Peak Heat Release Research Articles

An assessment of combustion, performance characteristics and emission control strategy by adding anti-oxidant additive in emulsified fuel

In the current scenario, the global researchers are focused on multidimensional fossil fuel facts, namely, depletion of fuels, energy crises, and emission threats. Hence, this condition of biofuel has potential worldwide acceptance. This research work uses the novelty of biofuel and biofuel emulsion, for the fuelling of IC engines for experimental analysis. The main objective of this work is to reduce harmful engine emissions, namely, nitrogen oxide, carbon monoxide, hydrocarbon, and smoke. The new feedstock of novel biofuel was obtained by solvent extraction method and which is now called raw Borassus Flabellifer Oil (BFO). Raw oil directly introduced in IC engine showed enhanced emission threats during last decade. Fuel modification is an attractive solution to avoid this threat. Emulsion technique is considered as a propitious method for alternative fuel. BFO emulsion fuel was prepared by adding 5% water and 2% of span80 surfactant by volume. Using emission reduction agent called antioxidant l-ascorbic acid as an additive in BFO emulsion fuel for scavenging the nitrogen radicals. The test result was analyzed in terms of combustion, performance and emission characteristics on a single cylinder DI diesel engine with raw BFO, emulsified BFO and additive mixed emulsified BFO respectively. Reduced emission of nitrogen oxide, smoke, hydrocarbon, and carbon monoxide by the use of additive mixed emulsified BFO fuel was observed. This includes improved engine efficiency, heat release rate, peak pressure and energy consumption than raw BFO and emulsified BFO.

Synergistic flame retardant effects of activated carbon and molybdenum oxide in poly(vinyl chloride)

AbstractThe synergistic effects of activated carbon (AC) and molybdenum oxide (MoO3) in improving the flame retardancy of poly(vinyl chloride) (PVC) were investigated. The effects of AC, MoO3 and their mixture with a mass ratio of 1:1 on the flame retardancy and smoke suppression properties of PVC were studied using the limiting oxygen index and cone calorimeter tests. It was found that the flame retardancy of the relatively cheaper AC was slightly weaker than that of MoO3. In addition, the incorporation of AC and MoO3 greatly reduced the total heat release and improved smoke suppressant property of PVC composites. When the total content of AC and MoO3 was 10 phr, PVC/AC/MoO3 had the lowest peak heat release rate and peak smoke production rate values of 173.80 kW m−2 and 0.1472 m2 s−1, which represented reductions of 47.3 and 59.9%, respectively, compared with those of PVC. Furthermore, thermogravimetric analysis and gel content tests were used to analyze the flame retardant mechanism of AC and MoO3, with results showing that AC could promote early crosslinking in PVC. Char residue left after heating at 500 °C was analyzed using scanning electron microscopy and Raman spectroscopy, and the results showed that MoO3 produced the most compact char, with the smallest and most organized carbonaceous microstructures. © 2017 Society of Chemical Industry

An experimental investigation of exergetic performance and emission characteristics of hydrogen supplemented biogas-diesel dual fuel engine

An experimental investigation of a conventional diesel engine with diesel, biogas and hydrogen as fuels has been carried out, while the engine is modified to operate in dual fuel mode using diesel as the pilot fuel and biogas as the main fuel respectively. In order to improve the biogas-diesel dual fuel engine performance and emission characteristics, small percentages of hydrogen supplementations, viz. 5%, 10%, 15% and 20%, in biogas were studied and the comparison was also made to that with the neat biogas-diesel dual fuel operation. Engine performance characterization has been done with exergy based approach, and major sources of irreversibilities in various engine processes are also investigated and compared for the above mentioned cases. The results show that hydrogen supplementations in biogas have lesser effect on the combustion characteristics at low load, while, at high load, the combustion patterns change significantly with higher heat release rates and peak combustion pressures. Furthermore, performance and emission characteristics are found nearly unaffected with 5% of hydrogen addition both at low and high loads. Nevertheless, further addition of hydrogen in biogas causes improvements in performance and emission characteristics of the dual fuel engine.

