with computations of one-dimensional freely-propagating ﬂames. The performance of these markers is studied based on the following two aspects: the spatial accuracy of the local heatreleaserate and the trend in the total heatreleaserate with equivalence ratio. The measured trend in the spatial distribution of radicals and the deduced heatreleaserate agree well with the computational values. The variation in the spatially integrated heatreleaserate as a function of equivalence ratio is also investigated. The results suggest that the trend in the variation of the integrated heatreleaserate and the spatial location of heatreleaserate can be evaluated by either of these markers. The OH-based marker showed certain sensitivity to the chemical mechanism as compared to the H-atom based marker. Both the OH-based and H-atom based techniques provide close estimates of heatreleaserate. The OH based technique has practical ad- vantage when compared to the H-atom based method, primarily due to the fact that the H-atom LIF is a two-photon process.
Figure 9. Heatreleaserate in the full- and reduced-scale tests. In the full-scale test , the fire source was installed in the corner, in the same place as in cases A1, B1, and C1 of this study. In each reduced-scale test, the time to reach the peak HRR converted using eq. (2) was 396, 1372, and 1614 s, respectively. The time to reach the peak HRR in the full-scale test was 430 s, similar to the result of case A1. Hence, we selected case A1 as the reference. The HRRs of the reduced-scale and full-scale subway cars are compared in Figure 9. The peak HRR of the reduced-scale model was 24.7 MW, or 50% that of the full-scale model (52.5 MW). Although there are many reasons for the discrepancy between the reduced- and real-scale tests, the amount of interior materials used in the reduced-scale model is the likely reason for this large difference. The total fire load of the trailer car used in the full-scale test was 21.4 GJ . The effective heat of combustion of a subway car with similar materials was 19.1 MJ/kg , and that of the reduced-scale model measured in the specimen test was 8.01 MJ/kg. The total fire load of the real-scale subway car, converted to the reduced-scale by using eq. (3), was 45.5 MJ. This value was much larger than that of the actually used reduced-scale model (17.0 MJ). Therefore, the peak HRR of the reduced-scale model was measured to be smaller than that of the real-scale subway car. Measuring the peak HRR more accurately will require consideration of the similarity of the fire load when installing combustibles in the reduced-scale model fire test.
attempts to predict fire development prior to the Dalmarnock experiments (Rein et al 2007) has showed some of the very considerable difficulties involved in doing this. Amongst other things, the work described in this chapter involves a relatively complex 3- dimensional fuel package of varying material types which is also subject to a forced ventilation and re-radiation effects. Therefore this work does not attempt to predict the fire growth a priori but uses published experimental data taken from one of the Runehamar tunnel fire experiment to ‘calibrate’ the heatreleaserate curve predicted using FDS 4.0.7. Similar to modelling work discussed in (Rein et al 2007), ‘calibrate’ in this context refers to a process to establish a relationship between the experimental value with the numerical analysis by considering the modelling approach used, the fuel arrangement, grid size and domain length. The objective of this simulation is to develop a simplified representation of wood and plastic pallets burning in a tunnel to illustrate that the simulation is able to reproduce a reasonable approximation of the fire growth characteristics and investigate the sensitivity of the baseline ‘calibrated’ model setup. When sufficient confidence level is achieved from the simulation, a similar approach can be used to establish the heatreleaserate for a design application. The work discussed in this chapter is applicable to scenarios where a similar fuel arrangement to the Runehamar tunnel fire experiment is used for the simulation. Further calibration work would be necessary if other types of fuel materials or fuel arrangement setup were used for the numerical analysis.
The spark timing plays a significant role in the combustion process and in deciding the engine parameters of SI engine. This paper aims at demonstrating the effect of advanced and retarded spark timing on the burn fraction variation versus crank angle, cumulative heatreleaserate versus the crank angle and the pressure variation as a function of crank angle with the help of MATLAB programs. For this purpose, a basic finite heatrelease model is used for the combustion process in SI engines. This model can also be extended to evaluate effect of spark timing on engine work and thermal efficiency. In each section of the paper, the codes used for analysis are provided for future research work. Salient results, such as peak pressure crank angles for different spark timings , are derived from analysis.
