DESCRIPTION

The present invention relates to a fuel for internal combustion engines in liquid form comprising LPG, according to the general part of claim 1.

It is known that transport fuels and in particular diesel and petrol, which are mostly used especially for the transport of people and goods by wheel, are one of the main causes of poor air quality; they are indicated as one of the major causes of CO2 release in the air, giving rise to the well-known “greenhouse effect”, with the equally well-known dramatic consequences, such as the so-called “global warming”.

It is also known that, for the purposes specified above, liquefied petroleum gases, in the abbreviation LPG, are often used, which are nothing more than a mixture of low molecular weight alkane hydrocarbons, mainly composed of Propane and Butane, with small quantities of ethane and unsaturated hydrocarbons, such as ethylene and butene.

It is known that LPG is liquefied by compression at relatively modest pressures, generally comprised between 2 and 8 bars, in order to reduce the bulk thereof and to ensure that the transport thereof is more economical and can take place at room temperature. In this way, a reduction of several hundred times of the density of the mixture with respect to the gaseous state is obtained, thus reducing the volume with the same mass. By way of example only, a 40 litre methane cylinder contains about 6 kilograms of gas, compressed to over 200 bar; conversely, a cylinder with the same volume of LPG contains about 20 kilograms and consequently the energy that can be supplied is about 3 times higher.

What is important to note is that LPG is a fuel, in addition to being easily obtainable and available, with a low environmental impact and a high energy and heat output. In particular, it gives rise to much less combustion products than petrol and diesel. Again, it results in less CO2 pollution.

It is also known that endothermic engines, in particular for transport purposes, are almost always designed to use diesel or petrol or fuels having similar characteristics. It is also known that devices suitable for allowing the supply of said engines by mixing petrol or diesel with LPG, which is injected in the gaseous state into the air intake ducts, are widely known on the market. This technique is known with the term “fumigation” and generally envisages the presence of a pump that pushes the LPG, still in the liquid state, into a vaporizer which transforms it into the gaseous phase thereof. The LPG is then injected into the air intake duct. Dedicated electronics (called ECU) governs the injection timing phase of the injectors, thus determining the quantity of LPG introduced into the engine to provide the energy requirements required by the various operating phases thereof.

It is therefore intuitive to think that if it were possible to supply the engines that use diesel or petrol with a compatible fuel and with the same energy performance, which has a lower content of diesel or petrol during the combustion thereof, it would be possible to obtain releases with a lower content of pollutants and with less CO2 emission with respect to the same engine supplied completely by means of petrol or diesel respectively. The purpose of the present invention is to realise a fuel for endothermic engines in liquid form comprising LPG in order to obtain "cleaner fuels" than those currently marketed and used for said engines and which is devoid of the drawbacks manifested by similar products of a known type. This is obtained, according to the invention, by mixing LPG with an additional fuel in liquid phase in the temperature range between -80°C and +100°C, being provided that the percentage of LPG present in the mixture is at most equal to 90%.

In fact, this additional fuel will advantageously consist of petrol or diesel, but also of biodiesel, bioethanol and DME (dimethyl ether).

In particular, the additional fuel could be composed of other fuels of vegetable origin, obtained from the fermentation of vegetable oils, for example, rapeseed and palm oil belonging to the HYO (Hydrogenated Vegetable Oils) family; from ethanol s and bioethanols, and DME (dimethyl ether); from biodiesel of an animal nature, such as animal fats and oils.

As regards the temperature range mentioned above, it should be noted that, since the additional fuel could also be, in principle, different from petrol and diesel, said temperature range corresponds to the one normally present, up to the most extreme conditions, during the use of endothermic engines, explicitly wanting to exclude the use of situations in which the additional fuel is in liquid phase through cryogenic applications and particular conditions in general.

The invention also relates to particular methods for dispensing the aforesaid one.

The present invention will be described in detail below, in some particular embodiments thereof, made only by way of non-limiting example, with the help of the accompanying drawing tables, in which;

- in figs. 1 and 2 two fuel dispensing methods according to the invention are illustrated;

- in fig. 3 shows a comparative table of the emissions found in a practical lab test on the same engine using a fuel comprising 100% of diesel and a fuel made up of 50% of diesel and 50% of LPG. - fig. 4 shows the temperature and pressure measurements of a fuel made up of 50% of diesel and 50% of LPG according to one of the tests carried out, which will be better explained later.

Preliminarily, it should be noted that the invention intends to protect a fuel for endothermic engines in liquid form capable of supplying, in particular, all the engines that operate by means of the Diesel (diesel) or Otto (petrol) cycle, using the same mechanical members originally provided for in the original project, for the supply by means of diesel or petrol, respectively, without making any structural changes to said engines. It must also be considered that, from a point of view of principle, the fuels according to the invention undoubtedly use LPG and therefore must be handled with the same equipment with which said LPG is currently handled. As is known, LPG is stored in normal pressure tanks and therefore it is evident that the tanks mentioned in the present invention must comply with the same standards which, in each country, concern the use of LPG only.

