INVENTOR

Andrew Higgs

PRIORITY CLAIM

[0001] The present application claims priority from U.S. Provisional Patent Application No. 61/615,493, filed 26-March-2013, which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

[0002] The present invention is generally related to a cross charge transfer engine, and more specifically to a cross charge transfer engine for an unmanned aerial vehicle (UAV).

BRIEF DESCRIPTION OF THE DRAWINGS

[0003] FIGURES 1-19 show various embodiments of a cross charge transfer engine and testing results thereof according to the present invention. DETAILED DESCRIPTION

[0004] In an embodiment of the present invention, a method for improving an operating performance of a four-cylinder cross charge transfer engine includes the steps of (1) converting the four-cylinder cross charge transfer engine to a two-cycle operation using a cross charge transfer kit; (2) during a flight operation of the converted two-cycle engine, cooling a cylinder block of the engine with a liquid fuel; (3) still during flight, lowering a viscosity of the liquid fuel as the fuel absorbs heat from the cylinder block; and (4) still during flight, injecting the lower viscosity fuel into the engine.

[0005] It is necessary to emphasize the importance of the very high volumetric efficiency of the traditional piston controlled ports employed by the standard two cycle engine. Until now no existing type of inlet valve could produce the essential requirements of presenting the maximum inlet area to the air in the minimum time. The new cross charge transfer (CCT) engine significantly increases both the utility and the efficiency of the of the two cycle engine, which may now be more efficiently scavenged. This technology may operate without complex mechanical components such as cams, valves mechanisms and the other various precision components necessary to operate them. The absence of these mechanical components eliminates a large number of moving parts, thereby considerably reducing the costs and maintenance requirements, whilst significantly increasing reliability and retaining the simple two cycle engine. As a result of this novel and advanced two cycle technology, additional significant benefits may be realized such as, but not limited to, a higher compression ratio, a reduced ignition delay, a multi-fuel capability, a reduction in hydrocarbon and nitrogen oxide emissions, which until now have been the exclusive domain of the four cycle engine. With this CCT engine, two cycle engine technology combined with the enormous benefits together with their appealing simplicity, offer a new generation of light weight high performance power plants that may out perform their four cycle cousins. [0006] Development work has enabled refinement to a point where UAV requirements for low mass engines could be seriously considered. Within an engine mass of only 17.45kg, at least one embodiment of the CCT engine may meet all the design criteria. Further subsequent contract work, in response to a NATO objective, has investigated the CCT engine on heavy fuel operation. This paper provides a comparison of the CCT engine with other typical UAV engines. Some of the heavy fueling development summary data is presented, together with predictive analysis of a more advanced fueling, and computational modeling considering possible higher power requirements from the same package.

[0007] In one embodiment and as best shown in FIGURES, the CCT engine is a 90° V4 cylinder engine and operates with two banks of paired cylinders. Air only is drawn into the pumping annulus through a valve. As the piston ascends the charge is transferred through a crossover system to the opposite smaller diameter or working cylinder. The engine then operates as a loop scavenged engine, except that the crankcase isolation afforded by the CCT system enables significant fundamental durability and operational advantages.

[0008] The use of Cross Charge Transfer technology and combustion allows the key advantages of two and four- cycle engines to be combined and elimination of the disadvantages inherent in each of these engine types. As in the case of four-cycle engines, the charging and lubrication processes are physically separate in the CCT design. This eliminates a major source of problems that is common in the traditional crankcase scavenged two-cycle engines. Isolation of the fresh charge from the crankcase is made possible by the provision of normal four-cycle engine compression and oil control rings on the larger diameter part of the piston. The crankcase, freed from any gas exchange functions, is well lubricated; the working processes being completely sealed above the piston.

