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This study presents the parametric investigation of syngas fuelled homogeneous charge compression ignition (HCCI) engine. The chemical kinetic simulation of the syngas HCCI engine is performed using the stochastic reactor model (SRM). This study first compares and evaluates the performance of different reaction mechanisms for the HCCI engine. The experimental combustion pressure data is compared with numerically investigated combustion pressure to validate the reaction mechanisms. Results indicate that a numerically simulated combustion pressure using a detailed reaction mechanism consisting of 173 reactions and 32 species (CRECK-2014) is well-matched with the profile of experimental combustion pressure. The validated reaction mechanism is further used to investigate the HCCI engine at different engine speeds for various equivalence ratio (ϕ) , syngas composition (hydrogen addition (H 2 :CO)) and inlet valve closing temperature (T i v c). The sensitivity analysis is performed to find the prominent reactions in the oxidation reaction mechanism. Based on the combustion characteristics, syngas HCCI maps are developed. The effect of engine operating conditions on combustion and emission characteristics is also investigated. Furthermore, the result of engine operating parameters on converting fuel energy into physical exergy, chemical exergy, work exergy, and heat loss exergy is also briefly discussed. • Parametric investigation of syngas fuelled HCCI engine conducted. • CRECK-2014 reaction mechanism consisting of 173-reactions and 32-species is used. • Syngas HCCI operating maps for optimal performance are developed. • Crank angle-based exergy analysis for syngas HCCI engine is performed. • X w o r k increases with an increase in the ϕ for constant engine speed, T i v c , and H 2 : C O. [ABSTRACT FROM AUTHOR]

Empathy and compassion are critical elements in counselling presence and practice. The present interpretive phenomenological study explored counsellor lived experiences of empathy and compassion. Through interpretative phenomenological analysis, findings highlighted how counsellors experience compassion and empathy, how boundaries shape wellness and practice with clients, and the impact of empathy and compassion over a career. The findings suggest that self‐other differentiation is key while using empathy to develop a strong therapeutic alliance and counsellor self‐care. Implications inform how counsellors can maintain wellness and learn to foster empathy and compassion in practice. [ABSTRACT FROM AUTHOR]

This work investigates the influence of fuel injection events on the nanoparticle emission characteristics of light-duty gasoline-diesel RCCI engine. The formation of nanoparticle emissions strongly depends on fuel injection events. The present study experimentally investigates the influence of diesel injection pressure, injection timing, and port-injected gasoline mass on the nanoparticles emitted from the gasoline-diesel RCCI engine. For this purpose, the engine is tested at different engine speeds and a fixed load of 1.5 bar BMEP without exhaust gas recirculation. The particle-size and number distribution (PSD) and total particle number (total PN) concentration are measured using a differential mobility spectrometer. The results depict that at higher diesel injection pressure (IP) operation, the peak of the NMP increases while the AMP peak decreases for neat diesel operation as well as RCCI engine. Nucleation, as well as accumulation mode particles, increases with advanced diesel injection timing in RCCI combustion. An increase in port fuel injected mass also leads to an increase in the total particle concentration and total unburned hydrocarbon (THC) emissions. [ABSTRACT FROM AUTHOR]

In this article, we explore potential benefits of yoga, an ancient Indian tradition for spiritual growth and development, for counselors. Counselors use themselves as instruments to support clients and are constantly exposed to the traumatic experiences of clients, which may leave them susceptible to secondary traumatic stress or compassion fatigue (Shallcross, 2011). Yoga can help counselors not only in achieving holistic wellness but also in developing a way of being consistent with the characteristics of an effective counselor. Furthermore, yoga, as a spiritual practice, can empower counselors to embark on a spiritual journey driven by their own personal experiences. [ABSTRACT FROM AUTHOR]

Investigating how counselors perceive technology as a tool for delivering counseling services is crucial to understand the usage and challenges that may have implications for training programs, policymaking, and allocation of resources. With the COVID-19 crisis and accompanying shelter-in-place and self-distancing guidelines, telemental health, including distance counseling, has become a satisfactory primary delivery system and is now expected to be part of routine counseling care. The present pre-COVID-19 study explored practicing counselors' perceptions of distance counseling regarding advantages and challenges. While noting benefits, results indicate continuing barriers to widespread telemental health use encompassing licensure, training, safety, privacy, evaluation, and regulatory policies. Also, attention is needed for therapeutic relationships and culturally alert digital interventions. In addition, counselors can take advantage of rapidly changing technologies to provide numerous innovative counseling services. [ABSTRACT FROM AUTHOR]

A novel circularly polarized hexagonal ring microstrip patch antenna with asymmetrical feed is proposed for S, C, and X‐band applications. A semi‐arc‐shaped slot is integrated into the ground plane, and the hexagonal ring is tilted by an angle of 25° with respect to the microstrip‐line feed (asymmetric), which creates a circularly polarized UWB. The simulation of the proposed antenna is carried out using Ansoft HFSS v.13 and the measurement is done with an N5230A vector network analyzer. The simulated and the measured results of our proposed antenna are in good agreement. The successful implementation of the asymmetrical feed shows a broader impedance bandwidth of 134% (B.W = 9.55 GHz) from 2.34 to 11.89 GHz at 7.12 GHz of the center frequency. The 3‐dB axial ratio B.W is 2.8% (7.1‐7.3 GHz) and 21.8% (9.8‐12.2 GHz) in the UWB range. The average gain of the proposed antenna is 4.15 dBi. Good RHCP waves are also found in the x‐z and y‐z planes. The proposed antenna can be effectively used in S, C, and X‐band applications. [ABSTRACT FROM AUTHOR]

