Release Rate Data Research Articles

Statistical Distribution of Heat Release Rate Data for Single Household Items

Statistical Distribution of Heat Release Rate Data for Single Household Items

Experimental and numerical investigations of forced response of multi-element lean-premixed hydrogen flames

Understanding the distinctive thermoacoustic properties of multi-element lean-premixed hydrogen flames is crucial for the development of hydrogen-capable gas turbines. Extending our earlier investigations of the self-excited dynamics of a cluster of lean-premixed pure hydrogen-air flames, here we explore the dynamic response to harmonic velocity perturbations, using an integrative approach combining loudspeaker-forced direct measurements and LES-based numerical simulations. Electronically-excited OH intensity distribution, generally assumed to be equivalent to the flame's heat release rate, shows an anchored conical reaction zone. Numerical simulations of heat release rate contours, however, reveal the formation of a more concentrated thin annulus region resembling an inverted V shaped layer, created by preferential diffusion of hydrogen molecules. This difference between OH-intensity distribution and heat release rate contours suggests consequential uncertainties in surrogate-dependent flame transfer function evaluations; the transfer function gains from measured data are well defined by a fast-decaying low-pass filter behavior, but the simulation result exhibits slowly-decaying large gain with slight overshoot over the entire range of frequency. Because the systematic uncertainties associated with the estimation of the flame's heat release rate cannot be accurately quantified, we rely on a reduced-order network modeling framework combined with direct measurement to test the accuracy of the prediction of the growth of self-sustained pressure fluctuations. We demonstrate that LES-based transfer functions predict the system's stability more accurately, and this suggests that the calculated heat release rate data are closer to the hydrogen flame's true heat release response than the wavelength-specific light intensity measurement. This assessment enables us to identify structurally simple moderate transverse oscillations of local regions containing atypically concentrated energy as pivotal processes controlling high-frequency hydrogen combustion dynamics.

N-Oktanol karışımlarıyla çalışan bir dizel motorun ısı yayılımı oranının değişimi için yeni matematiksel korelasyonlar: Sayısal, deneysel ve karşılaştırmalı bir analiz

The current literature reports a few papers regarding the prediction of heat release rate of a diesel engine fuelled with n-octanol blends using numerical methods. To address this gap, the main objective of presented study is to derive new correlations for estimating the variation in heat release rate of a diesel engine fuelled with diesel fuel and diesel fuel-biodiesel-n-octanol blends. For this purpose, three different ternary blends were prepared by varying the n-octanol concentration to 6% (OCT6), 8% (OCT8), and 10% (OCT10) by volume. The estimation of heat release rate was accomplished using the least-squares regression (sine, piecewise, and rational equations) and the function approximation (Padé approximation) methods. The ignition delay and peak heat release rate increased by 3.8462%, 5.9501% for OCT6; 7.6923%, 3.7125% for OCT8; and 8.9744%, 3.0755% for OCT10, respectively, compared to diesel fuel. The peak cylinder pressure of OCT6 and OCT8 was observed to be higher by 2.4378% and 1.3982%, respectively, whereas that of OCT10 is found to be lower by 1.9458%, compared to diesel fuel. Compared to the others, the suggested rational equation qualitatively and quantitatively achieved the best correlation with all experimental heat release rate data measured by both the author and some other authors.

An analytical approach to converting vibration signal to combustion characteristics of homogeneous charge compression ignition engines

Homogeneous charge compression ignition (HCCI) is a promising low-temperature combustion technique for low-emission internal combustion engines. Unlike conventional engines, HCCI lacks a direct ignition control mechanism, necessitating closed-loop combustion control. This study proposes a phenomenological-based, cost-effective, and non-intrusive approach using vibration data analysis to determine essential combustion parameters. Experiments were conducted on a single-cylinder research engine with an accelerometer attached to the engine head. The engine operation envelope covered the whole engine’s operating area in naturally aspirated HCCI mode. Wavelet analysis revealed that combustion-related frequencies centered around 500 Hz, independent of operating conditions. The correlation-seeking analysis included peak acceleration amplitude and its crank angle with peak heat release rate (HRR) data. The peak HRR location was accurately identified within one degree when vibration amplitude exceeded the 100 m/s2 threshold. This encompassed 98.5% of the analyzed combustion cycles. The peak HRR prediction accuracy had a maximum error below 21% and was suitable to monitor reaction rates, especially in incomplete combustion and high ringing cycles.

