Bulk Modulus of Air Content Oil in a Hydraulic Cylinder

2006 ◽  
Author(s):  
Jian Ruan ◽  
Richard Burton
Keyword(s):  
Pressure Gradient ◽  
Bulk Modulus ◽  
Critical Pressure ◽  
Dynamic Condition ◽  
Hydraulic Cylinder ◽  
Substantial Effect ◽  
Air Content ◽  
Proposed Model ◽  
Temporal Pressure ◽  
Entrained Air

A model of oil with entrained air content is developed which considers fluid compression and the subsequent dissolving of mixed entrained air. According to the model the mixed entrained air affects the "gross" bulk modulus below some critical pressure, but has no effect above this value due to the complete dissolving of the entrained air into solution. The critical pressure is shown to be proportional to the square root of the amount of the initial mixed entrained air. The temporal pressure gradient has also a substantial effect on the critical pressure value and thus on the bulk modulus. The critical pressure value increases but tends towards an upper value with increasing temporal pressure gradient (a true dynamic condition); the opposite occurs when the pressure gradient decreases as the critical pressure converges to a lower value (essentially a static value). Thus regions of static and dynamic bulk modulus can be established. The model predicts that the upper critical pressure value is some 1.8 times that of the static one. Experiments have been designed to verify the feasibility of the model by measuring the temporal pressure gradient against the variation of compressed oil volume. It is demonstrated that the model is verified not only for the case of positive pressures (above atmospheric pressure) but also for pressures less than atmosphere. Finally a comparison of the proposed model is made with those proposed in the literature. The bulk modulus predicted by the proposed model is a little larger than these given in literature. The reason for such difference is attributed to the result of air being dissolved into oil.

scholarly journals A Theoretical Model with Which to Safely Optimize the Configuration of Hydraulic Suspension of Modular Trailers in Special Road Transport

2020 ◽  
Vol 11 (1) ◽  
pp. 305
Author(s):  
Rubén Escribano-García ◽  
Marina Corral-Bobadilla ◽  
Fátima Somovilla-Gómez ◽  
Rubén Lostado-Lorza ◽  
Ash Ahmed
Keyword(s):  
Theoretical Model ◽  
Wind Turbine ◽  
Optimization Algorithm ◽  
Hydraulic Cylinder ◽  
Road Transport ◽  
Automatic Testing ◽  
Transport Systems ◽  
The Road ◽  
Proposed Model ◽  
On The Road

The dimensions and weight of machines, structures, and components that need to be transported safely by road are growing constantly. One of the safest and most widely used transport systems on the road today due to their versatility and configuration are modular trailers. These trailers have hydraulic pendulum axles that are that are attached in pairs to the rigid platform above. In turn, these modular trailers are subject to limitations on the load that each axle carries, the tipping angle, and the oil pressure of the suspension system in order to guarantee safe transport by road. Optimizing the configuration of these modular trailers accurately and safely is a complex task. Factors to be considered include the load’s characteristics, the trailer’s mechanical properties, and road route conditions including the road’s slope and camber, precipitation and direction, and force of the wind. This paper presents a theoretical model that can be used for the optimal configuration of hydraulic cylinder suspension of special transport by road using modular trailers. It considers the previously mentioned factors and guarantees the safe stability of road transport. The proposed model was validated experimentally by placing a nacelle wind turbine at different points within a modular trailer. The weight of the wind turbine was 42,500 kg and its dimensions were 5133 × 2650 × 2975 mm. Once the proposed model was validated, an optimization algorithm was employed to find the optimal center of gravity for load, number of trailers, number of axles, oil pressures, and hydraulic configuration. The optimization algorithm was based on the iterative and automatic testing of the proposed model for different positions on the trailer and different hydraulic configurations. The optimization algorithm was tested with a cylindrical tank that weighed 108,500 kg and had dimensions of 19,500 × 3200 × 2500 mm. The results showed that the proposed model and optimization algorithm could safely optimize the configuration of the hydraulic suspension of modular trailers in special road transport, increase the accuracy and reliability of the calculation of the load configuration, save time, simplify the calculation process, and be easily implemented.

scholarly journals THE INFLUENCE OF COARSE AGGREGATE CONCENTRATION ON THE STRENGTH OF CONCRETE AND ON THE POROSITY OF CONCRETE MORTAR/STAMBIOJO UŽPILDO KONCENTRACIJOS ĮTAKA BETONO STIPRUMUI IR SKIEDININĖS DALIES PORINGUMUI

