Differences in Formation Mechanism of Static Pressure Circumferential Distribution of Centrifugal Compressor Under Different Operating Conditions

2021 ◽  
Author(s):  
Botai Su ◽  
Ce Yang ◽  
Hanzhi Zhang ◽  
Xin Shi ◽  
Li Fu
Keyword(s):  
Static Pressure ◽  
Operating Conditions ◽  
Single Peak ◽  
Double Peak ◽  
Flow Rates ◽  
Flow Balance ◽  
Impeller Outlet ◽  
Outlet Flow ◽  
Small Flow ◽  
Large Flow

Abstract The casing-wall static pressure of the centrifugal compressor behaves the double-peak distribution in the circumference at small flow rates but the single-peak distribution at large flow rates. A previous study shows that the double-peak distribution is induced by the redistribution of impeller outlet flow rates. In this paper, by using the similar simplified method of directly imposing pressure boundary to the diffuser outlet, the original reason for the formation process difference of pressure distribution in the circumference at different operating conditions is further investigated. The results show that at large flow rates, under the combined action of the specific downstream pressure distribution and the flow performance of the compressor itself, alternating low/high velocity airflow zones similar to those at small flow rates cannot be established in the diffuser when the impeller outlet flow rates are redistributed. Therefore, the static pressure can only express the single-peak distribution in the circumference. In fact, whether the static pressure exhibits the double-peak or single-peak distribution in the circumference depends on whether the impeller outlet flow mutation can destroy the original flow balance. When the flow mutation is dominant, the double-peak distribution is created, whereas when the original flow balance is prevailing, the single-peak distribution is formed.

Optimization of Inlet Ring Groove Arrangement for Suppression of Unstable Flow in a Centrifugal Impeller

2005 ◽  
Author(s):  
Masahiro Ishida ◽  
Daisaku Sakaguchi ◽  
Hironobu Ueki
Keyword(s):  
Flow Rate ◽  
The Other ◽  
Centrifugal Impeller ◽  
Shape Parameters ◽  
Unstable Flow ◽  
Ring Groove ◽  
Flow Rates ◽  
Small Flow ◽  
Specific Speed ◽  
Large Flow

An optimization of the inlet ring groove arrangement has been pursued in the present study for obtaining better impeller characteristics and a wider operation range at both small and large flow rates in a high specific speed type centrifugal impeller with inducer. The effects of the shape parameters with respect to the inlet ring groove on the impeller characteristic and the flow incidence were analyzed mainly based on numerical simulations, but also compared to the experimental results. At small flow rates, a significant improvement in the impeller characteristic is achieved due to reduction in the excessive-positive flow incidence by optimizing both location and width of the rear groove near the inducer tip throat. On the other hand, the impeller characteristic is improved at large flow rates by implementing the corner radius at the rear groove edge and by placing another front ring groove in the suction pipe. As a result, by the optimized configuration of the front and rear ring grooves, the unstable flow range of the test impeller can be reduced by about 50% without deterioration of the impeller characteristic even at the 125% flow rate.

Predicting the Rate of 222Rn Entry from Soil into the Basement of a Dwelling Due to Pressure-Driven Air Flow

1988 ◽  
Vol 24 (1-4) ◽  
pp. 199-202 ◽  
Author(s):  
W.W. Nazaroff
Keyword(s):  
Indoor Radon ◽  
Air Flow ◽  
Entry Rate ◽  
Flow Rates ◽  
Small Flow ◽  
Recommended Guidelines ◽  
Large Flow ◽  
226Ra Content ◽  
Soil Level ◽  
Pressure Driven

Abstract A combination of analytical and numerical methods is applied to the problem of computing 222Rn transport from soil into a dwelling having a basement. Transport is assumed to occur solely by pressure-driven air flow, and the basement shell is assumed to have a single dominant leak that is uniformly distributed around the perimeter at the level of the floor. The results show that for small flow rates of air through the soil, the radon entry rate into the basement increases in proportion to ?Po, the outdoor-indoor pressure difference at the soil level. For large flow rates, the entry rate increases only in proportion to ?Po2/3, due to depletion of radon concentration in the soil. A sample calculation indicates that via this transport mode, soil having ordinary 226Ra content and moderately high permeability can be responsible for indoor radon concentrations of the order of 500 Bq.m-3, greater than recommended guidelines for new housing.

scholarly journals Experimental Study on Effects of Adjustable Vaned Diffusers on Impeller Backside Cavity of Centrifugal Compressor in CAES

