Internal combustion engine

Abstract

Internal combustion engine (1) with at least one combustion chamber (2), optionally at least one prechamber (3) for the at least one combustion chamber (2) and an intake system (4), wherein the intake system (4) comprises: - a liquid fuel supply (9) configured to provide a liquid fuel with an evaporation enthalpy of at least 600 kJ / kg, preferably at least 800 kJ / kg, more preferably at least 1.000 kJ / kg, - an air-fuel-mixer (10) mixing air with liquid fuel from the liquid fuel supply (9) and providing an air-fuel- mixture to the at least one combustion chamber (2) and optionally the at least one prechamber (3) and a compressor (6) compressing air and feeding the compressed air downstream into the at least one combustion chamber (2) and optionally into the at least one prechamber (3), wherein the air- fuel -mixer (10) is located downstream of the compressor (6) in the intake system (4).

Description

[0001] Internal combustion engine

[0002] The present invention concerns internal combustion engines with at least one combustion chamber, optionally at least one prechamber for the at least one combustion chamber and an intake system, wherein the intake system comprises :

[0003] - a liquid fuel supply configured to provide a liquid fuel with an evaporation enthalpy of at least 600 kJ / kg, preferably at least 800 kJ / kg, more preferably at least 1 . 000 kJ / kg,

[0004] - an air- fuel-mixer mixing air with liquid fuel from the liquid fuel supply and providing an air- fuel-mixture to the at least one combustion chamber and optionally the at least one prechamber and

[0005] - a compressor compressing air and feeding the compressed air downstream into the at least one combustion chamber and optionally into the at least one prechamber .

[0006] Internal combustion engines working on the basis of conventional liquid fuels like the fossil fuels gasoline or diesel are well known . However, due to economic and ecological reasons there is the desire to use other fuels than gasoline or diesel . For example , hydrogen is a promising fuel to meet the requirements of a sustainable energy carrier . Unfortunately, hydrogen is di f ficult to liquefy, to handle , to transport and to store . Other alternative fuels , e . g . methanol , which are liquid at standard conditions can be handled, transported and stored in an easier manner . However, such fuels are signi ficantly di f ferent in their chemical properties and / or their combustion behaviour in contrast to conventional fuels like the fossil fuels gasoline or diesel . As a result , new challenges arise for internal combustion engines working on the basis of such alternative liquid fuels . The object of the invention is therefore to improve the combustion of an internal combustion engine, in particular to reduce combustion shortcomings due to a liquid fuel.

[0007] Regarding the internal combustion engine, this object is achieved according to claim 1 in such a way that the air-fuel-mixer is located downstream of the compressor in the intake system.

[0008] Data concerning the evaporation enthalpy is described below and cited from "Thermodynamik der Verbrennungskraf tmaschine" from Rudolf Pischinger, Manfred Kell and Theodor Sams, 3. Edition, published 2009 by Springer Wien-New York, page 433 (https : / / doi . org / 1 Q , 1007 / 978 -3-211- 99277 -7 ) . The boiling points and evaporation enthalpies among other thermodynamical properties of different liquid fuels are stated in the following table, wherein the evaporation enthalpies relate to 1.013 bar and are described as "Verdampfungswarme [kJ / kg]".

[0009] Liquid fuels with an evaporation enthalpy of at least 600 kJ / kg, preferably at least 800 kJ / kg, more preferably at least 1.000 kJ / kg, are for example methanol or ethanol. Methanol shows an evaporation enthalpy, which is the "Verdampfungswarme [kJ / kg]" in above table, of 1.100 kJ / kg, whereas ethanol shows an evaporation enthalpy of 845 kJ / kg. Gasoline, which is "Euro Super" in above table, or diesel, which is "Diesel" in above table, are liquid fuels consisting of different hydrocarbons. According to above table gasoline / Euro Super shows an evaporation enthalpy of 420 kJ / kg and diesel / Diesel shows an evaporation enthalpy of 300 kJ / kg. So, liquid fuels with an evaporation enthalpy of at least 600 kJ / kg, preferably at least 800 kJ / kg, more preferably at least 1.000 kJ / kg, do not include gasoline or diesel.

[0010] So, in this document a liquid fuel with an evaporation enthalpy of at least 600 kJ / kg, preferably at least 800 kJ / kg, more preferably at least 1.000 kJ / kg, shall be understood as liquid fuel

[0011] - which is a pure substance wherein the pure substance shows an evaporation enthalpy of at least 600 kJ / kg, preferably at least 800 kJ / kg, more preferably at least 1.000 kJ / kg, at its respective boiling point and at 1,013 bar or

[0012] - which is a mixture of at least two ingredients wherein the mixture as whole shows an evaporation enthalpy of at least 600 kJ / kg, preferably at least 800 kJ / kg, more preferably at least 1.000 kJ / kg, at its respective boiling point and at 1,013 bar and / or

[0013] - which is a mixture of at least two ingredients wherein all ingredients separately show an evaporation enthalpy of at least 600 kJ / kg, preferably at least 800 kJ / kg, more preferably at least 1.000 kJ / kg, at their respective boiling points and at 1,013 bar.