2001 ◽  
Vol 7 (6) ◽  
pp. 446-452
Author(s):  
Gintautas Skripkiūnas ◽  
Vitoldas Vaitkevičius
Keyword(s):  
Stress Concentration ◽  
Water Absorption ◽  
Water Content ◽  
Coarse Aggregate ◽  
Concrete Strength ◽  
Structural Defects ◽  
Capillary Porosity ◽  
Air Content ◽  
Aggregate Concentration ◽  
Entrained Air

The results of experiments dealing with coarse aggregate concentration influence on the concrete strength and the structure of hardened cement paste and mortar of concrete are presented in the paper. Experiments were performed on concrete with dense coarse aggregate (crushed granite) which strength is more than strength of mortar and lightweight porous aggregate (expanded clay aggregate) with strength less than that of mortar. Physical and mechanical properties of concrete with dense coarse aggregate are presented in Table 1 and the concretes with the porous coarse aggregate in Table 2. The decrease of entrained air content with the increase of coarse aggregate concentration ϕσt were determined both for concretes with dense and porous coarse aggregate. The entrained air has a significant effect on concrete strength—1% of entrained air decreases the strength of concrete about 5% [11]. The influence of the coarse aggregate concentration on the compressive strength of concrete with the constant air content is presented in Figs 3 and 4. With the increase of coarse aggregate concentration the concrete strength decreases when the entrained air content in concrete is constant. The main reasons of the concrete strength reduction are the stress concentration and structural defects near the coarse aggregate. Coarse aggregate affects the structure of mortar. Dense coarse aggregate has negligible water absorption and does not change water content in mortar of concrete, and capillary porosity of mortar remains constant when the concentration of dense coarse aggregate ϕ st increases (Fig 5). Porous coarse aggregate (expanded clay aggregate) has large water absorption (more than 16%), therefore water content in mortar of concrete is reduced and capillary porosity of mortar is significantly reduced when the concentration of porous coarse aggregate ϕ st increases (Fig 5). The entrained air content in mortar with both dense and porous coarse aggregate decreases inverse proportionally to coarse aggregate concentration ϕ st (Fig 6). The investigations have shown that suitable selection of properties and volumetric concentration of coarse aggregate can reduce stress concentration in concrete and increase the concrete strength.

scholarly journals PROPERTIES OF MORTARS CONTAINING TIRE RUBBER WASTE AND EXPANDED POLYSTYRENE (EPS)

2018 ◽  
pp. 219-225 ◽  
Author(s):  
Adriane Pczieczek ◽  
Adilson Schackow ◽  
Carmeane Effting ◽  
Itamar Ribeiro Gomes ◽  
Talita Flores Dias
Keyword(s):  
Compressive Strength ◽  
Specific Gravity ◽  
Water Absorption ◽  
Expanded Polystyrene ◽  
Fine Aggregate ◽  
Tire Rubber ◽  
Air Content ◽  
Rubber Waste ◽  
Hardened State ◽  
Entrained Air

This study aims to evaluate the application of discarded tire rubber waste and Expanded Polystyrene (EPS) in mortar. For mortars fine aggregate was replaced by 10%, 20% and 30% of rubber and, 7.5% and 15% of EPS. We have verified the consistency, density, amount of air and water retentitivity in fresh state. The compressive strength, water absorption, voids ratio and specific gravity have been also tested in hardened state. The application of rubber powder contributed to the increase in entrained air content and in reducing specific gravity, as well as reducing compressive strength at 28 days. The addition of EPS also contributed to the increase of workability, water absorption and voids ratio, and decreased density and compressive strength when compared to the reference mortar. The use of rubber waste and EPS in mortar made the material more lightweight and workable. The mortars mixtures containing 10% rubber and 7.5% EPS showed better results.

Parameter Estimation in a Hydrostatic System Using Extended Kalman Filter

2001 ◽  
Author(s):  
Yuvin A. Chinniah ◽  
Richard Burton ◽  
Saeid Habibi
Keyword(s):  
Kalman Filter ◽  
Bulk Modulus ◽  
Extended Kalman Filter ◽  
High Performance ◽  
State Space Model ◽  
System Response ◽  
Actuation System ◽  
Accuracy And Precision ◽  
Hydrostatic System ◽  
Entrained Air

Abstract In this paper, the Extended Kalman Filter (EKF) estimation technique is applied to a novel hydrostatic actuation system referred to as the Electrohydraulic Actuator (EHA). A state space model of the EHA is developed and the effective bulk modulus is estimated in simulation. The EHA is a high performance actuation system capable of moving large loads with very high accuracy and precision. In a practical situation, this parameter is very difficult to measure directly as it depends on entrained air which cannot be known at a particular point of time. The bulk modulus is critical for system response and a low bulk modulus as a result of air in the system can seriously hinder the performance of EHA and cause safety problems.

