Tubular Propellant Research Articles

Calculation of closed combustion performance based on evolution of gun propellant burning surface

Abstract In order to enhance the combustion performance evaluation ability of irregularly shaped gun propellants and accelerate the development of propellant energy-release control technology, the present work provides the calculation method of closed combustion performance based on the evolution of gun propellant burning surface. The 3-D structure of the gun propellant should be built, and then a steady-state heat conduction equation with a source term is set, which can be considered as the Poisson equation with a diffusion term. The variable in the equation is the burned web thickness of the propellant grain. Afterwards, finite element meshing was performed on the 3-D structure to obtain a dynamic database of equivalent surfaces with burned web size. The pressure during the closed combustion process can be obtained from the mass conservation equation as a function of the burned web thickness. Furthermore, the combustion time field can be derived based on the functional relationship between burning-rate and pressure. Ultimately, the variation of gas pressure versus time in the closed bomb could be obtained. The results showed that the burnout time of the tubular propellant was 1.6 ms shorter than that of the inner pore offset 0.5 mm under the design conditions. This research can provide researchers with a new method for calculating the closed combustion performance of irregular gun propellants, which can be applied to the design of propellant shapes and the study of launch safety of propellant charges.

The Application of the Particle Element Method in Tubular Propellant Charge Structure: Lumped Element Method and Multiple-Element Method

Due to the orderly arrangement of tubular propellant, the permeability of combustion gases is improved, which is beneficial for enhancing the safety of the combustion system. However, current internal ballistic gas-solid flow calculation methods adopt a quasi-fluid assumption, which cannot accurately account for the characteristics of long tube shapes. Additionally, tubular propellants exhibit both overall movement and parameter distribution characteristics, necessitating the decoupling of gas and solid phases. These two deficiencies in previous studies have limited the effectiveness of gas-solid flow simulations for tubular propellant. This paper proposes a numerical calculation model suitable for tubular propellant charging based on the particle element method for internal ballistic two-phase flow. Firstly, considering the overall movement characteristics of tubular propellants, the concept of blank particle elements is introduced to represent pure gas phase regions. Then, based on computational requirements, the tubular propellants are divided to form the lumped element method and the multiple-element method. The moving boundary method is used to calculate the movement process of the propellant bed particle group and is compared with experimental results to verify the applicability of the two methods in tubular propellant beds. Analysis results show that the particle element method can effectively capture changes in the flow field inside the chamber and the position of tubular propellants. The lumped element method can quickly obtain the flow field distribution characteristics inside the chamber, while the multiple-element method can capture parameter distribution characteristics at different positions of the tubular propellants while ensuring overall movement.

Research and design of automatic cutting machine for propellant NDSI-2K and FCG-2.B41M

This article introduces the results of research on a new solution in the process of cutting and selecting propellants used for the double-based tubular propellant production line of Factory Z195/General Department of Defense Industry. The traditional method is usually manual, using the foot pedal force of the worker through a mechanical drive system to pull the cutting knife down to cut the propellant. It takes a lot of time, labor and product quality is not high. After cutting it is necessary to lathe the ends of propellant tube to meet technical requirements. With the new solution, the propellant is cut automatically, quickly, safely and accurately and the selection of the propellant is carried out through a weighing conveyor system based on the principle of classification by weight. The entire working process is controlled by a sensor systemand PLC programerthrough a monitoring computer located in the control room. Processing data can be stored and periodically exported for report purposes.

