AUTOMOBILE ENGINE

CROSS REFERENCE TO RELATED APPLICATION

This application is based on and derives the benefit of Indian Provisional Application 202141030568 filed on 07-Jul-2021, the contents of which are incorporated herein by reference.

TECHNICAL FIELD

[001] The embodiments herein generally relate to a forced air induction system for an engine and more particularly to an electro-mechanical centrifugal supercharger for use with automobile engine.

BACKGROUND

[002] Engine downsizing is a proven approach for achieving increased engine performance through superior fuel efficiency and to significantly reduce tailpipe emissions to address the current environment issues/ emission regulations. Usually, engine downsizing is achieved by reducing the swept volume of the engine and / or by increasing the power output of the engine by employing a forced air induction system. The forced air induction system is used to provide compressed air to the engine to produce more power thereby increasing the efficiency and performance of the engine. Most forced air induction systems of the engine use a turbocharger which is driven by exhaust gases from the engine. Though, turbocharger does not impart a direct mechanical load on the engine, turbocharger is subjected to exhaust back pressure on engines thereby increasing pumping losses. Turbo lag occurs because turbochargers rely on the buildup of exhaust gas pressure to drive a turbine of the turbocharger. The exhaust gas pressure of the engine at idle, low engine speeds, or low throttle is usually insufficient to drive the turbine of the turbocharger. Only when the engine reaches sufficient speed, the turbine spins fast enough to rotate the turbocharger compressor to provide compressed air with intake pressure above atmospheric pressure. Other forced air induction systems of the engine use a supercharger which is an air compressor mechanically driven by the engine to provide compressed air to the engine. However, supercharger imparts a mechanical load on the engine. Therefore, the turbocharger is effective at higher speeds of the engine whereas the supercharger is effective at lower speeds of the engine. [003] There are two main types of superchargers defined according to the method of gas transfer: positive-displacement compressors and centrifugal compressors. Centrifugal compressors are generally more efficient, smaller and lighter than positive-displacement counterparts. The disadvantage of the centrifugal compressors is that the supplied boost increases with square of the rotational speed, resulting in low boost in low engine speeds. Currently, the centrifugal superchargers which are available are not very efficient in comparison to screw type superchargers, as they are incapable of delivering the required/adequate air mass at lower engine speeds. For the centrifugal superchargers to overcome this deficiency they are to be designed to deliver higher mass flow at lower engine speeds, which can be achieved either by large size compressors or by higher compressor speeds at lower engine speeds. Due to the space constraint, the higher compressor speeds (compact compressor) are chosen.

[004] Most superchargers include an integral step-up gearbox to increase the speed of the air compressor to achieve optimal compressor efficiency. The step-up gearbox is complex in design and expensive. In most cases, the supercharger gearbox is a fixed high ratio gearbox and the supercharger is required to be disengaged from the engine to reduce the traction load of driving the supercharger or the parasitic losses when the engine is operating at higher speeds. Despite the high ratio of enhanced gearbox, there are upper limitations to an achievable ratio of the step-up gearbox, which in turn limits the higher speeds that an air compressor can attain at lower engine speeds, and complicates the design of the impeller of the compressor for such application. Hence, engines are provided with both the supercharger and the turbocharger. In such twin charged engines, a centrifugal clutch is used to engage the supercharger with the engine when the crankshaft of the engine is rotating at the lower speed. The centrifugal clutch disengages the supercharger from the engine and the turbocharger provides compressed air to the engine when the crankshaft is rotating at higher speeds.

[005] Further, in any vehicle, the typical driving conditions include: ignition, starting, idling, moving, steady state, cruising, accelerating (slow-medium-high), decelerating (slow- medium-high), shifting gears during acceleration and deceleration, braking and stopping. In each of the aforementioned driving conditions, the engine of the vehicle is subjected to different and varying loads such as transmission to wheels, turbocharger causing exhaust back pressure, drive to the supercharger, other front end accessories drive (FEAD), belt driven systems such as alternator, air conditioning compressor etc., Furthermore, the engine is subjected to different kinds of responses and behavior which provides undesirable experience to the driver, or /and deterioration of fuel economy and safety of the components of vehicle. [006] In order to rapidly increase the power output of the supercharged engine, the compressor of the supercharger may be driven by the crankshaft to accelerate the compressor. However, the load inertia reflected back to the motor, in any speed changing system, is a squared function of the speed ratio, thus transmitting a quantum reflected torque back through the driving elements of the supercharger to the crankshaft to oppose the torque created by the engine. These result in unexpectedly large and sudden reduction in the torque transmitted by the crankshaft to vehicle power transmission elements, which in turn causes the vehicle, powered by the engine and supercharger to decelerate rapidly, vehicle staggering undesirably and even lead to engine stalling.

