An enhanced compressor sub-idle map generation method

Several techniques have come about for the mathematical extrapolation of compressor maps from the idle region down to zero speed. Relatively little work has been done on methods which attempt to extract compressor sub - idle performance from physical grounds. This paper focuses on the design of an axial compressor rig to obtain sub - idle data in the form of locked rotor and windmill characteristics. The rig design is presented and the results obtained discussed. The data gathered is used to generate physics - based sub - idle compressor maps which are then compared to existing method s for sub - idle map generation. Interpolation from the locked rotor characteristic is shown to improve map generation over extrapolation methodologies, while the windmilling characteristic is shown to be an important addition to the interpolation process

Using point-of-sale data to examine tobacco pricing across neighbourhoods in Scotland

Objectives: To assess the geographical variation in tobacco price (cigarettes and roll-your-own (RYO) tobacco) in convenience stores across Scotland and how this relates to neighbourhood income deprivation, tobacco retail outlet density and urban/rural status. Methods: Tobacco price data from 124 566 shopping baskets purchased in 274 convenience stores during 1 week in April 2018 were obtained through an electronic point-of-sale system. These data were combined with neighbourhood-level measures of income deprivation, tobacco retail outlet density and urban/rural status. We examined brand price for 12 of the most popular cigarette brands and 3 RYO brands and variations in purchases by price segment; multivariable regression analysis assessed associations between area variables and tobacco price. Results: Most stores sold tobacco in all price segments. The lowest priced subvalue brands were the most popular in all neighbourhoods but were most dominant in shops in more deprived neighbourhoods. When total sales were assessed, overall purchase price varied significantly by neighbourhood income deprivation; packets of 20 cigarettes were 50 pence (5.6%) lower and RYO 34 pence (2.7%) lower among shops in the two highest income deprivation quintiles relative to the lowest. Analysis of individual brands showed that for 3 of the 12 cigarette brands considered, average prices were 12-17 pence lower in more deprived neighbourhoods with the most popular RYO brand 15 pence lower. There was limited evidence of a relationship with tobacco retail outlet density. Conclusion: Across Scottish convenience stores, the purchase price of cigarettes and RYO was lower in more income-deprived neighbourhoods. The lower prices primarily reflect greater sales of cheap brands in these areas, rather than retailers reducing the prices of individual brands

Estimation of resultant airframe forces for a variable pitch fan operating in reverse thrust mode

The resultant forces with a reverse thrust Variable Pitch Fan (VPF) during the aircraft landing run are computed from the installed reverse thrust flow field obtained from an airframe-engine-VPF research model. The research model features a reverse flow capable VPF design in a future, geared, high-bypass ratio 40000 lbf engine as installed onto a twin-engine airframe in landing configuration, complete with a rolling ground plane to mimic the runway. The reverse thrust flow field during the aircraft landing run is obtained from 3D RANS/URANS solutions of the model. The evolution of the installed dynamic reverse thrust flow field is characterized by the interaction of the VPF induced reverse flow with the free stream. Several flow features like reverse flow wash-down by the freestream, external swirling helical flow development, pylon flow obstruction, 180° flow turn into the engine, subsequent separated flows, wake interactions and multi-pass recirculating flows are observed. The resultant airframe forces due to the reverse thrust flow field is estimated by adaptations of momentum based far-field and near-field methods. In the active thrust reverser engagement regime of 140 to 40 knots, the VPF generates a sufficient axial airframe decelerating force in the range of 45% to 8% of maximum take-off thrust. A drag decomposition study and a notional ‘blocked-fan’ analysis are described to understand the stack-up of the axial decelerating force. Additionally, the resultant force has a landing speed dependent lateral force component because of the pylon obstruction induced flow non-uniformity. A beneficial downforce component due to upward deflection of streamlines is also observed. The quantification of the resultant forces from the baseline installed airframe-engine-VPF reverse thrust flow field is a necessary step to explore the feasibility of the VPF reverse thrust system for future efficient turbofan architectures, understand force generation mechanisms and to identify areas for subsequent design improvement

Estimation of resultant airframe forces for a variable pitch fan operating in reverse thrust mode

The resultant forces with a reverse thrust variable pitch fan (VPF) during the aircraft landing run are computed from the installed reverse thrust flow field obtained from an airframe-engine-VPF research model. The research model features a reverse flow capable VPF design in a future, geared, high-bypass ratio 40,000 lbf engine as installed onto a twin-engine airframe in landing configuration, complete with a rolling ground plane to mimic the runway. The reverse thrust flow field during the aircraft landing run is obtained from the three-dimensional RANS/URANS solutions of the model. The evolution of the installed dynamic reverse thrust flow field is characterized by the interaction of the VPF-induced reverse flow with the freestream. Several flow features like reverse flow wash-down by the freestream, external swirling helical flow development, pylon flow obstruction, 180 deg flow turn into the engine, subsequent separated flows, wake interactions, and multipass recirculating flows are observed. The resultant airframe forces due to the reverse thrust flow field are estimated by adaptations of momentum-based far-field and near-field methods. In the active thrust reverser engagement regime of 140 to 40 knots, the VPF generates a sufficient axial airframe decelerating force in the range of 45% to 8% of maximum takeoff thrust. A drag decomposition study and a notional “blocked-fan” analysis are described to understand the stack-up of the axial decelerating force. Additionally, the resultant force has a landing speed-dependent lateral force component because of the pylon obstruction-induced flow nonuniformity. A beneficial downforce component due to upward deflection of streamlines is also observed. The quantification of the resultant forces from the baseline installed airframe-engine-VPF reverse thrust flow field is a necessary step to explore the feasibility of the VPF reverse thrust system for future efficient turbofan architectures, understand force generation mechanisms, and to identify areas for subsequent design improvement

