Optimization of artillery projectiles base drag reduction using hot base flow

The paper describes a new method for determining the temperature of combustion products (CP) of fuel used in combined cycle plants (CCGTs) and steam turbine units (STUs) with their own fuel preparation and combustion system. The method is based on the use of reliable reference data on the thermophysical the CP properties for obtaining correlation dependencies of the individual true enthalpies of the Cp components in the form of polynomials. The application of the method of inversion of polynomials made it possible to obtain in explicit form the relation for the adiabatic CP temperature, which is easily extended to theoretical and balance temperatures. Based on the example of CP fuels of three aggregate states, it is shown that the method can be used to control the process of formation of nitrogen oxides in combustion chambers of gas turbine units (GTUs) and boiler furnaces of STU.

Experimental study of supersonic base flow at Mach 2 has been carried out to see the effect of cylinder when rotated counter clockwise inside the dead zone at variable locations near its base to control base pressure for different level of expansion for area ratio 9. Active cylinder of 2 mm diameter rotating counter clockwise when seen from top, is mounted as a controller. Three locations are chosen from the side wall of square duct namely at 2, 4, 6 mm respectively and 8 mm from square nozzle exit in the base region to mount the controller. Base pressure in recirculation zone and wall pressure along the square duct length has been measured with and without control. The experiments were carried out for NPR 2, 3, 6, 7.8 and 8.5. Cylinder when rotated counter clockwise as an active controller were found to reduce the base drag as high as 62 percent at NPR 8.5 when located near to duct wall and 50 percent when located away from duct wall for the same NPR. For perfectly expanded flows at NPR 7.8 the reduction in base drag was 53 percent near duct wall and 44 percent near duct wall. The active controller was up to 19 percentage effective for over expanded flows near to duct wall and up to 12 percent when located away from duct wall. Also, the control did not adversely affect the flow field.

The article describes a methodology for determining the deposition rate of particulate matter in relation to the operating conditions of the water-tube boilers operating in a dusty flue gas flow. The description of soot particles and the causes of their occurrence in the process of fuel combustion are given. The applied methodology uses criteria equations selected for the appropriate mode of particle deposition, and containing values depending on the deposition rate and diameter of carbonaceous particles, viscosity and temperature of combustion products. The methodology is considered on the example of the parameters of the operation of the KV-GM-0.8 boiler unit at rated power. The results of calculating the deposition rate of particulate matter in the combustion product stream with a temperature from 100 to 1100 °C are presented, where the diameter of solid particles, varying in the conversion from 0.01 to 0.35 microns, was taken into account during the calculations.

Erosive burning rate studies of composite propellants under high cross flow velocities

One of the main tasks of oil producing industry is the increase of producible oil index and the oil-field development rate. In the context of hydrocarbon crude stock reduction and the increasing energy consumption, the issue of hard to recover reserves development occurs and the high-viscosity heavy oil rates are considered to be such reserves. Chemical agents (resolvents) addition, mechanical effects, magnetic and electrostatic fields imposing, and thermal treatment are the basic methods of oil viscosity reduction. The main method of heating and viscosity reduction of hard to recover oil rates is the application of gas producers, which operate using solid fuel. The use of ballistite fuels in gas producers with the possibility of adding various coolants of different concentrations allows regulating temperature and emission characteristics of homogeneous combustion products to the level specified by the recovery methods. The paper presents the methods and the results of heat emission calculation of the combustion products of a gas producer that operates using solid fuel. Water is used as a coolant. The combustion products are represented by the aggregation of monodisperse system of sootflakes and gas phase. Using the method of computing experiment, the authors studied the influence of a coolant concentration (0 %, 10 % and 25 %) on the temperature and spectral and integral emission parameters (fluence rate and emissivity factor) of combustion products at different pressures (0,1 MPa and 7 MPa). It was established that the cooling agents addition influences on the fluence rate value more than the emissivity factor when the combustion products have only gas phase. The growth of soot content causes the increase of spectral and integral emission parameters even when adding agents lowering combustion products temperature. The authors present the characteristic curve of integral parameters on the emitting layer thickness.

