scholarly journals Nonlinear Model of Vibrating Screen to Determine Permissible Spring Deterioration for Proper Separation

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
Cristian G. Rodriguez ◽  
Manuel A. Moncada ◽  
Emilio E. Dufeu ◽  
Mario I. Razeto
Keyword(s):  
Nonlinear Model ◽  
Separation Efficiency ◽  
Angular Displacement ◽  
Operating Conditions ◽  
Angular Motion ◽  
Cyclic Loads ◽  
Heavy Duty ◽  
Vibrating Screen ◽  
Proposed Model ◽  
Three Degree Of Freedom

Springs of vibrating screens are prone to fatigue induced failure because they operate in a heavy duty environment, with abrasive dust and under heavy cyclic loads. If a spring breaks, the stiffness at supporting positions changes, and therefore the amplitude of motion and the static and dynamic angular inclination of deck motion also change. This change in the amplitude and in the inclination of motion produces a reduction in separation efficiency. Available models are useful to determine motion under nominal operating conditions when angular displacement is not significant. However in practice there is significant angular motion during startup, during shutdown, or under off-design operating conditions. In this article, a two-dimensional three-degree-of-freedom nonlinear model that considers significant angular motion and damping is developed. The proposed model allows the prediction of vibrating screen behavior when there is a reduction in spring stiffness. Making use of this model for an actual vibrating screen in operation in industry has permitted determining a limit for spring’s failure before separation efficiency is affected. This information is of practical value for operation and maintenance staff helping to determine whether or not it is necessary to change springs, and hence optimizing stoppage time.

"Recent Patents on the Triboelectrostatic Separation of Fly Ash"

2019 ◽  
Vol 13 ◽  
Author(s):  
Haisheng Li ◽  
Wenping Wang ◽  
Yinghua Chen ◽  
Xinxi Zhang ◽  
Chaoyong Li
Keyword(s):  
Fly Ash ◽  
Power Plants ◽  
High Efficiency ◽  
Separation Efficiency ◽  
High Reliability ◽  
Operating Conditions ◽  
Security Requirements ◽  
Unburned Carbon ◽  
Efficient Operation ◽  
Triboelectrostatic Separation

Background: The fly ash produced by coal-fired power plants is an industrial waste. The environmental pollution problems caused by fly ash have been widely of public environmental concern. As a waste of recoverable resources, it can be used in the field of building materials, agricultural fertilizers, environmental materials, new materials, etc. Unburned carbon content in fly ash has an influence on the performance of resource reuse products. Therefore, it is the key to remove unburned carbon from fly ash. As a physical method, triboelectrostatic separation technology has been widely used because of obvious advantages, such as high-efficiency, simple process, high reliability, without water resources consumption and secondary pollution. Objective: The related patents of fly ash triboelectrostatic separation had been reviewed. The structural characteristics and working principle of these patents are analyzed in detail. The results can provide some meaningful references for the improvement of separation efficiency and optimal design. Methods: Based on the comparative analysis for the latest patents related to fly ash triboelectrostatic separation, the future development is presented. Results: The patents focused on the charging efficiency and separation efficiency. Studies show that remarkable improvements have been achieved for the fly ash triboelectrostatic separation. Some patents have been used in industrial production. Conclusion: According to the current technology status, the researches related to process optimization and anti-interference ability will be beneficial to overcome the influence of operating conditions and complex environment, and meet system security requirements. The intelligent control can not only ensure the process continuity and stability, but also realize the efficient operation and management automatically. Meanwhile, the researchers should pay more attention to the resource utilization of fly ash processed by triboelectrostatic separation.

