Method for low power non-coking liquid hydrocarbon fuel vaporization and supercritical phase change

Methods for vaporizing hydrocarbon fuel and delivering the hydrocarbon fuel in either a vaporized phase or a supercritical phase to, for example, a combustion chamber are provided herein. A method of vaporizing a hydrocarbon fuel, wherein the hydrocarbon fuel is in a liquid phase at a first temperature and a first pressure, and wherein the first temperature of the liquid phase hydrocarbon fuel is less than its intrinsic oxidation or endothermic reaction temperature, the method may include lowering a pressure of the liquid phase hydrocarbon fuel from the first pressure to a second pressure; and heating the liquid phase hydrocarbon fuel from the first temperature to a second temperature, wherein the hydrocarbon fuel at the second temperature and the second pressure is in a substantially completely vaporized phase substantially without thermally oxidizing the hydrocarbon fuel, and wherein the hydrocarbon fuel in the substantially completely vaporized phase does not form carbonaceous contaminants.

FIELD OF INVENTION

Embodiments of the present invention generally relate to hydrocarbon fuels, more particularly, to a method for vaporizing or effecting a supercritical phase of a hydrocarbon fuel.

BACKGROUND OF THE INVENTION

Typical fuel systems use atomized fuel which produces micron sized liquid fuel particles which must evaporate into vapor during the combustion process. However, some particles may not evaporate quickly enough, leaving fuel unburned during combustion, thereby negatively affecting the overall efficiency of combustion. In addition, very high pressures and heavy associated equipment (e.g., common-rail direct-injection) is necessary to attain atomization. Using fully vaporized fuel resolves the unburned fuel issue. However, heating a hydrocarbon fuel to attain full vaporization potentially requires heating the fuel above certain limits that undesirably initiates thermal oxidation and endothermic reactions within the fuel. Thermal oxidation reactions can cause the formation of carbon particulates and carbonaceous deposits that, for example clog spray nozzles and cake onto surfaces.

Therefore, the inventor has provided an improved method for vaporizing hydrocarbon fuel and optionally initiating a supercritical phase.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the present invention relate to a method for vaporizing a hydrocarbon fuel having a first temperature and a first pressure, wherein the hydrocarbon fuel is in a liquid phase at the first temperature and the first pressure, and wherein the first temperature of the liquid phase hydrocarbon fuel is less than its intrinsic oxidation or endothermic reaction temperature, the method may include lowering a pressure of the liquid phase hydrocarbon fuel from the first pressure to a second pressure; and heating the liquid phase hydrocarbon fuel from the first temperature to a second temperature, wherein the hydrocarbon fuel at the second temperature and the second pressure is in a substantially completely vaporized phase substantially without thermally oxidizing the hydrocarbon fuel, and wherein the hydrocarbon fuel in the substantially completely vaporized phase does not form carbonaceous contaminants.

Embodiments of the present invention relate to a method for delivering a hydrocarbon fuel to a combustion chamber which may include flowing the hydrocarbon fuel from a hydrocarbon fuel source to at least one of a pressure-reducing device or a heat exchanger, wherein the hydrocarbon fuel is in a liquid phase at a first temperature and a first pressure, and wherein the first temperature of the liquid phase hydrocarbon fuel is less than its intrinsic oxidation temperature or endothermic reaction temperature; heating the liquid phase hydrocarbon fuel from the first temperature to a second temperature; flowing the liquid phase hydrocarbon fuel through the pressure-reducing device to reduce a pressure of the liquid phase hydrocarbon fuel from the first pressure to a second pressure, wherein the liquid phase hydrocarbon fuel substantially completely vaporizes at the second temperature and the second pressure within a first duration of time without forming carbonaceous contaminants; flowing the vaporized hydrocarbon fuel through a compressor to increase the pressure of the vaporized hydrocarbon fuel from the second pressure to a third pressure; heating the vaporized hydrocarbon fuel to increase a temperature of the vaporized hydrocarbon fuel from the second temperature to a third temperature, wherein the hydrocarbon fuel is either in a vapor phase at the third pressure and the third temperature or in a supercritical phase at the third pressure and the third temperature; and flowing the completely vaporized hydrocarbon fuel or supercritical hydrocarbon fuel into the combustion chamber.