Homogeneous charge compression ignition (HCCI) is a promising alternative combustion strategy having higher thermal efficiency while maintaining the NO x and soot emissions below the current emissions mandates. The HCCI combustion engine has typically lower operating load range in comparison to conventional engines. The HCCI combustion is constrained by various operational limits such as combustion instability limit, combustion noise limits, emission limits and peak cylinder pressure limit. High load limit of HCCI combustion is typically limited by very high heat release rate, which leads to ringing operation. Intense ringing operation leads to very high combustion noise, and heavy ringing operation can also damage the engine parts. Thus, it is important to investigate the characteristics of ringing intensity (RI) in HCCI engine. Hydrogen fueled HCCI engine combines the potential advantages of alternative fuel as well as the alternative combustion strategy. This study presents the RI characterization and prediction using chemical kinetics and artificial neural network (ANN) for hydrogen-HCCI operation. In the first part of the study, the effect of equivalence ratio (φ), inlet temperature (T ivc ), and engine speed on ringing intensity is investigated using chemical kinetics model. Based on ringing operation characteristics of hydrogen HCCI engine, ANN model is used to predict the ringing intensity (RI) for different engine operating conditions (i.e., φ T ivc , engine speed) and different combustion parameters. The result indicates that RI increases with advanced combustion phasing (CA 50 ), higher inlet temperature, and equivalence ratio. To control the ringing operation, the CA 50 position needs to be retarded by optimizing the T ivc and φ. Maximum engine operating range is found for lower engine speed (i.e., 1000 rpm) and reduces with increase in the engine speed. The results showed that the RI is strongly correlated to the CA 50 position with a correlation coefficient of 0.99 at constant inlet temperature. The ANN results also show that ANN model predicts RI with sufficient accuracy. The ANN model predicts RI with engine operating conditions as well as combustion parameters with a correlation coefficient of 0.97 and 0.95 respectively. [ABSTRACT FROM AUTHOR]

In the present study, combustion and emissions characteristics of a dual fuel engine has been investigated numerically. For numerical analysis, zero dimensional stochastic reactor model (0-D SRM) approach was used. SRM was validated with experimental results and used for parametric analysis of dual fuel engine by varying operating parameters such as premixing ratio of fuels, engine speed and exhaust gas recirculation (EGR) percentage. Numerically obtained results from 0-D SRM were found in good agreement with the experimental results. Combustion process in dual fuel engine has also been analysed using computational fluid dynamics (CFD) model using a commercial 3-D CFD engine simulation tool ‘STAR-CD’ in conjunction with mesh generator ‘es-ice’. During engine combustion simulation with the STAR-CD code, PVM−MF (progress variable model – multi fuel) combustion model was used, which specially developed to characterize the multi fuel combustion. Spray evolution and combustion process has been analysed in a sector of engine cylinder to reduce the computational time during simulations. Numerically simulated data using this model was also found in good agreement with the experimental data. It was found that engine performance improved at higher engine load conditions and carbon mono oxide as well as unburned hydrocarbon emissions reduced. Effect of EGR on combustion and performance characteristics of dual fuel engine was also analysed. [ABSTRACT FROM AUTHOR]

In present study, the effect of fuel premixing ratio, direct fuel injection timings and engine compression ratio on the soot particle emissions in nano-size range from a non-road compression ignition engine is investigated. Experiments are conducted on modified dual fuel single cylinder engine at 1500 rpm. To run the engine in dual fuel mode, port fuel injection (PFI) system is installed by modifying intake manifold of the engine and developing a PFI controller. Experiments are conducted for various fuel premixing ratio of gasoline/methanol-diesel at different engine load, diesel fuel injection timing and compression ratios. Differential mobility spectrometer based particle sizer is used for investigation of the soot particle number-size distribution, surface area-size distribution, particle mass-size distribution and total particle number concentration from the engine exhaust at various test conditions. Results revealed that total particle number concentration is higher at full engine load and increases with fuel premixing ratio (especially in case of methanol-diesel dual fuel operation). Additionally, the peak particle number and mass concentration reduces with an increase in compression ratio of the engine. [ABSTRACT FROM AUTHOR]

Hydrogen is a clean potential alternative fuel for internal combustion engines and completely eliminates the carbon based engine emissions (CO, CO 2 and unburned hydrocarbons). Homogenous charge compression ignition (HCCI) is a low temperature combustion mode with higher thermal efficiency and ultralow NO x emission. Hydrogen HCCI engine can combine potential benefit of fuel and combustion characteristics. In HCCI engine, combustion is governed by the chemical kinetics of the oxidation reactions. In-order to find a suitable reaction mechanism to numerically predict the combustion characteristics of hydrogen HCCI engine, 15 recent hydrogen combustion mechanisms are compared and analyzed. All mechanisms were simulated using a stochastic reactor model (SRM) to evaluate the combustion parameters for HCCI engine. Simulations were performed by varying inlet temperature (400–440 K), intake pressure (1.0–3.0 bar), engine speed (1000–3000 rpm) and relative air-fuel ratio (λ = 2 to 8) for all the mechanisms. Ignition delay predicted from different mechanism was compared with experimental data and ignition delay was also compared at engine like condition using all the test mechanisms. Error in prediction of different combustion parameters such as start of combustion (CA 10 ), maximum cylinder pressure (P max ) and maximum heat release rate (HRR max ) were evaluated using different hydrogen combustion mechanisms. It was found that a recently developed hydrogen mechanism (Maurya-2017) shows the closet resemblance with the experimental cylinder pressure data. The Oconaire-2004 mechanism was able to accurately predict the characteristics of hydrogen HCCI combustion. It was also found that NUIG-NGM-2010 and CRECK-2014 mechanisms were able to estimate the HCCI combustion characteristics under higher combustion temperature. [ABSTRACT FROM AUTHOR]

