Auxiliary power unit lubrication system, APU lubricant, and aircraft cabin air system

Abstract

The auxiliary power unit (APU) system, APU lubricant, and aircraft cabin air system comprising the APU system and lubricant, wherein the APU system comprises: an engine system including an engine compressor, a combustion chamber, and an engine turbine; a load compressor; a generator; an oil pump with an oil reservoir having an inlet and an outlet; and a flow path fluidly connected to the inlet, the outlet, the engine system, the load compressor, and the generator, wherein the flow path supplies a lubricant composition to one or more of the engine system, the load compressor, or the generator.

Description

Technical Field

[0001] The embodiments disclosed herein generally relate to auxiliary power unit (APU) lubrication systems, APU lubricants, and aircraft cabin air systems that include APU lubrication systems and lubricants. Background Technology

[0002] Aircraft lubrication systems are typically associated with the APU and one or more propulsion engines to dissipate heat and / or lubricate various components. Lubrication systems generally involve circulating heat-resistant and oxidation-resistant oils along flow paths through one or more components of the APU and propulsion engines. These oils typically contain valeric acid as a base oil component. The APU-loaded compressors and propulsion engine compressors, in particular, supply bleed air to the aircraft's Environmental Control System (ECS), which provides pressurization and regulation of cabin air. Due to various design and deterioration conditions, the APU and propulsion engines may leak very fine droplets of oil lubricant into the bleed air from the compressors. As a result, an odor may be noticeable in the aircraft cabin due to the use of APU or propulsion engine bleed air.

[0003] Odor incidents reported by airlines to the FAA between 2012 and 2017 revealed that known causes primarily included the APU (Air Processing Unit), but in some cases, propulsion engines. Once oil leaks from the APU or engine, air temperature and humidity encountered during certain flight segments (takeoff, climb, cruise, descent, etc.) have a significant impact on oil contaminated with the ECS (Electronic Control System). The release of valeric acid due to the deterioration of the lubricating oil base stock is particularly alarming, resulting in a nauseating and irritating odor even at very low concentrations. As described in EP3323728B1, an odor was detected in bleed air, with a peak concentration of valeric acid detected at approximately 0.5 ppb, and a “strong odor” was observed when the concentration increased to approximately 2 ppb. The loss of aircraft use due to subsequent cleanup is costly in terms of reduced labor and asset productivity.

[0004] In addition to the discomfort and loss of value caused by valeric acid exposure in aircraft cabin incidents, certain triaryl phosphates used as anti-wear additives have been subject to detailed review at high concentrations in aviation turbine oil formulations. Trimethylbenzene phosphate (TCP) is used in many products currently used in aircraft due to its excellent wear inhibition and load-carrying properties, but this compound has been reviewed due to the known neurotoxicity of its ortho-isomers at high concentrations. Since 2005, SAE International has recommended controlling the amount of mono, di, and tri-o-tolyl isomers of TCP to less than 0.2% by weight of the total amount of any TCP used in a fully formulated oil. Changes in the manufacturing and distillation processes of the TCP feedstock (cresol) have minimized the content of these ortho-isomers. The alternative triaryl phosphate used is isopropyltriphenyl phosphate (iPTPP), which has reduced wear inhibition and load-carrying capabilities as well as unique toxicity issues.

[0005] Therefore, it is still necessary to minimize odor while maintaining or improving the operation of the APU lubrication system and the aircraft cabin air system. Summary of the Invention

[0006] The embodiments herein disclose an auxiliary power unit (APU) system for an aircraft. The APU system includes: an engine system comprising an engine compressor, a combustion chamber, and an engine turbine; a load compressor; a generator; an oil pump with an oil reservoir having an inlet and an outlet; and a flow path fluidly connected to the inlet, outlet, engine system, load compressor, and generator, wherein the flow path supplies a lubricating oil composition to one or more of the engine system, load compressor, or generator, wherein the lubricating oil composition comprises: a. at least 80% by weight of a lubricating oil base oil comprising reaction products of: 1. a polyol selected from the group consisting of trimethylolethane, trimethylolpropane, trimethylolbutane, neopentyl glycol, and mixtures thereof; and 2. a mixture of C7-C10 straight-chain monocarboxylic acids, wherein the lubricating oil base oil comprises less than 0.2% by weight of C5 and C6 monocarboxylic acids; and b. 1% to 5% by weight of an anti-wear agent composition selected from compounds of formula I: R1, R2, and R3 are independently selected from the group consisting of phenyl, 3-tert-butylphenyl, and 4-tert-butylphenyl; wherein the anti-wear composition comprises: 1. at least 90 mol% of a compound of formula I, wherein at least one of the R1, R2, or R3 groups is selected from the group consisting of 3-tert-butylphenyl and 4-tert-butylphenyl; and 2. from 5 mol% to 27.5 mol% of a compound of formula I, wherein at least two of the R1, R2, or R3 groups are selected from the group consisting of 3-tert-butylphenyl and 4-tert-butylphenyl; and wherein the lubricating oil composition is free of tricresyl phosphate and isopropyltriphenyl phosphate.

[0007] The embodiments herein further disclose a lubricating oil composition for use in an auxiliary power unit (APU) system of an aircraft. The composition comprises a. at least 80% by weight of a lubricating oil base oil comprising a reaction product of: 1. a polyol selected from the group consisting of trimethylolethane, trimethylolpropane, trimethylolbutane, neopentyl glycol, and mixtures thereof; and 2. a mixture of C7-C10 straight-chain monocarboxylic acids, wherein the lubricating oil base oil comprises less than 0.2% by weight of C5 and C6 monocarboxylic acids; and b. 1% to 5% by weight of an anti-wear agent composition selected from compounds of formula I: R1, R2, and R3 are independently selected from the group consisting of phenyl, 3-tert-butylphenyl, and 4-tert-butylphenyl; wherein the anti-wear composition comprises: 1. at least 90 mol% of a compound of formula I, wherein at least one of the R1, R2, or R3 groups is selected from the group consisting of 3-tert-butylphenyl and 4-tert-butylphenyl; and 2. from 5 mol% to 27.5 mol% of a compound of formula I, wherein at least two of the R1, R2, or R3 groups are selected from the group consisting of 3-tert-butylphenyl and 4-tert-butylphenyl; and wherein the lubricating oil composition is free of tricresyl phosphate and isopropyltriphenyl phosphate.