Other and further embodiments of the invention are described in more detail, below.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention include methods for vaporizing a hydrocarbon fuel and delivering the hydrocarbon fuel in either a vaporized phase or a supercritical phase to, for example, a combustion chamber. Methods for vaporizing a hydrocarbon fuel and for delivering the hydrocarbon fuel in either a vaporized phase or a supercritical phase to, for example, a combustion chamber in accordance with embodiments of the present invention advantageously facilitate the vaporization and or supercritical phase change of a hydrocarbon fuel with reduced formation of, or without the formation of, carbonaceous contaminants and without initiating endothermic reactions. In addition, methods for vaporizing a hydrocarbon fuel and for delivering the hydrocarbon fuel in either a vaporized phase or a supercritical phase to, for example, a combustion chamber in accordance with embodiments of the present invention advantageously require less power than typical vaporization or supercritical phase change systems. Furthermore, embodiments of the present invention advantageously enable all engines, heaters, and fuel cells to use any type of hydrocarbon fuel.

FIG. 1depicts a flow diagram of a method100for vaporizing a hydrocarbon fuel in accordance with some embodiments of the present invention. As used herein, the term hydrocarbon fuel refers to a fuel comprising hydrogen and carbon and typically having a thermal oxidation temperature or endothermic reaction temperature at which contaminants form, which is lower than the vaporization temperature of the hydrocarbon fuel. The hydrocarbon fuel to be vaporized is in a liquid phase at a first temperature and first pressure. The first pressure is any pressure where the hydrocarbon fuel is in a liquid phase and the first temperature is any temperature that is less that the intrinsic oxidation temperature or endothermic reaction temperature of the liquid phase hydrocarbon fuel. In some embodiments, the first pressure is an ambient pressure (e.g., about 1 bar) and the first temperature is an ambient temperature (e.g., Standard Day 15° C. (59° F.)). The available range for the first temperature will vary depending on the specific hydrocarbon fuel to be vaporized. As described below with respect toFIG. 3, a pressure-enthalpy chart can be used to determine the first pressure and first temperature for a specific hydrocarbon fuel.

At102, a pressure of the liquid phase hydrocarbon fuel is lowered from the first pressure to a second pressure. At104, the liquid phase hydrocarbon fuel is heated from a first temperature to a second temperature.

The hydrocarbon fuel at the second temperature and second pressure is substantially completely, or completely, in a vaporized phase substantially without, or without, thermally oxidizing the hydrocarbon fuel and without initiating endothermic reactions, thereby reducing or preventing formation of carbonaceous contaminants. In some embodiments, the second pressure is a pressure which facilitates vaporization of the hydrocarbon fuel below the oxidation temperature and reaction temperature of the hydrocarbon fuel. In some embodiments, the second pressure may range from the vapor pressure of the hydrocarbon fuel at the lower of either the oxidation temperature or reaction temperature of the hydrocarbon fuel, down to full vacuum. In some embodiments, the available range for the second pressure will vary depending on the second temperature and the specific hydrocarbon fuel to be vaporized. In some embodiments, the second temperature is a temperature below the oxidation temperature and reaction temperature of the hydrocarbon fuel which vaporizes the hydrocarbon fuel at the second pressure. The available range for the second temperature will vary depending on the second pressure and the specific hydrocarbon fuel to be vaporized. As described below with respect toFIG. 3, a pressure-enthalpy chart can be used to determine an appropriate second pressure and second temperature to substantially completely, or completely vaporize a specific hydrocarbon fuel substantially without, or without, the occurrence of thermal oxidization and without initiating endothermic reactions.

In some embodiments, the hydrocarbon fuel is heated from a first temperature to a second temperature and then the pressure is reduced from a first pressure to a second pressure. In some embodiments, the hydrocarbon fuel is heated from a first temperature to a second temperature while simultaneously reducing the pressure from a first pressure to a second pressure. In each of the embodiments described above, the hydrocarbon fuel at the second temperature and second pressure is substantially completely, or completely, vaporized substantially without, or without, thermally oxidizing the hydrocarbon fuel to form carbonaceous contaminants and without initiating endothermic reactions.

