243 results found
Law AJ, Martinez-Botas R, Blythe P, 2023, Current vehicle emission standards will not mitigate climate change or improve air quality, SCIENTIFIC REPORTS, Vol: 13, ISSN: 2045-2322
Alvarez-Regueiro E, Yang B, Barrera-Medrano E, et al., 2022, Optimization of an Organic Ranking Cycle Radial Turbine Using a Reduced-Order Mode Coupled With Computational Fluid Dynamics, JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME, Vol: 144, ISSN: 0742-4795
Yang M, Shu M, Wang X, et al., 2022, Rotor-stator aerodynamic interaction of centrifugal compressor at pulsating backpressure conditions, INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW, Vol: 96, ISSN: 0142-727X
Yang B, Martinez-Botas RF, Newton P, et al., 2021, One dimensional modelling on twin-entry turbine: An application of TURBODYNA, Pages: 97-112
One-dimensional (1D) modelling is important for turbocharger unsteady performance prediction and system response assessment of internal combustion engine. Two limbs of twin-entry turbines deliver pulsating unsteady flows with 180° phase difference leading to significant mixing at the rotor inlet. Such effects cannot be reproduced in classic 1D modelling and hence the predictions by the latter are less satisfactory in twin-entry turbines. To solve this problem, the paper proposes a novel 1D modelling (TURBODYNA) and applies it to a twin-entry turbocharger turbine. Instead of applying constant pressure assumption at the limbs junction, TURBODYNA solves conservation equations during the mixing process. Unsteady source terms described by dynamic equations are added into Euler equation to simulation rotor unsteady performance. By comparing TURBODYNA with validated CFD, TURBODYNA not only provides a great agreement on turbine performances, but also accurately captures unsteady features with increased pulsating frequency.
Luczynski P, Hohenberg K, Freytag C, et al., 2021, Integrated design optimisation and engine matching of a turbocharger radial turbine, Pages: 174-190
This paper presents a novel methodology for engine tailored optimisation of turbocharger turbine design. Both the turbine rotor and volute geometries for a turbocharger radial turbine were parameterised in order to enable CFD calculations for variations of predefined design parameters. The results of this analysis where used to develop and validate two approaches for computationally efficient and reliable prediction of radial turbine performance maps, quantified by total-tostatic turbine efficiency and mass flow parameter. The first method utilises a meanline model which was calibrated to experimentally validated CFD data using a genetic algorithm. The second method makes use of an artificial neural network which was trained using the same CFD approach, to predict turbine performance as a continuous function of design and operating parameters. The modelling accuracy of both approaches was evaluated and compared. Finally, the meanline model was integrated into the calibrated 1D engine model of a turbocharged 1.6 litre gasoline engine. The meanline model was used to generate maps for a latin hypercube sample of four meanline design parameters. Five steady-state operating points and one transient operating point were simulated for each point in the sample, allowing the selection of optimised designs on the basis of fuel consumption and transient performance as objectives. Due to the use of a design of experiment approach, the impact of turbine design parameters on the engine performance could also be evaluated separately. Finite Element Analysis of the turbine wheel was conducted simultaneously for the assessment of stress in individual turbine geometries. Three optimised turbine designs were selected to cater to different engine operating scenarios: ecological, sustainable and sport driving. The presented investigation clearly displays the methodology and benefits of engine integrated turbocharger design optimisation.
Martos PA, Barrera-Medrano ME, Martinez-Botas R, et al., 2021, Flow field analsys and optimized design of a centrifugal compressor volute
Turbocharging has become a fundamental technology to realize engine downsizing, which is an attractive strategy for low carbon vehicles in the near term. The stable operation of turbocharger compressors at low and high flow rates is crucial to provide peak torque demand and rated power for turbocharged automotive engines. The scroll or volute is a key component in centrifugal compressors as its design not only impacts the compressor efficiency but also affects the operating range. This component causes a distorted pressure field upstream which can contribute to stall on the impeller, inducing surge. As the flow inside the volute is fully three dimensional and turbulent, a better understanding of flow mechanisms is key to enable a volute design methodology. In this study, a centrifugal compressor stage has been modelled numerically and validated by experimental results, to identify the geometric parameters of the volute which contribute to the main flow losses. By solving Reynolds average NavierStokes (RANS) equations using a commercial code, the threedimensional flow field of the compressor was modelled. Based on detailed analysis of this flow field, and the impact of various geometric parameters, an optimized volute was developed. The results showed that the total-to-total isentropic efficiency and surge margin could be improved by 1.5% and 4.5%, respectively at design speed.
