Cognition, Application and Discussion on Shaped Charge Hydraulic Smooth Blasting Technology

In the past, the main method of tunnel excavation in China was drilling and blasting, but the biggest shortcoming of the traditional drilling and blasting method is that it is easy to cause serious overexcavation and underexcavation. At the same time, the operation cycle time of this method is long, which leads to a serious waste of resources. Not only that, a large number of toxic gases and dust produced after blasting also do harm to the health of construction workers. So this is an urgent need for a new construction technology to solve this worldwide problem. In this situation, the leading experts in the field of tunnel, "The survey and design master of China" Shi Yuxin, Liu Pei, and well known expert in explosion field, yan-sheng ding, professor Chen Chengguang and Gu Yicheng, the experts group, cooperate with The Fifth Branch of China Railway 18th Bureau in northwest project management department, developed a new technology. This technology has passed the appraisal of scientific and technological achievements organized by Tianjin Science and Technology Commission, which is shaped hydraulic smooth blasting technology. The comprehensive evaluation of the technology is "international leading" level.This paper is mainly aimed at the drawbacks of drilling and blasting construction,combined with the author's cognition and discussion on the introduction of the new technology of cumulative hydraulic blasting and the practical application effect in the tunnel excavation process of the fourth company of China Railway 14th Bureau Group in the second division of the 9th bid section of Zhangjihuai Railway in Huainan Province.

Experimental Studies of Structural and Technological Parameters of a Downdraft Gasifier Based on Plant Biomass

The relevance of the study is conditioned upon the need to develop and implement structural and technological solutions to improve the efficiency of the chemical and thermal conversion of biomass into combustible gas. Within the framework of the above, the authors of this paper have designed a downdraft gasifier running on plant biomass. The presented research links the heat quantity received from the utilisation of syngas produced during the gasifier operation cycle with the parameters of the gas blow regime and the physico-chemical properties of biomass. For an in-depth study of the influence of the gas blow regime on the yield and calorific value of syngas produced from biomass, the authors introduce the concept of the blow coverage quality coefficient. This coefficient describes the quality of the cross-section coverage of the gasification chamber neck with gas currents of the tuyere zone. The purpose of this study is to establish the influence of the blow coverage quality coefficient, the volume of blow gases and the void ratio of the bulk biomass layer on the heat quantity received from syngas produced during the gasifier operation cycle. A multi-factor experiment was planned and performed, which relates the dependent factor to variables, and the corresponding response surfaces were constructed. The research findings are that the maximum value of the heat quantity received from the utilisation of syngas produced during the one-hour gasifier operation cycle was 519 MJ. This value is achieved with 0.8 blow coverage quality coefficient and a blow gas volume of 47.4 m3/h and 46.75% void ratio of the bulk biomass layer. The measurement results are highly consistent with the calculated data. The coefficient of determination was R2=0.983. The practical value of this study is to substantiate the rational design and technological parameters of the downdraft biomass gasifier operation, which will increase the efficiency of biomass energy production. The findings presented in this study can be used both to design new gasifiers and to improve the efficiency of the available ones

The Stability of the Model and Simulation, Control Issues for Ship System, Education, and Research

This article deals with the study of mathematical models and the assessment of the stability of the motion of ships, investigating properties of the system such as kinetics and stability. This is essential for the selection of suitable control methods according to the requirements set out for the problem. Some control methods require the author to specify control parameters before the operation of the system can be started. Therefore, the survey of the article is useful for the above problem. Control methods through simulation results (PID controller, lag compensator, and lead compensator) give me results that reflect properties of the system (the stability of the operation cycle of the ship model). In addition, control methods for this model, which serve for research and education, are also presented below. Simulation is done by Matlab.

Study on Operating Cost Economy of Battery-Swapping Heavy-Duty Truck in China

In recent years, battery-swapping heavy-duty trucks have seen rapid growth in China. Summarizing from the practical experiences gained in this development, and starting from market research and analysis of the most typical city of application case, Beijing, we aim to achieve the following: (ⅰ) Establish an operating cost model for battery-swapping heavy-duty trucks throughout a full operation cycle from the perspective of a heavy-duty truck freight transport capacity operator, based on four key cost dimensions, including transportation equipment, operation and maintenance, environmental protection compensation, and battery recycling compensation. (ⅱ) Calculate and compare the operating cost economy of battery-swapping heavy-duty trucks and other types of heavy-duty truck under different energy supplement modes, including charging, hydrogenation, and diesel. (ⅲ) Propose suggestions for faster and more successful heavy-duty truck electrification. The results indicate that battery-swapping heavy-duty trucks have good cost economy in a full operation cycle under specific scenario, and their economy will be improved with the popularization of battery-swapping stations.

