Ozone Addition Research Articles

Gas-phase aromatic compounds degradation by a partially TiO2 coated photoreactor assisted with ozone

Heterogeneous photocatalysis with TiO2 have been studied for VOCs degradation; however, aromatic VOCs degradation lead TiO2 deactivation. The objective of this study was to degrade aromatic VOCs by heterogeneous photocatalysis avoiding TiO2 deactivation. The experiments were conducted using a UV-C lamp (254nm), relatively humidity (RH – 26–60 %), and ozone (O3 – 2.38 to 5.35 %). Due to O3 addition, it was necessary to have uncoated regions in the quartz tube around the lamp to allow UV photons to reach the gas bulk and generate radicals from O3. Different quartz tube coating fractions were tested to analyze its influence on VOCs degradation. The highest toluene degradation was 99.2 % for the reactor with 90 % of coating, 3.4 % of O3, space time of 123s, and RH of 26 %. It was observed RH greater than 26 % affected the degradation achieved. Ozone addition allowed TiO2 use for 77h avoiding early catalyst deactivation. Besides that, the requirement of uncoated regions indicated that VOC oxidative reactions occur both on solid and gas phases. This suggested that the addition of O3 combined with the reactor configuration is a promising alternative for aromatic compound degradation by heterogeneous photocatalysis.

Water and air ozone treatment as an alternative sanitizing technology [abstract

PURPOSE: Investigate the effectiveness of ozone treatment as an alternative sanitizing technology to conventional disinfectants in reducing the microbial contamination of both water and air. METHODS: Ozone was added for 20 minutes to a well-defined volume of water and air by the system named “Ozonomatic®”. The effectiveness of ozonation was determined by counting CFU/m3 or mL of bacteria present in samples of air or water collected before (T0) and after (T1) the addition of ozone and comparing the microbial load of different bacteria present in ozonized and non-ozonized samples. RESULTS: When the ozonation equipment was located at 30 cm from the surface of the water in the bath tub in which the bacteria were inoculated, the treatment was able to reduce the microbial load present in the aerosol by 70.4% at a temperature of 36°C for 48 hours. Conversely, at 22°C for 5 days, only a modest decrease (9.1%) was observed. Escherichia coli and Pseudomonas aeruginosa were completely eliminated. A 93.9% reduction was observed for Staphylococcus aureus, followed by Streptococcus faecalis (25.9%). The addition of ozone to water was able to almost eliminate Staphylococcus aureus (98.9% reduction) and also to exert a strong impact on Legionella pneumophila (87.5% reduction). Streptococcus faecalis and Pseudomonas aeruginosa showed a decrease of 64.2% and 57.4%, respectively. Conversely, only a 26.4% reduction was observed for the bacterium Escherichia coli. This study showed that the addition of ozone in the air exerted a modest reduction on microbial load at 36°C, whereas no effect was observed at 22°C. CONCLUSIONS: Aqueous and gaseous ozone treatments were effective against microbial contaminants, reducing the CFU of the microorganisms and confirming its efficacy in water and air disinfection.

Spark Assisted Compression Ignition Engine with Stratified Charge Combustion and Ozone Addition

