The Optimal Design of DME Injection for NOx Reduction of the DME Dual Diesel (DDF/DME) Engine on a Heavy Duty Truck

Transcription

1 International Journal of Engineering Practical Research (IJEPR) Volume 3 Issue 4, November 24 doi:.4355/ijepr The Optimal Design of Injection for NOx Reduction of the Dual (/) Engine on a Heavy Duty Truck Li Shin Lu *, Horng Shing Chiou 2, Shah Rong Lee, Chao Wen Yen, Yang Tai Thomas Lin 3 Department of Mechanical Engineering, Taipei Chengshih University of Science and Technology No.2, Xueyuan Rd., 2 Taipei, Taiwan, R.O.C. 2 Department of Electrical Engineering, Taipei Chengshih University of Science and Technology No.2, Xueyuan Rd., 2 Taipei, Taiwan, R.O.C. 3 New Environment Foundation, 236, Sec. 2, Fuxing S. Rd., 6 Taipei, Taiwan, R.O.C. * lslu@tpcu.edu.tw; 2 hschiou@tpcu.edu.tw; srlee@tpcu.edu.tw; cwyen@tpcu.edu.tw; 3 yttlin36@ms48.hinet.net Abstract Introducing gas into the combustion air intake of a engine acts as an accelerant, promoting more complete combustion, and resulting 27.3 NOx emission reduction has been achieved using the / control system. The ESC 3 Mode tests of a Mitsubishi 7545 c.c., 6 cyl. engine with a / system are conducted. The optimal amount of the injection into each cylinder of the engine for NOx reduction purpose is derived as function of the boost pressure at the manifold. Experimental results show that the boost pressure is linear to the engine rpm for 5 load of / engine. This line is parallel to the boost pressure engine rpm line for 5 load of /LPG engine. A boost pressure oriented LPG injection controller has been developed to revamp on the engine of a 5 ton Taipei City refuse truck. The /LPG heavy duty truck has been running 8 months with 8 fuel saving rate and 32 smoke reduction rate. The boost pressure oriented injection controller for NOx reduction purpose is being fabricated and tested on the same heavy duty refuse truck. The average substitution of to is 27.5 by mass fraction. The cost of / system is only 5, USD per set. An efficient / system is important to the reduction of the NOx emissions of the 2, Euro II and Euro III standard heavy duty trucks and the set up of for transportation fuel industry in future Taiwan. Keywords / System; Optimal Design of Injection; oost Pressure Oriented Controller; Reduction of Nox Emissions Introduction Physical Properties of, LPG and, and the Combustion Systems Dimethyl Ether () is a clean and economical alternative fuel which can be produced from various resources as natural gas, coal or biomass through synthesis gas. The properties of are similar to those of LPG and it can be used for various fields: power generation fuel, transportation fuel, home fuel, etc. The physical properties of, LPG and are shown in Table. TALE PHYSICAL PROPERTIES OF AND OTHER FUEL. Properties LPG Chemical formula CH3OCH3 C3H8 oiling point ( o C) ~37 Liquid density (g/cm 2 o C) Specific gravity of gas vs. air Vapor pressure (atm) Cetane number 55~6 4~55 Net calorific value (kcal/kg) 6,9 2,368, From Table, similar to LPG, can rapidly blend with air to form a combustible mixture due to very low boiling point and high evaporation pressure. The pressures of and LPG are also similar, around 6 atm, therefore they are suitable for vehicle fuel use due to very low pressure of storage tank compared to 2 atm of CNG tank. DEM, with a lower self ignition temperature, high cetone number and short ignition delay period, is prone to compression ignition of engine. Pure, lower in heating value, can cause lower engine output. However, engines fuelled by blended with (/) can combine 89