Effect of guide rail profile errors on the motion accuracy for a heavy-duty hydrostatic turntable

2019 ◽  
Vol 233 (15) ◽  
pp. 5350-5362 ◽  
Author(s):  
Yongsheng Zhao ◽  
Hongchao Wu ◽  
Congbin Yang ◽  
Ligang Cai ◽  
Zhifeng Liu
Keyword(s):  
Machine Tool ◽  
Reynolds Equation ◽  
Machining Accuracy ◽  
Guide Rail ◽  
Heavy Duty ◽  
Motion Equations ◽  
Rotating Speed ◽  
Proposed Model ◽  
Reaction Forces ◽  
Profile Errors

The motion accuracy of hydrostatic turntable is the key in improving the machining accuracy of heavy-duty machine tool. However, the motion accuracy of hydrostatic turntable depends not only on the offset load but also on the rotating speed of the turntable as well as the profile errors of the guide rails. In this paper, a simulation model is developed to analyze the effect of guide rail profile errors on the motion accuracy of hydrostatic turntable. The reaction forces of preload thrust bearing and hydrostatic circular oil pads are obtained based on the Reynolds equation of the lubricant film. The motion equations of hydrostatic turntable are derived in which the profile errors of two guide rails are considered. The results show that the motion accuracy of hydrostatic turntable can be affected by wavelength, amplitude of profile errors and speed, and offset load of turntable. Finally, the motion accuracy of heavy-duty hydrostatic turntable used in XCKA28105 type turning and milling composite machine tool is obtained by using the presented method. Comparing with the experimental results, the proposed model can be used to predict the machining accuracy caused by the profile errors of guide rails for any heavy-duty hydrostatic turntable.

Experimental Investigation of a Heavy-Duty Compression-Ignition Engine Retrofitted to Natural Gas Spark-Ignition Operation

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
Jinlong Liu ◽  
Hemanth Kumar Bommisetty ◽  
Cosmin Emil Dumitrescu
Keyword(s):  
Natural Gas ◽  
Spark Ignition ◽  
Operating Conditions ◽  
Compression Ignition ◽  
Heavy Duty ◽  
Compression Ignition Engine ◽  
Engine Operation ◽  
Cycle Variation ◽  
Spark Timing ◽  
Ci Engines

Heavy-duty compression-ignition (CI) engines converted to natural gas (NG) operation can reduce the dependence on petroleum-based fuels and curtail greenhouse gas emissions. Such an engine was converted to premixed NG spark-ignition (SI) operation through the addition of a gas injector in the intake manifold and of a spark plug in place of the diesel injector. Engine performance and combustion characteristics were investigated at several lean-burn operating conditions that changed fuel composition, spark timing, equivalence ratio, and engine speed. While the engine operation was stable, the reentrant bowl-in-piston (a characteristic of a CI engine) influenced the combustion event such as producing a significant late combustion, particularly for advanced spark timing. This was due to an important fraction of the fuel burning late in the squish region, which affected the end of combustion, the combustion duration, and the cycle-to-cycle variation. However, the lower cycle-to-cycle variation, stable combustion event, and the lack of knocking suggest a successful conversion of conventional diesel engines to NG SI operation using the approach described here.

Vibration-Induced Loosening Performance of Preloaded Threaded Fasteners

2010 ◽  
Author(s):  
Xianjie Yang ◽  
Sayed Nassar
Keyword(s):  
Nonlinear Model ◽  
Excitation Amplitude ◽  
The Self ◽  
Transverse Displacement ◽  
Transverse Loading ◽  
Threaded Fasteners ◽  
Bolt Preload ◽  
Proposed Model ◽  
Number Of Cycles ◽  
Insight Into

In an effort to establish a theoretical outline of a criterion for preventing the vibration-induced loosening of preloaded threaded fasteners, this paper provides an experimental and analytical insight into the effect of the initial bolt preload and the excitation amplitude on the self loosening performance of cap screw fastener. A nonlinear model is used for predicting the clamp load loss caused by the vibration-induced loosening of cap screw fasteners under cyclic transverse loading. Experimental verification was conducted on the twisting torque variation and the effect of the preload level and transverse displacement amplitude. Comparison of the experimental and analytical results on the clamp load loss with the number of cycles verifies that the proposed model accurately predicts self-loosening performance.

