively smaller hence cheaper than usual control and intercept valves. Besides, four different valve seat angles were tested in order to investigate the valve seat angle influence. In order to further clarify measured phenomena, the wide range of numerical simulations were also carried out. Measurements were performed in the Aerodynamic laboratory of the Institute of Thermomechanics of the Czech Academy of Sciences in an air test rig installed in a modular aerodynamic tunnel. Numerical simulations were performed in the Doosan Skoda Power Company using a package of ANSYS software tools. Measurement results are compared with numerical and generalized in the form of valve characteristics and pressure oscillation maps. As a result of the pressure loss analysis, pressure losses in similar valve assemblies can be predicted with required accuracy for each new turbine where modern compact valves are used. As a result of the pressure oscillation analysis, operating conditions at which dangerous flow instabilities can occur were identified. Thanks to this, the areas of safe and dangerous operating conditions can be predicted so that the operational reliability of the valve can be guaranteed.

Springs® Design Optimized By Seawater Quality. Laboratory Pilot Tests

2021 ◽  
Author(s):  
Pierre Pedenaud ◽  
Marianna Rondon ◽  
Nicolas Lesage ◽  
Eric Tournis ◽  
Riccardo Giolo ◽  
...  
Keyword(s):  
Water Quality ◽  
Operating Conditions ◽  
Single Stage ◽  
Plant Performance ◽  
Future Application ◽  
Feed Water ◽  
Nanofiltration Membranes ◽  
Two Stage ◽  
Seawater Quality ◽  
The Impact

Abstract A new seawater laboratory pilot has been installed in order to evaluate the impact of the seawater quality on the performance of nanofiltration membranes and filters. The test program implemented was designed to produce the data required to optimize the design and operating parameters of a subsea sulfate removal plant, particularly with respect to the technology developed by Total, Saipem and Veolia, co-owners of the development. The equipment qualification plan is approaching completion with the development of subsea barrier-fluidless pumps, all-electric control systems, high-cycling valves operated by electric actuators and subsea water analyzers. This presented pilot laboratory study completes this plan. Nanofiltration membranes are commonly used to remove the sulfates found in seawater before the water is injected into wells. The principal advantages of relocating this equipment from topside to subsea are better reservoir sweep control, a substantial subsea water injection network reduction and savings on space and weight on the topsides deck. The move to subsea offers the opportunity to simplify the process due to improved deep water quality. This was previously demonstrated through a subsea test campaign. This new pilot study provides data both on the performance of a plant operating with different feed water quality and on the success of operating changes to further optimize the plant performance. The pilot has been installed at the Palavas-les-Flots site in France. Raw water collected from the basin was mixed with ultra-filtered water in order to calibrate the feed water quality. The pilot includes a two stage nanofiltration configuration and single stage nanofiltration unit. The two stage configuration was used to produce data for operation across an array of feed water quality and plant operating conditions. The single stage unit was used to produce data on membrane fouling over a long operating duration. Results from these tests and discussion on how this data relates to subsea plant performance shall be presented. This innovative approach enables a wide range of subsea water quality to be simulated and tested against different process configurations of the subsea unit. Indeed, for each industrial subsea application, the raw seawater quality is dependent on both the region and the depth of the seawater inlet. With this experimental data acquisition campaign and understanding of the seawater quality at inlet, the system design can be tailor-made for each future application case.

CFD Simulation of PWR Subchannel Void Distribution Benchmark

2010 ◽  
Author(s):  
Wang-Kee In ◽  
Chang-Hwan Shin ◽  
Tae-Hyun Chun
Keyword(s):  
Void Fraction ◽  
Cfd Simulation ◽  
Fluid Model ◽  
Small Diameter ◽  
Operating Conditions ◽  
Heated Wall ◽  
Bubble Generation ◽  
Void Distribution ◽  
Wide Range ◽  
Two Fluid Model

A CFD study was performed to simulate the steady-state void distribution benchmark based on the NUPEC PWR Subchannel and Bundle Tests (PSBT). The void distribution benchmark provides measured void fraction data over a wide range of geometrical and operating conditions in a single subchannel and fuel bundle. This CFD study simulated the boiling flow in a single subchannel. A CFD code was used to predict the void distribution inside the single subchannel. The multiphase flow model used in this CFD analysis was a two-fluid model in which liquid (water) and vapor (steam) were considered as continuous and dispersed fluids, respectively. A wall boiling model was also employed to simulate bubble generation on a heated wall surface. The CFD prediction with a small diameter of vapor bubble shows a higher void fraction near the heated wall and a migration of void in the subchannel gap region. A measured CT image of void distribution indicated a locally higher void fraction near the heated wall for the test conditions of a subchannel averaged void fraction of less than about 20%. The CFD simulation predicted a subchannel averaged void fraction and fluid density which agree well with the measured ones for a low void condition.

