The NK-33 and NK-43 rocket engines, developed for the first and second stages of the Russian N-l Lunar Vehicle, are built upon the design heritage of their predecessors, the NK-15 and NK-15B. A series of modifications were made during NK-33 and NK-43 development to increase reliability through the addition of a restart system to support engine verification testing as well as well as improve durability by modifying the engine to operate at 114%. Aerojet of Sacramento, CA began working with the NK-33 in 1991 and performed a series of five tests to demonstrate Evolved Atlas operation. Aerojet is currently modifying the NK-33 and NK-43 to meet Kistler Aerospace's design requirements. There is sufficient data indicating that Kistler's engine life requirement of 20 firings with one overhaul can be met with periodic scheduled maintenance. Engine HistoryThe Nikolai Kuznetsov Design Bureau, predecessor of NK Engines, was founded in 1946 and for 51 years has been designing and developing aircraft gas turbine engines and liquid propellant rocket engines for the aerospace and industrial gas turbine industries where the enterprise is well known for its high efficiency, reliable, lightweight aircraft engines.NK Engines' first turbine engine, the NK-12 turboprop, went into production in 1953. The first rocket engine, the 40-ton thrust NK-9, began production in 1959.In 1964, Sergei Korolev, head of Russia's manned spaceflight program, selected NK Engines to develop the engines for the N-l Lunar Launch Vehicle, Russia's greatest space endeavor at the time. This vehicle would be larger than the U.S. Saturn 5 and would require 43 engines for its four stages to send the Russian L-3 Lunar Complex to the Moon.The experience gained from the LOX/Kerosene NK-9 engine and its upper stage version (NK-9B) would be used to develop the N-l propulsion. The NK-9B would be used for the N-l third and fourth stages, and new 154-ton and 175-ton thrust engines designated NK-15 and NK-15B, would be designed for the first and second stages. As engine development progressed, the engine designations changed, as shown in Table 1.The test program for these engines was one of the most rigorous ever seen for a space launch vehicle. The NK-15 engine, the direct predecessor of the NK-33, accumulated more than 100,000 sec of test operating time before it was first flown on N-l in February 1969. After the second N-l flight later that year, the NK-33/43 design and development program for a multi-start version of the single start NK-15/15B engine was initiated.
In diesel engines, the combustion process takes place over a very short period of time (0.001 s). As a result, complete and timely combustion of fuel and good use of the air available in the engine cylinders can be achieved only with very high-quality mixing. The use of biofuels in modern diesel engines causes a number of problems associated with changes in the parameters of fuel supply and mixing. All types of fuel have different characteristics: density, viscosity, lubricating properties, self-ignition temperature, compressibility and. in this regard, the laws of fuel supply: spraying, combustion, will be different. The viscosity of biofuels is higher than that of diesel fuel. For this reason, its capacity through small holes in the nozzle of the nozzle (dh= 0.25...0.40 mm) lower than diesel fuel. Due to the small diameter of the holes in the nozzle nozzles and the increased viscosity of biofuels, the nozzle holes are quickly coked. At the same time, the shape and direction of the jet initially changes, and then the hole is completely coked and the fuel supply stops. Thus, for high-quality operation of the diesel engine on biofuels, it is necessary to modernize the design of the mixing and fuel supply system. This problem can be solved by using systems with separate combustion chambers, i.e. using vortex chamber mixing. In the vortex chamber, 60-80% of the fuel burns, the pressure increases and the burning torches of the fuel flow at high speed into the main over-piston plane of the combustion chamber, where there is a significant supply of air that is not used during the combustion of the charge in this chamber. At the same time, oxygen from the air is well used, and the operation of the diesel engine becomes more efficient at relatively low values of the excess air coefficient at the nominal mode and less toxicity of exhaust gases than for single-chamber diesels.
