GB2488378A

GB2488378A - Vehicle with assisted boost to turbocharger

Info

Publication number: GB2488378A
Application number: GB1105028.3A
Authority: GB
Inventors: Tsoi Hei Ma Thomas
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-02-28
Filing date: 2011-03-25
Publication date: 2012-08-29
Also published as: GB201104486D0; GB201103357D0; GB201105028D0; GB201103973D0

Abstract

A vehicle powered by a turbocharged internal combustion engine, wherein the engine has at least one air or gas nozzle 10 positioned within an air intake duct 30 upstream of the turbo-blower of the turbocharger and connected to receive compressed air or compressed gases from a compressed air or gas supply, such as a storage tank 20, on board the vehicle. The air or gas nozzle 10 is directed to deliver at least one jet of the compressed air or gases 12 towards the impeller of the compressor 32 such that the expanding momentum flux of the jet or jets 12 fills the frontal entry area of the impeller 14 thereby entraining and accelerating the intake air arriving at the impeller 14 and increasing the exit boost pressure produced by the turbo-blower 32 of the turbocharger.

Description

VEHICLE WITH ASSISTED BOOST TO TURBOCHARGER

Field of the invention

The present invention relates to means for improving performance and reducing fuel consumption of a vehicle powered by a turbocharged internal combustion engine.

Background of the invention

Turbocharged engines for application in road vehicles are usually provided with turbochargers matched for full boost at medium and high engine speeds. However, such turbochargers are over-sized at low engine speeds giving is insufficient boost at low engine speeds which is noticeable particularly during launch and sudden acceleration of the vehicle. This accounts for the sluggish response of the engine at low engine speeds commonly known as turbo-lag requiring longer time between gear shifts during acceleration of the vehicle and adversely affecting the performance and fuel consumption of the vehicle.

In order to improve the dynamic response of the engine and remove the turbo-lag, thereby enabling earlier gear shifts during acceleration of the vehicle and reducing the fuel consumption, several known methods have been proposed to provide assisted boost to the turbocharger.

One method described in JP2005220891A is to introduce an electrically driven supercharger in series with the turbocharger thereby providing an additional compression stage and increasing the final boost pressure supplied to the engine. Another method described in JP2007O71116A is to introduce an electric motor coupled to the drive shaft of the turbocharger to supplement the turbine thereby speeding up the turbocharger and increasing the exit boost pressure produced by the turbocharger.

Another method described in JP2006258082 and t.JS2008066466A1 is to introduce a let of compressed air into the exhaust duct of the engine upstream of the turbine of the turbocharger forming a mixed flow of exhaust gases and S compressed air feeding the turbine thereby increasing the speed of the turbocharger.

Another method described in EP0754843A2, US5461860A, KR20020030345A and JP2007056858A is to introduce lets of compressed air directed locally to impinge on the turbine blades of the turbocharger in order to speed up the turbocharger. Alternatively in US4689960A, US4696165A and 13S5218822A the lets of compressed air are directed locally to impinge on the impeller blades or between the diffuser blades of the turbo-blower of the turbocharger producing similar effect.

Another method described in JP2006258082 is to introduce a stream of compressed air blown obliquely into the intake duct of the engine downstream of the turbo-blower towards an intake valve of the engine in order to help supercharge the engine and eliminate the turbo-lag.

Another method, described in US7665302B2 and known commercially as pneumatic boost system (PBS), is to temporarily shut of f the air duct downstream of the turbo-blower at the same time pressurise the duct with compressed air from a compressed air storage tank. This interrupts the air flow from the turbo-blower while the engine is boosted independently from the air tank which supplies the full air flow requirement to the engine for a brief period. In that time the turbine of the turbocharger is driven strongly by the exhaust gases from the engine speeding up in readiness for the turbo-blower to be switched back to supply the engine at a higher boost thus removing the turbo-lag and enabling earlier gear shifts during acceleration of the vehicle reducing the fuel consumption of the vehicle.

Object of the invention The present invention aims to remove the turbo-lag and achieve further, more substantial, fuel saving in the vehicle by providing assisted boost to the turbocharger in a more effective manner.

Summary of the invention

According to the present invention, there is provided a vehicle powered by a turbocharged internal combustion engine, wherein the engine has at least one air or gas nozzle positioned within an air intake duct upstream of the turbo-blower of a turbocharger and connected to receive compressed air or compressed gases from a compressed air or gas supply on board the vehicle, and wherein the air or gas nozzle is directed to deliver at least one jet of compressed air or gases towards the impeller of the turbo-blower such that the expanding momentum flux of the jet or jets fills the frontal entry area of the impeller thereby entraining and accelerating the intake air arriving at the impeller and increasing the exit boost pressure produced by the turbo-blower.