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.

Hydrogen Fuelled Spark-Ignition Engines: Predictive and Experimental Performance

2003 ◽  
Author(s):  
Hailin Li ◽  
Ghazi A. Karim
Keyword(s):  
Compression Ratio ◽  
Power Efficiency ◽  
Spark Ignition ◽  
Operating Conditions ◽  
Spark Ignition Engine ◽  
Zone Model ◽  
Engine Fuel ◽  
Oxidation Reactions ◽  
Chemical Kinetic Model ◽  
Wide Range

Hydrogen is well recognized as a suitable fuel for spark-ignition engine applications that has many unique attractive features and limitations. It is a fuel that can continue potentially to meet the ever increasingly stringent regulations for exhaust and greenhouse gas emissions. The application of hydrogen as an engine fuel has been tried over many decades by numerous investigators with varying degrees of success. The performance data reported often tend not to display consistent agreement between the various investigators mainly because of the wide differences in engine type, size, operating conditions used and the differing criteria employed to judge whether knock is taking place or not. With the ever-increasing interest in hydrogen as an engine fuel, there is a need to be able to model extensively various features of the performance of spark ignition (S.I.) hydrogen engines so as to investigate and compare reliably the performance of widely different engines under a wide variety of operating conditions. The paper employs a quasi-dimensional two-zone model for the operation of S.I. engines when fuelled with hydrogen. In this approach, the engine combustion chamber at any instant of time during combustion is considered to be divided into two temporally varying zones: a burned zone and an unburned zone. The model incorporates a detailed chemical kinetic model scheme of 30 reaction steps and 12 species, to simulate the oxidation reactions of hydrogen in air. A knock prediction model, developed previously for S.I. methane-hydrogen fuelled engine applications (Shrestha and Karim 1999(a) and 1999(b)) was extended to consider operation on hydrogen. The effects of changes in operating conditions, including a very wide range of variations in equivalence ratio on the onset of knock and its intensity, combustion duration, power, efficiency and operational limits were investigated. The results of this predictive approach were shown to validate well against corresponding experimental results of our own and those of others, obtained mostly in a variable compression ratio CFR engine. On this basis, the effects of changes in some of the key operational engine variables, such as compression ratio, intake temperature and spark timing are presented and discussed. Some guidelines for superior knock free-operation of engines on hydrogen are made also.

Ethanol Mechanism Reduction Based on DRGEPSA Method at Various Operating Ranges

2020 ◽  
Author(s):  
Shrabanti Roy ◽  
Omid Askari
Keyword(s):  
Sensitivity Analysis ◽  
Error Propagation ◽  
Cfd Simulation ◽  
Reduction Process ◽  
Chemical Kinetic ◽  
Operating Conditions ◽  
Computational Time ◽  
Wide Range ◽  
Relation Graph ◽  
Future Work

Abstract Reducing the size of a detail chemical kinetic is necessary in the prospect of numerical computation. In this work a skeleton reduction is done on a detail mechanism of ethanol. The detailed ethanol mechanism used here is developed through reaction mechanism generator (RMG). The generated mechanism is validated at wide range of engine relevant operating conditions using laminar burning speed (LBS), ignition delay time (IDT) and species mole fraction calculation at different reactor conditions. This detail mechanism consists of 67 species and 1031 reactions. Though the mechanism is in a very good agreement at various operating ranges with experimental data, it is costly to use a detail mechanism for 3D computational fluid dynamics (CFD) analysis. To make the mechanism applicable for CFD simulation further reduction of species and reactions is essential. In this work a skeleton mechanism is generated using directed relation graph technique with error propagation and sensitivity analysis (DRGEPSA). The DRGEPSA method, works based on error calculation at user defined condition. This technique is a combination of two methods, directed relation graph with error propagation (DRGEP) and directed relation graph with sensitivity analysis (DRGASA). To ensure the wide range of applicability of the skeleton mechanism, IDT is calculated at temperature, pressure, and equivalence ratio ranges from 700–2000 K, 1–40 atm and 0.6–1.4 respectively. A 10% error estimation is considered during the process. Initially DRGEP is applied on the detail mechanism to eliminate unimportant species. Further, sensitivity analysis helps to identify and reduce more unimportant species from the mechanism. Reactions related to the deleted species are automatically removed from the mechanism in each step. The final skeleton mechanism has 42 species and 464 reactions. This skeleton mechanism is validated and compared with different IDT data for the conditions not used in reduction technique. Results of LBS and different species concentration from reactor conditions is considered for validation. The skeleton mechanism can reduce computational time by 35% for LBS and 25% for IDT calculation. For future work, this skeleton mechanism will be considered in optimum reduction process.

