SAE SRP-004-2017 Clean Snowmobile Challenge - 3 Refinement of Production Engines and New Control Strategies (To Purchase Call 1-800-854-7179 USA Canada or 303-397-7956 Worldwide).pdf

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1、 Clean Snowmobile Challenge 3:5HQHPHQWRI3URGXFWLRQ(QJLQHVDQG1HZ e-mail: copyrightsae.org; phone: +1-724-772-4028; fax: +1-724-772-9765./LEUDURI Nicholas Harker HYHORSPHQWRID0LOOHU William Silvis and Harry Pankratz, AVL North America Inc.viHYHORSPHQWRIDQ,Q6HUYLFH6QRZPRELOH(PLVVLRQ7HVW3URFHGXUHIRUWKH6

2、$( the Small Engine Technology Conference; the Noise and Vibration Conference; and the Powertrain, Fuels, and Lubricants Conference. Beyond this compendium, one ZLOODOVRQGMRXUQDOSDSHUVUHJDUGLQJVQRZPRELOHV ZKLFKby policy are not included in this compendium.Jay S. MeldrumLead Organizer of the SAE Clea

3、n Snowmobile Challenge viii5HIHUHQFHV1. Davis, G.W., Wilson, F., Schickel, B., andBaker, A., “Development of Clean Snowmobile Technology for Operation on High Blend Ethanol for the 2008 Clean Snowmobile Challenge,” SAE International Paper No. 2008-32-0053.2. Davis, G. W., “Development of a Flexible

4、FueledSnowmobile Operating on Ethanol BlendedGasoline for the 2010 SAE Clean SnowmobileChallenge,” SAE International Paper No. 2010-32-0083.3. Britanyak, P., Fuhrman, A., Dixon, D., DenBraven, K.R., and Harker, N., “University ofIdahos Flex-Fuel Two-Stroke Snowmobile,” SAEInternational Paper No. 201

5、0-32-0084.4. Blair, J. and Bower, G., “Development of a MillerCycle Powersports Engine,” SAE InternationalPaper No. 2014-32-0090.5. Birt, M. and Davis, G.W., Developing BestAvailable Technology in a Flex-Fuel Snowmobileby Using a Lean-Burn Miller Cycle,” SAEInternational Paper No. 2013-32-9176.6. Sa

6、ntora, M.J. and Savage, D., “ExhaustNoise Reduction in Two-Stroke Snowmobile:Development of a Mechanically Active QuarterWave Resonator,” SAE International Paper No.2015-01-2211.7. Miers, S.A., Green, C.A., Meldrum, J.S.,Lundberg, C., Silvis, W., and Pankratz, H.,“Measurement of Dry Soot and Particu

7、late Matterfrom Two-Stroke and Four-Stroke Snowmobiles,”SAE International Paper No. 2010-32-0042.8. Weingartz, C.J. and Miers, S.A., “Development ofan In-Service Snowmobile Emission Test Procedurefor the SAE Clean Snowmobile Challenge,” SAEInternational Paper No. 2009-01-2625.9. Meldrum, J.S. and Kn

8、ittel, J., “Sound Quality JuryAnalysis versus Sound Pressure Measurementin Snowmobiles,” SAE International Paper No.2009-01-2231.ABSTRACTClean snowmobile technology has been developed using methods which can be applied in the real world with a minimal increase in cost. Specifically, a commercially a

9、vailable snowmobile using a two cylinder, four-stroke engine has been modified to run on high-blend ethanol (E-85) fuel. Additionally, a new exhaust system which features customized catalytic converters and mufflers to minimize engine noise and exhaust emissions has developed. Finally, a number of a

10、dditional improvements have been made to the track to reduce friction and diminish noise. The results of these efforts include emissions reductions of 94% when compared with snowmobiles operating at the 2012 U.S. Federal requirements.INTRODUCTION The first snowmobile was developed in 1935 and was ca

11、pable of carrying 12 people. The introduction of the snowmobile meant that emergency medical personnel could get to those in need of care even during heavy snowfall. This often meant the difference between life and death. Snowmobiling as a recreation did not gain popularity until the late-1950s. Wit

12、hin a decade, dozens of manufacturers began producing snowmobiles. Only four manufacturers remain today, with global industry sales of approximately 200,000 snowmobiles annually 1.Due to rising concern pertaining to the noise and exhaust emissions of snowmobiles, they have come under increasing scru

13、tiny by the federal government. As snowmobiles are used in the winter season, the environmental impacts are the greatest due to colder denser air. The pollutants passed through the tailpipe into the cold, dense ambient air will not disperse as rapidly as they would in warmer conditions. These hazard

14、s are especially of concern to ecologically sensitive areas such as Yellowstone national park along with other national parks where snowmobile use is prevalent.The International Snowmobile Manufacturers Association (ISMA) estimates that snowmobiling generates over 27 billion US dollars (USD) of econ