According to a first aspect of the invention, the compressed air supply is a connection to a compressed air storage tank on board the vehicle.

According to a second aspect of the invention, the compressed air supply is a connection via a feedback loop at boost air pressure produced by the turbo-blower from a point downstream of an intercooler connected to the boost air delivery duct of the turbo-blower.

According to a third aspect of the invention, the compressed gas supply is a connection via a feedback loop at exhaust back pressure produced by the engine from a point -4 -downstream of an EGR cooler connected to an EGR pipe taking compressed exhaust gases recirculated from upstream of the turbine of the turbocharger.

Each of the above three options may be installed separately in the same vehicle each with its own set of air or gas nozzles and compressed air or gas supply, each working independently and each contributing to provide assisted boost to the turbocharger.

In any one of the above three options, a single air or gas nozzle may be positioned along the axis of the intake duct at an optimum distance from the impeller.

Alternatively, an annular air or gas nozzle or a ring of is individual air or gas nozzles may be positioned at the periphery of the intake duct. These air or gas nozzles, positioned at an optimum distance from the impeller of the turbo-blower, may be integrated into a modular section of an intake duct connected to the housing of the turbo-blower.

Alternatively and preferably, they are integrated into an extended intake housing of the turbo-blower.

The present invention in any one of the three aspects introduces the compressed air or compressed gases upstream of the turbo-blower arranged in such a way that the compressed air or gases goes towards the turbo-blower with high momentum and does not escape in the reverse direction to the ambient atmosphere. It can be switched on whenever a rapid surge of boost pressure from the turbocharger is required. Alternatively it can be maintained continuously to provide sustained assisted boost to the turbocharger.

The present invention in any one of the three aspects is effective for a substantial period of time depending on the availability of the compressed air or gas supply. This would be sufficient to provide assisted boost to the turbocharger for long enough to enable the engine driving -s-.

the vehicle to accelerate quickly past the lower speed range so that the turbocharger can take over without assisted boost as soon as the engine reaches the higher speed range.

As a result, there will be fuel saving derived from improved dynamic response of the engine as well as removal of the turbo-lag enabling earlier gear shifts during acceleration of the vehicle. This is the first source of driveability fuel saving with any one of the three aspect of the present invention.

Preferably, the jet of compressed air or compressed gases is variable according to the required boost pressure produced by the turbocharger. Also preferably, the turbocharger is equipped with a variable waste-gate or variable geometry turbine which automatically adjusts the flow velocity of the exhaust gases from the engine for driving the turbine of the turbocharger according to the required boost pressure produced by the turbocharger. As a result, the auxiliary load on the engine caused by the exhaust back pressure driving the turbocharger will reduce automatically as the assisted boost is increased, allowing more useful torque that will become available at the engine drive shaft while the Brake Specific Fuel Consumption (BSFC) of the engine will decrease. For example, the auxiliary load normally required for driving the turbocharger is in the order of 15% of the boosted engine power.. If the assisted boost from the air or gas jet reduces this auxiliary load by one third, the external torque available at the engine drive shaft will jump up automatically by 5% and the BSFC will decrease automatically by 5%. Hence there will be fuel saving derived from reducing the turbocharger auxiliary load for as long as the air or gas jet is in use limited only by the availability of the compressed air or gas supply. This is the second source of sustained fuel saving with any one of the three aspects of the present invention and can be achieved throughout the engine speed range using existing automatic control of the turbocharger at no extra cost.

The above two sources of fuel saving may not be fully realised however because they do not take into account the primary energy required to produce the compressed air or compressed gases. According to the second aspect of the invention, some primary energy may be saved during assisted boost by pressure amplification with positive feedback of cooled compressed air from a high pressure region downstream of the turbo-blower back towards the impeller of the turbo-blower. According to the third aspect of the invention, some primary energy may be saved during assisted boost by pressure amplification with positive feedback of cooled compressed exhaust gases from a high pressure region upstream of the turbine of the turbocharger back towards the impeller of the turbo-blower.

Turning the focus to the first aspect of the invention, the two sources of fuel saving do not take into account the primary energy required to produce the compressed air for storage in the tank and the energy losses during filling and emptying of the tank. These are addressed below by introducing additional features unique to the first aspect of the invention enabling the first and second sources of fuel saving to be fully realised.

In the first aspect of the invention, the provision of the compressed air storage tank allows the compressed air to be produced at an earlier time using energy that may otherwise be dumped or wasted, for example, energy recovered from braking of the vehicle. Thus by replenishing the compressed air storage tank for free using regenerative braking energy, further fuel saving may be achieved. This is the third source of zero direct energy fuel saving unique to the first aspect of the invention enabling the first and second sources of fuel saving to be fully realised.

