The Optimization Design for Energy Saving of the LPG Dual Fuel Diesel (DDF/LPG) Engine of a Heavy Duty Truck

Transcription

1 Advances in Energy Engineering (AEE) Volume 2, 24 The Optimization Design for Energy Saving of the LPG Dual Fuel Diesel (/LPG) Engine of a Heavy Duty Truck Yang Tai Thomas Lin *, Horng Shing Chiou 2, Li Shin Lu 3 New Environment Foundation 236, Sec. 2, Fuxing S. Rd., 6 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 Department of Mechanical Engineering, Taipei Chengshih University of Science and Technology No.2, Xueyuan Rd., 2 Taipei, Taiwan, R.O.C. * yttlin36@ms48.hinet.net; 2 hschiou@tpcu.edu.tw; 3 lslu@tpcu.edu.tw Abstract Introducing LPG gas into the combustion air intake of a diesel engine acts as an accelerant, promoting the even burning of the diesel fuel, and more complete combustion, resulting in more power being produced and fuel cost savings up to 2% is being achieved through some expensive, modern and sophistical electronic control technology in these few years in Australia,New Zealand,Europe,U.S,Japan and Korea. A much more economical technology by upgrading the early technology of dual fuel LPG engines based on a mechanical fumigation system to realized a significant increase in power and fuel cost savings has being developed and presented. The power map and the boost pressure for different loads through 5~3 engine rpm for both diesel engine and /LPG engine of a Mitsubishi 7545 c.c., 6 cyl. Engine are tested. The results show that the power increase percentage is in proportional to the boost pressure increase rate between the / LPG engine and the original diesel engine. Since both power and boost pressure are functions of the engine rpm, the fuel consumption of diesel fuel that is proportional to the power is in a function of boost pressure. Therefore, the optimal amount of LPG injection into each cylinder of diesel engine is in a function of boost pressure of the /LPG engine. The boost pressure oriented / LPG injection controller have been developed and installed on two ton and 5 ton refuse trucks and a 35 ton sandstone trailer respectively. All the three heavy duty / LPG trucks have run with better performance and 8% fuel cost saving for six months. The cost of the /LPG system of this research is only 5, U.S. dollars that is only /3 of those of the other modern /LPG Systems. Keywords /LPG; Combustion; oost Pressure; Oriented Controller; Optimal Injection of LPG; Low Cost Energy Saving System Introduction Every diesel combustion burns approximately 75% of the diesel in the chamber; by adding a shot LPG into the combustion chamber it is up to 95%. 3% LPG substitution for a Dutch trucking company resulted in 5% saving on fuel cost per vehicle with an overall return on investment of.5 years. There are 7 companies produce LPG dual fuel systems and another 6 are developing or produce LPG dual fuel conversion systems in the world. Two automotive research institutes, in India and China, are engaged in dual fuel engine developments (Seisler, 2). Mixing a shot of LPG with the air through the turbocharger improves the brake specific fuel consumption (SFC) or the thermal efficiency of the diesel engine. And cost saving up to 2% is been achieved through revamping a /LPG system with ECU and LPG injections near the air intake port of each cylinder of the engine for most heavy duty diesel engines of Euro III and Euro IV emission levels, besides 9~25% CO2 reduction and smoke and particulate emissions decrease significantly; to 4% to 6% by some claims. Four /CNG systems from Japan, USA and New Zealand have been revamped on the diesel buses to conduct the engine performance tests through chassis dynamometer and the off road tests on the high way and in sown town Taipei City, Taiwan, R.O.C. for several research projects since 998 (Lin and Liang, 998; Lin and Huang, 998; Lin, 999; Hsu et al., 2). The /CNG us Project was terminated due to refuelling station safety issues in districts in highly populated metropolitan city. However, 6 LPG 55

