Publications
243 results found
Padzillah MH, Rajoo S, Martinez-Botas RF, 2016, COMPARISON OF FLOW FIELD BETWEEN STEADY AND UNSTEADY FLOW OF AN AUTOMOTIVE MIXED FLOW TURBOCHARGER TURBINE, Jurnal Teknologi, Vol: 78, Pages: 1-7, ISSN: 0127-9696
Global decarbonizing efforts in transportation industry have forced the automotive manufacturers to opt for highly downsized high power-to-weight ratio engines. Since its invention, turbocharger remains as integral element in order to achieve this target. However, although it has been proven that a turbocharger turbine works in highly pulsatile environment, it is still designed under steady state assumption. This is due to the lack of understanding on the nature of pulsating flow field within the turbocharger turbine stage. This paper presents an effort to visualize the pulsating flow feature using experimentally validated Computational Fluid Dynamics (CFD) simulations. For this purpose, a lean-vaned mixed-flow turbine with rotational speed of 30000 rpm at 20 Hz flow frequency, which represent turbine operation for 3-cylinder 4-stroke engine operating at 800 rpm has been used. Results indicated that the introduction of pulsating flow has resulted in more irregular pattern of flow field as compared to steady flow operation. It has also been indicated that the flow behaves very differently between pressure increment and decrement instances. During the pressure decrement instance, flow blockage in terms of low pressure region occupies most of the turbine passage as the flow exit the turbine.
Robertson MC, Costall AW, Newton PJ, et al., 2016, Radial Turboexpander Optimization Over Discretized Heavy-Duty Test Cycles for Mobile Organic Rankine Cycle Applications, ASME Turbo Expo: Turbine Technical Conference and Exposition, Publisher: AMER SOC MECHANICAL ENGINEERS
Hey J, Malloy AC, Martinez-Botas R, et al., 2016, Online Monitoring of Electromagnetic Losses in an Electric Motor Indirectly Through Temperature Measurement, IEEE TRANSACTIONS ON ENERGY CONVERSION, Vol: 31, Pages: 1347-1355, ISSN: 0885-8969
Zhao R, Zhuge W, Zhang Y, et al., 2016, Numerical study of a two-stage turbine characteristic under pulsating flow conditions, JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY, Vol: 30, Pages: 557-565, ISSN: 1738-494X
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- Citations: 9
Yang M, Martinez-Botas R, Zhang Y, et al., 2016, Effect of Self-Recirculation-Casing Treatment on High Pressure Ratio Centrifugal Compressor, Journal of Propulsion and Power, Vol: 32, Pages: 602-610, ISSN: 1533-3876
Wu B, Merla Y, Yufit V, et al., 2016, Novel application of differential thermal voltammetry as an in-depth state-of-health diagnosis method for lithium-ion batteries, Journal of Power Sources, Vol: 307, Pages: 308-319, ISSN: 1873-2755
Understanding and tracking battery degradation mechanisms and adapting its operation have become a necessity in order to enhance battery durability. A novel use of differential thermal voltammetry (DTV) is presented as an in-situ state-of-health (SOH) estimator for lithium-ion batteries.Accelerated ageing experiments were carried on 5Ah commercial lithium-ion polymer cells operated and stored at different temperature and loading conditions. The cells were analysed regularly with various existing in-situ diagnosis methods and the novel DTV technique to determine their SOH. The diagnosis results were used collectively to elaborate the degradation mechanisms inside the cells. The DTV spectra were decoupled into individual peaks, which each represent particular phases in the negative and positive electrode combined. The peak parameters were used to quantitatively analyse the battery SOH.A different cell of the same chemistry with unknown degradation history was then analysed to explore how the cell degraded. The DTV technique was able to diagnose the cell degradation without relying on supporting results from other methods nor previous cycling data.
