International Journal of Modern Research in Engineering & Management (IJMREM) ||Volume|| 1||Issue|| 10 ||Pages|| 46-54 || November 2018|| ISSN: 2581-4540
Modeling and Development of Pneumatic Accumulating System Engr. Riaz Hussain1, Prof. Dr. Dur Muhammad2, Dr. Saifullah3, Engr. Muhammad Atif4 1
(Student of Mechanical Engineering Department, Mehran University of Engineering & Technology, Pakistan) 2,3,4 (Faculty Members of Mechanical Engineering Department, Mehran University of Engineering & Technology, Pakistan)
---------------------------------------------------------ABSTRACT-----------------------------------------------In the recent few years the quest for renewable energy has been increased. In developing countries like Pakistan, energy crises are considered as critical problem for country’s economy. In this scenario there are two possibilities either to improve the efficiency of energy conversion method or to discover new energy resources i.e. renewable sources. Therefore, the main concern of this study is to develop an accumulating system which can harness some amount of wasted energy of moving road vehicles. It has been found that road moving vehicles are wasting huge amount of their potential energy. This wasted energy can be harvested by installing a pneumatic accumulating system underneath the transient rout of moving vehicle, which can simulate wasted energy for useful work. For the proposed system, mathematical model with governing equations is developed, that shows efficient conversation of potential energy to the pressure energy. Developed model is programmed in MATLAB for the real time comparison of output. It is observed that the proposed system is applicable to extract wasted energy of road vehicle for useful purpose.
KEYWORDS: Energy, Accumulation, Pressure, Road Vehicle, Simulation ------------------------------------------------------------------------------------------------------------------------------------------Date of Submission: Date, 13 November 2018 Date of Accepted: 16 November 2018 -------------------------------------------------------------------------------------------------------------------------------------------
I. INTRODUCTION Energy is considered as crucial need for human life. Since ages, energy is being utilized by men in its basic to the modern and sophisticated forms. As the life standard rises with continuous increase in population ratio, the energy consumption and need for the development in urbanization progress also increases. It is foreseen by many researchers that current fossil fuel resource will come to end in near future. This fact encourages to search and spend in potential alternative sources to overcome energy crises. With this aim in mind, the goal of this study is to research possible renewable energy source. Today, millions of vehicles are moving on their transient route and wasting incredible amount energy in different forms. About 18~25% of energy is lost due to friction in braking, rolling and wind resistance [1]. Some amount of this energy can be gathered by installing a panel underneath the road, which can simulate wasted energy of moving vehicle. This study concentrates only on weight of moving vehicle to produce useful energy. The parameter such as effect of weight of vehicle, pressure energy stored in accumulator and vehicle speed is under consideration. Due to increasing need of energy, many of the researchers have shown their interest to overcome this issue. As Khalfan et.al in his study, designed a hydraulic system, which utilized weight of vehicle as external load to generate mechanical power. In this study 45% of energy conversion can take place through this mechanism [2]. Eduardo, et al., in his research gave the concept of regenerative braking system, which can convert wasted potential energy of vehicle into useful mechanical work [3]. Andrea Pirisi, et. al, worked on energy harvesting devices, and developed a prototype with tubular permanent magnet generator for optimization of energy form traffic [4]. In 2011, Shiraishi designed an advance type of accumulator (as flow damper) that can automatically regulate the flow rate of injected water in pressurized water reactor (PWR). In this design there is not any moving part so that, it doesn’t require maintenance [5]. Minav, et al., in his study worked on energy storage recovered from forklift which works on electro-hydraulic principle. They also developed an experimental setup [6]. Porumamilla, et al., developed a vibration free system by incorporating an active pneumatic system. In this study it was observed that natural frequency of system can be varied by using an air spring-based orifice accumulator [7]. Hung & Kawan AHN, developed an energy saving system, Hydrostatic Transmission (HST). In this model kinetic energy of fluid recovered by using hydraulic accumulator [8].
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Modeling and Development of Pneumatic Accumulating System. However, from the above citations, it is clear that, there are many ways to harness wasted energy of vehicles by utilizing their weight. In our proposed work, we are aiming to capture this wasted potential energy of road vehicle by developing a pneumatic actuating system. In this model accumulation tanks are used to store high pressure energy of compressed air, which can be converted into useful kinetic energy later. Because, it is observed from the cited work that, accumulators are mainly used for regulation of energy or to compensate the energy loss. Comparing to other mechanism of regarding this concept, accumulators are the only mechanical component that can offer maximum energy density, with maximum efficiency, and less maintenance cost.
