Low Temperature Combustion Research Articles

Надежность и безопасность газифицированных пунктов нагрева шахтного воздуха

Eighteen years operation experience of gas air heaters RG2000 for Ural mines is considered. Earlier published scientific research, and the accumulated actual data on the safe operation of gas air heating points for mine ventilation are analyzed. Special safety principles are formulated that are used when placing gas equipment near the air supply shafts of the mine. The data obtained over the long years of operation of an innovative technical air heating system were studied related to most important parameters including compliance with the sanitary and hygienic requirements for the mine ventilation air. The results are presented concerning the monitoring of the supply air, which confirm its stable and safe quality. It is noted that the Canadian mining occupational safety and health regulations allow to use direct gas-fired air heaters. The spread of this technology in our country is possible only if the strict Russian sanitary and hygienic requirements for air pollution at the production sites are met. For example, Russian regulations in the field of maximum permissible concentration of the nitrogen oxides are 3–10 times lower than the foreign ones. In this regard, the supply air heaters with direct gas heating cannot be used in Russia for ventilation of the underground workings. The results of a successful solution to the problem of heating mine air using an innovative technology of low-temperature flare impact combustion of a homogeneous methane-air mixture are presented in the article. This approach allows 10-40 times to reduce the ingress of harmful substances into the air supplied to the mine, which fully meets the current hygienic requirements and regulations at the mining enterprises of Russia.

Multipulse Ballistic Injection: A Novel Method for Improving Low Temperature Combustion with Early Injection Timings

Nowadays, increasingly stricter regulations on emission reduction are inducing rapid developments in combustion science. Low-temperature combustion (LTC) is an advanced combustion technology that increases an engine’s thermal efficiency and even provides low emissions of nitrogen oxides (NOx) and particulate matter (PM). The technology often uses early direct injections to achieve sufficient mixture homogeneity. This leads to increasing wall wetting and lower combustion efficiency. This paper introduces the Multipulse ballistic injection (MBI) method to improve combustion with early injection timings. The research was carried out in a four-cylinder medium-duty diesel engine with high-pressure exhaust gas recirculation (HP-EGR). The investigation was divided into two experiments. In the first experiment, MBI was examined without EGR, and in the second, EGR was applied to study its effects. It was found that the MBI strategy decreased wall wetting and increased homogeneity and the indicated mean effective pressure (IMEP) at early injection angles.

Hydrogen shift isomerizations in the kinetics of the first and second oxidation mechanism of diethyl ether combustion

The kinetics of ROO and OOQOOH radicals play an important role in simulating the ignition behavior of fuel during low-temperature combustion. Diethyl ether (DEE) was chosen in the present work because of its typical and representative character. In this work, we use the multi-structural torsional (MS-T) and multi-structural local quansi-harmonic (MS-LQH) methods to deal with multiple conformations and coupled torsion for structures of reactant, transition state and products, and use the multi-structure variational transition state theory (MS-VTST) to perform dynamic calculations for hydrogen shift isomerizations. Our results indicate that the multistructural anharmonicity effect plays a crucial role in determining the accuracy of the thermodynamic and kinetic quantities. Morever, the kinetics calculations indicate that rate constants for intramolecular hydrogen abstraction in the first oxidation mechanism (ROO → QOOH) and the second oxidation mechanism (OOQOOH → Products) exhibits different feature. This work will be helpful for understanding the oxidation mechanism of diethyl ether combustion.

Evaluating OMEx combustion towards stoichiometric conditions in a compression ignition engine

