bluuebunny/crossref_metadata_2025 huggingface dataset:
Balagan Is Theater Too: Performance and Accessibility in Daniil Kharms and Vsevolod Nekrasov
Authors: MORSE AINSLEY
Published: January 2019

The rediscovery of the OBERIU poets’ work in the 1960s was a major aesthetic revelation for contemporary Soviet poets. Alongside the obvious OBERIU critique of language and poetics of the absurd, other aspects of their work proved attractive and productive to Thaw‐era writers. In his writings on Daniil Kharms, the minimalist poet Vsevolod Nekrasov admiringly emphasized Kharms’s command of the “real” and “concrete” (in language and literature), as well as, somewhat paradoxically, the “theatrical.” An unofficial poet during the Soviet period, Nekrasov worked as a traveling theater critic in the 1960s–80s, and co‐authored a book on the nineteenth‐century realist playwright Alexander Ostrovsky. His take on Kharms and theater clearly reflects the priorities of his own poetic project, while shedding light on some of the paradoxes of OBERIU theater as well. To wit, the theater section of the 1927 OBERIU manifesto, authored by Kharms, rejects the traditional play’s realist imitation of life while declaring: “Our task is to present onstage the world of concrete objects in their interactions and collisions.” This paper explores the shifting meanings of concepts like “real” and “concrete,” and their ongoing significance for literature, through a sort of conversation between Nekrasov and Kharms.
Incest and the Limits of Family in the Nineteenth‐Century Russian Novel
Authors: BERMAN ANNA A.
Published: January 2019

While nineteenth‐century European literature is full of sibling incest, amorous liaisons between biological sisters and brothers are virtually non‐existent in the Russian tradition. However, Russian novels are replete with characters who are in love with someone like a sibling, be it a cousin, an in‐law, or a figurative adoptee or member of the household. Scholars have shied away from discussing this love that exists on the murky boundary of family, but doing so gives us a clearer understanding of how the family and love are defined in the nineteenth‐century Russian novel. This essay explores three kinds of incest on the lateral axis: that between close kin, characters who are like siblings though not technically related, and desire that is modeled on a sibling bond. Exploring these relationships reveals two opposed tendencies: a centrifugal, expansive tendency for the family vs. a centripetal tendency for romantic love. While the family extends and Russian visions of unity strive for greater and greater inclusion, keeping love in the family circle proves the safer and more desirable choice. These two tendencies ultimately fuse, as the expansiveness of the family dictates who is familiar enough to love.
Evaluation of time and resources required for professional dental cleaning in nursing home residents
Authors: Barbe Anna Greta , Kottmann Hannah Elisa , Müller Dirk , Simic Dusan , Derman Sonja Henny Maria , Wicht Michael Jochen , Noack Michael Johannes
Published: January 2019

Aim

We aimed to describe time requirements and costs associated with professional dental cleaning (PDC) performed by a dental nurse in one German nursing home, and to reveal potential differences in required time for demented versus nondemented and mobile versus immobile residents.

Methods and results

We performed a retrospective, cross‐sectional analysis of treatment time and costs, including a transparent, easily adaptable path of action that allows implementation of PDC in nursing homes. Total mean (±SD) treatment time for one session per resident was documented, including differences in demented and immobile residents, and projected treatment costs (€/$) per resident. We found no differences in required time for one PDC (37 ± 11 minutes) in residents with or without dementia (P = 0.803) or, immobile versus mobile residents (P = 0.396). Mean projected treatment costs of PDC were €14.98/$17.07 per resident per cleaning session, resulting in total costs of €13.5 million ($15.4 million).

Conclusion

Cognitive status and mobility does not affect the mean time required to perform PDC by a dental nurse in nursing home residents. Main cost factor is working time of dental staff; consumable supplies have less impact. Our data may stimulate to include PDC as initial step toward implementation of long‐term oral hygiene strategies.
Intensive care nurses’ perceptions of various ethics concerns affecting clinical research
Authors: Karjalainen Hannaleena , Halkoaho Arja , Pietilä Anna‐Maija , Bendel Stepani , Keränen Tapani
Published: January 2019

Background

Intensive‐care unit (ICU) nurses have an important role in the recruitment of patients for scientific research and in the performance of clinical research.

Aim

A study was conducted to examine ICU nurses’ perceptions of ethics‐related aspects of ICU‐based research. The study focused on nurse attitudes and knowledge related to clinical research, with special emphasis on perceptions of the informed‐consent process in ICU research.

Method

The study applied a descriptive qualitative approach, involving semi‐structured group interviews and theme‐based inductive content analysis. Subjects were ICU nurses (n = 28) at a university hospital ICU who had experience with research protocols applied in that unit.

Findings

The nurses had mainly positive perceptions of clinical studies. They found research beneficial for future patients and for society. The nurses considered the information given to them about the studies inadequate. They were concerned about the fact that the consent for research is almost always obtained at the beginning of the ICU care, when patients and relatives are still in the crisis period. This limits the possibility of understanding and assimilating the information provided on the study.

