PROCEEDINGS OF THE INSTITUTE OF VEHICLES 1(105)/2016 Marcin K. Wojs 1, Piotr Orliński 2, Stanisław W. Kruczyński 3 COMBUSTION PROCESS IN DUAL FUEL ENGINE POWERED BY METHANE AND DOSE OF DIESEL FUEL 1. Introduction Compression ignition engines are the most common source of power, which use oil fuels and can be applied in a wide variety of uses that support our lives because of its originally high efficiency, easy operability, and high levels of safety [1]. Leading into use the compression ignition engines powered by gas fuels is problematic on account of their design assumptions. Majority of suggested solutions is providing changes in the structure of the engine through the application of additional ignition systems. Another solution is implementing the preliminary dose of diesel fuel to gas fuel ignition [2, 3]. At present the market is dominated by fuels of the oil origin what results in heavy costs of using them. Using gas for powering engines of machines will allow from one side for limiting consuming fossil fuels still becoming more expensive [4]. However, on the other side it can contribute to increase the energy independence, by using another type of fuel such as methane. 2. Model and conditions of simulation in AVL Boost program The simulation model of the engine CDC 6T-590 was prepared using AVL software. It was in particular AVL BOOST ver. 2013 program. Conducted simulations of working cycle of dual fuel engine powered by diesel fuel and gas were aimed at the analysis of selected phenomena connected with possible course of the combustion process of dual fuel blend delivered to the cylinder. As a gas fuel methane CH 4 was used together with the preliminary dose of diesel fuel. In Fig. 1 the schema of CDC 6T-590 engine simulation model is shown. E1 SB1 MP3 3 I1 19 PL1 1 MP1 TC1 CO1 MP2 2 MP6 MP4 MP5 4 5 6 7 9 8 C1 C2 C3 C4 C5 C6 10 11 12 14 15 13 MP8 MP7 16 PL2 PL3 18 17 SB2 Fig. 1. The schema of CDC 6T-590 engine simulation model prepared in AVL BOOST software 1 Mgr inż Marcin K. Wojs, Institute of Vehicles, Warsaw University of Technology 2 Dr hab. inż. Piotr Orliński, Institute of Vehicles, Warsaw University of Technology 3 Prof. dr hab. inż. Stanisław W. Kruczyński, Institute of Vehicles, Warsaw University of Technology 61
In Fig. 2 it is presented the window of the program allowing to put the engine CDC 6T-590 basic geometrical data. However, Fig. 3 shows the window of the program on which the fuels applied for the simulation are defined. Presented case assumes 20% of diesel fuel and 80% of methane. Fig. 2. Basic dimensions of CDC 6T-590 engine Fig. 3. Fuels selection and their ratios 62
Fig. 4. Thermodynamics properties of diesel fuel Fig. 5. Thermodynamics properties of methane fuel Nevertheless, in Fig. 6 there is presented the way how to put the data for simulation of combustion process through Vibe function with division into two combustion phases. 63
Fig. 6. Putting the data necessary for combustion process simulation using Vibe double function Simulations were performed for rotational velocity referring to the maximum torque for the following engine working conditions: fuel: 20% diesel fuel, 80% methane tense of the compressor: 1,4 engine rotational velocity n=1600 obr/min Division of the quantity of the ensuing heat during combustion process: combustion phase I - 5% of the heat release in the time of 15 deg of crankshaft rotation, combustion phase II - 95% of the heat release in the time of 55-145 deg of crankshaft rotation (with calculation step 20 deg); combustion phase I - 20% of the heat release in the time of 15 deg of crankshaft rotation. combustion phase II - 80% of the heat release in the time of 95 deg of crankshaft rotation (with calculation step 20 deg) The beginning of combustion: 6 deg before TDC. 3. Results of simulation for dual fuel powered CDC 6T-590 engine Through simulations a series of results was obtained, from which were presented only selected calculations, referring to combustion process. Effects of simulations of ensuing heat, pressure in combustion chamber, temperature in combustion chamber and indicated mean pressure are presented suitably in Fig. 7 9. 64
