Cinematic and Kinetic Analyses of the Slider-Crank Mechanism in Engine of MF-285 Tractor

Transcription

1 Australian Journal of Basic and Applied Sciences, 5(12): , 2011 ISSN Cineatic and Kinetic Analyses of the Slider-Crank Mechanis in Engine of MF-285 Tractor 1 Mohaad Reza Asadi, 1 Heidar Abdollahian and 1 Behna Nilforooshan Dardashti 1 Departent of Mechanical Engineering, Islaic Azad University, Buinzahra branch, Qazwin, Iran. Abstract: MF-285 tractor has devoted the highest production level in Iran aong the other tractors. According to the literature, alfunction of the internal coponents of engine of this tractor is high; consequently research about it is necessary. In this regard, this paper presents the cineatic and kinetic analyses of the connecting rod. Besides ank echanis cineatic analysis, kinetic analysis of the connecting rod was done with regard to the forces resulting fro ignition pressure, ass distribution in the ank echanis as well as inertia forces. At the end, the graphs of displaceent, speed and acceleration of piston, and also the graphs of ignition pressure, forces on piston, forces on connecting rod and forces on bears in one coplete cycle according to the ank angle were drown by atheatica software. The axiu of piston speed equal with 13.5 /s, the axiu of piston acceleration equal 3550 /s 2, the axiu of ignition pressure equal 2950 KPa, the axiu expansion force on connecting rod equal N, the axiu of copression force on connecting rod equal N and the axiu force on bears equal N were calculated. By the result of this paper there is possibility stress, fatigue, odal, haronic and etc analyses of rotational part of engine of this tractor and suggest for iprovisation of this part. Key word: Tractor; Crank echanis; Analyses; Cineatic; Kinetic. INTRODUCTION Tractor, as the ost iportant agricultural achinery, has ain share in planting, retaining and harvesting operations and then in echanization sector. Hence, in order to reach sustainable agricultural and to inease echanization level quality and anufacturing technology of this agricultural achinery and also its quantity ust be reached to optiu level. Tractor MF-285 is ain production of Iran Manufacturing Tractor Co. Researches show that engine inner parts faults of MF-285 are ore than other ingredients of this tractor (Anonyous, 2008). Above stateents show the iportance of optiization of rotating parts of tractor MF-285 engine. The base of engine dynaic echanis operation is slider-ank echanis which consist ankshaft, connecting rod and piston. Pressure due cobustion, transferred fro piston (the part erely has reciprocating otion) to the connecting rod (the part has both linear and rotation otion) and finally to the ankshaft (the part has erely rotation otion). As investigation of phenoena like vibration, resonance, fatigue, noise..., and optiization of these parts, kineatics and kinetic of slider-ank echanis ust be known. Optiization of echanical instruents has been one of engineer goals. Below paragraphs are soe exaples: Cveticanin and Maretic have suarized dynaic analysis of a cutting echanis which is a special type of the ank shaper echanis (Cveticanin L, 2000). The influence of the cutting force on the otion of the echanis was Considered. The Lagrange equation was used and boundary values of the cutting force were obtained analytically and nuerically. Ha et al. (2006) have derived the dynaic equations of a slider-ank echanis. They, for this purpose, used Hailton s principle, Lagrange ultiplier, geoetric constraints and partitioning ethod (Ha JL, 2006). Their forulation was expressed by only one independent variable. Finally to obtain the best dynaic odeling, they copared obtained results and nuerical siulations. Also, a new identification ethod based on the genetic algorith was presented to identify the paraeters of a slider-ank echanis. Koser (2004) investigated on kineatic perforance analysis of a slider-ank echanis based on robot ar perforance and dynaics (Koser K., 2004). He analyzed kineatic perforance of the robot ar using generalized Jacobian atrix. It was obtained that the slider-ank echanis based robot ar had alost full isotropic kineatic perforance characteristics and its perforance was uch better than the best 2R robot ar. He used coplex algebra to solve that classical proble and he obtained solution as the root of a cubic equation within a defined range. Corresponding Author: Mohaad Reza Asadi, Departent of Mechanical Engineering, Islaic Azad University, Buinzahra branch, Qazwin, Iran. E-ail: Asadi_Reza2007@yahoo.co 3112

