Showing papers by "Gequn Shu published in 2013"

A review of waste heat recovery on two-stroke IC engine aboard ships

Abstract: Different types of waste heat recovery technologies available onboard ships have been discussed from the perspective of technical principle and application feasibility. Study of basic principle, novel methods, existing designs, theoretical and experimental analyses, economics and feasibility are discussed in this paper. The primary focus of this paper is to provide a better understanding of the options available for waste heat recovery and using in various applications onboard ocean-going ships to improve fuel economy and environmental compliance.

Simulations of a Bottoming Organic Rankine Cycle (ORC) Driven by Waste Heat in a Diesel Engine (DE)

Abstract: A bottoming waste-heat-recovery (WHR) model based on the Organic Rankine Cycle (ORC) is proposed to recover waste heat from exhaust gas and jacket water of a typical diesel engine (DE). The ORC model is detailed built based upon real structural and functional parameters of each component, and is able to precisely reflect the working process of the experimental ORC system constructed in lab. The DE is firstly tested to reveal its energy balance and the features of waste heat. The bottoming ORC is then simulated based on experimental data from the DE bench test using R245fa and R601a as working fluid. Thermodynamic evaluations are done on key parameters like waste heat recovered, expansion power, pump power loss and system efficiency. Results indicate that maximum expansion power and efficiency of the ORC are up to 18.8kW and 9.6%. Influences of engine condition, fluid mass flow and evaporating pressure on system performance are analyzed and meaningful regularities are revealed. The combined system of DE and bottoming ORC (DE-ORC) is also investigated. The results showed that the integration of the bottoming ORC greatly changed energy distribution of the DE, and the DE thermal efficiency is up to 47.2%, increasing by 9.0%.

The influence of lubricating oil on deposits formation in a diesel engine under the operation condition of high power density

Abstract: The requirements of higher power density and stricter regulations on emissions of internal combustion engines lead to lubricating oil's role shifting from simply lubricating to adapting higher power density and to achieving lower emissions. An important factor influencing an engine's power and emissions is the deposits in the engine. Lubricating oil is a chief contributor to deposits formation. The objective of this paper is to investigate the influence of lubricating oil on deposits formation when the engine is operated under high power density. Metal elements content in lubricating oil and changes to power and emissions were measured to verify deposits changes. Different power densities can be achieved by adjusting the fuel supply system in the engine. Three kinds of synthesised lubricating oils were used in the investigation. The temperature of the oil pan and cooling water was strictly controlled. The experimental results demonstrated well the influence of the quality of different kinds of oil on deposits formation. Copyright © 2013 John Wiley & Sons, Ltd.

Thermodynamic Analysis of a Novel Combined Power and Cooling Cycle Driven by the Exhaust Heat Form a Diesel Engine

Abstract: A novel combined power and cooling cycle based on the Organic Rankine Cycle (ORC) and the Compression Refrigeration Cycle (CRC) is proposed. The cycle can be driven by the exhaust heat from a diesel engine. In this combined cycle, ORC will translate the exhaust heat into power, and drive the compressor of CRC. The prime advantage of the combined cycle is that both the ORC and CRC are trans-critical cycles, and using CO₂ as working fluid. Natural, cheap, environmentally friendly, nontoxic and good heat transfer properties are some advantages of CO₂ as working fluid. In this paper, besides the basic combined cycle (ORC-CRC), another three novel cycles: ORC-CRC with an expander (ORC-CRCE), ORC with an internal heat exchanger as heat accumulator combined with CRC (ORCI-CRC), ORCI-CRCE, are analyzed and compared. The cycle parameters, including the coefficient of performance (cop), the cooling capacity (Qro) and expansion power of CRC (We) have been analyzed and optimized as the variation of the high pressure of ORC, the high pressure and the outlet temperature of gas cooler of CRC, and temperature drop of heat source in heat accumulator of ORC. The results indicate that there is an optimal high pressure of CRC (about 8.6 MPa to 8.8 MPa) for the combined cycles, at which the combined cycles achieve the optimal performance. The results also show that both the expander and heat accumulator could improve the system performance. The higher ΔTi could improve the system performance, but also resulting the more insufficiency of waste heat recovery.

