The present experimental work focuses on the combined effect of nano additives, combustion chamber geometry and injection timing in a single cylinder diesel engine fuelled with ternary fuel ...(diesel-biodiesel-ethanol) blends. Ternary fuel (TF) is doped with alumina nano additives and the resulting fuel is termed as high performance fuel (HPF). HPF is subjected to different combustion chamber geometries and TRCC (torroidal re-entrant combustion chamber) geometry is found to be effective among other geometries. HPF operated at TRCC chamber is subjected to four different injection timings namely, 21obTDC (HPF-TRCC21), 22obTDC (HPF-TRCC22), 23obTDC (HPF-TRCC23) and 24obTDC (HPF-TRCC24) respectively. BTE is lowered for HPF-TRCC21 and HPF-TRCC24 by 4.53% and 1.22% while highest BTE of about 33.8% is achieved for 22obTDC in comparison with other blends such as DIESEL-HCC23 (32.75%), HPF-TRCC21 (31.41%) and HPF-TRCC24 (32.53%). Lowest BSEC profile was achieved for HPF-TRCC22. HPF-TRCC22 resulted in lowered HC and CO emissions of about 9.18% and 16.83% in comparison with HPF-TRCC23. HPF-TRCC21 resulted in lowered NOx emissions by 22.53% along with higher HC and CO emissions by 6.13% and 20.51% in comparison with HPF-TRCC23. Cylinder pressure and HRR of HPF-TRCC22 stays at an acceptable range of 75.42 bar and 85.34 J/deg CA in comparison with other test blends. The DIESEL-RK theoretical simulation results are compared with the experimental study conducted at the same operating conditions and its revealed that TRCC combustion chamber geometry is better for enhanced performance and combustion characteristics.
•Novel study on combined effect of nano additives, geometry and injection timing.•In-cylinder flow simulation of different combustion chambers with DIESEL-RK software.•Ternary fuel with 20 ppm alumina nano additive was called high performance fuel.•22oTDC with torroidal re-entrant chamber ensued highest BTE and lowest BSEC.•At 22obTDC, HC and CO were lowered along with marginal higher NOx emissions.
The current study aims to evaluate the performance and emission characteristics of a modified common rail direct injection (CRDI) diesel engine fueled by Ricinus communis biodiesel (RCME20), diesel ...(80%), and their blends with strontium-zinc oxide (Sr@ZnO) nanoparticle additives. The Sr@ZnO nanoparticles were synthesized using aqueous precipitation of zinc acetate dehydrate and strontium nitrate. Several characterization tests were performed to study the morphology and content of synthesized Sr@ZnO nanoparticles. The Sr@ZnO nanoparticles were steadily blended with RCME20-diesel fuel blend in mass fractions of 30, 60 and 90 ppm using a magnetic stirrer and ultrasonication process. For a long term stability of nanoparticles, Cetyl trimethylammonium bromide (CTAB) surfactant was added. The physicochemical properties of the fuel blends were measured using ASTM standards. The CRDI engine was operated at two compression ratios 17.5 and 19.5, 1000 bar injection pressure, 23.5°BTDC injection timing and constant speed. For enhanced swirl and turbulence, and improved spray quality lateral swirl combustion chamber and 6-hole fuel injector were used. The compression ratio of 19.5 and 60 ppm of Sr@ZnO nano-additives showed overall enhancement in engine characteristics compared to RCME20 fuel. The engine characteristics such as BTE, HRR and cylinder pressure increased by 20.83%, 24.35% and 9.55%, and BSFC, ID, CD, smoke, CO, HC and CO2 reduced by 20.07%, 20.64%, 14.5%, 27.90%, 47.63%, 26.81%, and 34.9%, while slight increase in NOx for all nanofuel blends was observed.
