Investigation of LPG Combustion: Effect of Addition of Carbon Black and Alumina on Radiative Heat Flux

Khalid Waheed,Seung wook Baek,Irfan Javed,Yupiter Kristiyanto 한국연소학회 2013 KOSCOSYMPOSIUM논문집 Vol.2013 No.12

Particulate matter in industrial furnaces plays important role in extracting heat from flame. Effects of particle addition to LPG combustion was investigated in this research. Higher hear fluxes were obtained with addition of combustible carbon black and non-combustible alumina particles. These particles were introduce to the flame in suspension form with dilute concentrations of 0.1 wt. % and 0.5 wt. %. Higher radiative heat flux fractions were observed with addition of particles to LPG combustion with maximum increase comes with addition of noncombustible alumina particles.

Investigations on Thermal Radiative Characteristics of LPG Combustion: Effect of Alumina Nanoparticles Addition

Waheed, Khalid,Baek, Seung Wook,Javed, Irfan,Kristiyanto, Yupiter Gordon and Breach Science Publishers 2015 Combustion science and technology Vol.187 No.6

Experimental investigation of aerosols removal efficiency through self-priming venturi scrubber

Suhail Ali,Khalid Waheed,Kamran Qureshi,Naseem Irfan,Masroor Ahmed,Waseem Siddique,Amjad Farooq 한국원자력학회 2020 Nuclear Engineering and Technology Vol.52 No.10

Self-priming venturi scrubber is one of the most effective devices used to collect aerosols and soluble gas pollutants from gaseous stream during severe accident in a nuclear power plant. The present study focuses on investigation of dust particle removal efficiency of the venturi scrubber both experimentally and theoretically. Venturi scrubber captures the dust particles in tiny water droplets flowing into it. Inertial impaction is the main mechanism of particles collection in venturi scrubber. The water injected into venturi throat is in the form of jets through multiple holes present at venturi throat. In this study, aerosols removal efficiency of self-priming venturi scrubber was experimentally measured for different operating conditions. Alumina (Al2O3) particles with 0.4-μm diameter and 3950 kg/m3 density were treated as aerosols. Removal efficiency was calculated for different gas flow rates i.e. 3-6 m3/h and liquid flow rates i.e. 0.009–0.025 m3/h. Experimental results depict that aerosols removal efficiency increases with the increase in throat velocity and liquid head. While at lower air flow rate of 3 m3/h, removal efficiency decreases with the increase in liquid head. A theoretical model of venturi scrubber was also employed and experimental results were compared with mathematical model. Experimental results are found to be in good agreement with theoretical results.

Autoignition and combustion characteristics of heptane droplets with the addition of aluminium nanoparticles at elevated temperatures

Javed, Irfan,Baek, Seung Wook,Waheed, Khalid Elsevier 2015 Combustion and Flame Vol.162 No.1

