Combustion chamber development features for converted small gas turbine

The paper formulates the issue of development of experimental base with noninvasive optical-electronic tools for control of combustion in a combustion chamber of gas turbine engine. The design and specifications of a pilot sample of optronic system are explained; this noninvasive system was created in the framework of project of development of main critical technologies for designing of aviation gas turbine engine PD-14. The testbench run data are presented.

In the present work, a convergent–divergent nozzle with a multi‐inlet combustion chamber of a rocket engine is numerically investigated to precisely understand the flow dynamics and variation of flow properties like pressure, temperature, and velocity distribution. The work also deals with a modified combustion chamber having multiple inlets. According to the entry conditions, when the propellants enter the combustion chamber, they are burning due to high velocity and temperature. Then there is a rapid increase in temperature and pressure in the combustion chamber, and afterward, they decrease over the nozzle's length. In this study, three configurations have been prepared in the design modular of ANSYS, a combined setup of the convergent–divergent nozzle with a combustion chamber with four inlets, six inlets, and one with increased combustion chamber length called a modified combustion chamber configuration. In this analysis, an investigation is performed to see the effect of multi‐inlet and increased length of the combustion chamber on the convergent–divergent nozzle's exit velocity. The results show that the configuration with six inlets modified combustion chamber has a 26.3% increase in velocity than six inlets and 38.6% higher exit velocity than four inlets convergent–divergent nozzle of the rocket engine.

The gas turbine combustion chamber is one of the most critical components to be designed, because it must ensure a stable operation in a wide range of air/fuel ratio and load. Among several calculations involved in the design of a combustion chamber, the reference area is the most important physical parameter, especially by the great impact on other dimensions. In general, this parameter must be calculated from an analysis of the limitations imposed both chemical reactions and aerodynamics, i.e., based on combustion process requirements and maximum pressure drop allowable in the combustion chamber, respectively. So, the aim of this paper is investigate the influence of the reference area in the velocity profile, in the temperature distribution, in the mixing process and in the flame behavior, according to the reference area used in the combustion chamber. These numerical analyses were carried out using ANSYS CFX®, comparing them with the base value calculated by Lefebvre (5), for a thermodynamic cycle of 600 kW gas turbine engine, conduced in GateCycle® program. Finally, it can be concluded that some changes in the reference area calculated by Lefebvre (4) produces better results, especially by improving the burning process and the behavior of the flame.

This study is dedicated to investigations of the working process in a dual-fuel low-emission combustion chamber for a floating vessel’s gas turbine. As the object of the research, a low-emission gas turbine combustion chamber with partial premixing of fuel and air inside the outer and inner radial-axial swirls was chosen. The method of the research is based on the numerical solution of the system of differential equations which represent the physical process of mass and energy conservation and transformations and species transport for a multi-component chemically reactive turbulent system, considering nitrogen oxides formation and a discrete ordinates model of radiation. The chemistry kinetics is presented by the 6-step mechanism of combustion. Seven fuel supply operating modes, varying from 100% gaseous fuel to 100% liquid fuel, have been analysed. This analysis has revealed the possibility of the application of computational fluid dynamics for problems of dual-fuel combustion chambers for the design of a floating vessel’s gas turbine. Moreover, the study has shown the possibility of working in different transitional gaseous and liquid fuel supply modes, as they satisfy modern ecological requirements. The dependencies of the averaged temperature, NO, and CO concentrations along the length of the low-emission gas turbine combustion chamber for different cases of fuel supply are presented. Depending on the different operating modes, the calculated emission of nitrogen oxides NO and carbon monoxide CO at the outlet cross-section of a flame tube are different, but, they lie in the ranges of 31‒50 and 23‒24 mg/nm3 on the peak of 100% liquid fuel supply mode. At operating modes where a gaseous fuel supply prevails, nitrogen oxide NO and carbon monoxide CO emissions lie in the ranges of 1.2‒4.0 and 0.04‒18 mg/nm3 respectively.

