Experimental Study On Strengthening Solid-liquid Mixing Process By Chaotic Speed Stirrin

Stirring reaction is a very important production link in many industries such as metallurgy,petrochemical industry and architecture.The mixing isolation zone is easy to be formed during the traditional mechanical stirring process.Usually,the rotational speed is increased to improve the mixing efficiency,but this method leads to a huge waste of energy.The stirring process is one of the key targets of energy saving and consumption reduction policy.Strengthening the stirring process is an important measure to reduce energy consumption,but the common strengthening methods such as replacing the blades and changing the structure of the stirred tank cause high downtime costs.The chaoticspeed stirring method that has been proposed which has large fluctuations in speed and may cause equipment wear and product quality damage easily.Therefore,in order to achieve energy saving and consumption reduction in the mixing field and provide a flexible and universal chaotic mixing method for production,a new chaotic speed generation method,which integrates nonlinear mathematical theory and adopts electrified transmission,is proposed.In order to make the mechanism of chaotic-speed stirring strengthening better applied to production practice,the solid-liquid mixing water model experiment was carried out.The image processing techniques was used to realize the non-invasive detection of the mixing process.A power detector was used to collect the data of stirring power consumption.The mechanism of stirring process strengthening affected by the types of chaotic mappings,the strengths of chaotic mappings,the stirring speed change time and the reference speed were discussed.The diagram of Km-α has proposed to evaluate the chaotic strength of time series,which combined with the largest Lyapunov exponent and the 0-1 test for chaos to evaluate the chaotic mixture.The mixing time(denoted as θM)and ratio mixing energy(denoted as CM*),Betti number of mixing states(denoted as βM),and mixing energy per volume(denoted as Wv)were used to evaluate the mixing efficiency.The experimental results are as follows.(1)When the speed change time is 5 seconds,for the medium viscosity fluid,the mixing time can be shortened by 62.42%by using the stirring at chaotic speed.When the speed change time is 5 seconds and the speed threshold is 30,the working condition of reference speed is 150 r/min,which is generated by a strong Logistic-Cubic chaotic mapping,it is considered to be the best working condition.In this working condition,the mixing time is relatively short(θM is 50 s),the energy consumption is suitable(WV is 1.64 × 104 W/m3),and the effect of solid particle suspension is best(βM is 70).(2)The chaotic strength of the chaotic mappings,which are used to generate the chaotic speed,will affect the mixing effect.The rotational speed time series generated by the cascade mapping with strong chaoticity has strong volatility and high randomness within the controllable range.Therefore,when using the method of reference speed and cascade mapping to generate the stirring speed,it is recommended to use the strong chaotic mapping first.(3)The effect of speed change time on mixing time and specific mixing energy is negligible.The selection of an appropriate speed change time is conducive to the induction of chaotic convection in the mixed system.Therefore,with the increase of the speed change time,the suspension effect of solid particles shows a trend of first increasing and then weakening,with an increase rate of 18.92%.The increase of the reference velocity will bring stronger disturbances to the flow field,so the mixing time and specific mixing energy show a trend of first decreasing and then increasing respectively.At the same time,the suspension effect of solid particles showed a trend of strengthening first and then weakening.The increase of base speed entails greater energy consumption and results in a gradual increase in mixing energy per unit volume.In conclusion,chaotic-speed stirring can strengthen chaotic mixing of fluid.The results of water model experiments can provide theoretical references for efficient and energy-saving fluid mixing in stirred reactors.