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David Mills - One of the best experts on this subject based on the ideXlab platform.

  • Air-Only Relationships
    Pneumatic Conveying Design Guide, 2015
    Co-Authors: David Mills
    Abstract:

    Air supply and exhaust or venting pipelines can be of a considerable length with some systems, whether for positive pressure or vacuum systems, particularly if the air mover or the filtration plant is remote from the conveying system. In such cases, the evaluation of the air only pressure drop values in these pipeline sections is important, for they could represent a large proportion of the available pressure drop if they are not sized correctly. Airflow control is also important, particularly if plant air is used for a conveying system, or if the air supply to a system needs to be proportioned between that delivered to a blow tank and that directed to the pipeline. In addition, the pressure drop in the empty pipeline is a major consideration in the design of a pneumatic conveying system. If a positive Displacement Blower is used in combination with a long distance, small bore pipeline, for the suspension flow of a material, it is quite possible that the entire pressure drop would be utilized in blowing the air through the pipeline and that no material would be conveyed. The pressure drop for air only in a pipeline is significantly influenced by the air velocity that is required for the conveying of the material.

  • chapter 12 conveying capability
    Pneumatic Conveying Design Guide (Second Edition), 2004
    Co-Authors: David Mills
    Abstract:

    Publisher Summary The conveying characteristics for different materials vary significantly. This is particularly so for the materials capable of being conveyed in dense phase. At low values of airflow rate, the lines of constant conveying line pressure drop can have a wide variety of slopes. There is also the added complexity of different materials having different minimum conveying limits. Thus, for a given air flow rate and conveying line pressure drop, material flow rates for different materials vary considerably, and the air flow rate necessary to convey different materials can also vary considerably. If only low-pressure air is available for conveying a material through a pipeline, such as that from a positive Displacement Blower or a vacuum system, and below about I bar gauge, a material will only be conveyed in dilute phase through a pipeline, unless the conveying distance is very short. This chapter presents conveying data for four different materials.

  • Chapter 10 – Air only relationships
    Pneumatic Conveying Design Guide, 2004
    Co-Authors: David Mills
    Abstract:

    Publisher Summary Air supply and exhaust or venting pipelines can be of a considerable length with some systems, whether for positive pressure or vacuum systems, particularly if the air mover or the filtration plant is remote from the conveying system. In such cases, the evaluation of the air only pressure drop values in these pipeline sections is important, for they could represent a large proportion of the available pressure drop if they are not sized correctly. Airflow control is also important, particularly if plant air is used for a conveying system, or if the air supply to a system needs to be proportioned between that delivered to a blow tank and that directed to the pipeline. In addition, the pressure drop in the empty pipeline is a major consideration in the design of a pneumatic conveying system. If a positive Displacement Blower is used in combination with a long distance, small bore pipeline, for the suspension flow of a material, it is quite possible that the entire pressure drop would be utilized in blowing the air through the pipeline and that no material would be conveyed. The pressure drop for air only in a pipeline is significantly influenced by the air velocity that is required for the conveying of the material.

  • Chapter 12 – Conveying capability
    Pneumatic Conveying Design Guide, 2004
    Co-Authors: David Mills
    Abstract:

    Publisher Summary The conveying characteristics for different materials vary significantly. This is particularly so for the materials capable of being conveyed in dense phase. At low values of airflow rate, the lines of constant conveying line pressure drop can have a wide variety of slopes. There is also the added complexity of different materials having different minimum conveying limits. Thus, for a given air flow rate and conveying line pressure drop, material flow rates for different materials vary considerably, and the air flow rate necessary to convey different materials can also vary considerably. If only low-pressure air is available for conveying a material through a pipeline, such as that from a positive Displacement Blower or a vacuum system, and below about I bar gauge, a material will only be conveyed in dilute phase through a pipeline, unless the conveying distance is very short. This chapter presents conveying data for four different materials.

