High Brake Mean Effective Pressure Research Articles

Combustion and emission characteristics of ammonia-hydrogen fueled SI engine with high compression ratio

Ammonia combustion offers the advantage of zero carbon emissions. However, its high ignition energy requirement and slow flame propagation limit its use as an engine fuel. Employing a technological approach that combines a high compression ratio with spark ignition can be beneficial for enhancing ammonia combustion, and this approach warrants further in-depth research. This study investigates the combustion of ammonia within a spark-ignition engine with a compression ratio of 15:1. It enhances combustion by introducing hydrogen as a reactivity-enhancing fuel. Both ammonia and hydrogen are introduced into the engine's intake port. The findings suggest that efficient pure ammonia combustion occurs at low engine speeds (1000 r/min) and high brake mean effective pressure (BMEP exceeding 0.6 MPa). Pure ammonia combustion achieves a brake thermal efficiency of 33.7% at a BMEP of 0.94 MPa. Introducing hydrogen at an energy ratio of 2–16% expands the engine's load range. With hydrogen blending, the efficiency rises to 35.8% at a BMEP of 0.63 MPa. The research on NOx emissions reveals that, under specific operating conditions, there is a reduction reaction between unburned ammonia and NOx, leading to a decrease in NOx emissions as BMEP increases. This study can offer support for the application of ammonia engines.

Study on Hydrogen Direct Injection in RNG Combustion under Various Ignition Timings for Power Generation in a Retrofitted Gas Engine

Renewable natural gas (RNG) is attractive for energy policy goals in the world. Therefore, a regional system is designed to explore RNG combustion for power generation in localities. This study investigates a direct injection (DI) engine fueled with hydrogen (H2) blended into the simulated renewable natural gas, which consists of 50% methane (CH4) and 50% carbon dioxide (CO2) in volume. In order to obtain higher efficiency, comparisons between DI and port fuel injection (PFI) of H2 addition were made. Then, the volume percentage of H2 was changed from 20% to 100% by keeping the volume ratio of CH4 and CO2 at 1:1. Finally, results of power output, brake mean effective pressure (BMEP), brake thermal efficiency (BTE) and brake specific fuel consumption (BSFC) were discussed. Results showed that in contrast to PFI, H2 DI injection could increase efficiency by 4%. Additionally, H2 DI could retard the MBT ignition timing at 5 °CA. Compared with CH4/CH4 + CO2 combustion, under stoichiometric combustion, BMEP increases with H2 addition but BTE decreases significantly. However, by enlarging the excess air ratio (λ) to 1.24, both BMEP and BTE increase obviously with H2 addition. Moreover, when λ < 1.3, the MBT ignition timing should be advanced from −10 to 15 °CA top dead center (TDC). But the MBT ignition timing is fixed at −25 °CA TDC when λ is larger than 1.3. Furthermore, if efficiency is the priority, 30% H2 addition with λ at 1.24 (−15 °CA TDC) should be selected. If higher BMEP is preferred, 20% H2 addition with λ at 0.99 (−10 °CA TDC) should be selected.

An experimental study of various load control strategies for an ammonia/hydrogen dual-fuel engine with the Miller cycle

Hydrogen and ammonia, as two renewable carbon-free combustibles, are considered to be potentially excellent alternative fuels for internal combustion engines. Since hydrogen and ammonia have opposite and complementary combustion characteristics, the co-combustion of ammonia with hydrogen is reasonable. However, there are few detailed experimental studies of load control strategies for an ammonia‑hydrogen engine. In this study, four load control strategies including the variation of ammonia volume share (AVS), qualitative control, quantitative control, and adjustment of intake variable valve timing (VVT) are proposed and assessed for their applicability in an ammonia/hydrogen dual-fuel engine. The ignition and combustion characteristics of ammonia do not allow for high thermal efficiency, so the Miller cycle is introduced to improve engine performance. The engine employs fuel supply modes of ammonia port injection and hydrogen direct injection at 1500 rpm. In general, the engine achieves higher brake mean effective pressure (BMEP) and brake thermal efficiency (BTE) at different AVS. Moreover, qualitative control and adjustment of intake VVT allow the engine to own a wide regulation range of BMEP and maintain the BTE of more than 37% under most conditions. However, quantitative control appears to be an inadequate strategy for the engine due to the lower BMEP and BTE.

