Mathematical modelling and experimental validation of electrostatic sensors for rotational speed measurement

Recent research has demonstrated that electrostatic sensors can be applied to the measurement of rotational speed with excellent repeatability and accuracy under a range of conditions. However, the sensing mechanism and fundamental characteristics of the electrostatic sensors are still largely unknown and hence the design of the sensors is not optimised for rotational speed measurement. This paper presents the mathematical modelling of strip electrostatic sensors for rotational speed measurement and associated experimental studies for the validation of the modelling results. In the modelling, an ideal point charge on the surface of the rotating object is regarded as an impulse input to the sensing system. The fundamental characteristics of the sensor, including spatial sensitivity, spatial filtering length and signal bandwidth, are quantified from the developed model. The effects of the geometric dimensions of the electrode, the distance between the electrode and the rotor surface and the rotational speed being measured on the performance of the sensor are analyzed. A close agreement between the modelling results and experimental measurements has been observed under a range of conditions. Optimal design of the electrostatic sensor for a given rotor size is suggested and discussed in accordance with the modelling and experimental results

Comparative study of subsynchronous rotating flow patterns in centrifugal compressors with vaneless diffusers

A comparative experimental investigation of the unstable operating modes of a centrifugal compressor was made. Impeller and/or diffuser rotating stall was observed, depending on the flow conditions. The measured relative rotational speed of this perturbation is cross checked with other experimental data and it is shown that the rotational speed is strongly dependent on the type of rotating stall. The diffuser absolute inlet flow angle at the onset of diffuser rotating stall agrees well with the value predicted by an existing stability criterion

Optimization of Rotational Speed for Casting Al-Si Alloy Using Centrifugal Casting

An alloy is a material that has metallic properties and is formed by combination of two or more chemical elements of which at least one is a metal. Commonly, alloys have different properties from those of the component elements.In recent years aluminium alloys are widely used in automotive industries. This is particularly due to the real need to weight saving for more reduction of fuel consumption. The typical alloying elements are copper, magnesium, manganese, silicon, and zinc.Aluminium-Silicon alloys are of greater importance to engineering industries as they exhibit high strength to weight ratio, high wear resistance, low density, low coefficient of thermal expansion etc. Silicon imparts high fluidity and low shrinkage, which result in good cast ability and weldability.nbs

Fluidization of Group B particles with a rotating distributor

A novel rotating distributor fluidized bed is presented. The distributor is a rotating perforated plate, with 1% open-area ratio. This work evaluates the performance of this new design, considering pressure drop, Δp, and quality of fluidization. Bed fluidization was easily achieved with the proposed device, improving the solid mixing and the quality of fluidization. In order to examine the effect of the rotational speed of the distributor plate on the hydrodynamic behavior of the bed, minimum fluidization velocity, Umf, and pressure fluctuations were analyzed. Experiments were conducted in the bubbling free regime in a 0.19 m i.d. fluidized bed, operating with Group B particles according to Geldart's classification. The pressure drop across the bed and the standard deviation of pressure fluctuations, σp, were used to find the minimum fluidization velocity, Umf. A decrease in Umf is observed when the rotational speed increases and a rise in the measured pressure drop was also found. Frequency analysis of pressure fluctuations shows that fluidization can be controlled by the adjustable rotational speed, at several excess gas velocities. Measurements with several initial static bed heights were taken, in order to analyze the influence of the initial bed mass inventory, over the effect of the distributor rotation on the bed hydrodynamics.Publicad

Rotational speed control

Viewgraphs on rotational speed control are presented. The Centrifuge Facility Systems Study - 2.5 m centrifuge is shown. A life sciences centrifuge is scheduled to fly aboard Space Station Freedom. Live animal and plant specimens will be carried on the rotor and compared with microgravity specimens in racks

Pemodelan Daya Pengadukan Selama Proses Dehidrasi Osmotik Irisan Mangga dalam Larutan Gula

This study discusses mathematical model of agitation power due to the change of sugar solution concentration during the process of mango slices osmotic dehydration. The sugar solution agitation was performed in several levels of rotational speed to correlate the power number with the Reynolds number. Then, the obtained model was used to calculate the power consumption for various temperature and initial rotational speed of shaft. The results showed that the correlation can be used for various conditions of shaft rotational speed and solution concentration. Osmotic dehydration for 8 hours at conditions of 30-50OC with rotational speed of 143-525 rpm results in solution dilution from 61OBx to 50.5-52.5OBx. Temperature of 30OC with initial shaft rotational speed of 500 rpm results in power consumption ten times higher than that of 50OC and 148 rpm. Moreover, power consumption reduction up to 80% of initial energy consumption due to the dilution of the sugar solution during the osmotic dehydration process was obtained

Design concept to decrease relative speed of ball bearings

Intermediate ring decreases the rolling speed of a ball bearing relative to the rotational speed of the shaft. It has raceways on its inner and outer peripheries and an additional row of balls. The modification permits operation at much higher shaft speeds than usual

Stability in High-Speed Floating Bush Journal Bearings at Low Supplied Pressure (Part 1) : Effect of Oil Groove and Holes into Inner Oil Film and Slope at Bush Inner Side End on Stability

Floating bush journal bearings are widely used to support small-sized high-speed rotating machinery. When　the supplied pressure is low, the bearing shows peculiar phenomena. As the shaft rotational speed increases, the bush rotational speed levels off and the disappearance of the oil whip is observed. They can be explained qualitatively by applying the hydrodynamic lubrication model with the axial oil film rupture being considered. However, the predictions are in quantitatively poor agreement with the measurements. This experimental report shows the effect of the circumferential oil groove and holes into the inner oil film and the slope of the bush inner side end, which are not considered in the theoretical model, on the bush rotational speed and the high-speed stability. It is found that the bush rotational speed levels off at a lower shaft rotational speed, resulting in the lower bush speed, and that the oil whip disappears at a lower shaft speed, when the supplied pressure is lower. The groove, the driving torque of which cannot be negligible, lowers the bush rotational speed and heightens largely the stability in high-speed region. The effect of the hole, the geometry in the groove and the slope is small

Pengaruh Bentuk Baling-Baling Terhadap Kecepatan Putar Sebagai Media Pembelajaran

ABSTRACTAnemometer propellers have many forms, but there is no data yet to show the difference between propeller and rotational speed. So the purpose of this study is to determine the difference in rotational speed based on the shape of the anemometer propeller.The research method used was experimental research. The experiments were carried out using fan blades, scissors, a quarter cup, and a turbine. Data analysis used the formula of rotational speed, accuracy, and error during the experiment.The results showed that each form of the propeller on the anemometer produced a different rotational speed. The shape of the propeller that produces the greatest speed is obtained from the shape of a quarter cup propeller with an estimated speed. The results of the study are used as learning resources in the form of posters. The poster created has been tested for eligibility by the design validator and material validtor. Keywords: Propeller, Rotational Speed