Hydrogen is a potential alternative and renewable fuel for homogenous charge compression ignition (HCCI) engine to achieve higher efficiency and zero emissions of CO, unburned hydrocarbons as well as other greenhouse gases such as CO 2 and CH 4 . In this study, a detailed hydrogen oxidation mechanism with NO x was developed by incorporating additional species and NO x reactions to the existing hydrogen combustion mechanism (10 species and 40 reactions). The detailed hydrogen combustion mechanism used in this study consists of 39 species and 311 reactions. A reduced mechanism consisting 30 species and 253 reactions was also developed by using directed relation graph (DRG) method from detailed mechanism. Developed mechanisms were validated with experimental data by HCCI engine simulation using stochastic reactor model. Sensitivity analysis was performed to identify the most important reactions in hydrogen combustion and NO x formation in HCCI engine. Pathway analysis was also performed to analyze the important reaction pathways at different temperatures. Results revealed that H2 + HO2 [=] H + H2O2 and O2 + NNH [=] N2 + HO2 are the most significant reactions in the hydrogen HCCI combustion and NO x formation respectively. Detailed parametric study of HCCI combustion was conducted using developed chemical kinetic model. Numerical simulations are performed at different engine operating condition by varying engine speed (1000–3000 rpm), intake air temperature (380–460 K), and compression ratio (16–18) at different relative air fuel ratios (λ). The HCCI operating range was determined for different compression ratios and results show that operating range expands with increase in compression ratio. The effect of intake temperature, engine speed and equivalence ratio on cylinder pressure and heat release rate were investigated. Maximum thermal efficiency of 46% and maximum combustion efficiency of 98% was observed among all the test conditions. Parametric study of NO x emissions was also conducted and it was found that NO x emissions decrease exponentially from higher to lower engine loads. [ABSTRACT FROM AUTHOR]

Analysis of measured in-cylinder pressure data provides various parameters that characterize engine combustion process. Advanced engine control technologies use cylinder pressure based combustion parameters for closed loop control. Four step signal processing (i) absolute pressure correction, (ii) crank angle position referencing, (iii) cycle averaging and (iv) filtering is typically applied to get sufficiently accurate cylinder pressure data for an engine cycle. This paper focuses on cycle averaging and filtering of in-cylinder pressure signal from a conventional compression ignition (CI) engine. Experiments are conducted at different engine load and compression ratios at 1500 rpm. The in-cylinder pressure trace of 2500 consecutive engine cycles is recorded and analyzed. Effect of in-cylinder pressure signal noise and cyclic variation on combustion analysis is investigated. A method based on standard deviation of pressure and pressure rise rate is used to find sufficient minimum number of engine cycles to be recorded for averaging to get reasonably accurate pressure data independent of cyclic variability. [ABSTRACT FROM AUTHOR]

Ethanol fuelled homogenous charge compression ignition engine offers a better alternative to tackle the problems of achieving higher engine efficiency and lower emissions using renewable fuel. Present study computationally investigates the HCCI operating range of ethanol at different compression ratios by varying inlet air temperature and engine speed using stochastic reactor model. A newly developed reduced ethanol oxidation mechanism with NO x having 47 species and 272 reactions is used for simulation. HCCI operating range for compression ratios 17, 19 and 21 are investigated and found to be increasing with compression ratio. Simulations are conducted for engine speeds ranging from 1000 to 3000 rpm at different intake temperatures (range 365–465 K). Parametric study of combustion and emission characteristics is conducted and engine maps are developed at most efficient inlet temperatures. HCCI operating range is defined using combustion efficiency (>85%) and maximum pressure rise rate (<5 MPa/ms). In HCCI operating range, higher efficiency is found at higher engine loads and lower engine speeds. Emission characteristics of species (NO x , N 2 O, CO, CH 4 , C 2 H 4 , C 2 H 6 , CH 3 CHO, and HCHO) found in significant amount is also analysed for ethanol fulled HCCI engine. Emission maps for different species are presented and discussed for wide range of speed and load conditions. Some of unregulated species such as aldehydes are emitted in significantly higher quantities from ethanol fuelled HCCI engine at higher load and speed conditions. [ABSTRACT FROM AUTHOR]

