Start Of Main Injection Research Articles

Numerical Investigation and Multi-Objective Optimization of Internal EGR and Post-Injection Strategies on the Combustion, Emission and Performance of a Single Cylinder, Heavy-Duty Diesel Engine

This work presents a numerical study that investigates the optimum post-injection strategy and internal exhaust gas recirculation (iEGR) application with intake valve re-opening (2IVO) aiming to optimize the brake specific nitric oxide (bsNO) and brake specific soot (bsSoot) trade-off with reasonable brake specific fuel consumption (BSFC) via 1D engine cycle simulation. For model validation, single and post-injection test results obtained from a heavy-duty single cylinder diesel research engine were used. Then, the model was modified for 2IVO application. Following the simulations performed based on Latin hypercube DoE; BSFC, bsNO and bsSoot response surfaces trained by feedforward neural network were generated as a function of the injection (start of main injection, post-injection quantity, post-injection dwell time) and iEGR (2IVO dwell) parameters. After examining the effect of each parameter on pollutant emission and engine performance, multi-objective pareto optimization was performed to obtain pareto optimum solutions in the BSFC-bsNO-bsSoot space for 8.47 bar brake mean effective pressure (BMEP) load and 1500 rpm speed condition. The results show that iEGR and post-injection can significantly reduce NO and soot emissions, respectively. The soot oxidation capability of post-injection comes out only if it is not too close to the main injection and its efficiency and effective timing are substantially affected by iEGR rate and main injection timing. It could also be inferred that by the combination of iEGR and post-injection, NO and soot could be reduced simultaneously with a reasonable increase in BSFC if start of main injection is phased properly.

Split Injection Strategies for Biodiesel-Fueled Premixed Charge Compression Ignition Combustion Engine—Part II: Particulate Studies

Abstract In this study, experiments were performed in a single-cylinder research engine to investigate the particulate matter (PM) characteristics of the engine operated in premixed charge compression ignition (PCCI) mode combustion vis-a-vis baseline compression ignition (CI) mode combustion using three test fuels, namely, B20 (20% v/v biodiesel blended with mineral diesel), B40 (40% v/v/ biodiesel blended with mineral diesel), and baseline mineral diesel. The experiments were carried out at constant fuel injection pressure (FIP) (700 bar), constant engine speed (1500 rpm), and constant fuel energy input (0.7 kg/h diesel equivalent). PM characteristics of PCCI mode combustion were evaluated using two different fuel injection strategies, namely, single pilot injection (SPI) (35 deg before top dead center (bTDC)) and double pilot injection (DPI) (35 deg and 45 deg bTDC) at four different start of main injection (SoMI) timings. Results showed that both PCCI mode combustion strategies emitted significantly lower PM compared to baseline CI mode combustion strategy. However, the blending of biodiesel resulted in relatively higher PM emissions from both CI and PCCI combustion modes. Chemical characterization of PM showed that PCCI mode combustion emitted relatively lower trace metals compared to baseline CI mode combustion, which reduced further for B20. For detailed investigations of particulate structure, morphological characterization was done using transmission electron microscopy (TEM), which showed that PM emitted by B20-fueled PCCI mode combustion posed potentially lower health risk compared to baseline mineral diesel-fueled CI mode combustion.

Split Injection Strategies for Biodiesel-Fueled Premixed Charge Compression Ignition Combustion Engine—Part I: Combustion, Performance, and Emission Studies

Abstract In this study, a single-cylinder research engine was used to investigate the comparative combustion, performance, and emissions characteristics of the engine in a premixed charge compression ignition (PCCI) mode combustion vis-a-vis baseline compression ignition (CI) mode combustion using three test fuels, namely, B20 (20% v/v biodiesel blended with mineral diesel), B40 (40% v/v biodiesel blended with mineral diesel), and mineral diesel. For both combustion modes, experiments were performed at constant fuel injection pressure (FIP, 700 bar), engine speed (1500 rpm), and fuel energy input (0.7 kg/h diesel equivalent). PCCI mode combustion experiments were performed at four different start of main injection (SoMI) timings using two different pilot fuel injection strategies, namely, single pilot injection (SPI, 35 deg before top dead center (bTDC)) and double pilot injection (DPI, 35 deg, and 45 deg bTDC). Results showed that advancing SoMI timing for both CI and PCCI combustion modes resulted in knocking; however, the DPI strategy resulted in relatively lesser knocking compared with the SPI strategy. The performance of PCCI mode combustion was relatively inferior compared with baseline CI mode combustion; however, biodiesel blends slightly improved the performance of PCCI mode combustion. Overall, this study shows that the PCCI mode combustion operating load range can be improved by using the DPI strategy.

