Application of a Low-Solidity Cascade Diffuser to Transonic Centrifugal Compressor

1990 ◽  
Vol 112 (1) ◽  
pp. 25-29 ◽  
Author(s):  
H. Hayami ◽  
Y. Senoo ◽  
K. Utsunomiya
Keyword(s):  
Centrifugal Compressor ◽  
Performance Test ◽  
Pressure Ratio ◽  
Test Results ◽  
Vaneless Diffuser ◽  
Circular Arc ◽  
Transonic Centrifugal Compressor ◽  
Wide Range ◽  
Compressor Performance ◽  
Low Solidity Cascade Diffuser

Low-solidity circular cascades, conformally transformed from high-stagger linear cascades of double-circular-arc vanes with solidity 0.69, were used as a part of the diffuser system of a transonic centrifugal compressor. Performance test results were compared with data of the same compressor with a vaneless diffuser. Good compressor performance and a wider flow range as well as a higher pressure ratio and a higher efficiency, superior to those with a vaneless diffuser, where the flow range was limited by choke of the impeller, were demonstrated. The test circular cascade diffusers demonstrated a good pressure recovery over a wide range of flow angles, even when the inflow Mach number to the cascade was over unity.

Application of Low-Solidity Cascade Diffuser to Transonic Centrifugal Compressor

1989 ◽  
Author(s):  
H. Hayami ◽  
Y. Senoo ◽  
K. Utsunomiya
Keyword(s):  
Centrifugal Compressor ◽  
Performance Test ◽  
Pressure Ratio ◽  
Test Results ◽  
Vaneless Diffuser ◽  
Circular Arc ◽  
Transonic Centrifugal Compressor ◽  
Wide Range ◽  
Compressor Performance ◽  
Low Solidity Cascade Diffuser

Low-solidity circular cascades, conformally transformed from high-stagger linear cascades of double-circular-arc vanes with solidity 0.69, were used as a part of the diffuser system of a transonic centrifugal compressor. Performance test results were compared with data of the same compressor with a vaneless diffuser. Good compressor performance, a wider flow range as well as a higher pressure ratio and a higher efficiency, superior to those with a vaneless diffuser, where the flow range was limited by choke of the impeller, were demonstrated. The test circular cascade diffusers demonstrated a good pressure recovery over a wide range of flow angles, even when the inflow Mach number to the cascade was over unity.

Flow With Shock Waves in a Transonic Centrifugal Compressor With a Low-Solidity Cascade Diffuser Using PIV

2004 ◽  
Author(s):  
Hiroshi Hayami ◽  
Masahiro Hojo ◽  
Norifumi Hirata ◽  
Shinichiro Aramaki
Keyword(s):  
Shock Wave ◽  
Shock Waves ◽  
Centrifugal Compressor ◽  
Gas Flow ◽  
Pressure Ratio ◽  
Transonic Centrifugal Compressor ◽  
Image Velocimetry ◽  
Rotor Stator Interaction ◽  
Rotating Impeller ◽  
Low Solidity Cascade Diffuser

A single-stage transonic centrifugal compressor with a pressure ratio greater than six was tested in a closed loop with HFC134a gas. Flow at the inducer of a rotating impeller as well as flow in a stationary low-solidity cascade diffuser was measured using a double-pulse and double-frame particle image velocimetry (PIV). Shock waves in both flows were clearly observed. The effect of flow rate on a 3D configuration of shock wave at the inducer and a so-called rotor-stator interaction between a rotating impeller and a stationary cascade were discussed based on a phase-averaged measurement technique. Furthermore, the unsteadiness of inducer shock wave and the flow in a cascade diffuser during surge were discussed based on instantaneous velocity vector maps.

