Decrease In Combustion Temperature Research Articles

Numerical Investigation on Energetic, Combustion, and Emissions Parameters of a Diesel Engine Fueled With Diesel/Butanol and Diesel/Pentanol

Abstract In this article, the effect of butanol/diesel and pentanol/diesel blended fuel with different proportions on the energetic, combustion, and emissions parameters of a diesel engine was studied. First, an engine model was established using Diesel-RK software. The modeled engine was a direct injection diesel engine having a fixed compression ratio, injection timing, and speed of 17.5:1, 23 degbTDC, and 1500 rpm, respectively. After that, a set of experiments was conducted using a 5% pentanol and 95% diesel by volume fuel blend maintaining the same operating conditions as the simulation, and the results of the experiment were compared with the numerical result using the same blend. The simulated results were found to be in respectable agreement with experimental findings. The analysis of the simulated results shows that at 100% load using 15% butanol and 85% diesel by volume and 15% pentanol and 85% diesel by volume brake thermal efficiency was increased by 0.96% and 0.8%, respectively. The emission of NOx was reduced by 24.4% and 10.75% on average using butanol and pentanol blends, respectively. The instantaneous heat release rate and ignition delay increase with the higher alcohol–diesel blends, whereas the peak pressure rise and combustion temperature decrease. Smoke emissions were reduced by 3.31–8.75%, and specific particulate matter emissions decreased by 20.9% and 15.07%, respectively, on average with the addition of butanol/pentanol in neat diesel.

Feasibility of co-disposal of lignite and eucalyptus wood in coal-fired power plants: thermogravimetric characterization, typical gaseous pollutant emission characteristics, and economic analysis

ABSTRACT Energy issues are becoming increasingly prominent, and biomass blending in coal-fired power plants can improve combustion performance and reduce gaseous pollutant emissions, thereby improving economic efficiency. In this study, a thermogravimetric analyzer, a horizontal tube furnace, and an infrared flue gas analyzer were used to investigate the combustion behavior and gaseous pollutant emissions of the co-combustion of LC and EW. The results show that blending EW into LC cofiring can inhibit the release of volatile matter and promote the decomposition of fixed carbon and lignin simultaneously. The HHV of EW (15.88 MJ/kg) reaches 63.7% of LC’s (24.90 MJ/kg), indicating EW has a high energy utilization value. With increasing combustion temperature, the average value of CR S increased from 47.09% to 59.94%, and the average value of CR Cl increased from 26.15% to 52.15%, leading to a significant increase in SO2 and HCl emissions. The decrease in combustion temperature slightly promoted the release of N (CR N increased from 11.76% to 14.45%). The results of the economic analysis show that the cost of CaO and NH3·H2O used for removing gaseous pollutants decreased the most, and the economic efficiency increased the fastest to 14,000 RMB/day when the EW blending ratio increased from 10% to 20%.

Numerical Simulation of a Gas Burner Using Mixed Propane/Ammonia Fuel

In recent years, ammonia has received more and more interest to be used as carbon-free energy. In the present study, a computational model of a burner for the domestic hot water boiler in the building has been developed. The combustion characteristics of propane/ammonia-mixed fuel in the burner were investigated by numerical simulation under different ammonia blending ratios and equivalence ratios. Based on the flue gas concentration distribution of the numerical simulation results, the baseline carbon emission of hot water supply in a community was calculated. The results show that as the ammonia blending ratio increases, the overall combustion temperature decreases. At the outlet of the burner, when the ammonia blending ratio is 0.5, the emission concentration of carbon dioxide can be reduced by 31.4% compared to pure propane combustion. When the ammonia blending ratio increases from 0 to 50%, the carbon baseline emission decreases from 9.89 kg/GJ to 6.87 kg/GJ, and the carbon emission under the baseline decreases from 17.20 T to 11.94 T. The emission of NO pollutants remains basically unchanged due to the decrease of combustion temperature. It indicates that the mixed fuels can effectively reduce carbon emissions in domestic water heaters and have good potential for future application.