[0008] In one or more embodiments herein, the polyol of the lubricating oil base stock is a mixture of trimethylolpropane and neopentyl glycol. In one or more embodiments herein, the lubricating oil base stock contains less than 0.1% by weight of C7-C10 branched monocarboxylic acids.

[0009] In one or more embodiments herein, the anti-wear composition comprises less than 5 mol% of a compound of formula I, wherein the R1, R2, and R3 groups are phenyl. In one or more embodiments herein, the anti-wear composition comprises 70 mol% to 85 mol% of a compound of formula I, wherein one of the R1, R2, or R3 groups is selected from the group consisting of 3-tert-butylphenyl and 4-tert-butylphenyl. In one or more embodiments herein, the anti-wear composition comprises less than 5 mol% of a compound of formula I, wherein the R1, R2, and R3 groups are selected from the group consisting of 3-tert-butylphenyl and 4-tert-butylphenyl.

[0010] In one or more embodiments herein, the lubricating oil composition further comprises 0.1% to 5% by weight of one or more antioxidants selected from the group consisting of aromatic amines, aromatic amine oligomers, and mixtures thereof.

[0011] The embodiments herein further disclose an aircraft cabin air system. The aircraft cabin air system includes: an auxiliary power unit system as described in one or more embodiments herein; a propulsion engine system including a turbine; a compressor; a gearbox; an oil pump with an oil reservoir having an inlet and an outlet; and flow paths fluidly connected to the inlet, outlet, turbine, compressor, and gearbox, wherein the flow paths supply a propulsion engine lubricating oil composition to one or more of the turbine, compressor, or gearbox; and an environmental control system (ECS) including an air distribution system, one or more heat exchangers, and one or more air circulators, wherein the ECS is pneumatically connected to the auxiliary power unit system and the propulsion engine system.

[0012] In one or more embodiments herein, the propulsion engine lubricant composition comprises: a. at least 80% by weight of a base oil composition; and b. 1% by weight to 5% by weight of an anti-wear agent composition, said anti-wear agent composition being selected from compounds of formula I: R1, R2, and R3 are independently selected from the group consisting of phenyl, 3-tert-butylphenyl, and 4-tert-butylphenyl; wherein the anti-wear composition comprises: 1. at least 90 mol% of a compound of formula I, wherein at least one of the R1, R2, or R3 groups is selected from the group consisting of 3-tert-butylphenyl and 4-tert-butylphenyl; and 2. from 5 mol% to 27.5 mol% of a compound of formula I, wherein at least two of the R1, R2, or R3 groups are selected from the group consisting of 3-tert-butylphenyl and 4-tert-butylphenyl; and wherein the lubricating oil composition is free of tricresyl phosphate and isopropyltriphenyl phosphate.

[0013] In one or more embodiments herein, the propulsion engine lubricant composition comprises: a. at least 80% by weight of a base oil composition comprising: (i) a first base oil comprising a reaction product of: 1. a polyol ester selected from the group consisting of monopentaerythritol, dipentaerythritol, and mixtures thereof, and 2. a mixture of C5-C10 straight-chain or branched monocarboxylic acids; and (ii) a second base oil comprising a reaction product of: 1. a polyol ester selected from the group consisting of trimethylolethane, trimethylolpropane, trimethylolbutane, neopentyl glycol, and mixtures thereof, and 2. a mixture of C5-C10 straight-chain or branched monocarboxylic acids; and b. 1% to 5% by weight of an anti-wear composition selected from compounds of formula I: R1, R2, and R3 are independently selected from the group consisting of phenyl, 3-tert-butylphenyl, and 4-tert-butylphenyl; wherein the anti-wear composition comprises: 1. at least 90 mol% of a compound of formula I, wherein at least one of the R1, R2, or R3 groups is selected from the group consisting of 3-tert-butylphenyl and 4-tert-butylphenyl; and 2. from 5 mol% to 27.5 mol% of a compound of formula I, wherein at least two of the R1, R2, or R3 groups are selected from the group consisting of 3-tert-butylphenyl and 4-tert-butylphenyl; and wherein the lubricating oil composition is free of tricresyl phosphate and isopropyltriphenyl phosphate.

[0014] Further features and advantages of the embodiments will be described in the following detailed description, and some of these features and advantages will become apparent to those skilled in the art from the description or by practicing the embodiments described herein. It should be understood that the above and following detailed descriptions depict various embodiments and are intended to provide an overview or framework for understanding the nature and characteristics of the claimed subject matter. Attached Figure Description

[0015] Figure 1 The lubrication system of the aircraft's auxiliary power unit is schematically depicted.

[0016] Figure 2 The lubrication system of the propulsion engine is schematically depicted.

[0017] Figure 3 An environmental control system is schematically depicted. Detailed Implementation

[0018] Reference will now be made in detail to embodiments of APU systems and lubricant compositions used in APU systems, as well as aircraft cabin air systems. APUs and aircraft cabin air systems can be used in aircraft such as airplanes or helicopters. However, it should be noted that this is merely an illustrative embodiment of the embodiments disclosed herein. These embodiments are applicable to other technologies susceptible to problems similar to those discussed above.

