Vibration Analysis of Variable Compression Ratio Engine Using Virtual Instrumentation

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1 th International & 6 th All India Manufacturing Technology, Design and Research Conference (AIMTDR 14) December 1 th 14 th, 14, IIT Vibration Analysis of Variable Compression Ratio Engine Using Virtual Instrumentation Abhishek singh 1, H. Chelladurai and Akhileshkumar chaudhary 3 1,,3 Department of Mechanical Engineering, PDPM Indian Institute of design and manufacturing, Jabalpur, MP, 48, jn.abhisheksingh@gmail.com, chella@iiitdmj.ac.in, akhhichoudhary@gmail.com. Abstract Diesel engines have various vibration sources, such as fuel combustion pressure, fuel injection, reciprocating and rotating motions, valve operation, and gas flows. Many literature works are available in IC engine vibration measurement system. The uses of virtual instrumentation in vibration analysis are very scanty. The objective of the present work is to analyze the engine block vibration, performance and emission behavior of variable compression ratio diesel engine using virtual instrumentation. The main objective of this paper is to develop a low cost and effective IC engine block vibration measurement system using virtual instrumentation system. A systematically designed experiment using the central composite face centered design (CCFD) has been performed and parametric analysis of variable compression ratio engine (VCR) has been carried out to relate input and output parameters. The regression model has been developed to study the emission behavior of diesel engine at various operating conditions. From this study, it is observed that using a MEMS accelerometer sensor, the low cost virtual instrumentation vibration analysis system can be developed and results show that the increased fuel injection pressure increases the block vibration of engine and increase in compression ratio reduces block vibration,hc and CO emission but increases NO emission. Keywords: VCR engine, virtual instrumentation, data acquisition, vibration signal. 1 Introduction Combustion process of IC engine is a result of controlled explosion of fuel inside the combustion chamber. These explosions produce powerful pulses of energy which in response causes the engine to vibrate. The various engine running states causes different engine vibration conditions [ M.Venkatraman and G.Devaradjane(1)]. Combustion process also influences the performance and emission of engine. It is well known that the combustion process of engine is affected by various operating condition such as compression ratio (CR), fuel injection pressure (FIP), injection timing, part load condition, engine speed etc. In order to understand the engine performance, it is important to gain a good understanding of the complex dynamics of the process variables [Y. B. Mathuret al. (1), Sayin C et al. (9), A.P. Carlucci et al. (6), AgarwalAvinash K. et al. (13)]. In present work,effects of process variables on engine block vibration, performance, and emission has been investigated. The main objective of this paper is to develop a vibration acquiring system to measure the engine block vibration using virtual instrumentation. Virtual instrumentation (VI) is the use of customizable software and modular measurement hardware to create userdefined measurement systems. Labview platform was utilized to develop a data acquisition program for monitoring and storing the vibration signal. It is system design software that provides a facility to the researchers, to create tools for preparing measurement system and control. Experiments have been designed by central composite face centered (CCFC) design for three factor (i.e. CR, FIP, Load), three level. Based on the CCFC experiments have been conducted and analysis has been done using response surface methodology to relate input and output parameters. The current investigation intended to analyze the combined effect of compression ratio, injection pressure and different loading condition on Block vibration, Performance and emission of the engine. Methodology In the present work, the variable compression ratio (VCR), constant speed diesel engine was used for conducting the experiments. Engine has a facility to change its compression ratio from 14:1 to 18:1. The engine was equipped with conventional jerk type Bosch-4 in-line fuel injection pump. Injection pump inject the fuel to the cylinder with a pressure of 18bar, -1

