**3. Design assumptions for the test engine and selection of the base unit**

On the basis of the analyses in the field of variable compression ratio technology, taking into account all advantages and disadvantages of the known technologies for of variable compression ratio engines and existing prototypes as well as own manufacturing capabilities, it was decided that the construction of the test engine will be carried out according to for the kinematic system shown on case (g) in **Table 1**, that is, consisting of controlled positioning and movement of the cylinder head assembly along the cylinder axis. This solution is characterized by relatively low implementation costs due to the possibility of conversion of a standard piston engine into the VCR one, simplicity of construction and control, while ensuring a relatively wide range of changes of compression ratio at a high accuracy in positioning. The engine will be based on a serial produced combustion engine. It was assumed that for the purposes of the assumed scope of experimental tests, it will be necessary to obtain a wide range of compression ratio variation covering typical values for both spark and diesel engines, that is, from around 9:1 up to 19:1. The test engine should be also liquid cooled to ensure good temperature stability during research.

A medium-speed, liquid-cooled 4-cylinder diesel engine manufactured by VEB IFA-Motorenwerk Nordhausen type 4 VD 14.5/12-1 SRW was selected for the

#### **Figure 4.**

*The main cross sections of the 4 VD 14.5/12-1 SRW engine as the basis for the own designed research unit in the VCR technology with the dividing planes of the engine body shown [11].*

integrity can be pointed [6]. The gear-based crank mechanism (f) is very advanced technique extensively developed by MCE-5 research group [1, 2]. It shows high precision in CR control and profitable changes in piston kinematics that avoids side

Analyzing the possible solutions of VCR engines, both hypothetical constructions and actual prototype units, two general strategies for changing the value of the

1.The change and control of the compression ratio at the assumed level takes place by changing the position or geometry of the engine part, which consist of the cylinder head assembly. This method does not interfere with the moving parts of the crank-piston system, thus the friction losses and kinematics of the crank-piston system during engine operation remain unchanged or change in a

2.The change of the compression ratio is a result of the intended changes in the geometry and/or kinematics of the crank-piston system due to special constructions of mechanisms allowing for the correction of the distance between the top plane of the piston and the bottom plane of the head. In this case the power of friction losses in the crank-piston system usually increases, although it is also possible to be reduced (e.g., solution (f)—**Table 1**).

Sometimes variation of the compression ratio according to these concepts also causes an unfavorable change in the cylinder stroke volume (e.g., solution

*Forecasts for the development and share of selected advanced technologies in the combustion powerdrives of*

compression ratio during the engine run can be noticed.

*Numerical and Experimental Studies on Combustion Engines and Vehicles*

very small extent comparing to a conventional engine.

forces acting on the piston.

(d)—**Table 1**).

**Figure 3.**

**118**

*motor vehicles [10].*

construction of the VCR engine. The unique structural feature of this engine, which decided on its selection, was the physically existing plane that divides the crankcase from the cylinder assembly (see **Figure 4**).

The basic parameters of the 4 VD engine are as follows: cylinder diameter— 120 mm, piston stroke—145 mm, displacement—6560 ccm, original geometric compression ratio—18:1, valve drive system: OHV overhead valves with camshaft located in the crankshaft block, cam followers, sticks, valve arms mounted on the axle above the head. Detailed engine specifications are described in **Table 2**.

Geometric dimensions of the 4 VD 14.5/12-1 SRW engine allowed to determine how the compression ratio will change with the cylinder head assembly moving along the cylinder axis according to the relationship (Eq. (1)):

$$\mathbf{e}' = \frac{\frac{\mathbf{e} \cdot \mathbf{V}\_c}{\mathbf{e} - \mathbf{I}} + \pi \frac{\mathbf{D}^2}{4} \cdot \mathbf{h}}{\frac{\mathbf{V}\_c}{\mathbf{e} - \mathbf{I}} + \pi \frac{\mathbf{D}^2}{4} \cdot \mathbf{h}} : \mathbf{1} \tag{1}$$

range of these changes essentially coincides with the desired research scope of the engine. If necessary, it can be changed relatively easily by replacing the pistons with