2 International Journal of Engineering Practical Research (IJEPR) Volume 3 Issue 4, November 24 with both the high output and lower NOx emissions. Since / combustion systems are similar to /LPG systems which are very well developed and intensively studied, the /LPG engine experiences are vital to this research. /LPG Engine Technologies are Improving and ecoming More Widespread for On road Applications Contemporary gaseous dual fuel (DF) engines have been under development in Europe and the U.S. since the early 98s. A 2 inventory by Clean Fuels Consulting of companies engaged in dual fuel gaseous/ engines and vehicles natural gas and liquid petroleum gas (LPG) identified at least 34 different companies engaged in some form of development, production and sale of these emerging technologies (Seisler, 2). There are 2 companies actively engaged in developing, producing and selling dual fuel gaseous/ conversion systems. Seven of these produce LPG dual fuel systems and six are developing or produce both natural gas and LPG dual fuel conversion systems. The retail price of a /LPG system for heavy duty truck is around 3, U.S. dollars per truck. 3 LPG substitution for a Dutch trucking company results in 5 savings on fuel costs per vehicle with an overall return on investment of.5 years. This research has developed 3 boost pressure oriented /LPG systems which are revamped on a 5 ton Taipei City refuse truck, a ton New Taipei City refuse truck and a 35 ton sandstone trailer truck, respectively. All these 3 /LPG heavy duty trucks run 8 months with 8 fuel saving rate and 32 smoke reduction rate (Lin, 24). The cost of the boost pressure oriented LPG injection controlled /LPG system (25 LPG substitution) is around 5, U.S. dollars per truck. emissions laws of composite combustion mode of and are studied and the experimental results show that NOx and smoke emissions are reduced significantly for a 2, c.c., 4 cyl. light duty engine (Duan et al., 22). Experiment Device and Method Engine The experiment is conducted on Mitsubishi 6D6 AT six cylinder turbocharger intercooled engine of which the main technical parameters are shown in Table. During the experiment, the fuel temperature is controlled by the fuel temperature control device at no higher than 4. The temperature intercools after ail intake is maintained by the cooling control unit at no higher the 5. TALE 2 THE MAIN TECHNICAL PARAMETERS OF THE DIESEL ENGINE. Items Type Parameters Six cylinder with turbocharger Number of cylinder 6 Displacement 7545 c.c. The number of injector holes 6 Compression ratio 7.5: Rated power 22 HP/28 rpm Rated speed 3rpm Maximum torque 434 ft lb/6 rpm Year of make 996 Experiment Equipment / Related Experiments Review Due to its good fuel economy and adaptability, engines are widely used. However, high NOx emissions and smoke formation are always the main weak points and problem hard to deal with. To explore strategies to reduce NOx emissions from compression ignition engines has been conducted through a mixed mode combustion process utilizing a fumigated fuel and a pilot injection of fuel on a light duty engine. An approximately 2 reduction in NOx emissions is observed up to 35 energy equivalent (Chapman, 28). Combustion and FIG. SCHEMATIC DIAGRAM OF EXPERIMENT SETUP FOR ELECTRONIC INJECTION CONTROLLED / SYSTEM. The main equipment and instruments used for the experiment include: a GO Power DT water brake dynamometer with maximum power 5 HP, max. torque ft lb and max. speed 4 rpm, a eltone Technology T 2, CO, HC, CO2, O2 and NOx 9

