The development and application of a fluid-structure interaction model for simulating the transition of a through-wall defect in pressurised dense (150 bar, 283.15 K) and gas phase (34 bar, 283.15 K) CO2 pipelines into a running brittle fracture is presented. Given the economic incentives, the fracture model is employed to test the suitability of the existing stock of natural gas pipelines with the relatively high ductile to brittle transition temperatures of 0 o C and-10 o C for transporting CO2 in the terms of their resistance to brittle fracture propagation. The hypothetical but nevertheless realistic scenarios simulated involve both buried and above ground 10 km long, 0.6 m i.d pipelines. Based on the assumption of no blowout of the surrounding soil upon the formation of the initial leak, the results show that the transition of the leak into a running brittle fracture in buried CO2 pipelines is far more likely as compared to above ground pipelines. In addition, gas phase pipelines are more prone to undergoing a propagating brittle fracture as compared to dense phase pipelines despite the lower operating pressures of the former. Furthermore, counter-intuitively, isolation of the feed flow following the discovery of a leak is shown to facilitate brittle fracture failure. The initial defect geometry on the other hand is shown to have a profound impact on the pipeline's resistance to propagating brittle fractures.

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In this paper, the nonlinear harmonic method implemented in Fine/Turbo CFD code has been used to analyze the unsteady flow field in a transonic compressor. The numerical accuracy and computational efficiency of this method have been demonstrated by comparing its predictions with experimental data and conventional time-domain unsteady simulation for the test case. The rotor–stator interactions are studied in detail to improve the understanding of the flow physics involved. The deterministic stresses in the nonlinear harmonic method have also been compared to the time-domain unsteady postprocessing results to analyze distinct sources of unsteadiness. For the present case, the nonlinear harmonic method can not only capture the unsteady results satisfactorily, but also gain a significant computational advantage over conventional unsteady method.

This work investigated the effect of inclination angle on the minimum conveying velocity and the underlying mechanisms. Results showed that the pressure drop increased first and then decreased with the increasing inclination angle at the same mass flux and superficial gas velocity. The changing trend of minimum conveying velocity (u min) and the pressure drop near it can be divided into two types by taking 45 as the boundary, which was consistent with the difference in flow regimes near u min at different inclination angles based on results of high-speed photography and acoustic emission detection. Furthermore, the pressure drop was decomposed to investigate the underlying mechanism of the changing trend of u min. Results showed that the changing trend of u min was closely related to the particle velocity and the particle velocity obtained by high-speed photography was in good agreement with the theoretical analysis. K E Y W O R D S inclined pneumatic conveying, minimum conveying velocity (u min), particle motion characteristic, pressure drop

As one of the important factors affecting the stability of slide valves, the analysis and research of flow force are of great significance. In recent years, more and more experts and scholars have conducted research in this field, attempting to find methods to reduce or utilize the flow force of hydraulic spool valves. Flow force includes steady-state flow force and transient flow force, with steady-state flow force having the most significant impact on spool valves. The influencing factors of flow force are complex and diverse, including the cavitation phenomenon, shape of the throttling groove, and jet angle. At present, the main ways to reduce flow force are to design the structure of the spool valve, the structure of the valve sleeve, and the flow channel of the valve body. This article mainly reviews the definition, calculation methods, influencing factors, and methods for reducing the flow force of slide valves. This provides a new approach to reducing the flow force in hydraulic spool valves.