Energies ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 6187
Author(s):  
Zhihua Lin ◽  
Zhitao Zuo ◽  
Wenbin Guo ◽  
Jianting Sun ◽  
Qi Liang ◽  
...  
Keyword(s):  
Centrifugal Compressor ◽  
Static Pressure ◽  
Internal Flow ◽  
Operating Conditions ◽  
Test Facility ◽  
Angle Change ◽  
Temperature Loss ◽  
Impeller Outlet ◽  
Compressor Performance ◽  
Variable Operating Conditions

The impeller backside cavity (IBC) is a unique structure of centrifugal compressor in compressed air energy storage (CAES) systems, which affects the aerodynamic performance of centrifugal compressor, and the angle change of the downstream coupled adjustable vaned diffusers (AVDs) will affect the flow field inside the cavity and compressor performance. This paper relies on the closed test facility of the high-power intercooling compressor to measure static pressure and static temperature at different radii on the static wall of the IBC. The coupling relationship between the IBC and compressor under variable operating conditions is analyzed, and the influence of AVDs on the internal flow in IBC is studied. The results show that static pressure and static temperature rise along the direction of increasing radius, but static temperature drops near the coupling between the impeller outlet and the cavity inlet. Under AVDs’ design angle, static pressure and static temperature at each point, static pressure loss and static temperature loss in the direction of decreasing radius all increase as the flow decreases. Under variable AVDs’ angles, static pressure and static temperature will change differently, and respective loss will also be different.

scholarly journals An Experimental Study on the Fluid Forces Induced by Rotor-Stator Interaction in a Centrifugal Pump

2003 ◽  
Vol 9 (2) ◽  
pp. 135-144 ◽  
Author(s):  
Shijie Guo ◽  
Hidenobu Okamoto
Keyword(s):  
Centrifugal Pump ◽  
Static Pressure ◽  
Pressure Fluctuations ◽  
Strong Relationship ◽  
Operating Conditions ◽  
Flow Rates ◽  
Fluid Forces ◽  
Large Pressure ◽  
Rotor Stator Interaction ◽  
Frequency Components

The pressure fluctuations and the radial fluid forces acting on the impeller, the pressures in the volute, as well as the vibration of the shaft in a centrifugal pump were measured simultaneously, and their relationship was investigated. Experiments were done for various diffuser vanes, flow rates, and rotating speeds. It was demonstrated that both the blade-pressure fluctuations and the volute static pressures are nonuniform circumferentially (not axisymmetrical) under off-design operating conditions and that the two have a strong relationship. At high flow rates, the blade pressure fluctuations, induced by rotor-stator interactions, are large in areas where the volute static pressure is low. The traveling directions of the rotating pressure waves, the whirling directions of the radial fluid forces, and the most predominant frequency components of both the fluctuations and the forces are discussed, and an equation for predicting them is introduced. It was also noted that large alternating fluid forces are not necessarily associated with large pressure fluctuations. Furthermore, when measuring the radial fluid forces in the rotating frame, other frequency components, in addition to those related to the products of the diffuser vane number and the rotating frequency, may occur due to the circumferential unevenness of the pressure fluctuations on the impeller. These components are predictable.

Asymmetric Flow in Vaneless Diffusers of Centrifugal Blowers

1977 ◽  
Vol 99 (1) ◽  
pp. 104-111 ◽  
Author(s):  
Yasutoshi Senoo ◽  
Yoshifumi Kinoshita ◽  
Masahiro Ishida
Keyword(s):  
Reverse Flow ◽  
Flow Behavior ◽  
Maximum Velocity ◽  
Flow Rates ◽  
Velocity Flow ◽  
Special Relations ◽  
Small Flow ◽  
Vaneless Diffusers ◽  
Momentum Integral ◽  
Large Flow

An analytical method is proposed to evaluate the flow behavior in vaneless diffusers assuming that the flow is not symmetric between the walls. In the analysis momentum integral equations are used together with some special relations for the main flow or for the maximum velocity flow. According to the authors’ experiment, for the case of a small flow rate a reverse flow is observed on one wall near the inlet of the diffuser but at a larger radius the reverse flow disappears and another reverse flow is observed on the other wall. The predictions quantitatively agree well with experiments not only in the case of large flow rates but also in the case of small flow rates where the flow pattern is very complicated.