Conclusions

The role of ICU nurses in clinical studies should be more prominent and taken into account in the planning of ICU studies.
Struggling for a dignifying care: experiences of being next of kin to patients in home health care
Authors: Søvde Bente Egge , Hovland Gro , Ullebust Berit , Råholm Maj‐Britt
Published: January 2019

Background

Home healthcare services are becoming more complex as a result of changing demographics in society and patients having multiple health problems requiring advanced nursing care. Next of kin often experience that they put their own life on hold, and may feel that they stand alone when life takes an unexpected turn.

Aim

The aim of this study was to explore next of kin's views of dignity in home healthcare services.

Methods

This study has a qualitative approach and content analysis was applied. The purposeful sample consisted of next of kin to patients who received services from home healthcare or in nursing homes (n = 11). One focus group was conducted in 2016.

Results

Five themes emerged from the data analysis concerning struggling for a dignifying care in home healthcare services: Indignity implies double vulnerability, desire for respect and recognition, experiencing responsibility for a dignifying life, undignifying care due to lack of competence, and the home as a common sanctuary is gradually lost.

Conclusions

This study highlights the importance of ensuring dignity in care for patients living at home. Next of kin should be seen as a partner with the need for recognition and support. Maintaining human dignity for loved ones requires competence, respect and recognition.
Comparison of wiping methods for the removal of cleaning agent residue from hair follicles
Authors: Aoki Miku , Ogai Kazuhiro , Matsumoto Masaru , Susa Haruka , Yamada Kotoko , Yamatake Takafumi , Kobayashi Masato , Sugama Junko
Published: January 2019

Purpose

This study aimed to clarify the influence of different wiping methods on cleaning agent residue in hair follicles when using skin cleaning agents that are “removable‐by‐wiping.”

Methods

A total of 18 male volunteers were recruited and a cleaning agent containing 10% fluorescein sodium salt (cleaning agent) was used in this study. After gentle washing, the cleaning agent was removed via the washing method (control) or three distinct wiping methods (experiment). Hairs were obtained from the measurement area. The fluorescence intensities of the residual cleaning agent on the hair root and hair bulb were then evaluated after normalizing for autofluorescence from the hair. Fluorescence intensity was used to estimate the amount of cleaning agent residue.

Results

No significant differences were found among cleaning agent removal methods (hair root: P = 0.67, hair bulb: P = 0.62) with respect to the amount of residual cleaning agent on hair.

Conclusion

Cleaning agent residual index did not differ according to removal method. Cleaning agent remained in the hair follicle (hair roots, hair bulbs) despite removal from the skin by washing or wiping. Further studies are required to apply “removable‐by‐wiping” cleaning agents for people with vulnerable skin.
Early evolution of Nemopteridae illuminated with the first and oldest thread‐winged lacewing in Cretaceous amber
Authors: Lu Xiumei , Wang Bo , Yang Shiyan , Liu Xingyue
Published: January 2019

Nemopteridae are a charismatic family of lacewings distinguished by specialization of morphology in both larvae and adults as well as in their biology and behaviour. The evolutionary history of Nemopteridae is largely unknown due to the scarcity of fossil records. Here we report a new genus and species of Nemopteridae (Cretocroce xiai gen. et sp.n.) based on an exquisitely preserved adult specimen in mid‐Cretaceous Burmese amber. We place the new genus in the subfamily Crocinae, which is characterized by filamentous hindwings with a sensory function as an adaptation to their cavernicolous habitats. The new genus represents the first nemopterid in amber and the oldest crocine known to date. The new fossil crocine is nearly morphologically unchanged over 99 Ma compared with its modern counterparts. Moreover, it is estimated to be closely related to some extant crocines endemic to South America based on morphological phylogenetic analysis. The new finding provides direct evidence to demonstrate the antiquity of Crocinae morphological innovation and related biology, such as pollenophagous habits, and further corroborates Gondwanan origin of the subfamily.

The published work has been registered on ZooBank:
http://zoobank.org/urn:lsid:zoobank.org:pub:3D29DE48‐DBD8‐4614‐8387‐D9FCF90B0640.
Suppression of tryptophan synthase activates cotton immunity by triggering cell death via promoting SA synthesis
Authors: Miao Yuhuan , Xu Lian , He Xin , Zhang Lin , Shaban Muhammad , Zhang Xianlong , Zhu Longfu
Published: January 2019