In some embodiments, in order to utilize the vaporized fuel, for example within a combustion chamber, the pressure of the vaporized hydrocarbon fuel is increased to a third pressure and the temperature is increased to a third temperature. In some embodiments, the hydrocarbon fuel at the third pressure and the third temperature is maintained in a vaporized state. In some embodiments, the hydrocarbon fuel at the third pressure and the third temperature is in a supercritical phase. In order to maintain the hydrocarbon fuel in a vaporized phase at the third pressure, the temperature must be increased from the second temperature to a third temperature sufficient to maintain the hydrocarbon fuel in a vaporized phase at the third pressure. In some embodiments, the third pressure is substantially the same as the first pressure, for example an ambient pressure (e.g., about 1 bar). In some embodiments, the third pressure has a range of about the combustion chamber pressure to a pressure above the critical point of the hydrocarbon fuel. In some embodiments, the available range for the third pressure will vary depending on the third temperature and the specific hydrocarbon fuel to be vaporized. In some embodiments, the third temperature is a temperature that maintains the hydrocarbon fuel in a vaporized phase. In some embodiments, the third temperature is a temperature that enables the hydrocarbon fuel to enter its supercritical phase. The available range for the third temperature will vary depending on the third pressure and the specific hydrocarbon fuel vaporized. As described below with respect toFIG. 3, a pressure-enthalpy chart can be used to determine an appropriate third pressure and third temperature to maintain a specific hydrocarbon fuel in a vapor phase or a supercritical phase.

While many vaporization systems use pulsed energy to flash vaporize hydrocarbon fuel, such a process requires a large amount of energy. The inventor has observed that vaporizing the liquid phase hydrocarbon fuel at the second pressure advantageously allows the use of a second temperature below the oxidation temperature and reaction temperature of the hydrocarbon fuel. For example, the inventor has observed that the amount of energy needed to vaporize the liquid phase hydrocarbon fuel may be no more than the energy needed to lower the pressure to a second pressure while the second temperature can be obtained using, for example waste heat from a combustion chamber utilizing the hydrocarbon fuel. Therefore, embodiments of the present invention advantageously require less power than typical vaporization or supercritical phase change systems.

FIG. 2depicts a hardware implementation for the method100described above in accordance with some embodiments of the present invention. In some embodiments, the hardware implementation depicted inFIG. 2is coupled to a combustion chamber, such as an engine, to deliver vaporized hydrocarbon fuel or supercritical phase hydrocarbon fuel to the combustion chamber. In some embodiments, the hydrocarbon fuel is in a liquid phase in region 1 between the first thermodynamic point212and the second thermodynamic point204and in a vaporized phase in regions2and3between the second thermodynamic point204and the third thermodynamic point210. Regions1,2, and3inFIG. 2correspond to regions1,2, and3inFIGS. 3 and 4described below. Returning toFIG. 2, in some embodiments, a hydrocarbon fuel source200is coupled to a heat exchanger202to transfer heat to the hydrocarbon fuel as it passes through the heat exchanger202. The hydrocarbon fuel is in the liquid phase at a first thermodynamic point212having a first temperature and a first pressure. In some embodiments, the first pressure is any pressure where the hydrocarbon fuel is in a liquid phase and the first temperature is less that the intrinsic oxidation temperature or endothermic reaction temperature of the liquid phase hydrocarbon fuel. In some embodiments the first temperature is an ambient temperature (e.g., Standard Day 15° C. (59° F.)), and the first pressure is an ambient pressure (e.g., about 1 bar). The liquid phase hydrocarbon fuel passes through the heat exchanger202to increase the temperature of the liquid phase hydrocarbon fuel from the first temperature to a second temperature. The heated liquid phase hydrocarbon fuel then passes through a pressure reducing device, such as an orifice208, a venturi, a throttling valve, or the like, to lower the pressure of the heated liquid phase hydrocarbon fuel from the first pressure (for example, ambient pressure) to a second pressure lower than the first pressure. After passing through the pressure reducing device the liquid phase hydrocarbon fuel is at a second thermodynamic point204having a second temperature and second pressure, wherein the hydrocarbon fuel is advantageously substantially completely, or completely, vaporized substantially without, or without, thermally oxidizing the hydrocarbon fuel to form carbonaceous contaminants and without initiating endothermic reactions. As described above, vaporizing the liquid phase hydrocarbon fuel at the second pressure advantageously allows the use of a second temperature below the oxidation temperature and reaction temperature of the hydrocarbon fuel. For example, the inventor has observed that the amount of energy needed to vaporize the liquid phase hydrocarbon fuel may be no more than the energy needed to lower the pressure to a second pressure while the second temperature can be obtained using, for example waste heat from a combustion chamber utilizing the hydrocarbon fuel.

