Hydrogen powered car: Two-stage modelling system

This paper presents a research work on intelligent two-stage modelling system to estimate a hydrogen internal combustion engine performances including: engine torque and oxides of nitrogen emissions. In the created models, the ignition timing is chosen as a local input, while the engine speed, throttle position, injection duration, injection end angle and lambda are chosen as global inputs. While previous papers [1], [2], [3] and [4] included tuning procedures and hydrogen engine performances, intelligent emissions prediction of hydrogen car, and two-stage modelling of torque, this paper carries on from those observations to develop a completed two-stage modelling system of the converted hydrogen engine. More details on individual two-stage models are provided based on data recorded during the fine tuning process on dynamometer. This work is a step towards establishing intelligent two-stage modelling of hydrogen powered car via application of response surface methodology with hydrogen engine in the loop simulation and testing.     

Printable,Transparent, and Flexible Touch Panels Working in Sunlight and Moist Environments

The ongoing revolution of touch‐based user interfaces sets new requirements for touch panel technologies, including the need to operate in a wide range of environments. Such touch panels need to endure moisture and sunlight. Moreover, they often need to be curved or flexible. Thus, there is a need for new technologies suitable, for example, for home appliances used in the kitchen or the bathroom, automotive applications, and e‐paper. In this work, the development of transparent and flexible touch panels for moist environments is reported. A piezoelectric polymer, poly(vinylidene difluoride) (PVDF), is used as a functional substrate material. Transparent electrodes are fabricated on both sides of a PVDF film using a graphene‐based ink and spray coating. The excellent performance of the touch panels is demonstrated in moist and underwater conditions. Also, the transparent device shows very small pyroelectric response to radiative heating in comparison to a non‐transparent device. Solution processable electrode materials in combination with functional substrates allow the low‐cost and high‐throughput manufacturing of touch panels using printing technologies.     

Fundamental studies of driven and self-propelled rotary tool cutting processes—II. Experimental investigation

An extensive experimental investigation has been carried out to verify the developed mechanics of cutting analyses for the fundamental driven and self-propelled rotary tool cutting processes. This involved testing the dynamic or perfect equivalence between the rotary tool and equivalent classical processes over a wide range of inclination angles, cut thickness and rake angles using statistical processing techniques. The collinearity conditions at the shear plane and rake face have also been tested as part of the model verification. It has been shown that all the force components, deformation and basic cutting parameter trends and quantities required for perfect equivalence have been satisfied as were the necessary collinearity conditions. The verified models provide a deeper understanding of the cutting mechanics and characteristics of these ingenious material removal operations and form the basis for the development of predictive cutting models for the fundamental and complex practical rotary tool operations.     

Cluster characteristics of Geldart group B particles in a pilot-scale CFB riser. II. Polydisperse systems

Experiments with a focus on the impact of polydispersity on clustering characteristics (namely, appearance probability, duration, and frequency) of Geldart Group B particles in a circulating fluidized bed (CFB) riser have been performed. Three mixtures are considered: (i) a density-difference binary mixture, with species of different material density (ρ_s) but similar particle sizes (d_ave), (ii) a size-difference binary mixture, with species of different d_ave but similar material density ρ_s, and (iii) a continuous particle size distribution (PSD). Local cluster information spanning the entire riser was obtained over a range of operating conditions using a fiber optic probe. Results show that cluster trends for the binary mixtures are similar to those reported in the companion work for monodisperse materials (Chew et al., this issue) on two counts. First, local riser position has a significant influence on all three cluster characteristics, while effects of operating condition and material type are secondary. Second, among the three cluster characteristics, the cluster appearance probability is most influenced by local position, and least affected by operating condition and material type. Furthermore, the density-difference binary mixture exhibits a distinctly lower cluster duration than either of its constituent components. In contrast, the size-difference binary mixture has a cluster duration profile that mimics one constituent component, while the frequency profile mimics the other. Comparing the two binary mixtures at any riser location, the density-difference binary mixture has lower cluster duration and higher frequency than the size-difference binary mixture regardless of local position. Finally, with respect to the continuous PSD, which was investigated under a wider range of operating conditions, the effect of operating condition is more apparent. This deviation may be due to an inherent behavioral difference between binary mixture and continuous PSD and/or to the wider range of operating conditions examined.     