[0014] A pure substance comprises only one chemical molecule like pure methanol or pure ethanol whereas a mixture comprises at least two chemical molecules or with other words two ingredients. The liquid fuel in form of a mixture may be for example a mixture of different alcohols like methanol and ethanol. An important aspect of the invention is that the compressed air provided by the compressor is heated due to the compression and that the heat of the compressed air can be used to heat the liquid fuel from the liquid fuel supply when the liquid fuel is mixed with air by the air- fuel-mixer . Subsequently, the liquid fuel can be at least partially, preferably completely, trans ferred to the gas state within the air- fuel-mixture by the air- fuel-mixer . The originally liquid fuel which is at least partially, preferably completely, gasi fied or with other words trans ferred to the gas state within the air- fuel-mixture can be directed to the at least one combustion chamber and optionally to the at least one prechamber for combustion after the gasi fication .

[0015] As a result , the above-described aspect is beneficially supporting the combustion in the at least one combustion chamber and optionally in the at least one prechamber . So , a robust , stable and / or cost-ef ficient combustion of liquid fuels in internal combustion engines and / or gas engines with a liquid fuel supply can be achieved .

[0016] This aspect is especially important for liquid fuels with higher evaporation enthalpies than conventional liquid fuels like gasoline or diesel . In particular, liquid fuels like alcohols are di f ficult to use for an air- fuel-mixture due to their higher evaporation enthalpies and the higher energies they need for partial or complete evaporation . I f a critical amount of the liquid fuel stays liquid within the air- fuel-mixture until the air- fuelmixture arrives at the at least one combustion chamber and optionally the at least one prechamber combustion shortcomings occur . These combustion shortcomings result in insuf ficient combustion, disadvantageous performance of the internal combustion engine , damages and / or fouling of the internal combustion engine . This issue of said liquid fuels may also occur when the air- fuelmixture is suf ficiently evaporated within the air- fuel-mixer indeed but due to insuf ficient temperatures the originally liquid fuel within the air- fuel-mixture condensates again within the intake system, the at least one combustion chamber and / or the optional at least one prechamber o f the internal combustion engine .

[0017] This aspect is advantageous in the case of an internal combustion engine with at least two combustion chambers wherein each combustion chamber may be equipped with a port fuel inj ector . Due to the invention the port fuel inj ectors can be omitted in favour of an air- fuel-mixer located downstream of the compressor in the intake system . Hence , the omitting of several port fuel inj ectors reduces cost and maintenance . Moreover, individual port fuel inj ectors for individual combustion chambers are di f fering at least slightly in their inj ection behaviour, i . e . inj ection amount etc . So , the internal combustion engine does not run completely steady . Said aspect can ensure a steady and reliable run o f the internal combustion engine without any additional device to compensate for di f ferently working port fuel inj ectors .

[0018] The air which is mixed with the liquid fuel by the air- fuel-mixer may be in a preferred embodiment naturally occuring air . In another preferred embodiment the air may comprise at least one non- naturally-occuring-ingredient like a gas fuel from a gas fuel supply . Naturally occuring air itsel f is a mixture of nitrogen, oxygen and other substances with small concentrations . The at least one non-naturally-occuring-ingredient is either a substance which is usually not present in conventional air or a substance with a certain concentration that is usually not present in air . For example , methane or hydrogen are ingredients of naturally occurring air with small concentrations and may be added to the conventional air in such a way that the concentration of methane or hydrogen is signi ficantly higher than in conventional air .

[0019] According to a preferred embodiment the air- fuel-mixer is located downstream of the compressor and adj acent to the compressor in the intake system . Due to the downstream and adj acent position of the air- fuel-mixer in relation to the compressor the heat of the compressed air can be ideally used, and the evaporation of the liquid fuel can be favoured .

[0020] Further preferable embodiments of the invention are defined in the dependent claims .

[0021] In a preferred embodiment the air- fuel-mixer comprises a liquid fuel inj ector configured to inj ect the liquid fuel into the airfuel-mixer .

[0022] In another preferred embodiment the air- fuel-mixer comprises a liquid fuel inj ector configured to inj ect the liquid fuel into the air- fuel-mixer in a spraying manner .

[0023] Hence , the liquid fuel within the air- fuel-mixer can be better distributed which supports the evaporation .

[0024] In a preferred embodiment :

[0025] - the liquid fuel is partially, preferably completely, in the liquid state at 1 . 013 bar and at 0 °C and / or

[0026] - the liquid fuel is a pure substance or a mixture and / or

[0027] - the air- fuel-mixture is at least partially, preferably completely, in the gas state at 4 bar to 6 bar, preferably 5 bar to 6 bar, and at 30 °C to 60 °C, preferably 50 °C to 60 °C, and / or

[0028] - the volume fraction of the fuel in the air- fuel-mixture is between 10% v / v and 50% v / v, preferably between 20% v / v and 50% v / v .

[0029] In another preferred embodiment the originally liquid fuel within the air- fuel-mixture is at least partially, preferably completely, in the gas state at 4 bar to 6 bar, preferably 5 bar to 6 bar, and at 30 °C to 60 °C, preferably 50 °C to 60 °C .

[0030] The conditions within the at least one combustion chamber and optionally the at least one prechamber when charged with the airfuel-mixture can be 4 bar to 6 bar, preferably 5 bar to 6 bar, and 30 °C to 60 °C, preferably 50 °C to 60 °C . So , the originally liquid fuel can be at least partially, preferably completely, in the gas state when charged into the at least one combustion chamber and optionally the at least one prechamber .

