Showing papers on "Ignition system published in 2021"

Clean combustion and emissions strategy using reactivity controlled compression ignition (RCCI) mode engine powered with CNG-Karanja biodiesel

Abstract: Heterogeneous combustion in a diesel engine is noisier, uncontrolled and more polluting. This can be achieved with a strategic approach of a reactivity-controlled compression ignition (RCCI) mode engine that operates with low and high reactive fuel combinations. In the present work, a diesel engine is operated in RCCI mode with gaseous fuels viz. CNG as a primary fuel and a blend of diesel and Karanja biodiesel (BD20) as pilot fuel. This research aims to determine the operating limits of CNG fuel for less noisy combustion and clean exhaust. Further, relative air-fuel ratio (λ), cycle to cycle variations, combustion noise and emissions were studied for full load operation. The CRDI engine is optimized for diesel operation with a split injection strategy. The knock limits for CNG as the primary fuel are obtained. The combustion noise increases at a higher energy share by CNG. Also, higher values of HC and CO emissions are observed. This may be due to higher energy share values, flame speed and octane number of CNG fuel. Further, NOx emissions and smoke are decreased. The CNG induction of 10 ms with 90% ES can be noted as a knock limit for 3.5 kW power. The highest BTHE of 24.2% and least BSFC 0.3 kg/kWhr reported by 60%ES of LRF is better than diesel and KBD20 fuel. An optimum 60% energy share of CNG is observed for clean combustion and emissions strategy using the RCCI mode of a modified diesel engine.

NOx emission reduction techniques in biodiesel-fuelled CI engine: a review

Abstract: Compression ignition (CI) engines contribute more detrimental emissions when compared to petrol engines, especially NOx and smoke emissions. The main reason for diesel engines to emit higher NOx em...

A Review of Hydrogen as a Fuel in Internal Combustion Engines

Abstract: The demand for fossil fuels is increasing because of globalization and rising energy demands. As a result, many nations are exploring alternative energy sources, and hydrogen is an efficient and practical alternative fuel. In the transportation industry, the development of hydrogen-powered cars aims to maximize fuel efficiency and significantly reduce exhaust gas emission and concentration. The impact of using hydrogen as a supplementary fuel for spark ignition (SI) and compression ignition (CI) engines on engine performance and gas emissions was investigated in this study. By adding hydrogen as a fuel in internal combustion engines, the torque, power, and brake thermal efficiency of the engines decrease, while their brake-specific fuel consumption increase. This study suggests that using hydrogen will reduce the emissions of CO, UHC, CO2, and soot; however, NOx emission is expected to increase. Due to the reduction of environmental pollutants for most engines and the related environmental benefits, hydrogen fuel is a clean and sustainable energy source, and its use should be expanded.

Experimental and modeling study on the auto-ignition properties of ammonia/methane mixtures at elevated pressures

Abstract: Ammonia (NH3) is considered as a promising carbon free energy carrier for energy and transportation systems. However, its low flammability and high NOx emission potential inhibit the implementation of pure NH3 in these systems. On the other hand, methane is a favorable low emission fuel that can be used as a co-firing fuel in ammonia combustion to promote the reactivity and control the emission levels. However, knowledge of the ignition properties of NH3/CH4 mixtures at intermediate temperatures and elevated pressures is still scarce. This study reports ignition delay times of NH3/CH4/O2 mixtures diluted in Ar or Ar/N2 over a temperature range of 900–1100 K, pressures of 20 and 40 bar, and equivalence ratios of 0.5, 1.0, and 2.0. The results demonstrate that a higher CH4 mole fraction in the fuel mixture increases its reactivity, and that the reactivity decreases with increasing the fuel-oxygen equivalence ratio. The most recent mechanisms of Glarborg et al. (2018) and Li et al. (2019) were compared against the experimental data for validation purposes. Both mechanisms can predict the measurements fairly well, and key elementary reactions applied in both mechanisms were compared. A modified mechanism is provided, which can reproduce the measurements with smaller discrepancies in most cases. Detailed modeling for emissions indicated that adding CH4 to the fuel mixture increases the emission of NOx.