Low energy density fuels combined with low temperature combustion modes have demonstrated a great contribution to engine-out NOx and soot reduction. Additionally, synthetic fuels have become an important way of reaching carbon neutral utilization of hydrocarbon-based fuels and internal combustion engines. Specifically, poly-oxymethylene dimethyl ethers (OMEx) have demonstrated great advantages in combination with conventional fuels with higher energy content to compensate that aspect to reduce NOx emissions below the EU VI homologation normative while maintaining ultra-low soot emissions with a great benefit in CO2 emissions in a well-to-wheel basis. Nonetheless, the properties of this fuel in single-fuel combustion strategies are not thoroughly investigated in the literature. The objective of this work is to investigate the capabilities of OMEx fuel under conventional combustion modes compared to those of conventional diesel combustion. To do this, an experimental characterization under stoichiometric combustion has been carried out to evaluate the impact on engine hardware demand and total emissions. Additionally, a brief exploration under leaner conditions is performed. The results obtained from this work point out that, even under ultra-high EGR rates to reach high fuel-to-air ratios, OMEx fuel can emit ultra-low soot and NOx emissions with more than 90% reduction compared to diesel on engine out emissions. Under stoichiometric conditions, a significant increase appears on CO, UHC due to excessive usage of EGR and equivalent fuel consumption is penalized from 15% to 40% depending on the operating condition, but under slightly leaner conditions, a region where equivalent fuel consumption is improved with respect to CDC appears, and the four main pollutants investigated are almost EU VI compliant, exposing a very high potential for this fuel.

Routes for energy and bio-silica production from rice husk: A comprehensive review and emerging prospect

The high energy and silica contents of rice husks make them attractive for use in renewable energy and green chemical strategies. This review comprehensively discussed the potential route of rice husk utilization to energy and bio-silica simultaneously which is still lacking to investigate. The ash content in the dry rice husk could be up to 25 wt% and the high silica content in the rice husk ash could reach 99.77 d b. wt%. About 1 tonne/h of rice husk combustion could produce about 600–700 kWh of averaged net electricity so that it can be employed to support a small and simple power plant. Apart from that, applying acid leaching as a pretreatment before rice husk ash extraction with NaOH could achieve bio-silica with 98% recovery, 99.7% purity, and 400.69 m2/g surface area. Rice husk combustion in a suspension combustor seems to be appropriate to maintain the low combustion temperature at 700 °C in order to prevent the crystalline silica formation in the rice husk ash. The combustion efficiency is very high with 0.8% of unburnt carbon content in the ash as well as CO and NOx emissions are below 250 ppm. This review reveals that the industrial-scale for energy and amorphous bio-silica production from rice husk through a suspension combustor with optimized operating parameters emerges as a future prospect. It can lead to sustainability and self-reliance on chemicals and energy sectors, of which there are many research and development challenges to overcome.

Facile solution combustion synthesized, Li doped ZnO nanostructures for removal of abiotic contaminants

ZnO is a versatile photocatalytic material, yet it needed further modifications to explore it on the commercial scale. In the present study, photoactive Li doped ZnO nano-materials with different Li content were synthesized by adopting a facile low-temperature solution combustion approach. Li was introduced to improve ZnO characteristics correspond to photocatalytic efficiency. The effect of lithium doping on morphology, crystallinity, chemical state, and optical properties were investigated by utilizing various advanced techniques. The characterization analysis confirms the presence of thermally stable, well-crystalline wurtzite ZnO with a low bandgap and porous nature. Organic dye, Cibacron Red (CR), and a pesticide, Triclopyr (TC) were taken as model pollutants to evaluate the photodegradation performance of all samples under UV light source. Li doped ZnO nanomaterials containing 5 mol% Li attained the highest photocatalytic activity for the removal of both pollutants. The results of the study demonstrate that a strong electronic interaction between Li and ZnO results in the improvement of charge transferability and retards their recombination. The alteration in optical and surface properties of ZnO due to the substitution of Li into ZnO lattice was another reason for the superior activity of Li doped ZnO.

