Turbo Machines Research Articles

CFD Simulation to Enhance the Efficiency of Centrifugal Pump by Application of Inner Guide Vanes

In this research work the study of fitting the Inner guide vanes at the entrance of centrifugal fan impeller is to resolve the non-uniformity of the flow and to get rid of the vortices that are generated by the existence of Inner distortion. The main purpose of this work is to evaluate the use of the Inner guide vanes (IGV) made of sheet metal and fiber reinforced plastic to improve the fan performance and saving of energy. For this purpose the ring of blades in radial direction i.e. Radial cascade, with different exit blade angles of impellers is used. Comparison with free inner (without IGV) fans is performed. Measurement of static head, shaft power and energy savings at different loads are made for dissimilar cases. The study of these measurements gives some information concerning the operating range and how energy could be saved in V.A.V. (variable air volume) system in air conditioning. By using the above method the overall size of the fan could be reduced. Hence, after reviewing the available literature, Inner guide vanes are chosen for the study in the present research work. Poor efficiency and lack of capacity control range (which are often found with ageing centrifugal turbo machines like centrifugal compressor, centrifugal pump, and centrifugal fan) are observed when performance tested in various applications. For this reason, improvement in the stable operating range and reduction in part load power consumptions, particularly in off-design conditions was required. This was achieved by upgrading the aerodynamics and fitting Inner guide vane control to the machines in this work.

Experimental Installation for the Study of Nozzles Microturbines

Describes the experimental setup for studying the nozzles. Presents a methodology of the experiment and data processing of the results.Keywords: turbine, nozzle, nozzle box, small-size turbo machines, microturbines, velocity coefficient.

Miniaturization of an interferometric distance sensor employing diffractive optics

Abstract In order to improve safety, lifetime and energy efficiency of turbo machines, the behavior of the turbine blades has to be monitored during operation. This is a great challenge for metrology, since small, robust and non-contact position measurement techniques are required that offer both micrometer accuracy and microsecond temporal resolution. The Laser-Doppler-Distance (LDD) -Sensor proved to be an adequate technique to perform such measurements. However, the usage in turbo machines requires a miniaturized and temperature-stable sensor-head. In this paper we introduce a miniaturized design of the LDD-sensor that is based on common-path detection. First results indicated that the numerical aperture of the common-path detection is small in comparison to former implementations that used separate paths for illumination and detection. We find that decreasing the numerical aperture strongly increases the systematic measurement uncertainty. For this purpose a novel diffractive optical element containing a diffracting-lens was designed and used to increase the numerical aperture of the common-path detection without affecting the sensor size. Experiments prove that the new element reduces the relative systematic measurement uncertainty by a factor of ten. The mean systematic position measurement uncertainty amounts to Δz mean≈16 μm. The resulting sensor has dimensions of 25×25×60 mm3, offers temperature-stability and achieves micrometer resolution.

CFD ANALAYSIS OF FLOW THROUGH A CONICAL EXHAUST DIFFUSER

The exhaust diffuser of a fluid machine such as a gas turbine recovers static pressure by decelerating the flow and converting kinetic energy into pressure energy. It is hence a critical component in a turbo machine environment and plays a pivotal role in determining the performance of a turbo machine. Therefore, if the diffuser design is optimized for maximum pressure recovery, an increase in efficiency of the fluid machine can be brought about. Computational fluid dynamics (CFD) analysis was performed on diffusers with different half cone angles and based on the results obtained the geometry that yielded the maximum pressure recovery was identified. The diffuser with the optimized geometry was then fabricated and tested. The experimental value of the diffuser pressure recovery coefficient was calculated and compared with the theoretical value.

