Optimization of Recompression Reaction for Low-Load Operation of Residual-Effected HCCI

2008 ◽  
Author(s):  
H. H. Song ◽  
C. F. Edwards
Keyword(s):  
Low Load ◽  
Recompression Reaction

Understanding chemical effects in low-load-limit extension of homogeneous charge compression ignition engines via recompression reaction

2009 ◽  
Vol 10 (4) ◽  
pp. 231-250 ◽  
Author(s):  
H H Song ◽  
C F Edwards
Keyword(s):  
Ignition Delay ◽  
Homogeneous Charge Compression Ignition ◽  
Compression Ignition ◽  
Model Calculations ◽  
Load Limit ◽  
Low Load ◽  
Fuel Pyrolysis ◽  
Recompression Reaction ◽  
Lean Conditions ◽  
Homogeneous Charge

In-cylinder pre-processing (or recompression reaction) of pilot-injected fuel during negative value overlap (NVO) has been investigated as a method to extend the low-load limit of residual-effected homogeneous charge compression ignition (HCCI). In an effort to elucidate the chemical and thermal effects involved, model calculations have been performed on the recompression reaction and ignition delay of the recompression products using a reduced n-heptane mechanism (160 reactions, 1424 reactions) and a zero-dimensional kinetics model. Parametric studies were performed to cover possible operating choices for HCCI and to understand their effects on the recompression reaction and mixture ignitability. From the study it is demonstrated that the extent of recompression reaction is limited by chemical kinetics, not thermodynamics, and that residual oxygen during NVO is a determining species for the extent and speciation of the recompression reaction. The recompression product mixture exhibits an overall shorter ignition delay than those of the base fuel, except under lean conditions when significant oxidation during NVO leaves only a small amount of fuel available for main ignition. The thermal consequence of the recompression reaction is also largely dependent on oxygen: at near-stoichiometric conditions, the recompression reaction is endothermic from fuel pyrolysis, whereas at lean conditions, the exothermic recompression reaction becomes dominant. Therefore, the chemical and thermal consequences of the recompression reaction exhibit competing effects on mixture ignitability, which leads to an optimum oxygen concentration (equivalence ratio) for reducing ignition delay and extending HCCI operability.

Experimental study of recompression reaction for low-load operation in direct-injection homogeneous charge compression ignition engines with n-heptane and i-octane fuels

2009 ◽  
Vol 10 (4) ◽  
pp. 215-229 ◽  
Author(s):  
H H Song ◽  
A Padmanabhan ◽  
N B Kaahaaina ◽  
C F Edwards
Keyword(s):  
Direct Injection ◽  
Experimental Studies ◽  
Chemical Kinetic ◽  
Combustion Efficiency ◽  
Indicated Mean Effective Pressure ◽  
Load Limit ◽  
Low Load ◽  
Kinetic Mechanisms ◽  
Negative Valve Overlap ◽  
Recompression Reaction

Experiments have been reported in the literature in which the low-load limit of a retention-mode HCCI engine operating on gasoline has been significantly extended by pre-processing of the fuel during negative valve overlap. This paper presents experimental studies in which this low-load-limit extension is demonstrated and characterized using simple, single-component hydrocarbon fuels with relatively well-known chemical kinetics. The model fuels were n-heptane and i-octane and this choice was made both because of the extensive work that has been undertaken to develop their chemical kinetic mechanisms and because these fuels span the range of ignitability that is likely to be of interest for HCCI engines. The experimental results reported here show that both fuels exhibit load extension to as low as 1 bar net indicated mean effective pressure when operated at high residual mass fractions, low equivalence ratios, and an appropriate choice of compression ratio (13 for n-heptane, 18 for i-octane). Near the low-load limit, combustion is stable, exhibits slightly advanced timing, has relatively low unburned hydrocarbon emissions, negligible (< 5 ppm) NO emissions, and slightly increased CO emissions (compared to higher load conditions). The indicated efficiency of low-load operation with recompression reaction is somewhat reduced, mainly due to increased heat transfer and decreased combustion efficiency.

THE WORK OF AN ACTIVE CURRENT CORRECTOR AT LOW LOAD POWER EXAMINATION

2017 ◽  
Vol 2017 (46) ◽  
pp. 81-84
Author(s):  
V.M. Spirin ◽  
◽  
V.M. Gubarevych ◽  
V.G. Grebenyuk ◽  
S.V. Salko ◽  
...  
Keyword(s):  
Load Power ◽  
Low Load

The effectiveness of blood-flow restricted resistance training in the musculoskeletal rehabilitation of patients with lower limb disorders: A systematic review and meta-analysis

2021 ◽  
pp. 026921552110034
Author(s):  
Nico Nitzsche ◽  
Alexander Stäuber ◽  
Samuel Tiede ◽  
Henry Schulz
Keyword(s):  
Blood Flow ◽  
Resistance Training ◽  
Muscle Strength ◽  
Lower Limb ◽  
Meta Analysis ◽  
Load Resistance ◽  
Muscle Volume ◽  
Low Load ◽  
Study Characteristics ◽  
Musculoskeletal Rehabilitation

