Case Studies

Compressor and gas turbine Characteristics: This material is presented here to familiarize the reader with the behavior of these machines, classified under the broad term “turbomachinery.” Pumps and compressors are used to produce pressure; turbines produce power. These machines have some common characteristics. The main element is a rotor with blades or vanes, and the path of the fluid in the rotor may be axial, radial, or a combination of both. There are three methods of studying the elements of turbomachinery operation. First, by examining forces and velocity diagrams, it is possible to discover some general relationships between capacity, pressure, speed, and power. Second, comprehensive experimentation can be undertaken to study relationships between different variables. Third, without considering the actual mechanics, one can use dimensional analysis to derive a set of factors whose grouping can shed light on overall behavior. The analysis presented in this chapter shows the typical performance diagrams one can expect from turbomachines. Off-design performance is also important in understanding trends and operating curves.

Based on the fundamental research work of Fritz Haber, Carl Bosch and his engineering team developed the ammonia synthesis to technical operability using the promoted iron-based catalyst found by Alwin Mittasch and co-workers. Since then there has been no fundamental change in the synthesis reaction itself. Even today every plant has the same basic configuration as this first plant. A hydrogen-nitrogen mixture Reacts on the iron catalyst (today’s formula differs little from the original) at elevated temperature in the range 400 – 500 °C (originally up to 600 °C), operating pressures above 100 bar, and the unconverted part of the synthesis gas is recirculated after removal of the ammonia formed and supplemented with fresh synthesis gas to compensate for the amount of nitrogen and hydrogen converted to ammonia.
3H2 + N2 =2NH3

The kinetics of the nitrided layer thickness growth and its structure depend on the nitrogen flux from the atmosphere to the nitrided surface. A nitrogen flux to the surface is more significant than a diffusion flux into the substrate, during forming surface iron nitrides and the internal nitriding zone. For pure iron, nitrided under low pressure, cutting off the nitriding atmosphere creates a flux from the subsurface layer of nitrides to the surface. The purpose of this paper is to determine the direction of the nitrogen flux in a similar situation for steels containing nitride-forming elements, thus answering the question of the stability of the layer nitrided under such conditions. The surface of X37CrMoV5-1 steel was nitrided under low pressure (of 24 hPa) and annealed in a vacuum or nitrogen. The microstructure, thickness of the nitride layers nitrided layers, the thickness of the internal nitriding zone, surface hardness and stresses were examined. The highest values of the nitrided layer properties were observed for the samples saturated only with nitrogen obtained from ammonia dissociation or additionally heated in nitrogen. It has been shown that using a pure vacuum during the annealing stage leads to unfavourable changes in the structure of the nitrided layer formed and, in particular, to the decomposition of the iron nitride layer formed at the saturation stage and occurrence of the tensile stresses—what excludes practical application of such layer. Ultimately, it has been shown that in the low-pressure nitriding process, the stability of the nitride layer of the nitride surface strongly depends on the annealing atmosphere during the annealing stage, while the stability of the internal nitriding zone remains mainly at the same level.

Over the past years, failure due to heat affected zone stress relief or reheat cracking in austenitic stainless steels welds, and particularly in stabilized austenitic steels like 321 or 347 have been reported world-wide. More recently similar problems have been discovered on type 316 and 304 stainless steels working in the temperature range 520-550°C. It has been established that these cracks are generally concentrated in sites of high triaxial tension developed in the strain affected zone adjacent to welds as a result of the plastic strains introduced by the welding process, and that they are prevalent in thick sections or near very massive welds. A specific test has been conducted on a component in 304H stainless steel. This component comprises a very massive weld in OKR3U. It was heated at 550°C and kept at this temperature for about 18000h with several stops in order to perform non-destructive controls to follow the cracks evolution. In a first part the experimental device is described, then the different tests campaigns and the results of non-destructive controls are presented. In a second part damage evaluations are explained. Residual stresses due to welding operation being important in the mechanism, it is necessary to evaluate them with refined analyses. Then the creep damage is evaluated using different damage models in order to point out the important parameters.

Many centrifugal pump vibration problems are due to synchronous phenomena such as vane-pass frequency energy and running speed energy. To address such problems, guidelines have been developed to assist with their identification and to evaluate their severity. However, nonsynchronous phenomenon such as recirculation, stage-stall, and shaft instabilities can also cause vibration problems. These types of problems are more difficult or diagnose, since the excitation mechanisms are less obvious. Discussed herein are field measurements and computer analysis that were done to analyze and solve supersynchronous shaft vibration problem on a two-stage horizontal centrifugal coke crusher pump and a vertical single-stage centrifugal water pump. These pumps were marginally stable at low discharge pressures, but were unstable at high discharge pressures. Field tests indicated that the shaft instability vibrations of both pumps could be removed by installing vanes on the back side of the impellers (“pumpout” vanes). Although the pumpout vanes were very effective in eliminating the destabilizing forces on these pumps, the exact effects of the pumpout vanes on the rotor instabilities are not clearly understood. The authors feel that additional analytical and experimental work should be conducted to fully understand the effects of the pumpout vanes.