Experimental Analysis of Engine Performance and Exhaust Pollutant on a Single-Cylinder Diesel Engine Operated Using Moringa Oleifera Biodiesel

Abstract: In this investigation, biodiesel was produced from Moringa oleifera oil through a transesterification process at operating conditions including a reaction temperature of 60 °C, catalyst concentration of 1% wt., reaction time of 2 h, stirring speed of 1000 rpm and methanol to oil ratio of 8.50:1. Biodiesel blends, B10 and B20, were tested in a compression ignition engine, and the performance and emission characteristics were analyzed and compared with high-speed diesel. The engine was operated at full load conditions with engine speeds varying from 1000 rpm to 2400 rpm. All the performance and exhaust pollutants results were collected and analyzed. It was found that MOB10 produced lower BP (7.44%), BSFC (7.51%), and CO2 (7.7%). The MOB10 also reduced smoke opacity (24%) and HC (10.27%). Compared to diesel, MOB10 also increased CO (2.5%) and NOx (9%) emissions.

Higher Alcohol and Ether Biofuels for Compression-Ignition Engine Application: A Review with Emphasis on Combustion Kinetics

Abstract: High molecular weight alcohol and ether fuels with their advanced autoignition propensities and oxygenated molecular structures are promising future fuel candidates for compression-ignition engine ...

An experimental and kinetic modeling study of the auto-ignition of natural gas blends containing C1–C7 alkanes

Abstract: Ignition delay time measurements for multi-component natural gas mixtures were carried out using a rapid compression machine at conditions relevant to gas turbine operation, at equivalence ratios of 0.5–2.0 in ‘air’ in the temperature range 650–1050 K, at pressures of 10–30 bar. Natural gas mixtures comprising C1–C7 n-alkanes with methane as the major component (volume fraction: 0.35–0.98) were considered. A design of experiments was employed to minimize the number of experiments needed to cover the wide range of pressures, temperatures and equivalence ratios. The new experimental data, together with available literature data, were used to develop and assess a comprehensive chemical kinetic model. Replacing 1.875% methane with 1.25% n-hexane and 0.625% n-heptane in a mixture containing C1–C5 components leads to a significant increase in a mixture's reactivity. The mixtures containing heavier hydrocarbons also tend to show a strong negative temperature coefficient and two-stage ignition behavior. Sensitivity analyses of the C1–C7 blends have been performed to highlight the key reactions controlling their ignition behavior.

Challenges for turbulent combustion

Abstract: Turbulent combustion will remain central to the next generation of combustion devices that are likely to employ blends of renewable and fossil fuels, transitioning eventually to electrofuels (also referred to as e-fuels, powerfuels, power-to-x, or synthetics). This paper starts by projecting that the decarbonization process is likely to be very slow as guided by history and by the sheer extent of the current network for fossil fuels, and the cost of its replacement. This transition to renewables will be moderated by the advent of cleaner engines that operate on increasingly cleaner fuel blends. A brief outline of recent developments in combustion modes, such as gasoline compression ignition for reciprocating engines and sequential combustion for gas turbines, is presented. The next two sections of the paper identify two essential areas of development for advancing knowledge of turbulent combustion, namely multi-mode or mixed-mode combustion and soot formation. Multi-mode combustion is common in practical devices and spans the entire range of processes from transient ignition to stable combustion and the formation of pollutants. A range of burners developed to study highly turbulent premixed flames and mixed-mode flames, is presented along with samples of data and an outline of outstanding research issues. Soot formation relevant to electrofuels, such as blends of diesel-oxymethylene ethers, hydrogen-methane or ethylene-ammonia, is also discussed. Mechanisms of soot formation, while significantly improved, remain lacking particularly for heavy fuels and their blends. Other important areas of research, such as spray atomization, turbulent dense spray flames, turbulent fires, and the effects of high pressure, are briefly mentioned. The paper concludes by highlighting the continued need for research in these areas of turbulent combustion to bring predictive capabilities to a level of comprehensive fidelity that enables them to become standard reliable tools for the design and monitoring of future combustors.