Simulation Research on the Effect of Cooled EGR, Supercharging and Compression Ratio on Downsized SI Engine Knock

Abstract: Knock in spark-ignition(SI) engines severely limits engine performance and thermal efficiency The researches on knock of downsized SI engine have mainly focused on structural design, performance optimization and advanced combustion modes, however there is little for simulation study on the effect of cooled exhaust gas recirculation(EGR) combined with downsizing technologies on SI engine performance On the basis of mean pressure and oscillating pressure during combustion process, the effect of different levels of cooled EGR ratio, supercharging and compression ratio on engine dynamic and knock characteristic is researched with three-dimensional KIVA-3V program coupled with pressure wave equation The cylinder pressure, combustion temperature, ignition delay timing, combustion duration, maximum mean pressure, and maximum oscillating pressure at different initial conditions are discussed and analyzed to investigate potential approaches to inhibiting engine knock while improving power output The calculation results of the effect of just cooled EGR on knock characteristic show that appropriate levels of cooled EGR ratio can effectively suppress cylinder high-frequency pressure oscillations without obvious decrease in mean pressure Analysis of the synergistic effect of cooled EGR, supercharging and compression ratio on knock characteristic indicates that under the condition of high supercharging and compression ratio, several times more cooled EGR ratio than that under the original condition is necessarily utilized to suppress knock occurrence effectively The proposed method of synergistic effect of cooled EGR and downsizing technologies on knock characteristic, analyzed from the aspects of mean pressure and oscillating pressure, is an effective way to study downsized SI engine knock and provides knock inhibition approaches in practical engineering

Chemical kinetic modeling for the effects of methyl ester moiety in biodiesel on PAHs and NO x formation

Abstract: In order to investigate the effects of methyl ester moiety on polycyclic aromatic hydrocarbons (PAHs) and NOx formation in biodiesel combustion, the combined models were developed based on detailed methyl butanoate (MB) oxidation model and n-butane model. Also, PAHs detailed reaction mechanism and NOx formation mechanism were added to the detailed models to form the combined models. The combined models were used to compare the combustion of n-butane and MB in a shock tube simulation to understand the effects of methyl ester moiety. The results indicated that compared with n-butane, the methyl ester moiety in MB leads to different reaction pathways, more CO and CO2 formation and less formation of PAHs precursors such as ethylene and acetylene. In addition, a better chemical insight into the effects of methyl ester moiety on NOx formation was given, which will help to understand the combustion process of biodiesel.

Parametric and exergetic analysis of a two-stage transcritical combined organic Rankine cycle used for multiple grades waste heat recovery of diesel engine

Abstract: Diesel engine has multiple grades of waste heat with different ratios of combustion heat, exhaust is 400 °C with the ratio of 21% and coolant is 90 °C with 19%. Few previous publications investigate the recovery of multiple grades waste heat together. In this paper, a two-stage transcritical combined organic rankine cycle (CORC) is presented and analyzed. In the combined system, the high and low temperature stages transcritical cycle recover the high grades waste heat, and medium to low grades waste heat respectively, and being combined efficiently. Meanwhile, the suitable working fluids for high stage are chosen and analyzed. The cycle parameters, including thermal efficiency (ηth), net power output (Pnet), energy efficiency (ηexg) and global thermal efficiency of DE-CORC(ηglo) have also been analyzed and optimized. The results indicate that this combined system could recover all the waste heat with a high recovery ratio (above 90%) and obtain a maximum power output of 37kW for a DE of 243kW. The global thermal efficiency of DE-CORC can get a max value of 46.2% compared with 40% for single DE. The results also indicate that all the energy conversion process have a high exergy efficiency.

Analytical and Experimental Study on Bending Vibration of Internal Combustion Engines Shafting System Based on Wave Equations

Abstract: This paper proposes a new analytical approach to study the bending vibration of N step shafting system Changes of the shaft step properties under rotary condition are governed by two-dimensional wave equations The source of the bending vibration is first analysed Then strain and stress equations of the spinning shaft are established After Hamilton principle is applied, a two-dimensional wave equation is established After that, the calculation formula of one dimensional bending vibration response is obtained where a sinusoidal excitation force is applied on an arbitrary concentrated mass By using this formula, the total dynamic response can be obtained based on the principle of the linear superposition The calculated results were compared with measured results It was found they agree with each other in the vertical direction but not in the horizontal direction At the end of paper, the reason of difference is analysed

Dynamic response of functional virtual prototyping of motorcycle under combined excitations

Abstract: This paper developed 3D product models of motorcycle and engine by UGNX as well as virtual prototyping by ADAMS program with road roughness generated by MATLAB. Under the straight-line running condition, the dynamic responses of motorcycle multibody system to both road and engine excitations were compared with those to only road excitation in terms of vertical acceleration response, amplitude frequency response and power spectral density. The comparisons of simulation data showed that the response due to flat road excitation was around 20 Hz, while that to the combined excitations was in a wide frequency band, of which the major components focused on 10 Hz, 15 Hz, 35 Hz, 70 Hz, 100 Hz and even higher frequencies, reflecting the characteristics of engine excitation based on its unbalanced inertia force and torque. It is concluded that the high fidelity virtual prototyping can simulate the dynamics of motorcycle product well in investigating the vibration and ride comfort performance.