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The purpose of this study is to carry out energy and exergy analysis of fuels. Production of power and heat in industrialized countries is almost entirely based on combustion of fuels. Usually, combustion takes place in boilers or furnace; well-designed boilers have high thermal efficiencies of > 90 per cent. Even very high efficiencies, close to 100 per cent can be achieved depending on the applied fuel and boiler type. These high thermal efficiencies do suggest that combustion processes are highly optimized and do not need further improvements with regard to their thermodynamic performance. Second law (entropy or exergy) evaluations, however, shows that thermodynamic losses of boiler and furnaces are much larger than the thermal efficiencies do suggest. During combustion, air is predominantly used. When using air, the adiabatic combustion temperature depends only on the properties of fuel and air. The determining parameters for optimal fuel utilization are the fuel type, their composition and moisture content, the air temperature and air factor at combustion inlet.

Following assumptions are made for the analysis: calculation on the basis of 100 kg of dry and ash free fuel entering the control volume; fuel entering the control volume at T₀, P₀ and reacting completely with air entering separately at T₀, P₀ to form CO₂, SO₂, N₂ and H₂O, which exit separately at T₀, P₀ (T₀ = 298 K; P₀ = 1 atm); all heat transfer occurs at temperature T₀; and the chemical exergy of the ash has been ignored The availability change and the irreversibility for chemical reactions of hydrocarbon fuels were studied because fuel and dry air composed of O₂ and N₂ react to form products of combustion in the restricted dead state, and fuel and dry air composed of O₂ and N₂ react to form products of combustion which end up in the environmental (unrestricted) dead state. The difference between the above two statement, is the chemical availability of the product gases as they proceed from the restricted to the unrestricted dead state. These evaluations were made in terms of enthalpy and entropy values of the reacting species. T₀ extend these concepts to the most general situation, it is considered a steady-state control volume where the fuels enters at the restricted dead state, the air (oxidant) is drawn from the environment, and the products are returned to the unrestricted dead state.

It is evident from the analysis that an air factor of 1.10-1.20 is sufficient for liquid fuels, whereas solid fuels will require air factors of 1.15–1.3. When the temperatures of the products of combustion (T_p) are cooled down to that of T₀, the maximum reversible work occurs. From the analysis, it is clear that the rather low combustion temperature and the need for cooling down the flue gases to extract the required heat are the main causes of the large exergy losses. The maximum second law efficiency also occurs when T_p is set equal to T₀. The maximum second law efficiency per kilo mole of fuel is found to be 73 per cent, i.e. 73 per cent of the energy released by the cooling process could theoretically be converted into useful work. It is evident that reducing exergy losses of combustion is only useful if the heat transferred from the flue gas is used at high temperatures. Otherwise, a reduction of exergy loss of combustion will only increase the exergy loss of heat transfer to the power cycle or heat-absorbing process. The exergy loss of combustion can be reduced considerable by preheating combustion air. Higher preheat temperatures can be obtained by using the flue gas flow only for preheating air. The remainder of the flue gas flow can be used for heat transfer to a power cycle or heat-absorbing process. Even with very high air preheat temperatures, exergy losses of combustion are still > 20 per cent. The application of electrochemical conversion of fuel, as is realized in fuel cells, allows for much lower exergy loses for the reaction between fuel and air than thermal conversion. For industrial applications, electrochemical conversion is not yet available, but will be an interesting option for the future.

The outcome of the study would certainly be an eye-opener for all the stakeholders in thermal power plants for considering the second law efficiency and to mitigate the irreversibilities.

THE fuel content of an intercontinental aircraft at take‐off constitutes a considerable proportion of the all up weight of the aircraft. The weight of fuel in a typical subsonic passenger carrying aircraft at take‐off represents about 45 per cent of the aircraft's all up weight and this proportion increases to about 55 per cent in a typical supersonic transport aircraft. Due to the substantial change in the weight of these aircraft between the take‐off and landing phases, and the cost of the fuel, the importance of precise and effective fuel management will be readily appreciated if the trim of the aircraft and the operational economics is not to be disturbed during an intercontinental flight.

THE FUEL SYSTEM is a simple state‐of‐the‐art system which is designed to minimise system maintenance and provide a very high probability of mission success. It requires no fuel management or manipulation of system controls during a normal mission. It is designed to use MIL‐J‐5624G, grades JP‐4 and JP‐5 turbine fuel.

To prolong engine life and reduce exhaust pollution caused by gasoline engines, the aim of this paper was to compare the lubrication properties of biofuel (ethanol) blends and pure unleaded gasoline.

Biofuels with a concentration of 0, 1, 2, 5 and 10 per cent were added to unleaded gasoline to form ethanol-blended fuels named E0, E1, E2, E5 and E10. Next, the ethanol-blended fuels and unleaded gasoline were used to power engines to facilitate comparisons between the pollution created from exhaust emissions.

Using ethanol as a fuel additive in pure unleaded gasoline improves engine performance and reduces exhaust emissions. Because bioethanol does not contain lead but contains low aromatic and high oxygen content, it induces more complete combustion compared with conventional unleaded gasoline.

Using biofuels as auxiliary fuel reduces environmental pollution, strengthens local agricultural economy, creates employment opportunities and reduces demand for fossil fuels.

To operate satisfactorily in jet engines, fuels must satisfy certain minimum performance criteria embracing not only the obvious one of combustion, but also such aspects as thermal stability, flow at low temperatures, corrosivity, cleanliness, etc. To this end, internationally agreed specifications have been developed to ensure satisfactory fuel performance in all aviation gas turbines. This article concentrates on one such area, thermal stability, to illustrate some of the work performed on aviation kerosine at Shell's Thornton Research Centre in Cheshire. Here, for over forty years, realistic fuel system simulator rigs have been used to examine the influence of fuel properties and composition on various aspects of its performance. One conclusion of such work is that fuels possessing almost identical physical properties can, because of the presence of varying types and amounts of trace compounds, exhibit considerably different performance qualities.

