The noise generated by vacuum cleaners is one of the dominant noise sources among household appliances with its suction unit as the key element of noise generation. The dominant noise source in the ...suction unit is its impeller, and that is why there were numerous efforts made to reduce its noise. The years of its optimization have consequently led to a stage, where the possibilities for further noise level reduction are limited. Because human perception of noise is not only influenced by sound pressure levels, it is possible to alter the sound of the impeller to be less annoying to the user. A new centrifugal impeller design was optimized for sound quality, resulting in triangular-shaped flow channels. The optimization process of impeller geometry was based on the sound quality calculated from measured psychoacoustic metrics using two noise annoyance models, Guoqing’s and Lipar’s. The validation of the result was performed by listening tests. Forty individuals participated in the listening tests of the suction units tested and rated the sounds using two sets of semantic differentials. The first set was used to evaluate the sound quality of the impeller, while the second set was used for the validation of these listening tests by evaluating psychoacoustic metrics. Validation results confirm that Lipar’s model of noise annoyance is suitable for evaluating centrifugal blower impeller noise. The subjective evaluation of psychoacoustic metrics, via listening tests of impeller noise, suggests that fluctuation strength and tonality are important features for the sound quality of impeller noise.
Temporal flow characteristics of a 3D centrifugal impeller suction system were numerically studied in vacuum conditions. The blockage of the high-speed rotating impeller appeared, which greatly ...dropped the suction of the layer suction device. The temporal flow characteristics of the 3D centrifugal impeller suction system were worthy of attention in vacuum conditions. Separation vortices were generated near the blade suction surface. The blocking mechanism of the passage was further analyzed at different extremely low flow rates through the time-space evolution of the streamline. The Q-criteria was introduced to analyze the vortex evolution within the fluid domain of the impeller. Vortex evolution law was captured—the vortices always generated near the suction surface of the blade and moved to the pressure surface of the adjacent blade in the same passage and disappeared. The uniform distribution of three stall cells was captured through the diagram of turbulent kinetic energy. The flow rate increased, and the vortex evolution period gradually decreased. The comparison of pressure fluctuations in different conditions further demonstrated the flow mechanism at the vacuum flow rate was different from that at low flow rates. The sharp increase of pressure fluctuations near the blade pressure surface was consistent with the phenomenon near the suction surface. The pressure fluctuation at extremely low flow was mainly composed of scattered fluctuations caused by fluid separation. The steady and unsteady characteristics described the internal flow characteristics of this suction system at vacuum-flow rates. Theresults provide a profound design for vacuum cleaners.
The steady and unsteady characteristics of the internal flow in a high-speed centrifugal blower are studied by computational fluid dynamics (CFD) approach at low flow rates. It is demonstrated that ...as the flow rate decreases, the separation of flow in the blade passage becomes serious, and separated vortexes always occur on the suction surface of the blade which gradually expand and block the passage. The stall cells move downstream and generate vortices at the exit of the passage, resulting serious loss to the performance of the blower. Q-criteria is used to analyze the flow field and explore the evolution of the vortex structure in the impeller. It is further found that strong pressure fluctuations are caused by the rotating stall in the impeller. At the stall conditions, the instability characteristics are particularly obvious. At flow rates of 0.65Qn and 0.47Qn, the pressure fluctuation in the blade passage is dominated by the blade passing frequency, while a lower frequency dominates at 0.26Qn. Moreover, the flow on the suction surface of impeller blades fluctuates substantially. The characteristics of steady flow and unsteady flow can clearly explain the internal flow of centrifugal blower for vacuum cleaners at low-flow conditions, which can be widely used in various engineering designs of vacuum cleaners.
Safety and trouble-free operation are important factors that places aviation among the safest forms of transport. These parameters are achieved mainly by state-of-the-art diagnostic and maintenance ...programs and methods, which are constantly evolving and increasing their efficiency. The manuscript is focused on the use of a centrifugal blower, on which fault states were artificially simulated and subsequently analyzed by statistical methods not normally used in the field of vibrodiagnostics. The use of principal component analysis (PCA) method played a key role in evaluating the vibrodiagnostic signal of the measured device. The PCA method enabled the categorization of fault conditions and provided a unique view of diagnostic methods with reference to specific signals. The results of the presented research indicate the potential of the PCA method in practice and in the need to carry out further research for other fault conditions. The implementation of such a tool is a prerequisite for more effective determination of specific fault conditions and the use of the PCA method in vibrodiagnostics not only in aviation but also in general industry.
► A sequential intelligent diagnosis method for bearing faults is proposed by possibility theory and a fuzzy neural network. ► Non-dimensional symptom parameters are defined in the frequency domain ...with vibration signals. ► Possibility theory and the Mycin certainty factor are used to process the ambiguous relationship between symptoms and fault types. ► Fault types can be identified sequentially and automatically.
This paper presents an intelligent diagnosis method for a rolling element bearing; the method is constructed on the basis of possibility theory and a fuzzy neural network with frequency-domain features of vibration signals. A sequential diagnosis technique is also proposed through which the fuzzy neural network realized by the partially-linearized neural network (PNN) can sequentially identify fault types. Possibility theory and the Mycin certainty factor are used to process the ambiguous relationship between symptoms and fault types. Non-dimensional symptom parameters are also defined in the frequency domain, which can reflect the characteristics of vibration signals. The PNN can sequentially and automatically distinguish fault types for a rolling bearing with high accuracy, on the basis of the possibilities of the symptom parameters. Practical examples of diagnosis for a bearing used in a centrifugal blower are given to show that bearing faults can be precisely identified by the proposed method.