Interior ballistic two-phase flow model and its calculation for a mixed charge structure

The mixed charge for guns generally consists of two or more kinds of propellants. Medium and large caliber guns usually adopt the typical combination of tubular and granular propellants, not only meeting interior ballistic indexes but also improving launch safety. However, numerical investigations, charge design, and optimizations of such charge structures rely heavily on classical interior ballistic theory. To gain insight into some crucial phenomena in this complex interior ballistic process, a two-phase flow dynamic model of a 125 mm smoothbore gun with mixed charge (granular propellants, tubular propellants, and a combustible cartridge case) is developed. Unlike the previous form of solid governing equations, the conservation equations, surface temperature and combustion law functions are simultaneously established. The space-time conservation element and solution element (CE/SE) method is used to solve the mathematical model, simplifying the calculations of partial derivatives in source terms. Results show that the model can describe the combustion and flow, and the predicted projectile velocity agrees well with the measured one. In addition, the effects of the mass ratio of mixed propellants on interior ballistic performance are discussed in detail. As the tubular propellant mass decreases, ignition consistency deteriorates, particle accumulation intensifies, and the maximum pressure exceeds the permitted one, all of which may affect launch safety. The work in this paper provides a powerful tool for observing and predicting the interior ballistic process of the mixed charge.

Performance Analysis of Internal Ballistic Multiphase Flow of Composite Charge Structure

Different charge structures have different interior ballistic performance. Existing research is based on experimental measurements or the lumped parameter method to obtain limited ballistic characteristics, which indirectly impacts the analysis of the parameters’ distribution, requiring a complex modeling solution process. Besides this, the ignition performance of different charge structures needs to be further explored. The disadvantages of previous studies have limited the feasibility of further optimization of the composite charge structure. In this paper, we apply a two-dimensional two-phase flow method based on the Eulerian–Lagrangian model to study the performance of different composite charge structures. First, we establish the mathematical model of different particle types based on interior ballistics, which is directly related to the research foundation of subsequent ballistic performance. Next, we investigate the multi-scale reaction flow of complex charge structures by the two-phase flow method and obtain the distribution of parameters in the chamber. Finally, we conduct a study with different particle charge parameters to explore the sensitivity of ballistic characteristics to structural parameters. The results show that the tubular propellant has good ignition performance in different charge structures, and the ignition consistency can be improved by charging tubular propellant in the center of the chamber. However, more tubular propellants are ineffective at significantly improving ignition performance, and result in a decrease in combustion chamber pressure. These results may be promising for the optimization of various charge structures.

Creation and substantiation of the matrix for model series of tubular propeller turbines for small hydropower plants

The paper is devoted to further development of small hydropower on the basis of reliable and cheap unregulated tubular propeller hydroturbines with rigidly fixed operating and guide blades. Such turbines are used mainly at low-pressure small hydroelectric power stations. Their main drawback is the impossibility of generated power regulation. However, solutions that minimize this shortcoming are proposed in this paper. Matrix of 4 model series of tubular propeller hydroturbines has been created. The nomenclature of turbines presented in this matrix is aimed at improving technical characteristics of small hydropower plants and reducing their negative impact on the environment. The rules for equipping machine platforms of low-pressure small hydroelectric power plants with capacity up to 200 kW with models of turbines from the created matrix are proposed, and their technical and environmental justification is performed. According to the recommendations given in the paper, at least two different adjacent turbines from the same model line should be installed at one HPP. The best option is three different adjacent turbines from the same model series, but technical and economic analysis should be performed for more detailed justification of the choice of the number of turbines. This is the subject of our further investigations. The application of scientific and practical results presented in the paper will improve technical characteristics of small hydropower plants with tubular propeller turbines and minimize their possible negative impact on the life of river flora and fauna in lower basin.

Three-dimensional heat transfer characteristics of complex structure with nineteen tubular propellants under different heating rates

This work is focused to study heat transfer mechanism and cook-off response characteristics of the complex structure with nineteen tubular cluster double-base propellants. The three-dimensional unsteady heat transfer model with chemical reaction mechanism is developed to provide a detail means of capturing fundamental thermal phenomena of multiple materials occurring during heating process with different environmental heating rates. Comparisons of temperature variation of computational results are done with experiments, and a reasonable match has been obtained. Further, the cook-off response characteristics under slow heating conditions can be divided into two stage. The temperature rise in the first stage is dominated by the heat transfer mechanism between multiple martials with complicated structure, and the main factor in the other stage is chemical reaction effect of the double-base propellant that can release more reaction heat. The environmental heating rate has an obvious effect on the cook-off response parameters, including ignition temperature, delay time and response position. The results show that with an increase of heating rate, the cook-off response time exponentially decreases and can be expressed as: ti = 21.59exp(−logk/1.106)-0.07. Especially, the path of temperature rise has changed dramatically under the combined effects of different heat conductivities inside the motor and environmental heating rate.