Grinding of Riblet Structures on Free Formed Compressor Blades

The effectiveness of gas turbines can be improved significantly by decreasing the friction losses. Compared to smooth surfaces riblet-structures have been proven to reduce skin friction in turbulent flow up to 10 %. For the technical application on compressor blades in turbo machines, micro riblet-structures with a riblet width between 20 μm and 120 μm and a depth of the half width are required. Furthermore, the application on compressor blades needs ideal riblet-geometries with an aspect ratio of 0.5, trapezoid groove geometry and a shape accuracy of the compressor blade about 10 μm. This paper presents the relevant influencing factors on the overall shape accuracy as well as the riblet geometry in five axes grinding of riblet-structures on double curved compressor blades. The results show, that the shape accuracy is affected by the CAD data and the macro-geometry of the grinding wheel. Therefore, specialized requirements on the CAD data were defined in order to increase the shape accuracy. To decrease the influence of the grinding wheel geometry on the overall shape geometry, a method adjusting the grinding wheel geometry on double curved surfaces was developed. Furthermore, the effect of the 5 axes kinematic on the aspect ratio and the profile wear was examined.

CFD flow analysis in the centrifugal vortex pump

Purpose – Aging of the oil wells leads to a decrease in reservoir pressure and also to an increase in the water, gas and abrasive particles content. Therefore, there is a need for the oil pumps exploitation characteristics improvements. This paper aims to generate a valuable numerical model which will provide a useful tool to study various cases. Design/methodology/approach – Computational fluid dynamics (CFD) analysis of the generation of so-called coherent structures of eddies and turbulence in the peripheral area of the vortex rotor mounted at the back side of centrifugal rotor was undertaken. After detailed analysis of the influence of the used turbulence models on the results, a hybrid turbulent model Detached Eddies Simulation (DES) was chosen as the most suitable. Findings – Numerical control volume method with unsteady solver and DES turbulence model was proven to be valuable tool for flow analysis in the centrifugal pumps. Having in mind that DES turbulence model consumes much less computational time than large eddies turbulence model, this is a very useful fact that resulted from this research. Practical implications – The proven numerical model is robust and reliable enough to become a standard method in simulating flow and other physical phenomena occurring in centrifugal pumps and similar turbo machines. This makes it possible to easily research different factors that influence their performances. Originality/value – Comprehensive experimental and CFD study was performed which made it possible to conduct detailed validation and verification of described CFD model.

Selection of High Performance Alloy for Gas Turbine Blade Using Multiphysics Analysis

With the extensive increase in the utilization of energy resources in the modern era, the need of energy extraction from various resources has pronounced in recent years. Thus comprehensive efforts have been made around the globe in the technological development of turbo machines where means of energy extraction is energized fluids. This development led the aviation industry to power boost due to better performing engines. Meanwhile, the structural conformability requirements relative to the functional requirements have also increased with the advent of newer, better performing materials. Thus there is a need to study the material behavior and its usage with the idea of selecting the best possible material for its application.In this work a gas turbine blade of a small turbofan engine, where geometry and aerodynamic data was available, was analyzed for its structural behavior in the proposed mission envelope, where the engine turbine is subjected to high thermal, inertial and aerodynamic loads. Multiphysi...

Static characteristics of small aerodynamic foil thrust bearings operated up to 350,000 r/min

Foil bearings have been attracting considerable attention for their application in achieving low power consumption in small-sized turbo machines, excellent stability at high speeds, and durability at high temperature. Foil bearings with bump foils are one of the most suitable candidates for these applications as indicated in recent studies. However, it was reported that current small foil thrust bearings had insufficient load capacity to support thrust forces in practical high-speed turbo machines, and were needed to improve the load capacity at high speeds. As a first step in improving the load capacity of small foil thrust bearings, the load capacity and rotational torque of this type of foil thrust bearings that operate at up to 350,000 r/min were investigated experimentally and numerically in this paper. In the numerical calculation, the Reynolds and elasticity equations for the top foil were solved simultaneously by using the finite difference and the finite element method, respectively. It was experimentally and numerically found that the foil thrust bearings treated in this paper have the load capacity coefficient of 5.36 × 10−6 N/(mm)3 kr/min, which was comparable to that of the second-generation foil thrust bearings.

