Crank Angle Degrees Research Articles

Experimental study of combustion and emissions characteristics of low blend ratio of 2-methylfuran/ 2-methyltetrahyrofuran with gasoline in a DISI engine

The nearing depletion of fossil fuels and the possible consequences of its emissions on the global climate has prompted a worldwide probe for their alternatives. 2-methylfuran and 2-methyltetrahydrofuran are considered promising alternative fuels for spark ignition engines. In this study, the combustion and emission characteristics of low blending ratio MF20 (2-methylfuran 20 %, gasoline 80 % by volume) and MTHF20 (2-methyltetrahydrofuran 20 %, gasoline 80 % by volume) were first implemented and compared to neat gasoline in a single-cylinder direct injection spark ignition engine. The combustion performance of the test fuels was analyzed across a range of loads from 3.5 to 8.5 bar indicated mean effective pressure and fuel injection timings between 180 and 280 crank angle degrees before top dead center. Meanwhile, the compositions of the hydrocarbon emissions were experimentally investigated using the Fourier Transform Infrared Spectroscopy technique. Results show that MF20 exhibits advanced spark timing flexibility of 8 and 7 crank angle degrees before top dead center compared to the unleaded gasoline and MTHF20 respectively at the peak load. MTHF20 exhibits the highest maximum cylinder pressure at medium load compared to other fuels but drops sharply at peak load accompany with the audible knock. Additionally, MTHF20 exhibits specific fuel consumption advantage over MF20 across the entire load range. The unburned furan of the total hydrocarbon emissions was recorded to be 3 % of total hydrocarbon emissions. The concept of low blending ratio furan-based fuel proposed could provide a solution for the transition period of carbon neutrality.

Investigation of fuel temperature and injection timing effects on ammonia direct injection in an optical engine

This work investigates the effects of fuel temperature and injection timing on ammonia direct injection in an optical engine using a multi-hole injector. Flash-boiling may occur over various engine-relevant conditions due to ammonia’s high vapor pressure. This phenomenon impacts spray characteristics and, in severe cases, facilitates cavitation inside the nozzle. Both fuel temperature and injection timing (i.e., ambient conditions during injection) impact the intensity of flash-boiling during fuel injection. Therefore, this work varies fuel temperature (from 320K to 388K) and injection timing (from −60CADaTDC (crank angle degrees after top dead center) to −6CADaTDC) to assess their impact on injection mass flux, discharge coefficients, and macroscopic spray characteristics using an ammonia injection pressure of 200bar. For this purpose, the injection mass is measured by analyzing exhaust gas compositions during engine operation with ammonia injections but without combustion. In addition, diffuse background illumination (DBI) images capture the liquid phase of the fuel spray to characterize spray behavior. The findings reveal that increasing fuel temperature decreases ammonia’s injection mass by up to 12.8% but has little impact on discharge coefficients for late injection timings and high in-cylinder pressures. However, discharge coefficients decrease by up to 17.4% (from 0.58 to 0.48) for early injection timings if fuel temperatures are high. The individual sprays of the 6-hole GDI injector may collapse into a uniform spray at high-density conditions without flash-boiling or under strongly flash-boiling conditions. The findings clarify the impact of ammonia’s high vapor pressure on injection mass and prove the relevance of different spray collapse mechanisms in ammonia direct injection engines.

Computational study on the impact of gasoline-ethanol blending on autoignition and soot/NOx emissions under low-load gasoline compression ignition conditions

