**5. Test bed investigation**

We can see a turning of fuel jet to the spark plug, but concentration of fuel is observed on piston bowl. Near TDC some of liquid fuel flows to the squish region and sometimes cannot be burned. During motion of jet fuel vaporize and on its boundary is more vapours than in‐ side of jet. Because of restricted volume of this paper it cannot be presented distribution of equivalence fuel-air ratio. However near spark plug air excess coefficient is enough to begin

In the enclosed illustration (*Fig.23-24*) changes of temperature inside the cylinder the GDI engine from the moment of injection till the end of the combustion process are shown.

During injection process there is observed decrease of temperature of charge where is liquid fuel and is caused by vaporization process. When piston is near TDC temperature of charge in a squish region is higher than in the centre of combustion chamber. The process of com‐ bustion during stratified charge mode is irregular, as a result of conductivity of fuel and gas, first of all ignite the regions with fuel vapour surrounding liquid fuel. It can be observed also during visualization process. The distribution of temperature shows the whole process of combustion and it proceeds in another way than in conventional engine with homogene‐ ous charge. Just at the end of this process the charge in the middle of combustion chamber

of combustion process. Ignition of spark plug took place 10 deg before TDC.

**4.4. Analysis of temperature distribution in the cylinder GDI engine**

108 Advances in Internal Combustion Engines and Fuel Technologies

burns as a result of higher temperature and vaporization of fuel jet.

**Figure 23.** Temperature distribution in the cylinder for 590 before TDC

Test bed investigations were divided into two basis stages:

**1.** The first stage includes elaboration of the visualization process of fuel injection and combustion of stratified charges for various loads and chosen rotational speeds of engine.

By use of a VideoScope 513 D of the firm AVL the movement of fuel jet will be followed from the moment of injection, fuel rebouncing from the piston head, up to the moment of its entering under the ignition plug, and subsequently spreading of the flame from the moment of ignition until the end of the combustion process [7].

**2.** The second stage includes carrying out of test bed investigations aiming at determina‐ tion of increase in total efficiency of a Gasoline Direct Injection Engine.

#### **5.1. Visualization of injection combustion process during engine work on stratified mixture**

The carried out visualization concerned the process of injection and combustion during en‐ gine work on stratified mixture [10]. The recording was carried out for rotational speed of the engine 2400 [rpm] for partial load. The value of specific fuel consumption was 238 [g/ kWh]. The fuel injection took place for 780 CA before TDC.

Below, in the presented film frames (*Fig.25-26*) chosen photographs concerning fuel injection into the cylinder of GDI engine.

0

0

CA: 20.0

whole combustion chamber and the flame front moves towards the zone of expression

**5.2. Test bed investigations of the engine 4g93gdi**

characteristics of a Mitsubishi GDI engine of 1834 cm3

CA: 18.0

**Figure 27.** Moment of ignition took place for 10 deg CA before TDC. The photograph present the initial phase of flame development for 18 deg CA after TDC. High whirling occurring in the combustion chamber is clearly visible.

Stratified Charge Combustion in a Spark-Ignition Engine With Direct Injection System

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111

**Figure 28.** Photograph of the further development of the flame for 20 deg CA after TDC. The flame spreads over the

A roller chassis test bed equipped with a water, electrically controlled brake, whose maxi‐ mal moment is 180 [Nm] was adopted for a test bed for determination of speed and load

The system was equipped with a vehicle speed meter V [km/h] and power on wheels [kW].

capacity.

**Figure 25.** Photograph of the injected fuel jet for 62 deg CA before TDC. There is a small fuel dispersion on the other edges of the jet and its gradual evaporation. The fuel jet inside the core is very coherent.

**Figure 26.** Photograph of the injected fuel jet for 55 deg CA before TDC. In consequence of turbulence consid‐ erable evaporation of fuel has taken place, whereas a portion of the not evaporated part reaches the inclination of the piston head.

In *Fig.27-28* are shown chosen film frames from the visualization concerning the combustion way in the GDI engine during engine work on stratified mixture. The moment of ignition took place for 10 deg CA before TDC.

