جستجوی مقالات مرتبط با کلیدواژه « compressor » در نشریات گروه « مکانیک »

Turbofan engines have attracted a lot of attention due to their high propulsion power. Compatibility of the simultaneous operation of the two main components of the turbofan engine, i.e., compressor and turbine, is one of the main concerns of designers and manufacturers. Because the form of characteristic curves of turbine and compressor are different and almost contradictory and will cause stagnation. In order to prevent turbofan surge, determining the matching of different components of this type of motors has become very important. The sensitivity of different parameters in the design of these types of engines is very high and achieving precalculated simulations that can have less calculation error will reduce the cost and time of the design stage. In this research, a lowerror simulation is designed to calculate the matching line of turbofan engines. In the stages of this research, first, the parameters affecting the matching line have been determined, and the method of calculating it has been extracted and simulated. Validation has been done for this simulation using the specifications of the RR-Trent 772-60, PW-PW4098 engines. According to the experiment performed, the thrust fuel consumption has been calculated with an error accuracy of less than 0.05 and the amount of thrust for different engines is less than 2000 (lbs). In another experiment, the correctness of determining the matching line for different components of the turbofan engine has been confirmed using the available resources. On the other hand, the accuracy of the overlap of the matching line of the simulation is 92% for the RR-Trent 772-60 engine and 94.2% for the PW-PW4098 engine.

Today, due to the increasing weight of cars, the addition of turbochargers to internal combustion engines increases performance and at the same time, produces high noise in the range of 72 dB to 154 dB when the engine is running at high speeds and during the initial acceleration. To reduce the negative effects of these noises and increase the comfort of the car occupants, various methods such as including finite element analysis and numerical analysis of compressor blades to optimize pressure drop coefficients (ratio of turbine input to compressor output), sound pads and acoustic materials around engine parts including turbocharger parts and air manifold, are used. The purpose of this article is to express and classify the research done in the field of reducing annoying noises resulting from the operation of the car engine and turbocharger.

Minimizing the number of axial flow compressor stages for a specific work output, and thereby lowering the engine size and weight has always been the designer’s goal. A major limitation on the pressure rise in a subsonic axial-flow compressor stage is boundary layer separation on the blade suction surface. One method of mitigating the suction surface separation is to employ tandem airfoil blades. Tandem blading is a method of increasing the flow deflection by delaying the separation in diffusing cascade arrangements. The basic concept is that a new boundary layer forms on the second (aft) airfoil, allowing for high overall loading without the large flow separations that would be seen with a single airfoil. The unsteady 3D flow fields in a single-stage compressor with tandem blades under designed conditions are simulated numerically to investigate the stage performance and the aerodynamic interaction between the blade rows. In this work, the Time Transformation method (TT) to stage modeling has been employed to predicting stage compressor performance. In the compressor, three main aerodynamic structures are responsible for the unsteadiness of the flow: the wakes, the corner stalls and the tip-clearance flows. The study of the aerodynamic structures is the subject of this paper.

When the mass flow rate through the compressor is reduced at a constant pressure ratio, mass flow rate will drop to an extent that the complete reversal of flow and surge occurs. Recently many research focuses on turbocharger surge, however, there are not enough investigation on the effect of surge on the performance of the turbocharger. The aim of the paper is to investigate the effect of repetitive surge condition on the performance of gasoline engine turbocharger. An experimental investigation has been performed on the turbocharger test cell for 3 different shaft speeds. Turbine and compressor power and efficiency have been investigated while turbocharger was performed in the surge zone. After 4 times repetition of the test procedure, turbocharger failure occurred. Results show that at 180000 rpm and minimum flow, the pressure ratio of compressor decreased by 7 percent after repetitive surge condition. Moreover, turbocharger failure analysis has been performed for the turbocharger which is repeatedly in the surge zone. Investigation shows that there the reason for failure was excessive axial clearance which caused high-temperature signs on the thrust bearing.

The main design objective of axial compressor is the efficiency increasing، pressure ratio and weight loss. These three parameters are used as an objective function and they are computed according to adopted design procedures. In this paper، a design method is presented that named quasi-three-dimensional. Physical flow conditions are applied to design by some constraints to avoid irrational results. Some of these constraints help designer to impose considered requirements. In this paper، Hybrid Genetic Algorithm (HGA) is used for achieving the best design parameters that they construct a complex and non-linear design space. The radial distribution of several parameters is evaluated.