Barrera-Medrano ME, Newton P, Martinez-Botas R, et al., 2016, EFFECT OF EXIT PRESSURE PULSATION ON THE PERFORMANCE AND STABILITY LIMIT OF A TURBOCHARGER CENTRIFUGAL COMPRESSOR, ASME Turbo Expo: Turbine Technical Conference and Exposition, Publisher: AMER SOC MECHANICAL ENGINEERS
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- Citations: 3
Cicciotti M, Xenos DP, Bouaswaig AEF, et al., 2015, Physical modelling of industrial multistage centrifugal compressors for monitoring and simulation, PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART C-JOURNAL OF MECHANICAL ENGINEERING SCIENCE, Vol: 229, Pages: 3433-3448, ISSN: 0954-4062
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- Citations: 5
Yang M, Martinez-Botas R, Rajoo S, et al., 2015, An investigation of volute cross-sectional shape on turbocharger turbine under pulsating conditions in internal combustion engine, Energy Conversion and Management, Vol: 105, Pages: 167-177, ISSN: 0196-8904
Engine downsizing is a proven method for CO2 reduction in Internal Combustion Engine (ICE). A turbocharger, which reclaims the energy from the exhaust gas to boost the intake air, can effectively improve the power density of the engine thus is one of the key enablers to achieve the engine downsizing. Acknowledging its importance, many research efforts have gone into improving a turbocharger performance, which includes turbine volute. The cross-section design of a turbine volute in a turbocharger is usually a compromise between the engine level packaging and desired performance. Thus, it is beneficial to evaluate the effects of cross-sectional shape on a turbine performance. This paper presents experimental and computational investigation of the influence of volute cross-sectional shape on the performance of a radial turbocharger turbine under pulsating conditions. The cross-sectional shape of the baseline volute (denoted as Volute B) was optimized (Volute A) while the annulus distribution of area-to-radius ratio (A/R) for the two volute configurations are kept the same. Experimental results show that the turbine with the optimized volute A has better cycle averaged efficiency under pulsating flow conditions, for different loadings and frequencies. The advantage of performance is influenced by the operational conditions. After the experiment, a validated unsteady computational fluid dynamics (CFD) modeling was employed to investigate the mechanism by which performance differs between the baseline volute and the optimized version. Computational results show a stronger flow distortion in spanwise direction at the rotor inlet with the baseline volute. Furthermore, compared with the optimized volute, the flow distortion is more sensitive to the pulsating flow conditions in the baseline volute. This is due to the different secondary flow pattern in the cross-sections, hence demonstrating a direction for desired volute cross-sectional shape to be used in a turbocharger rad
Costall AW, Gonzalez Hernandez A, Newton PJ, et al., 2015, Design methodology for radial turbo expanders in mobile organic Rankine cycle applications, Applied Energy, Vol: 157, Pages: 729-743, ISSN: 0306-2619
Future vehicles for clean transport will require new powertrain technologies to further reduce CO2 emissions. Mobile organic Rankine cycle systems target the recovery of waste heat in internal combustion engines, with the exhaust system identified as a prime source. This article presents a design methodology and working fluid selection for radial turbo expanders in a heavy-duty off-road diesel engine application. Siloxanes and Toluene are explored as the candidate working fluids, with the latter identified as the preferred option, before describing three radial turbine designs in detail. A small 15.5. kW turbine design leads to impractical blade geometry, but a medium 34.1. kW turbine, designed for minimum power, is predicted to achieve an isentropic efficiency of 51.5% at a rotational speed of 91.7. k. min-1. A similar 45.6. kW turbine designed for maximum efficiency yields 56.1% at 71.5. k. min-1. This emphasizes the main design trade-off - efficiency decreases and rotational speed increases as the power requirement falls - but shows reasonable radial turbine efficiencies and thus practical turbo expanders for mobile organic Rankine cycle applications are realizable, even considering the compromised flow geometry and high speeds imposed at such small scales.