2 Advances in Energy Engineering (AEE) Volume 2, 24 refuelling stations for taxi have been built in Taiwan. Therefore the /CNG experiences are being applied to develop /LPG systems for heavy duty trucks to restore the weakening LPG refuelling station industry here. The turning table of the /CNG ECU which evaluate between signal RPM (Engine) and TPS (Accelerator position) active axle X, Y be axle Y signal TPS, axle X signal RPM can be multiplied by a factor of.64 (Wobble index of CNG=2735 kcal/nm 3 divided by Wobble index of LPG 2755 kcal/nm 3 ) to /LPG system. The evaporator of CNG should be changed to LPG evaporator too. /LPG system is shown in Fig.. Experiment Device and Method Engine The experiment is conducted on Mitsubishi 6D6 AT six cylinder turbocharger intercooled Diesel engine of which the main technical parameters shown in Table. During the experiment, the fuel temperature is controlled by the fuel temperature control device at no higher than 4. The temperature intercooled after ail intake is maintained by the cooling control unit at no higher the 5. TALE 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 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 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; LPG 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 FIG. SCHEMATIC DIAGRAM OF EXPERIMENT SETUP FOR THE /LPG SYSTEM. Experiment Results and Analysis Experiment Results The ESC 3 mode test on the Diesel engine s emissions and fuel consumption has been conducted at the Taiwan EPA authorities Automotive Research and Testing Center (ARTC). The power map of and Diesel engine is shown in Fig. 2. A high pressure turbocharger is added to the engine to form a regulated 2 stage turbocharger system for raising the boost pressure and torque in low rpm from 5 to. Torque (N.m ) with HP TURO with LP TURO 6 Diesel with HP TURO FIG. 2 POWER MAP OF /LPG AND DIESEL ENGINE WITH A MODIFIED REGULATED 2 STAGE TUROCHARGER SYSTEM Power (kw) 56

3 Advances in Energy Engineering (AEE) Volume 2, torque Power P P P P Torque (N.m ) Diesel torque boost pressure Diesel boost pressure FIG. 3 TORQUE AND OOST PRESSURE MAP OF /LPG AND DIESEL ENGINE WITH A REGULATED 2 STAGE TUROCHARGER SYSTEM. Fig. 2 reveals that the maximum load power of /LPG engine is averagely 23% higher than the original Diesel engine through the rpm range from 9 to 27. The SFC (in g/hp hr unit) of /LPG engine is about 6% lower than the original engine or the fuel cost savings is up to 2%, and accordingly CO2 exhaust is reduced by 2%. The overall LPG displacement mass rate of the /LPG fuel is about 8%. The torque and boost pressure map of /LPG and Diesel engine is shown in Fig. 3. The maximum torque of engine is 87 Nm which is 27% higher than 642 Nm of Diesel engine at engine speed of 7 rpm. When rpm is raised up to 27, the maximum load torque of engine is only 3% higher than that of Diesel engine. Averagely, the torque increase is 2% between the and original Diesel engine through the range from 9 to 27 rpm. Derivation of the Equation of LPG Injection for /LPG Engine In Fig. 4, the Diesel engine is running at a speed of R rpm and set r = R/3 rpm, the LPG injection mass flow rate mlpg m, where m is the mass flow rate of Diesel and is the ratio of LPG amount to Diesel fuel. When the LPG fuel is injected into the Diesel engine, the engine speed is raised to R rpm or r = R/3 rpm, and the power of Diesel engine P is also raised to P of engine r/r- oost Pressure (kg/cm 2 ) P P r r r r=r rpm/3rpm FIG. 4 POWER AND ENGINE SPEED RELATION OF THE AND ORIGINAL DIESEL ENGINE. The heating value of Diesel, H, is assumed to be DME, kcal/kg, and the heating value of LPG, 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 speed r, and T is the torque of Diesel engine at engine speed r. From Table 3 and Table 4, it can be found that for both Diesel 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 T r r T r r 2 r r (2) 57