The performance of a centrifugal compressor with a tandem impeller in off-design conditions

2019 ◽  
Vol 234 (2) ◽  
pp. 156-172 ◽  
Author(s):  
Ziliang Li ◽  
Xingen Lu ◽  
Ge Han ◽  
Yanfeng Zhang ◽  
Shengfeng Zhao ◽  
...  
Keyword(s):  
Centrifugal Compressor ◽  
Performance Enhancement ◽  
Pressure Ratio ◽  
Operating Conditions ◽  
Complex Flow ◽  
Maximum Enhancement ◽  
Operating Range ◽  
Wide Range ◽  
Compressor Performance ◽  
Low Efficiency

Centrifugal compressors often suffer relatively low efficiency and a terrible operating range particularly due to the complex flow structure and intense impeller/diffuser interaction. Numerous studies have focused on improving the centrifugal compressor performance using many innovative ideas, such as the tandem impeller, which has become increasingly attractive due to its ability to achieve the flow control with no additional air supply configurations and control costs in compressor. However, few studies that attempted to the investigation of tandem impeller have been published until now and the results are always contradictory. To explore the potential of the tandem impeller to enhance the compressor performance and the underlying mechanism of the flow phenomena in the tandem impellers, this paper numerically investigated a high-pressure-ratio centrifugal compressor with several tandem impellers at off-design operating speeds. The results encouragingly demonstrate that the tandem impeller can achieve a performance enhancement over a wide range of operating conditions. Approximately 1.8% maximum enhancement in isentropic efficiency and 5.0% maximum enhancement in operating range are achieved with the inducer/exducer circumferential displacement of [Formula: see text] = 25% and 50%, respectively. The observed stage performance gain of the tandem impellers decreases when the operating speed increases due to the increased inducer shock, increased wake losses, and deteriorated tandem impeller discharge flow uniformity. In addition, the tandem impeller can extend the impeller operating range particularly at low rotation speeds, which is found to be a result from the suppression of the low-momentum fluid radial movement. The results also indicate that the maximum flux capacity of the tandem impeller decreases due to the restriction of the inducer airfoil Kutta–Joukowsky condition.

scholarly journals Direction for High-Performance Supercritical CO2 Centrifugal Compressor Design for Dry Cooled Supercritical CO2 Brayton Cycle

2019 ◽  
Vol 9 (19) ◽  
pp. 4057 ◽  
Author(s):  
Cho ◽  
Bae ◽  
Jeong ◽  
Lee ◽  
Lee
Keyword(s):  
Mach Number ◽  
Centrifugal Compressor ◽  
Supercritical Co2 ◽  
Performance Test ◽  
Structural Integrity ◽  
Pressure Ratio ◽  
Compressibility Factor ◽  
Total Efficiency ◽  
Brayton Cycle ◽  
Compressor Performance

To overcome the degradation of the cycle efficiency of a supercritical carbon dioxide (S-CO2) Brayton cycle with dry cooling, this study proposes an improved design of an S-CO2 centrifugal compressor. The conventional air centrifugal compressor can achieve higher efficiency as backsweep angle increases. However, the structural issue restricts the maximum allowable angle (−50~−56°). In this study, an S-CO2 centrifugal compressor performance was examined while changing the backward sweep angle at impeller exit to study if the previous optimum backsweep angle for an air centrifugal compressor is still valid when the fluid has changed. It is shown through an analysis that an S-CO2 centrifugal compressor can achieve the highest efficiency at −70° backsweep angle, which is greater than the typical design value. The S-CO2 centrifugal compressor is less restricted from a structural integrity issue because it has low relative Mach number regardless of the low sound speed near critical point (Tc = 304.11 K, Pc = 7377 kPa). It is also shown in the paper that the variation of compressibility factor does not impact on its total to total efficiency since its Mach number is still lower than unity. Finally, it is also shown that a backward sweep impeller can achieve higher pressure ratio and operate stably in wider range as the mass flow rate is decreased. As further works, the suggested concept will be validated by the structural analysis and the compressor performance test.

