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Littérature scientifique sur le sujet « Variabili di Shape »
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Articles de revues sur le sujet "Variabili di Shape"
1
Setiono, Danang, Parjanto Parjanto et Djati Waluyo Djoar. « Identifikasi Morfologi Aksesi Srikaya (Annona squamosa) di Gedangsari Gunungkidul ». Agrosains : Jurnal Penelitian Agronomi 15, no 2 (20 septembre 2013) : 32. http://dx.doi.org/10.20961/agsjpa.v15i2.18994.
Texte intégralRésumé :
<p>The purpose of this study to determine the morphological characteristics and variability of planting sugar apple Gedangsari, Gunungkidul, Yogyakarta. Identify the morphological characteristics conducted on 36 plant samples (36 accessions) based method on stratified sampling and purposive sampling. The data were analyzed descriptively and clustering analysis. The results of the research showed that sugar-apple had pyramida canopy shape, plant height of 264±525 cm, oblongus leaves type, integer leaves margins, acuminatus leaves tip form, base acutus leaves, petiole cylindrical shape, dark green petiole, dark green color of the upper surface leaves, faded green color of the lower surface, leaves length 16.06±8.23 cm, leaves width 3,73±6,9 cm, leaves area 24,28±85,71 cm2, round shaped of rod, patens branching pattern, stem circumference 17,5±38 cm, axillary flos of flower layout, having 3 petals, whitish green of flower color, is cordate and round shape of fruit, fruit weight of 83,03±180,3 g, fruit circumference 22,4±19,36 cm, flesh thick 1,73±3,66 mm, whitish green and green of fruit color, the total amount of fruit scales 70±104,66, and the value of PTT between 18-29 obrix, blunt shape of fruit scales, ellipsoid shape of seeds, number seeds 7±70,66 and total seed weight 2,3±19,86g. There were variability include leaves length, leaves width, leaves area, stem girth, fruit weight, fruit girth, fruit flesh thickness, number of fruit scales, PTT values and fruit shape and the fruit skin’s color. The result of clustering analysis showed that similarity coefficient between the accessions was 66%.</p>
2
Pratama, Syamsu. « ANALISIS VARIABEL-VARIABEL YANG MEMPENGARUHI PERTUMBUHAN EKONOMI DI PROVINSI KEPULAUAN BANGKA BELITUNG TAHUN 2008-2015 ». Indonesian Journal of Statistics and Its Applications 3, no 2 (30 juin 2019) : 124–38. http://dx.doi.org/10.29244/ijsa.v3i2.194.
Texte intégralRésumé :
Economic growth of a region can assess from various aggregate sizes, one of them is GDRP (Gross Regional Domestic Product). Based on theory, GDRP can influenced by several variables, including world commodity prices which have the largest share of GDP, labor force participation rate (LFPR), Human Development Index (HDI), income inequality, open unemployment rate and percentage of the poor. In 2015 Bangka Belitung Islands Province GRDP had a share of around 0.5 percent of Indonesia's GDP. The largest share is West Bangka Regency with 11.46 trillion rupiahs, while the smallest one is East Belitung with 6.112 trillion rupiahs.To find out picture of economic growth and the influence of variable prices of palm oil commodities, LFPR, HDI income inequality, open unemployment and the percentage of the poor on economic growth in the Bangka Belitung Islands Province 2008-2015, the method used is descriptive analysis and panel data regression.The best model for estimating GDRP growth in Bangka Belitung Islands Province in 2008-2015 is the fix effect model with Seemingly Uncorrelated Regression Method. With alpha 5 percent, the variables that significantly influence economic growth are HDI, the percentage of the poor, labor force participation rate (LFPR), income inequality, open unemployment rate and world commodity prices.economic growth
3
Tarmizi, M., Hamdy Hady et Lusiana. « Faktor Internal dan Eksternal terhadap Harga Saham dengan Earning Per Share sebagai Variabel Intervening ». Journal of Business and Economics (JBE) UPI YPTK 7, no 3 (30 septembre 2022) : 409–15. http://dx.doi.org/10.35134/jbeupiyptk.v7i3.193.
