GB2533661A - 2 - stage compression and expansion wankel engines, with interstage intercooling, using exhaust powered wankel rotary superchargers, - Google Patents

Abstract

An internal combustion engine (ICE) 1 has an exhaust-driven supercharger 2, 3, 4. The compressor element of the supercharger is a positive displacement adiabatic compression engine 4 for charging air entering the ICE. The compression engine 4 is driven by a positive displacement adiabatic expansion engine 2 located in the exhaust line of the ICE 1, with power being transferred from the expansion engine 2 to the compression engine 4 via a shaft 3. The ICE 1, expansion engine 2 and compression engine 4 are preferably Wankel or Wankel-style rotary engines. A turbocharger 2 and intercoolers 6, 7 may be included. A centrifugal separator 1 with de-rotator 2 may separate unburnt lubricating oil from the exhaust gas (see figure 3). Means such as a bypass valves (not shown) may be provided for bypassing the compression and expansion engines.

Description

Intellectual Property Office Application No. GII1508063.3 RTM Date:27November 2015 The following terms are registered trade marks and should be read as such wherever they occur in this document: Mazda Ford EcoBoost Audi RX-7 RX-8 RX-9 Renesis Teflon Intellectual Property Office is an operating name of the Patent Office www.gov.uk/ipo -1 - 2-STAGE COMPRESSION AND EXPANSION WANKEL ENGINES, WITH INTER-STAGE INTERCOOLING, USING EXHAUST POWERED WANKEL ROTARY SUPERCHARGERS, + OPTIONAL INTERCOOLED TURDOCHARGING.

1 This invention relates to turbo-supercharging internal combust-ion (i.c.) engines, particularly Wankels, in a way that is simpler and more effective than Mazda's twin-sequential turbo system, and much less complex than Ford's EcoBoost system.

When i.c.engines are supercharged their fuel consumption per bhp throughout their rev range reduces due to i.c.engine shaft power being expended to drive the supercharger, although torque and throttle responsiveness increase significantly at idle and low revs due to pressure build-up across throttling butterfly valves at such revs. Conversely, when turbocharged their torque and throttle responsiveness at low revs is less than it otherwise would be due to the lower i.c.engine compression ratios required to obviate pre-ignition at full turbo-boost pressures, although fuel consumption per bhp reduces as turbo-boost press-ures increase due to the turbo's turbine increasing adiabatic expansion cooling of the i.c.engines exhaust/combustion gases.

It should be noted that the geometry of rotors eccentrically revolving within the 'rice-ball' shaped chamber of Wankel rota-ry i.c.engines, more-or-less, have one (1) particular compressssion and expansion ratio, which is lower than obtained in more efficient reciprocating piston i.c.engines. Therefore, means that could increase a Wankel i.c.engine's effective compression and expansion ratios throughout its rev range would be most beneficial -which is what Mazda wanted from their twin, one (1) small and one (1) larger, sequential turbo system in their RX-7 FD cars: obtain the torque benefits of spooling-up a small turbo at low revs and then the fuel economy from operating both turbos at higher revs, i.e. over a wider rev range than single turbos, or non-seqential twin-turbos, are effective over. Audi's '014 -'015 concept diesel's electric-assist sequential twin turbo system improves upon Mazda's turbo's increase in low rpm torque, virtually eliminating turbo lag, but suffers from reduced fuel economy below about 2,000 rpm due to the parasitic power consumption of its electric assist motor up to such revs.

It should also be noted that Ford's EcoBoost engines can obtain the low rpm torque benefits of supercharging when required, and do obtain the fuel economy of high boost turbocharging (as ena-bled with air-cycle refrigeration boosted intercooling) and the free' power output of throttle controlled superchargers during boost pressure limiting, idling and throttle lift-off.

