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"BUTTERFLY ENGINE"Proceedings of ICFD 10:Tenth International Congress of Fluid Dynamics The engine that is presented here is a similar innovation and has beennamed BUTTERFLY ENGINE, owing to its construction which resemblesthe wings of a butterfly. It is a rotary type engine, i.e. it provides directrotating output from the combustive power of the

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  • Proceedings of ICFD 10: Tenth International Congress of Fluid Dynamics

    December 16-19, 2010, Stella Di Mare Sea Club Hotel , Ain Soukhna, Red Sea, Egypt

    ICFD10-EG-3154

    BUTTERFLY ENGINE

    Author (1) AMAN SRIVASTAVA Ph: 91-9435744403 E-mail: [email protected]

    Co-Authors (2) ANOOP IYER

    Ph: 91-9011053116 [email protected] (3) ABHINAV AWASTHI

    Ph: 91-9923271407 [email protected]

    (4) SAURABH TIWARI Ph: 91-9836482306

    [email protected]

  • 2

    1. ABSTRACT It has been very wisely said that Innovation is the key to

    Development. Had it not been for innovation, the world would have been reduced to a bunch of stagnating ideas and rigid concepts.

    The engine that is presented here is a similar innovation and has been named BUTTERFLY ENGINE, owing to its construction which resembles the wings of a butterfly. It is a rotary type engine, i.e. it provides direct rotating output from the combustive power of the fuel hence reducing the mechanical losses involved in transfer of motion.

    The most nagging problems in technological development today are the fear of extinction of fossil fuels and the problem of pollution. So it is logical that the foremost reason as to this engine was developed is to achieve better fuel economy & efficiency.

    The engine is also developed in a way so that it can be used for versatile applications. It is compact, has higher power to weight ratio, and can be run using different kinds of fuels owing to some of its inherent design characteristics.

  • 3

    2. INTRODUCTION If we look back a century in time, we will be astonished to see the

    advances that we have made in leaps & bounds in the field of engine technology. From the very first engine (the one made by Karl Benz) to i-VTEC, we have indeed come a long way. So much so that in place of the box type, noisy, bulky structures that we called automobiles a century ago, we now have the most swanky, swift, smart pieces of technology that bring the bitumen to a boil and pump adrenaline into your veins like never before. And most of us would agree to the fact that in this drastic transformation of the face of automobiles, the development of engine has definitely played a pivotal role.

    A drastic innovation to one of the earliest engines gave rise to a rotary type internal combustion engine called Wankel engine which is a remarkable example in the field of innovation. It had a specialty of providing direct rotary output, thus reducing the mechanical losses & hence increasing the efficiency. It was initially incorporated in Mazda RX-7 & Rotary Genesis in RX-8.

    The correct conceptual & technical approach which is required in the analysis of the engine is very essential. Hence a number of papers and thesis were referred to have an insight of the various innovations across globe [11], [12], [13], [14], [15], [16].

    The engine that we present here has its basic components; a cylindrical casing, snitch, main output shaft, wings and a sprag clutch or ratchet and pawl mechanism. The flapping action of the wings is similar to the movement of wings of a butterfly, and hence the name BUTTERFLY ENGINE.

    The crude construction of the engine primarily consists of a cylindrical casing, a pair of snitches comprising of two wings and a cylindrical hub with sprag clutch or ratchet and pawl mechanism each. The snitch is linked to the main shaft through the sprag clutch mechanism (Ratchet and pawl Mechanism). Figure 1 is a labeled diagram of the engine, in its front view, illustrating the basic parts. The dimensions of the engine can be seen in figure 14. Figure 2 illustrates the two positions of working of the engine, explained later.

    Figures 3 and 4 show the component Casing. The casing as said earlier is just a cylindrical hollow structure. It can be compared to the Engine Block of a conventional engine as it encompasses all other components inside it. The protrusions at 900 from the casing, towards outside, are the nipples used for valves or port openings.

  • 4

    Figures 5 and 6 depict the snitch. The snitch is again a hollow cylindrical structure with diametrically opposite rectangle protrusions called wings. These protrusions act as pistons and seal against inside of the casing. The hollow center hub of the snitch encompasses the sprag clutch or the ratchet and pawl mechanism which itself is linked to the main output shaft running through the center. The wing is double the width of the hub of the snitch so that it meshes completely with the other snitch having similar structure; two snitches meshed together are shown in figures 8, 9 and 11. The ratchet and pawl mechanism of both the snitches are aligned in same direction.