FE Analysis Of Runner Blade For Small Bulb Turbine

The stress analysis of the rotor blade being the key phase of the turbomachine design requires much attention and careful determination of the blade loading to get realistic results. So due to the advantages of finite element analysis in the field of mechanical engineering it is widely used as simulation. The runner blades of the turbine are very critical part because its transfer fluid energy to convert the rotary or mechanical energy. The turbine runner blades are subjected to different load e.g. fluid or gas forces, inertia load, centrifugal forces. The primary reason of break down in turbine is the failure of blade. So, the proper blade design is require. The finite element analysis of bulb turbine is using software Creo. Initial studies focused on the modeling, meshing and physics definition of the problem. The results were analyzed for rotor and found location of several critical sections subjected to high stress concentration causing failure of rotor blade. Also found the effect of rotor speed on stress and displacement. Hence, the proper mechanical design of the turbo machine blade plays a vital role in the proper functioning of the turbo machine.

Analysis of Subsonic Incompressible Flow over a Rotating Disc

Flows induced by rotating objects appear in turbo-machinery, storage devices of computers and ocean circulations, and the investigation of these flows is very interesting. An accurate and reliable analysis of the turbo machine rotating parts is of major concern to ensure fail proof and long life turbine engines. In the case of low aspect ratio of blades makes it necessary to treat them as plates. One of the typical cases of these phenomena is the flow which develops between a rotating disc and a stationary disc (shroud), and the flow has been investigated numerically and experimentally. In this work the basic flow field is investigated over a rotating disk with the shroud at the top. There is a small inlet for air in the shroud and the inlet air gains radial, circumferential and axial velocity due to the rotating disc. An analysis is made to obtain exact solutions for the flow of air due to a disk rotating with a constant angular speed. The studies have been pursued on 4 different revolutions per minute (rpm) and 3 different heights. The various rpm at which experiments were done are 500rpm, 600rpm, 700rpm and 800rpm and the various heights are 5cm, 10cm and 15cm.

An Innovative Vertical Axis Current Turbine Design for Low Current Speed

This article presents the new innovative concept for optimal design of Vertical Axis Current Turbines (VACT) applicable in low current speed which is being increasingly used to harness kinetic energy of water and convert it into other useful forms of energy as a clean and renewable energy. Widespread commercial acceptability of these turbo machines depends upon their efficiency. This largely depends upon the geometric features of the hydro turbines such as operation of designed system, joints, number and shape of blades and etc. The concept of VACT was proposed to provide a solution for the case of low current force inflow to vertical axis turbines. VACT has four suitable blades with flexible hinge joint to guide the water in come to reduce the drag force, light shaft and arms with stiff metal to make rigid and strong structure. The current study discusses the components of VAC turbine, rigidity of structure, performance, executive concept, efficiency, material, gearbox, environmental impacts and prevention of water corrosion. The new proposed innovative concept of VACT has flexible hinge connection for changing the blades directions automatically to reduce hydrodynamic drag and increase the hydrodynamic pressure to rotate the main shaft and enhance the efficiency as well. Main shaft connected to epicyclical gearbox to provide the higher torque for maximum electric power generation.

Nonlinear Dynamical Analysis for a Plain Bearing

This paper investigates the nonlinear dynamic behavior for a plain classic bearing (fluid bearing) lubricated by a non-Newtonian fluid of a turbo machine rotating with high speed; this type of fluid contains additives viscosity (couple-stress fluid film). The solution of the nonlinear dynamic problem of this type of bearing is determined with a spatial discretisation of the modified Reynolds' equation written in dynamic mode by using the optimized short bearing theory and a temporal discretisation for equations of rotor motion by the help of Euler's explicit diagram. This study analyzes the dynamic behavior of a rotor supported by two couple-stress fluid film journal lubricant enhances the dynamic stability of the rotor-bearing system considerably compared to that obtained when using a traditional Newtonian lubricant. The analysis shows that the dynamic behavior of a shaft which turns with high velocities is strongly nonlinear even for poor eccentricities of unbalance; the presence of parameters of couple stress allows strongly attenuating the will synchrony (unbalance) and asynchrony (whipping) amplitudes of vibrations of the shaft which supports more severe conditions (large unbalances).