II. PHYSICAL MODEL OF THE SYSTEM Design of proposed system with required components is shown in figure 2.1. For the development of proposed system we have considered air as working medium. For this operation, the recommended components includes, spring loaded piston cylinder, transmission lines along with check valve, and accumulation tank. athematical Modeling of the Components of the System
Figure 2.1 Schematic view of proposed Prototype
III. MATHEMATICAL MODELING OF THE COMPONENTS OF THE SYSTEM The proposed system consists of components, spring loaded piston cylinder, transmission lines along with check valve, and accumulation tank. The block diagram for the mathematical model is presented in figure 3.1. Weight Atm. Air
Piston Cylinder Assembly
Pressure
Dynamics of Lines and Valves
Pressure
Dynamics of Accumulator
Accumulated Pressure
Figure 3.1 Block Diagram of Model of the System Design of Pressure Energy Generating Unit (Spring Loaded Piston Cylinder): In proposed model of the system as shown by block diagram in figure 3.1, the inlet parameters for piston cylinder assembly are weight of vehicle as external load, and air energy at atmospheric pressure. Assuming the Polytropic Process in cylinder, the equation of compression yields as:
…………….. (A) As area A of cylinder remains same throughout process. The equation A can be simplified as:
…………….. (B)
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Modeling and Development of Pneumatic Accumulating System. The equation (B) represents the pressure developed in cylinder when it is subjected to external load W. The effect of this external load is to do piston work only. This piston work is only responsible to develop pressure energy. The design consideration to achieve the desired Pressure depends upon compression ratio or ratio between maximum stroke length of cylinder and minimum swept distance by piston, and polytropic index n. As per market survey, there is variety of piston cylinders available with different specifications. For the development of proposed system, a cylinder with 80 mm bore size, and 50mm stroke length is selected. This selected cylinder with defined specification can develop maximum pressure of 4 bar. Whereas; the minimum pressure developed by this selected air cylinder is 0.2 bar. The ultimate goal of the model is to develop 4 bar pressure, when it is subjected to external load by a vehicle weighing approximately 1000 kg. To obtain appropriate compression ratio, the hit and trial technique performed with above equation (B). Table 1. shows the results of different compression ratios. From results it is observed that the approximate desire pressure is achieved at 16.667 of compression ratio, when the final stroke length reaches to 2.5mm. While performing this trial test polytropic index is calculated as 1.08. Table 1. Results of Compression Pressure vs Compression ratio Compression Ratio
Clearance stroke (mm)
Pressure (bars)
5
10
1.1374
6.25
7.5
1.44
10
5
2.405
16.66
2.5
4.1747
50
1
13.674
The figure 3.1 (a, b, c, d, e ) represents graphical responses of pressure developed in cylinder at different pressure ratios. It can be noticed from these responses, as the compression ratio increases, the pressure developed in cylinder also increases.
Figure 3.1 (a) Compression ratio 5
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Figure 3.1 (b) Compression ratio 6.25
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Figure 3.1 (c) Compression ratio 10
Figure 3.1 (d) Compression ratio 16.667
Figure 3.1 (c) Compression ratio 10 Modeling of Accumulation of Pressure Energy unit: Similarly, accumulation of pressure will carried out by using accumulating tanks. Therefore, Pressure energy accumulation model is developed as; …………….. (C) Where, is pressure accumulated in accumulator, is pressure energy developed by piston cylinder. For accumulation of high-pressure energy from cylinder to accumulator, the check is mounted valve on transmission lines between the piston cylinder and accumulator. Therefore, and are the Pressure used to open the check valve and back pressure developed in accumulator respectively. Since,
depends on the minimum force required to open the spring-loaded check vale and diameter of check valve. The limit of depends on stiffness of spring used in valve.
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Modeling and Development of Pneumatic Accumulating System. is the Back pressure developed in accumulator due to high energy accumulation in accumulation tank. Its value depends on volume of accumulator.
Where, h1 and h2 are the volumetric limits of the compression. Now the equation (C) yields as; …………….. (D) This model represents the energy accumulation in accumulation tanks. Hence, accumulation energy depends on pressure developed in cylinder and, maximum and minimum limits of compression. The accumulated energy will be less than the energy developed in cylinder, because of some losses during transferring of pressure energy. The maximum accumulation of energy depends on the number of strokes. As the number of strokes increases, the accumulation energy intensity will also increase. IV. EXPERIMENTAL RESULTS OF PRESSURE DEVELOPING UNIT: The following figure 4.1 represents the experimental results of pressure developed in cylinder. The bore of cylinder is about 80 mm, hence it results area of piston about 5025.6 mm2. It is observed that pressure developed in cylinder is polytropic ally and maximum pressure developed in the cylinder is 4 bar, when the clearance volume reaches to 12.566 mm3.