Partially premixed combustion of diesel-di-ethyl ether blends in light-duty commercial engine

Diethyl ether (DEE) has evolved as a potential alternative for partial diesel replacement in compression ignition (CI) engines. In this study, a light-duty commercial diesel engine was operated in partially premixed combustion (PPC) mode. This work investigated the engine characteristics with lower and higher DEE-diesel blends in PPC mode. The split ratio and the start of the main injection (SoMI) timings were maintained at 70:30 (Main: Pilot) and 9° bTDC, respectively, while the start of the pilot injection (SoPI) timing was varied from 25 to 40° bTDC. The performance, combustion, and regulated emission characteristics of the PPC engine were compared with the conventional diesel combustion (CDC) mode as a baseline. The PPC mode exhibited higher/ comparable brake thermal efficiency (BTE) than the baseline CDC mode. The DEE-diesel blends exhibited higher BTE than the diesel in PPC mode generally. The DEE40 showed greater improvement in BTE than DEE20 at lower brake mean effective pressure (BMEP). PPC mode fuelled with diesel and diesel-DEE blends showed lower brake specific fuel consumption (BSFC) than baseline CDC mode at lower BMEP, but it was comparable at higher BMEP. PPC mode showed higher carbon monoxide (CO) emissions than baseline CDC mode. CO emissions increased with advancing SoPI timing for all BMEPs, except 5.6 bar. Although, the PPC mode exhibited higher hydrocarbon (HC) emissions than the CDC mode. Diesel-DEE blends showed slightly higher HC emissions than diesel in PPC mode at lower engine BMEPs. NOx emissions in the PPC mode were 1.5 to 2 times the baseline CDC mode. This indicated that the PPC mode engine performance requires further optimization similar to CDC mode, which had optimized exhaust gas recirculation (EGR), and significantly reduced the nitrogen oxide (NOx) emissions.

Comparative Analysis of Combustion Behaviors and Emission Characteristics of Diesel Engines Fueled with Biodiesel or Biodiesel Blends

In this study, we carried out an experimental analysis of combustion behaviors and emission characteristics of pure biodiesel and biodiesel–dimethyl ether (DME) blends and determined the impacts of the biodiesel ratio and the nozzle parameter on the combustion pressure characteristics in the time domain/frequency domain and emission characteristics. The findings show that with a decrease in the biodiesel proportion in biodiesel–DME blends, the maximum combustion pressure and fuels in the premixed combustion stage decrease with a retarded maximum value phase, but the maximum heat release in diffusive combustion increases and the maximum amplitude of pressure rise acceleration decreases. All of the pressure level curves of BD100, BD80, and BD50 contain a rapid decrease stage 1, a slow decrease stage 2, and a fluctuating stage 3. With a decrease in the biodiesel proportion, the exhaust gas temperature, NOx emissions, and smoke emissions of BD100, BD80, and BD50 decrease gradually. Compared with a 5 × 0.43 mm nozzle, the maximum combustion pressure and maximum heat release rate of BD50 for a 4 × 0.35 mm nozzle were higher and the phase of the maximum value was advanced. Soot emissions for the 4 × 0.35 mm nozzle were lower, which is especially obvious under a high brake mean effective pressure (BMEP).

Experimental investigation on performance of hydrogen additions in natural gas combustion combined with CO2

Natural gas with H2 is widely used for lean-burn combustion, which leads to NOx emission as the main problem for it. For decreasing NOx emission and increasing thermal efficiency, the investigation on seeking the influence of H2 fractions on the mixture of CH4 and CO2 was conducted. Firstly, the ignition timing was decided through thermal efficiency and brake mean effective pressure (BMEP) for CH4 only. Then, combustion characteristics of CH4, CH4+CO2 and CH4+CO2+H2 were compared with volume percentage of H2 changing from 5% to 30%. Finally, the H2 injection strategy was checked between closed and open valve injections. Among these discussions, thermal efficiency, power output, BMEP and fuel consumption were evaluated. Results show that CO2 addition decreases power output and BMEP, leading to much more fuel consumption and lower thermal efficiency. When H2 is added, at the rich mixture conditions (λ＜1.0), power output and thermal efficiency decrease sharply as the mixture is enriched. However, at the lean-burn conditions (λ＞1.0), the decrease in flow rate of lower heating value (LHV) and increase in power output finally result in the higher efficiency with H2 addition. Moreover, when λ＞1.0, both low fuel consumption and high efficiency can be obtained with H2 addition to achieve the high BMEP. Furthermore, the open valve injection could obtain higher thermal efficiency, power output and BMEP with lower fuel consumption, suggesting that the H2 injection strategy should be well controlled with the ignition timing.