The variation of Net HeatReleaseRate with respect to crank angle for diesel and different blends B20% and B40% of neem biodiesel, at constant pressure 180 bar is shown in figures 32 and 33. At full load condition without EGR heatreleaserate of 20% and 40% blends with ethanol values found to be 27 j/deg CA and 25.77 j/deg CA.The blends B20% and B40% with ethanol 5% with EGR 5% the values found to be 27.88 j/deg CA and 25.76 j/deg CA. The blends B20% and B40% with ethanol 5% with EGR 10% the values found to be 26.5 j/deg CA. and 27.62 j/deg CA. The pure diesel shows the 28 j/deg CA. It was observed from the graph that there is an increase in the ignition delay for the blends. Among the fuels tested B40% with ethanol 5% with EGR 10% is found to have higher ignition delay. It is observed that the heatreleaserate curves of the diesel, neem biodiesel and their blends show similar patterns. The peak heatrelease rates of neem biodiesel and their blends are lower than that of diesel. There is decrease in peak heatreleaserate for EGR usage. Decrease in heatreleaserate is indication of incomplete combustion due to a less oxygen content because of using EGR 5% and 10%
ABSTRACT: Efforts are being made throughout the World to reduce the consumption of liquid petroleum fuels wherever is possible. Biodiesel is recently gaining prominence as a substitute for petroleum based diesel mainly due to environmental considerations and depletion of vital resources like petroleum and coal. According to Indian scenario, the demand for petroleum diesel is increasing day by day hence there is a need to find out an appropriate solution. This study investigates influence of injection timing of 20% blend Simarouba biodiesel on performance and combustion characteristics. The effect of varying injection timing was evaluated in terms of thermal efficiency, specific fuel consumption, heatreleaserate and peak cylinder pressure. By retarding injection timing brake thermal efficiency can be improved of S20
The calorific value of various biodiesel are less as compared to diesel which causes increase in specific fuel consumption, and any biodiesel has heatreleaserate will be low due to lower calorific value as compared with the diesel as shown in the results. Attaining pressure inside the cylinder operating with various biodiesels rapeseed biodiesel shows better results as compared diesel. From experimental investigation it is found that rapeseed biodiesel shown Brake thermal efficiency increases and specific fuel consumption decreases as compared to other biodiesels. In emission parameters, at full load operating condition of engine rapeseed biodiesel emissions of carbon monoxide CO was 0.04% as less compared to other biodiesels, and Unburnt Hydrocarbons (HC) was found to be decreased due to availability of Oxygen in the Rapeseed biodiesel as 10ppm very less compared to diesel . However emission of Nitrogen oxide (NO),carbon dioxide was increased as load increases . Biodiesel as an oxygenated fuel undergoes improved combustion in engine due to presence of molecular oxygen that leads to higher Nitrogen oxide emissions. The present experimental result supports that Rapeseed biodiesel can be successfully used in existing diesel engine without any modifications.
În acest articol, se prezintă experimente de ardere la scară redusă 1/10, în care s-a folosit modelarea după criteriul de similitudine Froude pentru a verifica în ce măsură motorina, benzina și etanolul pot reproduce cât mai precis caracteristicile și dinamica unui incendiu de autoturism într-un tunel rutier. Articolul de față se concentrează pe metode de calcul matematic și metode experimentale (la scara 1/10) care pot previziona valoarea fluxului termic degajat de la un incendiu (eng: HRR – HeatReleaseRate) izbucnit în interiorul unui tunel rutier. Conform teoriei scalării, a rezultat o valoare medie de 15 kW (considerând că, la scară reală, valoarea medie a HRR pentru un vehicul modern este de 5 MW). De asemenea s-au calculat dimensiunile tăvilor rectangulare pentru a asigura același HRR pentru cele trei lichide combustibile. Rezultatele privind fluxul termic degajat (HRR) obținute de la experimentele reduse la scară s-au validat prin compararea între ele a valorilor rezultate experimental cu valorile calculate. Validarea rezultatelor privind temperaturile de la nivelul plafonului de deasupra focarului s-a obținut prin compararea datelor obținute prin experimentele reduse la scară cu cele de la teste experimentale la scară reală/ naturală.