  • Case studies Part II: Coarse material
    Pneumatic Conveying Design Guide, 2004
    Co-Authors: David Mills
    Abstract:

    This chapter discusses a case study where a material has been chosen that has no natural dense phase conveying capability and so can only be conveyed in dilute phase suspension flow in a conventional pneumatic conveying system. The magnesium sulphate had a mean particle size of about 225 μm and so de-aerated very rapidly. The bulk density of the material was about l 010 kg/m 3 and the particle density 2350 kg/m 3 . As with dense phase conveying, the minimum conveying air velocity for a material is a critical design parameter; however, unlike dense phase conveying, there is no significant change in its value with solids loading ratio. To illustrate the scaling process for system design with regard to dilute phase conveying, the magnesium sulphate is used. It is suggested that a design should be considered for the conveying of the magnesium sulphate over a horizontal distance of 300m at a rate of 15 tonne/h and that a positive Displacement Blower having a I bar gauge delivery pressure capability should be used.

H. Johannes Pöpel - One of the best experts on this subject based on the ideXlab platform.

  • Oxygen transfer and aeration efficiency - influence of diffuser submergence, diffuser density, and Blower type
    Water Science and Technology, 1998
    Co-Authors: Martin R. Wagner, H. Johannes Pöpel
    Abstract:

    The main factors of fine bubble aeration systems in uniform arrangement in clean water are the air flow rate, the depth of submergence of the diffusers, and the diffuser density. While the influence of the air flow rate on the oxygen transfer parameters is known, knowledge of the influence of the depth of submergence and the diffuser density on the specific oxygen transfer efficiency SOTE [%/m] and on the specific oxygen absorption SOA [g/m3·m at STP] is very limited. Both parameters are of great importance in dimensioning fine bubble aeration systems. Therefore, a literature review was conducted to show the influence of the diffuser submergence and density and the type of Blower on oxygen transfer and aeration efficiency. The main review results are, that higher values of specific oxygen absorption can be obtained at higher diffuser density; secondly, the volumetric oxygen transfer rate VOTR [g/m3·h] is higher with increasing depth of submergence at the same air flow rate. Also it can be stated that with greater depth of submergence the specific oxygen absorption [g/m3·m at STP] is reduced. Dependent on the air flow rate and the pressure head, the energy consumption [Wh/m3·m at STP] of the Blowers used in wastewater treatment plants is different. For example, the energy consumption varies from 4.3 [Wh/m3·m at STP] (positive Displacement Blower) to 3.0 [Wh/m3·m at STP] (turbo-compressors) at a pressure of 10 m and an air flow rate of 5,000 m3/h at STP. From the results of the literature review the following conclusions can be drawn: (1) High specific oxygen absorption values (SOA) [g/m3·m at STP] can be achieved applying shallow tanks, high diffuser densities and low specific air flow rates; (2) High aeration efficiencies (AE) [kg/kWh] can be obtained by applying high volumetric oxygen transfer rates and adequate selection of the Blowers used at the wastewater treatment plants.

  • Oxygen transfer and aeration efficiency — Influence of diffuser submergence, diffuser density, and Blower type
    Water Science and Technology, 1998
    Co-Authors: Martin Wagner, H. Johannes Pöpel
    Abstract:

    The main factors of fine bubble aeration systems in uniform arrangement in clean water are the air flow rate, the depth of submergence of the diffusers, and the diffuser density. While the influence of the air flow rate on the oxygen transfer parameters is known, knowledge of the influence of the depth of submergence and the diffuser density on the specific oxygen transfer efficiency SOTE [%/m] and on the specific oxygen absorption SOA [g/m 3 ·m at STP] is very limited. Both parameters are of great importance in dimensioning fine bubble aeration systems. Therefore, a literature review was conducted to show the influence of the diffuser submergence and density and the type of Blower on oxygen transfer and aeration efficiency. The main review results are, that higher values of specific oxygen absorption can be obtained at higher diffuser density; secondly, the volumetric oxygen transfer rate VOTR [g/m 3 ·h] is higher with increasing depth of submergence at the same air flow rate. Also it can be stated that with greater depth of submergence the specific oxygen absorption [g/ m 3·m at STP] is reduced. Dependent on the air flow rate and the pressure head, the energy consumption [Wh/m 3 ·m at STP] of the Blowers used in wastewater treatment plants is different. For example, the energy consumption varies from 4.3 [Wh/m 3 ·m at STP] (positive Displacement Blower) to 3.0 [Wh/m 3 ·m at STP] (turbo-compressors) at a pressure of 10 m and an air flow rate of 5,000 m 3 /h at STP. From the results of the literature review the following conclusions can be drawn: (1) High specific oxygen absorption values (SOA) [g/m 3 ·m at STP] can be achieved applying shallow tanks, high diffuser densities and low specific air flow rates; (2) High aeration efficiencies (AE) [kg/kWh] can be obtained by applying high volumetric oxygen transfer rates and adequate selection of the Blowers used at the wastewater treatment plants.