[007] Further, increasingly stringent emissions regulations have driven many changes in diesel engines, one of which is the wide spread use of Exhaust Gas Recirculation (EGR). Engine manufacturers around the globe will be providing engines with full load EGR rates between 0% and 30% and turbocharging systems must be available to suit these. In terms of diesel performance, the mandatory EGR rate increase will require ever increasing brake mean effective pressure (BMEP) levels. The large scale upward BMEP shift for example from 22 bar for Diesel and 25 bar for gasoline necessitates a compressor pressure ratio greater than 4:1 for diesels and at least a similar pressure ratio for gasolines. For EGR to flow from the exhaust manifold through an EGR cooler and then to the intake manifold, the exhaust manifold must be at a higher pressure than the intake manifold. This results in “negative pumping work”, which means it reduces the work output and efficiency of the engine. The more EGR that is driven, the higher this negative pumping work becomes. In addition, the EGR is additional mass flow that must be pumped through the engine. This requires additional boost pressure to increase the density of the combined fresh air and EGR to match the volumetric flow of the engine. The turbocharger sees additional EGR flow as a reduced “fresh air volumetric efficiency of the engine. Assuming the fresh air mass flow remains the same, the boost must increase significantly to pump the EGR through the engine as well. At high levels of EGR (roughly 20-30%), the pumping work becomes much more severe and the turbocharger efficiencies start to fall off as the pressure ratio rises, increasing the pumping work unnecessarily. Above 25% EGR (at full load), generally two stage turbocharging becomes necessary which involves 2 series compressors and a parallel compressor for the turbine to achieve optimum efficiency considering the blade speed ratio (BSR) parameter. The optimal BSR for best isentropic efficiency (e.g. BSR=0.7 for an ideal free floating turbine).

[008] In a twin-charging / compound-charging arrangement, the above situation mandates the compressor delivery characteristics of the supercharger be matched to the boost and mass flow rates of the turbocharger. But due to space limitations for packaging design under the hood of a vehicle, not only eliminates even a remote possibility of using 2 compressors in series but mandates the single compressor to be small and compact but deliver higher mass flow rates with higher boost. It is known of the Centrifugal compressors that the supplied boost increases with square of the rotational speed. Therefore, for the same mass flow rate, for a smaller compressor size, the driving rotational speeds become ultra-high which is another limiting factor in mechanical devices of the known art.

[009] Therefore, there exists a need for electro-mechanical centrifugal supercharger, which obviates the aforementioned drawbacks.

OBJECTS

[0010] The principal object of an embodiment herein is to provide an electromechanical centrifugal supercharger.

[0011] Another object of an embodiment herein is to provide the electro-mechanical centrifugal supercharger, which is a highly responsive, very compact and include highly efficient gearbox with very high step up ratio, and capable of ratio/speed variation, and adapted to deliver ultra-high speeds (rpm) at engine low speeds coupled with a small and compact centrifugal compressor but can deliver higher boost, high mass flow rates at high isentropic efficiencies, and a clutching mechanism for engaging or disengaging when desired.

[0012] Another object of an embodiment herein is to provide the electro-mechanical centrifugal supercharger which includes a symmetrical double-sided impeller- parallel compressor.

[0013] Another object of an embodiment herein is to provide the electro-mechanical centrifugal supercharger, which enhances air boost to the engine whenever there is torque dip at engine crankshaft, which occurs during engine idling, low engine speeds, clutch pedal pressing and shifting gears, braking, and while the vehicle is moving on sloping surface.

[0014] Another object of an embodiment herein is to provide the electro-mechanical centrifugal supercharger which enables downsizing of the engine along with enhanced performance of the engine.

[0015] Another object of an embodiment herein is to provide the electro-mechanical centrifugal supercharger for the engine, which reduces inertia of rotating group (power train, engine boosting system and engine driven accessories (water pump, air conditioning compressor, etc.,)), which is about 40% less than that of the conventional one which translates to over 10% reduction in inertia of the rotating group and thereby helps in improving transient response.

[0016] Another object of an embodiment herein is to provide the electro-mechanical centrifugal supercharger for an exhaust gas recirculation (EGR) engine, which delivers additional boost pressure to increase the density of the combined fresh air and EGR to match the volumetric flow of the engine in a real time driving cycle.

[0017] Another object of an embodiment herein is to provide the electro-mechanical centrifugal supercharger which includes an electric machine and two-stage planetary type oil free power transmission units (gear boxes), where the electric machine is configured to vary the output speed of the first stage planetary type power transmission unit (gearbox).

[0018] Another object of an embodiment herein is to provide the electro-mechanical centrifugal supercharger which is operable to vary the pressure of air in at air inlet manifold of an engine independent of the engine speed, and in an efficient and cost-effective manner, thereby enabling the engine being very responsive to the changes in load depending on the driving condition of the vehicle.

[0019] Another object of an embodiment herein is to provide the centrifugal supercharger for a gasoline/diesel naturally aspirated engine, which can be operated for entire operating speed range of the engine.

[0020] Another object of an embodiment herein is to provide the electro-mechanical supercharger which provides enhanced effectiveness of centrifugal supercharging of diesel engines even at engine idling and low engine speeds and torque dip at engine crankshaft.

[0021] Another object of an embodiment herein is to provide the electro-mechanical supercharger for use in a twin charged engine for enhancing the performance of the vehicle and for reducing the fuel consumption of the vehicle.

[0022] Another object of an embodiment herein is to provide the electro-mechanical supercharger, which is reliable and enables precise operability.

[0023] Another object of an embodiment herein is to provide the electro-mechanical supercharger, which is compact and light weight and effectively delivers compressed air to the engine whenever there is torque dip (even at engine idling and low engine speeds) at engine crankshaft.

[0024] These and other objects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.