Several automobile manufacturers are interested in investigating of dual fuel internal combustion engines, due to high efficiency and low emissions. Many alternative fuels have been used in dual fuel mode for IC engine, such as methane, hydrogen, and natural gas. In the present study, a reactivity controlled compression ignition (RCCI) engine using gasoline/diesel (G/D) dual fuel has been investigated. The effect of mixing gasoline with diesel fuel on combustion characteristic, engine performance and emissions has been studied. The gasoline was injected in the engine intake port, to produce a homogeneous mixture with air. The diesel fuel was injected directly to the combus- tion chamber during compression stroke to initiate the combustion process. A direct injection compression ignition engine has been built and simulated using ANSYS Forte professional code. The gasoline amount in the simulation varied from (50%-80%) by volume. The diesel fuel was injected to the cylinder in two stages. The model has been validated and calibrated for neat diesel fuel using available data from the literature. The results show that the heatreleaserate and the cylinder pressure increased when the amount of added gasoline is between 50%-60% volume of the total injected fuels, compared to the neat diesel fuel. Further addition of gasoline will have a contrary ef- fect. In addition, the combustion duration is extended drastically when the gasoline ratio is higher than 60% which results in an incomplete combustion. The NO emission decreased drastically as the gasoline ratio increased. More- over, addition of gasoline to the mixture increased the engine power, thermal efficiency and combustion efficiency compared to neat diesel fuel.
Since the mixture is lean and fully controlled by chemical kinetics, there is a new challenge in developing HCCI engines as it is difficult to control the auto-ignition of the mixture and the heatreleaserate at high load operation, achieve cold start, meet emission standards and control knock[4,5]. The advantages of HCCI engines are:1. the same or even better power band compared to SI or CI engines,2. high efficiency engines due to no throttling losses and high compression ratio, 3. ability to be used in any engine configuration: automobile engines, stationary engines, high load engines or small size engines. However, HCCI engines have their own disadvantages such as high level of unburned hydrocarbons (UHC) and CO [4,6,7]as well as knocking issues if the mixture is relatively inaccurate[4,6,8]. Emissions regulations are becoming more stringent and even though CO, NO x and
Flashover is characterized by a sharp increase in burning rate and gas temperature. Thermal instability is con- sidered to be one of its mechanisms . In a compartment fire, thermal radiation from the hot smoke layer and heated wall and ceiling surfaces increases the burning rate of the fuel to release more heat. Consequently, the smoke layer becomes hotter and then thermal feedback is also augmented. A positive feedback loop is formed. A relatively small and localized fuel-controlled fire suddenly can jump in a short moment to a big ventilation controlled fire involving all the exposed combustibles. This rapid jump is called flashover. The thermal instabil- ity nature of flashover suggests that it is a nonlinear dynamical process. Therefore, nonlinear dynamics theory can be applied to study flashover and started about three decades ago. Since then, different dynamical models appeared in the literature -. These models are typically based on simplified energy balance equations for a single compartment fire with the number of system state variables ranging from one to three. Such an approach   was then updated and applied - to study flashover in an open kitchen fire as further illustrated in this paper. The nonlinear dynamics model developed will be used to predict the critical heatreleaserate ne- cessary for the onset of flashover in a small unit with an open kitchen. The effects of geometry of the residential unit, wall materials and radiation feedback on the occurrence of flashover were examined.