Texte intégralRésumé :
Penelitian ini bertujuan untuk mengetahui Pengaruh Return on Asset (ROA), Price Book Value (PBV), Nilai Tukar (Kurs) dan Inflasi terhadap pergerakan harga saham dengan Earning per Share (EPS) sebagai variabel intervening pada saham indeks LQ45 yang terdaftar di bursa efek indonesia 2017-2021. Sampel pada penelitian ini diambil dengan metode sampel jenuh (sensus) pada saham indeks LQ45 yang terdaftar di bursa efek indonesia 2017-2021. Jumlah sampel yang digunakan sebanyak 40 perusahaan. Metode analisis dari penelitian ini adalah menggunakan metode analisis regresi linier berganda. Hasil penelitian ini menunjukkan bahwa secara parsial Return On Asset (ROA) berpengaruh signifikan terhadap Earning per Share (EPS), Price Book Value (PBV) berpengaruh signifikan terhadap Earning per Share (EPS), Kurs berpengaruh signifikan terhadap Earning per Share (EPS), Inflasi berpengaruh signifikan terhadap Earning per Share (EPS), Return On Asset (ROA) berpengaruh signifikan terhadap terhadap Harga Saham, Price Book Value (PBV) berpengaruh signifikan terhadap terhadap Harga Saham, Kurs berpengaruh signifikan terhadap Terhadap Harga Saham, Inflasi berpengaruh signifikan terhadap terhadap Harga Saham, Earning per Share (EPS) berpengaruh signifikan terhadap Harga Saham, Return On Asset (ROA) tidak signifikan terhadap harga saham melalui Earning per Share (EPS) sebagai variabel intervening, Price Book Value (PBV) berpengaruh signifikan terhadap harga saham melalui Earning per Share (EPS) sebagai variabel intervening, Kurs berpengaruh signifikan terhadap harga saham melalui Earning per Share (EPS) sebagai variabel intervening dan Inflasi tidak signifikan terhadap harga saham melalui Earning per Share (EPS) terhadap harga saham melalui Earning per Share (EPS) sebagai variabel intervening pada saham indeks LQ45 yang terdaftar di bursa efek indonesia 2017-2021.
4
Puspita, Chaterina Dwi, et Neli Agustina. « POLA KONSUMSI, ELASTISITAS PENDAPATAN, SERTA VARIABEL-VARIABEL SOSIAL EKONOMI YANG MEMENGARUHI PENGELUARAN KONSUMSI RUMAH TANGGA ». Seminar Nasional Official Statistics 2019, no 1 (13 mai 2020) : 700–709. http://dx.doi.org/10.34123/semnasoffstat.v2019i1.46.
Texte intégralRésumé :
Pengeluaran konsumsi rumah tangga merupakan indikator utama kesejahteraan rumah tangga. Pengeluaran konsumsi rumah tangga memiliki share terbesar terhadap Produk Domestik Regional Bruto (PDRB) di Provinsi Bengkulu, yaitu 64,80 persen pada tahun 2017. Selain itu, rata-rata laju pertumbuhan Produk Domestik Regional Bruto (PDRB) Provinsi Bengkulu (5,63 persen) lebih tinggi dari pada rata-rata laju pertumbuhan Produk Domestik Bruto (PDB) nasional (5,27 persen) pada tahun 2012-2017. Namun, pembangunan ekonomi yang baik di Provinsi Bengkulu tidak diikuti dengan rendahnya angka kemiskinan yang dapat menggambarkan kesejahteraan rumah tangga di provinsi tersebut. Angka kemiskinan Provinsi Bengkulu berada di atas angka kemiskinan nasional pada tahun 2012-2017. Penelitian ini bertujuan untuk menganalisis gambaran umum pola konsumsi dan kesejahteraan di Provinsi Bengkulu serta pengaruh perubahan pendapatan (elastisitas pendapatan) dan karakteristik rumah tangga terhadap pola konsumsi makanan dan bukan makanan. Analisis data dilakukan dengan menggunakan Fungsi Engel Kuadratik dan metode regresi berganda dengan estimasi Robust. Hasil penelitian menunjukkan tingginya angka kemiskinan di Provinsi Bengkulu sejalan dengan pola konsumsi untuk rumah tangga, baik miskin maupun tidak miskin, yang masih memiliki rata-rata proporsi pengeluaran konsumsi untuk makanan lebih besar daripada bukan makanan. Pengeluaran konsumsi rumah tangga di perdesaan lebih responsif terhadap perubahan pendapatan rumah tangga serta pendapatan dan karakteristik rumah tangga signifikan terhadap proporsi pengeluaran konsumsi untuk beberapa komoditas makanan dan bukan makanan.