Improvements in Aerodynamic Performance and Noise Due to Low Solidity Cascade Diffuser in a Centrifugal Blower

2007 ◽  
Author(s):  
Daisaku Sakaguchi ◽  
Masahiro Ishida ◽  
Tengen Murakami ◽  
Hiroshi Hayami ◽  
Yasutoshi Senoo ◽  
...  
Keyword(s):  
Leading Edge ◽  
Aerodynamic Performance ◽  
Broadband Noise ◽  
Wake Flow ◽  
Frequency Noise ◽  
Vaneless Diffuser ◽  
Centrifugal Blower ◽  
Flow Rates ◽  
Small Flow ◽  
Large Flow

A high efficiency and a wide operating range are required in recent centrifugal compressors and blowers. Low solidity circular cascade diffuser (LSD) was proposed in place of vaned diffuser and channel diffuser for achieving both higher pressure ratio and wider operating range. In the present study, aerodynamic performance and noise characteristics of LSD were investigated changing a radial location of LSD leading-edge. It is known that an interaction occurs between jet-wake flow discharged from the rotating impeller and the LSD leading edge, however jet-wake flow pattern is almost uniformalized until the radial position of R = 1.20 in the vaneless diffuser. Aiming at reducing the noise generated by the interaction mentioned above, the LSD leading edge was moved from RLSD = 1.10 to 1.15 and 1.20 in a centrifugal blower with low specific speed. The frequency spectra of noise were analyzed and the noise due to LSD were discussed from the view point of overall noise, discrete frequency noise and broadband noise. In order to clarify the relationship between the flow field and the noise, flow behavior in the impeller as well as in the diffuser was simulated using a Navier-Stokes solver ANSYS-CFX. According to the present experimental results, about 40% improvement in diffuser performance and about 11% improvement in unstable flow range were achieved in small flow rates by the LSD compared with the vaneless diffuser except for a small deterioration in diffuser performance at the large flow rate. On the other hand, the noise increased clearly in the case of RLSD = 1.10 at the large flow rate and the small flow rates as well. By locating the LSD blade leading edge downstream farther from the impeller exit, a remarkable reduction in overall noise was achieved without deterioration of diffuser performance. It is found that the noise increase due to LSD is mainly dependent on the broadband noise based on the jet-wake flow, the interaction between the reverse flow and the impeller blades results in the discrete frequency noise defined by the frequency of cross product of the rotational speed of the impeller and the number of LSD blade, and a significant reduction in noise is achieved by uniformalization of the jet-wake flow.

Verified Accurate Performance Simulation Model of Direct Thermosyphon Solar Energy Water Heaters

1988 ◽  
Vol 110 (4) ◽  
pp. 282-292 ◽  
Author(s):  
P. A. Hobson ◽  
B. Norton
Keyword(s):  
Solar Energy ◽  
Operating Conditions ◽  
Test Facility ◽  
Flow Rates ◽  
Water Heaters ◽  
Accurate Performance ◽  
Small Flow ◽  
Energy Equations ◽  
Capacitance Effects ◽  
Friction Factor Correlation

A detailed analysis of the heat transfers and fluid flows within direct thermosyphonic solar energy water heaters has been undertaken. The collector energy equations were cast in a two-dimensional form in order that the heat transfer and thermal capacitance effects can be simulated accurately at the small flow rates encountered commonly in these buoyancy-driven systems. The use of an appropriate nonisothermal friction factor correlation when calculating energy losses in the collector’s riser pipes, produced predicted flow rates which were corroborated to within 2 percent by the values measured under steady flow conditions. For the laminar flow rates and the store configuration investigated, relaxation of the thermocline was shown to be dominated by axial conduction in the store walls. An indoor test facility, monitored and controlled by a microcomputer, enabled “real” operating conditions to be simulated. The predicted responses of the system to identical conditions showed good agreement with the corresponding experimental observations, the predicted heat delivery being within 2.8 percent of that measured.

Effect of Impeller Outlet Flow Affected by Casing Treatment on Rotating Stall in Vane-Less Diffuser in Centrifugal Turbomachinery

2018 ◽  
Author(s):  
Kazuhiro Tsukamoto ◽  
Shohei Suto ◽  
Kiyotaka Hiradate ◽  
Yasushi Shinkawa
Keyword(s):  
Static Pressure ◽  
Pressure Rise ◽  
Rotating Stall ◽  
The Other ◽  
Casing Treatment ◽  
Lower Flow ◽  
Operating Range ◽  
Other Hand ◽  
Impeller Outlet ◽  
Outlet Flow