Alvarez-Regueiro E, Barrera-Medrano E, Martinez-Botas R, et al., 2021, Numerical analysis of non-radial blading in a low speed and low pressure turbine for electric turbocompounding applications
This paper presents a CFD-based numerical analysis on the potential benefits of non-radial blading turbine for low speedlow pressure applications. Electric turbocompounding is a waste heat recovery technology consisting of a turbine coupled to a generator that transforms the energy left over in the engine exhaust gases, which is typically found at low pressure, into electricity. Turbines designed to operate at low specific speed are ideal for these applications since the peak efficiency occurs at lower pressure ratios than conventional high speed turbines. The baseline design consisted of a vaneless radial fibre turbine, operating at 1.2 pressure ratio and 28,000rpm. Experimental low temperature tests were carried out with the baseline radial blading turbine at nominal, lower and higher pressure ratio operating conditions to validate numerical simulations. The baseline turbine incidence angle effect was studied and positive inlet blade angle impact was assessed in the current paper. Four different turbine rotor designs of 20, 30, 40 and 50 of positive inlet blade angle are presented, with the aim to reduce the losses associated to positive incidence, specially at midspan. The volute domain was included in all CFD calculations to take into account the volute-rotor interactions. The results obtained from numerical simulations of the modified designs were compared with those from the baseline turbine rotor at design and offdesign conditions. Total-to-static efficiency improved in all the non-radial blading designs at all operating points considered, by maximum of 1.5% at design conditions and 5% at off-design conditions, particularly at low pressure ratio. As non-radial fibre blading may be susceptible to high centrifugal and thermal stresses, a structural analysis was performed to assess the feasibility of each design. Most of non-radial blading designs showed acceptable levels of stress and deformation.
Yang B, Martinez-Botas R, Xue Y, et al., 2021, One dimensional modelling for pulsed flow twin-entry turbine
One-dimensional (1D) modelling is critical for turbomachinery unsteady performance prediction and system response assessment of internal combustion engines. This paper uses a novel 1D modelling (TURBODYNA) and proposes two additional features for the application to a twin-entry turbocharger turbine. Compared to single-entry turbines, twin-entry turbines enhance turbocharger transient response and reduce engine exhaust valve overlap periods. However, out-of-phase high frequency pulsating pressure waves lead to an unsteady mixing process from the two flows and pose great challenges to traditional 1D modelling. The present work resolves the mixing problem by directly solving mass, momentum and energy conservation equations during the mixing process instead of applying constant pressure assumption at the limb-rotor joint. Comparisons of TURBODYNA and an experimentally validated CFD suggest that TURBODYNA can not only provide a very good agreement on turbine performance, but also accurately capture unsteady features due to flow field inertial and pressure wave propagation. Levels of accuracy achieved by TURBODYNA have proved superior to traditional 1D modelling on turbine performance and the generality of the current 1D modelling has been explored by extending the application to another turbine featuring distinct characteristics.
