Controlled Power Technologies Packages Its Switched Reluctance Systems in ‘RegEnBoost’ System for Enhanced Support for Downsizing
|The three components of the RegEnBoost system. Click to enlarge.|
Controlled Power Technologies (CPT) is packaging its three complementary switched reluctance machine-based systems—a fast-acting electric supercharger known as VTES (or variable torque enhancement system) (earlier post), a highly efficient liquid cooled integrated starter generator (ISG) known as SpeedStart (earlier post), and an advanced turbo-generator integrated gas energy recovery system known as TIGERS (earlier post) in a novel engine-boosting and power regeneration concept it calls ‘RegEnBoost’.
CPT says that the RegEnBoost system enables a typical family-sized car to achieve less than 100 g/km CO2 with a 1-liter gasoline engine, but when required can offer the same lively performance and in-gear acceleration of a 2-liter naturally aspirated powertrain. This CO2 level is comparable to that emitted by equivalent sized full hybrid vehicles, yet avoids their need for high voltage and the significant impact a hybrid’s large batteries and traction motors have on overall vehicle cost, mass and packaging.
RegEnBoost integrates the three devices into a powertrain electrical power network (PEPN), which also incorporates a DC to DC converter and an enhanced lead acid battery, optimized for fast energy storage and release. The combination of electronics, advanced battery technology and charging techniques ensures the system can deliver the required rapid charge and discharge performance, while at all times maintaining a stable 12 volts to the vehicle’s main electrical system.
The concept ensures long term energy storage for delivering short bursts of power to the VTES supercharger during vehicle accelerations and to the SpeedStart stop-start device during engine re-starts. Conversely, short bursts of power can also be absorbed by the SpeedStart generator to recharge the battery during vehicle decelerations. Power for the battery and VTES electric supercharger is not only supplied by the SpeedStart ISG but also the TIGERS exhaust driven turbo-generator. The electronic controls supervise the optimal switching between the SpeedStart and TIGERS electrical generators according to driving conditions and regenerative power availability.
A deep understanding by the CPT engineering team of the power and control electronics embedded within all three devices and the essential characteristics of the interconnecting network helps underpin the overall efficiency of the system, which in essence facilitates radical downsizing of gasoline and diesel engines without compromising vehicle performance.
Small displacement engines offer excellent CO2 and fuel economy benefits; they have lower parasitic losses and operate more efficiently under part load conditions. Small engines can also be turbocharged to deliver comparable torque and power to a larger naturally aspirated engine. However, with a conventional turbocharging system, the turbine size necessary to maximize efficient high speed performance gives unacceptable low speed response, which affects the driveability of the vehicle. Hence the industry trend to dual-charging systems, CPT notes.
The boosting element of CPT’s technology, which addresses this issue, is derived from the VTES electric supercharger, which can be installed in series with a simple fixed geometry turbocharger. Unlike a crankshaft driven mechanical supercharger or an additional exhaust driven turbocharger, the CPT method of boosting is completely independent of engine speed and offers precise electronic control. No matter how low the engine revs, the 2 kW electric supercharger remains highly responsive and extremely fast acting. This crucial difference means the technology is perfectly suited to maintaining vehicle performance and driveability—widely recognized as a critical marketing issue for any car maker contemplating radical engine downsizing.
Another key element of the RegEnBoost concept is delivered by CPT’s SpeedStart device, which outperforms existing designs of starter motors and alternators in almost every respect, according to CPT, providing an advanced 3kW stop-start solution that is more powerful, more efficient and more usable than first generation systems.
It’s the first design to integrate all the power and control electronics into a single electric motor assembly and by maximizing the number of stop-start events the system aims to significantly reduce fuel consumption and CO2 emissions. For the RegEnBoost concept it provides a vital additional role not only in terms of its advanced stop-start capability, but also for its potential in energy recovery and electrical regeneration under braking. This in particular helps the VTES electric supercharger boost the engine for acceleration without incurring a CO2 penalty.
A final key element of the RegEnBoost concept is the TIGERS turbo-generator. Coupled to an exhaust-driven turbine the second generation 2 kW air cooled device is intended to generate electrical power during high speed acceleration and steady state cruising, when it can more efficiently deliver electrical power than the SpeedStart device, which can therefore be temporarily powered down.