5
Fornari, Edoardo, et Sebastiano Grandi. « Le promozioni di prezzo sulle marche private : variabilitÀ tra categorie ed effetti competitivi inter-brand ». MERCATI & ; COMPETITIVITÀ, no 4 (décembre 2011) : 125–45. http://dx.doi.org/10.3280/mc2011-004009.
Texte intégralRésumé :
Il presente lavoro discute il tema delle politiche di pricing di breve periodo praticate dai retailers sui prodotti di marca commerciale. In particolare l'analisi si focalizza sull'elaborazione dei dati di sell-out 2008-2009 relativi alle categorie merceologiche di Largo Consumo Confezionato (LCC) nell'ambito del mercato italiano della Distribuzione Moderna (ipermercati e supermercati). In tale contesto emerge un crescente ricorso alla promozione di prezzo per le linee di private label, soprattutto all'aumentare del valore complessivo del giro d'affari di categoria, della pressione promozionale sulle marche industriali e dell'entitÀ media dello sconto. Il lavoro evidenzia altresě come l'efficacia delle promozioni sulla marca commerciale possa risultare estremamente elevata in termini di generazione di vendite incrementali, di aumento della market share e di contributo alle vendite complessive.
6
Sari, Ayu Nirmala, Evistiani Gulo, Arsiska F. Situmorang et Jamaluddin Jamaluddin. « PENGARUH EARNING PER SHARE, RETURN ON EQUITY DAN NET PROFIT MARGIN TERHADAP HARGA SAHAM PADA PERUSAHAAN BATU BARA YANG TERDAFTAR DI BEI PERIODE 2015-2019 ». SCIENTIFIC JOURNAL OF REFLECTION : Economic, Accounting, Management and Business 4, no 3 (1 juillet 2021) : 458–64. http://dx.doi.org/10.37481/sjr.v4i3.324.
Texte intégralRésumé :
Observation of the research results has a specific purpose to test any effect of the variabels Earning Per Share, Return On Equity, and Net Profit Margin on the share price of Coal Companies on the IDX for the 2015-2019 period. The population for this study used purposive sampling by using two analytical techniques used, namely multiple linear analysis and hypothesis testing using SPSS (Statistical Product and Service Solutions). Results The contribution of the three variabels is 25.5% and 74.5% is influenced by other factors. So based on the results of research tests there is a conclusion that the results of the Earning Per Share, Return On Equity variabel have no significant effect on stock prices, and Net Profit Margin has a significant effect on stock prices. Then the results of the three variabels Earning Per Share, Return On Equity, Net Profit Margin have an effect on the domain or simultaneously on stock prices.
7
Liberatore, Giovanni, Tommaso Ridi et Filippo Di Pietro. « Rilevanza ed affidabilità del valore contabile dell'avviamento e dei beni immateriali sul mercato italiano ». FINANCIAL REPORTING, no 3 (novembre 2012) : 31–50. http://dx.doi.org/10.3280/fr2012-003003.
Texte intégralRésumé :
Il presente lavoro si propone di indagare quale sia la rilevanza e l'affidabilità percepita dal mercato finanziario sul valore espresso nel bilancio d'esercizio sui beni immateriali e l'avviamento delle società quotate. Lo studio ha analizzato le aziende quotate al FTSE Italia All-share, nel periodo fra il 2002 ed il 2008. Attraverso un modello di regressione a più variabili si è verificato che: a) il valore contabile dei beni immateriali e dell'avviamento sono correlati positivamente al valore di mercato del capitale, b) la transizione agli IAS/IFRS non ha comportato un incremento della rilevanza ed affidabilità percepita dal mercato dei beni immateriali e avviamento.
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Novalia, Debi, Heri Junaidi et Rinol Sumantri. « Pengaruh Kepemimpinan Islami dan Religiusitas terhadap Kinerja Karyawan Melalui Kepuasan Kerja Karyawan Sebagai Variabel Intervening ». Syntax Literate ; Jurnal Ilmiah Indonesia 6, no 1 (28 février 2021) : 121. http://dx.doi.org/10.36418/syntax-literate.v6i1.2282.
