The Impediments to Nigeria Understanding Oil Production Volumes, Losses and Potential Solutions

The issue of the quantity of oil produced or missing has traditionally been played down in Nigeria. This is evident as no one in or outside Nigeria is able to quote a totally reliable production volume or loss figure. The aim of this study is thus to search for the root causes as to why there are difficulties in ascertaining the quantity of crude oil produced or missing per day and for potential solutions. The research assesses the present situation and problems requiring solution concerning Nigerian oil and gas measurement control. This is achieved through an intensive review of each of the notified bodies responsible for Nigeria’s oil and gas measurement control, using secondary resources. The bodies reviewed in this study are the Department of Petroleum Resources and the Weights and Measures Department. The study has identified knowledge impediments among the designated bodies. Also discovered were inadequate measurement equipment and absence of measurement guidelines, thus, no mechanisms were in place to address any mismeasurements or losses that are discovered. Provision of comprehensive training to the regulatory body to provide it with the necessary “teeth” to ensure effective delivery of it regulatory function has therefore been recommended as the key solution

Effects of ported shroud casing treatment on the acoustic and flow behaviour of a centrifugal compressor

[EN] Centrifugal turbomachines of smaller sizes operating at higher speeds have become pervasive due to the increased specific power and reliability achieved by improvements in manufacturing, materials and computational methods. The presence of these small turbomachines, specifically compressors, in helicopters, unmanned aerial vehicles (UAVs), auxiliary power units (APUs), turbochargers and micro gas turbines necessitates superior aerodynamic performance over a broad operational range which is widely achieved by ported shroud casing designs. In addition to aerodynamic performance, acoustic emissions have become a critical aspect of design for these small centrifugal compressors due to high operational speeds. Furthermore, the literature on the acoustic effects of the casing treatment is rather limited. Therefore, the impact of ported shroud casing treatment on the acoustic and flow features of the compressor operating at the design and near surge conditions have been quantified by numerically modelling the open and blocked configuration of the compressors. Upon comparing with experimental results, the numerical spectra are shown to capture the differences between the two configurations at the investigated operating points with reasonable accuracy. Although the casing treatment is generally seen to decrease the overall acoustic emission of the compressor at both operating conditions, increased propagation of tonal content in the direction upstream to the impeller is observed, particularly for design operation. Broadband characteristics in the lower and medium frequency regions usually associated with near surge operation including `whoosh' noise are observed to be alleviated by the ported shroud casing treatment.The author(s) disclosed receipt of the following financial support for the research, authorship and/or publication of this article: The project is sponsored and supported by BorgWarner Turbo Systems and the Regional Growth Fund (RGF Grant Award 01.09.07.01/1789C).Sharma, S.; Garcia Tiscar, J.; Allport, JM.; Barrans, S.; Nickson, AK. (2020). Effects of ported shroud casing treatment on the acoustic and flow behaviour of a centrifugal compressor. International Journal of Engine Research. 21(6):998-1011. https://doi.org/10.1177/1468087419880431S998101121

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

[EN] 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 in-duct 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. (C) 2019 Elsevier Masson SAS. All rightsThe project was sponsored and supported by BorgWarner Turbo Systems and the Regional Growth Fund (RGF Grant Award 01.09.07.01/1789C). The authors would like to thank BorgWarner Turbo Systems for permission to publish the results presented in this paper.Sharma, S.; Broatch, A.; Garcia Tiscar, J.; Allport, JM.; Nickson, AK. (2019). Acoustic characterisation of a small high-speed centrifugal compressor with casing treatment: an experimental study. Aerospace Science and Technology. 95:1-15. https://doi.org/10.1016/j.ast.2019.1055181159

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

[EN] 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. (C) 2019 Elsevier Ltd. All rights reserved.The project is sponsored and supported by BorgWarner Turbo Systems and the Regional Growth Fund (RGF Grant Award 01.09.07.01/1789C). The authors would like to thank BorgWarner Turbo Systems for permission to publish the results presented in this paper. The support of the HPC group at the University of Huddersfield is gratefully acknowledged.Sharma, S.; Broatch, A.; Garcia Tiscar, J.; Nickson, AK.; Allport, JM. (2019). Acoustic and pressure characteristics of a ported shroud turbocompressor operating at near surge conditions. Applied Acoustics. 148:434-447. https://doi.org/10.1016/j.apacoust.2019.01.005S43444714

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

[EN] 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.The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The project was sponsored and supported by the BorgWarner Turbo Systems and the Regional Growth Fund (RGF Grant Award 01.09.07.01/1789C).Sharma, S.; Garcia Tiscar, J.; Allport, JM.; Barrans, S.; Nickson, AK. (2021). Evolution of flow characteristics in a centrifugal compressor with an increase in operating speed. International Journal of Engine Research. 22(5):1592-1604. https://doi.org/10.1177/1468087420916606S1592160422

