Banana is a natural remedy for many ills. When compared 
to an apple, it has four times the protein, twice the carbohydrate, three
times the phosphorus, five times the vitamin A and iron, and twice the
other vitamins and minerals. It is also rich in potassium and is one of the
best value foods around. So maybe its time to change that well-known phrase
so that we say, “A banana a day keeps the doctor away!”
 Bananas contain three natural sugars – sucrose, fructose and glucose
combined with fiber. A banana gives an instant, sustained and substantial
boost of energy.

Research has proven that just two bananas provide enough energy for a
strenuous 90-minute workout. No wonder the banana is the number one fruit with the world’s leading athletes.

But energy isn’t the only way a banana can help us keep fit. It can also
help overcome or prevent a substantial number of illnesses and conditions,
making it a must to add to our daily diet.

DEPRESSION: According to a recent survey people suffering from depression, feel much better after eating a banana.
This is because bananas contain tryptophan, a type of protein that the body
converts into serotonin, known to make you relax, improve your mood and
generally make you feel happier.

Anemia: High in iron, bananas can stimulate the production of hemoglobin in
the blood and so helps in cases of anemia.

Blood Pressure: This unique tropical fruit is extremely high in potassium
yet low in salt, making it the perfect to beat blood pressure.  So much so,
the US Food and Drug Administration has just allowed the banana industry to
make official claims for the fruit’s ability to reduce the risk of blood
pressure and stroke

Brain Power: 200 students at  Middlesex school were helped
through their exams by eating bananas at breakfast, break, and
lunch in a bid to boost their brain power. Research has shown that the
potassium-packed fruit can assist learning by making pupils more alert.

Constipation: High in fiber, including bananas in the diet can help restore
normal bowel action, helping to overcome the problem without resorting to
laxatives.

Hangovers: One of the quickest ways of curing a hangover is to make a
banana milkshake, sweetened with honey. The banana calms the stomach and,
with the help of the honey, builds up depleted blood sugar levels, while
the milk soothes and re-hydrates your system.

Heartburn: Bananas have a natural antacid effect in the body, so if one
suffers from heartburn, try eating a banana for soothing relief.

Morning Sickness: Snacking on bananas between meals helps to keep blood
sugar levels up and avoid morning sickness.

Mosquito bites: Before reaching for the insect bite cream, try rubbing the
affected area with the inside of a banana skin. Many people find it
amazingly successful at reducing swelling and irritation.

Nerves: Bananas are high in B vitamins that help calm the nervous system.

Ulcers: The banana is used as the dietary food against intestinal disorders
because of its soft texture and smoothness. It is the only raw fruit that
can be eaten without distress in over-chronicler cases. It also neutralizes
over-acidity and reduces irritation by coating the lining of the stomach.

Temperature control: Many other cultures see bananas as a “cooling” fruit
that can lower both the physical and emotional temperature of expectant
mothers. In Thailand, for example, pregnant women eat bananas to ensure
their baby is born with a cool temperature.

Seasonal Affective Disorder (SAD): Bananas can help SAD sufferers because
they contain the natural mood enhancer tryptophan.

Smoking: Bananas can also help people trying to give up smoking. The B6 / B12
they contain, as well as the potassium and magnesium found in them, help
the body recover from the effects of nicotine withdrawal.

Stress: Potassium is a vital mineral, which helps normalize the heartbeat,
sends oxygen to the brain and regulates your body’s water balance. When we
are stressed, our metabolic rate rises, thereby reducing our potassium
levels. These can be rebalanced with the help of a high-potassium banana
snack.

Strokes: According to research in “The New England Journal of Medicine,”
eating bananas as part of a regular diet can cut the risk of death by
strokes by as much as 40%!

Warts: Those keen on natural alternatives swear that if you want to kill
off a wart, take a piece of banana skin and place it on the wart, with the
yellow side out. Carefully hold the skin in place with a plaster or
surgical tape!