BRIEF DESCRIPTION OF DRAWINGS

[0025] The embodiments of the invention are illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:

[0026] Fig. 1 depicts a side view of a centrifugal supercharger with a double-sided impeller parallel compressor driven by an ultra-high speed electro-mechanical, continuously variable and regenerative, oil free gearbox, with electric motor-generator unit placed outside the gearbox, according to embodiments as disclosed herein;

[0027] Fig. 2a depicts a sectional side view of the double-sided impeller of the parallel centrifugal compressor, according to embodiments as disclosed herein;

[0028] Fig. 2b depicts a perspective view of a rear half of a volute casing of the doublesided impeller of the parallel centrifugal compressor, according to embodiments as disclosed herein;

[0029] Fig. 2c depicts a perspective view of a front half of the volute casing of the double-sided impeller of the parallel centrifugal compressor, according to embodiments as disclosed herein;

[0030] Fig. 3a depicts a front view of the double-sided impeller of the parallel centrifugal compressor, according to embodiments as disclosed herein;

[0031] Fig. 3b depicts a side view of the double-sided impeller of the parallel centrifugal compressor, according to embodiments as disclosed herein;

[0032] Fig. 3c depicts a perspective view of the double-sided impeller of the parallel centrifugal compressor, according to embodiments as disclosed herein;

[0033] Fig. 4 depicts a sectional view of the design of ported shrouds of the front and rear sides of the compressor, according to embodiments as disclosed herein;

[0034] Fig. 5 depicts a sectional view of a bump-type foil air journal bearing, according to embodiments as disclosed herein;

[0035] Fig. 6 depicts a sectional view of a bump-type foil air thrust bearing, according to embodiments as disclosed herein; [0036] Fig. 7 depicts a perspective front and rear view of the end bearing support and a sectional view of the spokes supporting the bearing support hub, according to embodiments as disclosed herein;

[0037] Fig. 8 depicts a side sectional view and a front view of end cover flange of first planetary power transmission unit (gearbox), according to embodiments as disclosed herein;

[0038] Fig. 9 depicts a side sectional view and a front view of end cover flange of second planetary power transmission unit (gearbox), according to an embodiment as disclosed herein;

[0039] Fig. 10 depicts an arrangement of a supercharging system in an internal combustion engine, according to an embodiment as disclosed herein;

[0040] Fig. 11 depicts a sectional front view of air flow control mechanism (Section XX of Fig.1), according to an embodiment as disclosed herein;

[0041] Fig. 12 depicts a front view of a pressure actuation plate of air flow control mechanism, according to an embodiment as disclosed herein; and

[0042] Fig.13 depicts a side view of a centrifugal supercharger with the double- sided impeller parallel compressor driven by the ultra-high speed electro-mechanical, continuously variable and regenerative, oil free gearbox, with the electric motor-generator unit placed coaxially inside the gearbox, according to embodiments as disclosed herein.

DETAILED DESCRIPTION

[0043] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

[0044] The embodiments herein achieve an electro-mechanical centrifugal supercharger, which enhances air boost to the engine whenever there is torque dip at engine crankshaft, which occurs during engine idling, low engine speeds, clutch pedal pressing and shifting gears, braking, and while the vehicle is moving on sloping surface. Additionally, embodiments herein achieve performance enhancement of the internal combustion engine in an automotive application by way of power density and torque enhancement, fuel economy, emission reduction, better and smoother drivability and energy regeneration, through an electro-mechanical, ultra-high speed, continuously variable, oil-free, regenerative boosting/supercharging device. Furthermore, embodiments herein achieve method of engine downsizing, power density and torque enhancement, fuel saving, emission reduction, energy regeneration, boosting / supercharging device for use in internal combustion engine applications such as automotive. Also, embodiments herein achieve engine downsizing, power density and torque enhancement, fuel saving, emission reduction, energy regeneration, boosting / supercharging device which includes an output having an ultra-high speed when compared to an input speed provided at the input of the embodiments by an internal combustion engine, the output connected to at least one centrifugal compressor. Still, embodiments herein achieve centrifugal supercharger with a double-sided impeller parallel compressor driven by an ultra-high speed electro-mechanical, continuously variable and regenerative, oil free gearbox device which is adapted to be used as boosting device for downsizing of a diesel / gasoline naturally aspirated engine for entire operating speed range of the engine. Moreover, the embodiments herein achieve the ultra-high speed centrifugal supercharger device which provides enhanced effectiveness of boosting of diesel / gasoline engines at low engine speeds. Also, the embodiments herein achieve the ultra-high speed centrifugal supercharger device which does not require any major changes in the design of packaging under the hood as provided by the vehicle/engine OEM. Further, the embodiments herein achieve the ultra-high speed centrifugal supercharger device for use in a compound charged / twin charged engine. Furthermore, the embodiments herein achieve the ultra-high speed centrifugal supercharger device, which is reliable and enables precise operability of the stand alone or compounded boosting system. Also, the embodiments herein achieve the ultra-high speed centrifugal supercharger device which is compact and light weight. Referring now to the drawings, and more particularly to Figs. 1 through 13, where similar reference characters denote corresponding features consistently throughout the figures, there are shown embodiments.

[0045] As is known for any vehicle, the typical driving cycle consists of stages like: ignition, starting, idling, move on by accelerating and shifting gears upto a speed & momentum is reached (A batch of transient conditions), steady state, cruise, accelerating (slow-medium- high), decelerating (slow -medium-high), shifting gears during acceleration and deceleration, braking and stopping. At every aforementioned stage, the load & speed conditions are different and varying. It is expected of a vehicle to respond adequately against every demand over the entire driving cycle without adversely affecting the smoothness of driv ability and fuel economy.