LNG 이종연료 운전이 상업용 디젤 엔진의 출력 및 배출가스 특성에 미치는 영향

In order to additionally supply LNG to a heavy-duty commercial diesel engine, a dual fuel system was installed; engine power and exhaust gas emissions while operating in the ‘ND-13 mode’, in accordance with the notice from the Ministry of Environment, were investigated. The feasibility of retrofitting the dual fuel system and plans based on mixture rate, power, and emission reduction to enable commercialization were evaluated. The engine power and torque values were within ±5% of the values for the existing engine; these were within the legal modification range. In case of exhaust gas emissions, the decrease in CO 2 emission due to the increase in load was apparent; it was reduced by 15.3%. NO X emission decreased by 58%; this could be attributed to the decrease in combustion temperature owing to water injection. THC and CO increased significantly, possibly due to the reduced combustibility of natural gas owing to bulk quenching, water injection, and the absence of catalysts. Additional research focused on modification of mapping values and installation of oxidation catalysts to improve the combustion performance of the system, is warranted.

Ammonia blend ratio impact on combustion characteristics and NOx emissions during co-firing with sludge and coal in a utility boiler

This study investigates the effects of the ammonia blend ratio and the number of nozzle layers on boiler combustion characteristics and NOx emissions by the computational fluid dynamics simulation method. The conclusions indicate that, as ammonia is injected from a single-layer of secondary air nozzles, with the ammonia blend ratio increases, the combustion temperature decreases, when the blend ratio is 60%, the combustion temperature decreases by about 300 K. When ammonia is injected into the furnace from multiple-layers of nozzles, and under the premise of the same ammonia blend ratio, the overall impact on the furnace temperature is smaller than that of ammonia entering from a single-layer of nozzles. When the blend ratio of the ammonia is 40%, the NOx emission of ammonia entering the furnace from two layers of secondary air nozzles is about 22.47% higher than when it is injected into the furnace from a single-layer of nozzles. After raising the ammonia mixing ratio, the NOx at the furnace outlet shows an inverted-parabola change, which first decreasing and then increasing.

Energy and exergy analyses of hydrogen-fueled spark ignition engine with various air excess ratios and ignition timings

Many studies have been conducted to determine the efficiency and emission of hydrogen internal combustion engines. However, only a few of these investigations have performed exergy analysis (especially when important parameters, such as excess air ratio, vary) based on the second law of thermodynamics. Accordingly, in this study, experiments were conducted on a commercial automotive spark ignition engine. The engine is modified to run on hydrogen as fuel at 1500 rpm with various spark timings and excess air ratios under a wide-open throttle. In addition, zero-dimensional two-zone modeling was conducted by matching and examining the experimental results considering both energy (first law of thermodynamics) and exergy (second law of thermodynamics) analyses.The results indicate that with the same excess air ratio, the trend exergy analysis results, such as increasing exhaust exergy loss and decreasing heat transfer exergy loss by retarding ignition timing, are similar to the energy analysis results. Additionally, irreversibility increased as the spark timing retarded owing to the reduction in combustion temperature caused by prolonged combustion duration. In considering various excess air ratios, the gap between the energy and exergy analysis results was evaluated: the heat transfer exergy loss increased from 27% to 31%, the exhaust exergy loss decreased from 20% to 15%, and irreversibility was maintained at approximately 10%. Irreversibility was maintained because of the offset between the irreversibility increment (due to the decrease in combustion temperature) and decrement (due to the decrease in fuel amount). Moreover, the relationship between the thermo-mechanical exergy rise rate and behavior of each exergy component was examined.

