Assignment 2

AIM :- To run the case set up for finding important parameters and calculate the power output.

OBJECTIVES :-

The main objective of this challenge are-

• To find air flow rate
• To find BMEP (i.e. brake mean effective pressure)
• To find BSFC (i.e. brake specific fuel consumption)
• To find In-cylinder pressure
• Also to increase the power by taking constant rpm and changing some other relevent values.

THEORY AND INTRODUCTIONS :-

The important terms describe as follows-

1. AIR FLOW RATE :-

Air velocity (distance travelled per unit of time) is usually expressed in linear feet per Minute (LFM). By multiplying air velocity by the cross section area of a duct, you can determine the air volume flowing past a point in the duct per unit of time. Volume flow is usualy measured in Cubic Feet Per Minute (CFM).

2. Brake mean effective pressure (BMEP) :-

The term BMEP is an engineering term that means Brake mean Effective pressure. Mean is another word for average, which in this case means average effective pressure of all stroke cycles. This is used to evaluate all engines weather they are Two or Four cycles.

BMEP is a function of temperature of the gasses in the cylinder. To increase the temperature you need to burn more fuel, thus making more heat or another way is to make better use of the existing fuel.

3. Brake specific fuel consumption (BSFC):-

BSFC is a measure of the fuel efficiency of any prime mover that burns fuel and produces rotational or shaft power. It is typically used for comparing the efficiency of internal combustion engines with a shaft output.

It is the rate of fuel consumption divided by the power produced. It may also be thought of as power specific fuel consumption, for this reason. BSFC allows the fuel efficiency of different engines tobe directly compared.

4. In-Cylinder pressure :-

Peak cylinder pressures near TDC (where spark occurs) will be in the range of 300 psi for engines at light loads, to 1000 psi for production engines at full power to 1500 psi or greater for race engines. When the piston gets to the bottom on the cylinder (BDC) there may only be 100 to 500 psi in the cylinder.

QUE.1) Run the case at 1800 rpm and list down important parameters-

a) Air flow rate b) BMEP c) BSFC d) In-cylinder pressure

ANS.:- Following are the important parameters which I set by using N=1800 -

1.GT-SUITE run & Part statistics :-

Above picture shows different number of parts available in our geometry and their proparties at N=1800.

2. Simulation speed :-

Here given different RLT values and standerd deviations.

3. Engine geometry & engine operating conditions :-

Here given different parts of engine length like Bore, Stroke, Connecting rod, piston pin offset ..etc. Also given combustion start crank angle, different values of pressure and temperatures.

4. Engine MEP, Torque and Power :-

Different poissonus gasses evolved by the engine and In-cylinder MEP(mean effective pressure), Torque and power are given here.

5. Engine performance predictions :-

Here given, IMEP = 9.8bar FMEP = 1.08 bar PMEP = -0.06 bar BSFC = 260.2 g/KWHr Air flow rate = 24.7 Kg/hr

Brake power = 6.5 KW or 8.8 HP Brake torque = 34.7 Nm.

6. Engine performance (Fuel energy basis) :-

7. Key cylinder predictions :-

In cylinder pressures are-

IMEP = 9.8 bar PMEP = -0.06 bar Maximum pressure = 39.03 bar Intake pressure = 0.998 bar Exhaust pressure = 1.002 bar.

QUE.2) Increase the power output at 3600rpm by 10%.

ANS.:- In case set up I created 2-cases where rpm constant but other important values are change to increase the power as follows-

1. CASE SETUP :-

In above case set up we can see that, engine speed is constant i.e. 3600rpm. The other quantity are depends on me, I putted here-

If we want to increase the power then compression ratio must be increases, as compression ratio increases power, volumetric efficiency and thermal efficiency also increases. We can increases or take constant other quantity but compression ratio must be increases because it directly propotional to the power output. Compression ratio '15' is not practically true but if it increases then really engine power also increases as above.

2. Engine geometry :-

Above figure shows different data according to changing different quantity as-

Combustion satrt (crank angle) = -10.9 (for CR=8)

= -17.3 (for CR=15)

Other quantities are remains constant as above.

3. Key cylinder predictions :-

Here lot of quantity are changes according to compression ratio as above.

4. Engine performance predictions :-

Here is the main output as-

Brake power (at CR=8) = 15.9 KW

Brake power (at CR=15) = 17.6 KW

Brake torque (at CR=8) = 42.1 Nm

Brake Torque (at CR=15) = 46.7 Nm

From above values we can see that if compression ratio increases Power increases and vice versa. There have other terms also but that not affected more even that remain constant or increases in both the cases. Here not only Power increases, all important values also increases as we can see above.

5. Performance engine (Fuel energy basis) :-

Here % of fuel energy increases very high because of compression ratio increases and somewhat other values increases.

6. Engine performance (Fuel energy basis) :-

7. Engine MEP, Torque and Power :-

Here have different speed values of mean pressure, Torque and Power as shown in above.

On the basis of case setup we get the following plots are-

1. Heat transfer rate plot :-

At compression stroke heat transfer rate not changes, at power stroke it increases gradually from TDC to BDC and then from exhaust stroke it keep constant. This results clearly shown in above graph which is Heat transfer rate(KW) vs Crank Angle(deg).

2. Log plot :-

At start it keep constant but at reverse case it increase the pressure but decreases the volume as shown in above plot.

3. P-V diagram plot :-

Actual P-V diagram is somewhat different than theorotical P_V diagram. Inrtake valve have higher pressure and exhaust valve have lower pressure as air and fuel expanded as shown in above plot.

4. Pressure plot :-

At compression stroke pressure increases slowly then at power stroke pressure increases gradualy and from exhaust stroke it constant and very small as shown in above plot. Plot is in the range of -180deg to 540 deg.

5. NOx plot :-

At compression stroke NOx concentration is very low then from power stroke it increases at middle and then constant upto intake stroke and it fully lower down in intake stroke as shown in figure. concentration of NOx is higher in power stroke because here air and fuel completly mixes and combustion is takesplace and hen the distance between TDC and BDC increases so, concentration of NOx is also decreases, because the space of volume increases.

CONCLUSIONS :-

From above case set-up, we conclude following points-

1. For finding BSFC, BMEP, air fuel ratio, In-cylinder pressure ...etc we need to put compression ratio, combustion ratio, air fuel ratio...etc.
2. Actual P-V diagram is different than the theorotical P-V diagram.
3. As combustion increases pressure increases.
4. For increasing power we must need to increase compression ratio. Compression ratio is the ratio of stroke volume to the clearance volume and for increasing power or thermal efficiency we need to minimize the clearance volume, and that's why for increasing power we need to increase compression ratio.
5. But, in practical compression ratio increases, knocking and NOx concentration also increases and that's why in practical we should not increase the compression ratio, and this clear that from NOx plot.

In this way, I showing important parameter of case setup and improve the power more than 10% by constant engine speed and modifying all other related values and plotted the graph basis of that case setup.