Simplified Mechanism Model Research Articles

The construction of an alternative fuel skeleton with a simplified n-heptane / 1-butene mechanism

Diesel is an important energy in the current world development. The promotion of industrial development has also brought serious drawbacks, energy depletion, and environmental pollution. Hence, the construction of new alternative diesel fuel has become an indispensable problem. Based on the detailed mechanism model of n-heptane and 1-butene, the simplified mechanism model of n-heptane and 1-butene was constructed by using oxidation path and temperature sensitivity analysis and various mechanism simplification methods. The experimental results show that the ignition delay of the simplified mechanism and the concentration of main components meet the experimental requirements. Coupled with the two simplified mechanisms, a diesel simplified framework containing 136 components and 746 primitive reactions was constructed. The HCCI ignition time was calculated for the diesel simplified framework. The simplified framework of diesel oil can predict the ignition time of HCCI with high precision under different temperature conditions. It can accurately describe the fuel combustion process.

Integrated soft sensor of COD for WWTP based on ASP model and RBF neural network

For wastewater treatment process (WWTP), mechanism model for activated sludge process (ASP) is unsuitable for estimating the effluent COD (Chemical Oxygen Demand) as the parameters of ASM (Activated Sludge Model) series models are varying with operating conditions. This paper presents an integrated model to predict the effluent COD. The model consists of two sub-models which are simplified mechanism model of ASP and RBFNN (RBF Neural Network) with variable structure (VSRBFNN). ASP model can express the dynamic biochemical reactions occurred in WWTP, and VSRBFNN is used to reduce the prediction error of the ASP model as an error compensation model. To reduce the complexity of the mechanism model of ASP, the parameters of mechanism model are fixed. The layout and the parameters of VSRBFNN can be adjusted according to the training data, and the stable learning algorithm can restrict the modeling error of VSRBFNN within a bounded domain. The output value of the integrated model is weighted sum of those of two sub-models, where the weights denote the contributions of the two “sub-models” to the prediction error of integrated model and are rectified according to the relative prediction error online. The structure of the integrated soft sensor is concise and real-time capability is improved. Simulations show that the presented soft sensor has satisfactory prediction accuracy under various operating characteristics.

Numerical simulation of DDT process of aviation kerosene one-component alternative fuel

Aiming at the difficulty of numerical simulation of the DDT process during the detonation combustion of aviation kerosene, this paper has presented a single-component simplified mechanism of aviation kerosene to carry out the numerical simulation of the DDT detonation process. By simplifying the detailed mechanism of n-decane, the simplified mechanism of RP-3 aviation kerosene single-component alternative fuel was obtained, and the DDT process of aviation kerosene was numerically simulated, and the influence law of the obstacle blocking ratio and arrangement mode on the DDT process was analyzed. The results show that the simplified mechanism model for the single-component alternative fuel can better fit the combustion characteristics of aviation kerosene under high temperature and pressure. The numerical simulation results of the DDT process are analyzed, and it is found that the DDT time will increase with the increasing of blocking ratio. The DDT time at the same blocking ratio is shorter when the obstacles are symmetrically distributed.

An approximate solution of lithium ion diffusion process in spherical active particles with controllable error

As an important supplementary part of experiment, multi-scale modeling and simulation plays an important role in reasonable design and performance prediction of lithium-ion batteries. Due to the complexity of spherical diffusion equation, the calculation error of Li-ion diffusion process in solid spherical active particles is an important factor restricting the accuracy of the simplified mechanism model of Li-ion batteries. In this study, based on the quasi-steady state of spherical active particles in Li-ion diffusion processes, the concepts of zero-state response, zero-input response, and total response in the discipline of circuit analysis are introduced to expand the spherical diffusion equation, the analytical solution of Li-ion diffusion process in active particles is solved by using the variable-separation method, and an error-controllable method for solving the approximate solution of diffusion process in spherical particles is proposed and verified. Besides, the computational complexity of the algorithm is very low, therefore, this study is of great significant to construct the high-precision simplified mechanism model of Li-ion batteries and to realize the high-accuracy battery management algorithm on microprocessor systems.