Prediction of incipient cavitation in micro tubular propeller turbine

Abstract Cavitation is a phenomenon that cavities or bubbles form in a liquid when static pressure falls below the vapor pressure. It can damage the machine, hence it is recommended to be avoided in the design and operation of the machine. In this study, the cavitation characteristics were numerically investigated with a change in the flow rate of a micro tubular propeller turbine. Here, the rotational speed was set to the value corresponding to the best efficiency point for each flow rate. A multiphase flow analysis incorporating water and water vapor was conducted, using the Zwart-Gerber-Belamri (ZGB) model as the cavitation model. Results show that the tip clearance is the first region where the cavitation starts to occur as the flow rate increases. At this time, the Thoma number was found to be 1.178. The second region where the cavitation occurs with further increases in the flow rate is in the vicinity of the leading edge. It turned out that the leading edge cavitation occurs when the Thoma number is below 1.111. As the tip clearance increases, the range of the flow rate that cavitation does not occur increases, but it reduces turbine performance. Therefore, the selection of appropriate tip clearance given the operating flow rate range and performance needs to be considered.

Effect of Blade Leading and Trailing Edge Configurations on the Performance of a Micro Tubular Propeller Turbine Using Response Surface Methodology

With the recent rise in importance of environmental issues, research on micro hydropower, a kind of renewable energy source, is being actively conducted. In this study, a micro tubular propeller turbine was selected for study of micro hydropower in pipes. Numerical analysis was conducted to evaluate the performance. Response surface methodology using design of experiments was performed to efficiently investigate the effect of the blade leading and trailing edge elliptic aspect ratios on the performance. The trailing edge configuration was found to be more related to the performance, because of the drastic pressure variation due to the stagnation point formed, regardless of the leading edge configuration. To improve the performance, a NACA airfoil was introduced. The results show that the flow became more stable than the reference model, and the efficiency was increased by 2.44%.

Micro Axial Turbine Hill Charts: Affinity Laws, Experiments and CFD Simulations for Different Diameters

Water supply systems are one of the main hydraulic systems with significant potential for the installation of micro-hydropower devices. Although there are already some mini-hydropower applications in water supply systems, it is still a huge potential that continues to be under-exploited. The arrangement based on an axial turbine, such as an inline tubular propeller, with different diameters and rotational speeds suitable to exploit the existing potential in the water sector, is fully tested. The turbine with the nominal diameter of 85 mm was analysed through experimental campaigns and numerical models for a large range of heads and flow measurements to access its performance. A good correlation between the physical model and the numerical results were obtained, with mean values of deviation less than 5% regarding flow, mechanical power and efficiency. These results were extrapolated to other similar turbine with 170 mm, using affinity laws to investigate the power extraction performance. Both geometries were also numerically investigated using computational fluid dynamics (CFD) models and comparisons were made between the affinity model and experimental results. The results identified differences when compared with the classical affinity curves. Therefore, new formulations based on affinity equations were proposed for the analyzed axial turbine with different diameters without imposing a constant turbine efficiency since actually it does not keep constant as CFD calibrated model proved. Compared to experimental test efficiencies for different rotational speeds, the new proposed affinity laws provided a maximum error of 12% for both diameters.

