Enhancement of rate of heat transfer in HCCI engine with induction induced swirl and under varying compression ratios and boost pressures

T. Karthikeya Sharma,G. Amba Prasad Rao,K. Madhu Murthy 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.10

Better fuel economy and lower NOx and PM emissions are the two major issues perplexing the researchers as well as new engine developers. Of late a new combustion concept- HCCI has gained popularity in this direction. Low combustion chamber temperatures favorlow NOx emission formation. An attempt is made to study the effect of induction induced swirl in enhancing the rate of heat transfer toattain low in-cylinder temperatures favoring low NOx emissions formation. In this regard a computational study is undertaken in analyzingthe heat distribution to the engine parts in HCCI mode of combustion under four swirl ratios and operating parameters. Extensivenumerical study is carried out on a single cylinder 1.6 L, reentrant piston bowl CI engine. The analysis has been done using ECFM-3Zmodel of STAR-CD. Suitable modifications in the existing code are done to incorporate the HCCI mode of combustion. The ECFM -3Zmodel for HCCI mode of combustion is validated with the existing literature to make sure that the results obtained are accurate. The parameterslike compression ratio and boost pressure are varied under different swirl ratios to analyze the rate of heat transfer in the combustionchamber. The analysis resulted in achieving maximum increased heat transfer rates of 0.88% to the wall with swirl ratio 1,45.66% to the dome and 39.99% to the piston with swirl ratio 4; when the compression ratios are increase from 18 to 21. A maximumincrease in heat transfer rates of 15.82% to the wall, 26.41% to the dome and 27.46% to the piston with compression ratio 21; when theswirl ratio is increase from 1 to 4. Similarly a maximum increased heat transfer rates of 83.75% to the wall with swirl ratio 4, 88.04% tothe dome with swirl ratio 3 and 87.52% to the piston with swirl ratio 4; when the boost pressures are increase from 1 bar to 2 bar wereachieved. A maximum increase in heat transfer rates of 59.35% to the wall with boost pressure 1.5 bar, 81.32% to the dome and 76.34%to the piston with boost pressure 2 bar; when the swirl ratio is increase from 1 to 4 were obtained. The study revealed that apart fromadopting higher compression ratios and boost pressures adoption of high swirl ratios is observed to be contributing to a large extent inenhancing the rates of heat transfer which would lead to significant reduction in in-cylinder temperatures suitable for low NOx emissionformation in HCCI mode.

Simulation of Capacitively Graded Bushing for Very Fast Transients Generated in a GIS during Switching Operations

Rao, M.Mohana,Rao, T. Prasad,Ram, S.S. Tulasi,Singh, B.P. The Korean Institute of Electrical Engineers 2008 Journal of Electrical Engineering & Technology Vol.3 No.1

In a gas insulated substation (GIS), Very Fast Transient Over-voltages (VFTOs) are generated due to switching operations and ground faults. These fast transients are associated with high frequency components of the order of a few hundreds of MHz. These transients may cause internal faults i.e., layer-to-layer faults or minor faults in a capacitively graded bushing, which is one of the important pieces of terminal equipment for GIS. In the present study, the PSPICE model has been developed to calculate the voltage distribution across the layers of 420kV graded bushing for high frequency pulses of rise time 1 to 50ns, which simulate the VFTO. For this simulation, an equivalent electrical network of bushing with different equivalent layers has been considered. The effect of different equivalent layers modeling circuits on the non-uniform voltage factor has been analysed. The influence of copper strip inductance on voltage distribution across layers has also been analysed for various rise times of high frequency transients. Finally, the leakage current of the bushing is calculated for evaluating the bushing condition under these transients.

Computer Aided Identification of Inter-Layer Faults in Gas Insulated Capacitively Graded Bushing during Switching

Rao, M.Mohana,Dharani, P.,Rao, T. Prasad The Korean Institute of Electrical Engineers 2009 Journal of Electrical Engineering & Technology Vol.4 No.1

In a Gas Insulated Substation (GIS), Very Fast Transients (VFTs) are generated mainly due to switching operations. These transients may cause internal faults, i.e., layer-to-layer faults in a capacitively graded bushing as it is one of the most important terminal equipment for GIS. The healthiness of the bushing is generally verified by measuring its leakage current. However, the change in current magnitude/pattern is only marginal for different types of fault conditions. Leakage current monitoring (LCM) systems generate large amounts of data and computer aided interpretation of defects may be of great assistance when analyzing this data. In view of the above, ANN techniques have been used in this study for identification of these minor faults. A single layer perceptron network, a two layer feed-forward back propagation network and cascade correlation (CC) network models are used to identify interlayer faults in the bushing. The effectiveness of the CC network over perceptron and back propagation networks in identification of a fault has been analysed as part of the paper.

Simulation of Capacitively Graded Bushing for Very Fast Transients Generated in a GIS during Switching Operations

M. Mohana Rao,T. Prasad Rao,S.S. Tulasi Ram,B. P. Singh 대한전기학회 2008 Journal of Electrical Engineering & Technology Vol.3 No.1

In a gas insulated substation (GIS), Very Fast Transient Over-voltages (VFTOs) are generated due to switching operations and ground faults. These fast transients are associated with high frequency components of the order of a few hundreds of ㎒. These transients may cause internal faults i.e., layer-to-layer faults or minor faults in a capacitively graded bushing, which is one of the important pieces of terminal equipment for GIS. In the present study, the PSPICE model has been developed to calculate the voltage distribution across the layers of 420 ㎸ graded bushing for high frequency pulses of rise time I to 50 ㎱, which simulate the VFTO. For this simulation, an equivalent electrical network of bushing with different equivalent layers has been considered. The effect of different equivalent layers modeling circuits on the non-uniform voltage factor has been analysed. The influence of copper strip inductance on voltage distribution across layers has also been analysed for various rise times of high frequency transients. Finally, the leakage current of the bushing is calculated for evaluating the bushing condition under these transients.

Computer Aided Identification of Inter-Layer Faults in Gas Insulated Capacitively Graded Bushing during Switching

M. Mohana Rao,P.Dharani,T. Prasad Rao 대한전기학회 2009 Journal of Electrical Engineering & Technology Vol.4 No.1

In a Gas Insulated Substation (GIS), Very Fast Transients (VFTs) are generated mainly due to switching operations. These transients may cause internal faults, i.e., layer-to-layer faults in a capacitively graded bushing as it is one of the most important terminal equipment for GIS. The healthiness of the bushing is generally verified by measuring its leakage current. However, the change in current magnitude / pattern is only marginal for different types of fault conditions. Leakage current monitoring (LCM) systems generate large amounts of data and computer aided interpretation of defects may be of great assistance when analyzing this data. In view of the above, ANN techniques have been used in this study for identification of these minor faults. A single layer perceptron network, a two layer feed-forward back propagation network and cascade correlation (CC) network models are used to identify interlayer faults in the bushing. The effectiveness of the CC network over perceptron and back propagation networks in identification of a fault has been analysed as part of the paper.