The general and mental health of movers to more- and less-disadvantaged socio-economic and physical environments within the UK

Residential mobility may play an important role in influencing both individual health, by determining individual exposures to environments, and area health, by shaping area population composition. This study is the first analysis of migration within the UK to compare general and mental health among adults by age group and consider moves between neighbourhoods with different levels of both socio-economic and physical environment disadvantage. The analysis assesses 122,570 cases from the annual British Household Panel Survey, 1996–2006, based upon pooled data describing moves between consecutive waves of the survey. It assesses the rates and binary logistic regression model odds of self-reported general health and mental health problems of movers and stayers by age group. It also compares movers between Census Area Statistics wards in the UK with different levels of Carstairs and Multiple Environmental Deprivation Index (MEDIx) scores. At all ages, movers had similar or higher odds of poor general and mental health relative to non-movers. Risk of mental health problems were particularly elevated among movers and remained significant after adjustment for socio-demographic variables in most age groups. In adjusted analysis of all adults odds of poor general and mental health were most elevated among movers to more socio-economically deprived areas, with the highest odds for mental health (1.54 95% CI 1.27–1.86). In contrast, risk of poor mental health among total adults was greatest among movers to better physical environments (1.40 95% CI 1.16–1.70). This study therefore finds little evidence of ‘healthy migrant effects’ among recent movers within the UK and suggests movers have particularly elevated risk of mental health problems. It also indicates that selective migration may not contribute to poor health found in UK neighbourhoods with multiple physical environment deprivation. Further analysis should explore why people with mental health problems are more likely to move to socio-economically deprived neighbourhoods

Cross-sectional study of ethnic differences in the utility of area deprivation measures to target socioeconomically deprived individuals

Area deprivation measures provide a pragmatic tool for targeting public health interventions at socioeconomically deprived individuals. Ethnic minority groups in the UK experience higher levels of socioeconomic deprivation and certain associated diseases than the White population. The aim of this study was to explore ethnic differences in the utility of area deprivation measures as a tool for targeting socioeconomically deprived individuals. We carried out a cross-sectional study using the Health Survey for England 2004. 7,208 participants aged 16-64 years from the four largest ethnic groups in England (White, Indian, Pakistani and Black Caribbean) were included. The main outcome measures were percentage agreement, sensitivity and positive predictive value (PPV) of area deprivation, measured using Index of Multiple Deprivation 2004, in relation to individual socioeconomic position (measured by education, occupation, income, housing tenure and car access). We found that levels of both area and individual deprivation were higher in the Pakistani and Black Caribbean groups compared to the White group. Across all measures, agreement was lower in the Pakistani (50.9-63.4%) and Black Caribbean (61.0-70.1%) groups than the White (67.2-82.4%) group. However, sensitivity was higher in the Pakistani (0.56-0.64) and Black Caribbean (0.59-0.66) groups compared to the White group (0.24-0.38) and PPV was at least as high. The results for the Indian group were intermediate. We conclude that, in spite of lower agreement, area deprivation is better at identifying individual deprivation in ethnic minority groups. There was no evidence that area based targeting of public health interventions will disadvantage ethnic minority groups

Generating axial compressor maps to zero speed

Gas turbine performance models typically rely on component maps to characterize engine component performance throughout the operational regime. For the sub-idle case, the lack of reliable rig test data or inability to run design codes far from design conditions entails that component maps have to be generated from the extrapolation of existing data at higher speeds. This undermines the accuracy of whole-engine sub-idle performance models, at times impacting engine development and certification of aviation engines and the accuracy of start-up performance prediction in industrial gas turbines. One of the main components driving this issue is the core compression system, which can present operability concerns during light-up and which also sets the combustor airflow required for ignition. This paper presents, discusses, and draws on previous approaches to describe a method enabling the creation of sub-idle compressor maps from analytical and physical grounds. The method relies on the calculation of zero-speed and torque-free lines to generate a map down to zero speed along with analytical interpolation. A method for the interpolation process is described. A sensitivity study is carried out to assess the effects that different elements of the map generation process may have on the accuracy of the resulting performance calculation. Overall, a method for the generation of accurate, consistent maps from limited geometry data is identified.European Union: Horizon 2020 Clean Sky 2 Joint Undertakin