Modeling and Simulation Research of Hydraulic Cylinder Speed Control System Based on High-Speed On-Off Valve

2012 ◽  
Vol 590 ◽  
pp. 161-164
Author(s):  
Qin He Gao ◽  
Wen Liang Guan ◽  
Hai Zhou Song ◽  
Zhi Yong Yang
Keyword(s):  
Control System ◽  
Hydraulic System ◽  
High Speed ◽  
Speed Control ◽  
Hydraulic Cylinder ◽  
Simulation Research ◽  
Parallel Application ◽  
Proposed Model ◽  
Speed Control System ◽  
Small Flow

Application of high-speed on-off valve in the hydraulic cylinder speed control system was researched in this paper. Series and parallel application schemes between high-speed on-off valve and hydraulic cylinder are proposed. Model of high-speed on-off valve and hydraulic circuit were established to carry out simulation. The speed and acceleration curve of hydraulic cylinder were achieved by the means of simulation with Simulink. The simulation curves show that, two application schemes can both control the speed of hydraulic cylinder effectively. Series application scheme can be only applied to small flow hydraulic system; parallel application scheme has wider application.

A Robust Asymptotically Based Modeling Approach for Two-Phase Flow in Porous Media

2009 ◽  
Vol 131 (10) ◽  
Author(s):  
M. M. Awad ◽  
S. D. Butt
Keyword(s):  
Porous Media ◽  
Pressure Gradient ◽  
Single Phase ◽  
Present Model ◽  
Flow In Porous Media ◽  
Pressure Gradients ◽  
Two Phase ◽  
New Model ◽  
Proposed Model ◽  
Phase Liquid

A simple semitheoretical method for calculating the two-phase frictional pressure gradient in porous media using asymptotic analysis is presented. The two-phase frictional pressure gradient is expressed in terms of the asymptotic single-phase frictional pressure gradients for liquid and gas flowing alone. In the present model, the two-phase frictional pressure gradient for x≅0 is nearly identical to the single-phase liquid frictional pressure gradient. Also, the two-phase frictional pressure gradient for x≅1 is nearly identical to the single-phase gas frictional pressure gradient. The proposed model can be transformed into either a two-phase frictional multiplier for liquid flowing alone (ϕl2) or a two-phase frictional multiplier for gas flowing alone (ϕg2) as a function of the Lockhart–Martinelli parameter X. The advantage of the new model is that it has only one fitting parameter (p), while the other existing correlations, such as the correlation of Larkins et al., Sato et al., and Goto and Gaspillo, have three constants. Therefore, calibration of the new model to the experimental data is greatly simplified. The new model is able to model the existing multiparameter correlations by fitting the single parameter p. Specifically, p=1/3.25 for the correlation of Midoux et al., p=1/3.25 for the correlation of Rao et al., p=1/3.5 for the Tosun correlation, p=1/3.25 for the correlation of Larkins et al., p=1/3.75 for the correlation of Sato et al., and p=1/3.5 for the Goto and Gaspillo correlation.

Air-entrained grouts suitable for post-tensioning

1984 ◽  
Vol 11 (1) ◽  
pp. 92-98
Author(s):  
R. E. Loov ◽  
S. P. Hon ◽  
M. A. Ward
Keyword(s):  
Empirical Test ◽  
Structural Member ◽  
Test Method ◽  
Early Age ◽  
Air Content ◽  
Water To Cement Ratio ◽  
Post Tensioning ◽  
Entrained Air ◽  
Original Water ◽  
Test Bottle

Grouts in post-tensioning ducts can cause cracking of the structural member if the grout freezes at an early age. This laboratory program examines a range of cement–water grouts with differing w/c ratios, air contents, and ages. A new empirical test method employing a test bottle was introduced to study the performance of grouts during early freezing.It was determined using the bottle method and other experimental and analytical procedures that excessive grout dilation during early freezing could be avoided if the entrained air content of the grout exceeded[Formula: see text]where w/c is the original water-to-cement ratio of the grout and M is the fraction of the cement that has hydrated before the grout freezes.