[0009] Isolation of the crankcase also permits a full pressure lubrication system to be used, as in four-cycle engines. This simplifies fueling needs, with operation on neat fuels, avoiding the battlefield supply problems, uncertainty and risk of error inherent in the oil and fuel mixture required for conventional two-cycle UAV engines. Furthermore the inherent piston cooling characteristics of the CCT design offer a major durability advantage over conventional two- cycle engines, allowing much leaner fuel delivery than can be sustained with traditional crankcase scavenging, where usually piston overheating and consequent seizure are quite common.

[0010] The extremely smooth output torque, provided by a power stroke from each cylinder for every revolution, retains an advantageous two-cycle characteristic. A particularly smooth arrangement, which is also very compact, is provided for in this 90° V-4 layout. Having excellent balance, and with evenly spaced firing intervals, this gives very smooth torque characteristics, which cannot be achieved in a four-cycle engine with less than eight cylinders.

[0011] The CCT port layout adopted, concentrates the scavenge flow at the wall of the cylinder opposite the exhaust port. This compares with more evenly dispersed scavenge flows common in conventional engines. Scavenge flow within the CCT cylinder provides, in effect, a form of stratified charging and explains improvements in the fuel economy obtained with such a simple layout. This enables the CCT engines to compete easily with four-cycle engines in terms of fuel economy, especially under cruise conditions. Multi-cylinder CCT piston engines now achieve specific powers of 61kW/Litre, and are comparable with the high power outputs of four cycle counterparts. Simple optimization of the technology would see 75kW/ Litre. Operational size and weight factors lie between both two and four-cycle engines. The CCT multi-cylinder engines, however, tend to be closer to traditional two-cycle units in respect of performance and mass.

[0012] In at least one embodiment, the CCT engine may have the following durability and operational advantages: (1) Conventional 4 cycle wet sump lubrication; (2) No valves, springs, gears, or cams; (3) Low thermal loading of the piston; (4) High durability with low exhaust temp & low emissions; (5) Compact low mass design; (6) Low manufacturing cost; (7) Increase in reliability due to low parts count; (8) Extended oil change periods, oil does not degrade due to lack of blow by, (9) Designed to run on industry standard Jet fuel; and (10) Will run and perform excellent on all gasolines 91-95 including 100LL.

[0013] Computational engine modeling and computer aided drafting (CAD) tools have been used to optimize the engine design. Various computational models have been developed to optimize cylinder porting supported by techniques for simulation of pressure- time history in upper and lower cylinder, air box, inlet tract, charging and trapping efficiencies, main and auxiliary transfer and exhaust port mass flow rates, and reed valve flow area- time history. The software was also used to great effect in the study of exhaust system configurations. Software was also developed to study engine loading and bearing life. Finite Element Analysis (FEA) software was also used for key component analysis.

[0014] In one embodiment of the CCT engine shown below, cooling is provided by limited direct-flow water feeds to each cylinder.

Fig.14 CCT Liquid Cooled Engine Outline

Fig.15 CCT Liquid and Air-Cooled Engines

[0015] Two-cycle 90°V-4 engines, with each cylinder firing once per revolution give extremely smooth output torque characteristics, similar to that of aV-8 four-cycle engines. This feature is particularly valuable where minimal vibration and torque fluctuation must be achieved. Turning moment diagrams for the CCT engine, typical flat twin cylinder examples of two and four-cycle power plants and twin and single rotor Wankel engines.

[0016] Plotted to the same scale, these diagrams demonstrate the inherent smoothness of the CCT engine. The horizontal axis extends over two complete revolutions to allow one complete four-stroke cycle to be included. These engines are not of equal power and a factor, which is independent of power, is therefore useful. The ratio of Peak-to-Peak torque to mean torque provides such a factor, enabling a comparison of the fundamental characteristics of each type of engine. [0017] During each cylinder of the CCT engine has two firing strokes, resulting in eight power pulses during the two revolutions. The major advantage of eliminating all reversals of torque is thereby provided, the diagram being positive at all times. Each power pulse is comparatively small.

[0018] In the two-cycle flat twin the cylinders fire simultaneously, giving only two power pulses during the same period. The power pulses are much larger than in the CCT engine and, being added together are the cause of large fluctuations in the turning moment diagram. In the case of the four-cycle flat twin, the cylinders fire alternately, but only once every two revolutions.

