Higher Burning Rate Research Articles

Hydrogen generation, and its venting from nuclear reactors

Reactor fires and explosions are centred around the use of graphite as a neutron moderator, and the high temperature generation of hydrogen in reactions of steam and zirconium. An alternative to uncontrolled, excessive, build-up of pressure within the reactor, is the provision of a buffer vessel, within which there is permeable membrane separation of hydrogen from radioactive products. Possible rates of production of hydrogen are compared with the rates at which it might be separated and then flared in lifted jet flames, giving high burn rates. There are few data on the behaviour of H2 flares in air cross flows, and this is synthesised from available data for other flammable gases. Destruction of hydrogen lifted jet flames by the cross flow of atmospheric air would seem to be less likely than for hydrocarbon jet flames. The H2 relationships are different from those of the hydrocarbons, due to the higher chemical reactivity of H2, its small laminar flame thickness, reduced air requirement, higher acoustic velocity, and minimal flame lift-off distance. Flaring with micro-tubes might be advantageous for integrating flaring with membrane hydrogen separation, whilst high mass flow rates can be achieved with large diameter flares in the lifted flame, supersonic regime.

Energetic ionic liquid hydroxyethylhydrazinium nitrate as an alternative monopropellant

The propellant synthesis community is constantly looking for green alternative monopropellants. Energetic ionic liquids have several attractive properties such as high energy content, high bulk density, low vapor pressure, high thermal stability, wide liquidus range, low corrosiveness, low toxicity, and ease of handling. The combustion characteristics of an energetic ionic liquid hydroxyethylhydrazinium nitrate (HEHN) was conducted in a pressurized chamber. The performance of HEHN was compared to that of the monopropellant Otto fuel II (OF-II) typically used for torpedo-propulsion. A liquid strand combustion study was performed in an atmosphere of air and nitrogen with chamber pressures varying from 10 to 90 bar. Regressing surface profiles and subsequent burning rates were obtained at different chamber pressures. A B-type thermocouple of 46 µm wire diameter was used to measure the monopropellant flame temperature of HEHN. Thermogravimetric analysis was performed to study the thermal decomposition of HEHN to understand its thermal stability and Fourier transform infrared spectroscopy (FTIR) was utilized to determine the possible reasons behind the high burning rates of HEHN. The gains in the specific impulse and density specific impulse coupled with enhanced burning rates and reasonable thermal stability are expected to establish HEHN as a frontrunner for propulsion and power-generation in oxygen-deficient scenarios.

Exploring the Mechanical, Thermal and Ballistic Effects of Carbon Black on Paraffin-Based Fuels for Hybrid Rocket Motors

Paraffin-based hybrid propellants have been developed due to their high burning rate. However, they have some disadvantages such as inadequate mechanical properties and unstable burning. In this work, paraffin fuel grains with carbon black were evaluated to study the possible effects of this additive on the mechanical, thermal and ballistic properties of these grains, besides the already known effect of minimizing the thermal radiation inside the motor. The grains with carbon black showed significant changes in the thermal degradation profile and substantial improvement in burn stability.

UJI KARAKTERISTIK PEMBAKARAN HASIL DESTILASI KARET BEKAS-MINYAK DIESEL DENGAN MENGGUNAKAN DROPLET

This study aims to look at the combustion characteristics of destillates of used rubber and diesel oil using droplet, the characteristics observed were flash point, ignition delay time, burning rate, and visualization (hight) of fire. Variation in mix RCO 10%, 20%, 30%, 40%, 50%. The tool used is a tool designed by researchers. The result of the flash point study found that the highest velue was found in the mixture of RCO 10% which was 105,7oC and the lowest value was found in mixture of 50% which was 56,6oC. then the highest value of the ignition delay time is in the mixture of 10% which is 1,64 seconds and the lowest value in the mixture is 30% which is 0,98 seconds, then are result of the highest burning rate are found in the mixture 0f 40% which is 3,83 seconds and lowest value is mixed with 20% which is 3,1 second. Then the highest level of fire in the mixture of 10% is 82,3 mm and the lowest is in the mixture of 50% which is 73,2 mm. Keywords: Rubber Compound Oil, Droplet, Flash Point, Ignition Delay Time, Burning Rate

Effects of metal oxide nanoparticles on combustion and gas-generating performance of NaN3/Al composite powders ignited using a microhotplate platform