[0019] APU system like Figure 1 As shown, the APU system (100) includes an engine system (105); a load compressor (110); a generator (115); an oil pump (120) with an oil reservoir having an inlet (125) and an outlet (130); and flow paths (135, 140) in fluid communication with the inlet (125), the outlet (130), the engine system (105), the load compressor (110), and the generator (115). The engine system (105) is configured to power various systems such as the load compressor (110) and the generator (115), and includes an engine compressor, a combustion chamber, and an engine turbine. The engine system (105) drives the load compressor (110) via shafts (155) and gearboxes (115) for various accessories such as the generator (115) and the oil pump (120).

[0020] The load compressor (110) is configured to deliver compressed air to the ECS and provide aerodynamic power for the aircraft's main engine start-up capability. Outside air enters through inlet (145) and is compressed by the load compressor (110). The load compressor (110) may optionally include variable inlet guide vanes and / or a variable diffuser, which can allow for the management of a wide range of flow and pressure ratio conditions. Air from the load compressor (110) is directed through bleed air duct (150) to circulate through the air conditioning system to reduce its temperature before being used as fresh pressurized air to maintain the habitability and comfort of the aircraft cabin and cockpit.

[0021] The generator (115) is configured to provide power for ground and emergency flight needs. An engine system (105) drives a gearbox that provides mechanical power to the generator (115) via a shaft (155). The gearbox distributes some of the mechanical power from the shaft (115) to accessories such as the generator (115) and an oil pump (120). A recirculated oil flow path (135) includes an oil pump that draws oil from an oil reservoir (120) and supplies a filtered lubricating oil composition to one or more of the engine system (105), the load compressor (110), or the generator (115), whereby the oil provides necessary lubrication, thermal management, and debris removal.

[0022] Lubricating oil composition In embodiments described herein, the lubricating oil composition comprises a lubricating oil base oil and an anti-wear composition, wherein the lubricating oil composition is free of tricresyl phosphate and isopropyltriphenyl phosphate. As used herein, the term "free of" means that tricresyl phosphate and isopropyltriphenyl phosphate are not intentionally added to the lubricating oil composition.

[0023] In embodiments described herein, the lubricating oil composition comprises at least 80 wt% of a lubricating oil base oil and 1 wt% to 5 wt% of an anti-wear agent composition. All individual values ​​and subranges are included and disclosed herein. For example, in some embodiments, the lubricating oil composition comprises 80 wt%, 85 wt%, 87.5 wt%, 90 wt%, 92.5 wt%, or 95 wt% to 99 wt%, 97.5 wt%, 95 wt%, 92.5 wt%, or 90 wt% of a lubricating oil base oil, and / or 1 wt%, 1.25 wt%, 1.5 wt%, 1.75 wt%, 2 wt%, or 2.25 wt% to 5 wt%, 4.5 wt%, 4 wt%, 3.75 wt%, 3.5 wt%, 3.25 wt%, 3 wt%, 2.75 wt%, or 2.5 wt% of an anti-wear agent composition. In other embodiments, the lubricating oil composition comprises 90% or 92.5% to 99% or 97.5% by weight of a lubricating oil base oil and / or 1.5% to 2.75% or 2.5% by weight of an anti-wear agent composition.

[0024] In the embodiments described herein, the lubricating oil base stock is a reaction product of: (1) a polyol selected from the group consisting of trimethylolethane, trimethylolpropane, trimethylolbutane, neopentyl glycol, and mixtures thereof, and (2) a mixture of C7-C10 straight-chain monocarboxylic acids. In some embodiments, the lubricating oil base stock is a reaction product of: (1) a polyol selected from the group consisting of trimethylolpropane, neopentyl glycol, and mixtures thereof, and (2) a mixture of C7-C10 straight-chain monocarboxylic acids. In a further embodiment, the lubricating oil base stock is a reaction product of: (1) a polyol as a mixture of trimethylolpropane and neopentyl glycol, and (2) a mixture of C7-C10 straight-chain monocarboxylic acids. C7 to C10 straight-chain monocarboxylic acids include heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, and combinations thereof.

[0025] In embodiments herein, the lubricating oil base stock is a reaction product of: (1) a polyol selected from the group consisting of trimethylolethane, trimethylolpropane, trimethylolbutane, neopentyl glycol, and mixtures thereof, and (2) a mixture of C7-C10 straight-chain monocarboxylic acids, and comprising less than 0.2% by weight of C5 and C6 monocarboxylic acids. All individual values ​​and subranges are included and disclosed herein. For example, in some embodiments, the lubricating oil base stock comprises less than 0.15%, 0.125%, or 0.1% by weight of C5 and C6 monocarboxylic acids. In a further embodiment, the lubricating oil base stock is a reaction product of: (1) a polyol selected from the group consisting of trimethylolethane, trimethylolpropane, trimethylolbutane, neopentyl glycol, and mixtures thereof, and (2) a mixture of C7-C10 straight-chain monocarboxylic acids, and the C5 and C6 monocarboxylic acids are not intentionally added to the lubricating oil base stock.

[0026] In one or more embodiments herein, the lubricating oil base stock is a reaction product of: (1) a polyol selected from the group consisting of trimethylolethane, trimethylolpropane, trimethylolbutane, neopentyl glycol, and mixtures thereof, and (2) a mixture of C7-C10 straight-chain monocarboxylic acids, and comprising less than 0.1% by weight of C7-C10 branched monocarboxylic acids. All individual values ​​and subranges are included and disclosed herein. For example, in some embodiments, the lubricating oil base stock comprises less than 0.1% by weight, 0.08% by weight, or 0.07% by weight of C7-C10 branched monocarboxylic acids. In a further embodiment, the lubricating oil base stock is a reaction product of: (1) a polyol selected from the group consisting of trimethylolethane, trimethylolpropane, trimethylolbutane, neopentyl glycol, and mixtures thereof, and (2) a mixture of C7-C10 straight-chain monocarboxylic acids, and the C7-C10 branched monocarboxylic acids are not intentionally added to the lubricating oil base stock.