*Application of Variable Compression Ratio VCR Technology in Heavy-Duty Diesel Engine*

*DOI: http://dx.doi.org/10.5772/intechopen.93572*

The adopted concept of changing the compression ratio requires the use of an accurate, precise cylinder head assembly shifting mechanism in relation to the crankshaft block. The requirement of this mechanism, in addition to the high accuracy of positioning and rapid change of the position of the cylinders, is to transfer gaseous forces generated by the combustion process in individual engine

cylinders. The value of these forces can be determined from Eq. (2):

Fmax ¼ pmax �

where Fmax is the maximum force acting on the shifting system due to the gas pressure in the cylinder, pmax is maximum gas pressure in the cylinder, and D is

Assuming the maximum gas pressure in cylinders at 10 MPa, we obtain the force generated by a single cylinder at the level of 113 kN. Hence, the sliding mechanism must have adequate strength, but also rigidity, operational reliability, small dimensions and relatively high positioning resolution, especially in the range of high

The task of the newly designed mechanism for compression ratio changing is precise shifting the 4-cylinder "cylinder head" assembly in the range of 0–10 mm by means of synchronously rotating two eccentric shafts that are connected to the sliding elements by kind of yokes—connecting rods. The layout diagram and the source of the main mechanical loads are shown in **Figure 6**. The analysis of forces and torques shows that the eccentric shafts will be loaded with a twisting torque Ms of approx. 300 Nm each. **Figure 7** shows the location of eccentric shafts together with the shaft drive system. Both shafts have bearings on both ends and in the middle of their length. At the free ends of both shafts there are two geared right-angle power transmissions; their inputs are connected by a common drive shaft that is driven by a synchronous

<sup>π</sup> � <sup>D</sup><sup>2</sup>

<sup>4</sup> (2)

different volume of the combustion chamber [8, 9].

*Compression ratio versus cylinder shift value for 4 VD 14.5/12-1 SRW engine.*

cylinder diameter.

**121**

**Figure 5.**

values of compression ratio.

where ε´ is compression ratio as a function of the cylinder head assembly shift, ε is original compression ratio, Vc is cylinder displacement, D is cylinder diameter, h is shift value of cylinder head assembly relative to the initial position.

Eq. (1), substituted with appropriate values, shows that the range of the cylinder head assembly tilting from initial position up to 10 mm travel gives the compression ratio changes from 19:1 to 9:1, according to the curve shown in the **Figure 5**. The


#### **Table 2.**

*Original technical specification of the 4 VD 14.5/12-1 SRW engine [11].*

*Application of Variable Compression Ratio VCR Technology in Heavy-Duty Diesel Engine DOI: http://dx.doi.org/10.5772/intechopen.93572*

**Figure 5.** *Compression ratio versus cylinder shift value for 4 VD 14.5/12-1 SRW engine.*

range of these changes essentially coincides with the desired research scope of the engine. If necessary, it can be changed relatively easily by replacing the pistons with different volume of the combustion chamber [8, 9].

The adopted concept of changing the compression ratio requires the use of an accurate, precise cylinder head assembly shifting mechanism in relation to the crankshaft block. The requirement of this mechanism, in addition to the high accuracy of positioning and rapid change of the position of the cylinders, is to transfer gaseous forces generated by the combustion process in individual engine cylinders. The value of these forces can be determined from Eq. (2):

$$\mathbf{F}\_{\text{max}} = \mathbf{p}\_{\text{max}} \cdot \frac{\boldsymbol{\pi} \cdot \mathbf{D}^2}{4} \tag{2}$$

where Fmax is the maximum force acting on the shifting system due to the gas pressure in the cylinder, pmax is maximum gas pressure in the cylinder, and D is cylinder diameter.

Assuming the maximum gas pressure in cylinders at 10 MPa, we obtain the force generated by a single cylinder at the level of 113 kN. Hence, the sliding mechanism must have adequate strength, but also rigidity, operational reliability, small dimensions and relatively high positioning resolution, especially in the range of high values of compression ratio.