4 Advances in Energy Engineering (AEE) Volume 2, 24 The SFC ratio of the engine to original Diesel engine is then SFC P P P r r P P P r P r r P r r The energy saving rate r r s SFC The r/r is measured at different load conditions and rpm. The relation between r/r versus r is shown in Fig. 3. Optimization Design for a LPG Injection Controller The boost pressure of the original Diesel engine and that of the /LPG engine is expressible in the form as r (3) (4) expar (5) m DME km ( ) D k (8) where k[ ] can be obtained from the original Diesel engine s power map in Fig. 2. y linearing Equation (8) and extending to all range of acceleration position and rpm, the optimal mass injection rate of LPG, m Opt LPG, can be expressed as Opt D D m m..2 ( for.3) LPG D D m..28 ( for.3) Development of a oost Pressure Oriented LPG Mass Rate Injection Controller The boost pressure oriented LPG mass rate injection controlled /LPG system is shown in Fig. 5. A pedal pressure regulator and two LPG air relays are fixed on the /LPG system as shown in Fig. 6 and Fig. 7, respectively. 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 computation has been done. y eliminating the exp[ar] term, the boost pressure of the Diesel engine,, is expressible as From Equation (5), k FIG. 5 OOST PRESSURE ORIENTED LPG MASS RATE INJECTION CONTROLLED /LPG SYSTEM. ln r a (7) 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 DME The injection rate of DME, m DME, becomes as FIG. 6 SCHEMATIC DIAGRAM OF LPG AIR RELAY. 58

5 Advances in Energy Engineering (AEE) Volume 2, 24 (A) LPG FUEL TANK AND IN REFUELLING OF THE TRAILER FIG. 7 SCHEMATIC DIAGRAM OF PEDAL PRESSURE REGULATOR. Appications The boost pressure oriented /LPG injection controller have been developed and installed on two ton and 5 ton refuse trucks and a 35 ton sandstone trailer respectively, as shown in Fig. 8 and Fig. 9. () THE OOST PRESSURE ORIENTED CONTROLLER OF /LPG SYSTEM ON THE TRAILER FIG. 9 A 35 TON /LPG SANDSTONE TRAILER. (A) DIESEL REFUSE TRUCK All these heavy duty /LPG trucks have run with better performance and 5~2% fuel cost saving for six months. The cost of these /LPG system is only U.S. $5, that is only 3~4% of those of the other modern /LPG systems in the world market. Conclusions The /LPG system using sophistical electronic control unit has been tested to derive a boost pressure oriented equation for optimal LPG injection to Diesel engine. The much more lower cost /LPG system using boost pressure as an actuating force to control the LPG injection amount into the Diesel engine has be developed. All the three /LPG systems developed by this research have been installed on ton, 5 ton and 35 ton refuse trucks and sandstone trailer respectively, and have run successfully for six months. () /LPG DUAL FUEL SYSTEM INSTALLED ON TRUCK FIG. 8 A 5 TON TAIPEI CITY /LPG REFUSE TRUCK. ACKNOWLEDGMENT The authors wish to express gratitude to National 59

6 Advances in Energy Engineering (AEE) Volume 2, 24 Science Council of Taiwan, R.O.C. for financial support on engine tests. The authors also wish to give thanks to Dr. Stephen Shu Hung Shen, Minister of Environmental Protection Administration of Taiwan, R.O.C. for his conceptual inspirations and long time contact advices to this study. REFERENCES Hsu, S.L., Chou, W.K., Wu, H.P., Chen, H.C., enefit evaluation and safety administration system of the in use city bus converted into dual fuel CNG system, Research Project, Ministry of Transportation and Communications, April 2. (in Chinese) Lin, Y.T., Fleet tests of the.cng fuelled bus, Report of NSC/EPA Adjoin Project, NSC 88 EPA 2 4, Dec (in Chinese) Lin, Y.T. and Huang, R.F., Technological assessment for improving the emissions of the Diesel bus, EPA Report, EPA 87 FA , July 998. (in Chinese) Lin, Y.T. and Liang, C.Y. Liang, Cost effectiveness analysis of the /CNG system technology, Mechanical Engineering, Vol. 225, Oct (in Chinese) Seisler, J. M., A Strategic Roadmap to Market Development of Certified Heavy Duty Gausses Fuel (Methane/LPG) Diesel Engines, Report of Clean Fuels Consulting, russels, elgium, April 2. 6