Numerical prediction of the performance and emission of downsized two-cylinder diesel engine for range extender considering high boosting, heavy exhaust gas recirculation, and advanced injection timing

This study investigates the feasibility of a diesel engine to be applied as a power generator to extend the driving range of electric vehicles by evaluating the combustion and emission characteristics of the engine in the process of converting an existing diesel engine to a downsized diesel engine. The study was conducted under a wide range of operating conditions from 1250 to 2500 RPM. In addition, a simulation was performed to analyze the thermal characteristics of the engine under the application of exhaust gas recirculation (EGR) and the responsiveness of the combustion performance to an increase in the boost pressure. The EGR application caused ignition delay and reduced nitrogen oxide (NOx) emissions due to the low combustion temperature. In addition, the increase in boost pressure proved the feasibility of a downsized diesel engine to be used as power generator by improving the lowered performance with the application of EGR. By applying an appropriate advanced injection timing at the maximum load under each operating condition, both the combustion performance and brake-specific fuel consumption were improved; moreover, the NOx emission met the EURO-VI emission regulation. Through verification of the performance and emission of a downsized diesel engine, it was proved that the downsized diesel engine is an effective electric vehicle for power generators.

Low-temperature combustion of methane over graphene templated Co3O4 defective-nanoplates

Transition metal oxides are the potential catalysts to replace noble-metal based catalyst for the catalytic combustion of methane due to the tolerable reactivity and low cost. However, these catalysts are challenged by the low temperature reactivity. Herein, the surface defective Co3O4 nanoplates are realized through a facile co-precipitation and thermal reduction method with the association of GO. The resultant catalysts (CoGO50) demonstrate a superior low-temperature reactivity for the methane oxidation to CO2 and H2O in comparison with the common Co3O4 catalyst. The reliable stability of CoGO50 catalyst was proved by 80 h testing with intermittent feeding of water vapor. The experimental analysis demonstrates that the presence of a small amount of GO significantly affects the catalysts in surface valence state, active oxygen species and surface oxygen vacancies through reacting with the cobalt oxide as a reductant. Moreover, GO plays as 2D confine template to form smaller and thinner nanoplates. This work provides a facile method to control the surface properties of catalyst not only for Co3O4 based catalysts but also for wider solid catalysts.

Nonlinear Isotherm and Kinetic Modeling of Cu(II) and Pb(II) Uptake from Water by MnFe2O4/Chitosan Nanoadsorbents

Researchers are in continuous search of better strategies to minimize, if not prevent, the anthropogenic release of toxic heavy metals, such as Cu(II) and Pb(II), into drinking water resources and the natural environment. Herein, we report for the first time the low-temperature combustion synthesis of magnetic chitosan-manganese ferrite in the absence of toxic cross-linking agents and its removal of Cu(II) and Pb(II) from single-component metal solutions. The nonlinear Langmuir model best described the isotherm data, while the nonlinear pseudo-second order model best described the kinetic data, signifying monolayer Cu(II) or Pb(II) adsorption and chemisorption as the rate-determining step, respectively. Adsorption capacities by magnetic chitosan-manganese ferrite obtained for both metals were consistently higher than those by manganese ferrite, indicating that chitosan enhanced the performance of the magnetic adsorbent. The maximum adsorption capacities of magnetic chitosan-manganese ferrite for Cu(II) and Pb(II) were 14.86 and 15.36 mg g−1, while that of manganese ferrite were 2.59 and 13.52 mg g−1, respectively. Moreover, the adsorbents showed superior binding affinity and sorption for Pb(II) than Cu(II) owing to the stronger ability of the former to form inner-sphere complexes with manganese ferrite and magnetic chitosan-manganese ferrite. Finally, thermodynamic studies revealed that the uptake of either Pb(II) or Cu(II) by magnetic chitosan-manganese ferrite was spontaneous and endothermic. The as-prepared adsorbent was characterized for morphology, elemental composition, surface functional sites, and particle size using scanning electron microscopy, energy dispersive spectroscopy, Fourier transform infrared spectroscopy, and dynamic light scattering technique, respectively.