Paolo Pennacchi - One of the best experts on this subject based on the ideXlab platform.

  • Analytical model of a particular type of positive Displacement Blower
    Proceedings of the Institution of Mechanical Engineers Part C: Journal of Mechanical Engineering Science, 1999
    Co-Authors: Giovanni Mimmi, Paolo Pennacchi
    Abstract:

    AbstractMany papers exist in the literature that deal with the twin-screw compressor. This usually has two different rotors, a male and a female, and is commonly used to produce compressed gas for ...

  • Analytical Model of a Particular Type of Positive Displacement Blower
    Professional Engineering Publications:PO Box 24 Northgate Avenue Bury St. Edmunds IP32 6BW United Kingdom:011 44 1284 718681 011 44 1284 724384 EMAIL:, 1999
    Co-Authors: Mimmi G, Paolo Pennacchi
    Abstract:

    Many papers exist in literature which deal with the twin screw compressor; this usually has two different rotors, a male and a female, and is commonly used to produce compressed gas for industrial uses. However, a different type of positive Displacement rotary compressor with two screws is sometimes used; one of its typical applications is in car engine supercharging. Present paper deals with the latter type, which is defined as a two screw Blower. This Blower has two identical helical rotors, each with three lobes. The kinematics and the geometry of the rotors are analysed here, and a complete mathematical model for the rotor is defined. Moreover different possible shapes of the rotors, depending on the design parameters, are analysed and the limitations in the choice of the design parameters are presented. Finally an analysis of the theoretical specific slipping of the rotors is presented, showing which zones of the profile are the most stressed. This model will be useful for further studies on rotor pressure loads and Blower dynamics

Xiaomin Liu - One of the best experts on this subject based on the ideXlab platform.

  • Unsteady flow simulations in a three-lobe positive Displacement Blower
    Chinese Journal of Mechanical Engineering, 2014
    Co-Authors: Xiaomin Liu
    Abstract:

    To improve the performance of the positive Displacement Blower, it is imperative to understand the detailed internal flow characteristics or enable a visualization of flow status. However, the existing two-dimensional unsteady, three-dimensional steady or quasi-unsteady numerical simulation and theoretical analysis cannot provide the detailed flow information, which is unfavorable to improve the performance of positive Displacement Blower. Therefore, the unsteady flow characteristics in a three-lobe positive Displacement Blower are numerically investigated by solving the three-dimensional, unsteady, compressible Navier-Stokes equations coupled with RNG k-ɛ turbulent model. In the numerical simulation, the dynamic mesh technique and overset mesh updating method are adopted. Due to the air being compressed in the process of the rotors rotating, the variation of the temperature field in the positive Displacement Blower is considered. By comparing the experimental measurements and the numerical results on the variation of flow rate with the outlet pressure, the maximum relative error of the flow rate is less than 2.15% even at the maximum outlet pressure condition, which means that the calculation model and numerical computational method used are effective. The numerical results show that in the intake region, the fluctuations of the inlet flow are greatly affected by the direction of the velocity vectors. In the exhaust region, the temperature changes significantly, which leads to the increase of the airflow pulsation. Through analysis on the velocity, pressure and temperature fields obtained from the numerical simulations, three-dimensional unsteady flow characteristics in the positive Displacement Blower are revealed. The studied results will provide useful reference for improving the performance and empirical correction in the design of the positive Displacement Blower.

