1、SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirelyvoluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefro
2、m, is the sole responsibility of the user.”SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions.TO PLACE A DOCUMENT ORDER; (724) 776-4970 FAX: (724) 776-0790SAE WEB ADDRESS http:/www.s
3、ae.orgCopyright 2000 Society of Automotive Engineers, Inc.All rights reserved. Printed in U.S.A.SURFACEVEHICLE400 Commonwealth Drive, Warrendale, PA 15096-0001INFORMATIONREPORTSubmitted for recognition as an American National StandardJ1343REV.AUG2000Issued 1981-07Revised 2000-08Superseding J1343 OCT
4、1988(R) Information Relating to Duty Cycles and Average Power Requirementsof Truck and Bus Engine AccessoriesForewordThe objective of this report is to estimate a typical accessory drive load for heavy truck and busapplications. The accessory drive load is defined as the power needed for non-propuls
5、ion and non-requiredengine systems.1. ScopeThis report is intended to provide the information to estimate the accessory load of a typical heavytruck or bus. The components covered include: air compressors, alternators, refrigerant compressors, enginecooling fans and power steering pumps. The values
6、show an estimate of the average power requirementsand duty cycles for these accessories. This report does not address loads required for engine operation. Required systems include those needed forengine performance such as fuel pumps and electronic control modules (ECM).2. References2.1 Applicable P
7、ublicationsThe following publications form a part of this specification to the extent specifiedherein. Unless otherwise indicated, the latest version of SAE publications shall apply.2.1.1 SAE PUBLICATIONSAvailable from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001.SAE J1339Test Method for M
8、easuring Power Consumption of Truck and Bus Engine FansSAE J1341Test Method for Measuring Power Consumption of Hydraulic Pumps for Trucks and Buses3. Total Power ConsumptionThe total power consumption of engine driven accessories is the sum of theindividual loads. A maximum possible load can be dete
9、rmined by totaling the maximum loads of eachaccessory. The typical, or average, load for a single accessory can be estimated by multiplying its maximumload by a duty cycle representing the percentage of time it is used. The duty cycle will also represent theaverage power requirement of the accessory
10、 if it has a variable load potential. For example, a light may be on35% of the time, resulting in a 0.35 duty cycle multiplier. A hydraulic pump may be used 20% of the time andaverage 50% of its maximum load, resulting in a 0.10 duty cycle multiplier. The duty cycle of manyaccessories will vary with
11、 operating conditions such as day or night (e.g., head lights) and warm or coldambient temperatures (e.g., refrigerant compressors). The total, typical accessory load for a vehicle is thesum of the typical loads for the individual accessories in a particular operating condition. This report listsest
12、imates and duty cycles considered representative for the heavy truck and bus industry.COPYRIGHT Society of Automotive Engineers, Inc.Licensed by Information Handling ServicesSAE J1343 Revised AUG2000-2-4. Individual ComponentsThe typical accessories common to heavy trucks and busses are listed below
13、.Estimated loads and duty cycles are given.4.1 Air Brake CompressorsThe loads and duty cycles for air compressors for the applications are defined onFigure 1.FIGURE 1COMPRESSOR LOAD AND DUTY CYCLES4.2 AlternatorsThe power demand to the alternator(s) can be determined by estimating the average ampera
14、gedraw from the electrical accessories installed on the trucks and multiplying it by the voltage of the system.Most trucks in the USA use 12 V systems while European systems tend to be 24 V. Figure 2 shows the typicalcurrent demand for 12 V electrical components. All required loads (e.g., ignition a
15、nd/or ECMs) are included inthe engine net power definition and should not be included as accessories.COPYRIGHT Society of Automotive Engineers, Inc.Licensed by Information Handling ServicesSAE J1343 Revised AUG2000-3-FIGURE 2TYPICAL DRAW OF ELECTRICAL ACCESSORIES (WHEN SWITCHED ON)COPYRIGHT Society
16、of Automotive Engineers, Inc.Licensed by Information Handling ServicesSAE J1343 Revised AUG2000-4-The total loads can be calculated using the previous loads and equations. Total maximum load and totalaverage load can be calculated using Equations 1 and 2, respectively.(Eq. 1)(Eq. 2)4.3 Air Condition
17、ing CompressorThe duty cycle and horsepower for the air conditioning compressor, afterinitial cool-down, is shown in Figure 3. The Average Load column is equal to a typical compressor load timesthe duty cycle.FIGURE 3AIR CONDITIONING COMPRESSOR LOADS AND DUTY CYCLESBASED ON 30 C (86 F) AMBIENT CONDI