[0046] In an embodiment, the electro-mechanical centrifugal supercharger (100) includes a first step-up power transmission unit (GB 1, gearbox)) (also referred to as first power transmission unit in this description), a second step-up power transmission unit (GB2, gearbox)) (also referred to as second power transmission unit in this description), a parallel compressor (300), and an electric machine (112). The parallel compressor (300) having a double-sided impeller (303). For the purpose of this description and ease of understanding, the electro-mechanical centrifugal supercharger is explained herein below with reference to an internal combustion engine provided in a vehicle. However, it is also within the scope of the invention to provide the electro-mechanical centrifugal supercharger to be used in any other engines and other industrial applications without otherwise deterring the intended function of the electro-mechanical centrifugal supercharger as can be deduced from the description and corresponding drawings.

[0047] The supercharger (100) includes an input shaft at its input end that supports a pulley or a clutch (103). The input shaft is an integral part of the ring gear (107) of the planetary gearing of the first gearbox (GB 1) mounted on a bearing (113). The bearing (113) is housed in the front cover flange (104). An assembly of plurality of planet gears (106) and a rotational carrier (109) connected through plurality of carrier pins (114), mesh radially outwards with internal ring gear (107) and radially inwards with a sun gear (111) which is also the output member of the first gearbox (GB1). The plurality of planet gears (106) are mounted on a plurality of journal bearings (108) which are Foil Air bearings. The rotational carrier (109) is connected through a fixed ratio gearing to a pinion (110) mounted on the shaft of Electric Machine Motor- Generator (EM M-G) (112) which may also be a Permanent Magnet Brush- Less Direct Current (PM BLDC) type. Alternately the rotational carrier (109) may be connected to the shaft of the Electric Machine Motor Generator (EM M-G) (112) by toothed belt and pulley system (Not shown in the figure). In an alternate embodiment as shown in Fig. 13, the Electric Machine Motor-Generator (EM M-G) (112) may be coaxially mounted inside the housing of the first gearbox (GB1) making the arrangement furthermore compact and symmetrical. The operation of EM M-G (112) is controlled by Electronic Control Unit ECU (51) through Controller (52). The EM M-G (112) can operate as driving Motor or driven Generator. The entire set of planetary gearing of first gearbox (GB1) is housed in the body / housing (105) with the front cover flange (104). The output from output member of first gearbox (GB1) which is sun gear (111) is coupled to the input shaft of the second gearbox (GB2), the input shaft of second gearbox (GB2) as in case of first gearbox (GB1) is also an integral part of ring gear (204) of planetary gearing of second gearbox (GB2), and the shaft is secured in the output cover flange (202) through a journal bearing (203), being a Foil Air bearing. Assembly of plurality of planet gears (205) mounted in the fixed carrier which is an integral part of the housing (201) through plurality of carrier pins (208), mesh radially outwards with internal ring gear (204) and radially inwards with a sun gear (206) which is also the output member of the second gearbox (GB2). The plurality of planet gears (205) are mounted on plurality of journal bearings (207) which are Foil Air bearings. The shaft of sun gear (206) which is also the output shaft of the second gearbox (GB2) is supported in the housing (201) by a set of journal bearings (209) and a thrust bearing (210) both being Foil Air bearings. At the output side of the second gearbox (GB2) is an assembly of an Air flow control mechanism consisting of an orifice plate (211) coupled with a pressure actuation plate (212) through plurality of tensile resilient element 213. The output shaft of the gearbox GB2 is connected to the impeller 303 of the compressor (300), the impeller being a double-sided impeller and the compressor being a parallel compressor. The rear half of volute casing of the compressor (301) is connected to output cover flange (202) of gearbox GB2), and output cover flange (202) in turn being bolted to the housing (201). The impeller (303) is connected and supported on one side on the output shaft of sun gear (206) and on the other side in a journal bearing (304) in the hub of end support member (305) mounted in the front-end volute casing of the compressor (302) ensuring the axis alignment of the impeller. [0048] The input shaft of the supercharger (100) described herein is fixedly linked to engine speed. This is because the input shaft is coupled to the crankshaft of the engine via the pulley / clutch (103) mounted on the input shaft and a pulley /device mounted on the crankshaft. As the engine starts and the crankshaft begins to rotate, the same is transmitted to the pulley /clutch (103). The pulley or clutch (103) since connected to input shaft of the first gearbox (GB1) which is also the ring gear (107), drives the ring gear (107) at the same speed. The ring gear (107) in turn drives the plurality of planet gears (106) which in turn drive sun gear (111) which mesh radially inwards with plurality of planet gears (106). The rotational carrier (109) which carries the plurality of planet gears (106) is free to rotate in either direction. It is either held in fixed position or driven by the EM M-G (112) via pinion (110) mounted on its shaft.

[0049] As is known in the prior art of a typical planetary gearing, if the input is given to the ring gear and the carrier is fixed, the output speed at the sun gear is of a high step-up ratio. In the same arrangement, if the carrier is rotated at a speed in the direction of rotation of ring gear, the output speed at the sun gear further increases, the output speed increases proportionately and continuously with increase in speed of rotation of carrier in the same direction of rotation of ring gear. In the same way, if the carrier is rotated in the opposite direction to the rotation direction of ring gear, the output speed of the sun gear decreases. Hence, the output speed of sun gear continuously and proportionately decreases with increase in the speed of rotation of carrier in the opposite direction to the direction of rotation of ring gear. The speed increase and decrease ratios are governed by the following formulae.

