Proposal of a Load Sensing Two-Way Valve Model, Applying “Design of Experiments” Techniques to Simulations

2006 ◽  
Author(s):  
Andrea Vacca
Keyword(s):  
Design Of Experiments ◽  
Analytical Model ◽  
Flow Rate ◽  
Operating Conditions ◽  
Fractional Factorial ◽  
Geometrical Parameters ◽  
Screening Analysis ◽  
Load Sensing ◽  
Actual Behaviour ◽  
Wide Range

This paper defines an analytical model, based on results of simulations, for the description of the actual behaviour of a particular load sensing valve. The component considered for the analysis is typically applied in steering systems, with a load sensing control strategy, in presence of other actuators. Controlling the primary port flow rate is the valve's scope, the exceeding flow being discharged to the secondary port. A simple analytical model of the valve is commonly used in the industrial field and is useful for the understanding of its operation in a generic hydraulic system. However, experiments show that the actual behaviour is strongly influenced by the flow rate through the valve, and depends also on many geometrical parameters (i.e. shape of spool grooves, spool edges distance, etc.). The simple empirical model presented in this paper is defined considering only parameters primarily affecting the valve operation. As it often happens in searching for new models, the discovery of the most influencing factors presents several difficulties, because of their large number and, mainly, because it is difficult to consider all possible mutual interactions. Therefore, in this analysis, a stochastic-based method has been chosen, according to a technique known as "Design of Experiments" (DOE). In the first part of the paper, the author presents a screening analysis of the valve, under all the possible operating conditions. This procedure allows the identification of the most influencing parameters, for the development of the enhanced model of the valve. The configurations examined were chosen defining an optimal experimental plan, that allows an high significance of results with a restricted number of tests, through fractional factorial strategies. Further, this analysis gives a lot of useful information for the improvement of the valve design. In the remaining section of this paper, the author presents a correlative model of actual valve behaviour. This is generalized to a wide range of possible spool geometries, and is characterized by a simple formulation, accounting for only a few parameters, highlighted by the screening analysis. All results processed by DOE algorithms, implemented with MATLAB® scripts, are evaluated through simulations, instead of experiments. For this purpose, a previously developed AMESim® model of the valve (validated on the basis of laboratory tests) has been utilized.

scholarly journals Experimental Investigation and Modeling of Inertance Tubes

2005 ◽  
Vol 127 (5) ◽  
pp. 1029-1037 ◽  
Author(s):  
L. O. Schunk ◽  
G. F. Nellis ◽  
J. M. Pfotenhauer
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Acoustic Power ◽  
Operating Conditions ◽  
Thermodynamic Efficiency ◽  
Pulse Tube ◽  
Design Charts ◽  
Wide Range ◽  
Pulse Tube Refrigerators

Growing interest in larger scale pulse tubes has focused attention on optimizing their thermodynamic efficiency. For Stirling-type pulse tubes, the performance is governed by the phase difference between the pressure and mass flow, a characteristic that can be conveniently adjusted through the use of inertance tubes. In this paper we present a model in which the inertance tube is divided into a large number of increments; each increment is represented by a resistance, compliance, and inertance. This model can include local variations along the inertance tube and is capable of predicting pressure, mass flow rate, and the phase between these quantities at any location in the inertance tube as well as in the attached reservoir. The model is verified through careful comparison with those quantities that can be easily and reliably measured; these include the pressure variations along the length of the inertance tube and the mass flow rate into the reservoir. These experimental quantities are shown to be in good agreement with the model’s predictions over a wide range of operating conditions. Design charts are subsequently generated using the model and are presented for various operating conditions in order to facilitate the design of inertance tubes for pulse tube refrigerators. These design charts enable the pulse tube designer to select an inertance tube geometry that achieves a desired phase shift for a given level of acoustic power.