[0031] In a preferred embodiment the internal combustion engine comprises a, preferably only one single point , high pressure fuel dosing device for inj ecting the liquid fuel at a high pressure .

[0032] In a preferred embodiment the liquid fuel is individually or in combination selected from the group consisting of : alcohols , preferably methanol and / or ethanol , hydrocarbons , ammonia or ammoniac solution .

[0033] For example , the liquid fuel can be pure methanol or a mixture of methanol with another liquid fuel like ethanol .

[0034] Liquid fuels like methanol are preferred since fossil fuels are disadvantageous due to economic and ecological reasons . For example , methanol on the other hand can be produced by green technologies like wind, solar or hydropower by conversion of CO2 and H2 . Hence, methanol can be a green energy carrier . In contrast to other potential green energy carriers like hydrogen, methanol combines the advantages of green energy and the easy handling of liquid fuels . Therefore , the usage of liquid fuels like methanol is meeting the current requirements of sustainable energy carriers which can be simply handled, transported and stored . In a preferred embodiment the air- fuel-mixer is an evaporator configured to evaporate the air- fuel-mixture at least partially, preferably completely, and / or stabili ze the air- fuel-mixture at least partially, preferably completely, in the gas state .

[0035] Hence , the liquid fuel can at least partially, preferably completely, evaporate within the air- fuel-mixture . Moreover, this at least partial , preferably complete, gas state of the originally liquid fuel within the air-fuel-mixture can be maintained and the air- fuel-mixture can be directed to the at least one combustion chamber and optionally to the at least one prechamber for suf ficient combustion .

[0036] In a preferred embodiment the air- fuel-mixer is configured to maintain a pressure of 10 bar to 30 bar, and a temperature of at least 60 °C, preferably of 100 °C to 200 °C, preferably 125 °C to 180 °C, within the air- fuel-mixer .

[0037] Hence , the liquid fuel can at least partially, preferably completely, evaporate due to the suitable pressure and temperature ranges corresponding to the chemical properties of the used liquid fuel . Moreover, the pressure and temperature conditions are suf ficient to ensure that the air- fuel-mixture is still in a suf ficient state for combustion after leaving the air- fuel-mixer and when arriving the at least one combustion chamber and optionally the at least one prechamber .

[0038] In a preferred embodiment the intake system comprises a combustion chamber intake mani fold connecting the compressor with the at least one combustion chamber and wherein the air- fuel-mixer is part of the combustion chamber intake mani fold .

[0039] The combustion chamber intake mani fold in this document shall be understood as a connection between the compressor and the at least one combustion chamber or with other words as a line system connecting the compressor with the at least one combustion chamber . The combustion chamber intake mani fold may comprise one or more components like the air- fuel-mixer, a cooler, a flame arrestor and / or a throttle .

[0040] In a preferred embodiment the intake system comprises a combustion chamber intake mani fold connecting the compressor with the at least one combustion chamber and wherein the combustion chamber intake mani fold comprises at least one port fuel inj ector inj ecting liquid fuel from the liquid fuel supply into the combustion chamber intake mani fold, preferably into an at least one combustion chamber intake pipe of the combustion chamber intake mani fold .

[0041] Hence , by using of an air- fuel-mixture scavenged prechamber system in combination with a port fuel inj ection system a stable and ampli fied combustion system for monofuel operation can be achieved .

[0042] In a preferred embodiment the intake system comprises a combustion chamber intake mani fold and optionally a prechamber intake mani fold, wherein the air- fuel-mixer and / or the combustion chamber intake mani fold and optionally the prechamber intake mani fold comprise a mixing device to provide a uni formly distributed airfuel-mixture to the at least one combustion chamber and optionally to the at least one prechamber .

[0043] The prechamber intake mani fold in this document shall be understood as a connection between the compressor and / or the combustion chamber intake mani fold and the at least one prechamber or with other words as a line system connecting the compressor and / or the combustion chamber intake mani fold with the at least one prechamber . The prechamber intake mani fold may comprise one or more components like the air- fuel-mixer, a controlling device and / or a measuring device . In a preferred embodiment the prechamber intake mani fold comprises at least one interrelated line system or at least two line systems separated from each other .

[0044] In preferred embodiment of the internal combustion engine the combustion chamber intake mani fold comprises at least one combustion chamber intake pipe and / or the prechamber intake mani fold comprises at least one prechamber intake pipe , preferably wherein the origin of the at least one prechamber intake pipe is located within the length of the at least one combustion chamber intake pipe .

[0045] In a preferred embodiment the internal combustion engine comprises :

[0046] - a dosing device , preferably a dosing valve or ori fice , between the liquid fuel supply and the air- fuel-mixer for, preferably continuous or pulsed, dosing of the liquid fuel into the airfuel-mixer and / or

[0047] - a controlling device, preferably a controlling valve or ori fice , downstream of the air- fuel-mixer and / or

[0048] - a measuring device , preferably a mass flow sensor, upstream of the air- fuel-mixer and / or

[0049] - a detecting device , preferably a pressure sensor, within the at least one combustion chamber and optionally the at least one prechamber, and / or

[0050] - an exhaust system, wherein the exhaust system comprises a turbine , wherein the turbine is configured to drive the compressor .

[0051] With the dosing device the amount of liquid fuel provided to the air- fuel-mixer can be adj usted . Depending on the dosing device , the mode of operation, e . g . continuous or pulsed operation, and / or the air- fuel-ratio , also called lambda, can be controlled . The controlling device can be used to control the amount of airfuel-mixture provided by the air- fuel-mixer and directed to the at least one combustion chamber and optionally the at least one prechamber .