* - Negative sign shows the direction of rotation of output member is opposite to the direction of rotation of input member

[0050] In the embodiments of the present invention, the rotational carrier (109) of the first gearbox (GB1) is connected to the EM M-G (112) via pinion (110). The EM M-G (112) being a PM BLDC device or any other types of Electric Motor. The PM BLDC device is capable of rotating at variable speeds and in both clockwise and anti-clockwise directions or also holding in a fixed position depending on the respective command received from controller (52) which in turn receives the command from ECU (51) depending on the inputs received from various sensors in the vehicle about the instant desired output power and torque. In an alternate arrangement, holding the rotational carrier (109) of the first gearbox (GB1) in a fixed position can be achieved by other braking and releasing mechanisms while the EM M-G (112) being used for rotational drive in either direction. This feature enables the output speed of first gearbox (GB1) being extremely enhanced or reduced or incrementally increased or reduced with respect to the input speeds received from crankshaft, thus enables driving the input to the second gearbox (GB2) with a very wide range of speeds, being infinitely variable in the range. The second gearbox GB2 is a high fixed ratio speed enhancer as the carrier in this case is fixed, the final output speed at the sun gear (204) is an enhanced speed by fixed ratio times the input speed. As the input varies, the output too varies. With this arrangement the output speed of sun gear (204) can be ranging from ultra-high to moderate to low or even near zero being close comparative to a Continuously Variable Transmission CVT. Therefore, the speeds of output sun gear (204) are independent of crankshaft / engine speeds.

[0051] Fig. 10 shows the schematic layout of the boosting system in a compound charging system of an automotive I.C. Engine which includes the supercharger (100) of current invention along with other elements used, such as a Controller (52) connected on the downstream to EM M-G (112), and upstream to a Voltage Booster (DC to DC) (53) through a high voltage line V2. The Voltage Booster (53) is connected to a Capacitor (54) and an energy reservoir- store such as Batery (55) through a low voltage VI connection. The Controller receives signal from Electronic Control Unit ECU (51). The EM M-G (112) during intermitent periods not being engaged to do the work of either rotating or holding planets carrier (109) for varying the speed of gearbox (GB1), during which time the planetary gearing is yet in action and the carrier (109) is rotating continuously during the entire operating cycle of the engine except when supercharger (100) is disengaged with crankshaft by the clutch (103), the rotational speeds of carrier (109) which is in constant mesh with shaft of EM M-G (112) is used to generate energy by the EM M-G (112) and deliver for recharging batery (55) or capacitor (54), or alternately be used to power up other electric machines in the system needing input electric energy. This selection of EM M-G (112) to operate as motor or generator is controlled by the ECU (51) through controller (52).

[0052] For every specific point or stage in a real drive cycle of a vehicle, there is a corresponding demand of power and torque to be delivered with high rate of response. The ability to deliver such power and torque with high rate of response in any engine with boosting system can only be achieved if the compressor of the supercharger or turbocharger is able to deliver air at the required mass flow rate and pressure. Such compressor rating is determined by two important characteristics of the compressor namely size and speed, while its size gets defined by the packaging space availability, its speed, a size dependent variable gets defined by the relationship “boost increases with the square of the rotational speed”, which means smaller the size, higher is the impeller speed. At different acceleration rates (high, medium, low), at idling, at different deceleration rates (high, medium, low), at steady state, the corresponding boost and the response too are different. To cater to such extremely varying demand characteristics, the impeller of compressor has to spin at corresponding speeds which may be ultra-high or high or medium or low.

[0053] The above condition translates to a corresponding demand of a driving mechanism which can drive the impeller at such speed ranges of ultra-high to low coupled with a corresponding change response. The arrangement in the embodiments of this invention, the combined transmission capability of first gearbox (GB1) with a built-in feature for speed variation with help of EM M-G (112) as explained above in this disclosure and the second gearbox GB2 enables a capability and flexibility of delivering such speed ranges of ultra-high to low coupled with a corresponding change response in an I.C. Engine.

[0054] The aforementioned condition in a twin-charging / compound-charging arrangement, mandates the compressor delivery characteristics of the supercharger be matched to the boost and mass flow rates of the turbocharger. But due to limitations of size of compressor, in spite of the ultra-high speeds of the impeller, a conventional compressor cannot deliver the required mass flow rates at optimum isentropic efficiency of the compressor. This problem is overcome by deployment of parallel compressor in which runs a double-sided impeller. Fig. 2a shows a sectional side view of the parallel compressor (300). Air from a common inlet is split between the two impeller sides. Both impeller sides then discharge to a common diffuser followed by a volute as found in a conventional centrifugal compressor. The compressor has a front half volute casing (302), a rear half volute casing (301), a rotational double-sided impeller (303), an end support (305). The mating faces of the front and rear halves of volute casing forms the central plane of diffuser of the compressor. The central plane of the double-sided impeller is aligned to match the central plane of diffuser. Fig. 2b shows the perspective view of rear half volute casing (301). A plurality of curved inlet ducts (306R) are connected to matching inlet ducts (306F) in the front half of volute casing (302) to deliver air from main inlet to rear impeller. The objective in designing the three ducts (306) that provide inlet air to the rear side of double-sided impeller (303) is to provide as uniform axial flow into the impeller as possible, without swirl, while matching as closely as possible the inlet velocity and pressure field of the front impeller. Variation in the velocity field or a lower pressure would unbalance the two sides of double impeller, resulting in compromised performance.