Epoxy resin flame-retarded via a novel melamine-organophosphinic acid salt: Thermal stability, flame retardance and pyrolysis behavior

A melamine-organophosphinic acid salt (MDOP) was synthesized via neutralization of dibenzo[c,e][1,2]oxaphosphinic acid (DOPA) with melamine, and used as an additive-type flame retardant for epoxy resin (EP). Thermal stability and flame retardance was comprehensively evaluated via thermogravimetric analysis (TGA), UL-94 vertical burning test, limiting oxygen index (LOI) and cone calorimetry. The cured epoxy easily passed UL-94 V-0 rating with 0.33% content of P (5 phr MDOP); and LOI value of 38.0% was further achieved with 10 phr MDOP. The peak heat release (PHRR), total heat release (THR), total smoke production (TSP) and fire growth rate (FIGRA) were all reduced with the incorporation of MDOP. The pyrolysis behavior of the flame-retardant EP systems from Py-GC/MS and TG-FTIR suggested that MDOP played the role of flame retardance in both condensed and gaseous phases. Interestingly, the incorporation of MDOP did not deteriorate the mechanical properties of epoxy resin.

Effect of Organic Nano Carboncapsule Incorporated Modified Clay on Fire‐Retardancy of PMMA Nanocomposites

Here we investigate a new type of highly flame retardant poly(methyl methacrylate) (PMMA) nanocomposite by bulk polymerization of methyl methacrylate (MMA) in the presence of organic nano carboncapsule (OCNC/NCNC)‐incorporated modified montmorillonites (CL120, CL42). The morphology of the modified clay was confirmed by X‐ray diffraction (XRD), and Fourier transform infrared (FT‐IR) spectroscopy was used to identify the functional groups in the clay. The nano morphological characterization of the clay in the PMMA matrix was confirmed by XRD and transmission electron microscopy (TEM). The thermal and mechanical properties of the PMMA nanocomposites were investigated by thermogravimetry and dynamic mechanical analysis, respectively. PMMA containing organo nano carboncapsule‐doped CL42 modified cocoamphodipropionate (K2) (P‐O‐CL42) could achieve very high thermal stability compared to pristine PMMA. The 5% thermal decomposition temperature (T5d) increased by 63.2°C. Storage modulus of PMMA nanocomposites measured by DMA analysis. An enhancement of storage modulus and significant reduction in the peak heat release (PHR) rate were observed in the almost all PMMA nanocomposites as compared to pristine PMMA. Moreover, these results suggest that PMMA nanocomposites can have potential applications in the building industry and the medical field.

Computations of a Hydrogen-Fueled Scramjet Combustor on Locally Refined Meshes

Simulations of an experimental hydrogen-fueled scramjet combustor are conducted using a novel dynamic hybrid Reynolds-averaged Navier-Stokes/large-eddy simulation (DHRL) modeling framework. The combustor has a Mach 2 core flow with a ramp fuel injector resulting in an equivalence ratio of 0.17. Three grid resolutions are obtained using local refinement by a factor of two in each direction in the fuel mixing and combustion region, and results from the three grids are used to understand the effect of grid refinement. Simulations reproduce temperature, pressure, velocity, and fuel concentrations in reasonable agreement with experimental measurements. Although heat release decreases on average, as the mesh is refined, peaks of heat release are intensified causing locally elevated temperatures. Spectral analysis of turbulence kinetic energy and heat release suggests stringent resolution requirements for reacting simulations capable of accurately resolving the effects of chemical reactions. Using the medium grid the DHRL model is compared to the improved delayed detached eddy simulation (IDDES) model and two Reynolds-averaged Navier-Stokes (RANS) models. Overall, the DHRL framework significantly outperforms other methods when compared to the experimental pressure rise. Additionally, spectral analysis suggests that the current framework is capable of accurately resolving turbulent structures at frequencies higher than IDDES. The study is the first documenting the use of DHRL for supersonic reacting flow and results suggest that it is a viable alternative to existing turbulence treatments for these types of flows.