We investigated the effects of different metal oxide (MO) nanoparticles (e.g., CuO, KIO4, Fe2O3) on the combustion and gas-generating characteristics of sodium azide microparticle (NaN3 MP; gas-generating agent) and aluminum nanoparticle (Al NP; heat source) composite powders. The NaN3 MP/Al NP/MO NP composite powders were stably ignited using a microhotplate (MHP) heater. The addition of CuO and KIO4 to the NaN3 MP/Al NP composite powders resulted in relatively high burn rates and high pressurization rates upon MHP-assisted ignition. This suggests that the highly reactive CuO and KIO4 NPs significantly increased the combustion of the Al NPs; as a result, sufficient heat energy was generated via the active aluminothermic reaction to thermally decompose the NaN3 MPs. Finally, the gas generating properties of NaN3 MP/Al NP composite powders mixed with various MO NPs were tested using homemade inflatable small airbags. The airbags were fully inflated within ~20 ms when CuO and KIO4 NPs were added to the NaN3 MP/Al NP composite powders. However, the addition of Fe2O3 NPs to the NaN3 MP/Al NP composite powder resulted in a slow and only partial inflation of the airbag due to an incomplete aluminothermic reaction, which was due to a slow combustion reaction between the Al NPs and relatively weak oxidizer of the Fe2O3 NPs. This suggests that the rapid, stable, and complete thermal decomposition of NaN3 MP/Al NP composites can be effectively achieved by employing highly reactive nanoscale oxidizers.

The Effect of Electronic Module Utilization for Biomass Briquettes Experiment using Cocoa Shells and Sea Mango to Vocational School Students

The aims of this study are to identify the best carbon particle size and composition variations and to identify differences in student learning outcomes using demonstration experimental methods with learning video and e-module about the making of cocoa (Theobroma cacao L) shell and sea mango (Cerbera manghas) based bio charcoal briquettes. Briquetting process is carried out by drying raw materials, carbonizing, grinding, sieving, briquetting, and drying. Thirty agribusiness vocational students are selected as the subject to see the effectiveness of learning video and e-module for understanding the bio charcoal briquetting process. Students' understanding is assessed by pretest, posttest after learning with a video, and posttest after learning with e-module. The results show that briquettes with high sea mango concentrations have a high burning rate, water boiling test, and low specific fuel consumption. Briquettes containing small particle sizes have high values of relaxed density, relaxation ratio, and percentage of durability index. Based on the result, it can be concluded that the e-module is more effective than learning video for the student because it can cover wider and deeper materials. However, giving learning video to the students is still necessary so they may have a better visual experience regarding the briquetting process.

Experimental study on oxy-fuel combustion behavior of lignite char and carbon transfer mechanism with isotopic tracing method

In this work, the conventional combustion in O2/Ar and O2/CO2 atmospheres at temperatures of 700–1000 °C and isotopic tracing experiments at 700–800 °C were conducted respectively in a micro fluidized bed reactor to clarify the conversion characteristics of lignite char and influence mechanism of elevated CO2 concentrations. The isotopic method employing C18O18O provides an intuitive insight into the CO2 gasification behavior by tracking the evolution of the 18O atom throughout the oxy-fuel combustion. The results reveal that char conversion rate significantly reduces when the atmosphere is switched from O2/Ar to O2/CO2 at low temperature range (e.g. 700–800 °C), primarily caused by thermo-physical properties of CO2. However, at higher temperature range (e.g. 950–1000 °C), the C-O2 reaction is limited by the external O2 diffusion and the C-CO2 reaction contributes to the carbon consumption, resulting in a higher combustion rate, especially at O2-deficient conditions. The presence of the atomic 18O in the product C18O16O originating from C18O18O confirms that CO2 is indeed involved in the whole oxy-fuel combustion process and the overall reaction could be described as C + C18O18O+16O16O → 2C18O16O. Besides, total contributions to carbon conversion by the C-CO2 reaction decrease as O2 concentrations and particle sizes increasing.