[0027] Anti-wear composition In the embodiments described herein, the anti-wear composition is selected from compounds of formula I: (I) R1, R2, and R3 are independently selected from the group consisting of phenyl, 3-tert-butylphenyl, and 4-tert-butylphenyl.

[0028] The anti-wear composition comprises: 1. at least 90 mol% (or alternatively, at least 92.5 mol% or 95 mol%) of a compound of formula I, wherein at least one of the R1, R2, or R3 groups is selected from the group consisting of 3-tert-butylphenyl and 4-tert-butylphenyl; and 2. from 5 mol% to 27.5 mol% of a compound of formula I, wherein at least two of the R1, R2, or R3 groups are selected from the group consisting of 3-tert-butylphenyl and 4-tert-butylphenyl. All individual values ​​and subranges are included and disclosed herein. For example, in some embodiments, the anti-wear composition comprises: 1. 92 mol% to 99 mol% (or alternatively, 94 mol% to 99 mol% or 96 mol% to 99 mol%) of a compound of formula I, wherein at least one of the R1, R2, or R3 groups is selected from the group consisting of 3-tert-butylphenyl and 4-tert-butylphenyl; and 2. 10 mol% to 27.5 mol% (or alternatively, 15 mol% to 27.5 mol% or 17.5 mol% to 27.5 mol%) of a compound of formula I, wherein at least two of the R1, R2, or R3 groups are selected from the group consisting of 3-tert-butylphenyl and 4-tert-butylphenyl.

[0029] In one or more embodiments herein, the anti-wear composition comprises less than 5 mol% of a compound of formula I, wherein the R1, R2, and R3 groups are phenyl. All individual values ​​and subranges are included and disclosed herein. For example, in some embodiments, the anti-wear composition comprises 0 mol% or greater than 0 mol% up to 4.5 mol%, 4.0 mol%, or 3.5 mol% of a compound of formula I, wherein the R1, R2, and R3 groups are phenyl. Alternatively, the anti-wear composition comprises greater than 0 mol% up to 4.0 mol% or 3.5 mol% of triphenyl phosphate.

[0030] In one or more embodiments herein, the anti-wear composition comprises 70 mol% to 85 mol% of a compound of formula I, wherein one of the R1, R2, or R3 groups is selected from the group consisting of 3-tert-butylphenyl and 4-tert-butylphenyl. For example, in some embodiments, the anti-wear composition comprises 70 mol%, 72.5 mol%, or 75 mol% to 85 mol%, 82.5 mol%, 80 mol%, or 77.5 mol% of a compound of formula I, wherein one of the R1, R2, or R3 groups is selected from the group consisting of 3-tert-butylphenyl and 4-tert-butylphenyl. Alternatively, the anti-wear composition comprises 70 mol%, 72.5 mol%, or 75 mol% to 85 mol%, 82.5 mol%, 80 mol%, or 77.5 mol% of diphenyl tert-butylphenyl phosphate.

[0031] In one or more embodiments herein, the anti-wear composition comprises less than 5 mol% of a compound of formula I, wherein the R1, R2, and R3 groups are selected from the group consisting of 3-tert-butylphenyl and 4-tert-butylphenyl. All individual values ​​and subranges are included and disclosed herein. For example, in some embodiments, the anti-wear composition comprises greater than 0 mol% to 4 mol%, 3 mol%, 2.5 mol%, or 2 mol% of a compound of formula I, wherein the R1, R2, and R3 groups are selected from the group consisting of 3-tert-butylphenyl and 4-tert-butylphenyl. Alternatively, the anti-wear composition comprises greater than 0 mol% to 4 mol%, 3 mol%, 2.5 mol%, or 2 mol% of tris(tert-butylphenyl) phosphate.

[0032] Other components In one or more embodiments herein, the lubricating oil composition further comprises 0.1 wt% to 5 wt% of one or more antioxidants selected from the group consisting of aromatic amines, aromatic amine oligomers, and mixtures thereof. Antioxidants can be used to reduce the tendency of lubricating oils to deteriorate during use. All individual values ​​and subranges are included and disclosed herein. For example, in some embodiments, the lubricating oil composition further comprises 0.1 wt%, 0.5 wt%, 1.0 wt%, 1.5 wt%, or 2.0 wt% to 5 wt%, 4.5 wt%, 4.0 wt%, 3.5 wt%, or 3.0 wt% of one or more antioxidants selected from the group consisting of aromatic amines, aromatic amine oligomers, and mixtures thereof.

[0033] Exemplary aromatic amines may include, but are not limited to, diphenylamine, alkylated diphenylamine, styrenated diphenylamine, phenyl-N-naphthylamine, alkylated phenyl-N-naphthylamine, styrenated phenyl-N-naphthylamine, phenothiazine, alkylated phenothiazine, and styrenated phenothiazine. Exemplary aromatic amine oligomers may include the polymerization products of one or more diphenylamines, one or more phenylnaphthylamines, or one or more diphenylamines and one or more phenylnaphthylamines. In some embodiments herein, the lubricating oil composition further comprises 0.1% to 5% by weight of one or more aromatic amines. Other antioxidants such as hindered phenols may be added to the lubricant as monomeric antioxidants or together with aromatic amine antioxidants.

[0034] In one or more embodiments herein, the lubricating oil composition further comprises 0.1% to 5% by weight of one or more other components, such as metal rust inhibitors, corrosion inhibitors, hydrolytic stabilizers, other oxidation inhibitors, friction modifiers, defoamers, and rust inhibitors.

