Techno-Economic Model for a Quick Preliminary Feasibility Evaluation of Organic Rankine Cycle Applications

The investment decision support tool was developed, which can be applied to check the technical feasibility and economic viability of an Organic Rankine Cycle system, and to select the appropriate working fluid, based only on basic information on the waste heat source, i.e. source temperature and mass (heat) flow rate. Two profitability criteria, Net Present Value and Payback Period, were introduced for economic evaluation, while an Organic Rankine Cycle design correlations-based model was developed, and applied for prediction of technical parameters and components’ design estimation. Validation performed with the previously published data confirmed model accuracy in spite of its simplicity. The model gave quick answers, and was incorporated successfully into a decision algorithm, which was supported by a set of system component design and cost functions, and could serve as an effective tool for preliminary feasibility evaluation of any proposed Organic Rankine Cycle based waste heat recovery system. An example of model application over the broad range of waste heat source temperatures is presented and the results discussed in order to show its basic capabilities

THE EFFECT OF WATER EMULSIFIED IN DIESEL FUEL ON DIESEL EXHAUST EMISSION

Sažetak 10 i 15%-tnu stabiliziranu emulziju voda/gorivo (v/g) koristili smo s namjerom da se smanje štetne emisije ispušnih plinova. Stabilnu emulziju v/g s dugačkom postojanošću moguće je polučiti dodavanjem male količine odgovarajućeg emulgatora i primjenom vremenski kontroliranog postupka miješanja. Voda pomiješana s gorivom ima jak utjecaj na fizičke procese i kemijsku kinetiku stvaranja smjese, zapaljenje i izgaranje, te značajno smanjuje brzinu reakcija stvaranja zagađivača, posebno NOx i čađe. Na osnovi snimljenih krivulja osloba|anja topline i tlaka u cilindru, bilo je moguće naznačiti i razmotriti razlike tijekom izgaranja, uzrokovanih izgaranjem emulzije goriva i vode. Rezultati ispitivanja motora u širokom području opterećenja i brzina vrtnje pokazali su da se emisija NOx i čađe smanjuje od 20 do 50%, a da pri tome ne dolazi do pogoršanja specifične potrošnje goriva.Abstract The 10% and 15% water/fuel (W/F) stabilized emulsions have been used with the purpose to reduce diesel exhaust emissions. The stabilized long-term W/F emulsion may be obtained by adding a small amount of an appropriate emulsifier by applying time controlled mixing procedure. Water mixed with fuel has a strong effect on physics and chemical kinetics of the mixture formation, ignition, premixed and diffusion combustion, significantly reducing the reaction rate of pollutant formation, especially NOx and soot. From in-cylinder pressure time history and rate of heat release history it was possible to indicate and discuss the differences of combustion development when W/F emulsion is burnt. The results of engine testing in a broad field of engine loads and speeds have shown a NOx and soot emissions reduction from 20 to 50% without worsening the specific fuel consumption. The experimental results are presented and discussed here

Heat release characteristic in internal combustion engines with M-type fuel injection procedure

Opisivanje procesa izgaranja u motoru s unutarnjim izgaranjem (sui) obično se vrši putem takozvanih parametara izgaranja, kao što su: maksimalni tlak izgaranja, maksimalna temperatura ciklusa, kut početka izgaranja, kutni interval trajanja izgaranja, karakteristika oslobađanja topline, prirast ukupne količine razvijene topline, kutni interval pritajenog izgaranja, prijenos topline i slično. Zbog složenosti procesa izgaranja u motoru sui do danas još uvijek ne postoje modeli koji bi na efikasan i prije svega pouzdan način omogućili predviđanje karakteristike oslobađanja topline za vrlo široku paletu različitih tipova motora sui. Ciljano se istražuju fenomenološki, empirijski i CFD modeli za konkretne konstruktivne osobitosti motora i primijenjenog goriva. U okviru ovog rada predstavljen je način određivanja karakteristike oslobađanja topline putem aproksimativnih funkcija izgaranja na primjeru vrlo specifičnog načina pripreme smjese goriva i zraka, u dizelovom motoru sui, tzv. M-postupak ubrizgavanja goriva. Validacija primijenjenih aproksimativnih funkcija izvršena je preko eksperimentalnih rezultata ispitivanja na konkretnom motoru sui.The description of the combustion process in internal combustion engines is typically performed through so-called combustion parameters, such as: the maximum combustion pressure, maximum temperature of the cycle, crankshaft angle of the start of combustion, the angular interval of duration of combustion, the heat release characteristics, thee increment of the total amount of heat developed, the angular interval of combustion delay, the heat transfer etc. Due to the complexity of the combustion process in internal combustion engines to this day there are still no models that could efficiently and above all in a reliable way predict the heat release characteristics for a wide range of different types of IC engines. Phenomenological, empirical and CFD models for specific constructive characters of the engine and fuel applied are targeted explored. The paper presents a procedure for determining the heat release characteristics through approximate functions of combustion, using the example of a very specific way of preparing a mixture of fuel and air in the diesel engine, so-called M-procedure. The applied approximate function is validated through experimental test results on a specific IC engine

