WEICHAI POWER a Chinese company specializing in internal combustion engines (ICE) has unveiled a diesel engine with a record-breaking thermal efficiency of 53.09%. The announcement went public at an event held at the 2024 World Congress on Internal Combustion Engines. Moreover, the claim is validated by the TÜV SÜD and the China Automotive Technology & Research Center; both are acclaimed organizations on the subject matter.

The development did not come overnight, as Weichai Power has been performing research on high-efficiency diesel engines since 2015. The early variant of this engine broke the record of 50.23% thermal efficiency back in 2020. By the end of 2022, the company was able to increase the thermal efficiency up to 52.28%.

What is Thermal Efficiency of ICE Engine

The thermal efficiency of an internal combustion (IC) engine refers to the ratio of the mechanical energy to the heat energy contained in the fuel. In simpler terms, it’s a measure of how efficiently an engine converts fuel into useful work. The brake specific fuel consumption (BSFC) is the amount of fuel mass burned to generate a shaft horse power of 1kW per hour; BSFC is one of the mostly used parameter to define the fuel economy of an ICE. Comparatively, ICE powertrain is less efficient compared to other machines, such as an electric motor. For gasoline engines, thermal efficiency typically ranges from 20% to 30%; for diesel engines, it is generally higher, ranging from 30% to 40%.

How to Improve Thermal Efficiency of ICE

There are many parameters that have a direct effect on the engine’s thermal efficiency. The company claims to do it by refining the combustion system, air intake and fuel delivery system, successfully advancing high-expansion combustion, mixed-flow pressurization, efficient fuel injection and improving friction. The impact of these parameters on the engine performance is given below:

1. Air-Fuel Ratio: Maintaining the correct ratio of air to fuel ensures efficient combustion and minimizes wasted fuel.
2. Compression Ratio: A higher compression ratio tends to give better thermal efficiency, as it allows better combustion of the fuel-air mixture or charge.
3. Combustion Chamber Design: Optimized combustion chamber shapes can also improve charge mixing and combustion efficiency.
4. Ignition Timing: For gasoline engines with spark ignition, timing relative to the piston position optimizes combustion and increases the mechanical output.
5. Waste Heat Recovery: Exhaust gas recirculation (EGR) utilizes waste heat to improve overall efficiency.
6. Friction Reduction: Minimizing frictional losses within the engine components, such as pistons, bearings, and crankshaft.

What Are The Benefits of Engine Thermal Efficiency

It’s important to improve thermal efficiency in IC engines for several reasons:

1. Fuel Economy: Higher thermal efficiency means more energy from the fuel is being converted into useful work, resulting in better fuel economy or a lower value of BSFC.
2. Emissions Reduction: Improved efficiency leads to lower emissions of pollutants per unit of work output, contributing to environmental sustainability.
3. Cost Savings: Reduced fuel consumption translates to lower operating costs for vehicle operations.
4. Energy Security: Maximizing the efficiency of internal combustion engines helps conserve finite fossil fuel resources.

Enhancing thermal efficiency has a far-reaching impact, especially on diesel engines, because of their wide application in heavy vehicles. It is worth mentioning that the heavy vehicle sector is still struggling for an all electric conversion due to the relatively lower energy density of the batteries. It means that the retirement of the ICE will take longer in this sector; thus, an energy-efficient diesel engine has very bright prospects in this application. Moreover, converting diesel engines to run on hydrogen can further reduce emissions and dependency on fossil fuels. However, such an endeavor requires further modifications to the engine.