    The working of the engine is henceforth explained. Please refer to figure 2. As the charge enters the vertical chambers (A) in stage 1, the wings are forced to move towards the horizontal position. A similar suction process then occurs at the horizontal chambers (A) in stage 2, which forces the wings back to the original vertical position, thus compressing the charge. The power stroke is marked by the ignition of the charge in the vertical chambers, which is then followed by a similar combustion process in the horizontal chambers. In this way, the wings move to-n-fro like the wings of a butterfly.

    The movement of the wings causes the ratchet and pawl mechanism to rotate at a certain angle back and forth. As the ratchet and pawl mechanism allows its inner shaft to rotate only in one direction with respect to the outer part (like in a bicycle free-wheel), hence the main shaft rotates with the wings in only one direction. It is to be noted that both the snitches move exactly in opposite directions all the time. This causes the sprag or ratchet and pawl mechanism of each snitch to move in both the directions. However this motion is transferred to the main output shaft in only one direction. Thus the chemical energy of the fuel is directly converted to the rotary motion of shaft.

    Observing closely it may happen during practical application that the snitches may try to move in or out at different times during the suction or combustion process. Hence in the snitches a bevel gear meshing can be used between the pair so that each snitch forces the other to move in opposite direction to it. The bevel gear meshing is similar to the one used in a differential box of an automobile. Movement of any one snitch causes its bevel gear to move. The pinion gear causes the other snitch to move in opposite direction. Referring to figures 7 and 8 arrangement of the bevel gear can be seen. The bevel gears are supported by the snitch cylindrical hub and the main output shaft. The pinion gear can be supported using a small T- frame assembly as shown in figure 7.

  • 5

    A very clear picture of the engine can be obtained from the figures 9, 10 and 11. Figure 9 illustrates the engine in front view. The snitches and the wings can be seen making the four chambers for carrying out the combustion process. Figure 10 shows the top view where the main output shaft can be seen protruding out of the engine body. Figure 11 illustrates the engine in 3D view and is self explanatory in a way.

    The design has been already been granted Provisional patent in India with application number 2241/DEL/2010 on 21.09.2010.

  • 6

    3. MODEL FABRICATION A plastic or PVC model fabrication was necessary so as to obtain the

    correct representation of the engine in its working form. This model can provide with the calculations for its performance evaluation.

    To prepare a model one component of the engine had to be taken as a reference. Here the sprag clutch or the ratchet and pawl mechanism is taken as it is the only component of the engine which is most complicated in design. The sprag clutches are used in a wide variety of applications like automobile starter motor, overhead trolleys, conveyer belts etc. However, these sprag clutches are bulky, voluminous and very costly. Moreover, they have other components like O-rings, hub etc which are not required for our purpose.

    Preparing a sprag clutch or a custom made sprag clutch could be used however there are two alternatives still remaining which provide a similar mechanism.

    The alternatives are ratchet screwdriver and bicycle-free-wheel. Ratchet screwdriver are very small and they come in sets hence they are again not feasible for our application.

    The only option thus left is a bicycle free-wheel. The cogs on free-wheel surface are removed to suit the application. The cogs can be grinded on a bench grinder and used for the purpose.

    Other components are designed with respect to the ratchet and pawl mechanism finalized. A PVC pipe as a casing and acrylic pipes are used for making hub for free-wheel and main output shaft. The wings are made of acrylic sheets. Lego parts are used for making supports.

    Figures 12 & 13 depict the photographic views of the PVC prototype. The calculations in this paper are based on this model prepared with respect to its dimensions.

  • 7

    4. BASIC CALCULATIONS FOR THE ENGINE 4.1 FINDING BASIC PARAMETERS OF THE ENGINE Again referring to figure 2; at Stage 1 intake process occurs at the vertical chambers and they move to Stage 2 where similar process takes place in horizontal chambers. The angle between the centers of the wings is 2 (shown by 20). This angle becomes 180-2 (shown by 180-20) at the stage 2. Hence The area between the wings in Stage 1;

    A = (((2 x r2)/360) ((2 x s2)/360)) (A1).......(1) Where, r= internal radius of casing. s= outer radius of snitch. A1= Cross section area of wing. Clearance Volume= A x w .. (2) Where, w= Width of casing, here 6.5cm. Area between wings in Stage 2;

    A= ((((180-2 ) x r2)/360) (((180-2 ) x s2)/360)) (A1)...(3) Total Volume= A x w ... (4)

    Hence; Compression ratio= Total Volume/ Clearance volume (5) r= A/ A...(6)

    As stated in assumption we consider compression ratio as 10 and using the dimensions as shown in the Auto CAD figure: Hence; 10= A/ A.(7)

