102-110 Al-Khwarizmi Engineering Journal,Vol. 12, No. Comparative Study of between Spark Ignition Engine Compression Ignition Engine Department (Received http://dx.doi.org/10.22153/kej.2016.06.003 Abstract Many researchers consider Homogeneous Charge Compression Ignition (HCCI) engine mode as a promising alternative to combustion in Spark Ignition and Compression Ignition Engines. The HCCI engine runs on lean mixtures of fuel and air, and the combustion is produce mode was investigated in this paper. A variable compression ratio, spark ignition engine type TD110 was used in the experiments. The tested fuel was Iraqi conventional gasoli The results showed that HCCI engine can run in very lean equivalence ratios. The brake specific fuel consumption was reduced about 28% compared with a spark ignition engine. The experimental tests showed that the emissions concentrations were reduced by 91.27% for NOx, 85.99% for CO, 78.91% for CO hydrocarbons compared to the SI engine. HCCI engine produced little noise with about 26.68% less than SI engine Keywords: Homogeneous Charge Compression Ignition, HCCI, 1. Introduction The homogeneous charge compression ignition system (HCCI) can be considered as system with low emitted emissions, but lower efficiency compared to conventional engines. The HCCI engine emits low NOx emissions, virtually no particulate matters (PM) emissions. However, the marketing of HCCI technology still represents a huge challenge because of the narrow field of operation and the difficulties associated with the combustion phase [1]. The HCCI depends on the homogeneous mixture of the fuel by fuel and air before combustion starts and that th mixture is auto-ignited due to the temperatures of the compression stroke HCCI system is similar to SI system systems use a premixed charge. In the same time HCCI system is similar to CI system Khwarizmi Engineering Journal,Vol. 12, No. 4, P.P. 102- 110 (2016) of Performance and Emission Characteristics Spark Ignition Engine and Homogeneous Charge Compression Ignition Engine (HCCI) Nahedh Mahmood Ali Department of Materials Engineering / University of Technology Email: nahidh.mahmood60@gmail.com (Received 25 January 2016; accepted 15 June 2016) http://dx.doi.org/10.22153/kej.2016.06.003 Many researchers consider Homogeneous Charge Compression Ignition (HCCI) engine mode as a promising alternative to combustion in Spark Ignition and Compression Ignition Engines. The HCCI engine runs on lean mixtures roduced from the fuel autoignition instead of ignited by a spark investigated in this paper. A variable compression ratio, spark ignition engine type TD110 was used in the The tested fuel was Iraqi conventional gasoline (ON=82). The results showed that HCCI engine can run in very lean equivalence ratios. The brake specific fuel consumption reduced about 28% compared with a spark ignition engine. The experimental tests showed that the emissions reduced by 91.27% for NOx, 85.99% for CO, 78.91% for CO2, and 83.56% for unburned hydrocarbons compared to the SI engine. HCCI engine produced little noise with about 26.68% less than SI engine Homogeneous Charge Compression Ignition, HCCI, gasoline fuel, auto-ignition and combustion The homogeneous charge compression ignition as an attractive system with low emitted emissions, but lower efficiency compared to conventional engines. The HCCI engine emits low NOx emissions, and virtually no particulate matters (PM) emissions. However, the marketing of HCCI technology still represents a huge challenge because of the narrow field of operation and the difficulties associated attain of a by mixing the before combustion starts and that this ignited due to the high the compression stroke [2]. The system as both In the same time, system as both systems are auto-ignited However, the HCCI combustion process totally from the two types When the mixture is compressed, temperature and pressure increase. When the timing is controlled successfully, the mixture auto-ignites at a couple of degrees before TDC. The combustion starts at many locations simultaneously [4]. After ignition, the gas that burned first will expand and thereby compre part of the gas that did not burn yet. This compression, together with the overall rise in temperature and the time necessary for the chemical kinetics to start, leads to auto the rest of the mixture. HCCI combustion has thus no flame propagation [5]. As far as the mixture preparation is concerned, one approach is port-injection, leading homogeneous charge as in the SI engine. Another Al-Khwarizmi Engineering Journal (2016) Emission Characteristics Homogeneous Charge University of Technology Many researchers consider Homogeneous Charge Compression Ignition (HCCI) engine mode as a promising alternative to combustion in Spark Ignition and Compression Ignition Engines. The HCCI engine runs on lean mixtures ignited by a spark. This combustion investigated in this paper. A variable compression ratio, spark ignition engine type TD110 was used in the The results showed that HCCI engine can run in very lean equivalence ratios. The brake specific fuel consumption reduced about 28% compared with a spark ignition engine. The experimental tests showed that the emissions , and 83.56% for unburned hydrocarbons compared to the SI engine. HCCI engine produced little noise with about 26.68% less than SI engine. ignition and combustion. to initiate combustion. combustion process varies [3]. When the mixture is compressed, its pressure increase. When the timing is controlled successfully, the mixture ignites at a couple of degrees before TDC. The combustion starts at many locations . After ignition, the gas that burned first will expand and thereby compress the part of the gas that did not burn yet. This compression, together with the overall rise in temperature and the time necessary for the chemical kinetics to start, leads to auto-ignition of the rest of the mixture. HCCI combustion has thus As far as the mixture preparation is concerned, injection, leading to a nearly homogeneous charge as in the SI engine. Another Nahedh Mahmood Ali Al-Khwarizmi Engineering Journal, Vol. 12, No. 4, P.P. 102- 110 (2016) 103 one is a direct injection (DI), in which the fuel can be injected very early in the compression stroke or a later stage under very high pressure. The aim of both methods is to obtain an almost homogeneous charge [6]. The HCCI engine has no direct means to control the timing of ignition, unlike the SI and CI engines. The SI engine has ignition timing, and CI diesel cycle engine has a fuel injection beginning, and both are controlling directly the start of combustion [7]. However, in the HCCI engine, the ignition is controlled by controlling the conditions of the charge and the cylinder walls at a time when the intake valve closes. The ignition control is one of the biggest challenges with the practical implementation of HCCI engine technology [8]. The ignition timing cannot be controlled only indirectly through adjustments in the preparation of the cylinder charge [9]. The most common technological means to facilitate the self-ignition are: 1- Increasing the compression ratio [9]. 2- Using intake air heating [10]. 3- Trapping a high residual gas fraction (RGF) by some method that can alter valve timing and/or lift (e.g. variable valve timing (VVT), electronic valve control (EVC)) [11]. 4- Running the engine on mixtures of fuel with different reactivates and control each fuel fraction [12]. At present, several problems are blocking the road to successful integration of the HCCI concept in automotive applications: complex and expensive solutions (e.g. variable valve train systems) may be necessary to make HCCI combustion possible and the operating window of smooth HCCI operation is still of limited size. However, the most serious problem is the difficulty to control the moment of auto-ignition and the energy release rate. As the mixture in the cylinder is premixed, and no spark plug is used, the chemical processes determine the onset of auto-ignition, as well as the fuel burn rate [13]. Çınar et al. studied the effect of variable equivalence ratios and constant intake air temperature of 80 °C on HCCI engine operation experimentally. Two strategies were used in the study to obtain exhaust gas trapping and HCCI operation. The study findings showed that in- cylinder pressure and heat release rate decreased using, and more residual gases were trapped. The indicated thermal efficiency increased at 1000 rpm engine speed and stoichiometric air/fuel ratio [14]. Zhao reported that eliminating the local rich air–fuel mixtures and reduced combustion temperature in HCCI operation mode enable to decrease the PM and NOx emissions trade off without affecting the high thermal efficiency [15] Uyumaz conducted an experimental study to determine the impact of several blends of n- heptane-gasoline on HCCI combustion mode in four stroke port injection Ricardo Hydra test engine. The investigation was carried out at a constant engine speed of 1500 rpm and ʎ = 2. The tests examined the impact of inlet air temperature on HCCI combustion. The study results clarified that increasing the inlet air temperature forced the start of combustion to advance with all the tested blends. The results revealed that CO emissions decreased, and CO2 levels increased with the increase of inlet air temperature, due to better oxidization. The Maximum measured CO emissions were 0.144% (vol.) with B40 (40% n- heptane and 60% gasoline), 0.138% (vol.) with B30 (30% n-heptane and 70% gasoline) at 313 K inlet air temperature. HC emissions decreased with increasing the inlet air temperature due to rapid combustion that caused an improvement in chemical reactions at high inlet air temperatures. The maximum measured HC concentrations were 440 ppm and 438.88 for B30 blend at 313 K, and 333 K inlet air temperatures respectively. The study indicated that NOx levels were near zero at high combustion temperatures, due to the low temperature of combustion. At high inlet air temperatures, the measured NO concentrations were about 1 to 2 ppm [16]. The goal of this work is to compare practically between two combustion systems, (spark ignition engine and HCCI engine). The comparison will be for limited engine conditions; which were 1500 rpm engine speed, and full load operation. The engine speed of 1500 rpm was selected as it is relevance to a car's engine runs in city streets. The full load operation was chosen to examine the maximum operation limit before knock limit. 