Sharif Digital Repository

The performance parameter uncertainties of turbomachines at different rotational speed were determined by experimental and analytical consideration. The instruments/sensors were located and installed according to the standards for evaluating the performance characteristics of turbine and compressor in a turbocharger laboratory in a wide range of rotational speeds. The comparison of turbine and compressor sensitivity shows that the sensitivity of compressor to 1% shift in the pressure is higher than that for the turbine. Results also show that the sensitivities of efficiency and power of turbine reduce as rotational speed increases. The total uncertainty of turbine and compressor are obtained... 

The brushless doubly-fed induction generator (BDFIG) has substantial benefits, which make it an attractive alternative as a wind turbine generator. The aim of this work is to present a nodal-based magnetic equivalent circuit (MEC) model of the BDFIG which provides performance characteristics and flux density distributions. The model takes into account stator winding distributions, special configuration of rotor bars, slotting effects, teeth saturation, flux fringing and current displacement effects. The real flux tubes are considered for creating an MEC network and calculating its non-linear elements. A method for simplifying the rotor magnetic network has been applied and Gauss elimination... 

In this article, the effects of volute cross section shape and centroid profile of a radial ow compressor volute were investigated. The performance characteristics of a turbocharger compressor were obtained experimentally by measuring rotor speed and ow parameters at the inlet and outlet of the compressor. The three-dimensional ow field model of the compressor was obtained numerically solving Navier-Stokes equations with SST turbulence model. The compressor characteristic curves were plotted. For model verification, the results were compared with experimental data, showing good agreement. Modification of a volute was performed by introducing a shape factor for volute cross section geometry.... 

Brushless doubly fed machine (BDFM) shows promising results for wind power and adjustable-speed drive applications. Due to poor rotor magnetic coupling and relatively high value of slip, core loss is an important factor which can affect the steady-state and dynamic performance of BDFM. Specifically, core loss plays a major role when evaluating the efficiency of the machine. By now, there is no comprehensive study on core loss effect on performance characteristics of BDFM in the literature. In this paper, based on the derived relations and applying transformation of parameters from one winding to another one, the steady-state equivalent circuit model of BDFM without core loss is modified in... 

Using CNG as an additive for gasoline is a proper choice due to higher octane number of CNG enriched gasoline with respect to that of gasoline. As a result, it is possible to use gasoline with lower octane number in the engine. This would also mean the increase of compression ratio in SI engines resulting in higher performance and lower gasoline consumption. Over the years, the use of simulation codes to model the thermodynamic cycle of an internal combustion engine have developed tools for more efficient engine designs and fuel combustion. In this study, a thermodynamic cycle simulation of a conventional four-stroke spark-ignition engine has been developed. The model is used to study the... 

In this article, the effects of volute cross section shape and centroid profile of a centrifugal compressor volute were investigated. The performance characteristics of a turbocharger compressor were obtained experimentally by measuring rotor speed and flow parameters at the inlet and outlet of the centrifugal compressor. The three dimensional flow field model of the compressor was obtained numerically solving Navier- Stokes equations with SST turbulence model. The compressor characteristic curves were plotted. For model verification, the results were compared with experimental data, showing good agreement. Modification of a volute was performed by introducing a shape factor for volute cross... 

The flow field in axial turbines is complex and threedimensional. Therefore, experimental flow field is essential to determine the performance characteristics. However, such testing is always expensive and complex. Simulation of gas turbines is a simple way to reduce testing costs and complexity. The main objective of this paper is to make a detailed systematic analysis of two-stage, axial flow turbine by using of different loss models and a new suggested algorithm based on one-dimensional simulation. In one-dimensional modeling, the loss models have to be used to determine the entropy increase across each section of axial turbines stage at both the design and off-design conditions. The... 