    Which gives = 20.790 The volume obtained, by using the found, will be opposite to that assumed, i.e. the formula for A will give the volume of A . However it is not necessary as both the volumes are occurring simultaneously in consecutive chambers. RPM of engine at 31CPS= 1430RPM

    (31Cycles per second, i.e. 31 times the complete cycle operates in one chamber per second, is assumed for the calculations)

    Volume of upper chamber in stage 1 = 14.07cc Volume of upper chamber in stage 2 = 140.70cc Hence the basic parameters of the engine can be tabulated as follows:

  • 8

    Table 1. Basic Parameters of the engine Outer Dia. (cm) 13.97 Inner Dia. (cm) 11.43

    Length (cm) 6.50 Width of wings (cm) 0.60

    Comp. Ratio 10 Cycles per second 31

    Air fuel ratio 15 Vol. W/o wings (cc) 329.36

    Vertical angle (0) 20.79 Horizontal angle (0) 159.21 Upper volume (cc) 14.07 Wider volume (cc) 140.70

    RPM 1430 Max. Vertical Angle (0) 6.02

    Max. Horizontal Angle (0) 173.98 Min. Volume (cc) 0.55 Max. Volume (cc) 154.22 Max. Comp. Ratio 278.95

    Height of Wings (cm) 1.27 The maximum vertical and maximum horizontal angles possible are

    found out using some basic geometry and depend on the thickness of the wings and radius of the snitch. Maximum vertical angle will be decided when the wings are close enough to touch one another at the inner radius diameter position. This is given as

    2 X (900-COS-1(Thickness of wings/ Inner Diameter))..(8) Maximum horizontal angle possible is found by subtracting the above

    from 1800. Respective volumes and Maximum compression ratio possible are found out successively.

  • 9

    4.2 POWER CALCULATION [6], [7], [8], [10] Assumptions:

    (1) The cycle works under ideal Otto cycle. (2) No heat loss occurs during combustion process and volumetric

    efficiency is 100%. (3) Engine performs at a constant stoichiometric air: fuel ratio of 15:1. (4) The value of gamma ( ) is 1.4. (5) The value of gas constant (R) is 287 J/ (kg-K). (6) Calorific Value (C.V.) of petrol is 43.5MJ/kg and density ( f)

    760kg/m3. (7) Density of air ( a) is taken to be 1.17kg/m

    3 and specific heat at constant volume (Cv) as 0.717KJ/kg.K.

    (8) As the engine is running on petrol the compression ratio is taken to be 10.

    (9) The engine operates at 31CPS (31 cycles per second), i.e. 31 times the complete Otto cycle operates in one chamber per second. Referring to figure 15 which represents an the PV diagram of an ideal

    Otto cycle At state 1: P1= 1bar V1= V4 = 140.70cc T1= 25

    0C= 298K 1 2 (Adiabatic compression process) P1V1

    = P2V2 ......(9)

    V2= V3= 14.07cc Hence P2=25.12bar and T1V1

    ( -1)= T2V2( -1).............................................................................(10)

    Hence T2= 748.54K 2 3 (Isochoric heat addition process) P2/T2= P3/T3 .. (11) But QH = mf X C.V= m X Cv X (T3-T2)......................................................(12) QH= mf X C.V. = mf X 43.5 X 10

    3 KJ........................................................(13) Also, QH= ma X Cv X (T3-T2).....................................................................(14)

    = mf X 43.5 X 103 KJ = ma X 0.717 X (T3- 748.54)....................(15)

    But ma: mf = 15:1

  • 10

    Hence T3 = 4428.23K and P3= 148.60bar 3 4 (Adiabatic expansion process) P3V3

    = P4V4 .(16)

    Hence P4= 5.92bar and T3V3

    ( -1)= T4V4 ( -1) ...(17)

    Hence T4= 1762.91K Now; ma= (P1V1)/ (RT1) = (101325 X 140.70 X10

    -6)/ (275.03 X 298) = 1.74 X 10-4 kg and mf = ma/15 = (1.74 X 10

    -4) / 15 = 1.16 X 10-5 kg and QH = mf X C.V. = 1.16 X 10

    -5 X 43.5 X 106 = 504.60 J Hence Work Output = ((P1V1) (rp-1) (r

    ( -1)-1))/ ( -1) ...(18)