Primary metabolism plays an important role in plant growth and development, however the relationship between primary metabolism and the adaptive immune response is largely unknown. Here, we employed RNA interference (RNAi), virus‐induced gene silencing (VIGS) technology, phytohormone profiling, genetic studies, and transcriptome and metabolome analysis to investigate the function of the tryptophan synthesis pathway in the resistance of cotton to V. dahliae. We found that knock‐down of GbTSA1 (Tryptophan Synthase α) and GbTSB1 (tryptophan synthase β) induced a spontaneous cell death phenotype in a salicylic acid (SA)‐dependent manner and enhanced resistance to V. dahliae in cotton plants. Metabolome analysis showed that indole and indolic metabolites were highly accumulated in GbTSA1‐ or GbTSB1‐silenced plants. Transcriptomic analysis showed that exogenous indole promotes the expression levels of genes involved in SA synthesis and the defense response. Similarly, indole application strongly enhanced cotton resistance to V. dahliae. These results suggested that metabolic intermediates in the Trp synthesis pathway may be a signal to activate SA synthesis. These results also provided a strategy to elicit plant defense responses by the application of indole.
Driving Robotic Exoskeletons Using Cable-Based Transmissions: A Qualitative Analysis and Overview
Authors: Grosu Svetlana , De Rijcke Laura , Grosu Victor , Geeroms Joost , Vanderboght Bram , Lefeber Dirk , Rodriguez-Guerrero Carlos
Published: January 2019

Wearable robotics is a field receiving increasing attention from the scientific community. It has great potential to improve rehabilitation process or increase the human capabilities but faces a number of challenges. On the one side, powerful actuation is required, leading to considerable system weight. On the other side, due to the close physical interaction with a human and taking into consideration safety requirements, the displacement of the actuators is crucial to the operational efficiency and functionality of exoskeleton devices. One possible solution for the design of an operational and efficient wearable device is to relocate its actuators out of joints and transmit the force by means of cable-based transmission systems. This paper presents an overview of various cable-based configurations correlated to conventional mechanical designs and their implementation in exoskeleton's structures and an overview of exoskeleton robots including comparison and trend analyses.
A Simple Palladium Hydride Embedded Atom Method Potential for Hydrogen Energy Applications
Authors: Hijazi Iyad , Zhang Yang , Fuller Robert
Published: January 2019

When hydrogen is produced from a biomass or coal gasifier, it is necessary to purify it from syngas streams containing components such as CO, CO2, N2, CH4, and other products. Therefore, a challenge related to hydrogen purification is the development of hydrogen-selective membranes that can operate at elevated temperatures and pressures, provide high fluxes, long operational lifetime, and resistance to poisoning while still maintaining reasonable cost. Palladium-based membranes have been shown to be well suited for these types of high-temperature applications and have been widely utilized for hydrogen separation. Palladium's unique ability to absorb a large quantity of hydrogen can also be applied in various clean energy technologies, like hydrogen fuel cells. In this paper, a fully analytical interatomic embedded atom method (EAM) potential for the Pd-H system has been developed, that is easily extendable to ternary Palladium-based hydride systems, such as Pd-Cu-H and Pd-Ag-H. The new potential has fewer fitting parameters than previously developed EAM Pd-H potentials and is able to accurately predict the cohesive energy, lattice constant, bulk modulus, elastic constants, melting temperature, and the stable Pd-H structures in molecular dynamics (MD) simulations with various hydrogen concentrations. The EAM potential also well predicts the miscibility gap, the segregation of the palladium hydride system into dilute (α), and concentrated (β) phases.
Absorption Process in MgCl2–NH3 Thermochemical Batteries With Constant Mass Flow Rate
Authors: Hedayat Mofidi Seyyed Ali , Udell Kent S.
Published: January 2019

In this paper, the performance of a thermochemical battery based on magnesium chloride and ammonia pair with a constant mass flow rate of ammonia gas is studied through a series of experiments using single and multicell configurations. It is shown that a lower mass flow rate lowers the temperature of the reactive complex and increases the duration of the absorption process. However, it was observed that the reaction eventually becomes mass transfer limited which slows the absorption rate to values below those specified by the mass flow controller (MFC). It was shown in the single-cell reactor that a reaction zone starts at the inlet and moves toward the end of the reactor. The mass transfer limited reaction zone movement reduces the absorption rate and temperature in the reaction zone. The overall performance of a multicell thermal battery is also studied to analyze behavior of such reactors as well. It was shown that the controlling the flow rate of ammonia can cause the cells to deviate in absorption rate.
Performance Prediction and Optimization of an Organic Rankine Cycle Using Back Propagation Neural Network for Diesel Engine Waste Heat Recovery
Authors: Yang Fubin , Cho Heejin , Zhang Hongguang
Published: January 2019

This paper presents a methodology to predict and optimize performance of an organic Rankine cycle (ORC) using a back propagation neural network (BPNN) for diesel engine waste heat recovery. A test bench of an ORC with a diesel engine is established to collect experimental data. The collected data are used to train and test a BPNN model for performance prediction and optimization. After evaluating different hidden layers, a BPNN model of the ORC system is determined with the consideration of mean squared error (MSE) and correlation coefficient. The effects of key operating parameters on the power output of the ORC system and exhaust temperature at the outlet of the evaporator are evaluated using the proposed model and further discussed. Finally, a multi-objective optimization of the ORC system is conducted for maximizing power output and minimizing exhaust temperature at the outlet of the evaporator based on the proposed BPNN model. The results show that the proposed BPNN model has a high prediction accuracy and the maximum relative error of the power output is less than 5%. It also shows that when the operations are optimized based on the proposed model, the power output of the ORC system can be higher than the experimental results.
Dynamic Performance of an Oil Starved Squeeze Film Damper Combined With a Cylindrical Roller Bearing
Authors: Meeus H. , Fiszer J. , Van De Velde G. , Verrelst B. , Lefeber D. , Guillaume P. , Desmet W.
Published: January 2019

