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High pressure injection of natural gas is being investigated as a mean of fueling diesel engines and meeting increasingly stringent EPA regulations on emissions of nitrogen oxides and particulates. In the work described in this paper, the penetration into air of a sonic jet of methane emerging from a suddenly opened poppet valve has been modelled analytically and measured using flow visualization. The injection pressure ratios were in the range 1.5 to 5 and the conical jet sheet Reynolds numbers were in the range 7000 to 56000. Schlieren photographs revealed that the conical sheet gas jet exhibits an unstable behaviour between the upper and lower plates which simulate the fire deck and the piston. The integral model developed indicates the principal parameters on which the gaseous jet penetration depends and establishes the requirements for scaling. The conical sheet jet penetration is found to be approximately 30% less than that of round holes, given the same flow area.

Low temperature combustion (LTC) of diesel fuel offers a path to low engine emissions of nitrogen oxides (NOx) and particulate matter (PM), especially at low loads. Borescopic optical imaging offers insight into key aspects of the combustion process without significantly disrupting the engine geometry. To assess LTC combustion, two-colour pyrometry can be used to quantify local temperatures and soot concentrations (KL factor). High sensitivity photo-multiplier tubes (PMTs) can resolve natural luminosity down to low temperatures with adequate signal-to-noise ratios. In this work the authors present the calibration and implementation of a borescope-based system for evaluating low luminosity LTC using spatially resolved visible flame imaging and high-sensitivity PMT data to quantify the luminous-area average temperature and soot concentration for temperatures from 1350-2600 K.

The University of British Columbia was one of 64 schools entered in the 1972 Urban Vehicle Design Competition. This urban vehicle was the Grand Award winner at the competition. The vehicle components and design features which led to the design of a well-integrated urban vehicle are discussed. Details of the engine, chassis, body, electronics, and overall coordination of the project are outlined. The vehicle was built by the students themselves, starting with a Fiat 128 engine and drivetrain and natural gas fuel.

Operators of natural gas engines, used for both mobile and stationary applications, are increasingly looking at running these engines under very lean air-fuel ratios in order to reduce exhaust emissions and increase thermal efficiency. Lean operation of homogeneous-charge spark-ignited engines reduces peak combustion temperatures, thereby reducing NOx emissions. Lean operation is normally restricted, however, by the “lean-limit” of combustion, as measured by the air-fuel ratio above which ignition is impossible, or combustion is incomplete. Operation under lean conditions also reduces the mixture burning rate, which can lead to increased spark advance and lower thermal efficiency. In order to increase the burning rate under ultra-lean air-fuel ratios a new “Squish-Jet” combustion chamber concept has been developed.

Compression ignition engines, including those that use natural gas as the major fuel, produce emissions of NOx and particulate matter (PM). Westport Inc. has developed the pilot-ignited high-pressure direct-injection (HPDI) natural gas engine system. Although HPDI engines produce less soot than comparable conventional diesel engines, further reductions in engine-out soot emissions is desired. In diesel engines, multiple injections can help reduce both NOx and PM. The effect of post injections on HPDI engines was not studied previously. The present research shows that late injection of a second gas pulse can significantly reduce PM and CO from HPDI engines without significantly increasing NOx or fuel consumption. In-cylinder pressure measurements were used to characterize the heat release resulting from the multiple injections. Experiments showed that most close-coupled split injection strategies provided no significant emissions benefit and less stable operation.

This paper presents a sensitivity-based input selection algorithm and a layered modeling approach for improving Gaussian Process Regression (GPR) modeling with hyperparameter optimization for engine model development with data sets of 120 training points or less. The models presented here are developed for a Pilot-Ignited Direct-Injected Natural Gas (PIDING) engine. A previously developed GPR modeling method with hyperparameter optimization produced some models with normalized root mean square error (nRMSE) over 0.2. The input selection method reduced the overall error by 0.6% to 18.85% while the layered modeling method improved the error for carbon monoxide (CO) by 52.6%, particulate matter (PM) by 32.5%, and nitrogen oxides (NOX) by 29.8%. These results demonstrate the importance of selecting only the most relevant inputs for machine learning models.

The aim of this work is to carry out statistical analyses on simulated results obtained from large eddy simulations (LES) to characterize spark-ignited combustion process in a partially premixed natural gas mixture in a constant volume combustion chamber (CVCC). Inhomogeneity in fuel concentration was introduced through a fuel jet comprising up to 0.6 per cent of the total fuel mass, in the vicinity of the spark ignition gap. The numerical data were validated against experimental measurements, in particular, in terms of jet penetration and spread, flame front propagation and overall pressure trace. Perturbations in key flow parameters, namely inlet velocity, initial velocity field, and turbulent kinetic energy, were also introduced to evaluate their influence on the combustion event. A total of 12 simulations were conducted.