Simulation study on effects of EGR ratio and compression ratio on combustion and emission characteristics of PODE/methanol RCCI engine

In order to solve the problems of combustion instability and emission deterioration of reactivity controlled compression ignition (RCCI) engine under high load, the in-cylinder combustion model of polyoxymethylene dimethyl ethers (PODE)/methanol dual-fuel RCCI engine was constructed by CONVERGE software coupling with chemical reaction mechanism, and the influence mechanism of exhaust gas recirculation (EGR) ratio and compression ratio (CR) on engine performance, in-cylinder combustion and emission characteristics of PODE/methanol RCCI mode was systematically studied. Results show that with the increase of EGR ratio, the combustion phase of RCCI mode is gradually delayed, the ignition delay and combustion duration are extended, the CA50 phase is gradually delayed, the combustion temperature decreases, the mixture distribution becomes more uniform, and the combustion process becomes smoother. When the EGR ratio increases from 0 % to 30 %, NOx production is reduced by 47.3 %, ringing intensity (RI) and maximum pressure rise rate (MPRR) decreases by 1.31 MW/m2 and 0.37 MPa/°CA respectively, and brake thermal efficiency (BTE) decreases from 45.45 % to 43.19 %. With the reduction of CR, the combustion start point is gradually postponed, the peak heat release rate and combustion temperature continuously decrease, and both IMEP and BTE show a downward trend. The variation of CR breaks the trade-off relationship between NOx and soot, and improves combustion stability, but it is also limited by the BTE reduction. When the CR decreases from 17.5 to 15.5, NOx and soot production are reduced by 28.58 % and 20.1 %, RI and MPRR are reduced by 1.26 MW/m2 and 0.7 MPa/°CA respectively, and BTE decreases from 45.45 % to 44.52 %. Therefore, the CR of 16.5 is more suitable for stable operation of PODE/methanol dual-fuel RCCI engine at high load.

Combined effects of electric supercharger and LP-EGR on performance of turbocharged engine

LP-EGR and turbocharging can improve thermal efficiency, but its specific mechanism needs to be further studied from the energy conversion. The fast response characteristic of electric supercharger can make up for turbine lag. The effect of electric supercharger on the steady state and transient characteristics of a LP-EGR turbocharged engine are investigated. Under the condition of 1500 r·min−1 and 14 bar, the electric supercharger can increase the EGR rate from 5% to 30%. The introduction of exhaust gas can increase the intake volume and reduce the pumping losses. The increase of turbocharger power indicates the reduction of exhaust energy losses. The decrease of combustion temperature optimizes the combustion phase, increases the constant volume degree of combustion and reduces the heat transfer losses. The application of EGR improves the fuel economy by 5%. For emission, low temperature combustion and low oxygen content reduce NOx emission by 80%. Incomplete combustion losses increase THC emission. CO emission is related to excess-air coefficient, so it is basically unchanged. The electric supercharger can speed up the establishment of the intake manifold pressure. The power transient response time is shortened by 72%. The advance of torque platform improves the power performance of engine at low speed.

Calculation studies of the influence of exhaust gas recirculation on the characteristics of the natural gas-fueled diesel engine

When converting diesel engines to run on natural gas on the gas-diesel cycle, additional problems arise associated with the high thermal stress of the exhaust valves and valve seats at high loads and engine speeds. There is also an increase in NOx emissions due to higher combustion temperatures of natural gas. One of the ways to improve the economic and environmental performance of engines operating on a gas-diesel cycle with a lean air-fuel mixture is to optimize the combustion of the air-fuel mixture by using an exhaust gas recirculation system (EGR). The principle of operation of this system is as follows: exhaust gas entering the intake manifold and further into the combustion chamber reduces the oxygen concentration in the air-fuel mixture, which leads to a dilution effect and, accordingly, to a decrease in combustion temperature and a decrease in NOx content. In order to study the influence of EGR on the dual-fuel gas and diesel engine parameters in the AVL Boost software package, a computer model of the existing 6ChN13/15 engine was developed. A low-pressure EGR system with an exhaust gas cooler was simulated on this engine. Values of NOx emissions, brake specific fuel consumption (BSFC) and brake efficiency have been obtained at different recirculation rate by calculation method. These values allow to estimate the feasibility of using a cooled EGR in a natural gas-fueled diesel engine.

