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Y.Ando a aL/EWW 30(200.5)nO6-2218 2209 <br /> �-— IMDC <br /> OM2 SSldegim C <br /> 12 --t3—aatunl gas 25dagMTDC 30 <br /> 4 10 <br /> 0 0 <br /> 1400 1800 2200 2600 3000 3400 38W <br /> Phgi mSlieed[stei} <br /> Pig.2.Engine peril rm ums at WOT.-DZDC(before top dead aater)•■cnnk angl, <br /> maximum output and thermal efficiency than use of Gas 1. But at equal energy input. those values <br /> of Gas 1 are higher than those for natural gas. This is because for Gas 1 the throuIe was set at a <br /> wider opening than that for natural gas, owing to di$erence of stoichiometric amount of air, so <br /> Pumping losses are lower and performances are higher than those for natural gas operation. <br /> For Gas 2,performance at higher load is worse than ass 1.At higher engine speed(2800 min—1),the <br /> increased fuel input per cycle reduces the combustion speed,resulting in poorer performance.As shown <br /> in Fig.4,performance at lower engine speed(2000 min"t)is similar to Gast results. <br /> 3.1.3.Air excess ratio tests <br /> Air excess ratio GO texts were carried out by varying the air—fuel ratio (AIF) at WOT. Fig. 5 <br /> Shows thermal efficiencies of the engine operating on different fuel gases. In the can of Gas 1, <br /> special feature is that the engine can operate stably under the ultra lean condition of A=2. The <br /> thermal efficiency becomes worse when A exceeds 1.5 due to poor machine efficiency and <br /> decreased flame speed, but the engine operates stable enough. Stable lean limits of normal gasoline <br /> s Gasl 70 <br /> 4 GO 60 <br /> 3 —A-- natural pt SO <br /> 57 <br /> tr 2 40 <br /> 30 <br /> 0 ' <br /> 20 <br /> -1 10 <br /> .2 4 <br /> 0 3 l0 13 2D <br /> Enew Input[kW] <br /> Fig.3.Part load perfammwea at 1.0 air excess ratio,engine speed-2800 min- <br />