2. Experimental Set Up This study was carried out using a single cylinder, four strokes, and variable compression ratio, spark ignition engine and speed, type TD110, using hydraulic dynamometer, Fig. 1 illustrates the engine rig and the measuring instruments. Table 1 gives this engine specification. The engine was adjusted to overcome limitations in power output by making it full open throttle and adjusting the spark timing to be the optimum one for every operating condition. The Nahedh Mahmood Ali Al engine was also modified to use HCCI combustion mode by conversion conventional diesel combustion at high loads (with early injection). No manipulation in the architecture of the diesel combustion system. It was kept as it is: – Direct injection; – Flat cylinder head. Fig. 1. The engine rig and the measuring instruments Table 1, Engine specifications Referring to the study of the different HCCI concepts, the use of an early injection strategy was chosen. The dilemma with this method is how to avoid the collision of the fuel with the combustion chamber wall. Therefore, the point of this concept is to use a narrow the spray cone (less than 100 degrees) to reduce fuel collision with the wall of the combustion chamber and to improve the fuel-air there is considerable flexibility in the area of injection. The common rail fuel injection system Name plate varicomp type (GR06/000/037A) The manufacturing year Engine type Strokes numbers 4 strokes Piston diameter Stroke Swept volume 541 C.C Compression ratio Max. power output 4 kW at 2800 rpm Max. rpm 3600 R.P.M Inlet. valve open 54º BTDC Inlet valve closed 22º ATDC Exhaust valve open 22º BTDC Exhaust valve closed 54º BTDC Al-Khwarizmi Engineering Journal, Vol. 12, No. 4, P.P. 104 engine was also modified to use HCCI combustion mode by conversion conventional esel combustion at high loads (with early No manipulation in the general architecture of the diesel combustion system. It engine rig and the measuring to the study of the different HCCI an early injection strategy with this method is how to avoid the collision of the fuel with the combustion chamber wall. Therefore, the primary point of this concept is to use a narrow-angle of the spray cone (less than 100 degrees) to reduce ith the wall of the combustion air mixing, while flexibility in the area of the injection. The common rail fuel injection system has been selected because of the continuous increase in its flexibility. However, the early injection can cause advanced ignition timing and knock can be a problem. The compression ratio was investigated starting from CR=12 at full load operational cases (full load means any more load will cause knock). The nitrogen oxides (NOx), unburned hydrocarbon UBHC, CO2 were measured by Multi emissions analyzer. This device was calibrated at Central Organization for Standardization and Quality Control in Baghdad. The engine noise (o measured by a precision sound level meter equipped with microphone type 4615 was calibrated by standard pisto-phone 4220. The equivalence ratio which the measured air and fuel flow rates to the engine, defined as [14]: ∅ � actual fuel/air ratio stoichiometric fuel/ The following equations used to calculate the engine performance parameters 1- Brake power �� � ��∗�∗� ��∗���� �� 2- Fuel mass flow rate �� � !"#�� $% ���� # &" '()* �+ 3- Volumetric efficiency �� ,,,.'. � ��012∗�.34 5��� # �� ,6782. � 9:.; # � ��∗� # . � )� ?,?@6. )� ?6782. 4- Brake specific fuel consumption �ABC � )� " DE # 3600 IJ IK 5- Total fuel heat L' � �� # MN9 �� 6- The lost power to overcome the friction (friction power): BE � �#� 5O3.��P 7- Mechanical efficiency: <) � DQ RQ � DQ DQS Q varicomp type (GR06/000/037A) 1998 TD110 4 strokes 90 mm 85 mm 541 C.C 4-17.5 kW at 2800 rpm 3600 R.P.M 54º BTDC 22º ATDC 22º BTDC 54º BTDC arizmi Engineering Journal, Vol. 12, No. 4, P.P. 102- 110 (2016) has been selected because of the continuous However, the early injection can cause advanced ignition timing and knock. Therefore, it he compression ratio effect starting from CR=12:1 to 14.5:1 full load operational cases (full load concept means any more load will cause knock). nitrogen oxides (NOx), unburned 2, and CO concentration Multi-gas mode 4880 analyzer. This device was calibrated at Central Organization for Standardization and ity Control in Baghdad. The engine noise (overall sound pressure) precision sound level meter microphone type 4615; the device standard calibrator meter type The equivalence ratio which determined from the measured air and fuel flow rates to the engine, ratio air ratio The following equations used to calculate the engine performance parameters [14]: …. (1) �+ ATCU …. (2) V,(W IJ :*. …. (3) # V,(W IJ :*. …. (4) …. (5) consumption IJ IK.1W …. (6) …. (7) The lost power to overcome the friction …. (8) Mechanical efficiency: …. (9) Nahedh Mahmood Ali Al-Khwarizmi Engineering Journal, Vol. 12, No. 4, P.P. 102- 110 (2016) 105 8- Brake thermal efficiency � �7̂^&ك ا.4̂^"��ل /��2̂^&ارة% ٨٣.٥٦و _^̂��ر$̂^� Q��7̂^&ك . �:K�̂^�رو6�ر/�$�ت i�̂^& ا�7"&�̂^� =^̂8 H"^̂$HCCI ء أ�̂^@ /7̂^�ود�^̂N�N7̂^&ك % ٢٦.٦٨� =^̂� .ا.4"��ل /��2&ارة