Lower Flame Temperature Research Articles

Experimental investigation of nitrogen based emissions from an ammonia fueled SI-engine

This study concerns nitrogen based emissions from a hydrogen enriched ammonia fueled SI engine. These emissions deserve special attention as their formation may differ from conventional HC combustion due to the nitrogen content in the fuel. A range of experiments are conducted with a single cylinder 0.612l CFR engine with a compression ratio varying from 7 to 15 using a fuel composition of 80vol% NH3 and 20vol% H2. Wet exhaust samples are analysed with an FT-IR. Emission measurements reveal that nitric oxide stem from other reaction paths than the dissociation of molecular nitrogen. This causes the NO emissions to peak around 35% rather than 10% excess air, as is typical in HC fueled SI-engines. However the magnitude of NO emissions are comparable to that of measurements conducted with gasoline due to lower flame temperatures. Nitrogen dioxide levels are higher when comparing with gasoline, but has a relatively low share of the total NOx emissions (3–4%). Nitrous oxide is a product of NH2 reacting with NO2 and NH reacting with NO. The magnitude is largely affected by ignition timing due to the temperature development during expansion and the amount of excess air, as increased oxygen availability stimulates the formation of the NH2 radical and the levels of NO2 are higher. Under ideal operating conditions (MBT ignition timing) N2O levels are very low. The dominating contributors to unburned ammonia are chamber crevices as the magnitude of these emissions is greatly affected by the compression ratio. However, levels are lower than required in order to eliminate all NOx emissions with a SCR catalyst.

Stabilization and spheroidization of ammonium nitrate: Co-crystallization with crown ethers and spherical crystallization by solvent screening

Although ammonium nitrate (AN) is a clean burning (chlorine free), non-corrosive, low-hazard, low-flame temperature, inexpensive, easily available energetic material and gives maximum gas horse power per unit weight, propellants incorporating AN suffer from three significant drawbacks: (1) polymorphic (phase) transition near ambient temperature, (2) caking and smoke generation upon burning, and (3) poor flowability for packing. The first two disadvantages could be minimized by forming non-hygroscopic, smokeless 1:1 co-crystals of ammonium nitrate–benzo-18-crown-6 (1:1 co-crystals of AN–B18C6) with a melting point of 125–129°C, produced from the antisolvent precipitation method based on the systems of: ethanol–methyl-tert-butyl-ether (MTBE), methanol–ethyl acetate and methanol–MTBE. From the smoke test and burning characteristics, 1:1 co-crystals of AN–B18C6 is smokeless upon heating and exhibits a slower burning rate than the one of AN. Therefore, co-crystallization may become a solid-state modification method in the areas of propellants and explosives. The third drawback could further be eliminated by forming spherical agglomerates of 1:1 co-crystals of AN–B18C6 through the addition of water as a bridging liquid into the co-crystal slurry resulted at the end of the antisolvent precipitation method. Spherical agglomerates of 1:1 co-crystals of AN–B18C6 grown from Phase IV AN powders (0.32mmol) and B18C6 crystals (0.32mmol) in 0.64mL methanol+11.6mL MTBE+0.08mL water gave relatively high yield of 87.3%, high population density of 20.6/cm3, high sphericity, of 0.86, high friability of 100 showing a greater strength, and low angle of repose of 25.2° indicating a good flowability.

A comparative evaluation of gray and non-gray radiation modeling strategies in oxy-coal combustion simulations

Computational fluid dynamic simulations of oxy-coal combustion are demonstrated in a lab-scale furnace and full-scale boiler employing gray and non-gray formulations of recently proposed radiative property models for the gas-phase. The investigated scenarios included: air-firing, oxy-firing with dry and wet flue-gas recycle (FGR). The study confirms that the temperature and wall radiative flux profiles encountered during air firing can be replicated in both dry and wet FGR scenarios through an appropriate selection of (CO2 + H2O)/O2 molar ratios in the oxidizer stream. The computed temperature profiles were in reasonable agreement with the experimental measurements. In the lab-scale furnace, lower flame temperatures and smaller path lengths minimized the differences between the gray and non-gray model predictions. Within the full-scale boiler, large volume pockets were present where the radiation was dominated by the gas-phase. This combined with higher peak flame temperatures and longer path lengths resulted in: a 10% variation between the gray and non-gray radiative fluxes and a 50 K difference in the predicted average outlet gas temperatures.