However, Mazda's sequential twin-turbo system is complex (see its system 8 controls schematic!), and Audi's electric-motor-assisted ditto turbo system is yet more complex, with Ford's EcoBoost turbo + throttle controlled supercharger system being even more complex. Also, Audi's and Ford's reciprocating piston engines are much more complex and have many more moving parts than Mazda's, less easy to understand, Wankel rotary piston en- gines. To overcome the problem of obtaining the benefits, but not the penalties, of supercharging and turbocharging more sim- 1 ply than Mazda's, or Audi's, or Ford's systems, the present in-vention proposes substituting the non-positive displacement radial inlet turbines and centrifugal compressors of conventional turbochargers with, respectively, positive displacement exhaust adiabatic exhaust expansion engines (reverse acting superchar-gers, or exchargers) and positive displacement intake air adiabatic compression engines (superchargers) whose compressed air would be intercooled as per conventional turbos. Two (2), or more, such exhaust powered superchargers may be operated in parallel, typically with 'V' i.c.engines, or compound in-series operated, typically in heavy duty diesel engines, or to dieselise Wankel rotary i.c.engines.

It should be noted that a Wankel rotary i.c.engine with such exhaust powered intercooled supercharging being provided by same displacement size Wankel rotary superchargers and exchargers would have its effective compression and expansion ratios approximately doubled, with half of such compression (heat) intercooled. However, a reciprocating piston engine having the same compression ratio could not have its compression heat in-tercooled. Therefore, on a like-for-like basis, such Wankel engines could operate satisfactorily with higher compression ratios, or higher turbo-boost pressures (such Wankel engines can be turbold and eco-boosted), than piston engines.

Currently, the only positive displacement engines capable of of handling hot exhaust gases would be Wankel rotary and piston i.c.engines adapted to operate as air pumps. As pumps, their valves would be operated such that during compression the en-gines' exhaust valves would be open until compression ceased, and then its intake valves would open until expansion ceased when the exhaust valves would then open to start the said cycle of valve operations. Therefore, as pumps, such engine's intake and exhaust operations would be twice as frequent as when they operate as i.c.engines, and, of course, they would not have fuel injectors or spark/glow plugs. And such pumps can supercharge i.c.engine intake air. Since Wankel engines are much simpler than piston engines they are better suited to the simple duties of supercharging and expanding gases, and as super- chargers their casings, rotors and rotor tips could be non-metallic -rotor tips possibly being teflon, requiring no oil lubrication -and casings would not require water passageways. To some extent, exhaust ones could also be of lighter construction since the temperature and pressure of the exhaust gases it would handle, by definition, would be significantly less than peak combustion ones and they would not have to handle the explosive shocks of combustion ignition, and their oil injector lubrication requirements would also be less onerous. EA most simple and efficient eco-boost i.c.engine would be one with a Wankel excharger powering the Wankel supercharger of a, thereby, compression and expansion ratio doubled Wankel rotary i.c.engine (**) having almost zero reciprocating efficiency losses (only its rotor's eccentric rotation) -being a much simpler eco-boost system than Ford's EcoBoosts and having far fewer engine parts than Fords EcoBoost 4-stroke engines, being cheaper to manufacture as a consequence, and also more compact and lighter. As Colin Chapman once said "Simplify, then add 1 lightness", which this invention does all in one go. Also, since the frequency of combustion ignition events in Wankel engines is 50% more than in 4-stroke i.c.engines their conventional spark ignition systems could be substituted with simpler active-technology controlled glow-plugs (patent application filed), since such increased combustion frequency would often support a glow-plugs glow without support from an electrical power supply.

(**) For example: A twin-rotor (2 x 654 cc) Mazda 138 Renesis engine in an RX-8 has a fuel consumption of 24 mpg and outputs 228 bhp, whereas a triple-rotor (1 x 654 cc intercooled supercharger, 1 x Renesis 654cc i.c.engine, 1 x 654 cc excharger), without accounting for intercooler effect, would, notionally, have a fuel consumption of slightly less than 48 mpg and de-velop slightly less than 228 bhp -slightly less due to the parasitic losses of a 3rd rotor. Such a triple-rotor Wankel engine could be turbo'd and additionally intercooled to significantly increase bhp without unduly affecting fuel consumption (see Figure 2). And Mazda' s, next generation, 16X direct-in-injection larger displacement rotary engine is not only lighter but also affords increased torque throughout its rev range and improved thermal efficiency -a triple-rotored version of which Mazda might name as an eco Triple R-X-9, or in turbo guise an R-TripleXtra-9.