Squeeze film dampers (SFDs) are widely used to dissipate mechanical energy caused by rotor vibrations as well as to improve overall stability of the rotor system. Especially turbomachine rotors, supported on little damped rolling element bearings (REBs), are primarily sensitive to unbalance excitation and thus high amplitude vibrations. To ensure safe operation, potential failure modes, such as an oil starved damper state, need to be well examined prior to the introduction in the ultimate industrial application. Hence, the aim of this research project is to evaluate the performance of the rotor support for a complete oil starvation of the SFD. An academic rotor dynamic test bench has been developed and briefly presented. Experimental testing has been conducted for two static radial load cases resembling the full load and idle condition of a certain turbomachine. Evidently, the measurement results exposed severe vibration problems. Even a split first whirl mode arises due to a pronounced anisotropic bearing stiffness. Moreover, for the least radially loaded bearing, highly nonlinear behavior emerged at elevated unbalance excitation. Consequently, the rollers start to rattle which will have a negative effect on the overall bearing lifetime. To explain the nature of the nonlinear behavior, advanced quasi-static bearing simulations are exploited. A number of possible solutions are proposed in order to help mitigate the vibration issues.
Investigations on the Sealing Effectiveness and Unsteady Flow Field of 1.5-Stage Turbine Rim Seal
Authors: Cheng Shuxian , Li Zhigang , Li Jun
Published: January 2019

This paper presents a numerical investigation on the sealing effectiveness and unsteady flow field of a 1.5-stage turbine with the front and aft wheel-space cavities. The sealing effectiveness and flow structure are studied by solving three-dimensional unsteady Reynolds-averaged Navier–Stokes (URANS) equations and shear stress transfer (SST) turbulence model. The numerical pressure and swirl ratio distributions in cavities with two computational models are compared with experimental data to determine the position of stationary/rotating domain interface. The time-averaged mainstream pressure distribution and sealing effectiveness of the rim seal at the front and aft cavities are studied by the steady and unsteady calculations. The unsteady results agree well with experimental data by comparison of the steady calculations. The effects of coolant flow rates on the sealing effectiveness and the flow field of the rim seal at the front and aft cavities are investigated. The obtained results show that the sealing effectiveness of the rim seal at the aft cavity is much larger than that of the rim seal at the front cavity at the same coolant flow rate. The less mainstream pressure fluctuation near the aft rim seal clearance and the clockwise vortex due to the pumping effect in the aft rim seal leads to this result. The mainstream pressure fluctuation downstream of the blade and the sealing effectiveness of the rim seal at the aft cavity under five operating conditions are computed. It shows that the square root of the mainstream pressure fluctuation amplitude downstream of the blade is proportional to the mainstream flow rate. The increase of the mainstream flow results in gradual decrease of the sealing effectiveness of the rim seal at the aft cavity.
A Conceptual Study for the Smallest Possible Diesel Engine: Potential and Limitations
Authors: Jeihouni Yousef , Dhongde Avnish , Sankhla Harsh , Franke Michael
Published: January 2019

Downsizing of engines is a major area of interest in the combustion engines sector due to a variety of reasons, chief among which is the CO2 emission reduction due to increased power to weight ratio. Furthermore, the introduction of various auxiliary devices into an automotive product, as well as increased acoustic insulation, necessitate continuous trimming of the engine packaging space. In this paper, the potential and limitations of downsizing diesel engines to very small displacements is studied. The goal of the article is to determine the minimum displacement a diesel engine can achieve, given the limitations posed by state-of-the-art technology. At the same time, the objective is the maximization of power density with acceptable levels of fuel consumption. While the investigations focused on the thermodynamic behavior of downsizing, structural aspects were also considered.

On the basis of a literature study, the article illustrates the benchmarking of existing small gasoline and diesel engines for different applications. Thereafter, a matrix of engine configurations, which were relevant to the investigations, was generated. This included, among others, various bore / stroke combinations, compression ratios, piston and nozzle geometries, as well as valve diameters. Further, the influence of injection pressure, swirl and air-fuel ratio were included in the study. With the aid of the 1D simulation software GT-Power and the 3D CFD code Kiva-3V, a detailed thermodynamic analysis was performed on the chosen variants.