The task of the newly designed mechanism for compression ratio changing is precise shifting the 4-cylinder "cylinder head" assembly in the range of 0–10 mm by means of synchronously rotating two eccentric shafts that are connected to the sliding elements by kind of yokes—connecting rods. The layout diagram and the source of the main mechanical loads are shown in **Figure 6**. The analysis of forces and torques shows that the eccentric shafts will be loaded with a twisting torque Ms of approx. 300 Nm each.

**Figure 7** shows the location of eccentric shafts together with the shaft drive system. Both shafts have bearings on both ends and in the middle of their length. At the free ends of both shafts there are two geared right-angle power transmissions; their inputs are connected by a common drive shaft that is driven by a synchronous

construction of the VCR engine. The unique structural feature of this engine, which decided on its selection, was the physically existing plane that divides the crankcase

The basic parameters of the 4 VD engine are as follows: cylinder diameter— 120 mm, piston stroke—145 mm, displacement—6560 ccm, original geometric compression ratio—18:1, valve drive system: OHV overhead valves with camshaft located in the crankshaft block, cam followers, sticks, valve arms mounted on the axle above the head. Detailed engine specifications are described in **Table 2**.

Geometric dimensions of the 4 VD 14.5/12-1 SRW engine allowed to determine how the compression ratio will change with the cylinder head assembly moving

where ε´ is compression ratio as a function of the cylinder head assembly shift, ε is original compression ratio, Vc is cylinder displacement, D is cylinder diameter, h

Eq. (1), substituted with appropriate values, shows that the range of the cylinder head assembly tilting from initial position up to 10 mm travel gives the compression ratio changes from 19:1 to 9:1, according to the curve shown in the **Figure 5**. The

<sup>4</sup> � h

<sup>4</sup> � <sup>h</sup> : <sup>1</sup> (1)

along the cylinder axis according to the relationship (Eq. (1)):

*Numerical and Experimental Studies on Combustion Engines and Vehicles*

ε<sup>0</sup> ¼

is shift value of cylinder head assembly relative to the initial position.

Type 4-stroke, diesel Number of cylinders 4 Ignition order 1-3-4-2 Cylinder layout In-line Piston stroke 145 mm Cylinder diameter 120 mm Displacement 6560 ccm Compression ratio 18:1 Rated power 92 kW (125 KM) Cranckshaft speed at rated power 2300 rpm Maximum torque 430 Nm Cranckshaft speed at max. torque 1350 rpm Mean effective pressure 0.77 MPa

Specific fuel consumption for rated power 240 g/kW�h (175 g/KM�h) Minimum specific fuel consumption 218 g/kW�h (160 g/KM�h) Lubrication system Closed circulation, pressurized

Initial pressure of injector opening 17.5 MPa Engine starter Electric motor Power and supply voltage of engine starter 3 kW, 24 V

*Original technical specification of the 4 VD 14.5/12-1 SRW engine [11].*

**Table 2.**

**120**

Fuel delivery Direct injection (system MAN), single-hole sprayer,

in-line section fuel pump with mechanical regulation of engine speed

ε�Vc <sup>ε</sup>�<sup>1</sup> <sup>þ</sup> <sup>π</sup> D2

Vc <sup>ε</sup>�<sup>1</sup> <sup>þ</sup> <sup>π</sup> <sup>D</sup><sup>2</sup>

**Producer VEB IFA-Motorenwerk Nordhausen**

from the cylinder assembly (see **Figure 4**).

**Figure 6.** *Diagram of the yoke-eccentric cylinder sliding mechanism and the main sources of mechanical loads.*

Construction work began with the reverse engineering process on the research engine, that is, scanning the spatial engine body with the determination of characteristic points, surfaces, distances, clearances, etc., allowing the design and manufacture of other engine components and subassemblies. As previously mentioned, the characteristic feature of IFA 4 VD 14.5/12-1 SRW engine, which influenced the decision on its selection for adaptation works is the fact that the engine block is not permanently fixed to the cylinders. The division plane is shown in **Figure 9**. Its physical presence gave the opportunity to design and build an appropriate drive mechanism to realize the movement of the cylinders (together with the heads) in

*Overall views of the RA type TRAMEC bevel gearbox, Stöber SMS servomotor, and Stöber POSIDRIVE MDS*

*Application of Variable Compression Ratio VCR Technology in Heavy-Duty Diesel Engine*

*DOI: http://dx.doi.org/10.5772/intechopen.93572*

The basic elements of the cylinder sliding system are the servomotors chosen

*3D scanning image of the IFA 4 VD engine as a base for performing necessary design and technological changes; the green plane is marked showing the division plane between the crankcase block and the cylinder blocks.*

with catalogs, two bevel gears, drive couplings, and two eccentric shafts, connecting rods and a designed and made main support plate that keeps the

the vertical direction.

