Week 10: Project 1 - FULL HYDRO case set up (PFI)

AIM :- To setup the case for full hydrodynamics of IC engine and run the simulation to create the animation file so that varify the working performance.

OBJECTIVES :-

The main objectives of this project is as follows-

• To find the compression ratio for the given engine
• Describe the function of wall heat transfer model
• Calculate combustion efficiency of this engine
• Calculate power, Torque for this engine by using engine performance calculator in converge studio.
• Describe the significance of ca10, ca50 and ca90.
• Create animation file to varify the engine performance.

SOFTWARE USED :-

• Converge studio v3.0, to case setup and rectifying diagnosis error.
• Cygwin, to run the simulation and converting .post files to read the paraview.
• Paraview, to create contours and animation files.

THEORY AND INTRODUCTIONS :-

IC engine, any of a group of device in which the reactants of combustion (oxydizer and fuel) and the products of combustion serve as the working fluid of the engine. Such an engine gains it's energy from heat released during the combustion of the non reacted working fluids, the oxydizer fuel mixture. This process occurs within the engine and is part of the thermodynamic cycle of the device. Useful work generated by an IC engine results from the hot gaseous products of combustion acting on moving surfaces of the engine, such as the face of a piston, a turbine blade or a nozzle.

IC engines are the most broadly applied and widely used power generating devices currently in existance. e.g. are gasoline engine, diesel engine, gas turbine engine and rocket propulsion system. IC engines are devided into two groups are-

1. Contineous combustion engine, and
2. Intermittent combustion engine.

The contineous combustion engine is charecterised by a steady flow of fuel and oxydizer into the engine. A stable flame is maintained within the engine. The intermittent combustion engine is charecterised by periodic ignition of air and fuel is commenly reffered to as a reciprocating engine. Descite volumes of air and fuel are proposed in a cyclic manner. Gasoline piston engines and diesel engines are example of the second group.

CASE SETUP :-

The case setup for No hydro and full hydro are nearly same, but where is the difference that points I describe here. Once the geometry of No hydro created then following changes should be taken into account.

1. Geometry with spark modelling :-

Here, I provided 4 injectors, two on each port to inject the fuel into the combustion chamber by using co-ordinate system. Due to this spark ignited in the combustion chamber through spark plug. Injector port I divided into two halves so that fencing and considering different names.

2. Adaptive Mesh Refinement :-

In spark ignition system the main role quantity are velocity and temperature, Here I shown velocity profile, where

Embed type = Sub grid scale(to super qualifying the mesh)

Max embed level = 3

Timing control type = permanent (constant velocity at each crank angle)

Max cells = 2000000 (Cell size increases means the simulation time quite low and slightly decrease the accuracy)

Active region are those regions where actual piston movement affects.

3. Crank angle parameter :-

These all parameter are given which are taken from designer who design each parts and gives that measurments. Here showing neighboring parts of the engine are piston, liner and cylinder head. Considering the speed is 3000RPM. More the speed more the simulation rate.

4. Parcel simulation :-

Molecular weight of iso-0ctane is considering by default from converge. Critical temperature are according to engine type and fuel used in it.

5. Parcel species :-

6. Run parameter :-

This is the case for full hydrodynamic, transient solver.

7. Simulation time parameter :-

Stroke is start from -520 to 120 i.e. total 720 degree because it is four stroke engine.

8. Intake valve bottom boundary :-

Intake valve bottom, top and angle boundary have same boundary data i.e. temperature is 480k. These boundary are moving types.

9. General combustion modelling :-

Here, I putting the value of cyclic period, start time, end time regions and temporal type.

10. SAGE model combustion modelling :-

11. Source modelling-1 :-

Here have two sources, to sparking. Shape of fuel drop is spherical. energy - 0.02 joule, also specifying Mode, start time, end time and period.

12. Source modeling-2 :-

This is the second source.

13. Source shape modelling-1 :-

Actual co-ordinate place of source and radius is given here.

14. Source shape modeling-2 :-

15. Spray modelling collision :-

16. Spray modelling injector profile :-

Injector profile are created here in shpe with respect to crank angle and finaly gives the any name with .in extension file.