[0052] The measuring device can provide information concerning the compressed air from the compressor like the fluid flow, the pressure , the temperature and / or other parameters which are important for providing the desired air- fuel-mixture by the airfuel-mixer .

[0053] In a preferred embodiment the internal combustion engine comprises a control unit to control :

[0054] - the air- fuel-ratio of the air- fuel-mixture , preferably by means of the dosing device and / or the compressor, and / or

[0055] - the amount of the air-fuel-mixture provided to the at least one combustion chamber and optionally to the at least one prechamber, preferably by means of the controlling device .

[0056] An important parameter for the combustion is the air- fuel-ratio which is the mass ratio of air to a solid, liquid or gaseous fuel present in the combustion process . An air- fuel-ratio of 1 describes an air- fuel-mixture with the necessary amount of air to burn all the fuel completely and in a stoichiometric manner . An air- fuelratio > 1 describes a lean mixture with an excess of air compared to the necessary stoichiometric amount of air needed for the complete combustion of the fuel within the air- fuel-mixture . The opposite is a rich mixture . The air- fuel-ration may also be called lambda X .

[0057] The control unit can control the compressor and therefore the fluid flow and / or temperature of air . The control unit can also control the dosing device as described above . Hence , the control unit can control the air- fuel-ratio in di f ferent ways . With the additional help of the measuring device a monitored controlling can be realised .

[0058] In a preferred embodiment the at least one prechamber comprises a, preferably passive , prechamber gas valve .

[0059] Especially a passive prechamber gas valve is advantageous due to the reduced control ef fort and controlling equipment .

[0060] In a preferred embodiment the intake system comprises an intake bypass configured to direct air into the at least one combustion chamber and to bypass the compressor and the air- fuel-mixer .

[0061] In a preferred embodiment the air- fuel-mixer comprises a heating device for heating the air-fuel-mixture .

[0062] The heating device can be very advantageous in the case that the temperature of the compressed air is too low for the liquid fuel in use , i . e . startup or cold start of the internal combustion engine . Moreover, the heating device can compensate a lack of temperature due to low air- fuel-ratios of the desired air- fuelmixture .

[0063] In a preferred embodiment the internal combustion engine comprises a cooler to ensure the cooling of the air- fuel-mixture below a determined temperature , preferably wherein the air- fuel-mixer is located upstream of the cooler .

[0064] In the case of an air- fuel-mixture leaving the air- fuel-mixture with a temperature too high a cooler can ensure safe operation temperatures .

[0065] Due to the position of the air- fuel-mixer downstream of the compressor and upstream of the cooler the high temperature of the compressed air can be used for the evaporation of the liquid fuel and a lower temperature of the air- fuel-mixture can be ensured for safe operation .

[0066] In a preferred embodiment the intake system comprises a gas fuel supply and a gas mixer mixing air with a gas fuel from the gas fuel supply, preferably wherein the gas mixer is located upstream of the compressor and / or the gas fuel is individually or in combination selected from the group consisting of : natural gas , firedamp, biogas , hydrocarbons , preferably methane , molecular hydrogen .

[0067] An additional fuel in form of a gas fuel can be included to increase the performance , operation stability and / or the suf ficient combustion of the air- fuel-mixture .

[0068] In a preferred embodiment

[0069] - the gas mixer is configured to provide a first air- fuelmixture , preferably solely, to the air- fuel-mixer and

[0070] - the air- fuel-mixer is configured to provide , preferably simultaneously, a second air- fuel-mixture to the at least one combustion chamber and optionally to the at least one prechamber, wherein the second air- fuel-mixture is a mixture of the first air- fuel-mixture from the gas mixer and the liquid fuel from the liquid fuel supply .

[0071] Further details and advantages of preferred embodiments of the present invention are described by means of the specific description hereinafter . In the drawing :

[0072] Fig . 1 is an example of an embodiment of a proposed internal combustion engine .

[0073] Fig . 2 is another example of an embodiment of a proposed internal combustion engine . Fig. 1 shows an internal combustion engine (1) with at least one combustion chamber (2) , optionally at least one prechamber (3) for the at least one combustion chamber (2) and an intake system (4) , wherein the intake system (4) comprises:

[0074] - a liquid fuel supply (9) configured to provide a liquid fuel with an evaporation enthalpy of at least 600 kJ / kg, preferably at least 800 kJ / kg, more preferably at least 1.000 kJ / kg,

[0075] - an air-fuel-mixer (10) mixing air with liquid fuel from the liquid fuel supply (9) and providing an air-fuel-mixture to the at least one combustion chamber (2) and optionally the at least one prechamber (3) and

[0076] - a compressor (6) compressing air and feeding the compressed air downstream into the at least one combustion chamber (2) and optionally into the at least one prechamber (3) , wherein the air-fuel-mixer (10) is located downstream of the compressor (6) in the intake system (4) .

[0077] Fig. 1 shows an internal combustion engine with six combustion chambers 2, six prechambers 3 for each of the six combustion chambers 2, an intake system 4 and an exhaust system 17.

[0078] The intake system 4 of Fig. 1 basically comprises two parts, namely a first intake system part for feeding air and optionally a gas fuel to the combustion chambers 2 and a second intake system part for feeding a liquid fuel to the prechambers 3 and / or the combustion chambers 2.

