What is exhaust gas dilution?

Exhaust gas dilution is something I did not find an elaborate explanation for on the internet so here goes.

                In a naturally aspirated I.C. Engine, there are basically three ranges of operation:

1.       Idling Range

2.       Cruising Range

3.       Power Range

Exhaust gas dilution mainly occurs during idling and is insignificant during the other two ranges. The pressure distribution in the Inlet manifold, Exhaust manifold and Cylinder head while idling is given in the diagram below. We see that the pressure at the inlet manifold is very low when compared to the other two regions. This occurs due to the closed throttle.

Case 1: When fresh charge is admitted into the cylinder while idling, the quantity of fresh charge is quite less when compared to the charge admitted while throttling. The fresh charge and the exhaust gas in the cylinder mix up to reduce the air fuel ratio significantly. This results in poor combustion and as a result, a loss of power.

Case 2: With Nearly closed throttle, the pressre in the intake manifold is significantly less when compared to the other regions. The pressure differential causes a backward flow of exhaust gasses into the intake manifold as soon as the inlet valve opens. When the piston moves down, sucking the charge, the charge is already diluted with the exhaust gasses leading to poor combustion.

Case 1 and 2 both act together to dilute the intake charge to an extent where the engine stalls and shuts down.

This can be avoided by sending a richer mixture into the cylinder such that the air-fuel ratio stays within the combustible range even after dilution.
Image is from the book Internal Combustion Engines(2nd Edition)-V. Ganesan

What is a bad design?

“The aesthetic quality of a product is integral to its usefulness because products used every day have an effect on people and their well-being”, I found the above statement on the internet and its meaning is quite straightforward. A good design, from a Mechanical engineer’s point of view is the one that fulfills its desired purpose at the least cost and with the least possible amount of resources(Maybe minerals or materials or could also be labour) and has the maximum reliability. Well, all of it in one package is like building a heat engine with Carnot efficiency(ie., it is ideal). So design engineers will have to optimize the parameters to obtain the best bargain between the above mentioned parameters.

                Well, optimizing the parameters is one thing and obvious flaws in the designed component is another. To know what I mean, have a look at the two faucets:

The first one is from my bathroom(It is actually quite an old one) and it is a pathetic design. You will know why when you try to open the tap with soapy hands. There is absolutely no grip whatsoever. How hard could it be to design a faucet handle? The first and the most important parameter must be to ensure that the user can open and close it at all times and one doesn’t need to go to MIT to know that a bathroom faucet will be operated with soapy hands.

The second one however, is a beautiful design. First of all it only rotates by about 90 degrees so it can be operated fast and most importantly, it has a protrusion which ensures absolutely no slippage while being operated.

This is just an example as to how to approach an engineering design problem. The approach applies to everything from a shaving blade to a Bugatti Veyron.

Design evolution is also quite renowned where a design is first made, and based on the customer experience,(like an alpha test) the component is redesigned. This is being followed at every single company worldwide.

So, what is a bad design then? Simple, it is the one which does not satisfy the basic purpose of the design(In the case of the faucet, not being able to use the faucet) that’s all.

Why does HP not make fancy mice? and why are gaming mice so costly?

So, I just bought a beautiful new mouse…YAY!!!

I was looking for a big comfy and cheap wired mouse that would fit perfectly in my big hands because my faithful old Logitech cordless mouse, for some reason, seems to be draining its batteries every week and it’s tiny and uncomfortable. But I wanted something that would last for long (A Logitech or a HP) but for some reason when I went to the store I found that all logitechs and HP’s that are big and comfy are quite expensive. I don’t understand why they do that. Moreover, all they have to offer is the same old boring design that no one wants to buy anymore.

I found this at the store:

It is beautiful, big and soooo comfortable but, it may break down at any moment because it’s not branded and has absolutely no warranty of any kind. After a bargain, the owner gave it to me for about 300Rs(4.5$) which I still feel is a bit too expensive for something you don’t get a guarantee for but I couldn’t resist it there, the design, the look. Actually the build quality is really good, the mouse is sturdy and the sensitivity is pretty good for a product without a brand and a guarantee.

Although I don’t understand one thing…why do famous companies not make mouses that are fancy, have a gaming look and attract the youth, why stick with the same old design. Well I thought maybe the companies did make good mice but the store did not have enough variety. So, I checked on Amazon but with no luck. There are some tiny, girly looking and odd coloured mice that a few reputed companies do make but are really costly. I did find gaming mice that looked exacty like mine, but the starting price was about 1000Rs.

WHY SO??

Here is one more picture in the dark

What this blog is about

          As a mechanical Engineer in the Making, I often come across situations where I do not understand something in college, or I observe some component at work when I am out exploring stuff. The first thing I do then is "Google it". This is my humble attempt to give back my little something to Google, which not only taught me concepts that I could not understand but taught me how to learn new things in a fun way. Of course, Google has just been the mediator(or the connection) between me and all the knowledge stacked up in various websites, but without it, I would have been Tony Stark without the Ironman suit(If you know what I mean).

           So, my plan is simple(the way Elon Musk puts it...) all I am gonna do is post here whenever I learn something new(not necessarily by googling it), when I find something interesting, when I learn a new lesson in life with a hope that someday, when someone like me,  "google's" something up, with an open mind, to learn something new, it will be my post that teaches him/her a thing or two.
          I love cars and my fields of interest in college are Thermal and Design. So most of my posts are going to be based on them or interrelated topics like IC Engines etc. People also say I talk a lot of philosophy but that it left to you to decide. Have fun!!!