Dongmei Zhao, Yifan Xia, Haiwen Ge, Qizhao Lin, Jianfeng Zou and Gaofeng Wang
Ignition process is a critical issue in combustion systems. It is particularly important for reliability and safety prospects of aero-engine. This paper aims to numerically…
Abstract
Purpose
Ignition process is a critical issue in combustion systems. It is particularly important for reliability and safety prospects of aero-engine. This paper aims to numerically investigate the burner-to-burner propagation during ignition process in a full annular multiple-injector combustor and then validate it by comparing with experimental results.
Design/methodology/approach
The annular multiple-injector experimental setup features 16 swirling injectors and two quartz tubes providing optical accesses to high-speed imaging of flames. A Reynolds averaged Navier–Stokes model, adaptive mesh refinement (AMR) and complete San Diego chemistry are used to predict the ignition process.
Findings
The ignition process shows an overall agreement with experiment. The integrated heat release rate of simulation and the integrated light intensity of experiment is also within reasonable agreement. The flow structure and flame propagation dynamics are carefully analyzed. It is found that the flame fronts propagate symmetrically at an early stage and asymmetrically near merging stage. The flame speed slows down before flame merging. Overall, the numerical results show that the present numerical model can reliably predict the flame propagation during the ignition process.
Originality/value
The dedicated AMR method together with detailed chemistry is used for predicting the unsteady ignition procedure in a laboratory-scale annular combustor for the first time. The validation shows satisfying agreements with the experimental investigations. Some details of flow structures are revealed to explain the characteristics of unsteady flame propagations.
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Fangfang Xie, Dingyi Pan, Yao Zheng and Jianfeng Zou
The purpose of this paper is to propose a partitioned approach by coupling the smoothed profile method (SPM) and the Euler tension beam model in simulating a vortex-induced…
Abstract
Purpose
The purpose of this paper is to propose a partitioned approach by coupling the smoothed profile method (SPM) and the Euler tension beam model in simulating a vortex-induced vibration of both rigid and flexible cylinders at various reduced velocities.
Design/methodology/approach
For the fluid part, SPM in the framework of the spectral element method is adopted to simulate the flow. The advantage of SPM lies in modelling multiple complex shapes as it uses a fixed computational mesh without conformation to the geometry of the particles. For the structure part, an elastic-mounted rigid cylinder is considered in two-dimensional (2D) simulations, while a flexible cylinder with a Euler tension beam model is used in three-dimensional simulations.
Findings
Firstly, in the flow past a freely vibrating cylinder, the maximum vibration responses of the cylinder are about 0.73D and 0.1D in the y and x directions, respectively, which occur at the point Ur = 5.75 and are much higher than Ur = 5 in 2D simulations. It is found that the numerical results from the SPM solver are very consistent with those from the NEKTAR-Arbitrary Lagrangian Eulerian method (NEKTAR-ALE) solver or the NEKTAR-Fourier solver. Furthermore, the flow past the tandem cylinders is also investigated, where the upstream cylinder is static while the downstream one is free to vibrate. Specifically, the beating behaviour is captured from the vibration response of the freely vibrating cylinder under the reduced velocity of Ur = 6 with a gap distance of L = 3.5D.
Originality/value
The originality of the paper lies in coupling the SEM with the Euler beam model in simulating the vortex induced vibration (VIV) of flexible cylinders.
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Yang Zhang, Jianfeng Zou, Jiahua Xie, Xiaoyue Li, Zhenhai Ma and Yao Zheng
When a reflected shock interacts with the boundary layer in a shock tube, the shock bifurcation occurs near the walls. Although the study of the shock bifurcation has been carried…
Abstract
Purpose
When a reflected shock interacts with the boundary layer in a shock tube, the shock bifurcation occurs near the walls. Although the study of the shock bifurcation has been carried out by many researchers for several decades, little attention has been devoted to investigate the instability pattern of the bifurcation. This research work aims to successfully capture the asymmetry of the whole flow field, and attempt to achieve the instability mechanism of the shock bifurcation by a direct numerical simulation of the reflected shock wave/boundary layer interaction at Ma = 1.9. In addition, the reason for the formation of the bifurcated structure is also explored.
Design/methodology/approach
The spatial and temporal evolution of the shock bifurcation is obtained by solving the two-dimensional compressible Navier–Stokes equations using a seventh-order accurate weighted essentially non-oscillatory (WENO) scheme and a three-step Runge–Kutta time advancing approach.