[0019] Peak pressures within the four-cycle engine are much higher than in a two- cycle unit, resulting in stronger but less frequent power pulses. This makes the torque characteristics of the engine similar to the previous example.

[0020] Single rotor Wankel engines fire once per revolution, thus producing turning moment diagrams generally similar to the flat twin four-cycle. Operation on the four-stroke cycle entails negative periods or reversals in the turning moment diagram and torsional vibration levels that are still significant but lower than either of the flat twin engines. The single rotor Wankel engine is based on an NSU unit, and is indicative of any single rotor engine. The twin rotor unit demonstrates the advantage of adopting multiple rotors.

[0021] CCT engines eliminate most of the maintenance operations required with conventional two and four-cycle engines. Operating conditions in the crankcase of CCT engines are very similar to those in a four-cycle engine. The copious supply of oil to the working parts minimizes wear. However, blow-by gases, to which the bearings and the oil are usually exposed, are isolated above the piston. Bearing corrosion problems, well known in two-cycle engines, are therefore completely avoided. [0022] In addition to these more obvious points, analysis of oil, taken from an Automotive a CCT engine after 400 hours of use, revealed that the lubricant was still within the specification for new oil. Normal degradation of the additives had not occurred. The explanation is that in a four-cycle engine all of the oil passes at some time into the high temperature region adjacent to the piston compression rings and the valve train components, it is then returned to the crankcase. Therefore in a four-cycle engine all of the oil is exposed periodically to temperatures well in excess of the degrading point of the additive pack. This causes the qualities of the oil to decline throughout the period between oil changes. In CCT engines, however, the oil is not subjected to such high temperature zones. These points suggest that normal topping-up procedures are sufficient and that four-cycle type oil changes can be largely eliminated.

[0023] Development testing was carried out in parallel with computational gas dynamic modeling, including analysis of the pressure -time history, to achieve target power and fuel economy goals with the most simple low mass exhaust system. A separate system for each cylinder achieved maximum power of 35.4kW at 5250 RPM and specific fuel consumption (SFC) of 304g/kWh (see System Ref ETZ in Table.2 and Fig.6.). This system also offers a very low noise level and provides a reference against which alternative systems can be assessed. Development work resulting from computational modeling on alternatives, such as the QUBy and a range of more compact systems, culminated in a more compact JL18 system. The use of an attenuating muffler at the system outlet further reduces cruise SFC. Table 2, below, shows the results achieved with the best exhaust systems that have so far been developed for the CCT engine.

Table.2. Full and cruise load performance

The cruise loading in Table 2 is typically 65% of full power levels. Full load performance of the ETZ, JL18 and 2-1 systems is compared in Fig 16. The engine exhaust system was finalized into two optional systems; the 32.5kW 2 into one pipe and chamber JL18 system and the lighter 30.9kW 2-1 stub pipe system. The weight of these finalized exhaust systems are 1154g and 508g respectively. Two systems per engine may be required.

3500 4000 4500 5000 5500

Engine Speed (RPM)

Fig. 16 CCT performance with various exhaust systems and

using a 95RON Gasoline (CD) carburetter [0024] Naturally a V-4 cylinder layout spreads heat sources, since each cylinder is a comparatively small source and they are spaced apart. Thus the heat intensity is reduced compared with flat twin or in-line types of engine of the same power rating. Four-cycle and Wankel engine exhaust gas temperatures are considerably higher than those produced by CCT and two-cycle engines. Four-cycle engines typically emit gas in the 700-800C range whilst Wankel engines are around lOOOC. The CCT engine exhaust gas temperature is considerably lower in the 550-650C range.