There is a growing need for devices with small weight and large power density as a substitute for today’s accumulators widely used for electrical tools or as thrust application in the aerospace industry e.g. for small unmanned aerial vehicles (UAV). Systems burning liquid or gaseous fuels and working after the principle of the Brayton cycle became more and more interesting as a new field of research (powermems devices). This ongoing miniaturization of power devices such as ultra micro gas turbines requires a reliable and safe combustion of fuels. A new test rig for micro scale combustion chambers has been realized and tested with a new hydrogen prototype burner for a 600 W μ-scale gas turbine. By preheating and pressurizing the flow realistic combustion chamber inlet conditions for the design point and for μ-scale gas turbine part load conditions can be realized. Furthermore the quartz glass prototype burner offers visual access to the flame region during operation at atmospheric condition. Detailed investigations on the burning characteristics for different chamber configurations were carried out for an optimization of the burner concept and gas turbine integration. By changing air mass flow and thermal energy the results allow a mapping of the combustion chamber for setting the control laws of the μ-scale gas turbine. The test results prove a very good flame stability and burning efficiency for the micromix principle covering a wide range of power settings including the design point. Even at extreme part load conditions it was possible to handle all the operating points of the proposed μ-scale gas turbine. Based on the prototype burner results a realistic combustion chamber design for μ-scale gas turbine integration will be presented.

Статья посвящена вопросу снижения выбросов токсичных компонентов в камерах сгорания газотурбинных двигателей за счет использования слаботочных плазмохимических стабилизаторов. Проведен анализ нестационарных процессов в низкоэмиссионной камере сгорания газотурбинного двигателя с помощью современных инструментов вычислительной гидродинамики. Разработаны практические рекомендации по повышению экологичности горения газообразного топлива в низкоэмиссионной камере сгорания ГТД.

An experimental study on quenching crevice widths in the combustion chamber of a spark-ignition engine

The expediency of using vehicles of liquefied petroleum gas as a motor fuel, as com-pared with traditional liquid motor fuels, in particular with diesel fuel, is shown. The advantages of converting diesel engines into gas ICEs with forced ignition with respect to conversion into gas diesel engines are substantiated. The analysis of methods for reducing the compression ratio in diesel engines when converting them into gas ICEs with forced ignition has been carried out. It is shown that for converting diesel engines into gas ICEs with forced ignition, it is advisable to use the Otto thermo-dynamic cycle with a decrease in the geometric degree of compression. The choice is grounded and an open combustion chamber in the form of an inverted axisymmetric “truncated cone” is developed. The proposed shape of the combustion chamber of a gas internal combustion engine for operation in the LPG reduces the geometric compression ratio of D-120 and D-144 diesel engines with an unseparated spherical combustion chamber, which reduces the geometric compression ratio from ε = 16,5 to ε = 9,4. The developed form of the combustion chamber allows the new diesel pistons or diesel pistons which are in operation to be in operation to be refined, instead of making special new gas pistons and to reduce the geometric compression ratio of diesel engines only by increasing the combustion chamber volume in the piston. This method of reducing the geometric degree of compression using conventional lathes is the most technologically advanced and cheap, as well as the least time consuming. Keywords: self-propelled chassis SSh-2540, wheeled tractors, diesel engines D-120 and D-144, gas engine with forced ignition, liquefied petroleum gas (LPG), compression ratio of the internal com-bustion engine, vehicles operating in the LPG.