Study on clean technology-assisted combustion behavior and NO x emission using thermal imager for alternate fuel blends

The correlation between oxides of nitrogen emission and in-cylinder temperature of diesel engine fueled with various alternative fuels has been investigated in this research paper. Experimentations were performed in engine without any modifications using pure high-speed diesel fuel, used cooking oil biodiesel (UCO20), animal fat residue biodiesel (AFR20) and camphor oil (CMR20) at 20% volume concentration of biodiesel each. From combustion analysis, the heat release rate and peak cylinder pressure of biodiesel blends were about 13.487% lower and 4.819% higher than those of diesel fuel on an average, respectively. Longer combustion duration has been observed for all biodiesel blends at all load conditions. Oxides of nitrogen emission level show 16.405, 10.352 and 7.524% increment for UCO20, AFR20 and CMR20, respectively. Noteworthy NO x reduction of about 43.8% was recorded for diesel blended with camphor oil when compared to other biodiesel blends. The relationship between in-cylinder temperature and NO x emission concentration was premeditated through thermal imager. The result depicted that the increase in NO x concentration depends on augmented in-cylinder temperature for all test fuels.

Impact of Gas To Liquid and diesel fuels on the engine cold start

Low ambient temperatures during start process have a notable influence on the combustion process. A methodology to study parameters as indicated mean pressure and rate of heat release, obtained using on-line thermodynamic diagnosis under cold start, was developed in this work. For this study, the correction of the pressure level from the first cycle measured has been made. Two ambient temperatures (20°C and −7°C) and two engine temperatures (20°C and 70°C) were selected for this study. A Gas To Liquid fuel and two diesel fuels (one of them with 5.8% of biodiesel) were tested in a Euro 4 diesel light-duty vehicle. Values of indicated mean pressure were higher during the first thermodynamic cycle than those corresponding to idle conditions with all fuels tested. Low engine temperature (20°C) makes the combustion of fuel during pre-injection difficult and, consequently, only one peak of apparent heat release was registered. Fuel pre-injected burns together with fuel injected during the main injection. Besides, the effect of high cetane number of GTL is evident at low ambient temperature because its combustion takes place some degrees before compared to both diesel fuels tested.

Dual Fuel Combustion of N-heptane/methanol-air-EGR Mixtures

Numerical simulations are performed to study the combustion processes of n-heptane and methanol/air/EGR under high-temperature and high-pressure conditions relevant to a dual-fuel compression-ignition engine. Detailed chemical kinetic mechanism and transport properties are considered in the simulation. The simulations are carried out by performing three-dimensional (3D) direct numerical simulation (DNS) in a cuboid constant volume enclosure and two-dimensional (2D) DNS in a constant volume domain corresponding to the 3D domain. The results reveal three combustion modes involved in dual fuel engines, the ignition of the n-heptane jet, the propagation of thin reaction fronts in the methanol/air/EGR mixture, and finally the onset of ignition of the entire mixture. In dual-fuel combustion under high initial temperature conditions (1000K or higher) the three different combustion modes occur rather quickly with two distinct peaks of heat release corresponding to the two ignition modes. At low temperatures (800K or lower) the ignition delay time of the mixture is longer and more complete mixing is achieved before the onset of a single ignition of the n-heptane/methanol mixture.

Effects of Injection Timing and Pilot Fuel on the Combustion of a Kerosene-diesel/Ammonia Dual Fuel Engine: A Numerical Study

It is well-known that the transportation sector consumes much petroleum as vehicles move goods and people around. From the many renewable and sustainable fuels proposed, ammonia is one such candidate. In this work, ammonia is introduced into a diesel engine via dual fuel mode whereby the fumigated premixed ammonia in the combustion chamber is ignited by a pilot fuel. The effects of injection timing and pilot fuel on the combustion of a kerosene-diesel/ammonia dual fuel engine are numerically investigated using the KIVA4-CHEMKIN code. It is interesting to note that as the injection timing is advanced, primary as well as secondary heat-release peaks are observed. The secondary heat-release peak is due to the combustion of residual fuel near the cylinder liner as well as in the crevice region and this is caused by an increase in in-cylinder temperature as injection timing advances. Also, as the pilot fuel is changed from diesel to kerosene, the primary peak heat-release increases with advancing injection timing.