**Figure 8.**

*inverter.*

**Figure 9.**

**123**

**Figure 7.** *Project of the location of eccentric shafts with the drive system diagram.*

servomotor with a mechanical brake. The wheelbase of the shafts is approx. 380 mm, which directly fits to the design features of the test engine.

Analysis of loads shows that each of the bevel-geared transmissions has to transfer a maximum torque less than 300 Nm, while the main servomotor has to generate a double value of that torque, that is, at least 600 Nm.

Therefore, an appropriate selection of working elements has been made, taking into account the structural safety factors. The bevel gearboxes TRAMEC in the version RA 38AC 1:1 E B3 with the rated torque Ma = 320 Nm are used as the rightangle drives. As the servomotor a two-stage flat reducer, type Stöber SMS version F402AGN0470 EZ503U EL1, with an acceleration torque of 700 Nm, driven by the Stöber POSIDRIVE MDS5110A/L 11.0 kW 3 400 V inverter is used (**Figure 8**). All gear units are with reduced mid-gear lash to the value below 10 arc minutes.

*Application of Variable Compression Ratio VCR Technology in Heavy-Duty Diesel Engine DOI: http://dx.doi.org/10.5772/intechopen.93572*

#### **Figure 8.**

*Overall views of the RA type TRAMEC bevel gearbox, Stöber SMS servomotor, and Stöber POSIDRIVE MDS inverter.*

Construction work began with the reverse engineering process on the research engine, that is, scanning the spatial engine body with the determination of characteristic points, surfaces, distances, clearances, etc., allowing the design and manufacture of other engine components and subassemblies. As previously mentioned, the characteristic feature of IFA 4 VD 14.5/12-1 SRW engine, which influenced the decision on its selection for adaptation works is the fact that the engine block is not permanently fixed to the cylinders. The division plane is shown in **Figure 9**. Its physical presence gave the opportunity to design and build an appropriate drive mechanism to realize the movement of the cylinders (together with the heads) in the vertical direction.

The basic elements of the cylinder sliding system are the servomotors chosen with catalogs, two bevel gears, drive couplings, and two eccentric shafts, connecting rods and a designed and made main support plate that keeps the

#### **Figure 9.**

*3D scanning image of the IFA 4 VD engine as a base for performing necessary design and technological changes; the green plane is marked showing the division plane between the crankcase block and the cylinder blocks.*

servomotor with a mechanical brake. The wheelbase of the shafts is approx. 380 mm, which directly fits to the design features of the test engine.

*Diagram of the yoke-eccentric cylinder sliding mechanism and the main sources of mechanical loads.*

*Numerical and Experimental Studies on Combustion Engines and Vehicles*

generate a double value of that torque, that is, at least 600 Nm.

*Project of the location of eccentric shafts with the drive system diagram.*

**Figure 6.**

**Figure 7.**

**122**

Analysis of loads shows that each of the bevel-geared transmissions has to transfer a maximum torque less than 300 Nm, while the main servomotor has to

Therefore, an appropriate selection of working elements has been made, taking into account the structural safety factors. The bevel gearboxes TRAMEC in the version RA 38AC 1:1 E B3 with the rated torque Ma = 320 Nm are used as the rightangle drives. As the servomotor a two-stage flat reducer, type Stöber SMS version F402AGN0470 EZ503U EL1, with an acceleration torque of 700 Nm, driven by the Stöber POSIDRIVE MDS5110A/L 11.0 kW 3 400 V inverter is used (**Figure 8**). All gear units are with reduced mid-gear lash to the value below 10 arc minutes.

