Pulse Jet Engine- Jam Jar Jet
Author: Alvin Lee (forked from LabCoat)
I couldn’t find any source on the internet that provides an explanation about how the jam jar jet works so I came up with my own explanation…
The Jam Jar Jet is a simple construction. A suitable sized jar with a 1-1.5 cm hole drilled in the center of the cover. Fuel, usually methanol or ethanol, is poured into the jar and the jar is given a good shake to allow the fuel to evaporate and create a flammable mixture of fuel vapor. Then the jar is lit from the hole and the engine starts, with the flame oscillating back and forth, creating the characteristic murmur and interesting light show.
What creates the oscillation is something interesting.
First Stage- IgnitionIn the first stage when the jar is lit, the flame spreads and consumes most of the fuel air mixture inside the jar and this ignition causes much of the air to be pushed out with the flame front. The air exits the jar with some speed.
Second Stage- Decreasing pressure
Because the air exits the jar at quite a fast rate, and the air carries some momentum, it creates a partial vacuum inside the jar.(Due to the air’s inertia) Also, because the jar has a rather large surface area, the jar cools fast, contracting the air inside the jar. Both actions cause the pressure in the jar to drop.
Third Stage- ‘Strike back’
Since the existing flame front ‘rides’ on some residual fuel vapor and survives on the oxygen outside the jar, when air gets sucked into the jar, the flame also gets pulled into the jar. Meanwhile, the heat from the first combustion evaporates even more fuel, releasing high concentrations of fuel into the lower and middle part of the jar. As the flame front (which is moving with the air, rich in oxygen) meets the fuel vapor line, it starts another round of combustion since all 3 conditions for combustion is met (Heat- from flame front, Oxygen- from air being sucked in, Fuel- from fuel vapor line).
The process then repeats itself causing the flame to oscillate.
As the combustion progresses, the jar is ‘seasoned’ and the burning is stabilized.
Often, the jar may either refuse to light up or light up with a whoosh and then… nothing. Refusing to light up may be caused by too high a fuel concentration which the whoosh may be caused by too low a fuel concentration. It may also be caused by incorrect size of the hole being drilled.
[MJC InnoLog : Keep It Simple, Stupid]
11:23 PM
We're Recruiting!
Looking for people with interest in science especially those who can really think outside the box. You can join any of the sectors below, multiples are allowed. Take your time and look through what we have in our website. (Which contains lots of showcases on what we've done!) Just email us at MJCInnoLog [@] gmail [dot] com
In this section, you can conduct your own research, we’ll assist you in all ways we can. Have a great idea about a machine?Don’t waste it, construct it. Your idea may even enter competitions like RJC toy inventor’s challenge or even SSEF if its really good! If the machine is original, you’ll even get to patent it and/or have it displayed in school!
Got a land based racing car like a Tamiya Drift-Spec? Or a RC helicopter? In this section, we organises races, competitions or even friendly matches. This is an interest group where all the RC people come together. Its not just about playing with RC vehicles, its also about modifying and building. Fancy making robots or programming a vending machine? Here’s the place! However, the only thing you need is the equipments!
Want a lift? Fancy sending water rockets to the sky? Here in the Rocket section, we really build rockets, and fly them high. Expect modifications from simple fins to complicated parachutes. Be ready to use new ways of powering the rockets, from traditional pressure based water rockets to butane powered ones. With good practice, be sure to enter competitions and blow the other teams away!Interested? Simply email us your NIRC no., class, name, the section(s) you'd like to join and a short phase to discribe yourself and what you are good at. We'll get to you in at most 2 day's time.
[MJC InnoLog : Keep It Simple, Stupid]
8:37 PM
Innovation Logic is about this small group of people who wants to promote science in MJC through interesting science experiments and demonstrations. Innovation Logic strives to achieve a CCA status by end of 2008 and its members are currently working hard to achieve this goal. Currently, Innovation Logic is just a name enveloping this group of people and is currently promoting science activities through OSA. Innovation Logic wants to be an organiser of out of the box thinking styles for science. A fair statement:[MJC promotes students to become muggers and mugging is not getting you anywhere after graduation. We want people to be able to think on their feet and not just get good grades]. Remember, think out of the box. Outside the box is where we live!
Here are the current founding members of Innovation Logic.
Name: Alvin Lee
Civics Group: 07S201
Forte: Physics, Engineering, Invention, Theoretical Physics, Designer
Status: Active Founder
Quote: "Outside the box is where I live."
Call sign: Mad Scientist
[Alvin in a lab coat operating a HPLC machine in TEAMS]
Name: Natasha Kang
Civics Group: 07S309
Forte: Biology, Logistics, Accounting, Administrative, dunno liaoz
Status: Active Co-founder
Quote: "Maggots tried to jump onto my hands!"
