An Experimental Study on Fuel Combustion Under External Irradiance

In order to investigate the burning characteristics of a 0#diesel and 3#jet fuel,a small-scale experimental bench mainly composed of a cone calorimeter was arranged.The heat release and burning rates were investigated changing the external irradiance in order to clarify the triadic relationship among these quantities.The effective heat of combustion of 0#diesel and 3#jet fuel were 38.89 MJ/kg and 43.15 MJ/kg,respectively,with the corresponding combustion efficiencies being 96.78%and 99.60%(the effective peak heat of combustion being 1.665 times the mean value for both types of fuel).According to our experimental results,the heat release rate and burning rate of 0#diesel and 3#jet fuel both grow linearly with an increase in the external irradiance.Moreover,the heat release rate and burning rate of 3#jet fuel are greater than the equivalent values for the 0#diesel.The average smoke production rate of 0#diesel grows with an increase in the external irradiance,while for the 3#jet fuel it remains approximately the same.The specific extinction area of these two kinds of fuel shows a subtle decrease with the increase of external irradiance.The time to ignition of 3#jet fuel is smaller than 0#diesel for all the considered external irradiances,which indicates that 3#jet fuel is easier to ignite than the 0#diesel.

Theoretical Study of Combustion Processes in Aero Gas Turbines for Air Craft Engines

Combustion process involves various physical and chemical processes which govern and control flames initiation in aero gas turbine engines. During certain flying conditions, at full load, unexpected critical situation may take place in such engines called blow off conditions, which leads to flames diminishing in the combustion chamber of such engines. Gas motion, flow velocity and turbulence kinetic energy are the most important parameters in ensuring flame stabilities. These parameters play a tremendous role and effects on this phenomenon. In gas turbines, the flame exists within a high velocity, non-uniform and intensely turbulent flow field, therefore careful temperature control is vital. Another important factor which must be considered to avoid blow off conditions, is mixture strength. Nearly, all modern gas turbines, due to emissions restrictions, operate on lean mixture conditions which are hard to ignite and lower flame temperatures and thus more risk to reach blow off conditions which leads to a complete flame extinction. These conditions may exist in an air craft engines due to sharp changes in loading parameters, (θL): pressure (Pu), temperature (Tu), mass flow rate (), and cross sectional area (Au). At present there is no detailed theory of gas turbine combustion. Therefore, we must resort to simple models and experimental correlations. This paper investigates the blow-off phenomena in aero gas turbine engines, its causes and estimation of required energy to ensure recovery (re-ignition) again inside the combustion chamber. Identifying the conditions at which blow-off takes place and associated loading parameters (θL) which are a function of (A, T, P, and ). The paper also, quantify the recovery conditions (required energy to re-ignition, change in loading parameter (Δq) Power, Required VHRR: (Volumetric Heat Release Rate) and changes in other loading variables (ρ: density, T: Temperature, P: Pressure, and : mass flow rate) tarts with discussing causes of blow off along with effecting operating conditions.

Electrical Tracking,Erosion and Fire Retardancy Performance of Silicone Rubber Insulation Containing Aluminum Trihydrate,Graphene and Glass Fiber Additives

Silicone rubber composite is a priority electrical insulating material used in high-voltage outdoor insulation applications.Low electrical tracking/erosion and poor flame resistance performance of silicone rubber once ignited,substantially reduce its working life.This paper attempts to investigate tracking/erosion performance of room temperature vulcanized(RTV)silicone rubber along with flame retardant parameters using aluminum trihydrate(ATH),graphene nanosheets(GN)and milled glass fiber(GF)additives.The inclined plane test(IPT)was performed in line with criteria defined in IEC 60587 using step-up tracking voltage method while flame retardancy is evaluated according to ASTM E 1354.0 using a cone calorimeter.Results suggest 30% of ATH assists in improving physical tracking/erosion resistance of pristine silicone elastomer rubber by impeding development of leakage current and a great reduction in maximum average temperatures on the surface of RTV2.Further improvement in performance of RTV2 is achieved through introduction of 1%of GN and 5% of GF as seen in RTV4.Moreover,30% of ATH reduces heat release rate and smoke production rate,and this trend is improved with the introduction of GN/GF.RTV4 has pop up as the most promising silicone rubber composite with excellent electrical tracking,erosion,and flame resistance performance relative to its counterparts in this study.