Bin Mamat AMI, Martinez-Botas RF, Rajoo S, et al., 2015, Waste heat recovery using a novel high performance low pressure turbine for electric turbocompounding in downsized gasoline engines: Experimental and computational analysis, ENERGY, Vol: 90, Pages: 218-234, ISSN: 0360-5442
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- Citations: 30
Hu BZ, Copeland C, Lu P, et al., 2015, A New De-throttling Concept in a Twin-Charged Gasoline Engine System, SAE INTERNATIONAL JOURNAL OF ENGINES, Vol: 8, Pages: 1553-1561, ISSN: 1946-3936
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- Citations: 10
Padzillah MH, Rajoo S, Yang M, et al., 2015, Influence of pulsating flow frequencies towards the flow angle distributions of an automotive turbocharger mixed-flow turbine, ENERGY CONVERSION AND MANAGEMENT, Vol: 98, Pages: 449-462, ISSN: 0196-8904
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- Citations: 15
Khairuddin U, Costall AW, Martinez-Botas RF, 2015, INFLUENCE OF GEOMETRICAL PARAMETERS ON AERODYNAMIC OPTIMIZATIONOF A MIXED-FLOW TURBOCHARGER TURBINE, ASME Turbo Expo 2015: Turbine Technical Conference and Exposition, Publisher: ASME
This paper describes an optimization procedure to modify the geometry of a mixed-flow turbocharger turbine for improved aerodynamic efficiency. The procedure integrates parameterization of the turbine blade geometry, genetic algorithm optimization, and 3D CFD analysis using a commercial solver.Using a known mixed-flow turbocharger turbine as the baseline, the main features of the blade geometry — the hub, shroud, camberline, leading and trailing edge profiles—were separately adjusted by the genetic algorithm in the direction of better efficiency. Apart from optimizing the subject turbine for the operating point in question, more usefully this permits each geometrical feature to be ranked by their contribution to the change in efficiency. Cases were also run in which the hub and shroud curves were simultaneously adjusted. Analysis of CFD results provides additional insight into the underlying reasons for efficiency changes by examination of the relevant flow field features.The hub and shroud profiles were observed to have the greatest impact on turbine performance, optimization of which leads to an increase of 1.3 percentage points of efficiency. This compares to only 0.2 percentage points improvement following optimization of the outlet geometry.
Malloy AC, Martinez-Botas RF, Lamperth M, 2015, A criterion for determining the relative importance of the fluctuating component of a periodic heat source, ENERGY CONVERSION AND MANAGEMENT, Vol: 96, Pages: 12-17, ISSN: 0196-8904
Zhao R, Zhuge W, Zhang Y, et al., 2015, Study of two-stage turbine characteristic and its influence on turbo-compound engine performance, ENERGY CONVERSION AND MANAGEMENT, Vol: 95, Pages: 414-423, ISSN: 0196-8904
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- Citations: 50
Xenos DP, Cicciotti M, Kopanos GM, et al., 2015, Optimization of a network of compressors in parallel: Real Time Optimization (RTO) of compressors in chemical plants - An industrial case study, Applied Energy, Vol: 144, Pages: 51-63, ISSN: 0306-2619
The aim of this paper is to present a methodology for optimizing the operation of compressors in parallel in process industries. Compressors in parallel can be found in many applications for example in compressor stations conveying gas through long pipelines and in chemical plants in which compressors supply raw or processed materials to downstream processes. The current work presents an optimization framework for compressor stations which describe integration of a short term and a long term optimization approach. The short-term part of the framework suggests the best distribution of the load of the compressors (where the time scale is minutes) and the long-term optimization provides the scheduling of the compressors for large time periods (where the time scale is days). The paper focuses on the short-term optimization and presents a Real Time Optimization (RTO) framework which exploits process data in steady-state operation to develop regression models of compressors. An optimization model employs the updated steady-state models to estimate the best distribution of the load of the compressors to reduce power consumption and therefore operational costs. The paper demonstrates the application of the RTO to a network of parallel industrial multi-stage centrifugal compressors, part of a chemical process in BASF SE, Germany. The results from the RTO application showed a reduction in power consumption compared to operation with equal load split strategy.