Pilot-ignited high-pressure direct injection (HPDI) of natural gas in diesel engines results in lower emissions while retaining high thermal efficiency. As a study of HPDI technique, three-dimensional numerical simulations of injection, ignition and combustion were conducted. In particular, the effects on engine combustion of the injection interlace angle between the pilot diesel sprays and natural gas jets were investigated. Numerical simulations revealed ignition and combustion mechanisms in the engine with different injection interlace angles. The results show that altering the interlace angle changes the contact areas between the pilot diesel sprays and the natural gas jets; this affects the heat release rate. Statistical analysis was done to evaluate the expected value and variance of “closeness” between diesel sprays and natural gas jets for different injector tip configurations.

Heavy-duty diesel trucking is responsible for 25%-30% of the road transportation CO2 emissions in North America. Retrofitting class-8 trucks with a complementary hydrogen fuelling system makes it possible to co-combust hydrogen and diesel in the existing internal combustion engine (ICE), thus minimizing the costs associated with switching to non-ICE platforms and reducing the barrier for the implementation of low-carbon gaseous fuels such as hydrogen. This retrofitting approach is evaluated based on the exhaust emissions of a converted truck with several thousand kilometres of road data. The heavy-duty truck used here was retrofitted with an air-intake hydrogen injection system, onboard hydrogen storage tanks, and a proprietary hydrogen controller enabling it to operate in hydrogen-diesel co-combustion (HDC) mode.

Multidimensional simulations are being used to assist the development of a directly injected natural gas system for heavy-duty diesel engines. In this method of converting diesel engines to natural gas fueling, the gas injection takes place at high pressure at the end of the compression stroke. A small amount of pilot diesel fuel is injected prior to the natural gas to promote ignition. Both fuels are injected through a centrally located injector. The mathematical simulations are sought to provide a better understanding of the injection and combustion process of pilot-ignited directly-injected natural gas. The mathematical simulations are also expected to help optimize the injection process, looking in particular at the tip geometry and at the injection delay between the two fuels. The paper presents the mathematical model, which is based on the KIVA-II code. The model includes modifications for underexpanded natural gas jets, and includes a turbulent combustion model.

A Large Eddy Simulation (LES) numerical study of the Partially Stratified Charge (PSC) combustion process is here proposed, carried out with the open Source code OpenFOAM, in a Constant Volume Combustion Chamber (CVCC). The solver has already been validated in previous papers versus experimental data under a limited range of operating conditions. The operating conditions domain for the model validation is extended in this paper, mostly by varying equivalence ratio, to better highlight the influence of turbulence on flame front propagation. Effects of grid sizing are also shown, to better emphasize the trade-off between the level of accuracy of turbulent vortex description, and their impact on the kinematics of flame propagation. Results show the validity of the approach that is evident by comparing numerical and experimental data.

Heavy-duty (HD) vehicles are a crucial part of the transportation sector; however, strict governmental regulations will require future HD vehicles to meet even more rigid NOx emission standards than what already exist. The use of natural gas (NG) as the primary fuel in HD vehicles can immediately reduce the NOx emissions through lower flame temperatures as compared to traditional diesel and can serve as a precursor to even less carbon intensive fuels as they become more readily available. Pilot ignited direct injection natural gas (PIDING) engine technology is one example of how NG can be used in HD vehicles while maintaining diesel-like efficiency. However, NOx emissions still need to be mitigated to avoid negative air quality effects. Exhaust gas recirculation (EGR) is known to reduce in-cylinder temperatures and thus reduce in-cylinder NOx emissions in diesel engines, but the effects of EGR are not as well understood in PIDING engines.

A new fuel injector prototype for heavy-duty engines has been developed to use direct-injection natural gas with small amounts of entrained diesel as an ignition promoter. This “co-injection” is quite different from other dual-fuel engine systems, where diesel and gas are introduced separately. Reliable compression-ignition can be attained, but two injections per engine cycle are needed to minimize engine knock. In the present paper the interactions between diesel injection mass, combustion timing, engine load, and engine speed are investigated experimentally in a heavy-duty single-cylinder engine. For the tests with this injector, ignition delay ranged from 1.2–4.0 ms (of which injector delay accounts for ~0.9 ms). Shorter ignition delays occurred at higher diesel injection masses and advanced combustion timing. At ignition delays shorter than 2.0 ms, knock intensity decreased with increasing ignition delay.

Impending Environmental Protection Agency (EPA) regulations will place severe limits on exhaust emissions of heavy duty diesel engines for urban bus and highway truck applications. To meet this challenge an intensifier-injector system for natural gas fueling of diesel engines is being developed. The intensifier-injector concept employs electronically-controlled, late-cycle, direct injection of high-pressure natural gas with a pilot quantity of diesel fuel. Preliminary performance and emissions data are presented to indicate the potential for diesel engine efficiencies with reduced emissions with this method of natural-gas fueling.