<div class="section abstract"><div class="htmlview paragraph">Performance and emissions characteristics for stratified charge spark assisted compression ignition (SACI) with 30 ppm of added ozone (O<sub>3</sub>) were explored in a single-cylinder, optically accessible, spray-guided, research engine. For the present study, intake pressure and temperature were fixed at 1.0 bar and 42°C respectively, with a range of engine loads (1.5 – 5.5 bar indicated mean effective pressure) and speeds (800 – 1600 revolutions per minute) explored. Fuel stratification achieved by a late-cycle injection of ~ 10–25% of the total fuel was used to maintain stable operation at lower engine loads. For each condition spark timing, second injection SOI, and fuel split ratio between the main and second injection were optimized to maximize engine performance while maintaining nitrogen oxide emissions (NOx) below 5 g/kg-fuel.</div><div class="htmlview paragraph">Ozone addition was found to decrease specific fuel consumption by up to 9%, with across the board improvement in combustion stability relative to similar conditions without O<sub>3</sub>. The effect of O<sub>3</sub> addition was most substantial for the lowest loads. Moreover, because a higher fraction of the fuel burned was due to end-gas auto-ignition, specific NOx emissions likewise decreased by up to 30%. From complementary measurements of in-cylinder O<sub>3</sub> decomposition acquired via an ultraviolet light absorption diagnostic, it was observed that rapid decomposition of O<sub>3</sub> into molecular and atomic oxygen coincided with the onset of end-gas auto-ignition. The burst of resultant atomic oxygen was thought to accelerate low-temperature heat release (LTHR) reactions in the end gas. Optimal end-gas auto-ignition started between 20 and 30 crank angles before top dead center with temperatures at LTHR onset estimated to be between 575 and 700 K. An included analysis indicates that the spark deflagration was needed to add between 10 and 40 J of additional thermal energy to the end gas to achieve optimal auto-ignition.</div></div>

Effects of non-thermal plasma on the lean blowout limits and CO/NOx emissions in swirl-stabilized turbulent lean-premixed flames of methane/air

This study investigates experimentally the effects of non-thermal plasma (NTP) induced by a dielectric barrier discharge (DBD) reactor on the characteristics of swirl-stabilized turbulent lean-premixed methane/air flames in a laboratory scale combustor by systematically varying the applied AC voltage, VAC, and frequency, fAC. Especially, it is elucidated how the NTP influences the lean blowout (LBO) limits and the characteristics of CO/NOx emissions depending on flame configuration. Without applying the NTP as the mixture equivalence ratio, ϕ, decreases from the stoichiometry to an LBO limit, the flame configuration changes from an M-flame (Regime I) to a conical flame (Regime II) and to a columnar flame (Regime III) for the whole range of the mixture nozzle exit velocity, U0, (4–10 m/s). With the NTP, however, it exhibits only Regimes I and II at relatively-low U0 range (4–6 m/s), while all three regimes at relatively-high U0 range (7–10 m/s). For both velocity ranges, the LBO limits are significantly extended by the NTP enhancing the flame stability. Under the relatively-low U0 range, streamers induced by the DBD reactor play a critical role in stabilizing the flames such that the degree of extension of the LBO limit depends linearly on VAC and fAC. Under the relatively-high U0 range, however, ozone generated by the DBD reactor in Regime III is found to be a major reason in extending the LBO limit, which is substantiated by another flame regime diagram with ozone addition only, and hence, the extension of LBO limit minimally depends on fAC. Simultaneously, the NTP considerably reduces CO emission, while slightly increases NOx emission near the LBO limits due to the enhanced combustion by ozone.

Secondary organic aerosol formation from the laboratory oxidation of biomass burning emissions

Abstract. Biomass burning is an important source of aerosol and trace gases to the atmosphere, but how these emissions change chemically during their lifetimes is not fully understood. As part of the Fire Influence on Regional and Global Environments Experiment (FIREX 2016), we investigated the effect of photochemical aging on biomass burning organic aerosol (BBOA) with a focus on fuels from the western United States. Emissions were sampled into a small (150 L) environmental chamber and photochemically aged via the addition of ozone and irradiation by 254 nm light. While some fraction of species undergoes photolysis, the vast majority of aging occurs via reaction with OH radicals, with total OH exposures corresponding to the equivalent of up to 10 d of atmospheric oxidation. For all fuels burned, large and rapid changes are seen in the ensemble chemical composition of BBOA, as measured by an aerosol mass spectrometer (AMS). Secondary organic aerosol (SOA) formation is seen for all aging experiments and continues to grow with increasing OH exposure, but the magnitude of the SOA formation is highly variable between experiments. This variability can be explained well by a combination of differences in OH exposure and the total concentration of non-methane organic gases (NMOGs) in the chamber before oxidation, as measured by PTR-ToF-MS (r2 values from 0.64 to 0.83). From this relationship, we calculate the fraction of carbon from biomass burning NMOGs that is converted to SOA as a function of equivalent atmospheric aging time, with carbon yields ranging from 24±4 % after 6 h to 56±9 % after 4 d.