Abas M, Martinez-Botas R, 2015, Engine Operational Benefits with Cylinder Deactivation in Malaysian Urban Driving Conditions
Cylinder deactivation has been utilized by vehicle manufacturers since the 80's to improve fuel consumption and exhaust emissions. Cylinder deactivation is achieved by cutting off fuel supply and ignition in some of the engine cylinders, while their inlet and outlet valves are fully closed. The vehicle demand during cylinder deactivation is sustained by only the firing cylinders, hence increasing their indicated power. Conventionally, half the number of cylinders are shut at certain driving conditions, which normally at the lower demand regime. An optimal strategy will ensure cylinder deactivation contributes to the fuel saving without compromising the vehicle drivability. Cylinder deactivation has been documented to generally improve fuel consumption between 6 to 25 %, depending on the type-approval test drive cycle. However, type-approval test has been reported to differ from the "real-world" fuel consumption values. Therefore the documented fuel consumption might not be representable for consumers in their actual driving. The Malaysian authorities have been using the NEDC test to measure the emission and fuel consumption for declaration purposes, which may be misleading. This paper presents the measurement and analysis of an engine operating with cylinder deactivation, tested on a dynamometer in accordance to the actual driving conditions rather than the NEDC. This is to understand the actual benefits of cylinder deactivation in the real world. The regular Malaysian urban driving conditions were previously identified and applied in this analysis. To understand the engine operational behaviour, a piezoelectric sensor was instrumented on the engine to acquire the in-cylinder pressure traces. Test results from this study have shown that cylinder deactivation improves fuel consumption and thermodynamic efficiencies for the actual Malaysian driving conditions. The fuel consumption benefit also correlates well with the improvements on the mean effective press
Ismail MI, Costall A, Martinez-Botas R, et al., 2015, Turbocharger Matching Method for Reducing Residual Concentration in a Turbocharged Gasoline Engine
In a turbocharged engine, preserving the maximum amount of exhaust pulse energy for turbine operation will result in improved low end torque and engine transient response. However, the exhaust flow entering the turbine is highly unsteady, and the presence of the turbine as a restriction in the exhaust flow results in a higher pressure at the cylinder exhaust ports and consequently poor scavenging. This leads to an increase in the amount of residual gas in the combustion chamber, compared to the naturally-aspirated equivalent, thereby increasing the tendency for engine knock. If the level of residual gas can be reduced and controlled, it should enable the engine to operate at a higher compression ratio, improving its thermal efficiency. This paper presents a method of turbocharger matching for reducing residual gas content in a turbocharged engine. The turbine is first scaled to a larger size as a preliminary step towards reducing back pressure and thus the residual gas concentration in-cylinder. However a larger turbine causes a torque deficit at low engine speeds. So in a following step, pulse separation is used. In optimal pulse separation, the gas exchange process in one cylinder is completely unimpeded by pressure pulses emanating from other cylinders, thereby preserving the exhaust pulse energy entering the turbine. A pulse-divided exhaust manifold enables this by isolating the manifold runners emanating from certain cylinder groups, even as far as the junction with the turbine housing. This combination of appropriate turbine sizing and pulse-divided exhaust manifold design is applied to a Proton 1.6-litre CamPro CFE turbocharged gasoline engine model. The use of a pulse-divided exhaust manifold allows the turbine to be increased in size by 2.5 times (on a mass flow rate basis) while maintaining the same torque and power performance. As a consequence, lower back pressure and improved scavenging reduces the residual concentration by up to 43%, while the brake sp
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- Citations: 12
Hey J, Malloy AC, Martinez-Botas R, et al., 2015, Conjugate heat transfer analysis of an energy conversion device with an updated numerical model obtained through inverse identification, ENERGY CONVERSION AND MANAGEMENT, Vol: 94, Pages: 198-209, ISSN: 0196-8904
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- Citations: 10
Chiong MS, Rajoo S, Romagnoli A, et al., 2015, Non-adiabatic pressure loss boundary condition for modelling turbocharger turbine pulsating flow, Energy Conversion and Management, Vol: 93, Pages: 267-281, ISSN: 0196-8904
This paper presents a simplified methodology of pulse flow turbine modelling, as an alternative over the meanline integrated methodology outlined in previous work, in order to make its application to engine cycle simulation codes much more straight forward. This is enabled through the development of a bespoke non-adiabatic pressure loss boundary to represent the turbine rotor. In this paper, turbocharger turbine pulse flow performance predictions are presented along with a comparison of computation duration against the previously established integrated meanline method. Plots of prediction deviation indicate that the mass flow rate and actual power predictions from both methods are highly comparable and are reasonably close to experimental data. However, the new boundary condition required significantly lower computational time and rotor geometrical inputs. In addition, the pressure wave propagation in this simplified unsteady turbine model at different pulse frequencies has also been found to be in agreement with data from the literature, thereby supporting the confidence in its ability to simulate the wave action encountered in turbine pulse flow operation.
