Thermal Efficiency Improvement and its Mechanism at Low Load Conditions in Semi-Premixed Diesel Combustion with Twin Peak Shaped Heat Release

2019 ◽  
Author(s):  
Kazuki Inaba ◽  
Yosuke Masuko ◽  
Yanhe Zhang ◽  
Yoshimitsu Kobashi ◽  
Gen Shibata ◽  
...  
Keyword(s):  
Heat Release ◽  
Thermal Efficiency ◽  
Diesel Combustion ◽  
Efficiency Improvement ◽  
Low Load ◽  
Load Conditions ◽  
Twin Peak

scholarly journals Thermal efficiency improvement with super-charging and cooled exhaust gas recirculation in semi-premixed diesel combustion with a twin peak shaped heat release

2018 ◽  
Vol 20 (1) ◽  
pp. 80-91 ◽  
Author(s):  
Kazuki Inaba ◽  
Yuto Ojima ◽  
Yosuke Masuko ◽  
Yoshimitsu Kobashi ◽  
Gen Shibata ◽  
...  
Keyword(s):  
Heat Release ◽  
Oxygen Concentration ◽  
Thermal Efficiency ◽  
Fuel Injection ◽  
Combustion Efficiency ◽  
High Load ◽  
Exhaust Gas ◽  
Low Load ◽  
Load Conditions ◽  
Twin Peak

Thermal efficiency–related parameters in semi-premixed diesel combustion with a twin peak shaped heat release were experimentally investigated in a 0.55-L single-cylinder diesel engine. Here, the first heat release peak is realized with the premixed combustion at top dead center after the end of the first fuel injection with a sufficient ignition delay. The fuel injection quantity for the first combustion was maximized in a range to limit the rate of pressure rise below 0.6 MPa/°CA at 0.4 MPa IMEP, 0.8 MPa/°CA at 0.8 MPa IMEP, and 1.0 MPa/°CA at 1.3 MPa IMEP to ensure the large degree of constant volume heat release and to suppress smoke emissions. The second heat release peak is formed from the rate-controlled combustion with the second fuel injection immediately after the end of the first combustion. The influence of the intake oxygen concentration and the intake gas pressure on the thermal efficiency and the exhaust gas emissions was systematically examined at three load conditions (indicated mean effective pressure ≈0.4, 0.8, and 1.3 MPa). The results with two types of combustion chambers, a toroidal chamber expecting smaller cooling losses with weaker in-cylinder gas motion, and with a re-entrant chamber expecting better air utilization with stronger in-cylinder gas motion are compared. At the medium load, a significantly high indicated thermal efficiency exceeding 50% is established with a reduction in the intake oxygen concentration due to the smaller cooling loss. The indicated thermal efficiency improves with a decrease in the intake oxygen concentration as the reduction in the cooling loss is more significant than the increase in the exhaust loss. However, an excessive reduction in the intake oxygen concentration results in a deterioration in the indicated thermal efficiency due to a reduction in the combustion efficiency. At low load conditions, the indicated thermal efficiency is lower than at the medium load due to lower combustion efficiency and the improvement in the indicated thermal efficiency with reductions in the intake oxygen concentration is not significant as the combustion efficiency decreases with the decrease in the intake oxygen concentration. At the high load condition, the indicated thermal efficiency is lower due to a larger exhaust loss than at the low and medium load conditions and the indicated thermal efficiency decreases with the decrease in the intake oxygen concentration. With an increase in the intake gas pressure, the indicated thermal efficiency increases consistently mainly due to the reducing cooling loss. In comparison with the re-entrant combustion chamber, the indicated thermal efficiency with the toroidal combustion chamber is 1% higher due to a smaller cooling loss at the low load, almost comparable at the medium load and 1.2% lower at the high load due to the larger exhaust loss.

Semi-Premixed Diesel Combustion with Twin Peak Shaped Heat Release Using Two-Stage Fuel Injection

2016 ◽  
Author(s):  
Hideyuki Ogawa ◽  
Gen Shibata ◽  
Yuhei Sakane ◽  
Tatsuaki Arisawa ◽  
Tatstunori Obe
Keyword(s):  
Heat Release ◽  
Fuel Injection ◽  
Diesel Combustion ◽  
Two Stage ◽  
Twin Peak

Thermal Efficiency Improvements with Split Primary Fuel Injections in Semi-Premixed Diesel Combustion with Multi-Peak Shaped Heat Release

2019 ◽  
Author(s):  
Kazuki Inaba ◽  
Yosuke Masuko ◽  
Yanhe Zhang ◽  
Yoshimitsu Kobashi ◽  
Gen shibata ◽  
...  
Keyword(s):  
Heat Release ◽  
Thermal Efficiency ◽  
Diesel Combustion

Mechanism of thermal efficiency improvement in twin shaped semi-premixed diesel combustion

