Cooling Loss Reduction of Highly Dispersed Spray Combustion with Restricted In-Cylinder Swirl and Squish Flow in Diesel Engine

Abstract

Recently, there has been an increasing awareness of environmental and energy problems, which are global in scale. Diesel engines have better fuel consumption than gasoline engines, and there are great hopes for them because they are more flexible in terms of fuel diversification. However, diesel engines have more NOx and smoke than gasoline engines, and thus require expensive fuel injection components and emission control devices to clean these emissions. Inagaki et al. 1) proposed a new combustion concept that reduces NOx significantly below the Euro6 standard by operating PCCI (Premixed Charge Compression Ignition) in diesel engines that have highly dispersed spray from injectors with numerous small-diameter orifices with a narrow angle combined with low in-cylinder flow. A schematic diagram of an engine for the new combustion concept is shown in Fig. 1, and the basic specifications of the engine are shown in Table 1. The engine is based on a direct-injection diesel engine found in commercially available vehicles in Europe. A low pressure loop (LPL) EGR system was added to the original engine, which has a conventional high pressure loop (HPL) EGR system. The engine for the new combustion concept is using conventional diesel engine injection components to control costs, and have multi-orifice nozzles with orifices that are smaller than in conventional diesel engines. This type of nozzles with numerous small-diameter orifices can form the highly dispersed spray which can promote the entrainment under the restricted in-cylinder flows.

An experimental investigation on the influence of piston bowl geometry on RCCI performance and emissions in a heavy-duty engine

“…The purpose of this geometry was to modify the squish flow in order to enhance unburned products oxidation in this zone. Stepped geometry resulted in 4.6% lower piston surface than stock piston, which should limit heat transfer [41]. The second geometry was named as bathtub due to its similitude to the piston used in [40], but it is worthy to note that the central part of the piston used in the current work is not completely flat as in previous literature is.…”

Thermo-swing insulation to reduce heat loss from the combustion chamber wall of a diesel engine

“…As the result of these studies, TSWIN developed first in the world has been adopted to the 2.8 L ESTEC 1GD diesel engine. 25 No remarkable damage was detected on the insulation coating throughout every durability tests before the start of production. In this application, it was confirmed that TSWIN can be used together with low heat rejection combustion systems such as with low swirl and low squish apparatus, as the additional item to gain better thermal efficiency.…”

“…By using the low luminosity combustion fuel, radiative heat transfer should have been reduced compared to that of normal diesel fuel combustion. Even if the contribution of radiation is about 10% of total wall heat transfer in diesel combustion with normal diesel fuel, 24,25 it is considered that the influence could be limited and it would be possible to ensure the temperature swing phenomenon. The engine operating condition is 1200 rpm, 50% load, and the fuel quantity of about 38 mm 3 /stroke.…”

Effects of piston bowl geometry on Reactivity Controlled Compression Ignition heat transfer and combustion losses at different engine loads

“…The first geometry was named as steeped and maintains the stock piston central geometry with a modified transition to the squish region, as shown in Figure 2. The aim of this geometry is to modify the squish flow in order to facilitate the unburned products oxidation and to limit heat transfer in this region [30]. The designed geometry resulted in 4.6% reduced piston surface versus the stock piston.…”