    Where rp= P4/P1= P3/P2= 5.92 WORK OUTPUT= 235.29J

    The two vertical chambers, directly opposite, will undergo similar process simultaneously and the other two, horizontal chambers, will undergo similar processes simultaneously but with a lead (or lag) of one stroke. Hence for 1 cycle of vertical chambers power process will occur together in both and similar for horizontal chambers. Therefore for one complete cycle of all the chambers, four times the above energy will develop, with half occurring at one time and another half at other. And at 31CPS = 504.60 X 2 X 2 X 31= 29.17 KW = 39.12 hp.(19) Hence Torque= Power/ Rotational speed= 194.77 Nm Indicated thermal efficiency ( thm)

    thm =Total Output energy/ Energy developed by fuel...(20) thm = 29171.89 / (482.85 X 2 X 2 X 31) thm = 46.64%

  • 11

    5. ROTARY VALVE ANALYSIS [2], [3] The Butterfly engine uses a rotor valve as the use of poppet valve would

    make the structure extremely bulky and voluminous. Moreover the cam mechanism used for opening and closing the poppet valve would be extremely complicated. Hence rotary valves would prove to be very good alternative.

    The basic construction of a rotary valve is a rotor revolving inside a stator at a certain RPM with a small clearance to avoid contact and to prevent leakage through it. Both rotor and stator have one hole each. When the hole of rotor matches with that of stator the air fuel mixture supplied to the rotor starts flowing out of the stator. The eclipse movement of the rotor hole allows a bell shaped output flow of charge which is similar to poppet valve flow (as shown in figure 17).

    Referring to figure 16 a basic construction of a rotor valve is shown. For simplicity of calculation we have considered the radius of the rotor and stator to be same as distance between them extremely less. Considering the fabrication process the valve hole in the rotor and stator is basically drilled on a cylindrical curved surface. Hence the hole is not exactly a circle but an ellipse (as shown in figure 16).

    The minor axis length of the ellipse is the same as the diameter of the hole but the major axis depends on the time for which the holes overlap. To find the radius of the hole:

    In the SIMULATION OF THE ENGINE we shall see that for the vertical chambers suction process begins at 20.790, i.e. at vertical most position and ends at 159.210, i.e. horizontal most position. For horizontal chambers suction process begins at 159.210, i.e. horizontal most position and ends at 20.790, i.e. at vertical most position. Hence the net angle moved by the main output shaft during the suction process is (159.210-20.790)/2 = 69.210. As per the given RPM of 1430 the time required to move 69.210 is 0.0081sec.

    The suction of the next cycle starts after 276.840 (69.210 X 4) after start of one suction. Hence the rotor has to move 3600 when the main output shaft rotates 276.840, which gives the speed ratio as 1.30. Therefore, the angle moved by the rotor during suction process is 1.30 X 69.210 = 89.9730 900. The hole must cover of the rotor to provide the required amount of charge.

    Using basic geometry and trial and error method the radius of the hole and rotor can be optimized to suit the flow area available during the overlapping of the rotor and stator holes. A similar exercise has been done

  • 12

    for exhaust process and results were obtained. For the simulation process we have considered Intake Valve:

    Hole Radius, d/2 = 3mm Rotor Radius, D/2 = 7.64mm

    Exhaust Valve: Hole Radius, d/2 = 4.30mm Rotor Radius, D/2 = 10.95mm

    Some basic calculations for rotary valve are shown below Diameter of rotor hole = d mm Diameter of Stator = D mm Speed ratio of rotor and main shaft of engine = S Net angle moved by the rotor = Hence if a certain diameter of rotor and net angle movement is decided Speed ratio = / (((180-2 )-2 )/ 2)...(21) RPM of rotor = RPM of Main Shaft of Engine X Speed Ratio..(22) Diameter of Stator = (4 X d)/ ( X ( /180)) ...(23)

  • 13

    6. SIMULATION OF THE ENGINE [1], [4], [5], [6], [7], [9], [10]

    Here we have used a Zero-Dimensional model for the analysis which includes only thermodynamic concepts. In this method, only the heat transfer from engine walls to the chamber or vice versa is considered. This needs the heat transfer coefficient value which is extremely difficult to obtain. Some formulas used in simulation expression for heat transfer coefficient, mass fraction burned during combustion etc. are specific for a conventional ICE however modification with respect to this engine made them compatible for the calculations. The calculations were performed on computer which helped in calculations, iterations, graphs plotting and display value for every parameter at each step. The complete simulation was performed by considering certain fixed main shaft rotation. For every process, i.e. suction, compression, combustion, expansion and exhaust 18 divisions were made. For each and every position of main shaft the respective volume of a single chamber and the respective pressure and temperature were obtained.

