CHEN3001 Transport Phenomena Group

Assignment

Chemistry

Catalytic Converters

Table of Contents

Introduction

The overall performance modeling of the 3-manner catalytic converter (3WCC) is more and more used in automotive catalyst and improvement of conversion structures. Most of the fashions used on this application use the ‘firmness’ approach in calculating response kinetics. This technique is beneficial for predicting actual-international catalyst overall performance. However, sure enhancements, produced by using using in particular designed redox oscillations, can’t be expected. This report introduces a technique that integrates precise types of variables into an existing three-WCC quasi-regular model. A dynamic model advanced on this way is verified towards literature records and the outcomes of experimental investigations. It is confirmed, that the behavior of the catalyst underneath situations of bendy pipe formation differs notably from that predicted below the quasi-consistent-state speculation. More “strongly,” the upkeep of oxygen and the transient nature of the gasoline fluid exchange are shown to have an effect on dynamic conduct.

3-way catalytic converter, required device to govern CO, HC and NOx emissions of gasoline Engines, is a chemical reactor that works in transient situations. Temperature, flow rate and composition of the outgoing gas glide inside the transformer the honeycomb monolith is incredibly variable in step with driving mode, with a median time restrict for some seconds. At the same time, manipulate of the closed loop for the gasoline management device makes it even extra difficult, the passing instances of the formation of the feed gasoline in the everyday time scale less than a 2nd.

Transport Phenomenon and velocity distribution.

Transport Phenomenon

It is described by Quasi Mathematical model, which is summarized below:

• Calculation of convective temperature and weight switch from exhaust gasoline to catalytic space. The film ‘method’ is followed using mean values of the gas phase as well as values of stable fuel interactions inside the awareness of solid segment kinds.
• Calculation of various chemical reactions that arise in a catalytic web site based on Lang-gmuir Hinshelwood-primarily based measurements. Lumping ‘floor adsorption / desorption and pore diffusion phenomena inside the kinetic rate expression.
• The transition temperature of 2-D within the cylindrical converter is calculated considering the thermal conductivity of the substrate and the surrounding input and the heat loss within the surrounding environment by means of convection and radiation.

Velocity Distribution

For this case, A 2D model of those catalytic converters is modeled the use of GAMBIT which is a FLUENT preprocessor. A quadrilateral-written suit is produced and the net is examined for its first-class. After checking the fine of the fit, the FLUENT 5/6 answers are decided on and given the boundary type situations and continuous situations. Then the version assigned to the border area is sent as a 2D mesh file. The 2D mesh file of cylindrical converter is shown below:

Separate 2D solution technique, ambiguous answer structure and strong glide go with the flow are decided on for full speed production. The ordinary okay-ɛmodel is selected beneath the viscous version of the turbulent drift determine for regular wall function as a treatment for the adjacent wall. The power equation is enabled. The fluid medium is considered carbon monoxide because it controls the exhaust of cars. The access velocity is set to 30 m / sec and a temperature of 300K. The length and width of the hydraulic is about to decide the turbulence and the turbulence fee is considered to be 5. On exit pressure is set as zero gauge strain. The substrate location is considered to be the laminar and porous sector. The velocity simulation is shown below:

Governing Equations and Solution Methodology

Equations:

The governing equations for carbon monoxide are shown below:

Solution Methodology:

It can be obtained using the RH Redox submodel which is discussed below:

For this the water gas shift reaction can be considered, it is shown below:

The above reaction consumes extra CO leaving extra oxygen to be had hydrocarbon oxidation. According to the consequences from different studies reports, this response may be catalyzed through Rh or Pd, so long as the catalyst website online has oxidation to a few degree. The method of decreasing oxidative stress of active catalyst is considered mathematically with the aid of the version with energetic device counting submodel oxidation condition. It is notion that the lively metallic of water gas reaction is Rh, we outline  _Rh as part of Rh web sites, oxidized (energetic). We suppose, that Rh oxidation and reduction ranges can be expressed via the subsequent well known relationships (Koltsakis, 1999):

Where,

Now, after defining the oxidation and reaction rates, we get the first order differential equations as:

The above first order differential equation can then be solved by Eulers method.

For the above cases, the boundary conditions are shown in table below:

Physical Circumstances

The combination is made using the entire 1e-5 condition. Solution Techniques-Spatial distribution, Gradient-base for small square cell, Pressure Rate, Momentum. The kinetic power with turbulence and the rate of turbulence are assumed inside the second order, Surface monitors file in terms of the maximum go with the flow rate.

The opening and solution are began and automatic from the exhaust fuel inlet. The answer is used 2 hundred instances. It become discovered that the answer converges with the aid of approximately 90-160 repetitions. The place with the first holes is considered empty and then finished (i.e Porous unused and installed). At 30 m / s liquid (Carbon Monoxide) velocity simulation is made for these expenses.

The Table of Fluid Properties is shown below:

The table of Porous media properties is shown below:

Interpretation Question

Based on your analysis in determine the distribution of carbon monoxide concentration (or % conversion) as a function of channel length, if the mass flow rate of the flue gas is 0.015 kg/s (containing 1000 ppmv CO), the cross sectional area of the monolith is 80 cm2, and channel radius is 0.5 mm?

In this case, we have to find the volume of carbon monoxide indirectly, as it is fed through the cylindrical channel. So, it is asking for volume of cylinder in short, as a function of channel length. Now The volume (Concentration of carbon monoxide) will be given as:

Where, r = radius of channel which is 0.5 mm

Lc = Channel length.

So,

Conclusion

The above assignment deals with highlighting the information regarding the catalytic converters.

References

Cai, Z. J., Kang, W. M., Cheng, B. W., & Li, Y. B. (2012). Study on Characteristics of Gas Flow Velocity in Catalytic Converter with Porous. Applied Mechanics and Materials, 229-231, 391–394. https://doi.org/10.4028/www.scientific.net/amm.229-231.391

Koltsakis, G. C., & Stamatelos, A. M. (1999). Modeling dynamic phenomena in 3-way catalytic converters. Chemical Engineering Science, 54(20), 4567–4578. https://doi.org/10.1016/s0009-2509(99)00130-x

Santos, H., & Costa, M. (2009). Modelling transport phenomena and chemical reactions in automotive three-way catalytic converters. Chemical Engineering Journal, 148(1), 173–183. https://doi.org/10.1016/j.cej.2008.11.047