bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.
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.
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.
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.
Effect of Fuel Injection Timing During Negative Valve Overlap Period on a GDI-HCCI Engine
Authors: Ratnak Sok , Kusaka Jin , Daisho Yasuhiro , Yoshimura Kei , Nakama Kenjiro 
Published: January 2019

Gasoline Direct Injection Homogeneous Charge Compression (GDI-HCCI) combustion is achieved by closing early the exhaust valves for trapping hot residual gases combined with direct fuel injection. The combustion is chemically controlled by multi-point auto-ignition which its main combustion phase can be controlled by direct injection timing of fuel. This work investigates the effect of single pulse injection timing on a supercharged GDI-HCCI combustion engine by using a four-stroke single cylinder engine with a side-mounted direct fuel injector.
Injection of primary reference fuel PRF90 under the near-stoichiometric-boosted condition is studied. The fuel is injected during negative valve overlap (NVO) or recompression period for fuel reformation under low oxygen concentration and the injection is retarded to intake stroke for the homogeneous mixture. It is found that the early fuel injection in NVO period advances the combustion phasing compared with the retarded injection in the intake stroke. Noticeable slower combustion rate from intake stroke fuel injection is obtained compared with the NVO injection due to charge cooling effect. Zero-dimensional combustion simulations with multiple chemical reaction mechanisms are simulated to provide chemical understanding from the effect of fuel injection timing on intermediate species generations. The species such as C2H4, C3H6, CH4, and H2 are found to be formed during the NVO injection period from the calculations. The effects of single pulse injection timings on combustion characteristics such pressure rise rate, combustion stability, and emissions are also discussed in this study.
Design and Experimental Validation of a Spatially Discretized, Control-Oriented Temperature Model for a Ceria-Washcoated Gasoline Particulate Filter
Authors: Moser Sean , Onori Simona , Hoffman Mark 
Published: January 2019

Gasoline particulate filters (GPFs) are the most promising and practically applicable devices to reduce Particulate Matter (PM) and Particulate Number (PN) emissions from gasoline direct ignition engines. A model that can predict internal GPF temperature dynamics during regeneration events can then be implemented online to maintain GPF health and aide in exotherm control algorithms without the associated instrumentation costs. This work demonstrates a control-oriented model, which captures the thermal dynamics in a catalyzed, ceria-coated GPF in the axial direction. The model utilizes soot oxidation reaction kinetics to predict internal GPF temperature dynamics during regeneration events using three finite volume cells.
A model methodology initially proposed by Arunachalam et al [18] is utilized with the GPF of this work, validating the broad applicability of that methodology. Then, the model’s temperature prediction fidelity is improved through axial discretization. The zonal model parameters are identified via a Particle Swarm Optimization using experimental results from the instrumented GPF. Identified parameters from the various data sets are used to develop a linear parameter varying model for prediction of the axial temperature distribution within the GPF. The resulting model is then validated against an experimental data set utilizing the exhaust temperature entering the GPF. The spatial discretization methodology employed both enables the prediction of spatial temperature variation within the GPF and improves the accuracy of the peak temperature prediction by a factor ranging from 2–10x.
Modeling Fuel Effects in a Diesel Engine Using Multi-Component Fuel Surrogates in CFD
Authors: Puduppakkam Karthik V. , Naik Chitralkumar V. , Meeks Ellen 
Published: January 2019