2 Another research about transission angle was carried by Shrinivas and Satish (2002). They have suarized iportance of the transission angle for ost effective force transission. In this regard, they investigated 4-, 5-, 6- and 7-bar linkages, spatial linkages and slider-ank echaniss (Shrinivas SB, 2002). 2. Methods: 2.1 Kineatics Analysis Of Slider-Crank Mechanis: MF-285 engine has 4 cylinders with linear arrangeent. Engine configuration and qualifications has been shown in Table 1. Table 1: Configuration and qualifications of MF-285 engine (Anonyous, 2008). Nuber of Cylinders 4 Piston Course () 127 Cylinder diaeter () 101 Indicated Revolution (rp) 2000 Maxiu Revolution (rp) 2200 Indicated Engine Power (Hp) 71 Maxiu Torque (N/2) 278 Revolution in Maxiu Torque (rp) 1300 According to figure (1) distance of piston fro center of rotation can be obtained by below equations: Sp Rcos Lcos (1) That: R: Radius of ank shaft L: Length of connecting rod Fig. 1: Scheatics of ank echanis. With regard to triangular equations in OAB triangle: Rsin Lsin (2) By aid of above equation we can delete fro equation 1: S p R(cos 1 sin ) (3) By developing above equations we will have: 1 S P R cos (cos2 ) (4)

3 According to this point that is function of tie ( a t) for calculating speed and acceleration of connecting rod we calculate differential of equation 4 so: V R(sin sin 2 ) (5) 2 2 R (cos cos 2 ) (6) 2-2 Kinetics Analysis Of Connecting Rod: Forces Due To Ignition Of Fuel: During a work cycle which is a cobination of breathing, congestion, explosion and discharge stages, a lot of interactions occur in the engine which will affect on one another and ake the calculation difficult. For exaple, we can ention the heat transfer during the ignition between gas and the engine partition, the effect of the ixture for on the auto-engine and the effect of transfusion quality in the diesel engine. So, only by studying the actions and reactions one by one, we can reach to an accurate conclusion. Therefore, it is necessary to study the engine perforance under the siple hypotheses, and neglect the uniportant effects. The selected process for designing the diagra of gas pressure in ters of ank angle consists of following hypotheses (Asadi, M., 2008); 1. The ixture of gas and fuel is considered the ideal gas. 2. There is no physical or cheical change in the congested weather in the congestion stage and before the explosion. 3. Iediate alteration of gas and fuel ixture with the hot gas product of cobustion. 4. The congestion and explosion stages are adiabatic. 5. The suction and discharge occur in the atosphere pressure. The forces produced by cobustion, are the factors which ake the echanis ove. For dynaic calculations, we substitute the pressure on the piston with a force in the direction of the cylinder. Aount of this force in any oent is calculated fro this equation: F ). A (7) g ( Pg P0 P P g: the gas pressure at any oent P o: the pressure of the weather outside A P: the area of the piston surface The only unknown variable in the above equation is P g which is a function of the angle and is calculated fro therodynaics relationship by the above hypotheses. A) The Congestion Stage: Considering the adiabatic process of the gas congestion we will have: n P V 2 1 P V 1 2 P 1 and P 2 are respectively the priary and secondary pressure V 1 and v 2 are respectively the priary and secondary volue (8) The priary pressure changes, in ters of the oveent velocity of piston, the relative size of tubes, the appearance of tubes and other factors. When the engine works at low speed with axiu load, the pressure approaches the atosphere pressure. The analysis of indicator diagras has shown that the "n" value for this engine is about 1.21 (Prvardhans, 2005). The height of cylinder chaber is calculated through this equation: l h (9) r 1 l: the length of piston r: congestion ratio 3114

