Performance Degradation Due to Fouling and Recovery After Washing in a Multistage Test Compressor

2021 ◽  
Vol 143 (3) ◽  
Author(s):  
Nicola Casari ◽  
Michele Pinelli ◽  
Pier Ruggero Spina ◽  
Alessio Suman ◽  
Alessandro Vulpio

Abstract Land-based power units have to fulfill even more high levels of production and reliability. In harsh environments (desert and tropical installations, typically), the power unit ingests high amounts of dust that might deposit inside the compressor. In this paper, the analysis of a multistage compressor performance that operates under sandy and humid conditions has been assessed. The compressor units, which equips the Allison 250 C18 compressor, has been subjected to multiple runs under severe conditions of soil dust ingestion. The compressor has been operated according to subsequent runs, and at the end of each run, the performance curve was recorded; the performance losses, in terms of pressure ratio, have been measured during the operations. The characteristic curve of each run is representative of the level of contamination of the unit. Finally, the compressor has been washed, and the performance curve, in the recovered conditions, has been recorded. The results show the modification and the downward shift of the characteristic curves which lead to a gradual loss of the compressor performance. The curves realized after dust ingestion have been compared with the recovered curve after online washing. The measurement shows a promising recovery of the performances, even if the compressor flow path appears affected by localized deposits able to resist to the droplet removal action. Detailed photographic reports of the inlet guide vane (IGV) and the first compressor stages have been included in this analysis. After each run, the IGV, the rotor blade and stator vane of the first stage, and the hub and the shroud surfaces have been photographed. The pictures show the deposition patterns on the blades and the compressor surfaces. The comparison of the pictures of the internal surfaces, before and after the washing, highlights the parts that are more critical to clean and needy of attention during offline washing and overhaul.

Author(s):  
Nicola Casari ◽  
Michele Pinelli ◽  
Pier Ruggero Spina ◽  
Alessio Suman ◽  
Alessandro Vulpio

Abstract Land-based power units have to fulfill even more high levels of production and reliability. In harsh environments (desert and tropical installations, typically), the power unit ingests high amounts of dust that might deposit inside the compressor. In this paper, the analysis of a multistage compressor performance that operates under sandy and humid conditions has been assessed. The compressor units, that equips the Allison 250 C18 compressor, has been subjected to multiple runs under severe conditions of soil dust ingestion. The compressor has been operated according to subsequent runs and at the end of each run, the performance curve was recorded and the performance losses, in terms of pressure ratio, have been measured during the operations. The characteristic curve of each run is representative of the level of contamination of the unit. Finally, the compressor has been washed and the performance curve, in the recovered conditions, has been recorded. The results show the modification and the downward shift of the characteristic curves which lead to a gradual loss of the compressor performance. The curves realized after dust ingestion have been compared with the recovered curve after online washing. The measurement shows a promising recovery of the performances, even if, the compressor flow path appears affected by localized deposits able to resist to the droplet removal action. Detailed photographic reports of the IGV and the first compressor stages have been included in this analysis. After each run, the IGV, the rotor blade and stator vane of the first stage and the hub and the shroud surfaces have been photographed. The pictures show the deposition patterns on the blades and the compressor surfaces. The comparison of the pictures of the internal surfaces, before and after the washing, highlights the parts that are more critical to clean and needy of attention during offline washing and overhaul.


Author(s):  
Levi André B. Vigdal ◽  
Lars E. Bakken

The introduction of variable inlet guide vanes (VIGVs) upfront of a compressor stage affects performance and permits tuning for off-design conditions. This is of great interest for emerging technology related to subsea compression. Unprocessed gas from the wellhead will contain liquid condensate, which affects the operational condition of the compressor. To investigate the effect of guide vanes on volume flow and pressure ratio in a wet gas compressor, VIGVs are implemented upfront of a centrifugal compressor stage to control the inlet flow direction. The guide vane geometry and test rig setup have previous been presented. This paper documents how changing the VIGV setting affects compressor performance under dry and wet operating conditions. The reduced performance effect and operating range at increased liquid content are of specific interest. Also documented is the change in the VIGV effect relative to the setting angle.


