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In this work we have deposited silicon carbide (SiC) at 1300°C with the addition of small amounts of propylene. The use of propylene and high concentrations of methyitrichlorosilane (9 vol %) allowed the deposition of superhard SiC coatings (42 GPa). The superhard SiC could result from the presence of a SiC-C solid solution, undetectable by X-ray diffraction but visible by Raman spectroscopy. Another sample obtained by the use of 50 vol % Argon, also showed the formation of SiC with good properties. The use of a flat substrate together with the particles showed the importance of carrying out the analysis on actual particles rather than in flat substrates. We show that it is possible to characterize the anisotropy of pyrolytic carbon by Raman spectroscopy. [ABSTRACT FROM AUTHOR]

While the deformation and damage behavior of aluminum cylinder heads under complex thermal mechanical loading has been the subject of numerous studies in the past, cast iron cylinder heads have been in the focus of thermomechanical fatigue (TMF) only to a minor extent. In this paper, a feasible procedure is presented to set up material models and estimate service life of cast iron cylinder heads under variable thermomechanical loading conditions by the use of computer-aided engineering tools. In addition, the influence of thermal load and mechanical constraints on TMF life span is shown. A specimen model is used for parameter identification in material model setup and a cylinder head model is used for correlation with cracking phenomena. Investigation of different thermomechanical load influences is conducted on the cylinder head model. The principal strain and energy based fatigue criteria are used in assessment of TMF lifetime for the cast iron family and material specific evaluation procedures are pointed out. The results highlight the importance of exact definitions of the boundary conditions and underline the sensitivity of TMF lifespan of cast iron cylinder heads with respect to the defined boundary conditions. Considering this sensitivity, an approach conforming to the engine development requirements is proposed. It is shown that both the crack location and fatigue lifetime are predicted with high accuracy. [ABSTRACT FROM AUTHOR]

In this present work, the various emulsified fuel ratios of 50D:50E (50% Diesel No. 2: 50% ethanol 100% proof), 60D:40E, and 70D:30E have been prepared. Performance and emission tests are carried out for the emulsified fuel ratios and they have been compared with diesel fuel. The test results show that 50D.50E has given the best result based on the performance and less emission than the other fuel ratios. By keeping the selected fuel 50D:50E, the same performance and emission tests are conducted by varying their injection angles at 18 deg, 20 deg, 23 deg, and 24 deg. The outcome shows better performance and less emission by the fuel 50D:50E at 24 deg injection angle (IA). Further ignition delay, maximum heat release, and peak combustion pressure tests have been conducted. These results show that increase in IA decreases the delay period, thus increasing the pressure obtained at the maximum output. Also, P-θ diagram is drawn between crank angle and cylinder pressure. The maximum value is attained by the fuel 50D:50E at 24 deg IA. All the tests have been conducted by maintaining the engine speed at 1500 rpm. The result shows that 50D:50E ratio fuel has been identified as a good emulsified fuel and its better operation is obtained at 24 deg IA based on its best performance and less emissions. [ABSTRACT FROM AUTHOR]

Two prior papers and several patents have considered improvements to a gas turbine engine's cycle efficiency by using two turbines in series with an intermediate heat exchanger that preheats combustion air. This approach allows heating the combustion air to temperatures higher than those that can be achieved with "conventional regeneration" in which the combustion products are fully expanded across a turbine before any heat recovery. Since heat addition in the combustor of the "alternative regeneration" cycle occurs at a higher average temperature, then under certain conditions the cycle efficiency can be higher than that available from a cycle using conventional regeneration. This paper reconsiders the usefulness of the alternative regeneration cycle with more detailed modeling than has been presented previously. The revised modeling shows that the alternative regeneration cycle can produce efficiencies higher than conventional regeneration, but only for a more limited set of conditions than previously reported. For high-technology engines operating at high temperatures, the alternative regeneration cycle efficiencies can be three to four percentage points better than comparable conventional regeneration cycles. For lower-technology engines, which are more typical of those currently installed, improvements in efficiency only occur at lower values of heat exchanger effectiveness, which limits the usefulness of the alternative regeneration cycle. Also considered is an extension to the cycle that employs a second heat exchanger downstream of the second turbine for the purpose of further preheating the combustion air. In its optimum configuration, this "staged heat recovery" can produce additional small improvements of between 0.3 and 2.3 percentage points in cycle efficiency, depending on the particular cycle parameters assumed. [ABSTRACT FROM AUTHOR]

Low emissions of NO[subx] are obtained for a wide range of liquid fuels by using a staged prevaporizing-premixing injector. The injector relies on two stages of air temperature and fires into a laboratory jet-stirred reactor operated at atmospheric pressure and nominal Φ of 0.6. The liquid fuels burned are methanol, normal alkanes from pentane to hexadecane, benzene, toluene, two grades of light naphtha, and four grades of No. 2 diesel fuel. Additionally, natural gas, ethane, and industrial propane are burned. For experiments conducted for 1790 K combustion temperature and 2.3±0.1 ms combustion residence time, the NO[subx] (adjusted to 15% O[sub2] dry) varies from a low of 3.5 ppmv for methanol to a high of 11.5 ppmv for No. 2 diesel fuel. For the most part, the NO[subx] and CO are positively correlated with the fuel carbon to hydrogen ratio (C/H). Chemical kinetic modeling suggests the increase in NO[subx] with C/H ratio is caused in significant part by the increasing superequilibrium concentrations of O-atom created by the increasing levels of CO burning in the jet-stirred reactor. Fuel bound nitrogen also contributes NO[subx] for the burning of the diesel fuel. This paper describes the staged prevaporizing-premixing injector, the examination of the injector, and the NO[subx] and CO measurements and their interpretation. Optical measurements, using beams of He-Ne laser radiation passed across the outlet stream of the injector, indicate complete vaporization and a small variation in the cross-stream averaged fuel/air ratio. The latter is determined by measuring the standard deviation and mean of the transmission of the laser beam passed through the stream. Additional measurements and inspections indicate no pressure oscillations within the injector and no gum and carbon deposition. Thus, the NO[subx] and CO measurements are obtained for fully vaporized, well premixed conditions devoid of preflame reactions within the injector. [ABSTRACT FROM AUTHOR]