Browse Publications Technical Papers 2021-24-0039

What Are the Barriers Against Brake Thermal Efficiency beyond 55% for HD Diesel Engines? 2021-24-0039

This study focused on the technology integration to aim beyond 60% indicated thermal efficiency (ITE) with a single-cylinder heavy-duty diesel engine as an alternative to achieve 55% brake thermal efficiency (BTE) with multiple-cylinder engines. Technology assessment was initially carried out by means of a simple chart of showing ITE and exhaust heat loss as functions of cooling loss and heat conversion efficiency into indicated work. The proposed compression ratio (28:1), excess air ratio and new ideal thermodynamic cycle were then determined by a simple cycle calculation. Except for peak cylinder pressure constraint for each engine, the technical barriers for further ITE improvement are mainly laid in cooling loss reduction, fuel-air mixture formation improvement, and heat release rate optimization under very high temperature and density conditions with very high compression ratio (smaller cavity volume). For the significant cooling loss reduction, a new concept of in-cylinder wall surface coating combined with intake chilling was experimentally investigated based on the hypothesis of the cooling loss mechanism which relates the heat transfer phenomena on the surface not only during combustion period but also during exhaust and intake strokes. For the mixture formation improvement, several numerical or experimental case studies were carried out to find the guideline for the chamber shape and fuel injection equipment design. For the heat release rate optimization, a new thermodynamic cycle was proposed. Although the engine has not been fully optimized yet, 59.5% ITE was experimentally achieved with the single cylinder engine by utilizing these technologies without any significant drawbacks.


Subscribers can view annotate, and download all of SAE's content. Learn More »


Members save up to 16% off list price.
Login to see discount.
Special Offer: Download multiple Technical Papers each year? TechSelect is a cost-effective subscription option to select and download 12-100 full-text Technical Papers per year. Find more information here.
We also recommend:

Optical Diagnostics of Isobaric and Conventional Diesel Combustion in a Heavy-Duty Diesel Engine


View Details


Analysis of the Piston Group Friction in a Single-Cylinder Gasoline Engine When Operated with Synthetic Fuel DMC/MeFo


View Details


Influence of Injection Strategies on Engine Efficiency for a Methanol PPC Engine


View Details