Ported Shroud Flow Processes and Their Effect on Turbocharger Compressor Operation

Sharma, Sudhaa; Jupp, Martyn; Nickson, A.K.; Allport, John

doi:10.1115/gt2017-63678

Cited by 11 publications

(14 citation statements)

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“…In this section, the flow field characteristics including the flow through the PS cavity for the compressor operating near surge condition are investigated. A significant fraction of inlet mass flow is seen to be recirculated through the PS cavity as previously predicted using steady approach [30]. The fluid with high circumferential velocity is removed from the impeller passages and recirculated to the main flow via PS cavity.…”

Section: Flow Field Characteristicssupporting

confidence: 57%

“…14 clearly shows the turbulent features formed by the interaction of recirculated flow with the inlet flow. These turbulent structures are expected to be a significant source of the losses that are seen in the 'Inlet-PS' mixing region as second law analysis [30] points 'Inlet-PS' mixing region as the dominant sources of losses during near surge operation.…”

Section: Flow Field Characteristicsmentioning

confidence: 99%

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Acoustic and pressure characteristics of a ported shroud turbocompressor operating at near surge conditions

et al. 2019

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The operation of compressor at lower mass flow rates is limited by surge which is marked by large fluctuations in operational variables and accompanied by significant increase in noise. Ported shroud casing treatment is a widely used method to control the flow near unstable conditions in order to obtain a stable operation and enhance deep surge margin. The research on the acoustic effects of the ported shroud design is limited. Therefore, this paper numerically characterises the acoustic features of a turbocharger compressor with ported shroud design operating at marginal or soft surge conditions and investigates the correlation between acoustic characteristics and the spatial flow structures. The acoustic and the flow field features are analysed using spectral signatures obtained from an experimentally validated numerical model using both performance and acoustic measurements. Propagation of the frequency content through the ducts has been estimated with the aid of the beamforming and method of characteristics to enhance the content coming from the compressor. Expected acoustic phenomena such as rotating order tones and blade passing peaks are correctly identified in the modelled spectrum with the limitation to capture the specific broadband features. Hence, the numerical model can be used to further the research encompassing the impact these flow enhancement solutions have on the noise emission of the turbocharger. Inspection of the flow field shows radially exiting fluid at the ported shroud slot leading to the formation of the high-speed jets exiting the ported shroud cavity. Circumferential propagation of the stall cells is also identified in the impeller. Further inspection of the pressure field through modal decomposition implies the localisation of the energetic noise sources in the impeller downstream components. The influence of the ported shroud cavity on the acoustic characteristic of the compressor is not significant and is limited to the propagation of the tonal noise in the direction of impeller upstream.

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Section: Flow Field Characteristicssupporting

confidence: 57%

Section: Flow Field Characteristicsmentioning

confidence: 99%

Acoustic and pressure characteristics of a ported shroud turbocompressor operating at near surge conditions

et al. 2019

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“…The deviations in the spectra of the sensors forming duct arrays can be contributed to the three-dimensional effects caused by duct modes and the propagation of flow instability due to the operation of the compressor near surge. The deviation among the spectra of the inlet duct array is primarily due to duct modes as the flow instability is reported only to propagate few diameters upstream [33,41]. Furthermore, a similar pattern is observed in the inlet spectra at design operation conditions thereby implying this to be a feature dependent on geometry rather than the flow conditions.…”

Section: Ps Open Configurationmentioning

confidence: 70%

“…The air mass flow rate was regulated by the operation of a back pressure valve at the compressor outlet while the rotational speed of the compressor was regulated from the turbine end by controlling the conditions at the inlet of the turbine. Further details on the gas stand measurements are described in Sharma et al [33]. Following this procedure, the thermodynamic state values were recorded for various rotating speeds ranging from 55 krpm to 130 krpm.…”

Section: Measurement Set-upmentioning

confidence: 99%

Acoustic characterisation of a small high-speed centrifugal compressor with casing treatment: An experimental study

Sharma

Broatch

García-Tíscar

et al. 2019

Aerospace Science and Technology

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With the advancements in manufacturing, materials and computational methods, turbomachinery designs have become more efficient providing higher specific power and reliability with lower weight and cost. The rotational speed of turbomachines has increased while the overall machine size has decreased for a similar power output leading to the pervasive presence of small, high-speed turbomachines, specifically centrifugal compressors in helicopters, unmanned aerial vehicles (UAVs), auxiliary power units (APUs), turbochargers and micro gas turbines. In addition to superior aerodynamic performance over a wide range, increased operating speeds have made the acoustic emissions of small centrifugal compressors a critical aspect of design. Therefore, this work presents an experimental campaign to characterise the acoustic behaviour of a compressor with an intent to quantify the dominant features of the flow-induced noise for design and near surge operating conditions. Furthermore, the campaign is extended to establish the impact of the ported shroud casing treatment and operating speed on the acoustic emission of the compressor. The induct noise measurement method is used in this work to quantify the noise generated in the compressor by measuring pressure fluctuations near the inducer and diffuser while the propagation of the generated noise to the ducts is computed from an array of piezoelectric sensors. Spectra at the design operating point are dominated by tonal noise while broadband noise content is the dominant feature of spectra for near surge operation. Although the ported shroud cavity does not significantly alter the overall noise levels of the compressor operating at design condition, it does seem to propagate tonal noise. For near surge operation, the casing treatment positively impacts the acoustic emission with a reduction of approximately 10 dB in the range up to the blade pass frequency. Furthermore, various broadband features are also observed to be alleviated by the casing treatment.

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“…Details on the gas stand measurement are described in Sharma et al 11,36 . Schematic diagrams of the acoustic flow bench with the position of various sensors is shown in Fig.…”

Section: Assessment Of the Numerical Configurationmentioning

confidence: 99%

Evolution of flow characteristics in a centrifugal compressor with an increase in operating speed

Sharma

García-Tíscar

Allport

et al. 2020

International Journal of Engine Research

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Developments in materials, manufacturing and computing methods have catalysed the generation of efficient compressor designs with higher specific power outputs. Centrifugal compressors have become pervasive in environments demanding a combination of higher power with smaller sizes such as unmanned aerial vehicles, micro gas turbines and turbochargers. These compressors are expected to perform optimally in a range of operational speeds and mass flow states with low acoustic emissions. The impact of operating speed on the flow and acoustic characteristics of a ported shroud compressor has been explored in this work. The operation of the open and blocked configurations of the compressor at the design and near surge points each of a lower and a higher speedline was numerically and experimentally investigated. Comparing the results, the model was shown to predict the operation of the compressor for both configurations at the investigated operating points satisfactorily in terms of both performance and dominant acoustic features. With an increase in the velocity and the Mach number due to increased operational speed, changes in the flow behaviour in the inducer and diffuser were observed. An increase in operational speed was shown to generally increase the overall acoustic emission of the compressor for both configurations. The number of distinct tones in the acoustic output and their magnitude were also seen to be a function of operating speed.

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Ported Shroud Flow Processes and Their Effect on Turbocharger Compressor Operation

Cited by 11 publications

References 0 publications

Acoustic and pressure characteristics of a ported shroud turbocompressor operating at near surge conditions

Acoustic and pressure characteristics of a ported shroud turbocompressor operating at near surge conditions

Acoustic characterisation of a small high-speed centrifugal compressor with casing treatment: An experimental study

Evolution of flow characteristics in a centrifugal compressor with an increase in operating speed

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