DEVELOPMENT OF OFF-DESIGN TURBOCHARGER MODELLING COMBINED WITH 1-D ENGINE MODEL

The present work aims to carry out an off-design turbocharger modellingpowered by exhaust gases from a Wärtsilä 20V34SG engine. First of all, 1-D engine model was already developed in GT-Power software whileconsidering a thermodynamic turbocharger modelling with constantisentropic efficiencies. Secondly, by using the results from 1-D enginemodel, the off-design turbocharger modelling is calibrated separately inEES software, taking into account compressible assumption, trianglevelocities and geometric dimensions. The case study is derived from a R&Dproject (ANEEL PD-06483-0318/2018) that targets to cool and dehumidifythe intake air at compressor’s upstream through a cooling coil, therebyallowing engine’s operation at reduced knocking conditions. The brakemean effective pressure (BMEP) is varied in the range of 20 to 23.45 bar,corresponding to brake power from 8.7 to 10.2 MW, respectively. With theoff-design turbocharger modelling it is possible to analyze its operationalbehavior under higher BMEP, hence, allowing to predict some importantparameters. The results showed that the turbocharger is operating within themanufacturer’s limit for BMEP of 23.45 bar, presenting total-to-staticisentropic efficiencies of 0.81 and 0.784 for compressor and turbine,respectively, rotational speed around 28135 RPM, pressure ratio atcompressor of 4.567 and maintaining control on waste-gate valve.

Experimental investigation on combustion characteristics in dual-fuel dual-injection engine

Dual-injection strategy combined with dual-fuel can provide flexible and instantaneous blend ratios according to engine demands under different operating conditions. Furthermore, ethanol direct injection has the potentials to increase the engine compression ratio and thermal efficiency by taking advantages of ethanol fuel such as the high octane number and latent heat. Therefore, in order to maximize the charge cooling effect, a dual-fuel (gasoline and ethanol) dual-direct injection system is proposed and investigated in this paper. In current work, different injection modes in terms of knock suppression and combustion performance are compared and studied on a single-cylinder SI engine with stoichiometric air/fuel ratios. The results show that the new injection strategy of dual-fuel dual-direct injection mode can significantly expand engine load compared with conventional modes of gasoline direct injection plus ethanol port injection and ethanol direct injection plus gasoline port injection. Direct injection ethanol mode can reduce knocking tendency. However, with higher brake mean effective pressure, dual-fuel dual-injection mode shows higher knock tendency. Dual-fuel dual-injection mode can increase brake mean effective pressure and thermal efficiency simultaneously. However, the brake thermal efficiency behavior is non-linear when increasing brake mean effective pressure and direct injection ethanol mass fraction. The equivalent heat value brake specific fuel consumption decreases with the increase of direct injection ethanol ratio, and dual-fuel dual-injection mode has superior fuel conversion efficiency. Relatively high maximum pressure can be found in dual-fuel dual-injection mode. With the increase of ethanol ratio, the combustion phasing is further advanced, resulting in better combustion, which contributes to higher thermal efficiency.

Experimental investigation on the knocking combustion characteristics of n-butanol gasoline blends in a DISI engine

n-Butanol is a very competitive alternative biofuel for spark ignition (SI) engines given its many advantages. Current researches are mainly concentrated on the overall combustion and emissions performance concerning the feasibility of n-butanol gasoline blends in SI engines. In this work, focus was given on the knocking combustion characteristics of operation with pure n-butanol as well as a blend fuel with 20% volume content of n-butanol (Bu20), which was investigated experimentally in a direct-injection spark ignition (DISI) single cylinder engine. Operation condition is fixed at a constant engine speed of 1500r/min, using three throttle openings with stoichiometric air–fuel ratio. Spark timing was swept to achieve different knocking levels. The results of n-butanol and Bu20 were benchmarked against those obtained by the research octane number (RON) 92 commercial gasoline. Compared with the baseline fuel gasoline, neat n-butanol shows better anti-knock ability with more advanced knock limited spark timing, whereas slightly deteriorative knock resistance can be found for Bu20. It is hypothesized Bu20 has higher end gas temperature due to its higher brake mean effective pressure (BMEP) and faster burning rate compared with gasoline, which indicates the knock tendency depends not only on the fuel octane number, but also on the factors that affect the end gas thermodynamic state. The heavier knock propensity of Bu20 is furthermore confirmed by its more advanced knock onset and higher peak oscillation pressure. Results of fast fourier transform (FFT) indicate the knocking oscillation frequencies are mainly determined by the combustion chamber resonance modes. Statistics probability distribution and cumulative distribution are applied to evaluate the knock intensity variation for each fuel.