Author(s):  
Hani Mohtar ◽  
Pascal Chesse ◽  
David Chalet ◽  
Anthony Yammine

Engine downsizing is potentially one of the most effective strategies being explored to improve fuel economy. A main problem of downsizing using a turbocharger is the small range of stable functioning of the turbocharger centrifugal compressor at high boost pressures. Several stabilization techniques were studied to increase the compressor operating range without sacrificing the compressor efficiency. This paper presents an experimental study on a turbocharger compressor equipped with casing treatment (a map width enhancement system, MWE) and a variable inlet guide vane system (VIGV). A KKK turbocharger was modified and tested at Ecole Centrale de Nantes. The experimental program mainly dealt with traditional compressor performance measurements for an MWE (map width enhancement) structure with multitude of holes linking the annular flow passage and the impeller wheel, four different inner tubular length extensions and imparting positive and negative preswirl using VIGV system. The experimental studies have shown that while the MWE was advantageous in increasing pressure ratio at high compressor speeds, it failed in extending the compressor map. The different inner tubular length extensions have shown no significant effects on surge line improvement for this particular design. Results obtained from MWE system have been compared to those obtained when imparting positive and negative preswirl using an VIGV system.


Author(s):  
I. Kassens ◽  
M. Rautenberg

In a centrifugal compressor adjustable inlet guide vanes (IGV) in front of the impeller are used to regulate the pressure ratio and the mass flow. The stationary measurement of the velocity profile in front of the impeller with different angles of the IGV displays shock losses at the inlet edge of blade of the impeller. In the partial-load region (e.g. partial-load efficiency) the radial distribution of the flow influences considerably the performance of the impeller. The tested compressor consists of an adjustable IGV with straight vanes, a shrouded impeller and a vaneless, parallel diffuser. In the first measurement location, behind the IGV, total pressure, static pressure and flow angle were measured with a 5-hole cylinder probe. In the second measurement location, in front of the impeller, the measurement of the total pressure was carried out with a Kiel probe and the flow angle with a Cobra probe accordingly the static wall pressure was measured. Taking into consideration the fundamental thermodynamical equations it was possible to determine the velocity profiles because of the measured distributions of the flow angle in these two measurement locations. For different angles of the IGV and with various mass flows the distributions of the deflection defect behind the IGV are described. Starting with the measured distributions of the flow in front of the impeller the flow angles at the impeller inlet are calculated and the distributions of the incidence angle at the impeller inlet are figured out.


Author(s):  
Hans Ma˚rtensson ◽  
Jo¨rgen Burman ◽  
Ulf Johansson

As the first design in a demonstration program for future fighter engine fans a 400 mm 1-1/2 stage fan has been designed and built. A new method including mechanical constraints for designing the blades and gas path is used for the first time on a new design. The approach closely integrates CFD for performance and FE methods for the structure. By this, advanced computational analyses affect the design from the early stages. A design that is successful in achieving good efficiency based on CFD as well as reasonable aeromechanical properties based on FE is derived. The fan incorporates a front frame (FF), variable inlet guide vane (VIGV), rotor 1 (R1) and stator 1 (S1).


Author(s):  
Jack L. Kerrebrock ◽  
Alan H. Epstein ◽  
Ali A. Merchant ◽  
Gerald R. Guenette ◽  
David Parker ◽  
...  

The design and test of a two-stage, vaneless, aspirated counter-rotating fan is presented in this paper. The fan nominal design objectives were a pressure ratio of 3:1 and adiabatic efficiency of 87%. A pressure ratio of 2.9 at 89% efficiency was measured in the tests. The configuration consists of a counter-swirl-producing inlet guide vane, followed by a high tip speed (1450 feet/sec) non-aspirated rotor, and a counter-rotating low speed (1150 feet/sec) aspirated rotor. The lower tip speed and lower solidity of the second rotor results in a blade loading above conventional limits, but enables a balance between the shock loss and viscous boundary layer loss, the latter of which can be controlled by aspiration. The aspiration slot on the second rotor suction surface extends from the hub up to 80% span, with a conventional tip clearance, and the bleed flow is discharged at the hub. The fan was tested in a short duration blowdown facility. Particular attention was given to the design of the instrumentation to obtain efficiency measurements within 0.5 percentage points. High response static pressure measurements were taken between the rotors and downstream of the fan to determine the stall behavior. Pressure ratio, mass flow, and efficiency on speedlines from 90% to 102% of the design speed are presented and discussed along with comparison to CFD predictions and design intent. The results presented here complement those presented earlier for two aspirated fan stages with tip shrouds, extending the validated design space for aspirated compressors to include designs with conventional unshrouded rotors and with inward removal of the aspirated flow.