3 International Journal of Engineering Practical Research (IJEPR) Volume 3 Issue 4, November 24 emission analyser, and a Horiba Okuda DSM 24 opacity smoke meter. This experiment uses a dual fuel supply system: diesel going over a fuel consumption instrument though low pressure, high pressure pump into the injection nozzles; from the tank regulated through the pressure regulating valve to about.2 MPa, being led into the intake port near valve for rapid vaporization and mixing with air to form a premixed gas, which then enters the cylinder. The schematic of the experiment equipment setup for the electronic injection controlled / system is shown in Fig.. Experiment Results and Analysis The ESC 3 Mode tests on the engines and / engines emissions, torque, power mass flow, and boost pressure have been conducted at Taiwan EPA authorized Automotive Research and Testing Center (ARTC) and by this research are shown in Table 3 and Table 4 referred to Fig. 2. The boost pressure vs. engine speed curves under various loads for, /LPG and / engines, respectively, are shown in Fig. 3. Load () Idle (6 rpm) Max. Eng. speed Engine Speed (rpm) FIG. 2 SCHEMATIC DIAGRAM OF EUROPEAN STATIONARY CYCLE (ESC) 3 MODE. TALE 3 EUROPEAN STATIONARY CYCLE (ESC) TEST OF ORIGINAL DIESEL ENGINE. C D F NOx Mode A E CO HC (kg/min (kg/min (lbfft) ) ) (kg/cm No. (rpm) (hp) 2 (ppm () (ppm) ) ) *A: Engine speed (rpm), : Mass flow rate of (kg/min.), C: Mass flow rate of (kg/min.), D: Torque (lbf ft), E: Power (hp), F: oost pressure (kg/cm 2 ). TALE 4 EUROPEAN STATIONARY CYCLE (ESC) TEST OF DIESEL/ ENGINE. Mod C D F NOx A E CO HC e (kg/min (kg/min (lbfft) ) ) (kg/cm (rpm) (hp) 2 (ppm () (ppm) No. ) ) oost Pressure (kg/cm 2 ) /LPG / Engine Speed (rpm) FIG. 3 OOST PRESSURE VS. ENGINE SPEED UNDER VARIOUS LOADS. From Fig. 3, under 5 load, the boost pressure is linear with engine rpm for, /LPG and / engines. The NOx emissions vs. engine speed under various loads for and / engines is shown in Fig. 4. From Fig. 4, the NOx reduction effect of / engine to original engine is most significant under 5 load for all engine rpm. The substitution rate for all 3 Mode test of the / engine is calculated as shown in Table 5. The average substitution rate is 27.5 in weight, and 8.43 in energy equivalent. 9

4 International Journal of Engineering Practical Research (IJEPR) Volume 3 Issue 4, November 24 NOx (PPM ) Engine Speed (rpm) / FIG. 4 NOX EMISSIONS VS. ENGINE SPEED UNDER VARIOUS LOADS. TALE 5 THE SUSTITUTION RATE FOR ALL 3 MODE TEST OF / ENGINE. Mode Average Substitution rate The average values of Mode 3 emissions and SFC of and / engines are shown in Table 6. From Table 6, the ESC average values are about 5 above or below Mode 3 values of emissions and SFC for both and / engines. TALE 6 EMISSIONS AND SFC OF ESC AVERAGED VALUE AND MODE 3 VALUE IN DIESEL AND / ENGINES. Euro III HD Engine Emission Standard (ESC Average) (Mode 3) / (ESC Average) / (Mode 3) NOx CO HC SFC Unit: g / hp hr Emissions improvement from to / engines is shown in Table 7. From Table 7, the NOx emission improvement for / to engine is The CO and HC emissions increase for about 2 from to / engine. However, the / emissions still do not exceed the Euro III heavy duty engine standard. TALE 7 EMISSIONS IMPROVEMENT FROM DIESEL TO / ENGINE. Item Engine (ESC) / (ESC) NOx CO HC PM SFC Expected ut 2.662< ut.49<.3 5*.7 * /LPG and / engines are similar in ARTC U.S. TRANSIENT test of PM: from of.42 drop to / of.2 ( g / hp hr ). Derivation of the Equation of Injection for / Engine In Fig. 5, the engine is running at a speed of R rpm and set r = R/3 rpm, the injection mass flow rate m LPG m, where m is the mass flow rate of and is the ratio of LPG amount to fuel. When the fuel is injected into the engine, the engine speed is raised to R rpm or r = R/3 rpm, and the power of engine P is also raised to P of engine. Power P P P P P P r r r r=r rpm/3rpm FIG. 5 POWER AND ENGINE SPEED RELATION OF THE AND ORIGINAL DIESEL ENGINE. The heating value of, H, is assumed to be, kcal/kg, and the heating value of, H, is assumed to be 6,9 kcal/kg, and LPG H H, where.69. Then, P m H m H P m H P P () Since P T r and P T r, where T is the torque of engine in running at engine 92

