The use of afterburner in turbine engines increases the temperature of the exhaust nozzle, and this temperature increase necessitates the cooling of the nozzle components. This research discusses the analysis and optimization of the cooling system for the circular-to-rectangular transition duct at the inlet of the nozzle, utilizing a combined film and impingement cooling method. To more accurately achieve the optimal geometric model for three blowing ratios of 0.5, 1, and 1.5, effective parameters have been identified using the experimental design method. The simulation results indicate that the optimized geometries for all three blowing ratios of 0.5, 1, and 1.5 feature three rows of film cooling. Also, the two parameters of the film cooling hole diameter and the number of film cooling rows have the greatest effect on increasing the cooling efficiency. In the Blowing ratio of 1.5, by increasing the diameter of the film cooling holes and the number of cooling rows, the cooling efficiency has increased by 32 and 33%, respectively. Also, in the Blowing ratio of 0.5 and 1.5 blowing, the cooling efficiency increased from 0 to 20 degrees, and the cooling efficiency decreased from about 20 degrees onwards. In the blowing ratio of 1, the cooling efficiency increased from 0 to 30 degrees, and the cooling efficiency decreased from about 30 degrees onwards.

Using the Yang-Shih low Reynolds k-ε turbulence model, the mean flow field of a turbulent offset jet issuing from a long circular pipe was numerically investigated. The experimental results were used to verify the numerical results such as decay rate of streamwise velocity, locus of maximum streamwise velocity, jet half width in the wall normal and lateral directions, and jet velocity profiles. The present study focused attention on the influence of nozzle geometry on the evolution of a 3D incompressible turbulent offset jet. Circular, square-shaped, and rectangular nozzles were considered here. A comparison between the mean flow characteristics of offset jets issuing from circular and square-shaped nozzles, which had equal area and mean exit velocity, were made numerically. Moreover, the effect of aspect ratio of rectangular nozzles on the main features of the flow was investigated. It was shown that the spread rate, flow entrainment, and mixing rate of an offset jet issuing from circular nozzle are lower than square-shaped one. In addition, it was demonstrated that the aspect ratio of the rectangular nozzles only affects the mean flow field of the offset jet in the near field (up to 15 times greater than equivalent diameter of the nozzles). Furthermore, other parameters including the wall shear stress, flow entrainment and the length of potential core were also investigated.

In this research, in order to investigate the effect of the piezoelectric patch which is used as a sensor or actuator in rotating flexible structures such as a helicopter blade, the free vibrations of the rotating rectangular sheet with and without the piezoelectric patch have been presented. First-order shear deformation theory is considered for plate displacement and piezoelectric field. Considering the effect of Coriolis acceleration, centrifugal acceleration and centrifugal in-plane forces, the equations of motion are derived from Hamilton's principle and the electromechanical couple equation is obtained from Maxwell's equation. For piezoelectric, two electrical conditions, open circuit and closed circuit, which are used in sensors and actuators, respectively, have been considered. The equations are discretized with the help of the numerical method of generalized differential squares and the matrices of inertia mass, eccentricity, Coriolis and stiffness matrix are obtained. Natural frequency values for beam and rotating plate have been compared in Abaqus software. Also, the values obtained from the numerical solution in MATLAB have been verified with articles and ABAQUS, which have high accuracy. The effect of parameters such as hub radius, rotation speed, sheet thickness, aspect ratio, piezoelectric patch thickness and applied voltage on the natural frequency of the system has also been investigated.

Primary nozzle is one of the most important factors which has a large influence on the performance of thermo-compressors. Most of studies carried out until now, have been performed on single-nozzle thermo-compressors. In this paper, an actual industrial thermo-compressor is considered and the purpose is to study the effect of increasing primary nozzle number on the performance of this thermo-compressor. For this purpose, a triple-nozzle thermo-compressor is simulated numerically and its performance is compared with single-nozzle thermo-compressor. Ideal gas thermodynamic properties are considered to simulate the compressible flow within the thermo-compressor and numerical result is validated using the experimental result. In addition, the effects of variation in mixing chamber convergence angle and position of nozzles at the radial direction in triple-nozzle thermo-compressor are investigated. The numerical results show that at the same condition, a triple-nozzle thermo-compressor is able to provide superior critical back pressure and entrainment ratio than single-nozzle thermo-compressor. The proximity of nozzles (with 34% changes in radial distance) increases the critical back pressure about 8% and decreases the entrainment ratio about 5%. By increasing mixing chamber convergence angle about 66%, the value of critical back pressure decreases about 29% and the value of entrainment ratio decreases about 16% in single nozzle-thermo-compressor and 10% in triple-nozzle thermo-compressor. Also, by 8% reduction of mixing chamber convergence angle, the critical back pressure decreases 6% but entrainment ratio decreases about 2% in single-nozzle thermo-compressor and increases about 3% in triple-nozzle thermo-compressor.

