Service Exchange or Major Overhaul. Which Philosophy to Implement for Gas Turbine

Maintenance costs and machine availability are two of the most important concerns to gas turbine equipment owner. Therefore, a well thought out maintenance program that reduces costs while increasing equipment availability should be instituted. The correct implementation of planned maintenance relying on preventive maintenance optimization through perfect inspection frequency and scope provides direct benefits in the avoidance of forced outages, unscheduled repairs, and downtime. Major overhaul is carried out for each gas turbine every 48,000 firing hours which costs around 1 M USD for each engine and with more than 8 months unavailability for the unit. To increase equipment availability and enhance cost and time efficiency, alternatives approaches were evaluated including Service Exchange of gas turbines. It is found that service exchange is the best option for optimizing time and cost of overhaul of such engines. This paper is written to improve Major Overhaul practice for existing Gas Turbines from ongoing practice of routine major overhaul including engine strip down, inspection and repair to Service Exchange of Gas Generator and Power Turbine every 48,000 firing hours.

PHASE METHODS OF GAS GENERATORS CONTROL HYDROGEN STORAGE AND SUPPLY SYSTEMS

Methods of control of technical condition of gas generators of systems of storage and supply of hydrogen based on use of their phase-frequency characteristics are considered. Methods of control of gas generators are divided into two groups depending on the mathematical models used to describe the operation of such gas generators. It is shown that when using as such a mathematical model the transfer function of the gas generator in the form of an inertial link, it is possible to implement control algorithms both by its phase-frequency characteristics and by its time constant. In the first case, the phase-frequency characteristic is measured at an a priori set frequency. In the second case, there is no such restriction. When using as a mathematical model of the gas generator the transfer function in the form of a fractional-rational function of the second order, the implementation of algorithms for its control can be carried out directly using the phase-frequency characteristics of the gas generator. With this implementation of algorithms for monitoring the technical condition of gas generators, the measurement of the values of their phase-frequency characteristics is carried out at several frequencies. This approach to the control of gas generators can increase the reliability of its results. All methods of monitoring the technical condition of gas generators of hydrogen storage and supply systems are focused on the use of tolerance criteria. The parameters of the tolerance criteria can be both the values of the time constants of gas generators of hydrogen storage and supply systems, and fixed values of the phase-frequency characteristics of such gas generators. In the latter case, control algorithms are implemented that cover the entire operating frequency range of gas generators.

Study and Development of the Components of Gas Generator Compositions Based on the Ammonium Nitrate to Improve Blasting Operations Safety

The article is devoted to the study and development of the components of gas generator compositions based on the ammonium nitrate to improve safety of blasting operations. This is primarily due to the low cost of ammonium nitrate, low sensitivity to mechanical and detonation effects and a significantly lower content of harmful compounds in the combustion products compared to the analogues. PA-4 aluminum powder was used as fuel, carbon black powder — as a gas-forming agent. The effect was studied concerning different amounts of aluminum powder on the combustion characteristics of a gas generator composition based on the ammonium nitrate. Calculated and experimental data showed that it is unreasonable to introduce more than 5 % of aluminum into the composition. According to the results of the conducted study, a gas generator composition based on the ammonium nitrate was developed to increase blasting operations efficiency and safety. Laboratory and polygon studies confirmed the efficiency and safety of using gas generator compositions at the destruction of stone. Destruction of the stone occurred without scattering of individual fragments, formation, and propagation of an air shock wave. Thus, the urgent task is to ensure blasting operations safety using gas generator compositions, which will allow to eliminate the formation of harmful, toxic gases and the high explosive effect.

Improvement of Mixing Efficiency in the Combustion Chamber of a Powder-Fuel Ramjet Engine

The challenge of the powder-fuel ramjet is to improve the mixing effect of powder-fuel with oxidizing agents and combustion efficiency. To improve the mixing and combustion efficiency of the powder-fuel ramjet engine, three configurations in head shapes and three exhaust gas inlet patterns of the engine are designed based on a typical powder-fuel ramjet engine combustion chamber. The effect of the head shapes and exhaust gas inlet patterns is analyzed and compared by the three-dimensional numerical simulation method. A comprehensive model validation is built, and the calculation results of the k-ε standard model are compared with the experimental data. The results show that the cylindrical head forms a recirculation zone at the head of the combustion chamber, which leads to powder deposition in the head region of the chamber. The design with the round head and the coned head reduces the recirculation inside the head region, and the exhaust gas from the fuel gas generator has benefits in powder injection and mixing inside the combustion chamber. The exhaust gas inlet of the inclined six hole type has benefits in the mixing of powder and high temperature exhaust gas because it generates strong flow impingement in the core part of the chamber.

