En1000: Projects in Engineering Design 

 

Project Summary:

The prototype is a design for a plant oil fueled stove. This stove will have the ability to utilize one of four plant oils to produce an adjustable flame for cooking uses. The plant oil stove design is being planned under the constraints of cost, environmental impact, and attainable materials for the target areas of implementation.

 

 

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Intro:

The idea for this stove arose from the massive deforstation that is and has occured throughout the country of Haiti(Exhibit B). A major cause for this deforestation stems from the demand for charcoal, a

 

byproduct from deforested trees, to be used as a fuel source in cooking and other areas of commerce.  The hopes of building this stove would be to divert this detremintal trend of charcoal dependance to a renewable fuel source that would be economically viable and better for the enviroment. 

 

 

 

 

Exhibit A

 

One of the purposes for the design of this stove is to have the least amount of cultural impact. To do this the stove design will have the capability to have an duel burner system that can be inserted into widely used cooking structures in a target country.  Instead of attempting to introduce an entirely new cooking system which has the potential to be widely rejected, this stoves design will be made to allow for the user to maintain their cultural cooking practices while utilizing a different fuel source.

 

 

Some of the objectives for this stove that are goals to be met to make it a viable improvement or substitute for present cooking needs are outlined below.

 

• Low cost
• Effective for cooking, without giving a dramatic change in food taste.
• User friendly
• Non foreign looking to user/limited cultural impact.

 

Background:

 

Haitian Dependancy on charcoal and a Need for alternative cooking sources

www.haitiinnovation.org/en/2008/02/16/deforestation-haiti-weaning-country-wood-fuels

 

 

CASE STUDY:

 

Created by myself and 3 associates a case study outlining the viability of introducing a stove into haiti is introduced through the link below. This case study presents some of the major issues that are associated with introducing a plant oil based stove into both the rural and urban regions of Haiti. 

Empower Haiti Case Study

 

Here's What the border between Haiti and the Dominican Republic looks like today

 

 

Exhibit B

 

 

Jatropha Curcas seeds

 

 

This first link is a demonstration of the first prototype developed before the scope of this present project.

www.youtube.com/watch

 

This next link is for a biodiesel stove design for implementation in Haiti.

 

 

www.youtube.com/watch

These two links

 

lead to a video and information about the Protos stove distributed by Bosch and Siemens.

www.youtube.com/watch

www.bsh-group.com/index.php

 

Plus and Minus for the User:

	Base Cost	Fuel Cost	Environmental Impact from production or use	Cultural impact to cooking practices
Matt's Plant Oil Stove	$25-$35		Low	Low
Protos	N/A		Low	Moderate-Low
Sun Oven	$50	$0	Very Low	High, modifies cooking practices and foods cooked
Charcoal Barbeque/Stove	Negligible		Moderate-High	none
Kerosene Stove	$30-50		moderate	Moderate-Low

(Cultural Impact

 

is based on the use of the Charcoal Barbeque/Stove as being the most widely used cooking stove)

 

Cost Estimates: (data and sources can be seen in Empower Haiti Case Study)

 

Type of Stove	Initial Cost (USD)	Cost per use (USD)	Total Cost after 10 uses (USD)	Total Cost after 100 uses (USD)
Charcoal Barbeque/Stove	Negligible	$0.80	$8.00	$80.00
Sun Oven (with Charcoal Barbeque)*	$50	$0.24	$52.40	$74.00
Kerosene Stove^	$30-$50	$0.57	$35.70-$55.70	$87.00-$107.00
Matt's Plant Oil Stove^	$30	$0.45	$24.50	$65.00

 

Intellectual Property:

 

 

 

 

My Proposed Solution:

As briefly stated above I will be designing multiple working prototypes for a plant oil fueled moveable stove that can be used within a variety of presently used cooking structures. The stove will also contain an attacheable component that will allow it to be used without any other cooking structure. The final stove will be designed primarily of steel, copper, and brass components which will be attached through welding or soldering.  This design will achieve its combustion process through 4 stages; Containment and Pressurization, Flow rate regulation, Preheating Stage, Combustion stage.