  • Numerical investigation of the aerodynamic performance affected by spiral inlet and outlet in a positive Displacement Blower
    Chinese Journal of Mechanical Engineering, 2013
    Co-Authors: Xiaomin Liu, Renheng Gao
    Abstract:

    The flow in the positive Displacement Blower is very complex. The existing two-dimensional numerical simulation cannot provide the detailed flow information, especially flow characteristics along the axial direction, which is unfavorable to improve the performance of positive Displacement Blower. To investigate the effects of spiral inlet and outlet on the aerodynamic performance of positive Displacement Blower, three-dimensional unsteady flow characteristics in a three-lobe positive Displacement Blower with and without the spiral inlet and outlet are simulated by solving Navier-Stokes equations coupled with RNG k-ɛ turbulent model. In the numerical simulation, the dynamic mesh technique and overset mesh updating method are used. The computational results are compared with the experimental measurements on the variation of flow rate with the outlet pressure to verify the validity of the numerical method presented. The results show that the mass flow rate with the change of pressure is slightly affected by the application of spiral inlet and outlet, but the internal flow state is largely affected. In the exhaust region, the fluctuations of pressure, velocity and temperature as well as the average values of velocity are significantly reduced. This illustrates that the spiral outlet can effectively suppress the fluctuations of pressure, thus reducing reflux shock and energy dissipation. In the intake area, the average value of pressure, velocity and temperature are slightly declined, but the fluctuations of them are significantly reduced, indicating that the spiral inlet plays the role in making the flow more stable. The numerical results obtained reveal the three-dimensional flow characteristics of the positive Displacement Blower with spiral inlet and outlet, and provide useful reference to improve performance and empirical correction in the noise-reduction design of the positive Displacement Blowers.

Martin Wagner - One of the best experts on this subject based on the ideXlab platform.

  • Oxygen transfer and aeration efficiency — Influence of diffuser submergence, diffuser density, and Blower type
    Water Science and Technology, 1998
    Co-Authors: Martin Wagner, H. Johannes Pöpel
    Abstract:

    The main factors of fine bubble aeration systems in uniform arrangement in clean water are the air flow rate, the depth of submergence of the diffusers, and the diffuser density. While the influence of the air flow rate on the oxygen transfer parameters is known, knowledge of the influence of the depth of submergence and the diffuser density on the specific oxygen transfer efficiency SOTE [%/m] and on the specific oxygen absorption SOA [g/m 3 ·m at STP] is very limited. Both parameters are of great importance in dimensioning fine bubble aeration systems. Therefore, a literature review was conducted to show the influence of the diffuser submergence and density and the type of Blower on oxygen transfer and aeration efficiency. The main review results are, that higher values of specific oxygen absorption can be obtained at higher diffuser density; secondly, the volumetric oxygen transfer rate VOTR [g/m 3 ·h] is higher with increasing depth of submergence at the same air flow rate. Also it can be stated that with greater depth of submergence the specific oxygen absorption [g/ m 3·m at STP] is reduced. Dependent on the air flow rate and the pressure head, the energy consumption [Wh/m 3 ·m at STP] of the Blowers used in wastewater treatment plants is different. For example, the energy consumption varies from 4.3 [Wh/m 3 ·m at STP] (positive Displacement Blower) to 3.0 [Wh/m 3 ·m at STP] (turbo-compressors) at a pressure of 10 m and an air flow rate of 5,000 m 3 /h at STP. From the results of the literature review the following conclusions can be drawn: (1) High specific oxygen absorption values (SOA) [g/m 3 ·m at STP] can be achieved applying shallow tanks, high diffuser densities and low specific air flow rates; (2) High aeration efficiencies (AE) [kg/kWh] can be obtained by applying high volumetric oxygen transfer rates and adequate selection of the Blowers used at the wastewater treatment plants.