INDIAN INSTITUTE OF TECHNOLOGY MADRASBALANCING THE ROTOR OF TURBOCHARGERS BY REORIENTING THE ROTOR COUPLESPROJECT MEMBER: RUTURAJ BARGALGUIDE : Mr. A. GOPALAKRISHNANProblem StatementTo reduce the initial imbalance present in the turbocharger by reorienting the rotor couples.POSITIVE EFFECTS OF PROJECT The initial imbalance in the turbocharger can be reduced It will reduce the amount of material to be removed from the turbocharger core. The number of cuts and correction runs will decrease. The cycle time of balancing the turbocharger can be reduced. The number of rejection will decrease.Explanation for Imbalance A Turbocharger consists of three major components: Turbine wheel, Rotor shaft, Compressor wheel. Apart from these components Housing, Bearings are the important parts of turbocharger assembly. Almost all rotors of automotive turbochargers exhibit strong sub synchronous vibrations, as well as the more common unbalance vibrations found in other rotating machinery. These vibrations are undesirable because they generate noise, and can have large amplitudes that cause rotor-stator rub. Unbalance vibrations are harmonic, or synchronous, with shaft speed and generally arise from two main causes: mass eccentricity and shaft bow. Mass eccentricity is a natural phenomenon in all rotors due to the offset of mass centroid, and shaft bow is commonly caused by thermal effects.Method of balancing followed at TEL The turbocharger being studied is KP35 MSIL (Maruti Swift) Only the compressor wheel, turbine wheel and the turbocharger core are balanced in the turbocharger. The compressor wheel and the turbine wheel are balanced individually. The parts of the turbocharger are assembled at arbitrary positions to form the turbocharger core. The entire turbocharger core is balanced in a High Speed Core Balancing machine until the balancing values are within the limits.COMPRESSOR WHEEL BALANCINGPlane 1 Plane2The compressor wheel is balanced to the limits of 0.1 MMG.The imbalance mass and angle of the compressor wheel are measured at planes 1 & 2.Plane 3 Plane 4TURBINE WHEEL BALANCINGTurbine wheelThe Turbine wheel is balanced to the limits of 0.1 MMG. The imbalance mass and angle of the Turbine wheel are measured at planes 3 & 4 Turbocharger core assemblyBenchmark DataUsing the above mentioned procedure for balancing, I have taken the benchmark readings for 150 turbochargers and the observations were :1. Rejection rate : 24/150 = 16%2. Average cycle time : 109 seconds per turbocharger3. Average correction runs: 1.8 runs per turbocharger4. Average number of cuts: 3.2 cuts per turbocharger Reasons for RejectionINITIAL LIMITS : This is the scenario in which the incoming imbalance in the turbocharger is too high(M > 150mmg). It is not possible to remove so much material. This turbocharger is rejected immediately.MANUFACTURING LIMITS: When the depth of cut of the material to be removed is too high, the machine rejects the turbocharger.NUMBER OF CORRECTION RUNS: The company has set the maximum number of correction runs to 6. if the turbocharger is not balanced within 6 correction runs it is rejected.Rotary components taken into considerationPlane 3Plane 2Plane 4Plane 1SOLUTION- Balancing of Rotating MassesM2M1M3MAM4MBReference for angleSolutionPlane 1 : Compressor wheel nut planePlane 2 : Compressor wheel hub planePlane 3 : Turbine wheel nut planePlane 4 : Turbine wheel hub planePlane A : Balancing plane A on the compressor wheel nut planePlane B : Balancing plane B on the compressor wheel hub planeM1, R1 & 1 : Imbalance mass, radius and its angle at plane 1M2, R2 & 2 : Imbalance mass, radius and its angle at plane 2M3, R3 & 3 : Imbalance mass, radius and its angle at plane 3M4, R4 & 4 : Imbalance mass, radius and its angle at plane 4MA, RA & A : Balancing mass, radius and its angle to be placed at plane AMB, RB & B : Balancing mass, radius and its angle to be placed at plane BL2, L3, L4: Dimensions of the turbochargerLet plane A be the reference plane.SolutionPlane ImbalanceMass(m)Radius(r)Imbalance(m*r)Length from reference plane(l)Couple(m*r*l)1 M1 R1 M1R1 0 0A MA RA MARA 0 02 M2 R2 M2R2 L2 M2R2L2B MB RB MBRB L2 MBRBLB3 M3 R3 M3R3 L2 + L3M3R3L34 M4 R4 M4R4 L2 + L3 +L4 M4R4L4Let the force F = M*RSolutionBALANCING THE COUPLE:Summation of Horizontal components:FL Cos() + FBL2Cos(B) = 0FBL2Cos(B) = ConstantFBCos(B) =C1Equation1Summation of Vertical components:FL Sin() + FBL2Sin(B) = 0FBL2Sin(B) = ConstantFBSin(B) = C2 Equation2Solution(Eqn 2) divided by (Eqn 1)tan(B) = C2/C1B= tan-1(C2/C1)Substitute Bvalue in Eqn 1FB= C1/ Cos(B)BALANCING THE FORCE:Summation of Horizontal components:F Cos() + FACos(A)=0FACos(A) = C3 Equation 3SolutionSummation of Vertical components:F Sin() + FASin(A)= 0FASin(A)=C4 Equation 4Equation 4 divided by Equation 3tan(A)= C4/C3A= tan-1(C4/C3)Substitute Avalue in Equation 3FA= C3/ Cos(A)The values FA,Aand FB,Bof are known for a particular orientation of the compressor wheel with the turbine wheel. The Objective is to find the optimum orientation at which the resultant FAand FBof is the least.Solution The value of FAand FB needs to be calculated for every orientation or position of the compressor wheel with respect to the turbine wheel. Then the orientation/position at which the resultant of FAand FBis the least needs to be picked Rotate the compressor wheel by 1owith respect to the turbine wheel. This will result in the values of 1 and 2 change by 1o each. Calculate the new FAand FBvalues for the new 1 and 2 and check if the resultant of the new FAand FBis lower than the previous resultant of FAand FB. If the new resultant is lesser than the old resultant, then the old orientation of the compressor wheel is replaced with the new orientation. Now repeat the above method by varying 1 and 2from 0-360oand choose the 1 and 2 Test was being conducted on 10 KP35 Turbochargers. 