15、omic activity annually in the world economy. New snowmobile sales account for about 1.2 billion USD, while the remainder is accounted for by apparel and accessories, registrations, permits, tourism and spare parts. The snowmobiling industry accounts for nearly 95,000 fulltime jobs and 3,000 dealersh

16、ips. Approximately 10% of these 27 billion dollars is collected directly by the governments as tax revenue 1.Considering the economic impact alone, a blanket ban on snowmobiling is not a feasible option. The Clean Snowmobile Challenge (CSC), which is part of the collegiate design series created by t

17、he Society of Automotive Engineers (SAE), was created to challenge students to reduce the impact of snowmobiles in environmentally sensitive areas.Currently, U. S. national parks are operating under a temporary winter use plan which restricts the number of snowmobiles entering the parks per day. All

18、 snowmobiles are required to be Best Available Technology (BAT), which are the cleanest and quietest commercially available snowmobiles. Further, the EPA has issued a three phase reduction on snowmobile emissions. The regulations include a 30% reduction in emissions by 2006, a 50% reduction by 2010,

19、 and a 70% reduction by 2012. The specific limits are shown below in Table 1.Table 1 Exhaust Emission Standards for Snowmobiles 2 Phase In Emissions (g/kW-hr) Model Year% of sales HC HC+NOx CO2006 50 100 2752007-2009 100 100 2752010-2011 100 75 2752012 they have responded by further developing two-s

20、troke technology and shifting to four-stroke engines in place of the typical two-stroke engines. While the two-stroke engine offers the advantage in terms of weight and power output compared to a four-stroke engine, the disadvantage is that it emits much higher levels of exhaust pollutants. The four

21、-stroke engine is also quieter, and more fuel efficient when compared with an equivalent two-stroke engine. The four-stroke engine weight and volume disadvantage is a substantial challenge to overcome in a lightweight vehicle like a snowmobile.Kettering University has chosen to use four-stroke engin

22、e technology reasoning that this technology offers the best long-term potential to meet exhaust and noise emissions levels. DESIGN OBJECTIVES The design team was tasked with reducing exhaust emissions to levels which are below the 2012 standard. Additionally, noise levels were to be reduced to below

23、 the noise mandates of 78 dB(A). Achieving these goals would be a hollow victory if the cost and performance of the snowmobile were severely compromised. Snowmobiling is, after all, a recreational sport; thus the snowmobile must remain fun to drive and cost effective.Additionally, the snowmobile wil

24、l use a high-blend ethanol (E85) in order to more easily meet the emissions standards and make the snowmobile even more environmentally friendly.In order to meet these objectives, a commercially available 2007 Yamaha Phazer GT was modified for the 2008 CSC competition.SYSTEM MODIFICATIONS The base s

25、nowmobile was chosen because it comes with a four-stroke engine, under-seat exhaust system, and it is lightweight. The team focused on reducing emissions and noise, while maintaining the performance, comfort, safety and durability of the sled. ENGINEThe Yamaha Phazer GT is equipped with a 499cc four

26、-stroke normally aspirated two-cylinder engine (see Table 1). Given the lightweight design of this engine and limited space in the engine compartment, the original engine was retained and modified for use with E85 to improve power and emissions. In original form the Yamaha Phazer GT was rated to pro

27、duce 80 hp (60 kW) at 11,000 rpm while operating on gasoline. Initial dynamometer testing revealed a power output of 70 bhp (52 kW) at 10,500 rpm. The team did not run the engine to its maximum engine speed due to concerns with the ability of the dynamometer to hold steady state at high speeds. Tabl

28、e 2 Yamaha Phazer GT Specifications Displacement: 499 CC Configuration: Twin Cylinder Block Material: Aluminum Cam system: DOHC Ignition: Coil on plug Valves per cylinder: Three Compression ratio: 12.4:1 Bore in/mm: 3.03/77 Stroke in/mm: 2.11/53.6 Aspiration: Normal Engine Control System: BigStuff3

29、therefore, in order to deliver the same power (all other factors being roughly equal), an engine will consume about 1.4 times more E85. This would lead to a reduction in fuel economy, on a miles-per-gallon basis, of about 29%. However, in practice, automobiles have shown only about a 25% reduction 4

30、. Operating an engine at stoichiometric air-fuel mixtures will produce an increase in power because E85 has a stoichiometric air to fuel ratio of about 10 to 1, whereas that for gasoline is 14.7 to 1. Therefore, by running E85 and assuming similar volumetric efficiencies, more fuel can be delivered

31、to the engine. For the same amount of air as the equivalent gasoline fuelled engine, an engine operating on E85 can use approximately 1.48 times more fuel, while only 1.4 times as much fuel is required to release the same amount of energy. This potentially increases the power and torque output by ab

