Experimental determination and research on combustion characteristics domain of gas appliance

Journal of Harbin Institute of Technology( New Seres), voL 18, No. 1, 2011Experimental determination and research on combustioncharacteristics domain of gas applianceGAO Wen-xue, WANG Qi, CHEN Guan-yi, ZHAO Zi-ju高文学,王启,陈冠益,赵自军(1.SchoolofEnvironmentalScienceandEngineering,TianjinUniversity,Tianjin300072,China,wenxuegao@163.com:2. North China Municipal Engineering Design Research Institute, Tianjin 300074, ChiAbstract This manuscript developed an adjustability test system of gas appliances, and proposed determinationmethods of adjustability domain and technical approach of performance testing of gas appliance, in order to de-elop experimental determination, quantify the product performance, design quality and combustion characteris-tics of gas appliance, and provide test foundation and platform for product design, performance test, qualityassessment and technology upgrading for gas appliance industry aiming to multi-gas resources in China.Theflexible range of gas appliances to different gases and the interchangeability domain of city gases were deter-mined experimentally, together with the equation of combustion characteristics limit curves of gas appliancesThe results showed that the second gas appliance has the biggest capability for the change of gas quality, whichpermits an 11. 2% fluctuation in the Wobbe Index of gas; while the third gas appliance has the least capabilityfor the change of gas quality, which only permits a 1. 9% fluctuation in the Wobbe Index of gas. The paper alsoDocument code: AArticle I:10059113(2011)0140077404Each gas appliance is designed to adapt to a cer- tedain gas component. The first step to develop a gas ap-By experimental determination of combustion char-pliance, is to ascertain the family and group of the ref- acteristics of gas appliances, one can identify the ad-erence gas [ 1. Then the gas appliance is designed, justable capability and range of typical gas appliancesshaped or produced according to the reference gas. The to gas composition; can provide basic and essentialmain parameter of combustion stability and adaptability technical data for the production of gas appliances. Toof gas appliance is the combustion characteristic curve, research the adaptability of gas appliances and deter-which is received by different gases in one gas appli- mine the combustion characteristic and adjustable doance, including the lift flame( lift off ) flashback, main of them, can guide and improve the general de-yellow flame and the CO content limit curves 2. Most sign levels and technology upgrades of the whole gasstudies focus on the influences of combustion character- appliance's industry. Through the experimental testingistics of gas appliances when changes in gas composi- system of combustion characteristics of gas appliance,tion or interchangeability with one gas to another. Del- the testing measure of product design, quality assess-burge from France 3-6 produced a specific control gas ment and technology upgrading can be achieved, andurner, measured and determined the gas interchanged- test method and technology platform determining combility indices, and introduced the concept of"combus- bustion performance of gas appliance can be formedtion potential". The limit values of lift name, flashbackand incomplete combustion with the gas burner were 1 Experimental Test for Adjustability Domain De-obtained using the interchangeability index of Wobbetermination of Gas Appliancesnumber.combustionpoTentialbasedontheabovethree limit curves. He chose several kinds of typicalThe purpose of experiment is to determine the in-gas appliances to check test. However, as for determi- fluence of the main combustion characteristics on com-ning the combustion characteristics of a gas range and bustion stability and adaptability of gas appliance, andquantifying the adaptation domain of gas appliance to a- test thchieve the purpose of evaluating the quality or perform- with中国煤化工main in accordancets include the fol-ance testing for the gas appliance, there is little repCN Gooking appliancesReceived 2010-07-22Sponsored by the National Key Technologies R&D Program of China during the 11th Five-Year Plan Period( Grant No. 2006 B02)Journal of Harbin Institute of Technology(New Seres),VoL.18,No.1,2011with different heat input power, and carry out combus- tial, can be calculated respectively and Cartesian coor-tion experiments;(2)determination of the scope of dinate system with Wobbe number and combustion po-curve parameters of lift out, flashback and incom- tential as their y-axis and x-axis respectively are estab-plete combustion of gas applfiances;(3)basedlished. The limit curves of Wobbe number Ws-combus-perimental results, discussion about the applicability of tion potential CP in the range of i-C,Ho, N2, H,gas combustion parameters; and (4)determine suit- blendorit- blending- gas distribution are shown in Figs. 1-3able key gas combustion parameters of combustion perof1. 