RESULTS DISCUSSION Proceeding Of Mechanical Engineering Research Day 2015 (MERD’15).

56 Table 1 Stability time of hBN nanoparticles suspensions with different pH values pH 1 3 5 6 7 9 11 13 Stability [day] 2 2 2 2 2 30 60 60 The pH value of suspension without dispersing agent pHDay 2 3 30 60 1 3 5 6 7 9 11 13 The pH value of suspension without dispersing agent Figure 1 Photo of formation of hBN nanoparticles layer over time in different pH values The higher absorption of UV radiations in suspension stabilized by NaOH, confirmed the higher efficiency of electrostatic repulsive force. This behavior is attributed to the fact that the absorbed ions in electrostatic mechanism form a charged layer around the particles preventing aggregation. Adsorption of OH- ion in the alkaline region on the particles surface increases the repulsive force and results in the lengthening of the distance between particles or increases the thickness of the electrical double-layer, which causes an electrostatic stability. Figure 2 UV-Vis absorption of nano-oil in different pH values wavelength = 600 nm

4. CONCLUSIONS

In conclusion, the stability of the hBN nanoparticles in SAE 15W-40 diesel engine oil increases in the alkaline region with pH value of 11 – 13. The suspension was stable over the period of 60 days, as compared with the suspension in the acidic region. This is due to the electrostatic mechanism, which increases the repulsive force and results in thicken the electrical double-layer that provides stability.

5. ACKNOWLEDGEMENTS

The authors also gratefully acknowledge contributions from the members of the Green Tribology and Engine Performance G-TriboE research group. This research was supported by grants from the World Academy of Sciences TWAS [grant number: GLUAR2013FKM2A00003], Ministry of Education Malaysia [grant number: FRGS2013FKMTK01021F00163], and Universiti Teknikal Malaysia Melaka UTeM [grants number: PJP2012FKM40AS01044 and PJP2012FKM11AS01086]. 6. REFERENCES [1] C. Buzea, I. I. Pacheco, and K. Robbie, “Nanomaterials and nanoparticles: sources and toxicity.,” Biointerphases, vol. 2, pp. 17–172, 2007. [2] “Dispersing process.” [Online]. Available: http:www.inkline.grinkjetnewtechtechdispersi on. [Accessed: 01-Jan-2015]. [3] M. I. H. C. Abdullah, M. F. B. Abdollah, H. Amiruddin, N. Tamaldin, and N. R. M. Nuri, “Optimization of Tribological Performance of hBNAL 2 O 3 Nanoparticles as Engine Oil Additives,” Procedia Eng., vol. 68, pp. 313–319, 2013. [4] K. Lee, Y. Hwang, S. Cheong, L. Kwon, S. Kim, and J. Lee, “Performance evaluation of nano- lubricants of fullerene nanoparticles in refrigeration mineral oil,” Curr. Appl. Phys., vol. 9, no. 2, pp. 128–131, 2009. 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 10 20 30 40 50 60 70 A bs Time [day] pH 1 pH 3 pH 5 pH 6 pH 7 pH 9 pH 11 pH 13 __________ © Centre for Advanced Research on Energy Modeling for assessing the dynamic performance of pneumatic valve N.S. Osman 1, , A.Y. Bani Hashim 1 1, 2 Faculty of Manufacturing Engineering, Universiti Teknikal Malaysia Melaka, Hang Tuah Jaya, 76100 Durian Tunggal, Melaka, Malaysia. Corresponding e-mail: norsuriyanti.osmangmail.com Keywords: Pneumatic valve; control system; MATLAB ABSTRACT – The fundamental control system for an electro-pneumatic valve is explained where this work discusses of the mathematical model and MATLAB program used in controlling system of pneumatic valve. This paper presents an approach to assessment of the dynamics performance of pneumatic valves.

1. INTRODUCTION

Pneumatic is one of preferred power source in industries due to it is simple, cheap, easy to handle and maintenance and has a high degree of controllability. Within the pneumatic system, valve plays a significant rolein controlling fluid flow into different paths from one or more sources. In getting a good results in pneumatic system operation, users need to monitor and control the valve operating condition. Therefore, this requires the development of suitable control techniques in order to deal with nonlinearities that are common in valve[1].

2. BACKGROUND

Pneumatic valve commonly consists of a body with ports that are connected to internal flow passages by spools inside a cylinder. It is can be controlled either mechanically or electrically controlled. The movement of the spool restricts the flow of fluid. Thus the valve controls the fluid flow. Anothertypical application of this valve is to control the rate of air flow under a given set of pressure condition[2]. The pneumatic valve works when it is actuated either by actuator, followed by movement of spool or end with emission of gaseous. Figure 1 Main working principle of pneumatic valve

3. BASIC CONTROL SYSTEM

The basic mathematical model and control block diagrams will be utilized in modeling control system of pneumatic valve.

3.1 Mathematical Models

Mathematical models relating the various physical parameters may predict and improve the performance of the valve. This paper focuses on electro-pneumatic valve and the mathematical model involved can be separated into three major distinct parts, which are magnetic circuit, mechanical subsystem and air flow path see Figure 2. Figure 2 Basic mathematical model

3.1.1 Magnetic Circuit

In general, the mathematical model of the magnetic circuit can be concentrated to the electromagnetic force, magnetic flux and air gap[3]. Below are the mathematical model for the magnetic circuit. a Electromagnetic force on the armature M = 2 . � 2. � � 1 where B = the magnetic flux density A δ = the cross-sectional area of the air gap μ A = the magnetic permeability of air b Magnetic flux = ∅ � ; ∅= � � . �. I. � � � 2 where Φ = magnetic flux A δ = the cross-sectional area in the air gap μ A = the magnetic permeability of air I = the current of the control signal n C = the number of turns in the solenoid coil L M = the magnetic circuit length c Current control signal M= � δI . � - � � + � �� � 3 where ∂F∂I = the electromagnetic stiffness by a control signal current ∂F∂y = the electromagnetic stiffness by an armature movement I = the current of the control signal I 1 = the value of the control signal current when the valve armature begins to move y = the stroke of the armature