32、out 6%. Of course, in practice, many other operating variables can influence the performance. For example, sizing of the fuel injectors can limit upper end performance due to time and fuel flow limitations.FUEL SYSTEM MODIFICATIONS Before E85 could be used in the snowmobile several of the standard f

33、uel system components had to be upgraded due to the corrosive nature of ethanol. Further, the fuel system also had to meet the increased volumetric fuel flow rate.The in-tank fuel pump was replaced with an ethanol compatible, inline external fuel pump with a larger flow rate. The stock paper fuel fi

34、lter was replaced to accommodate the required increase in fuel flow. An E85 compatible adjustable fuel pressure regulator with gauge was also installed. Table 3 Fuel Properties 4 Physical Fuel Properties Gasoline - RegularUnleadedEthanol E-85 Formulation C4 TO C12H/C-chains C2H5OH85% ethanol (by vol

35、ume) 15% gasoline (by volume) Average Analysis (%mass) C: 85-88 H: 12-15 C: 52H: 13O: 35 C: 57 H: 13 O: 30 Octane - R+M/2 87 98-100 96 Lower Heating Value kJ/kg(Btu/lbm)43,000(18,500)26,750(11,500)29,080(12,500)Lower Heating Value - kJ/liter (Btu/gal)32,250(115,700)21,240(76,200)22,830(81,900)Heat o

36、f Vaporization - kJ/Kg (Btu/ lbm)330-400(140-170)842-930(362-400)812(349)Stoichiometric A/F (mass) 14.7 9 10 Conductivity - mhos/cm 1x10-14 1.35x10-9 1.4x10-9In the past the Kettering CSC team has sampled fuel system components and performed immersion testing in E85 in order to ensure that they were

37、 compatible with the fuel. The team recorded the initial condition of these component samples, and then placed them in a solution of E85 and sealed the containers. The samples were examined after a two week soaking period with no visual effects of deterioration observed. They were then returned to t

38、he container for a year with still no visible deterioration. Based on this past experience, the team believes that the stock fuel system parts that are retained will be durable in contact with E85. The original injectors were running near the upper limit of their pulse-width duty cycle, therefore in

39、creasing pulse-width was not an option. In order to enhance the fuel delivery capability to compensate for the increased fuel volume requirement, the original injectors should have been replaced with larger units. Unfortunately, the injectors used were of an unusual design which is not physically co

40、mpatible with prevailing injector types; therefore over-sized injectors could not be procured in time for the event. To meet the increased flow demands when using E85, fuel system pressure was increased. The team increased the fuel system pressure from 290 kPa (42 psi) to a new pressure of 655 kPa (

41、95 psi). This required changing fuel line components to ensure that they withstood the increased pressure. The downside to this approach is that the fuel spray pattern can sometimes change causing wall wetting leading to transient operation problems. Fortunately, this did not happen.3ENGINE CONTROL

42、UNIT The snowmobile was factory equipped by Yamaha with a Mitsubishi engine control unit (ECU); however there was no way for the team to access and reprogram it. The original plan was to use a Bosch M7.4.4 ECU; however, this was not possible due to the fact that the 499cc two cylinder engine is not

43、an even firing engine. The cylinders of the Yamaha fire 180 offset, then go through their exhaust and intake strokes and repeat the process, as seen in Figure 2. Unfortunately, the Bosch ECU can only handle even firing cycles. Figure 2 Yamaha 499 cc Four-stroke Engine Cycle As a result of this issue

44、, an ECU was found that allowed for uneven firing of the cylinders. A BigStuff3 (Hartland, MI) ECU with closed loop wide band oxygen sensor feedback was chosen. Closed loop engine control allows the ECU to monitor the oxygen content of the exhaust gases and adjust the air/fuel mixture accordingly. T

45、he Mitsubishi ECU was retained to control spark timing for the engine in order to reduce calibration time with the new engine controller. This meant that the engine would not operate at the optimum spark timing, since the original ECU was calibrated to operate using gasoline; however, the ECU does h

46、ave a knock sensor to control timing in order to protect the engine.Through the use of the BigStuff3 calibration software, the engine map was adjusted to avoid undesirable, excessively rich mixtures which increase emissions. Maintaining fuel economy based on speed and load conditions with the switch

47、 to E85 was also a goal of the new engine calibration. The new ECU also allows for tuning of the fuel delivery for individual cylinders, which gave the team even greater capabilities in adjusting for improved emissions. GAUGESThe Mitsubishi ECU was also retained in order to operate the factory gauge

48、 cluster. Any information that a potential rider might need to monitor was provided by this system.COLD START CHARACTERISTICS As shown in Table 3, the heat required for vaporization of ethanol blended fuels is much higher than that of gasoline. In cold weather starting conditions this presents a problem as ethanol will not vaporize at temperatures below 11C 4. Just as gasoline and diesel pump fuel is switched to a winter blend during the colder months, E85 is also adjusted to compensate for colder ambient temperatures. A ble