Increasing the burning rate through energetic compound tuning: Hybrids of the furazan and [1,2,4]triazolo[4,3-b][1,2,4,5]tetrazine ring systems

Combustion behavior, flame structure, and thermal decomposition of hybrid compounds based on tetrazine, triazole and furazan rings have been described. It has been found that the introduction of [1,2,4]triazolo[4,3-b][1,2,4,5] tetrazine core into the molecules of energetic materials allows obtaining energetic hybrid compounds with combustion rates greater than those of common explosive HMX and RDX. These hybrids have good thermal stability, which depends on the substituent at the furazan ring, and not on the triazolotetrazine core. Combustion with thermocouple-aided studies has shown that all triazolotetrazine hybrids are nonvolatile and have high burning surface temperatures which cause their condensed-phase combustion mechanism. Based on the condensed-phase combustion model, the constants of the leading combustion reactions were determined. It turned out that the burning rates of nitrogen-rich compounds of this study are controlled by the decomposition kinetics at surface temperature. It is shown that the two-stage decomposition of substances leads to the appearance of two regions in the burning rate-pressure dependences that related to each other by the instability region. The incorporation of the triazolotetrazine moiety into an energetic compound is a promising way to design new propellant components with high burning rates and attractive performance.

Kinetic modeling of PM combustion with relative velocity at low-temperature and numerical simulation of continuous regenerating type PM removal device that uses a fluidized bed

The size of particulate matter (PM) generated by combustion has decreased with the improvement of combustion technology. While small PM has a significant negative impact on the human body, it is difficult for a conventional PM removal device to collect small PM. We developed a fluidized bed type PM removal device with a focusing adhesion force. This device collects small PM effectively and can be operated as a continuous regeneration device at low temperature. To further develop this device, it is important to investigate the PM combustion characteristics in this device. The kinetic model constructed in conventional thermogravimetry could not accurately represent the combustion rates of the solid fuel in the fluidized bed. Therefore, a new thermogravimetric apparatus was constructed in this study that generates the direct collision of air with carbon to reproduce the fluidized bed combustion. The influence of the relative velocity between PM and gas on the combustion rate was investigated. The effect of relative velocity was represented as the mass transfer coefficient of kinetic model. It is observed that the combustion rate shows Arrhenius behavior, and kinetic parameters were determined by fitting. The kinetic model was applied to the numerical simulations of the PM removal device. The numerical collection efficiency was in good agreement with the experimental data. PM adhesion and combustion characteristics were investigated in numerical simulations. It is observed that the adhesion rate is high at a low void fraction and that the combustion rate is high at a high relative velocity. The PM combustion amount is high for the high adhesion and combustion rates. The total combustion amount is determined to be 55% of the total amount of PM deposition after 180 min at each set of conditions.

Numerical study on the approach for super-high thermal efficiency in a gasoline homogeneous charge compression ignition lean-burn engine

The approach for achieving super-high thermal efficiency in a gasoline homogeneous charge compression ignition lean-burn engine was studied using numerical simulation. A model engine was designed based on the split cycles, including the low-pressure cycle consisted of the turbocharger system and the high-pressure cycle controlled by the variable effective compression ratio ( ε) and the exhaust gas recirculation (EGR). Based on the model engine, load (L) – Φoxy (F) – EGR (E) – ε (E) cooperative control strategy was proposed to optimize the thermal efficiency and its interactive mechanism was clarified. The results revealed that the core of the load (L) – Φoxy (F) – EGR (E) – ε (E) strategy was the simultaneous optimization of the combustion process and the specific heat ratio ( γ) contributing to the piston work maximization. The optimum combustion phase was found in the range of 4°–9° crank angle after top dead center, and highest combustion rate under the rough combustion restriction was also required. Under this precondition, reducing ε to retard the combustion phase appropriately could mitigate the EGR usage to improve the γ. Based on the load (L) – Φoxy (F) – EGR (E) – ε (E) strategy, increasing the load was found to improve the thermal efficiency effectively by reducing the heat transfer loss. The highest brake thermal efficiency of 50% was reached when the gross indicated mean effective pressure was increased to 15 bar under the conventional engine condition. Further increasing the gross indicated mean effective pressure to 35 bar with elevated peak cylinder pressure of 400 bar could improve the brake thermal efficiency to 54% under the enhanced mechanical strength condition. To pursue super-high thermal efficiency, the approach of thermal insulation for the engine was proved to be more effective. It showed the potential to achieve the super-high brake thermal efficiency over 60% and maintain clean combustion by adopting the load (L) – Φoxy (F) – EGR (E) – ε (E) strategy in the model engine with thermal insulation and high mechanical strength.

