Development of Tools for Thermodynamic Calculation of Rocket Engine Characteristics using the Julia Programming Language

The experience in developing an algorithm and a program for the thermal-chemical calculation of the characteristics of a rocket engine is presented. The program is written in Julia. To calculate the equilibrium composition of combustion products the freely distributed library Ipopt is used. The program is interfaced to the database on thermodynamic properties of individual substances IVTANTERMO. For the convenience of processing, the information on thermodynamic properties is stored in two text files of a special form. The program has been developed using the simplest working process model according to which the flow is one-dimensional, the product flow is adiabatic, there are no friction losses, the product flow is equilibrium, and the speed of condensed particles is equal to the gas flow speed. Ratios for calculating the derivatives of composition, as well as equilibrium values of heat capacity and sound velocity are given. The text of the program can be used in the study process and can easily be adapted to more complex models of the rocket engine workflow. The calculation results obtained using the developed program are in good agreement with the results of TERRA calculations. The execution time of one calculation for a four-element fuel, which includes the determination of the combustion products characteristics in the chamber, the critical cross section and at the nozzle cross section, varies in the range of 3--5 s

Follow for Now, Volume 2: More Interviews with Friends and Heroes

Follow for Now, Vol. 2 picks up and pushes beyond the first volume with a more diverse set of interviewees and interviews. The intent of the first collection was to bring together voices from across disciplines, to cross-pollinate ideas. At the time, social media wasn’t crisscrossing all of the lines and categories held a bit more sway. Volume 2 aims not only to pick up where Follow for Now left off but also to tighten its approach with deeper subjects and more timely interviews. Featuring conversations with thinkers like Carla Nappi, Rita Raley, Dominic Pettman, Ian Bogost, Mark Dery, Douglas Rushkoff, and Dave Allen, and musicians like Tyler, The Creator, Matthew Shipp, Sean Price, Rammellzee, and Sadat X, as well as writers like Ytasha L. Womack, Chris Kraus, Pat Cadigan, Bob Stephenson, Simon Critchley, Simon Reynolds, Malcolm Gladwell, and William Gibson, Follow for Now, Vol. 2 is another critical cross-section of the now.

IMPROVING THE DESIGN OF THERMAL TOOLS FOR ROCK FRACTURING

The article deals with the main parameters of the thermodynamic working device for rock destruction due to the implementation of a new method of fuel mixture combustion in shock waves initiated by a high-speed torch burner in gas-dynamic combustion intensifiers. A device for thermal destruction of rocks has been developed, which belongs to the mining industry and can be used for directed impact on rocks when they are destroyed by hot gas jets in mining, stone processing and construction industries. Also, installed coaxial to the nozzle, with increasing inside diameter, a cylindrical nozzle, with two cascades of ejection holes - the first cascade is made at a distance from the Laval nozzle, equal to the distance to complete expansion of the jet of the torch, then, the accelerating section of the nozzle and the new, formed by burning the unburned fuel, jet of the burner. It is found that the cross sectional area of the inner hole of the cylindrical nozzle, is made with an excess of the area of the critical cross section of the nozzle Laval burner 2.5-3 times, in which, because of the rapid expansion of the gas flow in the nozzle, there is turbulization, with the formation of a powerful zone of heating of the gas flow and the appearance of a standing detonation wave in it. The drilling angle of the ejection holes of the first stage is 45-50º to the axis of the nozzle, which serves for ejection of atmospheric air, the oxygen of which reacts with the surplus of combustible in the main jet of the burner and the formation of a more powerful jet.

Numerical simulations of temperature fields in the uncooled nozzle of a short-range anti-aircraft rocket engine with an insert in the critical section made of various materials

The paper presents numerical simulations of transient heat conduction in the uncooled nozzle of a short-range anti-aircraft rocket engine. The calculations were made for the configuration of the nozzle with an insert in the critical section made of various materials. The inserts used were: POCO graphite, Al2O3 ceramics, ZrO2-3Y2O3 ceramics. For comparison, numerical simulations of the heat transfer in a nozzle made entirely of St 45 steel, the melting point of which is 1700K, were also carried out. The engine's working time was in the order of 3 s. Numerical simulations were performed using the COMSOL program. The calculation results are given in the form of temperature dependence and heat flux density as a function of time in the critical cross-section. Keywords: non-cooled nozzle, rocket engine, temperature field

Fatigue Failure of a Pressing Machine

This article presents an analysis of the causes of a fatigue crack in the guide bar of a pressing device. The detailed analysis included the analysis of a material’s microstructure and its cyclic properties. Direct measurements of the strains during operation allowed the nominal loading process in the critical cross-section of the press subassembly to be obtained. The notch effect of the inner thread of the guide bar was analyzed using a precision FEM (finite element method) model and was followed by the transformation of the nominal loading into the notch root. A methodological approach was formulated based on the analyses made, which lay in the statistical interpretation of the factors leading to an identification of the cause of an early fracture.

Assessment of in-Plane Behavior of Metal Compressed Members with Equivalent Geometrical Imperfection

A new procedure was presented with the objective of proving that it is the generalization of current attempts in designing compressed members and structures which is able to solve cases where other authors have problems. It is the further development of the former methods published by Chladný, Baláž, Agüero et al., which are based on the shape of the elastic critical buckling mode of the structure. Chladný’s method was accepted by CEN/TC 250 working groups creating Eurocodes. Both current Eurocodes EN 1993-1-1:2005 and EN 1999-1-1:2007 in their clauses 5.3.2(11) enable applying the geometrical equivalent unique global and local initial (UGLI) imperfection. The imperfection has the shape of the elastic critical buckling mode with amplitude defined in 5.3.2(11). UGLI imperfection is an alternative to the global sway and local bow initial imperfections defined in 5.3.2(3) and to the imperfections described in the clause 5.3.2(6). The determination of the location and value of UGLI imperfection proved to be onerous by some authors, especially in cases of members with variable cross-sections or/and axial forces. The paper also provides for special cases a procedure to detect the critical cross-section along the member which is defined as the one in which the utilization factor obtains maximum values. The new approach is validated by the investigation of five complex structures made of steel and one made of aluminum alloy solved by other authors. Comparisons of the results with those of other authors and with the Geometrically and Materially Nonlinear Analysis with Imperfections (GMNIA) results showed very good agreements with negligible differences. The information concerning the differences between current Eurocodes EN 1993-1-1:2005 and EN 1999-1-1:2007 is provided. Working drafts of Eurocodes of new generation prEN 1993-1-1:2020 and prEN 1999-1-1:2020 are also commented on.

Investigation of the Nominal Tooth Root Stress for External, Cylindrical Gears with Symmetric and Asymmetric Profile

The determination of tooth bending strength is a basic issue in gear design. This work presents the change of nominal tooth root stress of external toothed, cylindrical gears depending on the geometry used. The nominal tooth root stress is analyzed with using finite element simulations. The numerical calculations are executed in Abaqus. The imported geometries are produced by our own program in MATLAB. The boundary conditions to the models are defined accordance with the most significant analytical methods used in practice. This approach allows mapping direct correlation analysis by these calculations. The optimization of computational capacity used is also considered. In addition to the examination of the significant tooth stress value of symmetrical element pairs, the position of the critical cross-section is also analyzed. The effect of the asymmetric design of the tooth profile on the nominal tooth root stress is also presented in our investigations. The purpose of the numerical simulations carried out here is to determine the effect of the coast side angle on the magnitude of the significant tooth root stress and the position of the critical cross-section.

Secondary Moments due to Prestressing with Different Bond at the Ultimate Limit State

Secondary effects of prestressing develop in statically indeterminate structures (e.g., continuous beams) due to the restraint of deformations imposed by hyperstatic restraints. These effects may significantly influence internal forces and stresses in prestressed structures. Secondary effects are influenced by the redundancy of a structural system, which raises the question of whether they will remain constant after a change in the structural system, e.g., due to the development of plastic hinge(s) in a critical cross-section(s) or after the development of a kinematic mechanism, or if they will disappear when the structure changes into a sequence of simply supported beams. The paper deals with an investigation of the behavior of continuous post-tensioned beams subjected to an ultimate load with significant secondary effects from prestressing. A total of 6 two-span beams prestressed by tendons with different bonds were tested in a laboratory with a load that changed their structural system into a kinematic mechanism. The internal forces and secondary effects of the prestressing were controlled through measurements of the reactions in all the supports. The results revealed that the secondary effects remained as a permanent part of the action on the experimental beams, even after the development of the kinematic mechanism. The results obtained confirmed that secondary effects should be included in all combinations of actions for verifications of ultimate limit states (ULS).

Aerodynamic Design and Optimization of Pipe Diffuser for a High-Loading Centrifugal Compressor

Pipe diffuser draws more attentions these years as the stage pressure ratio and loads grow, since it is known that the pipe diffuser has a superior performance to the traditional vane diffuser as the diffuser inlet flow field is transonic or supersonic. Generally speaking, when the pressure ratio is high enough to give rise to the emergence of a critical cross-section, it would usually be in the diffuser, closing to the leading edge other than in the impeller. Therefore, the diffuser would have a significant impact on stage choke margin and its performance while be difficult to design and to match the impeller with satisfaction. To address the problem, a preliminary geometry design method for pipe diffuser is presented in this paper. In this paper, the performance and flow field analysis are based on numerical simulation carried out by Numeca, a commercial simulation software. For verified the calculated results′ reliability and grid independence, corresponding calculations and comparisons are conducted and discussed. Then, the performance of stage with pipe diffuser is compared with the stage with vane diffuser. Next, the specific effects of incidence on the performance and flow field are analyzed and discussed respectively. At last, an optimized aerodynamic structure of pipe diffuser is presented. As shown in the CFD results, the stage peak isentropic efficiency can reach up to 83.65% with the stage total pressure ratio slightly increased from 6.50 to 6.78, which means 4.29% of isentropic efficiency was raised by substituting the pipe diffuser for the vane diffuser.

Strength Analysis of AL-7F-1 Engine Turbine Rotor Blade

The key intent of the article is to describe clearly the strength issue of blades for aircraft engines, on the basis of which to create a calculation algorithm and apply it to a particular blade. The work then deals with a strength analysis of a rotor blade used in the gas turbine of an AL-7F-1 turbocharger aircraft engine. The article describes comprehensively in terms of strength the influences which act on the blade during operation. Generally, these loads can be divided into static load, which includes the tensile stress generated by the rotating mass of the blades, bending and torsion moments caused by the kinetic energy of the flowing gas. The last part of the article is dedicated to the issue of compensation of the bending moments acting on the turbine blades, resulting in analytical calculation of the blade inclination angles in the critical cross section.