Numerical investigation on effect of inlet nozzle size on efficiency and flow pattern in squirrel cage fans

Squirrel cage fan is a special type of turbo machines commonly used in industries and buildings (as a part of heating, ventilation and air conditioning (HVAC) systems). There are lots of important parameters that can affect the performance and efficiency (energy consuming). Experiments have shown that there are some turbulent areas in volute and impeller, and also in few cases, the relationships between the fan parameters, geometry and nondimensional parameters, and turbulent areas or performances were defined. In this paper, the effect of inlet-nozzle diameter on performance and flow pattern is considered. Three inlet nozzle sizes with respect to impeller size were chosen (smaller, nearly same, and bigger than inner impeller diameter), and numerical simulations with different turbulence models were performed to find the effect of inlet size on flow pattern, performance, and efficiency. For the validation of numerical results, some experiments were done, and all the performance parameters were compared to that of numerical results. These results showed good matching between experimental and numerical results. From each case study, flow pattern and its mechanism and the reasons of low efficiency are studied and presented.

Evaluation of performance of A1c and FPG tests for screening newly diagnosed diabetes defined by an OGTT among tuberculosis patients—A study from India

AimThe methods used for diagnosis of diabetes have limitations particularly in situations associated with stress hyperglycemia. Aim of this study was to evaluate the performance of A1c and fasting plasma glucose (FPG) tests for screening newly diagnosed diabetes (NDD) defined by OGTT among tuberculosis (TB) cases in India. MethodsA total of 983 subjects aged ≥18 years with TB were selected from 7 TB units – 4 urban, 2 rural and 1 semi-urban areas of Tamil Nadu, India, during August 2010–March 2011. Screening for diabetes was carried out by 2-h 75g OGTT. Classification of glucose intolerance status was based on WHO criteria. HbA1c was measured by high performance liquid chromatography using Bio-Rad turbo machine. HbA1c≥47.5mmol/mol was used for diagnosis of diabetes. FPG was estimated by glucose-oxidase method. Known cases of subjects with diabetes were excluded and final analysis was done using data of 779 individuals. The performance of A1c and FPG tests was evaluated against the results of OGTT using receiver operating characteristic curve analysis. ResultsPrevalence of NDD was 10.8%. The areas under the curve (AUC) were 0.754 [95% confidence interval (CI) 0.68–0.83] (p<0.001) for A1c and 0.662 (95% CI 0.58–0.74) for FPG (p<0.001) in NDD subjects. The HbA1c cut-off point of ≥47.5mmol/mol gave a sensitivity of 59.1% and specificity of 91.7%, and the respective values were 34.8% and 97.5% for FPG in subjects with NDD. ConclusionHbA1c performed better than FPG as a screening tool for newly diagnosed diabetes among subjects with TB.

The optimisation and analysis of a centrifugal slurry pump impeller with 2 blades

With FLUENT, which is Computational Fluid Dynamics (CFD) software, it becomes possible to define the performance of complicated flow in turbo machines like pumps and blowers. It is not only reduced costs but also saves time. This study is aimed to optimize a commercial slurry pump impeller. Therefore, four different types of impellers were designed with using various blade angles, blade length and splitter blade on the impeller, which is the most crucial component of the pump. As a result of analysis it was seen that every impeller affected on the pump performance at different flow rate.