When compression ignition engines operate with biodiesel, emissions of carbon monoxide (CO), particulate matter, and hydrocarbons are significantly reduced, whereas emissions of nitric oxides (NO<sub>x</sub>) increase substantially. Steam injection was used in this study to reduce NO<sub>x</sub> emissions and for its effects on the chemical equilibrium of combustion products. Variations in the thermodynamic properties of the combustion products at chemical equilibrium, as well as changes in the temperature of the adiabatic flame and the combustion products at chemical equilibrium, were studied during combustion of both conventional diesel fuel and biodiesel, with and without 5% steam injection. These variations were analyzed at different pressures, equivalence ratios, and temperatures of the unburned mixture. The results showed that when the flame temperature exceeded 1800 K, a decrease of 103 K in the maximum flame temperature due to steam injection reduced thermal nitric oxide (NO) production by 73%. The results also indicated that while NO emissions and adiabatic temperature decrease significantly, specific heat values increase as the steam injection rate was raised. At chemical equilibrium, combustion products contain only the most stable species in substantial quantities below 1300 K. The emission of CO and NO<sub>x</sub> by lean combustion systems indicates that chemical equilibrium is not maintained when the combustion products are cooled.

The aim of process control has been to control heating of steel tubes in front of roll-mill. Equal temperatures along 17m length steel tubes have been required. The temperature of charge direct to measure was not possible in reheating furnace from objective reasons. The temperature of combustion products in reheating furnace has been direct measured. Simulation model of reheating furnaces was used for development of control system. First simulations shown that is necessary to change construction of furnaces and the localization of burners. The proposal of creating burner's zone was done by simulation likewise. This way is well-know as a cooperation of design construction conditions by automation equipments. The control system consists of two levels. First stabilization level is based on algorithm bang-bang control. Second level adapts required values for first level on principle direct measured temperatures of charge outside furnace. The idea of control system was verified by simulation.

This paper proposes a method for solving the problem on determining the unknown composition of a gaseous hydrocarbon fuel during its combustion in real time. The problem had been defined as the inverse, ill-posed problem. A technique for measuring technological parameters makes it possible to specify it as a complex interpretation problem.To solve it, a method has been selected (selection), which is the most universal one. To implement it, a method has been constructed to compile a library in the form of a working three-dimensional array. The source data for each solution to a direct problem in the generated array are represented in the form of a single number. To this end, a position principle for recording decimal numbers has been applied.Compiling a working array employed a method for comparing the excess factor of an oxidizer and the ratio of volumetric consumption of an oxidizer and fuel. This has made it possible to apply the results from solving a direct problem on determining the temperature of combustion products in order to solve the inverse problem on determining this composition based on the measured temperature.A method has been devised for finding a solution among the elements of the working array based on the results from technological measurements of temperature of the combustion products of the burnt fuel and the ratio of the volumetric consumption of an oxidizer and fuel.The work shows the absence of errors introduced to the solution by an algorithm of the proposed method. When modeling precise technological measurements, errors are due only to the sampling of source data while solving a direct problem. The influence of measuring the technological parameters on accuracy in determining the composition of fuel has been defined. It does not exceed the magnitude that is permissible for engineering calculations.The proposed calculation method could make it possible to use under a managed mode, in energy and in the chemical industry, a large amount of hydrocarbon fuel gases that are currently considered waste. Their energy equivalent is comparable with the energy needs by the African continent.