For example, the compressed air storage tank may be replenished by the engine itself working temporarily as an air charger driven during deceleration or coasting of the vehicle using energy derived from braking of the vehicle.

The engine under such conditions is operated with fuel cut off and with an air throttle restricting the air flow S leaving the engine creating a high back pressure in the exhaust system of the engine and producing compressed air which is diverted from upstream of the air throttle to the compressed air storage tank. The air throttle, known commercially as exhaust brake, is installed in buses and heavy goods vehicles (HGV5) to provide additional engine braking power supplementing the wheel brakes, hence the compressed air to the air tank may be produced during braking integrated with the existing system of exhaust brake at no extra cost.

Alternatively, the compressed air storage tank may be replenished by a supercharger driven during deceleration or coasting of the vehicle using energy derived from braking of the vehicle. In a vehicle already equipped with a supercharger, the compressed air to the air tank may be produced while using the supercharger as additional vehicle brake supplementing the wheel brakes at no extra cost.

As a further alterative, the compressed air storage tank may be replenished using the existing turbocharger on the vehicle at times when there is excess boost air produced by the turbocharger which could be diverted to the air tank instead of being bypassed or dumped.

In case a high pressure air jet is used to provide assisted boost to the turbocharger, a high pressure air tank supplying the jet may be replenished by a reciprocating air compressor driven by the engine or using energy derived from braking of the vehicle during deceleration or coasting of the vehicle. Such air compressor is standard equipment on HGVs and buses for providing service air on board the vehicle hence the high pressure air jet may be supplied from the tank using existing equipment at no extra cost. To improve the system efficiency, less energy may be used to drive the reciprocating air compressor by connecting it to receive pressurised air from an intermediate pressure air tank which in turn is replenished using any one of the air charging devices described earlier.

Preferably, the compressed air storage tank has variable volume adjusted by a spring against the air pressure within the tank. Also preferably, the air pressure within the tank is maintained substantially constant as the spring adjusts against the variable volume. As a consequence of the tank design, all the air contained within the tank will be charged and discharged by positive displacement at constant pressure so that there will be no compression or expansion of the air in the tank during the filling and emptying processes and the full content of the tank will be available for supplying the air nozzle at constant pressure.

This is in contrast with a fixed volume air tank where only a small fraction of the air can be used to supply the air nozzle at sufficient pressure as it expands out of the tank reducing the pressure in the tank, while a substantial quantity of air remains in the tank not suitable for use at the reduced pressure but has to be re-compressed to full pressure each time the tank is replenished wasting energy.

For example, when compressed air is released from a fixed volume air tank by adiabatic expansion, the tank absolute pressure will drop by 27% while only 20% of the stored mass is discharged for use at a steadily decreasing pressure and 80% remains in the tank not suitable for use because of the consequent reduced pressure.

Thus the variable volume constant pressure air tank will conserve the compressed air energy more effectively during the filling and emptying processes and will supply the air nozzle at a constant pressure and with much larger useable air capacity than a fixed volume air tank of similar size (five times larger useable air capacity as demonstrated in the last example). This is the fourth source of zero energy loss fuel saving and large effective air storage capacity unique to the first aspect of the invention enabling the first and second sources of fuel saving to be fully realised.

For example, a variable volume constant pressure air tank of 2.5 times the displacement volume of the engine and replenished at approximately 2 bar absolute pressure using the turbocharger at times when there is excess boost air produced by the turbocharger, will be sufficient to supply the engine with 50% supplementary air from the air nozzle and assisted boost to the turbocharger for approximately revolutions of the four-stroke engine or 0.4 seconds at 1500 rpm engine speed whenever it is needed to remove the turbo-lag during launch or sudden acceleration of the vehicle. Thus a passenger car powered by a 1.5 litre turbocharged engine will only need a 4 litre variable volume constant pressure air tank at approximately 2 bar absolute pressure to remove the turbo-lag. Scaling up, a van or bus/HGV powered by a 2.5 litre or 7.5 litre turbocharged engine respectively will only need 10 litre or 30 litre respectively variable volume constant pressure air tank at approximately 2 bar absolute pressure to remove the turbo-lag and achieve the associated driveability fuel saving from assisted boost.

