NON COMBUSTIBLE AUTOMOTIVE ENGINE DESIGN USING MAGLEV TECHNOLOGY

Transcription

1 2011 2nd International Conference on Environmental Science and Technology IPCBEE vol.6 (2011) (2011) IACSIT Press, Singapore NON COMBUSTIBLE AUTOMOTIVE ENGINE DESIGN USING MAGLEV TECHNOLOGY G.Vimal Raj and N. Harish Kumar Dept of Electrical and Electronics Engineering Velammal Engineering College (Affiliated to Anna University) Chennai, India Abstract Nowadays electromagnetically levitating superconducting systems are an emerging trend in automotives. This is due to their frictionless motion. The superconducting magnetic levitation-suspension engine offers a simple and environment friendly solution in a different dimension. This non-combustible engine makes use of magnetic repulsion cum attraction forces for its reciprocating movement aided by superconducting repulsive phenomena which are analogous to that of the principles used in maglev trains to increase its performance. This paper deals with the proposed engine s design along with its constructional details, its working principle, and its indigenous control strategy accompanied by substantiating simulation results. II. THE DESIGN APPROACH The outer structure of the model is quite similar to that of conventional IC engine with a cylindrical top connected with crank case. The entire outer structure is hollow where the internal moving and stationary parts are placed as shown in Fig. 1 Our contributions towards the foundation of the practical implementation of our idea en-compasses a small prototype setup, generation of simulation results using various softwares such as MAXWELL 3D, VIZIMAG and PROTEUS ISIS. Keywords-Upper electromagnet; lower electromagnet; near end; faces. I. INTRODUCTION Traditional IC engines are expensive due to ecological incompatibility of its exhaust.presence of noise and vibrations invoke high maintenance of IC engines. Hence the alternative technologies such as electric motor drives were introduced, but the requirements of high voltage batteries, large size convertors, inability in driving heavy loads and their high power demands to cover long distances have made them ineffective for automotive drives. An attempt has been made to overcome all these drawbacks using superconducting maglev and suspension technologies. Our proposed design and its control strategy offer an innovative solution in the field of automotive drives. This idea implies modification of conventional IC engines by replacing the combustible part with a magnetically controllable system. Here the force required for the movement of piston is obtained with the help of magnetic attraction and repulsion forces aided by superconducting cylindrical walls of the engine. A brief description of the proposed design is provided subsequently. Figure 1. Design Structure This design consists of two electromagnets fixed inside at the upper and lower sections of the cylinder. The excitation is controlled using PWM technique, where the upper electromagnet consists of copper wire wounded on a cylindrical pole core with a concave shaped cylindrical disc as pole shoe thereby reducing the reluctance of the magnetic path hence spreading out the flux in the air gap radially. And the lower electromagnet is similar to upper electromagnet with a round rectangular cut at the center with a clearance for piston rod to move freely during reciprocating motion. Both the pole core and pole shoe are fabricated by laminations of annealed steel. The piston consists of two NdFeB (Neodymium) magnets in disc and donut shape. Where the disc shaped magnet is mounted over the donut shaped magnet (collectively known as the permanent magnet) and a V1-420