**Figure 10.** *Design of the cylinder support plate and its mounting on the screws fitted into the cylinder blocks.*

**Figure 11.** *Connecting yokes mounted with the eccentric shafts.*

**Figure 13.**

**125**

*eccentric shafts.*

*An isometric view of the VCR engine with assembled with the cylinder sliding system and the drive mechanism of*

*Application of Variable Compression Ratio VCR Technology in Heavy-Duty Diesel Engine*

*DOI: http://dx.doi.org/10.5772/intechopen.93572*

**Figure 12.** *View of the assembly of the cylinder blocks sliding system.*

*Application of Variable Compression Ratio VCR Technology in Heavy-Duty Diesel Engine DOI: http://dx.doi.org/10.5772/intechopen.93572*

**Figure 13.** *An isometric view of the VCR engine with assembled with the cylinder sliding system and the drive mechanism of eccentric shafts.*

**Figure 10.**

**Figure 11.**

**Figure 12.**

**124**

*Connecting yokes mounted with the eccentric shafts.*

*View of the assembly of the cylinder blocks sliding system.*

*Design of the cylinder support plate and its mounting on the screws fitted into the cylinder blocks.*

*Numerical and Experimental Studies on Combustion Engines and Vehicles*

cylinders. The main board (**Figure 10**, dark blue color) is seated and attached to the cylinder blocks using special threaded mounting bolts.

dimensions for the designed VCR engine were adopted from the HANOMAG D942

connecting yokes. To ensure proper dimensional accuracy, technological work was carried out on CNC machine tools. **Figure 11** shows the connecting yokes fastened

eccentric shafts for the cylinder sliding system together with a set of eight

*Application of Variable Compression Ratio VCR Technology in Heavy-Duty Diesel Engine*

the crankcase and fitted into the precise holes made in the cylinders body.

The entire design of the VCR engine, for a better illustration of its structure complexity, is presented in isometric views in **Figure 13**, while the finally completed research engine with variable compression ratio is presented in **Figure 14**.

Piston engine for many decades is a basic and commonly used source of mechanical drives in various types of machinery and technical equipment, including motor vehicles and other means of transportation. Despite the various controversial forecasts and views that have recently appeared, and not always are based on trusted and documented technical knowledge, the combustion engine will certainly remain an irreplaceable source of propulsion for many branches of transport and industry. One should keep in mind the intense scientific, technical, and technological progress that makes the final product even more and more technically perfect. Taking into account the current development trends that arisen from an experience of recent years, which are focused mainly on improving combustion processes, it can be noted that the presented technical development of VCR internal combustion

A great innovation and application potential is shown by the worked out original design, constructional and technological achievements covering a four-cylinder combustion engine with a variable compression ratio VCR feature. Attempts to develop such an original powerdrive unit, except for some major automotive industry efforts, were usually finished unsuccessfully. The developed design of the VCR engine opens up new research and development opportunities that were not available before. It concerns mainly to new directions of improvement of engine working processes and exploitation possibilities of internal combustion engines, that is, research on advanced, low-temperature combustion processes or research on the unification and flexible use of various fuels for transportation, including

Authors wish to thank to the Ministry for Science and Higher Education in the

engines gives a significant contribution in this process.

Republic of Poland for their financial support of this work.

alternative fuels of different reactivities.

**Acknowledgements**

**127**

The next key stage in the VCR engine design process was the exact machining of

The movement of the supporting plate together with the cylinders is enforced by an eccentric-crank mechanism driven by a complex servomechanism (**Figure 12**), that is, through two angle bevel gears and two eccentric shafts. The elements shown in orange make the assembly fixing the axle passing through the connecting rod holes. Eccentric shafts are mounted in sleeves welded to the transverse beams (green and yellow). The drive for eccentric shafts is transmitted via two ROTEX GS clutches. Any disorders and risk of misalignments in movement of the cylinder-cylinder head assembly is secured by set of sliding barrels. Sliding barrels are permanently fixed in

engines.

with the eccentric shafts.