The coating based on phenolic resin gives rigid polyurethane foam excellent flame retardant properties

AbstractA flame retardant coating was designed and synthesized using phenolic resin (PF), 9,10‐dihydro‐9‐oxa‐10‐phosphazephenanthrene‐10‐oxide (DOPO), and nano‐SiO2 as raw materials. The coating is applied to the surface of rigid polyurethane foam (RPUF) to give it a flame retardant effect. Based on the excellent adhesion of PF, the coating effectively suppresses heat transfer, and the synergistic effect of DOPO and nano‐SiO2 improves the flame retardancy of RPUF. In addition, vertical combustion experiments have shown that when the ratio of DOPO to nano‐SiO2 is 2:1, there is no dripping, the flame is self‐extinguishing, and the internal structure remains basically unchanged, resulting in the best flame retardant effect. The cone calorimetric test shows that the coating can effectively reduce the total heat release and heat release rate of the substrate, and the smoke release rate and total smoke release data show that its smoke suppression effect is significantly improved. Thermogravimetric analysis shows that the coating can effectively improve the residual carbon rate of RPUF, and its mechanical properties are good. This study confirms that coatings based on PF/DOPO/Nano‐SiO2 can effectively improve the flame retardancy of RPUF, providing a potential direction for the development of green insulation materials.

Study on the Combustion Mechanism of Diesel/Hydrogen Dual Fuel and the Influence of Pilot Injection and Main Injection

Hydrogen is a clean and renewable alternative fuel. In this paper, the combustion mechanism of diesel/hydrogen dual fuel is constructed and verified. The mechanism is combined with three-dimensional numerical simulation to study the effects of pilot injection and main injection on the combustion and emissions of a diesel/hydrogen dual fuel engine. The mechanism uses a 70% mole fraction of n-decane and 30% mole fraction of α-methylnaphthalene as diesel substitutes, and it combines n-decane, α-methylnaphthalene, NOX, PAH, soot and H2/C1-C3 sub-mechanisms to form a diesel/hydrogen dual fuel combustion mechanism. The mechanism was verified by chemical kinetics, including the ignition delay time, JSR (Jet Stirred Reactor) oxidation and laminar flame speed, and then, it was verified by computational fluid dynamics. The results show that the simulated values are in good agreement with the experimental values of cylinder pressure, heat release rate and emissions data. The mechanism can well predict the combustion and emissions of a diesel/hydrogen dual fuel engine. Compared with single injection, the peak heat release rate, peak cylinder pressure and MPIR (Maximum Pressure Rise Rate) increase with the increase in pilot mass percent from 5% to 20%, which makes the phase of CA10 and CA50 advance and reduces CO emissions, but NOX emissions increase. With the advance of pilot injection timing from 10° CA BTDC to 30° CA BTDC, the peak cylinder pressure increases, the peak heat release rate decreases, CA10 and CA50 advance, CO emissions decrease, NOX emissions increase and NOX emissions peak at 30° CA BTDC. When the pilot injection timing is further advanced from 30° CA BTDC to 50° CA BTDC, the peak cylinder pressure decreases, the peak heat release rate increases, CA10 and CA50 are delayed, CO and NOX emissions are reduced, and NOX emissions at 50° CA BTDC are lower than those at 10° CA BTDC. With the advance of main injection timing from 0° CA BTDC to 8° CA BTDC, CO emissions decrease, NOX emissions increase, the peak cylinder pressure increases, the peak heat release rate decreases slightly first and then increases, and the peak cylinder pressure and peak heat release rate corresponding to the overall phase shift forward. When the main injection timing is advanced to 6° CA BTDC, MPIR is 1.3 MPa/° CA, exceeding the MPIR limit of diesel engine 1.2 MPa/° CA.