4 The distance of the cylinder head to the piston est, while piston is at the botto dead center is: l rl l (10) r 1 r 1 Now we assue the piston is in the distance x fro the top dead center. The pressure in this stage will be: 1.21 rl rl P r l g Pi Pi x (11) x r 1 P 1: the gas pressure at the beginning of congestion B) The Explosion Stage: In this stage, the pressure is constant until the fuel is sprayed, and after the spraying interruption and explosion ending, the pressure deeases with the inease of the cobustion chaber volue. So we can define this stage consisting of two kinds of pressures: the constant pressure and the variable pressure. Knowing that the fuel spraying continues up to 30 degrees after the top dead center, so the pressure will be constant fro the top dead center to 30 degrees after top dead center, which is calculated by this equation: n P V 4 3 P V (12) 3 4 P 4: the gas pressure at the end of explosion stage P 3: the gas pressure in the fuel spraying stage V 4: the volue at the end of explosion stage V 3: the volue at the end of fuel spraying stage Fro the equation above, the pressure at the tie of fuel spraying was found 2950 KPa. The second stage of the explosion course begins after fuel spraying ending. The equation for this stage is: n P V 4 3 P V 3 4 P 4: the gas pressure at the end of explosion stage p 3: the gas pressure after the fuel spraying stage v 4: the volue at the end of explosion stage (the secondary volue) v 3: the volue after the fuel spraying stage As it was calculated, the distance of the cylinder head with the piston est while the piston is at the botto dead center, is found fro 10 equation. So the secondary volue in the explosion stage will be: rl V4 A P (13) r 1 A P: The area of piston surface Therefore we will have: P 4 V 3 P3 rl v 1 A p 1.21 (14) If the piston would be at the x distance of the top dead center, the pressure in this stage will be: 1.21 rl 1.21 Pg Pi x (15) r 1 P i: the gas pressure at the end of the explosion cycle 3115

5 In the suction and discharge stages, the chaber pressure is considered equal with the atosphere pressure on the basis of siplifying hypotheses The Masses Distribution In The Crank Mechanis: To avoid the coplicated calculations, the asses are divided to two parts in the ank echanis: 1) The reciprocating asses 2) The rotational asses As the connecting rod has both transferring and rotating oveents, we consider its asses concentrated on two ends (two eyes). So the ass in the sall eye perfors ere transferring oveents and the one in the big eye (ank end) does ere rotational oveent. The asses distribution is done by the following estiation (Naderi, H., 1982): p c L L L L c p (16) L p: the distance of the center of gravity with the center of the sall eye of the connecting rod L c : the distance of the center of gravity with the center of the big eye of the connecting rod L : the distance of the center of the sall eye with the big eye of the connecting rod M p: the concentrated ass in the sall eye M c: the concentrated ass in the big eye Figure (2) indicates this ass distribution. Fig. 2: The ass distribution in the piston eyes. p c Usually, the distribution of aforeentioned asses, are equal to the following values: (17) The total concentrated ass in the sall eye of the connecting rod which is characterized by ( a) is equal with: a (18) p p M p : the ass of the piston and piston pin M p: the concentrated ass of the connecting rod in the sall eye 3116

6 Fig. 3: The ass distribution to two concentrated asses a and R. R And the concentrated ass in the big eye of the connecting rod equals with: (19) c c c: the concentrated ass of the connecting rod in the big eye c: the ass of the ankshaft ank c Considering figure (4), c which is the ass of the ankshaft ank is calculated as following: cp 2cp 2w (20) R cp: pin journal of ankshaft which the connecting rod is locked on it. M w: the ass of ankshaft blade (ar of the ank) R: radius of the ank : The ain journal radius of the ankshaft Fig. 4: The cut schee of the ankshaft Inertia Forces: In the previous chapter, we divided all the asses to two parts: the reciprocating and rotational asses. Now we calculate the inertia forces caused by the oveent of these asses. The direction of inertia force of a (in the sall eye) is always along the cylinder axis and opposite the acceleration of piston direction and the inertia force direction of g is along the ank radius. The value of the reciprocating inertia force using the equation 6 is desibed as following: 2 Fi ar cos cos2 (21) F R The value of the rotational inertia force is desibed by the equation for rotational acceleration as following: 2 R cte (22) R The resultant of the forces in A (figure 5) is: F F l F g (23) 3117