Experimental investigations of the processes in gas generator of hydrogen-air energy storage

This paper describes the results of experimental investigation of the sample of the hydrogen-air gas generator unit with the expected average power of 65 kW. In total 5 test runs were made. Two tests showed that the mass flow and outlet gas temperature was in an agreement with the designed parameters. Additional attention should be paid to the cooling system design for the combustion chamber. In future such a gas generator in couple with the suitable gas turbine unit could be a part of the renewable energy accumulation system e.g. of hydrogen-air energy storage.

ALGORITHM FOR DETERMINATION OF RELIABILITY INDICATOR OF GAS GENERATOR OF HYDROGEN STORAGE AND SUPPLY SYSTEM

An algorithm for determining one of the indicators of reliability of the main element of the hydrogen storage and supply system – a gas generator has been developed. Such an algorithm is an integral part of the general algorithm to ensure the required level of fire safety of hydrogen storage and supply systems. The algorithm involves the implementation of several stages. At the first stage, using the expression for the amplitude-frequency characteristic of the gas generator, the functional dependences for its time constants are obtained. These functional dependencies include the values of the transmission coefficient and amplitude-frequency characteristics, which are determined at three a priori set values of frequency. In the second stage, the amplitude-frequency characteristic of the gas generator is determined. For this purpose, an array of data is used, which characterizes the reaction of the gas generator to the test effect in the form of an abrupt change in the area of its outlet. The amplitude-frequency characteristic of the gas generator is determined numerically, and its parameters are the increase in the pressure in the cavity of the gas generator and the time interval at which this increase is determined. The Kotelnikov-Nyquist-Shannon theorem is used to determine this time interval. At the third stage, the probability of the values of the time constants of the gas generator outside the tolerance zone is determined. For this purpose, models of gas generator time constants and their metrological characteristics are used. In the fourth stage, the probability of failure of the gas generator is determined, for which the information of the previous stage is used. At the last stage, the algorithm for determining the probability of failure of the gas generator of the storage and supply system of hydrogen, which is given in verbal form.

Shelf life of plasma focus chambers with deuterium-tritium filling

The paper presents the results of an experimental study of the shelf life of sealed plasma focus chambers with deuterium-tritium and deuterium fillings. Shelf life is defined as maintaining the level of neutron yield during operation of PF chambers as part of pulsed neutron generators after long storage intervals. The release of impurities from the inner surfaces of the PF chamber and the accumulation of he-lium He3 due to the decay of tritium in the volume of the sealed-off PF chambers leads to a significant decrease in the neutron radiation yield several years after the chamber is filled with the working mixture. The paper shows that the shelf life of the chambers is significantly increased when using a gas generator, in which hy-drogen isotopes are contained in a bound state, and are released into the inner volume of the chamber only for the duration of operation as part of neutron gen-erators. It has been shown experimentally that spherical chambers of the PF9 type provide a level of neutron radiation yield Y, close to the initial value in the manu-facture of chambers, after more than 10 years of storage.

Design of the Airbag Inflation System Applicable to Conventional and Autonomous Vehicles

The emergency transformation of various aspects of life and business these days requires prompt evaluation of autonomous vehicles. One of the primary reassessments deals with the applicability of the vehicle passive safety system to the protection of arbitrarily positioned passengers. To mitigate possible risks caused by the simultaneous deployment of several big airbags, a new principle of their operation is required. Herein, the aspirated inflator for a driver airbag is developed that can provide 50L-airbag inflation within 30–40 ms. As a result, about 3/4 of the air is to be entrained into an airbag from the vehicle compartment. The process is initiated by a supersonic pulse jet (1/3 air volume) generated pyrotechnically. Then the Prandtl–Meyer problem formulation enables guiding linear and angular dimensions of the essential parts of the device. Accordingly, a family of experimental models of varied geometry is fabricated and tested to determine their operational effectiveness in a range of motive pressure within ~ 3–7 MPa. Experiments are performed on a specially designed facility equipped with compressed-air tanks and a high-speed valve to mimic the inflator operation with the pyrotechnic gas generator. The aspirated inflator operability is characterized using multivariate measurements of pressure fields, high-speed video-recording of the airbag inflation process, and evaluation of aspiration (entrainment) ratio. The average volume aspiration ratio measured at 300 K is found to reach 2.8 and it’s expected to almost double at 1200 K.

Chemistry of the Gasification of Carbonaceous Raw Material

The paper represents the studies of the process of carbonaceous raw material gasification. The initial material is represented by bituminous coal of grade H with the carbon (C) content of 79.2-85.3 %. Experimental studies have been used to substantiate the parameters of combustible generator gases (СО, Н2, СН4) output depending on the temperature of a reduction zone of the reaction channel and gas flow velocity along its length. It has been identified that the volume of the raw material input to be used for gasification process changes in direct proportion depending on the amount of burnt-out carbon and blow velocity. The gasification is intensified in terms of equal concentration of oxygen and carbon in the reaction channel of an underground gas generator. The gasification rate is stipulated by the intensity of chemical reactions, which depend immediately on the modes of blow mixture supply. Moreover, they depend directly on the intensity of oxygen supply to the coal mass and removal of the gasification products.