A pyrolysis model for the thermal decomposition of low-density polyethylene blended with ammonium polyphosphate and pentaerythritol

In this work, a semi-empirical pyrolysis model is developed to predict the thermal decomposition behavior of an intumescent fire retardant (IFR) system consisting of ammonium polyphosphate/pentaerythritol (APP/PER) with the ratio 3:1 (wt/wt) in a low-density polyethylene (LDPE) matrix. This work is based on a previously developed semi-global reaction mechanism for the degradation of LDPE and APP/PER, which consists of two consecutive first-order reactions for the LDPE and five first and second-order reactions for the APP/PER combination. The apparent properties that define heat transport inside the pyrolyzing solid are determined via inverse modeling of cone calorimeter experiments for the pure LDPE and then for the complete IFR system. This is achieved by using the Shuffled Complex Evolution optimization algorithm. The flame heat flux in the cone calorimeter experiments is also evaluated by targeting the heat release rate (HRR) data in the optimization process of one of the cone radiative heat setups. The optimized parameters and flame heat feedback are in line with the literature and the robustness of the model is assessed by a comparison with the experimental data for a wide range of cone heat fluxes. Ignition times and peaks of HRR and total HRs are within the engineering accuracy whatever the flux conditions for both pure LDPE and the IFR system.

Mixed mode failure curve for an interface crack between single crystal silicon and silicone rubber

An interface crack between single crystal silicon (SC-Si) and silicone rubber was examined. Mixed mode fracture tests were performed on Arcan-type specimens at different mode mixities. It was observed during the tests that silicone rubber underwent large deformations before crack propagation. Nonlinear finite element analyses (FEAs) of the fracture tests were carried out in Abaqus. A cubic (anisotropic), linear elastic material model was used for SC-Si, while a Mooney–Rivlin (hyperelastic) model was used for the silicone rubber. The virtual crack closure technique (VCCT) which has been adopted for large deformations was employed to determine the energy release rates from the FEAs. A mixed mode failure criterion was obtained from the energy release rate data.

Effects of biohydrogen on premixed charge compression ignition engine operating at various inlet air temperatures

The usage of the diesel engine has been increasing every year and simultaneously the emissions by the fossil fuels are mounting up and damaging the environment. Hence, it is of profound interest to seek the solution to reduce the emissions released by fossil fuels. In this proposed study, the biohydrogen influence on the diesel engine has been examined. Since biohydrogen is a green gas, it reduces the emissions of certain pollutants significantly. Hence, here the diesel engine is tested with 10% and 30% of biohydrogen flow through air intake. Two different combinations such as DH10 (10% Biohydrogen and 90% diesel) and DH30 (30% biohydrogen and 70% diesel) were tested at different mean effective pressure (MEP). The MEP has been varied from 1.05 bars to 4.2 bars. Since the engine is operating on premixed charge compression ignition conditions, inclusion of the biohydrogen is challenging. To avoid biohydrogen backfire flame arrestor has been attached between the cylinder and flowmeter. The crucial parameters such as brake thermal efficiency, brake specific fuel consumption, heat release rate, cylinder pressure, combustion timing, and emissions data were collected and analyzed to understand the sustainability of the biohydrogen gas running on the diesel engine. Based on findings it is clear, adding the biohydrogen gas to the engine increases the BTE and HRR. Further the cylinder pressure values were also increased due to the usage of compressed gas. Nevertheless, the brake specific fuel consumption has been at higher levels due to the energy discrepancy. With regards to the emission, CO, CO2and NOx concentration in the exhaust tailpipe has decreased marginally, which is pleasing. Comparing DH10 and DH30, DH30 outperforms with regard to emission data. On the other hand, the performance values are superior for DH10 than DH30.

Electrospinning Drug-Loaded Alginate-Based Nanofibers towards Developing a Drug Release Rate Catalog.