Acoustic characteristics of a ported shroud turbocompressor operating at design conditions

[EN] In this article, the acoustic characterisation of a turbocharger compressor with ported shroud design is carried out through the numerical simulation of the system operating under design conditions of maximum isentropic efficiency. While ported shroud compressors have been proposed as a way to control the flow near unstable conditions in order to obtain a more stable operation and enhance deep surge margin, it is often assumed that the behaviour under stable design conditions is characterised by a smooth, non-detached flow that matches an equivalent standard compressor. Furthermore, research is scarce regarding the acoustic effects of the ported shroud addition, especially under the design conditions. To analyse the flow field evolution and its relation with the noise generation, spectral signatures using statistical and scale-resolving turbulence modelling methods are obtained after successfully validating the performance and acoustic predictions of the numerical model with experimental measurements. Propagation of the frequency content through the ducts has been estimated with the aid of pressure decomposition methods to enhance the content coming from the compressor. Expected acoustic phenomena such as `buzz-saw¿ tones, blade passing peaks and broadband noise are correctly identified in the modelled spectrum. Analysis of the flow behaviour in the ported shroud shows rotating structures through the slot that may impact the acoustic and vibration response. Further inspection of the pressure field through modal decomposition confirms the influence of the ported shroud cavity in noise generation and propagation, especially at lower frequencies, suggesting that further research should be carried out on the impact these flow enhancement solutions have on the noise emission of the turbocharger.The project was sponsored and supported by BorgWarner Turbo Systems and the Regional Growth Fund (RGF Grant Award 01.09.07.01/1789C). The authors would like to thank BorgWarner Turbo Systems for permission to publish the results presented in this article. The support of the HPC group at the University of Huddersfield is gratefully acknowledged.Sharma, S.; Broatch, A.; Garcia Tiscar, J.; Allport, JM.; Nickson, AK. (2020). Acoustic characteristics of a ported shroud turbocompressor operating at design conditions. International Journal of Engine Research. 21(8):1454-1468. https://doi.org/10.1177/1468087418814635S14541468218Sundström, E., Semlitsch, B., & Mihăescu, M. (2017). Generation Mechanisms of Rotating Stall and Surge in Centrifugal Compressors. Flow, Turbulence and Combustion, 100(3), 705-719. doi:10.1007/s10494-017-9877-zGonzalez, A., Ferrer, M., de Diego, M., Piñero, G., & Garcia-Bonito, J. . (2003). Sound quality of low-frequency and car engine noises after active noise control. Journal of Sound and Vibration, 265(3), 663-679. doi:10.1016/s0022-460x(02)01462-1Brizon, C. J. da S., & Bauzer Medeiros, E. (2012). Combining subjective and objective assessments to improve acoustic comfort evaluation of motor cars. Applied Acoustics, 73(9), 913-920. doi:10.1016/j.apacoust.2012.03.013Teng, C., & Homco, S. (2009). Investigation of Compressor Whoosh Noise in Automotive Turbochargers. SAE International Journal of Passenger Cars - Mechanical Systems, 2(1), 1345-1351. doi:10.4271/2009-01-2053Figurella, N., Dehner, R., Selamet, A., Tallio, K., Miazgowicz, K., & Wade, R. (2014). Noise at the mid to high flow range of a turbocharger compressor. Noise Control Engineering Journal, 62(5), 306-312. doi:10.3397/1/376229Torregrosa, A. J., Broatch, A., Margot, X., García-Tíscar, J., Narvekar, Y., & Cheung, R. (2017). Local flow measurements in a turbocharger compressor inlet. Experimental Thermal and Fluid Science, 88, 542-553. doi:10.1016/j.expthermflusci.2017.07.007Broatch, A., Galindo, J., Navarro, R., García-Tíscar, J., Daglish, A., & Sharma, R. K. (2015). Simulations and measurements of automotive turbocharger compressor whoosh noise. Engineering Applications of Computational Fluid Mechanics, 9(1), 12-20. doi:10.1080/19942060.2015.1004788Raitor, T., & Neise, W. (2008). Sound generation in centrifugal compressors. Journal of Sound and Vibration, 314(3-5), 738-756. doi:10.1016/j.jsv.2008.01.034Galindo, J., Tiseira, A., Navarro, R., & López, M. A. (2015). Influence of tip clearance on flow behavior and noise generation of centrifugal compressors in near-surge conditions. International Journal of Heat and Fluid Flow, 52, 129-139. doi:10.1016/j.ijheatfluidflow.2014.12.004Broatch, A., Galindo, J., Navarro, R., & García-Tíscar, J. (2014). Methodology for experimental validation of a CFD model for predicting noise generation in centrifugal compressors. International Journal of Heat and Fluid Flow, 50, 134-144. doi:10.1016/j.ijheatfluidflow.2014.06.006Semlitsch, B., & Mihăescu, M. (2016). Flow phenomena leading to surge in a centrifugal compressor. Energy, 103, 572-587. doi:10.1016/j.energy.2016.03.032Sundström, E., Semlitsch, B., & Mihăescu, M. (2018). Acoustic signature of flow instabilities in radial compressors. Journal of Sound and Vibration, 434, 221-236. doi:10.1016/j.jsv.2018.07.040Torregrosa, A. J., Broatch, A., Margot, X., & García-Tíscar, J. (2016). Experimental methodology for turbocompressor in-duct noise evaluation based on beamforming wave decomposition. Journal of Sound and Vibration, 376, 60-71. doi:10.1016/j.jsv.2016.04.035Nicoud, F., & Ducros, F. (1999). Flow, Turbulence and Combustion, 62(3), 183-200. doi:10.1023/a:1009995426001Chow, P., Cross, M., & Pericleous, K. (1996). A natural extension of the conventional finite volume method into polygonal unstructured meshes for CFD application. Applied Mathematical Modelling, 20(2), 170-183. doi:10.1016/0307-904x(95)00156-eKaji, S., & Okazaki, T. (1970). Generation of sound by rotor-stator interaction. Journal of Sound and Vibration, 13(3), 281-307. doi:10.1016/s0022-460x(70)80020-7Sivagnanasundaram, S., Spence, S., & Early, J. (2013). Map Width Enhancement Technique for a Turbocharger Compressor. Journal of Turbomachinery, 136(6). doi:10.1115/1.4007895Aubry, N. (1991). On the hidden beauty of the proper orthogonal decomposition. Theoretical and Computational Fluid Dynamics, 2(5-6), 339-352. doi:10.1007/bf00271473Wold, S., Esbensen, K., & Geladi, P. (1987). Principal component analysis. Chemometrics and Intelligent Laboratory Systems, 2(1-3), 37-52. doi:10.1016/0169-7439(87)80084-9LIANG, Y. C., LEE, H. P., LIM, S. P., LIN, W. Z., LEE, K. H., & WU, C. G. (2002). PROPER ORTHOGONAL DECOMPOSITION AND ITS APPLICATIONS—PART I: THEORY. Journal of Sound and Vibration, 252(3), 527-544. doi:10.1006/jsvi.2001.4041Abdi, H., & Williams, L. J. (2010). Principal component analysis. Wiley Interdisciplinary Reviews: Computational Statistics, 2(4), 433-459. doi:10.1002/wics.101Nikiforov, V. (2007). The energy of graphs and matrices. Journal of Mathematical Analysis and Applications, 326(2), 1472-1475. doi:10.1016/j.jmaa.2006.03.07