Octane Response in a Downsized, Highly Boosted Direct Injection Spark Ignition Engine

Increasingly strict government emissions regulations in combination with consumer demand for high performance vehicles is driving gasoline engine development towards highly downsized, boosted direct injection technologies. In these engines, fuel consumption is improved by reducing pumping, friction and heat losses, yet performance is maintained by operating at higher brake mean effective pressure. However, the in-cylinder conditions of these engines continue to diverge from traditional naturally aspirated technologies, and especially from the Cooperative Fuels Research engine used to define the octane rating scales. Engine concepts are thus key platforms with which to screen the influence of fundamental fuel properties on future engine performance. ‘ULTRABOOST’, a collaborative research project which is co-funded by the Technology Strategy Board (TSB), the UK's innovation agency, is a downsized, highly boosted, 2.0L in-line 4 cylinder prototype engine, designed to achieve 35% CO2 emissions reduction without compromising the performance of a 5.0L V8 naturally aspirated production engine. To probe engine response to fuel, a matrix of 14 formulations was tested at several engine conditions. This is the first in a series of fuel related papers and focuses on the engine's response to the research octane number (RON). The knock limited spark advance was determined for a series of fuels with RON varying from 95 to 112; octane was shown to provide 5 or 10° crank angle advance in knock limited spark advance at 2000 and 3000 rpm, respectively. This study demonstrates that fuel octane quality continues to be important for the performance of emerging downsized engine technologies. Furthermore, the trend for continued engine downsizing will increase the potential performance benefit associated with knock resistant fuels.

Analysis of Ignition Behavior in a Turbocharged Direct Injection Dual Fuel Engine Using Propane and Methane as Primary Fuels

Dual fuel engine combustion utilizes a high-cetane fuel to initiate combustion of a low-cetane fuel. The performance and emissions benefits (low NOx and soot emissions) of dual fuel combustion are well-known. Ignition delay (ID) of the injected high-cetane fuel plays a critical role in quality of the dual fuel combustion process. This paper presents experimental analyses of the ID behavior for diesel-ignited propane and diesel-ignited methane dual fuel combustion. Two sets of experiments were performed at a constant engine speed (1800 rev/min) using a four-cylinder direct injection diesel engine with the stock electronic conversion unit (ECU) and a wastegated turbocharger. First, the effects of fuel–air equivalence ratios (Фpilot ∼ 0.2–0.6 and Фoverall ∼ 0.2–0.9) on IDs were quantified. Second, the effects of gaseous fuel percent energy substitution (PES) and brake mean effective pressure (BMEP) (from 2.5 to 10 bars) on IDs were investigated. With constant Фpilot (>0.5), increasing Фoverall with propane initially decreased ID but eventually led to premature propane auto-ignition; however, the corresponding effects with methane were relatively minor. Cyclic variations in the start of combustion (SOC) increased with increasing Фoverall (at constant Фpilot) more significantly for propane than for methane. With increasing PES at constant BMEP, the ID showed a nonlinear trend (initially increasing and later decreasing) at low BMEPs for propane but a linearly decreasing trend at high BMEPs. For methane, increasing PES only increased IDs at all BMEPs. At low BMEPs, increasing PES led to significantly higher cyclic SOC variations and SOC advancement for both propane and methane. Finally, the engine ignition delay (EID), defined as the separation between the start of injection (SOI) and the location of 50% of the cumulative heat release, was also shown to be a useful metric to understand the influence of ID on dual fuel combustion. Dual fuel ID is profoundly affected by the overall equivalence ratio, pilot fuel quantity, BMEP, and PES. At high equivalence ratios, IDs can be quite short, and beyond a certain limit, can lead to premature auto-igniton of the low-cetane fuel (especially for a reactive fuel like propane). Therefore, it is important to quantify dual fuel ID behavior over a range of engine operating conditions.