Features of hydraulic calculation of marine vacuum fish pumping units

Цель статьи – модифицировать ранее разработанный метод гидравлического расчета вакуумной перекачивающей системы для течения в рыбонасосной установке, работающей на промысловом судне. Динамика откачивания и закачивания воздуха в буферную емкость не изменилась. Анализ экспериментальных данных показал, что гидравлические потери по длине трубопровода прямо пропорциональны величине массовой доли рыбы. В судовых условиях потери напора в местных гидравлических сопротивлениях могут иметь тот же порядок, что и потери по длине. В отличие от традиционных судовых систем течение жидкости в вакуумных рыбонасосных установках (ВРУ) является нестационарным из-за увеличения давления в буферной емкости, как на этапе всасывания, так и на этапе вытеснения. Что приводит к необходимости совместного решения уравнения Бернулли для нестационарных течений совместно с дифференциальными уравнениями для давления и объема жидкости в буферной емкости. Увеличение длины трубопровода или перепада высот приводит к снижению скорости движения водорыбной смеси и увеличению давления в буферной емкости. Как следствие, возрастает продолжительность цикла работы ВРУ и падает производительность. The purpose of the article is to modify a previously developed method of hydraulic calculation of a vacuum pumping system for a flow in a fish pump unit operating on a fishing vessel. The dynamics of pumping out and pumping air into the buffer tank did not change. Analysis of experimental data showed that hydraulic losses along the length of the pipeline are directly proportional to the value of the mass fraction of fish. In shipboard conditions, head losses in local hydraulic resistances can be of the same order as length losses. In contrast to traditional ship systems, the fluid flow in vacuum fish pumping units (VFP) is unsteady due to an increase in pressure in the buffer tank, both at the stage of suction and at the stage of displacement. This leads to the need of jointly solve the Bernoulli equation for unsteady flows together with differential equations for the pressure and volume of fluid in the buffer tank. An increase in the length of the pipeline or the height difference leads to a decrease in the speed of movement of the water-fish mixture and an increase in pressure in the buffer tank. As a result, the duration of the VFP operation cycle increases and the productivity decreases.

Excavator driver seat occupational comfort assessment with Lumbar Support Cushion

The operators of excavators often suffer from dreadful Whole-Body Vibration. Besides, the operators are subject to postural instability which is considered to be a serious occupational health hazard. The main objective of this study is to investigate the role of Lumbar Support Cushion in mitigation of Whole-Body Vibration and postural instability under three different operating conditions such as Front-Manipulator Motion, Swing Motion and Propel-Drive Motion. The obtained Vibration Dose Value reveals a significant difference between the operation cycle ( p < 0.001). Moreover, across the operation cycle with Lumbar Support Cushion a significant decrease in Vibration Dose Value (8) is observed on the operator seat-pan and backrest ( p < 0.05). Further, the effect of Whole-Body Vibration on physiological stress factors, a significant decrease in systolic blood pressure by 1.26%, pulse rate by 2.75% and Rate Pressure Product by 4%, is observed with the use of Lumbar Support Cushion ( p < 0.05) during the operation. The Lumbar Support Cushion helps in promoting a symmetric seating posture, and using Lumbar Support Cushion could help the excavator operator to increase in productivity during shift hour.

Analysis of Loading and Vibration Histories on Natural Frequencies and Modal Damping of Blades With Friction at Root Contact Interfaces

Gas turbine engines change the rotation speed during operation in a wide range from zero to the speed corresponding to the cruise flight and the history of the rotation speed variation is individual for each flight. During the engine operation the bladed disks pass different resonances frequencies and may experience significant vibration amplitudes. The vibrations can affect the interaction conditions at friction contact interfaces, including contact stresses distribution and their contact status. As a result, the contact conditions can differ from those that are established at the initial bladed disk assembling and these conditions are dependent on the history of the vibration that a bladed disk experiences during every engine operation cycle. The variation of the contact conditions at friction contact interfaces affects modal properties and modal damping characteristics of a bladed disk, and it is important to assess the possible variation of these properties during the engine exploitation. In this paper, a transient analysis is performed to simulate blade vibration under different loading histories occurred in a flight mission. The analysis is performed for different histories of the blade vibration and a method is proposed for the analysis of modal damping in the blade root joints under the influence of different loading histories. The influence of different loading histories, friction contact parameters, the vibration excitation levels and resonating modes on modal characteristics and modal damping factors is studied, The pre-stress effects due to blade assembling are also explored.