    Though the model is very basic however assuming certain data and introducing some multiplying factors we can arrive at results very close to the actual data. Assumptions:

    1. Only zero-dimensional approach was used i.e., only heat transfer from walls to the chamber was considered.

    2. Engine performs at a constant stoichiometric air: fuel ratio of 15:1. 3. The value of gamma ( ) is 1.4. 4. Calorific Value (C.V.) of petrol is 43.5MJ/kg and density ( f)

    760kg/m3. 5. Density of air ( a) is taken to be 1.17kg/m

    3 and specific heat at constant volume (Cv) as 0.717KJ/kg.K.

    6. The density of charge intake is 1.25kg/m3 and has Cp of 1.0631354kJ/kg-K and gas constant 275.03 J/kg-K. The charge is homogenous.

    7. The charge and exhaust gases are considered to be ideal gases. 8. For exhaust gases gas constant is 290.65J/kg-K and Cp is

    1.135317kJ/kg-K. 9. Leakage and discharge losses of gases are neglected. 10. Temperature of the mixture is uniform throughout the chamber.

  • 14

    11. As the engine is running on petrol the compression ratio is taken to be 10.

    12. The engine operates at 31CPS (31 cycles per second), i.e. 31 times the complete Otto cycle operates in one chamber per second.

    The complete engine cycle is divided in five parts, viz. Suction, Compression, Combustion, Expansion and Exhaust.

    Table 2. Engine Cycle PROCESS PERIOD OF OCCURANCE

    Suction 20.790-159.210 Compression 159.210-290 Combustion 290-20.790-290 Expansion 290-1480 Exhaust 1480-159.210-20.790

    (6.1) SUCTION

    The suction process occurs between 20.790 and 159.210 of wing angle. Based on the vertical most and horizontal most positions of the engine the main diameter was obtained. The value obtained for rotors movement during shaft movement was found out. As we are using a rotary valve the motion has to be clubbed with the main shaft, we assumed that the suction begins at vertical most position and ends at horizontal most position. Hence we could find after how much rotation of main shaft the rotary valve should complete its one rotation in order to carry out the next suction. The speed ratio obtained also helped in finding out the rotation of rotor of valve during which suction would occur. Assuming a certain value of valves hole- diameter the respective rotor suction was found to be 900. Hence 18 divisions were made for 50 movement of rotor. The exposed area during each interval was obtained and respective mass flow was obtained. The initial pressure inside the chamber at starting of suction was taken to be 1atm and exhaust temperature was assumed to be 576K. These assumptions were made only for starting purpose. However in later iterations a consistent value of pressure and temperature was obtained. The value of volume inside one chamber was obtained. Hence the mass coming inside the cylinder can be obtained by formula given by Heywood. dm = AValve X P0 X dt X [{(2 X )/(R X T X ( -1))} X (P/P0)

    ( -1)/ X {(P/P0)( -1)/ -1}]

    . (29) The heat transfer is given as

  • 15

    Q= h X Asurface X (Twall-Tnew) X dt(30) And the final temperature is given as

    Tcorrected = [(Qcond/ (mnew X Cp)] + Tnew ..(31) The Tcorrected obtained helps in finding out the Pcorrected. The value of Cp is found out using the mass fraction of burned gases inside and the fresh charge entering. Cp = (Fresh charge in cylinder/Net Mass) X Cpcharge+ (Mass of Exhaust/Net Mass) X Cpexh.(32)

    In this way for every step this analysis is carried out. The same procedure is followed for compression, combustion, expansion and exhaust. The difference exists only in the heat transfer coefficients.

    The heat transfer coefficient is followed using Woschinis Fomula.

    h= 0.82 X x-0.2 X P0.8 X Wmv0.8 X (Tnew)

    -0.53 (W/m2K)(33) Wmv= [C1Cm+ C2 (VsT1/ PV1) (P-Pmotor)]..(34) For gas exchange process (suction and exhaust), C1= 6.18 & C2= 0. For compression process, C1= 2.28 & C2= 0. For combustion and expansion, C1= 2.28 & C2= 3.24 X 10

    -3. and

    .(35) where, Pa= atmospheric pressure, 101325 N/m

    2 Vd= Displaced Volume r= P4/P1 The x in equation 33 is the characteristic dimension of a conventional engine. We had to use a different characteristic dimension for our engine. The volume of the cc at any position was a part of a cylinder. The cc obtained was equated to a part of cylinder with radius and height equal. cc= ( /3600) X ( X x3) ...(36) Hence here x denotes the characteristic dimension of the chamber.

