Virtual Valve Design for Three Dimensional Numerical Simulations of a Large-Bore Natural Gas Engine

2003 ◽  
Author(s):  
Gi-Heon Kim ◽  
Allan T. Kirkpatrick ◽  
Charles E. Mitchell
Keyword(s):  
High Pressure ◽  
Natural Gas ◽  
Numerical Models ◽  
Three Dimensional ◽  
Injection System ◽  
Limiting Factor ◽  
Mixing Enhancement ◽  
Length Scales ◽  
Poppet Valve ◽  
The Impact

One of the promising mixing enhancement technologies for natural gas engines currently used is high pressure fuel injection. Three dimensional computational simulations that can examine the entire injection and mixing process in engines using high pressure injection and determine the impact of injector design on engine performance are consequently of considerable interest. However, the cost of three dimensional engine simulations including a moving piston and the kinetics of combustion and pollutants production quickly becomes considerable in terms of simulation time requirements. The limiting factor is the modeling of the small length scales of the poppet valve flow. Such length scales can be two orders of magnitude smaller than cylinder length scales. The objective of this paper is to describe the development of a compatible virtual valve which can be substituted in three-dimensional numerical models for the complex shrouded poppet valve injection system actually installed in the engine to be simulated. Downstream flow characteristics of the jets from an actual valve and a virtual valve were compared. Various mixing parameters were evaluated in moving piston simulations that include the effect of the jet-piston interaction. Comparison of the results indicated that it is possible to design a simple converging-diverging fuel nozzle that will produce the same jet and subsequently the same large and turbulent scale mixing patterns as a real poppet valve.

Supersonic Virtual Valve Design for Numerical Simulation of a Large-Bore Natural Gas Engine

2007 ◽  
Vol 129 (4) ◽  
pp. 1065-1071 ◽  
Author(s):  
Gi-Heon Kim ◽  
Allan Kirkpatrick ◽  
Charles Mitchell
Keyword(s):  
High Pressure ◽  
Natural Gas ◽  
Large Scale ◽  
Numerical Models ◽  
Three Dimensional ◽  
Injection System ◽  
Limiting Factor ◽  
Length Scales ◽  
Poppet Valve ◽  
The Impact

In many applications of supersonic injection devices, three-dimensional computation that can model a complex supersonic jet has become critical. However, in spite of its increasing necessity, it is computationally costly to capture the details of supersonic structures in intricate three-dimensional geometries with moving boundaries. In large-bore stationary natural gas fueled engine research, one of the most promising mixing enhancement technologies currently used for natural gas engines is high-pressure fuel injection. Consequently, this creates considerable interest in three-dimensional computational simulations that can examine the entire injection and mixing process in engines using high-pressure injection and can determine the impact of injector design on engine performance. However, the cost of three-dimensional engine simulations—including a moving piston and the kinetics of combustion and pollutant production—quickly becomes considerable in terms of simulation time requirements. One limiting factor is the modeling of the small length scales of the poppet valve flow. Such length scales can be three orders of magnitude smaller than cylinder length scales. The objective of this paper is to describe the development of a methodology for the design of a simple geometry supersonic virtual valve that can be substituted in three-dimensional numerical models for the complex shrouded poppet valve injection system actually installed in the engine to be simulated. Downstream flow characteristics of the jets from an actual valve and various virtual valves are compared. Relevant mixing parameters, such as local equivalent ratio and turbulence kinetic energy, are evaluated in full-scale moving piston simulations that include the effect of the jet-piston interaction. A comparison of the results has indicated that it is possible to design a simple converging-diverging fuel nozzle that will produce the same jet and, subsequently, the same large-scale and turbulent-scale mixing patterns in the engine cylinder as a real poppet valve.

Influence of Different Parametrizations on the Optimum Design of a High Pressure Turbine Blade Firtree

2016 ◽  
Author(s):  
Frank Wagner ◽  
Arnold Kühhorn ◽  
Thomas Weiss ◽  
Dierk Otto
Keyword(s):  
High Pressure ◽  
Turbine Blade ◽  
Complex Geometry ◽  
Three Dimensional ◽  
Parametric Models ◽  
Limiting Factor ◽  
High Pressure Turbine ◽  
The Creation ◽  
High Flexibility ◽  
Critical Regions

