Presentation of Four-stroke Engine Design Elements

Email: rvvpetrescu@gmail.com Abstract: Having escaped the shadow of the global energy crisis by implementing nuclear fission, wind, solar, bioenergy, but also by producing and extracting (deep) gases capable of providing us with planetary reserves for two more. Or at least three thousand years, we have started to relax more energetically, but due to the huge pollution produced by cars, the rules of their increasingly drastic operation are constantly imposed, the cars always being equipped with new devices capable of reducing the level of the harm produced by them. The work presents a few original elements about the dynamic and kinematics of piston mechanism, used like motor mechanism from OTTO engines. One presents an original method to determine the efficiency of the piston mechanism used like a motor mechanism. With the relations of motor efficiency and piston acceleration on optimizing the Otto mechanism, which is the principal mechanism from internal-combustion engines. This is the way to diminish the acceleration of the piston and to maximize the efficiency of the motor mechanism. One optimizes the constructive parameters: e, r, l, having in view the rotation speed of drive shaft, n.


Introduction
The problem of replacing thermal motors with electric motors and vehicles equipped with internal combustion engines on gasoline, diesel or gas, with vehicles equipped with electric motors is becoming more and more pronounced.
Having escaped the shadow of the global energy crisis by implementing nuclear fission, wind, solar, bioenergy, but also by producing and extracting (deep) gases capable of providing us with planetary reserves for two more or at least three thousand years, we have started to relax more energetically, but due to the huge pollution produced by cars, the rules of their increasingly drastic operation are constantly imposed, the cars always being equipped with new devices capable of reducing the level of the harm produced by them.
Today, there are possibilities to create petroleum fuels from water or air using only photovoltaic solar energy, which would guarantee the production of classic fuels in any quantity to infinity, not to mention the fact that the gas extracted from the deep can be processed (in large plants) in liquid gases, diesel, gasoline or kerosene, they are now extracted in huge quantities for large periods of time, with the possibility of their permanent restoration. In addition, the humanity that has already tasted from the world energy crisis several times in a row has learned the mind and has taken drastic measures that now allow us even an energy relaxation.
One has additional fuels, bio, from vegetable oils, from algae, from plantations, or we can use hydrogen as a fuel and it can be extracted in any quantity by various methods, including from the water.
Today, fuel cell-type cars are already circulating that burn hydrogen in cells, in order not to explode and the heat obtained is chemically transformed into electrical energy stored in large lithium-ion batteries.
Already operating for about 20 years all kinds of hybrid vehicles, with combined solutions, gasolineelectric, diesel-electric, gas, gas-electric and all kinds of other possible variants, along with cars equipped with increasingly efficient electric motors, with increasing autonomy and shorter loading times.
We are constantly trying and improving the solutions with magnetic motors even though the life of the magnetized materials is still very short. There are also attempts to put the Watt or Stirling type external combustion thermal engines back into operation, some of them being successful.
In countries like Brazil, the USA, Germany, large quantities of biofuels, such as vegetable oils or vegetable alcohols, are used.
New and emerging solutions are always being tested, including cars with water, which could change the face of the world once started.
However, considering that the fleet of cars equipped with internal combustion thermal engines has far exceeded one billion worldwide and approximately 100 million cars equipped with the classic Otto engines are produced and introduced into circulation annually, the most immediate measure of reducing fuel and energy consumption, as well as of the harm produced by all these cars, their continuous improvement remains (Aabadi, 2019;Antonescu and Petrescu, 1985;1989;Antonescu et al., 1985a;1985b;1986;1987;1988;1994;