Ethanol is considered a potential biofuel for internal combustion engines. In this study, homogeneous charge compression ignition (HCCI) simulations of ethanol engine experiments were performed using stochastic reactor model (SRM). Detailed ethanol oxidation mechanism is developed by including NO x reaction in existing detailed oxidation mechanism with 57 species and 383 reactions. Detailed ethanol mechanism with NO x used in this study contains 76 species and 495 reactions. This mechanism was reduced by direct relation graph (DRG) method, which was validated with the experimental results. Existing Lu’s 40-species skeletal mechanism with NO formation were also compared with detailed and reduced mechanisms for predicting maximum cylinder pressure, maximum heat release rate and crank angle position of maximum cylinder pressure in HCCI engine. Reduced mechanism developed in this study exhibited the best resemblance with the experimental data. This reduced mechanism was also validated by measured engine cylinder pressure curves and measured ignition delays in constant volume reactors. The results showed that reduced mechanism is capable of predicting HCCI engine performance parameters with sufficient accuracy. Sensitivity analysis was conducted to determine the influential reactions in ethanol oxidation. Results also show that detailed and reduced mechanism was able to predict NO x emission in good agreement with the corresponding experimental data. [ABSTRACT FROM AUTHOR]

Biofuels are attracting global attention as alternate transportation fuels due to advantages of their being produced from locally available renewable resources, lower pollution potential, and biodegradable nature. Butanol is fast emerging as one of the competitive biofuels for use in transportation engines. Homogeneous charge compression ignition (HCCI) engines have shown great potential for higher engine efficiency and ultralow NOx and particulate matter (PM) emissions. This experimental study is therefore carried out to combine the advantages of biofuels and HCCI engines, both. Detailed performance, combustion, and emission characteristics of n-butanol fueled HCCI engine are investigated experimentally. The study is conducted on a four cylinder diesel engine, whose one cylinder was modified to operate in HCCI combustion mode. Port fuel injection technique was used for homogeneous charge preparation in the intake manifold. Auto-ignition of fuel in the engine cylinder was achieved by intake air preheating. In-cylinder pressure-crank angle data acquisition with subsequent heat release analyses and exhaust emission measurements were done for combustion and emission characterization. In this paper, the effect of intake air temperature and air-fuel ratio on the combustion parameters, thermal and combustion efficiency, ringing intensity (RI), and emissions from n-butanol fueled HCCI engine were analyzed and discussed comprehensively. Empirical correlations were derived to fit the experimental data for various combustion parameters. [ABSTRACT FROM AUTHOR]

Alcohols (ethanol and methanol) are being widely considered as alternative fuels for automotive applications. At the same time, homogeneous charge compression ignition (HCCI) engine has attracted global attention due to its potential of providing high engine efficiency and ultralow exhaust emissions. Environmental legislation is becoming increasingly stringent, sharply focusing on particulate matter (PM) emissions. Recent emission norms consider limiting PM number concentrations in addition to PM mass. Therefore, present study is conducted to experimentally investigate the effects of engine operating parameters on the PM size-number distribution in a HCCI engine fueled with gasoline, ethanol, and methanol. The experiments were conducted on a modified four-cylinder diesel engine, with one cylinder modified to operate in HCCI mode. Port fuel injection was used for preparing homogeneous charge in the HCCI cylinder. Intake air preheating was used to enable auto-ignition of fuel-air mixture. Engine exhaust particle sizer (EEPS) was used for measuring size-number distribution of soot particles emitted by the HCCI engine cylinder under varying engine operating conditions. Experiments were conducted at 1200 and 2400 rpm by varying intake air temperature and air-fuel ratio for gasoline, ethanol, and methanol. In this paper, the effect of engine operating parameters on PM size-number distribution, count mean diameter (CMD), and total PM numbers is investigated. The experimental data show that the PM number emissions from gasoline, ethanol, and methanol in HCCI cannot be neglected and particle numbers increase for relatively richer mixtures and higher intake air temperatures. [ABSTRACT FROM AUTHOR]

Homogeneous charge compression ignition (HCCI) engines have potential to provide both diesel like efficiencies and very low NOx and particulate matter (PM) emissions. There is growing global interest in using alternative biofuels in order to reduce the reliance on conventional fossil fuels. Therefore this experimental study was carried out to investigate performance, combustion and emission characteristics of HCCI engine fueled with ethanol and methanol and compare it with baseline gasoline fuel. The experiments were conducted on a modified four-cylinder four-stroke engine at different engine speeds using port fuel injection technique for preparing homogeneous charge. To achieve auto-ignition of air-fuel mixture in the combustion chamber, intake air pre-heater was used. In-cylinder pressure data acquisition with subsequent heat release analysis and exhaust emission measurements were done for combustion and emission diagnostics. In this paper, effect of intake air temperature and air-fuel ratio on combustion parameters, thermal efficiency, combustion efficiency, ringing intensity and emissions in HCCI engine is analyzed and discussed. Results show that methanol and ethanol are good replacements to gasoline in HCCI combustion mode. [ABSTRACT FROM AUTHOR]

Highlights: [•] Combustion phasing is analyzed by fitting probability density functions. [•] Combustion stability improves on increasing intake air temperature. [•] Test conditions with late start of combustion have larger cyclic variations. [•] Large deviations from normal distribution in combustion duration for knocking/misfire. [•] GEV distribution covers full range of distribution shapes for combustion duration/phasing. [Copyright &y& Elsevier]

