Xingyu Liang

Flame temperature theory-based model for evaluation of the flammable zones of hydrocarbon-air-CO2 mixtures

Theoretical models to evaluate the flammable zones of mixtures made up of hydrocarbon, carbon dioxide and air have been proposed in present study. A three-step reaction hypothesis for hydrocarbon combustion was introduced for predicting the upper flammability limit. The method to predict the parameters at fuel inertization point was put forward as well. Validation of these models has been conducted on existing experimental data reported in the literature, including the cases of methane, propane, propylene and isobutane, and an acceptable precision has been achieved. The average relative differences between the estimated results and experimental ones, except for the results at fuel inertization point, are less than 8.8% and 3.3% for upper and lower flammability limit, respectively. This work also indicated that these models possess practical application capacity and can provide safe prediction limits for nonflammable ranges of hydrocarbon diluted with carbon dioxide.

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

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%.

Theoretical Analysis of Engine Waste Heat Recovery by the Combined Thermo-Generator and Organic Rankine Cycle System

The combined thermo-generator and organic rankine cycle (TEG-ORC) used in exhaust heat recovery of internal combustion engine (ICE) is analyzed theoretically. Only about one third of the total energy released from fuel combustion is converted into useful work in engines, while the remaining energy goes into ambient environment, among which exhaust gas possesses high-grade thermal energy. Most of previous studies on energy recovery from engines have focused on exhaust heat recovery by ORC. However, if the heat is exchanged directly with high-temperature exhaust gas, organic working fluid would resolve with its lower decomposition temperature, and this is extremely harmful to ORC system. To avoid this phenomenon and utilize waste heat, preliminary thermoelectric modules are used to lower exhaust temperature and to generate electricity simultaneously. The heat rejected by TEG is used to preheat working fluid, and more energy is recovered to improve gross output power and thermal efficiency. A theoretical numerical model has been established in this paper to study the performances in both supercritical and subcritical combined TEG-ORC systems. The results suggest that, this model could efficiently identify the optimal performance parameters of both TEG and ORC systems. The utilization of TEG can extend the range of choosing working fluids if the temperature of waste heat source is high, so combined TEG-ORC system is suitable to recover waste heat from automotive vehicle engines, and thereby to improve the fuel economy of a passenger vehicle.

Axial vibration source identification of engine crankshaft based on auto-regressive and moving average model and analytic hierarchy process method

This paper presents a method to identify the root cause of the axial vibration of crankshafts for high speed diesel engines based on an auto-regressive and moving average model and the analytic hierarchy process. Through determining initial moving average variables and measuring axial/bending/torsional vibrations of a crankshaft at the free-end of a four-cylinder diesel engine, auto-regressive spectrum analysis is applied to the measured vibration signal. In an investigation of the root cause of the vibration, the hierarchy tree and judgment matrix are given to identify the main vibration root causes. The results show that the axial vibration of the crankshaft is mainly coupled and excited by the bending vibration at high speeds. But at low speeds, the axial vibration in some frequencies is coupled and excited primarily by the torsional vibration. Through investigation of the root cause of the axial vibration of the engine crankshafts, calculation accuracy of the vibration can be improved significantly.

A study of tyre, cavity and rim coupling resonance induced noise

The tyre cavity resonance induced noise and vibration currently have no effective mass production solutions. All proposed solutions are hard to service and difficult to maintain. Different analysis approaches are presented in this paper to verify computer simulation models. Modal analysis results of the tyre cavity, tyre and rim structures were compared and a complex nature of tyre cavity acoustics is understood. Modified air cavities have been simulated. The research in this paper aims to find effective solutions for elimination of the coupled resonance mode by shifting the tyre cavity modal frequency.

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

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.

Experimental Study on the Adhering Fuel Film of the Impinged N-Butanol-Diesel Blends

In this paper, the characteristics of the adhering fuel film after a spray impingement for the n-butanol-diesel blending fuels have been investigated under different injection pressures (60MPa, 80MPa, 100MPa, and 120MPa) and impingement angles (45°, 60°, 75° and 90° ). The blending fuels include the n-butanol (10%)-diesel (90%) volume ratio (B10), the n-butanol (20%)-diesel (80%) (B20) and the n-butanol (30%)-diesel (70%) (B30). The applied diesel is the commercial No. 0 diesel fuel. A cold rolling flat steel plate with a dry surface (Dry wall) and a plate coated with lubricating oil on its surface (Wet wall) were used as an impingement wall. Adhering ratio of each impinged fuel was calculated from the measurement with a precision balance, the adhering fuel film morphology data were captured using an oil film thickness measurement instrument. All experiments were conducted through a common-rail high-pressure fuel injection system where a single-hole nozzle is employed under the normal temperature and pressure. The experimental results demonstrate that the increase of the injection pressure leads to a lower adhering fuel ratio and a smaller distribution of the thick film regions. Meanwhile, with the reduction of the impingement angle, the oil on the wall shows the shape of droop with a thinner fuel film and the adhering fuel ratios decline gradually. The ratio of the adhered oil of B30 is lowest among the three blends, but the difference of their mean thickness on the wet wall is not huge and there is a large central thinner area for the film of B20 on the dry wall which means the faster rate of evaporation.Copyright

Research on the Effect of Urban Road Traffic Soundscape on Drivers' Psychological Acoustics

Like outside scenery, the car interior noise and road condition will affect the drivers mental state when driving. In order to explore the influence of external visual and auditory factors on the drivers mood in the driving process based on research of traffic soundscape, this paper has selected four backbone roads of Tianjin city (China) to test and drive a gasoline passenger vehicle at different speeds. Near Acoustic Holographic was used to scan interior acoustic field distribution, while the tracking shot of the drivers location was recorded by a Sony camera. People with different characteristics were invited to watch the video and completed a self-designed survey questionnaire. The external factors affecting the drivers mood were explored by analyzing all these data. After the investigation, we found that the sound field distribution inside the car could be affected directly and significantly by the opening and closing the car window when driving; in the case of keeping the window closed, the acoustic characteristics of the car cabin was relatively stable; and the visual impact factor of the drivers mood is mainly related to the traffic congestion degree and the construction quality of road surface, whereas the road appearance and aesthetics, which people usually concern about have very little influence.

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

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.

Investigation on Amorphous Particles Evolution of the Diesel Engine

Analysis of the changes in mass and size of particles formed during the diesel combustion process, the morphological characteristics, and the trace elements within these amorphous particles was carried out using a total cylinder sampling system installed on a direct injection diesel engine. Utilizing field emission transmission electron microscope technology, the results showed that the amorphous particles formed during the combustion process were abundant in metallic and non-metallic elements mainly derived from the lubrication oil, which was found to have entered the combustion process, oxidized and combusted, further increasing the absorbed carbon particles during the later stages of combustion.Copyright