Mathematical model and software for investigation of internal ballistic processes in high-speed projectile installations

This paper describes a software package that allows to explore the interior ballistics processes occurring in a shot scheme with bulk charges using propellant pasty substances at various loading schemes, etc. As a mathematical model, a model of a polydisperse mixture of non-deformable particles and a carrier gas phase is used in the quasi-one-dimensional approximation. Writing the equations of the mathematical model allows to use it to describe a broad class of interior ballistics processes. Features of the using approach are illustrated by calculating the ignition period for the charge of tubular propellant.

Energy production with a tubular propeller turbine

Micro-hydropower is a way of improving the energetic efficiency of existent water systems. In the particular case of drinking water systems, several studies have showed that pressure reducing valves can be by-passed with turbines in order to recover the dissipated hydraulic energy to produce electricity. As conventional turbines are not always cost-effective for power under 20 kW, a new energy converter is studied. A five blade tubular propeller (5BTP), assessed through laboratorial tests on a reduced model with a diameter of 85 mm diameter and a maximal output power of 300 W, is addressed in this work. Having showed promising potential for further development, since global efficiencies of around 60% were observed, the turbine has been further used to estimate the potential for energy production in a real case study. A sub-grid of the drinking water system of the city of Lausanne, Switzerland, has been used to obtain an annual energy production through hourly simulations with several turbines.

Energy Recovery Using Micro-Hydropower Technology in Water Supply Systems: The Case Study of the City of Fribourg

Water supply systems (WWSs) are one of the main manmade water infrastructures presenting potential for micro-hydropower. Within urban networks, local decentralized micro-hydropower plants (MHPs) may be inserted in the regional electricity grid or used for self-consumption at the local grid level. Nevertheless, such networks are complex and the quantification of the potential for micro-hydropower other than that achieved by replacing pressure reducing valves (PRVs) is difficult. In this work, a methodology to quantify the potential for hydropower based on the excess energy in a network is proposed and applied to a real case. A constructive solution is presented based on the use of a novel micro-turbine for energy conversion, the five blade tubular propeller (5BTP). The location of the MHP within the network is defined with an optimization algorithm that maximizes the net present value after 20 years of operation. These concepts are tested for the WSS in the city of Fribourg, Switzerland. The proposed solution captures 10% of the city’s energy potential and represents an economic interest. The results confirm the location of PRVs as potential sites for energy recovery and stress the need for careful sensitivity analysis of the consumption. Finally, an expedited method is derived to estimate the costs and energy that one 5BTP can produce in a given network.

Experimental characterization of a five blade tubular propeller turbine for pipe inline installation

The interest in micro-hydropower in existing infrastructure is increasing since this is a technology with low environmental impacts and potential for energy recovery in different types of installation. The technologies available for these schemes are still restricted and it is a current subject for research. In this work an experimental characterization of an inline tubular propeller suitable for pressurized systems, such as water supply and distribution networks, is presented. In the framework of the European Project HYLOW, started in 2008, a first prototype has been developed using CFD analysis and tested. Nevertheless, optimization and validation were still necessary. An improved model has been now adequately tested in the laboratory and proves to be interesting in terms of potential application. The experimental investigation evidenced that the new turbine has efficiencies of around 60% for low-headed operations, below 50 m.

On the Pressure Ratio in an H L Gun During Burning

It has been shown that some conditions regarding the lower limit to the volume ratio of the two chambers dependent on the propellant property and the leakage parameter may exist in order that the pressure ratio is to be less than the critical pressure ratio in an H/L gun during burning. Also for progressive propellants constant pressure ratio may not exist for other than tubular propellant.

