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101.
For the advanced power systems based on the use of microturbines, the major considerations are higher power density as well as higher efficiency for energy-saving. In order to achieve higher efficiency, recuperated systems which recover the exhaust heat then become mandatory and the paramount requirements for the recuperator are high effectiveness and low pressure loss. Here, the thermal design and model analysis of a proposed Swiss-roll recuperator for future higher efficiency microturbines were made with both theoretical approach and numerical simulation. The proposed Swiss-roll recuperator is basically the primary surface type. It is composed of two flat plates that are wrapped around each other, creating two concentric channels of rectangular cross-section. The characteristics of Swiss-roll recuperator resemble the counter-flow spiral plate heat exchanger and have the excellent performance in effectiveness and pressure-loss. From a theoretical analysis, the thermal characteristics of the Swiss-roll recuperator were investigated and its preliminary designs at a given effectiveness for an innovative micro gas turbine were also demonstrated, including the determination of the number of turns, the corresponding channel widths and the required number of transfer unit (NTU). The consequent pressure loss through the recuperator was also predicted. For a given design of the recuperator, the model simulation was then made to provide the insights and needs for further improving the performance of the Swiss-roll recuperator. 相似文献
102.
《Surface & coatings technology》1986,29(3):239-246
The performance of TiC-coated cemented carbide cutting tool inserts was evaluated in steel turning and cast iron milling. The machining behavior was correlated with the properties of the coating and the chemical vapor deposition parameters. It is shown that improved performance can be obtained by controlling the grain size and orientation of the coating, and by choosing appropriate parameters to minimize the formation of the substrate. 相似文献
103.
This paper presents a study to predict the pressures in the cylinder chambers of a variable-speed pump controlled hydraulic system using structured recurrent neural network topologies where the rotational speed of the pumps, the position and the average velocity of the hydraulic actuator are used as their inputs. The paper elaborates the properties of such networks in extended time periods through detailed simulation- and experimental studies where black-box modeling approaches generally fail to yield acceptable performance. As alternative estimation techniques, both linear- and extended Kalman filters are considered in this paper. The estimation properties of the devised network models are comparatively evaluated and their potential application areas are discussed in detail. 相似文献
104.
The reuse of multidisciplinary design knowledge is pivotal in product development because of the increasingly fierce market competition. It can assist designers, particularly those who lack sufficient experience, in making correct decisions and achieving rapid design. Traditionally, designers primarily acquire design knowledge through information retrieval, which is typically time-consuming and inefficient. A solution that is widely considered to overcome the deficiencies of traditional knowledge retrieval approaches and actively provide designers with necessary knowledge is knowledge push. However, achieving the timely push of required knowledge to designers during the design process remains a challenging task. Accordingly, this paper presents a time identification method based on cognitive load measurement to identify the suitable time for design knowledge push. First, behavioral indicators related to the changes in cognitive load are identified by investigating the influence of the load on three types of behaviors: mouse dynamics, keystroke dynamics, and emotional states. Second, the possibility and efficacy of inferring the cognitive load by simultaneously and unobtrusively tracking the three aforementioned behaviors are considered through behavioral observations. Finally, predicting the knowledge push time based on the cognitive load using classification algorithms is investigated. The experimental results indicate that the accuracy of the proposed method in inferring the cognitive load is 55%, and that of push time is 83%. 相似文献
105.
Predictive maintenance of lithium-ion batteries has been one of the popular research subjects in recent years. Lithium-ion batteries can be used as the energy supply for industrial equipment, such as automated guided vehicles and battery electric vehicles. Predictive maintenance plays an important role in the application of smart manufacturing. This mechanism can provide different levels of pre-diagnosis for machines or components. Remaining useful life (RUL) prediction is crucial for the implementation of predictive maintenance strategies. RUL refers to the estimated useful life remaining before the machine cannot operate after a certain period of operation. This study develops a hybrid data science model based on empirical mode decomposition (EMD), grey relational analysis (GRA), and deep recurrent neural networks (RNN) for the RUL prediction of lithium-ion batteries. The EMD and GRA methods are first adopted to extract the characteristics of time series data. Then, various deep RNNs, including vanilla RNN, gated recurrent unit, long short-term memory network (LSTM), and bidirectional LSTM, are established to forecast state of health (SOH) and the RUL of lithium-ion batteries. Bayesian optimization is also used to find the best hyperparameters of deep RNNs. Experimental results with the lithium-ion batteries data of NASA Ames Prognostics Data Repository show that the proposed hybrid data science model can accurately predict the SOH and RUL of lithium-ion batteries. The LSTM network has the optimal results. The proposed hybrid data science model with multiple artificial intelligence-based technologies also demonstrates critical digital-technology enablers for digital transformation of smart manufacturing and transportation. 相似文献
106.
Vibration suppression is a major difficulty in the grinding of low-stiffness large thin-wall shells. The paper proposes that effective workpiece vibration control can be performed by a novel force-controlled end-effector integrated into a robotic grinding workcell. First, a dynamics model is built to capture the characteristics and vibration suppression mechanism of force control-based robotic grinding, then a novel force control-based vibration suppression method is designed for grinding large thin-wall shells, and three robotic grinding tests are conducted to validate the effects of the new method and the grinding performance of the force control-based robotic grinding workcell. The results are: 75% reduction in the amplitude of workpiece vibration; effective suppression of non-tool passing frequency; stable grinding of large thin-wall shells remarkably enhancing grinding depth up to 0.3 mm per pass, grinding depth error less than ±0.1 mm, and significant improvement of the workpiece surface quality up to Ra=0.762 μm. 相似文献
107.
108.
《International Journal of Hydrogen Energy》2019,44(1):469-476
Explosion characteristics of the stoichiometric hydrogen/methane/air mixtures with different hydrogen fractions (λ) and different turbulent intensities (u'rms) in a fan-jet-stirred spherical explosion vessel. From the experimental results, it could be clearly found that both the maximum explosion overpressure (pmax) and the maximum rise rate of overpressure rose with the increase of u'rms, but the major reasons to such rising were not totally the same. In turbulence, with the increase of λ, pmax declined but (dp/dt)max rose, and such behaviours were mainly attributed to the completion on the variations between propagation speed and adiabatic explosion pressure. The explosion duration (tc) was also measured, it rose with the increase of u'rms and/or λ for the enhancement on propagation albeit such enhancement was attributed to different mechanism for different influence factors. The variations of deflagration index (KG) indicated that the hazardous level of stoichiometric hydrogen/methane mixtures would become more hazardous in the presence of turbulence. Furthermore, the heat loss during the explosion also was calculated and analysed. The results reported in this article could provide more basic but important information to practical utilizations of hydrogen/methane blended fuels, especially on the safety protection strategies. 相似文献
109.
110.
Every time a component’s design is changed, the corresponding manufacturing has to be changed as well. Due to several recent developments such as increasing market dynamics or ever-shorter product life cycles, the amount of component changes is rising sharply. Therefore, the number of manufacturing changes is increasing at a fast pace. Particularly for safety-critical components, the implementation of component changes within manufacturing poses a significant challenge. The reason for this is the high planning reliability required to implement a component change via a manufacturing change. This implementation has to be performed without endangering the component’s functionality, by causing any other change than the intended one. An approach for the systematic generation of manufacturing changes was developed as a contribution to increasing planning reliability and efficiency. The approach systematically enables technology planners to identify alternative manufacturing changes, to analyze the propagation of these changes, and to evaluate the alternatives to form a basis for decision-making. Its practical applicability is validated using a case study from medical technology. 相似文献