233 results found
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
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
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.
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
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
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
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
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.
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
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
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
Merla Y, Wu B, Yufit V, et al., 2018, An easy-to-parameterise physics-informed battery model and its application towards lithium-ion battery cell design, diagnosis, and degradation, Journal of Power Sources, Vol: 384, Pages: 66-79, ISSN: 0378-7753
Accurate diagnosis of lithium ion battery state-of-health (SOH) is of significant value for many applications, to improve performance, extend life and increase safety. However, in-situ or in-operando diagnosis of SOH often requires robust models. There are many models available however these often require expensive-to-measure ex-situ parameters and/or contain unmeasurable parameters that were fitted/assumed. In this work, we have developed a new empirically parameterised physics-informed equivalent circuit model. Its modular construction and low-cost parametrisation requirements allow end users to parameterise cells quickly and easily. The model is accurate to 19.6 mV for dynamic loads without any global fitting/optimisation, only that of the individual elements. The consequences of various degradation mechanisms are simulated, and the impact of a degraded cell on pack performance is explored, validated by comparison with experiment. Results show that an aged cell in a parallel pack does not have a noticeable effect on the available capacity of other cells in the pack. The model shows that cells perform better when electrodes are more porous towards the separator and have a uniform particle size distribution, validated by comparison with published data. The model is provided with this publication for readers to use.
Palenschat T, Mueller M, Rajoo S, et al., 2018, Steady-State Experimental and Meanline Study of an Asymmetric Twin-Scroll Turbine at Full and Unequal and Partial Admission Conditions, WCX World Congress Experience
© 2018 SAE International. All Rights Reserved. The use of twin-scroll turbocharger turbines has gained popularity in recent years. The main reason is its capability of isolating and preserving pulsating exhaust flow from engine cylinders of adjacent firing order, hence enabling more efficient pulse turbocharging. Asymmetrical twin-scroll turbines have been used to realize high pressure exhaust gas recirculation (EGR) using only one scroll while designing the other scroll for optimal scavenging. This research is based on a production asymmetrical turbocharger turbine designed for a heavy duty truck engine of Daimler AG. Even though there are number of studies on symmetrical twin entry scroll performance, a comprehensive modeling tool for asymmetrical twin-scroll turbines is yet to be found. This is particularly true for a meanline model, which is often used during the turbine preliminary design stage. This study presents the development of a generalized meanline model for a twin-scroll turbine, which can be used in the early design stages, concentrating on asymmetrical scrolls. The improvements from the previous meanline model, i.e., the inlet duct and interspace model, in order to enable asymmetrical scroll prediction is described. The latter is based on the popular theory of turbomachinery wakes mixing, adopted from literature. The model is validated against experimental cold gas stand data under equal and unequal-admission conditions. Comparison between the model and experiments indicates the importance of the inlet duct and interspace model between the scrolls in obtaining satisfactory predictions across different admission conditions, due to the non-symmetrical features between the scrolls.
Padzillah MH, Rajoo S, Martinez-Botas RF, 2018, A Detailed Comparison on the Influence of Flow Unsteadiness Between the Vaned and Vaneless Mixed-Flow Turbocharger Turbine, JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME, Vol: 140, ISSN: 0742-4795
Palenschat T, Cortell JF, Newton P, et al., 2018, Numerical study of the quasi-steady approach applied to an asymmetric twin-scroll volute turbocharger turbine for a heavy duty diesel engine under realistic boundary conditions, Pages: 443-458
This paper presents a numerical study on the validity of the quasi-steady approach with respect to an asymmetric twin-scroll turbocharger heavy duty diesel engine under realistic boundary conditions. The motivation of using the quasi-steady approach in this context is the possibility to speed up the evaluation process in early design steps while already taking into account boundary conditions more suitable than equal admission. As transient 3D CFD is computationally very expensive, the quasi-steady approach is used to reduce computational time drastically. However, the validity of the quasi-steady approach is widely discussed and does not hold for the volute. Furthermore, it has never been evaluated for an asymmetric twin-scroll turbine and unequal admission. A 3D CFD model is built in this paper using the Ansys tool chain. The computational model is validated against experiments carried out at the cold-gas turbocharger test facility of Imperial College London. The boundary conditions for the analysis are selected based upon the real load conditions of a Mercedes-Benz lorry on a given route and take into account equal and unequal admission between the two scrolls. A set of steady computations is performed using the unequal and equal boundary admission conditions of the discretised pulsations. The cycle efficiency is computed in order to find a metric to compare the steady and unsteady approaches. Following, unsteady computations are performed with unsteady boundary conditions to capture the real pulsating boundary conditions resulting from the engine. Steady as well as unsteady computations are compared in order to evaluate the validity of the quasi-steady approach. Finally, the same comparison is also shown based on experimental data.