In the present work, computational fluid dynamics (CFD) simulations of a single-cylinder gasoline compression ignition (GCI) engine are performed to investigate the impact of gasoline-ethanol blending on autoignition, nitrogen oxide (NOx), and soot emissions under low-load conditions. In order to represent the test gasoline (RD5-87), a four-component toluene primary reference fuel (TPRF)+ethanol (ETPRF) surrogate (with 10% ethanol by volume; E10) is employed. A three-dimensional (3D) engine CFD model employing finite-rate chemistry with a skeletal kinetic mechanism (including NOx sub-mechanism), adaptive mesh refinement (AMR), and hybrid method of moments (HMOM) is adopted to capture the in-cylinder combustion phenomena and soot/NOx emissions. The engine CFD model is validated against experimental data for three gasoline-ethanol blends: E10, E30 and E100, with varying ethanol content by volume. Model validation is carried out for a broad range of start-of-injection (SOI) timings (−21, −27, −36, and −45 crank angle degrees (°CA) after top-dead-center (aTDC)) with respect to in-cylinder pressure, heat release rate, combustion phasing, NOx and soot emissions. For relatively later injection timings (−21 and −27 °CA aTDC), E30 yields higher amount of soot than E10; while the trend reverses for early injection cases (−36 and −45 °CA aTDC ). On the other hand, E100 yields the lowest amount of soot among all fuels irrespective of SOI timing. Further, E10 shows a non-monotonic trend in soot emissions with SOI timing: SOI-36>SOI-45>SOI-21>SOI-27, while soot emissions from E30 exhibit monotonic decrease with advancing SOI timing. NOx emissions from various fuels follow a trend of E10>E30>E100. On the other hand, NOx emissions increase as SOI timing is advanced for all fuels, with an anomaly for E10 and E100 where NOx decreases when SOI is advanced beyond −36 °CA aTDC. Detailed analysis of the numerical results is performed to investigate the soot/NOx emission trends and elucidate the impact of chemical composition and physical properties on autoignition and emissions characteristics.

Numerical investigation of the effects of adding different gases on the performance and emissions of an ammonia-hydrogen dual-fuel engine

As an alternative to fossil fuels, there is growing interest in using ammonia in combustion systems, particularly in internal combustion engines. As a competent competitor to hydrogen, it has various advantages. However, adding an ignition promoter such as hydrogen is still necessary to maintain combustion stability. Since the engine using ammonia also suffers from high NOx emissions, in this study, the effects of adding different gases on the performance and emissions of an ammonia-hydrogen dual-fuel engine were numerically investigated. The base engine was a diesel engine whose parameters were accustomed to running with ammonia-hydrogen as fuel. Hydrogen was injected via the port in the intake stage at 180 crank angle degrees (CAD) and mixed with the cylinder charge. Ammonia was directly injected into the cylinder at 350–370 CAD. Different gasses, including argon, nitrogen, carbon dioxide, and oxygen, were injected into the cylinder at various crank angles before, during, and after ammonia injection (330–350 CAD, 350–370 CAD, and 370–390 CAD). A MATLAB code was prepared to solve the governing equations, and the combustion mechanism was implemented in Cantera. The results showed that adding CO2 before or concurrent with the ammonia injection timing had undesirable impacts on the peak in-cylinder pressure and NO and NO2 emissions. The O2 addition had a negative on the emissions. Adding N2 and Ar concurrently with the ammonia injection (350–370 CAD) could diminish NO and NO2 emissions without drastically affecting the peak in-cylinder pressure and temperature.

Effect of injection timings and injection pressure on knock mitigation with a compression stroke injection of hydrous ethanol in spark ignition

Direct injection fuel systems provide precise control over the amount of fuel injected and can enable higher compression ratio operation and earlier combustion phasing under knock-limited operation, particularly for fuels with a high cooling potential like hydrous ethanol, a blend of 92% ethanol and 8% water. Moving a portion of the total fuel mass from an intake stroke injection to a compression stroke injection can provide a knock suppression benefit, which can enable more efficient operation. In this work, the influence of injection pressure on this split injection spark ignition strategy is examined. The effect of injection pressure on two intake stroke injections were characterized, with an injection pressure of 200 bar improving combustion efficiency by ∼3 percentage points and advancing knock-limited CA50 by 1 crank angle degree over an injection pressure of 30 bar. Then, a compression stroke injection was introduced and swept into the compression stroke while maintaining the two intake stroke injections. Direct injections at an injection pressure of 30 bar enabled a small knock intensity reduction of ∼20%, whereas an injection pressure of 200 bar enabled a larger reduction of ∼90% in knock intensity. The spark timing advance permitted by the reduction in knock intensity with a compression stroke injection timing of −80 degrees after top dead center was 0.3 and 2.0 degrees at an injection pressure of 30 and 200 bar, respectively. Then, the second intake stroke injection was varied at 200 bar to evaluate how the stratification profile prior to the compression stroke injection impacted its ability to reduce knock intensity. It was found that compression stroke injections with an early second intake stroke injection was effective at reducing knock intensity throughout the compression stroke. As the second intake stroke injection was retarded, the early compression stroke injections became less effective at suppressing knock.