Effect of Negative Valve Overlap on Combustion and Emissions of CNG-Fueled HCCI Engine with Hydrogen Addition

In order to study the effect of negative valve overlap on combustion and emission characteristics of a homogeneous charge compression ignition engine fueled with natural gas and hydrogen, the test and the simulation were conducted using an engine cycle model coupling the chemical kinetic reaction mechanism under different valve timing conditions. Results show that the internal EGR formed by using negative valve overlap could heat the inlet mixtures and improve the spontaneous ignition characteristic of the engine. The residual exhaust gas could slow down the heat release rate, decrease the pressure rise rate and the maximum combustion temperature, and reduce the NOx emission simultaneously. Among the three NVO schemes, the strategy of changing the intake valve opening timing individually can create the least power loss, and the symmetric NVO strategy which changes both the exhaust valve closing timing and the intake valve opening timing simultaneously can achieve the best heating effect of inlet mixtures and the satisfactory decrease of combustion temperature, as well as the largest reduction of NOx emission.

EGR rate 변화에 따른 바이오디젤 정적 연소 특성에 관한 수치해석 연구

This paper was conducted to investigate the effect of EGR on the combustion characteristics, NO<SUB>X</SUB> and CO formation characteristics of constant volume combustion of the biodiesel fuel. To achieve this, methyl decanoate, methyl 9 decenoate, and n-heptane species were applied for the simulation of the biodiesel and diesel chemical reactions during the constant volume combustion process. The analysis of biodiesel-EGR combustion was performed by simultaneously considering the mole fraction which was composed of the N₂, H₂O, CO₂, and O₂ species according to the EGR rate (10~60%). As a result of the combustion characteristics, the maximum OH radical was reduced as the EGR rate increase, and the ignition delay was increased at the same time. Most of NO<SUB>X</SUB> emission was generated by the thermal NO<SUB>X</SUB> reaction, and it was not emitted after the EGR rate of 30% conditions due to the decrease of combustion temperature and oxygen concentration. The reactivity of CO generation was showed the high absolute rate of production in the reaction path related to the reactions of HCO radical, and it has a trade-off relationship with the tendency of NO<SUB>X</SUB> emissions. In addition, it was indicated that the UHC emission increased rapidly since the chemical reactions related to the fuel oxidation did not occur actively when the ambient temperature was 800~1,000 K and the EGR rate was 60% conditions.

Structural and magnetic properties of MgFe2O4 powders synthesized by solution combustion method: the effect of fuel type

Single phase MgFe2O4 powders were synthesized by solution combustion method using metal nitrates as oxidant and ethylenediaminetetraacetic acid (EDTA), citric acid and glycine as fuel. Thermal analysis showed the combustion reaction rate decreased from the glycine to citric acid and EDTA fuel, respectively, due to the chelation of cations by fuel. The structural analysis of X-ray diffraction patterns showed the partially inverse spinel structure of MgFe2O4 powders in which the inversion degree was dependent on the fuel type. The particle size decreased from 250 to 45 and 35 nm for the glycine to the citric acid and EDTA fuels, respectively, as a result of the decrease of combustion temperature. The MgFe2O4 powders synthesized by the EDTA fuel had the highest specific surface area and pore volume of 62 m2/g and 0.14 cm3/g. The magnetic properties were correlated to the inversion degree and particle size.

Photocatalytic performances of BiFeO3 powders synthesized by solution combustion method: The role of mixed fuels

Abstract Single phase BiFeO3 powders were prepared by solution combustion synthesis method for visible photodegradation of organic pollutants. The effects of mixed fuels on the combustion behavior, phase evolution, structure, microstructure, optical properties and photocatalytic performance were investigated by thermal analysis, X-ray diffraction, infrared spectroscopy; electron microscopy, and diffuse reflectance spectroscopy techniques. The as-combusted powders are composed of BiFeO3 phase together with impurity Bi2Fe4O9 and Bi24Fe2O39 phases which were almost eliminated by following the calcination at 600 °C. Particle size decreased from 700 nm to 250 nm using the mixture of fuels due to the decrease in combustion temperature. The BiFeO3 powders can absorb a wide range of visible light with band gap energy in the range of 1.88–2.17 eV. About 100% of methylene blue was photodegraded during 100 min visible light irradiation in the presence of BiFeO3 powders prepared by urea fuel.

