Gas diffusion Therefore obtained variety spectrum of y/R from axes or core boundary to outer boundary is 01. variety spectrum of u/u from axes or core boundary to boundary of diffusion isl-0 4. Characteristic of kinetics Proved by experiment, static pressure at any point in diffusion is equal to pressure of around air. Taking one diffusion segment . froml1-2 and 1-l 2-2, analyzing force in it. Owing to static pressure is equal in different section, then sum of outside force is o in axis x. Due to momentum equation, momentum conservation in different section, this is characteristic of kinetics of diffusion Take circular section as example apply momentum conservation equation. Momentum flex of outlet section is pod=provo Integrating momentum flex in any transverse section 2W27yU=2m1 momentum conservation formula 21 rpr 0= 2tpu ydy
21 Therefore obtained variety spectrum of y/R from axes or core boundary to outer boundary is 0 1.Variety spectrum of from axes or core boundary to boundary of diffusion is1 0。 m / 4. Characteristic of kinetics Proved by experiment, static pressure at any point in diffusion is equal to pressure of around air.Taking one diffusion segment from11—2 and 1—1、2—2, analyzing force in it.Owing to static pressure is equal in different section, then sum of outside force is o in axis x .Due to momentum equation,momentum conservation in different section, this is characteristic of kinetics of diffusion. Take circular section as example apply momentum conservation equation. Momentum flex of outlet section is ， Integrating momentum flex in any transverse section. 0 2 Q0 0 = r0 2 0 0 2 2 2 0 0 0 2 2 momentum conservation formula 2 (11 1 4) R R R ydy ydy r ydy = = ： — —
气流 由此得出yR从轴心或核心边界到射流外边界的变化范围为 0→1。D/Um从轴心或核心边界到射流边界的变化范围为1→0。 四、动力特征 实验证明,射流中任意点上的静压强均等于周围气体的压 强。现取11-2中1—1、2—2所截的一段射流脱离体,分析其 上受力情况。因各面上所受静压强均相等,则ⅹ轴外力之和为 零。据动量方程可知,各横截面上动量相等一动量守恒,这就 是射流的动力学特征。 以圆断面射流为例应用动量守恒原理 出口截面上动量流量为=pm,任意横截面上的动 量流量则需积分。 up2nydyD=[ 2Tpu'ydy 列动量守恒式 zp uo=b 2tpu'ydy 11-1-4)22
22 由此得出 y/R 从轴心或核心边界到射流外边界的变化范围为 0 1。 / m 从轴心或核心边界到射流边界的变化范围为1 0。 四、动力特征 实验证明，射流中任意点上的静压强均等于周围气体的压 强。现取11—2中1—1、2—2所截的一段射流脱离体，分析其 上受力情况。因各面上所受静压强均相等，则 x 轴外力之和为 零。据动量方程可知，各横截面上动量相等—动量守恒，这就 是射流的动力学特征。 以圆断面射流为例应用动量守恒原理 出口截面上动量流量为 ，任意横截面上的动 量流量则需积分。 0 2 Q0 0 = r0 2 (11 1 4) 2 2 0 2 2 0 2 0 0 2 0 — — 列动量守恒式： = = R R R r ydy ydy ydy
Gas arrosion ty R Fig. 11-2 Proved of diffusion calculation
23 M 0 x s x + y − y x r R y y 1 1 2 2 R y y dy Fig. 11—2 Proved of diffusion calculation
气流 ty R 图11-2射流计算式的推证
24 M 0 x s x + y − y x r R y y 1 1 2 2 R y y dy 图 11—2 射流计算式的推证
Gas arrosion 811-3 Kinetic analysis of diffusion in circular section Studying variety rule of diffusion velocity U in circular section and throughput along diffusion way s or x) due to characteristic of turbulent diffusion 1. Velocity of axes Um applying (11-1-4) n10 丌0Dy divide pRum obtain: 5y(22=2 R D 0 () RR substituting (11-1-3)0=1-()5]into,then R 「(1-n3)3ndn=B 25
25 §11-3 Kinetic analysis of diffusion in circular section Studying variety rule of diffusion velocity in circular section and throughput Q along diffusion way s （or x ） due to characteristic of turbulent diffusion. 1. Velocity of axes m 2 2 2 0 0 0 2 2 1 0 0 2 2 2 0 1. applying 11 1 4 2 divide obtain ( ) 2 ( ) ( ) substituting 11 1 3 [1 ( ) R m m m m r ydy R r y y d R R R y R = = − （ — — ） ： （ ） （ — — ） ＝ 5 2 1 1.5 2 2 2 0 ] into then [(1 ) − = ] d B