Ozone-assisted photocatalytic degradation of gaseous toluene from waste air stream using silica-functionalized graphene oxide/ZnO coated on fiberglass: performance, intermediates, and mechanistic pathways

The present study focused on the potential of an ozone-assisted photocatalytic process using the catalyst silica-functionalized graphene oxide/ZnO coated on fiberglass (Si-GO/ZnO-FG) in the removal of toluene from waste air stream. Here, a comparative examination was performed in terms of toluene removal efficiency in the photocatalytic process (UV/Si-GO/ZnO-FG) and photocatalytic ozonation (O3/UV/Si-GO/ZnO-FG). The gaseous intermediates resulting from degradation of toluene by different processes were analyzed using GC-MS. The results of this study indicated that with the addition of ozone to the UV/Si-GO/ZnO-FG process, toluene removal increased significantly from 76.18 to 87.8%. The reason for this incremental efficiency can be explained by the fact that with the addition of ozone, the production rate and the extent of hydroxyl radical (OH•) production grow significantly; thereby, more pathways are developed for toluene degradation. The major byproducts in toluene oxidation by photocatalytic and photocatalytic ozonation processes include formic acid, acetic acid, benzyl alcohol, benzaldehyde, p-cresol, hydroquinone, and benzoic acid. Given the intermediates and the dominant oxidants detected in the aforementioned process, the possible toluene degradation pathway by the utilized process was suggested.

Control of combustion phasing and operating range extension of natural gas PCCI engines using ozone species

There are two major issues that restrain premixed charge compression ignition (PCCI) engines from being widely employed for industrial applications: difficulties in combustion controllability and limited operating range. These restrictions become even more severe when the engine runs with a very low reactivity fuel, such as natural gas (NG). Ozone gas, which is a species with a very high level of chemical reactivity, can be utilized to control and enhance the combustion process in the PCCI combustion strategy. In the present study, coupled multidimensional computational fluid dynamics (CFD) with proper detailed chemical kinetic mechanisms is employed to investigate the effects of ozone addition to the intake air and fuel mixture in a PCCI engine with different intake temperatures and equivalence ratios. It can be inferred from the results that combustion phasing advancement is in a direct proportion to the amount of ozone addition. It is seen that even low amounts of ozone (10 ppm) have considerable influences on the engine performance and emissions. The results show that adding 1000 ppm ozone makes it possible to decrease the needed initial temperature for PCCI combustion by 80 K. The results also reveal that ozone addition makes it possible to run engine with ultra lean fuel mixtures. It can be concluded that adding controlled amounts of ozone can assist in controlling PCCI engines and also extend operating range of the engine to lower intake air temperatures and also leaner fuel mixtures.

Synergistic effects of trace concentrations of hydrogen peroxide used in a novel hydrodynamic cavitation device allows for selective removal of cyanobacteria

Here, we present an improved and verified rotating hydrodynamic cavitation device (RHCD) inspired by so-called cavitation heaters. The cavitation efficiency of the device is adjustable by rotation speed and flow rate and can be modified for selective removal of cyanobacteria from water with only temporal effect on algal growth or metabolic activity. Previous hydrodynamic cavitation devices have required several cycles to achieve cyanobacterial elimination (12–200 cycles, 5–200 min of treatment), while the RHCD is capable to remove 99% of cyanobacteria after a single cycle lasting 6 s. The device efficiency at cyanobacterial removal was synergistically enhanced through the addition of trace concentrations of hydrogen peroxide (45–100 µM H2O2), levels 10–1000 times lower than those used in previous studies. The RHCD is also capable to increase temperature, an additional advantage for potential technological applications. We discuss the potential use of this device over a broad spectrum of technological processes, and especially regarding the addition of hydrogen peroxide, ozone, or ferrates, which could open new areas in advanced oxidation technologies. It could also be used as an alternative or as a complement to sonochemical, microwave-assisted or electrochemical methods in chemical engineering processes requiring treatment of large volumes of liquids.