Dynamic Simulation and Optimization of Two-Stage Extractive Alcoholic Fermentation Process: Design Impact on Controllability

2006 ◽  
Vol 1 (1) ◽  
Author(s):  
Jobrun Nandong ◽  
Yudi Samyudia ◽  
Moses O Tadé
Keyword(s):  
Fermentation Process ◽  
Dynamic Performance ◽  
Operating Conditions ◽  
Single Stage ◽  
Extractive Fermentation ◽  
Two Stage ◽  
Stage Design ◽  
Simulation And Optimization ◽  
The Face ◽  
Two Stage Design

In this paper, we address dynamic controllability of the two different designs of extractive fermentation process, namely one-stage and two-stage designs. The operating conditions that maximize yields and productivity for both designs are determined by optimization using the method of factorial design and response surface analysis. The results show that in terms of the achievable yield and productivity, the performance of the two-stage design is comparable to that of the single-stage, but the former design leads to a significant reduction in the fermentor size required. Furthermore, we analyze the dynamic controllability of the two designs of extractive fermentation process using a so-called control relevant metrics to examine their closed-loop dynamic performance in the face of uncertainty. This analysis reveals that the single-stage design has more favorable dynamic controllability than the two-stage design.

Numerical Investigation of the Effect of Knock on Heat Transfer in a Turbocharged Spark Ignition Engine

2015 ◽  
Vol 137 (12) ◽  
Author(s):  
Arman Rostampour ◽  
Ali Nassiri Toosi
Keyword(s):  
Heat Transfer ◽  
Spark Ignition Engine ◽  
Integral Model ◽  
Dual Fuel ◽  
Average Pressure ◽  
Gas Temperature ◽  
Ignition Timing ◽  
Total Heat Transfer ◽  
Operating Cycle ◽  
Auto Ignition

This investigation deals with the EF7 (TC) engine, a dual fuel engine equipped with a turbocharger system, consequently with a high probability of knock inception. In this study, an operating cycle of the engine was simulated using KIVA-3V code. Some modifications were carried out on the KIVA method of calculating pressure in the intake port in order to simulate turbocharger pressure correctly. Auto-ignition and knock were then simulated using the auto-ignition integral model. The modified code and the simulation were verified using three different methods; in-cylinder average pressure, gas temperature of the exhaust port, and auto-ignition timing. The simulation results using the auto-ignition integral model, as compared with the experimental data, proved to be reasonably accurate. Following this validation, the effect of the knock phenomenon on the engine heat transfer through the walls was investigated. The simulations showed that the rate of heat transfer through the walls under knocking conditions is about 2.2 times higher than that under normal conditions. However, it was also shown that the total heat transfer increases about 15%.

A Mean-Value Model of Internal Combustion Engine Based on Variable Valve Phase Timing

2012 ◽  
Author(s):  
S. M. Navid Khatami ◽  
Olusegun J. Ilegbusi
Keyword(s):  
Gas Exchange ◽  
Phase Angle ◽  
Combustion Engine ◽  
Mean Value ◽  
Operating Conditions ◽  
Spark Ignition Engine ◽  
Wide Range ◽  
Mean Value Model ◽  
Variable Valve ◽  
Value Model

A simplified Mean-Value Model (MVM) is developed to represent spark ignition engine functions. The model is based on variable valve phase angle over a wide range of operating conditions. Gas exchange dynamics is simulated to determine the mass air flow into the cylinder. This flow is altered by variable valve phase mechanism. In this paper, phasing the exhaust and intake valves is considered equally (dual equal) and is equipped with hydraulics Continuous Variable Valve Timing (CVVT) mechanism. The model developed reflects these modifications and uses gas exchange dynamics to capture valve phase, manifold pressure, and engine rotating speed. The values of flow rates from this simplified mathematical model is compared and validated with engine-dynamometer experimental data. The results show strong agreement in a wide range of operating points while the variation of phase angle is limited to nominal values.

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