Optimisation design of process control strategy for biomass cracking reaction

Cone pyrolysis liquefaction reactor is the key core device of biomass energy production equipment. The study of the dynamics of the cone is of great significance to the bioenergy conversion technology. Proper control of the movement time of the heat carrier in the cone can prevent it. Biomass superheated carbonisation can increase the ratio of gas and liquid formation. It is a difficult and key technology in the design of the cone pyrolysis liquefaction reactor. The kinetic differential equation of the relative motion of heat carrier particles can be obtained by kinetic analysis and calculation. It can play a key role in the in-depth study of the structural size design of the cone and the optimisation of the structural size parameters. This study conducts a dynamic simulation of the physical simplification model of biomass energy production equipment. The computer simulation software was used to simulate the running process of the simplified cone mechanism model. A reasonable physical prototype that meets the process parameters is designed. In view of the above complex dynamic phenomena, it is necessary to comprehensively analyse various methods of dynamics, and use appropriate numerical analysis and computer-aided design methods to carry out system equipment research and design.

Hybrid soft sensor modeling for bisphenol‐A synthesis reaction process

AbstractTo online estimate the concentrations of key components at the outlet of bisphenol‐A (BPA) synthesis reactor, a hybrid modeling approach is proposed in this paper. First, the simplified mechanism model for the synthesis of BPA in an industrial fixed‐bed reactor is deduced on the basis of mass and energy balance. Second, considering that the initial concentrations of reactants at the inlet of BPA synthesis reactor cannot be measured in real‐time, the modified stochastic gradient boosting‐Gaussian process regression approach previously proposed by the authors is employed to online estimate the initial concentrations of reactants. Furthermore, modified stochastic gradient boosting‐Gaussian process regression method is also adopted to model the nonlinear influence of the reaction factors ( i.e., initial concentrations of reactants and inlet temperature) on the reaction rate constants in the simplified mechanism model. Finally, the hybrid modeling approach for BPA synthesis process is achieved by integrating the simplified mechanism model with the estimation models of initial concentrations and reaction rate constants. The feasibility and validity of the proposed hybrid model is verified through an industrial BPA synthesis process. On the basis of the hybrid model, the sensitivity analyses of the initial concentrations and inlet temperature are conducted, which can provide theoretical guidance for the operation optimization study in future work.

Theoretical Study of Structural and Spatial Properties of Kerogen

In this study, the structural information and spatial properties of the Longkou kerogen model were obtained by using molecular simulation methods. The density evaluation of the molecular model was carried out to investigate the morphological properties of internal pore structures that are limited or constrained by kerogen density. The density of the lowest-energy kerogen model is 1.01 g/cm3, which is consistent with its experimental value and close to the reference value for Green River Shale kerogen. Radial distribution function analysis indicated that the carbon skeleton of kerogen consists of significant amounts of sp2- and sp3-hybridized carbons. To further investigate the distribution characteristics of internal pore structures and provide valuable insights into the microstructures of the kerogen model, the morphology of pore volumes was created using Connolly surfaces. Meanwhile, a simplified mechanism model of kerogen pyrolysis was proposed based on the Mayer bond order analysis, which provided a strategy to accurately, quickly predict the cleavage behavior in the intrinsic structure of kerogen. This present study reveals inherent chemical features of kerogen and will aid in understanding the microscopic morphology characteristics of the pore network inside kerogen at the molecular level.

Numerical Simulation and Experimental Verification of an Alternative to Biomass Fuel

N-heptane was used as an alternative for biomass fuels research. A simplified mechanistic model of n-heptane oxidation has been studied in this paper. The calculation results reveal the relationship between ambience temperature and components. The environmental temperature acts on the chemical reaction mechanism, thus affecting the distribution of components. High temperature contributes to the formation of CO and C2H2, while low temperature contributes to the formation of CO2 and C2H2, and the influence of temperature on other components is not so obvious, such as C3H6 and so on. The experiment of biomass fuel combustion rate has a good agreement with that from the simulation of n-heptane, so we can conclude that this simplified n-heptane reaction mechanism model is a good alternative to biomass fuel study.

Hybrid position/force control of a spatial compliant mechanism

This paper provides a hybrid position/force control design for a flexible L-shape mechanism in a three dimensional (3D) environment. The analytical mechanism model was developed with a highly accurate dynamic system based on equivalent rigid link system theory and finite element discretisation without the need for any dedicated force/torque sensors. The gravity force and dynamic model nonlinear parameters were taken into account. This paper also presents and describes a real-time approach based on a comparison between joint acceleration and the time evolution of a simplified rigid mechanism model for estimating external forces applied on the tip of the mechanism. The most significant simulation results are presented and discussed; in particular, position controller has a high accuracy in terms of trajectory tracking with max error of 2.6 degree.