Improvement of Interior Ballistic Performance Utilizing Particle Swarm Optimization

This paper investigates the interior ballistic propelling charge design using the optimization methods to select the optimum charge design and to improve the interior ballistic performance. The propelling charge consists of a mixture propellant of seven-perforated granular propellant and one-hole tubular propellant. The genetic algorithms and some other evolutionary algorithms have complex evolution operators such as crossover, mutation, encoding, and decoding. These evolution operators have a bad performance represented in convergence speed and accuracy of the solution. Hence, the particle swarm optimization technique is developed. It is carried out in conjunction with interior ballistic lumped-parameter model with the mixture propellant. This technique is applied to both single-objective and multiobjective problems. In the single-objective problem, the optimization results are compared with genetic algorithm and the experimental results. The particle swarm optimization introduces a better performance of solution quality and convergence speed. In the multiobjective problem, the feasible region provides a set of available choices to the charge’s designer. Hence, a linear analysis method is adopted to give an appropriate set of the weight coefficients for the objective functions. The results of particle swarm optimization improved the interior ballistic performance and provided a modern direction for interior ballistic propelling charge design of guided projectile.

CFD and Experimental Study in the Optimization of an Energy Converter for Low Heads

This paper deals with new design of low head turbines, as feasible solutions to solve the lack of energy in rural and remote areas, or to provide energy from urban water pipe systems. Propeller turbines are then the subject of this research because they are suitable for small heads, discharges with little variability, easy to manufacture and with low costs associated. Hence, the aims are the design of quite simple tubular propeller turbines and the analysis of hydrodynamic behaviour for different number and configuration of blades, based on CFD analyses and experimental tests development. An advanced hydrodynamic code based on the finite volume method, as well as blades configuration and mesh specific models are used for the impeller and the turbine design. The blade geometry is optimized using mathematical formulations and experimental results, concerning the possible range of operation under best efficiency conditions. Performance curves are obtained for typical characteristic parameters allowing comparisons between CFD and experimental results. Based on the similarity theory applied to turbomachines it is possible to evaluate the hydrodynamic behaviour through a tubular propeller for different sizes, in a scale model application.

Experiments and CFD Analyses for a New Reaction Microhydro Propeller with Five Blades

AbstractThis works aims to develop and study a new reaction microhydro tubular propeller turbine with five blades as a promising answer to solve the lack of energy in rural and remote areas. The first stage is to validate numerical and experimental tests made for the flow behavior for different values of head, discharge, and rotational impeller speed. Using specific mathematical formulations, a blade model configuration is developed based on the velocity triangles at the impeller inlet and outlet and experimental results based on pressure, discharge, and velocity profiles in different turbine sections. Through characteristic parameters, performance curves are obtained allowing comparisons between experimental and computational fluid dynamics (CFD) results. Also, an evaluation of the hydrodynamic behavior is made for a scaled model application by similarity turbo machines theory.

Experimental Analysis of the Influence of Length to Diameter Ratio on Erosive Burning in a Solid Tubular Propellant Grain

Erosive burning usually refers to the increase in the propellant burning rate caused by high velocity combustion gasses flowing over the propellant surface. It may seriously affect the performance of solid-propellant rocket motors [1]. A series of experiments had been made to study the effects of length to the diameter ratio in a single tubular propellant grain on the erosive burning phenomenon. In the same combustion pressure and different grain geometries, the burning pattern of AP1based propellant were recorded. Furthermore, pressure-time curve for each condition was obtained. The mean velocity gradient is obtained by some thermo-gas-dynamical analysis on experimental data. The results can be used for preliminary design of AP based tubular propellant rocket motors. This method may be used for other types of tubular solid propellants which defer in chemical formulation.

English

Radial outward burning tubular propellant grain gives progressive burning profile, but trimming port at one end to conical form gives close to neutral burning profile. Though this configuration is easy to realize, but closeform burnback equation for performance prediction of such propellant geometry is not available. In this paper, close-form burnback equation for conically trimmed tubular propellant grain is developed. One propellant grain is also evaluated and performance matching to prediction by developed formulation is realised. Parametric study for different aspect ratio (L/D), diameter ratio (d/D) and slant angle (q) is carried out for a typical configuration and variation is explained. The developed formulation is simple, handy, easy and quick. Defence Science Journal, 2009, 59(5), pp.494-498 , DOI:http://dx.doi.org/10.14429/dsj.59.1550