Aerospoke nozzle is one kind of the converging-diverging nozzle that are more effective than of the Bell nozzle. The aerospike nozzle have high efficiency in the all Number of Pressure Ratio (NPR). Also, the usability as a vector thrust is the other benefits of the aerospike nozzle. The disadvantage of the aerospike nozzle it’ s heavier than as the Bell nozzle and the aerospike nozzle requires cooling system. There are afew studies about the aerospike nozzles and the use of this type of nozzles requires more experimental and theoretical studies. In this study reported the results of numerical simulation an axisymmetric aerospike nozzle. In This study used a structure grid and the K-ε turbulence model. The effected of NPR was investigated and the NPR varied between 2 to 50. The results show linear relation between NPR and nozzle mass flow rate. In the last part of this study the effected of the spike length was studied. The four defferent spikes was modeled by 20, 40, 60 and 80 percent length of the first spike length in 10 NPR and results show the cutting more than 40 percent length of the spike effect in flow quality.

Packing rectangular shapes into a rectangular space is one of the most important discussions on Cutting & Packing problems (C&P); such as: cutting problem, bin-packing problem and distributors pallet loading problem, etc. Assume a set of rectangular pieces with specific lengths, widths and utility values. Also assume a rectangular packing space with specific width and length. The objective function is, to pack the pieces into the space in Order to get the maximum sum of utility value of the packed pieces. To generate the related packing pattern this paper proposes a new formulation metl10dbased on the column generation, approach. In this method one each cycle of the algorithm; a one-dimensional pattern is generated based on the shadow prices 'Of the Simplex method. The set of generated one-dimensional patterns are used: to construct the two-dimensional packing pattern. Also, the proposed model and the present models in the.state-of-1beart have been compared.

We first prove that there always exists a maximal rectangularly dualizable graph for a given rectangularly dualizable graph and present an algorithm for its construction. Further, we show that a maximal rectangularly dualizable graph can always be transformed to an edge-irreducible rectangularly dualizable graph and present an algorithm that transforms a maximal rectangularly dualizable graph to an edge-irreducible rectangularly dualizable graph.

In this paper, the effect of nozzle divergent section geometry on fluid flow and heat transfer within the convergent-divergent nozzle numerically and experimentally is investigated. Axisymmetric supersonic flow simulation for the converging-diverging nozzle is conducted. The flow field is a steady turbulent two-dimensional flow. The working fluid is a combustion product and is considered as a compressible ideal gas. The flow field is simulated using the commercial code FLUENT. The equations are discretized implicitly with the second order of accuracy. In this study, two convergent-divergent nozzles have been analyzed that the divergent part of one is a cone-shaped and the other is bell-shaped. The calculated parameters in the simulation have been compared with the experimental results. Based on the simulation results and the values obtained in the experimental test, the error is less than 4% that is acceptable and appropriate. According to the results, flow simulation accuracy is appropriate.

Cyclones are conventional equipment for eliminating particulates from gas flows.Cyclones’ design is simple and they are reliable. However their efficiency for particulates less than 10 micrometer is very low. For this reason other equipment are used in industry. One of the efficient systems for eliminating particulates from gas, is cyclone-scrubbers. Cyclone-scrubber consists of a cyclone and a liquid that is injected by a pneumatic nozzle into gas entrance duct. Cyclone acts as a space for interaction between liquid and particles and a trap for the liquid-particle. Steady state and a long resident time for a specific particulate, lead to high removal efficiency for sub-micron particles. One of the advantages of cyclone-scrubber is low water usage. The ratio of liquid to gas is 0.2-0.5, which is less than other types of scrubbers (0.5-5.0).In this experiment, removal efficiency of cyclone for 4.5,9.0 and 13.0 m/s entrance velocity, were 85.5, 85 and 89.9%. In cyclone-scrubber, for the same conditions, the removal efficiency were 85.2, 95.6 and 97.4%. Removal efficiency for particles of 0.5 micron in cyclone was 3% while in cyclone-scrubber it was 63% with l/g=0.2.