Findings
The results show that the formation of shock bifurcation is mainly because of the shock/gradient field interaction, and the height of the bifurcated foot increases with the growth of the shock intensity and the gradient field. The unsteady asymmetry of the upper and bottom shock bifurcated structures is because of the vortex shedding with high frequency in the rear recirculation zone, which leads to the fluctuation of the recirculation area. The vortex shedding process behind the bifurcated structure closely resembles the Karman vortex street formed by the flow around the cylinder. The dimensionless vortex shedding frequency varies between 0.01 and 0.02. In comparison to the scenario at Ma = 1.9, the occurring time of instability is delayed and the upper and bottom bifurcated feet intersect in a relatively short time at Ma = 3.5. The region behind the bifurcated shock is a transitional flow field containing obvious cell structures and “isolated islands.”
Originality/value
This paper discovers an unsteady flow pattern of the shock bifurcation, and the mechanism of this instability in the reflected shock/boundary layer interaction is revealed in detail.
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Jianfeng Yang, Peng Xie and Xiaodong Ming
Based on conservation of resources theory, this study explored the relationship between multitasking and creative work involvement through the mediation of emotional exhaustion…
Abstract
Purpose
Based on conservation of resources theory, this study explored the relationship between multitasking and creative work involvement through the mediation of emotional exhaustion, taking regulatory focus as a first-stage moderator.
Design/methodology/approach
Based on a three-wave and two-source survey among a sample of 418 employees and 116 leaders, this study conducted multilevel analyses to examine the conceptual model.
Findings
The results showed that multitasking was negatively associated with creative work involvement and that emotional exhaustion mediated the relationship between multitasking and creative work involvement. Furthermore, promotion focus and prevention focus moderated the relationship between multitasking and emotional exhaustion and the indirect relationship between multitasking and creative work involvement via emotional exhaustion.
Practical implications
Organizations can promote creative work involvement through interventions that reduce employees' multitasking or emotional exhaustion. In addition, supervisors should be aware of the different responses to multitasking exhibited by employees with different regulatory focuses and could potentially assign multiple tasks to employees with either a high promotion focus or a low prevention focus.
Originality/value
This study contributes to the literature on multitasking and creative work involvement by exploring whether and how multitasking is related to creative work involvement.
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This chapter examines China’s corporate governance and accounting environment that shapes the adoption of internationally acceptable principles and standards. Specifically, it…
Abstract
This chapter examines China’s corporate governance and accounting environment that shapes the adoption of internationally acceptable principles and standards. Specifically, it examines international influences, including supranational organizations; foreign investors and international accounting firms; domestic institutional influences, including the political system, economic system, legal system, and cultural system; and accounting infrastructure. China’s convergence is driven by desired efficiency of the corporate sector and legitimacy of participating in the global market. Influenced heavily by international forces in the context of globalization, corporate governance and accounting practices are increasingly becoming in line with internationally acceptable standards and codes. While convergence assists China in obtaining legitimacy, improving efficiency is likely to be adversely affected given that corporate governance and accounting in China operate in an environment that differs considerably from those of Anglo-American countries. An examination of the corporate governance and accounting environment in China suggests heavy government involvement within underdeveloped institutions. While the Chinese government has made impressive progress in developing the corporate governance and accounting environment for the market economy, China’s unique institutional setting is likely to affect how the imported concepts are interpreted and implemented.
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Jianfeng Zhao, Bodong Liang and Qiuxia Chen
The successful and commercial use of self-driving/driverless/unmanned/automated car will make human life easier. The paper aims to discuss this issue.
Abstract
Purpose
The successful and commercial use of self-driving/driverless/unmanned/automated car will make human life easier. The paper aims to discuss this issue.
Design/methodology/approach
This paper reviews the key technology of a self-driving car. In this paper, the four key technologies in self-driving car, namely, car navigation system, path planning, environment perception and car control, are addressed and surveyed. The main research institutions and groups in different countries are summarized. Finally, the debates of self-driving car are discussed and the development trend of self-driving car is predicted.
Findings
This paper analyzes the key technology of self-driving car and illuminates the state-of-art of the self-driving car.
Originality/value
The main research contents and key technology have been introduced. The research progress as well as the research institution has been summarized.