Large eddy simulation of n-heptane/syngas pilot ignition spray combustion: Ignition process, liftoff evolution and pollutant emissions

The utilization of syngas in the internal combustion engine is one way to reach low carbon emission engine. The n-heptane/syngas pilot ignition spray combustion is simulated here by high fidelity model with different syngas compositions. It is found that the ambient syngas suppresses the ignition by diluting the ambient oxidizer (non-chemical effect) and by affecting the chemical reactions (chemical effect). The consumption of OH radicals through H2+OH = H + H2O and CO + OH = CO2+H in low temperature combustion (LTC) stage is shown to be the main reason for the suppression of ignition. Cool flame propagation into the rich mixture in the mixing layer of n-heptane jet is observed during the transition process from LTC to high temperature combustion (HTC). CO is found to assist the transition to HTC through CO + HO2 = CO2+OH. On the contrary, H2 slows down the cool flame propagation and narrows down the cool flame flammability range, which retards the onset of HTC. The effects of syngas compositions on the flame structure and emission formation are discussed in detail. Due to the upstream auto-ignition, a cool/diffusion/hot flame structure is identified at the liftoff position in dual-fuel case, which drastically changes the flame structure. And more soot formation in early stage is found in dual-fuel cases due to the naturally richer mixture.

Combustion in the ZrF4-Mg-Si and ZrF4-Al-Si systems for preparation of zirconium silicides

The exothermic reactions in the ZrF4−Mg-Si and ZrF4-Al-Si systems are investigated by a fast temperature recording (thermocouple) technique, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). A quenching method is used to arrest the combustion process and conduct a layer-by-layer analysis of the products by x-ray diffraction (XRD) and electron microscopy. Two seemingly similar reactive systems exhibited considerably different combustion characteristics, composition, and morphology. Based on these investigations, we propose and discuss phase formation mechanisms at the early stages for each system. Three different pathways involving the reaction of ZrF4 with other reagents and the Mg2Si intermediate are identified to occur in the ZrF4−Mg-Si system. Contrary to the complex mechanism in the ZrF4−Mg-Si system, the early stage of the combustion process for the ZrF4-Al-Si system involves the interaction of ZrF4 with Al-Si eutectic melt. The exothermic reaction between reduced solid Zr and Si melt is the primary heat-generating step for both systems in spite of substantial differences in the early stages of the reactions. The silicon content in the reactive mixtures governs the phase composition of products. The ZrSi2 phase, with a high growth rate, forms first on the Zr particle surfaces and then grows by a reactive diffusion mechanism. The ZrSi2+Zr reaction produces silicon-lean phases (e.g., ZrSi) when the silicon supply is limited. The combustion temperature also has a considerable influence on the phase compositions of the products. High combustion temperature in the ZrF4+2Mg+Si mixture enables the formation of multiphase products (α-ZrSi and β-ZrSi), whereas the relatively lower temperatures in the 3ZrF4+4Al+3Si mixture yields a single-phase α-ZrSi. Lower combustion temperatures also make the ZrF4-Al-Si system more advantageous for the preparation of zirconium silicides.

The effects of increasing FAME biodiesel content on combustion characteristics and HC emissions in high-EGR low temperature combustion

An experimental study was performed on a single-cylinder high-speed direct-injection diesel research engine to determine the effects of increasing biodiesel content on the combustion characteristics and HC emissions during high-EGR low temperature combustion operation. Two test points, a moderately dilute low-load condition and a high-EGR medium-load condition, were examined at a constant speed of 1500 rpm with a fixed input fuel energy content and start of injection timing.The results show the two operating conditions to have very different sensitivities to the fuel’s biodiesel content and, as a result, to demonstrate contrasting behaviour with respect to the variation of HC emissions with blend composition. For the low load, medium dilution case, ignition delay, combustion phasing and combustion duration are essentially independent of biofuel content while HC emissions are reduced with respect to the base diesel. For the high-EGR, medium load condition, ignition delay is reduced and combustion phasing advances with increasing levels of biofuel content. HC emissions increase with increasing biofuel content. Crank-angle aligned HC measurements indicate the significance of the piston/wall crevice volume as an HC source in high-EGR LTC.

Numerical Investigation of Negative Temperature Coefficient Effects on Sooting Characteristics in a Laminar Co-flow Diffusion Flame.

