In general, as compared to conventional combustion engines, the homogeneous charge compression ignition (HCCI) engine offers better fuel efficiency, NOx, and particulate matter emissions. The HCCI engine, on the other hand, is not connected to the spark plugs or the fuel injection system. This implies that the auto-ignition time and following combustion phase of the HCCI engine are not controlled directly. The HCCI engine will be confined to a short working range due to the cold start, high-pressure rate, combustion noise, and even knocking combustion. Biofuel innovation, such as ethanol-powered HCCI engines, has a lot of promise in today's car industry. As a result, efforts must be made to improve the distinctive characteristics of the engine by turning the engine settings to different ethanol mixtures. This study examines the aspects of ethanol-fueled HCCI engines utilizing homogenous charge preparation procedures. In addition, comparing HCCI engines to other advanced combustion engines revealed their increased importance and prospective consequences. Furthermore, the challenges of transitioning from conventional to HCCI engines are examined, along with potential answers for future upgrade approaches and control tactics.

Many worldwide scientists have concentrated on using waste heat recovery technology in automotive applications because of increasingly strict fuel consumption. The thermoelectric generator (TEG) has garnered significant interest in the automobile sector as a viable waste heat recovery solution over the past several decades. A short survey of thermoelectric materials and heat exchangers for TEG systems is initially presented in this paper. To overcome the heat exchanger's current shortcomings, some previous studies designed a variety of the heat exchanger geometry of the TEG system. They suggested concentric cylindrical TEG system utilizes an annular thermoelectric module instead of the traditional square-shaped one. It uses the heat pipe's benefits to improve radial heat transmission. A comparison of the water-inside and gas-inside arrangements indicated that the water-inside concentric cylindrical TEG system provided a greater power output in our simulations to test the performance of the proposed system.