Materials and Methods
The paper presents an original method of studying PISTON mechanisms used in internal combustion engines.
There are several diagrams, which take into account the acceleration of the piston according to the rotation angle of the crank. The efficiency of the entire mechanism is specified in each diagram, so that the designer (the motorist) can select the optimum dimensions of the elements of the mechanism (optimum design of the mechanism), according to the required input parameters, so that the motor mechanism works with maximum efficiency and keep the maximum acceleration values within normal allowable limits, regardless of the speed at which the engine will operate. The basic input elements (input parameters) are the crank length, r, connecting rod length, l, piston working axis offset relative to crank axis (motor shaft), e and engine working speed (shaft speed). motor). The main output parameters that need to be optimized are the piston acceleration, a and the total mechanical efficiency of the crank-piston-crank system, η.
The study is kinematic, but given that the total efficiency of the motor mechanism is constantly being pursued, it is possible to speak of a dual, kinematicdynamic method.
In Fig. 1 you can see the diagram of the acceleration of the piston according to the rotation angle of the cam: The efficiency of the motor mechanism is about 60%. A lower r/l ratio increases the efficiency of the mechanism and e will decrease efficiency when it takes values other than zero. Engine speed (motor shaft) does not directly influence the efficiency of the mechanism, but its increase produces a rapid increase in piston acceleration. As the peaks of the acceleration can be reduced by reducing the ratio r/l, we will observe how this reduction of the ratio r/l, is beneficial for both low values of acceleration as well as high values of efficiency.
In Fig. 2 the ratio r/l decreases to 0.66 and the yield increases to about 84%.
In Fig. 3 we continue to reduce the ratio r/l to 0.33 and we observe an increase in efficiency to 96%.
In Fig. 4 r/l becomes 0.23 and the efficiency of the motor mechanism acquires a comfortable value of about 98%, which would be sufficient for normal functioning of the mechanism and any further decrease of the r/l ratio appears as unnatural from this point of view. (further reduction of the r/l ratio is no longer necessary after reaching a practical efficiency of 98-99%. However, this reduction may be required for objective reasons when we want to greatly increase engine speed and the maximum acceleration must be maintained. within permissible limits, for example not to exceed the critical threshold of 100,000 [m/s 2 ]).  Fig. 6 r/l becomes 0.1 and η = 0.99666, a yield value that can be considered 100%.
In Fig. 8 the deviation e takes different values from zero e = -0.2 [m], r/l = 0.3 and the efficiency of the motor mechanism decreases considerably η = 0.45.

Fig. 3:
One continue to reduce the ratio r/l to 0.33 and we observe an increase in efficiency to 96% In Fig. 13 it return to the zero-disassembly mechanism (e = 0); r/l = 0.033 and we are now increasing the engine speed to n = 5500 [rot/min]. The In Fig. 16 we raise the engine speed to 30000 [rot/min] and the maximum piston acceleration takes about 100,000 [m/s 2 ]. Now a threshold (critical-limit value) has been reached for accelerations, so if we want to continue increasing the engine speed, the only possible way is to further decrease the ratio λ = r/l. In Fig. 17 the r/l was reduced to only 0.01 and the efficiency increased to about 99,997%; we remained at the engine speed of n = 30000 [rot/min], but the maximum acceleration decreased to only about 30000 [m/s 2 ]. Now we can further increase the engine speed to 40,000 [rot/min] and the maximum piston acceleration becomes about 55000 [m/s 2 ] (Fig. 18).
In Fig. 19 shows the piston acceleration diagram for a motor speed of 50,000 [rot/min]. The acceleration becomes 80000 [m/s 2 ].

Result and Discussion
The calculation relationships used written in the excel program are given in Table 1.
The most interesting situations were considered so that a builder of internal combustion thermal engines can choose the desired case depending on the constructive parameters desired in the design.   The computational relationships used to determine the total mechanical efficiency of the motor mechanism are original and they are synthesized by the authors through a personal method.
If one try to use the reverse piston mechanism, as a compressor mechanism and not a motor, we were surprised to find that the calculation relationships for determining the efficiency of the compressor mechanism change and the values that can be obtained for the effective efficiency of the compressor are generally much lower. than those of the piston, the maximums being somewhere between 50 and 60%. It can be seen here that the use of the engine mechanism in compressor mode is not efficient.
At the proposed engine mechanisms, at which the ratio λ = r/l decreases greatly, the piston-h stroke decreases and it is proportional to the crank length-r, so if we want to keep the cylinder intact (unchanged) we will have to increase the bore-R. For a decrease of r times n, R will increase √ (n) times. The problem arises only for overfilled motors, where the required cylinder size may be smaller, so that the bore increase may be slightly lower. Even under these conditions, very high-speed engines will have an almost imperceptible stroke and a very high bore.
Some diagrams of the piston acceleration, no longer look like the conventional ones ( Fig. 1, 2 , 8, 9, 10, 11 and 12). Their modified appearance has been specially introduced to highlight the different possible functional regimes of the piston (engine) mechanism. Even if some of them achieve very low yields, they may be usable for some specialized mechanisms! The OTTO piston mechanism, however, will operate at maximum efficiency, only when used as a motor mechanism, as if it were predestined for this mode of work.

Conclusion
Today, there are possibilities to create petroleum fuels from water or air using only photovoltaic solar energy, which would guarantee the production of classic fuels in any quantity to infinity, not to mention the fact that the gas extracted from the deep can be processed (in large plants) in liquid gases, diesel, gasoline or kerosene, they are now extracted in huge quantities for large periods of time, with the possibility of their permanent restoration. In addition, the humanity that has already tasted from the world energy crisis several times in a row has learned the mind and has taken drastic measures that now allow us even an energy relaxation. We have additional fuels, bio, from vegetable oils, from algae, from plantations, or we can use hydrogen as a fuel and it can be extracted in any quantity by various methods, including from the water.
Today, fuel cell-type cars are already circulating that burn hydrogen in cells, in order not to explode and the heat obtained is chemically transformed into electrical energy stored in large lithium-ion batteries.
Already operating for about 20 years all kinds of hybrid vehicles, with combined solutions, gasolineelectric, diesel-electric, gas, gas-electric and all kinds of other possible variants, along with cars equipped with increasingly efficient electric motors, with increasing autonomy and shorter loading times.
We are constantly trying and improving the solutions with magnetic motors even though the life of the magnetized materials is still very short.
There are also attempts to put the Watt or Stirling type external combustion thermal engines back into operation, some of them being successful.
In countries like Brazil, the USA, Germany, large quantities of biofuels, such as vegetable oils or vegetable alcohols, are used. New and emerging solutions are always being tested, including cars with water, which could change the face of the world once started.
However, considering that the fleet of cars equipped with internal combustion thermal engines has far exceeded one billion worldwide and approximately 100 million cars equipped with the classic Otto engines are produced and introduced into circulation annually, the most immediate measure of reducing fuel and energy consumption, as well as of the harm produced by all these cars, their continuous improvement remains.
The computational relationships used to determine the total mechanical efficiency of the motor mechanism are original and they are synthesized by the authors through a personal method.
If one try to use the reverse piston mechanism, as a compressor mechanism and not a motor, we were surprised to find that the calculation relationships for determining the efficiency of the compressor mechanism change and the values that can be obtained for the effective efficiency of the compressor are generally much lower. than those of the piston, the maximums being somewhere between 50 and 60%. It can be seen here that the use of the engine mechanism in compressor mode is not efficient.
At the proposed engine mechanisms, at which the ratio λ = r/l decreases greatly, the piston-h stroke decreases and it is proportional to the crank length-r, so if we want to keep the cylinder intact (unchanged) we will have to increase the bore-R. For a decrease of r times n, R will increase √ (n) times. The problem arises only for overfilled motors, where the required cylinder size may be smaller, so that the bore increase may be slightly lower. Even under these conditions, very high-speed engines will have an almost imperceptible stroke and a very high bore.
Some diagrams of the piston acceleration, no longer look like the conventional ones ( Fig. 1, 2 , 8, 9, 10, 11 and 12). Their modified appearance has been specially introduced to highlight the different possible functional regimes of the piston (engine) mechanism. Even if some of them achieve very low yields, they may be usable for some specialized mechanisms! The OTTO piston mechanism, however, will operate at maximum efficiency, only when used as a motor mechanism, as if it were predestined for this mode of work.

Acknowledgement
This text was acknowledged and appreciated by Dr. Veturia CHIROIU Honorific member of Technical Sciences Academy of Romania (ASTR) PhD supervisor in Mechanical Engineering.

Ethics
This article is original and contains unpublished material. Author declares that are not ethical issues and no conflict of interest that may arise after the publication of this manuscript.  Applied Sci., 9: 202-212. DOI: 10.3844/ajeassp.2016.202.212 Akhesmeh, S., N. Pourmahmoud andH. Sedgi, 2008. Numerical study of the temperature separation in the ranque-hilsch vortex tube. Antonescu, P., F. Petrescu and D. Antonescu, 1997. Geometrical synthesis of the rotary cam and balance tappet mechanism. Bucharest, 3: 23-23. Antonescu, P., F. Petrescu and O. Antonescu, 1994. Contributions to the synthesis of the rotating cam mechanism and the tip of the balancing tip. Brasov. Antonescu, P., F. Petrescu and O. Antonescu, 2000a. Contributions