Stratified Charge Combustion in a Spark-Ignition Engine With Direct Injection System http://dx.doi.org/10.5772/53971 111

**Figure 27.** Moment of ignition took place for 10 deg CA before TDC. The photograph present the initial phase of flame development for 18 deg CA after TDC. High whirling occurring in the combustion chamber is clearly visible.

**Figure 28.** Photograph of the further development of the flame for 20 deg CA after TDC. The flame spreads over the whole combustion chamber and the flame front moves towards the zone of expression

#### **5.2. Test bed investigations of the engine 4g93gdi**

Below, in the presented film frames (*Fig.25-26*) chosen photographs concerning fuel injection

**Figure 25.** Photograph of the injected fuel jet for 62 deg CA before TDC. There is a small fuel dispersion on the other

**Figure 26.** Photograph of the injected fuel jet for 55 deg CA before TDC. In consequence of turbulence consid‐ erable evaporation of fuel has taken place, whereas a portion of the not evaporated part reaches the inclination

In *Fig.27-28* are shown chosen film frames from the visualization concerning the combustion way in the GDI engine during engine work on stratified mixture. The moment of ignition

into the cylinder of GDI engine.

0

110 Advances in Internal Combustion Engines and Fuel Technologies

CA: -62.0

edges of the jet and its gradual evaporation. The fuel jet inside the core is very coherent.

CA: -55.0

0

of the piston head.

took place for 10 deg CA before TDC.

A roller chassis test bed equipped with a water, electrically controlled brake, whose maxi‐ mal moment is 180 [Nm] was adopted for a test bed for determination of speed and load characteristics of a Mitsubishi GDI engine of 1834 cm3 capacity.

The system was equipped with a vehicle speed meter V [km/h] and power on wheels [kW].

The system for fuel consumption measurement was equipped with apparatus of the type Flowtronic, measuring fuel consumption per hour Ge [l/h], connected to the fuel pump lo‐ cated in the fuel tank.

For determination of total efficiency of the engine Mitsubishi GDI of 1834 cm3

show the characteristic jump from one mode of work to the other.

speed of the engine.

full power

gine in function of rotational speed.

direct fuel injection use was made of the elaborated characteristics of speed obtained during test bed investigations the relation of specific fuel consumptions in function of rotational

Stratified Charge Combustion in a Spark-Ignition Engine With Direct Injection System

With regard to considerable decrease in fuel consumption per hour and per unit within the rotational speed from 750 - 2700 [rpm] caused by engine work in the mode of stratified fuelair mixture (λ ≅ 1,5-2,1 in dependence on engine rotational speed an load) the diagrams were to be complemented by additional characteristics of specific fuel consumption. With this aim in mind diagrams of specific fuel consumption in the same range of rotational speed 750 – 2700 [obr/min] were drawn in such a way as for an engine working on homoge‐ neous mixture ((λ≅1). In consequence of it the value of specific fuel consumption does not

*Fig.30-31* show traces of changes of specific fuel consumption and total efficiency of GDI en‐

**Figure 30.** Relation of specific fuel consumption and total efficiency in function of engine rotational speed for

capacity with

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The system for measurement toxic component content in exhaust gases of the Arcon Olivier K-4500 was connected by use of a sound to the exhaust system. The measurements consid‐ ered content of CO, CO2, O2, HC and the measurement of the coefficient of air excess λ.

The system for measurement of rotational speed of the engine was equipped with an encod‐ er of the crank angle of the firm *AVL* type *Angle Encoder 364* on a pulley.

Additionally a positioner permitting exact determination of the position of the accelerator.

All measurement systems were integrated with the central measurement computer mounted on the test bed for precise determination of all possible data for a given rotational speed and load of the investigated engine.

The scheme of the measurement test bed for determination of speed and load characteristics of the investigated engine was given in *Fig.29*.