Objective: This meta-analysis aimed to evaluate the effectiveness of low-load Resistance Training (RT) with or without Blood Flow Restriction (BFR) compared with conventional RT on muscle strength in open and closed kinetic chains, muscle volume and pain in individuals with orthopaedic impairments. Data sources: Searches were conducted in the PubMed, Web of Science, Scopus and Cochrane databases, including the reference lists of randomised controlled trials (RCT’s) up to January 2021. Review method: An independent reviewer extracted study characteristics, orthopaedic indications, exercise data and outcome measures. The primary outcome was muscle strength of the lower limb. Secondary outcomes were muscle volume and pain. Study quality and reporting was assessed using the TESTEX scale. Results: A total of 10 RCTs with 386 subjects (39.2 ± 17.1 years) were included in the analysis to compare low-load RT with BFR and high or low-load RT without BFR. The meta-analysis showed no significant superior effects of low-load resistance training with BFR regarding leg muscle strength in open and closed kinetic chains, muscle volume or pain compared with high or low-load RT without BFR in subjects with lower limb impairments. Conclusion: Low-load RT with BFR leads to changes in muscle strength, muscle volume and pain in musculoskeletal rehabilitation that are comparable to conventional RT. This appears to be independent of strength testing in open or closed kinetic chains.

scholarly journals Experiential and Strategic Emotional Intelligence Are Implicated When Inhibiting Affective and Non-Affective Distractors: Findings from Three Emotional Flanker N-Back Tasks

2021 ◽  
Vol 9 (1) ◽  
pp. 12
Author(s):  
Ming D. Lim ◽  
Damian P. Birney
Keyword(s):  
Working Memory ◽  
Emotional Intelligence ◽  
Experimental Evidence ◽  
Cognitive Processes ◽  
Response Times ◽  
Memory Task ◽  
Low Load ◽  
Affective Information ◽  
Accuracy Rates

Emotional intelligence (EI) refers to a set of competencies to process, understand, and reason with affective information. Recent studies suggest ability measures of experiential and strategic EI differentially predict performance on non-emotional and emotionally laden tasks. To explore cognitive processes underlying these abilities further, we varied the affective context of a traditional letter-based n-back working-memory task. In study 1, participants completed 0-, 2-, and 3-back tasks with flanking distractors that were either emotional (fearful or happy faces) or non-emotional (shapes or letters stimuli). Strategic EI, but not experiential EI, significantly influenced participants’ accuracy across all n-back levels, irrespective of flanker type. In Study 2, participants completed 1-, 2-, and 3-back levels. Experiential EI was positively associated with response times for emotional flankers at the 1-back level but not other levels or flanker types, suggesting those higher in experiential EI reacted slower on low-load trials with affective context. In Study 3, flankers were asynchronously presented either 300 ms or 1000 ms before probes. Results mirrored Study 1 for accuracy rates and Study 2 for response times. Our findings (a) provide experimental evidence for the distinctness of experiential and strategic EI and (b) suggest that each are related to different aspects of cognitive processes underlying working memory.

scholarly journals Epoxy\Epoxy Composite\Epoxy Hybrid Composite Coatings for Tribological Applications—A Review

Polymers ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 179
Author(s):  
M. M. A. Baig ◽  
M. Abdul Samad
Keyword(s):  
Tribological Properties ◽  
Hybrid Composite ◽  
Review Paper ◽  
Epoxy Composite ◽  
Composite Coatings ◽  
Load Bearing Capacity ◽  
Corrosive Media ◽  
Fluid Handling ◽  
Low Load ◽  
Made In

Epoxy composite coating systems generally find their usage in applications such as, fluid handling systems to protect components from corrosive media. However, their use in demanding tribological applications such as, in sliding components of machines, are known to be limited. This is often attributed to their low load bearing capacity combined with poor thermal stability under severe p-v regimes. Researchers have tried to enhance the tribological properties of the epoxy coatings using a combination of several types of micro/nano sized fillers to produce composite or hybrid composite coatings. Hence, this review paper aims to focus on the recent advances made in developing the epoxy coating systems. Special attention would be paid to the types and properties of nano-fillers that have been commonly used to develop these coatings, different dispersion techniques adopted and the effects that each of these fillers (and their combinations) have on the tribological properties of these coatings.

Study on bearing stiffness characteristics with residual stress in carburized layer

2020 ◽  
pp. 095440622096079
Author(s):  
Junshuai Liang ◽  
Ning Li ◽  
Jingyu Zhai ◽  
BaoGang Wen ◽  
Qingkai Han ◽  
...  
Keyword(s):  
Residual Stress ◽  
Contact Stiffness ◽  
Roller Bearing ◽  
High Load ◽  
Axial Stiffness ◽  
Fe Model ◽  
Low Load ◽  
Bearing Stiffness ◽  
Carburized Layer ◽  
Stiffness Characteristics

In this study, a layering method of carburized ring is presented. A finite element (FE) model for analyzing bearing stiffness characteristics is established considering the residual stress in the carburized layer. The residual stress in the carburized layer of a double-row conical roller bearing is tested and the influence of the distribution of residual stress in carburized layer on the bearing stiffness is investigated. Results show that the residual stress in the carburized layer increases the contact stiffness of the bearing by 5% in the low-load zone and 3% in the high-load zone. The radial stiffness of the bearing is increased by 5% in the low-load zone and 3% in the high-load zone. The axial stiffness is increased by 6%, and the angular stiffness increased by 4%. The larger the thickness of the carburized layer, the greater the residual compressive stress in the carburized layer, the deeper the position of the maximum residual stresses in the carburized layer will lead to the greater stiffness of the bearing.

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