Analysis of properties of inertia regulator of thrust control system of liquid rocket engine

The quality of the flight task of a space rocket system is determined among other things by the accuracy of maintaining and regulating the thrust of the rocket engine. Improving the accuracy and reducing errors in the engine mode control system will reduce the cost of space launches or allow you to put a large payload into orbit. The article presents a mathematical model of a controller with an inertial booster of a liquid-propellant rocket engine, identifies parameters and values that affect its accuracy, and considers measures to reduce static error

Energy-efficient outdoor air flow control in ventilation systems

A method for controlling the ventilation system flow characteristics is considered based on the forming principle an air temperature and carbon dioxide concentration predicted estimate in a room based on the changes dynamics analysis in these parameters in the supply and exhaust ducts. The expected microclimate parameters predicted assessment in real time opens up the possibility of using such elements and algorithms for controlling the ventilation and air conditioning system, which provide the required air quality with minimal energy consumption. The analysis calculates the finding probability the measured parameter inside or outside the control zone after a specified time interval. The algorithm for the control system actuators actuation for the channels of temperature and carbon dioxide concentration is presented in the block diagram form. The decision-making logic for actuating the actuators is based on the changes direction and intensity analysis in temperature and carbon dioxide concentration in the exhaust duct and the temperature difference between the supply and exhaust

Y. S. Hu, H. J. Wei, B. Yu, O. X. Yang, J. Wang, J. Wu. Research on the vapor injection of two-stage rotary compressor / trans. from Engl. M. A. Fedorova

In order to understand the vapor injection flow characteristics of two-stage rotary compressor in the course of compression, a mathematical model based on mass conservation equation, energy equation and thermodynamic identity was established and proved by P-V diagram testing results. Some useful conclusions about pressure in the intermediate chamber and mass flow of vapor injection in the course of compression were also given out. The results show that, gas backflow between the intermediate chamber and the vapor injection channel is an important defection of two-stage rotary compressor which can be solved by the application of injection valve in vapor injection channel. The injection valve can obviously reduce the gas backflow and the power loss in the course of compression while increasing the pressure fluctuation in the intermediate chamber. Experiments show that the COP of two-stage rotary compressor with the injection valve increased by over 2% in ASHRAE/T working condition.

Justification scheme for milling waffle background

In the manufacture of dry and fuel compartments of missiles ensuring weight tolerance is a priority. In practice, this is ensured by the introduction of lightweight materials together with the optimal design of the supporting set of ribs (waffle background) of orthotropic shells and waffle shells. The manufacturing technology of which is difficult and costly in view of the difficulty of ensuring the accuracy and perfection of the shape of the waffle background cell. In modern conditions, when manufacturing a waffle shell for a fuel tank, reinforcement processing is carried out by milling on a monolithic blank using specialized machine systems. At the same time, the choice of the waffle background processing scheme remains an urgent issue: on a flat panel or on a bent shell. The problem of selection arises due to the requirements for the accuracy of the waffle background. It is important to maintain the part mass tolerance and geometric perfection of the cell shape. All this generally affects the perception of design loads and the carrying capacity of the rocket. At the same time, the methods and processes of processing the waffle background should be productive and economically feasible. The proposed justification will make it possible at the start of the design of new promising products to more accurately determine the technological and production costs necessary for the production of parts with a waffle background with given parameters and accuracy.

Grieb M., Brümmer A. Investigation into the effects of surface condensation in steam-driven twin screw expanders / trans. from Engl. M. A. Fedorova

During the operation of twin screw expanders with slightly superheated vapours or even two-phase fluids, surface condensation on machine parts occurs during the filling period and the expansion phase when the working fluid is in contact with cooler inner surfaces. This heat exchange from the working fluid to adjacent machine parts effects the working cycle and the efficiency of these machines. Short time scales and the periodicity of the process indicate the condensation process is best described by models for dropwise condensation. In this paper the effects of surface condensation on the operation of twin screw expanders are initially discussed in a simulation-based investigation. Chamber model simulation coupled with a thermal analysis is used for the thermodynamic simulation, whereby heat transfer coefficients are systematically varied. It is found that during the inlet phase condensate emerges on the inner surfaces of the machine being substantially cooler than the working fluid. This results in a higher mass being trapped within the working chamber and, thus, an increasing mass flow rate of the machine. An increase in power output is, however, not observed. The results obtained from chamber model simulations are finally compared against experimental data of a screw expander prototype

The position of liquid fuel residues in tank of worked-off rocket stage during ballistic descent