Design and Development of a New Landfill/Biogas Engine Oil for Modern, High BMEP Natural Gas Engines

The use of higher brake mean effective pressure (BMEP) engines in landfill or alternative gas applications has dramatically increased in the past few years. Operators are using these engines due to their ability to provide lower emissions, coupled with improved economics for the end user due to the higher density or power output capability compared to an engine of similar size and displacement. Landfill gas (LFG) quality can vary greatly, along with the contaminant level due to the composition of the landfill. This environment poses unique challenges to both the engine and the engine oil, including shorter oil drain intervals, corrosive attack of engine components, with increased piston and combustion chamber deposits, to name but a few. Maintaining longer oil drain intervals minimizes unscheduled oil drains, which can decrease the overall cost of the landfill operation. High BMEP engines provide higher power output, however,at the cost of increased maintenance in severe fuel applications. Excessive piston crown and combustion chamber deposits from landfill gas impurities can have a deleterious effect on engine emissions, which may lead to the inability to meet local emissions regulations. Engine lubricants must provide adequate oil life along with minimizing deposit related issues that may negatively impact regular scheduled maintenance cycles, thus reducing engine downtime and increasing revenues. Traditionally, the approach has been that oils formulated for landfill applications used excess base reserve to sufficiently neutralize the acids being formed during the combustion process. Unfortunately, this approach increases the sulfated ash content of the lubricant, which lends itself to increased ash deposits and negatively impacts the combustion dynamics of these high BMEP engines, which are sensitive to ash deposition. Based upon requests for a longer life lubricant without compromising deposit control characteristics to serve landfill applications, a new product development project was specifically targeted for late model, high BMEP engines, which are prone to detonation and sensitive to ash related deposits. This paper presents the development bench testing, and proof of performance field evaluations of a new generation, low ash landfill gas engine oil.

Combustion behaviour of a heavy duty common rail marine Diesel engine fumigated with propane

This paper presents results from the testing of a heavy duty common rail marine Diesel engine with electronically controlled two stage liquid fuel injection, operating under load on a test bench with propane mixed into the inlet air at various rates. Results are presented for a range of engine loads, with brake mean effective pressure up to 22bar at 1800rpm. The electronic engine control unit is not modified and allowed to respond to the addition of propane according to its inbuilt map. This results in retarded injection timing with increased propane addition at some test points. At each test point, constant engine speed and brake torque are maintained for various rates of propane addition. Cylinder pressure and the injector activation voltage are recorded with a high speed data acquisition system. Apparent heat release rate is calculated from the measured cylinder pressure. At high rates of propane addition very high pressure rise rates and severe knock are measured. At the high brake mean effective pressure conditions tested, knock limits propane supply rates to less than 20% by energy. Small increases in thermal efficiency are indicated with moderate rates of propane addition. Exhaust emissions of NOx, CO, HC and smoke are measured. CO, HC and smoke emissions increase significantly with increasing propane addition. For high propane supply rates, two distinct peaks in heat release rate are measured. Analysis is made of the flammability of the propane–air mixtures at the elevated temperatures at the end of the compression stroke, using the modified Burgess–Wheeler Law. At propane supply rates greater than 25%, the propane–air mixture is flammable in its own right at compression temperature. The apparent heat release rate, fuel injection timing and flammability data allow analysis of the mechanism of the combustion process with propane fumigation.