Potential of the Variable Valve Actuation (VVA) Strategy on a Heavy Duty CNG Engine

2014 ◽  
Author(s):  
Mirko Baratta ◽  
Roberto Finesso ◽  
Daniela Misul ◽  
Ezio Spessa ◽  
Yifei Tong ◽  
...  
Keyword(s):  
Fuel Consumption ◽  
Operating Conditions ◽  
Intake Valve ◽  
Heavy Duty ◽  
Engine Emissions ◽  
Variable Valve Actuation ◽  
Cng Engine ◽  
Variable Valve ◽  
Working Point ◽  
Valve Actuation

The environmental concerns officially aroused in 1970s made the control of the engine emissions a major issue for the automotive industry. The corresponding reduction in fuel consumption has become a challenge so as to meet the current and future emission legislations. Given the increasing interest retained by the optimal use of a Variable Valve Actuation (VVA) technology, the present paper investigates into the potentials of combining the VVA solution to CNG fuelling. Experiments and simulations were carried out on a heavy duty 6-cylinders CNG engine equipped with a turbocharger displaying a twin-entry waste-gate-controlled turbine. The analysis aimed at exploring the potentials of the Early Intake Valve Closure (EIVC) mode and to identify advanced solutions for the combustion management as well as for the turbo-matching. The engine model was developed within the GT-Power environment and was finely tuned to reproduce the experimental readings under steady state operations. The 0D-1D model was hence run to reproduce the engine operating conditions at different speeds and loads and to highlight the effect of the VVA on the engine performance as well as on the fuel consumption and engine emissions. Pumping losses proved to reduce to a great extent, thus decreasing the brake specific fuel consumption (BSFC) with respect to the throttled engine. The exhaust temperature at the turbine inlet was kept to an almost constant value and minor variations were allowed. This was meant to avoid an excessive worsening in the TWC working conditions, as well as deterioration in the turbocharger performance during load transients. The numerical results also proved that full load torque increases can be achieved by reducing the spark advance so that a higher enthalpy is delivered to the turbocharger. Similar torque levels were also obtained by means of Early Intake Valve Closing strategy. For the latter case, negligible penalties in the fuel consumption were detected. Moreover, for a given combustion phasing, the IVC angle directly controls the mass-flow rate and thus the torque. On the other hand, a slight dependence on the combustion phasing can be detected at part load. Finally, the simulations assessed for almost constant fuel consumption for a wide range of IVC and SA values. Specific attention was also paid to the turbocharger group functioning and to its correct matching to the engine working point. The simulations showed that the working point on the compressor map can be optimized by properly setting the spark advance (SA) as referred to the adopted intake-valve closing angle. It is anyhow worth observing that the engine high loads set a constraint deriving from the need to meet the limits on the peak firing pressure (PFP), thus limiting the possibility to optimize the working point once the turbo-matching is defined.

scholarly journals Influence of the diesel pilot injector configuration on ethanol combustion and performance of a heavy-duty direct injection engine

2021 ◽  
pp. 146808742110012
Author(s):  
Nicola Giramondi ◽  
Anders Jäger ◽  
Daniel Norling ◽  
Anders Christiansen Erlandsson
Keyword(s):  
Direct Injection ◽  
Engine Performance ◽  
High Load ◽  
Operating Conditions ◽  
Injection System ◽  
Injection Timing ◽  
Diesel Combustion ◽  
Heavy Duty ◽  
Pure Ethanol ◽  
Ethanol Combustion