Pressure (MPa) 14 12 10 8 6 P1 (MPa) P2 (MPa) P3 (MPa) P4 (MPa) P5 (MPa) P6 (MPa) 4 2 0 270 300 330 360 390 420 450 480 510 540 Crankshaft rotational angle [deg] Fig. 7. The course of pressure inside combustion chamber as a function of crankshaft rotation angle (a fragment) for differentiated number of ensuing heat during first and second combustion phase: p1 combustion phase I: 5% of ensuing heat in the time of 15 deg of crankshaft rotation, combustion phase II: 95% of ensuing heat in the time of 55 deg of crankshaft p2 combustion phase I: 5% of ensuing heat in the time of 15 deg of crankshaft rotation, combustion phase II: 95% of ensuing heat in the time of 75 deg of crankshaft p3 combustion phase I: 5% of ensuing heat in the time of 15 deg of crankshaft rotation., combustion phase II: 95% of ensuing heat in the time of 95 deg of crankshaft p4 combustion phase I: 5% of ensuing heat in the time of 15 deg of crankshaft rotation., combustion phase II: 95% of ensuing heat in the time of 105 deg of crankshaft p5 combustion phase I: 5% of ensuing heat in the time of 15 deg of crankshaft rotation., combustion phase II: 95% of ensuing heat in the time of 125 deg of crankshaft p6 combustion phase I: 5% of ensuing heat in the time of 15 deg of crankshaft rotation, combustion phase II: 95% of ensuing heat in the time of 145 deg of crankshaft rotation. 65
Temperature (K) 2400 2200 2000 1800 1600 1400 1200 1000 800 600 400 200 T1 (K) T2 (K) T3 (K) T4 (K) T5 (K) T6 (K) 270 300 330 360 390 420 450 480 510 540 Crankshaft rotational angle [deg] Fig. 8. The course of temperature inside combustion chamber as a function of crankshaft rotation angle (a fragment) for differentiated number of ensuing heat during first and second combustion phase: T1 combustion phase I: 5% of ensuing heat in the time of 15 deg of crankshaft rotation, combustion phase II: 95% of ensuing heat in the time of 55 deg of crankshaft T2 combustion phase I: 5% of ensuing heat in the time of 15 deg of crankshaft rotation, combustion phase II: 95% of ensuing heat in the time of 75 deg of crankshaft T3 combustion phase I: 5% of ensuing heat in the time of 15 deg of crankshaft rotation, combustion phase II: 95% of ensuing heat in the time of 95 deg of crankshaft T4 combustion phase I: 5% of ensuing heat in the time of 15 deg of crankshaft rotation, combustion phase II: 95% of ensuing heat in the time of 105 deg of crankshaft T5 combustion phase I: 5% of ensuing heat in the time of 15 deg of crankshaft rotation, combustion phase II: 95% of ensuing heat in the time of 125 deg of crankshaft T6 combustion phase I: 5% of ensuing heat in the time of 15 deg of crankshaft rotation, combustion phase II: 95% of ensuing heat in the time of 145 deg of crankshaft rotation. 66
Q (J/deg) 160 140 120 100 80 60 Q1 (J/deg) Q2 (J/deg) Q3 (J/deg) Q4 (J/deg) Q5 (J/deg) Q6 (J/deg) 40 20 0 270 300 330 360 390 420 450 480 510 540 Crankshaft rotational angle [deg] Fig. 9. Velocity of heat ensuing as a function of crankshaft rotational angle for differentiated number of ensuing heat during first and second combustion phase: Q1 combustion phase I: 5% of ensuing heat in the time of 15 deg of crankshaft rotation. combustion phase II: 95% of ensuing heat in the time of 55 deg of crankshaft rotation. Q2 combustion phase I: 5% of ensuing heat in the time of 15 deg of crankshaft rotation, combustion phase II: 95% of ensuing