Texte intégralRésumé :
Penelitian ini bertujuan untuk mengetahui pengaruh kepemimpinan Islami dan religiusitas terhadap kinerja karyawan melalui kepuasan kerja karyawan sebagai variabel intervening di Waroeng Steak and Shake. Penelitian ini merupakan penelitian asosiatif kausal dengan menggunakan pendekatan kuantitatif. Sampel dari penelitian ini adalah karyawan Waroeng Steak and shake kantor pusat dan outlet di kota Palembang sebanyak 175 karyawan. Pengumpulan data menggunakan kuesioner yang valid dan reliabel. Analisis data dilakukan dengan menggunakan analisis regresi linier berganda. Hasil penelitian menemukan bahwa: (1) Kepemimpinan Islami berpengaruh positif terhadap kinerja karyawan; (2) Religiusitas berpengaruh positif terhadap kinerja karyawan; (3) Kepuasan kerja berpengaruh positif terhadap kinerja karyawan; (4) Kepuasan kerja memediasi pengaruh kepemimpinan Islami dan religiusiitas terhadap kinerja karyawan.
9
Hartin, Hartin. « Variabel-Variabel Perbaikan Mutu Pembelajaran : Pengamatan di SDN 18 Baruga, Kendari, Sulawesi Tenggara ». Shautut Tarbiyah 24, no 2 (17 mai 2020) : 221. http://dx.doi.org/10.31332/str.v24i2.1170.
Texte intégralRésumé :
AbstrakPembelajaran melibatkan hubungan edukatif antara guru dan peserta didik. Hubungan tersebut bertujuan membentuk pribadi-pribadi peserta didik yang penuh keunggulan. Sebagai manusia dewasan yang memiliki tanggung jawab edukatif, guru memikul beban besar dalam membangun manusia-manusia paripurna. Kompetensi mesti dipersiapkan, sebagai syarat dan jaminan hadirnya proses pembelajaran yang berkualitas. Kompetensi yang memadai membuat guru dapat memahami dengan baik tanggungjawabnya, dan konsisten dalam pelaksanaan. Tulisan ini menggambarkan ikhtiar guru di SDN 18 Baruga dalam membangun suasana pembelajaran yang tidak didominasi guru, tetapi perpaduan keterlibatan guru dengan peserta didik. Perkembangan teknik dan pendekatan pembelajaran tidak secara otomatis merubah iklim pembelajaran di kelas. Terlebih dalam praktik pembelajaran di tingkat Sekolah Dasar. Faktanya, para guru di SDN 18 Baruga telah mengerahkan berbagai cara dalam rangka perbaikan kualitas pembelajaran. Beberapa aspek yang menjadi perhatian para guru dalam rangka perbaikan pembelajaran adalah: 1) pendekatan pembelajaran yang relevan, salah satunya menguji coba model pembelajaran kooperatif; 2) memahami aspek-aspek psikis peserta didik, yaitu motivasi dan minat belajar; 3) menumbuhkan dasar-dasar etos kerja, sebagai pondasi karakter. Meskipun demikian, ikhtiar-ikhtiar tersebut dirasakan belum memenuhi harapan tentang pembelajaran berkualitas. Dibutuhkan kesepahaman para guru, lingkungan sekolah yang mendukung, dukungan pimpinan sekolah, ketersediaan sumber belajar, dan kegiatan ekstra yang relevan. Kata Kunci: Pembelajaran, Kompetensi Guru, Model PembelajaranAbstract Learning involves educative relationships between teachers and students. The relationship aims to shape the personalities of students who are full of excellence. As a dewasan man who has educational responsibility, the teacher carries a big burden in building complete humans. Competence must be prepared, as a condition and guarantee of the presence of a quality learning process. Adequate competence makes teachers able to understand their responsibilities well, and consistent in their implementation. This paper describes the efforts of teachers at SDN 18 Baruga in building a learning atmosphere that is not dominated by teachers, but a combination of teacher involvement with students. The development of learning techniques and approaches does not automatically change the climate of learning in the classroom. Especially in the practice of learning at the elementary school level. In fact, the teachers at SDN 18 Baruga have mobilized various methods to improve the quality of learning. Some aspects that concern the teachers in order to improve learning are: 1) the relevant learning approach, one of which is to test the cooperative learning model; 2) understanding the psychological aspects of students, namely motivation and interest in learning; 3) growing the basics of work ethic, as a character foundation. Nevertheless, these efforts are felt not to meet expectations about quality learning. Teachers' understanding, supporting school environment, support from school leaders, availability of learning resources, and extra relevant activities are needed. Keywords: Learning, Teacher Competence, Learning Model
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Febriani, Lisa. « Analisis Variabel Yang Mempengaruhi Harga Saham Syariah di Jakarta Islamic Index ». Jurnal Ekonomi 24, no 3 (7 janvier 2020) : 421. http://dx.doi.org/10.24912/je.v24i3.607.