Author(s):  
Matteo Cicciotti ◽  
Dionysios P. Xenos ◽  
Ala E. F. Bouaswaig ◽  
Nina F. Thornhill ◽  
Ricardo F. Martinez-Botas

This paper proposes a framework for detecting mechanical degradation online and assessing its effect on the performance of industrial compressors. It consists of a model of the machine in undegraded condition and of a degradation adaptive model. The proposed methodology for online degradation detection differentiates itself from those found in the literature as the undegraded model is not linearized and ambient/inlet conditions are explicitly taken into account. The degradation is modelled through adaptive parameters which are estimated and updated online through the solution of a constrained minimization problem within a moving window. It uses available process measurements of flow, pressures, temperatures and composition. The update of the parameters guarantees the model accuracy and it permits the estimation of the effects of mechanical degradation away from the compressor running line. The performance monitoring framework has been successfully applied on an industrial air centrifugal compressor. It was found that after 3250 hours of operation from the previous maintenance the efficiency and the pressure ratio had dropped approximately 5.5% and 2.5% of their respective undegraded values. Furthermore, it was found that the performance deviations from the baseline depend from the position of the operative point in the performance map. In fact, the pressure ratio drop was lower (2%) and efficiency drop was higher (6%) for lower inlet guide vanes opening whereas pressure ratio drop was higher (3%) and efficiency drop was lower (1.6%) for higher inlet guide vane opening.


Author(s):  
Emandi Rajesh ◽  
Bhaskar Roy

The modern engine has the requirement of high pressure ratio compressors. High diffusion blades are used to cater to this requirement. The high diffusion blades suffer from the low incidence range. A variable geometry inlet guide vane is used to improve the incidence range and to have an increased stable operating range. In this paper a variable camber inlet guide is proposed in place of an existing inlet guide vane (IGV) to operate the compressor at increased stable operating range or to operate at improved efficiency at off design point. Numerical analysis is carried out in ANSYS CFX©. The existing compressor consists of IGV (20 blades) , rotor (43 blades) and stator (52 blades). The rotor rotates at 2400 rpm in clockwise direction. The IGV blade is split two part forward blade and aft blade. Numerical studies are conducted to study the effect of varying the stagger angle on the performance of the compressor. The aft blade is given rotation in clockwise direction for +5° and +10°. The numerical results obtained are compared to the same stagger angle with full blades. It is observed that marginal improvement in the pressure ratio and efficiency. 7% stall margin improvement is achieved with slotted blade in place a fixed IGV at 0° setting angle. A new compressor characteristics is estimated which shows that the compressor can be operated to the left of the fixed-IGV-stage peak pressure with high efficiency.


Author(s):  
Hideomi Harada

In order to improve the operating range of a centrifugal compressor, computer-controlled variable inlet and diffuser vanes were attached to a compressor with a pressure ratio of 2.5. Low-solidity cascade vanes capable of controlling the vane angle up to 0 degrees from the tangential direction were used for the vaned diffuser. The compressor’s overall performance was then tested using a closed-loop test stand. By automatically adjusting the diffuser vanes to the most suitable flow angle, pressure fluctuations caused by the unstable flow in the diffuser during low-flow operation of the centrifugal compressor could be suppressed, and the compressor could be operated nearly up to the shut-off flow rate without any surge. The author experimentally confirmed the critical operating range of both the impeller and diffuser at two different tip speeds and five inlet guide vane angles. Furthermore, a three-dimensional viscous flow-analysis method was applied to the impeller, and a three-dimensional momentum integral analysis method was applied to the diffuser. Then the critical operating ranges obtained in the experiments were qualitatively validated. The operating range of a centrifugal compressor under low-flow conditions, which has until now been limited because of surge, dramatically improved in this study, thereby demonstrating that it may be possible to develop a surge-free centrifugal compressor.


1975 ◽  
Author(s):  
F. A. E. Breugelmans

A supersonic compressor stage has been designed for a high pressure ratio at a tip relative inlet Mach number of 2. The stage was operated in the original configuration, but serious inlet stall occurred at part-speed operation. An inlet blockage ring, a bleed system and a variable geometry inlet guide vane have been analyzed and applied to this configuration. The results obtained with the bleed system in the complete stage are presented. The rotor performance is discussed and compared with the stage performance.


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