<P><B>Abstract</B></P> <P>We investigate the effects of high ambient temperatures and various concentrations of nanoparticles (NPs) on the autoignition and combustion characteristics of heptane-based nanofluid droplets. A single, heptane (<I>n</I>-C<SUB>7</SUB>H<SUB>16</SUB>) droplet containing 0.5%, 2.5%, or 5.0% by mass of aluminium (Al) NPs mounted on a silicon carbide fibre was exposed to a rapid increase in temperature (from room temperature to temperatures in the range 600–850°C) at atmospheric pressure and under normal gravity, and the autoignition and combustion characteristics were observed. The ignition delay, burn rate, and combustion characteristics of pure and stabilised heptane droplets were also examined for comparison. The results show that, as with the pure heptane droplets, the ignition delay of the NP-laden heptane droplets (<I>n</I>-Al/heptane) followed an Arrhenius temperature dependence. The reduction in the ignition delay time with increasing temperature depended on the loading of NPs in the droplet. The overall activation energy obtained for dilute NP concentrations (0.5% by mass) was smaller, and that for dense (2.5% and 5.0%) concentrations of NPs was larger, than that of the pure heptane droplets. Consequently, the addition of 0.5% Al NPs to heptane resulted in ignition at 600°C, which is not observed with stabilised heptane or 2.5% and 5.0% <I>n</I>-Al/heptane droplets. At higher temperatures, the ignition delay of the <I>n</I>-Al/heptane droplets was comparable to that of pure heptane droplets. The combustion of the <I>n</I>-Al/heptane droplets did not follow the classical <I>d</I> <SUP>2</SUP>-law, in contrast to the combustion of the pure and stabilised heptane droplets. Regardless of the NP concentration, the <I>n</I>-Al/heptane droplets exhibited disruptive burning behaviour, which was characterised by multiple expansions and ruptures or ‘microexplosions’. During these microexplosions, the NPs were ejected from the droplets, and the intensity of the microexplosions increased with increasing temperature; consequently, the burning time and total combustion time of the droplet was reduced. Due to these intense and frequent microexplosions, almost no residue from the Al NPs remained on the fibre following combustion, and a separate Al flame was not observed. The average gasification (burn) rate of the <I>n</I>-Al/heptane droplets remained equal to that of pure heptane droplets at relatively low temperatures (600–700°C); however, at higher temperatures (750–850°C), it was significantly faster than that of the pure heptane droplets.</P>

Autoignition and combustion characteristics of kerosene droplets with dilute concentrations of aluminum nanoparticles at elevated temperatures

Javed, Irfan,Baek, Seung Wook,Waheed, Khalid Elsevier 2015 Combustion and Flame Vol.162 No.3

<P><B>Abstract</B></P> <P>In this experimental study, we investigated the effects of high ambient temperatures and dilute concentrations of nanoparticles (NPs) on the autoignition and combustion characteristics of kerosene-based nanofluid droplets. An isolated kerosene droplet containing 0.1%, 0.5% or 1.0% by weight of aluminum (Al) NPs suspended on a silicon carbide (SiC) fiber was suddenly exposed to an elevated temperature (in range 400–800°C) at atmospheric pressure (0.1MPa) under normal gravity, and the autoignition and combustion characteristics were examined. The ignition delay time, burning rate constant and combustion characteristics of pure and stabilized kerosene droplets were also observed for comparison. The results indicate that, similar to pure kerosene droplets, the ignition delay time of NP-laden kerosene (<I>n</I>-Al/kerosene) droplets also followed the Arrhenius expression and decreased exponentially with increasing temperature. However, the addition of dilute concentrations of Al NPs to kerosene reduced the ignition delay and lowered the minimum ignition temperature to 600°C, at which pure kerosene droplets of the same initial diameter were not ignited. In contrast to the combustion of pure and stabilized kerosene droplets, the combustion of <I>n</I>-Al/kerosene droplets exhibited disruptive behavior characterized by sudden reductions in the droplet diameter without any prior expansions caused by multiple-time bubble formation and their subsequent rupture at or near the droplet’s surface. This bubble pop-up resulted in droplet trembling and fragmentation and ultimately led to enhancement in gasification, vapor accumulation and envelope flame disturbance. The NPs were also brought out of the droplets through these disruptions. Consequently, the burning time and total combustion time of the droplets were reduced, and almost no residue remained on the fiber following combustion. Thus, the combustion rate of <I>n</I>-Al/kerosene droplets was substantially enhanced compared with pure kerosene droplets at all tested temperatures.</P>

Study of hydrodynamics and iodine removal by self-priming venturi scrubber

Ahad Jawaria,Rizwan Talha,Farooq Amjad,Waheed Khalid,Ahmad Masroor,Qureshi Kamran Rasheed,Siddique Waseem,Irfan Naseem 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.1