To minimise exhaust emissions, which with much reduced fuel consumption would be approximately halved per mile or per bhp, any lubricating oil injected into positive displacement exhaust system expansion engines should be centrifugally separated-out from their exhaust discharges into a collector tank and pumped, via a filter, into the respective i.c.engines fuel tank to then be burnt-off during combustion, but not to its oil lubrication system, if its lubricating properties have been compromised by exposure to high temperature exhaust gases. To regain otherwise lost spiral energy, as static pressure regain, separated-out spirally rotating exhaust gases exiting the said centrifugal separator should be de-rotated via a volute having a peripheral radial exit, as per a patent application for such volutes. In any case, with the compression ratio of such supercharged Wank-el rotary i.c.engines being about twice that of more conventional ones, their combustion temperatures would also be similarly higher, so much so that combustion of the 5W-30 injected lubricating oil would be more complete, reducing emissions.

Where the upstream i.e. engine is a Wankel rotary one with its own oil injection there would be some oil carryover into exhaust positive displacement expansion engines which, particularly in the case of it having three (3) oil injectors, as per Mazda's '91 -'02 RX-7 FD, could be calibrated to provide suff-icient oil carryover to lubricate one without the need for its own oil injector system. Alternatively, lubrication of positive displacement sealing interfaces might be obviated, or minimised if one (1), or both, such interfaces' materials' were so hard, heat resistant and co-efficient-of-friction low that lubri-cation of them was not essential.

To control boost pressures, flow through intake superchargers, or exhaust exchargers, or both, can be bypassed by means incorporating means for controlling such bypass flow connected, via control means, to means sensing intake port, or manifold boost pressures, and, or means sensing engine operating conditions such as incipient pre-ignition combustion knock, and tempera- tures. Where such means are provided for bypassing both intake and exhaust exchargers they can be schedule controlled such that at low and sub-zero ambients (after intercooling has been suppressed) bypasses around intake superchargers can be modu-lated open so that heated charge air would re-circulate around intake superchargers to get even hotter, and at higher ambient temperatures exhaust gases can be bypassed around exhaust exhargers to minimise heat build-up in them and heat transfer to intake superchargers, with both such bypasses being partially open during intermediate ambient temperatures; as controlled by control means connected to bypass flow varying means and to temperature, or density, or both, sensing means located downstream of intake system superchargers. Such said temperature and on density controls could also be connected to means actu-ating intercooler suppressing/bypassing means and be schedule integrated into the aforesaid scheduling of bypass controls. Such bypasses can also be opened when abrupt throttle lift-off is detected by a throttle control system's (TCS's) throttle rate-of-movement sensor which, together with throttle valve (Tv) opening (accompanied by cessation of fuel supply and, if applicable, spark or glow plug powering), would reduce coast-down 'throttling' of both the i.c.engine and its superchargers to improve fuel economy until brake application is sensed, or throttle application is sensed. In any case, means should be provided for bypassing gases around both intake and exhaust superchargers during idling -with such means controlled by the i.c.engine's TCS's idle control system -to bypass such supercharger's parasitic drag at idle, thereby enabling idle speed to be less than it otherwise be, reducing fuel consunption.

Ideally, intercoolers should be dual-function liquid-to-air intercooler-heaters (patent application filed) conected to not only liquid-to-ambient air heat exchangers, but also to liquidto-exhaust gas, or liquid-to-i.c.engine liquid coolant, heat exchangers which, for ease of packaging and to minimise fluid pressure drops, should be 'new' tube-in-tube heat exchangers in which fluid flows spirally rotate (patent application filed). In this way they can also alternately heat intake air to prevent intake system freeze-up during low and idling rpm's at sub -zero ambients, maintain adequate i.c.engine operating tempera-tures during low rpms at low ambients, and increase the rate of i.c.engine heat-up during start-ups in low ambients. To minimise engine bay space requirements exhaust tube-in-tube heat exchangers can be located in exhaust system tail-pipes and, as such, can be so configured as to double-up as exhaust system tail-pipe silencers. The functions of such dual-function intercooler-heaters can be sequentially controlled by control means connected to means sensing i.c.engine intake temperature, or density, or both, and which can be schedule integrated with the r= aforementioned supercharger bypass scheduling controls.