Exhaust gases provide an efficient and as yet unutilized method of power regeneration, particularly for a throttled gasoline engine, and further helps improve fuel economy and reduce CO2 emissions. The TIGERS system includes an electronically controlled full flow by-pass that ensures the desired proportion of exhaust gas is delivered to the turbo-generator as determined by the control system.
All three devices in the RegEnBoost concept are based on high efficiency switched reluctance (SR) electrical machines which, because of their flexibility, can be readily scaled to support engines up to approximately 3.5-liters capacity. Significant advantages include the simple construction from steel, aluminium and copper (avoiding precious rare earth materials), accurate control, very high power density and in excess of 80 per cent efficiency. A major part of CPT’s effort has concentrated on optimizing the technology for automotive applications and establishing a manufacturing strategy and supply base. World class manufacturing partners have already been identified.
VTES, SpeedStart and TIGERS are all fully-integrated standalone devices each highly effective in their own right, but their combination provides for a high level of synergy where careful management of energy flow offers potential efficiency gains greater than the sum of the individual parts. Moreover, there is very little modification to the base engine design enabling vehicle manufacturers to apply the system—or its individual components—at much lower cost than a full hybrid vehicle.
—Geoff Morris, CPT’s engineering director and chief technical officer
Low Carbon Vehicle Partnership Technology Challenge. CPT presented the RegEnBoost system as one of six emerging UK businesses to get the attention of senior automotive executives at a unique event organized by the Low Carbon Vehicle Partnership (LowCVP). The opportunity to pitch ideas directly to 16 major vehicle manufacturers and Tier 1 suppliers is the culmination of the LowCVP’s Technology Challenge; an industry initiative to help fast track innovations being developed by small- and medium-sized companies.
We’re delighted to be among the Technology Challenge winners and for this unique opportunity to present our RegEnBoost engine-boosting and power regeneration concept to so many carmakers at one fell swoop, also for the huge interest they’ve taken in this LowCVP initiative. Normally it would take months of effort to meet this number of vehicle and component manufacturers.
Inspired by the recommendations of the New Automotive Innovation and Growth Team (NAIGT) published May 2009, the LowCVP event sets out to create closer collaboration between the developers of new technology and the mainstream automotive industry. The event is being chaired by Professor Richard Parry-Jones, the newly appointed chairman of the recently established Automotive Council.
CPT was selected on a competitive basis from 17 entries covering widely varying technical innovations. The final selection of six companies by an expert panel was based on the merits and impacts of their technology for reducing vehicle CO2 emissions. Important criteria included their alignment with the NAIGT technology roadmap, commercial viability and ease of integration.
The other five winners of the challenge were:
Axon Automotive has a lightweighting solution for vehicles structures. Usually limited to use as panels, the company has developed a unique process for creating structural components from carbon fibre. They have also designed a 100 mpg UK (83 mpg US, 2.8 L/100km) plug-in hybrid scheduled for production in 2011. Formed in 2006, the company is a spin-out from the Honda Ecotechnology Centre at Cranfield University. It comprises materials experts and vehicle designers as well as body and powertrain engineers.
Brunel University has a novel regenerative engine braking technology known as ‘RegenEBD’ which utilizes a vehicle’s engine under braking to compress air for energy storage, engine stop-start and boost assist. Suitable for cars, buses and commercial vehicles, the technology’s development has been led by Professor Hua Zhao, director of the University’s Centre for Advanced Powertrain and Fuels at the University’s School of Engineering and Design, Uxbridge.
EVO Electric Limited, is a 2007 spin-out from Imperial College London to develop advanced electric machines and drive systems based on its proprietary axial flux technology. Axial Flux motors and generators are characterized by very high torque and power density. Based in Woking their flagship product, the Axial Flux Motor, is designed to meet the requirements of electric and hybrid vehicles with the technology applicable to all vehicle classes.
Libralato Engines is commercializing a compact, optimized type of rotary engine, ideally suited to operate in hybrid electric vehicles. Having unique, asymmetrical compression and expansion geometry, the Libralato engine has only four moving parts and is primed to deliver a step change in thermal efficiency.
Oxy-Gen Combustion delivers a solution to real deployment of Homogeneous Charge Compression Ignition (HCCI) engines and Controlled Auto-Ignition (CAI), technologies which have been widely touted in the future road map of the automotive industry for their low emission and fuel savings characteristics. Unlike hybrids these technologies do not require a change in the vehicle or engine architecture.