Fuel measuring and control systems have become progressively more sophisticated as aircraft performance has been extended both in the number of operating regimes and in operational capability. The fuel tank arrangements for the conventional aircraft types of the pre‐supersonic era, both piston and jet‐engined, allowed fairly straight‐forward fuel gauging and management. The tank dispositions were usually in line from left to right across the span of the wing. The advent of the swept wing aircraft introduced the complexities of fore and aft fuel balance in order to limit excursions of the CG about aft of the centre of lift. At the same time the operating economics of both military and civil aircraft, with massive fuel rate demand, required the development of fuel management systems capable of measuring and indicating fuel consumption and quantities to higher orders of accuracy.

This paper aims to investigate the effect of additives in Jet-A fuel blends, especially on performance, combustion and emission characteristics.

Jet-A fuel was formed by using Kay’s and Gruenberg–Nissan mixing rules by adding additive glycerol with TiO₂. While measuring the combustion performance, the amount of oxygen content present in fuel and atomization are the key factors to consider. As such, the Jet-A fuel was created by adding additives at different proportion. A small gas turbine engine was used for conducting tests. All tests were carried out at different load conditions for all the fuel blends such as neat Jet-A fuel, G10T (glycerol 10% with 50 ppm TiO₂ and Jet-A 90%), G20T (glycerol 10% with 50 ppm TiO₂ and Jet-A 90%) and G30T (glycerol 10% with 50 ppm TiO₂ and Jet-A 90%).

From tests, the G20T and G10T produced better results than other blends. The thermal efficiency of the blends of G20T and G10T are 22% and 14% higher than neat Jet-A fuel. Further, the improved static thrust with less fuel consumption was noticed in G20T fuel blend.

The G20T blends showed better performance because of the increased oxygenated compounds in the fuel blends. Moreover, the emission rate of environmentally harmful gases such as NOx, CO and HC was lower than the neat Jet-A fuel. From the results, it is clear that the rate of exergy destruction is more in the combustion chamber than the other components of fuel.

Today's jet fuels must adhere to tight specifications. Quality of fuel remains a prime concern. Thermal stability and lubricity are of great importance but pose problems as they tend to be mutually exclusive. Research continues in both areas in the search for improvements. Details the NATO single‐fuel concept whereby vehicles and aircraft alike can operate on the same fuel in battlefield operations. To attain this land vehicles would need to adapt to jet fuel. In a similar vein, moves are being made to bring about an international uniformity in specification of jet fuel. Finally details research into alternative fuels and concludes that continuing co‐operation between the fuel and hardware industries, improved methods of property measurement and research into alternative fuels are all vital for the future.

Engine component endurance is related to fuel properties. Decreasing the sulfur content of a fuel reduces its lubricity, thus damaging engines and fuel systems. Therefore, promoting the use of a biofuel must involve assessing the functionality and lubricity of the fuel.

The ball-on-ring (BOR) wear tester was applied to determine the optimal additive concentration and the mechanism of reduction of the wear and friction of the diesel engine fuel injection system. The lubricating efficiency of the fuels was estimated by using a photomicroscope to measure the average diameter of the wear scar produced on the test ball. An optical microscope and scanning electronic microscope were used for wear surface examinations.

The wear test revealed that the wear diameter of the steel ball lubricated with either the pure petrodiesel or 20 Wt.per cent Jatropha curcas biodiesel blends was 1.36 or 1.05 mm, respectively. The experimental results indicated that when Jatropha curcas biodiesel was added into petrodiesels to reduce friction, the wear resistance of the fuel blends increased concurrently with increasing Jatropha curcas biodiesel concentration. This was attributed to the presence of stearic acid in Jatropha curcas biodiesel blends. Stearic acid has a strong affinity for metal surfaces; therefore, a chemical coating was formed between the two motion surfaces to protect the two contacted surfaces from wear. Therefore, the proposed Jatropha curcas biodiesel can be used to effectively enhance the lubricity of a petrodiesel under the condition of boundary lubrication.

Using biofuels as the fuels for diesel engines can assist developed and developing countries in reducing the impacts of their fossil fuel consumption on the environment.

The depletion of fossil fuel and emissions of harmful gases forced the pioneers in search of alternate energy source. The purpose of this study is to present an effective use of hydrogen fuel for turbojet engines based on its exergetic performance.

This study was performed to measure the assessment of exergetic data of turbojet engines. Initially, the test was carried out on the Jet A-1 fuel. Then, a series of similar tests were carried out on turbojet engines with hydrogen fuel to measure their performance results. Finally, the exergetic values of both were compared with each other.

The introduction of hydrogen fuel reduced the exergy efficiency, and a 10 per cent reduction was observed in exergy efficiency. Simultaneously, the waste exergy rate increased by 9 per cent. However, because of the high specific fuel exergy, hydrogen fuel was better than Jet A-1 fuel. Note that parameters such as environmental effect factor and ecological effect witnessed an increase in their index owing to the addition of hydrogen.

Introduction of alternative blends is necessary for achieving lower emission of gases such as CO, NOx and CO₂ from gas turbine engines without compromising on performance. The Jet A fuels were replaced by blends to obtain better emission characteristics.

The use of hydrogen in turbojet engines showed an adverse effect on exergetic performance. However, it was very impressive to see a 200 per cent reduction in emissions. From the comparison of exergy efficiency results of inlet, combustion and nozzle, it is evident that the combustion chamber has the largest values of exergy ratio, waste exergy ratio, cost flow, ecological factor, environmental factor and fuel ratio owing to irreversibility in the combustion process.