[0055] Fig. 4 shows a sectional view of the parallel compressor (300) at the shrouds, showing impeller (303), the rear half volute casing (301) and the front half volute casing (302). As mentioned above, with symmetrical double-sided impellers, the parallel compressor suffers the imbalanced flow distributions at critical low speeds leading to instability. To improve stability, ported shrouds as shown in the Fig.4, are used in both sides of compressor. The recirculating cavity flow driven by the pressure difference across the upstream slot and the bleed slot, helps to improve stability by the combined action of (a) Unloading the inducer by altering the velocity triangle, and (b) Removal of weak boundary layer fluid on the shroud near the inducer. But this does not eliminate instability completely.

[0056] To achieve the rebalance of flow distributions of double-sided impellers, a method of increasing the radius of rear impeller to an optimum size is adopted as shown in Fig. 3b where in R+ is the radius of rear side impeller and R is the radius of front side impeller, R+ being greater than R, making the double impellers Asymmetrical as is designed/adopted here in this invention. By doing so, besides ensuring optimal pressure ratio and efficiency of compressor, the work capacity of rear impeller is enhanced, the working mode conversion process from parallel working mode of double- sided impeller to the single impeller working mode is delayed, and the stable working range of double-sided compressor is broadened. [0057] The use of a double-sided impeller (303) and the above-mentioned design methods used to further improve the performance of the double-sided impeller (303) result in eliminating the high thrust loads that are otherwise generated in a conventional compressor and the need for complex solutions to counter thrust loads.

[0058] In any transmission involving a gear train specially a speed enhancer, one of the critical limitations to achieve ultra-high speeds is the limitations of the bearings used for the purpose, for example rolling element bearings. The bearings are defined by the DN Factor which in turn defines the lubrication to prevent ‘lubricant starvation’ which occurs when bearing speed (N) exceeds the ability of the lubricant to flow back into the bearing track. This phenomenon can be the cause of metal-on-metal contact, which causes rapid wear and necessitates early replacement. Also, since the rolling fatigue life of bearing depends greatly upon the viscosity and film thickness between the rolling contact-surface, besides limiting the speeds, needs complex lubrication solutions. To overcome such limitations and achieve ultra- high speeds and eliminate the need for lubrication, the Foil Air Bearings (FAB) also called as Gas Foil Bearings (GFB) with key advantages of Low drag friction, high speed operation and the omission of an oil system are used in the embodiments of the current invention. FABs are based on the hydrodynamic pressure. Viscous drag forces between the moving runner surface and the air and the compliant spring-like structure of the bearing allow and form the film, which supports the bearing load. A journal type FAB as shown in Fig.5 is used on shafts for catering to the radial loads, and a Thrust type FAB as shown in Fig.6 are used for catering to the axial and thrust loads.

[0059] Fig.5 shows a front sectional view of a Journal FAB used in the embodiments of the invention disclosed herein such as FAB 108, 203, 207, 209 and 304. FABs are based on the hydrodynamic pressure. This pressure is induced by a generated slip stream between the turning bearing journal, in this case being shaft (204) and the bearing foil (203c). An elastic structure comprises one or more thin top foils (203c) supported by corrugated bumps (203b). The bump is designed so that bump stiffness is much lower than the stiffness of the hydrodynamic gas film and therefore controls the overall stiffness of the bearing. The controlled stiffness leads to the desirable properties of being able to accommodate misalignment, tolerance variation, differential thermal expansion, and centrifugal shaft growth. Therefore, an optimal film thickness is achieved and higher loadings are possible. FABs with practically no speed limitation for operation and their load bearing capacity increasing linearly with speed, become in terms of technical and commercial feasibility, best suited for the ultra- high-speed application. Due to friction contacts inside the corrugated structure a structural damping is induced. A tuning of the compliant structure in a bearing housing (203a) by staggering of bumps (203b), applying coatings on shaft (204) and the bumps (203b), which are high temperature resistant Solid-lubricants, results in higher load capacities and can reduce high sub synchronous whirl amplitudes.

[0060] Fig. 6 shows a sectional side view of the Thrust FAB (210) as shown in Fig.1. The thrust Foil Air Bearings are used to support axial loads and are made up of three main components. The backing plate (202) which is the housing of the second gearbox (GB2) serves as the base of the bearing. The bump foils (210a) create the spring-like characteristics of the bearing. The top foils (210b) provide a smooth surface for the gas film to develop on to generate hydrodynamic pressure. The surfaces of the top foil (210b), the bump foil (210a) and the runner (rotating element) are coated with solid-lubricants to decrease the friction coefficients between surfaces prior to forming the air film.

[0061] Due to the deployment of FABs in the embodiments declared herein, not only the problem of achieving the ultra-high speeds by conventional methods of known prior art is resolved but additionally eliminates the need for oil lubrication. But elimination of oil in the gearbox, poses a serious problem of lubricating gears, the main power transmitting elements. This critical problem is resolved by usage of innovative Solid-Lubricants that are capable of operating at very wide range of temperatures ranging from -170°C to 760 °C. The surfaces of the Gear Teeth are coated by Solid-lubricants such as NASA PS304 and NASA PS400 or the variants of MiTi-Korolon™ coatings, or derivatives such as Emraion™ or an apt variant of MoS2-WC. The Gear tooth geometry is further modified (not shown) to optimize the contact stresses and rolling action of mating gears and the coating to yield better efficiency. The same coatings are applied to the Top foil, Bump foil and the runner surfaces of FABs. Coatings play a major role in bearing operation at low speeds, when the gas film has not fully developed. They can decrease the friction coefficient between the surfaces, decreasing the torque at low speeds. With such methodology, the problems associated with heat management, oil and its circulation system maintenance, spin losses, inertia during cold start, reflected torque, additional weight of oil, bearing maintenance, associated with a gearbox are resolved, thereby enabling the oil-free gearbox using FABs to be extremely efficient.