  Forget the pills — eat a banana.  The vitamin B6 it contains regulates
blood glucose levels, which can affect your mood.

 

 

Air Standard Cycle of IC Engine

The cycle experienced in the cylinder of an internal combustion engine is very complex.First, air (CI engine) or air mixed with fuel (SI engine) is ingested and mixed with the slight amount of exhaust residual remaining from the previous cycle.

This mixture is then compressed and combusted, changing the composition to exhaust products consisting largely of COz, Hz 0, and Nz with many other lesser components. Then, after an expansion process, the exhaust valve is opened and this gas mixture is expelled to the surroundings. Thus, it is an open cycle with changing composition, a difficult system to analyze. To make the analysis of the engine cycle much more manageable, the real cycle is approximated with an ideal air-standard cycle which differs from the actual by the following:

1. The gas mixture in the cylinder is treated as air for the entire cycle, and property values of air are used in the analysis. This is a good approximation during the first half of the cycle, when most of the gas in the cylinder is air with only up to about 7% fuel vapor. Even in the second half of the cycle, when the gas composition is mostly CO2, H20, and N2, using air properties does not create large errors in the analysis. Air will be treated as an ideal gas with constant specific heats.

2. The real open cycle is changed into a closed cycle by assuming that the gases being exhausted are fed back into the intake system. This works with ideal airstandard cycles, as both intake gases and exhaust gases are air. Closing the cycle simplifies the analysis.

 

3. The combustion process is replaced with a heat addition term Qin of equal

energy value. Air alone cannot combust.

4. The open exhaust process, which carries a large amount of enthalpy, out of the system, is replaced with a closed system heat rejection process Qout of equal energy value.

5. Actual engine processes are approximated with ideal processes.

(a) The almost-constant-pressure intake and exhaust strokes are assumed to be constant pressure. At WOT, the intake stroke is assumed to be at a pressure Po of one atmosphere. At partially closed throttle or when supercharged, inlet pressure will be some constant value other than one atmosphere. The exhaust stroke pressure is assumed constant at one atmosphere.

(b) Compression strokes and expansion strokes are approximated by isentropic processes. To be truly isentropic would require these strokes to be reversible and adiabatic. There is some friction between the piston and cylinder walls but, because the surfaces are highly polished and lubricated, this friction is kept to a minimum and the processes are close to frictionless and reversible. If this were not true, automobile engines would wear out long before the 150-200 thousand miles which they now last if properly maintained. There is also fluid friction because of the gas motion within the cylinders during these strokes. This too is minimal. Heat transfer for anyone stroke will be negligibly small due to the very short time involved for that single process. Thus, an almost reversible and almost adiabatic process can quite accurately be approximated with an isentropic process.

(c) The combustion process is idealized by a constant-volume process (SI cycle), a constant-pressure process (CI cycle), or a combination of both (CI Dual cycle).

(d) Exhaust blowdown is approximated by a constant-volume process.

(e) All processes are considered reversible

 

Here are the some general formulas that will be used in this cycle as well as in my next post for analysis of different cycles.

Pv=RT

PV=mRT

P=pRT

dh= C_pdT

du=C_vdT

Pv^k=constant   (isentropic process)

Tv^k-1=constant   (isentropic process)

TP^(1-k)/K=constant   (isentropic process)

w_1-2 =(P₂v₂-P₁v₁) /(k-1)

where

P=pressure

v=specific volume of gas

 V=volume of cylinder

R=gas constant of air (0.287 kJ/kg-K)

T=temperature

m=mass of air

p=density

h=specific enthalpy

u=specific internal energy

C_p, C_{v =} specific heats ( for air Cp=1.108 kJ/ kg-K and Cv=0.821 kJ/kg-K

k=Cp / Cv  ( 1.35)

w=specific work

Air Standard Cycle of IC Engine Mechanical Engineering 360 – A complete Approach to Mechanical Engineering