7 Now we study the effect of resultant force (F) on the connecting rod. According to figure (6) and the trigonoetric relations we have: N F tan (24) F S (25) cos F cos cos K (26) F sin cos T (27) N force is exerted on the cylinder wall and the rod of connecting rod tolerates S force. S force is divided to two coponents in the big eye, which T coponent is responsible for the eation of the torque in the ankshaft. The resultant of K and T and F R forces are the force exerted on bearings. Fig. 5: The foreign forces on the piston handle without displaying the reactions. Fig. 6: The effect of N force on the big eye. 3118

8 Results: Figures 7,8 and 9 show the diagras of situation, speed and acceleration of the piston (that have been drown with the help of the Matheatica software) which have been achieved by placing the MF-285 tractor data in relations 4,5 and S p wt radian Fig. 7: Changes of piston situation at ankshaft angle regarding MF-285 tractor v /s Fig. 8: Changes of piston speed at ankshaft angle wt radian acceleration /s wt radian Fig. 9: The changes in the piston acceleration at ankshaft angle regarding MF-285 tractor. Also, the final relationship for gas pressure gained as following. Figure 10 shows the related diagra (the pressure changes regarding to ankshaft angle during a working cycle). P g x x / 6 13 / (28) 3119

9 pressure KPa ank angle degree Fig. 10: The diagra of pressure changes regarding to ankshaft angle for MF- 285 tractor. Figure 11 shows the su of inertia forces and gas pressure on the head of connecting rod during a working cycle. In figure 12, the su of forces on the bearings is shown. Fig. 11: The diagra of the su of forces on the connecting rod regarding to ankshaft angle for MF-285 tractor. Fig. 12: The su of forces on the bearings. Conclusion: The achieved diagras in the results part show the place, speed and acceleration of piston, the changing of forces on the connecting rod, bearing, and ank of the ankshaft regarding to ankshaft angle during a working cycle. As the entioned diagras show, the axiu aount speed of piston was 13/5 /s, the axiu aount acceleration of piston was 3550 /s 2, the axiu aount of cobustion pressure was 2950 kpa, the axiu aount of pressing force on the connecting rod was N, the axiu of pulling force on the connecting rod was 10288N, and the axiu of forces on the bearings was 3000N. Using the 3120

10 aforeentioned results and diagras, we can analyze the stress, fatigue, strain, odal, and haronic of the entioned coponents, and study the reasons for their alfunction, and offer the necessary suggestions for optiizing the. Therefore, analysis of stress, fatigue, strain, energy, odal and haronic of aforeentioned coponents with the help of the present results, can be suggested for future researches. REFERENCES Anonyous, "MF-285 Maintenance and Repayents catalogue," Iran Manufacturing Tractor Co,. Asadi, M., "Fatigue analyzing in MF-285 tractor connecting rod using finite eleent ethod," M.Sc. thesis, Departent of Mechanic of agricultural Machinery, University of Mohaghegh Ardabili, Ardabil. Cveticanin, L., R. Maretic, Dynaic analysis of a cutting echanis. Mech. Mach. Theory, 35(10): Ha, J.L., R.F. Fung, K.Y. Chen, S.C. Hsien, Dynaic odeling and identification of a slider-ank echanis. J. Sound Vib., 289(4): Koser, K., A slider-ank echanis based robot ar perforance and dynaic analysis. Mech. Mach. Theory, 39(2): Mahoodi, A., H. Rezakhah, "Reviewing fails of MF-285 tractor," Third student conference on Mechanic of Agricultural Machinary Eng., Shiraz. Naderi, H., Design of Internal Cobustion Engines, Mir Publication, Tehran, pp: 437. Prvardhans, shenoy and A. Fatei, Connecting Rod Optiization for Weight and Cost Reduction. Journal of Sound and Vibration, 243(3): Shrinivas, S.B., C. Satish, Transission angle in echaniss (Triangle in ech) Mach. Theory, 37(2):