In-cylinder in-depth combustion investigation for a heavy-duty diesel engine

This present study is part of the design improvement process of a specified high torque low-speed engine.This work aims at carrying out an in-depth analysis of in-cylinder combustion,mesh sensitivity,and engine performance at supercharge conditions to provide a foundation for the design improvement process of the given engine.The computational fluid dynamic(CFD)simulations are carried out on a 3D sector from-130°to 130°crank angle(CA)by employing appropriate models to represent the different physical and chemical processes and using the finite volume method for solving the governing differential equations.An extensive investigation has been carried out for the choice of base mesh size and the number of local and temporal refinements to capture the phenomena happening in the combustion chamber at diverse temporal and local scales.The present results have been validated against available literature experimental and simulation results.Primary field variables and the wellknown four phases of combustion have been studied for gaining in-depth insight into these phenomena.Cylinder average pressure,mean temperature,heat release rate(HRR),integrated heat release rate(IHRR),and emissions of CO_(2),CO,NOx,HC and soot are presented to assess the quality of combustion.Engine performance analysis has been done in terms of combustion ef-ficiency,gross work,power,torque,and integrated mean effective pressure(IMEP).The base mesh of 1.4 mm may be an appropriate choice during the injection and combustion process spanning throughout around 40CA from the start of injection while in the remaining simulation duration of around 220CA base mesh of 2 mm gives a sufficient resolution.It has been found that maximum heat release takes place in Phase-III,the mixing-controlled phase,of the combustion process.More than 98%combustion efficiency has been achieved in all the simulations.Around 99%of the total heat release and emissions production takes place within 60CA after top dead center(ATDC).

Combustion analysis of a hydrogen-diesel fuel operated DI diesel engine with exhaust gas recirculation

The rapid depletion of fossil fuel and growing demand necessitates researchers to find alternative fuels which are clean and sustainable. The need for finding renewable, low cost and environmentally friendly fuel resources can never be understated. An efficient method of generation and storage of hydrogen will enable automotive manufacturers to introduce hydrogen fuelled engine in the market. In this paper, a conventional DI diesel engine was modified to operate as gas engine. The intake manifold of the engine was supplied with hydrogen along with recirculated exhaust gas and air. The injection rates of hydrogen were maintained at three levels with 2 L/min, 4 L/min, 6 L/min and 8 L/min and 10 L/min with an injection pressure of 2 bar. Many of the combustion parameters like heat release rate （HRR）, ignition delay, combustion duration, rate of pressure rise （ROPR）, cumulative heat release rate （CHR）, and cyclic pressure fluctuations were measured. The HRR peak pressure decreased with the increase in EGR rate, while combustion duration increased with the EGR rate. The cyclic pressure variation also increased with the increase in EGR rate.

Pyrolysis,combustion,and fire spread characteristics of the railway train carriages:A review of development

Fires in the railway trains are prone to cause large numbers of casualties,serious economic losses,and huge negative social impacts.The railway train carriage is a special confined built environment,where the pyrolysis,combustion,and fire spread process are different from those fire accidents in open space.Identifying the fire characteristics of the railway train carriages is the key issue to determine the fire prevention and control strategy.Therefore,this paper attempts to assess and identify the characteristics of pyrolysis,combustion,and fire spread of railway trains based on the exising research.This review documents the pyrolysis and combustion characteristics of single train material and the combustible module,summarizes the heat release rate(HRR)calculation methods and the HRR profile for different types of trains,as well as introduces the research progress in the flame spread and flashover.The main gaps and issues to be solved in terms of the effects of train speed,altitudes,and application of new energy trains are further discussed.

Effect of Organo-Modified Nanosepiolite on Fire Behaviors and Mechanical Performance of Polypropylene Composites

The objective of the study was to investigate the effect of the organo-modified nanosepiolite(ONSep)on improving the fire safety of polypropylene(PP).The composites based on PP,flame retardant master batch(MB-FR,25 wt%PP+50 wt%decabromodiphenyl ether(DBDPE)+25%antimony trioxide(ATO))and ONSep were prepared via melt blending.The results of the limiting oxygen index(LOI)and vertical burning rating(UL-94)test indicated that PP/40 wt%MB composites had no rating with seriously dripping phenomenon,while the LOI value was only 22.5.However,as 4 wt%ONSep was added in PP/40 wt%MB composites,the composites achieved UL94 V-0 rating and the LOI value was 24.3.In comparison,PP/50 wt%MB composites could not reach the V-0 rating either.The TGA results revealed that the addition of ONSep enhanced the thermal stability of the PP/MB-FR composites.The cone calorimeter results indicated that the heat release rate,average mass loss rate,smoke production rate and smoke temperature of the PP/40 wt%MB-FR/4 wt%ONSep composites decreased in comparison with those of PP/40 wt%MB-FR composites.Simultaneously,the Young modulus and impact strength were also much better improved with the increase of ONSep loading.Therefore,the synergistic flame retardancy of ONSep in PP/MB-FR matrix significantly containing a halogen based flame retardant(DBDPE)significantly improved the fire safety and mechanical properties of the composites,and allowed to decrease the total amount of brominated fire retardants.