heat in the time of 75 deg of crankshaft Q3 combustion phase I: 5% of ensuing heat in the time of 15 deg of crankshaft rotation, combustion phase II: 95% of ensuing heat in the time of 95 deg of crankshaft Q4 combustion phase I: 5% of ensuing heat in the time of 15 deg of crankshaft rotation, combustion phase II: 95% of ensuing heat in the time of 105 deg of crankshaft Q5 combustion phase I: 5% of ensuing heat in the time of 15 deg of crankshaft rotation, combustion phase II: 95% of ensuing heat in the time of 125 deg of crankshaft Q6 combustion phase I: 5% of ensuing heat in the time of 15 deg of crankshaft rotation, combustion phase II: 95% of ensuing heat in the time of 145 deg of crankshaft rotation. 4. Conclusion Performed simulations of working cycle of the dual fuel engine powered by diesel fuel and methane were aimed at the analysis of selected phenomena connected with possible course of combustion process of dual fuel blend delivered to the cylinder. The most important of a point of view of the efficiency and durability of the engine phenomena are: 1. increase of the maximum cycle pressure, 2. extending the combustion process. 67
The results of computer simulation indicate that very high level of maximum pressure inside combustion chamber can be reached with relatively high quantity of heat, (20%) that will ensue in the first phase of combustion. Such phenomenon is possible in case, when blend ratio methane air in the whole combustion chamber volume is on the border of combustion (i.e. the ratio of methane in air - fuel blend in the range 2,2-9%), which means relatively low value of air fuel equivalence ratio for compression ignition engine powered by two fuels. Such blend after being ignited in many points inside combustion chamber through pilot injection of diesel fuel, is combusting rapidly, which results in very high increase of maximum cycle pressure and in the end with possible knock. In case of powering the engine by the blends with such composition it has to be taken into account the decrease of the tense of the compressor. It is aimed at limiting the pressure in the beginning of compression stroke in the combustion chamber. Certainly, the limited tense will effect in delivering to the cylinder lower quantity of air. So that, it will contribute to generate the conditions, in which the methane air blend will be on the border of combustion in the whole volume of combustion chamber. References: [1] Marcin K. Wojs, Piotr Orliński: Selected aspects of use dimethyl ether (DME) in compression ignition engines. Zeszyty Naukowe Instytutu Pojazdów 1(101)/2015, ISSN 1642-347X, str: 103-108, [2] Kruczyński S. W, Pawlak G., Marcin K. Wojs, Wołoszyn R.: Biogas as a perspective fuel for agriculture tractors. Zeszyty Naukowe Instytutu Pojazdów 1(92)/2013, ISSN 1642-347X, str: 151-156, [3] Orliński P.: Wybrane zagadnienia procesu spalania paliw pochodzenia roślinnego w silnikach o zapłonie samoczynnym, 2013. Instytut Naukowo-Wydawniczy "SPATIUM", ISBN 978-83-62805-92-1, [4] Maji S., Amit Pal, Arora B.B., Use of CNG and diesel in CI engines in dual fuel mode. SAE 2008-28-0072 (2008) Abstract The paper shows selected results of simulations performed in AVL Boost software, covering several aspects of methane combustion in compression ignition engine with the participation of pilot injection of diesel fuel. Keywords: dual fuel engine, methane, AVL Boost PROCES SPALANIA W SILNIKU DWUPALIWOWYM ZASILANYM METANEM I DAWKĄ PILOTUJĄCĄ OLEJU NAPĘDOWEGO Streszczenie Artykuł przedstawia wybrane wyniki symulacji przeprowadzonych w programie AVL Boost obejmujące wybrane aspektu procesu spalania metanu w silniku o zapłonie samoczynnym przy udziale dawki wstępnej oleju napędowego. Słowa kluczowe: silnik dwupaliwowy, metan, AVL Boost 68