Distribution of Polycyclic Aromatic Hydrocarbons in Coal Gangue and Emitted Gas with Low-Temperature Spontaneous Combustion in Situ

Five coal gangue samples from the Duerping Coal Mine in Shanxi, China, subjected to low-temperature combustion and their emitted gas samples were collected in situ at the combustion temperatures of 23, 33, 49, 57, and 70 °C. The concentrations of 16 polycyclic aromatic hydrocarbons (PAHs) in these samples were determined by high-performance liquid chromatography; these concentrations indicated that with decreasing combustion temperature, ∑16PAHs in coal gangue tend to decrease, whereas ∑16PAHs in emitted gas tend to increase. With the decrease of combustion temperature, the concentrations of Σ6LPAHs in coal gangue and emitted gas decreased, whereas the concentrations of Σ10HPAHs increased; therefore, the overall toxicity and carcinogenicity increased. The total index of PAHs in the samples ranged from 20.10 to 22.43 with a mean of 21.81. The ratio of Flua/(Flua + Pyr) ranged from 0.34 to 0.97 with a mean of 0.76. Finally, the proportions of Ant/(Ant + Phe), BaA/(BaA + Chr), and InP/(InP + Bghi) were approximately 1. These ratios and the total index of the PAHs could be used to identify the source of PAHs in the atmosphere and soil.

Experimental investigation on the use of water emulsified diesel in a single cylinder Compression Ignition engine

In this work, an experimental investigation has been carried on a single cylinder variable compression ratio CI engine to investigate its performance and emission characteristics using neat diesel and water emulsified diesel with 10% water content (WED10). The emulsion has been prepared in the laboratory using ultrasonic vibrator. The performance characteristics include brake thermal efficiency and BSFC, and the emission characteristics include NOx and HC emissions only. It is found that brake thermal efficiency undergoes no significant change for both the fuel variants and the BSFC is slightly reduced when only diesel is considered in the WED10. There is a considerable amount of reduction in NOx emission with the use of WED10. But HC emission increases with the use of WED10 due to decrease in combustion temperature and increase in ignition delay. Thus, WED10 may be considered as a viable alternate fuel having a greener emission and a comparable engine performance.

Oxy-fuel combustion study of biomass fuels in a 20 kWth fluidized bed combustor

Oxy-fuel combustion is one of the promising carbon capture technologies considered to be suitable for future commercial applications with stationary combustion plants. Although more and more biomass and waste are now being burned in stationary combustion plants, research on oxy-fuel combustion of biomass has received much less attention in comparison to oxy-fuel combustion of coal. In this work, a series of tests was carried out in a 20 kWth fluidized bed combustor under oxy-fuel conditions firing two non-woody fuels (miscanthus and straw pellets) and one woody fuel (domestic wood pellet). The effects of the combustion atmosphere (air and oxy-fuel) and oxygen concentration in the oxidant of the oxy-fuel combustion on gas emissions and temperature profiles were systematically studied with the overall excess oxygen coefficient in the combustor being maintained roughly constant throughout the tests. The experimental results showed that replacing the air with an oxy-fuel oxidant of 21 vol% O2 and 79 vol% CO2 resulted in a significant decrease in combustion temperature and ultimately led to the extinction of the biomass flame due to the larger specific heat of CO2 compared to N2. To keep a similar temperature profile to that achieved under the air combustion conditions, the oxygen concentration in the oxidant of O2/CO2 mixture had to be increased to 30 vol%. A drastic decrease in CO emissions was observed for all three biomass fuels (up to 80% reduction when firing straw) under oxy-fuel combustion conditions providing that the oxygen concentration in the oxidant of O2/CO2 mixture was above 25 vol%. NOx emissions were found to decrease with the oxygen concentration in the oxy-fuel oxidant, due to i) the increase of bed temperature, which implies more volatile-N released and converted in the dense bed zone and ii) the less dilution of the gases inside the dense bed zone, which leads to a higher CO concentration in this region enhancing the reduction of NOx. Similar NOx emissions to those obtained with air combustion were found when the oxygen concentration in the oxy-fuel oxidant was kept at 30 vol%. Further analysis of the experimental results showed that the gas emissions when firing the non-woody fuels were controlled mainly by the freeboard temperature instead of the dense bed region temperature due to the characteristically high volatile matter content and fines of this kind of biomass fuels.