Abstract: Several parameters derived from heat release analysis are used for combustion diagnostics and control in internal combustion engines. It is important to tune the input parameters used in heat release calculations, in order to get correct estimation of heat release rate. In this study, tuning of input parameters is carried out by using cumulative heat release calculations of cylinder pressure during motoring. This tuning procedure uses offline iterative processing of motoring in-cylinder pressure data. The tuned parameters obtained from this method can also be utilized for online analysis of combustion parameters. Input parameters used in these investigations are intake air temperature, intake air pressure, phasing between the acquired pressure and crank angle position, compression ratio and scaling factor of heat transfer coefficient. Effect of error in these input parameters on estimated combustion and performance parameters like IMEP, combustion phasing, combustion duration, heat release rate, and maximum mean gas temperature are evaluated. The relative importance of measurement error in input parameters and its maximum expected error in the final results is analyzed in a HCCI combustion engine. Results shows that measurement errors in phasing between pressure and crank angle position, compression ratio and inlet air pressure affect estimated combustion and performance parameters significantly. [Copyright &y& Elsevier]

Abstract: Combustion instability and cyclic variations lead to the requirement of closed loop control for use of homogeneous charge compression ignition (HCCI) engine technology for automotive applications. The closed loop control of HCCI combustion requires robust combustion timing parameters with a systematic and detailed study of its variations vis-à-vis engine operating conditions. An experimental study is conducted to provide insight into cyclic variations of HCCI combustion phasing for two fuels (gasoline and methanol) using statistical techniques. In this study, cycle-to-cycle variations of heat release parameters such as Maximum Rate of Heat Release (ROHRmax), 10% Mass Burn Fraction (MBF), 50% MBF, 90% MBF and Indicated Mean Effective Pressure (IMEP) of HCCI combustion engine fueled with methanol and gasoline were investigated using a modified two-cylinder, four-stroke engine. The experiments were conducted with different engine operating conditions at constant intake air temperature (140°C) and different air–fuel ratios at constant engine speed (1500rpm). To evaluate the cycle-to-cycle variations of combustion parameters at different test conditions, coefficient of variation (COV) and standard deviation of parameters were used. The results showed that CA50 (crank angle position of 50% MBF) is a robust parameter for the closed loop control of HCCI combustion. [Copyright &y& Elsevier]

Abstract: The homogeneous charge compression ignition (HCCI) is an alternative combustion concept for in reciprocating engines. The HCCI combustion engine offers significant benefits in terms of its high efficiency and ultra low emissions. In this investigation, port injection technique is used for preparing homogeneous charge. The combustion and emission characteristics of a HCCI engine fuelled with ethanol were investigated on a modified two-cylinder, four-stroke engine. The experiment is conducted with varying intake air temperature (120–150°C) and at different air–fuel ratios, for which stable HCCI combustion is achieved. In-cylinder pressure, heat release analysis and exhaust emission measurements were employed for combustion diagnostics. In this study, effect of intake air temperature on combustion parameters, thermal efficiency, combustion efficiency and emissions in HCCI combustion engine is analyzed and discussed in detail. The experimental results indicate that the air–fuel ratio and intake air temperature have significant effect on the maximum in-cylinder pressure and its position, gas exchange efficiency, thermal efficiency, combustion efficiency, maximum rate of pressure rise and the heat release rate. Results show that for all stable operation points, NO x emissions are lower than 10ppm however HC and CO emissions are higher. [Copyright &y& Elsevier]

Abstract: Combustion in HCCI engines is a controlled auto ignition of well-mixed fuel, air and residual gas. Since onset of HCCI combustion depends on the auto ignition of fuel/air mixture, there is no direct control on the start of combustion process. Therefore, HCCI combustion becomes unstable rather easily, especially at lower and higher engine loads. In this study, cycle-to-cycle variations of a HCCI combustion engine fuelled with ethanol were investigated on a modified two-cylinder engine. Port injection technique is used for preparing homogeneous charge for HCCI combustion. The experiments were conducted at varying intake air temperatures and air–fuel ratios at constant engine speed of 1500rpm and P-θ diagram of 100 consecutive combustion cycles for each test conditions at steady state operation were recorded. Consequently, cycle-to-cycle variations of the main combustion parameters and performance parameters were analyzed. To evaluate the cycle-to-cycle variations of HCCI combustion parameters, coefficient of variation (COV) of every parameter were calculated for every engine operating condition. The critical optimum parameters that can be used to define HCCI operating ranges are ‘maximum rate of pressure rise’ and ‘COV of indicated mean effective pressure (IMEP)’. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nanoparticle and carbonyl emission from methanol-diesel dual fuel was investigated. • Health risk assessment for nanoparticle and carbonyl emissions was conducted. • Methanol-diesel engines carbonyl emission has a higher cancer risk potential. • Diesel engine nanoparticles showed higher lung load and longer retention period. • At high loads, Methanol in diesel engines can reduce health risks significantly. Engine-emitted nanoparticles pose a threat to respiratory health, prompting the exploration of solutions like low carbon alternative fuels (methanol) and reactivity-controlled compression ignition (RCCI) engines. However, employing methanol in RCCI engines releases carcinogenic carbonyl compounds. The present study aims to experimentally investigate nanoparticle and carbonyl emissions from conventional diesel (CDC), gasoline-diesel RCCI (GD-RCCI) and methanol-diesel RCCI (MD-RCCI) engines. This study focuses on predicting lung loading caused by emitted nanoparticles and the potential cancer risk associated with carbonyl compounds. The investigation explores the impact of engine load (lower and medium) and fuel premixing ratio (r p) on particle and carbonyl emissions in RCCI engines. Findings reveal that MD-RCCI reduces total particle number (TPN) emissions by 60% compared to CDC. Results indicate that the concentration of nucleation mode particles (NMPs) decreases as engine load increases, while accumulation mode particles (AMPs) increase for both CDC and MD-RCCI combustion modes. With an increase in r p , the NMPs in the MD-RCCI and GD-RCCI engines are increased. Furthermore, the emission of HCHO and CH 3 CHO decreases with an increase in engine load. As the r p increases, HCHO and CH 3 CHO increase significantly. The forecast for lung loading reveals that nanoparticles emitted by CDC show a 30 % higher lung load compared to MD-RCCI. Additionally, as engine load increases, lung loading due to particles increases in CDC and decreases in MD-RCCI. In all test conditions, RCCI combustion demonstrates lower lung retention compared to CDC engine. The lung loading of particles of MD-RCCI decreases significantly with an increase in premixing ratio for a constant load as compared to GD-RCCI. The MD-RCCI engine shows higher cancer risk potential as compared to CDC and GD-RCCI engines. Operating the MD-RCCI engine at medium loads is advantageous for environmental and human health considerations. [ABSTRACT FROM AUTHOR]

