** **

**V Engine Design**

** **

** **

*ABSTRACT:*

*V engines in a characteristic aside, their reply kinematics-dynamic (operating in a dynamic viewpoint) is closely linked to constructive parameters of the engine, especially the constructive angle. For this reason, as generally constructive value angle was chosen randomly, after various technical requirements constructive or otherwise, inherited or calculated by various factors (more or less essential), but never got to discuss crucial factor (which takes account of the intimate physiology of the mechanism) angle that is constructive with his immediate influence on the overall dynamics of the mechanism, the actual dynamics of the mechanism with the main engine in the V suffered, the noise and vibration are generally higher compared with the similar engines in line. This paper aims to make a major contribution to remedy this problem so that the engine in V can be optimally designed and its dynamic behavior in the operation to become blameless, higher than that of similar engines in line. Theoretical calculations are difficult and complex, but the alteration constructive required of them is simple, consisting of the imposition of a list of constructive values of the angle alpha from which you can select the most convenient for each engine builder in V.*

**INTRODUCTION**

** **

Kinematics and dynamic synthesis of V engines can be done according to the constructive alpha angle (a). This constructive angle alpha (see Figure 1) was elected in generally follow different criteria or design requirements (it is determined by the number of cylinders and the condition for obtaining the ignitions uniformly distributed). This work proposes aggregating this angle after rigorous kinematics-dynamic criteria, so that the V engine obtained works silently, with vibration and noise much lower. It is even mainly disadvantage of a motor in V namely that it works with higher vibrations compared with a same power engine in line [1, 6-12].

The authors have studied this works for several years together with a collective joint research (UPB-Autobuzul plant) and dynamic behavior of the V engines [6-8], the level of vibration and noise produced, the level of vibration transmitted inside the vehicle, the possibility of limiting them through various solutions of gripping and containment of the engine. Results were good but not very good. After similar measurements done on other types of engines it was decided the use of engines in line, much quieter than the V. Meanwhile engines have improved but also international standards that limit vibration and noise levels have become more demanding. The engine in V has many fans, it is more compact, more dynamic, more robust, stronger, and higher operating efficiency compared to similar engines in line. But its fans are not only racing fans, motor and habit, there are a wide audience of consumers who want only cars equipped with nerve in V. As to conciliate them well and those who make rules to limit emissions of cars, it was thought that paper aims to provide an equitable solution regarding engines in V.

Fig. 1

** **

After decades of work in the mechanisms and machinery field, through experience, I noticed an interesting fact. At the engines in line forces and velocities transmission is normal from the driver (motor) shaft (from the crank shaft) to the pistons (through the rods), and vive versa (in the engine times). The engine in V transmission forces and velocities between elements is forced and unequal regardless of the meaning of transmission (from crank to pistons or from pistons to crank). Dynamics imposed to the main piston is one, and the secondary piston is required other, so that dynamic speeds (actual speeds required) differ, and with them and pistons to crank feedback (to crank shaft), as each would require another main shaft speed. If that’s a pair of pistons, for more pairs of pistons jerk resultant operation will be more and more powerful. Obvious solution is to optimize the dynamic of each pair of pistons in hand. This optimization was based on dynamic coefficients of each piston. Dynamic coefficient of a piston showing the actual crank angular velocity varies compared to required average angular velocity imposed by the motor shaft rotation speed. This variation [3, 4] is due to several factors, kinematics and dynamic, being itself a function and of engine constructive parameters.

The usual mechanisms have a single dynamic factor (coefficient), as is the case and in-line engines.

At the engine in V appear two dynamic factors imposed to the crank (and to the crank shaft) by the two pistons linked together (secondary piston rod link to the main piston rod; see the figure 1). The two dynamic factors differ among themselves and changes their values permanently depending on the crank angle position (crank shaft position).

This indicates that each piston (the primary and secondary) tries to impose its dynamic to the main shaft, so that the end result is an operation to struggle, since the two sets of pistons shoot one at one side and the other somewhere else.