In another example, a variable volume constant pressure air tank of 100 times the displacement volume of the engine and replenished at approximate 3 bar absolute pressure using the engine itself as a temporary air charger with fuel cut off in combination with an air throttle in the exhaust acting as exhaust brake, will be filled during braking in approximately 600 revolutions of the four-stroke engine or 18 second at 2000 rpm engine speed. This will be sufficient -10 -to supply the firing engine with 50% supplementary air from the air nozzle and assisted boost to the turbocharger for approximately 400 revolutions of the four-stroke engine or 12 seconds at 2000 rpm engine speed for free using energy derived from braking of the vehicle. Combined with variable waste-gate or variable geometry turbine control of the turbocharger which automatically reduces the flow velocity of the exhaust gases through the turbine and the associated auxiliary load on the engine driving the turbocharger during the time when the air nozzle is in use, substantial fuel saving can be achieved from assisted boost for approximately 12 seconds with each acceleration of the vehicle after regenerative braking in urban driving conditions. Thus an air hybrid car, van or bus/HGV powered by a 1.5 litre, 2.5 litre or 7.5 litre turbocharged engine respectively will only need 150 litre, 250 litre or 750 litre respectively variable volume constant pressure air tank at approximately 3 bar absolute pressure to achieve the above repeated fuel saving from regenerative assisted boost as well as improved dynamic response of the engine without turbo-lag and further driveability fuel saving.

In summary, any one of the three aspects of the present invention enables the aforementioned first and second sources of fuel saving to be realised derived from providing assisted boost to the turbocharger using compressed air or compressed gases taken from a compressed air or gas supply, Unique to the first aspect of the invention, further, more substantial, fuel saving can be achieved by ensuring zero direct fuel energy for producing the compressed air to the air tank and zero compression and expansion losses during filling and emptying of the air tank conserving compressed air energy and providing the maximum useable air capacity limited only by the size and duty cycle of the air tank. This represents an efficient air hybrid vehicle with regenerative braking and energy storage by compressed air -1:1 -with unlimited charge-and-discharge cycle-life capability for the air tank, and effective use of the stored air for assisted boost and reduced auxiliary load driving the turbocharger saving fuel working in synergy with existing systems on board the vehicle.

Brief description of the drawings

The invention will now be described further by way of example with reference to the accompanying drawings in which Figure la is a schematic drawing of the components for providing assisted boost to the turbo-blower of a turbocharger according to the first aspect of the invention, is Figure lb is an alternative schematic design similar to that in Figure la, Figure 2 is a schematic drawing of the components similar to Figure la for providing assisted boost to the turbo-blower according to the second aspect of the invention, Figure 3 is a schematic drawing of the components similar to Figure lb for providing assisted boost to the turbo-blower according to the third aspect of the invention, and Figure 4 is a schematic drawing of a vehicle powered by a turbocharged internal combustion engine provided with assisted boost according the first aspect of the invention.

Detailed description of the preferred embodiment

In Figure la, according to the first aspect of the invention, an air nozzle 10 is positioned within an air intake duct 30 upstream of the turbo-blower 32 of a turbocharger and connected to receive compressed air from a compressed air storage tank 20. The air nozzle 10 is directed to deliver a jet of compressed air 12 towards the -12 -impeller 14 of the turbo-blower 32 such that the expanding momentum flux of the jet 12, represented by the dotted lines, fills the frontal entry area of the impeller 14 thereby entraining and accelerating the intake air, s represented by the solid line flow arrows, arriving at the impeller 14 and increasing the exit boost pressure produced by the turbo-blower 32.

Alternatively in Figure ib, an annular air nozzle lOb is directed towards the impeller 14 of the turbo-blower 32 such that the expanding momentum flux of the jet l2b, represented by the dotted lines, fills the frontal entry area of the impeller 14. As a further alternative, the annular air nozzle may be substituted with a ring of is individual air nozzles. To provide control in Figures Ia and lb, a flow valve 44 is installed in the connection to the air nozzle 10 or lOb for switching and regulating the assisted boost to the turbocharger.

In Figure 2, according to the second aspect of the invention, an air nozzle 10 similar to that in Figure la, is connected to receive compressed air at boost air pressure produced by the turbo-blower 32 via a feedback loop, represented by the dashed line flow arrows, from a point downstream of an intercooler 50 connected to the boost air delivery duct of the turbo-blower 32. To provide control, a flow valve 52 is installed in the connection to the air nozzle 10 for switching and regulating the assisted boost to the turbocharger.

In Figure 3, according to the third aspect of the invention, an air nozzle lOb similar to that in Figure lb, is connected to received compressed exhaust gases at exhaust back pressure produced by the engine via a feedback loop, represented by the dashed line flow arrows, from a point downstream of an EGR cooler 54 connected to an EGR pipe taking compressed exhaust gases recirculated from upstream of the turbine 34 of the turbocharger. To provide control, a flow valve 56 is installed in the connection to the air nozzle lOb for switching and regulating the assisted boost to the turbocharger.

Each of the above three options for the compressed air or gas supply shown in Figures 1(a, b), 2 and 3 may be installed separately in the same vehicle each with its own set of air or gas nozzles, each working independently and each contributing to provide assisted boost to the turbocharger.

In any one of the above three options, the air nozzle or lOb, positioned at an optimum distance from the impeller 14 of the turbo-blower 32, may be integrated into a modular section of an intake duct connected to the housing of the turbo-blower 32. Alternatively and preferably, the nozzle 10 or lOb is integrated into an extended intake housing of the turbo-blower 32.

The present invention in any one of the three aspects introduces the compressed air or compressed gases upstream of the turbo-blower arranged in such a way that the compressed air or gases goes towards the turbo-blower 32 with high momentum and does not escape in the reverse direction to the ambient atmosphere. It can be switched on whenever a rapid surge of boost pressure from the turbocharger is required. Alternatively it can be maintained continuously to provide sustained assisted boost to the turbocharger.

The present invention in any one of the three aspects is effective for a substantial period of time depending on the availability of the compressed air or gas supply. This would be sufficient to provide assisted boost to the turbocharger for long enough to enable the engine driving the vehicle to accelerate quickly past the lower speed range -14 -so that the turbocharger can take over without assisted boost as soon as the engine reaches the higher speed range.

In Figure 4, a vehicle system is shown powered by a turbocharged internal combustion engine 16. The engine 16 has an intake duct 30 leading to the turbo-blower 32 of a turbocharger and the exhaust gases from the engine 16 are used to drive the turbine 34 of the turbocharger before they are discharged as indicated by the flow arrows.

Schematically similar to Figure la, according to the first aspect of the invention, an air nozzle 10 is positioned within the intake duct 30 upstream of the turbo-blower 32 and is connected to receive compressed air from a compressed air storage tank 20 by way of line 22 and control valve 44. The air nozzle 10 is directed to deliver a jet of compressed air towards the impeller of the turbo-blower 32 such that the expanding momentum flux of the jet fills the frontal entry area of the impeller thereby entraining and accelerating the intake air arriving at the impeller and increasing the exit boost pressure produced by the turbo-blower 32.

The turbine 34 of the turbocharger is equipped with an external variable waste-gate 38 or it is a variable geometry turbine 34 having effectively an internal waste-gate, designed to adjust automatically the flow velocity of the exhaust gases from the engine 16 for driving the turbine 34 according to the required exit boost pressure produced by the turbocharger. As a result, the auxiliary load on the engine 16 caused by the exhaust back pressure driving the -15 -turbocharger will reduce automatically as the assisted boost is increased, allowing more useful torque that will become available at the engine drive shaft driving the road wheels 18 while the Brake Specific Fuel Consumption (BSFC) of the engine will decrease. For example, the auxiliary load normally required for driving the turbocharger is in the order of 15% of the boosted engine power. If the assisted boost from the air jet reduces this auxiliary load by one third, the external torque available at the engine drive shaft will jump up automatically by 5% and the BSFC of the engine will decrease automatically by 5%. Hence there will be fuel saving derived from reducing the turbocharger auxiliary load for as long as the air jet from the nozzle 10 is in use limited only by the capacity of the air tank 20 and the duty cycle replenishing it. This is the second source of sustained fuel saving with the present invention and can be achieved throughout the engine speed range using existing automatic control of the turbocharger at no extra cost.

By the same principle, similar sustained fuel saving derived from reduced auxiliary load driving the turbocharger can be achieved using alternative compressed air or gas supplies such as those described in Figures 2 and 3 instead of the air tank to provide the assisted boost.

The above two sources of fuel saving may not be fully realised however because they do not take into account the primary energy required to produce the compressed air or compressed gases. In Figure 2, according to the second aspect of the invention, some primary energy may be saved during assisted boost by pressure amplification with positive feedback of cooled compressed air from a high pressure region downstream of the turbo-blower 32 back towards the impeller 14 of the turbo-blower. In Figure 3, according to the third aspect of the invention, some primary energy may be saved during assisted boost by pressure -16 -amplification with positive feedback of cooled compressed exhaust gases from a high pressure region upstream of the turbine 34 back towards the impeller 14 of the turbo-blower.

Returning to the vehicle with the compressed air storage tank 20 shown in Figure 4, the aforementioned two sources of fuel saving do not take into account the primary energy required to produce the compressed air for storage in the tank 20 and the energy losses during filling and emptying of the tank 20. These are addressed in Figure 4 by introducing additional features unique to the first aspect of the invention enabling the first and second sources of fuel saving to be fully realised.

In the first aspect of the invention, the provision of the compressed air storage tank 20 allows the compressed air to be produced at an earlier time using energy that may otherwise be dumped or wasted, for example, energy recovered from braking of the vehicle. Thus by replenishing the compressed air storage tank 20 for free using regenerative braking energy, further fuel saving may be achieved. This is the third source of zero direct energy fuel saving unique to the first aspect of the invention enabling the first and second sources of fuel saving to be fully realised.