In some embodiments, the liquid phase hydrocarbon fuel at the first thermodynamic point212may be passed through a pressure reducing device to reduce the pressure from the first pressure to the second pressure and then be heated from the first temperature to the second temperature using the heat exchanger202to substantially completely, or completely, vaporize the liquid phase hydrocarbon fuel substantially without, or without, thermally oxidizing the hydrocarbon fuel to form carbonaceous contaminants and without initiating endothermic reactions. In some embodiments, the orifice (or pressure reducing device)208may be heated to reduce the pressure of the liquid phase hydrocarbon fuel from the first pressure to the second pressure while heating the liquid phase hydrocarbon fuel from the first temperature to the second temperature.

In some embodiments, in order to utilize the vaporized fuel within a combustion chamber the pressure of the vaporized hydrocarbon fuel is increased to a third pressure, such as the ambient pressure, and the temperature is increased to a third temperature. In some embodiments, the hydrocarbon fuel at the third pressure and the third temperature is maintained in a vaporized phase. In order to maintain the hydrocarbon fuel in a vaporized state at the third pressure, the temperature must be increased from the second temperature to a third temperature sufficient to maintain the hydrocarbon fuel in a vaporized state at the third pressure. In some embodiments, the hydrocarbon fuel at the third pressure and the third temperature is in a supercritical phase. In order to alter the hydrocarbon fuel to a supercritical phase, the third pressure and the third temperature must be raised to above the critical point of the hydrocarbon fuel. Thus, the vaporized hydrocarbon fuel is sent through a compressor, such as a vacuum pump (or similar device), and a heater206to raise the pressure of the vaporized hydrocarbon fuel from the second pressure to the third pressure while heating the vaporized hydrocarbon fuel from the second temperature to the third temperature. After passing through the compressor and heater206, the vaporized hydrocarbon fuel is at a third thermodynamic point210having the third temperature which maintains the hydrocarbon fuel in either a vaporized phase or supercritical phase at the third pressure.

In some embodiments, the hydrocarbon fuel is a heavy hydrocarbon fuel. In some embodiments, the heavy hydrocarbon fuel is JP-8 fuel. JP-8 fuel is a kerosene type turbine fuel described in military specification document MIL-DTL-83133H, “Turbine Fuel, Aviation, Kerosene Type, JP-8 (NATO F-34), NATO F-35, and JP-8+100 (NATO F-37)” dated Oct. 25, 2011 and incorporated herein by reference. Complete vaporization of JP-8 fuel at ambient pressure (i.e., 1 bar) occurs above 204° Celsius (400° Fahrenheit). However, thermal oxidation reactions and coking, which can begin at JP-8 fuel temperatures between about 120° Celsius (248° Fahrenheit) and about 260° Celsius (500° Fahrenheit), causes the formation of carbonaceous contaminants in fuel systems that clog spray nozzles and cake on interior fuel-system surfaces. The method100described above advantageously vaporizes JP-8 fuel while overcoming thermal oxidation and coking issues. In addition, through the use of lower vaporization temperatures, the method100described above advantageously uses less power than typical vaporization systems which increase both the temperature and pressure of the target fuel.

FIG. 3depicts a pressure vs. enthalpy chart300for JP-8 fuel in accordance with some embodiments of the present invention. The chart300depicts multiple process paths312for liquid phase JP-8 fuel at a first thermodynamic point212to reach a second thermodynamic point204where the JP-8 fuel is completely vaporized substantially without, or without, thermally oxidizing to form carbonaceous contaminants and without initiating endothermic reactions. The JP-8 fuel begins in a liquid phase at the first thermodynamic point212having a first temperature, such as an ambient temperature (e.g., Standard Day 15° C. (59° F.)), and a first pressure, such as an ambient pressure (e.g. 1 bar).