Friction stir welding was invented by Wayne Thomas at TWI in 1991, with patents filed in Europe, the USA, Japan and Australia. Further work to study the process was undertaken at TWI in 1992 with the project titled, ‘Development of the New Friction Stir Technique for Welding Aluminum.’ Industrial production using FSW was in progress by the mid-1990s, making it one of the shortest time periods for any welding process to go from invention to widespread use. The non-consumable tool, with a profiled probe and shoulder, is rotated and plunged into the interface between two work pieces. It then traverses along the joint line, causing the material to heat and soften. The shoulder also acts to contain this plasticized material, which is mechanically mixed to create a solid phase weld.

The Barkhausen effect is a name given to the noise in the magnetic output of a ferromagnet when the magnetizing force applied to it is changed. Discovered by German physicist Heinrich Barkhausen in 1919, it is caused by rapid changes of size of magnetic domains (similarly magnetically oriented atoms in ferromagnetic materials).
On this work authors have compared the results obtained after a conventional creep failure analysis and magnetic Barkhausen noise. They chose one region without creep damage that was named as standard. Two other regions with creep damage were named as T1 and T2. The sample T1 after optical metallographic analysis has presented level A and B of creep damage according the method of Neubauer to estimate the rest life of creeping by replicas. The sample T2 after optical metallographic analysis has presented level C and D of creep damage according the same method. Based on the failure analysis, they evaluated MBR analysis and compared the results.
Creep damage is the root causes of many failure equipments on heavy industries that work at non conventional temperature, specially boilers and furnaces. It's very difficult detect regions with creep damage by others conventional NDT methods. Replicas are the most used NDT technique to detect creep damage but this technique is based on result of discrete point; may not cover the entire surface of tubes. The electromagnetic techniques are sensible to micro structural change that modifies the magnetic permeability of the material. The authors have emphasized these promising techniques - remote field and magnetic Barkausen noise. The details of the write-up may be downloaded clicking the blue rectangle below;

The main difficulty of axial thrust calculation lies in the correct prediction of the static pressure distribution over the external surface of the impeller hub and shroud. This distribution depends on a large set of parameters, including rotor geometry, operating conditions, properties of the process gas, leakages flows across the rotor-stator seals. A detailed fluid-dynamic model of the gas in the cavities between impeller and diaphragm was developed and applied first to stage model tests and then to high-pressure centrifugal compressors, and its predictability was assessed by direct comparison with experimental data. The compressors were tested in full load conditions, with thrust bearing pads equipped with load cells, and the thrust values were recorded for several points across the operating envelope.

Shell and tube heat exchangers are widely used in process industries for exchange of heat from one fluid to another by indirect means. Design of heat exchanger is lengthy and iterative procedure and overall cost of heat exchanger depends upon various independent variables. Here in present study, we have considered ammonia condenser for study purpose. As ammonia is produced widely in urea manufacturing industries. In present study, we have studied effect of various independent variables like tube outside diameter, tube length and baffle spacing on heat transfer coefficient and pressure drop.
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Scalene Hypercharge Corona Canon (SHYCOCAN™), is intended for realtime attenuation and disabling of certain viruses, including coronaviruses - the virus associated with COVID-19, and the elimination of expected viral loads of Influenza B. This device is a simple, portable, and sensitive methodology intended to disable air and surface borne coronaviruses. Exposure to atmospheric and surface contamination of SARS-CoV-2 can randomly occur. The SHYCOCAN technology is intended to inactivate coronaviruses in the air and on surfaces. The negative charge-seeking guidance mechanism of the virus’ Spike Protein can be disabled and neutralized by trillions of electrons generated per second by the SHYCOCAN™. High-intensity discharge of electrons relies on precision design and geometry of the proprietary Photon-Mediated Electron Emitters (PMEE) in the device. This unique and innovative device can be readily and cost-effectively manufactured to meet demand.

The development of a portable oxygen concentrator is of prime significance for patients with respiratory problems. This paper presents a portable concentrator prototype design using the pressure/vacuum swing adsorption (PVSA) cycle with a deep evacuation step (−0.82 barg) instead of desorption with purge flow to simplify the oxygen production process. The output of the oxygen concentrator is a ~90 vol % enriched oxygen stream in a continuous adsorption and desorption cycle (cycle time ~90 s). The size of the adsorption column is 3 cm in diameter and 20 cm in length.
A Li+ exchanged 13X nanosize zeolite is used as the adsorbent to selectively adsorb nitrogen from air. A dynamic model of the pressure and vacuum swing adsorption units was developed to study the pressurization and depressurization process inside the microporous area of nanosized zeolites. The describing equations were solved using COMSOL Multiphysics Chemical Engineering module. The output flow rate and oxygen concentration results from the simulation model were compared with the experimental data. Velocity and concentration profiles were obtained to study the adsorption process and optimize the operational parameters.
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The long history of ammonia production at BASF started with the development of the process in the early 20th century by Fritz Haber and Carl Bosch. In September 1913 in Ludwigshafen, Germany the first plant went into service with a capacity of 30 t (66 000 lbs) ammonia per day. Today BASF operates two plants in Ludwigshafen (Ammonia 3: conventional steam reforming plant, 1971, Ammonia 4: Braun purifier
plant, 1982) and one plant in Antwerp/Belgium (Uhde design, 1990). From the early days until now the limitation of material degradation processes at high temperatures to a tolerable scale was always a demanding task for the maintenance and operating staff in the plants to assure a safe and economic ammonia production. Read More..by downloading : click the blue rectangle