Preparation of Fine-grained Silicon from Serpentine Mineral by Magnesiothermic Reduction of Silica in the Presence of Reaction Products as Diluents

In the work, the preparation of fine-grained silicon was performed in combustion mode by magnesiothermic reduction of silica, obtained from serpentine mineral, which is characterized by a high specific surface area (about 560 m2/g) and high reaction activity. It is manifested by the fact that the measured combustion temperature exceeded the adiabatic combustion temperature calculated with the ISMAN THERMO software, by about 200 °C. In order to mitigate the synthesis conditions, combustion products (Si+2MgO) were used as diluting agents allowing a significant decrease of combustion temperature and a finer silicon powder without contaminating the target product with incidental reagents and without decreasing the yield of the target product. Based on the measured values of combustion parameters (combustion temperature and combustion wave propagation velocity) vs diluent amount, it was estimated that the effective activation energy for SiO2+2Mg reaction by the solid+liquid mechanism in the temperature interval 1400–2100 °C was about 65±3 kJ/mol.

Effects of Mn-doped ceria oxygen-storage material on oxidation activity of diesel soot

TG and DTG curves of diesel particle shift to the low temperature region with the increase of Mn doping into CeO2system, which indicates that the particle ignition combustion temperature decreases.

디젤-워터 에멀젼 연료의 조성에 따른 분무 특성에 관한 연구

Using Diesel-Water Emulsion fuel in commercial diesel engine can reduce NOx and soot when it is injected through the injector. Because water in Diesel-Water Emulsion fuel is vaporized ahead of diesel particle and it cause decrease of combustion temperature. Furthermore, research about the possibility of applicating Diesel-Water Emulsion fuels to commercial diesel engine is demanded in order to prove that Diesel-Water Emulsion fuel is able to apply commercial diesel engine without any replacement of equipments. This research analyzed applicable possibility of Diesel-Water Emulsion fuels to commercial diesel engine’s fuel injection system refering injection and spray characteristics. In this research, there are 3 experiments, that is injection quantity, spray visualization, and injection rate. Diesel-Water Emulsion fuel has less injection quantities compared to diesel fuel, and spray penetration length is more longer than diesel. Furthermore, emulsion fuels have less dispersed than diesel fuel. In conclusion, comparing with diesel fuel with only spray characteristics, Diesel-Water Emulsion fuel has bad effects about dispersion and vaporization.

EXHAUST GAS DOSE UNIFORMITY IN MODERN DIESEL ENGINES

Currently, the environment protection challenges the designers and manufacturers of combustion engines due to the fact that the engine emits toxic compounds, which are hazardous to the life organisms. Increasingly strict regulations concerning emission of the exhaust gases forces application of the innovative technologies or improvement of the presently used. One of systems, which reduce the toxicity of the exhaust gases, is the Exhaust Gas Recirculation (EGR) system. This solution reverse part of the exhaust gases back into the manifold and mixes it with fresh inlet air. In consequence, the combustion temperature decreases. Less oxygen reacts with nitrogen and more connects with carbon and hydrogen. Presently there are two types of EGR system i.e. internal and external. In case of the first one part of the exhaust gases remains in the combustion chamber after the combustion but its construction is not complicated. The external EGR system uses one valve of the exhaust gas recirculation system located on the manifold. This location can result of the uneven portion of exhaust gases directed to the combustion chamber. In consequence, the decrease on the temperature is also uneven and therefore different portion of nitrogen oxide in the exhaust gases.