Electrospinning natural polymers represents a developing interest in the field of biomaterials. Electrospun nanofibers have been shown to facilitate tissue regeneration and emulate body tissue, making them ideal for modern biomedical applications. These water-soluble natural polymers including alginate, have also shown promise as drug delivery vehicles. However, many biopolymers including alginate are inherently charged, making the formation of nanofibers difficult. To better understand the potential of natural polymer-based fibers in drug delivery applications, fiber formulations and drug loading concentrations of alginate-based scaffolds were investigated. It was found electrospinning poly(vinyl alcohol) with alginate facilitated fiber formation while the co-polymer agarose showed minor improvement in terms of alginate electrospinnability. Once uniform fibers were formed, the antibiotic ciprofloxacin was added into the polymer electrospinning solution to yield drug-loaded nanofibers. These optimized parameters coupled with small molecule release rate data from the drug-loaded, alginate-based fibers have been used to establish a catalog of small molecule release profiles. In the future, this catalog will be further expanded to include drug release rate data from other innately charged natural polymer-based fibers such as chitosan. It is anticipated that the cataloged profiles can be applied in the further development of biomaterials used in drug delivery.

In-vitro characterization of ranibizumab release from the Port Delivery System

The Port Delivery System with ranibizumab (PDS) consists of an implant that is a permanent, indwelling drug delivery device that can be refilled through a self-sealing septum and is designed to continuously release a customized formulation of ranibizumab into the vitreous by passive diffusion through a porous titanium release control element. Target release rates of ranibizumab via the implant used in studies of the PDS in patients with neovascular age-related macular degeneration were selected based on clinical and pharmacokinetic (PK) data from previously conducted intravitreal ranibizumab injection studies. In-vitro testing was performed to verify release rates with a range of ranibizumab concentrations before the phase II Ladder (NCT02510794) and phase III Archway (NCT03677934) trials of the PDS. Implants were filled with ranibizumab and were regularly transferred to new buffer-containing tubes to represent ocular ranibizumab clearance and release kinetics. Ranibizumab concentrations were measured and release rates calculated. Release rate data were fit to an exponential model and compared with expected release kinetics of diffusion. Release profiles of the implant releasing ranibizumab at concentrations of 10 mg/mL, 40 mg/mL, and 100 mg/mL were determined in the pre–phase II in-vitro studies. At day 3.5, mean (SD) ranibizumab release rates were 1.75 (0.07), 6.42 (0.35), and 16.69 (0.67) μg/d for PDS 10 mg/mL, 40 mg/mL, and 100 mg/mL, respectively. At month 6, mean (SD) release rates were 1.68 (0.05) and 4.16 (0.05) μg/d for PDS 40 mg/mL and 100 mg/mL, respectively. Measured release rates were within 90% of theoretical release rates during the course of drug release. PDS 100 mg/mL released 73% (SD, 1.92) of drug by month 6. In the pre–phase III in-vitro studies, mean (SD) release rates with PDS 100 mg/mL were 17.97 (0.90), 4.44 (0.11), and 2.45 (0.08) μg/d at 3.5 days, 6 months, and 9 months, respectively. Cumulative release (SD) was 73% (1.92) by month 6 and 87% (1.88) by month 9. The sustained, continuous, and reproducible release from the PDS observed in the in-vitro studies was also observed in Ladder and Archway. In conclusion, in-vitro studies were a powerful tool for characterizing and verifying ranibizumab release from the PDS implant and supported clinical evaluation of the PDS. PDS 100 mg/mL, which was associated with the longest therapeutic-level delivery of ranibizumab among the concentrations tested, was selected for evaluation in the pivotal phase III Archway trial.

Waste to energy conversion: Pyrolytic oil and biodiesel as a renewable fuel blends on diesel engine combustion, performance, and emissions