[0035] Aircraft cabin air system The embodiments herein also disclose an aircraft cabin air system. The aircraft cabin air system provides air conditioning with temperature, pressure, and humidity control capabilities, distributing air to various parts of the aircraft, such as the passenger cabin, cockpit, or cargo hold. As previously described, the aircraft cabin air system includes an APU system, a propulsion engine system, and an ECS as described herein. The ECS is aerodynamically connected to the APU system and the propulsion engine system. The propulsion system is designed to provide the necessary thrust to propel the aircraft through flight by exhausting high-speed airflow. Figure 2 As shown, the propulsion engine system (200) includes a turbine (205); a compressor (210); a gearbox (215); an oil pump (215) with an oil reservoir having an inlet (220) and an outlet (225); and flow paths (230, 235) in fluid communication with the inlet (220), outlet (225), turbine (205), compressor (210), and gearbox (215). A combustion chamber (240) and a fan (245) are also shown. The flow paths supply a propulsion engine lubricating oil composition to one or more turbines (205), compressors (210), or gearboxes (215), and may also include a fan (245). The turbine (205) and compressor (210) are mounted on a shaft (250), which is dynamically supported by bearings arranged in a plurality of bearing oil grooves, wherein the propulsion engine lubricating oil composition can be used to spray the bearings, and then collected and returned to the oil tank (215). The turbine (205) drives the compressor (210) via the shaft (250).

[0036] Outside air enters through inlet (255) and is compressed by compressor (210). Compressor (210) is configured to deliver a portion of the compressed bleed air to the ECS, while the majority of the compressed air is delivered to the combustion chamber to support the combustion of the jet fuel that powers the turbine. Compressor (210) may optionally include variable stator blades, which can allow for the management of a wide range of flow and pressure ratio conditions. Depending on engine operating conditions, bleed air is drawn from the low-pressure and high-pressure compressor sections. Figure 2 As shown, the compressor (210) also supplies high-pressure, high-temperature bleed air to the aircraft ECS and other aircraft systems (e.g., engine and aircraft de-icing, pressurized aircraft fluid systems, engine internal cooling) via valves and bleed air ducts (260). Bleed air is drawn from the low-stage and high-stage compressor sections depending on the engine operating conditions. For most engine high-power settings, such as takeoff, climb, and cruise, the low-stage (or low-pressure) is selected, and for lower engine power settings, such as descent, the high-stage (or high-pressure) is selected.

[0037] like Figure 3As shown, engine bleed air ducts (260A, 260B) and APU bleed air ducts (150) supply air to the environmental control system (300) via air supply ducts (330). That is, the environmental control system (300) is pneumatically connected to the auxiliary power unit system (100) and the propulsion engine system (200). The environmental control system (300) includes one or more heat exchangers (305) and one or more air circulators (305). Furthermore, the environmental control system (300) may also include an ozone converter (310), a hot air manifold (315), a filter (320), and / or an air mixing device (325). Air returning from the aircraft cabin passes through return air ducts (335). The environmental control system (300) delivers high-pressure, high-temperature air from the auxiliary power unit system (100) and the propulsion engine system (200) to various parts of the aircraft, such as the passenger cabin, cockpit, and cargo hold, to maintain a habitable and comfortable pressurized cabin.

[0038] As described herein, a flow path (230) in a propulsion engine system (200) supplies a propulsion engine lubricating oil composition to one or more turbines (205), compressors (210), or gearboxes (215), and may also include a fan (245). The propulsion engine lubricating oil composition comprises a propulsion engine lubricating oil base oil and an anti-wear agent composition, wherein the propulsion engine lubricating oil composition is free of tricresyl phosphate and isopropyltriphenyl phosphate.

[0039] In embodiments described herein, the propulsion engine lubricant composition comprises at least 80 wt% of a propulsion engine lubricant base oil and 1 wt% to 5 wt% of an anti-wear agent composition. All individual values ​​and subranges are included and disclosed herein. For example, in some embodiments, the propulsion engine lubricant composition comprises 80 wt%, 85 wt%, 87.5 wt%, 90 wt%, 92.5 wt%, or 95 wt% to 99 wt%, 97.5 wt%, 95 wt%, 92.5 wt%, or 90 wt% of a propulsion engine lubricant base oil, and / or 1 wt%, 1.25 wt%, 1.5 wt%, 1.75 wt%, 2 wt%, 2.25 wt%, or 2.5 wt% to 5 wt%, 4.5 wt%, 4 wt%, 3.75 wt%, or 3.5 wt% of an anti-wear agent composition. In other embodiments, the propulsion engine lubricant composition comprises 87.5% or 90% to 97.5% or 95% by weight of propulsion engine lubricant base oil and / or 2% or 2.5% to 4% or 3.5% by weight of an anti-wear agent composition.

[0040] In one or more embodiments herein, the propulsion engine lubricant base oil may comprise a first base oil and a second base oil. In some embodiments herein, the ratio of the first base oil to the second base oil is from 75:25 to 95:5. All individual values ​​and subranges are included and disclosed herein. For example, in some embodiments, the ratio of the first base oil to the second base oil is from 77.5:22.5 to 95:5, 80:20 to 95:5, or 85:15 to 95:5.

[0041] The first base oil is the reaction product of: (1) a polyol selected from the group consisting of pentaerythritol, dipentaerythritol, and mixtures thereof, and (2) a mixture of C5-C10 straight-chain and / or branched monocarboxylic acids. In some embodiments, the first base oil is the reaction product of: (1) pentaerythritol, and (2) a mixture of C5-C10 straight-chain and / or branched monocarboxylic acids. In other embodiments, the first base oil is the reaction product of: (1) a polyol selected from the group consisting of pentaerythritol, dipentaerythritol, and mixtures thereof, and (2) a mixture of C5-C10 straight-chain and branched monocarboxylic acids. In a further embodiment, the first base oil is the reaction product of: (1) pentaerythritol, and (2) a mixture of C5-C10 straight-chain and branched monocarboxylic acids. The monocarboxylic acid reacts with the synthetic alcohol in proportion to give fully esterified pentaerythritol or dipentaerythritol.

