Edelgasthermometrie im Tiefenwasser des Kivusees mit Löslichkeiten von Edelgasen bei höheren Temperaturen

<p>In natürlichen Gewässern werden Edelgaskonzentrationen häufig zur Bestimmung der Umgebungstemperaturen beim letzten intensiven Kontakt zur Atmosphäre (Äquilibration) verwendet. Dieses Verfahren nennt sich <em>Edelgasthermometrie </em>und wird unter anderem genutzt, um Grundwasserbildungstemperaturen und historische Temperaturschwankungen quantitativ zu bestimmen. Da bisher nur übliche Bildungstemperaturen von unter 35°C bekannt sind, hat man sich mit Löslichkeiten bis zu dieser Temperatur begnügt. Es gibt jedoch verschiedene Prozesse, wie etwa vulkanische Aktivität, die hohe Wassertemperaturen erzeugen können. Wir haben daher die Löslichkeiten von Edelgasen bei höheren Temperaturen bestimmt und diese mit Daten aus der Literatur kombiniert, um neue Löslichkeitsfunktionen zu generieren die den gesamten Bereich von 0 bis 80°C abdecken. Wir verwenden diese Funktionen, um publizierte Messungen der Edelgaskonzentrationen im Tiefenwasser des Kivusees zu analysieren, die ungewöhnlich niedrig sind. Der Kivusee liegt am Rande des Nyiragongo-Vulkans und speichert große Mengen an Kohlendioxid und Methan, die bei einer Ausgasung für die umliegende Bevölkerung tödlich wären. Vor allem jetzt, wo die industrielle Ausbeutung der Gaslagerstätte in die Schichtung des Sees eingreift ist es wichtig, die Dynamiken des Sees zu verstehen und nachzuvollziehen, woher das Defizit an Edelgasen stammt. Wir nutzen Edelgaskonzentrationen, -verhältnisse und kleinste-Quadrate-Approximation mit <em>Excess-air</em>, um Bildungstemperaturen abzuleiten. Am besten lassen sich die niedrigen Edelgaskonzentrationen mit einer atmosphärischen Äquilibrierung des Tiefenwassers bei ca. 60°C erklären, wobei dann nur ein minimales Defizit an Edelgasen übrig bleibt. Damit liefern die Edelgasdefizite KEINEN Hinweis auf eine frühere Entgasung des Sees. </p>

Estimates of the air-fuel ratio at the time of ignition in a pre-chamber using a narrow throat geometry

The benefits of pre-chamber combustion (PCC), such as improved engine efficiency and reduced NOx emissions, are primarily observed when operating at lean conditions with an active pre-chamber, where auxiliary fuel is supplied directly to the pre-chamber. Estimating the pre-chamber excess air ratio (λ) is important in the active pre-chamber concept to gain insights into the pre-chamber combustion phenomenon. Experimental investigations were performed using a narrow-throat pre-chamber at global-λ 1.6, 1.8, and 2.0. The fraction of fuel energy injected in the pre-chamber over the total fuel energy was fixed at 3%, 7%, and 13% for each global-λ. The mixture formation process inside the pre-chamber is first simulated using the 1-D simulation software GT-Power to analyze the pre-chamber λ at the ignition timing. However, the 1-D results were unable to reproduce the experimental observations on the pre-chamber pressure buildup accurately. Upon simulating the same conditions using the 3-D CFD software CONVERGE, the pre-chamber λ estimated from the CFD model is well-correlated to the experimental data. The CFD results indicate that the amount of fuel trapped in the pre-chamber at the inlet valve closing timing is over-predicted by the 1-D simulations. A correlation between the injected and the trapped fuel in the pre-chamber is proposed by theoretical scavenging models and applied to the 1-D simulation results to improve pre-chamber λ prediction accuracy.