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Ran Jiao, Yongfeng Rong, Mingjie Dong and Jianfeng Li
This paper aims to tackle the problem for a fully actuated unmanned aerial vehicle (FUAV) to perform physical interaction tasks in the Global Positioning System-denied…
Abstract
Purpose
This paper aims to tackle the problem for a fully actuated unmanned aerial vehicle (FUAV) to perform physical interaction tasks in the Global Positioning System-denied environments without expensive motion capture system (like VICON) under disturbances.
Design/methodology/approach
A tether-based positioning system consisting of a universal joint, a tether-actuated absolute position encoder and an attitude sensor is designed to provide reliable position feedback for the FUAV. To handle the disturbances, including the tension force caused by the taut tether, model uncertainties and other external disturbances such as aerodynamic disturbance, a hybrid disturbance observer (HDO) combining the position-based method and momentum-based technology with force sensor feedback is designed for the system. In addition, an HDO-based impedance controller is built to allow the FUAV interacting with the environment and meanwhile rejecting the disturbances.
Findings
Experimental validations of the proposed control algorithm are implemented on a real FUAV with the result of nice disturbance rejection capability and physical interaction performance.
Originality/value
A cheap alternative to indoor positioning system is proposed, with which the FUAV is able to interact with external environment and meanwhile reject the disturbances under the help of proposed hybrid disturbance observer and the impedance controller.
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Existing research on knowledge management processes (KMPs) and absorptive capacity (ACAP) is primarily conceptual and descriptive in nature, and empirical research confirming the…
Abstract
Purpose
Existing research on knowledge management processes (KMPs) and absorptive capacity (ACAP) is primarily conceptual and descriptive in nature, and empirical research confirming the real impact of KMPs when developing ACAP is lacking. Furthermore, the relationship between ACAP and organizational performance (OP) has not been adequately studied. Hence, the purpose of this paper is to introduce a comprehensive, delineated and integrated conceptual model which encompasses KMPs, ACAP and OP. Then, an empirical investigation is undertaken to test the relationships among the proposed study model variables.
Design/methodology/approach
In total, 245 questionnaires were useable. Partial least square 3.3.3 is utilized to examine the validity of the measurement model and test the hypotheses.
Findings
The findings of this study suggest that KMPs influence ACAP and ACAP affects OP. Finally, the results show that KMPs affect OP directly and indirectly through ACAP (mediator).
Practical implications
The results of this study help managers to ascertain the managerial practices that can be employed as well as determine the level of effort and resources necessary to enhance ACAP. Additionally, managers should shed additional light on the ACAP's positive implications for OP.
Originality/value
This study focuses on the conceptualization of KMP and empirically tests the effect of these individual processes on ACAP and on OP. Finally, the relationship between KMPs and OP, although implied, needs to be addressed empirically in the research literature through utilizing ACAP as mediator between KMPs and OP, this appears to be the first study to try to achieve this main objective.
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Muhammad Usman Shehzad, Jianhua Zhang, Mir Dost, Muhammad Shakil Ahmad and Sajjad Alam
Given the critical importance of green innovation (GI) for organizations in developing economies, this study aims to examine the interrelationship between knowledge management…
Abstract
Purpose
Given the critical importance of green innovation (GI) for organizations in developing economies, this study aims to examine the interrelationship between knowledge management (KM) enablers, KM processes and GI. The research also indicates that certain combinations of KM enabler dimensions and KM processes can lead to better GI.
Design/methodology/approach
The study sample consists of 328 participants from Pakistan's medium- and large-sized manufacturing enterprises. Smart PLS 3.2.9 is used to verify the relationships. Moreover, the fuzzy set qualitative comparative analysis (fsQCA) investigates configurational paths for improving GI.
Findings
The results demonstrate that KM enablers significantly affect two aspects of GI – green product and process innovation – and KM processes. Moreover, KM processes significantly enhance two aspects of GI. The fsQCA findings indicate multiple combinations of KM enablers and KM processes dimensions that result in better GI.
Research limitations/implications
To better understand the critical role of knowledge resources, future studies should explore the potential mediating mechanisms of KM processes or the moderating effects of strategic organizational factors in the relationship between KM enablers and GI.
Practical implications
The study offers valuable insight and a unique approach for policymakers and executives of corporations in developing countries to enhance their organizations' GI capacity through KM enablers and KM processes.
Originality/value
This research contributes to bridging research gaps in the literature and advances insights into the interrelationship among KM enablers, KM processes and GI. In addition, the study offers methodological significance by combining direct and configurational techniques to address two distinct facets of GI.