ABSTRACT The use of pyrolytic oil (WTPO) obtained from waste vehicle tires in Turkey is evaluated and encouraged within the scope of YEKDEM (Turkey Renewable Energy Resources Support Mechanism). In order to benefit from this incentive, WTPO must be used as the main fuel in diesel engines. For this reason, in this study, unlike all other studies in the literature, the use of WTPO at a high rate was examined. The effects of biodiesel and WTPO mixtures containing high WTPO on engine performance and emissions were investigated. The experiments were carried out at 2800 rpm engine speed, where the maximum power was obtained, and at 4 different loads as 100%, 75%, 50%, and 25%. When the obtained results are examined. The lowest brake thermal efficiency (BTE) value was obtained in P100 fuel at 25% load and its value was 16.21%. Brake specific fuel consumption (BSFC) data were similar for all test fuels under the same load conditions. Based on the heat release rate and in-cylinder pressure data, it was noted that biodiesel reduced the ignition delay time. The maximum in-cylinder temperature was 1723.4 K and the maximum exhaust temperature was 590°C with the use of P60B40 fuel. The lowest nitrogen oxides (NOx) value results were obtained at 100% load. Hydrocarbon (HC) emissions decreased from 1.13 g/kWh to 0.13 g/kWh for P100 fuel as load increased form 25% to 100%. All these results show that although the biodiesel additive slightly worsened the emissions, positive results were obtained for the performance data.

Properties of Mosquito Repellent-Plasticized Poly(lactic acid) Strands.

Poly(lactic acid) (PLA) is an attractive candidate for replacing petrochemical polymers because it is fully biodegradable. This study investigated the potential of PLA as a sustainable and environmentally friendly alternative material that can be developed into commercially viable wearable mosquito repellent devices with desirable characteristics. PLA strands containing DEET and IR3535 were prepared by twin screw extrusion compounding and simultaneously functioned as plasticizers for the polymer. The plasticizing effect was investigated by thermal and rheological studies. DSC studies showed that the addition of DEET and IR3535 into PLA strands reduced the glass transition temperature consistent with predictions of the Fox equation, thus proving their efficiency as plasticizers. The rheology of molten samples of neat PLA and PLA/repellents blends, evaluated at 200 °C, was consistent with shear-thinning pseudoplastic behaviour. Raman studies revealed a nonlinear concentration gradient for DEET in the PLA strand, indicating non-Fickian Type II transport controlling the desorption process. Release data obtained at 50 °C showed initial rapid release followed by a slower, near constant rate at longer times. The release rate data were fitted to a novel modification of the Peppas-Sahlin desorption model.

Pyrolysis Kinetics and Flammability Evaluation of Rigid Polyurethane with Different Isocyanate Content

Polyurethane (PU) is a typical product of the reaction between isocyanate and polyol, whose ratio would greatly influence material properties. In this paper, to investigate the influence of isocyanate on PU thermal stability and flammability, three kinds of rigid polyurethanes (RPUs) with different isocyanate ratio (1.05, 1.1, and 2.0) were manufactured in a laboratory and employed to have a series of TG (thermogravimetry), DSC (differential scanning calorimetry), and cone calorimetry tests. Kissinger’s method was used to calculate the activation energy and judge their stabilities. However, for such a complex degradation which consists of five reactions, it does not make sense by Kissinger method to obtain only two peak active energies. Considering complexity of PU degradation in air, genetic algorithm (GA) was employed to calculate kinetic triplets of five sub-reactions. The effects of isocyanate contents on each sub-reaction stability were obtained and then analyzed. By cone calorimeter testing, we found that great differences in heat release rate data. However, DSC analysis showed a complete opposite changed trend. Such difference is caused by DSC and calorimeter’s sample morphology, the former using grinded polyurethane powders but the latter polyurethane foam block.

Controlling the source of green tides in the Yellow Sea: NaClO treatment of Ulva attached on Pyropia aquaculture rafts