Investigation of gas exchange parameters of small two stroke engine correlated with hydrogen fuel supplement

Due to the lack of complete dedicated suction and exhaust strokes and obviate the need of valvetrain assembly in two stroke engines, the bottom surface of the piston and the crankcase is used as a scavenging pump leads to that about one fifth of the fresh charge is short-circuited to the exhaust results in very high hydrocarbon emissions and poor fuel consumption. It is suggested that a combination of gasoline and hydrogen could be a superior solution combining the advantages of both engine itself and hydrogen doping. An accurate amount of hydrogen that has high flame propagation speed blended with gasoline could provide faster combustion of fuel mixture over the few crank angle degrees in the short gas exchange process reducing short-circuited charge with little modifications to the engine system. In this paper hydrogen-gasoline blend as an alternative fuel in a 63.3 cc, air cooled single cylinder, crankcase scavenged two stroke engine is tested. The unseen decommissioning of small two stroke engine in near future, the attractiveness of studying alternative fuel specially hydrogen and absence of investigation of the effect of hydrogen fuel supplement on gas exchange parameters molded this paper.

Effects of operating parameters on start performance of compression ignition engine by using high-pressure direct-injection pure methanol fuel

Methanol was one of the research hotspots in internal combustion engines over recent years. The application of methanol is a promising approach to transport decarbonization due to low carbon content. However, the utilization of methanol in compression ignition (CI) engines faces some challenges as a result of low reactivity and high latent heat of vaporization, such as cold start and operation stability. Furthermore, the impact mechanisms of operating parameters on cold start and operation stability in CI engine have not been understood deeply. In this work, the effects of operating parameters on average cycle of start and coefficient of speed variation (CoVspeed) of idle were studied on a CI engine fueled by pure methanol fuel. Results show that the injection strategy of the minimum average starting cycle number is the pre-main injection, which includes lower injection pressure, −4 °CA ATDC (degree crank angle after top dead center) main timing, smaller pre mass, and larger pre-main interval. The injection strategy of the minimum CoVspeed of idle is the pilot-pre-main injection, which includes lower injection pressure, −4 °CA ATDC main timing, smaller pre mass, larger pre-main interval, smaller pilot mass, and shorter pilot-main interval. Under the same operating conditions, the average cycle of start is 12 and 5 for methanol and diesel respectively. The CoVspeed of idle is 6.72% and 0.53% for methanol and diesel respectively. When coolant temperature is 30 °C, the minimum intake temperature is 120 °C. Upon adjusting the coolant temperature to 80 °C, the minimum intake temperature decreases to 80 °C.

Numerical and experimental analysis of the combustion in a Single-Cylinder research engine with passive TJI pre-chamber operating with hydrated ethanol

Advanced ignition systems, such as turbulent jet ignition, have the capacity to improve the combustion process of internal combustion engines, increasing fuel conversion efficiency and reducing emissions, especially when applied with ethanol biofuel. Technologies that take advantage of the local energy potential, taking into account the geographic, demographic and social characteristics of each country, increase the diversity of solutions for the sustainable future of the transport sector. The present work aims to develop a system with a passive pre-chamber operating in turbulent jet ignition mode, applied to a single-cylinder research engine with a stoichiometric air–fuel mixture of ethanol. Numerical simulations were carried out and experimentally validated applying the commercial software CONVERGE CFD. The results showed that the optimized configuration presented higher fuel conversion efficiency, when compared to conventional spark ignition, thus producing greater savings per kilometer driven and lessing the dependence on fossil fuels. The pre-chambers with both lateral holes and a central hole showed a maximum NOx reduction of 5.9 g/kWh, reducing the second half of combustion by 6.2 crank angle degrees and the first half of combustion by up to 1.8 crank angle degrees compared to SI. This indicates a potential for increasing the compression ratio for pre-chamber configurations without the occurrence of knock. Furthermore, there is a direct relationship between the quenching of the jets after exiting the pre-chamber holes and turbulence, with quenching occurring when turbulent kinetic energy was greater than 15000 m2/s2.