17. Spray modelling injector species :-

18. Spray modelling injectors :-

19. Spray modelling wall Interaction :-

20. Spray modelling :-

21. Injector embeding :-

22. Large sphere embeding :-

23. Spherical embeding :-

Here I created three extra embeding by specifying start and end time. also specify the co-ordinates. It is use to embeded the inner body parts.

24. Injector setting :-

25. Region & initialization for cylinder region :-

Here cylinder and exhaust region are same because the same species are available there, due to that same pressure and temperature are taken there.

26. Output files :-

27. Compression ratio calculation :-

I calculated here, theorotically compression ratio is 11.9789 according to engine bore and stroke size.

28. Engine performance calculator :-

By loading .thermo and engine.in file we get here above values, some of them are-

Total duration = 240.199 degree

Gross work = 468.646 Nm and also different values with respect to crank angle.

These value are use to calculate different data for engine.

We also see here CA10, CA50 and CA90. So, what is this and what is the significance of these.

# Significance of CA10, CA50 and CA90 :-

It is the crank angle at 10%, 50% and 90% fuel combusted. From these value we can see that the actual change of crank angle with respect to fuel combustion. It can be shown in above results.

The physical significance of CA10 is that it is used to identify the start of ignition in a diesel engine, whereas the CA50 indicates the end of premixed combustion and the start of diffusion combustion of fuel used in the engine

The variation of CA50 and CA10-90 vs the brake torque. It was found that combustion is prolonged with the usage of jet-A1. Lower heating value and cetane number of Jet-A1 led to longer combustion. It may be mentioned that the highest combustion duration was observed with diesel because of the higher density. Combustion duration increases as the more charge mixture is delivered into the cylinder. It takes more time in order to complete the combustion at higher brake torques. Minimum combustion duration was obtained with A25 test fuel.

# Mass fraction Bum(MFB) :-

It is used to evaluate ignition delay and combustion duration by dividing the amount of accumulated fuel or accumulated heat during the combustion period by the total fuel or total heat release. The combustion state occuring in the cylinder can be distinguished by MFB.

From the start of the fuel injection , the crank position where MFB becomes 10% is noted as CA10, the point where MFB becomes 90% is noted as CA90.

CA50 denotes where the MFB is 50%, which means that 50% of injected fuel is converted into energy.

The difference between fuel injection point start and CA10 is called Flame development angle or ignition delay. The difference between CA10 and CA90 is called Rapid burning angle or Combustion duration.

RESULT PLOTS :-

From above case setup I created the following different plots as follows-

1. Different contours :-

Here showing different conours at start time i.e. t=0 sec. Pressure is very high at cylinder region, Temperature is high at exhaut region, velocity is quite high at exhaust region and crank angle effect is same everywhere. Pressure and temperature are inversaly proportional to each other but velocity is inversaly proportional to pressure and temperature.

2. Contours at t=20 sec :-

At some time after crank angle increases trimendously , which we can see above. As stroke start contour colour also changes with respect to time.

3. CO vs crank angle plot :-

Upto the expansion stroke carbon monoxide remains constant i.e. zero but as expansion stroke start fuel burnt and vapour created and that vapour some unburnt carbon also extracted, but the quantity of unburn gasses are very small than burnt fuel.

4. CO2 vs crank angle plot :-

At start CO2 get reduced but at end of the stroke it increases trimendously as given in above plot.

5. Cp vs crank angle plot :-

It is the pressure ratio and it changes fastly as crank angle changes.

6. Cv vs crank angle plot :-

It is the velocity ratio and it also fastly changes with respect to crank angle as shown in above plot. It is quite smaller value than pressure ratio.

7. Density vs crank angle plot :-

As expansion sroke start density also increases as shown in above plot.

8. Dynamic viscosity vs crank angle plot :-

9. Fuel spray for intake port region :-

10. Fuel spray mass :-

As combustion started more fuel are required and later on from expansion stroke it constant and minimum as shown in above plot.

11. Gamma vs crank angle plot :-

According to thermodynamics the value of gamma is not constant i.e. 1.4, it changes accordingly crank angle as shown in above plot.

12. Heat rejected per crank angle plot :-

This is the important plot, in which we can say that heat rejected at expansion stroke with respect to time and at other stroke it remains constant as shown in above plot.

13. Heat supplied vs crank angle plot :-

The effect of heat supplied is trimendously high at after expansion stroke and at power stroke. The output of heat supplied is to gain the power and that is very high here, as shown in above plot.