• Presents effect of diesel SOI and PFI mass on the particle and unregulated emissions. • SOI timing, PMR, and α show a good correlation with particle number concentration. • Depicts parameters useful for prediction, control, and model development for particles. • Advanced SOI timing and increase in 'm g ' lead to increase the peak of NMP and AMP. nucleation and accumulation mode particles. • Unsaturated hydrocarbons emission increases with advanced diesel SOI timings. The study aims to experimentally characterize the nano-particle emissions and un-regulated (i.e., saturated and unsaturated hydrocarbons and formaldehyde emissions) emissions. Present study experimentally investigates the effect of high reactivity fuel injection timings and port-injected-fuel mass on nano-particle and unregulated emissions in the gasoline-diesel RCCI engine. Additionally, empirical correlations are developed using experimental data for the estimation of particle emission characteristics. An automotive single cylinder diesel engine is modified for an in-cylinder blending of port-injection of gasoline during suction stroke and direct-injection of diesel fuel during the compression stroke. The experiments are performed on a modified engine for various diesel injection timings and port-injected gasoline mass using development electronic control unit (ECU). Nano-particle and unregulated emissions are measured using electrical mobility based particle-sizer and Fourier-transform infrared spectroscopy analyser respectively. Combustion analysis is performed by in-cylinder pressure measurement. The experimental data of nano-particle and combustion characteristics are used for the development of empirical correlation using a multivariable regression technique for determining the particle number characteristics. The parameters - premixing ratio, start of injection of diesel, and a novel parameter defined as premixed fraction of total heat release are used for the development of empirical correlations and found a good correlation for estimating the nano-particle emission characteristics. Results also indicate that advanced direct injection timing and increase in the port-injected gasoline mass leads to higher particle emissions as well as saturated, unsaturated hydrocarbon and formaldehyde emissions. [ABSTRACT FROM AUTHOR]

Abstract Fuel injection parameters such as fuel injection pressure (FIP) and start of injection (SOI) timing significantly affect combustion, performance, emission and durability of a common rail direct injection (CRDI) diesel engine. In this study, a state-of-the-art single cylinder research engine was used to investigate the effects of FIP and SOI timings on engine combustion characteristics, which affects heat transfer and soot formation as well. The experimental setup consisted of an instrumented single cylinder engine with provision to vary the fuel injection parameters along with online high speed combustion data acquisition and analysis system. Experiments were conducted at constant engine speed (1500 rpm) at four different FIPs (300, 500, 750 and 1000 bar), four different SOI timings and different fuel injection quantities. Combustion characteristics of the engine were analyzed using exhaustive heat release analysis based on in-cylinder pressure data. In direct injection compression ignition (DICI) engines, fuel vaporization and heat transfer characteristics affect fuel-air mixing, which is also influenced by the FIP and SOI timings. These injection parameters significantly control the rate of pressure rise (ROPR), and heat release rate (HRR), which in-turn affect the heat transfer from the engine cylinder as well as the engine power output. Therefore, it is necessary to optimize the fuel injection parameters to develop efficient and clean combustion diesel engines. Highlights • Heat transfer from cylinder walls affects combustion characteristics. • Combustion characteristics are highly dependent on SOI timings & FIP. • Increase in FIP led to higher peak cylinder pressure at all SOI timings. • At higher FIP, lower radiative heat losses from soot were observed. • IMEP increased with increasing FIP up to 500 bar and then decreased at 1000 bar. [ABSTRACT FROM AUTHOR]