Flash‐boiling occurs when a fuel is injected into a combustion chamber where the ambient pressure is lower than the saturation pressure of the fuel. It has been known that flashing is a favorable mechanism for atomizing liquid fuels. On the other hand, alternative fuels, such as gaseous fuels and oxygenated fuels, are used to achieve low exhaust emissions in recent years. In general, most of these alternative fuels have high volatility and flash‐boiling takes place easily in the fuel spray when injected into the combustion chamber of an internal combustion engine under high pressure. In addition the multicomponent mixture of high‐ and low‐volatility fuels has been proposed in the previous study in order to control the spray and combustion processes in an internal combustion engine. It was found that the multicomponent fuel produces flash‐boiling with an increase in the initial fuel temperature. Therefore, it is important to investigate these flash‐boiling processes in fuel spray.In the present study, the submodels of a flash‐boiling spray are constructed. These submodels consider the bubble nucleation, growth, and disruption in the nozzle orifice and injected fuel droplets. The model is implemented in KIVA3V and the spray characteristics of multicomponent fuel with and without flashing are numerically investigated. In addition, these numerical results are compared with experimental data obtained in the previous study using a constant volume vessel. The flashing spray characteristics from numerical simulation qualitatively show good agreement with the experimental results. In particular, it is confirmed from both the numerical and experimental data that flash‐boiling effectively accelerates the atomization and vaporization of fuel droplets. This means that a lean homogeneous mixture can be quickly formed using flash‐boiling in the combustion chamber. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(5): 369–385, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20117

Combustion process involves various physical and chemical processes which govern and control flames initiation in aero gas turbine engines. During certain flying conditions, at full load, unexpected critical situation may take place in such engines called blow off conditions, which leads to flames diminishing in the combustion chamber of such engines. Gas motion, flow velocity and turbulence kinetic energy are the most important parameters in ensuring flame stabilities. These parameters play a tremendous role and effects on this phenomenon. In gas turbines, the flame exists within a high velocity, non-uniform and intensely turbulent flow field, therefore careful temperature control is vital. Another important factor which must be considered to avoid blow off conditions, is mixture strength. Nearly, all modern gas turbines, due to emissions restrictions, operate on lean mixture conditions which are hard to ignite and lower flame temperatures and thus more risk to reach blow off conditions which leads to a complete flame extinction. These conditions may exist in an air craft engines due to sharp changes in loading parameters, (θL): pressure (Pu), temperature (Tu), mass flow rate (), and cross sectional area (Au). At present there is no detailed theory of gas turbine combustion. Therefore, we must resort to simple models and experimental correlations. This paper investigates the blow-off phenomena in aero gas turbine engines, its causes and estimation of required energy to ensure recovery (re-ignition) again inside the combustion chamber. Identifying the conditions at which blow-off takes place and associated loading parameters (θL) which are a function of (A, T, P, and ). The paper also, quantify the recovery conditions (required energy to re-ignition, change in loading parameter (Δq) Power, Required VHRR: (Volumetric Heat Release Rate) and changes in other loading variables (ρ: density, T: Temperature, P: Pressure, and : mass flow rate) tarts with discussing causes of blow off along with effecting operating conditions.

Within the context of an ever-increasing share of wind, solar and emerging tidal power, the need to store energy, not only on the short term, but also in the medium to long-term to balance out the power grid will become more important in the near future. One of the most promising routes for this mid- to long term storage, is to produce hydrogen through electrolysis using excess electricity and store it. Instead of using this hydrogen then to generate electricity in a conventional, large, power plant, a more efficient route is to use it in a Decentralised Energy System (DES) using micro Gas Turbines (mGTs). Although the mGT presents itself as a promising option to convert pure hydrogen into electricity in this DES framework, several challenges, linked to the necessary increase of Turbine Inlet Temperature (TIT) for efficiency increase to make the unit compatible and the use of pure hydrogen in the combustor, still need to be overcome. In this paper we present the first steps towards a fully hydrogen fuelled mGT. Firstly, a full thermodynamic cycle analysis was performed to determine the optimal operating parameters, such as compressor pressure ratio and mass flow rate, air-to-fuel ratio and TIT. Secondly, a full CFD design and optimisation of the compressor and the combustion chamber was performed (steady and transient RANS and LES). CFD simulations of the compressor and combustion chamber matched the 1D performance calculations and also reached the desired performance goals. This CFD supported validation of the component performance shows that the design of a pure hydrogen combustion chamber for mGT applications is possible.