2 Vibration Analysis of Variable Compression Ratio Engine Using Virtual Instrumentation which is initially set by the manufacture. Injection pressure can be further changed by changing the compression of injection pump spring. This is possible by placing a washer of.mm. Increase in pressure of fuel injection by placing 1 washer of. mm is found to be 4 bar. Hence, for the experiments injection pressure has been varied from 18bar to 7bar by placing and removing washer beneath the pump springs. Load on engine is changed by eddy current based dynamometer coupled with engine shaft. Engine block vibration measurement has been done by the capacitive accelerometer mounted over the engine block and virtual instrumentation. Method used to capture and analyze engine block vibration is illustrative in Figure1. Figure 1 conceptual model of vibration acquiring system.1 Sensor The accelerometer used in this study is an analog accelerometer. The sensor is a low profile capacitive accelerometer. A simplified model of the sensor is shown in Figure. Essentially, theree are variable capacitances, one on each side of the moving beam. The changes in distance between the beams (increasing area for a capacitor) cause changes in the voltage output, which is then used to calculate the acceleration [FahimKadhi et al. (13)]. Figure Simplified model of accelerometer In order to obtain an accurate g-force from the sensor readings, the data obtained from the sensor is plugged into specific equations. [K. ArunVenkateshet al. (1)]. Where: n = Microcontroller specification (number of bits) used in DAQ system. (i.e. 8 bit). Q (t) = output of accelerometer in volt at time t. Offset = output voltage of sensor at rest in volt (made it zero manually in LabVIEW program). g = gravity acceleration (i.e. 9.81m/s ). Sensitivity = sensitivity of sensor at selectable sensitivity range (i.e. 8mv/g in this work because sensitivity range selected as ±1.g). Offset output voltage of the sensor is the output voltage shown by it at rest of stationary condition when there is no vibration or movement. Offset voltage is the result of mismatching of the circuit or human error happened during mounting of sensor which are not possible to eliminate completely. Hence these made zero in the LabVIEW program by addition or subtraction.. Design of experiment Experiments have been designed by CCFC for three factor three level as shown in Table 1.All the experiments were obtained by central composite face centered design using the Design Expert statistical software. The number of experiments is estimated as N= f + f + n.; Where f = 3 (no of factors), n= 6(no of star point).the number of experiments in a CCFC matrix corresponding to three process variables is calculated as = For the same set of experiments performance (i.e. brake power and brake thermal efficiency) and exhaust emission (i. e. CO, NO, HC) has been measured and their regression model has been developed by response surface methodology. To measure the exhaust emission AVL Digas 444 gas analyzer is used. Table 1 design factors and level Factors Low 14:1 16:1 18:1 Injection pressure 18bar bar 7bar Load in KG 6 1 AVL Gas Analyzer is used to measure NO, CO, HC. Experimentation is done at different compression ratios with different loads (no load to full load) and different injection pressuree (18 to bar). 3 Experimental setup Medium...(1) High All the experiments have been performed on the single cylinder direct injection VCR engine with different operating conditions. Schematic diagram of the -

3 th International & 6 th All India Manufacturing Technology, Design and Research Conference (AIMTDR 14) December 1 th 14 th, 14, IIT Table Experimental data of output Load IP Vibration Emission Performance Load IP Vibration Emission Performance Run No. CR Kg Bar m/sec (g) CO HC NO BP BTHE Run No. CR Kg Bar m/sec (g) CO HC NO BP BTHE % ppm Ppm KW % ppm ppm KW experimental setup is shown in Figure 3. Experimental engine has a rated speed of rpm. Experiments were acquisition program is developed in LabVIEW such that all the signal processing is achieved using software. The conducted on variable compression ratio engine output of the sensor is fed into the data equipped with ENGINE SOFT software, which enables to calculate the performance of engine at every instant of time. The engine was coupled to a DC supply acquisitionsystem and then transferred to the computer where its signal processing is done in LABview program. eddy current based dynamometer to vary the load. Engine has a facility that, its compression ratio can be varied from 14:1 to 18:1. The fuel injection pressure can be varied from 18bar to 7bar by changing the compression of the injection spring by placing. mm thickness of washer. 3. Performance analysis Performance data of engine like Brake power and brake thermal efficiency at different operating condition has been collected from engine soft software. The collected data has been analyzed to find effect of operating parameters. Table shows the data of output. 4 Results and discussion 4.1Response surface methodology Response surface methodology (RSM) is a structured, organized method that is used to determine the relationship between the different input factors (Xs) affecting a process and the output of that process (Y). RSM helps to identify optimal conditions of the operating parameters K K i ii i ii i j i= 1 i= 1 i< j Y = β + β + β X + β X X ο Where: Y= output, β= constant, Xi and Xj = factors Figure 3 Schematic diagram of the experimental setup 3.1 Vibration analysis The Vibration data from engine block has been captured with the help of accelerometer and virtual instrumentation for each experiment. MMA7361L IC based sensor has been used to measure the engine block vibration, mounted over engine block. A data 4. Development of Regression model According to systematically designed experimental runs, the output response data was analyzed using statistical analysis 1. Regression equation for block vibration: Y (vibration) = (-.3473) + ( LOAD) + (.181 CR) + ( IP) + ( LOAD CR) + (-.631 LOAD IP) + (.8634 CR IP) + -3

