Sharif Digital Repository

Unsymmetrical Dimethyl hydrazine (UDMH) is used as stabilizer, fuel promoter, chemical in photography, and liquid fuel for fighter jet engines. Catalytic liquid phase hydrogenation of nitrosodimethylamine (NDMA) is one of the most efficient methods for the production of UDMH. Hydrogenation of NDMA to UDMH using a commercial 5% Pd/C catalyst in aqueous solution of NDMA was studied under constant temperature at 40°-70°C, ≤ 15 bar, and NDMA concentrations of 40-70 wt %. The effects of temperature, pressure, and NDMA concentration on NDMA conversion and yield of UDMH product in presence of undesired Dimethylamine (DMA) were studied. At NDMA concentration of > 50 wt %, the UDMH yield was < 0.89,... 

The casing treatment and flow injection upstream of the rotor tip are two effective approaches in suppressing instabilities or recovering from a fully developed stall. The current work presents a state of the art design for the blade tip injection. This is characterized by a high pressure fluid injecting means for delivery of a jet flow directly into the casing treatment machined into the shroud. The casing treatment is positioned over the blade tip region and exceeds the impeller axially by some 30% of the tip chord both in the upstream and downstream directions. Using an injected mass flow of around 2.4% of the annulus flow, the present design can improve stall margin by up to 7% by... 

In this paper the performance characteristics of a turbocharger twin-entry radial inflow gas turbine with asymmetrical volute and rotor tip diameter of 73.6 mm in steady state and under full and partial admission conditions are investigated. The employed method is based on one dimensional performance prediction which is developed for partial admission conditions. Furthermore, this method is developed for the asymmetrical volute of the turbine considering the flow specifications. Experimental investigation of the research was carried out on special test facilities under full and partial admission conditions for a wide range of speeds. A comparison of experimental and modeling results shows... 

In this paper, the application of neural networks for simulation and optimization of the cogeneration systems has been presented. CGAM problem, a benchmark in cogeneration systems, is chosen as a case study. Thermodynamic model includes precise modeling of the whole plant. For simulation of the steady sate behavior, the static neural network is applied. Then using dynamic neural network, plant is optimized thermodynamically. Multi layer feed forward neural networks is chosen as static net and recurrent neural networks as dynamic net. The steady state behavior of CGAM problem is simulated by MFNN. Subsequently, it is optimized by dynamic net. Results of static net have excellence agreement... 

Torsional aeroelastic analysis of a turbomachinery cascade comprised of three-layered sandwich blades embedded with Magnetorheological Elastomer (MRE) core layer is carried out in this paper. The MRE material is used as a constrained damping layer between two elastic skins in order to investigate its effects on the aeroelastic stability of a blade cascade. To formulate the structural dynamic of the blades, torsional theory of rectangular laminated plates is used and the unsteady Whitehead's aerodynamic theory is employed to model the aerodynamic loadings. Assumed modes method and the Lagrange's equations are used to derive the governing equations of motion of the coupled aeroelastic system.... 

Estimation of major turbocharger variables is essential for proper control and monitoring of a turbocharged engine. This work presents a novel algorithm to estimate turbocharger rotator speed, air temperature downstream a compressor and flow rate over the compressor using mean value models of engine subsystems. A nonlinear Luenberger observer is designed for a 1.7-lit gasoline turbocharged engine. The designed observed is shown analytically to be asymptotically stable. Performance of the designed observer is experimentally validated with the data collected from the engine. The results indicate the observer can capture major turbocharger's rotational dynamics and estimated turbocharger... 

In this research an analytical model for performance prediction of centrifugal compressors is developed. The loss mechanisms are investigated in impeller, diffuser and volute separately for wide operating rotational speeds of the compressor. The contributions of compressor components in total entropy generation are further studied using different experimental correlations and methods. The results are verified using experimental test results, carried out at Sharif University of technology Turbocharger laboratory which has been designed to derive performance curves of turbocharger compressors. The test rig is equipped to measure static and stagnation pressures at inlet and outlet of each... 

Estimation of major turbocharger variables is essential for proper control and monitoring of a turbocharged engine. This work presents a novel algorithm to estimate turbocharger rotator speed, air temperature downstream a compressor and flow rate over the compressor using mean value models of engine subsystems. A nonlinear Luenberger observer is designed for a 1.7-lit gasoline turbocharged engine. The designed observed is shown analytically to be asymptotically stable. Performance of the designed observer is experimentally validated with the data collected from the engine. The results indicate the observer can capture major turbocharger's rotational dynamics and estimated turbocharger... 

