Iraqi journal of mechanical and material engineering

Pollutants emitted from internal combustion engines cause significant environmental pollution, and the reduction of these pollutants is the goal of all. The deterioration of air quality is increasing year after year due to increasing the population and cars and low awareness of pollution reduction. In this study, the impact of recycling of exhaust gas in a spark ignition engine was tested on the NOx emitted from it, which is considered one of the most dangerous environmental pollutant. The results of the study showed that the brake specific fuel consumption increases by increasing the amount of the EGR interning the engine, also the brake thermal efficiency increases and the volumetric efficiency decreases with this increase. The NOx concentrations emitted are significantly reduced when high rates of EGR (15% and 20%) are added. The use of high octane fuel RON94.5 has helped to reduce the expected EGR damage, such as greater reduction in the specific fuel consumption, or a greater reduction in the volumetric efficiency.

In the present work, an experimental study on how to increase the heat transfer coefficient (HTC) in double pipe heat exchanger (DPHE) use of a variety of Al2O3 Nano-dispersion concentrations mixed in water as base fluid with air bubble injection for counter flow arrangement under turbulent flow conditions with (Re) Reynold number range from (6000 t0 45000) . The thermal performance of (DPHE) has been enhanced with the use of two techniques. The first, is represented by adding nanoparticles to hot water (inner pipe) raising the (HTC) inside the inner tube. Increase the volume concentration cause increase in the viscosity of the nanofluid leading to increase in friction factor .Secondly is represented by Air bubble injection in outer pipe with cold water to enhance the (HTC). The mobility of air bubbles inside the water from down to up by the force of the buoyancy, and the movement of these air bubbles results in significant mixture and turbulence within the water. The variations of number of thermal units (NTU), exergy loss, dimensionless exergy and (Nu) are evaluated. The investigated parameters were cold water volume flow rates (8, 10, 12 and14) l/min, flow in outer tube. Also, three different volume flow rates of air (12, 16 and 20) l/min mixed with water in outer tube. The volume flow rates of hot water remains constant at (8 l/min) flow in inner pipe with three volumetric concentrations of given nanofluid. The results showed that the air bubble injection throughout the tube gave maximum enhancement in heat transfer characteristics followed by the no air bubble injection. Since the enhancement in heat transfer characteristics varies linearly with the volumetric concentration of Nanofluids, Nanofluids with 0.3% of Al2O3 nanoparticles gave more enhancements in (HTC) than the case without nanofluid. The Nusselt number increased about (8% - 45%).

The kinematics modeling of the robot arm plays an important role in robot control. This paper presents the kinematic model of a three-degree of freedom articulated robot arm, which is designed for picking and placing an application with hand gripper, where a robot has been manufactured for that purpose. The forward kinematic model has been presented in order to determine the end effector’s poses using the Denavit-Hartenberg (DH) convention. For inverse kinematics, an algebraic solution based on trigonometric formulas mixed with geometric method was adopted for a 3 DOF modular manipulator taking into account the existence of a shoulder offset. MATLAB software was used as a tool to simulate and implement the motional characteristics of the robot arm, by creating a 3D visual software package under designing a Graphical User Interface \"GUI\" with a support simulation from robotic Toolbox (Rtb 10.3). Finally, an electronic interfacing circuit between the GUI program and the robot arm was developed using Arduino microcontroller to control the robot motion. The presented work can be applicable for learning the reality interface design methodology of the other kinds of robot manipulators and achieve a suitable solution for the motional characteristics.

The current paper reports the analysis and design of air quality and human thermal comfort in rooms using impinging jet ventilation system at different occupant distribution. Theoretical and experimental studies at different situations of occupant distribution used the square cross sectional supply air duct with height from the foot level end (0.1h). This work presents a numerical study for predicting the indoor airflow and temperature distribution by adopting impinging jet ventilation system in office room. The emergence of the three zones flow field of an impinging jet is mostly divided into three distinguished zones: impingement zone, wall jet zone and free jet zone which produce excessive kinetic energy at the stagnation zone and distribute approximately in the longitudinal and lateral directions over the floor. Acceptable Air Distribution Performance Index (ADPI), effective temperature and ventilation efficiency were found at situations of occupant distribution (when the occupant located at the center of the room one sitting in front of the other gives optimum human thermal comfort if compared with the other situations of occupant distributions).

This study aims to enhancement of heat transfer in double pipe heat exchanger by improving the thermal properties of base fluid which is water by adding AL2O3-Fe2O3 nanoparticles to the water. Al2O3-Fe2O3/water hybrid Nanofluid were examined experimentally and numerically at different flow rates ranging between (3 -7) Lpm at temperature of 25°C in an external tube while there was a hot water at a temperature of 60°C and a flow rate ranged between (3 – 5) Lpm running in the central tube of a double pipe counter heat exchanger. Also, the effect of various concentrations ranged between (0.05, 0.1, 0.15, 0.2, 0.25 and 0.3%) of Al2O3-Fe2O3 nanoparticles dispersed in water on the rate of heat transfer, friction coefficient were verified experimentally and numerically . The ratio of Al2O3-Fe2O3 is 0.5:0.5. The experimental and numerical study indicated that with the rate of heat transfer increases when the concentration of suspended nanoparticles in the base fluid increases , but on the other hand, the skin friction coefficient and pressure drop increases as well with increasing the concentration of nanoparticles. The maximum enhancement in heat transfer for AL2O3-Fe2O3 is about 6 % . The results from the experimental study were largely consistent with the numerical results.

In this work, fabrication of low temperature co-fired (LTCC) with different Talc content is performed. Density and mechanical characterization of the prepared samples has been examined. Three series of low temperature co-fired ceramics have been prepared. The glass part of these composites contains talc to enhance the mechanical properties. The densities, hardness and splitting strength are measured for these series to monitor the effect of composition on their properties. It is shown that the third series (Base3; Flint 25%, talc 35%, Pota ash 8%, Soda ash 12%, and Boric Acid 20%) of the higher talc content shoes the better densities and mechanical properties. The results are explained in terms of better balance of the ceramic-class content that enhances the measured properties.