319 平坦バーナー低温度炎におけるトルエン添加がアルデヒド類生成に及ぼす影響(OS5-4 燃焼技術の基礎と応用研究(4),OS5 燃焼技術の基礎と応用研究)

319 平坦バーナー低温度炎におけるトルエン添加がアルデヒド類生成に及ぼす影響(OS5-4 燃焼技術の基礎と応用研究(4),OS5 燃焼技術の基礎と応用研究)

Analysis of the behaviour of a 4-stroke Si engine fuelled with ammonia and hydrogen

The use of hydrogen as fuel represents a possible solution to reduce greenhouse gas emission from vehicles. Although proper engine running with hydrogen has been widely demonstrated, hydrogen storage onboard of the vehicle is a major problem.A promising solution is storing hydrogen in the form of ammonia that is liquid at roughly 9 bar at environmental temperature and therefore involves relatively small volumes and requires light and low-cost tanks.Ammonia can be burned directly in IC engines, however a combustion promoter is necessary to support combustion. As a matter of fact, the best (and carbon-free) promoter is hydrogen, which has very high combustion velocity and wide flammability range, whereas ammonia combustion is characterised by low flame speed and temperature, narrow flammability range and high ignition energy.The experimental activity shown in this paper is focused on analysing the behaviour of a 4-stroke twin-cylinder SI engine of 505 cm3 fuelled ammonia-plus-hydrogen. This engine was expressly chosen and modified to be placed in a range extended vehicle where hydrogen is obtained from ammonia by means of on-board catalytic reforming. The experimental results confirm that it is necessary to add hydrogen to air-ammonia mixture to improve ignition and to increase combustion velocity, with ratios that depend mainly on load and less on engine speed. Owing to intake air dilution and to lower flame speed of the ammonia-hydrogen-air mixture, a general decrement in engine performances has been detected in respect to the original gasoline version.

Simulation of nitrogen emissions in a premixed hydrogen flame stabilized on a low swirl burner

There is considerable interest in developing fuel-flexible, low emissions turbines for power generation. One approach is based on burning a variety of lean premixed fuels with relatively low flame temperatures. Such flames can be stabilized in a low swirl burner configuration, for example, using a variety of fuels such as pure hydrogen and hydrogen-seeded hydrocarbon mixtures. However, many hydrogen-rich fuels are thermodiffusively unstable and burn in cellular flame structures, which can have a significant impact on the local nitrogen chemistry. These cellular burning patterns are characterized by a local enhancement of fuel concentration and a corresponding increase in local flame temperature just downstream. In turn, these regions become sites for enhanced thermal NOx production. The structure of these cells, and their impact on the net emissions of a flame is influenced by the global flame stabilization mechanisms and by local turbulence properties. Here we investigate the role of thermodiffusive instabilities on NOx emissions in the context of a laboratory-scale low swirl burner fueled with a lean hydrogen–air mixture at atmospheric pressure. The simulations show how the cellular burning structures characteristic of lean premixed hydrogen combustion lead to local and global enhancements in the NOx emissions. We quantify the chemical pathways that lead to the formation of NO and N2O, and how they are enhanced within local regions of intense burning.