Green macroalgal blooms have occurred in the Yellow Sea for 13 consecutive years since 2007. However, effective control methods have not yet been successfully developed. Ulva prolifera attached on Pyropia aquaculture rafts was identified as the main source of the blooms, thus, eliminating the attached Ulva from the rafts should be the most efficient method to prevent and control these blooms. In this study, we designed a new molecular marker (rps2-trnL) to identify U. prolifera collected from the aquaculture site. Samples identified as U. prolifera were cultured, and different concentrations of sodium hypochlorite (NaClO) solution (0.2, 0.4, 0.6, 0.8, and 1.0%) were used to kill the alga. The measured chlorophyll content, light quantum yield, and photosynthetic oxygen release rate data from the laboratory experiment suggested that the appropriate concentration of NaClO solution should be 0.6–1.0%. To carry out a small-scale field trial, we developed a device that can spray NaClO on Ulva blades and recycle the residual liquid. Results showed that only the 1.0% NaClO solution could quickly kill the Ulva in outdoor experiments. During the treatment, very little NaClO dripped on the tidal flat, which indicated that the recycling device avoided a potential negative impact of residual solution on the marine ecosystem. By the beginning of November 2019, the Pyropia aquaculture area treated by NaClO was about 13,000 ha, covering about one-third of the total area at the coast of Jiangsu Province. Monitoring by an unmanned aerial vehicle showed that very little attached Ulva was present on the ropes after NaClO treatment, which indicated that it was an effective method to control the green tide. Also, the range of residual active chlorine within seawater during the treatment was only from 0.003 to 0.012 mg/L, which complied with Chinese national standards. However, further monitoring of the formation process of green tides should be conducted in future years to evaluate the effect of NaClO treatment.

Determining a Lower Bound Mixed Mode Failure Curve for An Interface Crack Between Single Crystal Silicon and Silicone Rubber

AbstractAn interface crack between single crystal silicon (SC-Si) and silicone rubber is examined. The first term of the asymptotic solution for this interface crack is derived. Mixed mode fracture tests were performed on Brazilian disk specimens at different mode mixities. Finite element analyses (FEAs) of these tests were carried out in abaqus. A cubic (anisotropic) material model is used for SC-Si. Two different material models were used for silicone rubber: a linear elastic model for the asymptotic solution and a Mooney–Rivlin (hyperelastic) model for the FEA. The FEAs showed that large deformations were relegated to a small region surrounding the crack tip. Hence, a K-dominate region exists in which linear elastic fracture mechanics (LEFM) may be used. From the FEAs of the Brazilian disk specimens, energy release rates were determined using the virtual crack closure technique (VCCT) and displacement extrapolation (DE) methods which were corroborated by J-integral values evaluated using the contour integral method. Elsewhere, it was demonstrated that properly implemented, the VCCT method may be used for interface cracks. A mixed mode failure criterion is obtained from the energy release rate data. The SC-Si failed before the interface crack propagated. Hence, the failure curve obtained in this study should be considered as a lower bound of the critical energy release rate for this material pair.

Analysis on the Fire Growth Rate Index Considering of Scale Factor, Volume Fraction, and Ignition Heat Source for Polyethylene Foam Pipe Insulation

The fire growth rate index (FIGRA), which is the ratio of the maximum value of the heat release rate (Qmax) and the time (tmax) to reach the maximum heat release rate, is a general method to evaluate a material in the fire-retardant performance in fire technology. The object of this study aims to predict FIGRA of the polyethylene foam pipe insulation in accordance with the scale factor (Sf), the volume fraction of the pipe insulation (VF) and the ignition heat source (Qig). The compartments made of fireboard have been mock-up with 1/3, 1/4, and 1/5 reduced scales of the compartment as specified in ISO 20632. The heat release rate data of the pipe insulation with the variation of Sf, VF, and Qig are measured from 33 experiments to correlate with FIGRA. Based on a critical analysis of the heat transfer phenomenon from previous research literature, the predictions of Qmax and tmax are presented. It is noticeable that the fire-retardant grade of the polyethylene foam pipe insulation could have Grade B, C, and D in accordance with the test conditions within ±15% deviation of the predicted FIGRA. In case of establishing the database of various types of insulation, the prediction models could apply to evaluate the fire-retardant performance.