[0079] The first intake system part of Fig. 1 comprises following components, beginning from the right-hand side of Fig. 1 and ending in the combustion chambers 2 :

[0080] - Air supply 5, providing air for air-fuel-mixtures, Gas fuel supply 26 , providing a gas fuel for air- fuelmixtures ,

[0081] - Gas mixer 27 , mixing the gas fuel from the gas fuel supply 26 with the air of the air supply 5 ,

[0082] - A compressor 6 , compressing air from the air supply 5 and / or the air- fuel-mixture from the gas mixer 27 and feeding the air and / or the air- fuel-mixture downstream into the at least one combustion chamber 2 by a combustion chamber intake mani fold 7 and into the at least one prechamber 3 by a prechamber intake mani fold 8 ,

[0083] - A cooler 25 , to ensure the cooling of the compressed air and / or the air- fuel-mixture below a determined temperature ,

[0084] - A flame arrestor 29 , protecting the first intake system part against backfiring of the combustion engine ,

[0085] - A throttle 30 , influencing a f luid flow of the air and / or the air- fuel -mixture ,

[0086] - A combustion chamber intake mani fold 7 , connecting at least the compressor 6 , the cooler 25 , the flame arrestor 29 , the throttle 30 and the six combustion chambers 2 , wherein the combustion chamber intake mani fold 7 divides into six combustion chamber intake pipe 22 before leading into the individual combustion chambers 2 .

[0087] As depicted in Fig . 1 the first intake system part further comprises an intake bypass 23 with a compressor bypass valve 28 and an additional flame arrestor 29 . The intake bypass 23 connects the air supply 5 with the combustion chamber intake mani fold 7 and bypasses at least the compressor 6 and a connection to the second intake system part , namely the origin of a prechamber intake mani fold 8 .

[0088] The second intake system part of Fig . 1 comprises following components , beginning from the left-hand side of Fig . 1 and ending in either the combustion chamber intake pipes 22 or the prechambers 3 :

[0089] - A liquid fuel supply 9, providing a liquid fuel in its liquid state to either the combustion chamber intake pipes 22 or the prechambers 3 ,

[0090] - Six port fuel inj ectors 21 , each connected with one of the six combustion chamber intake pipes 22 and configured to inj ect the liquid fuel from the l iquid fuel supply 9 into the corresponding combustion chamber intake pipe 22 to provide an air- fuel-mixture wherein this air- fuel-mixture comprises at least the originally liquid fuel from the liquid fuel supply 9 and air from the air supply 5 . This air- fuel-mixture may alternatively comprise the originally liquid fuel from the liquid fuel supply 9 and another air- fuel-mixture from the gas mixer 27 ,

[0091] - An air- fuel-mixer 10 , mixing air with liquid fuel from the liquid fuel supply 9 and providing an air- fuel-mixture ,

[0092] - A dosing device 13 , for, preferably continuous or pulsed, dosing of the liquid fuel into the air- fuel-mixer 10 ,

[0093] - A controlling device 14 , for controlling the amount of the air- fuel-mixture fed to the prechambers 3 ,

[0094] - A line with the dosing device 13 wherein the line connects the liquid fuel supply 9 with the prechamber intake mani fold 8 ,

[0095] - The prechamber intake mani fold 8 , starting from the first intake system part , to be more concrete starting from the combustion chamber intake mani fold 7 between the compressor 6 and the cooler 25 , and ending in the prechambers 20 . The prechamber intake manifold 8 connects at least the combustion chamber intake manifold 7 , the measuring device 15 , the airfuel-mixer 10 , the controlling device 14 and the six prechambers 3 , wherein the prechamber intake mani fold 8 divides into six prechamber intake pipes 31 before leading into the individual prechambers 3 . In Fig . 1 the combustion chamber intake mani fold 7 starts at the compressor 6, divides into six combustion chamber intake pipes 22 and ends at the six individual combustion chambers 2 .

[0096] In Fig . 1 the prechamber intake mani fold 8 starts at the combustion chamber intake mani fold 7 between the compressor 6 and the cooler 25 , divides into six prechamber intake pipes 31 and ends at the six individual prechambers 3 .

[0097] As depicted in Fig . 1 the air- fuel-mixer can be an evaporator 11 configured to evaporate an air- fuel-mixture wherein this air- fuelmixture comprises at least the originally liquid fuel from the liquid fuel supply 9 and air from the air supply 5 . This air- fuelmixture may alternatively comprise the originally liquid fuel from the liquid fuel supply 9 and another air- fuel-mixture from the gas mixer 27 .

[0098] As depicted in Fig . 1 the air- fuel-mixer 10 can comprise a liquid fuel inj ector 12 configured to inj ect the liquid fuel into the air- fuel-mixer 10 and a heating device 24 for heating the airfuel-mixture .

[0099] In a preferred embodiment of the internal combustion engine the at least one combustion chamber 2 and / or the at least one prechamber 3 comprises a, preferably passive , prechamber gas valve 20 .

[0100] In a preferred embodiment of the internal combustion engine the at least one combustion chamber 2 and / or the at least one prechamber 3 comprises a detecting device 16 , preferably a pressure sensor .