Texte intégralRésumé :
One of the methods used by companies to obtain company capital is by selling shares to the public through the capital market. Stock prices can change and this is changed by various factors. This study aims to determine the effect of Debt to Equity Ratio (DER), Earning per Share (EPS), and Return on Equity (ROE) on sharia stock prices listed in the Jakarta Islamic Index (JII) in 2014-2017, both partially and simultaneously. The data used in this study is secondary data taken from the Indonesia Stock Exchange website (www.idx.co.id), which is in the form of a company's annual financial report. The analysis technique used in this study uses Linear Regression Analysis. Based on the research results, it is known that partially DER has no significant effect on stock prices, while EPS and ROE have a significant effect on stock prices. Simultaneously, DER, EPS, and ROE significantly influence stock prices.
Thèses sur le sujet "Variabili di Shape"
1
LIMATOLA, GIOVANNI. « Infrared Linear Renormalons in Collider Processes ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2023. https://hdl.handle.net/10281/402371.
Texte intégralRésumé :
Al fine di descrivere appropriatamente le osservabili studiate tramite collisori
adronici e/o leptonici, risulta cruciale una corretta comprensione delle
correzioni non perturbative (che si manifestano come correzioni di potenza),
lineari nel rapporto tra una scala di energia non perturbativa e la
scala caratteristica del processo. Utilizzando un modello abeliano ricerchiamo
tali effetti nella distribuzione in momento trasverso di un bosone Z prodotto
con un jet in collisioni adroniche, essendo questa una delle osservabili meglio
misurate presso LHC. La presenza delle correzioni non perturbative di cui sopra
impedirebbe di raggiungere la precisione sperimentale, anche considerando
ordini superiori nello sviluppo perturbativo. Non avendo individuato alcuna
correzione di questo tipo tramite tecniche semi numeriche, abbiamo scelto di adottare
un approccio più rigoroso dal punto di vista teorico, fornendo una spiegazione
attorno al manifestarsi di tali correzioni di potenza.
Tale comprensione teorica è stata applicata allo studio delle variabili di shape
in annichilazione $e^+e^-$, con particolare attenzione allo studio del
C-parametro e del thrust, e ottenendo per tali osservabili una stima delle
correzioni non perturbative nella regione dei tre jet per la prima volta.
In tale lavoro è stata altresì ottenuta un'espressione fattorizzata per le
correzioni non perturbative per alcune osservabili, con un termine dipendente
dalla variazione dell'osservabile a seguito dell'emissione di un partone
soffice, e un termine costante e universale, proporzionale al cosiddetto
Milan factor.
Tali osservabili sono ampiamente utilizzate al fine di estrarre valori della
costante di interazione forte $\alpha_s$ e costituiscono il contesto ideale al fine
di compiere studi di QCD perturbativa.