Effect of extractives on the physicochemical properties of biomass pellets: Comparison of pellets from extracted and non-extracted sycamore leaves

Physicochemical properties of biomass pellets were compared following their preparation from extracted and non-extracted sycamore leaves. The goal was to achieve high-quality biomass pellets. Batches of pellets were prepared at different moisture contents and pressure. The properties, including pellet density, diametric compressive strength, and combustion performance, were analyzed. Pellets produced from extracted leaves had higher pellet density (between 1125 and 1250 kg·m-3) compared to those made from non-extracted leaves. In addition, data of the combustion experiment showed more weight loss in extracted leaves’ pellets and a higher burning rate (9.54%·min-1) than that of non-extracted leaves’ pellets (8.47%·min-1). Also, the pellets made from extracted leaves could be ignited and burned easily compared to non-extracted leaves. However, the diametric compressive strength was not always higher in extracted leaves’ pellets compared to non-extracted. In general, it was concluded that extraction could increase the pellet density and improve combustion performance but did not fit the purpose to increase the diametric compressive strength. The analysis and conclusions can provide a reference for the production of high-quality biomass pellets.

Experimental study on jet ignition and combustion processes of natural gas

Pre-chamber-type ignition system can provide multiple ignition points, high ignition energy and strong turbulent disturbance, which are beneficial for the ignition and flame propagation of natural gas engines especially in lean-burn mode. The impacts of pre-chamber geometric parameters and premixed gas parameters on ignition and the consequent combustion processes were investigated with optical diagnostics in combination with pressure acquisition in a constant volume chamber. Experimental results showed that a larger pre-chamber orifice diameter caused earlier ignition timing and lower ignition position. When the ignition position was at the center of the main chamber, the flame propagation rate of the mixture and the pressure rise rate in the main chamber reached their highest values. The flame would quench when the orifice diameter was smaller than a certain value. Increasing the volume of the pre-chamber led to a retarded appearance timing of the jet in the main chamber, however, more combusting mixture and wider distribution range could provide higher ignition energy, resulted in a higher combustion rate. When the fuel/air equivalence ratio was increased in the pre-chamber, the ignition ability was enhanced and lean burn limit in the main chamber was expanded. The initial pressure and temperature of premixed gas played important roles in chemical reaction rate in the main chamber.

Ferric Oxide Colloid: A Novel Nano-catalyst for Solid Propellants

Even though ammonium perchlorate (AP) is universal oxidizer; its initial decomposition is an endothermic process. This feature could render high burning rate regime. Ferric oxide particles are candidate catalyst for AP decomposition. This study reports on sustainable fabrication of colloidal ferric oxide particles. Ferric oxide particles demonstrated stable colloidal suspension with zeta value of 38.5 mV. TEM micrographs revealed mono-dispersed particles of 3 nm average particle size. XRD diffractogram demonstrated highly crystalline structure. Ferric oxide nanoparticles were coated with AP particles via co-precipitation technique. The efficiency of ferric oxide particles as nano-catalyst for AP was evaluated using DSC and TGA. Ferric oxide particles reduced AP initial endothermic decomposition by 40%. The following two exothermic decomposition peaks were combined together into one single peak with an increase in total heat release by 47.5%. These novel catalytic features can extend applications of ferric oxide particles in catalyzed combustion reactions.

A System Dynamics Model Examining Alternative Wildfire Response Policies

In this paper, we develop a systems dynamics model of a coupled human and natural fire-prone system to evaluate changes in wildfire response policy. A primary motivation is exploring the implications of expanding the pace and scale of using wildfires as a forest restoration tool. We implement a model of a forested system composed of multiple successional classes, each with different structural characteristics and propensities for burning at high severity. We then simulate a range of alternative wildfire response policies, which are defined as the combination of a target burn rate (or inversely, the mean fire return interval) and a predefined transition period to reach the target return interval. We quantify time paths of forest successional stage distributions, burn severity, and ecological departure, and use departure thresholds to calculate how long it would take various policies to restore forest conditions. Furthermore, we explore policy resistance where excessive rates of high burn severity in the policy transition period lead to a reversion to fire exclusion policies. Establishing higher burn rate targets shifted vegetation structural and successional classes towards reference conditions and suggests that it may be possible to expand the application of wildfires as a restoration tool. The results also suggest that managers may be best served by adopting strategies that define aggressive burn rate targets but by implementing policy changes slowly over time.