1 Experimental Samples and Gas MaterialsL. I I Experimental samplesIn order to test its combustion characteristic, weexceeding limit linerandomly selected the common type of gas cookingCH refpliances with natural gas. The reference gas is natural4 i-CH,H, boundary lineski-C.H,N, boundarygas of 12T, with a rated pressure of 2 kPa. Three gascooking appliances had been chosen, numbered as2 Flashback limit Tiample 1, 2 and 3 and the design heat load is 3.8kW, 4.0 kW, and 4.2 kW respectively; the first andsecond applicants are two-eyed type, but the third one501001502002503003504001.1.2 Feed gases for gas-blendingCombustion potential CPFeed gases for gas blending are selected from meth-I Lift out limit point3 CO content exceeding limitane, hydrogen, nitrogen, and iso-butane, with purities of▲ I l ft out fitting3 CO content exceeding fitting99.1%,99.%%,9.9%,99.2%, respectively.. The ref2 Flashback limit poterence gas for the appliances is methane.2 Flashback fitting curveo 4 i-CaH H, boundary line1. 2 Experimental Resultsi-CAHno N, boundary lineTo test the combustion characteristics of gas cooking appliances by the experimental, a testing-system has Fig. 1 The limit curves of wobbe numbers versus combus.been established. According to different combination oftion potentials of combustion characteristics of Samfeed gases, to control flow of mixed gas, when the limitple 1 in the range of i-C4Hie, N,, H, blending-gasconditions of lift out flashback and co content in fluegas exceed the standard occur, respectively, and theexperimental system can automatically collect and storethe data of feed gas flows component in mass or volumeand analyze the flue gas composition and content rele-vantly. Real-time record of the feed gas flow rate inexceeding limit lineeach branch is finished and the ratio of each componentCaHnH, boundary linein gas mixture in volume is calculated. Thus the com-ne..bustion parameters in gas mixtures can be calculatedout linCalculated parameters include: heat value, relative=xFlashback limit linedensity, flame speed, Wobbe number and combustionpotential, etc. Combination with mathematical statistic10and the limited experimental data processing methodthe experimental results are processed and analyzed0150200250300350400Combustion potential CPWhen the limit burning conditions of lift outflashback and CO content exceeding the standard of theI Lift out limit point3 CO content exceeding limit pointfirst, second and third cooking appliance occur, respec-a I Lift out fiting curve -3CO content exceeding fittingtively, the experimental system, the phy2 Flashback limit pointcurve CH, reference gasfeed gas in each branch can be collected and calculat-2 Flashback fitting curve°4iCHH2 boundary lited, respectively, and the volume fractions of the corre-onding components in blending-gas will be receivedAccording to the flow data of feed gas derived from中国煤化工 ers versus combustio-cteristics of the 2nthe system, the combustion parameters of Sample 1,2CN Gof i-CH,, N, H,g tolending-gas distributionflashback and CO exceeding the limit, such as heatue,relative density, Wobbe number, combustion poten-78Journal of Harbin Institute of Technology( New seres), vol 18, No 1, 20112 Analysis and Discussion2. 1 Adjustability Curves of Combustion Charac-teristics and Feasible Fluctuating Range ofso to 4CHsH, boundaryWobbe Number of Gas AppliancesCHa referenee gaAccording to test limits gas composition data30measured in the experiment, the corresponding com-20A 2 Flashback limit linebustion parameters of the limit gases have beelated. and combustion characteristics curvesin Figs. 1-3. The regression analysis and cuIcanconducted, with the fitting curve50 100 150 200 250n 300 350 400 shown in Tab. 1. At the same time, from Fig. I toI Lift out limit point3 C0 content exceeding limit point Fig 3 with 3 experimental gas appliance, the coordi-I Lif out fitting curve-3 CO content exceeding fitting nates of its reference point is the point where the purecurve CH, reference gas2 Flashback limit point o 4 i-CH H; boundary lineCH 4 gas sites, compared with the curves of lift out2 Flashback fitting curve-5 i-CH, N, boundary lineflashback and CO content exceeds limit , we can findout that the nearest point is the CO curve point.Fig 3 The limit curves of Wobbe numbers versus combus- The maximum allowable