In particular, it must be reminded that both diesel and petrol, like other fuels, are in the liquid state in ambient conditions, while LPG, which by its nature is a gas, remains liquid only when subjected to certain pressures that vary as temperature varies. It follows that, by keeping the fuel according to the invention in a pressure tank, the latter is destined to increase as the temperature increases.

It should also be reminded that it is known that, according to the Lavoisier law of mass conservation, the fuels used, at the time of their mixing (for example between diesel and LPG, as well as between petrol and LPG), remain stable at the time of their mixing, not giving rise to any chemical reaction. By way of example, by supplying a Diesel cycle endothermic engine by means of a fuel according to the invention which, by definition, consists of a lower percentage content of diesel, a smaller quantity of fine particles is produced, which is directly proportional to the decreased quantity of diesel present therein. Furthermore, in addition to the environmental benefits, it must be considered that LPG is generally less expensive than diesel or petrol. As to LPG, there is a European reference standard concerning the chemical-physical composition thereof (UNI EN 589: 2019 standard); in reality this composition changes continuously because, being a gas, LPG changes its properties according to the temperature of the storage tank. It should also be noted that the composition of LPG varies from country to country and is also different, even within a single country, between Summer and Winter and depends on the local commercial availability of Propane and Butane which undergo different uses depending on the season of the year. The formulation thereof and the characteristics of the various gases that make up the mixture that constitutes LPG differ, even if the two main gases (precisely Propane and Butane) come from natural gas refining or if they are obtained in a refinery by means of the so-called cracking process of crude oil.

The invention also provides for particular fuel dispensing methods according to the invention. A first dispensing method, schematically illustrated in fig. 1, provides for the insertion in an LPG tank 4, obviously equipped with all the necessary accessories and requirements to ensure an accurate measurement of the fluids and for safety, first of a pre-set volume of LPG and then, always with the same pump used for the transfer of LPG, of a pre-set volume of additional fuel, consisting, for example, of diesel or petrol, in order to obtain the desired percentage of LPG in the resulting mixture of said two fuels.

The dispensing method according to the invention should always start with the primary fuel diesel or petrol (liquid) since the pressure already present in the tank is certainly lower when it is less full. The desired quantity of LPG, being a gas and therefore compressible, can always be introduced under all pressure conditions. The thus obtained fuel mixture will be conveyed through a normal duct 103 to a usual pump 5 of fuel, which will, when necessary, both measure and supply the volume of the mixture delivered by said pump 5 of fuel to a user’s tank 10 in the quantity desired by the user by means of one or more guns 104 of the known type, which are normally used for the delivery of LPG alone. Obviously, with this dispensing method, the percentage of LPG present in the mixture is fixed in advance based on the introduction of the two fuels into the tank 4. This dispensing method is particularly advantageous in all cases in which the vehicles to be refuelled have characteristics such as not to require the use of fuel mixtures with percentages different from those found inside the tank 4.

According to an additional dispensing method, shown in fig. 2, conversely, the user’s tank 10 is filled with a pre-set quantity of the additional fuel, such as for example petrol or diesel, present in the tank 2; subsequently, said tank 10 is filled with LPG, present in the tank 1. The two fuels are both conveyed, separately and in sequence, to a common pump 3, connected by means of the duct 102 to the user’s tank 10.

In this way it is obviously possible to make sure that the percentage of the two fuels in the mixture is chosen directly by the user, based on his particular needs. From the operational point of view, it is obvious that columns equipped with dispensing guns and thrust pumps for LPG must be used, for the supply of both the latter and the additional fuel.

Again, from the operational point of view, for obvious reasons of simplicity of this dispensing method, it will be possible to provide that in the pump 3 it is possible to pre-set the percentage of LPG to be introduced into the tank of the vehicle. In this way the user, once he has established the quantity of mixture to be dispensed, will not have to worry about anything, since the dispensing device will first supply the additional fuel and, subsequently, after appropriate switching, the LPG, being in any case certain that the mixture with which his tank 10 is filled is made precisely with the desired percentage between the two fuels.

In order to check the results obtainable with the fuel according to the invention, laboratory tests were carried out in which different mixing volumetric proportions were experimented, in particular between diesel or petrol and LPG. In fact, as far as diesel is concerned, the engine began to show signs of anomaly once the percentage of diesel equal to 27% mixed with 73% of LPG was reached, all these values being always referred to the volume.

Conversely, as far as petrol engines are concerned, from a point of view of principle, they could reach 100% of LPG in the mixture, but it is preferable to stop at a percentage of LPG equal to 90% with 10% of petrol, in order to still guarantee the lubrication of the mechanical members as they were originally designed by the respective manufacturers. In particular this mixture, unlike what happens in the usual conversion of an Otto cycle engine operating with LPG only, allows to avoid the addition of additives for the lubrication of the engine.