Filtered containment system is a passive safety system that controls the over-pressurization of containment in case of a design-based accidents by venting high pressure gaseous mixture, consisting of air, steam and radioactive particulate and gases like iodine, via a scrubbing system. An indigenous lab scale facility was developed for research on iodine removal by venturi scrubber by simulating the accidental scenario. A mixture of 0.2 % sodium thiosulphate and 0.5 % sodium hydroxide, was used in scrubbing column. A modified mathematical model was presented for iodine removal in venturi scrubber. Improvement in model was made by addition of important parameters like jet penetration length, bubble rise velocity and gas holdup which were not considered previously. Experiments were performed by varying hydrodynamic parameters like liquid level height and gas flow rates to see their effect on removal efficiency of iodine. Gas holdup was also measured for various liquid level heights and gas flowrates. Removal efficiency increased with increase in liquid level height and gas flowrate up to an optimum point beyond that efficiency was decreased. Experimental results of removal efficiency were compared with the predicted results, and they were found to be in good agreement. Maximum removal efficiency of 99.8% was obtained.

Investigation of dust particle removal effi ciency of self-priming venturi scrubber using computational fl uid dynamics

Sarim Ahmed,Hassan Mohsin,Kamran Qureshi,Ajmal Shah,Waseem Siddique,Khalid Waheed,Naseem Irfan,Masroor Ahmad,Amjad Farooq 한국원자력학회 2018 Nuclear Engineering and Technology Vol.50 No.5

A venturi scrubber is an important element of Filtered Containment Venting System (FCVS) for theremoval of aerosols in contaminated air. The present work involves computational fluid dynamics(CFD) study of dust particle removal efficiency of a venturi scrubber operating in self-priming mode usingANSYS CFX. Titanium oxide (TiO2) particles having sizes of 1 micron have been taken as dust particles. CFD methodology to simulate the venturi scrubber has been first developed. The cascade atomizationand breakup (CAB) model has been used to predict deformation of water droplets, whereas the EulerianeLagrangian approach has been used to handle multiphase flow involving air, dust, and water. Thedeveloped methodology has been applied to simulate venturi scrubber geometry taken from the literature. Dust particle removal efficiency has been calculated for forced feed operation of venturi scrubberand found to be in good agreement with the results available in the literature. In the second part, venturiscrubber along with a tank has been modeled in CFX, and transient simulations have been performed tostudy self-priming phenomenon. Self-priming has been observed by plotting the velocity vector fields ofwater. Suction of water in the venturi scrubber occurred due to the difference between static pressure inthe venturi scrubber and the hydrostatic pressure of water inside the tank. Dust particle removal efficiencyhas been calculated for inlet air velocities of 1 m/s and 3 m/s. It has been observed that removalefficiency is higher in case of higher inlet air velocity.

Study of an improved and novel venturi scrubber configuration for removal of radioactive gases from NPP containment air during severe accident

Farooq Mujahid,Ahmed Ammar,Qureshi Kamran,Shah Ajmal,Waheed Khalid,Siddique Waseem,Irfan Naseem,Ahmad Masroor,Farooq Amjad 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.9

Owing to the rising concerns about the safety of nuclear power plants (NPP), it is essential to study the venturi scrubber in detail, which is a key component of the filtered containment venting system (FCVS). FCVS alleviates the pressurein containment byfiltering and venting out the contaminated air. Themain objective of this research was to perform a CFD investigation of different configurations of a circular, non-submerged, selfpriming venturi scrubber to estimate and improve the performance in the removal of elemental iodine from the air. For benchmarking, a mass transfer model which is based on two-film theory was selected and validated by experimental data where an alkaline solution was considered as the scrubbing solution. This mass transfer model was modified and implemented on a unique formation of two self-priming venturi scrubbers in series. Euler-Euler method was used for two-phase modeling and the realizable K ε model was used for capturing the turbulence. The obtained results showed a remarkable improvement in the removal of radioactive iodine from the air using a series combination of venturi scrubbers. The removal efficiency was improved at every single data point.