[0101] In a preferred embodiment of the internal combustion engine a control unit 19 is provided to control at least one of the following components or properties : The gas fuel supply 26 and the gas- fuel-mixer 26 ,

[0102] - The compressor 6 for controlling a fluid flow of the compressed air,

[0103] - The cooler 25 for cooling the temperature of the compressed air and / or the air- fuel-mixture ,

[0104] - The liquid fuel supply 9 ,

[0105] - The compressor bypass valve 28 ,

[0106] - The throttle 30 for controlling a fluid flow of an air- fuelmixture provided to the combustion chambers 2 ,

[0107] - The port fuel inj ector for controlling the amount and / or conditions of a fluid flow of the liquid fuel inj ected into the combustion chamber intake pipes 22 ,

[0108] - The measuring device 15, preferably for measuring a mass flow,

[0109] - The air- fuel-mixer, the liquid fuel inj ector 12 and / or the heating device 24 ,

[0110] - The controlling device 14 for controlling the amount of a fluid flow of the air-fuel-mixture from the air- fuel-mixer,

[0111] - prechamber gas valve 20 ,

[0112] - detecting device 16 , preferably for detecting a pressure within at least one of the combustion chambers 2 ,

[0113] - the turbine 18 and the driving of the compressor 6 by the turbine 18 ,

[0114] - the exhaust bypass valve 35 .

[0115] The exhaust system 17 of Fig . 1 comprises following components :

[0116] - A turbine 18 , connected to the compressor 6 by the turbine drive shaft 33 to drive the compressor 6 ,

[0117] - An exhaust exit 32 for exhaust gas ,

[0118] - An exhaust bypass 34 with an exhaust bypass valve 35 . The exhaust bypass 34 connects the combustion chambers 2 with the exhaust exit 32 and bypasses the turbine 18 . The working principle of the internal combustion engine shown in Fig . 1 can be exemplarily described as follows :

[0119] The air necessary for combustion is provided by the air supply 5 . The simplest embodiment of an air supply 5 is a simple pipe for intaking surrounding air . In a preferred embodiment the air supply comprises a filter and / or a dryer . The air may be compressed by the compressor 6 . Due to this compression the thermal energy of the air increases .

[0120] Next , the compressed and hot air i s fed into the combustion chamber intake mani fold 7 and shortly after the compressor 6 into the prechamber intake mani fold 8 as well . In the combustion chamber intake mani fold 7 the compressed and hot air is passing the cooler 25 , the f lame arrestor 29 and the throttle 30 . The fluid f low of the compressed and hot air is divided into the combustion chamber intake pipes 22 . Within the combustion chamber intake pipes 22 the port fuel inj ectors 21 add a determined amount of the liquid fuel provided by the liquid fuel supply 9 to the compressed and hot air . Due to the thermal energy of the air and the inj ection conditions of the liquid fuel the liquid fuel evaporates at least partially, preferably completely, and mixes with the air to form an air- fuel-mixture . This air- fuel-mixture is fed to the individual combustion chambers 2 .

[0121] Besides that , the compressed and hot air is also fed into the prechamber intake mani fold 8 and passes the measuring device 15 until the air reaches the air- fuel-mixer 10 . The air- fuel-mixer 10 is connected to the liquid fuel supply 9 . Hence , liquid fuel and the compressed and hot air can be mixed by the air- fuel-mixer 10 . Due to the thermal energy of the air and the inj ection conditions of the liquid fuel the liquid fuel evaporates at least partially, preferably completely, and mixes with the air to form an air- fuelmixture . This air- fuel-mixture is fed to the individual prechambers 3 by leaving the air- fuel-mixer 10 and flowing along the remaining prechamber intake mani fold 8 . Shortly before the individual prechambers 3 the prechamber intake mani fold 8 divides in six prechamber intake pipes 31 .

[0122] In the embodiment of Fig . 1 the compressed and hot air provided by the compressor 6 is , at least partially, directed into the airfuel-mixer 10 . The benefit of this embodiment is that the thermal energy generated by the compressor 6 can be used to evaporate the air- fuel-mixture at least partially, preferably completely and / or stabili ze the air- fuel-mixture at least partially, preferably completely, in the gas state .

[0123] The benefit of the air- fuel-mixer 10 is that the liquid fuel can be suf ficiently evaporated for the prechamber combustion . This is very important since the prechamber combustion serves as an ignition ampli fier and supports the combustion of the combustion chamber . On the other hand, condensation issues in the prechamber, especially with liquid fuels l ike alcohols and others , disturb a stable combustion and can be avoided by the air- fuel-mixer 10 .

[0124] The above-mentioned working principle is an example only and is not considered to limit the scope of the invention . Another working principle may include besides air from the air supply 5 a gas fuel from the gas fuel supply 27 which i s mixed with the air from the air supply 5 before this air- fuel-mixture is compressed and heated by the compressor 6 .

[0125] The embodiment of Fig . 1 is an example only and is not considered to limit the scope of the invention . The described components may vary in their amount and / or position within the internal combustion engine .

[0126] Fig . 2 shows another example of an embodiment of a proposed internal combustion engine . The embodiment of Fig. 2 is similar to the embodiment of Fig. 1 although there are some differences which are explained in the following. Despite that, all that has been said so far can apply in an analog manner if appropriately.

[0127] The combustion chamber intake manifold 7 depicted in Fig. 2 is essentially the same as the combustion chamber intake manifold 7 depicted in Fig. 1. The major difference between these two embodiments is that the air-fuel-mixer 10 is no more part the of prechamber intake manifold 8 but of the combustion chamber intake manifold 7.