4 Vibration Analysis of Variable Compression Ratio Engine Using Virtual Instrumentation (.4347 LOAD ) + (-.384 CR ) + (.1 IP ). Regression equation for Brake power: Y (Brake power) = ( ) + (.367 LOAD) + (.1641 CR) + ( IP) + ( LOAD CR) + ( LOAD IP) + ( CR IP) + ( LOAD) + (.4699 CR) + ( IP ) 3. Regression equation for BTHE: Y (BTHE) = (-7.8) + (.479 LOAD) + (1.977 CR) + ( IP) + ( LOAD CR) + (.1619 LOAD IP) + ( CR IP) + (-.388 LOAD ) + ( CR ) + (.338 IP ) 4. Regression equation for emission: Y (CO) = (.63643)+(-.16 LOAD) + (-.439 CR ) + (-.3 IP) + (.31 LOAD CR) + (.7 LOAD IP) + (-.49 CR IP) + (-. LOAD ) +(.184 CR ) + (.18 IP ) Y (HC) = (3.744) + ( LOAD) + ( CR) + ( IP) + (.461 LOAD CR) + ( LOAD IP) + (.1774 CR IP) + (.493 LOAD ) + ( CR ) + (.6879 IP ) Y (NO) = ( ) + ( LOAD) + ( CR) + (.1 IP) +.6 LOAD CR) + (-.86 LOAD IP) + (.68 CR IP) + (.6818 LOAD ) + (.776 CR ) + (.8137 IP ) The value of F-ratio in all cases is higher than tabulated value, which indicates that the obtained model is considered to be statistically significant. This value (p <.1) showed that, the quadratic regression model fits well to the experimental results. The high values of R (i.e., R = 98.37, 93.4, 93.4, 98.44, 9.6, 98.89) provides the proportion of variability in a data set that is accounted for the statistical model and it provides a measure of how well the future outcomes can be predicted by the model. In other words, the R provides the information about the goodness of model fit. Insignificant lack-of-fit indicates that there might be contributions in the regression response- relationship that are not accounted for the model. 4.3 Vibration main effect analysis Main effect result between block vibration and input parameters are shown in Figure 4 & Figure 6 from the figures it can be concluded that block vibration decreases with increase in compression ratio and load. The decreasing trend is due to increase in inside air temperature. This decreases ignition delay and reduces knocking tendency. Hence, reduces vibration amplitude. Whereas increase in injection pressure increases the block vibration because at higher injection pressure amount of fuel injected per cycle increases and at too high injection pressure homogenize mixing is also not possible which leads to increase in block vibration.figure and 7 shows the plot of predicted and actual data with respect to different input parameters. Amplitude m/s kg 6kg 1kg Figure 4 variation of block vibration with CR and load Amplitude m/s Figure variation of block vibration with CR Amplitude m/s bar bar 7bar Figure 6 variation of block vibration with FIP. 4.4 Emission main effect analysis Figure 8 shows the variation of HC carbon in PPM with input parameters. Emission of HC is mainly depends on the combustion of fuel inside the cylinder better the combustion lesser will be the HC emission and vice versa. From the figure it can be observed thatincrease in CR and IP reduces the HC emission because of better combustion. Figure 9 and 1 show the variation between the actual and predicted data of HC emission for different input parameters. -4

5 th International & 6 th All India Manufacturing Technology, Design and Research Conference (AIMTDR 14) December 1 th 14 th, 14, IIT Figure 11 shows the variation of CO emission with respect to different parameters. It can be observed from figures that an increase in compression ratio and injection pressure results in reduced co emission. The trend is due to complete combustion of fuel at higher CR and IP. Figure 1 and 13 shows the variation between the actual and predicted response of CO emission for various input parameters. Amplitude m/s IP in bar Figure 7 variation of block vibration with CR and IP HC (PPM) bar bar 7bar Figure 8 Variation in HC emission with CR and IP HC PPM Compression Ratio Figure 9 Variation in HC emission with CR HC PPM Figure1 Variation in HC emission with IP Emission of NO depends on the temperature of combustion gases coming out from the tail pipe. At elevated temperature oxygen and nitrogen reacts and results in increase of NO in exhaust Emission. Figure 14 shows the variation of NO emission with respect to various parameters. Results show that an increase in compression ratio and injection pressure increases the NO emission. At higher CR, more availability of oxygen and elevated temperature of air lead to increase in NO emission whereas at higher IP, more fuel being burnt leads to increase in NO emission. Figure and 16 shows the plot of actual and predicted data of NO emission for different input parameters with their effect. CO % CO% bar bar 7bar Figure 11 Variation in CO emission with CR and IP Figure 1 Variation in CO emission with CR and IP -