The fuel system largely determines the longevity of a diesel engine. This is due to the great influence of the fuel transfer process on its operating cycle. The operational characteristics, efficiency and ease of starting the engine are determined by the state of the engine power system, which is demanding for a diesel engine and requires careful regulation. The fuel injection process in a diesel engine largely depends on the design parameters of the fuel equipment. They change under the influence of external and internal factors. Reasonable standard terms and volumes of fuel equipment repairs are of great importance for the operation of diesel engines. These issues can be optimally solved only on the basis of statistical and experimental data on the nature and rate of growth, depending on the duration of operating conditions, superior types of wear on the working surfaces of the fuel system parts. The service life of fuel equipment is determined by the reliability and durability of precision pairs: plunger, pressure valves and injector nozzles. Operational defects of precision parts change by 12-17% such parameters of the injection process as cyclic feed, ignition timing, injection duration, maximum cycle pressure, can worsen the power and economic performance of a diesel engine. Therefore, the problem of improving the reliability and durability of precision pairs is relevant, the study of which is currently receiving much attention. Especially from precision pairs, pressure valves deserve attention. Their restoration after operation does not require expensive equipment and energy consumption, but the parameters of diesel engines depend to a large extent on their operation. Improving the injection characteristics of fuel equipment that has served its service life with a change in the parameters of the injection valve in the conditions of repair and maintenance workshops is quite affordable.
Analysis of the state and trends in the development of agricultural machines and the technical means that serve them shows that there is a constant process of creating more productive and economical equipment. This is primarily ensured by increasing unit capacity, increasing working and transport speeds, reducing time losses for auxiliary operations, reducing maintenance costs to a minimum; ensuring minimal impact on soil and plants; increasing reliability and wear resistance, as well as an increase in versatility and the appearance of special tractors for specific work; expansion of production of wheeled tractors with four driving wheels, wider use of hydraulic systems, electronics, automation, new materials, creation of comfortable working conditions and ease of management; ensuring labor safety. The main type of tractor in the most widespread range of capacities remains the wheeled one of the traditional layout scheme, the improvement of which is carried out taking into account the latest achievements of science and technology. There is a further update of articulated tractors with all driving wheels of the same size, with leading manufacturers experimenting with the installation of triangular track drives instead of wheels, which significantly increases their traction qualities. Characteristic features of tractors of the new generation are their universality and block-modular structure. So, depending on the market, different engines from well-known companies and unified transmissions are installed on one model of European tractors. Therefore, in this market, there is a tendency for manufacturers to cooperate with the aim of further increasing versatility, reliability, and simplifying operation: increasing the interval for changing engine oil to 500 hours, transmission oil to 2,000 hours, hydraulic oil to 1,000 hours. Cooperation also contributes to the expansion of opportunities for competition in the markets of different countries. The new generation of powerful wheeled tractors with a classic and system layout provides high efficiency mainly in technological operations with medium traction forces in combined, tillage and sowing units, which are equipped with implements with active working bodies, with front and rear GDP, as well as in transport operations.
The situation that has developed on the market of oil products in the conditions of the war with the invaders has led to a shortage of liquid fuels and a constant increase in the price, in particular of diesel fuel, prompting the producers of agricultural products to think about switching to alternative types of fuel. Research related to the production and use of biodiesel fuel is especially relevant in today's conditions. Scientists do not ignore this question, in particular, Vinnytsia National Agrarian University has devoted more than one research topic to the mentioned problem. In more detail, in the mentioned issue, research is being conducted aimed at determining the energy value of the obtained biofuels, namely, the lower calorific value. The purpose of the article is to create a methodology for determining the fatty acid composition of biodiesel fuel and determining its lower heat of combustion, which is necessary for the analysis and evaluation of the energy efficiency of alternative fuels. Research methods are based on D. I. Mendeleev's formula for determining the lower heat of combustion, which is based on data on the percentage content of the elemental composition of the fuel. The calculation of the elemental composition was carried out on the basis of the molecular weight data of the components of biodiesel fuel, which in turn were obtained by chromatographic analysis using a gas-liquid chromatograph. Similar calculations were made in Microsoft Excel spreadsheets. The article publishes the results of research on two samples of biodiesel fuel, made from two types of raw materials - sunflower and rapeseed oil. A method of determining the fatty acid composition of these samples and determining the lower heat of combustion of biodiesel fuel as a whole and its components has been developed. The results given in the tables can be the basis for further conclusions about the energy value of individual components included in the studied fuel.
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