# Simple 2D CFD analysis

Maximum project budget (150 USD, since i already have the ANSYS Fluent 13.2 case ready). Bid only if you have the skills necessary for the same.

I need to design an ejector system which has butane as the primary fluid and air as secondary fluid. I need that air to butane ratio be of the order 19:1, and for the same I need to find out the dimensions of the secondary flow passage (of air).

I am attaching the necessary file and their explanation.
1. 132_Fan.pdf - contains a system which is similar to what I want. I had conversed with the author Mr. Yong Fan for the procedure and here is the mail that he sent.

First determine the butane flow rate according to the heat generation required.
Then the throat diameter can be determined with providing the butane pressure and flow rate, and nozzle exit diameter with providing Mach number. For this part, you can find necessary mathematic descriptions in any text book of Aerodynamics.
Then determine the secondary nozzle diameter with target air/butane ratio and back pressure.
For this part, you should refer to my paper (I am attaching the same along-with) and the references listed in my paper.
Additionally, the length of secondary nozzle is normally chosen as 7-9 times the diameter with considering the balance of mixing and friction loss.

The first two steps have been done - I require 2 W of heat from the butane so considering a calorific value of butane as 43 MJ/kg, we get a required butane flow rate of around 4.5e-8 kg/sec, to generate the required heat (of 2 Watt). for this amount of mass flow of butane the primary nozzle throat dia is calculated (considering choked flow with supersonic flow at outlet for a CD nozzle) next the exit dia is found out for an exit Mach number of 1.5 (it is not a fixed requirement and this exit dia can be suitably modified to achieve the required air/butane flow rate - since i dont know exact value of Mach number to achieve the required air/butane ratio). You can get to know of the dimensions with the ansys fluent case setup (in workbench) that i am attaching. The back-pressure is around 100 Pa.
What remains is the area required for the air flow passage to achieve the required air/butane flow rate. Thats all, that is needed.

2. LIAO-DISSERTATION.pdf - it is a thesis that will help you with the manual calculation part, there is a very detailed chapter as to ejector physics. the paper also has a chapter of how to conduct cfd of ejector to guide you - in case you need an insight into the ansys fluent setup i am sending.

3. Axisymmetric Ejector Analysis.wbpz - is the Ansys Fluent 13.2 archive file that has all the setup - including the geometry and boundary conditions etc. In case you have any doubts kindly contact regarding the same.

4. science.pdf - one of the reference papers used by Yong Fan. you may find simple one dimensional equations for the ejector here.

I am planning to work with the winner of this bid for some advanced CFD analyses in near future (1-2 months down the line) in case i like the value and work.
in case you have any doubts kindly get in touch.

The air to butane ratio specified is mass ratio.

I need the provider to provide me with an ansys fluent solution where the solution yields air/butane mas ratio of 19:1 (or near to it). i will look into the solution myself and after satisfying myself i will make the final payment.
also it will help if you make some rough calculations to help me decide you as the winning bid, so that i am sure that you can execute the same.

Well some bidders are misunderstanding that this is a liquid gas or liquid liquid ejector.
I want to state that this is a gas-gas ejector, where butane is a primary gas (flows through CD nozzle) and air is secondary gas (flow of air is induced by butane).
A problem with current analysis (attached) is that at exit of supersonic CD nozzle (carrying butane) there is a shock and this increases the exit pressure to inlet pressure of air (1 atm), this is a waste of propulsive power and hence leads to less entrainment of air by butane. you need to solve this problem, you can change boundary conditions or geometry as needed to achieve this (air/butane mass ratio of around 19:1)

i am attaching another paper of Yong Fan which also includes the fluent cfd analysis details. go through it to understand the physics so you can predict what needs to be done to get a air:butane mass flow rate around 19:1

for those who do not have access to ANSYS 13, i am sending you the geometry file (parasolid and designmodeller), mesh file and fluent case file. also i am sending you the pdf showing step by step method to setup the case (including the boundary conditions and other parameters).