Yang B, Newton P, Martinez-Botas R, 2020, Understanding of Secondary Flows and Losses in Radial and Mixed Flow Turbines, JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME, Vol: 142, ISSN: 0889-504X
Palenschat T, Wahl P, Nakov G, et al., 2020, Optimization of an Asymmetric Twin Scroll Volute Turbine under Pulsating Engine Boundary Conditions
Future CO2 emission legislation requires the internal combustion engine to become more efficient than ever. Of great importance is the boosting system enabling down-sizing and down-speeding. However, the thermodynamic coupling of a reciprocating internal combustion engine and a turbocharger poses a great challenge to the turbine as pulsating admission conditions are imposed onto the turbocharger turbine. This paper presents a novel approach to a turbocharger turbine development process and outlines this process using the example of an asymmetric twin scroll turbocharger applied to a heavy duty truck engine application. In a first step, relevant operating points are defined taking into account fuel consumption on reference routes for the target application. These operation points are transferred into transient boundary conditions imposed on the turbine. These pulsating admission conditions to the turbocharger turbine are analyzed and subsequently discretized using the method of quasi-steadiness to avoid numerically very expensive unsteady CFD simulations. Following, an automated in-house developed workflow based on a parameterized model of the entire turbine stage is introduced and described. The parameterization is based on design parameters linked to aerodynamic properties, hence it is not limited to one specific geometry but rather able to represent a large variety of designs with comparatively few input parameters. Concluding, a meta-model based multi-disciplinary and multi-objective numerical optimization is performed to obtain the best geometry possible. The optimization objectives are linked to a perfect turbine-compressor matching with an existing benchmark compressor stage and regards to the engine's air fuel ratio and exhaust gas recirculation requirements. The entire optimization is based on numerical methods, that is, a CFD study. However, the numerical models used throughout the paper are validated against experimental data to ensure the quality and accu
Chiong MS, Tan FX, Rajoo S, et al., 2020, On-Engine Performance Evaluation of a New-Concept Turbocharger Compressor Housing Design
Following market demands for a niche balance between engine performance and legislation requirement, a new-concept compressor scroll has been designed for small to medium size passenger cars. The design adopts a slight deviation from the conventional method, thus resulting in broader surge margin and better efficiency at off-design region. This paper presents the performance evaluation of the new compressor scroll on the cold-flow gas-stand followed by the on-engine testing. The testing program focused on back-to-back comparison with the standard compressor scroll, as well as identifying on-engine operational regime with better brake specific fuel consumption (BSFC) and transient performance. A specially instrumented 1.6L gasoline engine was used for this study. The engine control unit configuration is kept constant in both the compressor testing. The intake and exhaust manifold has been customized to fit the turbochargers and kept identical between the standard and new compressor scroll installations. The turbocharger with new compressor scroll design is found to work at higher boost pressure and has better stage efficiency across most of the engine operating conditions. Largest efficiency difference was noted at part-load and low engine speed operation. In term of BSFC, 8-10% of improvement has been recorded with the new compressor scroll at high-load conditions. The compressor scrolls have been instrumented to measure instantaneous flow pressure in order to investigation potential reasons for performance improvement. The difference in efficiency between the compressor scrolls does not exhibit apparent trend with the scroll pulse pressure amplitude, but do show the likelihood of pulse flow and heat transfer effect. At the same time, the new compressor scroll was found to generally improve the engine transient response for the low-to-medium speed conditions. The transient gradient of the boost pressure for the new-concept compressor is noted to increase towards the
Lu X, Martinez-Botas R, Hey J, 2020, Analytical framework for disturbance energy balance in thermoacoustic devices, JOURNAL OF FLUID MECHANICS, Vol: 885, ISSN: 0022-1120
Hohenberg K, Martinez-Botas R, Łuczynski P, et al., 2020, Numerical and experimental investigation of a low order radial turbine model for engine-level optimisation of turbocharger design
