• Journal of Mechanical Science and Technology
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• v.15 no.8
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• pp.1181-1187
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• 2001

The radiation driven response function (R$\_$q/) for AP and HMX propellant was obtained and compared with experimental results by using a simple $\alpha$$\beta$γ flame model rather than with detailed chemistry. For an AP propellant, the profile of heat release was assumed by the experimental data. The calculated R$\_$q/ shows a frequency shift of the peak amplitude to the higher frequency and a decrease in the maximum amplitude as radiation increases. In addition, it was found the increase in the total flux could enhance the mean burning rate γ$\_$b/ while the phase differences between the radiation and resulting conduction could consequently reduce the fluctuating amplitude Δγ$\_$b/. Fortunately, this is the qualitative duplication of the behavior recently observed in the experiments of RDX propellants. For HMX, the response function R$\_$q/ has been calculated and showed a quite good agreement with the experimental data. Even though the fairly good agreement of R$\_$q/ with experimental ones, the unsteady behavior of HMX was not reproduced as the radiation input increased. This is due to lack of the material properties of HMX or the physical understanding of HMX burning at high pressure.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.3 s.234
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• pp.417-423
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• 2005

This paper describes the engine performance of a Homogeneous Charge Compression Ignition(HCCI) engine according to Exhaust Gas Recirculation(EGR), cylinder-to-cylinder, fuel of propane and butane. HCCI engines are being considered as a future alternative for diesel and gasoline engines. HCCI engines have the potential for high efficiency, very low NOx emissions and very low particulate matter(PM). On experimental work, we have done an evaluation of operating conditions in a 4-cylinder compression engine. The engine has been run with propane and butane fuels at a constant speed of 1800rpm. This work is intended to investigate the HCCI operation of the engine in this configuration that has been modified from the base diesel engine. The performance and emissions of the engine are presented. In this paper, the start of combustion(SOC) is defined as the $50{\%}$ point of the peak rate of heat release. SOC is delayed slightly with increasing EGR. As expected, NOx emissions were very low for all EGR range and nbuned HC and CO emission levels were high. CO and HC emissions are lower with using propane than butane as fuels of HCCI engines.

• Textile Coloration and Finishing
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• v.32 no.3
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• pp.150-157
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• 2020

Hexachloro-cyclophosphazene(HCCP), a formaldehyde-free flame retardant (FR), was steam-cured with triethanol amine(TEA) to impart durable flame-retardancy to cotton fabrics. While the HCCP treatment alone showed very limited resistance to repeated laundering cycles, the addition of TEA substantially improved the laundering durability of the FR cotton up to twenty laundering cycles. The extended washing resistance was accomplished by the increased nucleophilic substitution of unreacted P-Cl groups in HCCP by the TEA resulting in the more densely crosslinked FR networks. With increasing molar ratio of TEA to the HCCP up to 2, the flame retarding effectivity and the synergistic effectiveness improved to 2.8 and 1.8 respectively. TGA and microscale combustion calorimetry verified the pyrolysis and combustion behaviors of the FR-cotton, which showed lower maximum pyrolysis and combustion temperatures together with substantially decreased peak pyrolysis and heat release rate, synergistically yielding larger amounts of carbonaceous chars. The formaldehyde-free HCCP and TEA can be a durable FR finishing agents for cotton fabrics acting through a solid-phase flame-retarding mechanism.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 1997.11a
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• pp.85-92
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• 1997

Flammability of non-flame-retardant and flame-retardant materials was studied by using cone calorimeter Also, relations between the results obtained by using cone calorimeter and those obtained by the flammability test of japanese fire Service Law were examined. The results are as follows: 1) The ignition time of the molten specimens is relatively long, whereas the ignition time of the non-molten specimens is short. None of remarkable difference of the ignition time has been found between non-flame-retardant and flame-retardant materials specimens. 2) The peak heat release rates of flame-retardant materials are smaller than those of non-flame- retardant materials. 3) The carbon monoxide and smoke evolved from flame-retardant materials generate much more than those evolved from non-flame-retardant materials. 4) Even if flame-retardant materials are passed by the flammability test of Japanese Fire Service Law, they burn easily under external radiative heating condition.

• Journal of Ceramic Processing Research
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• v.20 no.4
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• pp.411-417
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• 2019

Graphene doped zinc oxide nanoparticles (G-ZnO) were prepared using modified hummer's technique together with the ultrasonic method and characterized by field emission scanning electron microscopy (FESEM), X-ray powder diffraction (XRD), fourier-transform infrared spectroscopy (FTIR) and high-resolution transmission electron microscopy (HRTEM). Different samples of epoxy resin nanocomposites reinforced with G-ZnO nanoparticles were prepared and were marked as F1 (without adding nanoparticles), F2 (1% w/w G-ZnO), and F3 (2% w/w G-ZnO) in combination of ≈ 56:18:18:8w/w% with epoxy resin/hardener, ammonium polyphosphate, boric acid, and Chitosan. The peak heat release rate (PHRR) of the epoxy nanocomposites was observed to decrease dramatically with the increasing G-ZnO nanoparticles. However, the LOI values increased significantly with the increase in wt % of G-ZnO nanoparticles. From the UL-94V data, it was confirmed that the F2 and F3 samples passed the flame test and were rated as V-0. The results obtained in the present work clearly revealed that the synthesized samples can be used as efficient materials in fire-retardant coating technology.