Investigation of Combustion Enhancement by Ozone in a Constant-Volume Combustion Bomb

This paper presents both experimental and numerical studies to investigate the impact of ozone concentration on a methane/air mixture combustion process. The experiments were conducted in a constant-volume combustion bomb at elevated initial pressures. Combustion pressure history, combustion duration, and burning rate were obtained at different air/fuel ratios, initial pressures, and ozone mixing ratios. The results suggested that ozone addition promoted combustion by increasing peak pressure and peak burning rate and decreasing combustion duration. Chemical kinetic calculation was carried out to assist in the understanding of how ozone enhanced the combustion process. The calculation results revealed that the dominant production and consumption reactions were enhanced by ozone addition. The promotion effect of ozone on the combustion process was mainly caused by the O atom decomposed from ozone. With ozone addition, the concentration of O, H, OH, and HO₂ increased more obviously in the early stage of the combustion process, and ozone mainly played an important role at the beginning of the mixture oxidation.

Improvement of heat & mass transfer with added ozone into drying air on corn-soy

Corn and soy have wide-ranging uses in food and biofuel industries due to its nutritional and energetic properties. In the present work, artificial drying experiments with hot air convection in different temperatures (30, 40 and 50 °C) were carried out with the addition of ozone (5, 10 and 15 min) applying a central composite design (CCD). The effective diffusion coefficient Deff as thermodynamic properties was evaluated with and without the incorporation of ozone into drying air on corn and soy. The CCD showed different Deff values and a numeric model was fitted to moisture diffusion during the drying-ozonation process (DOP) on corn-soy. Activation energy decreased from 43.90 to 35.20 kJ mol−1 for corn and 38.23 to 34.29 kJ mol−1 for soy when ozone was added into the drying air; similar observation occurred to enthalpy and entropy. Thus, the drying-ozonation process can be useful for technological purposes for energy improvement during postharvest stages, as well as maintaining the quality of cereal products and design of new dryers.

Damköhler Number Analysis on The Effect of Ozone on Autoignition and Flame Propagation in Internal Combustion Engines

Ozone-assisted combustion has shown promise in stabilizing combustion and extending operating range of internal combustion engines. However, it has been reported that sensitivity of ozone quantity on combustion varies significantly depending on combustion modes. For example, autoignition-driven combustion in homogeneous charge compression ignition (HCCI) engine was found to be highly sensitive to the ozone concentration, and up to 100 ppm was found to be sufficient to promote combustion. On the other hand, flame propagation in spark-ignition (SI) engine has been reported to be much less sensitive to the ozone amount, requiring ozone concentration about 3000 ∼ 6000 ppm to realize any benefit in the flame speed. A better understanding of the ozone sensitivity is required for combustion device design with ozone addition. In this study, a Damköhler number analysis was performed to analyze the vast difference in the ozone sensitivity between autoignition and flame propagation. The analysis showed that, for ozone to be effective in flame propagation, the contribution of ozone on chemistry should be large enough to overcome the diffused radical from the oxidation layer. It is expected that similar analysis will be applicable to any additives to provide an understanding of their effect.

The combination of coagulation and ozonation as a pre-treatment of ultrafiltration in water treatment

Ultrafiltration (UF) technology is considered an efficient water treatment method. In recent years, researchers have been committed to enhancing the treatment efficiency of UF and alleviating membrane fouling. An effective method is to achieve this is through the use of coagulation as a pre-treatment to UF; however, during a long term operation, membrane fouling can occur due to the residual organic matters and the generation of microorganisms. In this study, we combine coagulation and ozonation as a pre-treatment of UF and compare four types of pre-treatment: coagulation, ozonation, coagulation followed by ozonation (C–O) and ozonation followed by coagulation (O–C). Results showed that ozonation alone did not perform well. Both combinations of coagulation and ozonation enhanced the organic matter removal efficiency, although membrane fouling was lowest following the C–O pre-treatment as the microbial load was reduced. While a slight increase in the yield of disinfection by-products was observed with the addition of ozonation, the concentration remained below the Chinese standard for tap water quality (100 μg/L).