The ignition and combustion of natural gas directly injected into a multi-cylinder two-stroke diesel engine and ignited by a pilot liquid diesel injection has been investigated experimentally and with the aid of numerical simulation. Measurements of cylinder pressure and thermal efficiency were supplemented by endoscopic observation of flame development and three-dimensional numerical simulation of the ignition and combustion process. With gas/diesel fueling and appropriate injection timing, ignition delay and combustion duration can be about the same as with 100% diesel liquid fueling. Flame photography indicates that, for the same liquid diesel flow rate, subsequent injection of natural gas has a negligible effect on the ignition delay of the liquid fuel. Relative ignition timing is of major importance in obtaining successful combustion.

Natural gas has a high auto-ignition temperature, therefore natural gas engines use sparks, hot surfaces or separate diesel pilot injects to promote ignition. For example, the high-pressure direction-injection (HPDI) system, available commercially for heavy-duty truck engines, uses a small diesel injection just prior to the main gas injection. A new type of HPDI injector has been developed that injections diesel and gas simultaneously through the same holes. In this paper the operation and flow characteristics of this “co-injector” will be discussed. An injection visualization chamber (IVC) was developed for optical characterization of injections into a chamber at pressures up to 80 bar. A fuel supply system was constructed for precise control of injector fueling and injection timing. Diesel and natural gas are replaced by VISCOR ® and nitrogen to study non-reacting flows.

Soot emissions from direct-injection engines are sensitive to the fuel-air mixing process, and may vary between combustion cycles due to turbulence and injector variability. Conventional exhaust emissions measurements cannot resolve inter- or intra-cycle variations in particle emissions, which can be important during transient engine operations where a few cycles can disproportionately affect the total exhaust soot. The Fast Exhaust Nephelometer (FEN) is introduced here to use light scattering to measure particulate matter concentration and size near the exhaust port of an engine with a time resolution of better than one millisecond. The FEN operates at atmospheric pressure, sampling near the engine exhaust port and uses a laser diode to illuminate a small measurement volume. The scattered light is focused on two amplified photodiodes.

Measurements of performance and emissions of a Detroit Diesel 1-71 engine fueled with natural gas have been made using high-pressure direct-injection (HPDI). Natural gas is injected late in the compression cycle preceded by pilot injection of conventional liquid diesel fuel. With 6 nozzle holes for both natural gas and diesel pilot there was instability in engine operation at low load and wide scatter in emission measurements. Guided by numerical simulation results it was found experimentally that data reproducibility and engine operating stability could both be much improved by using unequal jet numbers for injection of natural gas and pilot diesel. In the range of 100 to 160 bar, combustion rate and NOx emissions increased with gas injection pressure. Best thermal efficiency results were obtained for a gas pressure of 130 bar. By adjusting beginning of injection, NOx reductions of up to 60 % from the diesel baseline could be obtained, while preserving conventional diesel efficiency.

Zirconium dioxide (ZrO2) doped with Yttria exhibits superplastic behaviour, corrosion resistance and excellent ion conducting properties [1] at moderate temperatures and thus it can be used as an electroceramic to measure the pH of high temperature water used in fuel cells. Several fabrication processes are available for preparation of zirconia ceramics. This research focused on the study of using Spark Plasma Sintering (SPS) process to prepare Yttria Stabilized Zirconia (YSZ) ceramic. 8 mol% YSZ was subjected to varying SPS sintering conditions. Samples were sintered by changing the heating cycle, dwell time, sintering pressure and cooling cycle. Subsequently, these parameters were related to the densification characteristics of the as-sintered YSZ. The results of specific gravity measurements and microstructure evaluation suggest that stepped heating followed by a slow cooling results in YSZ with highest relative density (99.9%).

High-pressure direct-injection (HPDI) in heavy duty engines allows a natural gas (NG) engine to maintain diesel-like performance while deriving most of its power from NG. A small diesel pilot injection (5-10% of the fuel energy) is used to ignite the direct injected gas jet. The NG burns in a predominantly mixing-controlled combustion mode which can produce particulate matter (PM). Here we study the effect of injection strategies on emissions from a HPDI engine in two parts. Part-I investigated the effect of late post injection (LPI); the current paper (Part-II) reports on the effects of slightly premixed combustion (SPC) on emission and engine performance. In SPC operation, the diesel injection is delayed, allowing more premixing of the natural gas prior to ignition. PM reductions and tradeoffs involved with gas slightly premixed combustion was investigated in a single-cylinder version of a 6-cylinder, 15 liter HPDI engine.