È dunque estremamente importante ottenere stime affidabili delle correzioni
non perturbative nell'intera regione di spazio delle fasi rilevante per i fit
di $\alpha_s$.Understanding leading non-perturbative corrections, showing up as linear power corrections, is crucial to properly describe observables both at lepton and hadron colliders. Using an abelian model, we examine these effects for the transverse momentum distribution of a $Z$ boson produced in association with a jet in hadronic collisions, that is one of the cleanest LHC observables, where the presence of leading non-perturbative corrections would spoil the chance to reach the current experimental accuracy, even considering higher orders in the perturbative expansion. As we did not find any such corrections exploiting semi-numerical techniques, we looked for a rigorous field-theoretical derivation of them, and explain under which circumstances linear power corrections can arise. We apply our theoretical understanding to the study of event-shape observables in $e^+e^-$ annihilation, focusing in particular on $C$-parameter and thrust, and obtaining for them an estimate of non-perturbative corrections in the three-jet region for the first time. We also derived a factorisation formula for non-perturbative corrections, with a term describing the change of the shape variable when a soft parton is emitted, and a constant universal factor, proportional to the so-called Milan factor. These observables are routinely used to extract the strong coupling constant $\alpha_s$ and they constitute an environment to test perturbative QCD. It is then extremely important to obtain reliable estimates of non-perturbative corrections in the whole kinematic region relevant for the $\alpha_s$ fits.
Actes de conférences sur le sujet "Variabili di Shape"
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Rathnaraj, J. David, B. Jefferson Raja Bose et Michael N. Kumar. « Simulation and Experimental Investigation of Variable Swirl Intake Port in DI Diesel Engine Using CFD ». Dans ASME 2006 2nd Joint U.S.-European Fluids Engineering Summer Meeting Collocated With the 14th International Conference on Nuclear Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/fedsm2006-98066.
Texte intégralRésumé :
Knowledge of the flow phenomena inside the cylinder is necessary for optimum design of the intake port and the piston cavity configurations. Recent trends in direct injection diesel engines have increased the need for clear understanding of the flow field, especially the swirl characteristics. The swirl flow is an essential parameter which affects the air fuel mixing, combustion efficiency and therefore the engine performance. The purpose of this study is to investigate the combustion, emission, spray and flow field phenomena of a D I diesel engine and to come up with a geometrical shape for a port and valve or valves that produce the optimum swirl ratio. The percentage opening of a helical port for the DI diesel engine is simulated and studied using Computational Fluid Dynamics with experimental validation. Steady flow rig experiments are most widely used to evaluate the swirl ratio of an intake port design. The three dimensional developing flow patterns are needed throughout the compression and combustion stroke to understand the various experimental results. Flow is simulated by solving governing equations, viz., conservation of mass and momentum using the simple-algorithm. Turbulence has been modeled by standard kφ–φ∈ model with standard wall treatment. The predictive accuracy of the calculation method is compared with detailed mass flow rate and paddle rpm measurements. The results are in good agreement with experimental results and clearly predict the under predictability of the paddle swirl meter in lower lifts. Emission standards, which demand large reduction in NOx and PM emission, require a more comprehensive study of all elements that contribute to emission formulation. The combustion chamber is subject of research and development in an effort to achieve optimized combustion system. The intake port fluid dynamics contribute to the fuel air mixing which in turn is the most important parameter for the control of fuel burning rate for diesel engines. The intake port fluid dynamics also significantly affects ignition delay, the magnitude and timing of the diffusion burn, the magnitude of the premixed burn and emission of nitrous oxide and soot. According to the Modulated Kinetics (MK) concept, which improves the emission performance of diesel engines, a D I Diesel engine requires higher intake swirl in the part-load region. The computations are used to optimize the swirl flow characteristics of an intake port system over a wide range of operating conditions. In this study, the numerical simulation of the helical intake port and variable swirl intake port for two-valve DI Diesel engines are discussed with experimental validation. The improvement of swirl generation capacity of the port design according to the stringent emission norms are also studied.
2
Boretti, Alberto. « Improving Efficiency and Power Density of Hydrogen Engines of Positive Ignition Single-Fuel and Compression Ignition Dual-Fuel designs ». Dans FISITA World Congress 2021. FISITA, 2021. http://dx.doi.org/10.46720/f2020-caf-001.