14. Hiroy soot vs crank angle plot ;-

The other effect also changes after and at expansion stroke as shown in above plot.

15. Kinetic viscosity vs crank angle plot :-

16. Liquid spray drop for intake port region :-

17. Liquid spray drops :-

18. Mass vs crank angle plot :-

Mass always increases as stroke changes as shown in above plot.

19. Mean temperature vs crank angle plot :-

Temperature value also changes at expansion stroke.

20. NOx vs crank angle plot :-

21. Pressure vs crank angle plot :-

From -90 degree expansion stroke start and from 20 degree it end and power stroke start as shown in above plot.

22. Surface mount device vs crank angle plot :-

23. Volume vs crank angle plot :-

Here showing clear volume change. From this plot we have to calculate compression ratio i.e. the difference between top and bottom stroke.

Copression ratio = Vmax - Vmin = 0.00058 - 0.00006 = 0.00052 m^3 = 0.52 cm^3.

24. DV10 vs crank angle plot :-

25. DV50 vs crank angle plot :-

26. DV90 vs crank angle plot :-

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The crankshaft is steered in axial direction by turned surface on the crank throws and contact faces on the end cover (DV10) and the intermediate bearing (DV20). On the surface the engine is tightned by means of oil seal ring fitted in the end covers. It showing engine mounting quality.

CALCULATIONS :-

a) From graph :-

From above result graph we can calculate following quantity are-

i) From volume vs crank angle plot,

Compression ratio = Maximum volume - Minimum volume = 0.00058/0.00006 = 9.67.

ii) From HR_intigrated and HR_rate plots,

Combustion efficiency = (heat supplied - heat rejected) / heat supplied = [(1233 - 55) / 1233 ]*100 = 95.54%

iii) From engine performance calculator image,

Net work =468.646 Nm

N = 3000rpm

Time = 1/N = 1/3000 = 0.00033 min = 0.02 sec

for 720 degree,

Time = 2*0.02 = 0.04sec

Power = Net work/time = 468.646/0.04 = 11716.15 watt = 11.71615 Kw

Now, Power = (2*pi*N*Torque)/60

11716.15 = (2*3.14*3000*Torque)/60

Torque = 702969/6.28 = 111937.739 Nm or 111.937739 KNm.

b) From theorotically,

i) Compression ratio is defined as the ratio of Maximum valume to the minimum valume in the cylinder of an IC engine. Mathmaticaly, it can be written as-

CR = Vmax/Vmin

where, Vmax= Vd + Vc = 5.74214e-4 m^3

Vmin = Vc = 5.74576e-5 m^3

Vd = displacement volume

Vc = Clearance volume

Hence, CR = 9.67.

ii) Combustion efficiency = (Heat supplied/ Heat rejected)*100

where, heat supplied = mass of fuel*calorific value of fuel = 3e-5*45e6 joule

Heat rejected = 1240 joule

Hence, Combustion efficiency = 95.54%.

iii) From energy performance calculator,

Work = 468.646 Nm

Duration = 240.199 deg

Crank angle speed = 3000 rpm = 50 rps

1 rotation = 360 deg

DPS(degree per sec) = 50*360 =18000

Time of every cycle = 240.199/18000 = 0.01334 sec

Hence, Power = 468.646/0.01334

Power = 35130.88 watt = 35.13 Kwatt.

Torque is engine ability to do work.

Power = (2*pi*N*T)/60

Hence, Torque = 111937.739 Nm = 111.937739KNm.

QUE. Why do we need a wall heat transfer model? Why can't we predict wall temperature from CFD simulations?

ANS. :-

# Need of wall heat transfer model :-

The heat loss through the walls of the engine is an important parameter during engine optimization, as it influences power, efficiency and emmisions and engine component thermo mechanical reliability. As a consequence, a correct estimation of wall heat fluxes is mandatory. However due to the complexity of the phenomenon involved in the heat transfer mechanism, such estimation is far from being trivial. Hence accurate modelling techniques need tobe available.

An important aspect of the optimization procedure of these engine technologies is the study of heat transfer through the walls of the engine. This has a direct influence of the power and efficiency of the engine since more heat is being lost means less power being transfer to the crankshaft. Besides this also influence on the thermal energy that is going out through the exhaust, due to which different after treatment tools are required. It also influenced the formation of pollutants. In fact gas temperature along with oxygen concentration is the main responsible for the Nitrogen oxyde formation and they affect unburnt hydrocarbons and soot as well. As legislation is imposing more and more stringent constraints on tailpipe emisions in internal combustion engines, engine designers are pushing for alternative solutions.