Figure 4.1 Experimental Results of Cylinder
V. THEORETICAL PRESSURE DEVELOPED IN CYLINDER: The value of pressure developed in cylinder depends on the compression ratio. To obtain the desire pressure results i.e. 4 bar pressure, hit and trial method was performed. It was observed that with different compression ratios, we have different pressure in cylinder. Consequently, at compression ratio of 16.66 we get 4.174 bar pressure. The percent error between experimental and theoretical results is about 4.185 %.
Figure 2. Theoretical Results of Cylinder
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Modeling and Development of Pneumatic Accumulating System. VI. SIMULATION FLOW CHART AND RESULTS: The figure 6.1 illustrates the flow chart for real time results of Simulation for developed mathematical model. The proposed design contains certain constant parameter, as stiffness of spring used with piston cylinder assembly having constant value of 19.07 N/mm. The pressure at the inlet of cylinder is also assumed to be constant that is equals to atmospheric pressure. The designed volumetric capacity of accumulation tank is constant that is 2300 mm3. The other accessories like connectors, valves, fluid transmitting pipes with high pressure bearing capacity, elbows and tees are of 8 mm. But in this study, we are considering losses in valves used for proper functioning of proposed system. For the design of model, Number of vehicles and Weight of vehicle are input parameters. These both input parameters are variable quantities. From the cylinder, we have notable quantity of pressure energy
. This pressure energy of cylinder is being
added to the accumulation chamber chamber.
Output of Pressure Energy Generating unit: The following figure 6.2 is generated by using curve fitting method in MATLAB. In this figure block dot spots indicates the experimental data points. Whereas, bold blue lines indicates the simulation results. While in this simulation result the error between experimental and simulation result is about 0.07913%. Here this error is called as root mean square error (RMSE).
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Modeling and Development of Pneumatic Accumulating System.
Figure 6.2, Pressure developed in cylinder with a 1000 kg load Output of Pressure Energy Accumulating unit: The maximum pressure developed in cylinder, during this cycle is 4 bar, and pressure accumulated is same 4 bar. Since at every 1st stroke pressure accumulation is same as developed in cylinder as per its compression ratio. For further strokes, accumulation pressure varies. At each stroke, accumulation pressure increase.
Figure 6.3 Accumulation Pressure in tanks Pressure Energy Accumulation with variable strokes: As figure 6.4 shows the accumulated pressure, when three loads, each of 1000 kg passed over the hump of the speed breaker. Here, pressure developed in cylinder is same, but the pressure accumulated in tanks is more than double. It means that, pressure accumulated in 1 st stroke is 4 bar, when another load of same magnitude passed over the hump, produces same pressure in cylinder but accumulation pressure energy will increase as per its pre charged value.
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VII. ADVANTAGES
• Renewable source of energy • Clean and Pollution Free Energy source • Low Maintenance Cost • Minimum loss • Maximum Energy Density
VIII. CONCLUSION In this study, we have tried to develop sustainable energy model that can harness the wasted energy of road vehicles, in the form of pressure energy. Pressure developed in cylinder depends on the capacity of cylinder, if we use cylinder with more capacity, we can developed more pressure energy. The accumulated pressure energy depends on the weight of the vehicle and number of vehicles passing over the road hump. This pressure energy can be converted for useful work. As, in previous section it is observed that we can developed enough pressure, that can be used for various purpose like, for Gas filling station, as Compressed Air, to run wind turbines etc. We can accumulate more pressure energy either by increasing number of cylinders or by using cylinder with maximum pressure developing capacity. We can also improve efficiency of proposed system by adjusting favorable backpressure in accumulator. Also, we can make improve the efficiency by minimizing pressure losses during transmission lines (tubes), and in connector or valves.
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[6] [7]
[8]
Engineering and Design "Elesvier", p. 3910–3924, 2011. T. Minav, A. Virtanen, L. Laurila and J. Pyrhonen, "Storage of energy recovered from an industrial forklift," Automation in Construction , vol. 22, no. 2012, pp. 506-515, 2012. H. Porumamilla, A. Keller and J. Vogel, "Modeling and Verification of an Innovative Active Pneumatic Vibration Isolation System," Journal of Dynamic System, Measurement, and Control, vol. 130, no. May 2008, 2008. T. Hung and K. Kawan AHN, "Modeling and simulation of hydrostatic transmission system with energy regeneration using Hydraulic accumuator," Journal of Mechanical Science and Technology, vol. 24, no. March 30, 2010, pp. 1163-1175, 2010.
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