 

Working Requirements:

 

1. Requirements
   • Must maintain a constant flame for 30 minutes to an hour 
   • Must have a practical distribution of heat on the cooking surface to be used.
   • Must be safe and easy to start
   • Final Prototype must contain two burners.
2. Constraints
   • Must be created from parts excessible to communities in urban Haiti.
   • Primary fuel must be plant oil
   • Must limit the use of fossil fuels or any form of wood during the preheating process.
3. Evaluation criteria
   • Ease of preheating process
   • Success of a consistent flame over a period to boil water
   • Safety 

 

 

Project Timeline

February: Brainstorming, material procurement for optimal design

March1-14: Prototype 2 construction, testing of optimal nozzle use, plant oil procurement

March 14-28: Prototype 3 construction, use of steel and welded joints

April: Final Prototype and Presentation 

 

First Prototype:

Brainstorms:

Here are the ideas I've come up with to build and test my solutions:

First Prototype: (here are my pictures, videos, schematics, drawings, brainstorm notes, parts list, and gatorade receipts)

 

Stove Detail

 

 

 

Burner Detail 

 

First Test and evaluation:

 

Results:

 

     The initial prototype was successful in achieving combustion of the fuel, but however it was inadequate in achieving the design criteria. As can be seen above by the test video the preheating process was reliant upon solely the preheating chamber to achieve a temperature where the castor oil would vaporize instead of developing a sustaining preaheating process from the heat resulting from the developing flame from the nozzle. The combustion processes issues also arose due to the lack of reliability of a constant flow of fuel resulting from a loss of canister pressure and the limited accuracy of the output valve.  In further prototypes a reworking of the canister and preheating coil design will be experimented upon to rectify these issues.

 

Second Prototype:

 

Prototype Pr-1

 

This prototype design be an improvement from the first through these new factors;

 

Improved Pressure Canister design

• Brass ball valve attached to the soldered/welded end cap will decrease possibilities for pressure losses from a treaded input cap.
• Pressure gauge will provide accurate pressure readouts of the canister throughout the cooking process.
• Output Valve are located at the base of the canister to utilize optimal amount of volume that the canister can provide to maximize cooking time while canister is in upright position.

 

 

 

 

To allow for the moderately vertical orientation of pressure canister a stand will be constructed

 

Canister Stand 

 

Various preheating coil designs as seen below will be tested to find an optimal geometry for sustainable preheating from the output flame.

 

Preaheating Coil Designs

 

 

Oval Spiral preheating coil

 

Double V preheating coil

 

 

Close up of Orifice in Double V coil

 

 

Preheating dish with burning alcohol

 

 

Second Test and Evaluation Results:

Double V coil:

     Positive - This preheating coil proved to be successfull in generating a flame at the oil canister pressures of 35-70 psi.

     Negative - The flame that was generated was not sufficient enough to be maintained over a period greater than a couple of seconds. This problem may have been from the limited flow variation capabilities of the brass ball valve and the air pockets within the oil.

 

Oval spiral coil:

     Negative - This coil was unable to produce a flame because of a carbon build up clog within the nozzle and coil. This build up occured because of the space within the nozzle body was large enough for the collection of carbon particles that blocked the oil flow through the nozzle orifice. Through inspection of the nozzle interior by irreperably dismantling it, carbon shards of 2mm diameter were discovered within both the nozzle and the copper coil.  These results demonstrate that in future preheating designs orifice diameters will be designed large enough so that a cleaning wire or implement can be inserted to clean out future clogs.

 

     

Fliqz has shut down their service. To access this video, email support with this video id: 5331d11b10234b5b8083a4e2094082da

 

Third Test and Prototype Addition Results:

 

     

The third test utilized the Double V preheating coil as the source of combustion along with a surrounding 4" diameter by 4" hieght cylinder that was used to generate a more stable combustion environment. The addition of the cylinder that served as a heat shield had a purpose of making a more efficient and safe system.  This cylinder would be used to contain any hot oil or flaming oil discharge coming out of the nozzle that are hazardous for the user.

Test Results: As can be seen in the video shown below this test had similar results to the second test results. the nozzle produced speratic flames for seconds at a time but did not sustain a flame without being ignited by flames from the preheating dish. An unexpected result that did occur that cannot be seen in this video is that the fuel source from the preheating dish transitioned from being fueled by the rubbing alcohol to the castor oil as it leaked out of the orifice nozzle. So inadvertantly the system was actually producing the regenerative process of preheating the fuel flow but combustion was occuring within the preheating dish instead of at the nozzle.