[0128] The working principle of the internal combustion engine shown in Fig. 2 can be exemplarily described as follows:

[0129] The air necessary for combustion is provided by the air supply 5. The air may be compressed by the compressor 6. Due to this compression the thermal energy of the air increases.

[0130] Next, the compressed and hot air is fed into the combustion chamber intake manifold 7 and shortly before the combustion chambers 2 into the prechamber intake manifold 8 as well.

[0131] In the combustion chamber intake manifold 7 the compressed and hot air provided by the compressor 6 is fed into the air-fuel-mixer 10.

[0132] The benefit of this embodiment in contrast to the embodiment of Fig. 1 is that the thermal energy generated by the compressor 6 can be used in a more efficient way since the loss of thermal energy is smaller due to the shorter distance between the compressor 6 and the air-fuel-mixer 10 or with other word due to the adjacent location of the air- fuel-mixer 10 downstream of the compressor 6 in Fig. 2. Moreover, the full fluid flow provided by the compressor 6 can be used for the air-fuel-mixer since no division between the combustion chamber intake manifold 7 and an optional prechamber intake manifold 8 takes place. Additionally, this embodiment reduces the engine parts and simplifies the construction of the internal combustion engine.

[0133] The air-fuel-mixer 10 is connected to the liquid fuel supply 9. Hence, liquid fuel and the compressed and hot air can be mixed by the air-fuel-mixer 10. Due to the thermal energy of the air and the injection conditions of the liquid fuel the liquid fuel evaporates at least partially, preferably completely, and mixes with the air to form an air-fuel-mixture. This air-fuel-mixture is further directed downstream along the combustion chamber intake manifold 7 and passes the cooler 25, the flame arrestor 29 and the throttle 30.

[0134] The fluid flow of the air-fuel-mixture is divided into the combustion chamber intake pipes 22. Within the combustion chamber intake pipes 22 the fluid flow of the air-fuel-mixture is divided once again into the remaining segment of the individual combustion chamber intake pipe 22 and an individual prechamber intake pipe 31. In the embodiment of Fig. 2 the prechamber intake manifold 8 consists solely of six separated and individual prechamber intake pipes 31. Hence, the air-fuel-mixture provided to the combustion chambers 2 and the prechambers 3 is basically the same. In contrast, the air-fuel-mixtures described in view of the embodiment depicted in Fig. 1 are provided independently from each other by the air-fuel-mixer 10 and the port fuel injectors 21. Both embodiments offer advantages due to the uniform air-fuelmixture or the different air-fuel-mixtures.

[0135] The above-mentioned working principle is an example only and is not considered to limit the scope of the invention. Another working principle may include besides the air from the air supply 5 a gas fuel from the gas fuel supply 27 which is mixed with the air from the air supply 5 before this air-fuel-mixture is compressed and heated by the compressor 6.

[0136] The described components of the embodiment of Fig. 2 may vary in their amount and / or position within the internal combustion engine. Moreover, the examples of Fig. 1 and Fig. 2 may be combined, e.g. the measuring device 15 and the controlling device 14 may be integrated in the combustion chamber intake manifold 7 of the embodiment in Fig. 2.

[0137] List of reference signs :

[0138] 1 internal combustion engine

[0139] 2 combustion chamber

[0140] 3 prechamber

[0141] 4 intake system

[0142] 5 air supply

[0143] 6 compressor

[0144] 7 combustion chamber intake mani fold

[0145] 8 prechamber intake mani fold

[0146] 9 liquid fuel supply

[0147] 10 air- fuel-mixer

[0148] 11 evaporator

[0149] 12 liquid fuel inj ector

[0150] 13 dosing device

[0151] 14 controlling device

[0152] 15 measuring device

[0153] 16 detecting device

[0154] 17 exhaust system

[0155] 18 turbine

[0156] 19 control unit

[0157] 20 prechamber gas valve

[0158] 21 port fuel inj ector

[0159] 22 combustion chamber intake pipe

[0160] 23 intake bypass

[0161] 24 heating device

[0162] 25 cooler

[0163] 26 gas fuel supply

[0164] 27 gas mixer

[0165] 28 compressor bypass valve

[0166] 29 flame arrestor

[0167] 30 throttle 31 prechamber intake pipe

[0168] 32 exhaust gas exit

[0169] 33 turbine drive shaft

[0170] 34 exhaust bypass 35 exhaust bypass valve

Claims

Patent claims1. Internal combustion engine (1) with at least one combustion chamber (2) , optionally at least one prechamber (3) for the at least one combustion chamber (2) and an intake system (4) , wherein the intake system (4) comprises:- a liquid fuel supply (9) configured to provide a liquid fuel with an evaporation enthalpy of at least 600 kJ / kg, preferably at least 800 kJ / kg, more preferably at least 1.000 kJ / kg,- an air-fuel-mixer (10) mixing air with liquid fuel from the liquid fuel supply (9) and providing an air-fuelmixture to the at least one combustion chamber (2) and optionally the at least one prechamber (3) and- a compressor (6) compressing air and feeding the compressed air downstream into the at least one combustion chamber (2) and optionally into the at least one prechamber (3) , wherein the air-fuel-mixer (10) is located downstream of the compressor (6) in the intake system (4) .