Numerical investigation on the combustion and emissions of a kerosene-diesel fueled compression ignition engine assisted by ammonia fumigation

As the world faces energy shortages, it is highly desirable to look for alternative fuels that are sustainable and renewable. Ammonia is one such candidate. In this numerical study, ammonia is applied to a diesel engine via fumigation and a pilot fuel is used to ignite the premixed ammonia. Numerical simulations are carried out using the KIVA4-CHEMKIN code in order to better understand the effects of ammonia combustion on engine performance and emissions. It is seen from this study that ammonia reduces carbon monoxide and carbon dioxide emissions as it replaces the carbon-based pilot fuels. Moreover, nitrogen oxide emissions decrease with little ammonia fumigation and increase with high ammonia fumigation. This is due to combustion temperature, ammonia quantity and ammonia-air kinetics. Furthermore, it is interesting to note that as the injection timing is advanced, primary as well as secondary heat-release peaks are observed. The secondary heat-release peak is due to the combustion of residual fuel near the cylinder liner as well as in the crevice region and this is caused by an increase in in-cylinder temperature as injection timing advances.

Thermal degradation and flame retardant properties of isocyanate-based flexible polyimide foams with different isocyanate indices

A series of isocyanate-based flexible polyimide foams were prepared with different isocyanate indices. The structure and properties of these polyimide foams were characterized in detail. The results indicated that with the increase of isocyanate index, the density decreased from 8.7kg/m3 to 5.7kg/m3. The open cell ratio was in the range of 94.9%–96.4% and less influenced by the content of isocyanate. The compression strength increased first with the increase of isocyanate index, and reached the maximum value at an isocyanate index of 1.04. All the polyimide foams possessed excellent thermal stability, with temperature at weight loss of 5% and 10% being in the range of 288.5–320.0°C and 337.7–369.0°C, respectively. The limiting oxygen index (LOI) values for all the samples were above 25%, indicating the high flame resistance character of polyimide. The heat release peak values, the total heat release and mean heat release rate exhibited similar trends of little changes with isocyanate index varying from 0.89 to 1.04 and increasing rapidly with the index more than 1.11, indicating the side products of amino or uramido produced by excess isocyanate would damage the flame resistance properties of polyimide foams severely.

Evolution of the nickel structure during deformation by shear under high pressure at 150°C

Initial single-crystal nickel deformed by shear under pressure at the temperature of 150°C has been studied. It has been found that, under these conditions, dynamic recrystallization develops in nickel. As a result, after true strain in the range of 4 < е < 9, a heterogeneous structure that consist of recrystallized grains of different defectiveness and microcrystallites is formed. Calorimetric studies have shown that the stored energy varies nonmonotonically with increasing true strain, which is associated with the cyclic character of dynamic recrystallization. In the calorimetric dependence, several peaks of heat release have been revealed that are connected with the nonsimultaneous occurrence of static recrystallization upon heating in nickel with a heterogeneous structure formed upon dynamic recrystallization.

Synthesis and evaluation of an efficient, durable, and environmentally friendly flame retardant for cotton

An efficient and durable formaldehyde-free flame retardant consisting of an ammonium salt of pentaerythritol tetraphosphoric acid (APTTP) was prepared by a solventless synthesis and characterized by Fourier-transform infrared (FT-IR) spectroscopy and nuclear magnetic resonance. The flame retardancy of the treated cotton fabric was enhanced, as assessed by limiting oxygen index (LOI), vertical flammability, and cone calorimetry measurements. The collected results demonstrated that cotton fabrics treated with APTTP exhibited high flame retardancy and excellent durability. Cotton fabric treated with a 140 g/L APTTP solution showed a LOI of 43.8%, and this value reduced to 26.9% after 50 laundering cycles. No after-flame and after-glow phenomena were presented during vertical flammability tests for all cotton fabrics treated with different concentrations of APTTP. Cone calorimetry results revealed a significant reduction in the intensity of the heat release rate and total heat release peaks. X-ray diffraction revealed that the crystalline particles of cotton fibers treated with APTTP were slightly affected compared with those of control sample. FT-IR spectroscopy results revealed that APTTP was grafted on the cotton fibers. Scanning electron microscopy showed that the surface of the treated cotton fibers remained smooth, while thermogravimetric analysis confirmed that the treated cotton fibers easily decomposed to form char. It was proposed that the flame retardant mechanism of APTTP occurred in the condensation phase.