[0062] However, operating FABs to come with a few challenges. These bearings are limited by lower load capacity during start/stop conditions. Initially, the bearing experiences high torque, as the foils rub against the runner surface. As speed is increased, the bearing begins to develop the gas film and the resulting hydrodynamic pressure, decreasing contact and thus the torque. The torque continues to decrease with speed until the gas film is fully developed, at which point the torque is entirely due to shear forces in the thin film. At this point, the torque again increases with speed as the shear forces in the air increase as the speed gradient increases. At higher speeds, the load capacity of foil gas thrust bearings has been found to decrease with speed. This is thought to be a result of a breakdown in thermal management, as the heat generated by the bearing becomes too great to be dissipated in the bearing. Again, touchdown during coast down is marked by increased torque, faster deceleration, and increased vibration.

[0063] The above-mentioned challenges for the FABs adopted in the gearbox and elsewhere in the disclosed embodiments of the current invention, can be effectively addressed by providing pressurized air which enables not only higher load carrying capacity during start/stop but also enhanced thermal management because of pressurized cooling effect for better performance. The method found to be most effective for the purpose is the ‘side feed pressurization’ air cooling, which improves the dynamic performance of the FABs, where it increases direct stiffness, damping and overall stability specially for high-speed operation. A forced cooling flow is streaming underneath the corrugated bearing structure and the clearance between bearing journal and top foil. Heat is transported by convection and conduction effects. Such method during start/stop conditions enables hydrodynamic bearings to behave hydrostatic taking advantage of available pressurized air.

[0064] Pressurized air cooling of the various elements shown in Fig.l such as FABs (108), (203), (207) and (209) in both gearboxes (GB 1) and (GB2), gears, and FAB (304) in end support (305) of supercharger (100) is achieved through an innovative, cost-effective method using the available high-pressure line and the low-pressure line in the system along with specially designed elements.

[0065] Fig. 10 shows the schematic layout of the boosting system in a compound charging system of an automotive I.C. Engine which includes the supercharger (100) of current invention along with other elements used. A closed loop air circuit is created by taking the input from the high-pressure line (60) at the downstream of the intercooler (IOC) and passing through a non-return check valve (61) to front end cover flange (104) located at the input end of the first gearbox (GB1), and then passing through first gearbox (GB1) and second gearbox (GB2) through orifice plate (211) coupled with a pressure actuation plate (212) of the flow control mechanism at the outlet and finally to the suction area of the compressor (300). An accumulator (62) is connected to the pipeline, midway between non-return check valve (61) and front-end cover flange (104). With such high-pressure line (60) being connected to the front-end cover flange (104) and the other end of second gearbox (GB2) being connected to the inlet space of the compressor (300) which is a below atmospheric pressure space, a pressure gradient is created between input and output of the gearbox. Fig. 8 shows the side sectional view of the front-end cover flange (104). The novel, unique design of flange (104), has a radially located inlet port (104 A), an air pocket, and plurality of conical exit ports (104B) connecting the air pocket and the face of the flange facing the inside of the gearbox (GBl), ports being positioned as radially spread on the face as shown in Fig. 8, the cones enlarging diametrically away from the air pocket. This conical design of plurality of exit ports (104B) enables the air passing from the high-pressure air pocket behind to expand into the housing of gearbox (GB 1) thereby achieving pressure drop but continue to be above ambient pressure and correspondingly drop in the air temperature. Such expanded cooled air, due to the aforementioned pressure gradient, flows from front end cover flange (104) through the first and second gearbox towards the output end of the second gearbox (GB2) through the ports provided in orifice plate (211) of the flow control mechanism in the output cover flange (202). Fig. 9 shows a front view and sectional side view of output cover flange (202) housing the flow control mechanism and the ports for air flow provided therein.

[0066] Fig. 11. shows the sectional front view of the flow control mechanism where the orifice plate (211) is fixed into the collar hub of output cover flange (202). The pressure actuation plate (212) of the design shown in Fig.12, positioned concentric to orifice plate (211 ) is connected to it with plurality of resilient tensile elements (213) keeping the orifices in the orifice plate (211) closed. As the air pressure in the entire gearbox (GB 1+GB2) increases and the combined force of the air in all the conical orifices in the orifice plate (211) exceeds a predetermined combined retaining force of the tensile resilient elements (213), the pressure actuation plate (212) pushed backwards by the air pressure and thus opening the conical orifices for the air to flow through the gap between the plates and the wide circumferentially placed gaps and through the ports in the output cover flange to the inlet of the real- half of the compressor. The exiting air from the orifices expand and drop in temperature to feed the suction inlet of compressor with cooled air. As the pressure decreases, the pressure actuation plate (212) withdraws into its closed position thereby closing the air flow through the orifices. Through such a method, cooled air streaming underneath the corrugated bearing structure and the clearance between bearing journal and top foil of the FABs a forced cooling flow is achieved where heat is transported by convection and conduction effects, thereby ensuring enhanced performance of FABs and consequently the oil free gearbox. The flow control mechanism explained above by enabling a pressurized environment at starting or stopping condition specifically solves the problem faced by FABs at start/stop conditions mentioned above, thereby further enabling gearboxes with FABs oil free and highly efficient under wider operating conditions.