In the results detailed in this article, a promising downsizing potential for a cylinder displacement well below 200cm3/cylinder has been established. Further, best-in-class power densities at acceptable fuel consumption levels could be achieved. This opens up the possibility for the application of such small diesel engines in a new range of applications. The challenges on the thermodynamic and structural fronts, which need to be met in order to achieve targets, are also highlighted.
Optimum Operating Strategies for Gas Engines Using Variable Intake Valve Train
Authors: Zelenka Jan , Hoff Claudio , Wimmer Andreas , Christen Claudio , Böwing Robert , Thalhauser Josef
Published: January 2019

The present publication describes investigations on a lean burn gas engine equipped with a variable intake valve train and demonstrates how steady state engine performance can be improved in comparison to a conventional state-of-the-art application with constant Miller timing.

As the knock border represents a significant limitation of the operating range of gas engines, the engine specific knock limit was derived from measurements on a single cylinder research engine and transferred to a 1D simulation model of the corresponding multicylinder engine; a large bore, two stage turbocharged gas engine in the 5 MW power range with a variable intake valve train. Special attention was given to the setup of the simulation model to improve prediction quality and reduce simulation effort.

An optimal strategy using the flexibility of a variable intake valve train for engine operation is presented that is capable of accommodating fluctuating gas qualities, which are described by the methane number. The operating strategy was derived from the 1D simulation model. The better performance than with a state-of-the-art strategy will be quantified in terms of engine efficiency while knocking combustion caused by low methane numbers is prevented.

Since ambient temperatures in certain regions where the engine is operated do not remain stable throughout the year and ambient pressure varies depending on sea level, these issues must also be addressed. The temperature and density of the intake air have a large influence on the performance of the turbocharging unit and thus overall engine efficiency. The simulation results show the engine’s behavior under varying ambient conditions and outline potential strategies for improvement made possible by using variable valve timing on the intake side.
Effect of Combustion Characteristics on Knocking in a Direct Injection Turbo-Charged Gasoline Engine
Authors: Oh Heechang , Son Jinwook , Lee Juhun , Woo Soohyung , Kim Youngnam , Hong Seungwoo
Published: January 2019

Experimental study on knocking characteristics in a direct injection turbo-charged gasoline engine was carried out. The thermodynamic analysis was conducted to investigate effects of the combustion phasing and the burning rate on the knocking behavior. The localization of knock events and the characterization of the early flame kernel propagation were conducted with the fiber optic sensor.

The advanced combustion phasing and the slower combustion speed generally increased the knocking probability. However, not only quasi-dimensional thermodynamic combustion characteristics but also the spatial parameter such as the flame propagation direction significantly affected the knocking occurrence. From the fiber optic sensor test results, knocking onset location was found to be closely correlated with the flame propagation direction and mainly observed in the opposite side to the main flame propagation direction. The flame propagation direction leaning to the exhaust side was identified to be favorable for the knocking mitigation because the end gas location on hotter exhaust side could be avoided.

Engine tests for various squish designs and tumble port designs were implemented to study the effect of the in-cylinder flow, which significantly affects previously discussed knocking-related parameters. As a result, tumble and squish flow significantly increased combustion speed and advanced combustion phasing. Fuel consumption could be also reduced due to suppressed knocking combustion. In addition, new tumble port design enabled the flame propagation to have favorable leaning direction.
Impact of a Holistic Turbocharger Model in the Prediction of Engines Performance in Transient Operation and in Steady State With LP-EGR
Authors: Serrano José Ramón , Arnau Francisco José , González Luis Miguel García-Cuevas , Gómez-Vilanova Alejandro , Guilain Stephane
Published: January 2019

Turbocharged engines are the standard powertrain type of internal combustion engines for both spark ignition and compression ignition concepts. Turbochargers modeling traditionally rely in look up tables based on turbocharger manufacturer provided maps. These maps as the only secure source of information. They are used both for the matching between reciprocating engine and the turbocharger and for the further engine optimization and performance analysis. In the last years have become evident that only these maps are not being useful for detailed calculation of variables like after-treatment inlet temperature (turbine outlet), intercooler inlet temperature (compressor outlet) and engine BSFC at low loads. This paper shows a comprehensive study that quantifies the errors of using just look up tables compared with a model that accounts for friction losses, heat transfer and gas-dynamics in a turbocharger and in a conjugated way. The study is based in an Euro 5 engine operating in load transient conditions and using a LP-EGR circuit during steady state operation.
Performance of Microemulsion Fuels As an Alternative for Diesel Engine
Authors: Abrar Iyman , Bhaskarwar Ashok N.
Published: January 2019