Optimization of Combustion Cycle Energy Efficiency and Exhaust Gas Emissions of Marine Dual-Fuel Engine by Intensifying Ammonia Injection

The capability of operational marine diesel engines to adapt to renewable and low-carbon fuels is considered one of the most influential methods for decarbonizing maritime transport. In the medium and long term, ammonia is positively valued among renewable and low-carbon fuels in the marine transport sector because its chemical elemental composition does not contain carbon atoms which lead to the formation of CO2 emissions during fuel combustion in the cylinder. However, there are number of problematic aspects to using ammonia in diesel engines (DE): in-tensive formation of GHG component N2O; formation of toxic NOx emissions; and unburnt toxic NH3 slip to the exhaust system. The aim of this research was to evaluate the changes in combustion cycle parameters and exhaust gas emissions of a medium-speed Wartsila 6L46 marine diesel engine operating with ammonia, while optimizing ammonia injection intensity within the limits of Pmax, Tmax, and minimal engine structural changes. The high-pressure dual-fuel (HPDF) injection strategy for the D5/A95 dual-fuel ratio (5% diesel and 95% ammonia by energy value) was investigated within the liquid ammonia injection pressure range of 500 to 2000 bar at the identified optimal injection phases (A −10° CAD and D −3° CAD TDC). Increasing ammonia injection pressure from 500 bar (corresponding to diesel injection pressure) in the range of 800–2000 bar determines the single-phase heat release characteristic (HRC). Combustion duration decreases from 90° crank angle degrees (CAD) at D100 to 20–30° CAD, while indicative thermal efficiency (ITE) increases by ~4.6%. The physical cyclic deNOx process of NOx reduction was identified, and its efficiency was evaluated in relation to ammonia injection pressure by relating the dynamics of NOx formation to local combustion temperature field structure. The optimal ammonia injection pressure was found to be 1000 bar, based on combustion cycle parameters (ITE, Pmax, and Tmax) and exhaust gas emissions (NOx, NH3, and GHG). GHG emissions in a CO2 equivalent were reduced by 24% when ammonia injection pressure was increased from 500 bar to 1000 bar. For comparison, GHG emissions were also reduced by 45%, compared to the diesel combustion cycle.

Experimental and cfd analysis of the influence of fuel injection timing on the behavior of a gasohol-based gdi engine

ABSTRACT This work examines the impact of FIT (Fuel Injection Timing) on engine’s performance of an automotive, Gasoline Direct Injection (GDI) engine using Gasohol (85% Gasoline + 15% Ethanol by mass) as fuel. The start of FIT was experimentally varied from −280 CAD (Crank Angle Degrees) to −330 CAD at 10 CAD intervals by using an open ECU. Experiments were performed at variable power outputs (such as 5, 8, 10, 13, 16, 18 and 21 kW) at a constant speed of 2500 rpm. CFD simulations were carried out for the above said conditions to understand engine’s behavior. Considering the conventional start of injection, advancing the FIT showed improvement the BTE (brake thermal efficiency) up to −320 CAD BTDC. The maximum BTE was observed as 31.8% at the engine power output of 21 kW (whereas it was 28.6% at −300°CAD). CFD results confirmed the improvement in the air-fuel mixing rate and swirl motion. With the use of advanced FITs, the emissions of carbon monoxide (CO) and hydrocarbons (HC) were decreased. The CFD emission results for CO and HC showed good agreement with the experimental findings. With the advanced FITs, NOx emissions showed an increase at all loads. The in cylinder pressure was observed to be higher with advanced FITs. Modeling results are very well supported with experimental pressures. It is concluded that advancing the fuel injection timing might improve the performance and lower HC and CO emissions of a Gasohol-based GDI engine. The optimized injection timing of −320 CAD could be recommended for the aforementioned engine’s greatest performance.