It is a common sense that diesel engines produce worse soot emission than gasoline engines, even though gasoline direct injection also brings about terrible sooting tendency. However, reports showed that diesel emits less soot than gasoline in laminar diffusion flames, which implies that soot emission is a combined effect of multiple factors, such as the combustion mode, physical properties of the fuel, and also fuel chemistry. This work, thus, conducted numerical calculations in laminar co-flow diffusion flames of fuels with different negative temperature coefficient (NTC) behaviors in an order of n-heptane > iso-octane > toluene to solely evaluate the chemical effect, especially the role of low-temperature combustion on soot formation. 2-Dimensional simulations were carried out to obtain the soot distributions, and 0-dimensional simulations were performed to analyze the chemical kinetics of polycyclic aromatic hydrocarbon (PAH) formation and low-temperature reaction sensitivities. The grids of the 2-D model converged at 80(r) × 196(z), and the boundary conditions of both models were set to eliminate the influence of physical factors as much as possible. The results showed that there were three main reactions associated to the formation of aromatic hydrocarbons A1 at the first-stage combustion in the n-heptane flame and the iso-octane flame, in which the reaction of C7H15 + O2 = C7H15O2 enhances the NTC behavior. The first two reaction pathways generated larger molecular hydrocarbons and were unfavorable by A1 formation and therefore inhabit the PAH formation, and 49.8% of C7H16 reacted through the large molecular pathways, while the percentage for C8H18, with weaker NTC behavior, was only 37%. Toluene with even weaker NTC behavior showed no low-temperature oxidation. Therefore, in a more general case, fuels with stronger NTC behavior smoke less, and this conclusion could be promising potential to reduce soot emission in future.

Investigation of Low-Temperature Lean Combustion Characteristics in Power Plants with External Heating of Components

An integral part of any open-type gas turbine plant is a low-emission combustion chamber, which is usually two-zone and cooled. One of the ways to reduce emission of harmful substanc-es is organizing low-emission low-temperature lean combustion with external heating of compo-nents. This paper investigates the effect of external heating of air and fuel gas on expansion of the lower combustion limit and stable flame position in a single-zone uncooled combustion chamber of a microgas turbine power plant. Stable position of the flame front in combustion chambers of this type mainly depends on the ratio between the average flow rate of the combus-tible-air mixture and the rate of turbulent combustion. This ratio depends on thermal, gas-dynamic, thermochemical and geometric factors. The purpose of this work is to substantiate the possibility of using the relative flow rate as a generalized characteristic. This goal was achieved in processing a large amount of published experimental data and numerical modeling of low-temperature combustion of lean mixtures. The most significant research result is determination of the range of relative flow rate (gk = 0.3…3.5·10-4 kg⁄s∙N), at which it is possible to ensure sta-ble flame position in a single-zone combustion chamber. Significance of the obtained results lies in the fact that using the relative flow rate makes it possible to quickly determine and analyze the geometric and gas-dynamic parameters and characteristics of turbulent combustion in com-bustion chambers of micro-gas turbine power plants.

The examination of injection strategies of jet propellant-8 for compression ignition engine with a low compression ratio

Jet Propellant-8 (JP-8) is used as a fuel for standard CI engine instead of diesel oil, especially in military applications on a large scale. For all such applications, the engine regulation parameters are optimal for diesel oil. The properties of kerosene-type fuel, encourage to test different strategies of mixture creation and combustion modes which could be more effective for JP-8 than these elaborated for diesel oil. The paper describes an experiment focused on finding an injection strategy for effective application of JP-8 to a CI engine with low compression ratio. To find an effective way of JP-8 application, the search described in the paper started from the investigation of Low Temperature Combustion (LTC) possibilities, including Homogeneous Charge Compression Ignition (HCCI) engine operation. It led to Partially Premixed Combustion (PPC) with the injection synchronised with the start of mixing controlled phase of combustion. It is also presented how small changes in the injection sequence could heavily influence the combustion phases and very significantly modify the combustion process. For the tests, a naturally aspirated AVL research engine equipped with a common rail system was adapted. The low compression ratio (CR=12:1) was applied. The experiment excluded Exhaust Gas Recirculation (EGR) and mixture dilution with the air. The paper contains the comparison of JP-8 combustion parameters, engine performance and emissions parameters obtained for different injection strategies.