Subsynchronous Vibration Patterns Under Reduced Oil Supply Flow Rates

2017 ◽  
Author(s):  
B. R. Nichols ◽  
R. L. Fittro ◽  
C. P. Goyne
Keyword(s):  
Flow Rate ◽  
High Speed ◽  
Operating Conditions ◽  
System Stability ◽  
Supporting Evidence ◽  
Test Rig ◽  
Flow Rates ◽  
Oil Supply ◽  
Bending Mode ◽  
Wide Range

Many high-speed, rotating machines across a wide range of industrial applications depend on fluid film bearings to provide both static support of the rotor and to introduce stabilizing damping forces into the system through a developed hydrodynamic film wedge. Reduced oil supply flow rate to the bearings can cause cavitation, or a lack of a fully developed film layer, at the leading edge of the bearing pads. Reducing oil flow has the well-documented effects of higher bearing operating temperatures and decreased power losses due to shear forces. While machine efficiency may be improved with reduced lubricant flow, little experimental data on its effects on system stability and performance can be found in the literature. This study looks at overall system performance of a test rig operating under reduced oil supply flow rates by observing steady-state bearing performance indicators and baseline vibrational response of the shaft. The test rig used in this study was designed to be dynamically similar to a high-speed industrial compressor. It consists of a 1.55 m long, flexible rotor supported by two tilting pad bearings with a nominal diameter of 70 mm and a span of 1.2 m. The first bending mode is located at approximately 5,000 rpm. The tiling-pad bearings consist of five pads in a vintage, flooded bearing housing with a length to diameter ratio of 0.75, preload of 0.3, and a load-between-pad configuration. Tests were conducted over a number of operating speeds, ranging from 8,000 to 12,000 rpm, and bearing loads, while systematically reducing the oil supply flow rates provided to the bearings under each condition. For nearly all operating conditions, a low amplitude, broadband subsynchronous vibration pattern was observed in the frequency domain from approximately 0–75 Hz. When the test rig was operated at running speeds above its first bending mode, a distinctive subsynchronous peak emerged from the broadband pattern at approximately half of the running speed and at the first bending mode of the shaft. This vibration signature is often considered a classic sign of rotordynamic instability attributed to oil whip and shaft whirl phenomena. For low and moderate load conditions, the amplitude of this 0.5x subsynchronous peak increased with decreasing oil supply flow rate at all operating speeds. Under the high load condition, the subsynchronous peak was largely attenuated. A discussion on the possible sources of this subsynchronous vibration including self-excited instability and pad flutter forced vibration is provided with supporting evidence from thermoelastohydrodynamic (TEHD) bearing modeling results. Implications of reduced oil supply flow rate on system stability and operational limits are also discussed.

Modelling of Partially Wetting Liquid Film Using an Enhanced Thin Film Model for Aero-Engine Bearing Chamber Applications

2020 ◽  
Author(s):  
K. Singh ◽  
M. Sharabi ◽  
R. Jefferson-Loveday ◽  
S. Ambrose ◽  
C. Eastwick ◽  
...  
Keyword(s):  
Thin Film ◽  
Contact Angle ◽  
Film Thickness ◽  
Liquid Film ◽  
Flow Rate ◽  
Operating Conditions ◽  
Film Model ◽  
Thin Film Model ◽  
Wide Range ◽  
Aero Engine

Abstract In the case of aero-engine, thin lubricating film servers dual purpose of lubrication and cooling. Prediction of dry patches or lubricant starved region in bearing or bearing chambers are required for safe operation of these components. In the present work thin liquid film flow is numerically investigated using the framework of the Eulerian thin film model (ETFM) for conditions which exhibit partial wetting phenomenon. This model includes a parameter that requires adjustment to account for the dynamic contact angle. Two different experimental data sets have been used for comparisons against simulations, which cover a wide range of operating conditions including varying the flow rate, inclination angle, contact angle, and liquid-gas surface tension coefficient. A new expression for the model parameter has been proposed and calibrated based on the simulated cases. This is employed to predict film thickness on a bearing chamber which is subjected to a complex multiphase flow. From this study, it is observed that the proposed approach shows good quantitative comparisons of the film thickness of flow down an inclined plate and for the representative bearing chamber. A comparison of model predictions with and without wetting and drying capabilities is also presented on the bearing chamber for shaft speed in the range of 2,500 RPM to 10,000 RPM and flow rate in the range of 0.5 liter per minute (LPM) to 2.5 LPM.

scholarly journals МЕТОД РАСЧЕТА ТЕРМОГАЗОДИНАМИЧЕСКИХ ПАРАМЕТРОВ ТУРБОВАЛЬНОГО ГТД НА ОСНОВЕ ПОВЕНЦОВОГО ОПИСАНИЯ ЛОПАТОЧНЫХ МАШИН. ЧАСТЬ 1. ОСНОВНЫЕ УРАВНЕНИЯ

