Achieving stable combustion without misfire and knocking is challenging in premixed charge compression ignition (PCCI) especially in small bore, air cooled diesel engines owing to lower power output and inefficient cooling system. In the present study, a single cylinder, air cooled diesel engine used for agricultural water pumping applications is modified to run in PCCI by replacing an existing mechanical fuel injection system with a flexible common rail direct injection system. An advanced start of fuel injection (SOI) and exhaust gas recirculation (EGR) are required to achieve PCCI in the test engine. Parametric investigations on SOI, EGR and fuel injection pressure are carried out to identify optimum parameters for achieving maximum brake thermal efficiency. An SOI sweep of 12 to 50 deg. CA bTDC is done and for each SOI, EGR is varied from 0 to 50% to identify maximum efficiency points. It was found that EGR helps in extending the load range from 20 to 40% of rated load.
The fuel economy of recent small size DI diesel engines has become more and more efficient. However, heat loss is still one of the major factors contributing to a substantial amount of energy loss in engines. In order to a full understanding of the heat loss mechanism from combustion gas to cylinder wall, the effect of hole size and rail pressure under similar injection rate conditions on transient heat flux to the wall were investigated. Using a constant volume vessel with a fixed impingement wall, the study measured the surface heat flux of the wall at the locations of spray flame impingement using three thin-film thermocouple heat-flux sensors. The results showed that the characteristic of local heat flux and soot distribution was almost similar by controlling similar injection rate except for the small nozzle hole size with increasing injection pressure.
Lean burn gasoline engines can achieve noteworthy fuel consumption and power output. However, when the mixture becomes lean, the ignition delay increases, and the flame propagation speed becomes slow, which lead to increase the combustion fluctuation. The glow plug is usually used to solve the cold start problem in diesel engines, where the compression temperature might not be high enough to ensure the proper ignition of the injected fuel, resulting in instability combustion and increased exhaust emissions. Based on this point, the present study intends to install a glow plug to the sub-chamber. Experiments were conducted on a modified single cylinder four-stroke CI engine (YANMAR TF120V) to operate as SI engine with a higher compression ratio compared to the conventional SI engines, 15.1:1. The engine is operated at a constant speed of 1000 rpm for different equivalence ratios with different voltage of glow plug which creates the temperature variation inside the sub-chamber.
In the present work, a relative comparison of addition of water to diesel through emulsion and fumigation methods is explored for reducing oxides of nitrogen (NOx) and smoke emissions in a production small bore diesel engine. The water to diesel ratio was kept the same in both the methods at a lower concentration of 3% by mass to avoid any adverse effects on the engine system components. The experiments were conducted at a rated engine speed of 1500 rpm under varying load conditions. A stable water-diesel emulsion was prepared using a combination of equal proportions (1:1 by volume) of Span 80 and Tween 80. The mixture of Span 80 in diesel and Tween 80 in water was homogenized using an IKA Ultra Turrax homogenizer with tip stator diameter 18mm at 5000 rpm for 2 minutes. The water-in-diesel emulsions thus formulated were kinetically stable and appeared translucent. No phase separation was observed on storage for approximately 105 days.
In the last decade, pollution by particulate matter and its effect on human health has increasingly become the focus of public attention. In order to monitor and evaluate particulate pollution, expensive measuring stations were placed at traffic hotspots and other selected locations. The measuring devices often precisely record the particle concentration, but have disadvantages in mobility and for measurements in large-area due to their size and investment costs. A measurement with high temporal and spatial resolution is not possible with these stations. This paper presents a new type of mobile particulate sensor based on the Plantower PMS 7003 particle sensor. In addition to the Plantower sensor, a rechargeable battery and newly developed control electronics are also installed in the particulate sensor. Due to the small size and the low manufacturing costs of the measuring system, mobile usage in higher quantity is possible.
Despite the increase in public attention to particulate matter emissions since the millennium and the known effects on the human organism, representative predictions on the dispersion of emissions in both urban and rural areas are hardly possible so far. Especially the validation of simulations with measurement results is not possible due to the limited number and high price of certified measuring instruments. Rather, the temporally high-resolution measuring instruments are only sporadically distributed within the city, so that emission dynamics at traffic hotspots, such as traffic jams or intersections, cannot be depicted. Furthermore, due to the small number of certified measuring instruments, fine dust pollution can only be interpolated over long distances. In this paper, first statements about the transport characteristics of particles at a road intersection will be made by using a variety of so-called low-cost particulate matter sensors.
Measuring brake emission is still a challenging non-standardized task. Extensive research is ongoing. Updates of work in progress are presented at SAE Brake Colloquium and PMP meetings. However, open items include how to achieve lower background concentration and how to design the brake enclosure. A low background concentration is essential as brake events are short and some emit in the range of reported background levels. Hence these emissions are difficult to distinguished from the background level. Even more critical, a high background concentration can result in a wrong particle number emissions value, either overestimated, background counted as emissions, or underestimated, background level subtracted, and low emission events no longer detected and counted. However, reducing the background level to less than 100 #/cm³ appeared to be quite challenging.
The particulate emissions of two brake systems where characterized in a dilution tunnel optimized for PM10 measurements. The larger of them employed a fixed caliper (FXC) and the smaller one a floating caliper (FLC). Both used ECE brake pads of the same lining formulation. Measured properties included gravimetric PM2.5 and PM10, Particle Number (PN) concentrations of both untreated and thermally treated (according to exhaust number regulation) particles using Condensation Particle Counters (CPCs) having 23 and 10 nm cut-off sizes, and an Optical Particle Sizer (OPS). The brakes were tested over a novel test cycle developed from the database of the Worldwide harmonized Light-Duty vehicles Test Procedure (WLTP). A series of WLTP tests were performed starting from unconditioned pads, to characterize the evolution of emissions until their stabilization. Selected tests were also performed over a short version of the Los Angeles City Cycle.