[0042] The second base oil is the reaction product of: (1) a polyol selected from the group consisting of trimethylolethane, trimethylolpropane, trimethylolbutane, neopentyl glycol, and mixtures thereof, and (2) a mixture of C5-C10 straight-chain or branched monocarboxylic acids. In some embodiments, the second base oil is the reaction product of: (1) a polyol selected from the group consisting of trimethylolpropane, neopentyl glycol, and mixtures thereof, and (2) a mixture of C7-C10 straight-chain or branched monocarboxylic acids. In a further embodiment, the lubricating oil base oil is the reaction product of: (1) a polyol as a mixture of trimethylolpropane and neopentyl glycol, and (2) a mixture of C7-C10 straight-chain or branched monocarboxylic acids. The monocarboxylic acid reacts with the synthetic alcohol in proportion to obtain a fully esterified polyol.

[0043] In the embodiments described herein, the anti-wear composition used in the propulsion engine lubricant composition is the same as that described above for the anti-wear composition used in the APU lubricant composition, and is incorporated herein by reference in this paragraph.

[0044] In one or more embodiments herein, the propulsion engine lubricant composition further comprises 0.1 wt% to 5 wt% of one or more antioxidants selected from the group consisting of aromatic amines, aromatic amine oligomers, hindered phenols, and mixtures thereof. Antioxidants can be used to reduce the tendency of lubricants to deteriorate during use. All individual values ​​and subranges are included and disclosed herein. For example, in some embodiments, the lubricant composition further comprises 0.1 wt%, 1.0 wt%, 2.0 wt%, 2.5 wt%, 3.0 wt%, or 3.5 wt% to 5 wt%, 4.9 wt%, 4.8 wt%, or 4.75 wt% of one or more antioxidants selected from the group consisting of aromatic amines, aromatic amine oligomers, hindered phenols, and mixtures thereof.

[0045] Exemplary aromatic amines may include, but are not limited to, diphenylamine, alkylated diphenylamine, styrenated diphenylamine, phenyl-N-naphthylamine, alkylated phenyl-N-naphthylamine, styrenated phenyl-N-naphthylamine, phenothiazine, alkylated phenothiazine, and styrenated phenothiazine. Exemplary aromatic amine oligomers may include the polymerization products of one or more diphenylamines, one or more phenylnaphthylamines, or one or more diphenylamines and one or more phenylnaphthylamines. Exemplary hindered phenols may include, but are not limited to, 6-di-tert-butylphenol; 2-tert-butyl-4-methoxyphenol; 3-tert-butyl-4-methoxyphenol; 2-tert-butyl-4,6-dimethylphenyl; 2,6-di-tert-butyl-4-ethylphenol; 2,6-di-tert-butyl-4-n-butylphenol; 2,6-di-tert-butyl-4-isobutylphenol; 2,6-di-tert-butyl-methylphenol; 2,6-di-cyclopentyl-4-methylphenol; 2-(α-methylcyclohexyl) 2,6-Dimethylphenol; 2,6-Di-octadecyl-4-methylphenol; 2,4,6-tri-cyclohexylphenol; 2,6-di-tert-butyl-4-methoxymethylphenol; 2,6-di-tert-butyl-4-methoxyphenol; 2-tert-butylhydroquinone; 2,5-di-tert-butylhydroquinone; 2,5-di-tert-pentylhydroquinone; 2,6-diphenyl-4-octadecoxyphenol; 2-tert-butyl-1,4-benzoquinone; tri-methyl-di-hydroquinoline.

[0046] In one or more embodiments herein, the lubricating oil composition further comprises 0.1% to 5% by weight of one or more other components, such as metal rust inhibitors, corrosion inhibitors, hydrolytic stabilizers, other oxidation inhibitors, friction modifiers, defoamers, and rust inhibitors.

[0047] Unbound by theory, the applicant unexpectedly discovered that by using different lubricant compositions in the APU and propulsion engine systems, cabin air quality could be improved by reducing odor and enhancing system operation and reliability.

[0048] Test methods Odor Sensitivity – HS-GC / MS The in-situ odor sensitivity of turbine oil products in the presence of heat and water was evaluated using headspace gas chromatography coupled with mass spectrometry (HS-GC / MS). Several propulsion engine and APU lubricant compositions (Table 2) were mixed with 1% by weight of water into 20-mL headspace (HS) vials with an air environment. Two HS sample vials were prepared for each oil and analyzed. The oil-water mixture was heated at 180 °C for 5 hours to produce characteristic fatty acids. Then, 1.0-mL of vapor from the prepared sample-HS vial was injected into the GC inlet for chromatographic separation and mass spectrometric detection. The concentration of fatty acids in the vapor was determined using the integrated peak area at m / z=60 and a calibration relative to an acetone-fatty acid standard solution.

[0049] Four-ball wear The four-ball wear test is used to evaluate the relative anti-wear properties of lubricants in sliding contact under static load. The effectiveness of the lubricant is determined by comparing the average size of the wear tracks acting on the three lower balls, where a lower diameter corresponds to improved wear resistance. The test equipment and procedures are used in duplicate according to ASTM D4172, and the average results are reported in Table 4.

[0050] Wear performance – WAM The Wedeven Associates Machine (WAM) is the test required for the certification of propulsion engine oils according to SAE AS5780. The WAM test uses a ball-and-disc machine that is subjected to progressively increasing loads until macroscopic wear failure occurs in the lubrication contact area, where performance is determined by the load stage at which this failure occurs. The test equipment and procedures used and followed in the implementation and the examples below are described in SAE Aerospace Recommendation ARP 6156. The test was repeated three times, and the average results are reported in Table 4.

[0051] Example The following specific examples illustrate the process and performance characteristics related to the invention described herein. Examples and comparative examples of the invention are provided below, with details of the formulations and results provided in the tables below.