High speed imaging of OH* chemiluminescence and natural luminosity of low temperature diesel spray combustion

This study focused on spray combustion of ultra low sulfur diesel (ULSD) fuel under low oxygen conditions with low temperature combustion (LTC) mode in an optically accessible constant volume combustion chamber. The ambient oxygen concentration was configured as 10% and 15% to achieve low flame temperature. The ambient gas temperature varied from 800K to 1200K. High speed imaging of OH* chemiluminescence and natural luminosity (NL) was used to visualize the instantaneous spray combustion process. The heat release rate was analyzed using the transient combustion pressure and the flame structure was studied based on the combustion images. Results show that a higher oxygen concentration case features a shorter ignition delay and higher heat release rate. The LTC mode can be realized by decreasing the oxygen concentration and ambient temperature simultaneously and it features a longer ignition delay, a slower reaction rate, and apparently lower soot radiation heat loss. The visualization results of NL and OH* show that the high temperature reaction occurs mainly in the mid-stream and downstream of the spray combustion, but not in the region very close to the chamber wall. This study validates the LTC process by showing very weak OH* chemiluminescence signal. The results also indicate that in order to realize LTC mode, it is important to control the ambient oxygen and ambient temperature at the same time. By only reducing the ambient oxygen concentration it may not be effective to suppress soot generation.

Emissions of Nitrogen Oxides from Flares Operating at Low Flow Conditions

Full scale flare tests have been conducted to test the impacts of flare operating conditions on the fraction of flared gases that are converted to carbon dioxide and water (combustion efficiency, CE) for flares combusting low heating value gases (∼350–600 BTU/scf) at low flow rates (∼0.1–0.25% of maximum flow). Flares produce lower flame temperatures when operating with low heating value gases at low combustion efficiencies than when operating with high heating value gases at high combustion efficiencies. This leads to reduced formation of nitrogen oxides (NOx) in the flame. For a series of tests conducted under low flow conditions, with low heating value gases, NOx emission factors ranged between 10 and 120% of the NOx emission factor reported in AP-42. Emissions of NOx were highest for air assisted flares operating at high CE and lowest for steam assisted flares operating at low CE. In general, emissions were lower in steam assisted flare tests than in air assisted flare tests conducted under similar co...

Plasma-assisted ignition and deflagration-to-detonation transition

Non-equilibrium plasma demonstrates great potential to control ultra-lean, ultra-fast, low-temperature flames and to become an extremely promising technology for a wide range of applications, including aviation gas turbine engines, piston engines, RAMjets, SCRAMjets and detonation initiation for pulsed detonation engines. The analysis of discharge processes shows that the discharge energy can be deposited into the desired internal degrees of freedom of molecules when varying the reduced electric field, E/n, at which the discharge is maintained. The amount of deposited energy is controlled by other discharge and gas parameters, including electric pulse duration, discharge current, gas number density, gas temperature, etc. As a rule, the dominant mechanism of the effect of non-equilibrium plasma on ignition and combustion is associated with the generation of active particles in the discharge plasma. For plasma-assisted ignition and combustion in mixtures containing air, the most promising active species are O atoms and, to a smaller extent, some other neutral atoms and radicals. These active particles are efficiently produced in high-voltage, nanosecond, pulse discharges owing to electron-impact dissociation of molecules and electron-impact excitation of N(2) electronic states, followed by collisional quenching of these states to dissociate the molecules. Mechanisms of deflagration-to-detonation transition (DDT) initiation by non-equilibrium plasma were analysed. For longitudinal discharges with a high power density in a plasma channel, two fast DDT mechanisms have been observed. When initiated by a spark or a transient discharge, the mixture ignited simultaneously over the volume of the discharge channel, producing a shock wave with a Mach number greater than 2 and a flame. A gradient mechanism of DDT similar to that proposed by Zeldovich has been observed experimentally under streamer initiation.