Experimental assessment of ozone production by multichannel plasma discharges for automotive applications

Ozone addition has come under study as a means of controlling ignition timing in low temperature combustion using highly dilute homogeneous mixture. In this context, this work aims to improve ozone production from air and simulated exhaust gas recirculation (EGR) in a homogeneous charge compression ignition engine using a cold plasma reactor based on multichannel dielectric barrier discharges. Ozone concentration was investigated as a function of energy deposition, gas characteristics, and distance from the source to measurement points. At a given specific input energy, experimental outcomes indicate a relatively high influence of the feeding EGR composition (O2–N2–CO2–CH4–H2O) and flow rate on the ozone production. However, no changes within experimental accuracy in ozone concentration were seen when changing the distance plasma-measurement points, allowing us to find the optimum position of the plasma reactor with respect to the engine inlet. In air, ozone concentration increased from 120 ppm to 1600 ppm, as the flow rate decreased from 200 to 2 slm. At a given voltage set point, the increase in gas pressure causes the decrease in energy deposition and thus the ozone concentration. In EGR mixtures, the lowest ozone concentration tends to stabilize around 50 ppm, which is acceptable for LTC applications.

Visible light photoelectrocatalysis for wastewater treatment using bifacial N-TiO2/Graphene/Ho2O3/Titanium nanocomposite: Artificial neural network modeling and evaluation of ozone addition

In this paper, N-TiO2/Graphene/Ho2O3/Titanium bifacial nanocomposite electrode was prepared. First, the effect of Ho2O3 to N-TiO2 wt.% in the nanocomposite preparation matrix was investigated through studying visible light photoelectrocatalysis process in industrial wastewater decolorization. Characterizations of optimum catalyst were performed using DRS, XRD, SEM and EDX analyses. Then, the effect of operating variables i.e. catalyst dosage (electrode number(s)), wastewater pH, applied bias potential, visible light power and contact time on the extent of wastewater decolorization was investigated by the visible light photoelectrocatalysis process. It was observed that almost 80% wastewater decolorization was achieved using the photoelectrocatalysis at the optimum conditions by N-TiO2/Graphene/(10%) Ho2O3. Artificial neural network was used for model the photoelectrocatalysis process and determine the relative importance of investigated operating variables. It was also established that combination of photoelectrocatalysis with ozonation yielded 100% decolorization in 90 min and 96% COD removal in 270 min under the optimized conditions. Moreover, the catalyst sheet was enough stable to be used in all wastewater treatment experiments.

Ignition control in a gasoline compression ignition engine with ozone addition combined with a two-stage direct-injection strategy

To control the ignition timing in a gasoline compression ignition (GCI) engine, ozone (O3) was introduced into the intake air. The O-radicals are decomposed from the O3 above 550 K during the compression stroke, and combine into oxygen (O2) in a very short time. The authors adopted two-stage direct injection to mix the fuel injected into the cylinder at very early timings with the O-radicals, before a reduction of the O-radicals would take place. The ignition timing of the second fuel injection for the main combustion is controlled by the heat release from the first fuel injection. In this paper, engine experiments were performed to examine the feasibility of the ignition control with a primary reference fuel, octane number 90 (PRF90). The O3 concentration, the quantity, and the timing of the first injection were changed as experimental parameters. The results showed that a very small quantity of O3, tens of ppm, is sufficient to promote the heat release of the first injected fuel. The heat release increases with the O3 concentration and the quantity of fuel in the first injection. The addition of O3 has no other impact on the ignition when the first injection timing is retarded to around −40°CA ATDC. In this manner, it is possible to control the ignition delays and to alter the combustion state from typical diesel combustion to premixed compression ignition combustion.

