Mehran University Research Journal of Engineering and Technology

4

Authors: Memon Z.A., Uqaili M.A., Soomro M.A.

Power quality is the regulation and stability in power in terms of current, voltage and frequency so as to keep these parameters under defined limits of use to satisfy the demand of electrical utility. Harmonic is one of the power quality problems which are because of distortions in sinusoidal supply voltage at the fundamental frequency. Harmonics cause significant effects at all levels of electrical utility i.e. domestic loads, commercial and industrial loads and control devices. These effects can be minimized with harmonic mitigation techniques. In this regard, shunt passive filter provides reliable, economic and cost effective solution when used with three phase converters. Moreover, six pulse converter circuit is used in conjunction with shunt passive filter which eliminates 3rd harmonics and reduces 5th and 7th harmonics as dominant harmonic levels. This work focuses on harmonic mitigation of three phase six pulse converter circuits by using shunt passive filters. In this context, hardware model is designed and its results are analyzed by using PQA (Power Quality Analyzer).

6

Authors: Shah W., Shah S.A.A., Shaikh F.K.

Various analytical methods have been proposed for the transient analysis of a queueing system in the scalar domain. In this paper, a vector domain based transient analysis is proposed for the hysteresis queueing system with internal thresholds for the efficient and numerically stable analysis. In this system arrival rate of customer is controlled through the internal thresholds and the system is analyzed as a quasi-birth and death process through matrix geometric method with the combination of vector form Runge-Kutta numerical procedure which utilizes the special matrices. An arrival and service process of the system follows a Markovian distribution. We analyze the mean number of customers in the system when the system is in transient state against varying time for a Markovian distribution. The results show that the effect of oscillation/hysteresis depends on the difference between the two internal threshold values.

8

Authors: Soomro A.S., Rajput A.Q.K., Karas I.R.

The landslide susceptibility models require the appropriate and reliable terrain analytical based study of the landslides prone areas using SRTM (Shuttle Radar Topography Mission) data, based on certain GIS (Geographical Information Systems) and remote sensing techniques. This research paper focuses on the analysis of the terrain conditions of Balakot region. The analytical operations have been used in the different phases: (i) Extracting the study area from the large data; (ii) preparing it into grid format; (iii) developing contour lines with certain contour intervals (iv) Re-classification of it into required classes and (v) preparation of digital terrain model with its different required various supplementary models for analyzing the terrain conditions of the study area located in Mansehra district, north part of Pakistan where the great earthquake induced landslide disaster occurred in October 2005. This analytical study has notified the different sensitive issues concerning to the critical slope angles, variation in the elevation and the surface of study area. The various distinctions in the terrain phenomenon validate the occurred and probable landslides because the topography of such study area can predict the various probable landslide hazards, vulnerability and risk threats in the region again. This analytical study can be useful for the decisive authorities by becoming pro-active to rebuild the region to mitigate the expected losses from the natural disaster.

8

Authors: Shah S.A.A., Abdul Sattar Larik,Ahsan Irshad

In this paper, ETAP (Electrical Transient Analyzer Program) GUI (Graphical User Interface) simulation tool has been used to perform the short circuit analysis of power transmission lines. The existing 500KV Hubco- Jamshoro Transmission network of National Transmission & Dispatch Company, Pakistan has been selected to simulate the network. We provide a method for the analysis of short circuit current values for four different faults, i.e. 3-phase, line-ground, line-line and line-line-ground. It also covers the improvement of voltage stability of the network after integration with proposed projects of Jhimpir and Gharo wind power plants. The results of 3-phase and single phase line to ground faults are carried out using conventional method and to validate them these are compared with that of simulated ones. This paper also provides a way of improvement in voltage stability of Hubco-Jamshoro transmission network after adding the proposed projects of wind power plants at Jhimpir and Gharo.

10

Authors: Syed N.H., Ali S.

This paper reports the experimental evaluation of the heat transfer coefficient (U) in a VRF (Vertical Tube Rising Film Evaporator). The aim is to describe the variation of U against different process parameters. Experiments were carried out for laminar flow conditions. The experimental unit is a floor standing tubular framework for a rising film evaporation system. There are many parameters affecting heat transfer coefficient in evaporators, but it was not possible to consider all of them, so parameters including, Reynolds Number (NRe), Temperature Difference (DT), Feed Temperature (Tf) and Re-circulation Ratio (R) were investigated while other factors were kept constant. The experimental results obtained showed that heat transfer coefficient increased with the increase in Reynolds number, feed temperature and temperature difference. The increase in re-circulation ratio also increased the heat transfer coefficient but up to the value of 0.85 and after this the heat transfer coefficient started decreasing slowly and then remained almost constant. An experimental correlation has been developed to relate the Nusselt number and the parameters investigated during the research work.

10

Authors: Shah A.N., Ge Y-S., Shaikh M.A.

