Design and Development of Gas Carburettor for a Gasifier-Engine System

Abstract

This work presents a novel design of a gas-carburettor for SI engine operated on producer gas in single fuel mode. For geometrical modelling of carburettor, the ANSYS workbench is used, while RNG k-ε turbulence model in conjunction with species transport model is employed for numerical simulations. This carburettor design was fabricated, the operations were performed to ensure load following flexibility of gas carburettor. CFD model for gas carburettor gives realistic predictions for qualitative trends of pressure drop at different load conditions.

Appendix

Model Equations (Manual: ANSYS Research Academic Version 13)

Since RNG k-ε turbulence model is more suitable for swirl flow problems as compared to standard k-εturbulence model. In the present work, therefore, RNG k-ε turbulence model is employed.

The transport equation for turbulent kinetic energy (k) and dissipation (ε) can be written using reference (Operation manual: ANSYS Research Academic version 13) as

$$\frac{\partial }{\partial t}\left( {\rho k} \right) + \frac{\partial }{{\partial x_{i} }}\left( {\rho ku_{i} } \right) = \frac{\partial }{{\partial x_{i} }}\left( {\alpha_{k} \mu_{eff} \frac{\partial k}{{\partial x_{j} }}} \right) + S_{k} + G_{k} + G_{b} - \rho \varepsilon - Y_{M}$$

(1)

$$\frac{\partial }{\partial t}\left( {\rho \varepsilon } \right) + \frac{\partial }{{\partial x_{i} }}\left( {\rho \varepsilon u_{i} } \right) = \frac{\partial }{{\partial x_{j} }}\left( {\alpha_{\varepsilon } \mu_{eff} \frac{\partial \varepsilon }{{\partial x_{j} }}} \right) + S_{\varepsilon } + C_{1\varepsilon } \frac{\varepsilon }{k}\left( {G_{k} + C_{3\varepsilon } G_{b} } \right) - C_{2\varepsilon } \rho \frac{{\varepsilon^{2} }}{k}$$

(2)

In above Eqs. (1)–(2), G_k designate to generation of turbulence kinetic energy caused by mean velocity gradients. The term G_b denotes the generation of turbulence kinetic energy caused by buoyancy. The influence of fluctuating dilatation in compressible turbulence to the overall dissipation rate is represented by term Y_M. The term $\alpha$ is used for inverse effective Prandtl number. S is user defined source term for turbulent kinetic energy and dissipation. The effective viscosity is designated by $\mu_{eff}$, while $u_{i}$ represents the velocity in corresponding direction. C₁ε(= 1.42), C₂ε(= 1.68) and C₃ε are model constants.