2021 ◽  
pp. 146808742110264
Author(s):  
Kazuki Inaba ◽  
Yanhe Zhang ◽  
Yoshimitsu Kobashi ◽  
Gen Shibata ◽  
Hideyuki Ogawa
Keyword(s):  
Heat Release ◽  
Thermal Efficiency ◽  
Gas Flow ◽  
Fuel Injection ◽  
Premixed Combustion ◽  
Combustion Noise ◽  
Diesel Combustion ◽  
Combustion Mode ◽  
Secondary Stage ◽  
Combustion Phase

Improvements of the thermal efficiency in twin shaped semi-premixed diesel combustion mode with premixed combustion in the primary stage and spray diffusive combustion in the secondary stage with multi-stage fuel injection were investigated with experiments and 3D-CFD analysis. For a better understanding of the advantages of this combustion mode, the results were compared with conventional diesel combustion modes, mainly consisting of diffusive combustion. The semi-premixed mode has a higher thermal efficiency than the conventional mode at both the low and medium load conditions examined here. The heat release in the semi-premixed mode is more concentrated at the top dead center, resulting in a significant reduction in the exhaust loss. The increase in the cooling loss is suppressed to a level similar to the conventional mode. In the conventional mode the rate of heat release becomes more rapid and the combustion noise increases with advances in the combustion phase as the premixed combustion with pilot and pre injections and the diffusive combustion with the main combustion occurs simultaneously. In the semi-premixed mode, the premixed combustion with pilot and primary injections and the diffusive combustion with the secondary injection occurs separately in different phases, maintaining a gentler heat release with advances in the combustion phase. The mechanism of the cooling loss suppression with the semi-premixed mode at low load was investigated with 3D-CFD. In the semi-premixed mode, there is a reduction in the gas flow and quantity of the combustion gas near the piston wall due to the suppression of spray penetration and splitting of the injection, resulting in a smaller heat flux.

A new concept of actively controlled rate of diesel combustion (ACCORDIC): Part II—simultaneous improvements in brake thermal efficiency and heat loss with modified nozzles

2018 ◽  
Vol 20 (1) ◽  
pp. 34-45 ◽  
Author(s):  
Noboru Uchida ◽  
Hiroki Watanabe
Keyword(s):  
Heat Release ◽  
Heat Loss ◽  
Heat Release Rate ◽  
Release Rate ◽  
Thermal Efficiency ◽  
Air Entrainment ◽  
Diesel Combustion ◽  
Brake Thermal Efficiency ◽  
Rate Profile ◽  
Late Part

A new diffusion-based combustion concept (named it as Actively Controlled Rate of Diesel Combustion) for the confirmation of brake thermal efficiency optimum heat release rate profile based on multiple fuel injectors has been investigated. The outstanding results are; it is possible to achieve desired heat release rate profile only by the independent control of injection timing and duration of three injectors installed to a cylinder. The optimum brake thermal efficiency was not achieved with the Otto-like cycle but with the Sabathe-like cycle as predicted by a zero-dimensional thermodynamic model. Furthermore, smoke emissions were concurrently reduced with NOx emissions by increasing fuel amount from the side injectors without any deterioration in CO and total hydrocarbon emissions. On the other hand, brake thermal efficiency itself was not so improved than expected, because of lower heat release in the late part of combustion and unexpected less heat loss reduction. To solve these issues, combustion visualization and numerical simulation analysis were carried out. The results suggested that the adjacent sprays with narrower angle from each side injector deteriorated air entrainment and mixture formation, which might also result in the deterioration in wall heat loss in the expansion stroke. To solve both issues simultaneously, modified nozzle to inject against the swirl from the side injectors was utilized and achieved an improvement in both brake thermal efficiency and heat loss. That is the interdependent and reciprocal control of in-cylinder flow and fuel injection will be one of the breakthrough technologies for current trade-offs by the temporal and spatial spray flame optimization. Furthermore, the nozzle having higher flow rate with less number of orifice was utilized for the side injectors. Even though the smoke emissions were not optimized yet, brake thermal efficiency was much improved with higher heat release rate in the late part of combustion.

Optimization of combustion noise and thermal efficiency in diesel engines over a wide speed and load operational range

2019 ◽  
Vol 21 (4) ◽  
pp. 698-712
Author(s):  
Gen Shibata ◽  
Kohei Yamamoto ◽  
Mikito Saito ◽  
Yuto Inoue ◽  
Yasumasa Amanuma ◽  
...  
Keyword(s):  
Heat Release ◽  
Thermal Efficiency ◽  
Engine Speed ◽  
Combustion Noise ◽  
Injection System ◽  
Injection Timing ◽  
Wide Range ◽  
Optimum Heat ◽  
Operational Range ◽  
Load Conditions