Figure 3 shows variations of the cylinder pressure with the crank position for constant intake mixture temperatures and various percentages of EGR for a fixed amount of pilot and gaseous fuels at 10 and 50 percents of full load of a dual fuel engine. It can be observed that by increasing the EGR percentages up to 4.8 and 4.1 and increasing intake mixture temperature up to 413 K and 347 K for 10 and 50 percents of full load, respectively, peak cylinder pressure increases and shifts to the suitable crank position (about 15˚CA ATDC) to improve performance parameters. Also, it is necessary to say that increasing the EGR percentages at a fixed temperature (413 K and 347 K for 10 and 50 percents of full load, respectively) to levels more than the specified values (4.8 and 4.1 for 10 and 50 percents of full load respectively) will lead to decrease the in-cylinder pressure. Figure 4 describes variations of the net heatreleaserate with crank position for constant intake mixture temperatures and various percentages of EGR for a fixed amount of pilot and gaseous fuels at 10 and 50 percents of full load of a dual fuel engine. As indicated in this figure, by increasing the EGR percentage and the intake mixture temperature to the aforementioned levels for 10 and 50 percents of full load, heatreleaserate increases. As stated before, EGR can promote the combustion process due to increasing total equivalence ratio, the intake temperature of the charge and preparing better fuel air mixing ready for combustion. Also, apart from its thermal effect, EGR tends to improve the preignition reaction rates of the cylinder charge by suitably seeding the intake charge with partial oxidation products that are sources of fruitful active radicals. But, with increasing the EGR percentages at the specified fixed temperatures to the levels more than the
Figure 9 shows the heatreleaserate for biodiesel blends in comparison of standard diesel at different engine operating conditions. After burning of fuel, fluctuation of heatreleaserate occurs. However, at B100 shows highest rate of heatrelease compare to diesel and other biodiesel blends, because of the higher cetane number and higher oxygen capacity of biodiesel that improves the burning quality of fuel and helps in firing at higher charge per units. Moreover B10, B20 and B50 have been established a corresponding rate of heatrelease with diesel. This is because, in low blends the concentration of biodiesel is low, that is way fuel does not cause a significant force on certain number, but it touches the air fuel mixture formation due to changes in viscosity and evaporation properties of the fuel. That is way lower blends showed a less charge per unit of heatrelease than B100.
Figure 7 represents equation (4), and Figure 8 represents equation (5). It was observed that increasing the SP dosage led to a decrease in the heatreleaserate during the dormant period while extending its duration. This is attributable to the slightly retarding effect that is commonly observed with superplasticizers . With respect to the effect of nS, increasing nS content was observed to increase heatrelease rates during the dormant period while reducing its duration. This is consistent with the fact that nS has an accelerating effect, which turns out to be noticeable even during the dormant period. In particular, the experimental results showed that the addition of 3.5% of nS increased q min between 26%
average unmixedness and the fluctuation in its magnitude in the mixing zone occur at the same driving frequency as where the Rayleigh index is positive, and vice versa. This means that thermo-acoustic coupling (the Rayleigh index) and the degree of mixing (unmixedness) are strong functions of the excitation frequencies, and that the modulations imposed on the degree of mixing causes fluctuations in thermo-acoustic coupling. One can intuitively expect this phenomenon from the reasoning that the fluctuations in local degree of mixing cause fluctuating flame surface area, which is directly related to the heatreleaserate. A practically wide range of data, when completed, will give a good idea how the ‘actuation’ through fuel flow modulation should be directed.
