摘要:

Modeling is important because it saves time, effort and cost needed for engine development and prediction of performance. In this work, losses due to imperfect construction of the real engine, including progressive combustion, valve timing and heat transfer have been modeled besides engine friction. Hence, it becomes possible to convert the output of the fuel-air cycle into net brake performance. Simulation of engine performance was carried out by varying engine speed, compression ratio and spark advance over wide range. Hence, it was possible to compare the results with those from experiments on a single cylinder engine. The model predictions were found to compare favourably with experiment within 4·6% in power and 2·9% in SFC. The losses considered in this work amount to about 14% of the fuel energy input.

ISSN:0884-3759    

DOI:10.1080/08843759608947625

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Modeling of a compression ignition engine was carried out covering losses emanent from imperfect construction of real engines such as progressive combustion, valve timing, and heat transfer. Furthermore, friction was included to obtain brake performance. Simulation of engine performance was tackled by varying engine speed, compression ratio and injection timing over wide range. The results were compared with those obtained from the experiemntal facility. Predictions by the model compare favourably with experiment within 9·3% and 9·7% for power and sfc respectively. The losses considered in this work amount to about 30% of the fuel energy input at the design point.

ISSN:0884-3759    

DOI:10.1080/08843759608947626

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Accurate molecular weight distributions are essential to the determination of the molecular structures of asphalt. Due to molecular complexity and interaction among the molecules of asphalt, precise measurement for the molecular weights of asphalt can not be achieved. In order to minimize the interactions of asphaltic materials, a petroleum asphalt sample was separated into saturates, naphthalene aromatics, polar aromatics, and asphaltenes. These Corbett fractions were then analyzed by gel permeation chromatography against nondispersive polystyrene standards. The molecular weights and the molecular size profiles were obtained. Among these Corbett fractions, naphthalene aromatics have the lowest number average molecular weight; saturates have the lowest weight average molecular weight and dispersity; and asphaltenes have the highest number and weight average molecular weights and dispersity.

ISSN:0884-3759    

DOI:10.1080/08843759608947627

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

In order to prevent the emission of SOx, with the flue gas, certain amount of the sulphur of the coal can be retained by adding an adequate amount of lime in the combustion chamber. In this study, two series of experiments were conducted by adding lime at the molar ratios of CaO/S = 0·5 to 2·0 using Ankara-Beypazan lignites, which have around 5 % sulphur content as received form. In one of the series lime was added directly in to the lump coal, and in the other, coal was briquetted together with lime using molasses as binder. It was observed from the experimental results that the increase in the lime ratio leads to an increase in the retained sulphur percentage while it leads to a considerable decrease in thermal efficiency. In order to retain 50 % of sulphur, it was necessary to add lime into lump coal at a CaO/S molar ratio of at least 1,1. This minimum ratio was 0·70 for briquetted coal. When lime was added at these ratios, the thermal efficiencies in the first case dropped to as low as 82 % and to 92 % in the second.

ISSN:0884-3759    

DOI:10.1080/08843759608947628

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Six different gasoline blends with different antiknock agents and aromatics content were investigated for its influence on SI engine nitrogen-oxides and carbon monoxide emissions at part- load operating conditions. The six fuel types used were leaded gasoline with 0·5 g Pb/1, commercial unleaded gasoline, unleaded synthetic gasoline and its blends with different proportions of methyl tertiary butyl ether MTBE l10, 15 and 20 vol%). A four- stroke, four- cylinder, spark- ignition Regata engine (type 138 B 3.000) was used for conducting this study. The exhaust gases were analyzed for nitrogen-oxides and carbon monoxide emitted at part-load operating conditions for the speed range of 1000 to 3000 rpm. The results of this investigation have shown that blending unleaded synthetic gasoline with ethers such as MTBE reduces the aromatic content of the fuel. The 20 vol% MTBE-fuel blend gave the lowest carbon monoxide emissions of all blends used at part load condition. On the other hand, the 10 vol% MTBE-fuel blend gave the lowest nitrogen-oxides emission of all blends at part-load condition. The carbon monoxide concentration in engine exhaust differs between increase and decrease at part-load condition when fuel aromatics content increases. It was also found that as the gasoline aromatics content increases in the blend, the nitrogen-oxides concentration in engine exhaust increases. So, substitution of MTBE for the higher aromatics gasoline blends may help improving state environment and air quality.

ISSN:0884-3759    

DOI:10.1080/08843759608947629

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The extraction kinetics of two lignites and one bituminous coal with benzene, toluene and pyridine were studied at both sub and supercritical conditions in a batch reactor equipped with a coal basket. The time-extract yield data of lignites at supercritical conditions could'nt be treated due to severe thermal decomposition and heating-up effects. The data for Zonguidak coal and those for subcritical extraction of Cizre lignite could be fitted into a first order rate equation with the rate constants changing 0·02-0·05 min−1range.

ISSN:0884-3759    

DOI:10.1080/08843759608947630

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The production of hydrogen by the decomposition of pure methane and methane/steam mixtures in a microwave -irradiated fixed bed reactor packed with devolatilized coal char was studied. Input power levels from 600–3500 W were used. Low conversions were obtained for pure methane as the feed, but 1:1 molar ratio mixtures of methane and steam gave high conversions. The effects of power level and feed flow rate were determined for the methane/steam case. Additionally, microwave heating and conventional heating were compared for the methane/steam case. Microwave heating was found to require temperatures 3050 °C lower to give the same methane conversions obtained with conventional heating, over a conversion range of 18-53%. Thus, it may be concluded that microwave heating promotes the methane/steam reaction in some type of unique manner.

ISSN:0884-3759    

DOI:10.1080/08843759608947631

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Addition of lime to paving asphalts is known to inhibit oxidative aging of pavements. The mechanism of the action of lime in retarding oxidation is not known. In this work, an asphalt was mixed with a vanadium chelate that is known to strongly promote oxidation in asphalts. This enhancement of oxidation was largely neutralized when the mixtures were combined with hydrated lime. It is possible that lime acts by suppressing the catalytic activity of naturally occurring vanadium compounds that occur in almost all asphalts, although other mechanisms for the action of lime are also possible. The use of vanadium compounds in asphalt aging tests also is discussed.

ISSN:0884-3759    

DOI:10.1080/08843759608947632

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor