SYstems for COnversion of MOtions and REnewable ENergies Motors
& Pumps
PRBC Concept

STIRLING's engines

Back to the main menu


1. Some facts 2. Sources of usable energies on a vehicle 3. Hybrid architectures 4. Specifications overview

The machines which are or will be presented in the column "motors & pumps" have been designed in the perspective to create thermal engines with ecological vocation. Naturally, from a motor mechanism, it is easy to convert the engine in pump or compressor.

The analysis which follows, rigorous and without concession, demonstrates that the current pollution due to to the road transportation is not directly connected to thermal engines, but to 3 factors bringing in them indirectly, by lessening importance:
* their misuse which is made
* their overconsumption of fossile fuels
* the very numerous chronic defects inherent to the binding kinematics of the mechanism piston / connecting rod / crankshaft

After this study, it becomes possible to define the specifications,
particularly ambitious and requiring, for engines of new generation designed by SYCOMOREEN.

1. Some facts

1.a) The internal combustion engines : an eternal success ?

             Most of the ground vehicles are moved by internal combustion engines. They have 2 main representatives:  gasoline engines with piloted ignition and Diesel engines with spontaneous ignition. These 2 types of engines have been produced mainly throughout the twentieth century thanks to the massive extraction of low-cost oil and gasoline. Nowadays, the differences between "Diesel" and "gasoline" is weaker and weaker.

            The success which knew these 2 technologies is largely due to fuels which they use. Hydrocarbons are indeed easily transportable and transvasable under liquid shape. Furthermore, thanks to the present dioxygen everywhere in the atmosphere, the chemical energy-to-weight that they can release is very high regarding those of other sources, what gets a strong autonomy for the vehicle. Besides, this chemical energy is easily produced by combustion with the dioxygen of the air. Gases under pressure so created exercise then mechanical constraints on parts in movement, generally transformed into continuous rotation motion by a kinematic chain.

However, the success of internal combustion engines, if it is still very present, gets out of breath for the following reasons:

* Exhaustion of the reserves of hydrocarbons (from 30 to 100 years according to the estimations)
* Extremely important taxes on fuels (approximately 250 %, various with the considered country)
* Engendered atmospheric pollution, mainly by oxides of nitrogen and carbon             

Some comments are necessary to precise what precedes:

* first point

            The exhaustion of the oil reserves does not mean for all the death of internal combustion engines. For the evoked reasons higher, this source of energy remains still indispensable for a vehicle from the point of view of its autonomy : other currently known sources of energy and potentially implantable on a vehicle, which are studied now for several years, even around twenty years (electric, hydraulic, pneumatic, hydrogen fuel cell, wind, solar energies), get an autonomy for the vehicle about 200 km or miles in the best case, because of an insufficient energy-to-weight ratio of such of "fuels" . The nuclear energy, used on submarines and aircraft carrier, is not possible for an automobile because it requires very big volumes for the devices of thermal exchanges between " warm irradiated water " and " cold not irradiated water ", as well as surrounding anti-radiationwalls. Furthermore, the radioactivity raises big problems in the event of an accident breaking the reactor.

        For sources of energy not embarked on the vehicle as the solar or wind energies, each will agree that they are far too much unpredictable for a ground vehicle, although they are attractive on the ecological plan. Their return is also very weak (generally less than 20 %).

        Furthermore, let us indicate that even in the absence of fossil reserves of hydrocarbons, mankind  is capable of making it in a most ecological way, for example by cultures of colza, we can obtain diesters used on the vehicles of competition such as Peugeot 406 "Pique" and "Coeur" which obtain ten years ago very honorable performances (approximately 170 HPs). Finally, we know how to make industrially big quantities of alcohol, and certain manufacturers studied the possibility of using it as fuel, even for greedy vehicles (Ford Taurus, "flex fuel" models), from the culture of sugar cane, either by means of biomass gazeification with the final reaction: 

industrial synthesis of methanol with catalytic process

* Second point

            The levy of the fuel by the States of industrial nations represents an enormous financial basket. We can simply indicate that the justification of this levy by ecological reasons isn't serious at all. Hydrocarbons are simply taxed because they represent 90 % of the energy used by vehicles, what allows automatically big comebacks of money.

        To summarize us, whatever is the considered source of energy, it is the one which is used mainly at some point which is surcharged independently of quite other consideration. The levy of hydrocarbons is not thus really a danger for internal combustion engines, because if another source of energy becomes widespread, this will thus be surcharged, so penalized, and this in favour of hydrocarbons.

* Third point

            The third point is by far the most important. The atmospheric pollution engendered by internal combustion engines is not indeed questionable and it is the main acceptable argument which questions the future of the internal combustion engine such as we know it today.

This pollution has a double impact :

Impact on the health of the population

The effects of exhaust gases, because of various toxic elements (carbon monoxides COx, nitrogen oxides NOx, derived of unburned hydrocarbons  HC, ozone O3, diverse dusts) are known still quantitatively badly, but qualitatively better encircled: more frequent and more severe asthma attacks, chronic respiratory difficulties, allergies, diverse cancers …

Impact on the planet Earth

It is due to the carbon dioxide CO2 which is a greenhouse gas. Recently, an unanimous consensus exists among the meteorologists and the scientists on the following facts:

1. There is well and truly a global warming of the planet since approximately one century.

2. This reheating is abnormal by the speed in which it occurs, 100 years being an extremely short duration in the temporal scale of the "normal" climate changes of the earth.