[0052] Table 1 – Raw Materials Lubricating oil compositions fluid A and fluid B were purchased from Boeing Distribution Services. Lubricating oil compositions fluid 1 and fluid C were prepared by blending a base oil with anti-wear agents, antioxidants, and other additives such as metal rust inhibitors, corrosion inhibitors, hydrolytic stabilizers, other oxidation inhibitors, friction modifiers, defoamers, and rust inhibitors. Details of each composition are shown in Table 2. In the case of fluid 1 and fluid C, the compositions are substantially the same except for the selected anti-wear additives.

[0053] Table 2 – Lubricating Oil Compositions The odor sensitivity of the fluid was measured before and after hydrolysis, and the results are reported in Table 3. The 4-ball wear and WAM load failure stages of the fluid were also measured, and the results are reported in Table 4.

[0054] Table 3 The results showed that for oils containing valeric acid, hexanoic acid, and heptanoic acid in the base oil, these components were measured in the headspace vapor after hydrolysis and degradation. Fluid 1, formulated to be free of valeric acid and hexanoic acid, did not show any of these two substances in the headspace vapor. The typical olfactory thresholds for hexanoic acid and heptanoic acid in humans are 13 ppb and 28 ppb, respectively, and for valeric acid, the odor is detected at concentrations as low as 0.5 ppb and described as having a strong odor at 2 ppb. Relative to the concentrations of valeric acid, hexanoic acid, and heptanoic acid measured in the headspace vapor in Table 3, it can be inferred that the degradation of fluids A and B would be detectable in the headspace vapor due to the unpleasant odor of valeric acid. However, fluid 1 does not exhibit this characteristic and nauseating odor because its fatty acid content is an order of magnitude lower than the reported threshold for heptanoic acid.

[0055] Table 4 Four-ball wear results showed that the composition containing the tBTPP mixture (fluid 1) exhibited higher wear resistance compared to compositions with similar TCP content (fluid A, fluid B). WAM failure loading results showed that at similar P treatment rates, the composition containing the tBTPP mixture (fluid 1) showed higher macroscopic wear resistance compared to those compositions containing TCP (fluid A, fluid B, and fluid C). Comparing model formulations with the same base oil and other additives, the incorporation of the tBTPP mixture resulted in a surprising improvement of approximately 6% for fluid 1 compared to fluid C.

[0056] The dimensions and values ​​disclosed herein should not be construed as strictly limited to the precise numerical values ​​stated. Rather, unless otherwise specified, each such dimension is intended to represent the value and a range of functionally equivalent values ​​around that value. For example, a dimension disclosed as “40 mm” is intended to represent “approximately 40 mm”.

[0057] Unless expressly excluded or otherwise limited, every reference cited herein (if any), including any cross-referenced or related patent or application and any patent application or patent claiming priority or benefit to this application, is hereby incorporated in its entirety by reference. Reference to any document does not imply that it is prior art relating to any invention disclosed or claimed herein, or that it, alone or in any combination with any other reference, teaches, suggests, or discloses any such invention. Furthermore, where any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a referenced document, the meaning or definition given to that term in this document shall prevail.

[0058] While specific embodiments of the invention have been described and illustrated, it will be apparent to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. Therefore, the appended claims are intended to cover all such changes and modifications that fall within the scope of the invention.

Claims

1. An auxiliary power unit (APU) system for an aircraft, the system comprising: An engine system, comprising an engine compressor, a combustion chamber, and an engine turbine; Load compressor; dynamo; An oil pump with an oil reservoir having an inlet and an outlet; as well as A flow path fluidly connected to the inlet, the outlet, the engine system, the load compressor, and the generator, wherein the flow path supplies a lubricating oil composition to one or more of the engine system, the load compressor, or the generator, wherein the lubricating oil composition comprises: a. At least 80% by weight of a lubricating oil base stock, said lubricating oil base stock comprising reaction products of the following substances:

1. Polyols selected from the group consisting of trimethylolethane, trimethylolpropane, trimethylolbutane, neopentyl glycol, and mixtures thereof, and 2. A mixture of C7-C10 straight-chain monocarboxylic acids. The lubricating oil base contains less than 0.2% by weight of C5 and C6 monocarboxylic acids; as well as b. An anti-wear composition of 1% to 5% by weight, said anti-wear composition being selected from compounds of formula I. ； R1, R2, and R3 are independently selected from the group consisting of phenyl, 3-tert-butylphenyl, and 4-tert-butylphenyl; The anti-wear composition comprises:

1. At least 90 mol% of a compound of formula I, wherein at least one of the R1, R2, or R3 groups is selected from the group consisting of 3-tert-butylphenyl and 4-tert-butylphenyl.

2. 5 mol% to 27.5 mol% of a compound of formula I, wherein at least two of the R1, R2, or R3 groups are selected from the group consisting of 3-tert-butylphenyl and 4-tert-butylphenyl; and The lubricating oil composition therein is free of tricresyl phosphate and isopropyltriphenyl phosphate.

2. The system of claim 1, wherein the polyol is a mixture of trimethylolpropane and neopentyl glycol.

3. The system of claims 1 and 2, wherein the lubricating oil base oil comprises less than 0.1% by weight of C7-C10 branched monocarboxylic acids.

4. The system of claims 1-3, wherein the anti-wear composition comprises less than 5 mol% of a compound of formula I, wherein the R1, R2 and R3 groups are phenyl groups.

5. The system of claims 1-4, wherein the anti-wear composition comprises 70 mol% to 85 mol% of a compound of formula I, wherein one of the R1, R2, or R3 groups is selected from the group consisting of 3-tert-butylphenyl and 4-tert-butylphenyl.

6. The system of claims 1-5, wherein the anti-wear composition comprises less than 5 mol% of a compound of formula I, wherein the R1, R2 and R3 groups are selected from the group consisting of 3-tert-butylphenyl and 4-tert-butylphenyl.