A Robust Asymptotically Based Modeling Approach for Two-Phase Flow in Porous Media

2008 ◽  
Author(s):  
M. M. Awad ◽  
S. D. Butt
Keyword(s):  
Porous Media ◽  
Pressure Gradient ◽  
Single Phase ◽  
Theoretical Method ◽  
Flow In Porous Media ◽  
Pressure Gradients ◽  
Two Phase ◽  
New Model ◽  
Proposed Model ◽  
Phase Liquid

A simple semi-theoretical method for calculating two-phase frictional pressure gradient in porous media using asymptotic analysis is presented. Two-phase frictional pressure gradient is expressed in terms of the asymptotic single-phase frictional pressure gradients for liquid and gas flowing alone. In the present model, the two-phase frictional pressure gradient for x ≅ 0 is nearly identical to single-phase liquid frictional pressure gradient. Also, the two-phase frictional pressure gradient for x ≅ 1 is nearly identical to single-phase gas frictional pressure gradient. The proposed model can be transformed into either a two-phase frictional multiplier for liquid flowing alone (φl2) or two-phase frictional multiplier for gas flowing alone (φg2) as a function of the Lockhart-Martinelli parameter, X. The advantage of the new model is that it has only one fitting parameter (p) while the other existing correlations such as Larkins et al. correlation, Sato et al. correlation, and Goto and Gaspillo correlation have three constants. Therefore, calibration of the new model to experimental data is greatly simplified. The new model is able to model the existing multi parameters correlations by fitting the single parameter p. Specifically, p = 1/3.25 for Midoux et al. correlation, p = 1/3.25 for Rao et al. correlation, p = 1/3.5 for Tosun correlation, p = 1/3.25 for Larkins et al. correlation, p = 1/3.75 for Sato et al. correlation, and p = 1/3.5 for Goto and Gaspillo correlation.

scholarly journals Toy model for the acceleration of blazar jets

2018 ◽  
Vol 616 ◽  
pp. A93 ◽  
Author(s):  
I. Liodakis
Keyword(s):  
Pressure Gradient ◽  
Lorentz Factor ◽  
External Pressure ◽  
Astrophysical Jets ◽  
Bl Lac Objects ◽  
Spectrum Radio ◽  
Proposed Model ◽  
Bl Lac ◽  
Accretion Rates ◽  
Theoretical Results

Context. Understanding the acceleration mechanism of astrophysical jets has been a cumbersome endeavor from both the theoretical and observational perspective. Although several breakthroughs have been achieved in recent years, on all sides, we are still missing a comprehensive model for the acceleration of astrophysical jets. Aims. In this work we attempt to construct a simple toy model that can account for several observational and theoretical results and allow us to probe different aspects of blazar jets usually inaccessible to observations. Methods. We used the toy model and Lorentz factor estimates from the literature to constrain the black hole spin and external pressure gradient distributions of blazars. Results. Our results show that (1) the model can reproduce the velocity, spin and external pressure gradient of the jet in M 87 inferred independently by observations; (2) blazars host highly spinning black holes with 99% of BL Lac objects and 80% of flat spectrum radio quasars having spins a > 0.6; (3) the dichotomy between BL Lac objects and flat spectrum radio quasars could be attributed to their respective accretion rates. Using the results of the proposed model, we estimated the spin and external pressure gradient for 75 blazars.

scholarly journals Characteristics of Entrained Air Voids in Hardened Concrete with the Method of Digital Image Analysis Coupled with Schwartz-Saltykov Conversion

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2439
Author(s):  
Teemu Ojala ◽  
Yanjuan Chen ◽  
Jouni Punkki ◽  
Fahim Al-Neshawy
Keyword(s):  
Image Analysis ◽  
Digital Image ◽  
Digital Image Analysis ◽  
Three Dimensional ◽  
Volume Density ◽  
Hardened Concrete ◽  
Air Voids ◽  
Air Content ◽  
Entrained Air ◽  
Number Of Classes

This paper presents the characteristics of air void systems in hardened concrete with the method of digital image analysis (DIA) coupled with Schwartz-Saltykov (SS) conversion. The results indicate that the DIA method coupled with SS conversion estimates the air content with more accuracy than it would without SS conversion; the correlation between air content obtained from the DIA method, and that from the thin section (TS) method is as good as the correlation observed between the pressure saturation (PS) method and the TS method. It was also found that the DIA method shows a better correlation with the TS method when the spacing factor without SS conversion is considered, while both methods show poor correlations when the corresponding specific surface is considered. In addition, it indicates that the peak of three-dimensional size distribution (3-DSD) of air voids after SS conversion falls in smaller voids, and 3-DSD of air voids shifts to a narrow size range, in comparison with the 2-DSD without SS conversion; the shape of the 3-DSD air voids remains constant irrespective of the class widths. Increasing the number of classes can minimise the standard deviation in the estimation, however, it also results in a leap in voids volume density, which will influence the estimation of air content.

Sign in / Sign up

Export Citation Format

Share Document