Microemulsions are sustainable alternatives to fos sil fuels, which could possibly be used without any modifications in current engines and storage-transportation-supply infrastructure. Our current work attempts to examine the usability of butanol-diesel-water microemulsion fuels in a diesel engine. A small percentage of water is desirable, as it reduces the NOx and smoke emissions. The microemulsion regions were mapped out in ternary phase diagrams, and the fuel was characterized as per ASTM D975, and further examined for its performance in a diesel engine. The formulated microemulsions satisfied the ASTM standards, and had properties (density, viscosity, flash points, cloud points, copper strip corrosion rating, sulfur content, and ash percent) close to those of neat diesel. The percentage change in property ε was calculated as [|(εdiesel − εmicroemulsion)|/εdiesel] × 100. The calorific values for the microemulsion fuels showed a maximum reduction of 8.31% as compared to that of neat diesel. The brake thermal efficiency, however, increased by 15.38% for the same, with respect to the value for neat diesel (2% higher overall efficiency of the engine). The brake specific fuel consumption was also lowered by 5.04%, and the maximum reduction in emissions of CO, unburnt HC, CO2, and NOx were observed to be 53.48%, 67.40%, 30.82%, and 41.72%, respectively, relative to those of neat diesel. The present experimental investigations thus suggest that the microemulsions could be used as a sustainable cleaner alternative to diesel.
Design of an Advanced Air Path Test Stand for Steady and Transient Evaluation
Authors: Vijayakumar R. , Burke R. , Liu Y. , Turner J. W. G.
Published: January 2019

Different air systems such as turbochargers (TC), hybrid boosting, turbo compounding and exhaust gas recirculation (EGR) are increasingly used to improve the thermal efficiency of internal combustion engines (ICE). One dimensional (1D) gas dynamic codes supports their development and integration by modelling the engine and air systems and reducing testing time. However, this approach currently relies on steady flow characteristic maps which are inaccurate for simulating transient engine conditions. This is a key weakness of using gas-stand measured maps in engine simulations. Performing TC mapping on an engine would in principle solve this problem, however engine-based mapping is limited by the engine operating range and on these facilities, high-precision measurements are challenging.

In addition, simple turbocharging can no longer be constrained to an individual TC supplying boost air to an engine. Instead, modern downsized engines require air-path system making use of multiple components including TCs, mechanical superchargers, electrically driven compressors (EDCs), EGR paths and control valves. Thus studying multiple air systems requires an experimental test facility to understand how they work in synergy. This is also useful in developing empirical models to minimize test time. Therefore the aim of this paper is to present a novel experimental facility that is flexibly designed for evaluating air systems individually and also at the system level representing a complicated air path both in steady and transient condition.

The advanced test facility is built around a 2.2 l diesel engine to test the above air systems which can isolate the thermal and load transients from engine pulsating flows. Removing the flow pulsation allows study of the system characteristics in a steady state. Several examples of component and system level tests including a two-stage air path comprising of a VGT (variable geometry turbine) TC and a 48V EDC with typical operating condition (provided by 1D modeling) are discussed.
A Comprehensive Ignition System Model for Spark Ignition Engines
Authors: Ge Haiwen , Zhao Peng
Published: January 2019

In the present paper, a comprehensive ignition system model (VTF ignition model) accounting for the practical module and working mechanism of a spark plug was developed, aiming to provide enhanced capability for the 3D combustion simulation of spark ignition engines. In this model, an electrical circuitry model is used to represent the ignition coil, spark plug, and air column. The air column is represented by a set of Lagrangian particles that move with the local flow field. Flame propagation is directly calculated using SAGE model with a reduced isooctane reaction mechanism. The new ignition system model is further implemented into CONVERGE through user defined functions and is verified by comparing with the conventional DPIK model. It is found that the VTF ignition model predicts slower combustion than the DPIK model, mainly due to more realistic energy deposit method and energy discharging rate. Furthermore, the VTF model also has the capability of predicting the arc motion and restrike phenomena associated with spark ignition processes. It is expected that with more validation with experiments, the new VTF model has the great potential to better serve the needs of engine combustion simulation.
Analysis of the Opportunities and Trade-Offs for an 48V Electrified Air Path
Authors: Liu Yang , Vijayakumar Ramkumar , Burke Richard
Published: January 2019

The electrification of powertrains is now the accepted roadmap for automotive vehicles. The next big step in this area will be the adoption of 48V systems, which will facilitate the use of technologies such as electric boosting and integrated startergenerators. The introduction of these technologies gives new opportunities for engine airpath design as an electrical energy source may now be used in addition to the conventional mechanical and exhaust thermal power used in super- and turbochargers. This work was conducted as part of the EU funded project “THOMSON” which aims to create a cost effective 48V system enabling engine downsizing, kinetic energy recovery, and emissions management to reduce the environmental impact of transportation. The paper presents a study on an electrified airpath for a 1.6L diesel engine. The aim of this study is to understand the design and control trade-offs which must be managed in such an electrified boosting system. A two-stage boosting system including an electric driven compressor (EDC) and a variable geometry turbocharger (VGT) is used. The air path also include low and high pressure EGR loops. The work was performed using a combination of 1D modelling and experiments conducted on a novel transient air path test facility.