Today the design processes in the aero industry face many challenges. Apart from automation itself, a suitable parametric geometry setup plays a significant role in making workflows usable for optimization. At the same time there are tough requirements against the parametric model. For the lowest number of possible parameters, which should be intuitively ascertainable, a high flexibility has to be ensured. Within the parameter range an acceptable stability is necessary. Under these constraints the creation of such parametric models is a challenge, which should not be underestimated especially for a complex geometry. In this work different kinds of parametrization with different levels of complexity will be introduced and compared. Thereby several geometry elements will be used to handle the critical regions of the geometry. In the simplest case a combination of lines and arcs will be applied. These will be replaced by superior elements like a double arc construct or different formulations of b-splines. There will be an additional focus on the variation of spline degree and control points. To guarantee consistency a set of general parameters will be used next to the specific ones at the critical regions. The different parameter boundaries have a influence on the possible geometries and should therefore be tested separately before an optimization run. The analysis of the particular parametrization should be compared against the following points: • effort for the creation of the parametrization in theory • required time for the implementation in the CAD software • error-proneness/robustness of the parametrization • flexibility of the possible geometries • accuracy of the results • influence of the number of runs on the optimization • comparison of the best results Even though this assessment matrix is only valid for the considered case, it should show the general trend for the creation of these kinds of parametric models. This case takes a look at a firtree of a high pressure turbine blade, which is a scaled version of the first row from a small to medium aero engine. The failure of such a component can lead to a critical engine failure. For that reason, the modeling/meshing must be done very carefully and the contact between the blade and the disc is of crucial importance. It is possible to use scaling factors for three dimensional effects to reduce the problem to a two dimensional problem. Therefore the contact description is shortened from face-to-line to line-to-point. The main aim of the optimization is the minimization of the tension (notch stress) at the inner bends of the blade respectively at the outer bends of the disc. This has been the limiting factor in previous investigations. At this part of the geometry the biggest improvement are expected from a superior parametrization. Another important constraint in the optimization is the pressure contact (crushing stress) between blade and disc. Additionally the geometry is restricted with measurements of the lowest diameter at specific fillets to fulfill manufacturing requirements.

scholarly journals The Impact of Covariance Localization for Radar Data on EnKF Analyses of a Developing MCS: Observing System Simulation Experiments

2013 ◽  
Vol 141 (11) ◽  
pp. 3691-3709 ◽  
Author(s):  
Ryan A. Sobash ◽  
David J. Stensrud
Keyword(s):  
System Simulation ◽  
Three Dimensional ◽  
Radar Data ◽  
Convective System ◽  
State Variables ◽  
Simulation Experiments ◽  
Length Scales ◽  
Convective Scale ◽  
The Impact ◽  
Prior State

Abstract Several observing system simulation experiments (OSSEs) were performed to assess the impact of covariance localization of radar data on ensemble Kalman filter (EnKF) analyses of a developing convective system. Simulated Weather Surveillance Radar-1988 Doppler (WSR-88D) observations were extracted from a truth simulation and assimilated into experiments with localization cutoff choices of 6, 12, and 18 km in the horizontal and 3, 6, and 12 km in the vertical. Overall, increasing the horizontal localization and decreasing the vertical localization produced analyses with the smallest RMSE for most of the state variables. The convective mode of the analyzed system had an impact on the localization results. During cell mergers, larger horizontal localization improved the results. Prior state correlations between the observations and state variables were used to construct reverse cumulative density functions (RCDFs) to identify the correlation length scales for various observation-state pairs. The OSSE with the smallest RMSE employed localization cutoff values that were similar to the horizontal and vertical length scales of the prior state correlations, especially for observation-state correlations above 0.6. Vertical correlations were restricted to state points closer to the observations than in the horizontal, as determined by the RCDFs. Further, the microphysical state variables were correlated with the reflectivity observations on smaller scales than the three-dimensional wind field and radial velocity observations. The ramifications of these findings on localization choices in convective-scale EnKF experiments that assimilate radar data are discussed.

scholarly journals HYDRAULIC RISK ASSESSMENT IN ARCHAEOLOGICAL SITES SUPPORTED BY AN INTEGRATED DIGITAL SURVEY – CFD (COMPUTATIONAL FLUID DYNAMICS) MONITORING APPROACH

2021 ◽  
Vol XLVI-M-1-2021 ◽  
pp. 155-163
Author(s):  
G. D’Agostino ◽  
M. Figuera ◽  
V. Pennisi ◽  
G. Russo ◽  
M. Sanfilippo ◽  
...  
Keyword(s):  
Numerical Models ◽  
Methodological Approach ◽  
Three Dimensional ◽  
Laser Scanner ◽  
Morphological Characteristics ◽  
Interdisciplinary Approach ◽  
Research Approach ◽  
Archaeological Heritage ◽  
The Impact ◽  
Main Entrance

