HOMOGENOUS COMBUSTION IN POROUS MEDIUM(A NEW CONCEPT OF I.C. ENGINE )

PREPARED BY:- UMANG TRIVEDI

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INDEXI. INTRODUCTION

II. WHY WE NEED IT?

III. HOMOGENEOUS COMBUSTION

IV. POSSIBLE COMBUSTION MODES OF A HOMOGENEOUS CHARGE

V. POROUS MEDIUM TECHNOLOGY

VI. PRINCIPLE OF THE POROUS MEDIUM-ENGINE

VII. POROUS MEDIUM WITH CLOSED CHAMBER

VIII. POROUS MEDIUM WITH OPEN CHAMBER

IX. ADVANTAGES OF PM TECHNOLOGY

X. CONCLUSION

XI. REFRENCES.

INTRODUCTIONEngine is one of the most hot topic where many research has been done and still many new are been developed.In that engine we want that which would give non-zero emission , less fuel consumption to with stand under wild range of speed and load is currently under research.Many new things are reached in this field as it has various scope of development in Porous Medium.Since a lot of new stuff are developed or its under develoPorous Mediument .Among them the new research is done in engine with homogeneous combustion using porous medium Technology.

WHY WE NEED IT?At present, the emissions of internal combustion engines can only be improved by catalytic treatments of the exhaust gases. 

Such treatments, however, result in high costs and relatively low conversion efficiency.

This suggests that a new combustion technique should be developed to yield improved primary combustion processes inside the engine with drastically reduced exhaust gas emissions.

So a technique was found which can be used in all engine with the steady state household.

The process of mixture formation, ignition & combustion in conventional engine is not effective due to the lack of mechanisms for homogenous combustion process.

Two parameters will be required for future internal combustion engine i.e. non-zero emission level & low fuel consumption.

COUNT..These parameter is strongly dependent on the process of mixture formation & combustion which are difficult to controlled in a conventional engine combustion system.   The question is remain unsolved is the method for realization of homogenous combustion in IC engine, specially if the variable engine operational conditions are considered.So here porous medium concept is introduced in order to overcome above difficulty. Porous Medium utilize the special features of highly porous media to support and controlled the mixture formation and combustion process in IC engine.

HOMOGENEOUS COMBUSTIONHomogeneous combustion in an IC engine is defined as a process characterized by a 3D-ignition of the homogeneous charge with simultaneous-volumetric-combustion.

Hence it ensures a homogeneous temperature field.

According to the definition given above, three steps of the mixture formation and combustion may be selected that define the ability of a given combustion system to operate as a homogeneous combustion system:

A. Homogenization of charge.

B. Ignition conditions.

C. Combustion process and temperature field.

COUNT…Four different ignition techniques may be selected:

A. Local ignition (e.g. spark plug).

B. Thermal self-ignition (e.g. compression ignition).

C. Controlled auto-ignition (e.g. low temperature chemical ignition).

D. 3D-thermal Porous Medium -self-ignition (3D-grid-structutre of a high temperature).

The last considered ignition system, has been recently proposed and uses a 3Dstructured porous medium for the volumetric ignition of homogeneous charge.

The Porous Medium has homogeneous surface temperature over the most of the Porous Medium-volume, higher than the ignition temperature.

In this case the Porous Medium-volume defines the combustion chamber volume.

Thermodynamically speaking, the porous medium is here characterized by a high heat capacity and by a large specific surface area.

POSSIBLE COMBUSTION MODES OF A HOMOGENEOUS CHARGE

1) Homogenous charge with local ignition. 4) Homogeneous charge with 3D-

thermal self-ignition in Porous Medium-volume

2) Homogeneous charge with compression ignition.

3) Homogeneous charge with controlled auto-ignition

The porous medium technology for IC engines means here the utilization of specific features of a highly porous media for supporting and controlling the mixture formation and combustion processes in I.C. engines. 

 The employed specific features of Porous Medium are directly related to a very effective heat transfer and very fast flame propagation within the Porous Medium.

The medium used is  SiC ceramic foam which looks as shown

in Figure.

POROUS MEDIUM TECHNOLOGY

COUNT.. Generally, the most important parameters of Porous Medium for application to engine combustion technology can be given as follows:

I.  Heat capacity,

II. Specific surface area,

III. Heat transport properties,

IV. Transparency for fluid flow,

V. Spray and flame propagation,

VI. Pore sizes, pore density,

VII. Pore structure,

VIII. Thermal resistance of the material,

IX. Mechanical resistance and mechanical properties under heating and cooling conditions

COUNT.. For IC engine application, the thermal resistance of the porous medium is one of the most important parameter defining its applicability of a given material to combustion in engine.