Particulate characteristics of low-temperature combustion (PCCI and RCCI) strategies in single cylinder research engine for developing sustainable and cleaner transportation solution

In this experimental study, particulate matter (PM) characterizations of different low-temperature combustion (LTC) strategies have been compared with conventional compression ignition (CI) combustion for finding out a sustainable and cleaner transport solution. LTC strategies included premixed charge compression ignition (PCCI) and reactivity-controlled compression ignition (RCCI) combustion. Particulate sampling and characterization were carried out in a single-cylinder diesel engine. All engine tests were performed at 1, 2, 3, 4 bar brake mean effective pressure (BMEP) at 1500 rpm. CI and PCCI combustion experiments were performed using mineral diesel as the test fuel. However, mineral diesel and methanol were used as high reactivity fuel (HRF) and low reactivity fuel (LRF), respectively in the RCCI combustion strategy. For all combustion strategies, fuel injection pressure (FIP) was kept constant at 500 bar. However, the number of injections and start of injection (SoI) timings were varied to optimize the engine performance. Results showed that the RCCI combustion strategy emitted a relatively lower concentration of particles than the other two strategies (PCCI and CI). A relatively higher number concentration of accumulation mode particles (AMP) compared to nucleation mode particles (NMP) in the exhaust of the RCCI combustion strategy was an important finding of this study. Number-size and mass-size distributions of particles emitted from different strategies also exhibited the dominant concentration of particles in the CI combustion strategy. PM bound trace metal analysis was yet another critical aspect of this study, which showed that both RCCI and PCCI strategies emitted a relatively lower concentration of trace metals than the conventional CI combustion strategy. Parametric analysis of different PM characteristics and NOx-PM trade-off analysis also demonstrated the importance of LTC strategies over the conventional CI combustion strategy. Overall, this study demonstrated that all LTC strategies could be used for PM and NOx reduction; however, the RCCI combustion strategy was more dominant in NOx and PM reduction, in addition to having an excellent capability of using alternative fuel in the quest for developing sustainable transport solution.

Magnetically Assembled Photonic Crystal Gels with Wide Thermochromic Range and High Sensitivity.

Thermochromic poly(N-isopropyl acrylamide) (PNIPAM) photonic crystal gels based on 1D magnetically assembling colloidal nanocrystal clusters have attracted much attention due to its convenient preparation process, striking color response, and good mechanical strength. However, there remain challenges to broaden the thermochromic range and improve the sensitivity for their iridescent color display. Here, a PNIPAM photonic gel with wide thermochromic range and high sensitivity is prepared by using four-arm star poly(ethylene glycol) acrylamide (PEGAAm) as cross-linker at appropriately reduced magnetic field strength as well as cross-linker content. PEGAAm improves the homogeneity of the microstructure in PNIPAM photonic gel and thus maintains the structure colors at a wide temperature range from room temperature to 44°C. The reduced magnetic field strength of 70Gs and low cross-linker content (the molar ratio of monomer to cross-linker of 300:1) lead to a large initial lattice spacing of the photonic gel and thus wide diffraction wavelength migration of 194nm. This optimized PNIPAM gel exhibits vivid iridescent colors from orange-red to indigo blue as temperature increases from 20 to 44°C with satisfactory repeatability. Therefore, it may be an ideal candidate for temperature sensors and displays with utility and accuracy such as low-temperature burns.