In particular, with the aforementioned maximum mixing percentage between diesel and LPG it was possible to supply a stationary engine (1400KW MTU Diesel cycle engine applied to an engine generator), without any operating anomalies having been detected, compared to the operation with 100 % of diesel. A similar test was carried out on a Mercedes ML270 Diesel Euro 3 SUV car and on a Volvo city bus with a B7 engine, always with Diesel cycle.

The following experiments were also carried out:

1. Visual check of any separation between the two fuels;

2. Measurement of intensity;

3. Detection of the pressure trend as the temperature varies;

4. Emission check.

Visual check

A 200 cc mixture with the percentage of 50% of diesel and 50% of LPG was inserted in a thermo-densimeter for LPG and it was monitored for over a year. The visual aspect has always remained the same, diesel and LPG have not separated and the pressure of the surface vapour tension, measured with a special pressure gauge, has not shown any appreciable variations.

Measurement of intensity

25 litres of diesel for transport and 25 litres of LPG for car were introduced into a tank equipped with adequate instruments for measuring pressure and temperature, as well as with the nozzles necessary for loading and unloading the mixture. This tank was placed on a stand 170 cm from the ground. A similar tank, this time empty, was also placed on a stand about 100 cm from the ground. The lower portions of the two tanks were connected with a usual 3/4 inch gas pipe on which there was a mass flow meter.

Vice versa, the two tanks were connected at the top by a 3/8 inch pipe adapted to reciprocally connect the tops of the aforementioned tanks. The upper valves were then opened and then the tops of the two tanks reached the identical pressure. The ball valves arranged at the lower duct were then opened and, due to the principle of communicating vessels, the liquid passed by gravity from the upper tank to the tank arranged inferiorly, passing through the mass flow meter which detected the density thereof. In particular, the density of the LPG detected at 19 °C was 0.564 Kg/1 and the diesel density detected at 12 °C was 0.839 Kg/1 finally, the overall density of the LPG/diesel mixture detected at 11 °C was 0.703 Kg/1. It should be noted that these values are not absolute and may vary for the reasons previously reported with regard to the specific physical -chemical composition of the LPG. Detection of the pressure trend

In order to know the behaviour of the mixture when the temperature varies, a mixture consisting of 50% of diesel and 50% of LPG was placed in a pressure tank; a thermometer and a pressure gauge were placed inside the tank and said tank was heated from the outside with hot air up to 360 degrees. Temperature and pressure measurements were then carried out and the results reported in the table shown in Fig-4.

Emission check

As is known, increasingly severe standards are issued for these emissions and manufacturers have encountered considerable problems in complying with them, in particular due to the presence of CO2 in relevant percentages in the air. The measurements on the quality and quantity of emissions were carried out in parallel with the consumption test and were carried out on the MTU stationary engine mentioned above. The values, visible in the table in fig. 3, were measured.

From the comparative analysis of the results that can be obtained with 50% of diesel and 50% of LPG, it can be seen that significant reductions in both NO _x , in CO, and in CO2, as well as particle emissions have been achieved. In particular, the reduction of CO2 is extremely significant which is allegedly one of the major causes of global warming.

From the foregoing, it can therefore be seen how, by means of the fuel according to the invention, it is possible to obtain an intrinsically more ecological fuel which gives rise to much lower emissions than using fuels of a known type such as petrol and diesel. However, it should be noted that, from a point of view of principle, the fuel according to the invention can be obtained by using other fuels of vegetable origin obtained from the fermentation of vegetable oils, for example, rapeseed and palm belonging to the HVO (Hydrogenated Vegetable Oils) family; from ethanol s and bioethanols and DME (Di -Meteil -Ether) ; from biodiesel of an animal nature, such as animal fats and oils.

Furthermore, this invention can be delivered with extremely simple dispensing methods such as those previously described in detail. It must also be considered that, since from a fiscal point of view all fuels are subject to the application of excise duties, the fuel referred to in the invention does not give rise to any particular problem in this regard. In practice, the problem of excise duties does not arise because the same excise duties in force in a specific country will apply and will be related to the quantities of diesel, petrol or other fuel and LPG used for mixing. By way of example only, as regards the excise duties in force in Italy relating to fuels on 4 November 2019, by mixing diesel and LPG for car in a percentage equal to 50%, it will be obtained that:

- the excise duty for transport diesel (6/1000 litres) will be equal to € 617.40;

- the excise duty for transport LPG (6/1000 litres) will be equal to 6 147.27. In practice, if these two fuels were mixed at 50%, the average excise duty will be equal to € 382.34/1000 litres, with a considerable reduction in the cost of fuel.