A regenerative supercritical-subcritical dual-loop organic Rankine cycle system for energy recovery from the waste heat of internal combustion engines

Organic Rankine cycle (ORC) system is considered as a promising technology for energy recovery from the waste heat rejected by internal combustion (IC) engines. However, such waste heat is normally contained in both coolant and exhaust gases at quite different temperatures. A single ORC system is usually unable to efficiently recover energy from both of these waste heat sources. A dual loop ORC system which essentially has two cascaded ORCs to recover energy from the engine’s exhaust gases and coolant separately has been proposed to address this challenge. In this way, the overall efficiency of energy recovery can be substantially improved. This paper examines a regenerative dual loop ORC system using a pair of environmentally friendly refrigerants, R1233zd and R1234yf, as working fluids, to recover energy from the waste heat of a compressed natural gas (CNG) engine. Unlike most previous studies focusing on the ORC system only, the present research analyses the ORC system and CNG engine together as an integrated system. As such, the ORC system is analysed on the basis of real data of waste heat sources of the CNG engine under various operational conditions. A numerical model is employed to analyse the performances of the proposed dual loop cycle with four pairs of working fluids. The effects of a regenerative heat exchanger and several other key operating parameters are also analysed and discussed in detail. The performance of the integrated engine-ORC system is then analysed under actual engine operating conditions which were measured beforehand. The performance of the proposed system under off-design conditions has also been analysed. The obtained results show that the proposed dual loop ORC system could achieve better performance than other ORC systems for similar applications

A NEW SPECIES OF THE GENUS ALLOCHTHONIUS (PSEUDOSCORPIONES, PSEUDOTYRANNOCHTHONIIDAE) FROM LIUPAN MOUNTAINS, CHINA, WITH THE DESCRIPTION OF THE MALE OF ALLOCHTHONIUS BREVITUS

A new pseudoscorpion species, Allochthonius (Allochthonius) jingyuanus sp. n., is described and illustrated from Liupan Mountains, China. The hitherto unknown male of Allochthonius (Urochthonius) brevitus Hu et Zhang, 2012 is described and illustrated

FIRST REPORT OF THE FAMILY LECHYTIIDAE (ARACHNIDA: PSEUDOSCORPIONES) FROM CHINA, WITH THE DESCRIPTION OF A NEW SPECIES

The family Lechytiidae is here reported from China for the first time. A new species of the genus Lechytia from Yunnan Province is described and illustrated under the name Lechytia yulongensis sp. n

Thermodynamic analysis of a dual-loop organic Rankine cycle (ORC) for waste heat recovery of a petrol engine

Huge amounts of low-grade heat energy are discharged to the environment by vehicular engines. Considering the large number of vehicles in the world, such waste energy has a great impact on our environment globally. The Organic Rankine Cycle (ORC), which uses an organic fluid with a low boiling point as the working medium, is considered to be the most promising technology to recover energy from low-grade waste heat. In this study, a dual-loop ORC is presented to simultaneously recover energy from both the exhaust gases and the coolant of a petrol engine. A high-temperature (HT) ORC loop is used to recover heat from the exhaust gases, while a low-temperature (LT) ORC loop is used to recover heat from the coolant and the condensation heat of the HT loop. Figure 1 shows the schematic of the dual-loop ORC. Differing from previous research, two more environmentally friendly working fluids are used, and the corresponding optimisation is conducted. First, the system structure and operating principle are described. Then, a mathematical model of the designed dual-loop ORC is established. Next, the performance of the dual-loop cycle is analysed over the entire engine operating region. Furthermore, the states of each point along the cycle and the heat load of each component are compared with the results of previous research. The results show that the dual-loop ORC can effectively recover the waste heat from the petrol engine, and that the effective thermal efficiency can be improved by about 20 ~ 24%, 14~20%, and 30% in the high-speed, medium-speed, and low-speed operation regions, respectively. The designed dual-loop ORC can achieve a higher system efficiency than previous ORCs of this structure. Therefore, it is a good choice for waste heat recovery from vehicle engines