A continued challenge to engine combustion simulation is predicting the impact of fuel-composition variability on performance and emissions. Diesel fuel properties, such as cetane number, aromatic content and volatility, significantly impact combustion phasing and emissions. Capturing such fuel property effects is critical to predictive engine combustion modeling. In this work, we focus on accurately modeling diesel fuel effects on combustion and emissions. Engine modeling is performed with 3D CFD using multi-component fuel models, and detailed chemical kinetics. Diesel FACE fuels (Fuels for Advanced Combustion Engines) have been considered in this study as representative of street fuel variability. The CFD modeling simulates experiments performed at Oak Ridge National Laboratory (ORNL) [1] using the diesel FACE fuels in a light-duty single-cylinder direct-injection engine. These ORNL experiments evaluated fuel effects on combustion phasing and emissions. The actual FACE fuels are used directly in engine experiments while surrogate-fuel blends that are tailored to represent the FACE fuels are used in the modeling. The 3D CFD simulations include spray dynamics and turbulent mixing.
We first establish a methodology to define a model fuel that captures diesel fuel property effects. Such a model should be practically useful in terms of acceptable computational turnaround time in engine CFD simulations, even as we use sophisticated fuel surrogates and detailed chemistry. Towards these goals, multi-component fuel surrogates have been developed for several FACE fuels, where the associated kinetics mechanisms are available in a model-fuels database. A surrogate blending technique has been employed to generate the multi-component surrogates, so that they match selected FACE fuel properties such as cetane number, chemical classes such as aromatics content, T50 and T90 distillation points, lower heating value and H/C molar ratio. Starting from a well validated comprehensive gas-phase chemistry, an automated method has been used for extracting a reduced chemistry that satisfies desired accuracy and is reasonable for use in CFD. Results show the level of modeling necessary to capture fuel-property trends under these widely varying engine conditions.
Analysis of Different Uniflow Scavenging Options for a Medium-Duty 2-Stroke Engine for a U.S. Light-Truck Application
Authors: Turner J. W. G. , Head R. A. , Wijetunge R. , Chang J. , Engineer N. , Blundell D. W. , Burke P. 
Published: January 2019

The work presented here seeks to compare different means of providing uniflow scavenging for a 2-stroke engine suitable to power a US light-duty truck. Through the ‘end-to-end’ nature of the uniflow scavenging process, it can in theory provide improved gas-exchange characteristics for such an engine operating cycle; furthermore, because the exhaust leaves at one end and the fresh charge enters at the other, the full circumference of the cylinder can be used for the ports for each flow and therefore, for a given gas exchange angle-area demand, expansion can theoretically be maximized over more traditional loop-scavenging approaches. This gives a further thermodynamic advantage.
The three different configurations studied which could utilize uniflow scavenging were the opposed piston, the poppetvalve with piston-controlled intake ports and the sleeve valve. These are described and all are compared in terms of indicated fuel consumption for the same cylinder swept volume, compression ratio and exhaust pressure, for the same target indicated mean effective pressure and indicated specific power.
A new methodology for optimization was developed using a one-dimensional engine simulation package which also took into account charging system work. The charging system was assumed to be a combination of supercharger and turbocharger to permit some waste energy recovery.
As a result of this work it was found that the opposed-piston configuration provides the best attributes since it allows maximum expansion and minimum heat transfer. Its advantage over the other two (whose results were very close) was of the order of 8.3% in terms of NSFC (defined as ISFC net of supercharger power). Part of its advantage also stems from its requirement for minimum air supply system work, included in this NSFC value.
Interestingly, it was found that existing experiential guidelines for port angle-area specification for loop-scavenged, piston-ported engines using crankcase compression could also be applied to all of the other scavenging types. This has not been demonstrated before. The optimization process that was subsequently developed allowed port design to be tailored to specific targets, in this case lowest NSFC. The paper therefore presents a fundamental comparison of scavenging systems using a new approach, providing new insights and information which have not been shown before.
Outcomes of pneumatic dilatation and Heller’s myotomy for achalasia in England between 2005 and 2016
Authors: Harvey Philip R , Coupland Ben , Mytton Jemma , Evison Felicity , Patel Prashant , Trudgill Nigel J 
Published: January 2019