 

 

 

Fourth Test with new additions:

To create an environment where the flow of oil to the burning process could be visually evaluated, threaded rubber tubing was added to the system between the preheating coil and the pressure canister. In addition to this a needle valve was substituted for the brass ball valve so that greater control could be attained for the flow of oil to the preheating stage.  The third addition to the system was that an open sided hexagonal heat shield was substituted for the cylinder because it allowed for a better airflow to the nozzle.

 

Results:

 

The results for this set up using the double v coil were positive in part but erratic becuase the positive results could not be reproduced more than once. For two seperate tests for periods of 9-10 minutes the stove was self sustaining. It produced a mostly yellow and orange flame that was combusting off of the oil and oil vapor that was flowing out of the nozzle.  Apart of producing the flame the nozzle sometimes produced a sputtering of combusting oil droplets that have been projected out of the nozzle.

 

The results for the 3rd prototype were unsuccessful because of an orifice diameter being to large to limit the outflow of oil. This coil almost allowed for a free flowing of oil through the nozzle even at the lowest opened setting alloweable for for the needle valve a flow rate low enough for the vaporization of the oil was unachievable. In addition to this, the coil geometry was not in an optimal design configuration because of the unavailability of the necessary tools to bend the coil with a consistent coil diameter.

 

 

3rd protype burner closeup

 

 

3rd prototype

 

 

 

5th Test:

This test incorporated two new preheating coil designs and testing of both Castor oil and sunflower oil. Sunflower oil was unsuccessfull because its lower viscosity allowed for a much more free flow of the oil, which didn't allow for it to be preheated enough to vaporize.

 

 

Swage lock ended coil:

As can be seen in the videos below castor oil as a fuel was successful while testing the coiled fuel line with the swage locked end cap. In fact the only limiting factor for continued combustion was the amount of oil that was used. One design consideration that was discovered was that the location of the rebounding plate in accordance to its distance from the burner is very sensitive for the ability of the regenerative preheating process. This test produced results of two runs of the stove producing regenerative flames for periods of over 10 minutes each. When the systems reproductive capabilities were tested on different days and ambient tempertures the continued combustion was unsuccessfull for the swage locked ended preheating coil for more than a period of 3 minutes.

 

4th Prototype

 

 

 

Crimped ended coil:

This design was successfull in creating a regerative heating and combustion process which would allow for continued use. This coil similar to the swage lock ended coil required that the oil be almost totally vaporized before it reached the burner holes to develop a viable flame that would not sputter burning oil droplets.

 

Boiling water test:

To see if this burner produced a viable flame for cooking a test was conducted to see if water could be boiled within a pot. Due to the geometry of the heat shield the test showed the flame was unevenly distributed around the pot. The pot containing about 400ml of water began to boil only after about 10 minutes of heating and it was apparent that mostly one side of the pot was being heating to above 100 degrees celcius. However, even though a blue flame could be seen at burner holes the majority of the flames were orange and produced a large amount of carbon build up on the rebounding plate.

 

 

5th prototype burner Closeup

 

 

5th Prototype

 

 

 

Carbon build up on rebounding plate after 25 minutes of stove burning

 

 

 

Final Results:

 

 

When comparing the final test's results from the 4th and 5th prototypes to the initial working requirements the prototype cannot be characterized as meeting the standards it needs to be a fully successful working stove. There are numerous safety concerns such as flame heights and widths, which can be limited but not fully fixed. Furthermore the flames produced barely enough heat to begin to boil water and the carbon build up would be a concern for continual use.

 

 

Safety:

 

• While the preheating coil was being heated by the alcohol's flames any oil that was residing within the coil was sometimes projected out of the nozzle landing a max distance of 4 ft from the burner.
• Also during preheating and working if any large air pockets were captured in the fuel line or preheating coil the flame size would increase dramatically to unsafe heights and diameters.
• The flamess size that was required for regenerative preheating reached to about 6 inches in diameter during the working process, which would not be safe for most cooking practices.

 

 

Design:

The tests show that a spiraled coil because of the ability of the combustion flames to reach the largest surface area of the copper coil is one of the optimum geometries for an efficient preheating process.  From the transition from the first prototype and the double v design to the 4th and 5th protype coils multiple burner holes were crucial for developing a more reliable and viable flame. 

 

 

 

 

 

 

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