**Figure 29.** The scheme of the test bed

For determination of total efficiency of the engine Mitsubishi GDI of 1834 cm3 capacity with direct fuel injection use was made of the elaborated characteristics of speed obtained during test bed investigations the relation of specific fuel consumptions in function of rotational speed of the engine.

The system for fuel consumption measurement was equipped with apparatus of the type Flowtronic, measuring fuel consumption per hour Ge [l/h], connected to the fuel pump lo‐

The system for measurement toxic component content in exhaust gases of the Arcon Olivier K-4500 was connected by use of a sound to the exhaust system. The measurements consid‐ ered content of CO, CO2, O2, HC and the measurement of the coefficient of air excess λ.

The system for measurement of rotational speed of the engine was equipped with an encod‐

Additionally a positioner permitting exact determination of the position of the accelerator.

All measurement systems were integrated with the central measurement computer mounted on the test bed for precise determination of all possible data for a given rotational speed and

The scheme of the measurement test bed for determination of speed and load characteristics

er of the crank angle of the firm *AVL* type *Angle Encoder 364* on a pulley.

cated in the fuel tank.

load of the investigated engine.

**Figure 29.** The scheme of the test bed

of the investigated engine was given in *Fig.29*.

112 Advances in Internal Combustion Engines and Fuel Technologies

With regard to considerable decrease in fuel consumption per hour and per unit within the rotational speed from 750 - 2700 [rpm] caused by engine work in the mode of stratified fuelair mixture (λ ≅ 1,5-2,1 in dependence on engine rotational speed an load) the diagrams were to be complemented by additional characteristics of specific fuel consumption. With this aim in mind diagrams of specific fuel consumption in the same range of rotational speed 750 – 2700 [obr/min] were drawn in such a way as for an engine working on homoge‐ neous mixture ((λ≅1). In consequence of it the value of specific fuel consumption does not show the characteristic jump from one mode of work to the other.

*Fig.30-31* show traces of changes of specific fuel consumption and total efficiency of GDI en‐ gine in function of rotational speed.

**Figure 30.** Relation of specific fuel consumption and total efficiency in function of engine rotational speed for full power

**5.** The results of computer calculations and stand research included in this work constitute a comprehensive complement of the knowledge about the creation and combustion of laminar loads in the gasoline engines with spark ignition with direct petrol injection. **6.** The increase in the total efficiency of GDI engine determined on the basis of test bed investigations varies within the limits Δη0 = 10 ÷ 17% in dependence on the rotational

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115

**7.** Applying the direct fuel injection of lean mixture combustion strategy definitely im‐ proves the working parameters of the internal combustion engine and constitutes the

*CV* <sup>1</sup> − specific heat of agent at constant volume in the initial point of combustion process,[kJ/

*CV* <sup>2</sup> − specific heat of agent at constant volume in the end of combustion process, [kJ/kgK]

*L <sup>p</sup>* − actually mass demand of air for combustion of 1 kg of fuel, [kmol/kg]

*γ* − coefficient of pollution of the fresh charge with rests of exhaust gases

*L <sup>S</sup>* − distance between the piston top and the head, [mm]

*x* − the distance of the piston from the TDC,[m]

*λ* − crank radius to connecting-rod length ratio

*s* − distance traveled by the fuel stream,[m]

*α* − actual angle of revolution of the crankshaft,[deg]

*T*<sup>2</sup> − charge temperature at the begining of the combustion process, [K] *Tm* − maximal tem‐

speed and load of the engine.

**7. Nomenclature**

perature of the cycle, [K]

*ω* − angular velocity,[rad/s]

*m*− Vibe's exponent, (m=3.5)

*t*1−<sup>5</sup> − times in sectors, [s]

*tinj* − time of injection, [s]

constans

*θ* − angle of combustion start,[m]

*φ<sup>Z</sup>* − total angle of combustion,[m]

*RW* − crank arm,[m]

kgK]

basis for further developmental work on this area.

**Figure 31.** Relation of specific fuel consumption and total efficiency in function of engine rotational speed for 3/4 rated power