2 piston rod connected to it with help of a hinge. This piston is free to move up and down between the two electromagnets during the reciprocating action producing a circular motion to shaft {8} connected inside crank case. The inner cylindrical walls between the two electromagnets are made up of Yttrium barium copper oxide (YBCO) a crystalline chemical compound which is a high temperature superconductor with a critical temperature above 77K [1]. The selected superconductor (YBCO) is economical and easy to fabricate providing good diamagnetic levitation effect [2]. III. WORKING PRINCIPLE The superconducting Maglev-suspension engine basically works on the principle of "forces of electromagnetic attraction and repulsion [3]"(in simple terms magnetic pull and push forces) aided by superconducting repulsive forces Miessner effect). Since the upper electromagnet {1} and the lower electromagnet {6} are supplied with electrical energy, an unit pole (both electromagnets must have the same polarity at any given instant of time) is assumed to be generated at the near end{10,15} of electromagnets, relative to the permanent magnet{14}.thus one electromagnet pushes the permanent magnet{14} and the other pulls it, where the repulsive maglev force produced due to movement of permanent magnet{14} by interaction with superconducting walls aids the reciprocating action[3]. The field strength of the permanent magnet {14} is so weak the it ranges only a few millimeters from its axis, therefore it is evident that it assists its motion only during the time of repulsion when the polarity of the near end changes at position {13, 5}. Refer Fig. 2 for the mechanism of the shaft {8} rotation can be described as under: A. The First Stroke Conventionally the permanent magnet {14} is assumed to be placed at position {5}, (i.e.) at the near end {10} of the lower electromagnet {6}) with its South pole facing the lower electromagnet {6}. When the Maglev-suspension engine is started by turning ON the control circuits at a time instant, T T=0, both the lower electromagnet {6} and the upper electromagnet {1} acquire the analogous polarity i.e.) South pole at their near ends {10, 15} during the first stroke. Hence the permanent magnet {14} experiences a force of repulsion (since face {3} has same polarity to that at near end {10}).Till, when time period, T=T1 the permanent magnet {14} experiences a strong repulsive force (pushing force) at near end {10} and undergoes an upward motion. At T=T1, the permanent magnet {14} reaches a position {16} (near the centre of the cylindrical portion) at which the permanent magnet {14} begins to experience a force of attraction due to the upper electromagnet {1}, this incidentally marks the end of the first half cycle of the first stroke where the shaft connected to the permanent magnet {14} completes one quarter of the revolution. During the beginning of the second half cycle, the permanent magnet {14} is pulled i.e.) attracted by the opposite polarity of the upper electromagnet {1} at the near end {15}. (Since the face {2} (side nearer to the upper electromagnet {1}) has North pole and the upper electromagnet's near end {15} has South pole).till, when T=T2, the permanent magnet {14} undergoes upward motion. When T=T2, the permanent magnet {14} gets to the near end {15} and reaches the position {13} and the shaft attached to the piston rod {11} connected to the permanent magnet {14} completes another quarter part of the revolution. This marks the end of the first stroke. Hence at the end of the first stroke, the permanent magnet {14} moves from position {5} to position {13} undergoing upward motion and the shaft {8} connected to the connecting rod {9} it complete one half of the entire revolution. Figure 2. Working Cycles: (a) first stroke (b) second stroke B. The Second Stroke The second stroke shown in Fig.2(b) is just similar to that of the first stroke but the difference lies in the fact that the permanent magnet {14} moves downwards due to repulsion since the polarity at the near ends {15,10} is changed(from South to North)by the control circuits. At T=T3 once again the permanent magnet {14} reaches position{16} mean while the shaft {8} completes three fourths of the revolution and marks the end of first half of the V1-421

3 second stroke. When T>T3 the permanent magnet is attracted by the near end {10} of the lower electromagnet {6} (Since face {3} is an South pole and near end {10} is an North pole) and at T=T4, the permanent magnet {14} reaches its initial position {5} marking the end of a complete revolution of the shaft {8}. IV. THE FORCE EXPRESSIONS AND CALCULATIONS A. Assumptions The diamagnetic levitating forces [2] provided by the superconductor {12} at the side walls are considered to be much greater than gravitational force. Hence gravitational force is considered negligible. Also as the motion is linear (against or assisted by gravity) the variation of the potential energy of the permanent magnet {14} also plays a major part, but since the change in height is not very much appreciable (i.e. negligible) it is not considered into account. In order to calculate the push and pull forces it is necessary to introduce two terminologies: 1) Magneto motive force F: It is the magnetic potential difference between any two points. The pulling and pushing operations of the permanent magnet depends on Magneto motive force F. For an electromagnet this force is related to the number of turns, the core material used and the amount of current [5]. So in order to pull a magnet from distance it is necessary to know the potential at the near ends {15, 10} and at the faces {2, 3}.Hence to find the force at a point from the electromagnet it is essential to find Magnetic field intensity,h. 2) Magnetic field intensity H :It is the amount of force exerted at a point by a magnet. This depends on the flux density and the permeability of the medium. 3) Expression for force F: Energy stored, in an inductor over a differential volume, V. Where differential length, dl and Air gap area between permanent magnet and a nearer electromagnet, S are the necessary factors for computing force, F. Equation (1) represents the required expression for force. In order to get the required force from (2) it is evident that by varying amount of current the criterion is satisfied. The value of field intensity at every instant required to fix a particular force for a given speed was calculated using MAXWELL 3D simulation software and VIZIMAG software. V. CONTROL BLOCK DIAGRAM The control system consists of a microcontroller AT89C51 interfaced with an electromagnet driver LMD18200T IC, distance sensor and a pressure transducer act as inputs. The Fig. 3 shows the block diagram of the control system. When the engine is started the microcontroller first checks distance between upper electromagnet and piston, accordingly energizing both the coils with same polarity setting up required current. When the piston approaches the near ends of the electromagnets the distance between the two is sensed and sent to the microcontroller which changes the polarity of the electromagnets. For speed control, the force is converted into a proportional analog signal using pressure transducer [4]. This signal is amplified and converted to digital data and given to the µc as in the new input. For a particular speed, the output of the distance sensor and the pressure transducer is compared by the microcontroller generating a set of signals to the driver circuit based on preloaded values in the lookup table. The microcontroller generates three signals (PWM, direction & brake) to the driver IC for controlling the excitation of the electromagnets. The circuit diagram for the control system was simulated using PROTEUS ISIS software is shown in Fig. 4 and the PWM waveform generated microcontroller is shown in Fig. 5. = µh² V = µh² dv B=µH dw =F x dl µh² dv = F x dl µh² dl x S = F x dl (since dv=dl x S) Figure 3. Control block diagram F= µh² x S (1) F=NI (2) V1-422