IntroductionAchalasia is a disorder characterised by failed relaxation of the lower oesophageal sphincter. The aim of this study was to examine, at a national level, the long-term outcomes of achalasia therapies.MethodsHospital Episode Statistics include diagnostic and procedural data for all English National Health Service–funded hospital admissions. Subjects with a code for achalasia who had their initial treatment between January 2006 and December 2015 were grouped by treatment; pneumatic dilatation (PD) or surgical Heller’s myotomy (HM). Procedural failure was defined as time to a further episode of the same therapy or a change to a different therapy. Up to three PDs were permitted without being considered a therapy failure.Results6938 subjects were included; 3619 (52.2%) were men and median age at diagnosis was 59 (IQR 43–75) years. 4748 (68.4%) initially received PD and 2190 (31.6%) HM. The perforation rate following PD was 1.6%. Mortality at 30 days was 0.0% for HM and 1.9% for PD, and <8% after perforation following PD. Factors associated with increased mortality after PD included age quintile 66–77 (OR 4.55 (95% CI 2.00 to 10.38), p<0.001), >77 (9.78 (4.33 to 22.06), p<0.001); Charlson comorbidity score >4 (2.87 (2.08 to 3.95), p<0.001); previous HM (2.47 (1.33 to 4.62), p<0.001); and repeat PD 1–3 (1.58 (1.15 to 2.16), p=0.005), >3 (1.97 (1.21 to 3.19), p=0.006). Durability of up to 3 PD and HM over 10 years of follow-up was 86.2% and 81.9%, respectively (p<0.001).DiscussionThe efficacy of PD for achalasia appears to be greater than HM over 10 years. There was no mortality associated with HM, but 1.9% of subjects died within 30 days of PD. Mortality was associated with increasing age, comorbidity, previous HM and repeat PD.
Exploring the underlying biology of intrinsic cardiorespiratory fitness through integrative analysis of genomic variants and muscle gene expression profiling
Authors: Ghosh Sujoy , Hota Monalisa , Chai Xiaoran , Kiranya Jencee , Ghosh Palash , He Zihong , Ruiz-Ramie Jonathan J. , Sarzynski Mark A. , Bouchard Claude 
Published: January 2019

Intrinsic cardiorespiratory fitness (CRF) is defined as the level of CRF in the sedentary state. There are large individual differences in intrinsic CRF among sedentary adults. The physiology of variability in CRF has received much attention, but little is known about the genetic and molecular mechanisms that impact intrinsic CRF. These issues were explored in the present study by interrogating intrinsic CRF-associated DNA sequence variation and skeletal muscle gene expression data from the HERITAGE Family Study through an integrative bioinformatics guided approach. A combined analytic strategy involving genetic association, pathway enrichment, tissue-specific network structure, cis-regulatory genome effects, and expression quantitative trait loci was used to select and rank genes through a variation-adjusted weighted ranking scheme. Prioritized genes were further interrogated for corroborative evidence from knockout mouse phenotypes and relevant physiological traits from the HERITAGE cohort. The mean intrinsic V̇o2maxwas 33.1 ml O2·kg−1·min−1(SD = 8.8) for the sample of 493 sedentary adults. Suggestive evidence was found for gene loci related to cardiovascular physiology ( ATE1, CASQ2, NOTO, and SGCG), hematopoiesis ( PICALM, SSB, CA9, and CASQ2), skeletal muscle phenotypes ( SGCG, DMRT2, ADARB1, and CASQ2), and metabolism ( ATE1, PICALM, RAB11FIP5, GBA2, SGCG, PRADC1, ARL6IP5, and CASQ2). Supportive evidence for a role of several of these loci was uncovered via association between DNA variants and muscle gene expression levels with exercise cardiovascular and muscle physiological traits. This initial effort to define the underlying molecular substrates of intrinsic CRF warrants further studies based on appropriate cohorts and study designs, complemented by functional investigations.NEW & NOTEWORTHY Intrinsic cardiorespiratory fitness (CRF) is measured in the sedentary state and is highly variable among sedentary adults. The physiology of variability in intrinsic cardiorespiratory fitness has received much attention, but little is known about the genetic and molecular mechanisms that impact intrinsic CRF. These issues were explored computationally in the present study, with further corroborative evidence obtained from analysis of phenotype data from knockout mouse models and human cardiovascular and skeletal muscle measurements.