Optimizing the Shape of a Compression-Ignition Engine Combustion Chamber by Using Simulation Tests

Abstract Modern solutions used in compression-ignition internal combustion engines are quite similar to each other. The use of high-pressure, direct fuel injection results in high combustion rates with controlled exhaust emissions. One of the combustion system quality criteria is to obtain adequately high thermodynamic indicators of the combustion process, which are obtained through, among others, the right combustion chamber geometry. Its shape influences the fuel atomization process, turbulence of fuel dose, evaporation and the combustion process. Optimizing the combustion chamber shape is one of the decisive factors proving the correct execution of the combustion process. This article presents the methodology of choosing the combustion chamber shape (changes of three selected combustion chamber dimensions) by using the optimization methods. Generating multidimensional data while maintaining the correlation structure was performed by using the Latin hypercube method. Chamber optimization was carried out by using the Nelder-Mead method. The combustion chamber shape was optimized for three engine load values (determined by the average indicated pressure) at selected engine operating conditions. The presented method of engine combustion chamber optimization can be used in low and high speed diesel propulsion engines (especially in maritime transport applications).

Performance of advanced composite solid rocket propellants based on novel oxidizers

Three novel high energy dense oxidizers (HEDO), Bis(2,2,2-trinitroethyl)oxalate (BTNEOx), 2,2,2-Trinitroethyl-nitrocarbamate (TNENC), 2,2,2-Trinitroethyl-formate (TNEF) have been prepared and studied as oxidizers in composite solid rocket propellants (CSRPs). For comparison, traditional CSRP containing ammonium perchlorate (AP) bonded by hydroxyl-terminated polybutadiene (HTPB) binder system was studied. The optimum oxidizer percentage with respect to the specific impulse was determined using the thermodynamic code (EXPLO5_V6.03). In addition, the optimum oxidizer mixture based on the novel oxidizers with AP was studied. The combustion properties and gaseous products of the optimum propellant compositions were calculated. A selected composition was prepared in the lab. scale and the burning rate was measured by the strand burner method. It was concluded that TNEF based propellant possess the maximum specific impulse of all the studied compositions. In addition, TNEF based propellant has a higher burning rate than the traditional CSRP composition.

An alternative approach to improve burning rate characteristics and processing parameters of composite propellant

Modification in burn rate of composite solid propellant has become a necessity of a mission. Burn rate can be modified by various mean viz. (i) tailoring the ammonium perchlorate (AP) particle size, (ii) use of nano-sized particles and (iii) incorporating burn rate modifiers. Literature discusses about various burn rate modifiers. Out of these, Iron oxide (Fe2O3)/IO is the well known burn rate enhancer. Here a systematic study was carried out by undertaking experiments at varying levels of IO in composite propellant compositions. This paper attempts to understand the effect of IO content and its specific surface area on burn rate characteristics of composite propellant. This study also attempts to find out alternative to ultrafine AP and nano burn rate enhancer to account for high burning rate of composite propellant along with reduced slurry viscosity and longer pot life for easy processing. As ultrafine AP and nano burn rate enhancers have their limitations in terms of (i) high end of mix (EOM) propellant slurry viscosity, (ii) difficulty in propellant processing, (iii) less reproducibility in attaining the similar particle size in each batch results in lesser repeatability in ballistic properties of propellant, (iv) hazards involved in size reduction, (v) limitations in handling, storage and shelf life and also (vi) the higher cost of nano particles. Therefore an extensive experimental study was performed to achieve this objective. In this study, we incorporated two different grades of IO(A) and IO (B) in composite propellant compositions. The average particle size of both grades of IO i.e., A and B are of ∼1 µm. But the specific surface area of IO (B) was about 15 times more than IO (A). The large difference in specific surface area of both IO was due to difference in the manufacturing process. During the manufacturing of IO, the calcination temperature plays very important role in deciding the specific surface area. High specific surface area is obtained if calcination is done at very high temperature (>1773 K). Burning rate measurements were carried out. It was observed that IO is a good burn rate enhancer. Initially, the burn rate increased with the increase in % of IO. But after that only a marginal enhancement in burn rate was observed. It was noticed that though both grades of IO are effective burn rate enhancer but IO(B) was 30% more effective than IO(A). Also it was found that IO(B) is an alternative to ultrafine AP and nano burn rate modifiers. This IO(B) was further used to develop the propellant compositions with high burn rate without incorporating ultrafine AP and nano particles. Viscosity measurement and mechanical properties determination revealed that both the IOs did not much adversely alter the processing characteristics and mechanical properties of propellant.