• Textile Coloration and Finishing
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• v.34 no.4
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• pp.217-223
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• 2022

Flame-retardant finished silk fabrics could release carcinogenic formaldehyde resulting from the conventional finishing agents. New water-soluble cyclophosphazene derivative can be used as a formaldehyde-free flame retardant for the silk protein. Dichloro tetrakis{N-[3-dimethylamino)propyl]methacrylamido}cyclophosphazene(DCTDCP) can be cured by heat or UV irradiation as a durable flame retardant for the silk fabrics. Treatment conditions were optimized including curing temperature and time, finishing formulations, and UV energy. At the 30% DCTDCP application, peak HRR and THR decreased by 42.6% and 49.6% respectively compared to the pristine silk fabrics. Also char residue increased up to 48% from 11% indicating solid-phase retarding mechanism. The flame-retardant silk fabrics showed a LOI of 31.1 and the washed sample maintained a LOI of 26.8 even after ten laundering cycles.

• Journal of ILASS-Korea
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• v.29 no.2
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• pp.60-67
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• 2024

This study compared exhaust gas recirculation (EGR) and excess air strategies for improving thermal efficiency and emissions of hydrogen combustion engines at low-load operation. The experimental investigation was conducted in a single-cylinder, heavy-duty engine under throttling and wide-open throttle (WOT) conditions. Although both EGR and excess air strategies reduced peak heat release rates and increased combustion durations, the net indicated thermal efficiencies were improved by reducing the pumping losses. Under the constraint of similar nitrogen oxides emissions, the EGR strategy had higher net indicated thermal efficiencies compared to the excess air strategy in throttling operation. However, the difference between their thermal efficiencies was reduced under WOT condition. The trend of reducing nitrogen oxides emissions according to the two strategies was similar.

• International Journal of Automotive Technology
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• v.8 no.4
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• pp.421-428
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• 2007

This paper investigates the combustion and emission characteristics of a compression ignition engine fueled with neat and blended Shell's gas-to-liquid (GTL) fuel, which was derived from natural gas through the Fischer-Tropsch process. The experiments were conducted in a 6-cylinder DI diesel engine with pump timing settings of $6^{\circ},\;9^{\circ}\;and\;12^{\circ}$crank angle before TDC over ECE R49 and US 13-mode cycles separately and compared to a conventional diesel fuel. The results show that GTL exhibited almost the same power and torque output, improved fuel economy and effective thermal efficiency. It was found that GTL displayed lower peak in-cylinder combustion pressure and maximum heat release rate (HRR), the timings of the peak pressure and the maximum HRR were generally delayed, and the combustion durations were almost equivalent for diesel and GTL under the same speed-load condition. The results also indicate that, compared to diesel fuel, GTL blends showed a trend forward decreasing four regulated emissions simultaneously and a higher GTL fraction in blends contributing to further reductions in the emissions. In particular and on average, neat GTL significantly reduced HC, CO, NOx and PM by 16.4%, 17.8%, 18.3% and 32.4%, respectively, for all cases.

• International Journal of Aeronautical and Space Sciences
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• v.18 no.4
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• pp.797-806
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• 2017

In this study, the reflection coefficient (RC) and the flame transfer function (FTF) were measured by applying acoustic excitation to a duct-type model combustor and were used to predict the frequency of the combustion instability (CI). The RC is a value that varies with the excitation frequency and the geometry of the combustor as well as other factors. Therefore, in this study, an experimentally measured RC was used to improve the accuracy of prediction in the cases of 25% and 75% hydrogen in a mixture of hydrogen and methane as a fuel. When the measured RCs were used, an unstable condition was correctly predicted, which had not been predicted when the RCs had been assumed to be a certain value. The reason why the CI occurred at a specific frequency was also examined by comparing the peak of the FTF with the resonance frequency, which was calculated using Helmholtz's resonator analysis and a resonance frequency equation. As the CI occurred owing to the interaction between the perturbation in the rate of heat release and that in the pressure, the CI was frequent when the peak of the FTF was close to the resonance frequency such that constructive interference could occur.

• Applied Chemistry for Engineering
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• v.24 no.2
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• pp.208-213
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• 2013

In this study, the effect of phosphorus flame retardants on the flame retardancy of the flexible polyurethane foam (PUF) was investigated. Tetramethylene bis(orthophosphorylurea) [TBPU] and phosphinyl alkylphosphate ester [CR-530], resorcinol bis diphenylphosphate [RDP], triethyl phosphate [TEP] were used as flame retardants. The results of thermogravimetric analysis (TGA) indicate that TBPU added PUF produces more charred residues than the other flame retardant added PUF. It was found that TBPU added PUF exhibits low mean heat release rate (HRR), peak HRR, effective heat of combusion (EHC), mass loss rate (MLR), CO yield and $CO_2$ compared to those other flame retardants.