Experimental Determination of the Efficiency and Emissions of a Residential Microcogeneration System Based on a Stirling Engine and Fueled by Diesel and Ethanol

Renewable forms of energy, such as biofuels, have the potential to displace fossil fuels in a wide variety of applications. Further benefit can be achieved through the use of combined heat and power devices, as this is accompanied with a considerable increase in energy efficiency and lower costs associated with fuel consumption. In this study, we examined the performance of a residential microcogeneration system based on a Stirling engine and fueled by diesel and ethanol. Run on diesel, and on a lower heating value basis, the system achieved a power efficiency of 12.1%, a thermal efficiency of 73.3%, and a total efficiency of 85.4%. Powered by ethanol, the corresponding efficiencies were 11.8%, 73.9%, and 85.7%, respectively. During steady state operation, the total unburned hydrocarbon emissions for both fuels were negligible, while the particulate emissions for ethanol and diesel were found to be 0.40 mg/kWh and 0.42 mg/kWh, respectively. Emissions were extremely low, as the combustor features a continuous premixed flame that facilitates the complete burnout of already evaporated fuel. Though emissions of nitrogen dioxide, methane, formaldehyde, and acetaldehyde were also negligible for both fuels, carbon monoxide and nitric oxide emissions for diesel (71 and 67 mg/m3, respectively) were much higher than those observed for ethanol (50 and 19 mg/m3, respectively). Lower nitric oxide emission levels for ethanol were attributed to its lower flame temperature, whereas reductions in carbon monoxide emissions were likely a result of a higher degree of fuel/air mixing with ethanol, due to higher gas jet velocities of the fuel exiting the orifices of the evaporator. Lastly, parametric studies on primary engine set points, including coolant temperature and exhaust temperature, were conducted to understand their effect on engine performance.

0207 密度擾乱が圧縮自着火低温度炎の形態に及ぼす影響(OS13-1 噴霧及び燃焼現象の解明とその利用技術,オーガナイズドセッション 13:「噴霧及び燃焼現象の解明とその利用技術」)

0207 密度擾乱が圧縮自着火低温度炎の形態に及ぼす影響(OS13-1 噴霧及び燃焼現象の解明とその利用技術,オーガナイズドセッション 13:「噴霧及び燃焼現象の解明とその利用技術」)

405 ポーリングバーナー低温度炎にトルエンを添加したときの自発光分光分布(OS6-2 燃焼現象の解明と高度利用技術2,OS6 燃焼現象の解明と高度利用技術)

405 ポーリングバーナー低温度炎にトルエンを添加したときの自発光分光分布(OS6-2 燃焼現象の解明と高度利用技術2,OS6 燃焼現象の解明と高度利用技術)

G070034 ジエチルエーテル平坦バーナー低温度炎におけるアセチレン添加の影響

G070034 ジエチルエーテル平坦バーナー低温度炎におけるアセチレン添加の影響

HVOF-Deposited WCCoCr as Replacement for Hard Cr in Landing Gear Actuators

WCCoCr coatings deposited by HVOF can replace hard Cr on landing gear components. Powders with two different WC particle sizes (micro and nano-) and geometries have been employed to study the effects on the coating’s properties. Moreover, coatings produced employing two sets of parameters resulting in high and low flame temperatures have been evaluated. Minor differences in microstructure and morphology were observed for the two powders employing the same spraying parameters, but the nano-sized powder exhibited a higher spraying efficiency. However, more significant microstructural changes result when the low- and high-energy spray parameters are used. Moreover, results of various tests which include adhesion, wear, salt fog corrosion resistance, liquid immersion, and axial fatigue strength, indicate that the coatings produced with high-energy flame are similar in behavior. On the other hand, the nanostructured low-energy flame coating exhibited a significantly lower salt fog corrosion resistance.

Flame structure investigations of oxy-fuel combustion

The increased instability of CO2 (or exhaust gas) recycled oxy-fuel flames is generally attributed to the increased specific heat of the gaseous mixture resulting in lower flame temperatures. In the present paper, we study the role of CO2 addition through exhaust gas recirculation on the combustion chemistry of an oxy-methane flame. A flame structure analysis of various combinations of methane-oxidant flames has been carried out using the GRI 3.0 325-step mechanism. Further, comparative reaction rate analysis has been carried out under nitrogen and CO2-dilutions to bring out the oxygen leakage in the two systems. These studies indicate that the presence of CO2 in the oxidant has a profound effect on the reaction mechanism principally through two reactions, one involving the H radical and another involving the HO2 radical, which become predominant in oxy-fuel combustion and contribute to the excessive oxygen leakage.