Fuel Injection Strategy for Utilization of Mineral Diesel-Methanol Blend in a Common Rail Direct Injection Engine

AbstractMethanol fueled internal combustion (IC) engines have attracted significant attention due to their contributions in reducing environmental pollution and fossil fuel consumption. In this study, a single-cylinder research engine was operated on MD10 (10% (v/v) methanol blended with mineral diesel) and baseline mineral diesel to explore an optimized fuel injection strategy for efficient combustion and reduced emissions. The experiments were conducted at constant engine speed (1500 rpm) and load (3 kW) using two different fuel injection strategies, namely, single pilot injection (SPI) and double pilot injection (DPI) strategy. For each pilot fuel injection strategy, the start of main injection (SoMI) timing was varied from −3 to 6° crank angle (CA) before top dead center (bTDC). To examine the effect of fuel injection pressure (FIP), experiments were performed at three different FIPs (500, 750, and 1000 bars). Results showed that the MD10 fueled engine resulted in superior combustion compared with baseline mineral diesel, which was further improved by DPI at higher FIPs. The use of DPI strategy was found to be more effective at higher FIPs, resulting in higher brake thermal efficiency (BTE), lower exhaust gas temperature (EGT), and reduced oxides of nitrogen (NOx) emissions compared with SPI strategy. Detailed investigations showed that the addition of methanol in mineral diesel reduced particulates, especially the accumulation mode particles (AMP). Different statistical analysis and qualitative correlations between fuel injection parameters showed that higher FIP and advanced SoMI timings were suitable for particulate reduction from the MD10 fueled engine.

Influences of biodiesel fuels produced from highly degraded waste animal fats on the injection and emission characteristics of a CRDI diesel engine

In the current study, biodiesel fuels produced from waste chicken fat and waste fleshing oil with high free fatty acid were tested in a four stoke, four-cylinder, water-cooled, turbocharged-intercooled, common rail direct injection (CRDI) diesel engine. Their effects on the injection and exhaust emission characteristics of the test engine were determined and compared with those of petroleum-based diesel fuel (DF) as the reference fuel. Engine tests were performed at different engine loads and constant engine speed of 2000 rpm. Injection characteristics showed differences with respect to engine load and fuel type. However, the effects of biodiesel fuels on the injection profiles were more dominant for main injection characteristics such as the start of main injection, end of the main injection, injection amount and injection rate and these effects became more pronounced with increasing engine load. Compared to DF, animal fat based biodiesels had better total hydrocarbon (THC) and carbon monoxide (CO) emissions, but their carbon dioxide (CO2) and especially nitrogen oxides (NOx) emissions were higher. In addition, waste fleshing oil-based biodiesel fuel emitted lower emissions than waste chicken fat-based biodiesel.

Evaluation of Fuel Injection Strategies for Biodiesel-Fueled CRDI Engine Development and Particulate Studies

Fuel injection parameters such as fuel injection pressure (FIP) and start of main injection (SoMI) timings significantly affect the performance and emission characteristics of a common rail direct injection (CRDI) diesel engine. In this study, a state-of-the-art single cylinder research engine was used to investigate the effects of fuel injection parameters on combustion, performance, emission characteristics, and particulates and their morphology. The experiments were carried out at three FIPs (400, 700, and 1000 bar) and four SoMI timings (4 deg, 6 deg, 8 deg, and 10 deg bTDC) for biodiesel blends [B20 (20% v/v biodiesel and 80% v/v diesel) and B40 (40% v/v biodiesel and 60% v/v diesel)] compared to baseline mineral diesel. The experiments were performed at a constant engine speed (1500 rpm), without pilot injection and exhaust gas recirculation (EGR). The experimental results showed that FIP and SoMI timings affected the in-cylinder pressure and the heat release rate (HRR), significantly. At higher FIPs, the biodiesel blends resulted in slightly higher rate of pressure rise (RoPR) and combustion noise compared to baseline mineral diesel. All the test fuels showed relatively shorter combustion duration at higher FIPs and advanced SoMI timings. The biodiesel blends showed slightly higher NOx and smoke opacity compared to baseline mineral diesel. Lower particulate number concentration at higher FIPs was observed for all the test fuels. However, biodiesel blends showed emission of relatively higher number of particulates compared to baseline mineral diesel. Significantly lower trace metals in the particulates emitted from biodiesel blend fueled engine was an important finding of this study. The particulate morphology showed relatively smaller number of primary particles in particulate clusters from biodiesel exhaust, which resulted in relatively lower toxicity, rendering biodiesel to be more environmentally benign.