The concept of combustion chamber modifications of diesel engines has been attracting much attention in the field of engine research. Many researchers are investigating modified combustion chambers ...in modern engines because several studies revealed encouraging results: improved brake thermal efficiency (BTE), and reduced brake specific fuel consumption (BSFC), hydrocarbon (HC), carbon monoxides (CO), soot and smoke emissions. However, further investigation is needed into chamber modification vis-a-vis the creation of ordered turbulence, which can help to control nitrogen oxides (NOx) emissions; besides, the rapid turbulence formations on piston crowns lead to impotent tendencies like knocking, system failure and unregulated emissions. A survey of recent studies in the literature has revealed that these chamber modifications can impact positively on air-fuel mixture rates, fluid distribution, heat transfer rates and emission formations. The primary focus of this study is to evaluate engine combustion characteristics,performance and emissions due to chamber modifications by investigating their effect on different chamber profiles and fuels. This critical analysis of these potential combustion factors can be useful to several research groups for understanding the key factors, challenges, and state of art of chamber modifications. It emerges from the literature that these modifications are easily adaptable and can accommodate a variety of research strategies and options. Thus, this review underscores that the continuation of this study should focus on compatible models with multiple advanced combustion strategies and computational tools in order to attain further refinements to the engine outcomes.
•Biodiesel combustion with modified chambers is reviewed and presented.•Chamber modifications showed improved biodiesel combustion characteristics.•Chamber modifications improve engine combustion with better air-fuel mixture rates.•Chamber modifications can reduce emissions with improved engine thermal efficiency.
•Reactor and continuum models were used for calculations of an ammonia-fueled gas turbine combustion chamber.•A gas turbine combustion chamber with mixing of components in the pre-chamber has been ...developed.•The influence of combustion chamber parameters on ammonia burnout was investigated at a thermal power of 1 MW.•Ammonia combustion is ensured with reactant residence times not exceeding 0.025 s.•The use of a radial-axial swirler increased the stability of the combustion process.
Achieving climate neutrality requires the use of alternative hydrogen carriers for energy purposes, with ammonia currently being considered. One potential application in the energy sector is gas turbine systems, for which combustion chambers need to be designed to efficiently combust ammonia within an airflow. This paper focuses on theoretical investigations of fuel combustion completeness and environmental cleanliness of a gas turbine combustion chamber with a thermal power output of 1.0 MW, operating on gaseous ammonia. A prospective scheme for organizing processes is proposed, based on pre-mixing ammonia with a portion of air in a special pre-chamber, the sequential introduction of the remaining air through a radial-axial swirler and a series of holes in the flame tube, ensuring stable fuel combustion. Two approaches were used for modeling combustion processes in such a combustion chamber: one based on chemical reactor theory and the other on three-dimensional hydrodynamic analysis. After conducting a detailed kinetic analysis, it was concluded that to maintain stable ammonia combustion while varying the air excess coefficient in the primary combustion zone from 1.4 to 2.0, the reactants need to remain in this zone for a duration exceeding 0.025 s. Based on these parameters, design schemes for two combustion chamber variants were developed, differing in combustion tube length and air distribution pattern, for operation with an ammonia flow rate of approximately 50 g/s and a pressure of 0.3 MPa, determining a gas outlet temperature of 1490 K. Three-dimensional calculations of aerodynamic flow structures, ammonia combustion, and formation of toxic components were conducted, revealing that the proposed process organization scheme ensures complete ammonia combustion and small nitrogen oxide emissions. These results have potential applications in the development of new gas turbine combustion chamber designs for decarbonized energy systems, including those integrated with solid oxide fuel cells.
Self-excited thermoacoustic instabilities in symmetric annular combustion chambers typically give rise to spinning, standing and mixed azimuthal modes which are time-varying in nature and occur in a ...highly noisy environment due to turbulent combustion. We investigate the effect of linear ramps of increasing and decreasing equivalence ratio on the operating limits and thermoacoustic dynamics, from near lean blow-off to near flashback, in a laboratory scale annular combustor. The combustor features 12 lean-premixed hydrogen–methane flames at a fuel composition of 70% hydrogen and 30% methane by power. Equivalence ratio ramps were conducted for different thermal powers P=4, 6 and 8 kW per burner and three different ramp times tramp=5, 20, 60 s to simulate dynamic operation. It was found that ramping leads to self-excited instabilities that exhibit repeatable modal dynamics which depend on thermal power, ramp direction and duration. Different types of hysteresis were observed between the upward and downward ramps which affected the amplitudes and the stable operating range. The hysteresis phenomena also showed repeatable behaviour in terms of the nature and orientation angle. In one specific case, the simultaneous existence of two spinning modes was observed before the appearance of mode hopping leading to both an increase in frequency and doubling of the amplitude. High-speed OH* chemiluminescence of the flames showed that the mode hopping was accompanied by a change in the flame shape which becomes more compact and distributed.