  • 16

    (6.2) COMPRESSION: Assumptions:

    1) Compression is assumed between 159.210 and 290. 2) It is assumed that no pre ignition takes place 3) The losses are assumed due to vaporization and convection heat loss

    due to radiation is neglected.

    After suction the next step in a conventional internal combustion engine is the compression stroke where the mixture of fuel and air is compressed to approximately 1/10 of its initial volume. For the analysis of compression stroke we started with the end values of suction analysis and started calculating pressures and temperatures using simple ideal gas equation for specified interval.

    The values of pressure and temperature are obtained based on the isentropic compression process. However due to the heat loss to the walls the value of Cp for the mixture varies according to the temperature. Values at the end of compression were carried to the combustion. (6.3) COMBUSTION:

    The process of combustion is initiated by the spark just before the completion of the compression stroke. In this stage there is sudden increase in temperature and pressure. Assumptions:

    1) The process of combustion is from 290 to 20.790 and back to 290. 2) The disassociation effects are neglected. 3) The process during the unburned zone is adiabatic. 4) The charge gets completely burnt. 5) Wiebes Model for combustion is assumed.

    First of all the mass fraction burned at every step of main shaft is found

    out using formula B = 1- e

    -a[( - S)/( )]^(1+m).(37) Where, a and m are certain constants. dB= B +d - B ...(38) Consequently the mass burnt and unburned at every position is calculated and respective Cp and Cv values are found out for the mixture inside.

  • 17

    The pressure rise in the chamber is a result of both the wings movement as well as combustion. The formula for progressive combustion pressure rise is given by

    P = [-P ( V/ V)] + [(P3 P2) (VTDC/V) x].(39) The first term, i.e. on left side of plus sign, is due to the volume

    change which is positive before TDC (Top dead center or vertical most position) and negative after TDC. The other term is due to the combustion effect. The value of x comes from the combustion model assumed (Square Law, Wiebes Model, cosine law etc.). Here we will be using Wiebes Model for our purpose. The value of Cp varies due to the presence of varied burned to unburned mass ratio as well temperature change which is taken into account during iteration. (6.4) EXPANSION: It is just the opposite of compression and allows a decrease in pressure as well as temperature in the chamber. The duration is from 290 to 1480. The heat transfer is still carried out between the wall and chamber depending on the wall temperature. (6.5) EXHAUST: The process involves exit of burned mass from cylinder to the atmosphere and is carried from 1480 to 159.210 and then to 20.790. The mass delivered is given as dm = AValve X P0 X dt X [{(2 X )/(R X T X ( -1))} X (P/P0)

    ( -1)/ X {(P/P0)( -1)/ -1}]

    (39) The valve area at every interval was obtained by eclipse area method.

    Here P0 represents the exhaust manifold pressure, which is 1atm. and P is the cylinder pressure.

    The logic to create the simulation model is that the amount delivered at every shaft angle movement is equal to the maximum amount of mass which can pass through that particular valve curtain area or equal to the mass which will lower the chamber pressure to 1atm and NOT below. The Cp value does not change in this process as complete chamber is comprised of same mixture and temperature is not much effective.

  • 18

    (6.6) RESULTS OF SIMULATION The results of simulation are as follows. The ideal parameters correspond to the ideal Otto cycle derived earlier with the same volumetric efficiency as that of actual simulation.

    Table 3. Simulation Results vs Ideal Otto Cycle Analysis for Butterfly Engine SIMULATION IDEAL OTTO CYCLE

    PEAK PRESS. (bar) 41.94 IDEAL PEAK PRESS. (bar) 148.60 PEAK TEMP. (K) 3137.36 IDEAL PEAK TEMP. (K) 4428.23

    WORK (W) 12102.08 IDEAL WORK (W) 29171.89 WORK (kW) 12.10 IDEAL WORK (kW) 29.17 WORK (hp) 16.23 IDEAL WORK (hp) 39.12

    TORQUE (Nm) 80.80 IDEAL TORQUE (Nm) 194.77 MEP (bar) 1.00 IDEAL MEP (bar) 2.40

    THERMAL 41.18% IDEAL THERMAL 46.64% The charts shown in figures 18 and 19 show the P-V and P- curve obtained from the simulation of the engine.

    To compare the performance of Butterfly engine with a conventional IC engine a similar simulation model was created for it. The size of the engine was taken equivalent to one of the chamber of the butterfly engine and simulation was performed. The engine parameters were

    The volume capacity is almost similar to one chamber of the Butterfly Engine used. The comparison of the simulation is given as below. The Butterfly engine results correspond to output of only one chamber and that of conventional engine correspond to only 1 cylinder.