Combined Impact of High Injection Pressure and Injection Timing on the Performance and Combustion of Common Rail Direct Injection (CRDI) Engine Fueled with a Simarouba Biodiesel Blend

This paper discusses the combined impact of high injection pressure and injection timings on the performance and combustion characteristics of a diesel engine using biodiesel ester of Simarouba oil (SOME) blends. A Kirloskar make single cylinder 3.7 kW (5 HP) capacity diesel engine was modified to operate with Common Rail Direct Injection (CRDI) system. Experiments were carried on this engine with CRDI setup, fueled with diesel and SOME biodiesel to optimize the combined Injection Pressure (IP) and Injection Timing (IT). A combination of three different IP of 600 bar, 800 bar, 1000 bar and four different injection timings (IT) of 10°, 18°, 23°, 28° before Top Dead Centre (bTDC) were tested at a constant Compression Ratio (CR) of 16.5, engine speed of 1500 rpm by varying load from 25% to 100% of full load. Maximum Brake Thermal Efficiency (BTE) was recorded at IP of 800 bar and IT of 18°bTDC CA combination for HSD, SOME 20 and SOME 30. Peak pressure and Heat Release Rates (HRR) were studied for IT of 23°bTDC and found maximum values with IP 800 bar for neat diesel (HSD). The findings of this study encourage and emphasize the probability of admitting the higher percentage biodiesel blends with HSD by the make use of a proper combination of high fuel injection pressure and injection timing. Hence it serves to overcome the depletion of neat diesel and its environmental issues.

Effects of center of heat release on combustion and emissions in a PCCI diesel engine fuelled by DMC-diesel blend

The experiments were performed in a reformed single cylinder common-rail diesel engine which adopts a low temperature premixed charge compression injection (PCCI) mode by a pilot-pilot-main injection strategy coupled with heavy EGR. The objective of this study was to examine the combustion, performance and emission characteristics of neat diesel and D10 (diesel fuel with 10% dimethyl carbonate (DMC) by volume) in five center of heat release (COHR) modes, since there is rare research considered these parameters together. The results show that the COHR has significant influence on the in-cylinder pressure, average bulk gas temperature and the major peak of heat release. By means of postponing fuel injection coupled with heavy EGR, a larger fraction of premixed combustion is achieved, while the stability of the combustion is not evidently affected. Both HC and CO emissions increase slightly with retarding COHR due to the decreased temperature during combustion, which does not favor a sufficient late oxidation. The additions of DMC can reduce PM more than 40% compared to neat diesel, while D10 fuel generates more NOx than the diesel fuel. With retardation of COHR, a tradeoff between NOx and PM emissions can be well tuned, thanks to a higher fraction of premixed combustion.

Effects of different piezo-acting mechanism on two-stage fuel injection and CI combustion in a CRDi engine

In this study, the effects of two piezo injectors operated by different mechanisms on multi-injection and Compression ignition (CI) combustion were investigated. High-pressure injectors for CI engines are divided into two categories according to the actuator: Solenoid and piezo injectors. It is commonly known that both injectors have a hydraulic circuit for fuel injection; thus, the performance of the injector is highly dependent on not only hydraulic characteristics such as volume of internal chambers and nozzle geometry, but also the actuation mechanism. Specially, the direct needle-Driven piezo injector (DPI) is introduced in this study and compared with the indirectacting Piezo injector (PI) to investigate the injection characteristics and influences on CI combustion performance by using spray visualization, injection rate measurement, and single cylinder diesel engine experiments, as well as numerical simulation for injection rate modeling of DPI. In the spray visualization experiment, a high-speed camera was used to examine spray tip penetration length and spray speed with respect to each injector. Also, in order to investigate injection rate information, which is a significantly dominant factor in combustion characteristics, the Bosch-tube method was adapted under the condition of a back pressure of 4.5 MPa, corresponding to engine motoring pressure. Also, a single-cylinder CRDi (Common-rail direct-injection) engine experiment was carried out to determine the effects of different piezo-acting mechanisms on two-stage fuel injection and CI combustion. From the key results obtained by this study, the direct needle-driven piezo injector has a faster SOI (Start of injection) and EOI (End of injection). In addition, the overall shape of the injection rate of DPI was narrow and the injection had a higher spray speed than that of PI. Also, DPI has a higher heat release rate and peak pressure, as verified by the engine experiment. In particular, it was found that DPI showed the possibility of combustion improvement when applying a pilot injection strategy.

