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Some experimental data indicate that an HCCI process of a highly diluted mixture is characterized with a two-stage profile of heat release after the heat release by low-temperature oxidation, and with slow CO oxidation into CO₂ at a low temperature. In the present paper, these characteristics are discussed using a detailed chemical kinetic model of normal heptane, and based on an authors' idea that an ignition process can be divided into five phases. The H₂O₂ loop reactions mainly contribute to heat release in a low-temperature region of the TI (thermal ignition) preparation phase. However, H+O₂+M=HO₂+M becomes the main contributor to heat release in a high-temperature region of the TI preparation phase. H₂O₂ is accumulated during the LTO (low-temperature oxidation) and NTC (negative temperature oxidation) phases, and drives the H₂O₂ loop reactions to increase the temperature during the TI preparation phase.

n-Tridecane is a low boiling point component of gas oil, and has been used as a single-component fuel for diesel spray and combustion experiments. However, no reduced chemical kinetic mechanisms for n-tridecane have been presented for three-dimensional modeling. A detailed mechanism developed by KUCRS (Knowledge-basing Utilities for Complex Reaction Systems), contains 1493 chemical species and 3641 reactions. Reaction paths during ignition process for n-tridecane in air computed using the detailed mechanism, were analyzed with the equivalence ratio of 0.75 and the initial temperatures of 650 K, 850 K, and 1100 K, which are located in the cool-flame dominant, negative-temperature coefficient, and blue-flame dominant regions, respectively.

In this study, we combined operational transfer path analysis (OTPA) method with CAE technique to obtain high contributing vibration modes. A rear frame model of a small construction machine was employed for the analysis. 20 vibration modes were obtained by CAE (eigenmode analysis) under 200 Hz. Subsequently, operational test, in which a sinusoidal input force was given, was carried out. For applying OTPA, acceleration signals at 15 points on the rear frame were used as the reference signals and the cab vibration positioned on the frame via rubber bushes was used as the response signal. These acceleration signals were then measured simultaneously in the operational condition. As the result of OTPA, high contributing principal component modes were calculated and high contributing vibration modes were also extracted using mode shape correlation between them. Two in the 20 calculated vibration modes remained as the important modes to the cab vibration through the analyses.

Ignition process chemistry was analyzed using a detailed chemical kinetic model of n-heptane generated by KUCRS (Knowledge-basing Utilities for Complex Reaction Systems), wherein pressure-dependent rate constants of the O₂ addition to alkyl radicals and hydroperoxy alkyl radicals and the thermal decomposition of ketohydroperoxides have been introduced. Then, the effect of the initial pressure and the individual effects of the initial fuel, O₂ and N₂ molar concentrations on a relationship between the initial temperature and the ignition delay were discussed. When the initial temperature increases, the branch of C₇H₁₄OOH removal into the second O₂ addition and the decomposition into C₇H₁₄cyO and OH is more sensitive to the pressure and the O₂ concentration, and thus, the LTO preparation phase is more affected by the pressure and the O₂ concentration. The LTO phase terminates mainly by the OH removal by intermediate species.

A systematic chemical lumping method has been proposed, based on the detailed kinetic analysis of hydrocarbon fuel ignitions. The model constructed by using this method contains two reaction sets, RO2 and fragment reaction package. The ignition characteristics of each fuel can be reflected by only adjusting several rate parameters in RO2 reaction package. From the comparison with detailed model, it was confirmed that this simplified model well reproduces the results of detailed one without missing the kinetics of hydrocarbon ignitions. We concluded that this new lumping approach has the possibility to be applicable to every hydrocarbon fuels.

Methyl butanoate (MB) and methyl decanoate (MD) are surrogates for biodiesel fuels. According to computational results with their detailed reaction mechanisms, MB and MD indicate shorter ignition delays than long alkanes such as n-heptane and n-dodecane do at an initial temperature over 1000 K. The high ignitability of these methyl esters was computationally analyzed by means of contribution matrices proposed by some of the authors. Due to the high acidity of an α-H atom in a carbonyl compound, hydroperoxy radicals are generated out of the equilibrium between forward and backward reactions of O₂ addition to methyl ester radicals by the internal transfer of an α-H atom in the initial stage of an ignition process. Some of the hydroperoxy methyl ester radicals can generate OH to activate initial reactions. MB has an efficient CH₃O formation path via CH₃ generated by the β-scission of an MB radical which has a radical site on the α-C atom to the carbonyl group.