A numerical investigation of NH3/O2/He ignition limits in a non-thermal plasma

Abstract: This numerical study of the ignition characteristics of ammonia in a pulsed plasma discharge includes the assembly of a kinetic model for the oxidation of ammonia/oxygen/helium mixtures under a plasma discharge. The model was used to perform a series of simulations under varying pulsed discharge frequencies and pulse numbers, at atmospheric pressure and moderate to high temperatures (600–1500 K). A zero-dimensional solver which combines the ZDPlasKin and CHEMKIN software is used to explore the effect of pulse number and frequency on ignition delay time. For a moderate amount of pulses, a reduction of 40–60% in ignition delay time is achieved, with higher pulse repetition frequencies (PRFs) yielding shorter ignition delay times. Analysis of OH radical time evolution reveals that high PRFs support an increasing radical pool at low temperatures, whereas at lower PRFs radicals recombine in between pulses. In the thermal runaway phase, the radicals formed in conventional chain branching events are prevalent, so that OH formed in later pulses has little effect. When looking low temperatures and high PRFs, higher pulse frequencies allow for lower initial temperatures which will result in ignition. At a high enough frequency, the hysteresis of ignition and extinction is altered due to a high amount of radicals supplied and sustained by the plasma, so that there is a smooth transition and reactions at all temperatures.

Sensitizing gaseous detonations for hydrogen/ethylene-air mixtures using ozone and H2O2 as dopants for application in rotating detonation engines

Abstract: The effect of ozone and hydrogen peroxide as dopants on hydrogen-air and ethylene-air detonations was investigated with one-dimensional ZND calculations. Also, the effects of dopants were studied numerically with argon and helium as diluents with an aim to reduce the temperature of detonation products while maintaining a detonation wave of sufficient strength such that its propagation is stable near its propagation limits. The primary goal of the present investigation is to isolate the chemical kinetic effects from fluid and gas dynamic effects by altering the ignition chemistry of an unburned mixture without significantly changing its thermodynamic and physical properties. The ZND calculations demonstrate that the addition of O3 and H2O2 in small quantities will substantially reduce the induction length (Δi) and time (τi), even with higher diluent percentages of argon and helium, making it a viable solution for reducing the operating temperatures of rotating detonation engines (RDEs). The effects of O3 and H2O2 are also studied numerically at lower equivalence ratios for H2/C2H4-air detonations with an aim to reduce the post-detonation temperatures below 2000 K for its application in practical engine cycles. Also, the efficacy of CF3I, as an ignition promoter at small quantities, is studied numerically for hydrogen-air detonations, and its performance is compared with O3 and H2O2.

Advances in combustion control for natural gas–diesel dual fuel compression ignition engines in automotive applications: A review

Abstract: Dual fuel engines that leverage gaseous fuels have existed for over a century, but advances in fuel injection technologies and electronic control have drastically changed the methods of combustion control used in automotive applications over this time. Early efforts to leverage natural gas on compression ignition engines utilized natural gas and diesel in a dual fuel arrangement but relied on map-based methods of dictating the quantities and timings of single injection events for each fuel. Multi-pulse injection and electronic fuel injection capabilities have enabled many new combustion strategies and necessitated the use of more complex control methods. Novel dual fuel combustion approaches like reactivity controlled compression ignition and the introduction of high pressure natural gas injection have provided cleaner, more efficient combustion processes for diesel–natural gas dual fuel engines but also introduced more complex combustion phenomenon. This paper examines the advances that have been made in combustion control on conventional and more advanced dual fuel engines that utilize natural gas along with diesel fuel and discusses the remaining challenges in this field.