Economy and emission characteristics of the optimal dilution strategy in lean combustion based on GDI gasoline engine equipped with prechamber

EGR and excess-air dilution have been investigated in a 1.5 L four cylinders gasoline direct injection (GDI) turbocharged engine equipped with prechamber. The influences of the two different dilution technologies on the engine performance are explored. The results show that at 2400 rpm and 12 bar, EGR dilution can adopt more aggressive ignition advanced angle to achieve optimal combustion phasing. However, excess-air dilution has greater fuel economy than that of EGR dilution owing to larger in-cylinder polytropic exponent. As for prechamber, when dilution ratio is greater than 37.1%, the combustion phase is advanced, resulting in fuel economy improving. Meanwhile, only when the dilution ratio is under 36.2%, the HC emissions of excess-air dilution are lower than the original engine. With the increase of dilution ratio, the CO emissions decrease continuously. The NOX emissions of both dilution technologies are 11% of those of the original engine. Excess-air dilution has better fuel economy and very low CO emissions. EGR dilution can effectively reduce NOX emissions, but increase HC emissions. Compared with spark plug ignition, the pre chamber ignition has lower HC, CO emissions, and higher NO emissions. At part load, the pre-chamber ignition reduces NOX emissions to 49 ppm.

Combustion of kerosene sprayed with a jet of superheated steam

In the present work, the effect of forced air supply on the combustion process of liquid hydrocarbons was studied using diesel fuel as an example. The content of the flame intermediate components and temperature distribution along the flame symmetry axis were studied using an atmospheric burner in which liquid fuel is atomized by a steam jet. The gas composition of equilibrium combustion products and heat release were also investigated. The influence of the excess air ratio in the combustion chamber of the burner device on the thermal and environmental characteristics was shown.

Improving the management of fuel combustion in ship boilers

Annotation – The article discusses the issues of increasing the efficiency of the combustion of liquid fuel in the furnaces of ship steam boilers using the proposed neural network system for automatic correction of the excess air coefficient. It is indicated that modern systems for automatic flame detection have a number of disadvantages, in particular, low sensitivity to extraneous illumination, etc. hot air or flue gases on the walls of the boiler furnace. Such pulsations reduce the reliability of the combustion monitoring and control system. Therefore, the task of developing and introducing on ships new, economically inexpensive and effective methods of effective control and management of the fuel combustion process in ship boilers using modern means of intelligent control is urgent. On the basis of the experiments carried out on a Mitsubishi MV 50 marine steam boiler and the collected experimental data, the values for training the neural network system of the air flow correction process, taking into account the color of the burner flame and the color of the flue gases, were obtained. The use of a trained neural network in the control system, taking into account the fuzzy expert system for monitoring the color of the flame and smoke, makes it possible to achieve the best excess air ratio depending on the steam load of the SEP units. Simulation modeling of the proposed neural system was carried out in a specialized program Matlab (Neural Networks Toolbox). The simulation results showed that the use of a neural network control system for the combustion of liquid fuel, using the example of a marine boiler, allows maintaining a given thermal regime over the entire range of steam load of the power plant units, and also allows timely correction of the excess air ratio, i.e. avoid excessive consumption of fuel.

Effect of Working Process Adjustable Parameters on the Formation of Nitrogen Oxides in a Hydrogen Diesel Engine

The article considers formation of nitrogen oxides in a hydrogen diesel engine with direct injection of gaseous hydrogen depending on the adjustable parameters of the working process: excess air ratio, cyclic hydrogen supply, advance angle and duration of hydrogen injection. It was found that in a number of cases the effect of these parameters on the working process and the emission of nitrogen oxides leads to results that differ significantly from those in traditional diesel engines running on hydrocarbon fuel. It is shown that by varying the specified controlled parameters, it is possible to minimize the concentration of nitrogen oxides in the exhaust gases of a hydrogen diesel engine.