The possible solution (unique solution) is matching the two dynamic factors. More specifically to write a mathematical relationship to match the main piston (main engine) dynamic coefficient expression with that of the secondary piston (secondary motor) (Now you can see that engine in V is built of two engines merged, see the fig. 1). Relations that results are quite complicated [5].

Optimization based on obtained relationship can be made in several ways. The most natural seems to be the optimization parameters in view of the engine builders of the V, particularly based on constructive angle alpha, which appears twice in the cinematic scheme of an engine in V: first he is mounting angle formed by the two axes of the two pistons coupled (angle formed by the axis of the main piston guide axis with the secondary piston guide axis); and the second time this item (constructive angle) appears on the element 2 (the rod of the main piston) between the two arms of the element 2 (AB and AC).

**SYNTHESIS OF THE ENGINE IN V**

** **

**3.1. Presentation**

In figure 1 is shown a V engine cinematic scheme.

The crank 1 rotates counterclockwise sense with angular velocity w and acts the rod 2 which moves the main piston 3 along the axis DB; the crank 1 acts and the rod 4 which in turn push or pull the piston 5 along the axis DD. Hence the constructive angle a between the two axes DB and DD. The same angle a consists of two arms of the rods 2; the first arm has a length l, and the second has the length a; this length a, plus the length b of the rods 4 must recompose the length of the first rods, l (a+b=l).

Driving force of the crank F_{m} is perpendicular to the crank arm r, in A. A part of it (F_{Bm}) is transmitted to the first arm of the connecting rods 2 (along l) towards the main piston 3. The second part of the driving force (F_{Cm}) is forwarded to the secondary piston 5, by the second arm of the first rod (along a).

**3.2. Forces and velocities**

A part x of the drive force F_{m} is transmitted towards the first piston (the element 3) and another part of it y is forwarded through the second piston (the element 5); sum of two parts x and y is 1 or 100% taken as a percentage.

The dynamic velocities have the same direction with forces [3-5], unlike the kinematic velocities imposed by the coupling links.

From the element 2 (the first arm of the first rod) forwarded through the main piston (the element 3) the force F_{B} and the velocity v_{BD}.

The kinematic velocity (imposed by linkages) of the point B has the known value v_{B} [5], generally different from the dynamic value v_{BD}. To force the main piston has a velocity equal to the dynamic (the real velocity) incorporate the dynamic coefficient D_{B}, (D_{B}=x.cos^{2}β with v_{BD}=D_{B}.v_{B}), so the dynamic speed is equal to the product between the cinematic velocity and dynamic coefficient D_{B}.

The driving velocity (with the same direction as the driving force and the same sense with this) is given by the relation (v_{m}=r.w).

In C, F_{Cm} and v_{Cm} are projected in F_{Cn} and v_{Cn}. They in turn are projected in D (on the DD axis) in the components F_{D} and v_{D} (dynamic velocity of the second piston). The cinematic (classic) velocity has another expression, ṡ_{D}. Now one introduces the second dynamic coefficient (from the second piston), D_{D} [5], (where *v _{D}=D_{D}.*

*ṡ*).

_{D}

**3.3. Determination of the dynamic coefficient D**

The mechanism dynamic coefficient D is imposed to all gear and influences its function varying the crank rotation speed (the crank shaft rotation velocity). Any mechanism must take practical only one dynamic factor, D.

To the engines in V the real dynamic coefficient is the result of a random momentary compromise between the two different dynamic coefficients imposed by the two pistons. For this reason the overall functioning of the V engine loud. The ideal solution (right) is obviously bringing the two dynamic factors to around or possibly even equal values. To this end were the two dynamic factors matched, to see what solutions exist to solve the obtained equation ina. The obtained expression is complex and has many variables (the various builder parameters of the engine in V). It sought an analytical synthesis using a complex computer program, by finding of the system alpha general solutions, regardless of the values of others constructive parameters, so that dynamic factors present equal values, and the engine so constructed to operate high efficiency without shocks and vibrations, without noise and with reduced noxious emissions, achieved with high power and lower fuel consumption. The cinematic chain composed of crankshaft, two pistons and two rods should function normally.