Machine Learning-Based Modeling and Predictive Control of Combustion Phasing and Load in a Dual-Fuel Low-Temperature Combustion Engine

<div>Reactivity-controlled compression ignition (RCCI) engine is an innovative dual-fuel strategy, which uses two fuels with different reactivity and physical properties to achieve low-temperature combustion, resulting in reduced emissions of oxides of nitrogen (NO<sub>x</sub>), particulate matter, and improved fuel efficiency at part-load engine operating conditions compared to conventional diesel engines. However, RCCI operation at high loads poses challenges due to the premixed nature of RCCI combustion. Furthermore, precise controls of indicated mean effective pressure (IMEP) and CA50 combustion phasing (crank angle corresponding to 50% of cumulative heat release) are crucial for drivability, fuel conversion efficiency, and combustion stability of an RCCI engine. Real-time manipulation of fuel injection timing and premix ratio (PR) can maintain optimal combustion conditions to track the desired load and combustion phasing while keeping maximum pressure rise rate (MPRR) within acceptable limits.</div> <div>In this study, a model-based controller was developed to track CA50 and IMEP accurately while limiting MPRR below a specified threshold in an RCCI engine. The research workflow involved development of an imitative dynamic RCCI engine model using a data-driven approach, which provided reliable measured state feedback during closed-loop simulations. The model exhibited high prediction accuracy, with an <i>R</i><sup>2</sup> score exceeding 0.91 for all the features of interest. A linear parameter-varying state space (LPV-SS) model based on least squares support vector machines (LS-SVM) was developed and integrated into the model predictive controller (MPC). The controller parameters were optimized using genetic algorithm and closed-loop simulations were performed to assess the MPC’s performance. The results demonstrated the controller’s effectiveness in tracking CA50 and IMEP, with mean average errors (MAE) of 0.89 crank angle degree (CAD) and 46 kPa and Mean absolute percentage error (MAPE) of 9.7% and 7.1%, respectively, while effectively limiting MPRR below of 10 bar/CAD. This comprehensive evaluation showcased the efficacy of the model-based control approach in tracking CA50 and IMEP while constraining MPRR in the dual-fuel engine.</div>

The Neutronic Engine: A Platform for Operando Neutron Diffraction in Internal Combustion Engines

<div>Neutron diffraction is a powerful tool for noninvasive and nondestructive characterization of materials and can be applied even in large devices such as internal combustion engines thanks to neutrons’ exceptional ability to penetrate many materials. While proof-of-concept experiments have shown the ability to measure spatially and temporally resolved lattice strains in a small aluminum engine on a timescale of minutes over a limited spatial region, extending this capability to timescales on the order of a crank angle degree over the full volume of the combustion chamber requires careful design and optimization of the engine structure to minimize attenuation of the incident and diffracted neutrons to maximize count rates. We present the design of a “neutronic engine,” which is analogous to an optical engine in that the materials and external geometry of a typical automotive engine have been optimized to maximize access of the diagnostic while maintaining the internal combustion chamber geometry and operability of the engine. The high transparency of aluminum to neutrons makes it the ideal window material for neutron diagnostics, which allows the neutronic engine to be a truly all-metal engine with the same load and boundary condition capabilities of a modern downsized passenger car engine. The neutronic engine will enable 3D and time-resolved measurements of strain, stress, and temperature fields as well as phase transformation, texture, and microstructure throughout the metal components of the combustion chamber.</div>

Impact of engine control variables on low load combustion efficiency and exhaust emissions of a methane-diesel dual fuel engine

