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.

The unstable flow with rotating-stall-like (RS) effects in a rotor-cascade of an axial COMPRESSOR was numerically investigated. The RS was captured with the reduction in mass flow rate and increasing of exit static pressure with respect to design operating condition of the single rotor. The oscillatory velocity traces during the stall propagation showed that the RS vortices repeat periodically, and the mass flow rate was highly affected by the blockage areas made by stall vortices. The results also showed that large scale vortices highly affects on the generation and growth of the new vortices. An unsteady two-dimensional finite-volume solver was employed for the numerical study which was developed based on Van Leer’s flux splitting algorithm in conjunction with TVD limiters and the κ-ε turbulence model was also employed. The good agreement of the computed mass flow rate with the experimental results validates the numerical study.

This paper describes the application of eigenvalue analysis for surge prediction in multi-stage axial flow COMPRESSORs. In this approach, the compression system is modeled using a stage-by-stage nonlinear modeling based on the conservation equations of mass, momentum and energy. By line arising the COMPRESSOR flow model at each steady state point, the small perturbation system matrices have been obtained. By analyzing the eigenvalues of the linearised model, the stability of the COMPRESSOR flow has then been investigated, and surge points for both low and high COMPRESSOR rotational speeds have been predicted. Finally, the results for a seven stage axial flow COMPRESSOR have been compared with experimental data in order to show the ability of the method.

In this article, aerodynamic stability of J79 COMPRESSOR was analytically investigated. For this purpose, conservation equations of mass, momentum and energy were applied with several assumptions .By accomplishment of equations related matrix as well as investigating its eigenvalues, the effect of parameters on aerodynamic stability were assessed. Due to the complexity of the equations used in the matrix, the equations codes in MATLAB and the desired matrix have been provided. By applying the geometry and flow characteristics of J79 engine on the matrix and extract the relevant diagrams, the effect of some parameters on the aerodynamic stability of the engine is evaluated. According to the results, by reducing the mass flow rate through the COMPRESSOR, the system tends to be working in an unstable condition. By increasing the ratio of upstream to downstream COMPRESSOR duct length, the aerodynamic stability of the system will increase. Increasing the plenum volume will yield to a considerable reduction in stability. But by increasing the volume of COMPRESSOR, the system stability will increase. Enhancing the combustion chamber temperature and also increasing the COMPRESSOR flow area have favorable effects on system stability. The results of this study compared with previous outcome. Significant achievements were observed between both aforementioned results Relatively good alignment between the results has also been observed.

In this paper a very fast 4-2 COMPRESSOR is introduced. Considering the fact that technological miniaturization is going to reach to its physical limits, there is no way except presenting new approaches and using new architectures. In this design we have improved the overall speed of the system using combined voltage and current mode circuits. All the simulation are done based on BSIMv3 and .25 urn technology. We have used Hspice and CosMos-Scope tools. The input patterns are generated and applied with MATLAB. According to the simulations, the proposed circuit has demonstrated significant improvement in terms of speed and power dissipation. The parameter used to compare the simulations reseals is PDP (power delay product). The other factor in order to compare these two designs is the number of transistors used. The proposed design illustrates 20% reduction in the transistor count.

A honeycomb panel consists of an array of open hexagonal cells which their walls are perpendicular to face sheets although other panel sandwiches don’t have these perpendicular walls. Their design is often performed based on minimum weight. This research is aimed at minimizations of weight by means of computing honeycomb core girth. Weight optimization is done by means of Naive and numerical procedures. Numerical optimization is done by the sequential quadratic programming (SQP) method. Geometric parameters and optimized weight are calculated for hexagonal and square cells. Optimized weights for these two cross-sections are compared.

Air conditioning systems are used in industries and residential environments with the aim of improving environmental conditions and creating a comfortable temperature for users. Considering the production of sound and vibration in most of its components, the lack of control of the production sound level always exposes the users to unwanted sound, which in addition to hearing complications, also causes fatigue and dissatisfaction with the environmental conditions. . COMPRESSORs are one of the most important sources of sound production in air conditioning systems, and screw COMPRESSORs are one of the most widely used in air conditioning industries. Therefore, the COMPRESSOR shell should be designed to minimize the transmission of sound from inside to outside. Since the maximum working temperature of COMPRESSORs is up to 80 degrees Celsius, therefore, in this research, an acoustic test was performed on a sample of a screw COMPRESSOR shell in two modes of ambient temperature and maximum working temperature inside the acoustic room, and the effect of temperature increase on the sound pressure level. transferred from the shell to the external environment is discussed. Finally, based on the frequency analysis performed in two conditions of ambient temperature and maximum working temperature and comparing the amount of sound transmitted to the environment at different frequencies, practical solutions to reduce the amount of transmitted sound pressure have been presented.

In this paper, a parametric study of COMPRESSOR performances is performed by the streamline curvature method. Effects of three input parameters in the design process, e. g., number of blades, distribution of blade thickness, and blade sweep angels, on the main objective parameters in the aerodynamic design, e. g., velocity distribution, efficiency, and pressure ratio, are investigated in the parametric study. Initially, a certain two-stage axial COMPRESSOR is designed by the streamline curvature method. Validation of the results is confirmed by comparing the obtained results with the experimental ones. Regarding various values for the aforementioned input parameters, the first stage of the axial COMPRESSOR is redesigned, and the output parameter is established. Therefore, the sensitivity of the design results to each of the aforementioned parameters is recognized. Results show that increasing the blades sweep angle causes the flow behavior, such as efficiency and pressure ratio in the axial fan, to improve while reducing it provides a completely contrary result. Also, reducing the rotors blades number leads to an increase in the pressure ratio and efficiency while its increase causes a contrary result. It is concluded that a reduction in the number of the blades has a stronger effect on the performance parameters than when it increases. The results also show that the effect of the thickness in the hub is greater than the thickness of the tip, and its increase leads to reduce both efficiency and pressure ratio.

The first row rotating blades of four axial-flow COMPRESSORs were prematurely fractured. Previous investigations showed that the site atmosphere contains corrosive compounds which lead to an increase in the possibility of pitting on the blades. To this end, experimental and numerical studies are considered. Replica testing, scanning electron microscope and fractography of the broken blade indicate that the pits join together and make one bigger pit under stress-corrosion cracking mechanism which reduces the failure time. 3-D models of the pitting on the blade under existing forces are analyzed by COMSOL Multiphysics software. Finite element analysis shows good similarities with fractography photos. Stress concentration and interaction of stresses around the pits are two mechanical reasons for the initiation and growth of cracks. Calculations show that the occurrence of stress-corrosion cracking at the location of the pit reduces the crack initiation time to half. The presence of pits increased the stress by approximately 130 MPa relative to the healthy blade. The part between the two pits with a stress of approximately 180 MPa showed the interaction of the two pits in the operating conditions of the COMPRESSOR blade.