This paper presents the development and validation of a meanline model by means of numerical and experimental methods, to determine it’s feasibility as an optimisation tool for turbocharger matching. Using a parametric turbine model, numerical experiments were conducted accounting for variations of several key turbine design parameters and a wide operating range. The resulting dataset was used to test the accuracy of the meanline model when calibrated to a baseline design and thus evaluate it’s ability of extrapolating to different designs. The loss models were examined in more detail, and a set of loss models which provided the most accurate results is presented. The meanline model was further validated experimentally using dynamometer test results of 6 turbine designs from the same parametric turbine model. The result showed that for design point and high power operation, an error of less than 3.1% and 2.0% was achieved for efficiency and mass flow parameter respectively. This led to the conclusion that the model would be sufficiently accurate to represent design changes relevant to turbocharger matching
Xue Y, Yang M, Martinez-Botas RF, et al., 2019, Unsteady performance of a mixed-flow turbine with nozzled twin-entry volute confronted by pulsating incoming flow, Aerospace Science and Technology, Vol: 95, Pages: 1-13, ISSN: 1270-9638
Turbine with twin-entry volute has advantage of utilising energy from pulsatile exhaust gas and improving low-speed torque of an internal combustion engine. This paper investigates unsteady performance of a mixed flow turbine with nozzled twin-entry volute confronted by pulsatile incoming flow. The turbine performance at pulsating conditions with different Strouhal numbers (St) is studied via experimentally validated numerical method. Results show that the unsteadiness of turbine performance is enhanced as Strouhal number increases. In particular, the cycle-average efficiency at St = 0.522 is about 3.4% higher than that of quasi-steady condition (St = 0). Instantaneous loss breakdown of the turbine shows that the entropy generation rate of turbine components reduces evidently at pulsating conditions as Strouhal number increases, especially for the nozzle. Specifically, the cycle-averaged reduction of the loss in the nozzle is 37.3% at St = 0.522 compared with that of St = 0. The flow analysis shows that secondary flow which contributes to the majority of loss in the nozzle, including flow separation, horseshoe vortex, and reversed flow near the leading edge, are notably alleviated as Strouhal number increases. The alleviation of the flow structures are resulted from two reasons: one is that the flow distortion at the nozzle inlet is evidently depressed by the pulsating conditions, the other is that the inertia of the low momentum flow in the nozzle damps flow evolution at pulsating incoming flow. Consequently, the loss is reduced and the turbine performance is benefited by the pulsating inflows.
Shu M, Yang M, Zhang K, et al., 2019, Experimental study on performance of centrifugal compressor exposed to pulsating backpressure, AEROSPACE SCIENCE AND TECHNOLOGY, Vol: 95, ISSN: 1270-9638
Yang B, Martinez-Botas R, 2019, TURBODYNA: Centrifugal/Centripetal Turbomachinery Dynamic Simulator and Its Application on a Mixed Flow Turbine, JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME, Vol: 141, ISSN: 0742-4795
Barrera-Medrano ME, Martinez-Botas R, Tomita I, et al., 2019, On the Effect of Engine Pulsations on the Performance of a Turbocharger Centrifugal Compressor, JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME, Vol: 141, ISSN: 0742-4795
The use of twin-scroll turbocharger turbine in automotive powertrain has been known for providing better transient performance over conventional single-scroll turbine. This has been accredited to the preservation of exhaust flow energy in the twin-scroll volute. In the current study, the performance comparison between a single and twin-scroll turbine has been made experimentally on a 1.5L passenger car gasoline engine. The uniqueness of the current study is that nearly identical engine hardware has been used for both the single and twin-scroll turbine volutes. This includes the intake and exhaust manifold geometry, turbocharger compressor, turbine rotor and volute scroll A/R variation trend over circumferential location. On top of that, the steady-state engine performance with both the volutes, has also been tuned to have matching brake torque. Such highly comparable setup enabled a more precise evaluation on the effect of pulse-isolation in the twin-scroll turbine volute during transient process. The steady-state performance comparison shows the amplitude of exhaust pulse in the twin-scroll volute is substantially higher than in the single-scroll volute, hence confirming the preservation of pulse exhaust energy. As a result, twin-scroll volute is found to be able to accelerate the engine boost pressure at a faster rate, therefore results in better transient response. The ultimate advantage of the twin-scroll turbine is further exemplified via engine Worldwide harmonized Light vehicles Test Cycle (WLTC) testing, where approximately 2.7% of averaged reduction in fuel consumption has been recorded. Majority of this improvement has been contributed by low to medium speed driving condition.