Universal concerns about degradation in ambient environment, stringent emission legislations, depletion of petroleum reserves, security of fuel supply and global warming have motivated research and development of engines operating on alternative combustion concepts, which also have capability of using renewable as well as conventional fuels. Low temperature combustion (LTC) is an advanced combustion concept for internal combustion (IC) engines, which has attracted global attention in recent years. LTC concept is different from the conventional spark ignition (SI) combustion as well as compression ignition (CI) diffusion combustion concepts. LTC technology offers prominent benefits in terms of simultaneous reduction of both oxides of nitrogen (NO x ) and particulate matter (PM), in addition to reduction in specific fuel consumption (SFC). However, controlling ignition timing and combustion rate are primary challenges to be tackled before LTC technology can be implemented in automotive engines commercially. This review covers fundamental aspects of development of LTC engines and its evolution, historical background and origin of LTC concept, encompassing LTC principle, its advantages, challenges and prospects. Detailed insights into preparation of homogeneous charge by external and internal measures for mineral diesel and gasoline like fuels are covered. Fuel requirements and fuel induction system design aspect for LTC engines are also discussed. Combustion characteristics of LTC engines including combustion chemistry, heat release rate (HRR), combustion duration, knock characteristics, high load limit, fuel conversion efficiencies and combustion instability are summarized. Emission characteristics are reviewed along with insights into PM and NO x emissions from LTC engines. Finally, different strategies for controlling combustion rate and combustion timings for gasoline and mineral diesel like fuels are discussed, showing the way forward for this technology in future towards its commercialization. [ABSTRACT FROM AUTHOR]

• Determinism in a computationally cheap parameter is investigated for a CNG-diesel RCCI engine. • Conventional dual-fuel to RCCI mode shifting is coupled with the onset of periodic-2 bifurcations. • A combination of higher CNG mass and advanced diesel injection timing leads to a higher periodic (3 and 4) nature of combustion dynamics. • Deterministic features of location of maximum pressure and combustion phasing are comparable in the RCCI regime. • A strong correlation and phase synchronization between location of maximum pressure and combustion phasing in RCCI regime. This study investigates the changing deterministic features of the cycle-resolved location of maximum pressure and its correlation with combustion phasing for dynamical transitions in the combustion of a CNG-Diesel RCCI engine. The investigation is performed using nonlinear dynamical and chaotic methods such as return maps, recurrence, and cross recurrence plots. The experiments are performed on a single-cylinder automotive engine operated in RCCI mode with the aid of the development ECU. The experiments are conducted by running the engine at a fixed engine speed of 1500 rpm and a load of 3 bar BMEP. Diesel fuel is injected directly into the cylinder by following a double injection strategy using an equal amount of fuel in both the pilot and main injections. The effect of the start of main injection timing of diesel on combustion dynamics is investigated at two different masses of CNG. The predominance of deterministic periodic features is discovered in the cycle-resolved dynamics of the engine combustion during the RCCI regime. Results show that with advancement in diesel injection timing, the mode of combustion shifts from conventional dual fuel to RCCI, and this shift is coupled to the onset of noisy periodic-2 bifurcations., The periodic-2 behavior even transforms to periodic-3 and 4 with an increasing advancement in diesel injection timing for engines operating with a higher CNG mass. For most of the operating conditions, the deterministic features in the location of maximum pressure are comparable with that of combustion phasing. Recurrence and cross recurrence plots-based methodology advocates for the existence of strong correlations or at least a phase synchronization between the location of maximum pressure and combustion phasing when the engine operates in the RCCI regime, irrespective of diesel injection timing and amount of port-injected CNG fuel. The presence of similar deterministic features in the location of maximum pressure and combustion phasing and a strong relationship between these two at intermediate diesel injection timings in the RCCI regime for both the CNG masses makes this regime most suitable for using the location of maximum pressure as a feedback/controlled parameter for model predictive control of the engine. [ABSTRACT FROM AUTHOR]

• Nonlinear dynamical and chaotic methods used investigate the cyclic combustion dynamics of RCCI engine. • Symbol sequence analysis, return maps, recurrence plots (RPs), RQA, and 0–1 test used for analysis. • The dominance of deterministic characteristics are found in the cyclic combustion dynamics at advanced SOI timings. • Laminarity is found to be the most robust RQA parameter to investigate any qualitative changes in combustion dynamics. • The onset of RCCI combustion mode is accompanied by the onset of a noisy period-2 bifurcation. This study uses nonlinear dynamical and chaotic methods to investigate the cyclic combustion dynamics of a CNG-Diesel reactivity control compression ignition (RCCI) engine. The experiments of RCCI combustion mode are conducted on a single-cylinder automotive diesel engine with the development ECU. Low reactivity fuel (i.e., CNG) is injected into the intake manifold, and high reactivity fuel (i.e., diesel) is injected directly into the engine cylinder during the RCCI experiments. Mass of fuel injection per cycle and their injection events are controlled by using ECU. The engine is tested for fixed engine load and speed of 3 bar BMEP and 1500 rpm, respectively. A double diesel injection strategy is used for injecting the diesel fuel into the engine cylinder. In-cylinder pressure is measured using a piezoelectric pressure transducer on a crank angle basis with a resolution of 0.1 CAD. Combustion parameters are calculated on a cyclic basis from measured in-cylinder pressure. In this study, the effect of diesel injection timing (SOI-2) on the behavior of combustion dynamics for two different masses of port-injected CNG fuel (m c) is investigated. The CA50 time series of 1000 consecutive engine cycles is analyzed for combustion dynamics analysis using symbol sequence analysis, return maps, recurrence plots (RPs), recurrence quantitative analysis (RQA), and 0–1 test. The peaks in symbol sequence histograms and the corresponding symbol series depict the period-2 nature of the cyclic combustion dynamics at the intermediate SOI-2 of 30° and 40° bTDC. Return maps also confirm the onset of noisy period-2 bifurcation at 30° bTDC SOI-2. The dominance of deterministic period-2 characteristics is found in the cyclic combustion dynamics at 30° and 40° bTDC SOI-2 using recurrence plots. The 0–1 test method depicts stronger chaotic cyclic combustion dynamics at 20° and 50° bTDC SOI-2. In summary, the present study supports the existence of a periodic window in between the chaotic combustion for the intermediate values of SOI-2. The dominance of the deterministic characteristics makes this regime of intermediate SOI-2 values suitable for a better cycle resolved control. [ABSTRACT FROM AUTHOR]

