Superchargers Coming Back Into Focus?
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DPNA295.qxp 2/23/07 2:38 PM Page 1 ENGINE TECHNOLOGY A cutaway of the supercharger used on the Kawasak i 250X personal watercraft, along with a schematic of the engine system. Two air bypass valves balance air flo w upstream, downstream or wastegate air under variou s conditions of load and speed. SUPERCHARGERS COMING With engine efBACK INTficiency demands growing and new design concepts, superchargers are getting another looO FOCUS? k BY ROB WILSON hen the subject is super many ways, superchargers were jus t conditions of engine speed and loa d chargers, the kneejerk re that — super. by two air bypass valves. sponse by motorheads far So perhaps it comes as no surpris e The Roots blower used in thi s Wand wide is “parasitic losses.” Tha t that for the 2007 model year, Kawasaki application is produced by Ogur a simple phrase often puts considera is launching a highperformance per Clutch Co. in Japan, with U.S. head tion of superchargers to rest in th e sonal water craft (PWC) called the Ultra quarters of Ogura Industrial Corp. i n current era where emissions, effi 250X that derives some of its “hair o n Somerset, N.J. ciency and fuel economy are th e fire” capability through a supercharger . “The Kawasaki application is cer drivers for engine manufacturers . The Rootsblown, 1.5 L, inline four tainly high profile and Ogura is excited But new technology and more effi cylinder, intercooled gasoline engin e to be a part of it,” said Frank Flemming, cient designs seem to be promptin g produces 250 hp remarkable for a n president of Ogura Clutch Co. “Wit h another look. engine that size. That’s 166 hp per L , the 250X, the use of supercharging i s The Roots blower design on whic h which is nothing short of astonishing . strictly performance driven and th e many superchargers are based, actu Kawasaki claimed the 250X is th e results speak for themselves. ally predates the internal combustio n most powerful PWC in the world. Th e “High performance has also charac engine, and these devices were being supercharger produces large boos t terized most applications for super used to optimize blast furnace outpu t even at low rpm, the company said , charging but there is an evolution hap in the 1870s. Uses have abounde d and acceleration from idle is not ham pening where other factors are no w over time. pered by turbo lag. coming into play. And the supercharg Twocycle diesels, of course, us e The blower for the 250X forcefeeds er we are bringing to the market today them to scavenge exhaust gas. Fo r 2 L of air for every revolution, yieldin g has far more flexibility and capability. ” aggressive air handling in tight spaces, highpressure intake air at all engin e Jim Ebisawa, engineering manager the reputation of Roots blowers wa s speeds and a flat, beefy torque curv e at Ogura Clutch Co., pointed out tha t never in dispute. over the operating range. Air pressure the Ogura TX series has adopte d The same can be said for high per is managed, balanced upstream o r Wankel rotary geometry design , formance and for power density. I n downstream or dumped under various which increases the working o r XX DIESEL PROGRESS NORTH AMERICAN EDITION March 2007 March 2007 DIESEL PROGRESS NORTH AMERICAN EDITION XX DPNA295.qxp 2/23/07 2:38 PM Page 2 ENGINE TECHNOLOGY ing on larger engines to optimize lowspeed and highspeed per formance; • as an additional, fast acting, air Ogura has adopted Wankeltype geome handling device to help emissio n try to improve volumetric efficiency. The compliance, improve fuel economy twin counterrotating rotors have a or both. crosssection shaped like a figure eight. Ogura has been working on devel The rotors are hollow from end to end for opment programs for diesel and gaso low inertia. line engines, mainly with engine dis placements smaller than 5 L, but a few upwards of 10 L. One program involves the KAD4 2 Volvo Penta marine diesel. Powere d by a turbocharged 3.6 L engine, th e sealed displacement of the pumpin g “There, the supercharger is driven al l boat simply couldn’t get up on plan e area and also improves volumetri c the time, but that need not be the case. due to low torque at low speed. Th e efficiency of the blower over the oper “For most of the pilot programs and addition of the Ogura supercharger to ating range. inquiries we are currently pursuing, a the 3.9 L diesel raised the torque a t Ebisawa said the TX volumetric effi clutch is certainly a big motivator o f 100 rpm by a factor of three and th e ciency advantage over other Root s the interest level. Almost all of ou r boat came up on plane. At 2500 rpm , blower designs can be more tha n superchargers have electric clutche s the turbocharger takes over and th e 20% at low speed and 10% on the top mounted on the front end and th e boat remained on plane. end. The design has fewer parts an d engine management system turns the Europe is described as somewha t is lightweight throughout its design. power on and off as needed. ” ahead in active development programs Twin counterrotating rotors blow This capability is probably the rea l for supercharger application. There i s ing the air within the supercharge r game changer. When torque is not re also greater recognition in Europe tha t housing are hollow from end to end , quired, the supercharger is switche d supercharging has great potential fo r resulting in a very lightweight design , off in milliseconds and only a belt an d coming emissions hurdles. Better com reducing their moment of inertia an d idler pulley remain as parasitic losses , bustion on diesel engines at lowe r thus the energy required to mak e very small ones at that. At any rate, the speed is of particular interest. them rotate. drive belt is there driving other acces And perhaps it can now be calle d The TX series superchargers ar e sories. When not required, the super adaptive supercharging. Why not ? designated by their theoretical dis charger is completely out of the circuit. The modus operandi is completel y charge per revolution. Thus the small To give an idea of response time , changed. Parasitic losses are no w est, the TX04, has a discharge vol engagement time is about 50 ms o n filtered out when the supercharge r ume of 0.4 L/rev, while the largest, the the smallest superchargers, on th e is disengaged. Now the supercharg TX28, has a discharge volume of 2. 8 largest about 50 ms. Disengagemen t er can bring a lot more air into pla y L/rev. The smallest weighs 11.6 lb . is 30 to 50 ms for all models . on demand without the traditiona l and the largest 31.3 lb. When torque is required, the en turbo lag. Maximum continuous speeds fo r gine management system cues th e Or maybe the requirement is fo r the TX series range from 9000 t o electromagnetic clutch to pick up th e more cool air to keep combustion tem 12,000 rpm and the maximum pres low inertia supercharger, producing a perature in the correct zone wher e sure ratio is given at 1.8:1. burst of power on demand. NOx generation remains under control. It happens that Ogura Industrial i s Where Flemming and Ebisawa se e For many compelling reasons, i t actually better known for its capabili the best fits are: seems the time for reexamination o f ties in clutches, but it has combine d • vehicles requiring high torque a t supercharger technology is at hand . this capability with the Wankel super low speed, with stopandgo driv The potential is much changed. dp charger design, and this is wha t ing, hilly and poor road conditions; results in a completely new tool for en • wherever large engine perform For More Information gine aspiration. ance or burst power is require d NowNow On This Company Go To: “On the Kawasaki 250X jet ski appli from a small engine and wher e cation, the only interest is high per weight limitations might call for a DirectLink @ formance and so that unit does no t small engine; WWW.DIESELPROGRESS.COM incorporate a clutch,” said Flemming . • in combination with turbocharg XX DIESEL PROGRESS NORTH AMERICAN EDITION March 2007 March 2007 DIESEL PROGRESS NORTH AMERICAN EDITION XX.