A conventional diesel engine when operated in the reactivity-controlled compression ignition (RCCI) combustion strategy faces challenges of high total hydrocarbon (THC) and carbon monoxide (CO) emissions leading to poor combustion efficiency at low engine loads. The oxides of nitrogen (NOx) versus smoke trade-off, encountered in conventional diesel combustion, is replaced by the NOx-THC trade-off in the RCCI operation. This work focuses on addressing the NOx-THC trade-off issue by systematically investigating the effects of engine control variables, such as, fuel injection timing, exhaust gas recirculation (EGR) and intake throttling, on a light duty compression ignition engine running in a methane-diesel dual fuel mode. The engine is operated at a load of 3 bar gross indicated mean effective pressure and at a speed of 1500 rev/min. Based on relationships identified between engine control variables, combustion parameters, emissions and engine performance, a bottom-up approach is used to combine the control variables synergistically to improve the NOx-THC trade-off. A combination of advanced start of injection timing of diesel (−35 degree crank angle (°CA) after top dead centre), 50% premix ratio and 55% EGR levels along with the end of port fuel injection of methane in the middle of the intake stroke (−270°CA), has resulted in a ∼34 percentage points (from 56% to 90%) improvement in combustion efficiency and a ∼9.5 percentage points improvement in thermal efficiency compared to the baseline low load dual fuel operation while maintaining good combustion stability. THC emission is reduced from 105 to ∼25 g/kWh whilst maintaining low levels of NOx (<0.3 g/kWh).

The Effects of Multistage Fuel-Oxidation Chemistry, Soot Radiation, and Real Gas Properties on the Operation Process of Compression Ignition Engines

The objectives of the study are to reveal the influence of multistage fuel-oxidation chemistry, thermal radiation of soot during the combustion of a small (submillimeter size) fuel droplet, and real gas effects on the operation process of compression ignition engines. The use of the multistage oxidation chemistry of iso-octane in the zero-dimensional approximation reveals the appearance of different combinations of cool, blue, and hot flames at different compression ratios and provides a kinetic interpretation of these phenomena that affect the heat release function. Cool flames are caused by the decomposition of alkyl hydroperoxide, during which a very reactive radical, OH, is formed. Blue flames are caused by the decomposition of H2O2 with the formation of OH. Hot flames are caused by the chain branching reaction between atomic hydrogen and molecular oxygen with the formation of OH and O. So-called “double” cool flames correspond to the sequential appearance of a separated cool flame and a low-intensity blue flame rather than two successive cool flames. The use of a one-dimensional model of fuel droplet heating, evaporation, autoignition, and combustion at temperatures and pressures relevant to compression ignition engines shows that the thermal radiation of soot during the combustion of small (submillimeter size) droplets is insignificant and can be neglected. The use of real gas caloric and thermal equations of state of the matter in a three-dimensional simulation of the operation process in a diesel engine demonstrates the significant effect of real gas properties on the engine pressure diagram and on the NO and soot emissions: real gas effects reduce the maximum pressure and mass-averaged temperature in the combustion chamber by about 6 and 9%, respectively, increases the autoignition delay time by a 1.6 crank angle degree, increase the maximum heat release rate by 20%, and reduce the yields of NO and soot by a factor of 2 and 4, respectively.

THE INFLUENCE OF INTAKE VALVE CLOSE TIMING ON THE ENVIRONMENTAL PERFORMANCE OF A SPARK IGNITION ENGINE USING GASOLINE AND NATURAL GAS

The tightening of environmental requirements has forced car manufacturers to look for various ways to reduce exhaust gas emissions. The existing structural solutions of internal combustion engines allow this type of pollution to be reduced by adjusting the intake valve timing. This is especially relevant when it comes to reducing spark ignition engine emissions when using natural gas as fuel. In this study, a wide range of intake valve timing adjustments from 24° to 54° every six crank angle degrees was taken at a constant engine speed (n = 2500 rpm) and different loads and fixed excess air ratios (λ = 1). The changes in oxygen (O2), carbon monoxide (CO), carbon dioxide (CO2), nitrous oxide (NOx), methane (CH4), and propane (C3H8) gas emissions were observed in the aforementioned intake valve timing range.

