【正文】 parameters of which can be estimated only indirectly or by special measurements. The quality with which ponents are mixed in the furnace chamber proper depends on the number, layout, and momenta of the jets flowing out from individual burners or nozzles, as well as on their interaction with the flow of flue gases, with one another, or with the wall. It was suggested that the gasjet throw distance be used as a parameter determining the degree to which fuel is mixed with air in the gas burner channel. Such an approach to estimating how efficient the mixing is may to a certain degree be used in analyzing the furnace as a mixing apparatus. Obviously, the greater the jet length (and its momentum), the longer the time during which the velocity gradient it creates in the furnace will persist there, a parameter that determines how pletely the flows are mixed in it. Note that the higher the degree to which a jet is turbulized at the outlet from a nozzle or burner, the shorter the distance which it covers, and, accordingly, the less pletely the ponents are mixed in the furnace volume. Once through burners have advantages over swirl ones in this respect. 大連交通大學(xué) 2020 屆本科生畢業(yè)設(shè)計外文翻譯 3 It is was proposed that the extent to which once through jets are mixed as they perate with velocity w2 and density ρ2 into a transverse (drift) flow moving with velocity w1 and having density ρ1 be correlated with the relative jet throw distance in the following way Where ks is a proportionality factor that depends on the ―pitch‖ between the jet axes (ks= –). The results of an experimental investigation inwhich the mixing of gas with air in a burner and then in a furnace was studied using the inpleteness of mixing as a parameter are reported in 5. A round once through jet is intensively mixed with the surrounding medium in a furnace within its initial section, where the flow velocity at the jet axis is still equal to the velocity w2 at the nozzle orifice of radius velocity of the jet blown into the furnace drops very rapidly beyond the confines of the initial section, and the axis it has in the case of wallmounted burners bends toward the outlet from the furnace. One may consider that there are three theoretical models for analyzing the mixing of jets with flowrate G2 that enter into a stream with flowrate G1. The first model is for the case when jets flow into a ―free‖ space (G1= 0),the second model is for the case when jets flow into a transverse (drift) current with flowrate G1 ? G2， and the third model is for the case when jets flow into a drift stream with flowrate G1G2. The second model represents mixing in the channel of a gas burner, and the third model represents mixing in a furnace chamber. We assume that the mixing pattern we have in a furnace is closer to the first model than it is to the second one, since 0 G1/G2 1, and we will assume that the throw distance h of the jet being drifted is equal to the length S0 of the ―free‖ jet’s initial section. The ejection ability of the jet being drifted then remains the same as that of the ―free‖ jet, and the length of the initial section can be determined using the wellknown empirical formula of . Abramovich [6] ：S0= , (2)where a is the jet structure factor and r0 is the nozzle radius. At a = , the length of the round jet’s initial section is equal to 10 r0 and the radius the jet has at the transition section (at the end of the initial section) is equal to r0. The mass flowrate in the jet is doubled in this case. The corresponding minimum furnace crosssectional area Ff for a round once through burner with the outlet crosssectional area Fb will then be equal to and the ratio Ff/Fb≈20. This value is close to the actual values found in furnaces equipped with once through burners. In furnaces equipped with swirl burners, a= and Ff/Fb≈10. In both cases, the interval between the burners is equal to the jet diameter in the transition section d tr , which differs little from the value that has been established in practice and remended in [7]. The method traditionally used to control the furnace process in large boilers consists of 大連交通大學(xué) 2020 屆本科生畢業(yè)設(shè)計外文翻譯 4 equipping them with a large number of burners arranged in several tiers. Obviously, if the distance between the tiers is relatively small, operations on disconnecting or connecting them affect the entire process only slightly. A furnace design employing large flatflame burners equipped with means for controlling the flame core position using the aerodynamic principle is a step forward. Additional possibilities for controlling the process in TPE214 and TPE215 boilers with a steam output of 670 t/h were obtained through the use of flatflame burners arran