6 Vibration Analysis of Variable Compression Ratio Engine Using Virtual Instrumentation CO% NO (PPM) NO PPM IP in bar Figure 13 Variation in CO emission with IP 18bar bar 7bar Figure 14 Variation in NO emission with CR and IP actual predicted Compression Ratio Figure Variation in NO emission with CR. 4. Performance main effect analysis From the Figure 17 it can be observed that Brake power increases with increase in compression ratio and injection pressure. The reason is that, at higher compression ratio combustion process is better. Brake power (KW) bar bar 7bar Figure 17 Variations in BTHE with CR and IP. NO PPM Figure 16 Variation in NO emission with IP Hence, Brake power at high compression ratio is high whereas high injection pressure results in better fuel atomization and increases Brake power. Figure 18 and 19 shows the plot of actual and predicted data of brake power for different input parameters with their effect on the brake power. Brake power (KW) Compression Ratio Figure 18 Variations in BP (kw) with CR. Figure shows the plot between break thermal efficiency (BTHE) and different operating parameters (i.e. compression ratio and injection pressure). Results show that BTHE increases with increase in the parameters (i.e. CR, IP). The reason is that, an increase in CR and IP results in better combustion processes and hence, increases BTHE. Figure 1 and shows the difference between the actual and predicted data of BTHE for different input parameters with their effect on the BTHE. Brake power (KW) Figure 19 Variations in BTHE with IP. -6

7 th International & 6 th All India Manufacturing Technology, Design and Research Conference (AIMTDR 14) December 1 th 14 th, 14, IIT BTHE % BTHE % BTHE % compression ratio Figure Variations in BTHE with CR and IP bar bar 7bar CR Figure 1 Variations in BTHE with CR Figure Variations in BTHE with IP Conclusions A vibration analysis system has been successfully developed with the help of virtual instrumentation. Analysis of vibration shows that the increase in injection pressure increases the block vibration of engine which could result in damage of parts whereas decrease in compression ratio also increases the vibration level as shown by the results obtained. Emission characteristics of engine have also been study for different parameters. Result shows that an increase in compression ratio reduces the HC and CO emission but increases the NO emission. Injection pressure also shows the same effect on emission as shown by compression ratio. Performance (i.e. Brake power and Brake thermal efficiency) of engine has also been studied at different input condition.result shows that anincrease in compression ratio and injection pressure result in increase in Brake power and thermal efficiency. Regression model of all the output has also been developed with goodness of fit which means of how well the future outcomes can be predicted by the model. References Agarwal, A K,Srivastava, D K, Dhar, A,Maurya, R K, Shukla, P D and Singh, A P ( 13) Effect of fuel injection timing and pressure on combustion, emissions and performance characteristics of a single cylinder diesel engine,elsevier journal, Fuel volume 111, pp Carlucci, A.P.Chiara,F.F. and Laforgia,D. (6) Analysis of the relation between injection parameter variation and block vibration of an internal combustion diesel engine, Journal of Sound and Vibration volume 9, pp Kadhi, F, Mast A and Rosborough, B, A Data report.( access on 13 July 13) Mathur, Y. B. Poonia,M. P. Jethoo, A. S. and Singh,R. (1) Optimization of Compression Ratio of Diesel Fuelled Variable Compression Ratio Engine, International Journal of Energy Engineering, Volume, pp Sayin C, Canakci M.,(9) Effects of injection timing on the engine performance and exhaust emissions of a dual-fuel diesel engine Energ Convers Manage vioume, pp3-13. Venkatesh, K A,Mathivanan,N. (1) Design of MEMS Accelerometer based Acceleration Measurement System for Automobiles measurement science review, Volume 1, pp Venkatraman, M. and Devaradjane,G. (1)Experimental Investigation of Effect of Compression Ratio, Injection Timing and Injection Pressure on the Performance of a CI engine Operated with Diesel-Pungam Methyl Ester Blend, IEEE, 1.119/FAME