Abstract. This paper presents a methodological approach for analysing and evaluating hydraulic risks in complex archaeological areas, and thereby substantially improve general preservation and conservation efforts involving cultural heritage.The hypogeum of Calaforno (province of Ragusa, Sicily) represents a unique sample of rock-cut architecture in terms of size and architectural features, and an ideal candidate for the case study due to its high historical, archaeological and cultural significance, as well as its intrinsic fragility and criticality associated with hydrogeological and seismic factors.The interdisciplinary research approach involved archaeological and engineering contributions towards the development of numerical models for the assessment of hydraulic risks threatening archaeological heritage. The morphological characteristics of the site rendered the use of a Laser Scanner necessary for three-dimensional survey.The prehistoric structures currently undergoing excavation outside the main entrance of the monument have raised concerns regarding the impact of the Manna stream, which flows a few meters from the main entrance to the hypogeum, which has seen periodic flooding in some of its rooms. Simulations of these flooding events were performed in order to attain better understanding of the hydraulic phenomena influencing the site, especially regarding the dynamics associated with surface runoff.The interdisciplinary approach to this research, combining in-depth archaeological expertise with digital 3D surveying and modelling technologies, has proven fundamental to the effective monitoring of this morphologically complex site, and should perhaps be considered integral to any preventive assessment and risk management initiative involving cultural heritage.

Vortex Transport and Blade Interactions in High Pressure Turbines

2003 ◽  
Author(s):  
V. S. P. Chaluvadi ◽  
A. I. Kalfas ◽  
H. P. Hodson
Keyword(s):  
High Pressure ◽  
Flow Field ◽  
Rotor Blade ◽  
Delta Wing ◽  
Classical Model ◽  
Three Dimensional ◽  
Axial Flow ◽  
Passage Vortex ◽  
Blade Row ◽  
The Impact

This paper presents a study of the three-dimensional flow field within the blade rows of a high-pressure axial flow steam turbine stage. Half-delta wings were fixed to a rotating hub to simulate an upstream rotor passage vortex. The flow field is investigated in a Low-Speed Research Turbine using pneumatic and hot-wire probes downstream of the blade row. The paper examines the impact of the delta wing vortex transport on the performance of the downstream blade row. Steady and unsteady numerical simulations were performed using structured 3D Navier-Stokes solver to further understand the flow field. The loss measurements at the exit of the stator blade showed an increase in stagnation pressure loss due to the delta wing vortex transport. The increase in loss was 21% of the datum stator loss, demonstrating the importance of this vortex interaction. The transport of the stator viscous flow through the rotor blade row is also described. The rotor exit flow was affected by the interaction between the enhanced stator passage vortex and the rotor blade row. Flow underturning near the hub and overturning towards the mid-span was observed, contrary to the classical model of overturning near the hub and underturning towards the mid-span. The unsteady numerical simulation results were further analysed to identify the entropy producing regions in the unsteady flow field.

The Impact of New Technologies on Nigeria's Oil Reserves

1993 ◽  
Vol 11 (5) ◽  
pp. 414-422
Author(s):  
Adebayo Aina
Keyword(s):  
Natural Gas ◽  
Oil And Gas ◽  
New Technologies ◽  
Three Dimensional ◽  
Petroleum Exploration ◽  
Seismic Survey ◽  
Oil Reserves ◽  
Technological Developments ◽  
Oil And Natural Gas ◽  
The Impact

Two key technological developments in petroleum exploration - three dimensional seismic survey (3-D Seismic) and integrated seismic interpretation workstations - have led to significant discoveries of oil and gas in the various Nigerian oil provinces where they have been introduced. These new technologies were introduced in Nigeria in the mid-1980s and have since resulted in significant additions to the country's proven crude oil and natural gas reserves.

The Research of Structural Optimization on Diesel Engine Injection Nozzle

2010 ◽  
Vol 97-101 ◽  
pp. 2571-2575
Author(s):  
Ming Hai Li ◽  
Hong Jiang Cui ◽  
Yun Dong Han ◽  
Ang Li
Keyword(s):  
Diesel Engine ◽  
Flow Field ◽  
Numerical Models ◽  
Three Dimensional ◽  
Injection Pressure ◽  
Injection System ◽  
Flow Structures ◽  
Spray Nozzle ◽  
Cad Cam ◽  
Flow Turbulence

In order to improve the performance of 16 V280 diesel engine, the three-dimensional numerical models of the flow field in the nozzle which belongs to the injection system was built, and different detailed flow structures was captured under different pressure conditions. Through the analysis of the flow field, the unsuitable position of the nozzle was located, and the methods which combine CAD / CAM / CFD was applicated to optimize the structure of the nozzle. The analysis results indicate that with the increase of the injection pressure; the flow turbulence intensity increases; the more energy get lost, which was caused by turbulence; the coefficient of flow decreases. After the spray nozzle structure was changed into sphere pin valve, the mass flux under the same level of injection pressure was improved greatly.

scholarly journals Complementing Syngas with Natural Gas in Spark Ignition Engines for Power Production: Effects on Emissions and Combustion