Pre-mixed diesel combustion has the potential of offering high thermal efficiency with low emissions; however, this may result in loud combustion noise because of the high maximum rate of pressure rise. Combustion noise and thermal efficiency work in a trade-off relation, and it has not been possible to achieve high thermal efficiency with low combustion noise, so far. Our laboratory has worked on combustion noise simulations calculated from the heat release history, and it is now possible to calculate a heat release shape for high thermal efficiency with low combustion noise. In this article, the objective of the research is the reduction of combustion noise by multiple fuel injections with high indicated thermal efficiency for a wide range of engine speeds and loads. The engine employed in the simulations and experiments is a supercharged, single-cylinder direct-injection diesel engine, with a high-pressure common rail fuel injection system. The heat release is approximated by Wiebe functions, and the combustion noise and indicated thermal efficiency are calculated in simulations. The engine operational range was divided into 12 conditions, four engine speed conditions each at three engine load conditions, and the optimum heat release shape for low combustion noise with high indicated thermal efficiency was calculated by a genetic-based algorithm method. The parameters for the genetic-based algorithm simulation were the number of injections, each injection timing, the heating value in each heat release, and the combustion period of each injection. The optimum heat release shape is a delta triangle (Δ)-shaped heat release (the heat release increase in the expansion stroke) with a high degree of constant volume for all conditions; however, the optimum number of heat releases and the injection timing are different depending on the engine speed and load conditions. The simulated results were confirmed by engine tests.

Low Temperature Combustion Within an HSDI Diesel Engine Using Multiple Injection Strategies

2007 ◽  
Author(s):  
Tiegang Fang ◽  
Robert E. Coverdill ◽  
Chia-Fon F. Lee ◽  
Robert A. White
Keyword(s):  
Low Temperature ◽  
Heat Release ◽  
Injection Pressure ◽  
High Load ◽  
Injection Timing ◽  
Diesel Combustion ◽  
Low Temperature Combustion ◽  
Combustion Mode ◽  
Temperature Combustion ◽  
Load Conditions

Low Temperature Compression Ignition (LTCI) combustion employing multiple injection strategies in an optical High-Speed Direct Injection (HSDI) diesel engine was investigated in this work. Heat release characteristics were analyzed through the measurement of in-cylinder pressure. The whole cycle combustion process was visualized with a high-speed digital video camera by imaging natural flame luminosity and three-dimensional-like combustion structures were obtained by taking flame images from both the bottom of the optical piston and the side window simultaneously. The NOx emissions were measured in the exhaust pipe. The effects of pilot injection timing, pilot fuel quantity, main injection timing, operating load, and injection pressure on the combustion and emissions were studied. Low temperature combustion mode was achieved by using a small pilot injection with an injection timing much earlier than TDC followed by a main injection after TDC. For comparison, experiment of a diffusion diesel combustion case was also conducted. Premixed-combustion-dominated heat release rate pattern was seen for all the low temperature combustion cases, while a typical diffusion flame combustion heat release rate was obtained for the conventional combustion case. Highly luminous flame was observed for the conventional combustion condition while much less luminous flame was seen for the low temperature combustion cases. For the higher load and lower injection pressure cases, liquid fuel being injected into low temperature premixed flame was observed for certain cases, which was different from the conventional diesel combustion with liquid fuel injected into hot premixed flame. Compared with the conventional diffusion diesel combustion, simultaneous reduction of soot and NOx was obtained for the low temperature combustion mode at both the same and increased injection pressure with similar operating load. For high load conditions, higher NOx emissions were obtained than the low load conditions with the same injection pressure due to a higher in-cylinder temperature under high load conditions with more fuel burned. However, compared with the diffusion combustion mode with a lower load at lower injection pressure, a significant reduction of soot was achieved for the high load conditions, which shows that increasing injection pressure greatly reduce soot emissions.

scholarly journals The Effect of Pure Oxygenated Biofuels on Efficiency and Emissions in a Gasoline Optimised DISI Engine

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3908
Author(s):  
Tara Larsson ◽  
Senthil Krishnan Mahendar ◽  
Anders Christiansen-Erlandsson ◽  
Ulf Olofsson
Keyword(s):  
Internal Combustion Engines ◽  
Negative Impact ◽  
The Other ◽  
Nox Emissions ◽  
Combustion Engines ◽  
Engine Efficiency ◽  
Spark Timing ◽  
Low Load ◽  
Oxygenated Fuels ◽  
Load Conditions

The negative impact of transport on climate has led to incentives to increase the amount of renewable fuels used in internal combustion engines (ICEs). Oxygenated, liquid biofuels are promising alternatives, as they exhibit similar combustion behaviour to gasoline. In this article, the effect of the different biofuels on engine efficiency, combustion propagation and emissions of a gasoline-optimised direct injected spark ignited (DISI) engine were evaluated through engine experiments. The experiments were performed without any engine hardware modifications. The investigated fuels are gasoline, four alcohols (methanol, ethanol, n-butanol and iso-butanol) and one ether (MTBE). All fuels were tested at two speed sweeps at low and mid load conditions, and a spark timing sweep at low load conditions. The oxygenated biofuels exhibit increased efficiencies, even at non-knock-limited conditions. At lower loads, the oxygenated fuels decrease CO, HC and NOx emissions. However, at mid load conditions, decreased volatility of the alcohols leads to increased emissions due to fuel impingement effects. Methanol exhibited the highest efficiencies and significantly increased burn rates compared to the other fuels. Gasoline exhibited the lowest level of PN and PM emissions. N-butanol and iso-butanol show significantly increased levels of particle emissions compared to the other fuels.

Sign in / Sign up

Export Citation Format

Share Document