    Table 4. Conventional ICE configuration Bore Radius (cm) 3.423 Stroke (cm) 3.423 Displaced Volume (cc) 126.00 Compression Ratio 10 Air Fuel Ratio 15 Conn. Rod (cm) 17 RPM 3788 Volumetric Efficiency (%) 100 Clearance Vol. (cc) 14.07 Total Volume (cc) 140.70

  • 19

    Table 5b. Engine Performance

    Conventional Engine (single cylinder) PEAK PRESSURE (bar) 109.80

    PEAK TEMP. (K) 2785.93 WORK (J) 167.70 WORK (kJ) 0.168

    TORQUE (Nm) 0.423 MEP (bar) 2.14

    THERMAL 28.58% The work output from one chamber of the Butterfly Engine is less than that of the conventional engine however as the former have three other chambers similar to it hence the total work obtained from it is much higher.

    Table 5a. Engine Performance Butterfly Engine (single chamber) PEAK PRESSURE (bar) 41.94

    PEAK TEMP. (K) 3137.36 WORK (J) 97.60 WORK (kJ) 0.98

    TORQUE (Nm) 0.65 MEP (bar) 1.00

    THERMAL 41.18%

  • 20

    7. CONCLUSION

    As seen in the paper the design can be used as an efficient internal combustion engine with suitable fabrication. As the volume depends on the square of the radii larger volume of cylinder may be utilized compared to its size. The compression ratio as seen can be varied to a very large value hence the combustion properties can be enhanced very easily. It can also be changed as per the angles at which the opposite snitches move back, i.e. the 2 angle shown in figure 2.

    More types of fuels can be used in the engine as they can be compressed to a very large value. Better combustion results in better exhaust properties causing lesser unwanted emissions. The flame front available during the combustion is forcing itself on two sides and moving both the wings in opposite directions. This helps in better utilization of combustion power. The performance deciding part of the engine is the ratchet and pawl mechanism, which if designed properly can make the designing of rest of the parts very easy. Hence the engine can prove to be a new revolution in coming days when we are going to face the crisis of the conventional energy resources and have to move towards new other forms. The cranking or starting of the engine requires a quick and calculated clockwise and anti-clockwise movement of the main output shaft which may be achieved using several mechanisms and depends on the compression ratio required for burning of the fuel inside.

    In another aspect, using an efficient concept to provide a rotation to the main shaft, the design can be used for pump/ compressor application just like the conventional engine designs are. A pneumatic or hydraulic motor can also be obtained providing a steady and calculated flow into the chambers. Any usage where rotation of a certain object is required, like in a pipe spinner or a roughneck, the design can be used very efficiently. Some of the many tasks that still need to be accomplished regarding the engine are listed below.

    1. The heat transfer coefficient values for the simulation are actually for a conventional IC engine. The actual values applicable for this engine are still not known. The simulation model generated is also a zero-dimensional model which is very basic in nature. A further more analysis has to be done in order to get more accurate results. More sophisticated models like phenomenological models can be applied to have more accurate results.

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    2. As the basic crude model is ready, development of engine with precise machining, proper calculations, sealing and theoretical aspects has to be carried out in detail. The complete analysis would require a lot of experiments and computations regarding the material selections, manufacturing processes, thermal stability, stress analysis etc.

    3. The seals need to be designed for the wings along the inside of casing and for the snitches against each other. The seals need to control the pressure and allow smooth movement of the parts. The design presented here does not include the design for the seal however more work has to be done in order for it.

    4. The ratchet and pawl mechanism is the most critical part and needs to be designed with very high precision.

    5. Valve mechanisms have to be sorted out. Although an alternative of rotary valve is presented, still being the key feature in performance of an engine it needs exhaustive study.

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    8. NOMENCLATURE - Diameter A, A- Area between wings A1- Cross Section area of wings - Angle made by wings with vertical 2 - Angle made between wings r- Internal radius of casing s- Outer radius of snitch w- Width of Casing P- Pressure V- Volume T- Temperature - Gamma Value for a particular gas (Cp/Cv) Cp- Specific Heat constant of a gas at constant pressure Cv- Specific Heat constant of a gas at constant volume R- Universal Gas constant Q- Heat transferred h- Heat transfer Coefficient ma- Mass of charge mf- Mass of fuel a- Density of Charge f- Density of fuel CV- Calorific value of fuel - Efficiency dm- Mass transferred through the valve AValve- Valve area exposed t- time T- Temperature ASurface- Surface area inside the chamber Twall- Temperature of the wall of chamber B- Mass ratio of burned d- Diameter of hole of the rotary valve D- Diameter of hole of the Rotor/ Stator - Net angle moved by the rotor S- Speed ratio of main output shaft and rotary valve

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    9. ACKNOWLEDGEMENT

    We take this opportunity to express our gratitude and deep routed feelings for those who patronized the cause of our project on Butterfly Engine and paved our way to a better comprehension of the facts related to it in a different perspective.