Thanks to its properties and production pathways, ethanol represents a valuable alternative to fossil fuels, with potential benefits in terms of CO2, NOx, and soot emission reduction. The resistance to autoignition of ethanol necessitates an ignition trigger in compression-ignition engines for heavy-duty applications, which in the current study is a diesel pilot injection. The simultaneous direct injection of pure ethanol as main fuel and diesel as pilot fuel through separate injectors is experimentally investigated in a heavy-duty single cylinder engine at a low and a high load point. The influence of the nozzle hole number and size of the diesel pilot injector on ethanol combustion and engine performance is evaluated based on an injection timing sweep using three diesel injector configurations. The tested configurations have the same geometric total nozzle area for one, two and four diesel sprays. The relative amount of ethanol injected is swept between 78 – 89% and 91 – 98% on an energy basis at low and high load, respectively. The results show that mixing-controlled combustion of ethanol is achieved with all tested diesel injector configurations and that the maximum combustion efficiency and variability levels are in line with conventional diesel combustion. The one-spray diesel injector is the most robust trigger for ethanol ignition, as it allows to limit combustion variability and to achieve higher combustion efficiencies compared to the other diesel injector configurations. However, the two- and four-spray diesel injectors lead to higher indicated efficiency levels. The observed difference in the ethanol ignition dynamics is evaluated and compared to conventional diesel combustion. The study broadens the knowledge on ethanol mixing-controlled combustion in heavy-duty engines at various operating conditions, providing the insight necessary for the optimization of the ethanol-diesel dual-injection system.

CFD Investigation of Downhole Natural Gas Separation Efficiency in the Churn Flow Regime

2021 ◽  
Author(s):  
Charles Okafor ◽  
Patrick Verdin ◽  
Phill Hart
Keyword(s):  
Natural Gas ◽  
Flow Regime ◽  
Gas Separation ◽  
Separation Efficiency ◽  
Operating Conditions ◽  
Analytical Models ◽  
Design Stage ◽  
Average Error ◽  
Multiphase Model ◽  
Churn Flow

Abstract Downhole Natural Gas Separation Efficiency (NGSE) is flow regime dependent, and current analytical models in certain conditions lack accuracy. Downhole NGSE was investigated through 3D Computational Fluid Dynamics (CFD) transient simulations for pumping wells in the Churn flow regime. The Volume of Fluid (VOF) multiphase model was considered along with the k – ε turbulence model for most simulations. A mesh independence study was performed, and the final model results validated against experimental data, showing an average error of less than 6 %. Numerical simulation results showed that the steady state assumption used by current mathematical models for churn flow can be inaccurate. Several key parameters affecting the NGSE were identified, and suggestions for key improvements to the widely used mathematical formulations for viscous flow provided. Sensitivity studies were conducted on fluid/geometric parameters and operating conditions, to gain a better understanding of the influence of each parameter on NGSE. These are important results as they equip the ESP engineer with additional knowledge to maximise the NGSE from design stage to pumping operations.

The Use of Electrostatic Charge Measurements as an Early Warning of Distress in Heavy-Duty Gas Turbines

2001 ◽  
Author(s):  
G. L. Lapini ◽  
M. Zippo ◽  
G. Tirone
Keyword(s):  
Monitoring System ◽  
Early Warning ◽  
Gas Turbines ◽  
Electrostatic Charge ◽  
Electric Utility ◽  
Operating Conditions ◽  
System Response ◽  
Jet Engines ◽  
Heavy Duty ◽  
Demonstration Program

The idea of measuring the electrostatic charge associated with the debris contained in the exhaust gases of a gas turbine (sometimes named EDMS, Engine Debris Monitoring System, or EEMS, Electrostatic Engine Monitoring System) has been demonstrated by several authors as an interesting diagnostic tool for the early warning of possible internal distresses (rubs, coating wear, hot spots in combustors, improper combustion, etc.) especially for jet engines or aeroderivative gas turbines. While potentially applicable to machines of larger size, the possibility of transferring this monitoring technology to heavy-duty gas turbines, which have exhaust ducts much bigger in size and different operating conditions, should be demonstrated. The authors present a synthesis of their experience and of the most significant data collected during a demonstration program performed on behalf of ENEL, the main Italian electric utility. The purpose of this program was to test this concept in real operating conditions on large turbines, and hence to evaluate the influence of the operating conditions on the system response and to assess its sensitivity to possible distresses. A good amount of testing has been performed, during this program, both on a full scale combustion rig, and on two machines rated at about 120 MW, during their normal and purposely perturbed operating conditions in a power plant. The authors, on the basis of the encouraging results obtained to date, comment on the work still required to bring this technology to full maturity.

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