Effect of Long-Chain Bonding Agent on the Combustion of Composite Propellant and Modification of Combustion Performance Using Nano Additives

ABSTRACT Novel long-chain bonding agent MST was synthesised and introduced into the bonding agent matrix in order to enhance the mechanical properties of composite propellant by improving the interfacial interactions between the bonding agent and solid particles, in order to withstand stresses produced due to combustion loading conditions, changes in environmental condition, transportation and handling without effecting on the ballistic performance. In this work, the replacement of the long-chain MST bonding agent instead of the most famous reference MAPO bonding agent has improved the mechanical properties especially strain value corresponding to stress value which doubling the maximum strain value with an acceptable value of maximum stress with a good value with Young’s modulus in propellant formulations. Different compositions of composite propellant were carried, in order to measure the linear burning rate and to study the effect of the replacing MST bonding agent instead of tradition bonding agent MAPO. Due to the presence of a bonding agent, the burning process of the composite propellant should become more regular and stable burning but it reduces slightly the burning rate as in formulation F2 in which the pressure exponent (n) value reached .067. It should be modifying the reduction in burning rate due to the presence of MST in order to achieve promising burning properties. By using nano-aluminum it was secured improving performance and achieved a high burning rate of the propellant formulations based on MST bonding agent as well as the composite propellant formulations based on MAPO bonding agent. And by using nano-copper chromite the values of the burning rate of composite propellant formulations became greater than those values of formulations based on nano-aluminum with the same weight ratio and particle size, due to the nature of copper chromite and its effect on the binder and the ammonium perchlorate.

Heretophase Ceramics in the Hf–Si–Mo–B System Fabricated by the Combination of SHS and Hot Pressing Methods

This work is devoted to the fabrication of heterophase powder and consolidated ceramics based on hafnium and molybdenum borides and silicides by combining self-propagating high-temperature synthesis (SHS) and hot pressing (HP). Composite ceramic HfB2–HfSi2–MoSi2 SHS powders are fabricated according to the magnesium-thermal reduction flowsheet from oxide raw materials, in which the combustion wave has temperatures of 1750–2119 K and rather high mss combustion rates of 8.4–9.3 g/s. The structure of synthesized SHS powders consists of relative coarse MoSi2 grains up to 10 μm in size, submicron elongated HfB2 grains mainly located inside the MoSi2 grains, and rounded Si precipitates. The composition with a lower boron concentration contains numerous polyhedral HfSi2 grains smaller than 10 μm in size. The resulting powders have an average particle size of ~6 μm with a maximal size up to 26 μm. The phase compositions of the ceramics consolidated by the HP method and synthesized SHS powders are identical. The microstructure of compact samples consists of faceted elongated HfB2 grains 0.5–10.0 μm in size, polyhedral HfSi2 and MoSi2 grains up to 8–10 μm in size, and silicon interlayers. The consolidated ceramics have a high structural and chemical homogeneity, low residual porosity of 1.1–1.7%, high hardness of 11.7–12.6 GPa, and thermal conductivity of 62–87 W/(m K).

Ignition and Combustion Behaviors of High Energetic Polyhedral Boron Cluster

AbstractCompounds containing [B10H10]2− cluster are promising candidates that can be used as high energetic fuels and burning rate modifiers for propellants. The ignition and combustion behaviors of [N(C2H5)4]2B10H10 were investigated using a laser ignition system in air. Results show that [N(C2H5)4]2B10H10 (∼2.0 mm) is ignited with a delay of around 350 ms and threshold ignition energy of 0.7 J at laser ignition power density of 1.14×107 W/m2. Furthermore, the combustion of [N(C2H5)4]2B10H10 in air is found to undergo three stages of decomposition, incomplete combustion of the volatile pyrolytic products, and ejection and combustion of the molten dehydrogenated framework, giving massive smoke and a characteristic pyrotechnic flame.