The effect of impeller outlet flow affected by a recirculating casing treatment on rotating stall in a vane-less diffuser in centrifugal turbomachinery was investigated experimentally. Centrifugal compressors require higher efficiency and wider operating range. At lower flow rates, rotating stall sometimes occurs in a vane-less diffuser and generates significant subsynchronous vibrations, which often mark the limit of the operating curve of actual compressors. For this reason, the vibration and load on thrust and radial bearings should be reduced when rotating stall occurs. Many studies have investigated rotating stalls in vane-less diffusers in centrifugal turbomachinery. On the other hand, few studies have investigated how stall characteristics change when a casing treatment which is an effective means of expanding the operating range of the centrifugal compressor, is implemented. From this aspect, this research experimentally investigated the effect of the impeller outlet flow on rotating stall in a vane-less diffuser and evaluated the possibility of decreasing shaft vibration. Two different centrifugal impellers with the same recirculating casing treatment were investigated to examine the effect of the impeller outlet flow field. Impeller-A had a smaller exit blade angle with a higher deceleration ratio of impeller relative velocity from inlet to outlet. Impeller-B had a larger exit flow angle with a lower deceleration ratio. Both impellers had the same meridional geometry. Experimental results showed that both impellers obtained map width expansions for lower flow rate regions of more than 10% from the casing treatment. In the case of Impeller-A, the static pressure rise increased as a result of the casing treatment. However, the pressure fluctuations at the diffuser due to the rotating stall increased. On the other hand, in the case of Impeller-B, the static pressure rise increased at the vane-less diffuser instead of the impeller. In Impeller-B, the casing treatment decreased the pressure fluctuation at the diffuser due to the rotating stall and kept the static pressure rise with a negative slope. The results indicate that improving the outlet flow in cases such as Impeller-B may decrease the shaft oscillations due to rotating stall.

scholarly journals Pressure Fluctuation Characteristics of High-Speed Centrifugal Pump with Enlarged Flow Design

Processes ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 2261
Author(s):  
Jianyi Zhang ◽  
Hao Yang ◽  
Haibing Liu ◽  
Liang Xu ◽  
Yuwei Lv
Keyword(s):  
Centrifugal Pump ◽  
High Speed ◽  
Guide Vane ◽  
Pressure Fluctuations ◽  
Centrifugal Pumps ◽  
Flow Rates ◽  
Impeller Outlet ◽  
Low Specific Speed ◽  
Blade Frequency ◽  
Large Flow

The pressure fluctuations of high-speed centrifugal pumps are the hotspot in pump research. Pressure fluctuations is differ for different structural designs and flow structures. High-speed centrifugal pumps are usually designed to increase efficiency with an enlarged flow design at a low specific speed, which changes the structure of the pump. In order to analyze the pressure fluctuations of a high-speed centrifugal pump with an enlarged flow design, the pressure was measured, and the flow field of the pump was simulated with different flow rates. Through analysis, we found that pressure fluctuations varied periodically and was consistent with the blade frequency. The pressure fluctuations at the guide vane and the interference region were also closely related to the vortices at the impeller outlet, which changed differently at different flow rates. The results showed that the high-speed centrifugal pump with an enlarged design had better performance at a large flow rate. The results in this paper can provide reference for the design of a pump that should be designed with the enlarged flow method.

Formation mechanism of static pressure circumferential double-peak distribution in a centrifugal compressor under the action of downstream boundary

2021 ◽  
pp. 095440702098307
Author(s):  
Botai Su ◽  
Ce Yang ◽  
Hanzhi Zhang ◽  
Xin Shi ◽  
Li Fu ◽  
...  
Keyword(s):  
Flow Field ◽  
Pressure Distribution ◽  
Mass Flow Rate ◽  
Formation Mechanism ◽  
Flow Rate ◽  
Centrifugal Compressor ◽  
Static Pressure ◽  
Double Peak ◽  
Static Pressure Distribution ◽  
Impeller Outlet

In the centrifugal compressor applied in the automobile turbochargers, the asymmetric structure of volute causes the non-uniform flow field in the impeller and compressor stall. The non-uniformity of the flow field in the compressor can be reflected by the casing-wall static pressure distribution. In this study, by removing the volute and directly imposing different simplified static pressure boundary conditions at the diffuser outlet, the formation mechanism of casing-wall static pressure circumferential double-peak distribution of the compressor is explored. It is found that the mass flow rate is redistributed at the impeller outlet due to local high static pressure induced by the volute tongue, which results in the formation of two airflow regions with high velocity in the diffuser, ultimately leading to the static pressure circumferential double-peak distribution in the diffuser and the impeller. Noted that because of the existence of the blades, the airflow regions with high and low velocity formed in the diffuser are locked within a limited range of one or more widths of the blade passage. When the number of blades in the compressor is large, the static pressure can appear as multi-peak distribution in the circumferential direction. Moreover, the result of the mass flow rate redistribution at the impeller outlet is determined by the static pressure distribution characteristics at the diffuser outlet.

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