Experimental and numerical investigations to study the effect of add one slot to the impeller blades on the rotating stall and pressure fluctuations in a high speed centrifugal blower. The ...experimental test rig which includes a blower of centrifugal, transducer of pressure as well measurement instrumentations which constructed for this study. A data acquisition system (hardware) and its (software) have been developed to transfer the signal from transducer of pressure to the computer then analysis with time. The experimental work has been implemented through measuring the static pressure variation as well fluctuating of pressure for two cases of impeller (without slot and with one slot). Static pressure has been taken in different points prepared on the front-wall of the volute casing along one track for two cases of the impeller. This track is angular track about the impeller. The results of experimental show that the fluctuations of pressure increase with the mass flow rate decrease. Also the results indicate that fluctuations of pressure decrease with adding slots into the impeller blades. The simulation of numerical has been carried out on blower of centrifugal into analysis both field of flow and fluctuations of pressure through using ANSYS (FLUENT 15). The simulation of numerical has been completed through solve the continuity and momentum equations with moving reference framework technique inside the blower. The numerical simulation results show a good agreement with the results of experimental.
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•An attempt made to explore energy efficient volute for industrial blowers.•Parallel wall volutes assessed for aerodynamic performance against rectangular.•Increased efficiency of 6% ...achieved with R 4.0 parallel wall volute.•Parallel wall volutes can be an efficient and effective alternative.
In this article, parallel wall volutes are proposed as an alternate and energy efficient volute to the commonly used rectangular volute for an industrial centrifugal blower. A detailed comparison of performance between parallel wall and rectangular volute are made for four different width ratios. The stage performance analysis suggests that the parallel wall volutes perform better in terms of both specific work developed and total-total isentropic efficiency. From component performance assessment, parallel wall volutes found to have higher static pressure recovery and lower loss for the full operating range considered. The flow field reveals that the parallel wall volute shows more uniform static pressure distribution at the volute inlet compared with the rectangular volute. The detailed aerodynamic performance analysis reveals that the overall performance of a centrifugal blower can be improved up to 6% with parallel wall volute. Moreover, it is demonstrated that the rectangular volute can be replaced with parallel wall volute without modifying foundation, inlet and outlet duct.
Experimental and numerical investigations to study the effect of adding one slot to the impeller blades on the rotating stall and pressure fluctuations in a high-speed centrifugal blower. The ...experimental test rig includes a blower of the centrifugal, transducer of pressure as well measurement instrumentations which were constructed for this study. A data acquisition system (hardware) and its (software) have been developed to transfer the signal from the transducer of pressure to the computer then analysis with time. The experimental work has been implemented by measuring the static pressure variation as well fluctuating of pressure for two cases of impeller (without slot and with one slot). Static pressure has been taken in different points prepared on the front wall of the volute casing along one track for two cases of the impeller. This track is an angular track about the impeller. The results of the experiment show that the fluctuations of pressure increase with the mass flow rate decrease. Also, the results indicate that fluctuations of pressure decrease with adding slots into the impeller blades. The simulation of numerical has been carried out on blower of centrifugal into analysis both field of flow and fluctuations of pressure through using ANSYS (FLUENT 15). The simulation of numerical has been completed through solve the continuity and momentum equations with the moving reference framework technique inside the blower. The numerical simulation results show a good agreement with the results of the experiments.
•Validated simulation model is opted for optimization of volute by Taguchi method and ANOVA.•Optimized volute is analyzed and compared with original volute by experimental analysis.•Experimental ...analysis suggest better performance of optimized volute compared to original.
The performance of centrifugal blower is enhanced with an optimization process on the blower volute using Taguchi method and ANOVA approach. The important geometrical parameters of volute are prioritized by applying first level of analytic hierarchy process. The analytic hierarchy process (AHP) is a structured technique for organizing and analyzing complex decisions, based on mathematics and psychology. Based on review of literatures, three levels are defined for each geometrical parameter. Reduction in the percentage variation of static pressure at impeller outlet, minimization of losses inside volute and maximization of stagnation pressure at volute outlet are selected as quality characteristics to ensure the enhancement of centrifugal blower performance. In this process, numerical simulation of 3-D flow in single stage centrifugal blower volute is carried out by FLUENT software for matrix experiments. These matrix experiments are suggested by Minitab software. The simulation case is carried out by flow, turbulence and Energy equations using SIMPLE pressure–velocity coupling. Standard discretisation method is used to solve pressure whereas; others are solved by second order upwind discretisation method. The realizable k–ε is adapted as turbulence model. Stator–rotor interactions are defined by means of mixing plane model of multiple rotating reference frames. Impeller is situated in rotating reference frame whereas; volute is in fixed reference frame. The process reveals that optimization of the original geometry of blower, at 1.5 times width of impeller, 24° tongue angle and 10% reduction in volute outer radial locations, pressure head and flow uniformity increases compared to other cases; this improvement takes place due to reduction in the non-uniformity of flow at impeller outlet and losses inside the volute passages. The experimental performance of optimized configuration is carried out and compared with existing centrifugal blower. The result indicates better performance in case of optimized volute than original configuration of volute. In case of optimized centrifugal blower, 7.4% higher efficiency is observed at the design rated speed compared to existing centrifugal blower.
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