[0025] The maximum noise level recorded at full power with the simple unattenuated two-into-one stub pipe system was 125.3dBA. The noise level with more advanced exhaust systems was typically of the order of 106.5dBA at full power, reducing to 103.8dBA at the nominal 65% cruise load condition. All measurements were recorded inside the test laboratory at positions one meter from the engine. Although impractical for many pre-existing aircraft, we has demonstrated the benefits of applying a more advanced exhaust systems where allowance is made for their installation. This gave a significant reduction in fuel consumption and greatly improved stealth and loiter characteristics.

[0026] None of the SFC figures recorded in this paper relate to systems that take advantage of the inherent stratified charge porting, already designed into the CCT engine. This porting system has proved extremely effective on an alternative CCT engine of 994cm", providing exceptional improvements in fuel economy, achieving levels down to 261g/kWh. Despite some work using semi-direct or transfer port injection of gasoline, most of the CCT engine development work has used carburetter based fueling systems. Using the simple stub type exhaust systems described above minimum SFC levels as low as 318g/kWh have been achieved. If more advanced low noise emission exhaust systems are to be considered levels below 300g/kWh have been recorded using simple CD type carburetter technology. Ignoring the complexity of computer controlled electronic ignition, then 250~60g/kWh should be possible. Use of direct injection would further secure the significant low SFC levels and would of course allow easier altitude compensation control. Furthermore due to the inherent ability to achieve high charging and scavenging efficiencies, high altitude operational benefits over conventional naturally aspirated engines should be easily apparent with the CCT engine.

[0027] The CCT engine has been the subject of research work into the feasibility of spark ignition operation on heavy fuels, notably kerosene JET A-l . Work has so far concentrated on semi-direct electro-magnetic injection methods with excellent power levels being achieved. Summary data for the engine is presented in Table.3.

[0028] The data presented is extracted from a more detailed study however power within 5% of gasoline levels have so far been achieved. Further fuel system development is expected to yield significantly lower SFC results and predictive work on this aspect is presented below.

Table. . Summary Gasoline and Heavy Fuel performance - CCT V4580ee [0029] A further very recent study to assess the expected benefits of adopting a more advanced heavy fuel system, building on the previous heavy fuel development work as reported above, has also been made. 95RON Gasoline data shown in Fig 17 and 18 is reproduced from results achieved with simple carburetter technology. However lower gasoline SFC should be achievable via use of direct injection. This approach could achieve levels as low as 270g/ kWh similar to those observed on our larger 994cm" research engine. A minimum JET A-l SFC of 360g/kWh is predicted in Fig 19.

2500 3000 3500 4000 4500 5000 5500 6000

Engine Speed (RPM)

Fig. 17 Expected JET-A full load results using more advanced fuel system technology

2500 3000 3500 4000 4500 5000 5500 6000

Engine Speed (RPM)

Fig. 18 Predicted Propeller load data using more advanced JET A-l fueling system

[0030] In response to needs for very low mass propulsion systems exceeding the current high power to weight ratio already achieved by the existing CCT engine, a study was initiated to consider a revised CCT offering higher maximum power speed up to 6500 RPM. This resulted in the CCT HS (high speed) engine. The predicted full load performance for the high speed CCT engine is presented in Fig 19. Redesign of the cylinder porting has been considered to allow higher maximum power/speed to be achieved. Our initial analysis shows a maximum power of 41.4k W. Maximum torque of 64.7Nm is computed at 6000 RPM. It is considered that a further significant increase is easily achievable.

[0031] The basic engine mass in Table 4 includes allowances for various ignition systems and a carburetter. More advanced fuel systems will increase these figures slightly. The ultra low mass version of the engine is based on a study employing magnesium castings for crankcase and cooling jacket components. Ultimate specific fuel consumption will depend largely on the final fuelling and exhaust systems selected. We would however expect specific fuel consumption similar to the levels achieved by the CCT engine with a gasoline minimum of 300-325g/kWh or 360g/kWh with JET A-l fuelling using a simple exhaust system. External dimensions for the engine are expected to be unchanged from the CCT engine outline shown previously.