3. This reheating is widely attributable in the human activities which released millions of tons of CO2 in the atmosphere by exploiting fossil fuels as hydrocarbons and coal.

massive release of CO2 in the atmosphere.

Internal combustion engines are then on the target, although it is necessary to put in perspective their role. The diverse factories, the incinerators, the heating of dwellings or the thermal power plants using petroleum or coal have a role at least equivalent to that of the engines. However, this is not  a reason for not to wonder about the pollution of engines and to try to limit it.
COx/NOx pollution of transportation

Let us clarify here certain points. The pollution of a vehicle riding on clear road, at practically constant speed, in a suitable driving regime allowing an optimal thermodynamic return for the engine, is acceptable: on one hand, we shall have the weakest consumptions for the automobile, on the other hand, the volume of exhaust gas rejected by km is weak as far as the speed of the car is suitable (more than 50 km/h), what means that the air is not strikingly polluted by the passage of the car. Finally, the concentration of population on such roads is weak, what means that few persons will inhale the polluted air, and that, even if they inhaled it, this would not be dramatic for their health because it would not too much be polluted.

            Contrary to the pollution of a vehicle in an urban environment which is unacceptable for 2 main reasons :

*  It is extremly important because of the combination of several factors :

                   -  The high concentration of vehicles, which is polluting in itself, leads to phenomena amplifying even more this pollution :

- Slowings down, synonyms for accelerations and for frequent brakings and for losses by Joule effect : there is overconsumption of fuel, thus overpollution..

- Engines working at low rpm with a practically stopped vehicle: not only engines have no thermodynamic optimal return, but in more they work " for nothing " because the vehicle don't need power in this case.

- The exhaust gases are confined in limited areas which are insufficiently aerated by the wind : spaces between stopped cars or between buildings, etc…

* Cities include an important population. It is not thus acceptable for the health of this population that the air is polluted there. The nose and the mouth of the children are notably at the level of mufflers, really in the worst place!

smog of megalopolises

        In spite of all these problems, 99.9 % of the ground vehicles use internal combustion engines as unique mechanical source of energy. The manufacturers and States "mobilize" themselves in a particularly shy way to develop alternative solutions, and the population complains more about the noise and the problems of car park of the automobiles than about gases which they are emitting. Yesterday as today, internal combustion engines continue to know a real, but unfounded success, because no one seems to have anything better.

1.b) The internal combustion engines : harmful invention ?

        At this step of our analysis, internal combustion engines appear as a necessary invention to move, because the energy which they use is easy to exploit, but terribly polluting, notably in city. But must we necessary disdain this technology? In fact, internal combustion engines are victims of their absurd use, wich is the result of complex socio-economic and potilitical couplings.          

Quite as a pencil is very useful to write and very dangerous if we plant him in the eye of your neighbour, internal combustion engines are very useful to move, but dangerous if they are badly used, what is regrettably the case. Their mode of functioning is indeed totally unsuitable for the use which is made on urban routes:           

* The car burns fuel even when it is stopped, what can be 30% of the duration of an urban itinerary : this is a nonsense so economic as ecological.

* The available power, even with small capacities vehicles ("city car"), is disproportionate with regard to the real needs of an urban itinerary : and so except the periods of stop, the speed limits and the corks make that the vehicle rarely uses more than 50 % of its resources (Cf. fig. 1.).

15 à 30 Ch are largely sufficient for running a vehicle  from 0 to 50 km/h in a relatively short duration, as the theorem of kinetic energy demonstrates it :      

where m is the mass of the vehicle (1000 kg), vmax its running speed (50 km/h), v0 its intial speed (0 km/h), P the power delivered by the motor (20 Ch, equal to 14.3 kW) and Dt the necessary duration for changing the speed from v0 to vmax.

In this calculation, all the friction to the progess of the vehicle (tires, imperfect transmission) and the aerodynamic resistance have been neglected , what is a good approach below 50 km/h.

The numerical result is Dt = 6.75 s, what is not so long after a red light of one minute and the other one 100 m farther.

To end, the internal combustion engine is not harmful, but the usage which is made is it enormously !
It is radically necessary to change the way we use it... but how?

1.c) How to use in best an internal combustion engine ?

            All which precedes shows the necessity of adding to internal combustion engines one or several other sources of mechanical energy with different advantages which would allow to pollute less during urban routes, and perhaps even not to pollute any more. Particulary in the stop, the ideal would be to consume no energy, what is very logical and seems regrettably not to be evident for everyone.            

            We have just put a major idea in the problematics of design. The most known example is the thermal / electric hybrid engine which only some very rare Japanese manufacturers like Honda or Toyota succeeded in industrializing recently, although the idea dates more than 50 years ago!  (Cf. Fig. 2.)

Architecture the hybrid motorised device of the "Honda IMA"Electrical reversible engine (motor/generator) of the Honda IMA

Fig. 2

Motorized device of the Honda IMA (Integrated Motor Assist) :

We distinguish to the left a 4 cylinders engine followed by a very compact electric motor directly coupled on the crankshaft, then, to the right, by the transmission towards the gearbox. On the right, the sight of the windings of the electric engine of only 65 mm in thickness. This engine develops 6 kW at 1000 rpm, what allows to increase the engine torque of 5.7 daN.m, that is approximately 1/3 of the total couple that the motorized group can deliver.

1. Some facts 2. Sources of usable energies on a vehicle 3. Hybrid architectures 4. Specifications overview
SYstems for COnversion of MOtions and REnewable ENergies Motors
& Pumps
PRBC Concept
Back to the main menu