The simulation results illustrate the trade-off between using electrical energy from in the EDC or thermal energy in the turbocharger to deliver the engine boost pressure. For a same engine boost target, the use of the EDC allows wider VGT opening which leads to lower engine backpressure (at most 0.4bar reduction in full load situation) and reduced pumping losses. However, electricity consumed in EDC either needs to be provided from the alternator (which increases the load on the engine) or by depleting the state of charge of the battery. The location of charge air coolers (pre- or post-EDC) is also investigated. This changes the EDC intake temperature by 100K and the intake manifold by 5K which subsequently impacts on engine breathing. An experimentally validated model of a water charge air cooler model has been developed for predicting flow temperature.
Numerical Studies of Combustion Recession on ECN Diesel Spray A
Authors: Fang Xiaohang , Ismail Riyaz , Davy Martin H. , Camm Joseph
Published: January 2019

It is known that low-temperature combustion (LTC) strategies can help simultaneously reduce nitrogen oxides (NOx) and particulate matter (PM) emissions from diesel engines to very low levels. However, it is also known that LTC may cause emissions of unburned hydrocarbons (UHC) to rise — especially in low load operating conditions. Recent studies indicate that end-of-injection (EOI) processes may support ignition recession back to injector nozzle thereby helping to reduce these emissions. This paper contributes to the physical understanding of this EOIphe-nomenon, combustion recession, using computational fluid dynamics studies at LTC conditions. Simulations are performed on a single-hole injection of n-dodecane under a range of Engine Combustion Network’s “Spray A” conditions. The primary objective of this paper is to assess the ability of a Flamelet Generated Manifold (FGM) combustion model to predict and characterize combustion recession. First, a baseline condition FGM simulation is compared with two other combustion models namely the Well Stirred model (WSR), the Representative Interactive Flamelet model (RIF) using the commercially-available CFD solver, CONVERGE. Further studies were carried out for FGM model alone including: varying ambient temperature conditions and chemical mechanisms. Two chemical kinetics mechanisms with low temperature chemistry for n-dodecane are employed to help to predict the occurrence of combustion recession. All simulations are performed under the Reynolds-Averaged Navier-Stokes (RANS) framework in a grid-converged Lagrangian spray scenario. The simulation of combustion recession is qualitatively validated against experimental data from literature and the efficacy of each model in predicting combustion recession is evaluated. Overall, it was found that the FGM model was able to capture the combustion recession phenomenon well — showing particular strength in predicting distinct auto-ignition events in the near nozzle region.
Diesel Engine Acoustic Emission Airflow Clogging Diagnostics With Machine Learning
Authors: Cowart Jim , Moore Patrick , Yosten Harrison , Hamilton Leonard , Luning Prak Dianne
Published: January 2019

A diesel engine electrical generator set (’gen-set’) was instrumented with in-cylinder indicating sensors as well as acoustic emission microphones near the engine. Air filter clogging was emulated by progressive restriction of the engine’s inlet air flow path during which comprehensive engine and acoustic data were collected. Fast Fourier Transforms (FFTs) were analyzed on the acoustic data. Dominant FFT peaks were then applied to supervised machine learning neural network analysis with MATLAB based tools. The progressive detection of the air path clogging was audibly determined with correlation coefficients greater than 95% on test data sets for various FFT minimum intensity thresholds. Further, unsupervised machine learning Self Organizing Maps (SOMs) were produced during normal-baseline operation of the engine. Application of the degrading air flow engine sound data was then applied to the normal-baseline operation SOM. The quantization error of the degraded engine data showed clear statistical differentiation from the normal operation data map. This unsupervised SOM based approach does not know the engine degradation behavior in advance, yet shows clear promise as a method to monitor and detect changing engine operation. Companion in-cylinder combustion data additionally shows the degrading nature of the engine’s combustion with progressive airflow restriction (richer and lower density combustion).
Prediction of Cyclic Variability and Knock-Limited Spark Advance (KLSA) in Spark-Ignition (SI) Engine
Authors: Yue Zongyu , Edwards K. Dean , Sluder C. Scott , Som Sibendu
Published: January 2019