Fig. 19 CCT HS Engine performance prediction (95RON Gasoline or JET A-l fuel)

[0032] The design and development of the CCT engine has met and surpassed all the specified goals of low mass, high reliability, low vibration and torque fluctuation, good fuel consumption and power density.

[0033] The operation on heavy fuel (kerosene JET A-l) has also been demonstrated, achieving power output within 5-% of gasoline levels. Further kerosene fuel consumption benefits could be realized with more advanced fueling methods. The higher maximum power speed CCT HS engine suggests a gasoline power output of 41.1kW (or 40.4kW using JET A-l) at 6500RPM could be achievable.

[0034] Another embodiment of the present invention is directed toward methods and techniques for upgrading existing general aviation (GA) aircraft to run on jet fuel as well as other types of fuel. The Cross Charge Transfer Engine (CCT) is a basis for a new line of light weight high performance, high reliability and low operating cost aircraft engines designed to run on Jet fuel as well as other fuels making them truly multi fuel capable.

[0035] Aviation gas, commonly referred to as AVGAS, use is only about 0.76 million gallons a day, compared to 372 million gallons of normal pump gasoline and 68 million gallons of Jet fuel. Although the use of AVGAS is fairly small, it contains tetraethyl lead, lead pollution from engine exhaust is dispersed into the air and is easily inhaled. Lead is a toxic metal that accumulates and has subtle and insidious neurotoxic effects especially at low exposure levels, such as low IQ and antisocial behavior. It has particularly harmful effects on children. The majority of the piston engine general aviation (GA) fleet need AVGAS due to certain unique properties, knock resistance, volatility, fluidity, stability to name just a few. Unlike the general automotive market that changed to unleaded fuel twenty years ago, the GA market is not in such a fortuitous position, this is due to the age of the power plants, the old design of the engine (circa 1940s) and the lack of investment to name a few. [0036] Retrofitting the existing market, (roughly 190,000 piston engine aircraft in the USA) is far simpler than trying to bring to market a new engine to replace all the existing fleet. Whilst a new CCT engine design would suit the manufactures and supplier of new aircraft a new CCT engine would not address the existing market needs. The CCT retrofit kit will allow most of the GA aircraft engines to be upgraded. This will reduce the need to rely on AVGAS, reduce the harmful exhaust emissions and allow the current infrastructure to be used.

[0037] Development work has enabled refinement to a point where GA & UAV requirements for non AVGAS, low mass engines could be seriously considered. Design and development of an advanced 30-35kW aircraft engine, overcoming conventional engine drawbacks has been developed and tested. Within an engine mass of only 17.45kg the original CCT V4 35 c.i engine has met all the initial design criteria. Further subsequent work investigated the CCT engine on heavy fuel operation. Some of the heavy fueling development summary data is presented, together with predictive analysis and computational modeling considering possible higher power requirements from the same package.

[0038] The current CCT engines are a V4 and a twin cylinder engine and they operate with banks of paired cylinders. Air only is drawn into a pumping annulus through the valves. As the piston ascends the charge is transferred through a crossover mechanism to the opposite working cylinder. The engine then operates as a loop scavenged engine, except that the crankcase isolation afforded by the CCT system enables significant, fundamental durability and operational advantages over current 4 cycle engines.

[0039] The use of Cross Charge Transfer and combustion allows the key advantages of two and four-cycle engines to be combined and the elimination of the disadvantages inherent in each of these engine types. As in the case for four-cycle engines, the charging and lubrication processes are physically separate in the CCT design. This eliminates a major source of problems that is common in the traditional crankcase scavenged two-cycle engines. Isolation of the fresh charge from the crankcase is made possible by the provision of normal four-cycle engine compression and oil control rings on the pumping part of the piston. The crankcase, thus freed from any gas exchange functions, is well lubricated; the working processes being completely sealed above the piston.