Parametric optimization and heat transfer analysis of a dual loop ORC (organic Rankine cycle) system for CNG engine waste heat recovery

In this study, a dual loop ORC (organic Rankine cycle) system is adopted to recover exhaust energy, waste heat from the coolant system, and intercooler heat rejection of a six-cylinder CNG (compressed natural gas) engine. The thermodynamic, heat transfer, and optimization models for the dual loop ORC system are established. On the basis of the waste heat characteristics of the CNG engine over the whole operating range, a GA (genetic algorithm) is used to solve the Pareto solution for the thermodynamic and heat transfer performances to maximize net power output and minimize heat transfer area. Combined with optimization results, the optimal parameter regions of the dual loop ORC system are determined under various operating conditions. Then, the variation in the heat transfer area with the operating conditions of the CNG engine is analyzed. The results show that the optimal evaporation pressure and superheat degree of the HT (high temperature) cycle are mainly influenced by the operating conditions of the CNG engine. The optimal evaporation pressure and superheat degree of the HT cycle over the whole operating range are within 2.5–2.9 MPa and 0.43–12.35 K, respectively. The optimal condensation temperature of the HT cycle, evaporation and condensation temperatures of the LT (low temperature) cycle, and exhaust temperature at the outlet of evaporator 1 are kept nearly constant under various operating conditions of the CNG engine. The thermal efficiency of the dual loop ORC system is within the range of 8.79%–10.17%. The dual loop ORC system achieves the maximum net power output of 23.62 kW under the engine rated condition. In addition, the operating conditions of the CNG engine and the operating parameters of the dual loop ORC system significantly influence the heat transfer areas for each heat exchanger

Two new species of the pseudoscorpion genus Lagynochthonius from China (Pseudoscorpiones: Chthoniidae)

Two new pseudoscrorpion species belonging to the genus Lagynochthonius of the family Chthoniidae are described from China: Lagynochthonius brachydigitatus sp. n., from Zhejiang Province, and L. medog sp. n., from Xizang Autonomous Region. Lagynochthonius microdentatus Hu & Zhang, 2012 is found to be a junior primary homonym of L. microdentatus Mahnert, 2011 and is replaced with Lagynochthonius harveyi Hu & Zhang, nom. n

Exploring the Association between Job Attributes and Housing Rents: A Case Study of Guangzhou

The association between jobs and housing rents has garnered significant attention from scholars. However, the current body of literature only examines a limited number of job-related characteristics when investigating the link between jobs and housing rents, without delving into more comprehensive job attributes. This study utilizes job data sourced from the job search website Zhilian to conduct a comprehensive analysis of how housing rents are associated with job attributes (specifically, job position features, employer features, and distant job accessibility) at various spatial scales. The analysis is based on a sample of 3,850 communities in Guangzhou, China. This study reveals that housing rents are associated with job attributes at varying spatial scales, with the magnitude of impact generally diminishing as the spatial scale expands. When considering job attributes, it is found that employer features hold the highest level of significance, followed by job position features, while distant job accessibility is deemed to be of lesser importance. The aforementioned findings contribute novel insights into the association between specific job characteristics and housing rents. This information can prove valuable for policymakers as they strive to formulate affordable housing strategies that align with prevailing employment conditions

Liveness-Based RRT Algorithm for Autonomous Underwater Vehicles Motion Planning

Motion planning is a crucial, basic issue in robotics, which aims at driving vehicles or robots towards to a given destination with various constraints, such as obstacles and limited resource. This paper presents a new version of rapidly exploring random trees (RRT), that is, liveness-based RRT (Li-RRT), to address autonomous underwater vehicles (AUVs) motion problem. Different from typical RRT, we define an index of each node in the random searching tree, called “liveness” in this paper, to describe the potential effectiveness during the expanding process. We show that Li-RRT is provably probabilistic completeness as original RRT. In addition, the expected time of returning a valid path with Li-RRT is obviously reduced. To verify the efficiency of our algorithm, numerical experiments are carried out in this paper