4 VI. EXPERIMENTAL SIMULATION AND RESULTS A miniaturized model (prototype) of our projected design was practically implemented. A similar software generated setup for the electromagnets and permanent magnet piston of our model (crank and shaft {8} arrangements are omitted for calculation purpose) is shown in Fig. 7 and Fig. 8 shows the force produced by both the electromagnets and permanent magnet piston. Figure 4. Circuit Simulation Figure 5. CRO output waveforms Figure 7. Simulation of our Model Figure 6. Flow chart of the process The above flowchart depicts the entire process taking place in the control circuit as shown in Fig.7. Figure 8. Simulation output data s V1-423

5 The scrutinized trace of flux density Vs distance between the electromagnets is shown Fig. 9. The Fig. 10 shows the VIZIMAG simulation output showing how magnetic flux lines produced by the two electromagnets and permanent magnet piston links each other with reaction to superconductors producing strong diamagnetic levitation effect at side of piston. It also clearly depicts how these flux lines varies during the reciprocating movement of piston. Thus it helps us to set the parameters of electromagnets and permanent magnet. The experiment s scope is actually limited to the prototype and an all-encompassing analysis is done using MAXWELL 3D, VIZIMAG and PROTEUS ISIS simulation softwares for future enhancement of the design due to its rigid hardware nature. The simulation s focal aim is to provide an unambiguous idea on the distribution of the magnetic parameters. Figure 9. Flux Density Graph (a) (b) (c) Figure 10. Trace of magnetic flux line using VIZIMAG (d) On further investigation the following fallouts were observed. The magnetic field intensity (H) is a function of space (decreases with increase in distance of separation). V1-424

6 The required force for levitation and suspension decreases as the distance between them decreases since area of CS decreases. The superconducting forces too were simulated and their presence was found to favor the movement of the piston thereby increasing the overall efficiency. The projected control system provides an optimized control over the entire arrangement. On further exploration the losses due to friction and the requirements for maintenance are found to be lesser compared to other engines. Since the setup is energized from a supply, this suffers from magnetic losses (core loss, eddy current losses) hence obviously a trade-off exists between the magnetic losses and mechanical losses (e.g. friction which is not prominent here), but on the whole this provides a lucid solution for environmental problems leaving no residues. VII. CONCLUSION This paper is aimed at providing a long term solution for automotive drives from a different perspective. The initial experimental and simulation results were found to be satisfactory and the further enrichment aspects are also provided. Hence this non-combustible maglev engine is more eco-friendly than conventional engines. Hope this design marks a new era in automobiles. REFERENCES [1] A.C. Rose-Innes and E.H. Rhoderick, Introduction to Superconductivity,Pergamon Press, Oxford,1978,pp [2] D. Mayer, Magnetic levitation and it s applications, in Czech, Electro 1/2003,pp [3] B.V.Jayawant, Electromagnetic levitation and suspension techniques, Edward Arnold, London, [4] M. Zayadine, S. Colombi. Active Control of a Magnetic Suspension System, International Symposium MV2 on Active Control in Mechanical Engineering, pp , Hermes, Paris, [5] M. Kihara An introduction to Electromagnet Design,June, 2000, unpublished. V1-425