Phytochemical mediated synthesis of praseodymium doped beta-eucryptite nanophosphor for ultraviolet stimulated fluorescence based unclonable security applications

Herein, we reported the preparation of orange-red emitting Pr3+ (1–11 mol %) doped beta-eucryptite (LiAlSiO4) nanophosphors via a simple low-temperature solution combustion method. The prepared beta-eucryptite revealed hexagonal crystal structure. The Pr3+doped beta-eucryptitedisplays broad emission peak at 608 nm along with a weak intensive peak at 632 nm ascribed to1D2→3H4and 3P0→3F2transitions, respectively. Furthermore, color coordinates of Pr3+ doped beta-eucryptite nanophosphors are well located in orange-red region. In the dispersion of ac conductivity over the frequency band comprises with two significant frequency nonresponsive and responsive conductive bands. The luminescent unclonable security ink is prepared using Pr3+doped beta-eucryptite nanophosphorsto encode security labels and are completely invisible under normal white light, while it exhibits clear orange-red emission upon ultraviolet 365 nm light. The overall aforementioned results clearly validated that the Pr3+doped beta-eucryptitenanophosphors is establish to be a suitable component for multifunctional applications.

An innovative research on variable compression ratio in RCCI strategy on a power generator diesel engine using CNG-safflower biodiesel

The CNG usage as a fuel in IC engines have many advantages such as decreasing CO2 and PM and smoke emissions and in many cases reducing NOx emission, along with its low prices and naturally abundance spread on the world. In heavy loaded operation of diesel engines, it becomes very hard to control excessive NOx, and PM formation in the exhaust emissions and smoke accumulation especially for biodiesel usage. In the present study, in order to achieve the usability of higher percentages of biodiesel with CNG, the low temperature combustion of reactivity controlled compression ignition (RCCI) strategy have been applied in a single cylinder diesel engine with variable compression ratios. The CNG, as the low reactivity fuel, was subjected to the intake manifold as the substitute the gas with 5%, 10% and 15% of biodiesel under 1500 rpm and 10.8 kW(full load) load of the engine with variable compression ratios from 13:1 to 19:1 in order to investigate the effects of compression ratios on RCCI operation with high percentages of biodiesel and CNG usage. Apart from the main performance, emissions and combustion indicators of diesel engines tests, 3 novel parameters (SPE, STE and SHRE) were created for the first time in order to deeply evaluate the combustion. Mean of cylinder pressure was increased while combustion duration was lowered for CNG usage with biodiesel. BTE was increased while BSEC and BSFC were decreased in either operation of biodiesel/CNG RCCI and various CR. In addition, NOx emissions were lowered for CNG usage and CR decrease, along with smoke decrease for biodiesel/CNG RCCI combustion.

Evaluation of reactivity controlled compression ignition mode combustion engine using mineral diesel/gasoline fuel pair

Stricter emission norms, scarce availability of conventional fuel resources, and moderate engine efficiency are primary concerns for both spark ignition (SI) and compression ignition (CI) engines. The use of advanced low-temperature combustion technologies can resolve these issues, amongst which reactivity-controlled compression ignition (RCCI) mode combustion has emerged as an important one. RCCI mode combustion exhibits significantly lower exhaust emissions (oxides of nitrogen [NOx] and particulate matter [PM]) compared to CI mode combustion and delivers higher BTE compared to SI mode combustion. In this study, RCCI mode combustion has been investigated in a single-cylinder research engine using gasoline and mineral diesel as low reactivity fuel (LRF) and high reactivity fuel (HRF), respectively. Experiments have been performed at different premixed ratios of LRF (premixed ratio [rp] = 0, 0.25, 0.50, and 0.75) and four-engine loads (1 bar to 4 bar BMEP) at a constant engine speed of 1500 rpm. The use of gasoline in RCCI mode combustion resulted in relatively smoother RCCI mode combustion compared to baseline CI mode combustion. The presence of low reactivity gasoline led to a slightly retarded start of combustion (SoC) and combustion phasing (CP), which improved the performance of the RCCI mode combustion engine. RCCI mode combustion produced relatively lower NOx emissions compared to baseline CI mode combustion. However, hydrocarbon (HC) and carbon monoxide (CO) emissions from RCCI mode combustion were significantly higher than the CI mode combustion. Lower PM emissions from RCCI mode combustion was an important observation of this investigation. Qualitative correlations between different parameters such as PM number and mass-size distributions, total particulate mass (TPM)-NOx, etc., revealed that RCCI mode combustion was capable of simultaneous reduction of NOx and PM, which is otherwise difficult in conventional CI mode combustion engines