Progress on Facilities and Methodology to Evaluate Abradable Seal Coatings

To improve gas turbine performance, it is essential to decrease back flow gases in the high-temperature combustion region of the turbo machine by reducing the shroud/rotor gap. An abradable seal coating will function effectively. The present work described an advanced detection technology and test rigs to study abradability of the seal coatings. Several early used analytical methods were also reviewed in the work as comparison,like NASAPWA and Sulzer Innotec, have developed abradable test rigs and specified different experimental parameters by simulating the determined working conditions. Thence, suggestions to further develop evaluation methods for seal coatings were proposed and discussed.

“Injection Pump for CCS”

In this paper, key point for design of CO2 injection pump is explained. Material selection guide line is explained firstly both for main parts and wearing parts. Consideration of corrosion and low viscosity is important. Next, pump structure is explained. Design of thrust balancing device is very important because density of CO2 will vary from inlet to outlet. Critical design point is explained, when inlet condition is close to border between liquid and vapour zone. Then, influence of temperature fluctuation is explained. Next, seal and seal system suitable for CO2 injection pump is explained.Supply experience of acid gas injection pump is introduced.Finally, optimum selection of turbo machines for CO2 pressurizing is reported.

Formulation of a Transfer Function between Rotor Responses on a High Speed Balancing Machine and in Turbo Machinery by System Identification

In this paper the authors propose an innovative method for the determination of a transfer function (MTF) between the rotor responses on a balancing machine (HSB) and on turbo mach inery (SP). The prediction of the rotor behavior in its turbo machine final housing is a crucial problem for turbo machinery manufacturers and very co mp lex to solve using classical approaches. The proposed method uses a particular MTF formu la, calcu lated with a black/bo x approach based on the application of the theory of System Identification, using the rotor responses in SP and in HSB as input and output respectively. MTF was determined by a regression analysis of the responses in HSB and SP of 10 rotors; subsequently it was tested and validated on other 15 rotors. The results demonstrate that proposed MTF simulates a rotor behavior in SP with a satisfactory overlapping of the measured output.

Experiments and CFD Analyses for a New Reaction Microhydro Propeller with Five Blades

AbstractThis works aims to develop and study a new reaction microhydro tubular propeller turbine with five blades as a promising answer to solve the lack of energy in rural and remote areas. The first stage is to validate numerical and experimental tests made for the flow behavior for different values of head, discharge, and rotational impeller speed. Using specific mathematical formulations, a blade model configuration is developed based on the velocity triangles at the impeller inlet and outlet and experimental results based on pressure, discharge, and velocity profiles in different turbine sections. Through characteristic parameters, performance curves are obtained allowing comparisons between experimental and computational fluid dynamics (CFD) results. Also, an evaluation of the hydrodynamic behavior is made for a scaled model application by similarity turbo machines theory.

Approaches to experimental validation of high-temperature gas-cooled reactor components

The special feature of high-temperature gas-cooled reactors (HTGRs) is stressed operating conditions for equipment due to high temperature of the primary circuit helium, up to 950°C, as well as acoustic and hydrodynamic loads upon the gas path elements. Therefore, great significance is given to reproduction of real operation conditions in tests. Experimental investigation of full-size nuclear power plant (NPP) primary circuit components is not practically feasible because costly test facilities will have to be developed for the power of up to hundreds of megawatts. Under such conditions, the only possible process to validate designs under development is representative tests of smaller scale models and fragmentary models. At the same time, in order to take in to validated account the effect of various physical factors, it is necessary to ensure reproduction of both individual processes and integrated tests incorporating needed integrated investigations. Presented are approaches to experimental validation of thermohydraulic and vibroacoustic characteristics for main equipment components and primary circuit path elements under standard loading conditions, which take account of their operation in the HTGR. Within the framework of the of modular helium reactor project, including a turbo machine in the primary circuit, a new and difficult problem is creation of multiple-bearing flexible vertical rotor. Presented are approaches to analytical and experimental validation of the rotor electromagnetic bearings, catcher bearings, flexible rotor electromagnetic bearings system operability.