Impact Assessment of New Energy Characteristics on Regional Power Grid Considering Multiple Time Scales

[Introduction] With the development of new energy, the influence of new energy uncertainty and time characteristics on power grid is increasing day by day. Traditional new energy indexes are difficult to describe the interaction between power grid and new energy. It is necessary to establish evaluation system and index to quantify the impact of new energy on power grid. [Method] Construct the evaluation system from multi-dimensional and multi-scale and establish new energy output characteristic index, electric quantity characteristic index, peak regulation characteristic index and flexibility demand index to analyze the new energy output characteristics, the relationship between new energy output and electric quantity, the influence of new energy on peak regulation and the influence of new energy fluctuation on power grid at critical moments. Typical scene features were mined by applying indexes from different time scales such as year, season, month, day and hour. [Result] All kinds of indexes of the evaluation system has been calculated by taking the actual wind power, PV power and load in a certain area as an example. The results show quantitatively the influence of regional new energy on power grid and its distribution characteristics at different time scales. The engineering practicability of the proposed index system is verified. [Conclusion] The proposed index calculation method is quick and simple and the physical meaning of indexes is clear and intuitive and helpful to guide the planning and dispatching of new energy

Damage and failure mechanism of pre-static loaded rock under cyclic impact

To study the damage and failure mechanism of rocks under the coupling effect of high ground stress static load and cyclic impact disturbance generated by mining and excavation, the multi-strain rate dynamic static superposition rock mechanics test system was used to carry out the experiments with different pre-imposed static loads (0.45/0.65/0.85σc) superimposed cyclic impact and the same pre-imposed static load superimposed with cyclic impact loads of different frequencies (0.5/1.0/2.0 Hz). The experimental results indicate that the peak strength of rocks in the dynamic static superposition test is smaller than that in the static load test, and the maximum deformation is greater than that in the static load test, indicating that the dynamic static superposition load has a significant promoting effect on rock damage. The evolution of strength, deformation, and failure under dynamic and static superimposed loads are consistent, also, peak strength, fracture duration are linearly negatively correlated with pre-loading static, and logarithmically positively correlated with cyclic impact frequency. The maximum strain, fracture fractal dimension, and fragment fractal dimension are linearly positively correlated with pre-loading static, and logarithmically negatively correlated with cyclic impact frequency. Under different dynamic and static superpositions, the evolution trend of the fractal dimension of rock surface cracks and fragment sizes are basically consistent, and the former is larger than the latter, that shows the synchronicity of the development of rock surface and internal cracks, and rock surface cracks are more prone to generation and expansion. As the pre-loading static increases or the impact frequency decreases, the rock failure gradually intensifies, and the failure mode undergoes a transition from “inclined shear failure to vertical tensile failure to overall burst failure”. The burst failure position extends from bottom to overall. To quantify the damage mechanism of pre-loading static and cyclic impact, a dynamic static superimposed damage factor evolution model was established, which comprehensively considers static load damage, different peak, frequency, and number of cyclic impact damage, and strain rate strengthening effects. Further dynamic and static superposition experiments were conducted, and the error rates of rock peak strength obtained from theoretical calculations and experimental results were 0.5%, 1.8%, 0.6%, and 1.7%, respectively, the errors were relatively small. The theoretical calculation strength based on the superposition of dynamic and static damage factors is lower than the experimental strength. Preliminary analysis shows that this is due to the microscopic hysteresis of damage development under high-frequency cyclic impact. The actual cumulative damage generated by cyclic impact is less than single impact damage multiplied by cycle number. In the later stage, the microscopic testing can be carried out to explore the evolution law of rock microscopic damage under cyclic impact and further improve the theoretical model