Call sign: nutz 8P
[Natasha making a very delicious lemon tea ice pack in the Sec 1 camp]
Name: Mdm. Fong
Forte: Physics, Being light-minded, Roller skating
Status: Active Teacher In Charge
Quote: "You do already then show me, don't tell me your ideas"
Call sign: Lao Da (Big Boss)
[Mdm. Fong during teacher's day celebration 2007]
[MJC InnoLog : Keep It Simple, Stupid]
10:28 PM
If you people happen to make a trip down to MJC's School Library, you should have noticed a display table near the entrance of the library. What you have seen is Innovation Logic's Macs Museum. The Macs Museum comprises of two different sections, whereby one section is on fries from five different fast food outlets and the the other focuses on the top four popular burgers found in McDonald's.
Innovation Logic was first inspired after watching a video clip on the Long Lasting Fast Food experiment held in America in June 2007. [Link:Long Lasting Fast Food Credits:junsulovex] As this video was taken in the US, Innovation Logic hence was inquisitive to find out if the fast food in Singapore was also as unhealthy as it was in the United States. Thus, on the 24th January 2008, Wednesday, we went down to Ikea and Tampinese Mall to purchase our neccessary equipment, as well as the burgers and fries we were going to experiment on for the next few months.
The following photos will be on what we're done on the 24th January 2008. [Credits: Alvin and I]
Ikea: To buy our glass jars to contain the fast food.
Ikea: Our Initial Choice of Glass Jars - but "Aroma Sealing Lid" will not survive students' tampering with the jars. This lid is easiy removed.
Ikea: New choice of glass jar.
Ikea: Coming to a final decision of which jar to use.
MJC School Library: Transfering of the Fast Food into the Glass Jars.
MJC School Library: Labelling of the Jars.
MJC School Library: MAC Fries in Jar.
MJC School Library: Some Burgers and Fries.
MJC School Library: The Finished Display.
[MJC InnoLog : Keep It Simple, Stupid]
11:01 PM
Secondary One Science Camp came and went so abruptly, we're actually wondering, Hey??!! After all our preparation for just one day?
Basically,the Secondary One Science Camp is a pupil initiated and pupil run, one day camp targeted at secondary one pupils organized by an adhoc committee formed by science representatives from different classes. This committee is headed by members of the science society ('07).
This is in line with the college science enrichment aim to promote curiousity and ignite the passion in science. It also provides a platform for science representatives and science society members to realize their leadership potential as well. [Quoted from our Mdm Elsie Fong]
Our main aims in this camp is also, to provide opportunities for Meridian Junior College pupils to develop engaging interactive activities to teach certain scientific concepts. Plus, to nurture leadership qualities as well as improve self confidence of Science representatives and science society members.
Okay. Enough of wordy posts. Here's some Photos (Press to enlarge). [Credits: Alvin & Esther]
Biology: Microscopy - Chloroplasts of a unknown water plant
Biology: Microscopy - Chloroplasts again
Biology: Food Test - Special thanks to our science rep. (:
Biology: Food Test - Secondary One Kids at work
Biology: Food Test - RANDOM photo
Chemistry: Making an Iced Seng Pao - Demonstration of making one without the use of a freezer.
Chemistry: Making an Iced Seng Pao - Science Rep Gawking at a Secondary One tying up his soon-to-be iced Seng Pao.
Physics: Simplest Form of a Motor - This is the finished product of the motor taught to the Secondary Ones. (Designed & Produced by Alvin)
Physics: Copper Plating - The Before and After MJC Badge after copper plating. (Produced by Alvin)
[MJC InnoLog : Keep It Simple, Stupid]
11:40 PM
MJC Science Society in the year 2007 has tried out a few prototypes of rockets, designing credits to Alvin. The Poster below consists of snapshots from the video of the water rocket launching that was carried out during the year 2007 which depicts the main events that occur during the launching of the water rocket.( press to enlarge) Enjoy. :)
Yupp. Now let the mad scientists explain how it works.The rocket was filled with a small amount of butane gas, which acts as a fuel, this upon combustion will push the water out of the bottle at a very fast speed. The recoil from that propels the rocket at about 211 G. The fuel mixture is ignited by a mechanism called the HAVIS(High Ampherage & Voltage Ignition System). This new technology is comparable to the multi staged water rocket and may become an alternative for amateur rocket scientists out there. The rocket can be filled with other fuel such as hydrogen, acetylene, ethanol and many others.Hydrogen rockets are still under prototyping as the fuel is relatively unstable.
Now, the following video is actually the real test launch of the water rocket as you have seen in the poster above, carried out in our school, MJC.
MJC Water Rocket Test Launch:
(Backward forked to LabCoat)
That's about it. (:
[MJC InnoLog : Keep It Simple, Stupid]
10:45 PM