7. The system of claims 1-6, wherein the lubricating oil composition further comprises 0.1% to 5% by weight of one or more antioxidants selected from the group consisting of aromatic amines, aromatic amine oligomers and mixtures thereof.

8. An aircraft cabin air system, comprising: The auxiliary power unit system as described in claims 1-7; The propulsion engine system includes a turbine and a compressor. ； Gearbox; An oil pump with an oil reservoir having an inlet and an outlet; And a flow path fluidly connected to the inlet, the outlet, the turbine, the compressor, and the gearbox, wherein the flow path supplies a propulsion engine lubricating oil composition to one or more of the turbine, the compressor, or the gearbox; as well as An environmental control system (ECS) includes an air distribution system, one or more heat exchangers, and one or more air circulators, wherein the environmental control system is pneumatically connected to the auxiliary power unit system and the propulsion engine system.

9. The aircraft cabin air system of claim 8, wherein the propulsion engine lubricating oil composition comprises: At least 80% by weight of base oil composition, and An anti-wear composition comprising 1% to 5% by weight, wherein the anti-wear composition is selected from compounds of formula I. ； R1, R2, and R3 are independently selected from the group consisting of phenyl, 3-tert-butylphenyl, and 4-tert-butylphenyl; The anti-wear composition comprises:

1. At least 90 mol% of a compound of formula I, wherein at least one of the R1, R2, or R3 groups is selected from the group consisting of 3-tert-butylphenyl and 4-tert-butylphenyl.

2. 5 mol% to 27.5 mol% of a compound of formula I, wherein at least two of the R1, R2, or R3 groups are selected from the group consisting of 3-tert-butylphenyl and 4-tert-butylphenyl; and The lubricating oil composition therein is free of tricresyl phosphate and isopropyltriphenyl phosphate.

10. The aircraft cabin air system of claim 8, wherein the propulsion engine lubricating oil composition comprises: a. At least 80% by weight of a base oil composition, said base oil composition comprising: (i) A first base oil, wherein the first base oil comprises the reaction products of the following substances:

1. Polyol esters selected from the group consisting of pentaerythritol, dipentaerythritol, and mixtures thereof, and 2. A mixture of C5-C10 straight-chain or branched monocarboxylic acids; and (ii) A second base oil, wherein the second base oil comprises the reaction products of the following substances:

1. Polyol esters selected from the group consisting of trimethylolethane, trimethylolpropane, trimethylolbutane, neopentyl glycol, and mixtures thereof, and 2. A mixture of C5-C10 straight-chain or branched monocarboxylic acids; and b. An anti-wear composition of 1% to 5% by weight, said anti-wear composition being selected from compounds of formula I. ； R1, R2, and R3 are independently selected from the group consisting of phenyl, 3-tert-butylphenyl, and 4-tert-butylphenyl; The anti-wear composition comprises:

1. At least 90 mol% of a compound of formula I, wherein at least one of the R1, R2, or R3 groups is selected from the group consisting of 3-tert-butylphenyl and 4-tert-butylphenyl.

2. 5 mol% to 27.5 mol% of a compound of formula I, wherein at least two of the R1, R2, or R3 groups are selected from the group consisting of 3-tert-butylphenyl and 4-tert-butylphenyl; and The lubricating oil composition therein is free of tricresyl phosphate and isopropyltriphenyl phosphate.

11. A lubricating oil composition for use in an auxiliary power unit (APU) system of an aircraft, said composition comprising: a. At least 80% by weight of a lubricating oil base stock, said lubricating oil base stock comprising reaction products of the following substances:

1. Polyols selected from the group consisting of trimethylolmethane, trimethylolethane, trimethylolpropane, trimethylolbutane, neopentyl glycol, and mixtures thereof, and 2. A mixture of C7-C10 straight-chain monocarboxylic acids. The lubricating oil base stock contains less than 0.2% by weight of C5 and C6 straight-chain or branched monocarboxylic acids; and b. An anti-wear composition comprising 1% to 5% by weight of a mixture of compounds having Formula I. ； R1, R2, and R3 are independently selected from the group consisting of phenyl, 3-tert-butylphenyl, and 4-tert-butylphenyl; The anti-wear composition comprises:

1. At least 90 mol% of a compound of formula I, wherein at least one of the R1, R2, or R3 groups is selected from the group consisting of 3-tert-butylphenyl and 4-tert-butylphenyl.

2. 5 mol% to 27.5 mol% of a compound of formula I, wherein at least two of the R1, R2, or R3 groups are selected from the group consisting of 3-tert-butylphenyl and 4-tert-butylphenyl; and The lubricating oil composition therein is free of tricresyl phosphate and isopropyltriphenyl phosphate.

12. The composition of claim 11, wherein the polyol is a mixture of trimethylolpropane and neopentyl glycol.

13. The composition of claims 11 and 12, wherein the lubricating oil base oil comprises less than 0.1% by weight of C7-C10 branched monocarboxylic acids.

14. The composition of claims 11-13, wherein the anti-wear composition comprises less than 5 mol% of a compound of formula I, wherein the R1, R2, and R3 groups are phenyl groups.

15. The composition of claims 11-14, wherein the anti-wear composition comprises 70 mol% to 85 mol% of a compound of formula I, wherein one of the R1, R2, or R3 groups is selected from the group consisting of 3-tert-butylphenyl and 4-tert-butylphenyl.

16. The composition of claims 11-15, wherein the anti-wear composition comprises less than 5 mol% of a compound of formula I, wherein the R1, R2 and R3 groups are selected from the group consisting of 3-tert-butylphenyl and 4-tert-butylphenyl.

17. The composition of claims 11-16, wherein the lubricating oil composition further comprises 0.1% to 5% by weight of one or more antioxidants selected from the group consisting of aromatic amines, aromatic amine oligomers, and mixtures thereof.

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