# Prediction of Wall Heat Temperature from CFD simulation :-

As near wall gas temperature are relevently higher than wall temperature during compression and combustion, engine flows can not be considered isothermal at all. As a consequence, models able to account for variations of gas proparties with temperature were proposed.

As we know NS equations are governing equations of fluid dynamics and to solve it numerically we have multiple commercial codes based on FVM. In this method, the computational domain is being decomposed at a number of small finite volume or computational cells.

As we know this process of decomposition is called meshing. The bodies in the flow are often treated as "VOID" or "HOLES". The surface of the body becomes one of the boundaries of the computational domain and the appropriate boundary conditions must be set on it to obtain a numerical solution.

eg. For incompressible flows, we have to solve only for momentum equations (i.e. equation for components of fluid velocity vector). For such a case treating a body as a 'hole' in the mesh seems tobe a reasonable approach- the body is solid, there is nothing to flow within it and in the body connected frame of refference, all the velocities are zero . The wall boundary conditions, in this case are 'No slip' (zero normal velocity) for inviscid flow.

A boundarycondition for energy equations at the surface of the body is ADIABATIC wall conditions for most of the cases. Applying this boundary conditions seems reasonable in case that we assume there is no heat transfer between flow and the body if we have perfect insulator on the surface of the body. Modern codes have the capability of solving energy equations both for fluid flow and for a body (for a solid body it turns to heat transfer equation). Such a problem is called "conjugated heat transfer problem".

RESULT ANIMATION FILES :-

1. FLAME OF PROPOGATION OF FULL HYDRODYNAMICS :-

From this animation we see that, at first stroke fuel and air not mixes proparly so the flame should forms but after first completion of stroke air and fuel mixes very well and burn fuel very well so that, we get red flame i.e. the burning flame. In this animation we can see that only mixure of air and fuel inside the cylinder. Piston moves from bottom dead centre to top dead centre.

2. VELOCITY OF PARCELS FOR FULL HYDRODYNAMICS :-

From above animation we can see that, when piston goes from BDC to TDC fuel and air mixes but when piston goes from TDC to BDC air and fuel enters into the combustion chamber, and thereafter due to compression stroke this mixture burnt very well then at expansion stroke mixture expanded and at last at power stroke we get power. The velocity of fue and air is very high so that it ignited suddenly.

3. TEMPERATURE OF PARCELS FOR FULL HYDRODYNAMICS :-

The working of Temperature of parcels is same as that of velocity of parcels. Here we can see that due to high temperature dry air enters into the combustion chamber so that mixture burn immedietly as shown in above animation. Due to high temperature more unburnt carbon particles are form.

CONCLUSIONS :-

From above setup, result plots and animation files for full hydrodynamic case we can conclude that-

1. At intake port more temperature are consider so that dry air enters into the combustion chamber.
2. Cyclic mode are consider because of compression and expansion stroke, by which crank angle changes periodically.
3. Fuel particle size are always spherical because it takes high mass and density.
4. Injector are put at intake port so that fuel enters into the combustion chamber.
5. Injector big and small embedding are consider for showing the spark field very well at spark plug mouth.
6. Engine performance calculator used to calculate different quantity by importing .thermo and engine .in files.
7. Different types of crank angle calculated at fuel combustion level like 10%, 50% and 90%.
8. 10% showing at start and 90% showing At just end of the fuel combustion what much crank angle changes.
9. Contour showing different colours according to fuel and air mixture.
10. Showing different quantity with respect to crank angle, so that we observe how air and fuel ratio are maintained.
11. Heat rejected and heat supplied plot showing that combustion efficiency.
12. On the basis of results I calculated different quantity in graphically and theorotically, we get both are same.
13. And finally from different animation files we conclude, how air and fuel mixes with each other and what is the effect of velocity and temperature happen on the combustion chamber.

So, In this way I setup the case for full hydrodynamics, plotted the different graphs, calculated required quantity, creating animation files and finally writting conclusion so that we get the clear idea about full hydrodynamics and it's setup. The performance of this engine is very well by setting up this way.