2018 ◽  
pp. 48-58
Author(s):  
Людмила Георгиевна Бойко ◽  
Олег Владимирович Кислов ◽  
Наталия Владимировна Пижанкова
Keyword(s):  
Gas Turbine ◽  
Flow Rate ◽  
Pressure Ratio ◽  
Turbine Engines ◽  
Geometrical Parameters ◽  
Gas Turbine Engines ◽  
Balance Equations ◽  
Wide Range ◽  
In Series ◽  
Multistage Compressor

Gas turbine engines processes mathematic simulations are widely used in different steps of its living cycle. All engine simulations may be divided into different difficulty levels: higher simulation level allows doing a more pre­cise description of physical processes in main units of gas turbine engines and their elements. It gives the oppor­tunity for getting better arrangement of calculation results and experimental data, reduce the quality of factors, which are traditionally used in determine engine operational characteristics with 1-level models.The purpose of the article is to describe the thermogasdynamic parameters and maintenance perfomances cal­culation method, which based on second level mathematic simulation. Its main feature is blade-to-blade turbomachines description (multistage compressor and multistage cooling gas turbine), which allows to take into account blade and flow path geometrical parameters. Their changing during the gas turbine engine design and de­velopment processes influence its performances: thrust, fuel consumption, efficiency as functions of values of flow rate, rotational speed, engine entrance conditions and so on. All these dependences could be defined by using proposed calculation method.In distinction from methods which are noted, this method allows to concede compressor or turbine incidence angles, drag values, pressure ratio, surge margin in design and off-design  engine regimes. The opportunity to take into account by-passing and air bleeding from compressor blade channels and their engine parameters influence is very important also.The article includes calculation method main points, block-scheme, equations system, which gives the opportunity of alignment the engine units and their elements in wide range of state working regimes. Set of equations consists of flow rate balance equations through the stages of multistage compressor and turbine, combustion chamber and connected channels. Also system includes power balance equations, by-passing, air bleeding from compressor stages channels, its admission into the cooling turbine stages and ac­counts their thermodynamic parameters. Compressors and turbines maps parameters are calculated with main turbomachinery theory lows and semi-empirical dependences.This article is the first in series of articles, which considers this problem

scholarly journals The Statistical Optimisation of Recombinant β-glucosidase Production through a Two-Stage, Multi-Model, Design of Experiments Approach

2019 ◽  
Vol 6 (3) ◽  
pp. 61
Author(s):  
Albert Uhoraningoga ◽  
Gemma K. Kinsella ◽  
Jesus M. Frias ◽  
Gary T. Henehan ◽  
Barry J. Ryan
Keyword(s):  
Design Of Experiments ◽  
Incubation Time ◽  
Metal Ion ◽  
Streptomyces Griseus ◽  
Fold Increase ◽  
Fractional Factorial ◽  
Model Design ◽  
Two Stage ◽  
Screening Design ◽  
Wide Range

β-glucosidases are a class of enzyme that are widely distributed in the living world, with examples noted in plants, fungi, animals and bacteria. They offer both hydrolysis and synthesis capacity for a wide range of biotechnological processes. However, the availability of native, or the production of recombinant β-glucosidases, is currently a bottleneck in the widespread industrial application of this enzyme. In this present work, the production of recombinant β-glucosidase from Streptomyces griseus was optimised using a Design of Experiments strategy, comprising a two-stage, multi-model design. Three screening models were comparatively employed: Fractional Factorial, Plackett-Burman and Definitive Screening Design. Four variables (temperature, incubation time, tryptone, and OD600 nm) were experimentally identified as having statistically significant effects on the production of S.griseus recombinant β-glucosidase in E. coli BL21 (DE3). The four most influential variables were subsequently used to optimise recombinant β-glucosidase production, employing Central Composite Design under Response Surface Methodology. Optimal levels were identified as: OD600 nm, 0.55; temperature, 26 °C; incubation time, 12 h; and tryptone, 15 g/L. This yielded a 2.62-fold increase in recombinant β-glucosidase production, in comparison to the pre-optimised process. Affinity chromatography resulted in homogeneous, purified β-glucosidase that was characterised in terms of pH stability, metal ion compatibility and kinetic rates for p-nitrophenyl-β-D-glucopyranoside (pNPG) and cellobiose catalysis.