“White Flight” or positive contact? Local diversity and attitudes to immigration in Britain

Does the local presence of immigrant groups increase White hostility to immigration? Most research finds that diverse neighborhoods reduce White opposition to minorities and immigration. However, most studies at higher geographies find the reverse effect. We confirm this pattern for England and Wales for 2009-2012. Yet, contextual studies are open to selection bias, which is where this article makes its main contribution. Is White tolerance in diverse neighborhoods the result of a positive effect of inter-ethnic contact, or does it arise from White flight, with anti-immigrant Whites exiting diverse areas but remaining within wider geographies as radicalized opponents of immigration? We provide the first attempt we are aware of to track the opinions of in- and out-migrants, as well as stayers, from local areas over an extended period. We use 20 years of large-scale geocoded British longitudinal data and find only limited evidence of selection effects associated with White flight

Personality Traits and Personal Values:A Meta-Analysis

Personality traits and personal values are important psychological characteristics, serving as important predictors of many outcomes. Yet, they are frequently studied separately, leaving the field with a limited understanding of their relationships. We review existing perspectives regarding the nature of the relationships between traits and values and provide a conceptual underpinning for understanding the strength of these relationships. Using 60 studies, we present a meta-analysis of the relationships between the Five-Factor Model (FFM) of personality traits and the Schwartz values, and demonstrate consistent and theoretically meaningful relationships. However, these relationships were not generally large, demonstrating that traits and values are distinct constructs. We find support for our premise that more cognitively based traits are more strongly related to values and more emotionally based traits are less strongly related to values. Findings also suggest that controlling for personal scale-use tendencies in values is advisable