Performance Test Results of the Supercritical CO2 Compressor for a New Gas Turbine Generating System

2010 ◽  
Author(s):  
Masanori Aritomi ◽  
Takao Ishizuka ◽  
Yasushi Muto ◽  
Nobuyoshi Tsuzuki
Keyword(s):  
Flow Rate ◽  
Centrifugal Compressor ◽  
Rotational Speed ◽  
Gas Turbines ◽  
Supercritical Co2 ◽  
Performance Test ◽  
Permanent Magnets ◽  
Pressure Ratio ◽  
Test Results ◽  
Institute Of Technology

Supercritical carbon dioxide (S-CO2) gas turbines can generate power at high cycle thermal efficiency, even at modest temperatures of 500–550°C, because of their markedly reduced compressor work near the critical point. Furthermore, the reaction between Na and CO2 is milder than that between H2O and Na. A more reliable and economically advantageous power generation system could be achieved by coupling with a sodium-cooled fast reactor. At Tokyo Institute of Technology, numerous development projects have been conducted for development of this system in cooperation with JAEA. Supercritical CO2 compressor performance test results are given as described herein. A centrifugal compressor is chosen for the performance test. Main compressor parts are stored in a pressure vessel. Maximum design conditions of the supercritical CO2 test apparatus are pressure of 11 MPa, temperature of 150°C, the flow rate of 6 kg/s and rotational speed of 24,000 rpm. The centrifugal compressor has an electric motor with permanent magnets on the rotor surface, with speed control by an inverter up to 24,000 rpm, a rotor shaft for the impeller, and a motor supported by gas bearings. Different compressor design points are examined using impellers of three kinds; test data are obtained using those impellers under steady state conditions with changing pressure, temperature, flow rate, and compressor rotor speed. The pressure ratio (compressor outlet pressure/inlet pressure) is obtained with the function of compressor rotational speed and the fluid flow rate. The data cover a broad region from sub-critical to supercritical pressure. Such data were obtained for the first time. No unstable phenomenon was observed in the area where the CO2 properties change sharply. Data of the pressure ratio vs. flow rate were coincident with the fundamental compressor theory.

scholarly journals Dual Pressure Ratio Compressor

1989 ◽  
Author(s):  
Charles J. Paine
Keyword(s):  
Centrifugal Compressor ◽  
Pressure Ratio ◽  
Test Results ◽  
Vaneless Diffuser ◽  
High Pressure Turbine ◽  
Auxiliary Power Unit ◽  
Auxiliary Power ◽  
Further Development ◽  
Compressor Efficiency ◽  
Flow Splitter

The dual pressure ratio centrifugal compressor was conceived and developed as part of an advanced auxiliary power unit (APU) program (Ref. 1). The objective was to provide relatively low pressure bleed flow and high pressure turbine flow from a single stage centrifugal compressor. Concept feasibility was first demonstrated by modifying and rig testing an existing centrifugal compressor. Subsequently, a second compressor (reference compressor), meeting the overall APU power section and bleed cycle pressure ratio requirements was designed and rig tested. This configuration was then scaled and tested in an APU. Test results showed that the compressor efficiency and pressure ratio were approximately as predicted for the flow split off to the turbine (referred to as the turbine flow side). The bleed flow side vaneless diffuser experienced a strong flow separation. Mechanical problems were also encountered with the flow splitter shroud. Although further development was indicated to correct the mechanical and aerodynamic problems encountered, the experiment provided a benchmark for the dual pressure ratio compressor concept.

Improvement of the Flow Range of Transonic Centrifugal Compressors With a Low-Solidity Cascade Diffuser

2000 ◽  
Author(s):  
Hiroshi Hayami
Keyword(s):  
Centrifugal Compressor ◽  
High Speed ◽  
Pressure Ratio ◽  
Input Power ◽  
Velocity Of Sound ◽  
Centrifugal Compressors ◽  
Vaned Diffuser ◽  
Transonic Centrifugal Compressor ◽  
Series Of Experiments ◽  
Low Solidity Cascade Diffuser

If the pressure ratio of a typical single-stage centrifugal compressor is larger than four, the velocity relative to the impeller and to the diffuser exceeds the velocity of sound. The flow range of transonic centrifugal compressors with a vaned diffuser is usually very narrow. Low-solidity cascade diffusers with solidity 0.69 have been successfully applied as a part of the diffuser system of a transonic centrifugal compressor. On the basis of this type of diffuser, a series of experiments to broaden the operating range are discussed focusing on the control of the geometry of impeller and/or diffuser; one was to reduce the inducer blade turning upstream of the throat, and the other was to reduce the inlet passage width of diffuser. The milder inducer blade camber realized the improvement in flow range by 1.5 times to the original one. Regarding the diffuser inlet passage width contraction, the flow range was not broadened so much owing to the change in impeller characteristics, but the input power was reduced and then the high speed efficiency was much improved.