The fuel properties in Gasoline Combustion ignition modes (GCI) have been adapted by mixing high reactivity fuels for improving poor combustion stability with pure gasoline. Precise control of the ...injector tip temperature, as well as the fuel temperature, are considered as the essential boundary conditions to conduct the fundamental investigation on combustion process of GCI spray. Therefore, the impacts of an injector cooling jacket on the spray and combustion developments of a mixture contains 60% gasoline and 40% hydrogenated catalytic biodiesel are studied using a constant volume combustion chamber (CVCC) working under GCI mode. A dummy injector is equipped with a thermocouple to measure the effects of the cooling jacket and ambient temperature on tip temperature. The Schlieren imaging and Diffused Background Illumination Extinction Imaging techniques are employed to visualize the reacting spray development and in-flame soot formation. The results illustrate that the injector tip temperature is well-controlled with aiding of the cooling jacket, which only increases by 35 K with increasing ambient temperature by 250 K. Furthermore, it is found from the optical experiments that the liquid length, ignition delay and lift-off length are enlarged for the cooling mode compared to that of the uncooled one. The cooling jacket also brings in a larger overlapping area between liquid length and flame lift-off length. However, the in-flame soot production for the cooling jacket is increased more than twice compared to that of the uncooled one.
The present work introduces an annular combustion chamber operated at intermediate pressures. The combustor is operated with CH4-H2 blends leading to a variety of azimuthal combustion instabilities. ...The influence of the hydrogen content, the air mass flow rate and the equivalence ratio on the instabilities is investigated over a wide range of operating conditions with mean chamber pressures from 1.5 to 3.3 bar. This leads to a range of exit boundary conditions, from partially to fully reflecting. It is found that pure methane and methane-hydrogen mixtures with low hydrogen contents result in stable combustion. However, when the hydrogen content reaches 25% by volume high-amplitude instabilities are excited, which exhibit higher order harmonics with significant pressure amplitude contributions. Such harmonic response was not previously observed in atmospheric annular combustors. The amplitudes decrease slightly when the H2 content is increased further. The harmonic response is found to be amplitude dependent with fewer significant harmonic contributions occurring at low-amplitudes and a cut-on amplitude of the fundamental mode at which higher harmonics become significant. The interaction between the harmonic components of the pressure amplitudes is shown to follow a quadratic relationship. The modal response was analyzed and it was found that all high-amplitude instabilities feature clockwise spinning modes whereas lower-amplitude instabilities feature counter clockwise spinning modes. Finally, a low- and high-amplitude case were investigated in detail and phase-averaged images are discussed. The low-amplitude instabilities result in flame dynamics similar to those observed in atmospheric combustors previously whereas the high-amplitude instabilities exhibit large oscillations in the flame height and intensity. A characterization of the boundary conditions is also provided for numerical simulations which includes temperature measurements, acoustic characterization and cold flow velocity profiles.
•Novel research octane number and octane sensitivity characterization technique.•Ignition delay measurements predict research octane number and octane sensitivity.•Research octane number and octane ...sensitivity predicted using 40 mL sample volume.•Methodology validated over a wide variety of fuel chemistry.
Current research octane number (RON) and motor octane number (MON) gasoline performance characterization techniques use dated, complex engine testing methodology and limit researchers’ ability to easily characterize small volumes of experimental fuels. A novel methodology is presented that correlates measured ignition delay (ID) time to RON in an Advanced Fuel Ignition Delay Analyzer (AFIDA) constant-volume combustion chamber device at a single pressure/temperature condition, with an r2 of 0.99 and standard error (SE) of 1.0. The correlation of the slope of the ID time between two additional temperature points to octane sensitivity (S) produces an r2 of 0.97 and SE of 0.69; however, fuels with S > 12 are indistinguishable. These results are based on methodology calibration using 31 primary and toluene reference fuels containing 0%─40% ethanol with RON values ranging from 85 to 113. Validation of these methods using a 102-sample fuel matrix spanning an array of base fuels and additive chemistry designed to test the robust applicability of the method, along with pump gasoline and high-octane surrogate blend samples, demonstrates an r2 of 0.94 and SE of 1.3 for the RON correlation over all samples, whereas the equivalent S correlation produces an r2 of 0.78 and SE of 1.2 by excluding two additives, 3-pentanone and diisobutylene, which displayed poor S correlation results. This novel AFIDA analysis method can be performed in 1 h and with 40 mL of fuel, offering significant improvements in time and volume requirements over traditional techniques.
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