[0067] Fig. 7 shows perspective view of front and rear side of the end support member (305) along with a sectional view of aerodynamic shape of its spokes which offer least resistance to air flow, the end support member (305) being located at the inlet of front end of parallel compressor (300) shown in Fig.l. The end support bearing (304) which is also a FAB, is housed in the hub of end support member (305). The design of hub has plurality of openings which open on the inside face on the face of FAB where dump element is located. This is in the suction line of compressor and therefore has both force and direction of flow towards the impeller. Heat is transported by convection and conduction effects. This air flow characteristic in the suction line coupled with openings provided in the hub of end support member (305) ensures pressurized air cooling of FAB (304).

[0068] As a result of the innovative combination of every novel aspect explained above which every aspect besides being itself an augmenter to the overall efficiency or performance of the combination either complements the presence of the other or is a solution to the part challenge posed by the adoption of other, is the device of the current invention.

[0069] The technical advantages of the electro-mechanical supercharger (100) are as follows. Due to its flexibility of combination of modular gearboxes enabling adoption of 2 stages in tandem or single stage transmission with either a double sided impeller parallel compressor or a conventional compressor coupled with speed variability feature enables a wide spectrum of possibilities to address varying challenges in case of extreme downsizing, packaging constraints of across categories and variants, a - adoption to Gasoline or Diesel NA engines, b - adoption as retrofit to in-use vehicles where most modifications are extremely difficult, c - adoption in case of compound charging of Turbo charged engines and d - adoption to augment Mini Hybrid vehicles. Even in Comparison with most advanced Electric Superchargers, to reach ultra-high speeds, the challenges faced by them in terms of, 1. electric energy - complexity & cost, 2 - Heat transfer /cooling management of the electric motor - the device in the current invention scores better on all fronts: technology, cost, adaptability, retrofitability etc.,. Applications of Air supply for Fuel Cells, Hydrogen Fuel cells etc.

[0070] Further, 1 ^st stage gearbox is additionally provided with an arrangement to drive the planet carrier by an inbuilt adjoining electric machine such as a PM BLDC motor-generator with a brake controlled by a controller such as ECU is capable of infinitely varying its speed and thus speed of carrier and consequently the output speed of 1 ^st gearbox. The Electric Machine can operate as a Generator when not engaged in varying the driving speeds, and can recharge a battery or Supercapacitor, or drive another electric driving element in the system which needs input electric energy

[0071] Furthermore, the journal and thrust bearings used in the gearboxes are the innovative Bump-type Foil Air Bearings (FAB) also called as Gas Foil Bearings (GFB), in place of conventional rolling element bearings. FABs critical advantageous characteristics are self-acting hydrodynamic “float on air” without any external pressurization, no practical speed limitations (DN) resulting in higher power, no lubrication required resulting in Lower weight and complexity, sustains high temperatures upto 1200° F resulting in higher efficiency, compliant spring” foil support to Accommodate misalignment & distortion and no maintenance required which Reduces operating costs.

[0072] Solid-Lubricant coating for the surfaces of the Gear Teeth with solid-lubricant coatings such as NASA PS304 and NASA PS400 or the variants of MiTi-Korolon™ coatings, or derivatives such as Emralon™ or a tooth coating of Molybdenum Disulphide MoS2-WC. The Solid-Lubricant coating endures temperatures in the range of -170 ⁰ C to +760 ⁰ C. Modified teeth geometry of the gears in the planetary gearing to accommodate the Solid- lubricant coatings such as NASAPS304 (US Patent No. 5866518) and NASA PS400 (US Patent No. 8753417) or the variants of MiTi-KorolonTM coatings, or derivatives such as Emralon™ or a tooth coating of MoS2-WC and a reduced preload. Complete elimination of lubricating oils and the lubrication system resulting in an Oil-free Gearbox. This is made possible due to usage of both Foil Air Bearings which need no lubrication and that the rotating journals and critical elements of Foil Air Bearings are coated with solid-lubricants sustaining temperatures upto 1200 °F, and the Gear Teeth coated with Solid-lubricants. Thus, eliminating the Spin power losses i.e churning and windage losses that are present as a result of oil drag on the periphery and faces of the gears, pocketing/oil squeezing of lubricant from the cavities of the gear mesh and viscous dissipation of the bearing, being very high at high operating conditions. This not only reduces significant power losses, fuel penalty, costs and sealing complexity, but also results in increased transmission efficiency of the gearbox with Nil maintenance and very high durability. Such oil-free gearboxes find instant applications in food and pharma industry machinery too. Usage of Foil Air Bearings which have contactless running, and elimination of oil churning and splashing, the Noise is reduced to significantly low level, making the entire system operation more silent. Provision of pressurized air cooling through the gearbox using the pressure gradient created between input and output of the gearbox for enabling side feed pressurization of Foil Air Bearings which improves the dynamic performance of the FABs, where it increases direct stiffness, damping and overall stability specially for high-speed operation. A forced cooling flow is streaming underneath the corrugated bearing structure and the clearance between bearing journal and top foil Heat is transported by convection and conduction effects.

[0073] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.