Fig. 2

Fig. 3 Fig. 4

**DYNAMIC ANALYSIS**

Analysis of dynamic system revealed a range of values for angle alpha that the theory exposed are likely to lead to the synthesis of V-optimal engine (see the table 1) [5].

For some constructive parameters randomly taken (r=0.01 [m], l=0.1 [m], a=0.03 [m], b=0.07 [m]) and for a chosen speed of motor shaft (n=5000 [r/m]), it obtains three different diagrams for the displacement and acceleration of the pistons, corresponding to three alpha angles chosen randomly (5^{0}, 75^{0} and 95^{0}), (see the figures 2-4).

Value of five degrees are at the beach of values indicated as appropriate, so that acceleration peaks hardly exceed the value of 1000 [m/s^{2}] to both pistons (see the figure 2).

Diagrams in figures 3 and 4 are somewhat similar (but not identical) and present relevant cases also, even if the acceleration peaks have increased at about 3500 [m/s^{2}] for the secondary piston and approximately 30,000 [m/s^{2}] for the main piston. The angles of 75 and 95 degrees can also be used (at least for the indicated constructive parameters), to take into account and ignition requirements uniformly distributed.

A V-engine which reaching local at the primary piston a peak of acceleration of 30000 [m/s^{2}] to a motor shaft speed of 5000 [r/m] (it comes only a local impact) will work similar to engines in line but the power and efficiency higher.

However the use for alpha of constructive values shown in the table 1 may lead to the construction of a V engine quieter than the one in line.

Fig. 5

**CONCLUSIONS**

** **

SPECIFICATIONS: Acceleration diagrams presented were constructed based on an original method; they are the result of complex calculations with dynamic accelerations and dynamic coefficients which contain the vibrations and pulses; the relationships of calculation can not present classical accelerations known!

A-When shocks are very small, diagrams show even the accelerations.

b-When the shocks are visible the diagrams show the accelerations and their peaks.

c-When the shocks are large or very large, the diagrams will present only the shocks; in this case the accelerations overlapping shocks; accelerations are lower than the shocks and no longer can see (these cases but would not be desirable).

With the values in the table of constructive angle alpha can synthesize a quieter engine in V, regardless of the values of other constructive parameters of the engine.

A first observation arising from reading the values indicated for optimal alpha angle from the table, is that the values close to 90 degrees aren’t present, and in general for these values design software looks a worse dynamics of engine in V. But that these values are used specifically to build engines in V, values determined by the number of cylinders and the condition for obtaining the ignitions uniformly distributed.

For the alpha values who do not appear in table, the built engine works with very large shocks which very difficult can be isolated even with the most modern rubber pads so that vibrations are felt in the vehicle interior, bringing with them uncomfortable and insecure amplified and by the unnatural noises produced by shock.

An important observation would be that today are used “new cinematic schemas of engines in V” (see the figure 5) which to eliminate the vibrations have a single piston mounted on a spindle maneton and have inclined the axes first to right the second to left to give the appearance of the engine in V. It’s a pseudo-engine in V and the added efficiency disappears. The cylinders capacity should be increased to mimic the engine power in V, but also increases fuel consumption.

In this way, and the cylinders in line can be considered an engine in V with alpha of 0 degrees and boxer cylinders may be considered a V engine with alpha of 180 degrees.

**REFERENCES**

** **

[1] GRUNWALD B., *Teoria, calculul şi construcţia motoarelor pentru autovehicule rutiere*. Editura didacticã şi pedagogică, Bucureşti, 1980.

[2] Petrescu, F.I., Petrescu, R.V., *Câteva elemente privind îmbunătăţirea designului mecanismului motor,* Proceedings of 8^{th} National Symposium on GTD, Vol. I, p. 353-358, Brasov, 2003.