[0040] Isolation of the crankcase also permits a full pressure lubrication system to be used, as in four-cycle engines. This simplifies fueling needs, with operation on neat fuels only, avoiding battlefield supply problems, uncertainty and risk of error inherent in the oil and fuel mixture required of conventional two-cycle engines. Furthermore the inherent piston cooling characteristics of the CCT design offer a significant major durability advantage over conventional two-cycle engines, allowing much leaner fuel delivery than can be sustained with traditional crankcase scavenging, where usually piston overheating and consequent seizure are quite common.

[0041] The extremely smooth output torque, provided by a power stroke from each cylinder for every revolution, retains an advantageous two-cycle characteristic. A particularly smooth arrangement, which is also very compact, is provided for in this particular V-4 layout. Having excellent balance, and with evenly spaced firing intervals, this gives very smooth torque characteristics, which cannot be achieved in a four-cycle engine with less than eight cylinders.

[0042] The CCT port layout adopted, provides, in effect, a form of stratified charging and explains the improvements in fuel economy obtained with such a simple layout. This enables the CCT engines to compete easily with four-cycle engines with fuel economy, especially under cruise conditions. Multi-cylinder CCT piston engines now achieve specific powers of 61kW/Litre, and are comparable with the high power outputs of four cycle counterparts. Simple optimization of the technology would see 75kW/Litre. Operational size and weight factors lie between both two and four-cycle engines. The CCT multi-cylinder engines, however, tend to be closer to two-cycle units regarding performance and mass due to the reduction of parts.

[0043] Computational engine modeling and CAD has been used to optimize the engine design. Various computational models have been developed to optimize cylinder porting supported by techniques for simulation of pressure-time history in upper and lower cylinder, air box, inlet tract, charging and trapping efficiencies, main and auxiliary transfer and exhaust port mass flow rates, and valve flow area- time history. The software was also used to great effect in the study of exhaust system configurations. Software was also developed to study engine loading and bearing life. Finite Element Analysis software was also used for key component analysis.

[0044] CCT engines eliminate most of the maintenance operations required with conventional two and four-cycle engines. Operating conditions in the crankcase of CCT engines are very similar to those in the four-cycle engine. The copious supply of oil to the working parts minimizes wear and keeps temperatures under control. However, blow-by gases, to which the bearings and the oil are usually exposed, are isolated above the piston. Corrosion problems, well known in aircraft engines, are therefore completely avoided. (The corrosion in the typical aircraft engine is caused by the lead in the fuel that "blows by" the piston rings and into the crankcases, causing the oil to degrade and become very acidic). Along with these obvious points, analysis of oil, taken from a CCT engine after 400 hours of use, revealed that the lubricant was still within the specification for new oil. Normal degradation of the additives had not occurred. The explanation is simple, in a four-cycle engine all the oil passes at some time into the high temperature region adjacent to the piston compression rings and the valve train components, it is then returned to the crankcase. Therefore in a four-cycle engine all the oil is exposed periodically to temperatures well in excess of the degrading point of the additive pack. This causes the qualities of the oil to decline throughout the period between oil changes. In CCT engines, however, the oil is not subjected to such high temperature zones. These points suggest that normal topping-up procedures are sufficient and that four-cycle type oil changes can be largely eliminated.

[0045] In response to needs for very low mass propulsion systems exceeding the current high power to weight ratio already achieved by the existing CCT engine, a study was initiated to consider a revised CCT offering higher maximum power speed up to 6500 RPM. This resulted in the CCT V4 high speed engine. Our initial analysis shows a maximum power of 41.4kW. Maximum torque of 64.7Nm is computed at 6000 RPM. It is considered that a further significant increase is easily achievable.

[0046] The current focus of activities is the development of an "upgrade kit" to suit both the Lycoming and Continental type engines of the flat 4 variety, followed later by kits for the flat 6 units. The CCT kit is intended to be applied to the existing engine and will allow the use of Jet fuel to be used. Predicted power output estimates for the converted engine are, as follows (1) 2700 RPM; 173.5 BHP; (2) 2900 RPM; 189.4 BHP; (3) 3000 RPM; 197.3 BHP; and (4) 3500 RPM; 237.2 BHP.