Liu H, Romagnoli A, Ismail MI, et al., 2018, Multi-injection turbine housing: A novel concept for performance improvement in radial turbines, Pages: 291-308
Secondary flow injection is a way which allows for the efficiency of a turbomachine to be increased further, after blade design optimizations have already been performed. In this paper, a novel method for improving turbine performance using secondary flow injection through an injection slot over the turbine shroud is investigated. Numerical simulations were conducted on a mixed flow turbocharger turbine to test the effectiveness of secondary flow injection. An optimization using Genetic Algorithm was performed at peak efficiency at 50% turbine design speed to determine the injection set up which gives the highest turbine efficiency. The final optimized point gave an increase in efficiency of 2.6 percentage points compared to the baseline turbine. Flow analysis shows that injection partially blocks the flow passage near the blade tip, forcing turbine passage flow to migrate towards the hub. This apparently weakens the hub suction side separation vortex and reduces entropy generation from the vortex. However, entropy generation near the blade tip is increased, and the tip leakage vortex structure has become a counter-rotating vortex pair. Overall, injection reduces the entropy generation in the turbine by 10.7% at the optimized point. The optimized set of injection parameters was then used across 4 different speed lines to generate the turbine performance maps. The turbine maps show an overall increase in turbine efficiency, but a slight decrease in mass flow parameter and increased back pressure. The turbine maps are then used in an engine simulation to predict engine performance with and without injection. Engine performance at full load and part load conditions are simulated at 4 different engine speeds. The engine simulation results show that injection increases the turbocharger boost pressure. As a result, the brake specific fuel consumption (BSFC) of the engine is reduced throughout the engine speeds tested. The greatest reduction in BSFC is at 1050 rpm, where f
Barrera-Medrano ME, Martinez-Botas R, Tomita I, et al., 2018, On the effect of engine pulsations on the performance of a turbocharger centrifugal compressor, Pages: 101-125
In an IC engine, the centrifugal compressor is placed upstream of the inlet manifold and therefore, it is exposed an unsteady flow regime caused by the inlet valves of the cylinder arrangement. This valve motion sets a pulsating state at the compressor exit, having greater influence when the operation is near the surge margin of the compressor; it may therefore limit further the engine minimum flow rate. This paper presents the experimental results of the evaluation of the surge dynamics on a compressor with induced downstream pulsating flow. Different pulsation levels are achieved by the variation of four different parameters on the induced pulse: pulse frequency, amplitude, the presence of a storage volume (plenum) and pulse location. Each of the four pulse parameters was evaluated independently in order to assess its effect on the compressor stability limit. The main effect on the surge margin of the compressor has been found to be due to the presence of a volume in the system for all cases, whether steady or unsteady/pulsating condition, and at all frequencies. It was found that the magnitude of the pulse frequency determines the hysteresis behaviour of the system that leads to a phase difference between the convected terms (volume flow) and the acoustic dominated terms (pressure), and therefore this affects the onset of flow instability, surge, in the compression system under study. Based on these results, the compressor performance, and particularly its stability limit, is strongly influenced by the downstream conditions of the system where the compressor is placed. The nature of downstream conditions influences the compressor characteristic curve, and in some cases the compressor "feels" like another machine just by means of varying the downstream state at the compressor exit. The presence of a pulsating state at the compressor outlet increases the inertia of the compression system and thus it affects the compressor transient response. The outlet pu
Abel M, Newton P, Martinez-Botas RF, et al., 2018, 3D COMPUTATIONAL ANALYSIS OF A COMPRESSOR FOR HEAVY DUTY TRUCK ENGINE TURBOCHARGERS, ASME Turbo Expo: Turbomachinery Technical Conference and Exposition, Publisher: AMER SOC MECHANICAL ENGINEERS
Xue YX, Yang MY, Deng KY, et al., 2018, Performance and flow analysis of a mixed flow turbine with twin-entry nozzled volute, Pages: 425-441
This paper studies the performance and detailed flow field of a nozzled turbine with twin-entry volute (developed by Imperial College London) at different admission conditions via experimentally validated numerical method. Two partial admissions are analysed which are the admission near hub side (referring as HI) and near shroud side (referring as SI), respectively. Results manifest that the efficiency of the case of HI is moderately higher than that of SI although their flow capacity is the same. The performance of unequal admission is bounded by that of the full admission and the partial admission. The breakdown of the flow loss in turbine components shows that significant discrepancies exist among different admissions. The flow loss in the volute Is nearly the same for two cases. However, the loss is moderately higher in the nozzle for SI at all turbine loadings, but notably lower in the rotor for this case when compared with its counterpart. This is caused by the load-dividing between these two cases: the more expansion is divided to the rotor for HI, while more expansion is divided to the nozzle for SI. Flow analysis shows that higher entropy is generated in the nozzle for SI due to strong flow separation on the suction surfaces near the leading edge because of large incidence angle. On the other hand, the flow aligns well with the vane angle for HI near the hub, but a large size vortex rolls up near the shroud side which corresponds to the high entropy generation. Downstream the nozzle, a 'tornado' vortex is developed in the rotor passages for the case HI, which leads to higher entropy generation and hence higher flow loss in rotor. This studyunveils the flow mechanism of performance distinctions at different admission conditions for the turbine with twin-entry nozzled volute, which may enlighten performance improvement of the turbine and hence the internal combustion engine.
Ardani MI, Patel Y, Siddiq A, et al., 2017, Combined experimental and numerical evaluation of the differences between convective and conductive thermal control on the performance of a lithium ion cell, Energy, Vol: 144, Pages: 81-97, ISSN: 0360-5442
Testing of lithium ion batteries is necessary in order to understand their performance, to parameterise and furthermore validate models to predict their behaviour. Tests of this nature are normally conducted in thermal/climate chambers which use forced air convection to distribute heat. However, as they control air temperature, and cannot easily adapt to the changing rate of heat generated within a cell, it is very difficult to maintain constant cell temperatures. This paper describes a novel conductive thermal management system which maintains cell temperature reliably whilst also minimising thermal gradients. We show the thermal gradient effect towards cell performance is pronounced below operating temperature of 25 °C at 2-C discharge under forced air convection. The predicted internal cell temperature can be up to 4 °C hotter than the surface temperature at 5 °C ambient condition and eventually causes layers to be discharge at different current rates. The new conductive method reduces external temperature deviations of the cell to within 1.5 °C, providing much more reliable data for parameterising a thermally discretised model. This method demonstrates the errors in estimating physiochemical paramet ers; notably diffusion coefficients, can be up to four times smaller as compared to parameterisation based on convective test data.
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