This paper presents the comparison of unregulated emissions such as carbonyls and BTEX (Benzene, Toluene, Ethyl Benzene, and Xylenes) species emanated from a light duty SI (Spark Ignition) vehicle E-0 (fuelled on gasoline) and E-10 (ethanol-gasoline blend). Meanwhile, the ozone forming potential of these pollutants based on their ozone SR (Specific Reactivity) has also been addressed in this study. The experiments were performed on transient as well as steady-state modes in accordance with the standard protocols recommended for light duty vehicle emissions. Carbonyls and BTEX were analyzed by HPLC (High Performance Liquid Chromatography) with UV detector and GC/MS (Gas Chromatography/Mass Spectroscopy), respectively. Formaldehyde and acetaldehyde were the predominant components of the carbonyls for E-0 and E-10, respectively. During transient mode, formaldehyde, acrolein + acetone, and tolualdehyde pollutants were decreased but, acetaldehyde emissions increased with E-10 as compared to E-0. The BTEX emissions were also decreased with E-10, relative to E-0. During the steady-state modes, formaldehyde, acrolein + acetone and propionaldehyde were lower, aromatic aldehydes were absent, but acetaldehyde pollutants were higher with E-10 compared to E-0. The BTEX emissions were decreased at medium and higher speed modes however, increased at lower speed mode with E-10 as compared to E-0. Total BTEX emissions were maximal at lower speed mode but, least at medium speed mode for both the fuels. SR of the pollutants was higher over transient cycle of operation, compared with steady-state mode. Relative to E-0, E-10 displayed lower SR during both transient as well as steady-state mode.

10

Authors: Abro M.I., Baloch M.M., Jokhio M.H.

The effect of heat treatment on locally manufactured low alloy steel grade SUP9 most frequently used in making leaf springs for automobiles was studied. While for determination of toughness and hardness Charpy impact testing machine and Rockwell hardness tester were used. The cryogenic test temperatures were achieved by soaking the samples in liquid nitrogen and temperature was measured using digital thermometer capable of reading the temperature from -40-200oC. Hardening, tempering and austempering treatments were conducted using muffle furnace and salt bath furnace. After heat treatment samples were quenched in oil. The results of present work confirmed that toughness and hardness are inversely related with each other and are highly dependent on the type of heat treatment employed. Highest toughness was measured after austempering at 450oC. Effect of test temperature revealed that toughness of the samples increased significantly with decreasing temperature. DBTT (Ductile to Brittle Transition Temperature) of the austempered samples was observed at -10oC, whereas, that of tempered samples could not be determined. Based on the test results authors wish to recommend the 600oC tempering temperature in place of 450oC where normally tempering is practiced in Alwin industry Karachi during manufacturing of leaf spring.

12

Authors: Ghani U., Wormleaton P.R., Ghumman A.R.

In this research work, predictions have been made for the transport and deposition of incoming sediments in an open channel. Attempt has been made to understand the behavior of sediments flowing in the channel. The geometry consisted of a meandering compound channel with a constant inflow of sediments. For this purpose, 3D version of CFD (Computational Fluid Dynamics) code FLUENT has been used as a research tool. The turbulence closure of Reynolds Averaged Navior-Stokes equation was performed with standard - turbulence model. The Lagrangian particle tracking technique available in the code has been used for modeling sediment movement and deposition. For this purpose, nine different ranges of the particle diameters were released at the inlet of the channel. Initially, the model was validated using point velocities in the downstream direction and discharge values at five cross sections along the meander wavelength. The channel used for simulation purposes had a rectangular section. Once the model validated, it was then used for simulation of sediments. The numerical modeling gave a detailed picture of sediment deposited and transported through the channel. As the model was used with - turbulence model and Lagrangian particle tracking technique and then validated, it showed that when this combination of particle tracking and turbulence closure option will be used, the prediction will be fairly good and trustworthy. A number of numerical experiments were conducted to get the impact of sediment inflow velocity and its diameter on deposition patterns. It showed that boundary shearing stresses and secondary flows had considerable impact on sediment deposition in a river bend. The current study revealed that CFD technique can be used for predicting sediment distribution patterns with reasonable confidence. Such prediction techniques are not only economical but also provide details of complex flow and sediment movement behavior which are difficult to get through experimentation. The results predicted can be utilized in handling the deposition and erosion of the sediments in the meandering channels and design of natural and man-made meandering channels can be improved. It will also be helpful in designing proper flushing arrangements of deposited sediments.

18

Authors: Syed H.F., Ilyas M., Qazi A.

Strengthening of masonry against seismic events is very essential and getting maximum attention of researchers around the globe. An extensive experimental program was carried out to study the in-plane lateral performance of un-reinforced masonry, strengthened and retrofitted masonry wall panels under lateral cyclic loading. Twenty tests were carried out; four tests under monotonic lateral loading, twelve tests under static cyclic loading and four tests under pure compression. The test results were analyzed in five groups and this paper presents the analysis of group 4, which deals with effect of axial pre-compression on masonry seismic performance. Three single leaf panels with aspect ratio of 0.67 having size 1.65x1.1m were constructed using same material and workmanship. All the three un-reinforced walls were tested under 0, 0.5 and 1.0MPa vertical pre-compression and displacement controlled static cyclic loading. The wall tested under 0.5MPa pre-compression was reference specimen. The key parameters studied were hysterics behavior, peak lateral load, ultimate lateral displacement, energy dissipation, ductility, response factor and damping ratio. It was observed that level of axial pre-compression has significant effect on lateral capacity, failure mode and performance of masonry. In case of zero pre-compression the lateral capacity was very less and wall went into rocking failure at early stages of loading. Increase in pre-compression to 1.0MPa enhanced the lateral capacity by a factor of 1.92 times. After analysis of test results, it is found that pre-compression has significant effect on lateral capacity, failure mode and performance of masonry. In case of zero pre-compression the lateral capacity was very less and wall went into rocking failure at early stages of loading. Increase in pre-compression to 1.0MPa enhanced the lateral capacity by a factor of 1.92 times. After analysis of test results, it is found that pre-compression has very significant effect on lateral strength, energy dissipation and overall seismic performance.