A very low-power RF front-end based on a new current reuse QLMV cell (Quadrature VCO-LNA-Mixer) is proposed for GPS applications. The front-end, designed in 0.18μm CMOS technology, provides improved performance characteristics while consuming only 1 mA current. Simulation results are presented and compared with recently published works in the field  

Using hybrid energy storage system is a method for increasing the storage capability of solar thermal energy. If multiple energy storage devices with complementary performance characteristics are used together, the resulting system will be a 'Hybrid Energy Storage System'. In other words, a Hybrid Energy Storage System (HESS) has several media available for storage at any time. In this way, increase in storable energy is obtained without increasing collectors' area. When there are more than one storage mediums, the system should be able to choose the best medium for storing energy according to the conditions. In the previous works, an optimizer program was used to find the proper medium... 

In this paper, the effect of blade number on the vibration behavior of industrial fans has been studied experimentally and numerically. Two similar industrial fans with similar specifications and only different blade numbers were chosen in a plant. The vibration levels were measured on these fans and the results revealed that the blade passage phenomenon is the main cause of vibrations on both fans. Both fans and their structures were modeled numerically and the performance characteristics, vibratory forces and vibration response of structure were calculated. The results showed that the number of blade has small effect on vibratory forces compared to the performance characteristics. The... 

Using linear position sensors is necessary in linear motion control systems. In this paper the influence of winding's pole pairs on the accuracy of linear resolver is studied. 2-D and 3-D time stepping finite element method (FEM) is used to calculate the performance characteristics of the resolver. The effect of finite mover's length, transverse edge effect and the end windings length are discussed in detail. Then a prototype of the studied resolver along with its experimental test setup is built. Good correlation between simulation and experimental results verified the simulation process. © 2017 IEEE  

In this study, an automotive air conditioning system is simulated by considering HFO-1234yf (2,3,3,3-tetrafluoropropene) as the drop-in replacement of HFC-134a. The simulated air conditioning system consists of a multi-louvered fin and flat-plate type evaporator, a wobble-plate type compressor, a mini-channel parallel-flow type condenser and a thermostatic expansion valve. The thermodynamic properties of the refrigerants are extracted from the REFPROP 8.0 software, and a computer program is simulated for the thermodynamic analysis. Two different conditions have been considered in this program for the cycle analysis: for the first state, the cooling capacity is taken as constant, and for the... 

Feasibility of an innovative buzz detection technique through measuring the static pressure outside a mixed-compression supersonic inlet is studied. The buzz is an instability phenomenon that occurs almost in all supersonic inlets. During the buzz, shock oscillation along with pressure and mass flow fluctuations affects the performance characteristics of the inlet. The main objective of this paper is to introduce a simple and easy-to-implement method for investigation of the buzz phenomenon in a supersonic inlet. The experimental data for far field-based are compared with those of the model-based one at free stream Mach numbers of 1.8, 2.0, and 2.2 and at zero degrees angle of attack for a... 

In this paper, numerical and experimental investigation of the performance and internal flow field characteristics of the twinentry radial inflow turbine under full and partial admission conditions are presented. The turbine is tested on a turbocharger test facility, which was developed for small and medium size turbochargers. The flow pattern in the volute and impeller of a twin-entry turbine is analyzed using fully three-dimensional viscous program. The computational performance results are compared with the experimental results, and good agreement is found. The flow field at the outlet of the turbine is investigated using a five-hole pressure probe. The tests are performed for both full... 

In this research, the centrifugal compressor of a turbocharger is investigated experimentally and numerically. Performance characteristics of the compressor were obtained experimentally by measurements of rotor speed and flow parameters at the inlet and outlet of the compressor. Three dimensional flow field in the impeller and diffuser was analyzed numerically using a full Navier-Stokes program with SST turbulence model. The performance characteristics of the compressor were obtained numerically, which were then compared with the experimental results. The comparison shows good agreement. Furthermore, the effect of area ratio and tip clearance on the performance parameters and flow field was... 

In this research, the centrifugal compressor of a turbocharger is investigated experimentally and numerically. Performance characteristics of the compressor were obtained experimentally by measurements of rotor speed and flow parameters at the inlet and outlet of the compressor. Three dimensional flow field in the impeller and diffuser was analyzed numerically using a full Navier-Stokes program with SST turbulence model. The performance characteristics of the compressor were obtained numerically, which were then compared with the experimental results. The comparison shows good agreement. Furthermore, the effect of area ratio and tip clearance on the performance parameters and flow field was...