Research on shock wave characteristics in the isolator of central strut rocket-based combined cycle engine under Ma5.5

A numerical calculation of shock wave characteristics in the isolator of central strut rocket-based combined cycle (RBCC) engine fueled by kerosene was carried out in this paper. A 3D numerical model was established by the DES method. The kerosene chemical kinetic model used the 9-component and 12-step simplified mechanism model. Effects of fuel equivalence ratio, inflow total temperature and central strut rocket on-off on shock wave characteristics were studied under Ma5.5. Results demonstrated that with the increase of equivalence ratio, the leading shock wave moves toward upstream, accompanied with higher possibility of the inlet unstart. However, the leading shock wave moves toward downstream as the inflow total temperature rises. After the central strut rocket is closed, the leading shock wave moves toward downstream, which can reduce risks of the inlet unstart. State of the shear layer formed by the strut rocket jet flow and inflow can influence the shock train structure significantly.

Investigation of a Simplified Mechanism Model for Prediction of Gallium Nitride Thin Film Growth through Numerical Analysis

A numerical procedure was performed to simplify the complicated mechanism of an epitaxial thin-film growth process. In this study, three numerical mechanism models are presented for verifying the growth rate of the gallium nitride (GaN) mechanism. The mechanism models were developed through rate of production analysis. All of the results can be compared in one schematic diagram, and the differences among these three mechanisms are pronounced at high temperatures. The simplified reaction mechanisms were then used as input for a two-dimensional computational fluid dynamics code FLUENT, enabling the accurate prediction of growth rates. Validation studies are presented for two types of laboratory-scale reactors (vertical and horizontal). A computational study including thermal and flow field was also performed to investigate the fluid dynamic in those reactors. For each study, the predictions agree acceptably well with the experimental data, indicating the reasonable accuracy of the reaction mechanisms.

Research on one Bio-inspired Jumping Locomotion Robot for Search and Rescue

Jumping locomotion is much more effective than other locomotion means in order to tackle the unstructured and complex environment in research and rescue. Here, a bio-inspired jumping robot with a closed-chain mechanism is proposed to achieve the power amplification during taking-off. Through actuating one variable transmission mechanism to change the transmission ratio, the jumping robot reveals biological characteristics in the phase of posture adjustment when adjusting the height and distance of one jump. The kinematics and dynamics of the simplified jumping mechanism model in one jumping cycle sequence are analysed. A compliant contact model considering nonlinear damping is investigated for jumping performance under different terrain characteristics. The numerical simulation algorithm with regard to solving the dynamical equation is described and simulation results are discussed. Finally, one primary prototype and experiment are described. The experimental results show the distance of jumping in the horizontal direction increases with the increasing gear ratio, while the height of jumping decreases in reverse. The jumping robot can enhance the capability to adapt to unknown cluttered environments, such as those encountered in research and rescue, using this strategy.

Screw theory based motion analysis for an inchworm-like climbing robot

SUMMARYTo obtain better performance on unstructured environments, such as in agriculture, forestry, and high-altitude operations, more and more researchers and engineers incline to study classes of biologically inspired robots. Since the natural inchworm can move well in various types of terrain, inchworm-like robots can exhibit excellent mobility. This paper describes a novel inchworm-type robot with simple structure developed for the application for climbing on trees or poles with a certain range of diameters. Modularization is adopted in the robot configuration. The robot is a serial mechanism connected by four joint modules and two grippers located at the front and rear end, respectively. Each joint is driven by servos, and each gripper is controlled by a linear motor. The simplified mechanism model is established, and then is used for its kinematic analysis based on screw theory. The dynamics of the robot are also analyzed by using Lagrange equations. The simulation of the robot gait imitating the locomotion of real inchworm is finally presented.