ENERGY LOSSES IN FUEL INJECTOR

Sažetak Sve stroži zahtjevi glede smanjenih emisija zagađujućih tvari od motornih vozila u cestovnom prometu dovode do zahtjeva za stalnim unapređenjem tehničkih rješenja na motoru, te zahtjeva za korištenjem alternativnih goriva. Primjena alternativnih goriva kod dizelovih motora može biti raznovrsna što dovodi do zaključka o nužnosti kvalitetnog poznavanja značajki goriva i njihovog utjecaja na karakteristike ubrizgavanja. Analizom primjene različitih alternativnih goriva uočeno je da se osnovni pokazatelji procesa ubrizgavanja kao što su: tlak ubrizgavanja, trajanje procesa ubrizgavanja, količina ubrizganog goriva, itd. mijenjaju, što značajno utječe na proces izgaranja u dizelovom motoru. Zbog toga je nužno da se za optimalni proces izgaranja u dizelovom motoru podesi sustav za ubrizgavanje goriva. Posebno interesantno mjesto u sustavu za ubrizgavanje goriva je brizgaljka, gdje se vrši pretvorba potencijalne u kinetičku energiju, uz prisutnost značajnih energetskih gubitaka. Stoga je posebna pažnja posvećena obradi eksperimentalnih rezultata karakteristika ubrizgavanja i nabrojenih osnovnih pokazatelja procesa ubrizgavanja. Nakon provedene analize pristupilo se definiranju energetskih gubitaka u brizgaljci što će biti prezentirano u radu.Abstract New demands regarding reducing emissions of pollutants from motor vehicles in road transport lead to requests for continual improvement of technical solutions of the IC engine on one hand, as well as using of alternative fuels on the other. Application of alternative fuels in IC diesel engines could be different and it makes a conclusion based on necessity of well knowing fuel characteristics and its influences on injection characteristics. Based on analysis of different used alternative fuels, it has been noticed that basic parameters of fuel injection process, like injection pressure, injection duration, fuel injected amount, etc. were changed, influencing combustion process in the IC diesel engine. According to these facts, in order to make an optimal combustion process in the IC diesel engine, it is necessary to set up fuel injection system. A special part of fuel injection system is the injector, where transformation from potential to kinematic energy of fuel is conducted, with significant energy losses. Therefore special attention was dedicated to processing experimental results, first of all to shape the injection rate, as well as other mentioned injection characteristics. After analysis, a definition of energy losses in the injector was done and presented in the paper

INFLUENCE OF ALTERNATIVE FUELS ON COMBUSTION INDICATORS WITH DIESEL ENGINES

Sažetak Svakodnevno smanjivanje prirodnih rezervi goriva fosilnog porijekla, kao i neprestani porast troškova njihove eksploatacije uvjetuje sve intenzivnija istraživanja o mogućim alternativnim izvorima energije koji bi s jedne strane smanjili ovisnost o uvozu skupe sirove nafte i njezinih proizvoda, a ujedno doprinijeli smanjenju emisije toksičnih tvari koje se oslobađaju njezinim izgaranjem. Kao rezultat takvog razmišljanja većina razvijenih industrijskih zemalja u Europi nastoji ispuniti prijedlog Europskog parlamenta i Vijeća za promicanje uporabe biogoriva, u kojem se predlaže postupna zamjena benzina i dizelskog goriva u iznosu od 5,75 % od njihovih ukupno prodanih količina s biogorivima, mjereno po njihovom energetskom sadržaju, do 2010. godine. U okviru ovog rada razmatrana je uporaba biogoriva u dizelovim motorima s unutarnjim izgaranjem namijenjenih za pogon motornih vozila i strojeva. Akcent je stavljen na proces izgaranja tzv. biodizel goriva, kao potpune zamjene klasičnom dizelskom gorivu, te njegovih mješavina s njim, gdje vrlo važnu ulogu ima početak, karakter oslobađanja topline i vrijeme trajanja procesa izgaranja. Prikazani su rezultati proračuna relevantnih parametara procesa izgaranja tako dobivenih goriva, kao i njihova usporedba s odgovarajućim parametrima izgaranja dizelskog goriva fosilnog porijekla. Rezultati provedenih proračuna su verificirani namjenskim ispitivanjima na konkretnom dizelovom motoru.Abstract Constant lowering of natural reserves of fossil fuels as well as continuous increasing of its exploitation costs influences more intensive researching in finding alternative energy recourses that are able to decrease an import dependent of expensive raw oil and its products from one side and give contribution to decreasing toxic emission as a product of combustion process. As result of this consideration majority of developed European countries endeavor to fulfill proposals of the European parliament and the Council for promotion bio fuels to substitute petroleum and diesel fuels with bio fuels in proportion of 5.75% of their total sold amount, measured by its energy content, by the year 2010. In the paper usage of bio fuels in IC diesel engines for mobile applications is considered. Accent is given on combustion processes of so called biodiesel fuel, as a full alternative for classical diesel fuel, as well as their blends, where important role has beginning, character of heat release and duration of combustion process. Calculation results of relevant combustion parameters for the used fuels and comparison with appropriate parameters of combustion processes with fossil origin based diesel fuel are presented. Verification of the calculation results where carried out through tests made on one diesel engine