Modified Chilled Coil Model Development and Application to Turbine Inlet Air Cooling

2021 ◽  
Vol 29 (01) ◽  
pp. 2150006
Author(s):  
Gopalakrishnan Anand ◽  
Ellen Makar
Keyword(s):  
Air Temperature ◽  
Flow Rate ◽  
Operating Conditions ◽  
Performance Data ◽  
Surface Model ◽  
Air Cooling ◽  
Ambient Temperatures ◽  
Turbine Inlet ◽  
Wide Range ◽  
Coil Performance

A Turbine Inlet Air Conditioning (TIAC) system can chill the inlet air of the turbine to maintain maximum turbine performance at all ambient temperatures. However, turbine characteristics, performance guarantees and bell-mouth icing considerations require accurate prediction of the chilling coil performance over a wide range of operating conditions. A modified wet-surface model (MWSM) is developed to more accurately predict the chilling coil performance. The higher accuracy of the model is demonstrated by applying the model to simulate performance data of two different coils. The data covered a wide range of operating conditions with ambient temperature vary from [Formula: see text]C to [Formula: see text]C dry bulb and [Formula: see text]C to [Formula: see text]C wet bulb. The turbine flow rate varies from 100% to 43% with chilled air temperature in the range of 3.3–[Formula: see text]C and chilling load variation of 100% to 5%. The chilled water flow rate varies from 100% to 32% with supply glycol-water temperature in the range of [Formula: see text]2.2–[Formula: see text]C. The MWSM uses 11 empirical parameters evaluated from the coil performance data and is able to correlate the data with an adjusted coefficient of determination ([Formula: see text]) of over 99%. The higher accuracy of the modified model enables the development of a more robust controls strategy required to maintain the inlet air temperature at the set point with varying ambient temperatures and chilling load conditions. The model can also be applied to other chilling and dehumidification applications especially those experiencing wide variations in operating conditions and load or those requiring close control of the chilling and dehumidification process.

Computational Investigation of the Flow Field Inside an Submersible Tubular Pump

2011 ◽  
Author(s):  
Yan Jin ◽  
Chao Liu ◽  
Jiren Zhou ◽  
Fangping Tang
Keyword(s):  
Flow Field ◽  
Flow Rate ◽  
Optimization Design ◽  
High Efficiency ◽  
Simple Algorithm ◽  
Operating Conditions ◽  
Rotating Speed ◽  
Pumping System ◽  
Wide Range ◽  
Engineering Costs

Submersible tubular pump is particularly suitable for ultra-low head (net head less than 2 m) pumping station which can reduce the excavation depth, lower engine room height, simplify hydraulic structure, and save civil engineering costs. Submersible tubular pump with smaller motor unit can reduce the flow resistance. The flow field inside the submersible tubular pump is simulated in a commercial computation fluid dynamics (CFD) code FLUENT. The RNG k-ε turbulent model and SIMPLE algorithm are applied to analyze the full passage of a submersible tubular pump, the performance of pump such as head, shaft power and efficiency are predicted based on the calculation of different operating conditions. The simulations are carried out over a wide range of operating points, from 0.8 of the reference mass flow rate at the best efficiency point (BEP) to the 1.28 of the BEP flow rate at the same rotating speed. For verifying the accuracy and reliability of the calculation results, a model test is conducted. The comparison of simulation results and the experiment data show that the calculation performances are agree with the experiment results in the high efficiency area and large discharge condition, but in the condition of low discharge, it exists deviations between the two results. Compare with the numerical simulation and experiment, which can provide more evidences for the hydraulic performance prediction and optimization design of submersible tubular pump pumping system.

An Experimental Investigation of HCCI Combustion Stability Using N-Heptane

2007 ◽  
Author(s):  
Hailin Li ◽  
W. Stuart Neill ◽  
Wally Chippior ◽  
Joshua D. Taylor
Keyword(s):  
Heat Release ◽  
Flow Rate ◽  
Combustion Process ◽  
Operating Conditions ◽  
Combustion Stability ◽  
Fuel Flow Rate ◽  
Fuel Flow ◽  
Air Temperatures ◽  
Wide Range ◽  
Cyclic Variations