    We extend our cordial & humble gratitude to Dr. S.A. Channiwala, Department of Mechanical Engineering, SVNIT (Sardar Vallabhbhai National Institute of Technology), Surat, whose effective guidance, valuable time and constant inspiration made it feasible and easy for us to carry out the work in a smooth and productive manner.

    We would be failing in our duties if we were not to thank SVNIT Surat, our alma mater, and its esteemed faculty for their unwavering support in helping us to take this project to its successful completion.

    Last but not the least, we would like to thank our parents & family members, whose unwavering support in us made it possible for us to conclude the project successfully.

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    10. REFERENCES

    [1] Ms. Sweety; Simulation of an internal combustion engine; ME dissertation Mech. Dept., SGU, 2001.

    [2] Mr. Vikas J. Patel; Experimental and analytical investigations of multi-cylinder hydrogen fueled S.I engine; Mech. Dept., SGU, 2000.

    [3] Mr. Kashyap K. Bharath, Mr. Rakesh Kumar, Mr. Nainish U. Shah, Mr. Rajeev Premi Mogha and Mr. K. V. Anudeep; Design and development of delayed entry valve for multi cylinder hydrogen fueled engine- a new approach to control the backfire.

    [4] Dr V. Ganesan; Computer Simulation of Spark Ignition Engine Processes; University Press; 2002.

    [5] Dr V. Ganesan; Computer Simulation of Compression Ignition Engine Processes; University Press; 2002.

    [6] Dr V. Ganesan; Internal Combustion Engines; Tata McGraw Hill; 2007.

    [7] John B. Heywood; Internal Combustion Engine Fundamentals; McGraw Hill Publication; 1995.

    [8] Julian Happian-Smith; An Introduction to Modern Vehicle Design; Butterworth Heinmann Publication; 2004.

    [9] Matthew Oswald; Combustion Modeling; FSAE modeling report. [10] CSU Engine web pages; Colorado State University. [11] Guido A Danieli; A performance model of a Wankel engine

    including the effects of burning rates, heat transfer, leakage and quenching compared with measured pressure time histories, MIT thesis, 1976.

    [12] Masaki Ohkubo, Seiji Tashima, Ritsuharu Shimizu, Suguru Fuse and Hiroshi Ebino; Mazda Motor Corporation; Developed technologies of new rotary engines, SAE 2004-01-1790.

    [13] Nathan Lee Moulton; Performance measurement and simulation of a small internal combustion engine, University of Maryland, Thesis 2007.

    [14] Ralph M Watson; The development of an engine with a higher compression ratio; California institute of technology 1929.

    [15] Hon Man Chenug; Columbia University; A practical burn rate analysis for use in engine development; MIT Thesis; 1993.

    [16] Ruonan Sun, Rick Thomas and Charles L. Gray, Jr.; EPA; An HCCI Engine: Power Plant for a Hybrid Vehicle; SAE 2004-01-0933.

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    11. FIGURES

    FIGURE 1- Front view of the engine illustrating main components.

    True dimensions can be seen in the FIGURE 14.

    Stage 1 Stage 2

    FIGURE 2- Front View of the engine illustrating the two stages of

    operation. True Dimensions can be seen in FIGURE 14.

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    FIGURE 3- Drawing of Casing

    FIGURE 4- 3D view of Casing

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    FIGURE 5- Drawing of the snitch

    FIGURE 6- 3D view of the snitch

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    FIGURE 7- A Snitch with bevel gear arrangement

    FIGURE 8- Two snitches meshed together with Ratchet & Pawl

    mechanism inside each. The main output shaft runs through the centre of the snitch.

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    FIGURE 9- Front view of the Engine with casing.

    FIGURE 10- Top view of the engine

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    FIGURE 11- 3D View of Butterfly Engine

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    FIGURE 12- PVC Model Fabricated

    FIGURE 13- PVC Model Fabricated

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    All dimensions in cm.

    FIGURE 14- Engine Dimensions

    FIGURE15- PV diagram of an Ideal Otto Cycle

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    FIGURE 16- Rotary Valve

    FIGURE 17- Flow area for a rotary valve

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    FIGURE 18- Pressure and Volume Curve

    FIGURE 19- Pressure and Curve