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3688
Author(s):  
Carlo Caligiuri ◽  
Urban Žvar Baškovič ◽  
Massimiliano Renzi ◽  
Tine Seljak ◽  
Samuel Rodman Oprešnik ◽  
...  
Keyword(s):  
Natural Gas ◽  
Spark Ignition ◽  
External Input ◽  
Spark Ignition Engine ◽  
Experimental Methodology ◽  
Pollutant Emission ◽  
Limiting Factor ◽  
Main Research ◽  
Partial Load ◽  
The Impact

Power generation units based on the bio-syngas system face two main challenges due to (i) the possible temporary shortage of primary sources and (ii) the engine power derating associated with the use of low-energy density fuels in combustion engines. In both cases, an external input fuel is provided. Hence, complementing syngas with traditional fuels, like natural gas, becomes a necessity. In this work, an experimental methodology is proposed, aiming at the quantification of the impact of the use of both natural gas and syngas in spark ignition (SI) engines on performance and emissions. The main research questions focus on investigating brake thermal efficiency (BTE), power derating, and pollutant emission (NOx, CO, THC, CO2) formation, offering quantitative findings that present the basis for engine optimization procedures. Experimental measurements were performed on a Toyota 4Y-E engine (a 4-cylinders, 4-stroke spark ignition engine) at partial load (10 kW) under different syngas energy shares (SES) and at four different spark ignition timings (10°, 25°, 35° and 45° BTDC). Results reveal that the impact of the different fuel mixtures on BTE is negligible if compared to the influence of spark advance variation on BTE. On the other hand, power derating has proven to be a limiting factor and becomes more prominent with increasing SES. An increasing SES also resulted in an increase of CO and CO2 emissions, while NOx and THC emissions decreased with increasing SES.

Customising semi-active resetable device behaviour for abating seismic structural response

2009 ◽  
Vol 42 (3) ◽  
pp. 147-156
Author(s):  
Geoffrey W. Rodgers ◽  
J. Geoffrey Chase ◽  
Kerry J. Mulligan ◽  
John B. Mander ◽  
Rodney B. Elliott
Keyword(s):  
High Pressure ◽  
Structural Control ◽  
Hysteresis Loops ◽  
Structural Response ◽  
Initial Pressure ◽  
Working Fluid ◽  
Limiting Factor ◽  
Base Shear ◽  
Active Structural Control ◽  
The Impact

Semi-active resetable actuators have been shown to be capable of significantly improving seismic structural response and customising structural hysteresis loops to reduce both displacement and base shear demands. Hence, device behaviour and dynamics can be tailored to the application. However, the maximum forces produced, in particular with air as the working fluid, can be a limiting factor to avoid extreme device sizes. This investigation incorporates an actively controlled (stored) high-pressure air source to enhance the capabilities of such resetable devices. The devices are designed using a validated non-linear model incorporating the dynamics and non-linearities of the working fluid, valves, sensor lags and computational limitations. Initial simulations show 100-600% increases in the peak device forces, with 100% obtained when the initial pressure is doubled. In addition, the high pressure source allows greater manipulation of the device behaviour and response. This additional flexibility enables, for example, devices that are more resistant or resist differently in opposing directions. The impact of device enhancements over standard resetable devices is then demonstrated experimentally. This paper extends these novel resetable devices to create more flexible and actively controlled devices for semi-active structural control. Finally, a “net-zero base shear design” concept is presented, where the added damping reaction forces are exactly offset by structural response reductions to give large displacement reductions with no overall change to base shear forces – maximising control with no impact on the foundations.

An experimental study for effect factors of the roller tappet induced impact noise in high-pressure fuel system of GDi engine

2020 ◽  
Vol 234 (10-11) ◽  
pp. 2473-2484
Author(s):  
Hui-Min Shen ◽  
Pei Tang ◽  
Chong Lian ◽  
Liangliang Hu ◽  
Shuang Wei
Keyword(s):  
High Pressure ◽  
Direct Injection ◽  
Gasoline Direct Injection ◽  
Injection System ◽  
Effect Factors ◽  
Fuel Pump ◽  
Impact Noise ◽  
Transmission Part ◽  
The Time Domain ◽  
The Impact

With the wide application of gasoline direct injection system, its noise problem is becoming increasingly prominent under serious competitive environment. As the primary noise source of the engine in idle condition, the significant noise generated by the low-to-high pressure transmission part of high-pressure fuel pump becomes more and more serious. This paper focuses on the driving component of high-pressure fuel pump, the roller tappet, and experimentally studies effect factors of impact noise induced by it at engine idle. Both the impact occurrence time and position are analyzed from the combined vibration acceleration and crankshaft/camshaft rotation angle signals in the time domain according to the structure and kinematic mechanism of the roller tappet. The influences of the axial clearance between roller and tappet shell, the engine rotation speed and the lubrication conditions are investigated by experiments. The experimental results show that the lubrication is the primary factor for the roller tappet induced impact noise reduction. A significant improvement about 83% can be achieved under pressure lubrication.

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