Shu M, Yang M, Martinez-Botas F, et al., 2019, Unsteady Responses of the Impeller of a Centrifugal Compressor Exposed to Pulsating Backpressure, JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME, Vol: 141, ISSN: 0742-4795
Mahyon NI, Li T, Martinez-Botas R, et al., 2019, A new hollow fibre catalytic converter design for sustainable automotive emissions control, CATALYSIS COMMUNICATIONS, Vol: 120, Pages: 86-90, ISSN: 1566-7367
Xue Y, Yang M, Martinez-Botas RF, et al., 2019, Loss analysis of a mix-flow turbine with nozzled twin-entry volute at different admissions, ENERGY, Vol: 166, Pages: 775-788, ISSN: 0360-5442
Teo AE, Chiong MS, Yang M, et al., 2019, Performance evaluation of low-pressure turbine, turbo-compounding and air-Brayton cycle as engine waste heat recovery method, ENERGY, Vol: 166, Pages: 895-907, ISSN: 0360-5442
Yang B, Martinez-Botas R, 2019, Turbodyna: Centrifugal/centripetal turbomachinery dynamic simulator and its application on a mixed flow turbine
1D modelling is crucial for turbomachinery unsteady performance prediction and system response assessment. The purpose of the paper is to describe a newly developed 1D modelling (TURBODYNA) for turbomachinery. Different from classic 1D modelling, in TURBODYNA, rotor has been meshed and its unsteadiness due to flow field time scale is considered. Instead of direct using of performances maps, source terms are added in Euler equation set to simulate the rotor. By comparing 1D modelling with 3D CFD results, It shows that rotor unsteadiness is indispensable for a better prediction. In addition, different variables response to pulse differently. In the rotor, mass flow is close to quasi-steady while entropy is significantly unsteady. TURBODYNA can capture these features correctly and provide an accurate prediction on pressure wave transportation.
Robertson MC, Newton PJ, Chen T, et al., 2019, DEVELOPMENT AND COMMISSIONING OF A BLOWDOWN FACILITY FOR DENSE GAS VAPOURS, ASME Turbo Expo: Turbomachinery Technical Conference and Exposition, Publisher: AMER SOC MECHANICAL ENGINEERS
Abel M, Martinez-Botas RF, Woehr M, et al., 2019, 3D COMPUTATIONAL LOSS ANALYSIS OF A COMPRESSOR FOR HEAVY DUTY TRUCK ENGINE TURBOCHARGERS, ASME Turbo Expo: Turbomachinery Technical Conference and Exposition, Publisher: AMER SOC MECHANICAL ENGINEERS
Chiong MS, Rajoo S, Martinez-Botas RF, et al., 2019, MEANLINE MODELING OF ASYMMETRICAL TWIN -SCROLL TURBINE: LOSS COEFFICIENT TRANSFERABILITY BETWEEN TURBINES OF DIFFERENT SIZES, ASME Turbo Expo: Turbomachinery Technical Conference and Exposition, Publisher: AMER SOC MECHANICAL ENGINEERS
Shu M, Yang M, Zhang K, et al., 2019, EXPERIMENTAL STUDY ON CENTRIFUGAL COMPRESSOR PERFORMANCE AT PULSATING BACKPRESSURE CONDITIONS, ASME Turbo Expo: Turbomachinery Technical Conference and Exposition, Publisher: AMER SOC MECHANICAL ENGINEERS
Meroni A, Robertson M, Martinez-Botas R, et al., 2018, A methodology for the preliminary design and performance prediction of high-pressure ratio radial-inflow turbines, ENERGY, Vol: 164, Pages: 1062-1078, ISSN: 0360-5442
Shu M, Yang M, Deng K, et al., 2018, Performance Analysis of a Centrifugal Compressor Based on Circumferential Flow Distortion Induced by Volute, JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME, Vol: 140, ISSN: 0742-4795
Cao K, Newton P, Flora H, et al., 2018, The development of a novel unsteady flow control method: Controlling the rotating nozzle ring, PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART C-JOURNAL OF MECHANICAL ENGINEERING SCIENCE, Vol: 232, Pages: 4495-4509, ISSN: 0954-4062
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