*DOI: http://dx.doi.org/10.5772/intechopen.93572*

**4. Conclusion**

To allow the additional space for insertion of a flexible seal gasket between crankshaft block and cylinder blocks it was necessary to change the pistons with the larger height ones by at least 5 mm. Suitable pistons that meet the necessary

**Figure 14.** *View of the complete VCR engine during functional tests.*

*Application of Variable Compression Ratio VCR Technology in Heavy-Duty Diesel Engine DOI: http://dx.doi.org/10.5772/intechopen.93572*

dimensions for the designed VCR engine were adopted from the HANOMAG D942 engines.

The next key stage in the VCR engine design process was the exact machining of eccentric shafts for the cylinder sliding system together with a set of eight connecting yokes. To ensure proper dimensional accuracy, technological work was carried out on CNC machine tools. **Figure 11** shows the connecting yokes fastened with the eccentric shafts.

The movement of the supporting plate together with the cylinders is enforced by an eccentric-crank mechanism driven by a complex servomechanism (**Figure 12**), that is, through two angle bevel gears and two eccentric shafts. The elements shown in orange make the assembly fixing the axle passing through the connecting rod holes. Eccentric shafts are mounted in sleeves welded to the transverse beams (green and yellow). The drive for eccentric shafts is transmitted via two ROTEX GS clutches. Any disorders and risk of misalignments in movement of the cylinder-cylinder head assembly is secured by set of sliding barrels. Sliding barrels are permanently fixed in the crankcase and fitted into the precise holes made in the cylinders body.

The entire design of the VCR engine, for a better illustration of its structure complexity, is presented in isometric views in **Figure 13**, while the finally completed research engine with variable compression ratio is presented in **Figure 14**.

## **4. Conclusion**

cylinders. The main board (**Figure 10**, dark blue color) is seated and attached to the

To allow the additional space for insertion of a flexible seal gasket between crankshaft block and cylinder blocks it was necessary to change the pistons with the larger height ones by at least 5 mm. Suitable pistons that meet the necessary

cylinder blocks using special threaded mounting bolts.

*Numerical and Experimental Studies on Combustion Engines and Vehicles*

**Figure 14.**

**126**

*View of the complete VCR engine during functional tests.*

Piston engine for many decades is a basic and commonly used source of mechanical drives in various types of machinery and technical equipment, including motor vehicles and other means of transportation. Despite the various controversial forecasts and views that have recently appeared, and not always are based on trusted and documented technical knowledge, the combustion engine will certainly remain an irreplaceable source of propulsion for many branches of transport and industry. One should keep in mind the intense scientific, technical, and technological progress that makes the final product even more and more technically perfect. Taking into account the current development trends that arisen from an experience of recent years, which are focused mainly on improving combustion processes, it can be noted that the presented technical development of VCR internal combustion engines gives a significant contribution in this process.

A great innovation and application potential is shown by the worked out original design, constructional and technological achievements covering a four-cylinder combustion engine with a variable compression ratio VCR feature. Attempts to develop such an original powerdrive unit, except for some major automotive industry efforts, were usually finished unsuccessfully. The developed design of the VCR engine opens up new research and development opportunities that were not available before. It concerns mainly to new directions of improvement of engine working processes and exploitation possibilities of internal combustion engines, that is, research on advanced, low-temperature combustion processes or research on the unification and flexible use of various fuels for transportation, including alternative fuels of different reactivities.

#### **Acknowledgements**

Authors wish to thank to the Ministry for Science and Higher Education in the Republic of Poland for their financial support of this work.

*Numerical and Experimental Studies on Combustion Engines and Vehicles*

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*DOI: http://dx.doi.org/10.5772/intechopen.93572*

*Application of Variable Compression Ratio VCR Technology in Heavy-Duty Diesel Engine*

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[9] Woś P, Jakubowski M. Variable Compression Ratio Engine. Patent No. 217826. Warsaw: The Patent Office of the Republic of Poland; 29 August 2014

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[7] Moteki K, Aoyama S, Ushijima K, Hiyoshi R, Takemura S, Fujimoto H, et al. A study of a variable compression ratio system with a multi-link mechanism. SAE Paper No. 2003-01-0921. Warrendale PA,

Jakubowski M, Kuszewski H, Lejda K, Ustrzycki A. Design of Affordable