Influence of injection timing on performance, emission and combustion characteristics of a DI diesel engine running on fish oil biodiesel

The ever increasing demand and depletion of fossil fuels along with environmental concern has prompted search for alternate fuels. Biodiesel is poised to make important contributions to world energy since it is renewable, bio degradable and non-toxic in nature. Various oils have been used in biodiesel production owing to their availability among which fish oil is a significant one. In the present work, experimental investigations were carried out on a single cylinder four stroke, air cooled, constant speed, direct injection diesel engine with a rated output of 4.4 kW at 1500 rpm at different loads and at different injection timings, 21°, 24° and 27°bTDC for studying the performance, emission and combustion characteristics of direct injection (DI) diesel engine fuelled with Ethyl Ester of Fish Oil (EEFO) and its blends. For a diesel engine, injection timing is a major parameter that sensitively affects the engine performance, emission and durability. Oxides of Nitrogen (NOx), Unburnt Hydrocarbon (UBHC) and Carbon Monoxide (CO) emissions in biodiesel blends were lower than diesel, whereas smoke was found to be higher. The brake thermal efficiency for B20 was higher compared to diesel in the entire load spectra. The ignition delay and combustion duration were shorter for biodiesel blends than diesel which results in lower heat release rate, peak pressure and rate of pressure rise. Retardation of injection timing caused decrease in emission and combustion parameters like NOx, HC, CO, peak pressure, ignition delay, combustion duration and heat release rate which increased with advancement in injection timing.

Effect of hydrogen–diesel dual-fuel usage on performance, emissions and diesel combustion in diesel engines

Diesel engines are inevitable parts of our daily life and will be in the future. Expensive after-treatment technologies to fulfil normative legislations about the harmful tail-pipe emissions and fuel price increase in recent years created expectations from researchers for alternative fuel applications on diesel engines. This study investigates hydrogen as additive fuel in diesel engines. Hydrogen was introduced into intake manifold using gas injectors as additive fuel in gaseous form and also diesel fuel was injected into cylinder by diesel injector and used as igniter. Energy content of introduced hydrogen was set to 0%, 25% and 50% of total fuel energy, where the 0% references neat diesel operation without hydrogen injection. Test conditions were set to full load at 750, 900, 1100, 1400, 1750 and finally 2100 r/min engine speed. Variation in engine performance, emissions and combustion characteristics with hydrogen addition was investigated. Hydrogen introduction into the engine by 25% and 50% of total charge energy reveals significant decrease in smoke emissions while dramatic increase in nitrogen oxides. With increasing hydrogen content, a slight rise is observed in total unburned hydrocarbons although CO2 and CO gaseous emissions reduced considerably. Maximum in-cylinder gas pressure and rate of heat release peak values raised with hydrogen fraction.

Assembly and reaction characterization of a novel thermite consisting aluminum nanoparticles and CuO nanowires

A novel approach for assembling Al/CuO thermite consists of aluminum nanoparticles and cupric oxide nanowires has been successfully developed in this study. Aluminum nanoparticles were driven into gaps in the cupric oxide nanowires layer on a copper wire through electrophoretic deposition in this method. The cupric oxide nanowires along with oxide layers were grown on the copper wire via thermal oxidation, and the remaining copper core was the negative electrode that attracted aluminum particles carrying positive surface charges in the ethanol/water solution during electrophoretic deposition. A nanothermite shell enclosing the copper wire was obtained after the process. Considerable heat release from the thermite wire was observed starting from ∼400°C in differential scanning calorimetry measurements. Exothermic solid–solid thermite reactions were fully ignited at 529°C, and the heat release peaked at 566°C. Above the melting temperature of aluminum, another heat release peak, which could be associated with reactions between liquid aluminum and the remaining oxides, was detected at 760°C. Overall heat release of the nanothermite wire assembled with 80V and 10s electrophoretic deposition was 3108J/g. Reaction propagation speed along the nanothermite wire with 10s electrophoretic deposition was the highest at 43.8cm/s, and longer deposition durations resulted in slower burning speeds.