Using an existing control volume based computer code, swirling flow field and COMBUSTION of fuel and air are computed. In order to model turbulent stresses, a modified Bossinisque scheme in swirling flows is used. Turbulent flow is modeled using a RNG k-ε model and COMBUSTION is modeled by two well-known models, i.e., the bi-molecular Arrhenius relation and the EBU (Eddy Break Up) model. The results of the numerical solution of a COMBUSTION CHAMBER are compared with the existing experimental data for velocity and temperature distributions. The comparison shows satisfactory agreement between numerical and experimental results. The lower reaction rate computed using the above models is used in the computation. In this study, variable fluid properties have been used and their effects are presented. It is shown that the existence of either swirl or COMBUSTION shortens the length of the recirculating region and the same effect is produced by using RNG k-€ instead of the standard turbulence model.    

In this study, the COMBUSTION performance of C30 microturbine COMBUSTION CHAMBER with biogas fuel with different mass fractions of CO2 has been analyzed and investigated. By assuming the periodic geometry and the two-stage reaction of fuel and oxide, the computational cost was reduced. To simulate the flow inside the CHAMBER, three-dimensional Navier-Stokes equations and the k-ε turbulence model have been used to model the effects of turbulence. The flow inside the COMBUSTION CHAMBER with different fuel components was analyzed with the EDDY DISSIPATION COMBUSTION model. To validate the solution and compare the results with the fabricated sample, pure CH4 was used as fuel. In this study, it was found that in the case of a constant mass flow rate of the consumed fuel, increasing the share of CO2 in the fuel with different mass fractions, due to the decrease in the calorific value created, caused a decrease in the production temperature, and it was also found that the use of biogas as a premix caused a decrease The amount of NOx becomes desirable. According to the obtained results, it is suggested that the amount of CO2 in the fuel is at most 10%, because the temperature has decreased by only 38 Kelvin and the amount of NOx in the output is 1.4 ppm.

Liquid rocket engines occasionally experience severe pressure fluctuations and flame oscillations resulting in injector damage and total engine failure. High frequency COMBUSTION instability is caused by the coupling between the COMBUSTION process and the COMBUSTION CHAMBER acoustic field. Therefore, knowledge of the COMBUSTION CHAMBER acoustic characteristics is essential in dealing with this phenomenon. An experimental approach for determination of the COMBUSTION CHAMBER acoustic characteristics is outlined here. An acoustic laboratory, consisting of a hemi-anechoic room, sound generation, recording devices and complete three dimensional sweeping capabilities, has been designed and built. The experimental set up and the measurement procedures have been validated by determining natural acoustic modes of several sizes of open and closed ended cylindrical combustor. Such measurements and comparisons have provided insight into acoustic interaction in the three dimensional CHAMBER and the effects of different boundary conditions. The phenomenon of the destruction of standing waves has been observed. Experimental results indicate that, at frequencies where the ratio of the wave length of the standing wave to the diameter of the CHAMBER is about 1/7, the destruction of the standing wave is observed.Acoustic mode shapes and frequencies for combustor CHAMBERs, including the convergent part of the nozzle, have been measured and the results have been fitted with modified theoretical relations.

COMBUSTION CHAMBERs are an important part of power generation systems that affect their efficiency and environmental pollutions. To reduce the pollutions, lean premixed COMBUSTION was introduced to be used instead of traditional non-premixed flames, however, this method has more tendency to become unstable. The thermal and acoustics interactions can amplify the acoustic waves and produce noise and increase the vibration level of the liner. The continuation of large amplitude vibrations can lead to failure. Therefore, the vibration modeling of the liner is very important. In this research, the vibration of a liner in a COMBUSTION CHAMBER is investigated. The modal parameters in the cold and hot states are extracted from the finite element model. Then, model updating is utilized to modify the finite element model of the liner based on the experimental data. The flow analysis is also performed to obtain the pressure and velocity fluctuations during the analysis time. These data are used to model the flame as an acoustic source. Then, the transient analysis is evaluated to find the response of the liner due to this source. The results show the effectiveness of the updated model to predict the modal parameters and the vibration amplitude of the liner.

Liquid propellant missiles are commonly applied to launch satellites that must be located in upper orbits. These systems normally use hydrogen and oxygen propellants that are non-hypergolic mixtures. In this study, the test results of a designed hydrogen/oxygen engine were evaluated, and a designed spark igniter was successfully used to start the engine. Seven hot tests were carried out to determine the performance of the engine. The effect of oxygen to fuel ratio (O/F ratio) at a constant COMBUSTION CHAMBER pressure (800 kPa) showed that the maximum value of the specific impulse (Isp) and characteristic velocity (C*) occurs at an O/F ratio of about 2. 8. Experimental tests at the constant O/F ratio of 2. 8 showed that performance parameters, such as Isp and C*, were enhanced when the CHAMBER pressure was increased. However, the trend was sluggish at pressures higher than 800 kPa.