Texte intégralRésumé :
The latest advances in power density and efficiency of internal combustion engines (ICEs), both diesel direct injection (DI) compression ignition (CI), and gasoline positive ignition (PI), DI and jet ignition (JI), ICEs, are transferrable to single fuel or dual fuel hydrogen engines (H2-ICEs). H2-ICEs have the potential to deliver peak efficiency about 50%, peak power efficiency above 46%, and cycle average efficiency above 35% when fitted to hybrid powertrains. The major hurdles to achieve these performances are the development of hydrogen injection system. Dual fuel DI diesel-hydrogen CI ICEs have the potentials to deliver extremely low emissions of the regulated pollutants, NOx, unburned hydrocarbons (HC), CO and particulate matter (PM), and CO2 emission. Hydrogen PI ICEs with DI and JI have the potentials to deliver extremely low emissions of the regulated pollutant NOx, practically zero emissions of regulated pollutant PM, and practically zero emission of CO2 (while a small amount of lubricating oil may end up in the combustion chamber, but this amount is negligible). The PI ICEs allow much higher power densities, being the combustion event controlled by the turbulent mixing rather than vaporization, mixing and diffusion times. Thus, combustion duration is about independent of the engine speed in PI ICEs but increasing with the engine speed in CI ICEs. While combustion of hydrogen only in a CI engine is still troublesome, needing added research and development, much simpler is the use of hydrogen and diesel in a dual fuel CI engine accepting the DI of both diesel and hydrogen. While the dual-fuel DI diesel-hydrogen CI ICEs are a workable short-term replacement of the traditional hydrocarbon fueled PI ICEs, as cryogenic H2-ICES may share infrastructure and fuel system technology with LNG-ICEs, the hydrogen PI ICEs with DI and JI are an even better environmentally-friendly proposal while offering better performances. Simulations are presented for a dual duel diesel-hydrogen engine featuring two injectors per cylinder, one for the diesel and one for the hydrogen. The coupling of a pilot/pre-injection of diesel with a main injector of hydrogen is straightforward. Mixed modes of combustion are possible injecting part of the hydrogen before, and a part after the diesel injection ignition. The engine has a super turbocharging, where the turbocharger shaft is connected to the crankshaft by gears and a continuously variable transmission. Steady-state maps are presented in detail. Even if this aspect is not investigated, thanks to the super turbocharging, the engine has excellent transient behaviors, in decelerations (energy recovery) as well as accelerations (no turbo-lag). Dual fuel CI ICEs have also the advantage of a hydrogen city driving delivering extremely low emissions of pollutants as well as CO2, and a diesel interstate and rural areas driving delivering still relatively low emissions of pollutants as well as CO2.
3
Baratta, Mirko, Andrea E. Catania et Francesco C. Pesce. « Computational and Experimental Analysis of Direct CNG Injection and Mixture Formation in a Spark Ignition Research Engine ». Dans ASME 2010 Internal Combustion Engine Division Fall Technical Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/icef2010-35103.
Texte intégralRésumé :
Direct injection (DI) of compressed natural gas (CNG) under high pressure conditions is a topic of great interest, owing to its potential for improving SI engine performance and fuel consumption. However, relevant technical difficulties have yet to be resolved in order to stabilize combustion process, especially for stratified engine operating conditions. The present paper is focused on experimental and numerical investigations of the jet formation and fuel-air mixing process in a research optical-access single-cylinder engine. The engine is based on the multi-cylinder engine under development within the European Community (EC) VII Framework Program (FP) InGAS Integrated Project, and features a centrally mounted poppet-valve injector on a pent-roof combustion chamber with a bowl in piston. Experimental investigations were made by means of the planar laser-induced fluorescence technique, and revealed a cycle-to-cycle jet shape variability. In particular, for specific cylinder pressure values at the start of injection, the jet can adhere to chamber walls for a relevant number of cycles, leading to an ‘umbrella-like’ shape. This can change the mixing capabilities of the combustion chamber and cause instabilities in the combustion process. The mentioned behaviour is strongly dependent not only on the injection and cylinder pressures, but also on important design parameters, such as needle cone angle and in-chamber injector protrusion. For this reason, in order to obtain a deep insight into the injected gas behaviour on an average cycle basis, the experimental investigation was supported by a numerical analysis. Simulations were carried out by an optimized variable-density finite-volume numerical model which was built within the Star-CD environment. A previously developed and validated ‘virtual injector’ model was implemented. The outcomes of the numerical model were compared to laser-induced fluorescence images, for both stratified- and homogeneous-charge engine operating conditions and a good agreement was obtained, substantiating the reliability of the applied computational model. Then, the effects of the injector protrusion in the combustion chamber and of injection timing were analyzed, and their impact on jet stability and mixture-formation process was analyzed.