This study presents comprehensive thermoeconomic and thermoenvironomic modeling and analysis of selected gas turbine power plants in Nigeria using the first and second laws of thermodynamics (exergy) concept. Exergetic analysis was conducted using operating data obtained from the power plants to determine the exergy destruction and exergy efficiency of each major component of the gas turbine in each power plant. The results of the study showed that the combustion chamber (CC) is the most exergy destructive component compared to other cycle components. The percentage of exergy destruction in CC varies between 86.05% and 94.6%. By increasing the gas turbine inlet temperature (GTIT), the exergy destruction of this component can be reduced. The total exergy improvement potential of the selected plants varies from 54.04 to 159.88 MW. The component with the highest exergy improvement potential is the CC, which has the value that varies from 30.21 to 88.86 MW. Thermoeconomic analysis showed that the cost of exergy destruction is high in the CC, and an increase in the GTIT effectively decreases this cost. The exergy costing analysis revealed that the unit cost of electricity produced in the plants ranged from cents 1.99/kWh (N3.16/kWh) to cents 5.65 /kWh (N8.98/kWh). Thermoenvironomic analysis showed that the CO2 emissions varied between 100.18 and 408.78 kg CO2/MWh, while cost rate of environmental impact varied from 40.18 $/h (6, 388.62 N/h) to 276.97 $/h (44, 038. 23 N/h). The results further showed that CO2 emissions and cost of environmental impact decrease with increasing GTIT. The sustainability index increase with increasing GTIT. Finally, this study will assist efforts to understand the thermodynamic losses in the gas turbine cycle, and to improve efficiency as well as provide future recommendations for better performance, sustainability, and lessening environmental impact of power plant.

The gas turbines are generally used for large scale power generation. The basic gas turbine cycle has low thermal efficiency, which decreases in the hard climatic conditions of operation, so the cycles with thermodynamic improvement is found to be necessary. Among several methods shown their success in increasing the performances, the steam injected gas turbine cycle (STIG) consists of introducing a high amount of steam at various points in the cycle. The main purpose of the present work is to improve the principal characteristics of gas turbine used under hard condition of temperature in Algerian Sahara by injecting steam in the combustion chamber. The suggested method has been studied and compared to a simple cycle. Efficiency, however, is held constant when the ambient temperature increases from ISO conditions to 50°C. Computer program has been developed for various gas turbine processes including the effects of ambient temperature, pressure ratio, injection parameters, standard temperature, and combustion chamber temperature with and without steam injection. Data from the performance testing of an industrial gas turbine, computer model, and theoretical study are used to check the validity of the proposed model. The comparison of the predicted results to the test data is in good agreement. Starting from the advantages, we recommend the use of this method in the industry of hydrocarbons. This study can be contributed for experimental tests.

Chapter Thirty One - Gas Turbines

Gas turbines are one type of internal combustion drive, the initial mover utilizes gas combustion as a fluid to rotate the turbine with internal combustion. Gas turbines at private companies producing electricity use the initial movers, namely gas turbines and steam turbines. Therefore, it is also called the "Steam Gas Power Plant/PLTGU.”Private company especially in Block 2, uses two gas turbine units with Mitsubishi GT 2.1 specifications which are used as the initial drive of the generator. Types of overhauls in gas turbines are divided into three, including turbine inspection, combustor inspection, and major inspection. In maintaining the reliability of the GT 2.1 Gas Turbine, an overhaul combustion inspection was carried out in the combustion chamber because there was an increase in heat rate of 17,9% which caused a decrease in thermal efficiency and net turbine power of the GT 2.1 Gas Turbine by 17% and 2,1%. So that steps are taken to optimize the GT 2.1 Gas Turbine with the combustion inspection method by repairing and cleaning the combustion bucket nozzle. Increased thermal efficiency by 27,8% or 27,13% to 36,01% from data before overhaul. This was also followed by an increase in compressor power and turbine power so that the net turbine power increased by 38% or 141339,35 hp to 195246,54 hp.