The Effect of Injection Timings on Performance and Emissions of Compressed Natural-Gas Direct Injection Engine

Abstract

This experimental part investigates the effect of injection timing on performance and emissions of homogenous mixture compressed natural-gas direct injection. The engine of 1.6 L capacity, 4 cylinders, spark ignition, and compression ratio of 14 was used. Performance and emission were recorded under wide-open throttle using an engine control system (Rotronics) and the portable exhaust gas analyser (Kane). The engine was tested at speed ranging from 1500 revolutions per minute (RPM) to 4000 RPM with 500 RPM increments. The engine control unit (ECU) was modified using Motec 800. The injection timings investigated were at the end of injection (EOI) 120 bTDC, 180 bTDC, 300 bTDC, and 360 bTDC. Results show high brake power, torque, and BMEP with 120 as compared with the other injection timings. At 4000 RPM the power, torque, and BMEP with 120 were 5% compared to that with 180. Furthermore, it shows low BSFC and high fuel conversion efficiency with 120. With 360, the engine produced less CO and CO2at higher speeds.

Natural Gas Engine Technologies: Challenges and Energy Sustainability Issue

“…Unlike the two studies discussed earlier, the injection duration was held constant, and the start of injection was varied from 150 to 210° BTDC with a 10° crank angle (CA). The maximum pressure, a higher heat release rate, and the shortest heat release duration were observed with 180° BTDC, similar to the observations of Aziz et al [164] and Aljamali et al [206]. They reported that injection timing had considerable influence over the combustion characteristics, for late injection in particular.…”

“…A similar study was conducted by Aljamali et al [206] on a four-stroke four-cylinder directinjection spark-ignition engine by varying the injection timings on 120° BTDC, 180° BTDC, 300° BTDC, and 360° BTDC. The speed was varied from 1500 rpm to 4000 rpm with an interval of 500 rpm.…”

“…There are various efforts reported in the literature to improve the performance of CNG SIDI engines by injecting the fuel late after the inlet valve closes (IVC), thereby improving the volumetric efficiency drop [162,[206][207][208][209][210]. When fuel is injected after the inlet valve closes (IVC), the air-breathing capacity of the engine does not get influenced by the type of fuel.…”

Compressed Natural Gas Direct Injection: Comparison Between Homogeneous and Stratified Combustion

“…Using the CNGDI engine installed on a test bed, experimental investigations can be performed in order to study the performance and exhaust emissions of homogenous mixture and stratiied mixture [12].…”

“…The main factor afecting the brake torque is the lack of chemical energy conversion to mechanical energy, which is strongly related to volumetric eiciency, fuel mixing, net heat release rate and cylinder pressure [12].…”