[0047] The modified engines will weigh less, have the same TBO of 2000 hours, will burn less fuel, will burn any fuel and will have significantly increased time between oil changes. As the kit is a retrofit kit, the existing airframe mounts and fittings can be used. The initial target group for this upgrade will be the experimental market.

[0048] The design and development of the various prototypes of CCT engine has met and surpassed all the specified goals of low mass, high reliability, low vibration and torque fluctuation, good fuel consumption and power density. The operation on heavy fuel (kerosene JET A-1) has been demonstrated, achieving high power outputs within 5-% of gasoline levels. Further kerosene fuel consumption benefits will be realized with more advanced fueling methods, along with higher power outputs. The higher maximum speed V4 35 c.i CCT engine suggests a gasoline power output of 41.4kW (or 40.4kW using JET A-l) at 6500RPM can easily be achievable within a package of 17.5kg, or 15.4kg using magnesium cases. Considering these results it is believed that the retrofit kit for the existing General Aviation market will be successful and the program is currently in an advanced phase.

[0049] Yet another embodiment of the present invention includes a cross charge transfer kit configured to change a Lycoming four-cylinder aircraft engine from a four cycle operation to a 2 cycle operation. By way of example, the Lycoming engine may take the form of the Lycoming CCT engine. By changing to the 2 cycle operation, the kit doubles the amount of firing pulses per unit of time, which in turn halves the interval between combustion pulses. The result is a smoother crankshaft torque output. In addition, the kit alters the basic frequency of torsional vibrations, which thus leads to lower vibrational loads in the aircraft structure and a reduction in aircraft resonances. The kit may cause an increase in heat from the combustion chamber to the cylinder; however this may be handled effectively by liquid cooling.

[0050] Cooling of the engine is achieved by a liquid medium, which may take the form of any suitable medium. In one embodiment, the system uses fuel as the cooling medium to cool the engine. Using the fuel, which may take the form of kerosene and/or distillates, has the secondary effect of keeping the fuel warm at high altitudes to minimize or eliminate the issue of congealing due to low temperature while maintaining the ability to atomize the fuel. Further, the engine weight may be reduced by using the fuel to remove heat from the cylinder block.

[0051] Using jet fuel in a non C.I engine (compression Ignition engine, e.g., a diesel engine) is difficult due to volatility issues. Heavy fuel such as kerosene and distillates can be used in S.I (spark ignition) engines, however starting and warm up is difficult. The high manifold temperatures necessary to warm these fuels to the right level to allow adequate distribution may be so high that carbonaceous deposits will accumulate in the cylinders, manifolds and on the spark plug. Starting and more importantly re-starting at low temperatures becomes difficult. In an aircraft environment, the inability to re-start the engine would be unacceptable.

[0052] Thus in another embodiment of the present invention, fuel is routed through the cylinder block to warm the fuel while contemporaneously heat from the engine. The heat transferred to the fuel from the CCT engine lowers the viscosity of the jet fuel to a viscosity level close to room temperature gasoline. The warmer fuel may be effectively injected into the engine without need for high pressure pumps or high pressure fuel rails, which in turn simplifies the system and helps reduce an overall weight of the system. Using this method to increase and to maintain adequate temperature in the fuel may negate or balance any losses that would normally be incurred by heating the manifolds to heat the fuel and hence to reduce the power output.

[0053] The various embodiments described above can be combined to provide further embodiments. All of the above patents, patent applications and publications referred to in this specification are incorporated herein by reference. Aspects can be modified, if necessary, to employ devices, features, and concepts of the various patents, applications and publications to provide yet further embodiments.

[0054] These and other changes can be made in light of the above detailed description. In general, in the following claims, the terms used should not be construed to limit the invention to the specific embodiments disclosed in the specification and the claims, but should be construed to include all types of engines (e.g. , different shapes, volume ratios, designs and sizes) operable using a variety of fuels in accordance with the claims. Accordingly, the invention is not limited by the disclosure, but instead its scope is to determined entirely by the following claims.