Relevance. Saving natural gas, reducing heat and steam emissions into the environment through deep utilization of heat from exhaust gases in a waste heat boiler and heat and moisture in a condensation waste heat boiler. Aim. Development of a combined gas-steam plant scheme and its calculation methods. Objects. Combined gas-steam plant with the introduction of water vapor into the combustion chamber of a gas turbine and deep heat recovery in a waste heat boiler and a condensing heat and moisture recovery unit from the exhaust gases. Methods. Numerical methods based on material and energy balances of systems and elements of gas-steam plants. Results. The authors have developed the thermal scheme of a combined gas-steam plant with water vapor introduction into the combustion chamber of a gas turbine and deep heat recovery in a waste heat boiler and heat and moisture from exhaust gases in a condensing waste heat boiler. Rhey developed as well the algorithm for calculating this scheme. Based on this scheme the authors written the calculation program in the EXCEL spreadsheet package using the Coolprop database of functions for calculating thermodynamic and thermal physical parameters of substances. This program allows calculating indicators with changes in the outside air parameters, the fuel burned composition, the air compression degree in the compressor, the flow rate of steam introduced into the combustion chamber, the temperature of combustion products at the inlet of the gas turbine, the electrical load on the gas turbine generator, and the exhaust gases temperature at the outlet of the heat recovery unit. The paper introduces the example of the circuit calculation for one variant of the initial data. This example showed that with the given initial data, when using the heat leaving in the waste heat boiler and condensing heat recovery unit in additional Rankine cycles, it is possible to obtain, relative to the electric power of the gas turbine of 100 MW, an increase in power of 12.34 MW: of which 8.94 MW in the steam turbine and 3.40 MW in the turbine on a low-boiling working fluid. The electrical efficiency of the combined gas-steam plant was 57.68%: while the efficiency of the gas turbine was 51.35%, the efficiency of the steam turbine was 83.48% and the efficiency of the turbine on a low-boiling working fluid was 4.86%.

The supersonic base flow of a blunted cone-cylinder rocket model in the presence of a central propulsive jet is investigated numerically by solving three-dimensional Reynolds averaged Navier—Stokes equations in an unstructured mesh using a commercial computational fluid dynamics software. The effect of the computational grid and the turbulence model in predicting the radial variation of base pressure has been brought out. Very fine grid ( y+∼ 2) is required to correctly predict the base pressure. The renormalized group k—ɛ turbulence model performs better compared to the k—ω turbulence model in predicting the base pressure. It was observed that the base flow characteristics in the lower and upper portions of the base are significantly different due to the influence of model support.

Large eddy simulation of fuel variability and flame dynamics of hydrogen-enriched nonpremixed flames

The paper experimentally investigates the integral characteristics of the processes involved in the reduction of gas temperature by injecting the aerosol flow of water droplets into a counter flow of combustion products (period of steady low gas temperature Tg’ compared to the initial Tg, range of temperature decrease (ΔTg=Tg-Tg’), rate of temperature recovery, the geometric dimensions of the temperature traces and their lifetime). We use the following recording devices: fast-response thermocouples (heat inertia less than 0.1 s), a multichannel recorder, a high-speed video camera (up to 105 frames per second), as well as a cross-correlation hardware and software package (with optical methods for recording the front and trace of the aerosol). The temperature trace of an aerosol is defined as the area with the temperature Tg’ lower than the initial Tg by at least 10 K. We determine how the following group of factors affects the characteristics of temperature traces of water droplets: size (0.04-0.4 mm) and concentrations (3·10-5- 11·10-5 m3 of droplet/m3 of gas) of droplets in a pulse, the initial temperature of water (280-340 K), the duration of a pulse (1-5 s), the temperature (350- 950 K) and velocities (0.5-5 m/s) of combustion products. The temperature in a trace of water droplets during their motion in a flame can be reduced due to rapid vaporization or heat exchange between the gases and water. The conditions are identified, under which the low temperature of gases in a trace of droplet aerosol can be preserved for a long time (20–30 s). Finally, we forecast the parameters of temperature traces under the conditions of actual fires with combustion product temperatures over 1000 K.

Comparative analysis of hydrogen/air combustion CFD-modeling for 3D and 2D computational domain of micro-cylindrical combustor

In this paper, the combustion and NOx emission characteristics of a 300 MW tangential boiler are simulated, we obtain the flue gas velocity field in the hearth, component concentration distribution of temperature field and combustion products, and the speed, temperature, concentration of oxygen and NOx emissions compared with the test results in the waisting air distribution conditions, found the simulation values coincide well with the test value, to verify the rationality of the model. At the same time, the flow field in the furnace, the combustion and the influence of NOx emission characteristics are simulated by different conditions, including compared with primary zone secondary waisting air distribution, uniform air distribution and pagodas go down air distribution, the results show that, waisting air distribution is useful to reduce NOx emissions.

Modelling of diesel spray flames under engine-like conditions using an accelerated Eulerian Stochastic Field method