This paper deals with utilization of the network method to fast analysis of the gas turbine combustors. In this method, a combustor is divided into several independent flows by some nodes and interconnecting elements. The fundamental equations which should be satisfied in the network method are conservation equations of mass and energy at each node and the pressure drop-flow rate correlation for each element. These equations constitute a system of equations of flow rate and pressure drop. Solving this system using a set of initial value gives pressure, flow rate, and density at each node that finally leads to a converging solution. The conventional relations for pipes and orifices are used for flow modeling. In order to COMBUSTION modeling, equilibrium assumption is applied in the primary and secondary COMBUSTION zones. The dilution effect is considered by entering the air from dilution holes into the flow of COMBUSTION products. The liner temperature is calculated by considering the effects of convection and radiation in the combustor. By the network method in a can type combustor, at the first step a cold flow analysis is performed and the flow rate and the pressure drop in each element are obtained. In the next step by including the COMBUSTION of kerosene and heat transfer, the distribution of flow rates, pressure, temperature, and species concentration of COMBUSTION products are calculated. The computation results are compared with the existing experimental data and an excellent agreement is seen. The quality of results and the solution procedure of the problem show that the network method is able to present a costly and accurate analysis to help the combustor designers.

The cylinder working fluid mean temperature, rate of heat fluxes to COMBUSTION CHAMBER and temperature distribution on COMBUSTION CHAMBER surface will be calculated in this research. By simulating thermodynamic cycle of engine, temperature distribution of COMBUSTION CHAMBER will be calculated by the Crank-Nicolson method. An implicit finite difference method was used in this code.Special treatments for piston movement and a grid transformation for describing the realistic piston bowl shape were designed and utilized. The results were compared with a finite element method and were verified to be accurate for simplified test problems. In addition, the method was applied to realistic problems of heat transfer in an Isuzu Diesel engine, and gave good agreement with available experimental.

Nowadays, a great deal of efforts is being carried out to reduce NOx emission in gas turbines. NOx emission depends closely on the flame temperature. Water or steam injection reduces the pick temperature and NOx emission. In this paper, after modeling the COMBUSTION CHAMBER, steam, with steam to fuel ratios of 0.5 and 1, is injected into the CHAMBER and its effect on the NOx emission reduction is studied. The FLUENT software is used for solving the related reactive flow. It is concluded that, NOx emission decreases considerably, but CO emission increases.  

This study examines the effects of temperatures and directions of the magnetic fields in the COMBUSTION CHAMBERs on flame characteristics for boiler COMBUSTION in power generation systems by burning olive oil droplets. The variations in the temperature of the COMBUSTION CHAMBER are 40°C, 50°C, and 60°C. Meanwhile, the directions of the magnetic fields are the repulsive magnetic field (north-north) and the attractive magnetic field (north-south). In the experiment, a droplet of olive oil was placed at a type K thermocouple junction between the two bar magnets. A 250 fps high-speed camera recorded the flame from its ignition to its extinction. The results of this study found that temperature and direction of the magnetic fields in the COMBUSTION CHAMBER have an effect on the characteristics of the flame, where the attractive magnetic field (north-south) resulted in increased burning of droplets, round flame, low altitude, increased temperature, and shorter ignition delay time, compared to the repulsive magnetic field (north-north) and without a magnetic field. Furthermore, the COMBUSTION CHAMBER temperatures of 40°C, 50°C, and 60°C produced flame temperatures of 799. 94°C, 829. 25°C, and 879. 50°C, and flame heights of 5. 97 mm, 5. 35 mm, and 4. 23 mm, respectively. The strong magnetic fields increased the concentration of oxygen and fuel molecules around the COMBUSTION reaction zone, causing shorter droplet COMBUSTION and releasing a large amount of energy. These findings are beneficial for designing efficient industrial heat generators with a magnetic field. The results of this study are therefore crucial as a basis for considering the substitution of fossil fuels with environmentally friendly vegetable oils.

The solar-natural gas hybrid system is a suitable solution for medium-scale energy supply for domestic and industrial use. This study considers a spherical concentrator with a spherical cavity receiver as a solar system and a COMBUSTION CHAMBER that burns natural gas. The effect of various design parameters is investigated to obtain the best-configured system for Shahrekord City, Iran. The results show that the optimum receiver tube should use a 5 mm diameter tube that turns 17 loops inside the receiver. Therminol as a working base fluid with three different nanoparticles of copper, copper oxide, and alumina is examined. The highest performance is achieved at Reynold number 200 by a 5% volume concentration of copper nanofluid. Natural gas COMBUSTION provides heat energy to reach the target temperature (600 K). The effect of the number and distances of the burners for straight and U-shaped tubes has been compared in the COMBUSTION CHAMBER. The best configuration is found and the performance of this system is calculated for four sample days of a year. This calculation shows that using solar energy can save 30 to 50 % of natural gas COMBUSTION depending on the season of the year.