[3] Petrescu, F.I., Petrescu, R.V., *An original internal combustion engine, *Proceedings of 9^{th} International Symposium SYROM, Vol. I, p. 135-140, Bucharest, 2005.

[4] Petrescu, F.I., Petrescu, R.V., *Determining the mechanical efficiency of Otto engine’s mechanism,* Proceedings of International Symposium, SYROM 2005, Vol. I, p. 141-146, Bucharest, 2005.

[5] Petrescu, F.I., Petrescu, R.V., *V Engine Design,* Proceedings of International Conference on Engineering Graphics and Design, ICGD 2009, Cluj-Napoca, 2009.

[6]. FRĂŢILĂ, Gh., SOTIR, D., *PETRESCU, F*., *PETRESCU, V.,* ş.a. *Cercetări privind transmisibilitatea vibraţiilor motorului la cadrul şi caroseria automobilului.* În a IV-a Conferinţă de Motoare, Automobile, Tractoare şi Maşini Agricole, CONAT-matma, Braşov, 1982, Vol. I, p. 379-388.

[7]. MARINCAŞ, D., SOTIR, D., *PETRESCU, F*., *PETRESCU, V.*, ş.a. *Rezultate experimentale privind îmbunătăţirea izolaţiei fonice a cabinei autoutilitarei TV-14.* În a IV-a Conferinţă de Motoare, Automobile, Tractoare şi Maşini Agricole, CONAT-matma, Braşov, 1982, Vol. I, p. 389-398.

[8]. FRĂŢILĂ, Gh., MARINCAŞ, D., BEJAN, N., FRĂŢILĂ, M., *PETRESCU, F.,* *PETRESCU, R.,* RĂDULESCU, I. *Contributions a l’amelioration de la suspension du groupe moteur-transmission. *În buletinul Universităţii din Braşov, Seria A, Mecanică aplicată, Vol. XXVIII, 1986, p. 117-123.

[9]. Fjoseph L. Stout – Ford Motor Co., I. *Engine Excitation Decomposition Methods and V Engine Results.** *In SAE 2001 Noise & Vibration Conference & Exposition, USA, 2001-01-1595, April 2001.

[10]. D. Taraza, “Accuracy Limits of IMEP Determination from Crankshaft Speed Measurements,” *SAE Transactions, Journal of Engines *111, 689-697, 2002.

[11]. FROELUND, K., S.G. FRITZ, and B. SMITH., *Ranking Lubricating Oil Consumption of Different Power Assemblies on an EMD 16-645E Locomotive Diesel Engine*. Presented at and published in the Proceedings of the 2004 CIMAC Conference, Kyoto, Japan, June 2004.

[12]. Leet, J.A., S. Simescu, K. Froelund, L.G. Dodge, and C.E. Roberts Jr., *Emissions Solutions for 2007 and 2010 Heavy-Duty Diesel Engines*. Presented at the SAE World Congress and Exhibition, Detroit, Michigan, March 2004. SAE Paper No. 2004-01-0124 , 2004.

Authors:

**Florian Ion Petrescu**, **PhD. Eng.** Lecturer at Polytechnic University of Bucharest, TMR Department (Theory of Mechanisms and Robots Department), petrescuflorian@yahoo.com, 0214029632;

**Relly Victoria Petrescu, PhD.** **Eng.**, Lecturer at Polytechnic University of Bucharest, GDGI Department (Department of Descriptive Geometry and Engineering Graphics), petrescurelly@yahoo.com, 0214029136.

** **

_{ }

p.MsoNormal, li.MsoNormal, div.MsoNormal { margin: 0mm 0mm 0.0001pt; font-size: 12pt; font-family: “Times New Roman”; }a:link, span.MsoHyperlink { color: red; text-decoration: underline; }a:visited, span.MsoHyperlinkFollowed { color: purple; text-decoration: underline; }span.shorttext { }span.mediumtext { }div.Section1 { page: Section1; }div.Section2 { page: Section2; }ol { margin-bottom: 0mm; }ul { margin-bottom: 0mm; }