At the second thermodynamic point204the JP-8 fuel is completely vaporized at a second temperature of about 120° Celsius (248° Fahrenheit) and a second pressure of about 0.07 bar. Table306depicts other exemplary temperature-pressure combinations at which the JP-8 fuel can be completely vaporized without forming carbonaceous contaminants. The inventor has found that 0.07 bar is the approximate maximum pressure that facilitates vaporization of JP-8 fuel below JP-8 reaction temperatures. By lowering the JP-8 pressure further below about 0.07 bar, the JP-8 fuel can be completely vaporized at even lower temperatures, thereby further reducing the chance of inadvertent thermal oxidation and coking.

The multiple process paths312represent different hardware configurations that can be implemented to transform the JP-8 fuel from the liquid phase at the first thermodynamic point212to the vapor phase at the second thermodynamic point204. One exemplary hardware configuration is depicted inFIG. 2, wherein the liquid phase JP-8 fuel is heated and then has the pressure reduced to vaporize the liquid JP-8 fuel. Other possible hardware configurations are described above, such as reducing the pressure of the JP-8 fuel followed by heating the JP-8 fuel or simultaneously reducing the pressure of the JP-8 fuel and heating the JP-8 fuel. As depicted inFIG. 3, the multiple process paths312reach the second thermodynamic point204without traversing the coking region302. The coking region302represents pressure-temperature combinations at which the JP-8 fuel will thermally oxidize to form carbonaceous contaminants, and (or also) initiate endothermic reactions. The pressure and temperature of the vaporized JP-8 fuel is then increased to reach the third thermodynamic point210. The JP-8 fuel at the third thermodynamic point210has a third pressure and third temperature that maintains the JP-8 fuel in a vapor phase. For example the JP-8 fuel at the third thermodynamic point210has a third pressure at the ambient pressure (e.g. 1 bar) and a third temperature of 204° Celsius (400° Fahrenheit). In some embodiments, the JP-8 fuel can have a third pressure and third temperature above the critical point of the JP-8 fuel, resulting in a supercritical phase for the JP-8 fuel. In some embodiments, the third pressure is about 23.4 bar and the third temperature is about 410° Celsius (770° Fahrenheit) for the JP-8 fuel to be in a supercritical phase.

InFIG. 4, the pressure vs. enthalpy chart400for JP-8 fuel depicts a process path402for liquid phase JP-8 fuel at the first thermodynamic point212, wherein, instead of avoiding the coking region302to reach the second thermodynamic point204, the process path402goes through the coking region302by heating the JP-8 fuel at a temperature greater than 120° Celsius (248° Fahrenheit). However, in order to avoid thermal oxidation of the hydrocarbon fuel and avoid endothermic reactions, the process path402traverses the coking region302within a first duration of time, which is insufficient for the JP-8 to thermally oxidize or initiate endothermic reactions. In some embodiments, the JP-8 fuel is completely vaporized in less than about one second. The pressure and temperature of the vaporized JP-8 fuel is then increased to reach the third thermodynamic point210. The JP-8 fuel at the third thermodynamic point210has a third pressure and third temperature that maintains the JP-8 fuel in a vapor phase. For example the JP-8 fuel at the third thermodynamic point210has a third pressure at the ambient pressure (e.g. 1 bar) and a third temperature of 204° Celsius (400° Fahrenheit). In some embodiments, the JP-8 fuel can have a third pressure and third temperature above the critical point of the JP-8 fuel, resulting in a supercritical phase for the JP-8 fuel. In some embodiments, the third pressure is about 23.4 bar and the third temperature is about 410° Celsius (770° Fahrenheit) for the JP-8 fuel to be in a supercritical phase. Table406depicts pressure and temperature combinations at which the process path402of the JP-8 fuel traverses the coking region302requiring the JP-8 fuel to be vaporized in less than about one second.