The results of modeling the behavior of liquid residues of the rocket fuel component in the fuel tank of the worked-off rocket stage on a ballistic trajectory are presented. The simulation is carried out for the following variants: during the controlled descent of the rocket stage and when using the technology of evaporation of liquid rocket fuel residues in the tanks of the spent stage. It is established that during the controlled descent of the spent rocket stage along the ballistic trajectory at the site of its turn and up to heights of 20 km, the liquid under the influence of overloads is distributed in the form of a film in the area of the bottom and side surface with a coverage area of up to 35 %. At the height of the maximum value of the axial overload, liquid fuel residues in the form of a film move to the area of the bottom and the adjacent side surface of the fuel tank. The total coverage area is about 22 %. The introduction of a hot coolant into the fuel tanks to vaporize the liquid remnants of rocket fuel radically changes the picture of the behavior of the liquid. Due to the high speed of the coolant in the tank, axial overload has little effect on the distribution of fuel residues in the rocket tank

Multipurpose conversion of marine diesel engines when creating piston motor-compressor units

This paper present an assessment of the energy efficiency of various combinations of piston stages of an internal combustion engine, a compressor, and a Rankine engine as part of piston motor-compressor units based on modernized marine diesel engines. An eight-cylinder single-row diesel engine 8Ch23/30-1 is chosen as the object of research, the base of which is used as a single platform for creating powertechnology units for various purposes and power. The proposed variants for converting the original engine allow, with minimal costs for the development of design and manufacturing technology, to create gas engine compressor units with reduced fuel consumption and improved weight and size characteristics in comparison with the known mobile compressor stations driven by diesel internal combustion engines. In the paper, on the basis of the developed mathematical models of working processes, the possibility of joint operation of diesel cylinders with piston expanders of the Rankine cycle and one or more stages of a piston compressor is assessed. Various possible combinations of diesel cylinders, compressor cylinders and expander cylinders are considered, as well as the dependences of engine power and compressor performance depending on the number of compressor stages and the number of diesel power cylinders used.

M. W. Tofique, A. Löf, C. Millward, Z. Günther. Testing and calculation of impact fatigue strength of Flap-X and SS 716 flapper valve steel grades / trans from Engl. M. A. Fedorova

During the operation of reciprocating compressors, the flapper valve opens and closes under fluid pressure and flow. As it closes, it strikes against the valve seat, generating stresses and noise. This cycle of loading produces bending and impact fatigue stresses in the reed. This load pattern is repeated billions of times during the service life of a compressor and it defines the service life and reliability. The goal of this study was to calculate the impact fatigue strength of the Flap-X and the SS 716 grades and, to provide the compressor manufacturers with the information they can use to specify a steel grade to be used in their compressors, for reliable service. Impact fatigue tests were conducted on a custom-built impact fatigue test rig that used air pulses to produce movement of the reed valves manufactured by a major European compressor manufacturer Nidec Global appliance GmbH, at a frequency of 315 Hz and pulse width of 2,2 milliseconds. The testing was conducted according to the staircase test method detailed in the International Standard SS-ISO 12107:2012. The impact fatigue strength of the Flap-X and SS 716 steel valves was calculated in terms of the impact velocity according to the modified staircase test method in the standard. The test results and their statistical analysis showed that the impact fatigue strength of the Flap-X grade was higher compared to the SS 716 grade. The calculation and testing of the impact fatigue strength of the flapper valve steel grades could help the compressor designers to select the optimum material for their compressor designs, to provide reliable service. The higher impact fatigue strength of the Flap-X grade, lower failure rate and longer impact fatigue life will allow the compressor manufacturers to design thinner valves, as Flap-X can sustain higher impact fatigue stresses reliably for longer time and, at the same time help reduce noise, as thinner valves produce less noise for a given pressure and frequency.

Compressor equipment for enhancing efficiency of solid organic waste processing plants

The article describes the experience of the Compressor holding company in the creation of compressor equipment for various industries. The use of compressors as part of complexes for the processing of organic waste in the framework of solving urgent environmental problems has been demonstrated. The process of compression of synthesis gas to increase the efficiency of the processing process has been investigated. To ensure stable parameters, reliable operation of syngas reciprocating compressors is required in wide ranges of operating parameters. Ensuring the operability of the compressor in wide ranges of parameter variation requires multivariate calculations in order to find the best design parameters of the compressor. A compressor is proposed for the most efficient implementation of the task and its characteristics are calculated.

Automation of technological process of filling chambers during pneumatic vacuum tests

The scheme and technology of the automated process of filling chambers with control gas are considered. Mathematical description of the functioning of filling system served as a basis for the development of design and analysis procedure of performance characteristics is constructed.