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

the thermodynamic conditions in the combustion chamber, which determine the

*Numerical and Experimental Studies on Combustion Engines and Vehicles*

**2. Technical methods for implementation of variable compression ratio**

Theoretically, there are several possible methods of using the variable compression ratio VCR technology in piston engines. Some of them were used in prototype

**Table 1** schematically presents selected VCR layouts together with a brief analysis of their technical and operational features, including advantages or disadvantages in relation to the conventional construction of the engines. Noteworthy is the solution (f) of a complex lever-gear crank system, developed and applied by the French research group MCE-5 Development [2], as well as the SAAB SVC engine [3, 4], according the principle (a) and solution (c) implemented in the FEV

There are many specific and unique constructions of VCR engines or even engine

a. articulated monohead—the SAAB completely functional engine SVC [3, 4],

b. piston of variable deck height—different layouts presented by Daimler-Benz

e. secondary moving piston or valve in cylinder head—different Ford and

g. precisely shifted cylinder block—cylinder head assembly—used in authors'

Each of above are presented and widely discussed by Shaik et al. [6]. The SAAB's SVC engine according to the solution (a) has been developed earlier by Larsen [3]. The compression ratio is variable from 8:1 to 14:1. Similarly to the shifted cylinder head method (g), it reveals good compression ratio control ability, but with slight change in piston kinematics. As a common drawback of both systems, a worse reliability and durability characteristic can be pointed. The solution (b) based on piston deck height variation uses a complicated special piston construction [6]. It also does not provide easy and precise control of compression ratio. Eccentric on main bearings (c) seems to be devoid of substantial disadvantages, but it makes the crankshaft block more complex. This solution is developed by FEV and used in their concept VCR car [5]. Nissan Motors developed a multilink rod-crank mechanism [6] according to the layout (d). It provides moderate compression ratio control ability at significant change in piston kinematics. Changing compression ratio using a small chamber with moving piston/valve (e) is relatively simple method to be applied in standard engines conversion into the VCR engines. As the drawback of this manner for changing compression ratio, the poor combustion chamber

ideas and patents. **Table 1** collects the best-known approaches for VCR engine:

c. eccentrics on crankshaft bearings developed by FEV [5],

d. multilink rod-crank mechanisms developed by Nissan [7],

f. gear-based crank mechanisms by MCE-5 [1, 2],

initiation and course of combustion process.

**technology in piston engines**

Motorentechnik research engine [5].

and Ford, as well [6],

Volvo/Alvar proposals [6],

own project [8, 9].

**116**

engines and they undergo operational tests.

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 forces acting on the piston.

Despite the fact that the idea of variable-pressure VCR engines is associated with significant construction and technological complexity and many operational problems, it is estimated that it starts to become a technical standard for automotive

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

Therefore, it was accepted that development and building a prototype variable compression ratio engine, along with the acquired knowledge and experience, will allow for successive improvement of the design and, as a result, get a fully functional, unique research instrument that makes possible to perform a number of

**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

A medium-speed, liquid-cooled 4-cylinder diesel engine manufactured by VEB

*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].*

IFA-Motorenwerk Nordhausen type 4 VD 14.5/12-1 SRW was selected for the

piston engines in the near future (see **Figure 3**).

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

innovative scientific works.

research.

**Figure 4.**

**119**

Analyzing the possible solutions of VCR engines, both hypothetical constructions and actual prototype units, two general strategies for changing the value of the compression ratio during the engine run can be noticed.


**Figure 3.**

*Forecasts for the development and share of selected advanced technologies in the combustion powerdrives of motor vehicles [10].*

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

Despite the fact that the idea of variable-pressure VCR engines is associated with significant construction and technological complexity and many operational problems, it is estimated that it starts to become a technical standard for automotive piston engines in the near future (see **Figure 3**).

Therefore, it was accepted that development and building a prototype variable compression ratio engine, along with the acquired knowledge and experience, will allow for successive improvement of the design and, as a result, get a fully functional, unique research instrument that makes possible to perform a number of innovative scientific works.