Analisa Efisiensi Termal Water Tube Boiler Berdasarkan Rasio Udara Bahan Bakar LPG Untuk Memproduksi Saturated dan Superheated Steam

Boiler adalah suatu bejana tertutup yang terbuat dari baja dan digunakan untuk menghasilkan steam. Agar dapat menghasilkan steam diperlukan pembakaran. Pembakaran merupakan reaksi eksotermis yang berlangsung sangat cepat, yang membebaskan energi berupa panas dan nyala api (flame temperature) serta mampu menyebarkan panas melalui suatu medium. Agar pembakaran terjadi dengan optimal maka harus memperhatikan nilai rasio udara bahan bakar atau Air Fuel Ratio (AFR). Tujuan dari penelitian ini untuk meningkatkan efisiensi termal water tube boiler. Bahan bakar yang digunakan adalah gas LPG. Oleh karena itu, pada penelitian kali ini akan difokuskan untuk menentukan rasio udara dengan bahan bakar gas yang paling tepat sehingga didapatkan hasil pembakaran dan produksi steam yang maksimal. Rasio udara bahan bakar gas dan excess air yang digunakan yakni, 15,78 (5%), 15,93 (6%), 16,08 (7%), 16,23 (8%), 16,38 (9%).

Potential of alcohol fuels in active and passive pre-chamber applications in a passenger car spark-ignition engine

Both the shift from fossil to alternative fuels and the implementation of a pre-chamber combustion system allow for an increase in the efficiency of an internal combustion engine through optimizing its combustion process, while simultaneously reducing the engine-out emissions. The combination of alcohol-based fuels and pre-chamber combustion concepts has not been investigated on spark-ignition engines with high compression ratios in a passenger car size. This study presents investigations to show the potential in maximum achievable lean limit and net indicated efficiency. In particular, we present investigations of two alternative alcohol fuels on a direct-injection spark-ignition single-cylinder research engine for passenger car applications with a compression ratio of 16.4. The engine was operated with both an active and a passive pre-chamber, and the experimental results were compared to those of conventional spark-ignition operation. Direct injection was used for both the main combustion chamber and the pre-chamber. Methanol and ethanol were used as fuels for the main combustion chamber, whereas exclusively ethanol was used for the pre-chamber fueling. The performance of the alcohol fuels in all combustion configurations was evaluated in both part-load and high-load conditions. In particular, investigations of the combustion behavior over a variation of the excess air ratio at indicated mean effective pressures of 6 and 15 bar were performed. It can be concluded that with the use of methanol as fuel for the main combustion chamber, both higher excess air ratios and higher indicated efficiencies were achieved compared to the use of ethanol as the main combustion chamber fuel. In particular, a maximum net indicated efficiency of 48% at an excess air ratio of 2.0 was achieved with methanol. Moreover, active pre-chamber operation extended the lean limit to an excess air ratio of 2.3 compared to the maximum lean limit of 1.7 in passive pre-chamber operation.

Моделювання якісного складу паливно-повітряної суміші у факельному запальнику камер згоряння ГТД

The qualitative composition of the fuel-air mixture, which is formed in the torch igniter of the combustion chamber of the gas turbine engine (GTE), determines the efficiency and reliability of their work. The main task of the study is to determine the qualitative composition of the fuel-air mixture near the electric spark plug of the GTE torch igniter depending on its geometric features and engine operation condition. The composition of the mixture was evaluated using analytical, experimental, and numerical methods. According to the analytical model, a significant over-enrichment of the fuel-air mixture in the igniter housing was established and confirmed experimentally. A numerical model was used to determine the fields of mass concentration of fuel particles in the fuel-air mixture in the torch igniter housing, considering the peculiarities of airflow and fuel supply for different combinations of GTE design features and operating conditions. The influence of geometric parameters of the housing and external factors was investigated using the numerical model of stationary combustion of fuel-air mixture, which was prepared in the torch igniter housing of GTE combustion chamber by evaporation and spraying of aviation kerosene particles in the air stream. The implementation of a small-factor experiment allowed to establish the degree of influence of each factor under study and their interaction on the excess air coefficient. The correlation coefficient between the coefficient of excess air near the spark plug and the average flame temperature is set. Given the absence of serial designs of controller torch ignites, it is proposed to use a pulsed fuel supply to control the quality of the fuel-air mixture. Further ways of research to increase the reliability of ignition of both the torch igniter from the electric spark plug and the combustion chamber of GTE from the flame is outlined.