Evaluation of a Pilot Anaerobic Secondary Effluent for Potable Reuse: Impact of Different Disinfection Schemes on Organic Fouling of RO Membranes and DBP Formation

Anaerobic biological secondary treatment has the potential to substantially reduce the energy cost and footprint of wastewater treatment. However, for utilities seeking to meet future water demand through potable reuse, the compatibility of anaerobically treated secondary effluent with potable reuse trains has not been evaluated. This study characterized the effects of different combinations of chloramines, ozone, and biological activated carbon (BAC), applied as pretreatments to mitigate organic chemical fouling of reverse osmosis (RO) membranes, and the production of 43 disinfection byproducts (DBPs). The study employed effluent from a pilot-scale anaerobic reactor and soluble microbial products (SMPs) generated from a synthetic wastewater. Ozonation alone minimized RO flux decline by rendering the dissolved organic carbon (DOC) more hydrophilic. When combined with chloramination, ozone addition after chloramines maintained a higher RO flux. BAC treatment was ineffective for reducing the pressure and energy requirements for a set permeate flux. Regardless of pretreatment method prior to RO, the total DBP concentrations were <14 μg/L upstream of RO. After treatment by RO, the UV/hydrogen peroxide advanced oxidation process, and chloramination, the total DBP concentrations were ≤5 μg/L. When DBP concentrations were weighted by metrics of toxic potency, the total DBP calculated toxicity was 4-fold lower than observed previously in full-scale potable reuse facilities receiving aerobically treated secondary effluent. The RO fouling and DBP formation behavior of anaerobic SMPs were similar to that of the pilot-scale anaerobic effluent. The results of this study are promising, but more research is needed to evaluate whether anaerobic effluent is suitable as an influent to potable reuse trains.

Reactivity of the anti-Criegee intermediate of β-pinene with prevalent atmospheric species

The reaction of the anti-Criegee intermediate (anti-CI) of β-pinene with prevalent atmospheric species has been investigated using quantum-chemical calculations. The calculations predict that the ozone addition to CI occurs with a Gibbs energy of activation (ΔG‡) of 77 kJ mol−1. The CI reaction with CH4, C2H6, NH3, and chlorinated ethanes is not energetically favored and has high barriers in the range of 253 to 362 kJ mol−1. The more probable reaction with SO2 forms a secondary ozonide (SOZ) intermediate with a barrier of 9 kJ mol−1, while the ΔG‡ to dissociation is 101 kJ mol−1. Among the reactions studied, the one with $$ \dot{\mathrm{N}} $$ O had the lowest ΔG‡ for its rate-determining step. The ΔG‡ values of the first step addition of O3, NH3, SO2, and $$ \dot{\mathrm{N}} $$ O do not exceed 84 kJ mol−1. In contrast to previous predictions, the $$ \dot{\mathrm{N}} $$ O reaction with the CI did not proceed through cyclic adduct formation. The findings agree with previous studies which found that CIs act as oxidizing agents, converting SO2 to SO3, and $$ \dot{\mathrm{N}} $$ O to $$ \dot{\mathrm{N}} $$ O2. Thus, the CIs of biogenic compounds should be added to the list of atmospheric oxidizing agents along with O3, NO3, and OH radicals.

The Addition of ViriditecTM Aqueous Ozone to Peracetic Acid as an Antimicrobial Spray Increases Air Quality While Maintaining Salmonella Typhimurium, Non-pathogenic Escherichia coli, and Campylobacter jejuni Reduction on Whole Carcasses.