In this paper the quantitative estimation on the flexural rigidity of the structural adhesive-aided joint (adhesive joint, weldbonded joint etc.) of the single-lap form in steel is carried out, based on the experiment using three-point bending test and the calculation treating the adhesive joint as the composite beam. Relationships of the flexural rigidity of the adhesive joint with its various elements and the agreement between experimental results and calculated results are in detail discussed. Moreover, factors which govern the flexural rigidity of the weldbonded joint are made clear experimentally.

This paper describes a simulation program of gas exchange processes in a multi-cylinder internal combustion engine and also describes its applicability to automotive engines which are operated under various engine speed and load conditions. This simulation program has sufficient flexibility to incorporate almost all intake and exhaust systems of today’s high speed automotive multi-cylinder engines. To improve the predicting accuracy, a finite difference scheme is used for solving equations defining gas flow dynamics in these systems and moreover a modified Constant-Pressure Theory is used for modeling branches of intake and exhaust manifolds. In order to evaluate the accuracy of the simulation program, predicted results were compared with experimental data and satisfactory agreement was obtained.

This paper deals with a non-destructive detection method of fatigue crack in spot-welded joints under tensile-shear repeated load. We developed the non-destructive method, according to which the generation time, the crack length and the propagation speed of fatigue crack can be quantitatively estimated by utilizing information obtained from strain gages bonded on the electrode indentations of spot welds. Specimens used in this experiment are made of various kinds of thin steel sheets.

This study intends to make clear the effects of the property of base metal, specimen width, sheet thickness and nugget diameter on the initiation life of fatigue crack and the propagation life in single-spot-welded joint specimens under tensile-shear repeated load, and using these results to establish an empirical formula according to which the ΔL-N diagram can be drawn. It was confirmed that accuracy of the empirical formula is at considerable high level, when this formula is applied for data of hitherto published many reports, and the predicted results obtained by this formula are compared with these experimental results.

The ignition delay times of n-C7H16, i-C8H18, and a blend of them at different fuel, O2 and N2 concentrations were computed using a detailed chemical kinetic mechanism generated by KUCRS. For each fuel, the dependences of ignition delay time on fuel, O2 and third body concentrations and on the heat capacity of a mixture were distilled to establish a power law equation for ignition delay time. For n-C7H16, ignition delay time τhigh without low-temperature oxidation at a high initial temperature between 1000 K and 1200 K was expressed using the scaling exponents for fuel, O2 and third body concentrations and heat capacity of 0.54, 0.29, 0.08, and - 0.38, respectively. Low-temperature oxidation induction time τ1 at a low initial temperature between 600 K and 700 K was expressed using the scaling exponents for fuel, O2 and third body concentrations and heat capacity of 0.03, 0.18, 0.04, and - 0.17, respectively.

To execute the computational fluid dynamics coupling with fuel chemistry in internal combustion engines, simplified chemical kinetic models which capture the low-temperature oxidation kinetics would be required. A steady-state analysis was applied to see the complicated reaction mechanism of alkylperoxy radicals by assuming the steady state for hydroperoxyalkyl (QOOH) and hydroperoxyalkylperoxy (OOQOOH) radicals. This analysis clearly shows the systematic trend of the reaction rate for the chain-branching and non-branching process of alkylperoxy (ROO) radicals as a function of the chain length and the carbon class. These trends make it possible to classify alkylperoxy radicals by their chemical structures, and suggest a reduced low-temperature oxidation chemistry.

The interaction between spark discharge and low-temperature oxidation (LTO) was investigated using an optical compression and expansion machine fueled with n-C7H16 or i-C8H18 for an equivalence ratio of 0.33. Charge pressure was adjusted so that the compression stoke could induce LTO for n-C7H16, but could not lead to high-temperature reactions. A spark was discharged in the field before, during, or after the LTO for n-C7H16 or in the field without LTO for i-C8H18. Reaction zones were induced in the field after the LTO, whereas no reaction zones were induced in the fields before the LTO and without LTO. Local ignitions were induced in the areas surrounding the propagating reaction zones. The reaction zone propagation with the low equivalence ratio must be a different phenomenon from conventional flame propagation. The reaction zones can compress or heat the surrounding areas containing H2O2 and CH2O, and accelerate an H2O2 regeneration loop in the pre-reaction zones.