5 International Journal of Engineering Practical Research (IJEPR) Volume 3 Issue 4, November 24 speed r, and T is the torque of engine at engine speed r. From Table 3 and Table 4, it can be found that for both and engines, the torque T is in proportional to turbocharged pressure that is equal to the atmospheric pressure plus the boost pressure,, i.e. T /( ) const. and T /( ) const.. Substituting these equations into Equation (), it yields Or Therefore P T r r r r P T P r P P r P P P r r T r r T 2 r r The SFC ratio of the engine to original engine is then SFC P P P r r P P P r The energy saving rate r r P r r P r r (2) (3) s (4) SFC The r/r is measured at different load conditions and rpm. r computation has been done. y eliminating the exp[ar] term, the boost pressure of the engine,, is expressible as From Equation (5), k ln r (7) a Trying a = 2.233, r and relation is formed as r Since r/r is also linear with r, therefore, Equation (2) can be expressed as k m m The injection rate of, m, becomes as km k ( ) m where k[ ] can be obtained from the original engine s power map. y linearing Equation (8) and extending to all range of acceleration position and rpm, the optimal mass injection rate of, Opt m, can be expressed as D (8) Opt 2 (9) m m c c where the constants c and c 2 are obtained from experiments. Development of a Pressure Oriented Mass Rate Injection Controller to Install on a 5-Ton Freight Truck The boost pressure of the original engine and that of the / engine are expressible in the form as expar (5) And kexpar (6) where exp[ar] is the exponential function of rpm, a and k are constants evaluated at each rpm from the measured boost pressure and the curve fitting FIG. 7 SCHEMATIC DIAGRAM OF AIR RELAY. 93

6 International Journal of Engineering Practical Research (IJEPR) Volume 3 Issue 4, November 24 The boost pressure oriented mass rate injection controlled / system is shown in Fig. 6. Two air relays are fixed on the / system as shown in Fig. 7. The / dual fuel system installed on a 5 ton freight truck is shown in Fig. 8. The / heavy duty truck is running in the street of Taipei City, Taiwan. / system are conducted and the NOx emissions reduction of 27.3 as the / system is utilized on the Engine. The boost pressure oriented controller optimal amount of the injection into each cylinder of the engine has been developed in this research. The cost of this newly invented and efficient / system is about 2 to those of the electronic type / systems that have been widely sold in the world market. The substitution rate is 27.5 by mass fraction and this is important to the set up of for transportation fuel industry in future Taiwan. ACKNOWLEDGMENT The authors wish to express gratitude to EPA and National Science Council of Taiwan, R.O.C. (Grant NSC 2 EPA F ) for financial support on engine tests. REFERENCES FIG. 6 OOST PRESSURE ORIENTED MASS RATE INJECTION CONTROLLED / SYSTEM. FIG. 8 / DUAL FUEL SYSTEM INSTALLED ON A 5 TON TRUCK. Conclusions The ESC 3 Mode tests for the emissions of a Mitsubishi 7454 c.c., 6 cyl. engine with a Chapman, Elana M., NOx Reduction Strategies for Compression Ignition Engines, The Pennsylvania State University Ph.D. Dissertation, 28. Duan, Junfa, Sun, Yongsheng, Yang, Zhenzhong, and Sun, Zhiqiang, Combustion and Emissions Characteristics of Engine Operating on Composite Combustion Mode of and, Proceeding of 22 International Conference on Mechanical Engineering and Material Science (MEMS 22). Lin, Yang Tai T., The Strategic Energy Planning on Use of iogas for Fuelling Heavy Duty Trucks in Taiwan, Renewable Energy and Power Quality Journal, ISSN x, No. 2, April 24. Seisler, J. M., A Strategic Roadmap to Market Development of Certified Heavy Duty Gausses Fuel (Methane/LPG) Engines, Report of Clean Fuels Consulting, russels, elgium, April 2. 94