An investigation on erosion behavior of HVOF sprayed WC–CoCr coatings

Present work is an investigation of slurry erosion behavior of WC–CoCr cermet coatings deposited with two different WC grain sizes. HVOF thermal spray process was employed due to its high velocity and low flame temperature characteristics resulting in quality coating. HVOF spraying was assisted with in-flight particle temperature and velocity measurement system to control its heating. Slurry erosion testing was performed using a pot-type slurry erosion tester to evaluate slurry erosion resistance of the coatings. Two parameters were considered for testing viz. erodent particle size and slurry concentration. Surface morphology was examined using SEM images and phase identification was done by XRD. The erosion behavior and mechanism of material removal was studied and discussed based on microstructural examination. It was observed that WC–CoCr cermet coating deposited with fine grain WC exhibits higher slurry erosion resistance under all testing conditions as compared to conventional cermet coating.

Factors controlling pure-phase magnetic BiFeO 3 powders synthesized by solution combustion synthesis

Bismuth ferric oxide nanopowders were prepared through combustion method. Pure phase and well-crystallized BiFeO 3 can be obtained by controlling the combustion process, fuel type and fuel-to-oxidant ratio. The evolutions of phase constitution and structural characteristics of the as-resulted nanopowders were investigated by X-ray diffraction, scanning electron microscope, and simultaneous thermogravimetric analysis. The results revealed that both the type and amount of fuel have to be carefully considered because they play an important role in total reaction characteristics. Among all tested fuels, l-α-alanine and glycine are the suitable fuels for BiFeO 3 synthesis. For α-alanine, the optimal fuel-to-oxidant ratio is 0.22, which results in a suitable flame temperature for BiFeO 3 formation. Still, too little fuel would result in only amorphous phase powders due to the low flame temperature and too much fuel would lead to transformation of the BiFeO 3 phase to impurities because of the high flame temperature involved. The resulting BiFeO 3 nanopowders exhibited strong H 2O 2-activiting ability and weak magnetism. When BiFeO 3 nanopowders were used as a heterogeneous Fenton-like catalyst to degrade rhodamine B (RhB), the apparent rate constant for RhB degradation in the presence of H 2O 2 at pH 5.0 was evaluated to be 0.048 min −1.

G070052 ジエチルエーテル平坦バーナー低温度炎におけるトルエン添加の影響([G07005]エンジンシステム部門一般セッション(5):代替燃料)

Burner low-temperature flames were established on a Powling burner with a diethyl-ether/toluene/air (toluene content in fuel by liquid volume: 0.5 vol% and 1.0 vol%) at an equivalence ratio of 2.0, under the atmospheric pressure, in order to understand the low-temperature ignition inhibition mechanism by toluene. Aromatic hydrocarbons and unsaturated aliphatic hydrocarbons measurement are preformed by a liquid and gas-chromatograph. The temperature in the low-temperature flames were measured using a fine thermocouple. The formation of aromatic hydrocarbons in the yellow column is promoted by toluene addition. Toluene addition retarded the cool-flame appearance and reduced the distance between cool and blue flames. The similarity to burner low-temperature flames and a compression ignition low-temperature flames can be confirmed also here.

401 プロピレンをバーナー低温度炎に添加したときの芳香族生成挙動(OS6-1熱機関・燃焼現象の高度解析)

401 プロピレンをバーナー低温度炎に添加したときの芳香族生成挙動(OS6-1熱機関・燃焼現象の高度解析)

B223 ジエチルエーテル平坦バーナ低温度炎におけるエチレン添加の影響(OS-10:内燃機関(2))

B223 ジエチルエーテル平坦バーナ低温度炎におけるエチレン添加の影響(OS-10:内燃機関(2))