2. Internal combustion engine (1) according to claim 1, wherein the air-fuel-mixer (10) comprises a liquid fuel injector (12) configured to inject the liquid fuel into the air-fuel-mixer (10) .

3. Internal combustion engine (1) according to claim 1 or 2, wherein :- the liquid fuel is partially, preferably completely, in the liquid state at 1.013 bar and at 0 °C and / or- the liquid fuel is a pure substance or a mixture and / or- the air-fuel-mixture is at least partially, preferably completely, in the gas state at 4 bar to 6 bar, preferably5 bar to 6 bar, and at 30 °C to 60 °C, preferably 50 °C to 60 °C, and / or- the volume fraction of the fuel in the air-fuel-mixture is between 10% v / v and 50% v / v, preferably between 20% v / v and 50% v / v.

4. Internal combustion engine (1) according to any of the preceding claims, wherein the liquid fuel is individually or in combination selected from the group consisting of: alcohols, preferably methanol and / or ethanol, hydrocarbons, ammonia or ammoniac solution.

5. Internal combustion engine (1) according to any of the preceding claims, wherein the air-fuel-mixer (10) is an evaporator (11) configured to evaporate the air-fuel-mixture at least partially, preferably completely, and / or stabilize the air-fuel-mixture at least partially, preferably completely, in the gas state.

6. Internal combustion engine (1) according to any of the preceding claims, wherein the air-fuel-mixer (10) is configured to maintain a pressure of 10 bar to 30 bar, and a temperature of at least 60 °C, preferably of 100 °C to 200 °C, preferably 125 °C to 180 °C, within the air-fuel-mixer (10) .

7. Internal combustion engine (1) according to any of the preceding claims, wherein the intake system (4) comprises a combustion chamber intake manifold (7) connecting the compressor (6) with the at least one combustion chamber (2) and wherein the air-fuel-mixer (10) is part of the combustion chamber intake manifold (7) .

8. Internal combustion engine (1) according to any of the preceding claims, wherein the intake system (4) comprises a combustion chamber intake manifold (7) and optionally a prechamber intake manifold (8) , wherein the air-fuel-mixer(10) and / or the combustion chamber intake manifold (7) and optionally the prechamber intake manifold (8) comprise a mixing device to provide a uniformly distributed air-fuel-mixture to the at least one combustion chamber (2) and optionally to the at least one prechamber (3) .

9. Internal combustion engine (1) according to any of the preceding claims comprising:- a dosing device (13) , preferably a dosing valve or orifice, between the liquid fuel supply (9) and the airfuel-mixer (10) for, preferably continuous or pulsed, dosing of the liquid fuel into the air-fuel-mixer (10) and / or- a controlling device (14) , preferably a controlling valve or orifice, downstream of the air-fuel-mixer (10) and / or- a measuring device (15) , preferably a mass flow sensor, upstream of the air-fuel-mixer (10) and / or- a detecting device (16) , preferably a pressure sensor, within the at least one combustion chamber (2) and optionally the at least one prechamber (3) , and / or- an exhaust system (17) , wherein the exhaust system (17) comprises a turbine (18) , wherein the turbine (18) is configured to drive the compressor (6) .

10. Internal combustion engine (1) according to any of the preceding claims, preferably to the previous claim, wherein the internal combustion engine (1) comprises a control unit (19) to control:- the air-fuel-ratio of the air-fuel-mixture, preferably by means of the dosing device (13) and / or the compressor ( 6 ) , and / or- the amount of the air-fuel-mixture provided to the at least one combustion chamber (2) and optionally to the at least one prechamber (3) , preferably by means of the controlling device.

11. Internal combustion engine (1) according to any of the preceding claims, wherein the at least one prechamber (3) comprises a, preferably passive, prechamber gas valve (20) .

12. Internal combustion engine (1) according to any of the preceding claims, wherein the intake system (4) comprises an intake bypass (23) configured to direct air into the at least one combustion chamber (2) and to bypass the compressor (6) and the air-fuel-mixer (10) .

13. Internal combustion engine (1) according to any of the preceding claims, wherein the air-fuel-mixer (10) comprises a heating device (24) for heating the air-fuel-mixture.

14. Internal combustion engine (1) according to any of the preceding claims, wherein the internal combustion engine (1) comprises a cooler (25) to ensure the cooling of the air-fuelmixture below a determined temperature, preferably wherein the air-fuel-mixer (10) is located upstream of the cooler.

15. Internal combustion engine (1) according to any of the preceding claims, wherein the intake system (4) comprises a gas fuel supply (26) and a gas mixer (27) mixing air with a gas fuel from the gas fuel supply (26) , preferably wherein the gas mixer (27) is located upstream of the compressor (6) and / or the gas fuel is individually or in combination selected from the group consisting of: natural gas, firedamp, biogas, hydrocarbons, preferably methane, molecular hydrogen.

16. Internal combustion engine (1) according to the previous claim, wherein- the gas mixer (27) is configured to provide a first airfuel-mixture, preferably solely, to the air-fuel-mixer (10) and- the air-fuel-mixer (10) is configured to provide, preferably simultaneously, a second air-fuel-mixture to the at least one combustion chamber (2) and optionally to the at least one prechamber (3) , wherein the second airfuel-mixture is a mixture of the first air-fuel-mixture from the gas mixer (27) and the liquid fuel from the liquid fuel supply (9) .

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