Thermal efficiency

About: Thermal efficiency is a research topic. Over the lifetime, 20911 publications have been published within this topic receiving 302373 citations. The topic is also known as: thermodynamic efficiency & efficiency.

Carrot-inspired solar thermal evaporator

Abstract: Solar steam generation appears as an emerging green strategy due to its potential applications in water desalination, power generation and chemical purification. Although a variety of efforts have been devoted to developing high-efficiency solar steam generation devices, a number of challenges remain, including the relatively low thermal efficiency, the complicated process, the high cost, and the difficulty in cycling. Herein, inspired by the natural water transportation in plants, a cheap carrot-inspired solar thermal evaporator (ethanol-treated-carrot biochar, ECB) has been reported by utilizing its inherent structure, which achieves a record high evaporation rate of 2.04 kg m−2 h−1 and an apparent energy conversion efficiency of 127.8% under one-sun illumination. The inherent structure not only enables sufficient water transportation, but also offers a high light-to-heat conversion efficiency originating from the carbonized surface. Furthermore, the excellent durability and environmental stability of the biochar allow for convenient recycling programs and practical applications.

Homogeneous charge compression ignition combustion: Advantages over compression ignition combustion, challenges and solutions

Abstract: The homogeneous charge compression ignition (HCCI) engine uses a relatively new mode of combustion technology. In principle, there is no spark plug or injector to assist the combustion, and the combustion auto-ignites in multiple spots once the mixture has reached its chemical activation energy. It is noticeably faster than either compression ignition (CI) or spark ignition combustion (SI). The HCCI combustion mode provides better thermal efficiency and maintains low emission by modifying CI as well as SI engines. A wide variety of fuels, combinations of fuels and alternative fuels can be used in this technology. However, some challenges including combustion phase control, limited operating range, cold start, a high level of noise and homogeneous charge preparation need to be overcome for successful operation of HCCI engines. The objective of this study is to illustrate the engine performance and emission characteristics of HCCI engines at different test conditions and various challenges associated with these engines. Also introduced is a potential guideline to overcome these challenges and improve engine performance and emission characteristics. From the review, it can be concluded that HCCI combustion can be applied in existing CI engines with modifications and the most significant result of applying this combustion is the lower NOx and soot emissions with almost the same performance as with CI combustion.

Optimization of operational parameters on performance and emissions of a diesel engine using biodiesel

Abstract: This work investigates the influence of compression ratio on the performance and emissions of a diesel engine using biodiesel (10, 20, 30, and 50 %) blended-diesel fuel. Test was carried out using four different compression ratios (17.5, 17.7, 17.9 and 18.1). The experiments were designed using a statistical tool known as design of experiments based on response surface methodology. The resultant models of the response surface methodology were helpful to predict the response parameters such as brake specific fuel consumption, brake thermal efficiency, carbon monoxide, hydrocarbon and nitrogen oxides. The results showed that best results for brake thermal efficiency and brake specific fuel consumption were observed at increased compression ratio. For all test fuels, an increase in compression ratio leads to decrease in the carbon monoxide and hydrocarbon emissions while nitrogen oxide emissions increase. Optimization of parameters was performed using the desirability approach of the response surface methodology for better performance and lower emission. A compression ratio 17.9, 10 % of fuel blend and 3.81 kW of power could be considered as the optimum parameters for the test engine.