Engine knock remains one of the major barriers to further improve thermal efficiency of Spark Ignition (SI) engines. Knock can be suppressed by lowering the compression ratio, or retarding the spark ignition timing, however, at an expense of efficiency penalty. SI engine is usually operated at knock-limited spark advance (KLSA) to achieve possibly maximum efficiency with given engine hardware and fuel properties, such as Research Octane Number (RON), Motor Octane Number (MON), and heat of vaporization, etc. Co-optimization of engine design and fuel properties is promising to improve the engine efficiency and predictive CFD models can be used to facilitate this optimization process. However, difficulties exist in predicting KLSA in CFD simulations. First, cyclic variability of SI engine demands that multi-cycle results are required to capture the extreme conditions. Secondly, Mach Courant-Friedrichs-Lewy (CFL) number of 1 is desired to accurately predict the knock intensity (KI), resulting in unaffordable computational cost, especially for multi-cycle simulations. In this study, a new approach to numerically predict KLSA using large Mach CFL number of 50 is proposed. This approach is validated against experimental data for a boosted Direct Injection Spark Ignition (DISI) engine at multiple loads and spark timings. G-equation combustion model coupled with well-mixed chemical kinetic model are used to predict the turbulent flame propagation and end-gas auto-ignition, respectively. Simulations run for 10 consecutive engine cycles at each condition. The results show good agreement between model predictions and experiments in terms of cylinder pressure, combustion phasing and cyclic variation. Engine knock is predicted with early spark ignition timing, indicated by significant pressure wave oscillation and end-gas heat release. Maximum Amplitude of Pressure Oscillation (MAPO) analysis is performed to quantify the KI, and the slope change point in KI extrema is used to indicate the KLSA accurately. Using a smaller Mach CFL number of 5 also results in the same conclusions thus demonstrating that this approach is insensitive to the Mach CFL number. The use of large Mach CFL number allows us to achieve fast turn-around time for multi-cycle engine CFD simulations.
Numerical Simulation of Re-Entrant Bowl Effects on Natural Gas SI Operation
Authors: Liu Jinlong , Dumitrescu Cosmin E.
Published: January 2019

Heavy-duty compression-ignition (CI) engines converted to natural gas (NG) spark ignition (SI) operation have the potential to increase the use of NG in the transportation sector. A 3D numerical simulation was used to predict how the conventional CI combustion chamber geometry (i.e., re-entrant bowl and flat head) affects the combustion stability, performance and emissions of a single-cylinder CI engine that was converted to SI operation by adding a low-pressure gas injector in the intake manifold and a spark plug in place of the diesel injector. The G-equation based 3D CFD simulation investigated three different combustion chamber configurations that changes the size of the squish region at constant compression ratio and clearance height. The results show that the different flame propagation speeds inside and outside the re-entrant bowl can create a two-zone combustion phenomenon. More, a larger squish region increased flame burning speed, which decreased late-combustion duration. All these findings support the need for further investigations of combustion chamber shape design for optimum engine performance and emissions in CI engines converted to NG SI operation.
An Exhaust Gas Temperature Increase Technique Using EGR Device for the Application of Waste Heat Recovery Technology on a Lean Burn Gas Engine
Authors: Ichikawa Yasuhisa , Sekiguchi Hidenori , Bondarenko Oleksiy , Hirata Koichi
Published: January 2019

This study aims to develop an exhaust gas temperature increase technique of a lean burn gas engine, to improve the performance of the waste heat recovery devices that potentially can be installed in the future. This paper shows the exhaust gas temperature increase technique using an EGR device.

In our experiments, the lean burn gas engine has the rated power output of 400 kW with spark-ignition and pre-chamber systems. The EGR device was developed and installed to the gas engine. The experimental results showed that the exhaust gas temperature was increased to +30 °C at the EGR rate of 15 % with maintained NOx emission and CA MFB 50% by decreasing the relative air/fuel ratio (Λ) and advancing the ignition timing (θig). In addition, the gross generation efficiency was slightly increased with increasing the EGR rate. This result was explained using three factors; the internal engine efficiency, the combustion efficiency, and the recirculated energy rate.
Numerical Study on Evaporation of Lubricating Oil Droplets Under Natural Gas Engine Conditions
Authors: Feng Liyan , Wang Zixin , Yi Ping , Gong Weixin , Cui Jingchen , Chen Lei , Tian Jiangping , Long Wuqiang
Published: January 2019

The distribution of lubricating oil droplets in cylinder is one of main causes of abnormal combustion of natural gas engines. The evaporation of lubricating oil droplet is one of the key sub-processes controlling its auto-ignition event. The components of lubricating oil with different carbon number (16–50) shows significantly different evaporation and ignition characteristics from gasoline and diesel fuels. Even though there are many evaporation models focusing on the evaporation behaviors of multi-component droplets, most of them are limited to the liquid fuels, which are composed by more volatile hydrocarbons. Therefore, understanding the evaporation characteristics of lubricating oil droplets is very important for investigating the mechanism of abnormal combustion of natural gas engines. In this study, a multi-component evaporation model for lubricating oil was developed, which considers several key characteristics in the droplet evaporation process, including the finite heat conduction and limited mass diffusion in liquid phase, multi-component diffusion in gas phase, real vapor-liquid equilibrium at the droplet interface, as well as the nitrogen quantity dissolved in liquid phase. The simulation results by this model were compared with experimental results, and good agreements have been achieved. Then, this model was used to study the evaporation behaviors of different hydrocarbon droplets, including lubricating oil droplet. The influences of ambient temperatures and pressures, as well as methane concentration on evaporation characteristics (namely the heat up period, average evaporation rate, and droplet lifetime) were investigated. The results show that both heat up period and evaporation rate of lubricating oil droplets increase as the methane concentration increases. Besides, the droplet lifetime monotonically decreases as the ambient pressure decreases. This is different from the diesel and gasoline droplets, for which the effects of pressure on the droplet evaporation behaviors are depended on the ambient temperature.