Ruichen Wang

An investigation of the acoustic characteristics of a compression ignition engine operating with biodiesel blends

In this paper, an experimental investigation has been carried out on the acoustic characteristics of a compression ignition (CI) engine running with biodiesel blends under steady state operating conditions. The experiment was conducted on a four-cylinder, four-stroke, direct injection and turbocharged diesel engine which runs with biodiesel (B50 and B100) and pure diesel. The signals of acoustic, vibration and in-cylinder pressure were measured during the experiment. To correlate the combustion process and the acoustic characteristics, both phenomena have been investigated. The acoustic analysis resulted in the sound level being increased with increasing of engine loads and speeds as well as the sound characteristics being closely correlated to the combustion process. However, acoustic signals are highly sensitive to the ambient conditions and intrusive background noise. Therefore, the spectral subtraction was employed to minimize the effects of background noise in order to enhance the signal to noise ratio. In addition, the acoustic characteristics of CI engine running with different fuels (biodiesel blends and diesel) was analysed for comparison. The results show that the sound energy level of acoustic signals is slightly higher when the engine fuelled by biodiesel and its blends than that of fuelled by normal diesel. Hence, the acoustic characteristics of the CI engine will have useful information for engine condition monitoring and fuel content estimation.

Modelling and validation of a regenerative shock absorber system

For effective energy regeneration and vibration dampening, energy regenerative suspension systems have received more studies recently. This paper presents the dynamic modeling and a test system of a regenerative shock absorber system which converts vibration motion into rotary motion through the adjustment of hydraulic flow. Hydraulic circuit configuration achieves the one way flow and energy regeneration during both compression and extension strokes. The dynamic modeling is performed for the evaluation of design concept and the feasibility studies of regenerative shock absorber system theoretically. Based on simulated results, the efficiency of hydraulic transmission is optimized and validated in test system. The results show that the performance of hydraulic fluid, the features of rotary motion and the capability of energy regeneration are verified and compared between dynamic modeling and experiments. Meanwhile, the average power of 118.2W and 201.7W with the total energy conversion of 26.86% and 18.49% can be obtained based on experiments under sinusoidal inputs with 0.07854m/s and 0.1256m/s respectively.

Multipath ultrasonic gas flow-meter based on multiple reference waves

ABSTRACT Several technologies can be used in ultrasonic gas flow‐meters, such as transit‐time, Doppler, cross‐correlation and etc. In applications, the approach based on measuring transit‐time has demonstrated its advantages and become more popular. Among those techniques which can be applied to determine time‐of‐flight (TOF) of ultrasonic waves, including threshold detection, cross correlation algorithm and other digital signal processing algorithms, cross correlation algorithm has more advantages when the received ultrasonic signal is severely disturbed by the noise. However, the reference wave for cross correlation computation has great influence on the precise measurement of TOF. In the applications of the multipath flow‐meters, selection of the reference wave becomes even more complicated. Based on the analysis of the impact factors that will introduce noise and waveform distortion of ultrasonic waves, an averaging method is proposed to determine the reference wave in this paper. In the multipath ultrasonic gas flow‐meter, the analysis of each path of ultrasound needs its own reference wave. In case study, a six‐path ultrasonic gas flow‐meter has been designed and tested with air flow through the pipeline. The results demonstrate that the flow rate accuracy and the repeatability of the TOF are significantly improved by using averaging reference wave, compared with that using random reference wave.

Effect of the turning characteristics of underfloor wheel lathes on the evolution of wheel polygonisation

During both running and wheel cut operations, wheels of railway vehicles and the friction rollers that support and drive the wheelset on a typical wheel cut lathe are subject to wear and hence are likely to develop out-of-round characteristics after sustained use. The resulting out-of-round wheels can significantly affect the ride quality and can potentially increase the incidence of fatigue-related component failures due to the resulting higher intensity loading cycles. Furthermore, the corresponding out-of-round characteristics of the lathes friction rollers will continue to degrade the subsequent cut quality of wheels. For the analysis of the out-of-round characteristics caused by an underfloor wheel lathe used for the high-speed trains in China, a mathematical model based on a typical electric multiple unit (EMU) vehicles wheelsets and their interactions with the wheel lathe friction rollers was established. Factors influencing the cut quality of the wheels, including the number of cuts, eccentricity forms of the friction rollers and the longitudinal spacing of the two rollers, have been analysed. The results show that two cuts can effectively remove the higher order polygon on the wheel surface. The eccentricity and phase angle of the friction rollers have no influence on the cut quality of higher order polygons, whereas they are the primary cause for the fourth-order polygons. The severity of the fourth-order polygon depends on the level and the phase of the eccentricity of the friction rollers. The space of the two rollers can also significantly affect the cut quality. Obtaining the theoretical and practical value for the maintenance of polygonised wheels using the underfloor lathe is the main outcome of this study.

Review on wave energy technologies and power equipment for tropical reefs

As a promising renewable resource to replace part of the energy supply, the wave energy is having more and more interest worldwide. This paper presents a comprehensive analysis of different wave energy technologies in order to identify more promising methods for power supply to tropical reefs. It starts with summarizing the characteristics of tropical reefs in which the most suitable places to be exploited are showed, and the classification of different types of wave energy converters according to their construction features. It is also described in detail each of the stages that are part in the energy conversion. On the basis of the characteristics of tropical coral reefs the paper puts forward a new type of raft wave energy device which can achieve high operational reliability and adaptability with cost-effective deployment.

Research on effect of gas-charged accumulator capacity on hydraulic regenerative shock absorber system

Regenerative shock absorber is able to improve the energy conservation, ride comfort and handling of vehicles by suppressing oscillatory motion due to road roughness. This paper presents the performance studies of modelling and testing for a hydraulic regenerative shock absorber system with different sizes of gas-charged accumulator in order to improve the stability of hydraulic behaviour and power regeneration. The model is proposed to stabilize hydraulic flow with variable accumulator capacity with the impressive power regeneration efficiency which is almost constant, and obtained agreeable results between predicted and measured in sinusoidal oscillation. In addition, Random road profiles are also generated as vibration source to investigate the capability of power regeneration experimentally. The results show that the stability and continuity of power regeneration is observably improved by adjusting accumulator capacity.