18、TIONS4.4 Engine Cooling Fans and DrivesThe power requirements of the engine cooling fan and drive are closelyrelated to the engine heat rejection along with radiator, shroud and chassis configuration. The power neededto drive a cooling fan at rated engine speed may be 15 to 30 kW (20 to 40 HP) or mo
19、re. Since fan power varieswith the fan rpm and design, it is necessary to provide a common method for evaluating the fans. Theprocedure presented in SAE J1339, is of sufficient accuracy to give comparative results. For a typical class 8line haul tractor trailer or truck the engine cooling fan is onl
20、y needed approximately 5 to 10% of the time whensupplemented with an adequate volume of ram air. Local delivery trucks and busses may have significantlyhigher fan-on percentages, possibly in the 10 to 20% range or higher. Some busses also use multiple fans forseparate radiator and charge air coolers
21、. The fan-on time may also vary substantially depending on airconditioning compressor input to the fan clutch and the vehicles duty cycle. Figure 4 shows typical values forseveral applications. It should be noted that these values are rough estimates and may dramatically impactaverage accessory load
22、s. The significant distinction between average fan load and maximum fan load shouldalso be considered.Total Maximum Load = (Constant Loads + Intermittent Loads)Total Average LoadConstant Loads + 0.35Intermittent Loads()=COPYRIGHT Society of Automotive Engineers, Inc.Licensed by Information Handling
23、ServicesSAE J1343 Revised AUG2000-5-FIGURE 4TYPICAL FAN LOADS AND DUTY CYCLESBASED ON 30 C (86 F) AMBIENT CONDITIONS4.5 Power Steering PumpsDue to the large variations in power steering pumps, it is recommended that thepower requirement be obtained from the performance data for the pump in question.
24、 See SAE J1341. Dutycycles for the various types of operation are defined in Figure 5. For the purposes of estimating average load,the maximum loads are typically in the 5-15 HP range.FIGURE 5POWER STEERING DUTY CYCLE BY APPLICATION5. Example of Accessory Load CalculationThe following example demons
25、trates the use of the above dataand equations to determine the maximum and average accessory loads of a sleeper-type, line-haul tractor-trailer. Figure 6 lists the typical, alternator-driven electrical loads. The maximum and average loads are listedand totaled.FIGURE 6EXAMPLEELECTRICAL ACCESSORIESCO
26、PYRIGHT Society of Automotive Engineers, Inc.Licensed by Information Handling ServicesSAE J1343 Revised AUG2000-6-Figure 7 lists all the accessory loads that would be expected in this type of vehicle. The totals for eachcategory are listed at the bottom of the Figure. This analysis reviews the truck
27、 while driving, during the daywith no rain, with the cab and sleeper heaters on. Other analyses should be performed to estimate theaccessory loads during other operational cycles including: driving-night, parked-idling, parked-idling w/heater,etc. It is assumed that the engine is a turbocharged dies
28、el with an air compressor, air conditioning & heater,and power steering.FIGURE 7EXAMPLETOTAL ACCESSORY LOADS6. Notes6.1 Marginal IndiciaThe change bar (l) located in the left margin is for the convenience of the user in locatingareas where technical revisions have been made to the previous issue of
29、the report. An (R) symbol to the leftof the document title indicates a complete revision of the report.PREPARED BY THE SAE TRUCK AND BUS ENGINE PERFORMANCE ANDAPPLICATION SUBCOMMITTEE OF THE SAE TRUCK AND BUS POWERTRAIN COMMITTEECOPYRIGHT Society of Automotive Engineers, Inc.Licensed by Information
30、Handling ServicesSAE J1343 Revised AUG2000RationaleNot applicable.Relationship of SAE Standard to ISO StandardNot applicable.ApplicationThis report is intended to provide the information to estimate the accessory load of a typicalheavy truck or bus. The components covered include: air compressors, a
31、lternators, refrigerantcompressors, engine cooling fans and power steering pumps. The values show an estimate of theaverage power requirements and duty cycles for these accessories. This report does not address loads required for engine operation. Required systems include thoseneeded for engine perf
32、ormance such as fuel pumps and electronic control modules (ECM).Reference SectionSAE J1339Test Method for Measuring Power Consumption of Truck and Bus Engine FansSAE J1341Test Method for Measuring Power Consumption of Hydraulic Pumps for Trucks and BusesDeveloped by the SAE Truck and Bus Engine Performance and Application SubcommitteeSponsored by the SAE Truck and Bus Powertrain CommitteeCOPYRIGHT Society of Automotive Engineers, Inc.Licensed by Information Handling Services
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