Energy Recovery in Passenger Cars

The turbocharged direct injection stoichiometric spark ignition gasoline engine has less than diesel full load brake engine thermal efficiencies and much larger than diesel penalties in brake engine thermal efficiencies reducing the load. This engine has, however, a much better power density, and therefore may operate at much higher brake mean effective pressure (BMEP) values over driving cycles thus reducing the fuel economy penalty of the vehicle. This engine also has the advantage of the very well developed three way catalytic (TWC) converter after treatment to meet future emission regulations. Replacement of fossil gasoline with renewable gasoline-like fuels has major advantages. Ethanol and methanol have larger than gasoline resistance to knock and heat of vaporization, and this ultimately translates in larger than gasoline compression ratio and boost pressure and spark advances closer to maximum brake torque producing better efficiencies both full and part load. For the specific of these novel turbocharged direct injection stoichiometric spark ignition renewable gasoline-like engines coupled to a hybrid-electric power train, the paper considers the option to boost the total fuel conversion efficiency generating both mechanical and electric energy. When the internal combustion engine operates, significant fuel energy is lost in both the exhaust and the coolant. Part of this energy is recovered here by using organic Rankine cycle (ORC) systems fitted to both the exhaust and the coolant, with their expanders driving generators charging the battery of the car. The exhaust and the coolant organic Rankine cycle are effective in increasing the amount of fuel energy converted in usable power over the full range of loads and speeds. The organic Rankine cycle system fitted on the exhaust permits to increase the usable power versus the fuel energy flow rate of a 3.4% on average, with top improvements up to 6.4%. The system is effective particularly at high speeds and loads. The organic Rankine cycle system fitted on the coolant permits to increase the usable power versus the fuel energy flow rate of a 1.7% on average, with top improvements up to 2.8%. The system is effective particularly at low speeds and loads. The two combined organic Rankine cycle systems permit to increase the usable power versus the fuel energy flow rate of a 5.1% on average, with top improvements up to 8.2%.

On Comparative Performance Testing of Prechamber and Open Chamber Laser Ignition

Laser ignition is a potential ignition technology to achieve reliable lean burn ignition in high brake mean effective pressure (BMEP) internal combustion engines. The technology has the potential to increase brake thermal efficiency and reduce exhaust emissions. This submission reports on engine testing of a Caterpillar G3516C stationary natural gas fueled engine with three types of ignition approaches: (i) nonfueled electric prechamber plug with electrodes at the base of the prechamber, (ii) nonfueled laser prechamber plug with laser spark in the middle of the prechamber, and (iii) open chamber plug with laser spark in the main chamber. In the second configuration, a stock nonfueled prechamber plug was modified to incorporate a sapphire window and a focusing lens to form a laser prechamber plug. A 1064 nm Q-switched Nd:YAG laser was used to create laser sparks. For these tests, a single cylinder of the engine was retrofitted with the laser plug while the remaining cylinders were run with conventional electric ignition system at baseline ignition timing of 24 deg before top dead center (BTDC). The performances of the three plugs were compared in terms of indicated mean effective pressures (IMEP), mass burn fraction duration and coefficient of variation (COV) of IMEP, and COV of peak pressure location. Test data show comparable performance between electric and laser prechamber plugs, albeit with a lower degree of variability in engine’s performance for electric prechamber plug compared to the laser prechamber plug. The open chamber plug exhibited poorer variability in engine performance. All results are discussed in the context of prechamber and engine fluid mechanics.

Effects of charge temperature and exhaust gas re-circulation on combustion and emission characteristics of an acetylene fuelled HCCI engine

In this work, experiments were conducted on a homogeneous charge compression ignition (HCCI) engine with acetylene as the sole fuel at different power outputs. Initially, the intake air was heated to different temperatures in order to determine the optimum level at every output. Charge temperatures needed were in the range of 40–110 °C from no load to a BMEP (Brake Mean Effective Pressure) of 4 bar. Subsequently, exhaust gas re-circulation (EGR) was done at the identified charge temperatures and brake thermal efficiency was found to improve. At high BMEPs, use of EGR led to knocking. Thus, fine control over charge temperature and EGR quantity is needed at these conditions. Nitric oxide and smoke levels were very low. However, HC levels were high at about 1700–2700 ppm. Brake thermal efficiencies were comparable to or even better than the compression ignition mode of operation.

Hydrous ethanol vs. gasoline-ethanol blend: Engine performance and emissions

This work compares the performance and emissions from a production 1.0-l, eight-valve, and four-stroke engine fuelled by hydrous ethanol (6.8% water content in ethanol) or 78% gasoline-22% ethanol blend. The engine was tested in a dynamometer bench in compliance with NBR/ISO 1585 standard. The performance parameters investigated were torque, brake mean effective pressure (BMEP), brake power, specific fuel consumption (SFC), and thermal efficiency. Carbon monoxide (CO), carbon dioxide (CO 2), hydrocarbons (HC) and oxides of nitrogen (NO X ) exhaust emissions levels are also presented. The results showed that torque and BMEP were higher when the gasoline-ethanol blend was used as fuel on low engine speeds. On the other hand, for high engine speeds, higher torque and BMEP were achieved when hydrous ethanol fuel was used. The use of hydrous ethanol caused higher power at high engine speeds, whereas, for low engine speeds, both fuels produced about the same power. Hydrous ethanol produced higher thermal efficiency and higher SFC than the gasoline-ethanol blend throughout all the engine speed range studied. With regard to exhaust emissions hydrous ethanol reduced CO and HC, but increased CO 2 and NO X levels.