The influence of pilot injection on high-temperature ignition processes and early flame structure in a high-speed direct injection diesel engine

Simultaneous high-speed natural luminosity and OH* chemiluminescence imaging is used to characterize high-temperature ignition processes in conventional diesel combustion with a pilot-main injection strategy in a single-cylinder, light-duty optical diesel engine. High-speed imaging provides temporally and spatially resolved information in terms of high-temperature ignition processes and flame structure during the combustion. Using these imaging measurements, the high-temperature inflammation and the diffusion flame development processes are analyzed. The chemiluminescence signal shows a hot, reactive mixture, which gradually decreases after the peak release of the pilot combustion and lasts long after the apparent heat release has ended. Therefore, when the reactive pilot mixture exists near the main injection jets, the high-temperature ignition of the main injection is apparently initiated through interactions with the reactive pilot mixture. High-temperature autoignition, another process by which ignition of the main injection occurs, is observed in main injection plumes where the chemiluminescence signal of the reactive pilot mixture becomes very weak or is absent at the start of main injection. As the reaction of the main injection continues, the non-premixed main injection jet structure is developed and the high-temperature reacting region expands throughout the jet.

Fuel-Injection Strategy for PCCI Engine Fueled by Mineral Diesel and Biodiesel Blends

Premixed-charge compression ignition (PCCI) combustion is a novel combustion concept, whereby a partially homogeneous fuel–air mixture burns predominantly in a premixed combustion phase, which results in lower emissions of nitrogen oxides (NOx) and particulates. This experimental study explored the possibility of PCCI combustion using three test fuels, namely, 20% (v/v) biodiesel blended with mineral diesel (B20), 40% (v/v) biodiesel blended with mineral diesel (B40), and baseline mineral diesel. To investigate the combustion, performance, and emission characteristics of the PCCI engine, experiments were performed in a single-cylinder research engine equipped with a common rail direct injection (CRDI) system. The effects of the fuel-injection pressure (FIP) and the timing of the start of main injection (SoMI) were investigated by varying the FIP from 400 to 1000 bar and the SoMI timing from 12° to 24° bTDC, respectively. Detailed investigations of the particulate morphology, particulate number–size distri...

Effect of fuel injection parameters on combustion stability and emissions of a mineral diesel fueled partially premixed charge compression ignition (PCCI) engine

This experimental study focuses on developing new combustion concept for compression ignition (CI) engines by achieving partially homogeneous charge, leading to low temperature combustion (LTC). Partially premixed charge compression ignition (PCCI) combustion is a single-stage phenomenon, with combustion shifting towards increasingly premixed combustion phase, resulting in lower in-cylinder temperatures. PCCI leads to relatively lower emissions of oxides of nitrogen (NOx) and particulate matter (PM) simultaneously. To investigate combustion, performance and emission characteristics of the PCCI engine, experiments were performed in a mineral diesel fueled single cylinder research engine, which was equipped with flexible fuel injection equipment (FIE). Effects of fuel injection pressure (FIP) were investigated by changing the FIP from 400bar to 1000bar. Experiments were carried out by varying start of main injection (SoMI) timings (from 12° to 24° before top dead center (bTDC)), when using single pilot injection. This experimental study included detailed investigations of particulate characteristics such as particulate number-size distribution using engine exhaust particle sizer (EEPS), particulate bound trace metal analysis using inductively coupled plasma-optical emission spectrometer (ICP-OES), and soot morphology using transmission electron microscopy (TEM). PCCI combustion improved with increasing FIP (up to 700bar) due to superior fuel atomization however further increasing FIP deteriorated PCCI combustion and engine performance due to intense knocking. NOx and PM emissions were also found to be lowest at 700bar FIP. Moreover, count mean diameter (CMD) of particulate was maximum at 700bar FIP. Therefore, medium FIP (700bar) was the most suitable FIP for PCCI combustion.