N.B. Because, as mentioned, Wankel i.c.engine and, therefore, I Wankel supercharger compression ratios are relatively low such that their effective combined heat-of-compression, particularly with inter-cooling, would not, in piston engine terms, be overly excessive. It would, therefore, be feasible to also turbocharge Wankel supercharged Wankel i.c.engines, particularly if the turbochargers charge air was intercooled upstream of the Wankel superchargers and were fitted with turbocharger efficiency-improving pre-rotating and de-rotating volutes. Boost pressure and intercooling control of such turbocharging can be by con- ventional means, which can be integrated into the aforemention-supercharger boost pressure control systems, or arranged to limit control boost pressures upstream of said superchargers. Such turbocharged and supercharged -light, simple, high revvin and, most of all, fuel efficient -Wankel i.c.engines would LB also be particularly suitable for light and short-haul 'planes.

This invention will now be described solely by way of example with reference to the accompanying schematic drawings: Figure 1 shows a Wankel engine supercharged by an intercooled Wankel supercharger powered by an exhaust Wankel rotary excharger -i.e. a triple-rotor Wankel engine..

Figure 2 shows such a supercharged Wankel engine with a turbo-charger intercooled by an additional intercooler.

Figure 3 shows an exhaust oil and particulates centrifugal separator system for such triple-rotor Wankel engines.

In figure 1, Wankel rotary i,c.engine l's exhaust gases are adiabatically expansion cooled by Wankel rotary excharger 2, whose output shaft 3 powers Wankel rotary supercharger 4, and whose adiabatically compression heated air is cooled by 'new' (patent application filed) air-to-coolant liquid tube-in-tube intercooling heat exchanger 5 that rotates both of the flows passing through it. Intercooler 5 is connected via flow and return pipes 6 & 7 to ambient air-to-coolant liquid finned coil heat exchanger 8 through which coolant is circulated by electric centrifugal pump 9. Intercooler 5 is cooled by electric axial flow fan 10. The speeds of the variable speed electric motors driving pump 9 and fan 10 are sequentially controlled by an electronic control unit connected to charge-air temperature limit sensor 11. Wankel i.c.engine 1 outputs power via shaft 12 whose power output is varied by electric butterfly throttle valve (TV) 13 which is controlled by a throttle-by-wire (TBW) system, which is connected to engine L's electronic control unit (ECU) which, if it senses pre-ignition knock, modulatingly closes TV 13 until such knock is suppressed. and in doing so, reduces both the flow of, and the pressure of, charge air en-tering i.c.engine 1.

In figure 2, Wankel rotary i.c.engine 1 is turbocharged by turbocharger 2 and supercharged by exhaust powered Wankel supercharger 3. Turbocharger 2 is fitted with pre-rotator 4 and de-rotator 5, and its boost pressured air is intercooled by charge air to-water intercooler 6. Wankel supercharger 3's further pressurised air is intercooled by charge air-to-water inter- 1 cooler 7. Charge air-to-water intercoolers 6 & 7 are 'new' tube -in-tube heat exchangers (patent application filed) whose water connections are connected via flow and return pipework to ambient air-to-water heat exchanger 8. Water, or more precisely, coolant, is circulated through said pipework and heat exchange-rs by centrifugal pump 9 which is fitted with an efficiency increasing and water cavitation preventing pre-rotator (not shown for clarity). Said pipework is connected via feed & expansion pipe 10 to i.c.engine l's coolant system.