Homogeneous charge compression ignition versus dual fuelling for utilizing biogas in compression ignition engines

In this work, biogas was used in a compression ignition (CI) engine in the homogeneous charge compression ignition (HCCI) mode as well as in the dual-fuel mode together with diesel. In the HCCI mode, the charge temperature and amount of diesel injected into the intake manifold were used to control combustion. The presence of carbon dioxide in biogas suppresses the high heat release rates normally encountered in neat-diesel-fuelled HCCI engines. Efficiencies close to diesel operation together with extremely low levels of nitric oxide (NO) and smoke were attained in a brake mean effective pressure (BMEP) range from 2.5bar to 4bar in the biogas—diesel homogeneous charge compression ignition (BDHCCI) mode. Proper control over the charge temperature was essential. Thermal efficiency was higher and NO, hydrocarbon, carbon monoxide, and smoke levels were lower than in the biogas—diesel dual-fuel mode. Thus, the BDHCCI mode is a viable option for using biogas in CI engines in the medium-load ranges. Operation of the engine in the CI mode with diesel below a BMEP of 2.5bar, then in the HCCI mode up to a BMEP of 4bar, and in the dual-fuel mode at higher BMEPs could lead to good overall performance and low emissions.

Combustion characteristics of a direct-injection engine fueled with natural gas–hydrogen blends under different ignition timings

In this paper, combustion characteristics of a direct-injection spark-ignited engine fueled with natural gas–hydrogen blends under various ignition timings and lean mixture condition were investigated. The results show that the ignition timing has significant influence on engine performance, combustion and emissions. The time intervals between the end of fuel injection and ignition timing are very sensitive to direct-injection gas engine combustion. The turbulence in combustion chamber generated by the fuel jet maintains high and relatively strong mixture stratification is presented when decreasing the time intervals between the end of injection and the ignition timing, giving fast burning rate, high brake mean effective pressure, high thermal efficiency and short combustion durations. For specific ignition timing, the brake mean effective pressure and the effective thermal efficiency increase and combustion durations decrease with the increase of hydrogen fraction in natural gas. Exhaust HC concentration decreases and exhaust NO x concentration increase with advancing the ignition timing while the exhaust CO gives little variation under various ignition timings.

ディーゼルエンジンの最新技術 新中速ディーゼル機関シリーズの開発と実績 ２２ＨＬＸ，２８ＨＬＸ，３４ＨＬＸ

The circumstances of medium speed diesel engine have been severe to keep up with the environmental problem such as global warming or IMO regulation. To adapt the market trend, the authors developed a series of“Neo”medium speed diesel engines, model 22HLX, 28HLX and 34HLX. This paper describes design features, development processes and principal inspection results of these engines. On the development, extensive cost analysis of existing engines was made to realize extremely low cost/output rate. Performance simulation, FEM analysis, 3D module planning and component tests were also carried out. As the result, the engines having high reliability and friendly handling with advantageous performance were developed. These engines achieved high output with increasing power rate (24.5MPa⋅m/s) as the product of high brake mean effective pressure (2.45MPa) and increased mean piston speed (10m/s) . High thermal efficiency was achieved by prolonged piston stroke, soft-Miller-cycle and high performance radial turbocharger. Lightweight mono-block piston and compound oil-groove big-end bearing, for example, were the key components to realize such high output engines. Concurrent engineering and virtual factory production were applied by means of unity administration of allied factories. First productions were successfully launched from 1998 to 1999, and the longest running hours reached over 18000 hours in October of 2001. The FOC, LOC and exhaust gas temperature was at low level as expected. At the first principal inspection, the piston top land and piston ring grooves were far clean rather than previous engines. Piston and cylinder liner condition was perfect.