In this research, design methods of radial flow compressor volutes are reviewed; the main criteria in volute primary designs are recognized and the most effective ones are selected. The effective parameters, i.e., spiral cross-section area, circumferential area distribution, exit cone, and tongue area of the compressor volute are parametrically studied to identify the optimum values. A numerical model has been prepared and verified through experimental data which are obtained from the designed turbocharger test rig. Different volutes are modeled and numerically evaluated using the same impeller and vane-less diffuser. For each model, the volute total pressure ratio, static pressure recovery... 

Reversible axial flow fans, used in tunnel ventilation systems are designed in a way that as the direction of impeller rotation changes, suction and discharge directions change without any sensible change in flow rate and pressure. Also, their reversibility must be higher than 90%. Therefore, the blade profiles of these fans (S-shaped or elliptic) are designed symmetrically. In the current work, a reversible axial flow fan was studied experimentally and numerically in various ambient conditions and blade positions. Additionally, the experimental test of the fan was performed according to the AMCA-210 standard. Comparison of simulation and experimental results indicated the acceptable... 

This paper concerns an understanding of thrust vectoring, in the presence of co-flowing secondary air. An experimental and computational study was performed on a circular-shape nozzle, integrated with a Coanda surface, to investigate the feasibility of multi-directional deflection of the engine exhaust gases. The vectoring angle was controlled by the relative blowing momentum of air that was injected tangentially through the slots, surrounding the main nozzle. A state of the art design that uses a small step, just after the main nozzle to turn the flow into eddy, was also employed to enhance the effectiveness of the method. The secondary section was divided into four identical sections for... 

This paper presents a new design process of a low-cost swirler employed in axial micro-turbines. The swirler is simple in design, inexpensive and easy to produce and has good adaptability to different potential conditions without major changes. The blades are shaped from trapezoid-shaped steel sheets curved to a certain radius to form a tin airfoil with suitable outlet angle distribution from hub to tip. The formed blades are then welded between two concentric rings to form a round cascade. Correction from flow to blade angles, namely induced incidence and trailing edge deviation angles, were calculated by CFD analysis and considered in blade shape design. The manufactured prototype made on... 

In this research the design methods of radial flow compressor volutes are reviewed and the main criterions in volute primary designs are recognized and most effective ones are selected. The effective parameters i.e. spiral cross section area, circumferential area distribution, exit cone and tongue area of the compressor volute are parametrically studied to identifythe optimum values. A numerical model is prepared and verified through experimental data which are obtained from the designed turbocharger test rig. Different volutes are modeled and numerically evaluated using the same impeller and vane-less diffuser. For each model,the volute total pressure ratio, static pressure recovery and... 

This research numerically and experimentally investigates a small turbocharger radial flow compressor with a vane-less diffuser and volute. The geometry of the compressor is obtained via component scanning, through which a 3D model is prepared. The flow inside this model is numerically analyzed by using a Navier-Stokes solver with a shear-stress transport turbulence model. The characteristic curves of the compressor and the contributions of its components to total pressure drop are acquired by measuring the static and total pressures at different cross sections of the compressor. Numerical results are verified with the experimental test results. The model results exhibit good agreement with... 

The pulsating flow in the exhaust gas of a SI engine causes an unsteady flow at the inlet to the turbocharger turbine. In a four cylinder four stroke engine, the pulse frequency varies between 20 and 200 Hz. Three dimensional pulsating flows in a vane-less turbocharger turbine of a 1.7 liters SI engine are simulated numerically and validated experimentally. Simulations are done for 720 degree engine cycle at three engine speeds. The results are shown the inlet pulsating flow has significant effects on several turbine parameters especially the inlet total pressure, the reduced mass flow rate and the efficiency. The results show a very good agreement between the three-dimensional unsteady... 

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... 

Detection and isolation of faults in the exhaust gas path of a turbocharged spark ignition (SI) engine is an essential part of the engine control unit (ECU) strategies to minimize exhaust emission and ensure safe operation of a turbocharger. This paper proposes a novel model-based strategy to detect and isolate an exhaust manifold leakage and a stuckclosed wastegate fault. The strategy is based on a globally optimal parameter estimation algorithm which detects a virtual hole area in the exhaust manifold. The estimation algorithm requires observation of the exhaust manifold’s input and output flows. The input flow is estimated by a nonlinear Luenberger observer which is analytically shown to... 

This research proposes a new method for optimisation of a power generation system based on exergy fuel cost and external social cost of air pollution. A thermodynamic model is provided to estimate the outlet mass flow rates of CO2, CO, NO and NO2 for a gas turbine based on maximising the first and second law efficiencies and minimising the objective function. Results show that inclusion of the external social cost of air pollution increases the optimum excess air ratio if temperature constraint due to metallurgical consideration is disregarded. Otherwise external social cost of air pollution is independent of optimised conditions  

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...