Currently, the most utilized antimicrobial in processing facilities is peracetic acid, PAA; however, this chemical is increasingly recognized as a hazard to human health. Preliminary evidence suggests that ozone, when introduced in a specific manner, can reduce the noxious nature of PAA. Therefore, the objective of the current study was to evaluate the efficacy of TetraClean Systems aqueous ozone, O3, in combination with PAA as an antimicrobial spray on whole chicken carcasses. This trial used 70 whole hen carcasses (7 treatments; 10 replications) that were inoculated in a 400 mL cocktail containing Salmonella, Escherichia coli, and Campylobacter (107 CFU/mL) and allowed to adhere for 60 min at 4°C for a final concentration of 105 to 106 CFU/g. The experimental 5 s (4×) spray treatments included: a no treatment negative control, TW; TW + O3 (10 ppm), TW + PAA (50 ppm), TW + PAA (500 ppm), TW + O3 + PAA (50 ppm), and TW + O3 + PAA (500 ppm). During treatment application, ambient PAA vapor was measured with a ChemDAQ Safecide PAA vapor sensor. After treatment, carcasses were immediately rinsed in 400 mL of nBPW for 2 min. Following rinsing, the dot method was utilizing for enumeration with 10 μL of rinsate being serially diluted, plated on XLD and mCCDA agar, and incubated aerobically at 37°C for 24 h or microaerophilically at 42°C for 48 h. Log-transformed counts were analyzed using ANOVA in JMP 14.0. Means were separated using Tukey’s HSD when P ≤ 0.05. There was a significant treatment effect among Salmonella, E. coli, and Campylobacter counts, and a significant treatment effect among ambient PAA (P < 0.05). TW + O3 + PAA (500 ppm), reduced Salmonella significantly compared to TW (5.71 and 6.30 log CFU/g). Furthermore, TW + PAA (500 ppm), reduced the presence of E. coli significantly compared to TW or no treated control (5.57 and 6.18 log CFU/g). Also, TW + PAA (50 ppm), TW + PAA (500 ppm), and TW + O3 + PAA (500 ppm) significantly reduced Campylobacter compared to carcasses not treated (4.80, 4.81, and 4.86 log CFU/g). Lastly, the addition of ozone significantly reduced the ambient PAA when O3 was added to 500 ppm of PAA, as TW + O3 + PAA (500 ppm) produced less ambient PAA than TW + PAA (500 ppm) (0.052 and 0.565 ppm). In conclusion, the addition of ozone to PAA may demonstrated the ability to effectively reduce ambient PAA, thus increasing employee safety.

Kinetic Enhancement of Microchannel Detonation Transition by Ozone Addition to Acetylene Mixtures

The kinetic acceleration of deflagration-to-detonation transition (DDT) of acetylene/oxygen mixtures at lean conditions in a microchannel is investigated using ozone addition. Equivalence ratios and ozone concentration are varied to understand the thermal and kinetic impacts, respectively, on DDT transition. The addition of ozone is found to drastically reduce the DDT time and onset distance via kinetic enhancement. The results show that, with a small amount of ozone addition, the DDT time is reduced by up to 77.5%; whereas it only slightly increases the Chapman–Jouguet velocities by 6.7%. Moreover, the addition of 1% ozone extends the DDT limit from equivalence ratios of 0.3 to 0.2. Furthermore, it is observed that ozone addition has a much larger effect on DDT time than the increase of the equivalence ratio. The present results suggest that, for accelerating DDT, the kinetic effect via ozone addition is much greater than the thermal effect. By using the ozone dissociation chemistry with an acetylene kinetic model (HP-Mech), the kinetic effect of ozone on DDT acceleration is examined. The present finding provides new insight into controlling engine knocking and detonation transition in detonation engines.

Isolating the effect of induction length on detonation structure: Hydrogen–oxygen detonation promoted by ozone

The effect of ignition promoters on H2O2 detonation structure was evaluated with one-dimensional ZND calculations and experimental detonation cell measurements. Test conditions include a sweep of ozone concentration (up to 3000 PPM by mole), initial pressure (10 to 30 kPa), equivalence ratio (0.4–1.5), Ar and N2 dilution (up to 50%), and CF3I concentration (up to 3000 PPM). The ZND calculations demonstrate that ozone addition reduces induction length without affecting heat release length or thermodynamic properties such as CJ speed, allowing for a unique evaluation of the effect of ignition delay on detonation structure. Experimentally and within the conditions tested, ozone addition acts to reduce detonation cell size by up to 70%. In addition, measured cell width is found to better correlate with induction length than with total reaction length, defined as induction length plus exothermic length. The results confirm that the detonation structure is controlled largely by chemical length scales. Also studied is the addition of CF3I, which is traditionally used as a fire suppressant. Although at high concentrations CF3I displays a radical scavenging function, at the concentrations considered in the current work, CF3I also acts as an ignition promotor due to the production of the I atom, which promotes chain branching during ignition. Finally, the ozone and CF3I additives were found to have, at most, a minor effect on cell regularity.