Kant M, Romagnoli A, Mamat AMI, et al., 2015, Heavy-duty engine electric turbocompounding, PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART D-JOURNAL OF AUTOMOBILE ENGINEERING, Vol: 229, Pages: 457-472, ISSN: 0954-4070
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- Citations: 22
Malloy AC, Martinez-Botas RF, Lamperth M, 2015, Measurement of Magnet Losses in a Surface Mounted Permanent Magnet Synchronous Machine, IEEE TRANSACTIONS ON ENERGY CONVERSION, Vol: 30, Pages: 323-330, ISSN: 0885-8969
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- Citations: 21
Newton P, Martinez-Botas R, Seiler M, 2015, A Three-Dimensional Computational Study of Pulsating Flow Inside a Double Entry Turbine, JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME, Vol: 137, ISSN: 0889-504X
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- Citations: 19
Gambhir A, Tse LKC, Tong D, et al., 2015, Reducing China’s road transport sector CO2 emissions to 2050: Technologies, costs and decomposition analysis, Applied Energy, Vol: 157, Pages: 905-917, ISSN: 1872-9118
The growth of China’s road transport sector has driven huge increases in China’s oil demand and CO2 emissions over the last two decades, and these trends are likely to continue in the absence of specific measures to reduce the average carbon intensity of road vehicles. This paper describes a model, provided in full online, to undertake scenario analysis on the cost and CO2 emissions impact of substituting current vehicle drivetrain types with alternatives during the period 2010–2050. A detailed decomposition of the additional costs and CO2 emissions savings of each low-carbon vehicle type into their component parts is undertaken to calculate the marginal abatement cost of each vehicle and drivetrain type in 2050. The results indicate that passenger cars and heavy-duty trucks constitute the majority of future CO2 emissions savings potential, but that, using the central cost assumptions, alternative vehicle drivetrains are significantly more cost-effective for trucks than passenger cars. The low-carbon scenario sees demand for oil products (gasoline and diesel) more than 40% below the business-as-usual scenario in 2050. The total mitigation cost in 2050 is (US2010)$64 billion per year, or 1.3% of the total annual expenditure on road transport in China in 2050, using a discount rate of 5% to annualise vehicle purchase costs, although this cost increases with higher discount rates. A sensitivity analysis demonstrates that measures in addition to those assumed in the low-carbon scenario could achieve further emissions reductions, in some cases at negative costs. The availability and transparency of the model allows testing and development of a range of further scenarios and sensitivities, to aid in planning an optimal decarbonisation strategy for this highly carbon-intensive sector.
Wu B, Yufit V, Merla Y, et al., 2015, Differential thermal voltammetry for tracking of degradation in lithium-ion batteries, Journal of Power Sources, Vol: 273, Pages: 495-501, ISSN: 0378-7753
Monitoring of lithium-ion batteries is of critical importance in electric vehicle applications in order to manage the operational condition of the cells. Measurements on a vehicle often involve current, voltage and temperature which enable in-situ diagnostic techniques. This paper presents a novel diagnostic technique, termed differential thermal voltammetry, which is capable of monitoring the state of the battery using voltage and temperature measurements in galvanostatic operating modes. This tracks battery degradation through phase transitions, and the resulting entropic heat, occurring in the electrodes. Experiments to monitor battery degradation using the new technique are compared with a pseudo-2D cell model. Results show that the differential thermal voltammetry technique provides information comparable to that of slow rate cyclic voltammetry at shorter timescale and with load conditions easier to replicate in a vehicle.
Chiong MS, Rajoo S, Romagnoli A, et al., 2015, ASSESSMENT OF PARTIAL-ADMISSION CHARACTERISTICS IN TWIN-ENTRY TURBINE PULSE PERFORMANCE MODELLING, ASME Turbo Expo: Turbine Technical Conference and Exposition, Publisher: AMER SOC MECHANICAL ENGINEERS
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- Citations: 2
Bin Mamat AMI, Martinez-Botas RF, Chiong MC, et al., 2015, Exhaust Gas Energy Recovery Via Electric Turbocompounding, 7th International Conference on Applied Energy (ICAE), Publisher: ELSEVIER SCIENCE BV, Pages: 1555-1559, ISSN: 1876-6102
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- Citations: 5
Cao K, Yang M, Martinez-Botas RF, 2015, A NUMERICAL INVESTIGATION ON A NEW PULSE-OPTIMIZED FLOW CONTROL METHOD FOR TURBOCHARGER TURBINE PERFORMANCE IMPROVEMENT UNDER PULSATING CONDITIONS, ASME Turbo Expo: Turbine Technical Conference and Exposition, Publisher: AMER SOC MECHANICAL ENGINEERS
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- Citations: 5
Chebli E, Casey M, Martinez-Botas R, et al., 2014, The Variable Outlet Turbine Concept for Turbochargers, JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME, Vol: 136, ISSN: 0889-504X
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- Citations: 6
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