A view of the thermal test of SiC-reactors for engine application is shown in Fig.

PRINCIPLE OF THE POROUS MEDIUM-ENGINE

The Porous Medium-engine is here defined as an internal combustion engine with the following processes realized in a porous medium: internal heat recuperation, fuel injection, fuel vaporization, mixing with air, homogenization of charge, 3D-thermal self ignition followed by a homogeneous combustion.

Porous Medium-Engine may be classified with respect to the heat recuperation as: Engine with periodic contact between Porous Medium and working gas in cylinder (closed chamber). Engine with permanent contact between Porous Medium and working gas in cylinder (open chamber).

On the other hand, possible positioning of the Porous Medium combustion chamber in engine can be used to design different engines: A. Cylinder head (Porous Medium is stationary).

B. Cylinder (Porous Medium is stationary).

C. Piston (Porous Medium moves with piston).

One of the most interesting features of Porous Medium -engine is its multi fuel performance. The Porous Medium-engine concept may be applied to both two and four-stroke cycles.

POROUS MEDIUM WITH CLOSED CHAMBER

The Porous Medium-engine cycle with a case of closed Porous Medium chamber, i.e. engine with a periodic contact between working gas and Porous Medium-heat recuperator.

At the end of the expansion stroke the valve controlling timing of the Porous Medium chamber closes and fuel is injected in the Porous Medium-volume.

This volume represents in thermodynamic sense a low pressure chamber and a long time is available for fuel injection and its vaporization in the Porous Medium.

These processes may continue through exhaust, intake and compression strokes

COUNT…Near the TDC of compression the valve in Porous Medium chamber opens and the compressed air flows from the cylinder into the hot Porous Medium volume containing fuel vapors.

Very fast mixing of the gaseous charge occurs and the resulting mixture is ignited in the whole Porous Medium volume.

The resulting heat release process performs simultaneously in the whole Porous Medium volume.

The three essential conditions for a homogeneous combustion are here fulfilled:

I. Homogenization of charge in Porous Medium -volume,

II. 3D-thermal self ignition in Porous Medium ,

III. Volumetric combustion with a homogeneous temperature field in Porous Medium-volume.

Additionally, the Porous Medium -material deals as a heat capacitor and, hence, controls the combustion temperature

POROUS MEDIUM WITH OPEN CHAMBER

The Porous Medium-engine is a combustion system characterized by a permanent contact between working gas and Porous Medium-volume, as schematically shown in Figure

Here, it is assumed that the Porous Medium-combustion chamber is mounted in the engine head.

During the intake stroke there is a weak influence of the Porous Medium-heat capacitor on the in-cylinder air thermodynamic conditions.

Also during the early compression stroke, only a small amount of air is in contact with hot porous medium process (non-isentropic compression) increases with continuing compression, and at the TDC the whole combustion air is closed in the Porous Medium volume.

COUNT.. Near the TDC of compression the fuel is injected in to Porous Medium volume and very fast fuel vaporization and mixing with air occur in 3D-structure of Porous Medium-volume.

Again, the requested 3D-thermal self-ignition of the resulting mixture follows in Porous Medium-volume together with a volumetric combustion characterized by a homogeneous temperature distribution in Porous Medium combustion volume.

Again, all necessary conditions for homogeneous combustion are fulfilled in the Porous Medium combustion chamber.

 ADVANTAGES OF PM TECHNOLOGY 1)Very low emissions level due to homogeneous combustion and controlled  temperature in the PM-combustion zone.

2) Theoretically higher cycle efficiency due to similarity to the Carnot cycle.

3) Very low combustion noise due to significantly reduced pressure peaks.

4) Nearly constant and homogeneous combustion temperature field in the PM-       volume.

5) Very fast combustion.

6) Multi-fuel system.

7) May operate with homogeneous charge: from stoichiometric to very lean mixture  compositions.

8) Weak effect of in-cylinder flow structure, turbulence or spray atomization     

Conclusion There is no doubt that the future of internal combustion engine is related to the homogeneous combustion process in a wide range of engine operational conditions.

This technique shows potential for a near-zero combustion emissions & Moreover, this kind of combustion system is less fuel specific.

 the realization of homogeneous combustion in IC engine under variable loads and speeds will probably require new concepts for mixture formation and controlled ignition conditions under different engine loads. 

And all above it need to be economical dealing with compression temp., compression stroke, ignition , mixing ratio so still needed to developed in this field.

REFRENCES 1) http://engineringcorner.blogspot.in/2011/09/new-concept-of-ic-engine-with.html.

2) http://www.ijltet.org/wp-content/uploads/2012/07/6.pdf,

3) http://www.geedindia.org/papers/adil_vikas_abhi.pdf