VEHICLE FUEL COMBUSTION CO2 EMISSION

Sažetak Prikazan je utjecaj motornih goriva i pogonskih motora osobnih vozila na emisiju ugljičnog dioksida CO2. Definirani su maseni i volumetrijski indeks i faktor emisije fosilnih goriva i izračunate njihove vrijednosti za najvažnija fosilna motorna goriva. Predstavljen je trend smanjenja specifične emisije CO2 [g CO2/km] osobnih vozila za razdoblje 1995.–2020. koji su predložili proizvođači vozila. Analizirani su procesi pretvaranja primarne energije goriva u pogonskim motorima vozila i njihov utjecaj na stupanj iskorištenja motora i emisiju CO2 vozila. Na osnovi rezultata statističke obrade podataka o deklariranom – tvorničkom i cestovnom specifičnom utrošku goriva [l/100 km] triju grupa vozila s benzinskim motorom, grupiranih po stapajnom obujmu motora, zbirno je ocijenjen utjecaj emisije CO2 na okoliš.Abstract The aim of this paper is to evaluate the contribution of vehicular fuel and IC engines on CO2 emission. Definitions of mass and volumetric emission indexes and emission factor are given, and the calculated values for mostly used CnHm fossil fuels are presented. The scenario of European carmaker voluntary agreement to reduce the specific CO2 emission [g CO2/km] over the years 1995 through 2020 is discussed. The role of fuel energy conversion process in vehicle engines is analyzed and its effect on fuel consumption [l/100 km] and CO2 emission is summarized. Average values of standardized (ECE) and road (test) fuel consumption performances of vehicles with SI engines have been calculated and associated CO2 emissions are presented. The requisite approaches to reduce vehicle CO2 emission are discussed

Skrb za pitno vodo

Safeguarding Drinking WaterLjubljana's water resources lie in the immediate vicinity of built-up urban areas or even below them. For decades, they have been safeguarded as water-protection areas, which are specified by implementing regulations. However, formal protection through regulations is insufficient if the goal is to manage these sources in a sustainable manner. One of the most important goals of sustainable management is maintaining suitable provision of fresh drinking water without using any technological procedures toVodni viri mesta Ljubljane so v neposredni bližini pozidanih mestnih zemljišč ali celo pod njimi. Že desetletja jih varujejo vodovarstvena območja. Eden od najpomembnejših ciljev trajnostnega upravljanja je ohranjanje ustrezne oskrbe z naravno pitno vodo brez tehnoloških postopkov njene priprave, kar Ljubljančani uvrščajo visoko na lestvici vrednot življenja v glavnem mestu Slovenije. Upravljanje ogroženih vodnih virov v urbanih okoljih zahteva celosten pristop in stalne aktivnosti. S pomočjo računalniških orodij znamo sisteme simulirati in tako pridobiti dodatna védenja o njihovem delovanju. Ta so v pomoč pri dolgoročnih odločitvah ali na primer ob okoljskih nesrečah. Za ustrezno načrtovanje so potrebna strokovna orodja, ki omogočajo zanesljive, pregledne in kvantitativne ocene učinkov ukrepov. Razpolaganje z zanesljivimi ocenami stanja in napovedmi olajšuje delo odločevalcem in tudi komunikacijo med deležniki. Povezava v monografiji predstavljenih postopkov in rezultatov v sistem izvedljivega upravljanja z vodnimi viri v Ljubljani je dosežek, ki je lahko zgled številnim podobnim okoljem, ne le v Sloveniji, ampak tudi širše

Simulation of the transient operation of an internal combustion engine

V prispevku sta predstavljena nelinearni model enovaljnega dizelskega motorja za preračun prehodnih delovnih režimov motorja in napoved spremenljivega momenta in vrtilne frekvence motorja. Model je razvit iz modela za simuliranje termodinamčinega krožnega procesa motorja v ustaljenih razmerah, razširjen z modelom dinamike ročičnega mehanizma predstavlja motor kot nelinearni dinamični sistem. Spremenljiva vrtilna frekvenca motorja je rezultat reševanja enačbe dinamike zveze motor - breme, pri čemer je spremenljivi moment motorja določen v odvisnosti od lege (kota) ročične gredi. Model smo preverili z rezultati meritev enovaljnega dizelskega motorja. Primerjava računskih in izmerjenih vrtilnih frekvenc je pokazala zelo dobro ujemanje ponavljajočih se sprememb vrtilne frekvence in odziva motorja med naglim pospeševanjem.A non-linear, transient, single-cyliner Diesel engine simulation has been developed to predict the instantaneous engine speed and torque. The basis of the model is a thermodynamic, steady state Diesel engine cycle simulation. The transient extension of the original model represents the Diesel engine as a non-linear dynamic system. The instantaneous crankshaft speed is determined from the solution of the engine -external load dynamic equation, where the engine torque is tracked on the crank-angle basis. Validation of the transient model during rapid engine acceleration shows that both the cyclic fluctuations in the instanttaneous engine speed line and the overall engine response are in good agreement with experimental measurements