Reliable Thermoelectric Module Design under Opposing Requirements from Structural and Thermoelectric Considerations

Structural reliability of thermoelectric generation (TEG) systems still remains an issue, especially for applications such as large-scale industrial or automobile exhaust heat recovery, in which TEG systems are subject to dynamic loads and thermal cycling. Traditional thermoelectric (TE) system design and optimization techniques, focused on performance alone, could result in designs that may fail during operation as the geometric requirements for optimal performance (especially the power) are often in conflict with the requirements for mechanical reliability. This study focused on reducing the thermomechanical stresses in a TEG system without compromising the optimized system performance. Finite element simulations were carried out to study the effect of TE element (leg) geometry such as leg length and cross-sectional shape under constrained material volume requirements. Results indicated that the element length has a major influence on the element stresses whereas regular cross-sectional shapes have minor influence. The impact of TE element stresses on the mechanical reliability is evaluated using brittle material failure theory based on Weibull analysis. An alternate couple configuration that relies on the industry practice of redundant element design is investigated. Results showed that the alternate configuration considerably reduced the TE element and metallization stresses, thereby enhancing the structural reliability, with little trade-off in the optimized performance. The proposed alternate configuration could serve as a potential design modification for improving the reliability of systems optimized for thermoelectric performance.     

Coactive scheduling and checkpoint determination during high levelsynthesis of self-recovering microarchitectures

The growing trend towards VLSI implementation of crucial tasks in critical applications has increased both the demand for and the scope of fault-tolerant VLSI systems. In this paper, we present a self-recovering microarchitecture synthesis system. In a self-recovering microarchitecture, intermediate results are compared at regular intervals, and if correct saved in registers (checkpointing). On the other hand, on detecting a fault, the self-recovering microarchitecture rolls back to a previous checkpoint and retries. The proposed synthesis system comprises of a heuristic and an optimal subsystem. The heuristic synthesis subsystem has two components. Whereas the checkpoint insertion algorithm identifies good checkpoints by successively eliminating clock cycle boundaries that either have a high checkpoint overhead or violate the retry period constraint, the novel edge-based schedule, assigns edges to clock cycle boundaries, in addition to scheduling nodes to clock cycles. Also, checkpoint insertion and edge-based scheduling are intertwined using a flexible synthesis methodology. We additionally show an Integer Linear Programming model for the self-recovering microarchitecture synthesis problem. The resulting ILP formulation can minimize either the number of voters or the overall hardware, subject to constraints on the number of clock cycles the retry period, and the number of checkpoints     

How would you integrate the equations of motion in dissipative particle dynamics simulations?

In this work we assess the quality and performance of several novel dissipative particle dynamics integration schemes that have not previously been tested independently. Based on a thorough comparison we identify the respective methods of Lowe and Shardlow as particularly promising candidates for future studies of large-scale properties of soft matter systems.     

ANALYSIS OF THE PERFORMANCE OF NON-UNIFORMLY ACTIVE CATALYST PELLETS FOR A NON-ISOTHERMAL SERIES REACTION

An analysis of the influence of the non-uniform distribution of the active species in a catalyst pellet on the effectiveness factor and selectivity for the case of a series non-isothermal reaction is carried out. The case in which the desired reaction has a lower activation energy than the undesired reaction is considered. The effect of different reaction parameters on the selectivity for a single pellet is studied, and the optimum activity distribution is determined for high values of Thiele modulus. It is shown that temperature gradients within the pellet have a detrimental effect on local and overall selectivity and that these gradients are a strong function of the distribution of catalytically active material within the pellet.     

Progress Towards an Optimization Methodology for Combustion-Driven Portable Thermoelectric Power Generation Systems

There is enormous military and commercial interest in developing quiet, lightweight, and compact thermoelectric (TE) power generation systems. This paper investigates design integration and analysis of an advanced TE power generation system implementing JP-8 fueled combustion and thermal recuperation. In the design and development of this portable TE power system using a JP-8 combustor as a high-temperature heat source, optimal process flows depend on efficient heat generation, transfer, and recovery within the system. The combustor performance and TE subsystem performance were coupled directly through combustor exhaust temperatures, fuel and air mass flow rates, heat exchanger performance, subsequent hot-side temperatures, and cold-side cooling techniques and temperatures. Systematic investigation and design optimization of this TE power system relied on accurate thermodynamic modeling of complex, high-temperature combustion processes concomitantly with detailed TE converter thermal/mechanical modeling. To this end, this paper reports integration of system-level process flow simulations using CHEMCAD? commercial software with in-house TE converter and module optimization, and heat exchanger analyses using COMSOL? software. High-performance, high-temperature TE materials and segmented TE element designs are incorporated in coupled design analyses to achieve predicted TE subsystem-level conversion efficiencies exceeding 10%. These TE advances are integrated with a high-performance microtechnology combustion reactor based on recent advances at Pacific Northwest National Laboratory (PNNL). Predictions from this coupled simulation approach lead directly to system efficiency?Cpower maps defining potentially available optimal system operating conditions and regimes. Further, it is shown that, for a given fuel flow rate, there exists a combination of recuperative effectiveness and hot-side heat exchanger effectiveness that provides a higher specific power output from the TE modules. This coupled simulation approach enables pathways for integrated use of high-performance combustor components, high-performance TE devices, and microtechnologies to produce a compact, lightweight, combustion-driven TE power system prototype that operates on common fuels.