6837092895

10    Diagnostyka’ 4(48)/2008

KEKEZ, AMBROZIK, RADZISZEWSKI, Modeling of Cylinder Pressure in Compression Ignition Engine ...

°CA

- 2000

0

extemal spccd characteristic and load charactcristic regimes, with the crankshaft speeds from the rangę of 1000 to 2000 rpm. The engine was fueled by diesel oil. The results of experimental research were used to build the model of engine work.

2. TEST STAND

Experiinental research was madę on the test stand which consists of: diesel engine Perkins AD3.152UR, water brake and control panel. The system for engine research had 4 measurement chains, shown in Fig.l. Pressure was measured by ąuartz piezoelectric transducers. Measured values were recorded in function of cranksliaft angle degrees (°CA). The value of angle was recorded by rotaiy pulse transducer and system of maiking and synchronization of cranksliaft position. The engine was fueled by diesel oil. Measureincnts were donc when engine operated in extemal speed characteristic regime with the cranksliaft speeds 1000. 1200, 1400. 1600. 1800 and 2000 rpm. Cylinder pressure values were recorded eveiy 1.4 °CA (exactly 512 measurements for one working cycle of 4-stroke engine). At each measurement point. values of parameters were recorded. for 50 consecutive working cycles. Indicator diagrams. acąuired in this way. were averaged.

Fig. 1. Błock diagram of measurement system for sclected work parameters of intemal combustion engine [7]

3. RESULTS OF EXPERIMENTAL RESEARCH AND MODELING OF PRESSURE CURVE

Fig. 2 shows acąuired indicator diagrams of cylinder pressure. for different rotational speeds and for ranges 180-540 and 340-390 °CA. For the latter rangę, the differences between pressure curves for different rotational speeds are noticeable. Fast pressure inerease starts at 3.5 to 4 MPa, and 353° to 359° CA. When rotational speed of crankshaft inereases, maximum cylinder pressure decreases. but the cranksliaft angle, at which it appears, inereases. Maximuin value of slope of the tangent linę to the pressure curve decreases with inerease of rotational speed [5]. Knowledge of first and second derivative of pressure curve with rcspect to crankshaft angle allows determining llie start of self-ignition, which is about 352 °CA [5],

a)

pc, MPa 9

b)

pc, MPa 9

340    350    360    370    380    390

°CA

Fig. 2. Indication diagram of cylinder pressure in AD3.152UR diesel engine working at extemal speed characteristic and fueled by diesel oil, in function of cranksliaft angle, for different CA speeds: a) in the rangę of 180° - 540°, b) in the rangę of 340° - 390°

The calculations were madę by means of GFSm system!5], proposed by the autliors. and rated ainong genetic-fuzzy Systems. GFSm crcates Mamdani fuzzy model (Fig.3) or Takagi-Sugeno fuzzy model, which describes relations between input and output variables. and which describes given phenomena or process. Genetic algorithm searches for Solutions using meclianisms borrowed from naturę: natural selection and heredity. Population of possible Solutions, represented by so-called indiyiduals or chromosomes. is clianged: partially randomly and partially on the basis of 'ąuality” of a given solution. "Good” Solutions have bigger chance to reproduce. and "bad" Solutions have smaller chance