For example in Figure 4, the compressed air storage tank 20 is replenished by the engine 16 working temporarily as an air charger driven during deceleration or coasting of the vehicle using energy derived from braking of the vehicle. The engine 16 under such conditions is operated with fuel cut off and with an air throttle 40 restricting the air flow leaving the engine 16 creating a high back pressure in the exhaust system of the engine 16 and producing compressed air which is diverted automatically from upstream of the air throttle 40 by way of check valve 36 and line 42 to the compressed air storage tank 20. The air throttle 40, known commercially as exhaust brake, is -17 -installed in buses and HGVs to provide additional engine braking power supplementing the wheel brakes, hence the compressed air to the air tank 20 may be produced during braking integrated with the existing system of exhaust brake at no extra cost. An intercooler 46 may be provided to cool the compressed air before it arrives at the tank 20.

Other methods (not shown in Figure 4) are possible, for those familiar with the state of the art, to replenish the compressed air storage tank. For example, the tank may be replenished by a supercharger driven during deceleration or coasting of the vehicle using energy derived from braking of the vehicle. In a vehicle already equipped with a supercharger, the compressed air to the air tank may be produced while using the supercharger as additional vehicle brake supplementing the wheel brakes at no extra cost.

The compressed air tank may also be replenished using the existing turbocharger on the vehicle at times when there is excess boost air produced by the turbocharger which could be diverted to the air tank before or after an intercooler instead of being bypassed or dumped.

Also for those familiar with the state of the art, in case a high pressure air jet is used to provide assisted boost to the turbocharger, a high pressure air tank supplying the jet may be replenished by a reciprocating air compressor driven by the engine or using energy derived from braking of the vehicle. Such air compressor is standard equipment on HGVs and buses for providing service air on board the vehicle hence the high pressure air jet may be supplied from the tank using existing equipment at no extra cost. To improve the system efficiency, less energy may be used to drive the reciprocating air compressor by connecting it to receive pressurised air from an intermediate pressure air tank which in turn is replenished using any one of the air charging devices described earlier. -I8

Returning to Figure 4, the compressed air storage tank has variable volume adjusted by a spring 28 against the air pressure within the tank 20. The tank assembly comprises an inflatable bellows or air bag 20 confined within a casing 24 and preloaded by the spring 28 to extend in length when the air pressure within the bellows 20 exceeds a predetermined value above the ambient pressure as air is blown into the bellows 20.

The casing 24 has diverging sides guiding the extending bellows 20 and is closed off by a moveable end wall 26 held against the bellows 20 by the spring 28. The end wall 26 has adjustable dimensions matching and closing off the widening opening of the diverging sides as the bellows 20 extends along the casing 24. The divergence of the sides and the corresponding increased area of the end wall are such that the air pressure within the bellows 20 is maintained substantially constant as the bellows 20 extends against the spring 28, the resultant pressure force under such conditions exerted by the bellows 20 distributed across the increased area of the end wall 26 being sufficient to counteract the increased resisting force of the spring 28 as the bellows 20 extends against the spring 28.

As a consequence of the above tank design, all the air contained within the tank 20 will be charged and discharged by positive displacement at constant pressure so that there will be no compression or expansion of the air in the tank during the filling and emptying processes and the full content of the tank 20 will be available for supplying the air nozzle 10 at constant pressure. This is in contrast with a fixed volume air tank where only a small fraction of the air can be used to supply the air nozzle at sufficient pressure as it expands out of the tank reducing the pressure in the tank, while a substantial quantity of air remains in the tank not suitable for use at the reduced pressure but has to be re-compressed to full pressure each time the tank -19 -is replenished wasting energy. For example, when compressed air is released from a fixed volume air tank by adiabatic expansion, the tank absolute pressure will drop by 27% while only 20% of the stored mass is discharged for use at a steadily decreasing pressure and 80% remains in the tank not suitable for use because of the consequent reduced pressure.

Thus the variable volume constant pressure air tank 20 in Figure 4 will conserve the compressed air energy more effectively during the filling and emptying processes and will supply the air nozzle 10 at a constant pressure and with much larger useable air capacity than a fixed volume air tank of similar size (five times larger useable air capacity as demonstrated in the last example) . This is the fourth source of zero energy loss fuel saving and large effective air storage capacity unique to the first aspect of the invention enabling the first and second sources of fuel saving to be fully realised.