9 of the turbochargers were assembled in the optimum orientation and one was assembled at a position 180oopposite to the optimum orientation. The individual imbalance values of the compressor wheel and the turbine wheel are noted and substituted in the program. The program provides the optimal orientation for the particular compressor wheel and turbine wheel combination. The reference of the compressor wheel and the turbine wheel are aligned. Then the compressor wheel is rotated by the suggested angle and the turbocharger is assembled at that orientation. The turbocharger is then sent into the high speed core balancing machine and the readings were noted.TESTING THE METHOD ON KP35 TURBOSMEASURING M/C -Kokusai-016COMPRESSOR WHEEL (Balancing Spec: 0.1 MMG)S.NO PLANE 1 F1ANGLE 1PLANE 2 F2ANGLE 21 0.014 286 0.010 692 0.012 10 0.024 1343 0.025 88 0.106 2594 0.022 75 0.034 2715 0.007 10 0.027 1576 0.014 90 0.020 2087 0.011 308 0.030 2418 0.025 300 0.014 289 0.023 337 0.008 22310 0.010 155 0.060 323INDIVIDUAL COMPRESSOR WHEEL AND TURBINE WHEEL BALANCING VALUES - KP35BALANCING M/C-Chiron ( TEL-1980-048)MEASURING M/C Kokusai-015TURBINE WHEEL (Balancing Spec: 0.1 MMG)S.NO PLANE 1 F4ANGLE 4PLANE 2 F3ANGLE 3A 0.046 147.300 0.038 194.090B 0.049 265.68 0.037 135.14C 0.052 163.4 0.039 166.08D 0.04 152.95 0.039 197.07E 0.047 336.9 0.02 288.3F 0.049 216.82 0.046 169.51G 0.046 131.75 0.055 139.34H 0.046 7.73 0.040 182.43I 0.051 253.45 0.026 292.43J 0.025 126.03 0.039 240.37CombinationOptimal t1Optimal t2Rotate compressor wheel byCycle time(Sec)No of correction runsNumber of cuts1-A 206 349 -80 61 1 22-B 176 300 166 60 1 23-C 202 13 114 74 1 34-D 178 14 103 63 1 25-E 62 209 52 70 1 26-F204 322114 56 1 17-G132 65-176 83 1 38-H16 104 76 801 39-I286 172 -51 601 2OPTIMAL ORIENTATION FOR TURBOCHARGERSAssembling the turbocharger at optimum orientation has shown positive results in all the parameters. Rejection rate= 0% Average Correction Runs = 1 runs per turbocharger Average Number of cuts = 2.22 cuts per turbocharger Average Cycle Time = 67.44 seconds per turbochargerRESULTS FROM OPTIMAL ORIENTATION Timeline of ProjectPeriodTask15thDecember 1stJanuary Understanding Turbochargers and their operation2ndJanuary - 20thJanuary Understanding balancing procedure at TEL21stJanuary 6thFebruary Gathering the Benchmark data for 150 samples 7thFebruary - 28thFebruary Finding a theoretical solution1stMarch 31stMarch Implementation of solution and Individual Balancing1stApril - 15thAprilGolden Core Testing and Data Validation 15thApril 8thMay Final Testing and Data collection RANDOM ORIENTATION OPTIMAL ORIENTATION Rejection rate = 24/150 = 16% Average Correction Runs = 1.8runs per turbocharger Average Number of cuts = 3.2 cuts perturbocharger Average Cycle Time = 109 seconds perturbocharger Rejection rate = 0% Average Correction Runs = 1 runs perturbocharger Average Number of cuts = 2.22 cuts perturbocharger Average Cycle Time = 67.44 secondsper turbochargerCONCLUSIONIt is seen that the results from the project are promising. Assembling the compressor wheel at the angle suggested by the equation and the program has shown positive results. There is a decrease in the number of correction runs, the cycle time and the number of cuts on the compressor wheel. Also the rejection percentage for the sample size is zero. Another method to consider for reducing the initial imbalance is a matching technique during the assembly of the turbocharger. If the imbalance values of all the compressor wheels and the turbine wheels are known and recorded prior to assembly, then it is possible to find out the compressor wheel and turbine wheel pair that matches the best amongst all the wheels. For example, if there are 10 compressor wheels and 10 turbine wheels in a particular lot. It is possible to find out the compressor wheel and turbine wheel pair (For e.g. Compressor wheel No1 assembled with Turbine wheel No 6) which will have the least initial imbalance. FUTURE SCOPEREFERENCES1. Hung Nguyen-Schfer (2012). Rotordynamics of Automotive Turbochargers Springer Publications.2. ISO 1940/1, "Balance Quality Requirements of Rigid Rotors." International Organization for Standardization. 3. ISO 1925, Balancing Vocabulary. International Organization for Standardization. 4. J.S.Rao, Rotor Dynamics, New Age International (P) Ltd., India, 19965. Neville F. Rieger (1986). Balancing of Rigid and Flexible Rotors.6. R.S Khurmi (2007). Theory of Machines, Chand Publications.