Influence of the injector setup on digital and continuous injection rate-shaping performance in diesel engine passenger cars

Injection continuous rate-shaping strategies, realized by means of state-of-the-art Common rail solenoid and direct acting piezoelectric injectors, have been tested at a dynamometer cell. NOx, soot, combustion noise and heat release rate data, pertaining to the two injector types, have been compared, based on a pilot-main injection calibration. The performance of the solenoid injectors resulted to be in line with that of the direct acting piezoelectric injectors.Digital and continuous rate-shaping strategies have then been investigated at a hydraulic rig in solenoid injectors. The cycle-to-cycle dispersion in the injected mass increases significantly in the closely-coupled injection regime, where the overall injected quantity raises up as the dwell time progressively reduces. However, as the dwell time is diminished to values well within the injection fusion zone, the cycle-to-cycle dispersion of the injected mass again improves and this confirms that is possible to implement effective continuous injection rate-shaping schedules also for the solenoid injectors.A previously developed one-dimensional model of a solenoid fuel injection system has been applied to perform parametric analyses on the solenoid injector setup: mechanical, electromagnetic and hydraulic parameters have been changed in order to investigate their effect on the closely-coupled injections. The objective is to provide design keys for realizing more efficient injection rate-shaping schedules in order to improve engine emissions, fuel consumption and combustion noise.Finally, the performance of two production solenoid injectors, which feature a different internal layout, has been compared in the short dwell time range and the experimental results have been successfully interpreted on the basis of the injector parametric analyses.

Study on the fire growth in underground green corridors

Underground green corridors are getting popular worldwide intending to integrate greenery into built environments. Green corridors provide greenery benefits and aesthetic pleasing view. Proper irrigation is necessary to maintain live plants in green walls. Automated irrigation with adequate amounts and proper drainage is vital to avoid overflows and drowning of plants. Due to improper irrigation plants in green walls can die quickly, creating a potential fire risk in underground green corridors. This paper aims at investigating the ignition, fire propagation and smoke propagation in underground green corridors. Numerical simulations with computational fluid dynamics (CFD) and physical scale modeling experiments were performed. The simulation has been completed based on heat release rate (HRR, kW/m2) data obtained from the cone calorimeter experiments for three plant species, namely; Hedera helix, Peperomia obtusifolia and Aglaonema commutatum. CFD simulations were conducted for an underground passage with a green wall. Results showed that a fire does not occur in underground corridors with fresh and live plants. However, fire risk increases gradually with drying out of plants. For dry plants, the surface temperature may reach above 850 °C. The fire spreads rapidly in about 20 s. An experimental study was carried out on a reduced-scale underground green corridor to investigate the fire and smoke propagation. It is observed that in the vertical direction fire spreads up to the ceiling rapidly. However, fire spreads slowly in the horizontal direction along the green wall. The experiments show that when the green wall is ignited, it may tremendously affect the evacuation due to smoke spread along the corridor and fire propagation in the vertical direction. It is recommended to decrease the fire risk in underground corridors with properly maintained green walls, especially in evacuation paths. This work is an initial study towards the analysis of fire and smoke propagation in underground green corridors.

Simulation of Hydrogen Combustion Characteristics in Argon-Oxygen Compression Ignition Engine using Large Eddy Simulation (LES) Turbulence Model

Hydrogen combustion in a noble gas atmosphere will increase thermal efficiency because of higher specific heat ratio. During the compression stroke, noble gas produces a higher temperature at the same compression ratio compared to standard air compression. Argon is the best noble gas in this study because it is abundant and readily available. In this study, argon replaced the nitrogen and formed the argon-oxygen atmosphere in a compression ignition engine. The objectives of this study are to determine the suitable initial temperature for simulation work based on the experimental value and to study the effect of injection parameter changes towards combustion and emission characteristics. This study uses Converge V2.4 CFD simulation based on Yanmar NF19SK engine parameter. The turbulence model used Large Eddy Simulation (LES) due to accessibility in extensive eddies calculation that has a significant fraction of energy. Thus, combustion analysis accuracy also increased. Base grid of 5mm with adaptive mesh refinement (AMR) and fix embedding is chosen based on simulation time and computer storage. Combustion simulations involve changing of initial temperature, the start of injection (SOI) and injection pressure to obtain pressure and heat release rate data. At intake temperature of 370K, hydrogen combustion shows the highest peak pressure, and for intake temperature at 500K, SOI of 700 °CA produces the highest peak pressure for the combustion. Ignition delay increases as the temperature and injection pressure decrease.