For example in Figure 4, a variable volume constant pressure air tank of 100 times the displacement volume of the engine 16 and replenished at approximate 3 bar absolute pressure using the engine 16 as a temporary air charger with fuel cut off in combination with air throttle 40 in the exhaust system acting as exhaust brake, will be filled during braking in approximately 600 revolutions of the f our-stroke engine or 18 second at 2000 rpm engine speed. This will be sufficient to supply the firing engine 16 with 50% supplementary air from the nozzle 10 and assisted boost to the turbocharger for approximately 400 revolutions of the four stroke engine or 12 seconds at 2000 rpm engine speed for free using energy derived from braking of the vehicle.

Combined with variable waste-gate 38 or variable geometry turbine control of the turbocharger which automatically reduces the flow velocity of the exhaust gases through the turbine 34 and the associated auxiliary load on the engine 16 driving the turbocharger during the time when the air -20 -nozzle 10 is in use, substantial fuel saving can be achieved from assisted boost for approximately 12 seconds with each acceleration of the vehicle after regenerative braking in.

urban driving conditions. Thus an air hybrid car, van or S bus/HGV powered by a 1.5 litre, 2.5 litre or 7.5 litre turbocharged engine respectively will only need 150 litre, 250 litre or 750 litre respectively variable volume constant pressure air tank at approximately 3 bar absolute pressure to achieve the above repeated fuel saving from regenerative assisted boost as well as improved dynamic response of the engine without turbo-lag and further driveability fuel saving.

In another example not shown in Figure 4, for those Is familiar with the state of the art, a variable volume constant pressure air tank of 2.5 times the displacement volume of the engine and replenished at approximately 2 bar absolute pressure using the turbocharger at times when there is excess boost air produced by the turbocharger, will be sufficient to supply the engine with 50% supplementary air from the air nozzle and assisted boost to the turbocharger for approximately 10 revolutions of the four-stroke engine or 0.4 seconds at 1500 rpm engine speed whenever it is needed to remove the turbo-lag during launch or sudden acceleration of the vehicle. Thus a passenger car powered by a 1.5 litre turbocharged engine will only need a 4 litre variable volume constant pressure air tank at approximately 2 bar absolute pressure to remove the turbo-lag. Scaling up, a van or bus/HG'! powered by a 2.5 litre or 7.5 litre turbocharged engine respectively will only need 10 litre or litre respectively variable volume constant pressure air tank at approximately 2 bar absolute pressure to remove the turbo-lag and achieve the associated driveability fuel saving from assisted boost.

In summary, any one of the three aspects of the present invention enables the aforementioned first and second -21 -sources of fuel saving to be realised derived from providing assisted boost to the turbocharger using compressed air or compressed gases taken from a compressed air or gas supply, S Unique to the first aspect of the invention, further, more substantial, fuel saving can be achieved by ensuring zero direct fuel energy for producing the compressed air to the air tank and zero compression and expansion losses during filling and emptying of the air tank conserving compressed air energy and providing the maximum useable air capacity limited only by the size and duty cycle of the air tank. This represents an efficient air hybrid vehicle with regenerative braking and energy storage by compressed air with unlimited charge-and-discharge cycle-life capability is for the air tank, and effective use of the stored air for assisted boost and reduced auxiliary load driving the turbocharger saving fuel working in synergy with existing systems on board the vehicle.

