Transition region ignition characteristics of n-heptane fuel sprays

Ignition studies were perferred on monodisperse n-heptane sprays at atmospheric pressure over a range of equivalence ratios and droplet diameters. A capacitive discharge spark ignition system was used as the ignition source, providing independent control of spark energy and duration. Preliminary measurements were made to optimize spark duration and spark gap, optimum conditions being those at which the maximum frequency or probability of ignition was observed. The effect of spark duration on ignition frequency for several spark energies was determined for equivalence ratios of 0.5 and 1.0 and initial droplet diameters of 28 and 68 microns. Spark duration had little effect on ignition frequency over the entire 15 to 170 mu s range examined. Spark durations of 70 to 80 mu s were used for all subsequent work. The spark gap was optimized at equivalence ratios of 0.6, 0.8 and 1.0 and initial droplet diameters of 30, 40, 50, 60 and 70 microns by varying the electrode spacing from 0.5 to 5.0 mm while maintaining a constant spark energy. The optimum gap was determined to be 3.0 mm for nearly all conditions

Spark Ignition of Monodisperse Fuel Sprays

A study of spark ignition energy requirements was conducted with a monodisperse spray system allowing independent control of droplet size, equivalent ratio, and fuel type. Minimum ignition energies were measured for n-heptane and methanol sprays characterized at the spark gap in terms of droplet diameter, equivalence ratio (number density) and extent of prevaporization. In addition to sprays, minimum ignition energies were measured for completely prevaporized mixtures of the same fuels over a range of equivalence ratios to provide data at the lower limit of droplet size. Results showed that spray ignition was enhanced with decreasing droplet size and increasing equivalence ratio over the ranges of the parameters studied. By comparing spray and prevaporized ignition results, the existence of an optimum droplet size for ignition was indicated for both fuels. Fuel volatility was seen to be a critical factor in spray ignition. The spray ignition results were analyzed using two different empirical ignition models for quiescent mixtures. Both models accurately predicted the experimental ignition energies for the majority of the spray conditions. Spray ignition was observed to be probabilistic in nature, and ignition was quantified in terms of an ignition frequency for a given spark energy. A model was developed to predict ignition frequencies based on the variation in spark energy and equivalence ratio in the spark gap. The resulting ignition frequency simulations were nearly identical to the experimentally observed values

Modelling and Experimental Study of Dissimilar Arc Stud Welding of AISI 304L to AISI 316L Stainless Steel

This paper has aimed to try and establish a successful weld joint between AISI 304L stainless steel as a stud and AISI 316L stainless steel as a plate by using an arc stud welding process. The effect of different current and time welding on the torque results was experimentally studied, by using three-level of each process parameter. The post-weld heat treatment (PWHT) was carried out on the optimum sample of torque, to study the effect of PWHT on mechanical properties (torque and hardness) and microstructure of the welding zone. In the present work, A 3-D finite element model was developed by using ANSYS software version 18 to analyze the influence of time and current welding on the temperature distribution and residual stresses of the resultant welded joints. A transient thermal model was built to predict the temperature distribution whereas the residual stresses were determined by using a static structural model. The PWHT has been used to reduce the amount of residual stresses and enhance the mechanical properties of the welded joint. The micro-hardness based on the Vickers test and the microstructure of welded specimens with and without PWHT have been investigated. The simulation results reveal that the generated temperature and the residual stress is strongly affected by the time and current welding. The mechanical test results indicated that the PWHT prompted an improvement in the hardness values

A Digital Identity Management Model for the Jordanian Online Press and Publication Law to Sustain the National E-Commerce Strategy in Jordan

The purpose of this study is to propose a compromise to the Jordanian press and publication law that witnessed a controversy between the government and some of the civil society groups due to the latest amendments that were added to this law, the new model is suggested and the recommendations will follow

Modelling and Experimental Study of Dissimilar Arc Stud Welding of AISI 304L to AISI 316L Stainless Steel

This paper has aimed to try and establish a successful weld joint between AISI 304L stainless steel as a stud and AISI 316L stainless steel as a plate by using an arc stud welding process. The effect of different current and time welding on the torque results was experimentally studied, by using three-level of each process parameter. The post-weld heat treatment (PWHT) was carried out on the optimum sample of torque, to study the effect of PWHT on mechanical properties (torque and hardness) and microstructure of the welding zone. In the present work, A 3-D finite element model was developed by using ANSYS software version 18 to analyze the influence of time and current welding on the temperature distribution and residual stresses of the resultant welded joints. A transient thermal model was built to predict the temperature distribution whereas the residual stresses were determined by using a static structural model. The PWHT has been used to reduce the amount of residual stresses and enhance the mechanical properties of the welded joint. The micro-hardness based on the Vickers test and the microstructure of welded specimens with and without PWHT have been investigated. The simulation results reveal that the generated temperature and the residual stress is strongly affected by the time and current welding. The mechanical test results indicated that the PWHT prompted an improvement in the hardness values