Experimental and Numerical Evaluation of an HCCI Engine Fueled with Biogas for Power Generation under Sub-Atmospheric Conditions

Energy transition to renewable sources and more efficient technologies is needed for sustainable development. Although this transition is expected to take a longer time in developing countries, strategies that have been widely explored by the international academic community, such as advanced combustion modes and microgeneration, could be implemented more easily. However, the implementation of these well-known strategies in developing countries requires in-depth research because of the specific technical, environmental, social, and economic conditions. The present research relies on the use of biogas-fueled HCCI engines for power generation under sub-atmospheric conditions provided by high altitudes above sea level in Colombia. A small air-cooled commercial Diesel engine was modified to run in HCCI combustion mode by controlling the air–biogas mixture temperature using an electric heater at a high speed of 1800 revolutions per minute. An experimental setup was implemented to measure and control the most important experimental variables, such as engine speed, biogas flow rate, intake temperature, crank angle degree, intake pressure, NOx emissions, and in-cylinder pressure. High intake temperature requirements of around 320 ∘C were needed to achieve stable HCCI combustion; the maximum net indicated mean effective pressure (IMEPn) was around 1.5 bar, and the highest net indicated efficiency was close to 32%. Higher intake pressures and the addition of ozone to the intake mixture were numerically studied as ways to reduce the intake temperature requirements for stable HCCI combustion and improve engine performance. These strategies were studied using a one-zone model along with detailed chemical kinetics, and the model was adjusted using the experimental results. The simulation results showed that the addition of 500 ppm of ozone could reduce the intake temperature requirements by around 50 ∘C. The experimental and numerical results achieved in this research are important for the design and implementation of HCCI engines running biogas for microgeneration systems in developing countries which exhibit more difficult conditions for HCCI combustion implementation.

Thermodynamic analysis of heat transfer reduction in spark ignition using thermal barrier coatings

This work uses a 0D thermodynamic engine model coupled to a 1D surface temperature solver to study the potential of low thermal inertia thermal barrier coatings (TBCs) on combustion chamber surfaces to increase the efficiency of spark ignition engines. Under ideal conditions, coating the piston crown, head, and valve faces with a TBC with a thermal inertia of 640 J/m2 K s1/2 resulted in less than a 1% relative improvement in efficiency. Despite using a low thermal inertia coating to avoid open cycle charge heating, the reduction in closed cycle heat transfer, which is the pathway to increasing efficiency, increased knock propensity. Therefore, any efficiency gain through closed cycle heat transfer reduction in spark ignition is offset by the need to retard spark timing to counter knock. An exergy analysis of completely blocking heat transfer for a 10 crank-angle degree window showed that on a low compression engine, like those used for stoichiometric gasoline spark ignition, the maximum efficiency gain achievable was limited compared to a higher compression ratio engine. Furthermore, the high gas temperatures of stoichiometric operation mean that even state-of-the-art TBCs cannot elevate surface temperatures enough purely through temperature swing to achieve a significant reduction in heat transfer near top dead center, where work availability is highest. Overall, these results indicate that low thermal inertia TBCs are ill-suited for achieving an efficiency benefit in spark ignition through a heat transfer reduction pathway. Instead spark ignition TBC research should explore ways to use low thermal inertia TBCs to achieve open cycle charge cooling to reduce knock propensity.

Experimental investigation of ethanol diesel dual fuel DI diesel engine

This paper investigates the combustion and performance characteristics of an ethanol – diesel dual fuel direct injection diesel engine. An air-cooled constant speed single cylinder diesel engine was operated with dual fuel mode in which ethanol was injected in the inlet manifold and diesel was injected inside the cylinder. An electronic fuel injection system operated by LabView software was used to inject the ethanol. Virtual instrumentation principle was used to generate output pulses for triggering ethanol injection. Diesel fuel was injected by conventional mechanical fuel injection system. The engine was loaded by an eddy current dynamometer. A piezoelectric pressure pickup with charge amplifier connected to PC based data acquistion system recorded cylinder pressure data at every crank angle interval. A crank angle degree marker measures the crank angle position for every crank angle. Tests were conducted on the engine in diesel and ethanol – diesel dual fuel mode. The cylinder pressure traces were used to calculate the heat release rates and combustion parameters. Optimum ethanol quantity was injected at every operating point. An AVL five-gas analyzer was used to measure the different exhaust pollutants. The smoke emission was measured by an AVL smoke meter in Hatridge equivalent percentage. Experimental results show that 40% of diesel can be replaced by ethanol at full load and there was 5.5% reduction in specific energy consumption. Also it was found that 32% reduction in smoke level (Opacity) and 25% reduction in NOx emissions at full load operating condition. It was also observed that the engine was running smoothly without knocking.