Alcohol fuels, primarily ethanol and methanol, have emerged as one of the important alternatives for sustainable transportation and power generation applications, due to the overall lower carbon dioxide (CO2) emissions. The higher octane number of alcohol makes it suitable for spark ignition (SI) engines while lower blend ratios can be used for compression ignition (CI) engines as well. Since significant work and exploration have already been performed for the application of alcohol in SI engines, the present study is primarily focused on alcohol utilization in CI engines. This review majorly consists of three parts: first, a discussion on the physical and chemical properties of ethanol and methanol from the fuel perspective, second, combustion, and engine performance of CI engines fueled with alcohol and lastly, emissions characterization of alcohol as fuel. A summary of this review is provided which highlights the potential of alcohol utilization in the form of blend or under dual-fuel combustion modes, as well as neat alcohol fueled CI engine. Alcohol-fueled CI engine improves the soot-NOx trade-off characteristic in comparison to conventional diesel combustion, this fuel could be an enabler to meet future emissions regulations. Overall lower CO2 emissions (up to 15% lower compared to diesel) by utilizing alcohol as fuel make it suitable for sustainable transportation. [ABSTRACT FROM AUTHOR]

Background In recent years, it has been well documented that gut flora not only influence mosquito physiology, but also significantly alter vector competency. Although, salivary gland and gut constitute key partners of the digestive system, it is still believed that salivary glands may harbor less flora than gut (Parasit Vectors 6: 146, 2013). Methods Using a metagenomic approach, we have identified for the first time the diverse microbial community associated with these two physiologically different tissues of the digestive system in the mosquito Anopheles culicifacies. Results A total of 17 different phyla could be assigned to the whole metagenomic dataset, predominated by the phylum Proteobacteria, Firmicutes, Bacteriodetes, Tenericutes and Actinomycetes. Common bacteria included the members of Enhydrobacter, Agromonas, Serratia, Ralsonia, Lactobacillus, Pseudomonas, Streptococcus, Rubrobacter, Anaerococcus, Methylobacterium, Turicibacter, Elizabethkingia etc. in both the tissues representing 'core microbiota' of the mosquito digestive system. Salivary associated unique bacterial community included the members of Chloriflexi, Chlorobi, Cyanobacteria, Nitrospira, TM7, Armatimonadetes, Planctomycetes, Fibrobacteres etc. Conclusion We find that the salivary gland microbial community structure is more diverse than gut of the mosquito, probably due to differential feeding associated engagements such as food acquisition, ingestion and digestion processes. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to investigate the effects of blending ratio of Karanja oil methyl ester (KOME) on spray characteristics and to analyze the engine performance and exhaust emissions of Karanja biodiesel blend vis-a-vis baseline diesel. Spray characteristics were analyzed using injection rate and spray visualization experiments for the following injection pressures: 50, 100 and 150 MPa. Engine performance, emission and combustion characteristics were also investigated at various engine operation conditions. From a comparison of the spray evolution of Karanja biodiesel 40% (v/v) blend (KB40) vis-a-vis baseline diesel, the spray shape revealed a narrower and deeper penetrating spray development process for KB40. However, at an ambient pressure of 4 MPa, which is considered to be similar to the cylinder pressure of a test engine, KB40 exhibited a spray evolution behavior (spray penetration and shape) closely resembling that of diesel. In the engine experiment, lower max torque, brake thermal efficiency (BTE) and exhaust gas temperature, in addition to higher brake-specific fuel consumption (BSFC) were observed for biodiesel blend compared to diesel due to lower heating value of Karanja biodiesel. [ABSTRACT FROM AUTHOR]

Highlights: [•] Fuel injection pressure & timings affect engine performance, emissions and combustion. [•] Rapid combustion, higher cylinder pressure & ROHR at advanced injection timings. [•] Superior performance at lower FIP giving lower BSFC & emissions, & higher BTE. [•] Emission characteristics improve with advanced fuel injection timings. [•] Particulate number concentration in a CI engine increases with increasing engine load. [Copyright &y& Elsevier]

Abstract: Particulate and NOx emissions from diesel engine are the biggest challenges faced in making diesel engines environmentally benign. Measures adopted for reducing gravimetric particulate emission to meet the prevailing emission regulations necessarily always do not reduce particulate number concentration, which has profound adverse health effects. Therefore it is important to investigate effect of fuel injection parameters, especially fuel injection pressure and start of injection timings on particulate size and number distribution in diesel exhaust. In the present study, a single cylinder research engine is used for experimental assessment of the effects of fuel injection strategies and start of fuel injection timing on particulate size–number, surface area, and volume concentration distributions by using engine exhaust particulate sizer (EEPS) spectrometer. Investigations have been conducted at three different fuel injection pressures (300, 500, 750bar) and four different start of injection timings. The experimental data indicates that the particulate size–number concentration increases with increasing engine load (BMEP) and it reduces with increasing fuel injection pressure. [Copyright &y& Elsevier]