Claims

-22 -CLAIMS1. A vehicle powered by a turbocharged internal combustion engine, wherein the engine has at least one air or gas nozzle (10) positioned within an air intake duct (30) upstream of the turbo-blower (32) of a turbocharger and connected to receive compressed air or compressed gases from a compressed air or gas supply (20) on board the vehicle, and wherein the air or gas nozzle (10) is directed to deliver at least one jet of compressed air or gases (12) towards the impeller (14) of the turbo-blower (32) such that the expanding momentum flux of the jet or jets (12) f ills the frontal entry area of the impeller (14) thereby entraining and accelerating the intake air arriving at the impeller (14) and increasing the exit boost pressure produced by the turbo-blower (32).
2. A vehicle as claimed in claim 1, wherein the compressed air supply is a connection to a compressed air storage tank (20) on board the vehicle.
3. A vehicle as claimed in claim 1, wherein the compressed air supply is a connection via a feedback loop at boost air pressure produced by the turbo-blower (32) from a point downstream of an intercooler (50) connected to the boost air delivery duct of the turbo-blower (32).
4. A vehicle as claimed in claim 1, wherein the compressed gas supply is a connection via a feedback loop at exhaust back pressure produced by the engine from a point downstream of an EGR cooler (54) connected to an EGR pipe taking compressed exhaust gases recirculated from upstream of the turbine (34) of the turbocharger.
5. A vehicle as claimed in any preceding claim, wherein the jet of compressed air or compressed gases from -23 -the air or gas nozzle (10) is variable according to the required boost pressure produced by the turbocharger.
6. A vehicle as claimed in any preceding claim, wherein the turbocharger is equipped with a variable waste-gate (38) or variable geometry turbine (34) which automatically adjusts the flow velocity of the exhaust gases from the engine (16) for driving the turbine (34) of the turbocharger according to the required boost pressure produced by the turbocharger.
7. A vehicle as claimed in claims 1 and 2, wherein the compressed air storage tank (20) is replenished by the engine itself working temporarily as an air charger driven during deceleration or coasting of the vehicle using energy derived from braking of the vehicle, the engine (16) under such conditions being operated with fuel cut off and with an air throttle (40) restricting the air flow leaving the engine (16) creating a high back pressure in the exhaust system of the engine (16) and producing compressed air which is diverted from upstream of the air throttle (40) to the compressed air storage tank (20) -
8. A vehicle as claimed in claims 1 and 2, wherein the compressed air storage tank is replenished by a supercharger driven during deceleration or coasting of the vehicle using energy derived from braking of the vehicle.
9. A vehicle as claimed in claims I and 2, wherein the compressed air storage tank is replenished using the existing turbocharger on the vehicle at times when there is excess boost air produced by the turbocharger.
10. A vehicle as claimed in claims 1 and 2, wherein the compressed air storage tank is replenished by a reciprocating air compressor driven by the engine or using energy derived from braking of the vehicle.-24 -
11. A vehicle as claimed in claims 1 and 2, wherein the compressed air storage tank (20) has variable volume adjusted by a spring (28) against the air pressure within the tank (20).S12. A vehicle as claimed in claims 1 and 2 and 11, wherein the air pressure within the tank (20) is maintained substantially constant as the spring (28) adjusts against the variable volume.13. A vehicle as claimed in claims 1 and 2, wherein assisted boost is provided to the turbocharger of the engine (16) by filling the air storage tank (20) using the said turbocharger at times when there is excess boost air produced by the turbocharger, and supplying the stored compressed air to the air nozzle (10) for increasing the exit boost pressure produced by the turbocharger at times when rapid acceleration is initiated in the vehicle.14. An air hybrid vehicle as claimed in claims 1 and 2, wherein regenerative assisted boost is provided to the turbocharger of the engine (16) by filling the air storage tank (20) during deceleration or coasting of the vehicle with compressed air produced using energy derived from braking of the vehicle, and supplying the stored compressed air to the air nozzle (10) for increasing the exit boost pressure produced by the turbocharger during acceleration or cruising of the vehicle.15. A vehicle as claimed in claims 1 and 3, wherein assisted boost is provided to the turbocharger of the engine (16) by pressure amplification with positive feedback of cooled compressed air from a high pressure region downstream of the turbo-blower (32) towards the impeller (14) of the turbo-blower (32).-25 - 16. A vehicle as claimed in claims 1 and 4, wherein assisted boost is provided to the turbocharger of the engine (16) by pressure amplification with positive feedback of cooled compressed exhaust gases from a high pressure region S upstream of the turbine (34) of the turbocharger towards the impeller (14) of the turbo-blower (32) 17. An air nozzle module for use in a vehicle as claimed in any one of claims 1 to 16, wherein the air or gas nozzle (10, ba) is integrated into a modular section of an intake duct (30) connected to the intake housing of the turbo-blower (32) of a turbocharger.18. A turbocharger for use in a vehicle as claimed in any one of claims 1 to 16, wherein the air or gas nozzle (10, lOa) is integrated into an extended intake housing (30) of the turbo-blower (32) of the turbocharger.19. An exhaust brake module for use in a vehicle as claimed in claim 7, wherein a compressed air connection is integrated into a modular housing of the air throttle (40) for delivering compressed air from the engine (16) to the compressed air storage tank (20) 20. A compressed air storage tank for use in a vehicle as claimed in claim 12, wherein the tank comprises an inflatable bellows (20) confined within a casing (24) which is closed off by a moveable end wall (26) held against the bellows (20) by a spring (28), characterised in that the casing (24) has diverging sides and the moveable end wall (26) has adjustable dimensions matching and closing off the widening opening of the diverging sides such that the air pressure within the bellows (20) is maintained substantially constant as the bellows (20) inflates along the casing (24), the resultant pressure force under such conditions exerted by the bellows (20) distributed across the adjustable area of the end wall (26) being sufficient to counteract the -26 -increasing resisting force of the spring (28) as the bellows (20) inflates against the spring (28) 21. A vehicle as claimed in any preceding claim, s wherein several assisted boost systems are installed separately in the same vehicle each with its own set of air or gas nozzles and compressed air or gas supply, each working independently and each contributing to provide assisted boost to the turbocharger.