Other, more complex, configurations are possible. For example, there could be two (2), or more, Wankel i.c.engines supercharged by a single exhaust powered Wankel rotary supercharger, or where there is more than one (I) Wankel i.c.engine each such one could be separately supercharged by a respective exhaust powered Wankel rotary supercharger. And two (2), or more, i.e. engines could be in-series connected via a common power output shaft, or in-parallel connected via ring gear to a single power output shaft (e.g. three (3), or four (4), with ring gears could be radially clustered around an output shaft's single ring gear).

In figure 3, centrifugal separator 1, complete with de-rotator 2, separarates-out any carried-over unburnt lubricating oil injected into the system's three (3) Wankel rotary engines and any exhaust particulates upstream of the exhaust system's catalytic converter. Such separated-out oil and particulates drain into tank 3, fitted with high and low level oil sensors 4 A 5 which, via a control unit, switches oil pump 6's electric motor on and off. Particulates, and any other contaminants, in the oil discharged from tank 3 are removed by oil filter 7. Cleaned oil discharged from pump (fitted with a pre-rotator) is pump-ed to the oil injection system's supply tank. With such cleaning-up of exhaust gases upstream of catalytic converters it would be feasible, for example, to increase the number of oil injectors used in Mazda's 13B Renesis Wankel engines from two (2) to three (3) to increase their reliabilty [Renesis engines with two (2) oil injectors suffered significantly more warranty claims than Mazda's previous three (3)-oil-injector FD engines) without causing fouling of catalytic converters.

Claims (9)

1. CLAIMS: 1 1) A system for outputting power incorporating exhaust powered superchargers comprising of at least one (1), or more internal combustion (i.c.) engines, one (1), or more, positive displacement adiabatic expansion engines in i.c.engine exhaustsystems, one (1), or more, positive displacement adiabatic compression engines in i.c.engine air intake systems and power transmission shafts interconnecting each said expansion engine to one (1) of the said compression engines.
2. 2) A system incorporating exhaust powered superchargers accord-ding to claim 1, in which there are means for cooling charge air discharged from adiabatic compression engines.
3. 3) A system incorporating exhaust powered superchargers accord-ing to claim 1, or claim 2, in which there are means for limiting adiabatic compression engine discharge pressures.
4. 4) A system incorporating exhaust powered superchargers according to any preceding claim in which, there are means for varying the exhaust gas expansion and the charge air com-pression of adiabatic engines.
5. 5) A system incorporating exhaust powered superchargers according to any preceding claim, in which there are means for by- es passing flows around adiabatic expansion and adiabatic com-pression engines, or only adiabatic compression engines, controlled by i.c.engine idle control systems.
6. 6) A system incorporating exhaust powered superchargers accord- ing to any preceding claims, in which, where not already in-cluded, there are means for bypassing flows around adiabatic expansion and adiabatic compression engines, and in which such bypassing means are actuated open by control means connected to means sensing i.c.engine throttle lift-off and can be subsequently closed when a respective vehicle's brakes are actuated.
7. 7) A system incorporating exhaust powered superchargers according to any preceding claims, in which, where not already in-eluded, there are means for bypassing flows around exhaust adiabatic expansion engines upstream of exhaust catalytic converters, and in which such bypassing means are controlled by control means connected to means sensing catalytic converter temperatures.
8. 8) A system incorporating exhaust powered superchargers according to any preceding claims, in which flow from exhaust positive displacement adiabatic expansion engines passes through one (1), or more, centrifugal separators.
9. 9) A system incorporating exhaust powered superchargers according to claim a, in whch spirally rotating exhaust gases from said centrifugal separators is de-rotated by volutes having peripheral flow outlets, as per a patent application for such de-rotators.11) A system incorporating exhaust powered superchargers according to any preceding claim, in which there are turbo-= charging means incorporating means for limiting turbocharger charger charge air pressures.12) A system incorporating exhaust powered superchargers according to claim 11, in which there are means for cooling turbocharged charge air.13) A system incorporating exhaust powered superchargers according to claim 11, in which there are means for pre-rotating and, or, de-rotating turbocharger flows.14) A system incorporating exhaust powered superchargers according to any preceding claims, in which where there are de-rotators, at least one (I) such of them incorporates means for sound attenuating them, as per a patent application for sound attenuating de-rotators.