change in Wobbe index3r cooking appliance in the range of i-CH,N,,(me x 100%)permitted is calcuH, blendinggas distributionlated and is listed in Tab. 1Tab. 1 The fitting curve of the boundary line of gas cooking appliances and the maximum allowable change in Wobbe indexNumber of appliancesThe fitting curvesThe maximum allowabley=97.5e+32.27e.0yLift out curvey=00045x2-0.8011x+5899CO exceeding curvey=-0.0056x2+0.3198x+50.5121Flashback curvey=-0.0069x2+2.0473x-102.5272Co exceeding curvey=-000012-0.0108x2+0.58X+47.841111.2Lift outy=-0.3694x+39.7986y=0.00102+0.0542x+10.72llCO exceeding curvey=-0.0029x2+0.1504x+49.7921Tab 1 shows the second sample of gas cooking ap- potential, and yellow tip index, the conclusion are aspliance has the largest capacity adapt to changes in test follows: the two-dimensional graphics established withgas compositions, the maximum allowable change in Wobbe number Ws versus gas flame burning velocitiesWobbe index was 11. 2%. While the third sample has can form a similar smooth curve and similar closed surthe weakest capacity of change in test gas composi- rounded area, but not as good as those formed with thtions, the maximum allowable change in Wobbe index parameter of Ws versus CP. While the two-dimensionalwas only 1. 9%; when small changes occur in gas com- graphic established with heat value( Hs) versus com-position can make with CO gas level excessively中国煤化工 of which curves2.2 Applicability of Gas Combustion Parameters and foexpress the com-Based on the calculation of other combustion pa-bustiolCNMHG1 torameters,such as high heat value, relative density, Fig 3, the coordinates graphics established with thegas flame burning velocity, Wobbe number, burning two parameters of Wobbe number(Ws)versus combusJournal of Harbin Institute of Technology( New Seres), Vol. 18, No. 1, 2011tion potential(CP), the smoothed combustion charac- of limit combustion conditions such as lift out, flashteristic limit curve of lift out, flashback, and CO ex- back and CO content in flue gas exceeded the standardceeding can be received, and a stable closed adjust- limit, and the location site of reference gas in the re-ability domain of gas appliance can be formed2.3 Combustion Adaptability of Gas Appliance2)The whole gas-blending distribution boundaryThe reference gas is located in the closed region of of i. C4H1o, H2, N, as feed gas is irregularly closedlimit curve of lift out, flashback and CO exceeding the triangle, when Wobbe number and combustion poten-mit,i-C H1o, H2 boundary line, i-CH1o, N2 tial as gas- blending control parameters. And the com-boundary line, and the combustion requirements of gas bustion adjustability domain of gas appliances is aappliance can meet that of the reference gas. Based on closedrounded by five smooth curves orthe combustion adjustability tests with test gas appli- straight linesances above, the ultimate combustion parameters range3)The combustion characteristics adaptation in-of gases can be gotten, from which we can see: the dex of the composition of natural gas applied to the excommon adjustability domain for the three feed gases of. perimental batch, must fall within the common adjustC.,o,H2,N2,are shown in Fig.47.ability domain, only by which can the gas applianceng pr4)The experimental system and method intro-The second gas cook,py一 The first gasduced above can provide scientific, quantitative evaluThe third gas cooking appation methods and techniques measures for combustion≥6d43c0adjustability judgment, design quality level evaluationof gas appliances and city gas interchangeabilityH, fitting curveReferencesout I[1] GB/T13611-2006. Classification and Essential Property of2 Flashback limit TineCity Gas. Beijing: Standards Press of China, 2006[2 Tongji University, Chongqing University of Civil Engineering, Harbin University of Civil Engineering, et al. GasCombustion and Applications. Beijing: China Building In-50100150200250300350400dustry Press, 200[3] Pu Rongxiu Gas interchangeability review. Ci(6):49-65Fig4 The common combustion adjustability domain of the [4]Delburge Lecture. Gas flame stability and gasthree cooking samplesbility( 1). Gas and Heat, 1982(5): 52-60.[5] Delburge Lecture. Gas flame stability and gas3 Conclusionsbility( Il). Gas and Heat, 1982(6): 44-53[6] Marcogaz. Towards a harmonised EU specification on1) The combustion performance of gas appliancesquality: Maragaz Contribution. Proceedings of the ascan be defined and evaluated by the two combustionWorld Gas Conference. Amstardam. 2006. 1-9parameters of Wobbe number(ws) and combustion [7] Gao Wenxue. Research on City Gas Interchangeability Thepotential( CP)of test gases, the bounded closed region中国煤化工CNMHG