The relationships between the octane number and the carbon atom number and the molecular structure of alkanes were comprehensively analyzed by using the detailed kinetic model generated by there automatic reaction scheme generation tool, KUCRS [1, 2]. The octane number is an index showing the ignition delay in the engine temperature regime, that is, the engine ignition temperature range. The high octane number is observed in the following two cases; 1 The ignition delay of the low temperature region is large. 2 The ignition delay of the low temperature region is the same, but the transition temperature for NTC (Negative Temperature Coefficient) region is low.

One of the authors has proposed to use the decay rate of EHRR, the effective heat release rate, d2Q/dθ2 as an index for the rapid local combustion [1]. In this study, EHRR profiles and the cylinder gas pressure oscillations of the low and high speed knock are analyzed by using this index. A delayed rapid local combustion, such as an autoignition with small burned mass fraction can be detected. In the cases of the low speed knock, it has been agreed that a rapid local combustion is an autoignition. Although whether the cylinder gas oscillation is provoked by an auto ignition in a certain cycle or not is an irregular phenomenon, the auto ignition takes place in almost all of the cycles in the knocking condition. Mixture mass fraction burned by an auto ignition is large. A small auto ignition may induce a secondary auto ignition, in many cases, mass burned by the secondary auto ignition is extremely large.

The purpose of this study is to examine the cause of combustion fluctuation in a partially loaded two-stroke engine with respect to the hydrocarbon (HC) concentration in the cylinder. HC concentration in the cylinder, exhaust gas velocity and pressure were simultaneously measured in order to determine the influence of HC concentration on combustion fluctuation. A correlation between cyclic variation in HC concentration in the cylinder and IMEP was confirmed. The way in which the HC concentration influenced the combustion states in the next cycle made clear. A decrease of HC concentration cause the delay of early flame development and combustion, the decrease of HC concentration had an great influence on the combustion states. The relationship between combustion states and HC concentration was discussed. The relative value of IMEP and HC concentration were closely related to the HC concentration in the cylinder.

Diffuse axonal injury (DAI) is the most frequent type of closed head injury involved in vehicular accidents, and is characterized by structural and functional damage of nerve fibers in the white matter that may be caused by their overstretch. Because nerve fibers in the white matter have an undulated network-like structure embedded in the neuroglia and extracellular matrix, and are expected to be much stiffer than other components, the strain in the nerve fiber is not necessarily equal to that in the white matter. In this study, the authors have measured strain of the nerve fibers running in various directions in porcine brain tissue subjected to uniaxial stretch and compared them with global strain (tissue strain). The nerve fiber strain had a close correlation with their direction, and was smaller than surrounding global strain.

A novel rotational internal combustion engine is invented and investigated. In this engine, no eccentric rotational component is used, resulting in vibration-free operation. For this characteristics, this engine will be suitable for usage in silent environment, e.g. co-generation house plant, handy-usage and so on. The engine mainly consists of a rotor casing and two types of rotor; cycloid rotor and trochoid rotor. The shape of the cycloid rotor is characterized by epicycloid surface and lobes, and the trochoid rotor also superior-epitrochoid surface and concaves. As mentioned above, fundamental process of intake, compression, ignition, expansion and exhaust for working gas is automatically performed by the constant speed rotation of both of rotors. In this paper, first, the typical configuration including two designing procedure of the rotors are described in detail. Next the cyclic behavior of the working process is explained.

To satisfy the stringent regulations for exhaust gas emissions from gasoline-powered vehicles, large amounts of Rh and Pd have often been employed in three-way catalysts (TWCs) as the main active components. On the other hand, Pt-based TWCs are not often used in gasoline vehicles because Pt is readily sintered by its exhaust gases at approximately 1000 °C [1, 2]. In general, Pt-based TWCs must be located away from large thermal loads to maintain the active sites for gas purification. Based on this background, we previously reported that employing a small amount of CeO2 calcined at 1000 °C (cal-CeO2) in Pt-based TWCs was one of the most effective approaches for improving the catalytic activity without increasing the amount of Rh and Pd [3]. The effect of cal-CeO2 was attributed to the higher redox performance and Pt dispersion derived from the strong interactions between Ce and Pt.