scholarly journals Comparison of Two Diffusers in a Transonic Centrifugal Compressor

2003 ◽  
Vol 9 (4) ◽  
pp. 279-284 ◽  
Author(s):  
Koji Nakagawa ◽  
Hiroshi Hayami ◽  
Yuichi Keimi
Keyword(s):  
Numerical Simulation ◽  
Centrifugal Compressor ◽  
Flow Separation ◽  
Pressure Ratio ◽  
Maximum Pressure ◽  
Vaned Diffuser ◽  
Transonic Centrifugal Compressor ◽  
Flow Mechanisms ◽  
Series Of Experiments ◽  
Low Solidity Cascade Diffuser

Flow mechanisms suppressing the flow separation in two diffusers, a low-solidity cascade diffuser and a vaned diffuser with additional small vanes near the inlet, were compared mainly by numerical simulation. As the superiority of the low-solidity cascade diffuser was expected, a series of experiments was conducted using a transonic centrifugal compressor with a maximum pressure ratio of 7. The performance of the compressor with the vaned diffuser was comparable to that of the low-solidity cascade diffuser only between the surge point and the design flowrate at a pressure ratio of 3.5. The maximum flowrate of the vaned diffuser was lower than that of the low-solidity cascade diffuser. At higher rotational speeds, the pressure ratio at the surge point, the efficiency, and the flow range of the low-solidity cascade diffuser exceded those of a vaned diffuser at a pressure ratio of 3.5.

scholarly journals On the Performance Prediction of a Centrifugal Compressor Scaled Up

1982 ◽  
Author(s):  
T. Mashimo ◽  
I. Ariga ◽  
T. Sakai ◽  
I. Watanabe
Keyword(s):  
Centrifugal Compressor ◽  
Performance Prediction ◽  
Prediction Method ◽  
Tip Clearance ◽  
Wall Friction ◽  
Test Results ◽  
Flow Losses ◽  
Wide Range ◽  
Compressor Performance ◽  
The Individual

A centrifugal compressor performance prediction method, in which each loss generated within the compressor stage was estimated by recognizing the individual relationship with Mach number, was investigated over a wide range of sizes and types. Calculation formulae for the losses were established by analyzing test results. It was confirmed that the formulae could be applied to predict the performance levels of compressors with impeller diameters from 78 mm to 640 mm by refering to unpublished test data obtained experimentally by other researchers. From the results, it could be deduced that: (1) The wall friction losses and the secondary flow losses within the compressor decreased with increase of impeller size. (2) The leakage flow losses were found to increase when scaling up the compressor, even when tip clearance/blade height were held constant. The present paper presents a progress report of work still underway.

Centrifugal Compressor Performance Improvements Through Impeller Splitter Location

2017 ◽  
Vol 140 (5) ◽  
Author(s):  
C. Xu ◽  
R. S. Amano
Keyword(s):  
Centrifugal Compressor ◽  
Aerodynamic Performance ◽  
Low Flow ◽  
Performance Tests ◽  
Test Results ◽  
Operational Cost ◽  
Vaneless Diffuser ◽  
Location Optimization ◽  
Performance Improvements ◽  
Compressor Performance

The splitter blades are very common to use for centrifugal compressor impellers to improve the compressor performance and manufacturing capability. In this study, a low-flow single-stage centrifugal compressor with a vaneless diffuser was used to investigate the location effects of the impeller splitter between two main blades. It is demonstrated that the splitter position provides an opportunity to improve the compressor performance and reduce the operational cost. The splitter location optimizations were performed numerically, and the optimal splitter location was identified. A prototype was built for the impeller with optimal splitter position. The performance tests were performed, and test results are compared with numerical analyses. The studies indicated that splitter positions have impacts on the compressor stage performances. The studies showed that the traditional splitter located in the middle of the two main blades is not the optimal location for aerodynamic performance. The splitter location optimization provided the opportunity to improve the centrifugal compressor performance further.

Sign in / Sign up

Export Citation Format

Share Document