In this paper, cyclic variations in the combustion process of a single-cylinder HCCI engine operated with n-heptane were measured over a range of intake air temperatures and pressures, compression ratios, air/fuel ratios, and exhaust gas recirculation (EGR) rates. The operating conditions produced a wide range of combustion timings from overly advanced combustion where knocking occurred to retarded combustion where incomplete combustion was detected. Cycle-to-cycle variations were shown to depend strongly on the crank angle phasing of 50% heat release and fuel flow rate. Combustion instability increased significantly with retarded combustion phasing especially when the fuel flow rate was low. Retarded combustion phasing can be tolerated when the fuel flow rate is high. It was also concluded that the cyclic variations in imep are primarily due to the variations in the total heat released from cycle-to-cycle. The completeness of the combustion process in one cycle affects the in-cylinder conditions and resultant heat release in the next engine cycle.

scholarly journals Determination of critical operating and geometrical parameters in diesel injectors through one dimensional modelling, design of experiments and an analysis of variance

2017 ◽  
Vol 232 (13) ◽  
pp. 1762-1781 ◽  
Author(s):  
Francisco J Salvador ◽  
Marcos Carreres ◽  
Marco Crialesi-Esposito ◽  
Alejandro H Plazas
Keyword(s):  
Design Of Experiments ◽  
Mass Flow Rate ◽  
Analysis Of Variance ◽  
Mass Flow ◽  
Flow Rate ◽  
Control Volume ◽  
Geometrical Parameters ◽  
One Dimensional ◽  
Injection Process ◽  
Rate Profile

In this paper, a design of experiments and a statistical analysis of variance (ANOVA) are performed to determine the parameters that have more influence on the mass flow rate profile in diesel injectors. The study has been carried out using a one dimensional model previously implemented by the authors. The investigation is split into two different parts. First, the analysis is focused on functional parameters such as the injection and discharge pressures, the energizing time and the fuel temperature. In the second part, the influence of 37 geometrical parameters, such as the diameters of hydraulic lines, calibrated orifices and internal volumes, among others, are analysed. The objective of the study is to quantify the impact of small variations in the nominal value of these parameters on the injection rate profile for a given injector operating condition. In the case of the functional parameters, these small variations may be attributed to possible undesired fluctuations in the conditions that the injector is submitted to. As far as the geometrical and flow parameters are concerned, the small variations studied are representative of manufacturing tolerances that could influence the injected mass flow rate. As a result, it has been noticed that the configuration of the inlet and outlet orifices of the control volume, together with the discharge coefficient of the inlet orifice, among a few others, play a remarkable role in the injector performance. The reason resides in the fact that they are in charge of controlling the behaviour of the pressure in the control volume, which importantly influences injector dynamics and therefore the injection process. Variations of only 5% in the diameter of these orifices strongly modify the shape of the rate of injection curve, influencing both the injection delay and the duration of the injection process, consequently changing the total mass delivered.

Thermal Performance Analysis of the Stationary Reflector/Tracking Absorber (SRTA) Solar Concentrator

1975 ◽  
Vol 97 (3) ◽  
pp. 451-456 ◽  
Author(s):  
J. F. Kreider
Keyword(s):  
Fluid Flow ◽  
High Temperature ◽  
Flow Rate ◽  
Thermal Performance ◽  
Concentration Ratio ◽  
Heat Energy ◽  
Operating Conditions ◽  
Fluid Flow Rate ◽  
Wide Range ◽  
Temperature Heat

The performance of a novel solar energy concentrating system consisting of a fixed, concave spherical mirror and a sun-tracking, cylindrical absorber is analyzed in detail. This concentrating system takes advantage of the spherical symmetry of the mirror and its linear image which, when taken together, form a tracking, solar-concentrating system in which only the small cylindrical absorber need move. The effects of mirror reflectance, concentration ratio, heat transfer fluid flow rate, radiative surface properties, incidence angle, an evacuated absorber envelope, and insolation level upon thermal performance of the concentrator are studied by means of a mathematical model. The simulation includes first order radiation and convection processes between the absorber and its concentric glass envelope and between the envelope and the environment; radiation processes are described by a dual-band, gray approximation. The energy equations are solved in finite difference form in order that heat flux and temperature distributions along the absorber may be computed accurately. The results of the study show that high-temperature heat energy can be collected efficiently over a wide range of useful operating conditions. The analysis indicates that mirror surface reflectance is the single most important of the principal governing parameters in determining system performance. Efficiency always increases with concentration ratio although the rate of increase is quite small for concentration ratios above 50. High fluid flow rate (i.e., lower operating temperature), an evacuated envelope, or a highly selective surface can enhance performance under some conditions. The conclusion of the study is that high-temperature heat energy can be generated at high efficiency by the present concentrator with present technology in sunny regions of the world.

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