NISCAIR Online Periodicals Repository Collection: IJEMS Vol.13(4) [August 2006]

Optimization of inlet valve closure timing and clearance volume of a SI engine for better performance at part loadsA numerical and experimental approach

Title: Optimization of inlet valve closure timing and clearance volume of a SI engine for better performance at part loadsA numerical and experimental approach

Authors: J M Mallikarjuna, J M; V Ganesan, V

Abstract: In this paper, a computer simulation and experimental investigations on a single cylinder, four-stroke, spark ignited engine are carried out to optimize inlet valve closure timing and clearance volume for better part-load performance. The simulation procedure involves thermodynamic and global modeling techniques. Many sub-models have been used for predicting heat transfer, friction and gas exchange processes. Unburned hydrocarbons, carbon monoxide and nitric oxide emissions are also predicted. Experiments have been conducted on a single cylinder, air-cooled, four-stroke, spark-ignited engine. In this work, by varying inlet valve closure timing (IVCT) and clearance volume, geometric expansion ratio (GER) of engine alone is varied, while effective compression ratio (ECR) is kept constant, thereby GER/ECR ratio is altered. For modified engine, GER/ECR ratio is varied from 1.25 to 2. Experiments have been conducted for two effective compression ratios, viz., 7 and 8 at a speed of 1200 rpm. Performance and exhaust emission characteristics have been measured at different loads and GER/ECR ratios. The predicted performance and emission characteristics are compared with measured values and the agreement between the two is found to be good. It is observed that, for modified engine, considerable improvements have been found in the reduction of pumping losses (about 25.8 to 56%), increase in the brake thermal efficiency (about 13.6 to 25%), and reduction in unburned hydrocarbon emissions (about 18.5 to 58%). Finally, for modified engine, it is found that GER/ECR ratio of 1.5 gives the best performance compared to standard engine for both compression ratios.

Page(s): 307-321

Overview literature on atomic force microscopy (AFM): Basics and its important applications for polymer characterization

Title: Overview literature on atomic force microscopy (AFM): Basics and its important applications for polymer characterization

Authors: Jagtap, R N; Ambre, A H

Abstract: Atomic force microscopy (AFM) is a relatively new technique used for the surface characterization of polymers. It is capable of producing images of a non-conducting polymer surface without any chemical etching or staining. The unique feature of this technique as compared to other microscopy techniques is that we can study the mechanical properties of the polymer surface and it also does not involve the use of electron beam radiation that damages the polymer surface. This paper describes the various applications of atomic force microscopy like evaluation of mechanical properties, determining the chemical composition, studying photo-oxidative degradation of polymers, measuring the surface adhesion forces, studying the thermal phase transitions in polymers and determining the molecular weight and polydispersity index of polymer brushes. These applications have been elucidated with suitable examples.

Page(s): 368-384

Diffusion bonding of fine grained high carbon steels in the super-plasticity temperature range

Title: Diffusion bonding of fine grained high carbon steels in the super-plasticity temperature range

Authors: Taşkın, Mustafa; Orhan, Nuri; Ozan, Sermin

Abstract: In this study, diffusion bonding behaviour of two high carbon hypoeutectoid steels was investigated. The steel specimens were heat treated to induce a fine grain structure and diffusion bonded within a temperature range where these steels exhibit superplasticity. The results showed that these steels could be bonded successfully at 650^oC and 735^oC within the superplastic temperature range, but poor diffusion bonds were fabricated at a temperature of 850^oC. The poor bonding was attributed to an increase in grain size, which not only reduce grain boundary diffusion mechanisms, but also a loss in superplastic deformation behaviour could be expected.

Page(s): 362-367

Synthesis and characterization of greenish-blue light emitting lithium-boron complex for organic light emitting diode applications

Title: Synthesis and characterization of greenish-blue light emitting lithium-boron complex for organic light emitting diode applications

Authors: Misra, Aparna; Kumar, Pankaj; Kumar, Lokendra Kumar; Dhawan, S K Dhawan; Kamalasanan, M N; Chandra, Subhas

Abstract: A lithium-boron complex, lithium tetra (2-methyl 8-hydroxy quinolinato) boron (LiBqm₄), which emits greenish-blue light has been synthesized by the reaction of LiBH₄ with 2-methyl 8-hydroxyquinoline in a molecular weight ratio of 1:4, and used for organic light emitting diodes (OLEDs) fabrication. The complex has been characterized by optical absorption, Fourier Transform Infrared (FTIR), photoluminescence (PL) and electroluminescence (EL) spectroscopic methods. The thermo-gravimetric analysis (TGA) suggests that the material is quite thermally stable up to 380^oC. An optical band gap of 3.15 eV using the well-known Tauc relation and an exciton binding energy of 0.69 eV has been evaluated. OLEDs have been fabricated in ITO/N,N′-di-(3-methyl-phenyl)-N,N′diphenyl-4,4′diaminobiphenyl(TPD)/LiBqm₄/Al configuration. PL and EL peaks exist at 503 nm. I-V characteristic of device reveals that at higher voltages the current follows I ⍺ V^m law, where m > 1.

Page(s): 357-361