INITIAL RESULTS ON A NEW LIGHT-DUTY 2.7L OPPOSED-PISTON GASOLINE COMPRESSION IGNITION MULTI-CYLINDER ENGINE

Gasoline compression ignition (GCI) is a cost-effective approach to achieving diesel-like efficiencies with low emissions. The fundamental architecture of the two-stroke Achates Power Opposed-Piston Engine (OP Engine) enables GCI by decoupling piston motion from cylinder scavenging, allowing for flexible and independent control of cylinder residual fraction and temperature leading to improved low load combustion. In addition, the high peak cylinder pressure and noise challenges at high-load operation are mitigated by the lower BMEP operation and faster heat release for the same pressure rise rate of the OP Engine. These advantages further solidify the performance benefits of the OP Engine and emonstrate the near-term feasibility of advanced combustion technologies, enabled by the opposed-piston architecture. This paper presents initial results from a steady state testing on a brand new 2.7L OP GCI multi-cylinder engine designed for light-duty truck applications. Successful GCI operation calls for high compression ratio, leading to higher combustion stability at low-loads, higher efficiencies, and lower cycle HC+NOX emissions. Initial results show a cycle average brake thermal efficiency of 31.7%, which is already greater than 11% conventional engines, after only ten weeks of testing. Emissions results suggest that Tier 3 Bin 160 levels can be achieved using a traditional diesel after-treatment system. Combustion noise was well controlled at or below the USCAR limits. In addition, initial results on catalyst light-off mode with GCI are also presented.

Jet-Niche Technology Influence Potential on the Economic and Operating Parameters of the Fire-Engineering Equipment

The Power engineering is an inseparable part of the contemporary world that has a negative influence on the ecology; in particular it provokes the pollution of atmosphere with such harmful emissions as nitrogen and carbon oxides. Different methods are used to reduce the emission of harmful substances. The efficiency of such methods is increased when these are used in combination and not separately. The recirculation of flue gases and the use of contemporary technologies for municipal boilers, in particular jet-niche technology (JNT) enabled the reduction of NOx and СО emissions to the levels that meet the requirements of European standards simultaneously improving the efficiency of the operation of the fire-engineering facility. The principle of operation of the JNT is based on the formation of the compact stable self-controlled vortex structure and on the interaction system of flammable and oncoming oxidizer flows. This technology enables the operation at minimum recirculation values and it means that all boiler parameters can be retained, in particular starting characteristic, combustion stability and unavailability of vibration modes including a high level of fuel burnout. The obtained research data showed that NОх values were in the range of 80 to 140 mg/m3 when the oxygen content at the furnace inlet was 20% and lower for different boiler systems (DKBR-10, KVGM-6.5, PTVM-50) at CO values close to 50 mg/m2. Hence, the use of the burners of a JNT type enables the reduction of NОхemissions and retains the combustion process efficiency.

Quantitative analysis of combustion process of marine dual fuel engine under the framework of iconology

The methane (CH4) burning interruption factor and the characteristic values characterizing the flame combustion state in the engine cylinder were defined. The logical mapping relationship between image feature values and combustion conditions in the framework of iconology was proposed. Results show that there are two periods of combustion instability and combustion stability during the combustion of dual fuel. The high temperature region with a cylinder temperature greater than 1800K is the largest at 17°CA after top dead center (TDC), accounting for 73.25% of the combustion chamber area. During the flame propagation, the radial flame velocity and the axial flame velocity are “unimodal” and “wavy,” respectively. During the combustion process, the CH4 burning interruption factor first increased and then decreased. The combustion duration in dual fuel mode is 21.25°CA, which is 15.5°CA shorter than the combustion duration in pure diesel mode.