Effects of injection pressure and timing on low load low temperature gasoline combustion using LES

Low Temperature Gasoline Combustion is a novel combustion strategy that employs the use of a fuel like gasoline whose autoignition characteristics are sensitive to varying concentrations of fuel. It has the potential to dramatically reduce nitrogen oxide (NOx) and soot emissions relative to conventional combustion modes with similar thermal efficiency and has the added production benefit of using a widely available fuel. To address efficiency at low loads, a single direct injection (S-DI) is used that stratifies the fuel enough to get sufficient combustion performance. But with the increased fuel stratification, there is the potential to create undesirable fuel distributions that could increase harmful NOx emissions. This work uses three-dimensional computational fluid dynamics (3D-CFD) to investigate the effects of injection parameters including injection pressure, start of injection timing, and intake valve closing temperature on this S-DI strategy using a medium-duty engine at two low load conditions. A computational model was developed and validated to experimental data collected on this engine using Large Eddy Simulations turbulence modeling to resolve the complex flow phenomena and turbulent mixing prevalent in this combustion strategy.Injection pressure was increased in six increments from 120 bar to 342 bar at constant start of injection (SOI) of 45 crank angle degrees before top dead center and the effects on performance and emissions are analyzed at two load operating conditions of 2 and 3 bar. Then, at each injection pressure, the start of injection timing was delayed to analyze its impact on combustion performance. The tradeoffs for performance and emissions with these injection parameters are explored along with suggestions for further investigations to improve this S-DI injection process.

Combustion characteristics of a turbocharged direct-injection hydrogen engine

The direct injection hydrogen internal combustion engines avoid backfires and have a higher power density, especially when coupled with a turbocharger. However, while previous researches have focused on specific aspects of direct injection hydrogen internal combustion engines, their whole combustion characteristics remain largely unclear. Therefore, this study aims to comprehensively investigate the combustion characteristics of turbocharged direct injection hydrogen internal combustion engines across the entire operating map in order to optimize their performance. The combustion characteristics are hypothesized to be significantly influenced by operating parameters, including the equivalence ratio, spark timing, start of injection, and other relevant factors. To achieve this, the experiments were conducted on a 2.0 L turbocharged direct injection hydrogen internal combustion engine, covering a wide range of operating conditions. Specifically, the engine speeds varied from 1000 to 4000 rpm, loads ranged from 3.7 to 10.6 bar, equivalence ratios spanned from 0.33 to 0.71, spark timing was adjusted within a range of 21 degrees of crank angle, and start of injection varied within a range of 80 degrees of crank angle. The experimental results reveal notable findings regarding the turbocharged direct injection hydrogen internal combustion engine. For instance, the maximum pressure rise rate of the turbocharged direct injection hydrogen internal combustion engine (3.85 bar/°CA at 1500 rpm) at various engine speeds at wide open throttle are greater than those of a turbocharged port fuel injection hydrogen internal combustion engine and a gasoline engine. Furthermore, variations in equivalence ratio and spark timing cause significant increases in pressure rise rate by 328.4% and 233.3%, respectively. The peak pressure rise rate characteristics provide valuable insights for optimizing the noise, vibration and harshness of turbocharged direct injection hydrogen internal combustion engines. Additionally, the burning duration demonstrates an initial increase and subsequent decrease with changes in the start of injection, aiding in the determination of the optimal start of injection for achieving high brake thermal efficiency. Overall, this research provides valuable insights into the macroscopic combustion characteristics of a turbocharged direct injection hydrogen internal combustion engine across different operating conditions. These findings not only can be directly applied to hydrogen internal combustion engines of the same displacement and type, but also can be applied to the design and development of hydrogen internal combustion engines with different displacements and types.