Effect of split fuel injection and EGR on NOx and PM emission reduction in a low temperature combustion (LTC) mode diesel engine

In this study, an advanced combustion concept ‘premixed charge compression ignition’ (PCCI) has been explored for application in diesel engines. PCCI combustion is a single-stage combustion process, in which a large fraction of fuel burns in premixed combustion phase resulting in relatively lower in-cylinder temperatures compared to compression ignition (CI) combustion. However at high loads, PCCI combustion results in severe knocking and higher oxides of nitrogen (NOx) emissions. This limits the applicability of this combustion concept up to medium engine loads. This limitation of PCCI combustion can be resolved by altering in-cylinder pressure-temperature history at the time of fuel injection. This can also be resolved by deploying suitable split fuel injection strategy and exhaust gas recirculation (EGR), which control combustion events such as start of combustion (SoC) and combustion phasing, leading to lower knocking and NOx emissions. To investigate the effects of various split injection strategies and EGR on PCCI combustion, engine experiments were conducted at different start of main injection (SoMI) timings (12, 16, 20 and 24° bTDC), start of pilot injection (SoPI) timings (30, 35 and 40° bTDC) and EGR rates (0, 15 and 30%). This study also included detailed particulate characterization such as particulate number-size distribution using an engine exhaust particle sizer (EEPS) and particulate bound trace metal analysis by inductively coupled plasma-optical emission spectrophotometry (ICP-OES). PCCI combustion was found to be superior at 35° bTDC SoPI timing and 15% EGR. At retarded SoPI timing (30° bTDC), PCCI combustion resulted in slightly higher NOx and particulate emissions, however at too advanced SoPI timing (40° bTDC), PCCI combustion showed relatively inferior engine performance. Application of EGR improved PCCI combustion and emission characteristics, however at high EGR, PCCI combustion resulted in inferior engine performance due to reduction in bulk in-cylinder temperatures. Overall, this study showed that PCCI combustion stability, knocking and NOx emissions can be optimized by selecting suitable combination of SoMI and SoPI timings, and EGR rate.

Experimental investigations of the effect of pilot injection on performance, emissions and combustion characteristics of Karanja biodiesel fuelled CRDI engine

Pilot and post injections are being used in modern diesel engines for improving engine performance in addition to meeting stringent emission norms. Biodiesel produced from different feedstocks is gaining global recognition as partial replacement for mineral diesel in compression ignition (CI) engines. In this study, 10%, 20% and 50% Karanja biodiesel blends were used for investigation of pilot injections, injection pressures and injection timings on biodiesel blends. Experiments were carried out in a single cylinder CRDI research engine in multiple injection mode at 500 and 1000 bar fuel injection pressure (FIP) under varying start of pilot injection (SOPI) and start of main injection (SOMI) timings. Brake specific fuel consumption (BSFC) increased with increasing Karanja biodiesel concentration in test fuels however brake thermal efficiency (BTE) of biodiesel blends was slightly higher than mineral diesel. Lower biodiesel blends showed lower brake specific carbon monoxide (BSCO) and brake specific hydrocarbon (BSHC) emissions than mineral diesel. Brake specific nitrogen oxides (BSNOx) emissions from KOME20 and KOME10 were higher than mineral diesel. Combustion duration of KOME50 was also higher than mineral diesel.

Diesel Engine performance improvement in a 1-D engine model using Particle Swarm Optimization

AbstractA particle swarm optimization (PSO) technique was implemented to improve the engine development and optimization process to simultaneously reduce emissions and improve the fuel efficiency. The optimization was performed on a 4-stroke 4-cylinder GT-Power based 1-D diesel engine model. To achieve the multi-objective optimization, a merit function was defined which included the parameters to be optimized: Nitrogen Oxides (NOx), Nonmethyl hydro carbons (NMHC), Carbon Monoxide (CO), Brake Specific Fuel Consumption (BSFC). EPA Tier 3 emissions standards for non-road diesel engines between 37 and 75 kW of output were chosen as targets for the optimization. The combustion parameters analyzed in this study include: Start of main Injection, Start of Pilot Injection, Pilot fuel quantity, Swirl, and Tumble. The PSO was found to be very effective in quickly arriving at a solution that met the target criteria as defined in the merit function. The optimization took around 40-50 runs to find the most favourable engine operating condition under the constraints specified in the optimization. In a favourable case with a high merit function values, the NOx+NMHC and CO values were reduced to as low as 2.9 and 0.014 g/kWh, respectively. The operating conditions at this point were: 10 ATDC Main SOI, -25 ATDC Pilot SOI, 0.25 mg of pilot fuel, 0.45 Swirl and 0.85 tumble. These results indicate that late main injections preceded by a close, small pilot injection are most favourable conditions at the operating condition tested.