Effects of passive pre-chamber jet ignition on combustion and emission at gasoline engine

Pre-chamber jet ignition is a promising way to improve fuel consumption of gasoline engine. A small volume passive pre-chamber was tested at a 1.5L turbocharged GDI engine. Combustion and emission characteristics of passive pre-chamber at low-speed WOT and part load were studied. Besides, the combustion stability of the passive pre-chamber at idle operation has also been studied. The results show that at 1500 r/min WOT, compared with the traditional spark ignition, the combustion phase of pre-chamber is advanced by 7.1°CA, the effective fuel consumption is reduced by 24 g/kW h, and the maximum pressure rise rate is increased by 0.09 MPa/°CA. The knock tendency can be relieved by pre-chamber ignition. At part load of 2000 r/min, pre-chamber ignition can enhance the combustion process and improve the combustion stability. The fuel consumption of pre-chamber ignition increases slightly at low load, but decreases significantly at high load. Compared with the traditional spark ignition, the NOx emissions of pre-chamber increase significantly, with a maximum increase of about 15%; the HC emissions decrease, and the highest decrease is about 36%. But there is no significant difference in CO emissions between pre-chamber ignition and spark plug ignition. The intake valve opening timing has a significant influence on the pre-chamber combustion stability at idle operation. With the delay of the pre-chamber intake valve opening timing, the CoV is reduced and can be kept within the CoV limit.

A Numerical Study on the Effects of EGR Dilution in a Pre-Chamber Ignited Natural Gas Engine

Lean burn natural gas engines offer low particulate emissions than diesel counterparts and provides higher efficiency when compared to stoichiometric operation. However, with the lean burn strategy, three-way catalysts (TWC) compatibility is lost due to the oxidized exhaust stream. In comparison, the exhaust gas recirculation (EGR) dilution strategy can maintain compatibility with emission after-treatment systems. The maximum tolerated EGR levels are limited by the combustion stability degradation resulting from unfavorable mixture gas composition. Prechamber spark ignition (PCSI) systems, known to increase dilution tolerance in SI engines under lean conditions, was evaluated as a means to improve EGR dilution tolerance. Scavenging of residuals within the pre-chamber is typically a concern with these systems and as such studies on these systems working with various levels of EGR ratios are rare. In this work, an unscavenged (or unfueled, or passive) PCSI system installed in a medium-duty natural gas engine is modeled using CONVERGE CFD code. Simulation results are compared against the experimental data in terms of in-cylinder pressure and heat release rates from low to high (10% to 22%) EGR levels. The prediction capability of two combustion models, a multi-zone well-stirred reactor model and a flamelet-based combustion model, i.e. G-equation, are compared and evaluated under these conditions within the RANS framework. The G-equation model predictions agreed well with experiments up to 18.8% EGR dilution level. In comparison, the MZ-WSR model predicted slow prechamber combustion at all dilution levels which influenced the main chamber combustion phasing.

Influence of H2 enrichment for improving low load combustion stability of a Dual Fuel lightduty Diesel engine

Dual Fuel (DF) combustion can help to reduce the environmental impact of internal combustion engines, since it may provide excellent Brake Thermal Efficiency (BTE) combined with ultra-low emissions. This technique is particularly attractive when using biofuels, or fuels with a low Carbon content, such as Natural Gas (NG). Unfortunately, as engine load decreases and the homogeneous NG-air mixture tends to become very lean, the high chemical stability of NG can be a serious obstacle to the completion of combustion. As a result, BTE drops and UHC and CO emissions become very high. A possible way to address this problem could be the addition of hydrogen (H2) to the NG-air mixture. In this paper, a numerical study has been carried out on an automotive Diesel engine, modified by the authors in order to operate in both conventional Diesel combustion and DF NG-diesel mode. A previous experimental characterization of the engine is the basis for the CFD-3D modeling and calibration of the DF combustion process, using a commercial software. The effects on combustion stability and emissions of different NG-H2 mixtures (six blends with 5%, 10%, 15%, 20%, 25%, and 30% by volume of hydrogen) are numerically investigated at a low load (BMEP = 2 bar, engine speed 3000 rpm). The results of the CFD-3D simulations demonstrate that NG-H2 blends are able to decrease strongly CO, UHC, and CO2 emissions at low loads. Advantages are also found in terms of thermal efficiency and NOx emissions.