Study on Petroleum Wharf and Reservoir VOCs Emissions and Photochemical Reaction

Focusing on the environmental problems caused by VOCs emission and photochemical reactions in petroleum wharf and reservoir areas, a field experiment was conducted in Zhanjiang port. The VOCs emission and photochemical reaction, VOCs source model and the photochemical reaction mechanism were discussed. Through analyzing and comparing the measured and simulated results, firstly, a simplified mechanism model with the chain reaction balance coefficient is developed; secondly, VOCs emission amount during the temperature rising period (3h daily) is corrected as doubling the normal dose; thirdly, VOCs consumption amount during the photochemical reaction period (6h daily) is estimated as being 71.8% of VOCs emission amount; finally, the derived photochemical reaction equilibrium coefficient of O3 and PM were 0.084 and 0.79. Seven kinds of emission source models (including pipeline and valve leakage, fixed tank big breath with oiling, floating roof tank oiling and pumping loss, fixed tank small breath with temperature rising, oil storage still loss of internal and external floating roof tanks, ship and tank loading emissions) were applied to analyze the operation scenario and emission inventory in typical petroleum wharf and reservoir areas, of which the annual throughput is 3000 ´ 104 tons, and the annual average temperature is 22 °C. The calculated annual VOCs emission with modification is 1555.88 t. Using the VOCs emission and photochemical reaction models for different regions of the port, VOCs and PM emission inventories of major Chinese ports were calculated. The total emission amounts of VOCs and PM in 2012 were approximately 43296 t and 6140 t, mainly distributed in the port group located areas in Yangtze River Delta, Bohai rim and Pearl River Delta, as well as Beibu Gulf, Strait West. As the emission sources located more densely and the emission more intense, there will be more adverse cumulative effect on the regional air quality. Therefore, it is necessary to adopt more active and effective air pollution prevention and control measures in petroleum wharf and reservoir areas.

Hybrid Modeling of Flotation Height in Air Flotation Oven Based on Selective Bagging Ensemble Method

The accurate prediction of the flotation height is very necessary for the precise control of the air flotation oven process, therefore, avoiding the scratch and improving production quality. In this paper, a hybrid flotation height prediction model is developed. Firstly, a simplified mechanism model is introduced for capturing the main dynamic behavior of the process. Thereafter, for compensation of the modeling errors existing between actual system and mechanism model, an error compensation model which is established based on the proposed selective bagging ensemble method is proposed for boosting prediction accuracy. In the framework of the selective bagging ensemble method, negative correlation learning and genetic algorithm are imposed on bagging ensemble method for promoting cooperation property between based learners. As a result, a subset of base learners can be selected from the original bagging ensemble for composing a selective bagging ensemble which can outperform the original one in prediction accuracy with a compact ensemble size. Simulation results indicate that the proposed hybrid model has a better prediction performance in flotation height than other algorithms’ performance.

Inferential Model for Industrial Polypropylene Melt Index Prediction with Embedded Priori Knowledge and Delay Estimation

Melt index inferential model plays an important role in the control and optimization of polypropylene production. This study proposed a novel multiple-priori-knowledge based neural network (MPKNN) inferential model for melt index prediction. The prior knowledge from the industrial propylene polymerization process is fully exploited and embedded into the construction of multilayer perceptron neural network in the form of nonlinear constraints. Meanwhile, an adaptive PSO-SQP (particle swarm optimization-sequential quadratics programming) is proposed to optimize the network weights. The proposed MPKNN model has good fitting and prediction ability. Meanwhile, it can avoid unwanted zero value and wrong signal of the model gains. By embedding priori knowledge, the model ensures the safety in the quality control of melt index. In addition, a hybrid model combining the MPKNN model with a simplified mechanism model is proposed to enhance the extrapolation capability. A normalized mutual information method is emplo...

On the Stiffness Affected by the Allocation of Actuators of a Parallel Manipulator

The stiffness of a parallel manipulator is not only concerned with its detailed structure but also affected by the allocation scheme of actuators. Even though the precise values of stiffness cannot be derived since the link structure is not definitive at the stage of mechanism design, the effect of the allocation of actuators on the mechanism stiffness can be qualitatively evaluated in order to guild the optimal allocation. In this paper, the mechanism stiffness of a parallel manipulator is classified into the actuated stiffness and the structural stiffness. The actuated stiffness is obtained through the principle of virtual displacement and Jacobian matrix, and it is presented as a stiffness matrix which contains all the stiffness components and maps the stiffness of each actuator into the stiffness of the moving platform. The proposed analysis method of the actuated stiffness is suitable for all types of actuators. The structural stiffness is analyzed based on the principle of virtual force. A parallel mechanism is converted into a stationary structure when all active joints are frozen. The stationary structure is regarded as the combination of the basic links which are categorized according to their geometric shapes, join types, and load conditions. The proposed analysis method of structural stiffness takes account of all kinds of internal forces such as axial force, shearing force, bending moment, and torque. It can be seen that the allocation scheme of actuators plays an important role in the contribution to the stiffness of a parallel mechanism. The stiffness analysis that is usually investigated at the stage of structure design in the traditional process of mechanical design is considered in anticipation at the stage of mechanism design in the proposed approach. The stiffness of the moving platform affected by the allocation of actuators is analyzed through the simplified mechanism model without the detailed geometric shapes or physical parameters of link parts, which is able to guild the optimal selection of an allocation scheme of actuators at the early stage of the design process.