46 The above figures reflect the pressure variations observed for each of the corresponding cases. As observed in the pressure trace of the 50dBTDC sparking case, the autoignition starts later than TDC, represented by the heatrelease peaks around 7dATDC. Secondly, the heat released is not very high, compared to other cases, especially during autoignition. This could be attributed to the extended flame propagation phase, which begins around 40dBTDC, earlier than the other cases. This extended burning due to flame front propagation could result in a large part of the fuel being consumed before TDC is reached. This phenomenon was also observed and explained by Yun . Also, the conditions favorable for autoignition of the limited lean fuel mixture remaining in the cylinder are reached after TDC, resulting in a late autoignition. In the case of 30dBTDC sparking, the pressure in the cylinder during the combustion cycle is very high, so is the heat releases as seen in Fig. 3.13. The autoignition phase begins very early, around 8 degrees before TDC. This early autoignition during compression stroke, causes a significant increment in heatreleaserate, which is reflected in the pressure curve as well. Although this high expulsion of heat energy may lead to higher pressures, this case however is not a very favorable one. The multiple spikes, which occur after autoignition begins, signifies instability in the ignition process. The sharp spike of heatrelease following this section signifies a very high energy release in short time-span, which is possible grounds for knocking. A reason for such an immense energy release for this spark timing could be that the kernel formation occurs at elevated temperature and pressure conditions, which might accelerate the reaction process during the flame propagation stage, causing autoignition to occur earlier.
Figure 9 shows variation of NOx emissions with respect to brake power the shows evidence that at initial brake power Cotton seed biodiesels are have very less emissions 78 PPM. At maximum brake power compared to all bio diesels has less emissions 2000 PPM . In the figure as brake power increases NOx emissions are increasing drastically due to low heatreleaserate.
A fire test with this exact storage configuration was not found to provide a heatreleaserate to input into our FDS modeling. To determine the heatreleaserate of a fire in the PFE Storage we will have to come up with an estimate based on a similar configuration fire test. The exact composition of the cabinets and contents is not described in the design documents and due to nature of the facility will not likely be made available to the fire protection designer because of military secrecy classification. As discussed in the office space design fire it is not recommended by SFPE to try to extrapolate a design fire HRR by combining other design fire tests as there is too much uncertainty introduced into the results when this is attempted. Since we cannot test a mockup cabinet, we will have to utilize what we determine to be an equivalent stand-in for the cabinet.
ABSTRACT: The study investigates the effect of aluminium oxide nanoparticles as an additive to Madhuca Indica (mahua) methyl ester blends on performance, emission analysis of a single-cylinder direct injection diesel engine operated at a constant speed at different operating conditions. The test fuels are indicated as B10A0.2, B10A0.4, B20A0.2, B20A0.4 and diesel respectively. The results indicate that the brake thermal efficiency for aluminium oxide nanoparticles blended biodiesel increases slightly when compared to the mineral diesel. The carbon monoxide (CO), unburnt hydrocarbon (HC) and smoke emission marginally decrease as compared to mineral diesel. Oxides of nitrogen (NOx) emissions are minimum for the aluminium oxide nanoparticles blended mahua methyl esters. Higher cylinder gas pressure and heatreleaserate were observed for aluminium oxide nanoparticles blended mahua methyl ester. From the study, the blending of aluminium oxide nanoparticles in biodiesel blends produces a most promising results in engine performance and also reduces the harmful emission from the engines.
The variation of Net HeatReleaseRate with respect to crank angle for diesel and different blends B20% and B40% of neem biodiesel, at constant pressure 180 bar is shown in figures 27-28. At full load condition without EGR heatreleaserate of 20% and 40% blends with ethanol values found to be 27 j/deg CA and 25.77 j/deg CA. The blends B20% and B40% with ethanol 5% with EGR 5% the values found to be 27.88 j/deg CA and 25.76 j/deg CA. The blends B20% and B40% with ethanol 5% with EGR 10% the values found to be 26.5 j/deg CA. and 27.62 j/deg CA. The pure diesel shows the 28 j/deg CA. It was observed from the figure that there is an increase in the ignition delay for the blends. Among the fuels tested B40% with ethanol 5% with EGR 10% is found to have higher ignition delay. It is observed that the heatreleaserate curves of the diesel, neem biodiesel and their blends show similar patterns. The peak heatrelease rates of neem biodiesel and their blends are lower than that of diesel. There is decrease in peak heatreleaserate for EGR usage. Decrease in heatreleaserate is indication of incomplete combustion due to a less oxygen content because of using EGR 5% and 10%